阅读说明：本技术 用于调色剂添加剂的复合颗粒 (Composite particles for toner additives ) 是由 屠海若 熊锦程 P.S.帕伦博 D.福米切夫 于 2019-08-06 设计创作，主要内容包括：金属氧化物-聚合物复合颗粒具有40-75nm或100-150nm的中值颗粒尺寸D50和至少0.06的平均RTA。替代地或另外,金属氧化物-聚合物复合物包括在尺寸、颗粒尺寸分布、或形状方面不同的两群或更多群金属氧化物颗粒。替代地或另外,使用包括烷基硅烷的多组分疏水化用体系来制造金属氧化物-聚合物复合颗粒使所述复合颗粒的摩擦电荷增加。(The metal oxide-polymer composite particles have a median particle size D50 of 40-75nm or 100-150nm and an average RTA of at least 0.06. Alternatively or additionally, the metal oxide-polymer composite includes two or more groups of metal oxide particles that differ in size, particle size distribution, or shape. Alternatively or additionally, the use of a multi-component hydrophobizing system comprising alkylsilanes to make metal oxide-polymer composite particles increases the triboelectric charge of the composite particles.)

1. A metal oxide-polymer composite particle in powder form comprising a polymer matrix and a plurality of metal oxide particles, wherein:

the metal oxide particles are surface-modified with a first hydrophobizing system comprising a bifunctional component via which the metal oxide particles are covalently attached to the polymer matrix;

the polymer of the polymer matrix is a polymer or copolymer of the difunctional component; and

the metal oxide-polymer composite particles have a median particle size D50 of 40-75nm and an average RTA of at least 0.06.

2. A metal oxide-polymer composite particle in powder form comprising a polymer matrix and a plurality of metal oxide particles, wherein:

the metal oxide particles are surface-modified with a first hydrophobizing system comprising a bifunctional component via which the metal oxide particles are covalently attached to the polymer matrix;

the polymer of the polymer matrix is a polymer or copolymer of the difunctional component; and

the metal oxide-polymer composite particles have a median particle size D50 of 100-150nm and an average RTA of at least 0.06.

3. The composite particles of claim 1 or claim 2, wherein the metal oxide particles have a monomodal size distribution.

4. The composite particle of any one of claims 1-3, wherein the composite particle has an average particle roughness of greater than 1.22.

5. The composite particle of any one of claims 1-4, wherein the composite particle has an average particle roughness of greater than 1.25.

6. The composite particles of any one of claims 1-5, wherein at least a portion of the surface of the metal oxide-polymer composite particles is modified with a second hydrophobizing agent.

7. The composite particle of any one of claims 1-6, wherein the average RTA is from 0.08 to 0.13.

8. The composite particles of any one of claims 1-7, wherein the metal oxide-polymer composite particles comprise at least 15% metal oxide.

9. The composite particle of any one of claims 1-8, wherein the bifunctional component has the formula [ R [ ]³ _3-x(OR¹)_x]SiR²Q, where x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is a firstOr ethyl and Q is a substituted or unsubstituted vinyl, acrylate, or methacrylate group, with the proviso that when Q is a substituted or unsubstituted vinyl, n is from 2 to 10.

10. The composite particle of any one of claims 1-9, wherein the first hydrophobizing system further comprises a monofunctional component covalently attached to the metal oxide particle.

11. The composite particle of claim 10 wherein said monofunctional component has the formula (OR)¹)_4-zSiR⁴ _zWherein R is¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl radical or R²Ph, wherein Ph is an unsubstituted phenyl group or a phenyl group substituted with a C1-C10 branched or unbranched alkyl, halogen, C1-C10 alkyl ether, methoxy, ethoxy, or hydroxy.

12. A toner composition comprising the metal oxide-polymer composite particles of any one of claims 1-11 disposed about the surface of the toner particles.

13. A toner composition comprising: toner particles mixed with a powder comprising metal oxide-polymer composite particles comprising a polymer matrix and a plurality of metal oxide particles, wherein:

the metal oxide particles are surface-modified with a first hydrophobizing system comprising a difunctional component via which the metal oxide particles are covalently attached to the polymer matrix and a monofunctional component which is covalently attached to the metal oxide particles;

at least a portion of the surface of the metal oxide-polymer composite particles is modified with a second hydrophobizing agent, wherein the polymer of the polymer matrix is a polymer or copolymer of the bifunctional component; and

the triboelectric charge of the toner under HH conditions is at least 9% greater in magnitude than the triboelectric charge of a toner comprising a control metal oxide-polymer composite in which the monofunctional component is replaced with the difunctional component.

14. The toner composition of claim 13, wherein the triboelectric charge of the toner under LL conditions is at least 10% greater in magnitude than the triboelectric charge of a toner comprising a control metal oxide polymer complex in which the monofunctional component is replaced with the difunctional component.

15. The toner composition of claim 13 or 14, wherein the monofunctional component and the difunctional component each include a silane group.

16. The toner composition of any of claims 13-15, wherein the monofunctional component has the formula (OR)¹)_4-zSiR⁴ _zWherein R is¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl group.

17. The toner composition of any of claims 13-16, wherein the monofunctional component has a solubility of 10 to 0.06g/L, preferably 9 to 0.03g/L, more preferably 8 to 0.1g/L, most preferably 7 to 0.5 g/L.

18. A method of making a composite particle comprising:

preparing an aqueous dispersion comprising metal oxide particles and a first hydrophobizing system comprising a difunctional component and a monofunctional component, wherein the difunctional component and the monofunctional component become chemically linked to the metal oxide particles;

adding a polymerization initiator to the aqueous dispersion to form metal oxide-polymer composite particles having metal oxide particles at their surface, wherein the polymer matrix of the metal oxide-polymer composite particles is a polymer or copolymer of the first hydrophobizing system; and

drying the metal oxide-polymer composite particles to form a powder.

19. The method of claim 18, further comprising, before or after drying, treating the metal oxide-polymer composite particles with a second hydrophobizing agent to produce hydrophobized metal oxide-polymer composite particles.

20. The method of claim 18 or 19, wherein the monofunctional component and the difunctional component both comprise silane groups.

21. The method of any one of claims 18-20, wherein the monofunctional component has the formula (OR)¹)_4-zSiR⁴ _zWherein R is¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl group.

22. The method of any one of claims 18-21, wherein the bifunctional component has the formula [ R [ ]³ _3-x(OR¹)_x]SiR²Q, where x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate, or methacrylate group, with the proviso that when Q is a substituted or unsubstituted vinyl, n is from 2 to 10.

23. The method of any one of claims 18-22, wherein the dispersion further comprises one or more of: styrene, substituted or unsubstituted acrylate or methacrylate monomers, olefin monomers, vinyl esters, or acrylonitrile.

24. The method of any one of claims 18-23, wherein the monofunctional component has a solubility of 10-0.06g/L, preferably 9-0.03g/L, more preferably 8-0.1g/L, most preferably 7-0.5 g/L.

25. A metal oxide-polymer composite particle in powder form comprising a polymer matrix and a plurality of metal oxide particles, wherein:

the plurality of metal oxide particles comprises at least a first group of metal oxide particles and a second group of metal oxide particles, the first group of metal oxide particles having a different size, shape, or particle size distribution relative to the second group;

the metal oxide particles are surface-modified with a first hydrophobizing system comprising a bifunctional component via which the metal oxide particles are covalently linked to the polymer matrix,

at least a portion of the plurality of metal oxide particles protruding into and out of the polymer matrix,

the polymer matrix comprises a polymer or copolymer of a first hydrophobizing system,

at least a part of the surface of the metal oxide-polymer composite particle is modified with a second hydrophobizing agent, and

the metal oxide-polymer composite particles have an average SF-1 of 110-185 and an average RTA of 0.06-0.19.

26. The composite particle of claim 25, wherein the first hydrophobizing system further comprises a monofunctional component covalently attached to the metal oxide particle.

27. The composite particle of claim 25 or 26 wherein the difunctional component has the formula [ R [³ _3-x(OR¹)_x]SiR²Q, where x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate, or methacrylate group, with the proviso that when Q is substituted or unsubstitutedWhen the vinyl group is (C), n is 2 to 10.

28. The composite particle of claim 27 wherein said monofunctional component is of the formula (OR)¹)_4-zSiR⁴ _zWherein R is¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl radical or R²Ph, wherein Ph is an unsubstituted phenyl group or a phenyl group substituted with a C1-C10 branched or unbranched alkyl, halogen, C1-C10 alkyl ether, methoxy, ethoxy, or hydroxy.

29. The composite particle of any one of claims 25-28, wherein the median particle size D50 of the first and second populations has a ratio of about 40:1 to about 1.5: 1.

30. The composite particle of any one of claims 25-29, wherein the ratio of the first population and the second population, D75/D25, has a ratio of about 40:1 to about 1.1: 1.

31. The composite particle of any one of claims 25-30, wherein the mass ratio of the first population to the second population is from about 1:20 to about 20:1, e.g., from about 1:15 to about 15:1, from about 1:10 to about 10:1, from about 1:5 to about 5:1, or from about 1:2 to about 2: 1.

32. The composite particle of any one of claims 25-31, wherein the metal oxide-polymer composite particle has a volume average particle size of about 20nm to about 1000 nm.

33. The composite particle of any one of claims 25-32, wherein the metal oxide-polymer composite particle has an average roughness P of about 1.22 to about 1.9²/4πS。

34. The composite particle of any one of claims 25-33, wherein the polymer matrix comprises polymers of styrene, unsubstituted or substituted acrylates or methacrylates, olefins, vinyl esters, and acrylonitrile, and copolymers and mixtures thereof.

35. A toner composition comprising the composite particles of any of claims 25-34 disposed on the surface of toner particles.

36. A method of making a metal oxide-polymer composite particle, comprising:

preparing an aqueous dispersion comprising a first hydrophobizing system and at least a first population of metal oxide particles and a second population of metal oxide particles in an aqueous medium, the first population of metal oxide particles having a different size, shape, or particle size distribution than the second population, wherein the first hydrophobizing system comprises a composition having the formula [ R [ ]³ _3-x(OR¹)_x]SiR²A difunctional component of Q, wherein x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate, or methacrylate group, with the proviso that when Q is a substituted or unsubstituted vinyl, n is 2 to 10;

incubating the dispersion for a predetermined amount of time;

adding a free radical initiator to the dispersion;

allowing the chemical groups of the first hydrophobizing system to become part of the polymer, thereby forming metal oxide-polymer composite particles; and

drying the metal oxide-polymer composite particles to obtain a powder.

37. The method of claim 36, further comprising treating at least a portion of the metal oxide particles with a second hydrophobizing agent, wherein treating can be performed after formation or before preparation of the metal oxide-polymer composite particles.

38. The method of claim 36 OR 37, wherein the first hydrophobizing system further comprises a compound having the formula (OR)¹)_4-zSiR⁴ _zA monofunctional component of (1), wherein R¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl radical or R²Ph, wherein Ph is an unsubstituted phenyl group or a phenyl group substituted with a C1-C10 branched or unbranched alkyl, halogen, C1-C10 alkyl ether, methoxy, ethoxy, or hydroxy.

39. The method of any one of claims 36-38, wherein the first population and the second population have a ratio of D50 of about 40:1 to 1.5: 1.

40. The method of any one of claims 36-39, wherein the ratio of the first population and the second population, D75/D25, has a ratio of about 40:1 to about 1.1: 1.

41. The method of any one of claims 36-40, wherein the mass ratio of the first population to the second population is about 1:20 to about 20: 1.

42. The method of any one of claims 36-41, wherein the emulsion further comprises one or more of: styrene, substituted or unsubstituted acrylate or methacrylate monomers, olefin monomers, vinyl esters, or acrylonitrile.

43. The method of any one of claims 36-42, wherein at least a portion of the metal oxide particles protrude into and out of the polymer matrix.

44. The method of any one of claims 36-43, wherein the metal oxide-polymer composite particles have a volume average particle size of about 20nm to about 1000 nm.

45. The method of any one of claims 36-44, wherein the metal oxide-polymer composite particles have a specific density of about 30% to about 90% of the specific density of the metal oxide when measured by the Hepycnometer method.

46. The method of any one of claims 36-45, wherein the metal oxide-polymer composite particles have an average SF-1 of about 110 to about 185 and an average RTA of about 0.06 to about 0.19.

47. The method of any one of claims 36-46, wherein the metal oxide-polymer composite particles have an average roughness P of about 1.22 to about 1.9²/4πS。

48. A metal oxide-polymer composite particle made by the method of any one of claims 18-24 or 36-47.

Technical Field

The present invention relates to the manipulation of the size, morphology, and triboelectric charge (tribocharge) of metal oxide-polymer composite particles.

Background

Electrophotographic imaging involves uniformly charging the surface of a photoreceptor drum or belt; exposing the surface of the photoreceptor and forming a charge pattern, i.e., a latent image, reflecting information to be transferred into a real image on the surface of the photoreceptor; developing the latent image with electrostatically charged toner particles comprising a colorant dispersed in a binder resin; transferring the developed toner to a substrate such as paper; fusing the image to the substrate; and preparing the photoreceptor surface for the next cycle by erasing the residual electrostatic charge and cleaning the residual toner particles from the photoreceptor drum.

Toners for use in electrophotography and electrostatic printing include a binder resin and a colorant and may further include a charge control agent, an offset (offset) preventing agent, and other additives. To improve selected properties of the toner particles (including flowability, transferability, fixability, and cleaning properties), external toner additives such as metal oxide particles are often combined with the toner particles. A wide variety of external additives may be used in a single toner composition to enhance different properties of the toner. For example, some additives may be selected to improve chargeability, i.e., triboelectric charge. Others may be selected to improve cleaning performance or moisture resistance. Of course, it is preferred that the toner additives optimized for one function not be detrimental to the function imparted by the various additives.

One function imparted by the toner additive is spacing and maintaining fluidity. If the toner particles adhere to each other, they do not flow as well; the additive is used to reduce the cohesion (cohesion) of the toner powder. The additive particles tend to be hard. On the other hand, the toner is formed of a softer polymer. The resulting agglomeration of toner particles is detrimental to both the operation of the electrophotographic apparatus and the print quality. Indeed, as manufacturers have sought to reduce the energy required to produce printed pages, they have turned to softer polymers (i.e., lower Tg polymers) to reduce the amount of heat required to fuse the toner to the substrate. However, hard additive particles may become embedded in soft toner particles, thereby reducing the effectiveness of the additive. Increasing the size of the additive particles reduces intercalation; however, larger particles are also heavier and exhibit a higher rate of falling from the toner particles. Of course, the additive particles falling from the toner cannot function as part of the toner composition. The metal oxide-polymer composite particles described in U.S. patent No.9,568,847 act as spacers between toner particles while exhibiting both limited embedment and limited dropping in the toner particles. Now, it is desirable to further manipulate the roughness, shape, and size of metal oxide composite particles to improve their free-flowing properties and to manipulate their triboelectric charge characteristics and refractive index.

Disclosure of Invention

In one aspect, a metal oxide-polymer composite particle in powder form comprises a polymer matrix and a plurality of metal oxide particles, wherein: the metal oxide particles are surface-modified with a first hydrophobizing system comprising a bifunctional component via which the metal oxide particles are covalently attached to the polymer matrix; the polymer of the polymer matrix is a polymer or copolymer of the difunctional component; and the metal oxide-polymer composite particles have a volume weighted median particle size D50 of 40 to 75nm and an average RTA of at least 0.06, e.g., 0.06 to 0.019, 0.08 to 0.015, or 0.08 to 0.13.

Alternatively, the metal oxide-polymer composite particles in powder form comprise a polymer matrix and a plurality of metal oxide particles, wherein the metal oxide particles are surface-modified with a first hydrophobizing system comprising a bifunctional component via which the metal oxide particles are covalently linked to the polymer matrix; the polymer of the polymer matrix is a polymer or copolymer of the difunctional component; and the metal oxide-polymer composite particles have a volume weighted median particle size D50 of 100-150nm and an average RTA of at least 0.06, e.g., 0.06-0.019, 0.08-0.015, or 0.08-0.13.

For any of these composite particles, the metal oxide particles may have a monomodal size distribution. The composite particles may have an average particle roughness of greater than 1.22, such as greater than 1.25, or up to 1.35, 1.60, 1.70, or 1.90. At least a portion of the surface of the metal oxide-polymer composite particles can be modified with a second hydrophobizing agent. The metal oxide-polymer composite particles may include at least 15% metal oxide.

The difunctional component may have the formula [ R³ _3-x(OR¹)_x]SiR²Q, where x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate, or methacrylate group, with the proviso that when Q is a substituted or unsubstituted vinyl, n is from 2 to 10. The first hydrophobizing system can further include a monofunctional component, such as a silane, covalently attached to the metal oxide particles. The monofunctional component may have the formula (OR)¹)_4-zSiR⁴ _zWherein R is¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl radical or R²Ph, wherein Ph is an unsubstituted phenyl group or a phenyl group substituted with a C1-C10 branched or unbranched alkyl, halogen, C1-C10 alkyl ether, methoxy, ethoxy, or hydroxy.

Any of the above-described composite particles may be disposed about the surface of the toner particles to form a toner composition.

In another aspect, a toner composition includes: toner particles mixed with a powder comprising metal oxide-polymer composite particles comprising a polymer matrix and a plurality of metal oxide particles. The metal oxide particles are surface-modified with a first hydrophobizing system comprising a difunctional component via which the metal oxide particles are covalently attached to the polymer matrix and a monofunctional component covalently attached to the metal oxide particles. At least a portion of the surface of the metal oxide-polymer composite particles is modified with a second hydrophobizing agent, and the polymer of the polymer matrix is a polymer or copolymer of the bifunctional component. The triboelectric charge of the toner under HH conditions is at least 9% greater in magnitude than the triboelectric charge of a toner comprising a control metal oxide-polymer composite in which the monofunctional component is replaced with the difunctional component.

Alternatively or additionally, the triboelectric charge of the toner under LL conditions is at least 10% greater in magnitude than the triboelectric charge of a toner including a control metal oxide polymer composite in which the monofunctional component is replaced with the difunctional component. Both the monofunctional component and the difunctional component may include silane groups. The monofunctional component may have the formula (OR)¹)_4-zSiR⁴ _zWherein R is¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl group. The solubility of the monofunctional component may be 10 to 0.06g/L, preferably 9 to 0.03g/L, more preferably8-0.1g/L, most preferably 7-0.5 g/L.

In another aspect, a method of making composite particles includes preparing an aqueous dispersion including metal oxide particles and a first hydrophobizing system, the first hydrophobizing system comprising a difunctional component and a monofunctional component, wherein the difunctional component and the monofunctional component become chemically linked to the metal oxide particles; adding a polymerization initiator to the aqueous dispersion to form metal oxide-polymer composite particles having metal oxide particles at their surface, wherein the polymer matrix of the metal oxide-polymer composite particles is a polymer or copolymer of the first hydrophobizing system; and drying the metal oxide-polymer composite particles to form a powder.

The method can further include, before or after drying, treating the metal oxide-polymer composite particles with a second hydrophobizing agent to produce hydrophobized metal oxide-polymer composite particles. Both the monofunctional component and the difunctional component may include silane groups. The monofunctional component may have the formula (OR)¹)_4-zSiR⁴ _zWherein R is¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl group. The difunctional component may have the formula [ R³ _3-x(OR¹)_x]SiR²Q, where x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate, or methacrylate group, with the proviso that when Q is a substituted or unsubstituted vinyl, n is from 2 to 10. The dispersion may further comprise one or more of the following: styrene, substituted or unsubstituted acrylate or methacrylate monomers, olefin monomers, vinyl esters, or acrylonitrile. The solubility of the monofunctional component may be 10 to 0.06g/L, preferably 9 to 0.03g/L, more preferably 8 to 0.1g/L, most preferably 7 to 0.5 g/L.

In another aspect, a metal oxide-polymer composite particle in powder form can include a polymer matrix and a plurality of metal oxide particles. The plurality of metal oxide particles includes at least a first group of metal oxide particles and a second group of metal oxide particles, the first group of metal oxide particles having a different size, shape, or particle size distribution relative to the second group. The metal oxide particles are surface modified with a first hydrophobizing system comprising a difunctional component, the metal oxide particles are covalently attached to the polymer matrix via the bifunctional component, portions of the plurality of metal oxide particles are embedded within and protrude from the polymer matrix (i.e., at least a portion of the plurality of metal oxide particles (which may include at least a portion of each population of metal oxide particles) protrude into and protrude from the polymer matrix), the polymer matrix comprises a polymer or copolymer of a first hydrophobizing system, at least a portion of the surface of the metal oxide-polymer composite particles is modified with a second hydrophobizing agent, and the metal oxide-polymer composite particles have an average SF-1 of 110-185 and an average RTA of 0.06-0.19.

The first hydrophobizing system can further include a monofunctional component, such as a silane, covalently attached to the metal oxide particles. The difunctional component may have the formula [ R³ _3-x(OR¹)_x]SiR²Q, where x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate, or methacrylate group, with the proviso that when Q is a substituted or unsubstituted vinyl, n is from 2 to 10. The monofunctional component may have the formula (OR)¹)_4-zSiR⁴ _zWherein R is¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl radical or R²Ph, wherein Ph is an unsubstituted phenyl group or a branched or unbranched alkyl group having from C1 to C10, halogen, C1 to C10 alkyl ether, methoxy, ethoxy, orA hydroxy-substituted phenyl group.

The volume weighted median particle size D50 of the first population and the second population may have a ratio of about 40:1 to about 1.5: 1. The widths of the volume weighted particle size distributions of the first population and the second population as described by the ratio D75/D25 may have a ratio of about 40:1 to about 1.1: 1. The mass ratio of the first population to the second population can be from about 1:20 to about 20:1, for example, from about 1:15 to about 15:1, from about 1:10 to about 10:1, from about 1:5 to about 5:1, or from about 1:2 to about 2: 1. The metal oxide-polymer composite particles can have a volume weighted median particle size D50 of from about 20nm to about 1000 nm. The metal oxide-polymer composite particles may have an average roughness P of about 1.22 to about 1.9²(ii)/4 π S, wherein P is the perimeter of an image of the metal oxide-polymer composite particle and S is the area of the image of the particle and wherein both P and S are determined from a transmission electron micrograph. The polymer matrix may include polymers of styrene, unsubstituted or substituted acrylates or methacrylates, olefins, vinyl esters, and acrylonitrile, as well as copolymers and mixtures thereof. The composite particles may be disposed on the surface of toner particles to form a toner composition.

In another aspect, a method of making metal oxide-polymer composite particles includes preparing an aqueous dispersion including a first hydrophobizing system in an aqueous medium and including at least a first group of metal oxide particles and a second group of metal oxide particles, the first group of metal oxide particles having a different size, shape, or particle size distribution than the second group, wherein the first hydrophobizing system includes particles having a formula [ R [ ]³ _3-x(OR¹)_x]SiR²A difunctional component of Q, wherein x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate, or methacrylate group, with the proviso that when Q is a substituted or unsubstituted vinyl, n is 2 to 10; incubating (incubating) the dispersion for a predetermined amount of time; adding a free radical initiator to the dispersion; containerAllowing the chemical groups of the first hydrophobizing system to become part of the polymer, thereby forming metal oxide-polymer composite particles; and drying the metal oxide-polymer composite particles to obtain a powder.

The method can further include treating at least a portion of the metal oxide particles with a second hydrophobizing agent, where treating can be performed after formation or before preparation of the metal oxide-polymer composite particles. The first hydrophobizing system may further comprise a compound having the formula (OR)¹)_4-zSiR⁴ _zA monofunctional component of (1), wherein R¹Is methyl or ethyl, z is 1 or 2, and R⁴Is a branched or unbranched C1-C10 alkyl radical or R²Ph, wherein Ph is an unsubstituted phenyl group or a phenyl group substituted with a C1-C10 branched or unbranched alkyl, halogen, C1-C10 alkyl ether, methoxy, ethoxy, or hydroxy. The first and second populations of D50 may have a ratio of about 40:1-1.5: 1. The ratio of the first population and the second population, D75/D25, can have a ratio of about 40:1 to about 1.1: 1. The mass ratio of the first population to the second population may be from about 1:20 to about 20: 1.

The emulsion may further comprise one or more of: styrene, substituted or unsubstituted acrylate or methacrylate monomers, olefin monomers, vinyl esters, or acrylonitrile. At least a portion of each population of metal oxide particles can protrude into and out of the polymer matrix. The metal oxide-polymer composite particles can have a volume weighted median particle size D50 of from about 20nm to about 1000 nm. The specific density of the metal oxide-polymer composite particles is about 30% to about 90% of the specific density of the metal oxide when measured by helium pycnometry (pycnometry). The metal oxide-polymer composite particles can have an average SF-1 of about 110 to about 185 and an average RTA of about 0.06 to about 0.19. The metal oxide-polymer composite particles may have an average roughness P of about 1.22 to about 1.9²/4πS。

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention as claimed.

Drawings

The present invention is described with reference to the several figures of the drawing, in which,

fig. 1A is a schematic diagram illustrating the effect on particle size and roughness when metal oxide-polymer composite particles according to embodiments of the present invention are manufactured using metal oxide particles of different sizes.

Fig. 1B is a schematic diagram illustrating several measurements used for characterizing particles using transmission electron microscopy.

Fig. 2-6 are transmission electron micrographs of metal oxide-polymer composite particles made according to various embodiments of the present invention.

Fig. 7 is a transmission electron micrograph of colloidal silica.

FIG. 8 is a set of graphs generated from statistical modeling of cohesion with respect to particle size and additive average RTA at 15% (A), 30% (B), and 45% (C) additive coverage on model toners.

Fig. 9 is a graph showing the change in cohesion with surface coverage for composite particles with different RTAs.

Detailed Description

In one embodiment, making metal oxide-polymer composite particles with a first hydrophobizing system that includes a difunctional component and an alkyl-based monofunctional component results in the following particles: in the case where it is used as an external additive of a toner, it may increase the triboelectric charge of the toner.

In another embodiment, metal oxide-polymer composite particles having a volume weighted median particle size D50 of 40-75nm, such as 40-70nm or 40-65nm, and an average RTA of at least 0.06, such as 0.06-0.019, 0.08-0.015, or 0.08-0.13, enhance the free flow characteristics of the toner in the event they are used as an external additive to the toner.

In another embodiment, metal oxide-polymer composite particles having a volume weighted median particle size D50 of 100-150nm, such as 105-150nm or 110-150nm, and an average RTA of at least 0.06, such as 0.06-0.019, 0.08-0.015, or 0.08-0.13, are better able to promote blocking resistance in the toner composition while improving free flow relative to smoother spacer particles.

In another embodiment, a toner composition comprises: toner particles mixed with a powder comprising metal oxide-polymer composite particles comprising a polymer matrix and at least two populations of metal oxide particles having different sizes, shapes, or particle size distributions. The surfaces of the metal oxide particles are modified with a first hydrophobizing system comprising a bifunctional component via which the metal oxide particles are covalently linked to the polymer. At least a portion of the first population of metal oxide particles, the second population of metal oxide particles, or both, protrude into and out of the polymer matrix, which is a polymer or copolymer of the first hydrophobizing system. Such a mixture of two or more groups of metal oxide particles enables manipulation of the size, particle roughness, and shape of the resulting composite particles, as shown in fig. 1A. In fig. 1A, the combination of a first population of metal oxide particles 10 with larger metal oxide particles 12 or smaller metal oxide particles 14 allows for the production of metal oxide composite particles 100, 120, and 140 having different particle sizes. The particles 140 are smaller than the particles 100, and the particles 100 are smaller than the composite particles 120. The schematic depicts equivalent ratios of metal oxides (10, 12, and 14) and matrix material 16.

Metal oxide particles suitable for use with the present invention include silica, alumina, ceria, molybdenum oxide, titania, zirconia, zinc oxide, iron oxides (including but not limited to magnetite (Fe)₃O₄) And various forms of Fe₂O₃) Niobium oxide, vanadium oxide, tungsten oxide, tin oxide, clay, or a mixture or mixed oxide of any two or more of these. For use as an external toner additive, the metal oxide particles will typically include at least one of silica, alumina, and titania,such as silica and/or titania. The metal oxide particles may have two or more different particle sizes. For example, metal oxide particles having different compositions may have different particle sizes. Alternatively or additionally, the particles of a particular metal oxide, such as silica, may have a bimodal or multimodal particle size distribution. Of course, mixtures of two different metal oxides having the same or different compositions and two or more different particle sizes, shapes, or particle size distributions may also be employed.

When two different sized particles are used, their volume weighted median particle size D50 may have a ratio of about 40:1 to about 1.5:1, e.g., about 35:1 to about 2:1, about 25:1 to about 2.5:1, about 20:1 to about 3:1, about 15:1 to about 4:1, or about 10:1 to about 5: 1. D50 can be measured by centrifugal sedimentation photometry (disc centrifuge photosedimentometry) or transmission electron microscopy. Alternatively or additionally, the metal oxide particles may have a bimodal or multimodal particle size distribution. The ratio of particle sizes corresponding to the peaks of the particle size distribution may be similar to those listed above. Alternatively or additionally, the two or more metal oxide particles may have similar D50, but different shapes. Alternatively or additionally, the different metal oxide particles may have a similar D50, but their particle size distribution may have a different width. One indication of the magnitude of the particle size distribution (breakidth) is the ratio D75/D25, i.e., the ratio of 75% by volume of particles smaller than it to 25% by volume of particles smaller than it. The ratio of the amplitudes of the size distributions, as measured by D75/D25, for the two different sized particles may be 40:1 to 1.1: 1.

Suitable particles include, but are not limited to, precipitated, colloidal, and fumed metal oxide particles. The metal oxide particles can be made using techniques known to those skilled in the art. Exemplary commercially available titanium dioxide particles include TIO-W1215 titanium dioxide from Cerion, TiSolB titanium dioxide from Nyacol, and Cristal ACTIV^TMS5-300B titanium dioxide. Exemplary commercially available tin oxide particles include Sn15 tin oxide from Nyacol.

Precipitated metal oxide particles may be manufactured using conventional techniques and are often formed by agglomerating desired particles from an aqueous medium under the influence of a high salt concentration, acid, or other agglomerating agent. The metal oxide particles are filtered, washed, dried and separated from the remainder of the other reaction products by conventional techniques known to those skilled in the art. The precipitated particles are often aggregated in the sense that numerous primary particles agglomerate with one another to form aggregated clusters that are somewhat spherical. Non-limiting examples of commercially available precipitated metal oxides include those from PPG Industries, incProducts and products available from Evonik CorporationAnd (5) producing the product.

The manufacture of fumed metal oxides is a well documented process that involves the hydrolysis of a suitable feed vapor (e.g., aluminum chloride for fumed alumina, or silicon tetrachloride for fumed silica) in a flame of hydrogen and oxygen. During combustion, molten particles of generally spherical shape are formed and the particle diameter can be varied by control of process parameters. These molten spheres, called primary particles, fuse with each other at their points of contact by undergoing collisions to form branched, three-dimensional chain-like aggregates. The formation of aggregates is considered irreversible due to the fusion between primary particles. During cooling and collection, the aggregates undergo further collisions, which can cause some mechanical entanglement to form agglomerates. These agglomerates are believed to be loosely held together by van der waals forces and can be reversed, i.e., deagglomerated, by proper dispersion in a suitable medium. Mixed or co-pyrolyzed metal oxide particles may also be produced using conventional techniques known to those skilled in the art, including, for example, those described in GB 2296915a to Ettlinger et al, the specification of which is incorporated herein by reference in its entirety.

Alternative metal oxide morphologies can be obtained using the methods disclosed in: U.S. patent nos. 4,755,368, 6551567, and 6,702,994; U.S. patent publication nos. 20110244387; mueller et al, "Nanoparticle synthesis at high production rates by flame gasification Science", Chemical Engineering Science 58:1969 (2003); and Naito et al, "New Submicron silicon Produced by the heated Process", published in NIP 28: International Conference on Digital Printing Technologies and Digital Fabric 2012,2012, page 179-182, the entire contents of which are incorporated by reference. These methods typically result in metal oxide particles having low structure and surface area. Many of these particles are pyrophoric, i.e., they are made in a flame. Other methods of making fumed particles are disclosed, for example, in Kodas and Hampsden-Smith, Aerosol Processing of Materials, Wiley-VCH, 1998. Suitable fumed metal oxides for use in the composite particles provided herein are small, e.g., having a volume average diameter of less than 200 nm.

The colloidal metal oxide particles are often non-aggregated, individually discrete (primary) particles, which are typically spherical or nearly spherical in shape, but may have other shapes (e.g., shapes having a generally elliptical, square, or rectangular cross-section). Colloidal metal oxides are commercially available or can be prepared by known methods from various starting materials (e.g., wet-type metal oxides). The colloidal metal oxide particles are typically made in a similar manner to the precipitated metal oxide particles (i.e., they are agglomerated from an aqueous medium), but still dispersed in a liquid medium (often water, either alone or with a co-solvent and/or stabilizer). The metal oxide particles can be prepared, for example, from silicic acid derived from an alkaline silicate solution having a pH of about 9 to about 11, wherein the silicate anions undergo polymerization to produce discrete silica particles having the desired particle size in the form of an aqueous dispersion. Typically, the colloidal metal oxide starting material will be available as a sol, which is a dispersion of the colloidal metal oxide in a suitable solvent (most often water, either alone or together with co-solvents and/or stabilisers). Ginseng radix (Panax ginseng C.A. Meyer)See, for example, Stoeber et al, "Controlled Growth of Monodisperses silicon Spheres in the Micron Size Range", Journal of Colloid and Interface Science,26,1968, pp.62-69; akitoshi Yoshida, Silica Nucleation, Polymerization, and Growth prediction of Monochromatic solutions, in Colloidal Silica Fundals and Applications, pages 47-56 (H.E. Bergna)&Roberts, CRC Press: Boca Raton, Florida, 2006); and Iler, R.K., The Chemistry of Silica, page 866 (John Wiley)&Sons: New York, 1979). Non-limiting examples of commercially available colloidal metal oxides suitable for use in the present invention include those from Nissan ChemicalProduct, available from w.r.grace&Of CoProduct, NexSil available from Nyacol Nanotechnologies, Inc^TMAnd NexSil A^TMSerial products, Quartron available from Fuso Chemical^TMProducts, and products obtainable from Akzo NobelAnd (5) producing the product.

The colloidal metal oxide particles can have a median particle size D50 (volume weighted) of about 5 to about 300nm, e.g., about 5 to about 10nm, about 10 to about 20nm, about 20nm to about 30nm, about 30 to about 50nm, about 50 to about 70nm, about 70 to about 100nm, about 100nm to about 125nm, about 125nm to about 150nm, about 150nm to about 175nm, about 175nm to about 200nm, about 200nm to about 225nm, about 225nm to about 250nm, about 250nm to about 275nm, or 275nm to about 300 nm. Of course, mixtures of particles of different volume weighted median particle size D50 may include particles having particle sizes in two or more of these ranges. The metal oxide particles may be spherical or non-spherical. For example, the aspect ratio of the metal oxide particles can be from about 1.5 to about 3, such as from about 1.5 to about 1.8, from about 1.8 to about 2.1, from about 2.1 to about 2.5, from about 2.5 to about 2.8, or from about 2.8 to about 3. Particle size is measured by disk centrifuge sedimentation photometry or transmission electron microscopy after dispersion of the particles, as described in the examples below.

In one embodiment, to produce the composite particles, the metal oxide particles are treated with a first hydrophobizing system. The first hydrophobizing system can include one or more hydrophobizing components. Preferably, the first hydrophobizing system comprises at least one bifunctional component comprising: a first reactive group, such as a silane, that can be covalently or non-covalently attached to the metal oxide particle, and a second reactive group that can be incorporated into the polymer of the metal oxide-polymer composite particle. In certain implementations, the difunctional component will have a molecular weight of less than 300. "hydrophobic" metal oxide particles, as that term is used herein, encompass different levels or degrees of hydrophobicity. The degree of hydrophobicity imparted to the metal oxide particles will vary depending on the type and amount of treatment agent used. Hydrophobic metal oxide particles for use with the present invention can, for example, have from about 15% to about 85% of the available metal oxide surface hydroxyl groups reacted away, e.g., from about 25% to about 75% or from about 40% to about 65% or a percentage of the available metal oxide surface hydroxyl groups reacted away that is within any range bounded by any two of the above endpoints. When a second hydrophobizing agent is used, it will react with a portion of the surface hydroxyl groups of the metal oxide to form covalent or non-covalent bonds, as discussed below.

The difunctional component may have the formula [ R³ _3-x(OR¹)_x]SiR²Q, where x is 1, 2, or 3, R¹Is methyl or ethyl, R²Is of the general formula C_nH_2nWherein n is 1-10, R³Is methyl or ethyl and Q is mercapto, glycidyl, or a substituted or unsubstituted vinyl, acrylate or methacrylate group, with the proviso that when Q is unsubstituted or substituted vinyl, n is 2-10. The first hydrophobizing system may further comprise a compound having the formula (OR)¹)_4-zSiR⁴ _zWherein z is 1Or 2 and R⁴Is a branched or unbranched C1-C10 alkyl radical or R²Ph, wherein Ph is an unsubstituted phenyl group or a phenyl group substituted with a C1-C10 branched or unbranched alkyl, halogen, C1-C10 alkyl ether, methoxy, ethoxy, or hydroxy. Exemplary agents suitable for use in the system for the first hydrophobization include, but are not limited to, (3-acryloxypropyl) trimethoxysilane, isobutyltrimethoxysilane, propyltrimethoxysilane, mercaptopropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, (3-acryloxypropyl) triethoxysilane, 3-methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, methacryloxymethyltrimethoxysilane, methacryloxymethyltriethoxysilane, (3-acryloxypropyl) methyldimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-butenyltrimethoxysilane, isobutyltrimethoxysilane, propyltrimethoxysilane, mercaptopropyltrimethoxysilane, mercaptosilane, glycidyloxypropyltrimethoxysilane, glycidyloxypropyldimethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-butenyltrimethoxysilane, 3-butenyl triethoxysilane, 4-pentenyl trimethoxysilane, 5-hexenyl trimethoxysilane, 5-hexenylmethyl dimethoxysilane, 3-methacryloxypropyl dimethylmethoxysilane, diisobutyldimethoxysilane, and diisopropyldimethoxysilane. When the metal oxide particles are not silica, a di-or tri-functional silane should be used (i.e., x should be 2 or 3).

The solubility of the components of the first hydrophobizing system may be from 10 to 0.06g/L, preferably from 9 to 0.03g/L, more preferably from 8 to 0.1g/L, most preferably from 7 to 0.5 g/L. If the solubility of the components of the first hydrophobicizing system is too high or too low, the components will, in theory, not form a satisfactory emulsion.

In some embodiments, R⁴Preferably branched or unbranched C1-C10 alkyl groups. When R is⁴The triboelectric charge of the metal oxide-polymer composite particles when branched or unbranched alkyl groups are used with other R's when used⁴Higher when the radical or when no monofunctional component is used at all. For example, relative to the use of metal oxide-polymer composite particles that do not include monofunctional componentsThe toner of (1), wherein the toner employing the metal oxide-polymer composite particles as an external additive can increase the magnitude of the triboelectric charge (magnetic) under low temperature/low humidity (LL) conditions by at least 10%, such as up to 45%, e.g., 12% -42%, 15% -40%, 17% -37%, 20% -35%, 23% -32%, or 25% -30%. Alternatively or additionally, the magnitude of the triboelectric charge of such toners may be increased by at least 9%, for example, up to 33%, such as 12% -30%, 15% -28%, or 17% -25% under high temperature, High Humidity (HH) conditions, relative to toners using metal oxide-polymer composite particles that do not include a monofunctional component. Typically, the triboelectric charge under both HH and LL conditions changes with the addition of the alkyl-containing monofunctional component, and the change in HH and the change in LL triboelectric charge can be any combination of ranges selected from the above list.

At least a portion of the metal oxide particles may be treated with a second hydrophobizing agent either before or after treatment with the first hydrophobizing system or after formation of the metal oxide-polymer composite particles (in which case only the exposed surfaces of the metal oxide particles are treated), in addition. Preferred agents for use as the second hydrophobizing agent are silazane compounds, siloxane compounds, and silane compounds, and silicone fluids having some solubility in water with or without the use of co-solvents. Mixtures of two or more reagents may be used. Preferably, the silicone fluid used as the second hydrophobizing agent has a number average molecular weight of at most 500. Examples of the silane compound include alkylsilanes, and alkoxysilanes. Alkoxysilanes include compounds having the general formula: r'_xSi(OR”)_4-xWherein R' is selected from C₁-C₃₀Branched and straight-chain alkyl, alkenyl, C₃-C₁₀Cycloalkyl, and C₆-C₁₀Aryl radical, R' is C₁-C₁₀Branched or straight chain alkyl, and x is an integer from 1 to 3. When the metal oxide particles do not comprise silica, using a di-or trifunctional silane or using a siloxane or organosilicon fluid as a second hydrophobizing agent withMonofunctional silanes will provide better attachment than monofunctional silanes.

Non-limiting examples of silane compounds that can be used as the second hydrophobizing agent as taught herein include trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-octyltriethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, and the like. Amine functionalized alkylalkoxysilanes may also be used. Non-limiting examples of useful siloxane compounds include octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, and the like. Non-limiting examples of useful silazane compounds include Hexamethyldisilazane (HMDZ), hexamethylcyclotrisilazane, octamethylcyclotetrasilazane, and the like. For example, HMDZ can be used to cap unreacted hydroxyl groups on the surface of the metal oxide particles. Exemplary hydrophobicity-imparting agents also include hexamethyldisilazane, isobutyltrimethoxysilane, octyltrimethoxysilane, and cyclic silazanes such as those disclosed in U.S. patent No. 5989768. Such cyclic silazanes are of the formulaIs represented by the formula (I), wherein R₇And R₈Independently selected from: hydrogen, halogen, alkyl, alkoxy, aryl, and aryloxy; r₉Selected from: hydrogen; (CH)₂)_rCH₃Wherein r is an integer of 0 to 3; c (O) (CH)₂)_rCH₃Wherein r is an integer of 0 to 3; c (O) NH₂；C(O)NH(CH₂)_rCH₃Wherein r is an integer of 0 to 3; and C (O) N [ (CH)₂)_rCH₃](CH₂)_sCH₃Wherein r and s are integers from 0 to 3; and R is₁₀Represented by the formula [ (CH)₂)_a(CHX)_b(CYZ)_c]Wherein X, Y and Z are independently selected from: hydrogen, halogen, alkyl, alkoxy, aryl, and aryloxy, and a, b, and c are integers from 0 to 6, which satisfies the condition that (a + b + c) is equal to an integer from 2 to 6. The cyclic silazane can be of the formulaA five-or six-membered ring of (5), wherein R₁₁Represented by the formula [ (CH)₂)_a(CHX)_b(CYZ)_c]Wherein X, Y and Z are independently selected from: hydrogen, halogen, alkyl, alkoxy, aryl, and aryloxy, and a, b, and c are integers of 0 to 6, which satisfy the condition that (a + b + c) is equal to 3 or 4.

Suitable silicone fluids for use as the second treatment agent include both non-functionalized silicone fluids and functionalized silicone fluids. Depending on the conditions used to surface treat the metal oxide particles and the particular silicone fluid employed, the silicone fluid may be present as a non-covalently bonded coating or may be covalently bonded to the surface of the metal oxide particles. Non-limiting examples of useful non-functional silicone fluids include polydimethylsiloxane, polydiethylsiloxane, phenylmethylsiloxane copolymers, fluoroalkylsiloxane copolymers, diphenylsiloxane-dimethylsiloxane copolymers, phenylmethylsiloxane-diphenylsiloxane copolymers, methylhydrosiloxane-dimethylsiloxane copolymers, hydroxy-functional or terminal siloxanes, polyoxyalkylene modified silicones, and the like. The functionalized silicone fluid may include, for example, functional groups selected from the group consisting of: vinyl, hydride, hydroxyl, silanol, amino, and epoxy. The functional groups may be bonded directly to the silicone polymer backbone or may be bonded through an intermediate alkyl, alkenyl, or aryl group.

Alternatively or additionally, the metal oxide particles may be treated with the dimethylsiloxane copolymer disclosed in U.S. patent publication No.20110244382, the contents of which are incorporated herein by reference. Exemplary dimethylsiloxane copolymers include copolymers of the formula:

wherein R is₁is-H, -CH₃；R₂＝-H、-CH₃；R₃＝-CH₃、-CH₂CH₃、-CH₂CH₂CH₃、CH₂Ar、-CH₂CH₂Ar、-Ar、-CH₂CH₂CF₃or-CH₂CH₂-R_fWherein R is_fIs C₁-C₈A perfluoroalkyl group; r₄is-CH₃、-CH₂CH₃、-CH₂CH₂CH₃、-CH₂CH₂CF₃or-CH₂CH₂-R_fWherein R is_fIs C₁-C₈A perfluoroalkyl group; r₅is-CH₃、-CH₂CH₃、-CH₂Ar、-CH₂CH₂Ar, or-Ar; r₆is-H, -OH, -OCH₃or-OCH₂CH₃(ii) a Ar is unsubstituted phenyl or substituted with one or more methyl, halogen, ethyl, trifluoromethyl, pentafluoroethyl, or-CH₂CF₃A group-substituted phenyl group, n, m, and k are integers, n.gtoreq.1, m.gtoreq.0, and k.gtoreq.0, and wherein the copolymer has a molecular weight of 208 to about 20,000.

Alternatively or additionally, the second hydrophobizing agent may be a charge modifying agent. Any of the charge modifiers disclosed in U.S. patent publication No.2010/0009280, the contents of which are incorporated herein by reference, may be used herein. Exemplary charge modifiers include, but are not limited to, 3- (2, 4-dinitrophenylamino) propyltriethoxysilane (DNPS), 3, 5-dinitrobenzoylamino-n-propyltriethoxysilane, 3- (triethoxysilylpropyl) -p-nitrobenzamide (TESPBMA), pentafluorophenyltriethoxysilane (PFPTES), and 2- (4-chlorosulfonylphenyl) ethyltrimethoxysilane (CSPES). The metal oxide particles should be post-treated with a charge modifier comprising nitro groups after the copolymer, as the hydrogen radical groups can reduce the nitro groups.

Alternatively or in addition to the second hydrophobizing agent, the metal oxide particles may be treated with a third hydrophobizing agent after formation of the metal oxide-polymer complex. The third treatment agent may be an alkylhalosilane or a silicone fluid having a number average molecular weight greater than 500. The alkylhalosilanes include those having the formula R'_xSiR”_yZ_4-x-yWherein R' and R "are as defined above, Z is halogen, preferably chlorine, and y is 1, 2, or 3.

Depending on the interaction between the second hydrophobizing agent (when used after formation of the metal oxide-polymer particles) and/or the third hydrophobizing agent and the polymer component of the metal oxide-polymer composite particles, these agents may also surface treat the exposed polymer surfaces of the metal oxide-polymer composite particles.

The polymer employed in the metal oxide-polymer composite particles may be the same as or different from the polymer or copolymer of the first hydrophobizing system. That is, when the first hydrophobizing system includes one or more polymerizable groups, the same materials can simply be used to form the polymer. In certain implementations, the polymer of the difunctional component is not a polyether. Alternatively or additionally, the polymer of the difunctional component is an acrylate or methacrylate polymer. Alternatively or additionally, different monomers or crosslinkers may be used which are copolymerizable with the terminal groups on the difunctional component. Suitable monomers that can be used to make the metal oxide-polymer composite particles include substituted and unsubstituted vinyl and acrylate (including methacrylate) monomers and other monomers that polymerize via free radical polymerization. Exemplary monomers include styrene, acrylates and methacrylates, olefins, vinyl esters, and acrylonitrile and are readily available to those skilled in the art, for example, from Sigma-Aldrich (Milwaukee, WI). Such comonomers may also be substituted with C1-C3 alkyl, halogen, and/or hydroxyl groups. Substituted comonomers include, but are not limited to, hydroxypropyl methacrylate, trifluoropropyl methacrylate, and alpha-methylstyrene. Any of these monomers may be used alone, in a mixture to form a copolymer, or in combination with a crosslinking agent. Exemplary crosslinking agents include divinyl-terminated versions of the difunctional components (e.g., where the silane is replaced with a vinyl group) or other well-known vinyl crosslinking agents such as divinyl benzene and ethylene glycol dimethacrylate. Alternatively or additionally, the comonomer or crosslinker may be reacted with the silane. For example, a silanol-terminated siloxane polymer or a copolymer of the above formula (1) may be used in combination with the first hydrophobizing system. The comonomer or crosslinker can be added at the same time as the first hydrophobizing system or at a different time. The amount of crosslinking agent can be adjusted to control the degree of crosslinking in the final polymer.

The metal oxide-polymer composite particles can be made by producing a dispersion of metal oxide particles in a fluid that includes a first hydrophobizing system, an optional monomer, and an aqueous phase. Polymerization of the polymerizable species of the organic phase results in the composite particles. In one exemplary procedure, an emulsion or mixture is prepared with the first hydrophobizing system and optional comonomers and crosslinking agents and metal oxide particles in a ratio of from about 0.5 to about 40, e.g., from about 1 to about 1.5, from about 1.5 to about 2, from about 2 to about 3, from about 3 to about 10, from about 15 to about 30, or from about 10 to about 20 (polymerizable species/metal oxide) by mass in an aqueous medium (e.g., water with an optional co-solvent such as an alcohol, e.g., isopropanol). The total amount of metal oxide particles and polymerizable species relative to the total amount of solvent may be from about 5 wt% to about 45 wt%, e.g., from 5 wt% to about 15 wt%, from about 15 wt% to about 20 wt%, from about 20 wt% to about 30 wt%, from about 30 wt% to about 40 wt%, or from about 40 wt% to about 45 wt%.

Optionally, the pH is brought to about 8.0-10 and the dispersion is stirred (typically 1-3 hours) while maintaining the temperature at 25-60 ℃. After agitation, the initiator is present at a level of about 0.1 to about 4% by weight, e.g., about 0.1 to about 0.5%, about 0.5% to about 1%, about 1% to about 1.5%, about 1.5% to about 2%, about 2% to about 2.5%, about 2.5% to about 3%, about 3% to about 3.5%, or about 3.5% to about 4% relative to the monomer. The initiator may be introduced as a powder or as a solution in ethanol, acetone, or other water-miscible solvent. Suitable initiators include, but are not limited to, oil soluble azo or peroxide thermal initiators such as 2, 2' -azobis (2-methylpropionitrile) (AIBN), benzoyl peroxide, t-butyl peracetate, and cyclohexanone peroxide. A wide variety of suitable initiators are available from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). The initiator may be dissolved in the monomer prior to introduction of the metal oxide and may be partitioned between the monomer and the aqueous phase. The resulting solution was incubated at 65-95 ℃ for 4-6 hours with stirring. The resulting slurry can be dried at 100-130 ℃ overnight and the residual solids milled to produce a powder. Other methods of isolating the particles from the liquid may also be used to dry the particles. When the second hydrophobizing agent is added after the formation of the metal oxide-polymer complex, it may be introduced before the drying step. For example, the second hydrophobizing agent can be added with incubation at 60-75 ℃ and the slurry stirred for a further 2-4 hours.

One skilled in the art will recognize that variables such as the solids loading in the mixture or emulsion, the ratio of polymer and metal oxide, the pH of the aqueous phase, and the incubation temperature, in addition to the size and shape of the two or more populations of metal oxide particles and their ratio relative to each other in the reaction mixture, will affect the morphology of the composite particles. In fact, for a given diameter of metal oxide-polymer composite particle, significant variations in metal oxide particle size and solids loading in the mixture or emulsion can be utilized to adjust the shape and particle roughness of the composite particle. In certain embodiments, the composite particles have metal oxide particles disposed within the composite particles (i.e., entirely within the polymer phase) and protruding from the surface. In these embodiments, the metal oxide particles contribute to the mechanical reinforcement of the composite particles, increasing their compressive strength.

The degree of surface treatment of the metal oxide with the first hydrophobizing system can be controlled by adjusting the pH and temperature of the initial solution. The rate of adsorption of the difunctional component and any monofunctional component on the metal oxide particles (which adsorption may be followed by formation of siloxane bonds between the surface and the respective component) may also be controlled by the selection of a leaving group on the silane-based difunctional or monofunctional component, e.g., ethoxy groups tend to hydrolyze more slowly than methoxy groups.

The size and particle size distribution of the metal oxide-polymer composite particles can be controlled by adjusting the ratio and relative particle size and/or particle size distribution of the metal oxide particles. To the extent that the size of the metal oxide-polymer composite particles is affected by the size of the metal oxide particles, for a given composite particle made with first metal oxide particles, the size of the composite particle can be increased by replacing at least a portion of the first metal oxide particles with second metal oxide particles having a larger diameter. Likewise, replacing at least a portion of the first metal oxide particles with second metal oxide particles having a smaller diameter will reduce the size of the resulting composite particles.

Regardless of the metal oxide particle size distribution, the roughness of the metal oxide-polymer composite particles can be adjusted by varying the reaction conditions. Generally, increasing the pH of the reaction mixture (e.g., by adding ammonium hydroxide or using a base-stabilized metal oxide dispersion) will increase the particle roughness or RTA. Reducing the solids loading in the reaction medium will also increase particle roughness and RTA.

When a mixture of two groups of metal oxide particles is used, the ratio of the first metal oxide particles to the second metal oxide particles may be from about 1:20 to about 20:1, for example from about 1:15 to about 15:1, from about 1:10 to about 10:1, from about 1:5 to about 5:1, or from about 1:2 to about 2:1, by mass. The desired ratio of the first metal oxide particles and the second metal oxide particles may vary depending on the desired composite particle size and the particle sizes of the first and second metal oxide particles.

At least a portion of the metal oxide particles in the composite particles may be completely embedded within the polymer portion of the composite particles. Alternatively or additionally, at least a portion of the metal oxide particles may be partially embedded in the polymer portion of the composite particles; that is, portions of the metal oxide particles protrude into and out of the polymer matrix. In certain embodiments, the metal oxide particles exposed at the surface of the composite can protrude from the surface of the metal oxide-polymer composite particles by about 0% to about 95%, for example, about 5% to about 90%, about 10% to about 20%, about 20% to about 30%, about 30% to about 40%, about 40% to about 50%, about 50% to about 60%, about 60% to about 70%, about 70% to about 80%, or about 80% to about 90% of their length as measured for the metal oxide particles observable by electron microscopy of at least 200, preferably at least 500, metal oxide-polymer composite particles. The amount of metal oxide particles protruding from the surface of the metal oxide-polymer composite particles may vary depending on the size and/or shape of the metal oxide particles and the ratio of the median particle size D50 or particle size distribution (described as D75/D25) of one or more groups of metal oxide particles.

The metal oxide-polymer composite particles may be round. It will be appreciated that the round particles need not be spherical, but will typically have a "bumpy" surface depending on the extent to which the metal oxide particles are exposed at the surface of the composite particle. Alternatively, using two populations of metal oxide particles with large size differences will also result in the formation of non-equiaxed (non-equiaxed) particles. Such particles combine irregular shape with high particle roughness.

The shape and degree of "ruggedness" or roughness of the metal oxide-polymer composite particles can be analyzed by TEM (transmission electron microscope) evaluation. Conventional image analysis software is used to define the perimeter P of the TEM image of the particle. The same software was used to calculate the particle image area S and determine the maximum Feret (Feret) straight across the particleDiameter (D)_{Maximum of})20 measured between two parallel lines 22 each tangent to the particle (see fig. 1B). These measurements are performed on a plurality of TEM images for a plurality of particles, preferably at least 100 particles, more preferably at least 500 particles.

SF-1 is an indicator of how much the particle shape deviates from the sphere and is taken as 100(π D)_{Maximum of} ²Calculated as/4S). The SF-1 of an ideal spherical particle is 100. The larger the SF-1, the larger the deviation of the particle shape from the sphere. The composite particles may have an average SF-1 of from about 110 to about 185, for example from about 110 to about 125, from about 125 to about 150, or from about 150 to about 185.

The roughness of the particles can be taken as P²[ 4 ] S (John C. Russ, The Image Processing Handbook, CRC Press, 4 th edition, 2002). Fig. 1B illustrates that the particle roughness can be considered as the ratio between the area of an imaginary circle 24 having a circumference of the same length as the circumference 26 of the particle 28 and the area of the actual particle. The roughness of the ideal spherical particles is 1.0. However, the particle roughness of spherical particles with rough surfaces can be much higher than 1. Grain roughness is particularly sensitive to surface texture and roughness at very fine scales. Since the particle roughness equation includes both perimeter and image area, it also indicates the particle shape, and in particular the deviation of the particle shape from a sphere. For example, the particle roughness is 1.19 for ellipses having axes 1 and 2, and 1.51 for ellipses having axes 1 and 3. Therefore, as the surface roughness increases and the deviation of the particle shape from the sphere increases, the particle roughness increases. The average roughness of the metal oxide-polymer composite particles may be 1.15 to 1.9, such as 1.15 to 1.2, 1.2 to 1.5, 1.5 to 1.7, or 1.7 to 1.9. To improve free flow, the average roughness of the metal oxide-polymer composite particles is preferably greater than 1.22, such as greater than 1.25.

Alternatively or additionally, the same image analysis software may be used to construct a convex hull (covex hull)30 around the particle image and determine the area C within the hull, referred to as the "hull area". The convex shell is a curved convex confinement surface that surrounds the entire particle. It is produced by: a pair of parallel lines is moved until they just touch the outside of the particle image. The angle of the parallel lines is then changed and the process is repeated until the entire path of the protruding housing is defined. As shown in fig. 1B, the protruding shell resembles a rubber ring that is tightened around the pellet. The Relative Trench Area (RTA) is defined by (C-S)/S, where S is the grain image area. The value of RTA increases with increasing protrusion from the surface. The RTA of a perfect sphere, ellipse, or any protruding object is 0. The RTA of a typical non-aggregated colloidal silica is about 0.01. The metal oxide-polymer composite particles can have an average RTA of 0.01 to about 0.19, such as about 0.03 to about 0.15, about 0.05 to about 0.13, or about 0.07 to about 0.11. To promote toner free flow, the average RTA is preferably greater than 0.06 or 0.08, e.g., 0.06 to 0.13. The average RTA is measured using an image of at least 100 particles, preferably at least 500 particles. Of course, using more particle images will provide greater sensitivity and facilitate distinguishing between different particle morphologies.

Preferably, the metal oxide composite particles have an average SF-1 in the above range or any sub-range and an average RTA in the above range or any sub-range. Further, they may have an average particle roughness within the above range or any sub-range. Particles having at least the average SF-1 and average RTA as described above may exhibit improved drop properties in toner relative to smoother or more rounded particles.

Alternatively or additionally, the metal oxide-polymer composite particles may have a median particle size or diameter D50 (volume weighted) of from about 20nm to about 1000 nm. For example, D50 of the metal oxide-polymer composite particle may be 20nm to 100nm, 100nm to 200nm, 200nm to 300nm, 300nm to 400nm, 400nm to 500nm, 500nm to 600nm, 600nm to 700nm, 700nm to 800nm, 800nm to about 900nm, or 900 to 1000 nm. The particle size of the metal oxide composite particles can be measured by a disk centrifugal sedimentation light measurement method.

As demonstrated in the examples, toner cohesion increases with particle size and decreases with particle "rugosity" as measured by RTA. Toner cohesion is inversely related to free flow. To improve toner free flow, the metal oxide-polymer composite particles so produced preferably have a D50 of 40 to 75nm, for example 40 to 70nm or 40 to 65nm, an average RTA of at least 0.06 or at least 0.08, for example 0.06 to 0.019, 0.08 to 0.015, or 0.08 to 0.13, and optionally an average particle roughness of at least 1.22, for example from 1.25 to 1.60 or 1.70 or from 1.22 to 1.35. It is expected that particles with a D50 of less than 40nm will have a greater tendency to become embedded in the toner surface, and that particle size is inversely related to free-flow properties.

To improve blocking resistance and prevent toner particles from sticking to each other, the metal oxide-polymer composite particles preferably have an average RTA of at least 0.06 or at least 0.08, such as 0.06-0.019, 0.08-0.015, or 0.08-0.13, and alternatively or additionally an average particle roughness of at least 1.22, such as at least 1.25 or at least 1.3, such as from 1.25 to 1.60 or 1.70, or from 1.22 to 1.35, in D50 of 100-150nm, such as 105-150nm or 110-150 nm. Toner free-flow properties tend to decrease as the size of the external additive increases. However, larger particles are better able to avoid becoming embedded in soft toner surfaces. By increasing the roughness of the composite particle, the free-flow properties improve, thereby offsetting the effect of the increased size and allowing the composite particle to be optimized to maintain blocking resistance and free-flow properties.

The metal oxide-polymer composite particles preferably have a density less than the specific density (specific density) of the metal oxide itself (e.g., silica has 2.2g/cm³Has a specific density of 3.6g/cm of titanium dioxide³Density of (d). For example, the specific density of the composite particle may be about 30% to about 35%, about 35% to about 40%, 40% to about 45%, about 45% to about 50%, about 50% to about 55%, about 55% to about 60%, about 60% to about 63%, about 63% to about 67%, about 67% to about 70%, about 70% to about 73%, about 73% to about 76%, about 76% to about 79%, about 79% to about 82%, about 82% to about 85%, or about 85% to about 90% of the specific density of the metal oxide contained therein. Density can be measured by the helium pycnometer method. In some embodiments, by use in the complexesTwo different sizes of metal oxide particles, the size and shape of the composite particles can be varied while maintaining a desired density. Maintaining a desired density may allow the technician to reduce or maintain drop performance or other aspects of toner performance during fusing, or may allow the particle morphology to change without changing its refractive index.

The metal oxide-polymer composite particles can be used as external additives for both conventional and chemical toners. Conventional toners may be prepared by a number of known methods, such as by blending and heating the resin, pigment particles, optional charge-enhancing additives, and other additives in conventional melt extrusion equipment and associated equipment. Conventional equipment for dry blending of the powders may be used to mix or blend the carbon black particles with the resin. Other methods include spray drying and the like. Compounding of the pigment and other ingredients with the resin is typically followed by mechanical grinding and classification to provide toner particles having the desired particle size and particle size distribution. Chemical toners, also known as chemically prepared toners, are made in the liquid phase; the resin particles are typically formed in the presence of a colorant. For example, processes have been developed in which a polymer latex is combined with an aqueous pigment dispersion and agglomerated using a coagulant to form polymer particles. Another process involves aqueous suspension polymerization of a dispersion of a pigment in at least one monomer. Furthermore, pigment/polyester resin dispersions have been prepared and combined with water, after which the solvent is evaporated.

For both conventional and chemically prepared toners, the metal oxide-polymer composite particles may be combined with toner particles in the same manner as conventional additives, such as fumed metal oxides or colloidal metal oxides. For example, the toner composition may be formulated by: an appropriate amount of the metal oxide-polymer composite particles is mixed with toner particles having an appropriate size in a blender. Alternatively or additionally, the metal oxide-polymer composite particles may be combined with a toner to be used as an external additive by: the toner particles are dry blended with the core-shell composite particles using a Henschel (Henschel) or other suitable mixer, such as the mixers described in US9470993, US9500970, US9575425, JP2019-095616, JP2018-045006, or JP 2018-036596. Alternatively, the dispersion of metal oxide-polymer composite particles may be combined with toner particles by a wet blending process (e.g. as disclosed in WO 2014/153355). For example, the toner may be sonicated with the dispersion of composite particles until a well-mixed dispersion is obtained. Toner particles having metal oxide-polymer particles disposed or distributed about their surface can then be recovered from the dispersion, such as by vortexing and drying or by other methods of recovering the particles from the dispersion. Alternatively or additionally, the metal oxide-polymer composite particles may be combined with the toner at the same time as other external additives, such as additional inorganic, composite, or organic particles, or in a separate mixing step. A wide variety of particles useful as external toner additives are known to those skilled in the art and may be used in combination with one or more of the metal oxide-polymer composite particles provided herein. Exemplary external additives known to those skilled in the art include, but are not limited to, fumed silica, colloidal silica, titanium dioxide, polymer particles, fatty acid salts, and other external additives suitable for use with toners. Fumed silica and other naturally hydrophilic materials are typically rendered hydrophobic for use as toner additives.

In certain embodiments, the metal oxide-polymer composite particles comprise from about 0.5% to about 7% (by weight) of the toner composition, for example, from about 0.5% to about 1%, from about 1% to about 1.5%, from about 1.5% to about 2%, from about 2% to about 2.5%, from about 2.5% to about 3%, from about 3% to about 3.5%, from about 3.5% to about 4%, from about 4% to about 4.5%, from about 4.5% to about 5%, from about 5% to about 5.5%, from about 5.5% to about 6%, from about 6% to about 6.5%, or from about 6.5% to about 7% (by weight) of the toner composition. The metal oxide-polymer composite particles may be distributed on the surface of the toner particles. Preferably, the surface coverage caused by the metal oxide-polymer composite particles is from about 10% to about 90% of the toner surface, e.g., 10% to 20%, 15% to 25%, 20% to 30%, 25% to 35%, 30% to 40%, 15% to 80%, 25% to 75%, 30% to 70%, 35% to 65%, 40% to 60%, 45% to 55%, or 10% to 45%. The optimum surface coverage of the metal oxide-polymer particles on the toner will depend on other materials, such as inorganic particles or polymer particles, which also serve as external additives, and on the nature and composition of the toner and any carrier or developer used with the toner. The distribution of the metal oxide-polymer composite particles on the toner may be relatively uniform. For example, the coefficient of variation of the distribution of the composite particles on the toner as measured by scanning electron microscopy as described in US20150037719 (the contents of which are incorporated herein by reference) may be less than 0.40, for example less than 0.30, for example, 0.05-0.15, 0.10-0.20, or 0.15-0.25.

The metal oxide-polymer composite particles preferably exhibit low drop levels, which can enhance toner durability and improve print quality over long print runs. Although the retention of the composite particles on the toner particles depends in part on the composition of the toner, proxy tests may be used to compare the performance of metal oxide-polymer composite particles and metal oxide particles of comparable size and shape. For example, tests similar to those described in US2003/0064310A1, US2010/0009282A1, US2006/0240350A1, and U.S. Pat. No.9,568,847 may be used.

The metal oxide-polymer composite particles should have sufficient mechanical strength for mixing with toner particles according to methods typically used by those skilled in the art, such as by using a henschel mixer or other fluidized mixer or blender. Preferably, the metal oxide composite particles have sufficient strength to withstand collisions between toner particles (having the metal oxide-polymer composite particles distributed on the surface) during a development cycle of an electrophotographic process. The mechanical strength of the particles can be evaluated by formulating a chemical toner with the composite particles. The toner/particle formulation is then mixed with a carrier, such as a silicone-coated Cu-Zn ferrite carrier (30-90 μm particle size), to form a mixture having 2% (weight/weight) of toner. The mixture is then placed in a mixing vessel at a fill factor of about 70% to about 90% and tumbled in an agitator (referred to as a three-dimensional mixer) that moves the mixing vessel in a rhythmic three-dimensional motion. The mixing vessel is moved at a frequency of about 50 to about 70 cycles per minute over a volume of about 6 to about 8 times the volume of the vessel. Exemplary agitators include a Turbula mixer available from Willy a. bachoven AG, an inverina mixer available from Bioengineering AG, and a dynaMix 3-dimensional mixer from Glen Mills. After a specified period of time, the samples were analyzed by SEM. If the composite particles have sufficient mechanical strength, they do not flatten or deform during mixing. Any flattening or deformation will manifest as a change in particle diameter in the SEM. In a preferred embodiment, the diameter of the metal oxide-polymer composite particles changes less than 25%, preferably less than 20%, for example less than 10%, after 10 minutes of mixing.

Alternatively or additionally, the metal oxide-polymer composite particles may be used as a cleaning aid. The function and method of use of cleaning aids are discussed in U.S. patent No.6311037, the contents of which are incorporated herein by reference. In short, after printing an image, the elastic blade removes the excess toner from the photoreceptor. Abrasive (abrasive) particles may facilitate more complete removal of excess toner that may otherwise be transferred to subsequent replicas, creating a "shadow" effect in which a blurred image of a previous replica appears on one or more subsequent replicas. Generally, two different types of particles are currently used as cleaning aids. The crushed or precipitated inorganic particles (e.g., metal oxides, nitrides, carbides) have a hardness and shape suitable for abrasive cleaning applications. However, they have a broad particle size distribution. The larger particles may scratch the surface of the photoreceptor and the smaller particles may be smaller than the gap (clearance) between the cleaning blade and the photoreceptor. Colloidal silica has a uniform particle size, but has limited cleaning ability due to its smooth surface. The metal oxide-polymer composite particles combine the advantages of both particles-they have irregular surfaces that are penetrated (puncutate) by hard abrasive metal oxide particles and have a narrow particle size distribution. The metal oxide-polymer composite particles used as cleaning aids can be incorporated into the toner formulation or can be contained in a separate reservoir from which they are delivered to the photocopier's drum in the vicinity of the cleaning blade.

The metal oxide-polymer composite particles are preferably in powder form. Preferably, they exhibit a low moisture content, e.g., less than about 10% moisture by weight, e.g., about 0% to about 3%, about 1% to about 4%, about 3% to about 5%, about 5% to about 7%, or about 7% to about 10% moisture, after equilibration at 50% relative humidity and 25 ℃ under a pressure of about 1 atm. Moisture content can be measured by: after incubation for 20 minutes at a selected relative humidity value between 0 and 95%, 100mg of the sample are dried in a glass vial in an oven at 125 ℃ for 30 minutes, discharged (e.g. by briefly (briefly) keeping them under Haug One-Point-Ionizer (Haug North America, Williamsville, NY) and then loaded into an instrument which will measure the mass of the sample.

The metal oxide-polymer composite particle powder may be ground or milled or may be classified as described in JP2018036596 (e.g. by sieving, filtering, air classification, or other methods known to those skilled in the art). The degree of aggregation of the metal oxide-polymer composite particle powder can be less than 70%, for example, less than 60%, for example, 10% -70%, 20% -60%, 30% -50%, or 25% -40%. The degree of aggregation can be measured in a Hosokawa PT-X powder tester equipped with a Digiviblog Model 1332A digital display type vibrometer (Showa Sokki Co., Ltd.). Sieves having openings of 38 μm (400 mesh), 75 μm (200 mesh) and 150 μm (100 mesh) were sequentially stacked on the vibration table of the powder tester from the bottom. The measurement was carried out at 23 ℃ and 60% Relative Humidity (RH). The vibration width of the vibration table was adjusted in advance so that the displacement value of the digital display type vibration meter was 0.60mm (peak to peak). The metal oxide-polymer composite particles were allowed to equilibrate at 23 ℃ and 60% RH for 24 hours before 5.0g was weighed out and placed on a 150 μm sieve at the uppermost stage of the powder tester. The sieve was vibrated for 30 seconds, and then the mass of the composite particles remaining on each sieve was measured to calculate the degree of aggregation based on the following equation. The degree of aggregation (%) { (sample mass on sieve with 150 μm opening (g))/5(g) } × 100+ { (sample mass on sieve with 75 μm opening (g))/5(g) } × 100 × 0.6+ { (sample mass on sieve with 38 μm opening (g))/5(g) } × 100 × 0.2.

The metal oxide-polymer composite particles can be combined with toner particles to form a toner. Conventional toners may be prepared by a number of known methods, such as by blending and heating the resin, pigment particles, optional charge-enhancing additives, and other additives in conventional melt extrusion equipment and associated equipment. Conventional equipment for dry blending of the powders may be used to mix or blend the carbon black particles with the resin. Other methods include spray drying and the like. Compounding of the pigment and other ingredients with the resin is typically followed by mechanical grinding and classification to provide toner particles having the desired particle size and particle size distribution. Chemical toners, also known as chemically prepared toners, are made in the liquid phase; the resin particles are typically formed in the presence of a colorant. For example, processes have been developed in which a polymer latex is combined with an aqueous pigment dispersion and agglomerated using a coagulant to form polymer particles. Another process involves aqueous suspension polymerization of a dispersion of a pigment in at least one monomer. Furthermore, pigment/polyester resin dispersions have been prepared and combined with water, after which the solvent is evaporated.

The metal oxide-polymer composite particles can provide a wide variety of benefits to toners in which they are used as external additives. For example, they may complement the properties of other external additives used in combination with them (e.g., fumed or sol-gel (colloidal) silica, titanium dioxide; mixed metal oxides such as, but not limited to, strontium titanate and strontium zirconate; waxes; fatty acid salts; polymer particles; and other materials typically used to enhance the free-flowing and triboelectric charge properties of the final toner product).

The invention will be further clarified by the following examples, which are intended to be only exemplary in nature.

Examples

To prepare samples for TEM, the particles in the aqueous dispersion were diluted with ethanol and sonicated with a probe sonication processor for 10 minutes. Sufficient dilution and dispersion is required to ensure good separation of each individual particle from adjacent particles. The suspension was dropped onto a 200 mesh carbon coated copper grid for TEM analysis. TEM images were obtained on a JEOL JEM-1200EX microscope at an acceleration voltage of 80 kV. The image resolution is typically set to 2 nm/pixel and the image size is 2048 pixels × 2048 pixels. Any inhomogeneous image background, if any, is first corrected using ImageJ software available from National Institutes of Health, and then image noise is reduced and contrast is improved with appropriate digital filters. The image is then segmented into binary images (binary images) with separate images of each individual particle. The size and shape of each particle was determined using an ImageJ particle analyzer and then combined to generate a distribution of the shape and size of all particles in the sample (excluding aggregates comprising more than one primary composite particle). The values of SF-1, particle roughness, and RTA provided for the following composite particles are the average of measurements from at least 500 particles; the value of colloidal silica is the average of measurements from at least 100 particles.

To prepare samples for the disk centrifugal sedimentation photometry, a 0.05 wt% dispersion of composite particles was prepared in a 15mL glass vial in reverse osmosis treated water containing 0.05 wt% Triton X-100 surfactant. An SMT UH-50 homogenizer with 50 watt output was used to agitate it for 20 minutes at 90% power using a 3mm x 136mm titanium tip (tip) set at 0.5mm from the bottom of the vial.

To combine the toner with the composite particles, an IKA M20 Universal mill was used to mix silica-polymer composite particles with a black polyester chemical toner from Sinonar corp. having a particle size of about 8 microns in an amount to achieve 30% surface coverage. In order to prevent overheating and melting of the toner, mixing was performed three times as follows: a 15 second pulse followed by a 15 second cooling interval.

The toner surface coverage C is calculated using the following relation:

C＝[w/(100％-w)]×[(ρ_t×d_t)/(π×ρ_a×d_a)]×[(√3)/2]

wherein w is the weight% of the additive and ρ_t、d_t、ρ_a、d_aDensity (ρ) and diameter (d) of toner and additive particles, respectively. The additive particle size is determined by disc centrifugal sedimentation photometry (CPS) and the additive density is measured by helium pycnometer method. The (aggregate) toner density was presumed to be 1.2g/cm³And the particle size was 8 microns.

A developer was prepared by: 2 parts by weight of the formulated toner was mixed with 98 parts of a silicone resin coated Cu-Zn ferrite carrier (carrier particle size 60-90 microns, from Powdertech Co. Ltd.). The developer was conditioned for several hours at 30 ℃ and 80% relative humidity corresponding to HH (high temperature/high humidity) conditions, or at 18 ℃ and 20% RH corresponding to LL (low temperature/low humidity). After conditioning, tribostatic charges were developed by rolling the jar containing the developer on a roller mill for 30 minutes at 185 rpm. Triboelectric charge was measured using a Vertex T-150 tester from Vertex Image Products, Inc. 1g of charged developer was placed in a Faraday cage. Blowing the toner from the carrier was performed using an approximately 20psi air jet for 1 minute. The electrostatic charge on the toner remaining in the faraday cage carrier was measured by a built-in electrometer (electrometer) in a Vertex tester, and the mass of blown toner was determined as the difference between the weight of the faraday cage before and after blowing.

Toner cohesion was measured using a Hosokawa PT-X powder tester. 2g of toner mixed with additives was placed on the upper screen of a stack of three screens (75, 45 and 25 micron openings) and each screen was allowed to vibrate at an amplitude of 1.0mm and a frequency of 50-60Hz for 20 seconds. The cohesion is calculated according to the following formula: cohesion(M)% of Property_t/M_init)+(M_m/M_init)*0.6+(M_b/M_init) 0.2 x 100%, wherein M_t、M_mAnd M_bIs the weight of toner remaining on the top, middle, and bottom screens, respectively, when vibration stops, and M_initIs the weight of the initial sample.

Example 1: synthesis of composite particles using a mixture of Snowtex O40(ST-O40) and Snowtex O (ST-O).

This example illustrates the progressive reduction in composite particle size when the larger ST-O40 colloidal silica is replaced with smaller ST-O colloidal silica. For example 1A, to a 3000mL four-necked round bottom flask equipped with an overhead stirrer motor, condenser and thermocouple were added 909mL of DI water, 257g of ST-O40 silica dispersion in water (manufactured by Nissan Chemical;. 22nm particle size, pH 4.0, concentration 41% by weight), and 4.56g of 5M aqueous ammonium hydroxide solution. The dispersion was stirred for 5 minutes and 131g of 3-methacryloxypropyltrimethoxysilane (MPS, CAS #2530-85-0, Mw 248.3) was added. The temperature was raised to 50 ℃ and the mixture was stirred at 200rpm for 3 hours. 2, 2' -azobisisobutyronitrile (also abbreviated as AIBN, CAS #78-67-1, Mw 164.2) was added and the temperature was raised to 80 ℃ over 30 minutes. After 90 minutes at 80 ℃, the reaction mixture was cooled to 65 ℃ and filtered through a 200 mesh screen to remove the agglomerate pieces. 23g of 1,1,1,3,3, 3-Hexamethyldisilazane (HMDZ) was added to the mixture and the reaction was continued for an additional 5-8 hours at 65 ℃ before the reaction mixture was transferred to Pyrex trays and dried overnight at 120 ℃.

Examples 1B-1D were prepared following the same procedure as described for example 1A. The only difference was that a mixture of ST-O40 and ST-O (12nm diameter, Nissan Chemical) silica was used (the silicas were added one after the other to the reaction flask). Table 1 below contains information about the amount of chemicals used. This method can be used to prepare particles having the median particle sizes (as measured by disc centrifuge sedimentation photometry) listed in the table below. The change in size does not necessarily cause a significant change in particle roughness or RTA. For example, the process of example 1A can be used to prepare particles having an average SF-1 of 141-146, an average particle roughness of 1.29-1.32, and an average RTA of 0.092-0.097. The process of example 1B can be used to prepare particles having an average SF-1 of 147-152, an average particle roughness of 1.27-1.30, and an average RTA of 0.090-0.096. Fig. 2A and 2B illustrate how the respective compositions listed below in examples 1A and 1B can be used to make particles into which both types of silica particles have been incorporated.

TABLE 1

Example 2: synthesis of composite particles using Snowtex O40(ST-O40) and a mixture of ST-O40 and ST-OL.

This example demonstrates that the composite particle size increases when the smaller colloidal silica ST-O40 is replaced with a larger ST-OL silica. The method of example 1 can be used at the amounts of reagents in table 2 below to produce particles having the listed median particle sizes. Figures 3A-3C illustrate how the respective compositions listed below in examples 2A-2C can be used to make particles into which both types of silica particles have been incorporated. The arrows in fig. 3B point to the ST-OL particles. The process of example 2A can be used to prepare particles having an average SF-1 of 128-134, an average particle roughness of 1.24-1.29, and an average RTA of 0.068-0.077. The process of example 2B can be used to prepare particles having an average SF-1 of 132-139, an average particle roughness of 1.23-1.28, and an average RTA of 0.063-0.073. The process of example 2C can be used to prepare particles having an average SF-1 of 140-144, an average particle roughness of 1.27-1.31, and an average RTA of 0.057-0.067.

TABLE 2

Example 3: synthesis of composite particles having irregular shape and relatively smooth surface

Particles having a median particle size D50 of 125-150nm such as those shown in FIGS. 4A and 4B can be made using the process of example 1 with ST-OL silica (45-50nm particle size) instead of the silica and monomer-silica ratio of 1.4 listed in example 1. The process of example 3 can be used to prepare particles having an average SF-1 of 131-152, an average particle roughness of 1.21-1.36, and an average RTA of 0.045-0.079.

Example 4: synthesis of composite particles with irregular shape and high surface roughness

Particles such AS those shown in fig. 5A and 5B can be made using the process of example 1 except that no ammonium hydroxide is added, replacing the silica listed in example 1, the monomer-to-silica ratio of 2, and the solids concentration in the reaction mixture of 5.4% with Ludox AS-40 silica (WR Grace, 22nm particle size, 40% solids in dispersion). The process of this example was used to prepare particles having an average SF-1 of 144-162, an average particle roughness of 1.49-1.65, and an average RTA of 0.108-0.142.

Example 5: synthesis of composite particles with spherical shape and varying surface roughness

A) Particles having a median particle size D50 of 115-140nm, such as those shown in FIGS. 6A and 6B, can be made using the process of example 1at a monomer-to-silica ratio of ST-O40 silica and 3. The process of this example was used to prepare particles having an average SF-1 of 116-119, an average particle roughness of 1.19-1.22, and an average RTA of 0.038-0.042.

B) Particles having a median particle size D50 of 45-70nm but much higher surface roughness than those of example 5A can be made using the process of example 1at ST-O silica and a monomer-silica ratio of 1.25, such as shown in fig. 6C and 6D. The amounts of reagents that can be used to make the granules of both examples 5A and 5B are listed in table 3 below. The process of this example was used to prepare particles having an average SF-1 of 135-140, an average particle roughness of 1.22-1.25, and an average RTA of 0.079-0.086.

TABLE 3

Example 6 comparative example 1

TEM images of spherical colloidal silica with smooth particle surface, MP-1040 colloidal silica (Nissan Chemical Inc.) were taken and parameters describing the particle shape were measured (fig. 7). The average SF-1 was 113, the average grain roughness was 1.15, and the average RTA was 0.030.

Example 7

This example illustrates the use of an alkylsilane as the monofunctional component along with the difunctional component of the first hydrophobizing system to increase the triboelectric charge of the silica-polymer composite particles. For examples 7A and B, a solution of 19g of ST-O40 silica in 68g of deionized water was stirred at room temperature, after which 0.19g of 5N ammonium hydroxide was added to bring the pH to about 9.3. A mixture of a)4.9g of n-propyltrimethoxysilane (NPTMS) or b) Phenyltrimethoxysilane (PTMS) and 4.9g of MPS was added all at once. The temperature was then ramped up (ramp) to 40 ℃ over 1 hour and held at that same temperature for 1.5 hours. Next, 0.1g AIBN was added and the temperature was ramped up to 80 ℃ and held for 1.5 hours. The reaction mixture was cooled to 65 ℃, after which 2.5g hexamethyldisilazane was added and the mixture was incubated at 65 ℃ for 3 hours. The resulting precipitate was filtered by suction, washed with deionized water, and dried under vacuum. The resulting filter cake was dried in an oven at 120 ℃ for several hours and then ground in an IKA mill.

For example 7C, a solution of 45g of ST-O40 silica in 160g of deionized water was stirred at room temperature, after which 0.48g of 5N ammonium hydroxide was added to bring the pH to about 9.3. A mixture of 11.5g of diisopropyldimethoxysilane (DIPDMS) and 11.5g of MPS was added all at once. The temperature was then ramped up to 40 ℃ over 1.5 hours and held at that same temperature for 2 hours. The temperature was then ramped to 60 ℃ and the mixture incubated for 45 minutes. Next, 0.5g AIBN was added and the temperature was ramped up to 75 ℃ and held for 2 hours. The reaction mixture was cooled to 65 ℃, after which 4.3g hexamethyldisilazane was added and the mixture was incubated at 65 ℃ for 6 hours. The resulting precipitate was filtered by suction, washed with deionized water, and dried under vacuum. The resulting filter cake was dried in an oven at 120 ℃ for several hours and then ground in an IKA mill.

These methods can be used to make samples such as those in table 4 below, formulated as toners with 30% coverage. The column "hydrophobicity" indicates that in methanol-water solutions with methanol concentrations below the indicated percentage, the sample will not be wetted; that is, the material will float on the surface. In contrast, the process of example 1A can be used to make composite particles as follows: it can be used for producing a toner having a triboelectric charge of-52 to-50 under LL condition and a triboelectric charge of-22.5 to-21.5 under HH condition. The results show that the use of alkylsilanes in addition to MPS increased the triboelectric charge, whereas the use of aromatic phenylsilanes did not increase the triboelectric charge significantly.

TABLE 4

Type of silane	LL	HH	Hydrophobicity
				Phenyltrimethoxysilane	-52.5 to-51.0	-23.8 to-18.9	30％
Diisopropyl dimethoxysilane	-73.5 to-69.2	-29.7 to-28.5	20％
				N-propyl trimethoxy silane	-58.0 to-57.0	-25.0 to-23.6	40％

Example 8 improvement of particle roughness

Metal oxide-polymer composite particles having the following characteristics (table 5) can be manufactured using the method of example 1 except that ammonium hydroxide is not added, using Ludox AS-30 silica (WR Grace, 12nm, 30% solid loading in dispersion) and Ludox AS-40 silica, and adjusting the amounts of silica dispersion and water to maintain the solid loading and monomer-silica ratio. The Ludox silica is stabilized with ammonium hydroxide, increasing the pH of the reaction mixture and increasing the roughness of the resulting composite particles.

TABLE 5

Examples	Type of silica	D50(nm)	RTA	Roughness of
					8A	AS-30	62-66	0.105-0.115	1.33-1.36
8B	AS-40	106-110	0.095-0.105	1.33-1.36

Example 9 positively charged composite particles

The particles having the properties described in examples 1A and 5B were further treated with a cyclic silazane. 300g of the composite particle powder was placed in a1 gallon Nalgene bottle and charged with 4.3g or 5.5g of a powder having R therein₁₁Is- (CH)₂CH(CH₃)CH₂) A formula (A) to (B)And 10mL of 2-propanol. The bottle was tightly closed and rolled on a roller mill at about 90rpm for 1 hour. The sealed bottle was allowed to stand overnight at room temperature before the powder was transferred to a Pyrex tray and deaminated in a dry air oven at 120 ℃ for 3-4 hours. The use of cyclic silazane treatment allows the amine groups to attach to the particle surface and allows these composite particles to exhibit a positive triboelectric charge without changing the particle morphology.

Example 10 comparative example

ST-XL and ST-YL silicas (surface area 60m each)²And 45m²Nissan Chemicals, Inc.) was treated with HMDZ as described in US7811540 to make every 1nm²Having about 10 HMDZ molecules on the surface of the silicaHydrophobically treated particles. The same silica was treated with HMDZ and the cyclic silazane described in example 9 as described in US8455165 to make every 1nm²The silica surface has hydrophobically treated particles of 5 to 10 HMDZ molecules and about 1.6 cyclic silazane molecules. The resulting powder was milled in an IKA 11 laboratory mill (IKA Corporation) before being used in example 11.

Example 11 cohesion measurement

Particles having the morphology and composition described in examples 1A, 2C, 4, 5B, 8A, 8B, and 9, particles of example 10, and CAB-O-SIL TG-C110 colloidal silica (HMDZ treated silica having a particle size of 115nm, SF-1 of 111, average particle roughness of 1.23, and average RTA of 0.0256) were fabricated as described above into toners having coverage amounts selected from 15%, 30-32%, and 45%. Toner cohesion was measured in triplicate.

Statistical analysis of the collected data was performed using JMP software package (version 12.0.1, SAS Institute, Inc.). A linear regression model was used. In this regression model, toner cohesion is a dependent variable and toner surface coverage, additive particle size, and additive morphology described as RTA are independent variables. The model includes an intercept, linear terms with respect to toner coverage and particle size, and a quadratic term in terms of RTA. Only statistically significant terms with p-values less than 0.05 were included. The model does not show a relationship between surface treatment (i.e. HMDZ/cyclicity versus HMDZ alone) and toner cohesion. 100 observations were used in this model. R²81.4% and significance in the F test was<0.0001。

The linear regression model was used to generate a response surface (stress surface) for toner cohesion as a function of additive particle size and RTA at 15, 30, and 45% toner surface coverage (FIG. 8; the solid line curve is a function generated by the model; the dashed lines on either side indicate confidence limits). The response surface shows that the lowest cohesion should be expected when mixing the model toner with additives having a RTA in the range between 0.060 and 0.120. The results show that the cohesion increases with increasing particle size and decreasing surface coverage. Fig. 9 shows a graph of cohesion with respect to surface coverage for toners made with composite particles having the properties described in example 2A (dashed line) and example 8B (solid line). The average RTA for samples made according to example 8B was higher than example 2A, demonstrating that increasing RTA decreases cohesiveness and increases free-flow.

The foregoing description of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

The claims are set forth below.