阅读说明：本技术 不易收缩热膨胀微胶囊及其应用 (Heat expansion microcapsule not easy to shrink and application thereof ) 是由 刘峰 高英 何健平 李玲玲 于 2019-09-12 设计创作，主要内容包括：本发明公开了一种不易收缩热膨胀微胶囊及其应用,不易收缩热膨胀微胶囊,由外壳和作为芯剂的挥发性溶剂构成,外壳为包括以腈类单体、具有环氧基的单体、丙烯酸酯类单体、烷基乙烯基醚类单体、乙酸乙烯酯单体和咪唑类交联剂为原料,在引发剂的存在下聚合而成的聚合物,重量百分比用量为：腈类单体30～90％、具有环氧基的单体1～50％、丙烯酸酯类单体5～60％、烷基乙烯基醚类单体0～50％、乙酸乙烯酯单体0～50％、咪唑类交联剂0.1～20％、交联剂0.01～5％和引发剂0.01～5％,本发明可作为轻质化材料应用,具有合适的T<Sub>开始</Sub>和较高的发泡倍率,具有高耐热性和气体阻隔性,不容易收缩,有更宽的使用温度范围。(The invention discloses a microcapsule with low possibility of contraction and thermal expansion and application thereof, the microcapsule with low possibility of contraction and thermal expansion is composed of a shell and a volatile solvent as a core agent, the shell is a polymer which is polymerized by taking nitrile monomers, monomers with epoxy groups, acrylate monomers, alkyl vinyl ether monomers, vinyl acetate monomers and imidazole cross-linking agents as raw materials in the presence of an initiator, and the weight percentage is as follows: 30-90% of nitrile monomer, 1-50% of monomer with epoxy group, 5-60% of acrylate monomer, 0-50% of alkyl vinyl ether monomer, 0-50% of vinyl acetate monomer, 0.1-20% of imidazole crosslinking agent, 0.01-5% of crosslinking agent and 0.01-5% of initiator Start of And higher foaming ratio, high heat resistance and gas barrier property, difficult shrinkage and wider use temperature range.)

1. The heat expansion microcapsule not easy to shrink is characterized by comprising a shell and a volatile solvent wrapped in the shell and used as a core agent, wherein the shell is a polymer which is polymerized by using nitrile monomers, monomers with epoxy groups, acrylate monomers, alkyl vinyl ether monomers, vinyl acetate monomers and imidazole cross-linking agents as starting raw materials in the presence of an initiator, and the weight percentage of each component is as follows:

2. the non-shrinkable thermal expansion microcapsule according to claim 1, wherein the weight percentages of the respective components are as follows:

3. a non-shrinkable thermal expansion microcapsule according to claim 1 or 2, wherein said nitrile monomer is one or more selected from acrylonitrile, α -chloroacrylonitrile, α -ethoxyacrylonitrile and fumaronitrile.

4. A non-shrinkable thermal expansion microcapsule according to claim 1 or 2, wherein said monomer having an epoxy group is one or more selected from glycidyl acrylate and glycidyl methacrylate.

5. A non-shrinkable heat expandable microcapsule according to claim 1 or 2, wherein the acrylic monomer is at least one selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, dicyclopentenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and isobornyl methacrylate.

6. A non-shrinkable thermal expansion microcapsule according to claim 1 or 2, wherein the alkyl vinyl ether monomer is one or more selected from ethyl vinyl ether, propyl vinyl ether and butyl vinyl ether.

7. A non-shrinkable thermal expansion microcapsule according to claim 1 or 2, wherein said imidazole based cross-linking agent comprises:

(1) the structure of the 2-4-dialkyl imidazole is shown as the following (I):

n is 0-20, and m is an integer of 0-20;

(2) 2-alkylimidazole of the following structure (II):

n is an integer of 0-20;

(3) 2-phenylimidazole, the structure of which is shown as (III):

8. a non-shrinkable thermal expansion microcapsule according to claim 7, wherein said imidazole based cross-linking agent is selected from the group consisting of 2-methylimidazole (2MZ), 2-ethyl-4-methylimidazole (2E4MZ), 2-phenylimidazole (2PZ), 2-undecylimidazole (C)₁₁Z) or 2-heptadecylimidazole (C)₁₇Z)。

9. The heat expansion microcapsule not easy to shrink as claimed in claim 8, wherein the imidazole crosslinking agent is 2-ethyl-4-methylimidazole.

10. A non-shrinkable thermal expansion microcapsule according to claim 1 or 2, wherein said crosslinking agent is selected from one or a mixture of two or more (including two) of the following compounds:

divinylbenzene, ethylene glycol di (meth) acrylate, di (ethylene glycol) di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, 1, 3-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, triallylformal tri (meth) acrylate, allyl methacrylate, trimethylolpropane tri (meth) acrylate, tributylene glycol di (meth) acrylate, allyl methacrylate, and the like, PEG #200 di (meth) acrylate, PEG #400 di (meth) acrylate, PEG #600 di (meth) acrylate, 3-acryloxydiol monoacrylate, triacyl formal, triallyl isocyanate, triallyl isocyanurate, divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, or tetraethylene glycol divinyl ether.

11. A non-shrinkable thermal expansion microcapsule according to claim 1 or 2, wherein said initiator is selected from one or a mixture of two or more (including two) of the following compounds:

dicetyl peroxydicarbonate, bis (4-t-butylcyclohexyl), peroxydicarbonate, peroxodioctoic acid, dibenzoic acid peroxide, dilauric peroxide, didecanoic peroxide, t-butyl peracetate, t-butyl peraurate, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, cumene ethylperoxide, diisopropylhydroxydicarboxylate, 2 '-azobis ((2, 4-dimethylvaleronitrile), 2' -azobis (isobutyronitrile), 1 '-azobis (cyclohexane-1-carbonitrile), dimethyl 2,2, -azobis (2-methylpropionate) or 2, 2' -azobis [ 2-methyl-N- (2-hydroxyethyl) -propylene oxide.

12. A non-shrinkable thermal expansion microcapsule according to claim 1 or 2, wherein said volatile solvent is a compound having a boiling point not higher than the softening temperature of the polymer of said shell.

13. The microcapsule according to claim 1 or 2, wherein a surface modifier is further attached to the outer surface of the microcapsule.

14. The non-shrinkable thermal expansion microcapsule according to claim 13, wherein the attached surface modifier is one or more of organic or inorganic modifiers, and the organic modifiers include, but are not limited to: metal soaps such as magnesium stearate, calcium stearate, zinc stearate, barium stearate, and lithium stearate; synthetic waxes such as polyethylene wax, lauric acid amine, myristic acid amide, palmitic acid amide, stearic acid amide or hardened castor oil; polyacrylamide, polyimide, nylon, polymethyl methacrylate, polyethylene, polytetrafluoroethylene, or the like; the inorganic modifier includes, but is not limited to: talc, mica, bentonite, sericite, carbon black, aluminum disulfide, tungsten disulfide, graphite fluoride, calcium fluoride, boron nitride, silica, alumina, mica, calcium carbonate, calcium hydroxide, calcium phosphate, magnesium hydroxide, magnesium phosphate, barium sulfate, titanium dioxide, zinc oxide, ceramic beads, glass beads or crystal beads.

15. The use of the non-shrinkable heat expandable microcapsule according to any one of claims 1 to 14 as a lightweight material in the fields of paper making, printing inks, putties, sealants, ultralight clays, base coatings, adhesives, degumming of adhesives, artificial leather, genuine leather, paints, non-woven fabric materials, paper and cardboard, paper, cardboard, plastics, coatings of metals and fabrics, explosives, cable insulation layers, thermoplastics, thermoplastic elastomers, styrene-butadiene rubber, natural rubber, vulcanized rubber, silicone rubber, and thermosetting polymers.

Technical Field

The invention relates to a heat expansion microcapsule which is not easy to shrink and application thereof.

Background

The heat-expandable microcapsules have been widely used as a light-weight additive and a surface-modifying additive, and are also used for foaming ink, wallpaper, and plastics or rubber for the purpose of reducing weight.

The heat expansion microcapsule is a microcapsule with a core-shell structure, which is formed by taking a thermoplastic polymer as a shell and encapsulating volatile substances such as aliphatic hydrocarbon and other volatile solvents. For example, patent ZL201210109302.3 discloses the following method: is prepared from olefinic polymerizable monomer and volatile substance through suspension polymerization, and the acrylamide monomer is used to replace methacrylonitrile monomer in existing technique to obtain the product with higher T_{Start of}(typically 160 ℃ C. to 200 ℃ C.) and a high expansion capacity.

However, in some applications, consumers desire lower T for thermally expandable microcapsules supplied by suppliers_{Start of}(generally 80-160 ℃) and has better temperature resistance T_{Maximum of}(generally 120-200 ℃), difficult shrinkage and wider use temperature range. Properties of the thermally expandable microcapsules prepared in patent ZL201210109302.3 (mainly T)_{Start of}And T_{Maximum of}) And shrink resistance have not been satisfactory to users.

Therefore, the method does not contain methacrylonitrile which has complex production process and high price and has lower T_{Start of}(generally 80 ℃ C. to 160 ℃ C.) and a higher expansion capacityThe heat expansion microcapsule which is easy to shrink becomes the technical problem to be solved by the invention.

Disclosure of Invention

The invention aims to disclose a heat expansion microcapsule which is not easy to shrink and application thereof, so as to overcome the defects in the prior art.

The microcapsule is composed of a shell and a volatile solvent which is wrapped in the shell and used as a core agent, wherein the shell is a polymer which is polymerized by taking nitrile monomers, monomers with epoxy groups, acrylate monomers, alkyl vinyl ether monomers, vinyl acetate, imidazole cross-linking agents and the like as starting raw materials in the presence of an initiator;

the weight percentage of each component is as follows:

preferably, the weight percentage of each component is as follows:

the nitrile monomer is selected from more than one of acrylonitrile, alpha-chloroacrylonitrile, alpha-ethoxyacrylonitrile or fumaronitrile, and particularly preferably acrylonitrile;

the monomer with epoxy group is selected from more than one of glycidyl acrylate or glycidyl methacrylate;

the acrylic ester monomer is selected from more than one of methyl acrylate, ethyl acrylate, butyl acrylate, dicyclopentenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobornyl methacrylate and the like;

the alkyl vinyl ether monomer is selected from more than one of ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether and the like;

the imidazole crosslinking agent comprises:

(1) the structure of the 2-4-dialkyl imidazole is shown as the following (I):

n is 0-20, and m is an integer of 0-20;

(2) 2-alkylimidazole of the following structure (II):

n is an integer of 0-20;

(3) 2-phenylimidazole, the structure of which is shown as (III):

preferably, the imidazole-based crosslinker is selected from 2-methylimidazole (2MZ), 2-ethyl-4-methylimidazole (2E4MZ), 2-phenylimidazole (2PZ), 2-undecylimidazole (C)₁₁Z) or 2-heptadecylimidazole (C)₁₇Z), and the like.

Preferably, the imidazole crosslinking agent is selected from the following structural formula: 2-ethyl-4-methylimidazole:

the imidazole crosslinking agent can be a commercial product, such as a product of Hubei Xinkang pharmaceutical chemical industry Co.

The crosslinking agent is a compound containing one or more (two or more) crosslinking functional groups, and specifically, the crosslinking agent is selected from one or more (two or more) mixtures of the following compounds:

divinylbenzene, ethylene glycol di (meth) acrylate, di (ethylene glycol) di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, 1, 3-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, triallylformal tri (meth) acrylate, allyl methacrylate, trimethylolpropane tri (meth) acrylate, tributylene glycol di (meth) acrylate, allyl methacrylate, and the like, PEG #200 di (meth) acrylate, PEG #400 di (meth) acrylate, PEG #600 di (meth) acrylate, 3-acryloxydiol monoacrylate, triacyl formal, triallyl isocyanate, triallyl isocyanurate, divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, or tetraethylene glycol divinyl ether, and the like;

the selection of the initiator is suitable for the invention, and the existing initiator (such as organic peroxide or azo compound) for free radical polymerization is suitable for the invention, and the specific initiator is selected from one or a mixture of more than two of the following compounds:

dicetyl peroxydicarbonate, bis (4-t-butylcyclohexyl), peroxydicarbonate, peroxodioctoic acid, dibenzoic acid peroxide, dilauric peroxide, didecanoic peroxide, t-butyl peracetate, t-butyl peraurate, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, cumene ethylperoxide, diisopropyl hydroxydicarboxylate, 2 '-azobis ((2, 4-dimethylvaleronitrile), 2' -azobis (isobutyronitrile), 1 '-azobis (cyclohexane-1-carbonitrile), dimethyl 2,2, -azobis (2-methylpropionate), 2' -azobis [ 2-methyl-N- (2-hydroxyethyl) -propane ], or the like;

the volatile solvent may have a boiling point not higher than the softening temperature of the polymer of the outer shell, and C3 to C15 aliphatic hydrocarbon compounds are preferably used, more preferably the volatile substance is C4 to C12 linear or branched saturated hydrocarbon compounds, and still more preferably the volatile substance is C4 to C9 linear or branched saturated hydrocarbon compounds, and examples of the volatile solvent include: low molecular weight hydrocarbons such as butane, isobutane, isopentane, neopentane, n-hexane, heptane, isooctane, octane, petroleum ether, and the like; tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, trimethyl-n-propylsilane, and the like. Among them, preferred are butane, isobutane, isopentane, n-hexane, petroleum ether, isooctane, and the like. These volatile solvents may be used alone or in combination of two or more, and the content of the volatile solvent is 5 to 50 wt%, preferably 10 to 50 wt%, more preferably 15 to 40 wt%, and most preferably 20 to 35 wt%, based on 100 wt% of the total weight of the provided thermally expandable microcapsule.

Preferably, a surface modifier is further attached to the outer surface of the hard-shrinkage thermal expansion microcapsule to further improve the dispersibility or the fluidity;

the surface modifier attached is one or more of organic or inorganic modifiers, and the organic modifiers include but are not limited to: metal soaps such as magnesium stearate, calcium stearate, zinc stearate, barium stearate, and lithium stearate; synthetic waxes such as polyethylene wax, lauric acid amine, myristic acid amide, palmitic acid amide, stearic acid amide or hardened castor oil; polyacrylamide, polyimide, nylon, polymethyl methacrylate, polyethylene, polytetrafluoroethylene, or the like; the inorganic modifier includes, but is not limited to: talc, mica, bentonite, sericite, carbon black, aluminum disulfide, tungsten disulfide, graphite fluoride, calcium fluoride, boron nitride, silica, alumina, mica, calcium carbonate, calcium hydroxide, calcium phosphate, magnesium hydroxide, magnesium phosphate, barium sulfate, titanium dioxide, zinc oxide, ceramic beads, glass beads, or crystal beads, and the like.

The amount of the surface modifier attached is not particularly limited, but is 0.1 to 95 parts by weight, preferably 0.5 to 60 parts by weight, more preferably 1 to 50 parts by weight, and most preferably 3 to 30 parts by weight, based on 100 parts by weight of the total weight of the unattached thermally expandable microspheres, in consideration of the fact that the function of the surface modifier can be sufficiently exerted.

The preparation method of the present invention can be carried out by a conventional suspension polymerization method, for example, a method reported in patent ZL201210109302.3, in which a swellable substance and a polymerizable compound including a polymerizable monomer are kept in suspension by continuous stirring or addition of a dispersion stabilizer (e.g., magnesium hydroxide or colloidal silica) and the polymer is allowed to form a spherical shape by suspension polymerization.

As for the suspension polymerization temperature, it may be determined depending on the kind of the initiator used, and the suspension polymerization temperature recommended in the present invention is 30 to 100 ℃, preferably 35 to 80 ℃, and more preferably 40 to 70 ℃.

The pressure at the initial stage of polymerization is preferably 0 to 5.0MPa, more preferably 0.1 to 3.0MPa, particularly preferably 0.2 to 2.0MPa in gauge pressure.

Maximum foaming temperature (T) of the thermally expandable microcapsules of the present invention_max) The temperature is not particularly limited, and is preferably in the range of 120 to 200 ℃. When the maximum foaming temperature is less than 120 ℃, the heat resistance of the thermally expandable microcapsules is lowered, and at high temperatures, the thermally expandable microcapsules are likely to crack or shrink, and sometimes cannot be foamed at a high expansion ratio.

The present inventors have found that a relatively low and wide initial foaming temperature can be obtained by using a polymer containing a nitrile-based monomer, a monomer having an epoxy group and an imidazole-based crosslinking agent in a heat-expandable microcapsule, and that the resulting heat-expandable microcapsule has high heat resistance and gas barrier properties, is less likely to shrink at a use temperature, and has a wide use temperature range, thereby completing the present invention.

In the present specification, the maximum foaming temperature is a temperature at which the thermally-expansible microcapsules are heated from room temperature and the diameters thereof are measured, or a temperature at which the thermally-expansible microcapsules reach the maximum displacement amount.

The preferable range of the foaming starting temperature (Ts) of the heat expansion microcapsule difficult to shrink is 80-160 ℃.

The volume average particle diameter of the heat-expandable microcapsule of the present invention is not particularly limited, but the lower limit is preferably 1 μm and the upper limit is preferably 50 μm. When the volume average particle diameter is less than 1 μm, for example, when the thermally expandable microcapsule is blended with a matrix resin and molded, the cells of the resulting foam molded article are too small, and the weight reduction may be insufficient. When the volume average particle diameter exceeds 50 μm, for example, when the thermally expandable microcapsule is blended with a matrix resin and molded, the cells of the obtained foam molded article become too large, which may cause a problem in terms of strength and the like. A more preferable lower limit and a more preferable upper limit of the volume average particle diameter are 5 μm and 45 μm, respectively.

When the polymerization is substantially complete, microspheres of an aqueous slurry or dispersion are obtained, which can be used as such or dewatered by any conventional method (e.g. bed filtration, pressure filtration, leaf filtration, rotary filtration, belt filtration or centrifugation) to obtain a so-called wet cake. However, the microspheres may also be dried by any conventional method (e.g., spray drying, rack drying, tunnel drying, rotary drying, drum drying, through air drying, turbo rack drying, disc drying, fluidized bed drying, or the like).

The attachment of the surface modifier may be performed by mixing the unattached thermally expandable microspheres and the surface modifier. The mixing is not particularly limited, and may be carried out in a vessel having a stirring device. Further, a powder mixer capable of performing ordinary shaking or stirring may be used. Examples of the powder mixer include a ribbon blade type mixer, a vertical screw type mixer, and the like, which can perform shaking stirring or stirring. In addition, a super mixer, a high-speed mixer, an SV mixer, or the like, which is a multifunctional powder mixer having higher efficiency by combining stirring apparatuses in recent years, may be used.

The heat-expandable microcapsule which is not easily shrunk provided by the present invention can be used as a light material for paper making, printing ink (such as water-based ink, solvent-based ink, plastisol, ultraviolet curing ink, etc.), putty, sealant, ultralight clay, bottom coating, adhesive, degumming of adhesive, artificial leather, genuine leather, paint, non-woven fabric material, paper and paperboard, coating (such as non-slip coating, etc.) for various materials such as paper, paperboard, plastic, metal and fabric, explosive, cable insulation, thermoplastic (such as polyethylene, polyvinyl chloride and ethylene-vinyl acetate) or thermoplastic elastomer (such as styrene-ethylene-butylene-styrene copolymer, styrene-butadiene-styrene copolymer, thermoplastic polyurethane and thermoplastic polyolefin), styrene-butadiene rubber, styrene-butadiene-styrene copolymer, styrene copolymer, Natural rubber, vulcanized rubber, silicone rubber, thermosetting polymers (e.g., epoxy, polyurethane, and polyester), and the like.

The raw materials of the present invention may be any of commercial products unless otherwise specified.

The invention has the beneficial effects that: the heat-expandable microcapsule obtained by the invention has simple production process and mild operation condition, and the epoxy monomer is used for replacing expensive methacrylonitrile, thereby reducing the cost; and the obtained microcapsules have a suitable T_{Start of}(generally 80-160 ℃) and higher expansion ratio, and the obtained thermal expansion microcapsule has high heat resistance and gas barrier property, is not easy to shrink at the use temperature, has wider use temperature range, and has good application in light materials.

Detailed Description

The invention is further illustrated by the following examples. In the examples listed, all parts and percentages in the examples refer to parts and percentages by weight unless otherwise indicated, and the analysis of the thermally expandable microcapsules employs the following methods and apparatus:

(1) analysis of particle size distribution characteristics:

the particle size distribution of the heat-expandable microcapsules was measured by a particle size distribution laser diffraction analyzer LS13320 manufactured by Bekman coulter corporation. The average diameter is measured as the volume average particle diameter.

(2) Analysis of foaming characteristics:

the properties of the heat-expandable microcapsules were measured by a thermomechanical analyzer TMA Q-400 manufactured by TA Instrument Co. Samples were prepared from 1.0mg of thermally expandable microcapsules contained in an aluminum pan of 6.7mm diameter and 4.5mm depth. The aluminum pan was then sealed with an aluminum pan of 6.5mm diameter and 4.0mm depth. Depending on the TMA extended probe type, the sample temperature was increased from ambient to 280 ℃ at a ramp rate of 20 ℃/min and a force of 0.1N was applied by the probe. The analysis is performed by measuring the vertical displacement of the probe.

-expansion start temperature (Tstart): temperature (. degree. C.) at which probe displacement starts to increase.

Maximum foaming temperature (Tmax): temperature (deg.C) at which probe displacement reaches a maximum.

Maximum foaming displacement ((Dmax): displacement (. mu.m) at which the probe displacement reaches a maximum.