阅读说明：本技术 一种分散助剂及其碳纳米管分散液和导电浆料 (Dispersing auxiliary agent, carbon nanotube dispersion liquid and conductive paste ) 是由 陈新江 张伟强 刘琪高 袁芳 于 2021-08-06 设计创作，主要内容包括：本发明涉及一种分散助剂及其碳纳米管分散液和导电浆料,分散助剂为具有羟基和羧基的超支化聚酯,含该分散助剂的分散液还包括碳纳米管、分散剂和水,分散剂为含颜料亲和基团的共聚物。本发明的分散液采用含颜料亲和基团的共聚物作为分散剂,同时采用具有特定超支化结构的超支化聚酯作为分散助剂,使得一方面,该具有特定超支化结构的超支化聚酯容易吸附在碳纳米管表面,另一方面,该超支化聚酯具有一定羟基和羧基的亲水性基团,与分散剂协同作用,使得碳纳米管含量提升时,碳纳米管仍然能够长期稳定均匀分散在水中,而不产生团聚和沉淀。(The invention relates to a dispersing auxiliary agent, a carbon nano tube dispersion liquid and conductive slurry thereof, wherein the dispersing auxiliary agent is hyperbranched polyester with hydroxyl and carboxyl, the dispersion liquid containing the dispersing auxiliary agent also comprises a carbon nano tube, a dispersing agent and water, and the dispersing agent is a copolymer containing pigment affinity groups. The dispersion liquid adopts the copolymer containing pigment affinity groups as the dispersing agent, and simultaneously adopts the hyperbranched polyester with a specific hyperbranched structure as the dispersing auxiliary agent, so that on one hand, the hyperbranched polyester with the specific hyperbranched structure is easy to adsorb on the surface of the carbon nano tube, and on the other hand, the hyperbranched polyester has certain hydrophilic groups of hydroxyl and carboxyl and has a synergistic effect with the dispersing agent, so that the carbon nano tube can still be stably and uniformly dispersed in water for a long time without agglomeration and precipitation when the content of the carbon nano tube is increased.)

1. An aqueous carbon nanotube dispersion comprising carbon nanotubes, a dispersant and water, characterized in that: the dispersing agent is a copolymer containing pigment affinity groups, the dispersion liquid further comprises a dispersing auxiliary agent, and the dispersing auxiliary agent is hyperbranched polyester with hydroxyl and carboxyl.

2. The aqueous carbon nanotube dispersion according to claim 1, wherein: the hyperbranched polyester has one or more of the following groups: C6-C20 chain alkyl, C2-C20 chain alkenyl, 3-8 membered ring with 1 or 2 unsaturated double bonds, phenyl, naphthyl.

3. The aqueous carbon nanotube dispersion according to claim 1, wherein: the dispersing assistant has a structure shown in a formula I or is a metal salt formed by a compound with the structure shown in the formula I,

in the formula I, n is an integer of 10-40, m is an integer of 5-20, R₁Represents the main structure of hyperbranched polyester, R₂Selected from C6-C20 chain alkyl; C2-C20 catenary alkenyl; a 3-8 membered ring having 1 or 2 unsaturated double bonds; phenyl unsubstituted or substituted by a substituent selected from C1-C6 alkyl, carboxy; naphthyl that is unsubstituted or substituted with a substituent selected from the group consisting of C1-C6 alkyl, carboxy.

4. The aqueous carbon nanotube dispersion according to claim 3, wherein: the dispersing auxiliary is prepared by reacting hydroxyl hyperbranched polyester with anhydride; and/or, the metal salt is selected from sodium salt, potassium salt; and/or, in formula I, n-m is greater than 5.

5. The aqueous carbon nanotube dispersion according to claim 4, wherein: the hydroxyl hyperbranched polyester is aliphatic hydroxyl hyperbranched polyester with the molecular weight of 500-5000; and/or the acid anhydride is one or more of phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, 2, 3-naphthalene dicarboxylic anhydride and dodecenyl succinic anhydride.

6. The aqueous carbon nanotube dispersion according to claim 4, wherein: the hydroxyl hyperbranched polyester has the following structural formula,

7. the aqueous carbon nanotube dispersion according to claim 1, wherein: the carbon nano tube is one or a combination of more of a single-wall carbon nano tube, a double-wall carbon nano tube, a multi-wall carbon nano tube, a carboxylated carbon nano tube and a hydroxylated carbon nano tube; and/or the pipe diameter of the carbon nano tube is 2-150 nm; and/or the length of the carbon nano tube is 1-50 mu m.

8. The aqueous carbon nanotube dispersion according to any one of claims 1 to 7, wherein: in the aqueous carbon nanotube dispersion liquid, the mass content of the carbon nanotubes is 1-20%; and/or the mass ratio of the dispersing agent to the dispersing auxiliary agent is 1-10: 1.

9. The aqueous carbon nanotube dispersion according to claim 1, wherein: in the aqueous carbon nanotube dispersion liquid, the mass content of the carbon nanotubes is 5-20%; and/or the aqueous carbon nanotube dispersion liquid also comprises an antifoaming agent, and the antifoaming agent accounts for 0.2-1% of the aqueous carbon nanotube dispersion liquid by mass.

10. A method for producing the aqueous carbon nanotube dispersion liquid according to any one of claims 1 to 9, comprising:

and stirring and dispersing the solution containing the dispersing agent, the solution containing the dispersing aid and water, then adding the carbon nano tubes, stirring and dispersing, and then grinding to obtain the dispersion liquid.

11. The method of producing an aqueous carbon nanotube dispersion according to claim 10, further comprising a step of dropping an antifoaming agent during the stirring dispersion process performed after the addition of the carbon nanotubes, wherein the grinding is performed after the completion of the dropping of the antifoaming agent.

12. The aqueous carbon nanotube conductive slurry comprises aqueous high-molecular film-forming resin and is characterized in that: the conductive paste further comprises the aqueous carbon nanotube dispersion according to any one of claims 1 to 11.

13. A dispersing aid as claimed in any one of claims 1 to 6.

14. A method of preparing a dispersing aid according to claim 13, wherein: the preparation method comprises the following steps: dissolving hydroxyl hyperbranched polyester in a solvent, then adding acid anhydride and a catalyst, reacting at 70-120 ℃, evaporating the solvent after the reaction is finished, cooling, and adjusting the pH value to 6.0-9.0 to obtain the dispersing aid.

15. The method for producing a dispersion aid according to claim 14, characterized in that: the catalyst is one or a combination of more of triethylamine, N-dimethylbenzylamine and tetrabutylammonium bromide; and/or the solvent is one or the combination of more of isopropanol, propylene glycol methyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, 1, 4-dioxane, dimethyl sulfoxide and N, N-dimethylformamide; and/or the feeding molar ratio of the acid anhydride to the hydroxyl hyperbranched polyester is (5-20): 1.

16. an electroconductive paste comprising an electroconductive agent, characterized in that: the conductive paste further comprises the dispersion aid according to claim 13 or the dispersion aid produced by the method for producing a dispersion aid according to claim 14 or 15.

Technical Field

The invention relates to the technical field of carbon material dispersion, in particular to a dispersion auxiliary agent, a carbon nano tube dispersion liquid and conductive slurry thereof.

Background

CNTs are seamless hollow nano-scale coaxial cylindrical tubular materials assembled by rolling or nesting single-layer or multi-layer graphite sheets, and are classified into single-wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs) according to the difference of the number of layers. The carbon atoms on the side wall of the CNTs mainly form highly delocalized pi electrons with adjacent carbon atoms in an sp2 hybridization mode, so that strong van der Waals force exists among the CNTs, and the CNTs are aggregated into a bundle and are not easy to disperse, thereby restricting the application of the CNTs. Meanwhile, a high-concentration carbon tube has great advantages in operation links such as transportation and use compared with a low-concentration carbon tube, so that many applications tend to use high-concentration carbon tube slurry, and how to prepare high-concentration carbon nanotube slurry while maintaining good dispersion of carbon nanotubes also becomes a problem to be solved.

Hyperbranched Polymer (HBP for short) has various special properties such as amorphous shape, non-chain entanglement, low viscosity and the like due to the three-dimensional dendritic structure different from linear Polymer, and is widely applied to various materials. Meanwhile, the hyperbranched dispersant is a common auxiliary agent which can stably disperse inorganic pigments such as carbon black, titanium dioxide and the like in water and oil systems. Structurally, the hyperbranched dispersant is a high molecular material consisting of a plurality of branched central atoms and a plurality of anchor points on branched chains. It is the structural particularity that the dispersant has super dispersing and stabilizing capability.

In the prior art, hyperbranched polymers are also used for dispersing carbon nanotubes, such as nano carbon material dispersion liquid disclosed in Chinese patent CN102180458A, and a preparation method and equipment thereof, the dispersion liquid comprises a nano-carbon material, a dispersion solvent and optionally a dispersion auxiliary agent and a stabilizing agent, wherein the nano-carbon material is more than one of graphene, a carbon nano-tube, nano-carbon fiber, fullerene, carbon black and acetylene black, the dispersion auxiliary agent is a surfactant, a biological macromolecule or a hyperbranched polymer, the hyperbranched polymer is a hyperbranched polymer of triarylamine and derivatives thereof, or hyperbranched polyamic acid containing triphenylamine structure, and hyperbranched polymer obtained by dehalogenation and polycondensation of tri (4-bromophenyl) amine and 1, 4-divinyl, or hyperbranched polymer obtained by polycondensation of Grignard reagent compound of tri (4-bromophenyl) amine. The dispersion is obtained by pre-dispersion treatment and high-pressure dissociation dispersion treatment.

Although the dispersion can be stable for a long period of time, there still exist some problems such as: the hyperbranched polymer only plays a role in solubilizing the dispersion of the carbon material in the liquid organic medium; the mass content of the carbon material in the dispersion liquid is not more than 5%, and the concentration of the carbon material is still low; high-pressure dissociation and dispersion treatment is also needed in the preparation process, the operation is complicated, the preparation process is complex, and the production efficiency is low.

Hyperbranched polymers have also been reported for use in aqueous dispersion systems of carbon nanotubes, as has been reported in chinese patent CN108559092A, a carbon material dispersant comprising an amphiphilic hyperbranched polymer having a backbone structure with amine groups and a mono-, poly-, fused-or heterocyclic aromatic group non-covalently associated with a graphene structure covalently bonded to said backbone structure, a method for preparing the same, and an aqueous dispersion of a stable carbon material containing the same. The aqueous dispersion is formed by grinding a mixture of graphite (e.g., carbon nanotubes) and a carbon material dispersant in the presence of an aqueous solvent.

Although the dispersion can exist stably for a long time, the concentration of the carbon material in the aqueous dispersion is extremely low, as in examples 7 and 8 in the document, the feeding mass content of the carbon nanotubes in the aqueous dispersion is only 0.5-1%, and the content of the carbon nanotubes is extremely low; and when the aqueous dispersion is prepared, the dispersing agent, the carbon nano tubes and water are ground and dispersed, then the mixture is kept stand, the supernatant is taken and subjected to centrifugal separation, the upper black clear liquid is a carbon nano tube aqueous solution, and the lower precipitate is a carbon nano tube aggregate, so that the aqueous dispersion is not a uniform dispersion liquid, and the concentration of the carbon nano tubes in the aqueous dispersion is lower and even lower than 1 percent under the condition of extremely low feeding content.

In summary, in the prior art, there still exist problems that when the content of the carbon nanotubes is increased, the carbon nanotubes have poor dispersion effect in water, and are easy to agglomerate and wind.

Disclosure of Invention

The invention aims to solve the problems of poor dispersion effect in water, easy agglomeration and precipitation and the like when the content of carbon nanotubes is increased in the prior art, and provides an aqueous carbon nanotube dispersion liquid and a preparation method thereof.

The second object of the invention also provides a conductive paste.

The third object of the present invention is to provide a dispersion aid for carbon nanotubes and the like which is useful for dispersion in water, and a method for preparing the same.

In order to achieve the purpose, the technical scheme is as follows:

the aqueous carbon nanotube dispersion liquid comprises carbon nanotubes, a dispersing agent and water, wherein the dispersing agent is a copolymer containing pigment affinity groups, and the dispersion liquid also comprises a dispersing auxiliary agent which is hyperbranched polyester with hydroxyl and carboxyl.

Further, the hyperbranched polyester has one or more of the following groups: C6-C20 chain alkyl, C2-C20 chain alkenyl, 3-8 membered ring with 1 or 2 unsaturated double bonds, phenyl, naphthyl.

The hyperbranched polyester molecular structural formula of the dispersing auxiliary agent has certain hydrophilic groups of hydroxyl and carboxyl, and also has conjugated systems such as benzene rings and the like, so that adsorption is enhanced through pi-pi action, and on the other hand, the dispersing auxiliary agent and the dispersing agent are compounded and cooperated to add the carbon nano tube into a mixed solution to be ground and dispersed to obtain the high-solid-content aqueous carbon nano tube dispersing liquid.

In some preferred and specific embodiments, the dispersing aid has a structure of formula I, or is a metal salt formed from a compound having a structure of formula I,

in the formula I, n is an integer of 10-40, m is an integer of 5-20, R₁Represents the main structure of hyperbranched polyester, R₂Selected from C6-C20 chain alkyl; a C2-C20 linear alkenyl group, a 3-8 membered ring having 1 or 2 unsaturated double bonds; phenyl unsubstituted or substituted by a substituent selected from C1-C6 alkyl, carboxy; naphthyl that is unsubstituted or substituted with a substituent selected from the group consisting of C1-C6 alkyl, carboxy.

Preferably, the metal salt is selected from sodium salt, potassium salt. The method for forming the metal salt may be to react a compound having a structure represented by formula I with a base.

Further, the dispersing aid is prepared by reacting a hydroxy hyperbranched polyester with an acid anhydride.

The synthetic route is as follows:

preferably, the hydroxyl hyperbranched polyester is aliphatic hydroxyl hyperbranched polyester with the number average molecular weight of 500-5000. More preferably, the number average molecular weight of the hydroxyl hyperbranched polyester is 1000-4000. For example, the hydroxy hyperbranched polyester has the following structure (i.e., R)₁May be provided by the following structure), but is not limited thereto,

according to the invention, the hydroxyl hyperbranched polyester can be chosen, for example, from Boltorn H20, Boltorn H30 from Perstorp.

Preferably, the anhydride is one or more of phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, 2, 3-naphthalene dicarboxylic anhydride, and dodecenyl succinic anhydride. Such as anhydrides having the structure (i.e., R)₂May be provided by the following structure), but is not limited thereto,

it can be seen that the sterically hindered dispersing aids have two special structural features: the first one contains one or more groups (anchoring groups or adhesion groups) called pigment affinity, all of which have firm and durable adsorption force on the surface of the pigment, and the benzene ring structure is similar to a five-membered ring or a six-membered ring structure on the carbon nano tube, so that the copolymer can generate the effect similar to pi-pi superposition with the carbon nano tube, and the copolymer is easy to adsorb on the surface of the carbon nano tube; secondly, these products contain resin-miscible segments (hydrocarbon structures) which, after adsorption of the dispersing aid on the pigment surface, extend as far as possible from the pigment surface into the surrounding resin solution.

Preferably, n-m is greater than 5.

Preferably, when the acid value in the reaction system is equal to the theoretical acid value, the reaction is terminated. Further preferably, the theoretical acid value is 50. + -. 10% of the initial acid value in the reaction system.

In some embodiments, the reaction is carried out in the presence of a catalyst and a solvent.

Preferably, the catalyst is one or more of triethylamine, N-dimethylbenzylamine and tetrabutylammonium bromide.

Preferably, the solvent is one or more of isopropanol, propylene glycol methyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, 1, 4-dioxane, dimethyl sulfoxide and N, N-dimethylformamide.

Preferably, the feeding molar ratio of the acid anhydride to the hydroxyl hyperbranched polyester is (5-20): 1. further preferably, the feeding molar ratio of the acid anhydride to the hydroxyl hyperbranched polyester is (5-16): 1.

according to the invention, the dispersion liquid prepared by using the copolymer containing pigment affinity groups as the dispersing agent has more stable surface hydrophilicity, and meanwhile, the hyperbranched polyester with a specific structure is used as the dispersing auxiliary agent, so that the steric hindrance effect of the dispersion liquid can be improved, the dispersion liquid has better compatibility with aqueous high-molecular film-forming resin, and has higher compatibility and stability than the dispersion liquid prepared by using other small-molecular anionic-cationic dispersing agents, so that the prepared aqueous carbon nanotube conductive slurry has better stability and uniformity, and further, the film formed by the aqueous carbon nanotube conductive slurry has more uniform and stable conductivity, more stable adhesive force and more uniform thickness.

Further, the copolymer containing the pigment affinity group comprises one or more of waterborne super-molecular polymer containing carbonyl, polycaprolactone, polyacrylic acid serving as a main chain, highly optimized special polymeric side chains, polyethylene glycol and polyvinyl alcohol. Typical copolymer solutions containing pigment affinic groups according to the present invention are the polymeric dispersant DISPERBYK2012 or the polymeric dispersant DISPERBYK190 from byk.

Preferably, the carbon nanotube is one or more of a single-walled carbon nanotube, a double-walled carbon nanotube, a multi-walled carbon nanotube, a carboxylated carbon nanotube and a hydroxylated carbon nanotube.

Preferably, the diameter of the carbon nanotube is 2 to 150nm, further 10 to 150nm, and further 10 to 100 nm.

Preferably, the length of the carbon nanotube is 1-50 μm.

According to the present invention, the content of the carbon nanotubes in the aqueous carbon nanotube dispersion may be 1% to 20%. In some preferred and specific embodiments, the mass content of the carbon nanotubes is 5 to 20%. In some particularly preferred embodiments, the carbon nanotubes are present in an amount of 10 to 14% by mass.

In some preferred and specific embodiments, the mass ratio of the dispersing agent to the dispersing aid is 1-10: 1. Preferably, the mass ratio of the dispersing agent to the dispersing assistant is 2-6: 1.

In some preferred and specific embodiments, the mass ratio of the carbon nanotubes to the dispersant in the aqueous carbon nanotube dispersion is 2-15: 1-10. Preferably, the mass ratio of the carbon nanotubes to the dispersing agent is 2-10: 1-8.

In some preferred and specific embodiments, the aqueous carbon nanotube dispersion further comprises an antifoaming agent, and the antifoaming agent is present in the aqueous carbon nanotube dispersion in an amount of 0.2 to 1% by mass.

Preferably, the antifoaming agent comprises a silicone-based antifoaming agent and/or a polymeric antifoaming agent.

Further preferably, the silicone-type antifoaming agent includes polydimethylsiloxane and/or ethylene glycol siloxane.

Further preferably, the polymeric antifoaming agent comprises one or more of a higher alcohol, polyoxyethylene oxypropylene glycerol, and a copolymer of ethylene oxide and propylene oxide.

According to the present invention, the inventors found in a large number of experimental studies that the use of a copolymer containing a pigment affinity group in combination with a dispersion aid containing a hyperbranched polyester having a specific structure unexpectedly can significantly increase the mass content of carbon nanotubes, and in some embodiments, increase the mass content of carbon nanotubes to 20% and still obtain a uniform and stable aqueous carbon nanotube dispersion.

The second technical scheme adopted by the invention is as follows: a preparation method of the aqueous carbon nanotube dispersion comprises the following steps:

and stirring and dispersing the solution containing the dispersing agent, the solution containing the dispersing aid and water, then adding the carbon nano tubes, stirring and dispersing, and then grinding to obtain the dispersion liquid.

In some preferred and specific embodiments, the preparation method further comprises a step of dropping an antifoaming agent into the stirring dispersion process performed after the addition of the carbon nanotubes, and the grinding is performed after the dropping of the antifoaming agent is completed.

In some preferred and specific embodiments, the dispersant and the dispersing aid are respectively fed in the form of a solution, and the mass ratio of the carbon nanotubes, the solution containing the dispersant, the solution containing the dispersion aid and the defoaming agent is (2-100): (1-100): (1-20): 1. preferably, the feeding mass ratio of the carbon nano tube, the solution containing the dispersing agent, the solution containing the auxiliary dispersing agent and the defoaming agent is (20-70): (10-60): (1-10): 1.

in some preferred and specific embodiments, the dispersion is fed in the following proportions by weight percent: 5-20% of carbon nano tube, 3-18% of solution containing the dispersing agent, 1-4% of solution containing the auxiliary dispersing agent, 0.2-1% of defoaming agent and the balance of water.

Preferably, the specific steps for preparing the dispersion are as follows:

(1) stirring and dispersing the solution containing the dispersing aid, the solution containing the dispersing agent and water at a first stirring speed;

(2) adding carbon nanotubes into the system in the step (1), stirring and dispersing at a second stirring speed, then stirring and dispersing at a third stirring speed, and controlling an antifoaming agent to be added into the system at the third stirring speed;

wherein the first stirring speed is less than a third stirring speed, and the second stirring speed is less than the third stirring speed;

(3) and (3) grinding the dispersion system obtained in the step (2) by using a grinder to obtain the aqueous carbon nanotube dispersion liquid.

Preferably, the mill is a horizontal pin sand mill.

Preferably, the first stirring speed is 200-400 rpm, the second stirring speed is 500-1200 rpm, the third stirring speed is 800-1600 rpm, and the rotation speed of the grinder is 1200-2500 rpm.

The third technical scheme adopted by the invention is as follows: the aqueous carbon nanotube conductive slurry comprises aqueous high-molecular film-forming resin and the aqueous carbon nanotube dispersion liquid.

Preferably, the aqueous polymer film-forming resin comprises one or more of aqueous polyurethane, aqueous acrylic resin, aqueous phenolic resin and aqueous polyester resin.

Further, the conductive paste also comprises a rheological additive, wherein the rheological additive comprises one or more of a thickening agent, a leveling agent and an anti-settling agent.

The particular choice of rheology aid is not particularly critical, for example, the thickener may be one or more of a urea modified polyurethane, polyurea, aqueous bentonite. The leveling agent can be one or more of isopropanol, propylene glycol methyl ether, diethylene glycol butyl ether and dipropylene glycol methyl ether. The anti-settling agent can be one or more of modified urea solution, modified polyamide solution and urea modified polyurethane solution. Certain adjuvants can be used as both thickening agents and anti-settling agents. Thus, in certain embodiments only a thickener or anti-settling agent may be added.

According to some specific and preferred embodiments, the preparation method of the aqueous carbon nanotube conductive paste comprises the following steps:

(1) stirring and mixing the aqueous carbon nanotube dispersion liquid and the aqueous polymer film-forming resin at a stirring speed of 600-1200 rpm;

(2) and (2) adding the rheological additive into the system in the step (1), and stirring and mixing at a stirring speed of 200-400 rpm to obtain the aqueous carbon nanotube conductive slurry.

Preferably, the stirring time in the step (1) is controlled to be 30-60 min; and (3) controlling the stirring time of the step (2) to be 10-30 min.

Preferably, the feeding mass ratio of the carbon nano tube, the aqueous polymer film-forming resin and the rheological additive is (0.2-2): (1-30): 1.

in some preferred and specific embodiments, the conductive paste includes, in weight percent: 50-80% of dispersion liquid, 10-30% of water-based polymer film-forming resin and 0.3-1% of rheological additive.

The fourth technical scheme adopted by the invention is as follows: the dispersing aid of the present invention as described above, i.e., a hyperbranched polyester having hydroxyl groups and carboxyl groups. The dispersing aid is beneficial to the dispersion of the carbon nano tube. It is expected that the dispersing aid also has a promoting effect on the dispersion of other sp2 carbons such as graphene powder or few-layer graphene sheets.

The fifth technical scheme adopted by the invention is as follows: a preparation method of the dispersing aid comprises the steps of dissolving hydroxyl hyperbranched polyester in a solvent, adding acid anhydride and a catalyst, reacting at 70-120 ℃, evaporating the solvent after the reaction is finished, cooling, and adjusting the pH value to 6.0-9.0 to obtain the dispersing aid.

Further, the catalyst is one or more of triethylamine, N-dimethylbenzylamine and tetrabutylammonium bromide.

Further, the solvent is one or more of isopropanol, propylene glycol methyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, 1, 4-dioxane, dimethyl sulfoxide and N, N-dimethylformamide.

Further, the feeding molar ratio of the acid anhydride to the hydroxyl hyperbranched polyester is (5-20): 1. preferably, the feeding molar ratio of the acid anhydride to the hydroxyl hyperbranched polyester is (5-16): 1.

further, the feeding mass ratio of the catalyst to the hydroxyl hyperbranched polyester (0.1-1) is as follows: 100.

further, the pH value is adjusted by adopting alkali liquor. Preferably, the base is selected from sodium hydroxide, potassium hydroxide.

The dispersing aid is synthesized in one step, and the process is simple.

The invention also provides conductive paste which comprises a conductive agent and the dispersing aid. The conductive agent is, for example, a carbon nanotube, graphene powder, few-layer graphene sheet, or the like. Due to the adoption of the dispersing aid, the content of the conductive agent can be increased and a good dispersing effect is still maintained.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

the dispersion liquid of the invention adopts the copolymer containing pigment affinity groups as the dispersing agent, and simultaneously adopts the hyperbranched polyester with a specific structure as the dispersing auxiliary agent, on one hand, the hyperbranched polyester with the specific structure is easy to be adsorbed on the surface of the carbon nano tube, on the other hand, the hyperbranched polyester with the specific structure has firm and durable adsorption force on the surface of the pigment, and has synergistic effect with the dispersing agent, when the content of the carbon nano tube is increased, the carbon nano tube can still be stably and uniformly dispersed in water for a long time without agglomeration and precipitation, so that the carbon nano tube dispersion liquid with high solid content can be obtained, and experiments show that the solid content of the carbon nano tube can be increased to 20%.

The dispersion liquid solves the problems of poor stability, low concentration and the like of the carbon nano tube in an aqueous environment through the synergistic effect of the dispersing agent and the dispersing auxiliary agent, has the advantage of low viscosity, and can be applied to various conductive materials.

The dispersion liquid is obtained by mixing, grinding and dispersing all the raw materials, the preparation method is simple, the operation is convenient and fast, and the production efficiency of the dispersion liquid is greatly improved.

The conductive slurry with high and stable carbon nanotube content can be prepared by adopting the dispersion liquid disclosed by the invention, so that the finally prepared conductive slurry has the advantages of uniform film thickness, no shrinkage cavity and good uniformity, and can realize uniform and stable conductive effect.

Drawings

FIG. 1 is an IR spectrum of the dispersing aid of example 2 in comparison with its raw material;

FIG. 2 is a graph showing the effect of dispersion of the aqueous carbon nanotube dispersion of example 2;

FIG. 3 is a comparative graph showing the particle size distribution curves of the aqueous carbon nanotube dispersion of example 2 before standing (a) and after standing for 90 days (b);

fig. 4 is a graph showing the effect of dispersing the carbon nanotube dispersion liquid of comparative example 2.

Detailed Description

The present invention will be further described with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not mentioned are conventional conditions in the industry. The technical features of the embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

The hydroxyl hyperbranched polyesters used in the following examples and comparative examples were from Boltorn H20 from Perstorp, having the following structure:

example 1

The aqueous carbon nanotube dispersion with high solid content provided in this example is prepared by the following method:

(1) preparation of dispersing aid

35g of hydroxyl hyperbranched polyester is added into a four-neck flask with a stirrer, a condenser pipe, a thermometer and a nitrogen inlet and dissolved in 300mL of DMF, the mixture is heated to be completely dissolved, a certain amount of phthalic anhydride (the molar ratio of the anhydride to the hydroxyl hyperbranched polyester is 7: 1) and 0.5g of catalyst N, N-dimethylbenzylamine are added under the protection of nitrogen, the temperature is raised to 95 ℃ after the phthalic anhydride and the hydroxyl hyperbranched polyester are dissolved, the reaction is carried out until the theoretical acid value is reached (half of the initial acid value), after part of solvent is evaporated, the reaction temperature is reduced to 50 ℃, a 30 wt% sodium hydroxide aqueous solution is used for neutralizing the system until the pH value is 7.0-8.0, and finally, a yellow transparent solution with 40% solid content, namely a solution containing dispersing aid-A, is obtained.

(2) Preparation of aqueous carbon nanotube Dispersion

The feeding composition of the aqueous carbon nanotube dispersion liquid is as follows by mass content of 100%:

the preparation method comprises the following steps:

firstly, weighing water, a dispersing auxiliary agent and a dispersing agent according to a formula proportion, mechanically stirring for 10 minutes at 400rpm, then adding a carbon nano tube, stirring for 20 minutes at low speed of 600rpm by a high-speed dispersion machine, then adjusting to high speed of 1200rpm, stirring for 30 minutes, dropwise adding a defoaming agent at a speed of 50g/min in the process of high-speed stirring, then introducing into a sand mill at 2000rpm, carrying out turbine grinding for 90 minutes, and stopping sanding to prepare uniform dispersion liquid; standing and defoaming to obtain carbon nanotube dispersion liquid for later use.

The dispersions of this example were tested for solids content, viscosity and stability and the results are shown in Table 1.

Example 2

The aqueous carbon nanotube dispersion with high solid content provided in this example is prepared by the following method:

(1) preparation of dispersing aid

35g of hydroxyl hyperbranched polyester is added into a four-neck flask with a stirrer, a condenser pipe, a thermometer and a nitrogen inlet and dissolved in 300mL of DMF, the mixture is heated to be completely dissolved, a certain amount of dodecenyl succinic anhydride and trimellitic anhydride (the feeding molar ratio of the anhydride to the hydroxyl hyperbranched polyester is 5: 1) and 0.8g of catalyst N, N-dimethylbenzylamine are added under the protection of nitrogen, the temperature is raised to 110 ℃ after the dodecenyl succinic anhydride and trimellitic anhydride are dissolved, the reaction is carried out until the theoretical acid value is half of the initial acid value, after a part of solvent is evaporated, the reaction temperature is reduced to 50 ℃, the pH value of the reaction solution is neutralized to 7.0-8.0 by using 30 wt% of sodium hydroxide aqueous solution, and finally 40% of yellow transparent solution, namely the solution containing the dispersing assistant-B, is obtained.

The infrared detection of the dispersing aid-B and the raw materials thereof is carried out, and the result is shown in figure 1, which proves that the dispersing aid-B is successfully prepared.

(2) Preparation of aqueous carbon nanotube Dispersion

The feeding composition of the aqueous carbon nanotube dispersion liquid is as follows by mass content of 100%:

the preparation method comprises the following steps:

firstly, weighing water, a dispersing auxiliary agent and a dispersing agent according to a formula proportion, mechanically stirring for 10 minutes at 400rpm, then adding a carbon nano tube, stirring for 20 minutes at low speed of 600rpm by a high-speed dispersion machine, then adjusting to high speed of 1200rpm, stirring for 30 minutes, dropwise adding a defoaming agent at the speed of 50g/min in the process of high-speed stirring, then introducing into a sand mill at 2000rpm, carrying out turbine grinding for 90 minutes, and stopping sanding to prepare uniform dispersion liquid; standing and defoaming to obtain carbon nanotube dispersion liquid for later use.

When 0.01g of the dispersion was dropped into 500mL of water, the effect of dispersing in water after 5 seconds was as shown in FIG. 2, and it was found that the carbon nanotubes rapidly diffused in the aqueous solution.

The dispersion of this example was tested for solid content, viscosity and stability as shown in table 1, and the particle size distribution of the dispersion of this example before and after standing for 90 days was tested as shown in fig. 3, in which (a) is a particle size distribution graph before standing, (b) is a particle size distribution graph after standing for 90 days, and the particle size distribution graphs in (a) and (b) are substantially identical, and it was found that the carbon nanotubes can be stably and uniformly dispersed in water without agglomeration and precipitation before and after standing for 90 days.

Example 3

This example provides an aqueous carbon nanotube conductive paste prepared by the following method:

66.5g of the aqueous carbon nanotube dispersion liquid prepared in the example 2 and 14g of aqueous polyurethane resin (30% of solid content) are mixed, dispersed in a high-speed dispersion machine at 600rpm for 30 minutes, and then added with 1.2g of a leveling agent and an anti-settling agent (the mass ratio of the leveling agent to the anti-settling agent is 2.5: 1), mechanically stirred at 300rpm for 10 minutes, and kept stand for defoaming to obtain the final product of the aqueous carbon nanotube conductive slurry.

Coating the aqueous carbon nanotube conductive slurry into a sample film of 20 cm multiplied by 30 cm by a blade coating process, observing the surface of the sample film, wherein the surface is uniform and has no obvious shrinkage cavity, the film thickness is 10+/-1 micron by a height gauge, and the surface square resistance is 210+/-5 omega by a square resistance instrument

Comparative example 1

The aqueous carbon nanotube dispersion liquid provided in this comparative example is different from example 1 in that a different dispersion aid is used, and the other examples are the same as example 1.

Specifically, the dispersing aid in this example was prepared by the following method:

adding hydroxyl hyperbranched polyester into a four-neck flask with a stirrer, a condenser pipe, a thermometer and a nitrogen inlet, dissolving the hydroxyl hyperbranched polyester in a proper amount of DMF (dimethyl formamide), heating to completely dissolve the hydroxyl hyperbranched polyester, adding a certain amount of succinic anhydride and a catalyst N, N-dimethylbenzylamine (the molar ratio of the anhydride to the hydroxyl hyperbranched polyester is 7: 1) under the protection of nitrogen, heating to 85 ℃ after the hydroxyl hyperbranched polyester is dissolved, reacting to a theoretical acid value (half of the initial acid value), evaporating part of the solvent, reducing the reaction temperature to 50 ℃, neutralizing the reactant solution to a pH value of 7.0-8.0 by using 30 wt% of sodium hydroxide aqueous solution, and finally obtaining 40% of yellow transparent solution, namely the solution containing the dispersing aid-C.

The dispersions of this example were tested for solids content, viscosity and stability and the results are shown in Table 1.

Comparative example 2

The aqueous carbon nanotube dispersion provided by the comparative example comprises the following feeding components by mass content of 100 percent:

the preparation method comprises the following steps:

firstly weighing water and a dispersing agent according to a formula proportion, mechanically stirring for 10 minutes at 400rpm, then adding carbon nano tubes, stirring for 20 minutes at low speed of 600rpm by a high-speed dispersion machine, then stirring for 30 minutes at high speed of 1200rpm, dropwise adding a defoaming agent at a speed of 50g/min in the process of high-speed stirring, then introducing into a sand mill at 2000rpm, carrying out turbine grinding for 90 minutes, and stopping sanding to prepare uniform dispersion liquid; standing and defoaming to obtain carbon nanotube dispersion liquid for later use.

The effect of dispersing in water after 10 seconds by dropping 0.01g of the dispersion in 500mL of water is shown in FIG. 4, and the dispersion speed is slightly slower than that in example 2, indicating that the water solubility and dispersibility are slightly lower.

The dispersions of this example were tested for solids content, viscosity and stability and the results are shown in Table 1.

In the above examples and comparative examples, the acid value was measured by the following method:

accurately weighing 2g (accurate to 0.0001g) of resin sample in a dried conical flask, accurately adding 50mL of toluene-absolute ethyl alcohol mixed solvent, adding 3 drops of phenolphthalein indicator after dissolving, titrating by using a calibrated KOH solution of about 0.1mol/L under continuous shaking until pink, and keeping 30s for no continuous color change to obtain the end point. The volume amounts of the KOH standard solutions used are recorded. Simultaneously, a blank test is carried out by adopting a corresponding mixed solvent, and the volume amount of the KOH standard solution is recorded. The acid value (A) is calculated as follows:

in the formula: a-acid number of sample, mg KOH/g;

V₁titration of the sample consumes a volume, mL, of potassium hydroxide standard solution;

V₂titration of a blank test consumes a volume, mL, of potassium hydroxide standard solution;

C_KOH-concentration of potassium hydroxide standard solution, mol/L;

m-mass of sample, g.

Table 1 shows the results of the performance test of the dispersions of examples 1 to 2 and comparative examples 1 to 2

Case(s)	Solids content/%	Viscosity/cps	Stability of
				Example 1	12	110	No sedimentation for 90 days
Example 2	14	90	No sedimentation for 90 days
				Comparative example 1	12	200	After 90 days, there was a settlement
Comparative example 2	12	285	After 90 days, there was a settlement

It can be seen from the above examples and comparative examples that, after the dispersing aid is added, the viscosity of the carbon nanotube dispersion is reduced and the stability is improved under the steric hindrance and pi-pi action of the dispersing aid.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.