A microgel dispersion and preparation method thereof

Abstract

The present invention discloses a microgel dispersion and its preparation method. This dispersion, which can be selectively crosslinked, is obtained by free radical dispersion polymerization in an aliphatic hydrocarbon solvent. The dispersion comprises polymer nanoparticles of an ethylenically unsaturated monomer, a soluble dispersant for stabilizing the particles, and a hydrocarbon continuous phase. The dispersion particles have a particle size of 100 to 400 nm and a high refractive index. The material of the invention is suitable for use in coating compositions based on film-forming polymers, such as thermosetting acrylic or alkyd resins, containing aromatic or aliphatic hydrocarbon solvents.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile coating materials, and particularly relates to a microgel dispersion and a preparation method thereof. Background Art

[0002] Microgel dispersions consist of particles of approximately 0.01 to 0.8 microns stably dispersed in an organic solvent (primarily aliphatic hydrocarbons). They offer advantages over conventional solution-based resins in terms of low pollution, resource conservation, and ease of application. They are already widely used by major automakers in Europe and the United States, and practical application has also begun in China. Automotive coatings using microgel dispersions exhibit excellent rheological properties during application and demonstrate superior anti-sagging performance in one-coat-one-bake (1C1B) and two-coat-one-bake (2C1B) coating systems, particularly in automotive topcoats. Furthermore, as a high-solids component in 2C1B clearcoats, they offer substantial practical value and exhibit unique coating properties, such as drying properties, durability, and solvent resistance, compared to traditional solvent-based coatings.

[0003] Dispersants are crucial for controlling particle size during the polymerization of microgel dispersions. They stabilize highly polar polymer particles in less polar solvents. Key characteristics of dispersants are their average chain length, composition, and functional groups. Low-molecular-weight dispersants contain reactive double bonds, allowing the dispersant chains to covalently bond to the microgel particles, facilitating their dispersing and stabilizing effects. The morphology of the dispersant incorporated into the growing chains influences particle growth and stability. By reacting the epoxy groups of glycidyl (meth)acrylate with a copolymer composed of (meth)acrylic acid and its ester units containing carboxyl groups, the double bonds are randomly distributed between the chains. Uncontrolled placement of the double bonds within the dispersant chains results in multiple attachment sites for the dispersant on the particle surface.

[0004] By using a cobalt chain transfer agent during the free radical polymerization process to synthesize poly(meth)acrylic acid and its esters, each chain ends in a double bond, making it more effective than dispersants with double bonds randomly grafted onto the backbone. Dispersants with terminal double bonds can extend from their anchor point on the particle into the solvent, providing superior dispersion stability. Summary of the Invention

[0005] The object of the present invention is to provide a microgel dispersion and a preparation method thereof.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides a technical solution: a soluble dispersant, wherein the raw material formula of the soluble dispersant comprises the following raw materials in parts by weight: 15-50 parts of xylene, 5-20 parts of prepolymer, 20-80 parts of dropwise addition material A, 2-20 parts of dropwise addition material B, and 0.01-0.15 parts of terminator; the dropwise addition material A is composed of a mixture of at least one of acrylic acid and its ester monomers, vinyl monomers, and nitrile monomers and an initiator; the dropwise addition material B is composed of N ,N',N",N"'-(tetrafluoroborate)bis[M-(2,3-butanedione oxime)]cobalt(II) and bis(difluorodiphenylglyoxime boronate)cobalt are mixed with toluene to form the prepolymer; the raw material formula of the prepolymer includes the following raw materials in parts by weight: 45-70 parts of 2-hydroxystearic acid, 20-60 parts of xylene, 0.05-3 parts of p-toluenesulfonic acid, 2-12 parts of glycidyl methacrylate and 0.01-1 part of 2-(dimethylamino)isobutanol.

[0007] The preferred technical solution is: the acrylic acid and its ester monomers are at least one of methyl acrylate, n-butyl acrylate, methyl methacrylate, n-butyl methacrylate, isooctyl acrylate, isooctyl methacrylate, lauryl acrylate, lauryl methacrylate, acrylic acid, allyl (meth)acrylate, glycol di(meth)acrylate, divinylbenzene, hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate and methacrylic acid.

[0008] The preferred technical solution is: the vinyl monomer is at least one of styrene and N-phenyl substituted maleimide.

[0009] The preferred technical solution is: the nitrile monomer is acrylonitrile.

[0010] The preferred technical solution is: the terminator is catechol, and the initiator is tert-butyl peroxyethylhexanoate.

[0011] The preferred technical solution is: the preparation method of the prepolymer comprises: adding 2-hydroxystearic acid, xylene, and p-toluenesulfonic acid into a reaction container, heating until the acid value reaches 31 to 35 mgKOH / g; then cooling, adding glycidyl methacrylate and 2-(dimethylamino)isobutanol, and reacting until the acid value is less than or equal to 1 mgKOH / g to obtain a dispersant prepolymer.

[0012] To achieve the above-mentioned purpose and other related purposes, the technical solution provided by the present invention is: a method for preparing a soluble dispersant, characterized in that it includes: heating xylene and a prepolymer to 120-160°C, then adding dropwise material A and dropwise material B to the reaction system within 100-300 minutes, and keeping the temperature for 10-60 minutes after the addition is completed; then adding a terminator to terminate the reaction; then keeping the reaction at the reaction temperature for 50-200 minutes, and then cooling to room temperature to obtain a soluble dispersant.

[0013] To achieve the above-mentioned object and other related objects, the present invention provides a technical solution: a microgel dispersion, characterized in that the raw material formula of the microgel dispersion includes the following raw materials in parts by weight: 15-50 parts of a hydrocarbon solvent, 3-10 parts of a soluble dispersant according to any one of claims 1-6, 3-20 parts of a first drop-added material, 20-80 parts of a second drop-added material, 1-8 parts of a third drop-added material, and 1-9 parts of a fourth drop-added material; the first drop-added material includes an initiator and methyl methacrylate, the second drop-added material includes at least one of styrene, butyl acrylate, methacrylic acid, hydroxyethyl acrylate, divinylbenzene and hexanediol diacrylate and an initiator; the third drop-added material includes a chain transfer agent and a hydrocarbon solvent; and the fourth drop-added material includes an initiator and a hydrocarbon solvent.

[0014] The preferred technical solution is: the initiator is at least one of tert-butyl peroxyethylhexanoate, di-tert-butyl peroxide and azobisisoheptanenitrile; and the chain transfer agent is dodecanethiol.

[0015] A preferred technical solution is that the dispersed polymer in the microgel dispersion is insoluble in the dispersion medium in a dispersed state, and the solubility parameter difference between the dispersed polymer and the hydrocarbon solvent is greater than or equal to 2.

[0016] To achieve the above-mentioned and other related purposes, the present invention provides a technical solution: a method for preparing a microgel dispersion, characterized in that it comprises the following steps:

[0017] Step 1: Add a hydrocarbon solvent and a soluble dispersant to a reaction vessel, raise the temperature to 80-95°C, then add the first drop of feed within 5-20 minutes, and keep warm for 5-30 minutes;

[0018] Step 2: After the insulation is completed, the second and third drops of feed are added within 100-300 minutes, and then the fourth drop of feed is added within 5-20 minutes. The mixture is kept warm for 0.5-2 hours and cooled to room temperature to obtain a microgel dispersion.

[0019] The preferred technical solution is: the hydrocarbon solvent is at least one of n-hexane, n-heptane and n-nonane.

[0020] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0021] 1. The soluble dispersant prepared by the present invention is an amphiphilic polymer (hydrophilic and lipophilic polymer) formed by the polymerization of two components of different polarity. It has a lower polarity than the dispersion particles, and a reactive double bond is connected to the end of each dispersant molecule through chain transfer. The dispersant has a molecular weight (Mw) of less than 10,000 Da. During the dispersion polymerization process, it is covalently bonded to the polar chains of the dispersion particles, distributing itself more stably on the surface of the dispersion particles, thereby preventing flocculation and controlling particle size.

[0022] 2. The microgel dispersion of the present invention uses a soluble dispersant as a steric stabilizer to form protective micelles, and uses a peroxide free radical initiator or an azo initiator to initiate free radical polymerization of ethylenically unsaturated monomers in the protective micelles to obtain the microgel dispersion.

[0023] 3. By using a cobalt chain transfer agent during the free radical polymerization process to synthesize poly(meth)acrylic acid and its esters, the present invention ensures that each chain terminus contains a double bond, making it more effective than dispersants with double bonds randomly grafted at any position on the main chain. Dispersants with terminal double bonds can extend from their anchor point on the particle into the solvent, providing excellent dispersion stability.

[0024] 4. The selectively cross-linkable microgel dispersion of the present invention is obtained by free radical dispersion polymerization in an aliphatic hydrocarbon solvent. It comprises polymer nanoparticles of ethylenically unsaturated olefin monomers, a soluble dispersant for stabilizing the particles, and a hydrocarbon continuous phase. The dispersion particles have a particle size of 100 to 400 nm and a high refractive index. The material of the present invention is suitable for use in coating compositions based on film-forming polymers, such as thermosetting acrylic or alkyd resins, containing aromatic or aliphatic hydrocarbon solvents. DETAILED DESCRIPTION

[0025] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in these embodiments.

[0026] Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.

[0027] Example 1: Preparation method of a soluble dispersant

[0028] The preparation method of the soluble dispersant is as follows:

[0029] Table 1 Prepolymer

[0030] Element parts by weight 12-Hydroxystearic acid 53.5 Xylene 39.6 p-Toluenesulfonic acid 0.2 Glycidyl methacrylate 6.5 2-(Dimethylamino)isobutanol 0.2

[0031] Table 2 Soluble dispersant 1

[0032]

[0033]

[0034] First, prepare a dispersant prepolymer. Add 12-hydroxystearic acid, xylene, and p-toluenesulfonic acid to a reaction flask according to Table 1 and raise the temperature to 150°C until the acid value reaches 31-35 mgKOH / g. Then, cool the reaction to 140°C and add glycidyl methacrylate and 2-(dimethylamino)isobutanol. React until the acid value is less than 1 mgKOH / g to obtain the dispersant prepolymer.

[0035] The base material according to Table 2 was added to the reactor and heated to 140°C. Then, dropwise additions A and B were added dropwise to the reactor at a constant rate for 240 minutes, followed by an additional 30-minute hold. The reaction was terminated by adding a terminator. The reaction temperature was maintained for 120 minutes, followed by cooling to room temperature to obtain soluble dispersant 1.

[0036] Example 2: Preparation method of a soluble dispersant

[0037] The preparation method of the soluble dispersant is as follows:

[0038] Table 3 Soluble dispersant 2

[0039]

[0040]

[0041] The dispersant prepolymer is the same as that in Example 1.

[0042] The base material according to Table 3 was added to the reactor and heated to 140°C. Then, dropwise additions A and B were added dropwise to the reactor at a constant rate for 240 minutes, followed by an additional 30-minute hold. The reaction was terminated by adding a terminator. The reaction temperature was maintained for 120 minutes, followed by cooling to room temperature to obtain soluble dispersant 2.

[0043] Example 3: A microgel dispersion and its preparation method

[0044] The preparation method of microgel dispersion is as follows:

[0045] Table 4: Microgel Dispersion 1

[0046] Element parts by weight base material n-heptane 32 Soluble dispersant 1 8 First drop of feed Azobis(2,2-diisoheptylnitrile) 1 Methyl methacrylate 8 Second drop of feed Styrene 12 Butyl acrylate 17 Methacrylic acid 5 Hydroxyethyl acrylate 4.7 Hexanediol diacrylate 2.5 Azobis(2,2-diisoheptylnitrile) 2 The third drop of feed Dodecanethiol 0.8 n-heptane solvent 3 The fourth drop of feed Azobis(2,2-diisoheptylnitrile) 1 n-heptane 3

[0047] In the first step, the base material, wherein the soluble dispersant is from Example 1, is added to the reactor, the temperature is raised to 90° C., and then the first drop of material is added, the addition is completed within 10 minutes, and the temperature is kept for 15 minutes. In the second step, the second and third drops of material are added to the reactor, the additions are completed within 180 minutes, and then the fourth drop of material is added, the addition is completed within 10 minutes, the temperature is kept for 1 hour, and the temperature is cooled to room temperature to obtain microgel dispersion 1.

[0048] Example 4: A microgel dispersion and its preparation method

[0049] The preparation method of microgel dispersion is as follows:

[0050] Table 5 Microgel Dispersion 2

[0051] Element parts by weight base material n-heptane 32 Soluble dispersant 2 8 First drop of feed Azobis(2,2-diisoheptylnitrile) 1 Methyl methacrylate 8 Second drop of feed Styrene 12 Butyl acrylate 17 Methacrylic acid 5 Hydroxyethyl acrylate 4.7 Hexanediol diacrylate 2.5 Azobis(2,2-diisoheptylnitrile) 2 The third drop of feed Dodecanethiol 0.8 n-heptane 3 The fourth drop of feed Azobis(2,2-diisoheptylnitrile) 1 n-heptane 3

[0052] In the first step, the base material, wherein the soluble dispersant is from Example 2, is added to the reactor, the temperature is raised to 90° C., and then the first drop of material is added, the addition is completed within 10 minutes, and the temperature is kept for 15 minutes. In the second step, the second and third drops of material are added to the reactor, the additions are completed within 180 minutes, and then the fourth drop of material is added, the addition is completed within 10 minutes, the temperature is kept for 1 hour, and the temperature is cooled to room temperature to obtain microgel dispersion 2.

[0053] Example 5: A microgel dispersion and its preparation method

[0054] The preparation method of microgel dispersion is as follows:

[0055] Table 6: Microgel Dispersion 3

[0056] Element parts by weight base material n-heptane 32 Soluble dispersant 2 8 First drop of feed Azobis(2,2-diisoheptylnitrile) 1 Methyl methacrylate 8 Second drop of feed Styrene 12 Butyl acrylate 17 Methacrylic acid 5 Hydroxyethyl acrylate 4.7 Divinylbenzene 2.5 Azobis(2,2-diisoheptylnitrile) 2 The third drop of feed Dodecanethiol 0.8 n-heptane 3 The fourth drop of feed Azobis(2,2-diisoheptylnitrile) 1 n-heptane 3

[0057] In the first step, the base material, wherein the soluble dispersant is from the example, is added to the reactor, the temperature is raised to 90°C, and then the first drop of material is added, the addition is completed within 10 minutes, and the temperature is kept for 15 minutes. In the second step, the second and third drops of material are added to the reactor, the addition is completed within 180 minutes, and then the fourth drop of material is added, the addition is completed within 10 minutes, the temperature is kept for 1 hour, and the temperature is cooled to room temperature to obtain microgel dispersion 3.

[0058] Comparative Example 1

[0059] The preparation method of the soluble dispersant is as follows:

[0060] Table 7 Soluble dispersant 3

[0061]

[0062]

[0063] The dispersant prepolymer was prepared according to Example 1.

[0064] The base material according to Table 4 was added to the reactor and heated to 140°C. Then, dropwise additions A and B were added dropwise to the reactor at a constant rate for 240 minutes, followed by an additional 30-minute hold. The reaction was terminated by adding a terminator. The reaction temperature was maintained for 120 minutes, followed by cooling to room temperature to obtain soluble dispersant 3.

[0065] The preparation method of microgel dispersion is as follows:

[0066] Table 8: Microgel Dispersion 4

[0067]

[0068]

[0069] In the first step, the base material was added to the reactor and the temperature was raised to 90°C. Then, the dropwise material A was added and the mixture was dripped over 10 minutes and kept warm for 15 minutes. In the second step, the dropwise materials B and C were added to the reactor and the mixture was dripped over 180 minutes. Then, the dropwise material D was added and the mixture was dripped over 10 minutes. The mixture was kept warm for 1 hour and cooled to room temperature to obtain microgel dispersion 4.

[0070] Experimental results

[0071] The microgel dispersion was stored at 50°C for 14 days and then evaluated for appearance, fineness and particle size.

[0072] Table 9: Storage stability results

[0073] project Example 3 Example 4 Example 5 Comparative Example 1 Appearance Unstratified Unstratified Unstratified Slight delamination Fineness <5μm 10μm <5μm 50μm Particle size 78nm 105nm 84nm 213nm

[0074] As can be seen from the above table, compared with the microgel dispersions of the present invention (Examples 3, 4, and 5), the comparative example 1 in which no Co(II) dispersion stabilizer is used exhibits relatively poor storage stability.

[0075] The above description is only used to explain the preferred embodiments of the present invention and is not intended to limit the present invention in any form. Therefore, any modifications or changes made to the present invention under the same inventive spirit should still be included in the scope of protection intended by the present invention.

Claims

1. A soluble dispersant, characterized in that: The raw material formula of the soluble dispersant includes the following raw materials in parts by weight: 15-50 parts of xylene, 5-20 parts of prepolymer, 20-80 parts of drop material A, 2-20 parts of drop material B, and 0.01-0.15 parts of a terminator; the drop material A is composed of a mixture of at least one of acrylic acid and its ester monomers, vinyl monomers, and nitrile monomers and an initiator; the drop material B is composed of a mixture of at least one of N,N',N",N"'-(tetrafluoroborate)bis[M-(2,3-butanedione oxime)]cobalt(II) and bis(boronated difluorodiphenylglyoxime)cobalt, and toluene; the raw material formula of the prepolymer includes the following raw materials in parts by weight: 45-70 parts of 2-hydroxystearic acid, 20-60 parts of xylene, 0.05-3 parts of p-toluenesulfonic acid, 2-12 parts of glycidyl methacrylate, and 0.01-1 part of 2-(dimethylamino)isobutanol.

2. The soluble dispersant according to claim 1, wherein: The acrylic acid and its ester monomers are at least one of methyl acrylate, n-butyl acrylate, methyl methacrylate, n-butyl methacrylate, isooctyl acrylate, isooctyl methacrylate, lauryl acrylate, lauryl methacrylate, acrylic acid, allyl (meth)acrylate, glycol di(meth)acrylate, divinylbenzene, hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate and methacrylic acid.

3. The soluble dispersant according to claim 1, wherein: The vinyl monomer is at least one of styrene and N-phenyl substituted maleimide.

4. The soluble dispersant according to claim 1, characterized in that: The nitrile monomer is acrylonitrile.

5. The soluble dispersant according to claim 1, characterized in that: The terminator is catechol, and the initiator is tert-butyl peroxyethylhexanoate.

6. The soluble dispersant according to claim 1, characterized in that: The preparation method of the prepolymer includes: adding 2-hydroxystearic acid, xylene, and p-toluenesulfonic acid into a reaction container, heating until the acid value reaches 31-35 mgKOH / g; then cooling, adding glycidyl methacrylate and 2-(dimethylamino)isobutyl alcohol, and reacting until the acid value is less than or equal to 1 mgKOH / g to obtain a dispersant prepolymer.

7. A method for preparing the soluble dispersant according to any one of claims 1 to 6, characterized in that: include: Heat xylene and prepolymer to 120-160°C, then add dropwise material A and dropwise material B to the reaction system within 100-300 minutes, and keep warm for 10-60 minutes after the addition is completed; then add a terminator to terminate the reaction; then keep at the reaction temperature for 50-200 minutes, and then cool to room temperature to obtain a soluble dispersant.

8. A microgel dispersion, characterized in that: The raw material formula of the microgel dispersion includes the following raw materials in parts by weight: 15-50 parts of a hydrocarbon solvent, 3-10 parts of a soluble dispersant according to any one of claims 1-6, 3-20 parts of a first drop-added material, 20-80 parts of a second drop-added material, 1-8 parts of a third drop-added material, and 1-9 parts of a fourth drop-added material; the first drop-added material includes an initiator and methyl methacrylate; the second drop-added material includes at least one of styrene, butyl acrylate, methacrylic acid, hydroxyethyl acrylate, divinylbenzene and hexanediol diacrylate and an initiator; the third drop-added material includes a chain transfer agent and a hydrocarbon solvent; and the fourth drop-added material includes an initiator and a hydrocarbon solvent.

9. The microgel dispersion according to claim 8, characterized in that: The initiator is at least one of tert-butyl peroxyethylhexanoate, di-tert-butyl peroxide and azobisisoheptonitrile; and the chain transfer agent is dodecanethiol.

10. The microgel dispersion according to claim 8, characterized in that: The dispersed polymer in the microgel dispersion is insoluble in the dispersion medium in a dispersed state, and the solubility parameter difference between the dispersed polymer and the hydrocarbon solvent is greater than or equal to 2.

11. A method for preparing the microgel dispersion according to claim 8, characterized in that: The following steps are involved: Step 1: Add a hydrocarbon solvent and a soluble dispersant to a reaction vessel, raise the temperature to 80-95°C, then add the first drop of feed within 5-20 minutes, and keep warm for 5-30 minutes; Step 2: After the insulation is completed, the second and third drops of feed are added within 100-300 minutes, and then the fourth drop of feed is added within 5-20 minutes. The mixture is kept warm for 0.5-2 hours and cooled to room temperature to obtain a microgel dispersion.

12. The method for preparing a microgel dispersion according to claim 11, wherein: The hydrocarbon solvent is at least one of n-hexane, n-heptane and n-nonane.

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