CN107434842B

CN107434842B - Core-shell structure hydroxyl acrylic resin emulsion and preparation method and application thereof

Info

Publication number: CN107434842B
Application number: CN201610357368.2A
Authority: CN
Inventors: 韩强; 乔义涛; 刘旭阳; 马吉全; 张梓军; 张琴花; 孙家宽; 华卫琦
Original assignee: Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd
Priority date: 2016-05-26
Filing date: 2016-05-26
Publication date: 2020-07-28
Anticipated expiration: 2036-05-26
Also published as: CN107434842A

Abstract

The invention relates to a core-shell structure hydroxyl acrylic resin emulsion, a preparation method thereof and a water-based paint taking the resin as a film forming matter. The preparation method of the hydroxyl emulsion comprises the following steps: firstly, preparing an aqueous solution of acrylic resin A with low molecular weight by free radical polymerization, and then carrying out emulsion polymerization by replacing an emulsifier with the aqueous solution of A to prepare the hydroxyl acrylic resin emulsion. The resin consists of a shell A and a core B, wherein A is low molecular weight acrylic resin, and B is acrylic resin emulsion particles. The obtained hydroxyl acrylic emulsion is matched with an aqueous amino resin or an aqueous polyurethane curing agent to prepare a paint film which has the characteristics of high glossiness, high hardness, good chemical resistance and the like and can be used as a film forming material for preparing high-performance environment-friendly protective paint.

Description

Core-shell structure hydroxyl acrylic resin emulsion and preparation method and application thereof

Technical Field

The invention relates to a core-shell structure hydroxyl acrylic resin emulsion which is suitable for serving as a hydroxyl component in woodware coatings, water-based anticorrosive coatings and the like, and belongs to the field of industrial protective coatings.

Background

Acrylic resin has the advantages of good weather resistance, good chemical stability, high glossiness and the like, and is widely used in the field of coatings. The hydroxyl acrylic resin is matched with isocyanate or amino resin for use and is applied to bi-component polyurethane paint or amino baking paint, most of the hydroxyl acrylic resin in the existing woodware and metal protective paint is solvent type resin, more than 50 wt% of organic solvent is contained, and the solvents not only pollute the environment, but also damage the human health. With the stricter environmental protection requirements in the global scope, the water-based hydroxyl acrylic resin coating product is widely applied.

The aqueous hydroxy acrylic resin is classified into a dispersion type and an emulsion type according to different synthesis processes. The hydroxy acrylic resin dispersoid is obtained by synthesizing hydroxy acrylic resin containing hydrophilic carboxylate by a solution polymerization method and then dispersing. The hydroxyl content is higher, the prepared coating film has excellent chemical resistance, but the production process is complex, the molecular weight is low, most of the coating film contains higher organic solvent, and the cost is higher.

In contrast, the emulsion type hydroxy acrylic resin is prepared by adopting an emulsion polymerization process, the production process is simple, the cost is low, but the final performance of the prepared paint film is influenced by the conventional micromolecular emulsifier or reactive emulsifier. In addition, in the emulsion polymerization process, since macromolecular radicals are enclosed in emulsion particles isolated from each other, only the initial radicals (or active chains with extremely low molecular weight) diffused from the aqueous phase into the emulsion particles can undergo a chain termination reaction with the original radical chains in the emulsion particles, while the radicals in different emulsion particles do not collide with each other to cause a chain termination possibility. Therefore, compared with other free radical type polymerization processes, due to the isolation effect of the closed latex particles, the emulsion polymerization reaction has low chain termination rate and long service life of macromolecular free radicals, and can have sufficient time for chain growth, the molecular weight of the polymer prepared by the emulsion method is much larger than that of the polymer prepared by other polymerization methods, and the hydroxyl in the emulsion is easily embedded and cannot play a role in crosslinking in the film forming process due to the larger molecular weight, so that the final performance of a paint film is also influenced.

CN200510134997.0 discloses an emulsion type hydroxyl-containing acrylic resin with a core-shell configuration, wherein a reactive emulsifier with higher cost is adopted to reduce the influence of a conventional micromolecule emulsifier on a resin paint film, but the resin is prepared by a conventional emulsion polymerization method, and the obtained resin has higher molecular weight and is not beneficial to the crosslinking and film forming of the final resin.

CN201010118868.3 discloses an acrylate hybrid emulsion, which is prepared by a seed emulsion polymerization process and consists of large particles composed of polymers with rich hydroxyl groups on the surface layer and small particles composed of polymers with rich carboxylate on the surface layer, and has a high hydroxyl group content, but the synthesized acrylate hybrid emulsion is composed of various particles, the cost is high, and the resin contains a conventional small molecular emulsifier, which results in insufficient film forming resistance.

Therefore, there is a need to develop a novel hydroxyl acrylic resin emulsion with high gloss, high hardness, high resistance, and low cost to meet the application in wood coatings, water-based anticorrosive coatings, and the like.

Disclosure of Invention

The invention aims to provide a core-shell structure hydroxy acrylic resin emulsion, wherein hydroxy acrylic resin in the emulsion has a shell structure with lower molecular weight, so that hydroxy is not easy to embed, the hydroxy is easier to perform crosslinking reaction with a curing agent in a film forming process, and a prepared paint film has higher crosslinking density.

The invention also aims to provide a preparation method of the core-shell structure hydroxyl acrylic resin emulsion.

The invention also aims to provide the application of the resin emulsion composition in water-based paint, and the water-based paint prepared by the resin has the characteristics of high glossiness, high hardness, good chemical resistance and the like.

In order to achieve the above purpose, the invention is realized by the following technical scheme:

a core-shell structure hydroxyl acrylic resin emulsion comprises a shell A and a core B:

the raw materials for preparing the shell A comprise: alkyl (meth) acrylate and/or vinyl monomers, hydroxyalkyl (meth) acrylates, (alkyl) acrylic acids, neutralizing agents, initiators I, organic solvents and optionally chain transfer agents;

the raw materials for preparing the inner core B comprise: alkyl (meth) acrylate and/or vinyl monomers, optionally hydroxyalkyl (meth) acrylate, initiator II and redox initiator;

the acid value of the shell A is 50-250mgKOH/g, preferably 85-190 mgKOH/g; the hydroxyl value is 50-215mgKOH/g, preferably 104-190 mgKOH/g.

The mass ratio of A to B in the hydroxyl acrylic resin emulsion is 1:2-5:1, preferably 2:3-3: 2; the hydroxyl value of the emulsion is as follows: 18 to 195mgKOH/g, preferably: 70 to 160 mgKOH/g.

The solid content of the hydroxyacrylic resin emulsion of the present invention (i.e., the content of the hydroxyacrylic resin in the hydroxyacrylic resin emulsion) is 30 to 50% by weight, preferably 35 to 45% by weight, based on the total mass of the hydroxyacrylic resin emulsion.

In the invention, the raw materials for preparing the A are used in the following amounts by weight:

in the invention, the raw materials for preparing the B are used in the following weight portions:

in the raw materials for preparing A and B, the alkyl (meth) acrylate has 1-20 carbon atoms of alkyl group, and is independently selected from one or more of methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isooctyl (meth) acrylate, isobutyl (meth) acrylate, isobornyl (meth) acrylate, and the like, preferably one or more of methyl methacrylate, butyl acrylate, and isooctyl acrylate.

The vinyl monomers are respectively and independently selected from one or more of styrene, α -methyl styrene, vinyl acetate and the like, and styrene is preferred.

The hydroxyalkyl (meth) acrylate has an alkyl group having 1 to 20 carbon atoms, and is independently selected from one or more of hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate, preferably one or more of hydroxyethyl methacrylate, hydroxyethyl acrylate and hydroxypropyl acrylate, and more preferably hydroxyethyl methacrylate.

In the present invention, in the raw material for preparing a, the number of alkyl carbon atoms of the (alkyl) acrylic acid is 1 to 20, and preferably, the (alkyl) acrylic acid includes, but is not limited to, methacrylic acid and/or acrylic acid, and more preferably, methacrylic acid.

In the invention, a neutralizing agent is also required to be added in the process of preparing A, wherein the neutralizing agent is a basic compound, and comprises but is not limited to one or more of ammonia water, triethylamine, N-dimethylethanolamine, AMP-95, N-dimethylethanolamine, triethanolamine, sodium hydroxide, potassium hydroxide and the like, preferably one or more of N, N-dimethylethanolamine, triethylamine and ammonia water, more preferably ammonia water, and usually ammonia water with the concentration of 25 wt%; in the present invention, when ammonia water is contained in the neutralizing agent, the ammonia water is based on the mass of ammonia contained therein.

In the present invention, in the raw materials for preparing a, the initiator i includes, but is not limited to, one or more of Azobisisobutyronitrile (AIBN), Benzoyl Peroxide (BPO), di-t-butyl peroxide (DTBP), di-t-amyl peroxide (DTAP), etc., preferably Azobisisobutyronitrile (AIBN).

In the present invention, in the raw material for preparing a, the organic solvent includes, but is not limited to, one or more of ethanol, acetone, butyl cellosolve, xylene, and the like, preferably ethanol.

In the present invention, a chain transfer agent is optionally added during the preparation of A, and the chain transfer agent includes but is not limited to one or more of n-dodecyl mercaptan, isooctyl 3-mercaptopropionate, α -methylstyrene dimer and the like, preferably α -methylstyrene dimer.

The number average molecular weight Mn of the shell A is 500-10000, preferably 3000-8000.

In the invention, in the raw materials for preparing B, the initiator II is a water-soluble initiator, and includes but is not limited to one or more of ammonium persulfate, potassium persulfate, sodium persulfate and the like, and ammonium persulfate is preferred.

In the present invention, in the raw materials for preparing B, the redox initiator includes, but is not limited to, one or more of tert-butyl hydroperoxide (TBHP), tert-amyl hydroperoxide (TAHP), sodium bisulfite, sodium dithionite, isoascorbic acid, and the like, preferably tert-butyl hydroperoxide and/or isoascorbic acid, more preferably a mixture of tert-butyl hydroperoxide to isoascorbic acid in a mass ratio of 2: 1.

The preparation method of the core-shell structure hydroxyl acrylic resin emulsion comprises the following steps:

(1) adding an organic solvent into a reactor, heating, uniformly mixing raw materials (methyl) acrylic acid alkyl ester and/or vinyl monomers, (methyl) acrylic acid hydroxyalkyl ester, (alkyl) acrylic acid, 80-90wt% of initiator I based on the total amount of the initiator I and an optional chain transfer agent according to a ratio, adding the mixture into the reactor for reaction, then supplementing the rest initiator I and preserving heat to obtain a hydroxy acrylic resin solution, cooling to a temperature lower than the boiling point of the neutralizer, adding water and removing the organic solvent to obtain an aqueous solution of A;

(2) adding 40-80wt% of the aqueous solution A obtained in the step (1) into a pre-emulsifier, adding the raw material (methyl) acrylic acid alkyl ester and/or vinyl monomer for preparing B and optional (methyl) acrylic acid hydroxyalkyl ester according to the proportion, adding water and mixing to obtain a pre-emulsion;

(3) adding the rest A aqueous solution, 30-70wt% of initiator II based on the total amount of the initiator II and water into an emulsion polymerization kettle, and stirring to prepare a kettle bottom solution;

(4) and (3) adding the pre-emulsion obtained in the step (2) and the residual initiator II into the kettle bottom liquid obtained in the step (3), then adding a redox initiator, and keeping the temperature until the residual monomer is less than 100ppm, thus obtaining the hydroxyl acrylic resin emulsion with the shell A and the core B.

Wherein, the organic solvent in the step (1) is heated to the reaction temperature of 70-140 ℃, and the raw materials are dripped into the reactor after being uniformly mixed, wherein the dripping time is 3-12 hours, preferably 6-10 hours; after the rest of the initiator I is added, the heat preservation time is 1 to 2 hours.

Adding a neutralizing agent into the step (1) until the neutralization degree is 80-120%, adding water to the solid content of 30-50 wt% before removing the organic solvent, then removing the organic solvent to 500-2000ppm by reduced pressure distillation, and supplementing water to the solid content of 30-50 wt%, thus obtaining the aqueous solution A.

The pre-emulsion obtained in step (2) has a concentration of 45 to 70 wt.%, preferably 50 to 60 wt.%.

Heating the kettle bottom liquid in the step (4) to 60-85 ℃, and then dropwise adding the pre-emulsion and the initiator II into the kettle bottom liquid of the polymerization kettle for 2-8 hours, preferably 3-5 hours; the holding time after adding the redox initiator is 0.5-4 hours.

The invention further provides application of the core-shell structure hydroxyl acrylic resin emulsion in water-based paint. The core-shell structure hydroxy olefine acid resin emulsion prepared by the invention is used as a main film forming material of a water-based paint and is matched with an auxiliary agent, a color seasoning and the like for use.

The invention has the beneficial effects that:

the resin shell A in the hydroxyl acrylic resin emulsion is prepared by a solution polymerization method, has lower molecular weight, is not easy to embed hydroxyl, is easy to perform crosslinking reaction with a curing agent in a film forming process, and the prepared paint film has higher crosslinking density and provides high gloss and high tolerance; the inner core B is prepared by adopting an emulsion polymerization method, has higher molecular weight, plays a role in supporting a framework in a resin film forming process and provides high hardness.

Meanwhile, the emulsion does not contain a conventional micromolecular emulsifier or a reactive emulsifier, so that the influence of the residue of the emulsifier on the resin performance can be effectively avoided;

the paint prepared by the emulsion is green and environment-friendly, and can be used together with aqueous amino resin or aqueous polyurethane cross-linking agent to prepare aqueous amino baking paint or self-drying bi-component polyurethane paint.

The specific implementation mode is as follows:

the method according to the invention will be further illustrated by the following examples, but the invention is not limited to the examples listed, but also encompasses any other known modification within the scope of the claims of the invention.

Example 1

Preparation of an aqueous A-1 solution:

adding 300 parts (by mass, the same below) of xylene into a reaction vessel, and stirring and heating; 100 parts of styrene, 150 parts of hydroxyethyl methacrylate, 40 parts of methacrylic acid, 9 parts of di-tert-butyl peroxide (DTBP) and 2 parts of isooctyl 3-mercaptopropionate are added into a dropping pot and mixed uniformly. And dropwise adding the mixed monomer in the dropwise adding tank into the reaction vessel when the temperature of the reaction vessel rises to 130-140 ℃, wherein the dropwise adding time is 4 hours, and after the dropwise adding of the monomer is finished, 1 part of di-tert-butyl peroxide (DTBP) is added and the reaction temperature is kept for 1-2 hours. And (2) cooling to 30-50 ℃, adding 38 parts (by mass percent, based on the mass of ammonia contained in the solution) of ammonia water solution, then adding 400 parts of water, removing ethanol under reduced pressure, and supplementing water until the solid content of the resin aqueous solution is 40 wt% to obtain a resin A-1 aqueous solution, wherein the hydroxyl value is 215mgKOH/g, and the acid value is 85 mgKOH/g.

Example 2 to example 6

Aqueous solutions A-2, A-3, A-4, A-5 and A-6 were prepared according to the formulation of Table 1, respectively, under substantially the same conditions as in example 1, except that the components were in parts by mass.

TABLE 1 preparation of A-2, A-3, A-4, A-5 and A-6 raw materials data sheet

Examples 7-12 are methods for preparing core-shell structured hydroxyacrylic resin emulsions based on the aqueous resin A solutions prepared in examples 1-6, as follows:

example 7

100 parts of water and 347 parts of an aqueous solution of A-1 resin are introduced into a pre-emulsifier, stirred rapidly at 1000r/min for 5 minutes, after complete dissolution, 35.6 parts of MMA, 50 parts of St and 30 parts of HEA monomer mixture are added and stirring is continued. Adding 400g of water and the rest of the A-1 resin aqueous solution prepared in the example 1 into a reaction kettle with a stirring device, a condenser and a thermometer, stirring at 150r/min, heating to 80 ℃ after the solution is completely dissolved, adding 14 parts (mass fraction of 10 wt%) of APS aqueous solution into the reactor, respectively dropwise adding the pre-emulsion and 6 parts (mass fraction of 10 wt%) of APS aqueous solution by using a peristaltic pump, and finishing dropwise adding for 4 hours. After the pre-emulsion and the initiator solution are added, 10 parts of an isoascorbic acid aqueous solution (10 mass percent) and 2 parts of tert-butyl hydroperoxide are added into the reaction system and the temperature is kept for 1 hour. And (3) filtering and discharging when the temperature is reduced to 30-40 ℃ to obtain the product, wherein the solid content of the prepared hydroxyl acrylic resin emulsion is 30%, and the theoretical hydroxyl value is 195 mgKOH/g.

Example 8

100 parts of water and 400 parts of A-2 resin aqueous solution are added into a pre-emulsifier, quickly stirred for 5 minutes at 1000r/min, and after the water and the resin aqueous solution are completely dissolved, 200 parts of MMA, 200 parts of BA and 50 parts of HPA monomer mixed solution are added and stirred continuously. 400 parts of water and the rest of the aqueous solution of the A-2 resin prepared in example 2 were added to a reaction kettle equipped with a stirrer, a condenser and a thermometer, stirred at 150r/min, and after complete dissolution, the temperature was raised to 80 ℃, and then 20 parts (10 mass percent) of an aqueous solution of potassium persulfate was added to the reactor, and then the preemulsion and 20 parts (10 mass percent) of an aqueous solution of potassium persulfate were added dropwise by a peristaltic pump, and the dropwise addition was completed within 4 hours. After the pre-emulsion and the initiator solution are added, 20 parts of an isoascorbic acid aqueous solution (mass fraction: 10%) and 4 parts of tert-butyl hydroperoxide are added into the reaction system and the temperature is kept for 1 hour. And filtering and discharging the material to obtain the product when the temperature is reduced to 30-40 ℃. The solid content of the prepared hydroxyl acrylic resin emulsion is 42 percent, and the theoretical hydroxyl value is as follows: 70 mgKOH/g.

Example 9

200 parts of water and 300g A-3 parts of an aqueous resin solution are added to a pre-emulsifier and rapidly stirred at 1000r/min for 5 minutes, after complete dissolution, 100 parts of EHA and 564 parts of St monomer mixture are added and stirring is continued. 700 parts of water and the rest of the aqueous solution of the resin A-3 prepared in example 3 were added to a reaction kettle equipped with a stirrer, a condenser and a thermometer, stirred at 150r/min, and after complete dissolution, the temperature was raised to 80 ℃, and then 20 parts (10 mass percent) of an aqueous solution of sodium persulfate was added to the reactor, and then the pre-emulsion and 46.4 parts (10 mass percent) of an aqueous solution of sodium persulfate were added dropwise by a peristaltic pump, and the dropwise addition was completed within 4 hours. After the pre-emulsion and the initiator solution were added, 30 parts of an isoascorbic acid aqueous solution (10% by mass) and 6 parts of t-butyl hydroperoxide were added to the reaction system and the temperature was maintained for 1 hour. And filtering and discharging the material to obtain the product when the temperature is reduced to 30-40 ℃. The solid content of the prepared hydroxyl acrylic resin emulsion is 50 percent, and the theoretical hydroxyl value is as follows: 18 mgKOH/g.

Example 10

100 parts of water and 400 parts of an A-4 resin aqueous solution are added into a pre-emulsifier, rapidly stirred for 5 minutes at 1000r/min, and after complete dissolution, 149 parts of MMA, 140 parts of St and 20 parts of HEMA monomer mixed solution are added and stirring is continued. 300 parts of water and the residual A-4 resin aqueous solution prepared in example 4 were added to a reaction kettle equipped with a stirrer, a condenser and a thermometer, stirred at 150r/min, and after complete dissolution, the temperature was raised to 80 ℃, and then 16 parts (mass fraction 10%) of an APS aqueous solution was added to the reactor, and then the pre-emulsion and 16 parts (mass fraction 10%) of the APS aqueous solution were added dropwise by a peristaltic pump, and the addition was completed over 4 hours. After the pre-emulsion and the initiator solution were added, 16g of an aqueous solution of erythorbic acid (10% by mass) and 3.2 parts of t-butyl hydroperoxide were added to the reaction system and the temperature was maintained for 1 hour. And filtering and discharging the material to obtain the product when the temperature is reduced to 30-40 ℃. The prepared hydroxyl acrylic resin emulsion contains about 40 percent of solid content, and has the hydroxyl value: about 80 mgKOH/g.

Example 11

500 parts of an aqueous A-5 resin solution are added to a pre-emulsifier and rapidly stirred at 1000r/min for 5 minutes, after complete dissolution, 80 parts of St are added and stirring is continued. 100 parts of water and the rest of the aqueous solution of the A-4 resin prepared in example 4 were added to a reaction kettle equipped with a stirrer, a condenser and a thermometer, stirred at 150r/min, and after complete dissolution, the temperature was raised to 80 ℃, and then the pre-emulsion and 10 parts (mass fraction: 10%) of the aqueous solution of APS were added dropwise by a peristaltic pump, respectively, after 2 hours. After the pre-emulsion and the initiator solution were added, 1g of an aqueous solution of erythorbic acid (10% by mass) and 0.7 part of t-butyl hydroperoxide were added to the reaction system and the temperature was maintained for 1 hour. And filtering and discharging the material to obtain the product when the temperature is reduced to 30-40 ℃. The prepared hydroxyl acrylic resin emulsion contains about 40 percent of solid content, and has the hydroxyl value: about 161 mgKOH/g.

Example 12

Adding 400 parts of water and 400 parts of an A-6 resin aqueous solution into a pre-emulsifier, quickly stirring for 5 minutes at 1000r/min, after complete dissolution, adding 100 parts of MMA, 90 parts of St and 80 parts of EHA monomer mixed solution, and continuing stirring. 400 parts of water and the rest of the A-4 resin aqueous solution prepared in example 4 are added into a reaction kettle with a stirring device, a condenser and a thermometer, stirred at 150r/min, heated to 80 ℃ after being completely dissolved, and then 20 parts (mass fraction 10%) of APS aqueous solution are added into the reaction kettle, and then the pre-emulsion and 20 parts (mass fraction 10%) of APS aqueous solution are respectively added dropwise by a peristaltic pump, and the dropwise addition is finished within 4 hours. After the pre-emulsion and the initiator solution were added, 20g of an isoascorbic acid aqueous solution (10% by mass) and 4 parts of t-butyl hydroperoxide were added to the reaction system and the temperature was maintained for 1 hour. And filtering and discharging the material to obtain the product when the temperature is reduced to 30-40 ℃. The prepared hydroxyl acrylic resin emulsion contains about 40 percent of solid content, and has the hydroxyl value: about 76 mgKOH/g.

Example 13

The hydroxyl acrylic resin emulsions prepared in examples 7 to 12 were used for the preparation of the properties of the one-component amino stoving varnish in the following manner:

(1) under the dispersion condition of 1000R/min, water BYK190, Tego910W and titanium dioxide R-706 are added to prepare white slurry.

(2) The hydroxy acrylic resin emulsions prepared in examples 5 to 8 were added separately under dispersion conditions of 500r/min, followed by addition of N, N-dimethylethanolamine, water and stirring for 20 min.

(3) Adding a proper amount of amino resin 325 from Cyanote corporation, uniformly stirring, adding a proper amount of thickener and/or film-forming aid to adjust to a proper viscosity, finally adding the white slurry prepared in the step (1), adding water to adjust until the solid content is about 25%, and fully stirring to obtain the single-component amino baking varnish white paint.

(4) The paint films were baked at 180 ℃ for 20min, and the properties of the paint films obtained from the hydroxy acrylic resin emulsions of examples 7-12 are shown in Table 2.

Comparative example

Adding 150 parts of water and 2 parts of sodium dodecyl sulfate into a pre-emulsifier, quickly stirring for 5 minutes at 1000r/min, after complete dissolution, adding 40 parts of MMA, 100 parts of St, 50 parts of BA and 15 parts of HMEA monomer mixed solution, and continuously stirring for 30 minutes at 1000r/min to obtain stable pre-emulsion. Adding 150 parts of water and 2 parts of sodium dodecyl sulfate into a reaction kettle with a stirring device, a condenser and a thermometer, quickly stirring at 1000r/min, adding 10 parts of MMA and 20 parts of St mixed solution after complete dissolution, and quickly stirring at 1000r/min for 10 min. And (3) reducing the stirring speed to 120r/min, heating to 80 ℃, adding 5 parts (mass fraction of 10%) of APS aqueous solution into the reactor to initiate polymerization for 30min, dropwise adding the pre-emulsion and 20 parts (mass fraction of 10%) of APS aqueous solution by using a peristaltic pump and a syringe pump respectively, and finishing dropwise adding for 4 hours. 5 parts of an aqueous sodium hydrogen sulfite solution (mass fraction: 10%) and 1 part of t-butyl hydroperoxide were added to the reaction system within 0.5 hour after the completion of the addition of the pre-emulsion and the initiator solution and the mixture was kept at 90 ℃ for 1 hour to remove the residual monomers. And (3) filtering and discharging when the temperature is reduced to 30-40 ℃ to obtain a product, wherein the solid content of the resin solution is about 44%, and the hydroxyl value is as follows: 45 mgKOH/g. The resin solution obtained was subjected to paint film preparation according to the procedure of example 13, the properties of which are specified in Table 2.

TABLE 2 paint film Properties Table

It can be seen from the above that: the core-shell structure hydroxyl acrylic resin emulsion prepared by the invention is obtained by emulsion polymerization, the molecular weight is higher, the shell resin has higher hydroxyl content, and more crosslinking points can be provided in the film forming process.

The paint film prepared by the emulsion has high hardness, high luster and good solvent resistance. The hydroxyl acrylic resin emulsion prepared by the invention has low VOC content, is an excellent base material for preparing high-performance environment-friendly industrial anti-corrosion and decorative paint, and can be widely applied to coating systems in various fields including metal, wood ware, glass and the like.

Claims

1. A core-shell structure hydroxyl acrylic resin emulsion comprises a shell A and a core B:

the acid value of the shell A is 85-190 mgKOH/g; the hydroxyl value is 50-215 mgKOH/g;

the dosage of the raw materials for preparing the A is as follows according to the parts by weight:

100-220 parts of alkyl (meth) acrylate and/or vinyl monomer;

40-180 parts of hydroxyalkyl (meth) acrylate;

30-135 parts of (alkyl) acrylic acid;

5-10 parts of an initiator I;

5-22 parts of a neutralizing agent;

0-2 parts of a chain transfer agent;

120 portions of organic solvent and 300 portions;

the dosage of each raw material for preparing the B is as follows according to parts by weight:

80-670 parts of (methyl) acrylic acid alkyl ester and/or vinyl monomer;

0-50 parts of hydroxyalkyl (meth) acrylate;

1-6.7 parts of an initiator II;

2-9 parts of redox initiator;

the mass ratio of A to B in the emulsion is 1:2-5: 1;

the vinyl monomers used for preparing the shell A and the inner core B are respectively and independently selected from one or more of styrene, α -methyl styrene and vinyl acetate;

the preparation method of the hydroxyl acrylic resin emulsion comprises the following steps:

(1) adding an organic solvent into a reactor, heating, uniformly mixing raw materials (methyl) acrylic acid alkyl ester and/or vinyl monomer, (methyl) acrylic acid hydroxyalkyl ester, (alkyl) acrylic acid, 80-90wt% of initiator I based on the total amount of the initiator I and an optional chain transfer agent according to a ratio, adding the mixture into the reactor for reaction, then supplementing the rest initiator I and preserving heat to obtain a hydroxy acrylic resin solution, cooling to a temperature lower than the boiling point of the neutralizer, adding water and removing the organic solvent to obtain an aqueous solution of A;

2. The hydroxyacrylic resin emulsion of claim 1, wherein the hydroxyl value of the shell A is 190mgKOH/g and 104-.

3. The hydroxyacrylic resin emulsion according to claim 1, characterized in that the hydroxyl number of the emulsion is: 70 to 160 mgKOH/g.

4. The hydroxyacrylic resin emulsion according to claim 1, characterized in that the mass ratio of A to B in the emulsion is 2:3-3: 2; the hydroxyl value of the emulsion is as follows: 70 to 160 mgKOH/g.

5. The hydroxyacrylic resin emulsion according to claim 1, wherein the raw materials for preparing the A are used in the following amounts, in parts by weight:

140-200 parts of alkyl (meth) acrylate and/or vinyl monomer;

80-150 parts of hydroxyalkyl (meth) acrylate;

40-100 parts of (alkyl) acrylic acid;

7-9 parts of an initiator I;

9-12 parts of a neutralizing agent;

0-1.5 parts of a chain transfer agent;

150 portions of organic solvent and 250 portions of organic solvent.

6. The hydroxyacrylic resin emulsion according to claim 1, characterized in that the raw materials for preparing B are used in the following amounts, in parts by weight:

85-400 parts of alkyl (methyl) acrylate and/or vinyl monomer;

0-30 parts of hydroxyalkyl (meth) acrylate;

2-4 parts of an initiator II;

3-6 parts of redox initiator.

7. The hydroxyacrylic resin emulsion according to any one of claims 1 to 6, characterized in that,

the hydroxyalkyl (meth) acrylate used for preparing the shell A and the core B has an alkyl group having 1 to 20 carbon atoms.

8. The hydroxyacrylic resin emulsion according to claim 1, characterized in that the vinyl monomer used for preparing the shell A and the core B is styrene;

the hydroxyalkyl (meth) acrylates used to prepare shell a and core B are each independently selected from one or more of hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate.

9. The hydroxyacrylic resin emulsion of claim 8, wherein the hydroxyalkyl (meth) acrylates used for preparing the shell A and the core B are each independently one or more selected from hydroxyethyl methacrylate, hydroxyethyl acrylate and hydroxypropyl acrylate.

10. The hydroxyacrylic resin emulsion according to claim 9, characterized in that the hydroxyalkyl (meth) acrylate used for preparing the shell a and the core B is hydroxyethyl methacrylate.

11. The emulsion of claim 1, wherein the alkyl group of the alkyl (meth) acrylate used for preparing the shell A and the core B has 1 to 20 carbon atoms.

12. The hydroxyacrylic resin emulsion according to claim 11, wherein the alkyl (meth) acrylates used for preparing the shell a and the core B are each independently selected from one or more of methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isooctyl (meth) acrylate, isobutyl (meth) acrylate, and isobornyl (meth) acrylate.

13. The hydroxyacrylic resin emulsion of claim 12, wherein the alkyl (meth) acrylates used to prepare shell a and core B are each independently selected from one or more of methyl methacrylate, butyl acrylate and isooctyl acrylate.

14. The hydroxyacrylic resin emulsion according to any one of claims 1 to 6, characterized in that the (alkyl) acrylic acid has an alkyl group having 1 to 20 carbon atoms.

15. The hydroxyacrylic resin emulsion according to claim 14, characterized in that the (alkyl) acrylic acid is methacrylic acid and/or acrylic acid.

16. The hydroxyacrylic resin emulsion according to claim 15, characterized in that the (alkyl) acrylic acid is methacrylic acid.

17. The hydroxyacrylic resin emulsion according to any one of claims 1 to 6, characterized in that the neutralizing agent is a basic compound;

the initiator I is one or more of azodiisobutyronitrile, benzoyl peroxide, di-tert-butyl peroxide and di-tert-amyl peroxide;

the organic solvent is one or more of ethanol, acetone, ethylene glycol monobutyl ether and xylene.

18. The hydroxyacrylic resin emulsion of claim 17, wherein the neutralizing agent is one or more of ammonia, triethylamine, N-dimethylethanolamine, AMP-95, triethanolamine, sodium hydroxide, and potassium hydroxide.

19. The hydroxyacrylic resin emulsion of claim 18, wherein the neutralizing agent is one or more of N, N-dimethylethanolamine, triethylamine and ammonia water.

20. The hydroxyacrylic resin emulsion according to claim 19, characterized in that the neutralizing agent is ammonia;

the initiator I is azobisisobutyronitrile;

the organic solvent is ethanol.

21. The hydroxyacrylic resin emulsion according to any one of claims 1 to 6, characterized in that,

the chain transfer agent is one or more of n-dodecyl mercaptan, isooctyl 3-mercaptopropionate and α -methyl styrene dimer;

the initiator II is a water-soluble initiator; the redox initiator is the combination of one or more of tert-butyl hydroperoxide and tert-amyl hydroperoxide and one or more of sodium bisulfite, sodium hydrosulfite and isoascorbic acid.

22. The hydroxyacrylic resin emulsion according to claim 21, characterized in that,

the chain transfer agent is α -methyl styrene dimer;

the initiator II is one or more of ammonium persulfate, potassium persulfate and sodium persulfate;

the redox initiator is tert-butyl hydroperoxide and erythorbic acid.

23. The acrylic emulsion according to claim 22,

the initiator II is ammonium persulfate;

the redox initiator is tert-butyl hydroperoxide and erythorbic acid, and the mass ratio of the tert-butyl hydroperoxide to the erythorbic acid is 2: 1.

24. Use of the core-shell hydroxyl acrylic resin emulsion of any one of claims 1 to 6 in water-based coatings.