CN101787098B - Preparation method and application of acrylate hybrid emulsion - Google Patents

Abstract

The invention discloses a preparation method and an application of an acrylate heterozygotic emulsion. In the invention, the acrylate heterozygotic emulsion is synthesized by adopting a seed emulsion polymerization process and combining a process of instantly neutralizing and segmentally adding polar monomers. The acrylate heterozygotic emulsion comprises macroparticles consisting of polymers P2 rich in hydroxyl groups on a surface layer and microparticles consisting of polymers P1 rich in carboxylate on the surface layer. Compared with a conventional hydroxy acrylate emulsion, the acrylate heterozygotic emulsion has smaller mean grain size and wider grain size distribution on emulsion particles. The acrylate heterozygotic emulsion can be adopted to prepare aqueous bi-component polyurethane wood coatings, and a coating layer of the coating has excellent property of resisting water and solvents, high crosslinking density and hardness, good mechanical property, scratching resistance and wear resistance. The acrylate heterozygotic emulsion has compact coating structure, high glossiness and better combination property, and not only can be applied to high-grade wood coatings, but also can be applied to automotive refinish paint, metallic anti-corrosion paint, other industrial protective paint, and the like.

Description

Preparation method and application of acrylate hybrid emulsion

technical field

The present invention relates to the preparation method of acrylate hybrid emulsion and its application, in particular to the preparation method of acrylate hybrid emulsion and its application in the preparation of water-based two-component polyurethane wood coatings;

Background technique

At present, the industrial coating and civil decoration industries have put forward higher requirements for the performance, safety, energy saving and environmental protection of coatings. Waterborne two-component acrylic polyurethane coatings are high-quality coatings with both performance and environmental protection. It not only has solvent The two-component polyurethane coating has the advantages of high hardness, good medium resistance, low film forming temperature and strong adhesion, and low volatile organic compound (VOC) content. It has great potential in the fields of wood furniture, automobiles, metal anticorrosion and industrial protection. Broad application prospects.

Waterborne two-component acrylate polyurethane coating is composed of hydrophilic modified (or unmodified) low viscosity polyisocyanate curing agent (A component) containing isocyanate group (NCO) and hydroxyl (OH) waterborne polyacrylate Polyol (B component) composition. The content of B-component water-based hydroxyacrylic resin in water-based two-component coatings is relatively high. It has adjustable polymer structure, designable emulsion particle configuration, and can also impart various functions to the coating film (such as waterproof, anti-skid, Fire protection and anti-mold, etc.), are the decisive factors for the performance of waterborne two-component polyurethane coatings.

Water-based hydroxyacrylic resin can be divided into two types: hydroxyacrylic acid aqueous dispersion type and hydroxyacrylic acid emulsion type according to the preparation method. The aqueous dispersion of hydroxyacrylic acid is obtained by synthesizing hydroxyacrylic acid polymer containing hydrophilic carboxylate through solvent polymerization, and then dispersing it in water under the action of mechanical shearing force. U.S. Patent USP5876802 (1999.3.2) reported a kind of polyester polyol modified with organic fluorine as hydroxyl component, mixed with polyisocyanate curing agent to prepare a waterborne two-component polyurethane coating with excellent physical and chemical properties, There are defects such as low solid content, low polymer weight average molecular weight and high VOC content. Hydroxyacrylate emulsion is prepared by emulsion polymerization. U.S. Patent USP 7402632 (2008.7.22) reports a functional group-terminated polyacrylate emulsion, and isocyanate curing agent to prepare water-based two-component polyurethane coatings, which can be cured at room temperature , the coating film has good weather resistance, adhesion and stain resistance, but there are disadvantages such as low hydroxyl content, low solid content, poor dispersion of polyurethane curing agent, and poor appearance of the two-component coating film. .

Waterborne two-component polyurethane coatings have excellent performance and environmental protection, and have broad market prospects. However, due to the weak emulsification ability of the hydroxyl component on the curing agent, uneven mixing, excessive emulsifier residues in the coating film, and many side reactions involved in the film formation process, resulting in poor appearance of the coating film of waterborne two-component polyurethane coatings , The gloss is not high, the physical and chemical properties of the coating film are not good, and other defects restrict the further development and application of water-based two-component polyurethane coatings.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art, and provide a preparation method and application of acrylate hybrid emulsion. Aiming at the problems that the hydroxyl group component of waterborne two-component polyurethane coatings has poor emulsification ability to hydrophilic modified curing agent, and the hydroxyl value of hydroxyacrylate emulsion is not high and the content of emulsifier is too high, it provides a high hydroxyl value self-emulsifying High capacity acrylate hybrid emulsion. The acrylate hybrid emulsion prepared by the invention is used to prepare water-based two-component polyurethane coatings, and its coating layer has excellent water resistance and solvent resistance, high crosslink density and high hardness, good mechanical properties, scratch resistance and wear resistance ;The coating structure is dense, the gloss is high, and the overall performance is good. It can be used not only in high-grade wood coatings, but also in automotive refinishing paints, metal anti-corrosion paints and other industrial protective paints.

The present invention adopts the seed emulsion polymerization process, combined with instant neutralization and polar monomers (containing carboxylic acid monomers and hydroxyl-containing monomers) and other processes to synthesize the hydroxyl value of 15 ~ 120mgKOH/g (solid resin), Acrylate hybrid emulsion (PAH) with a solid content of 45-50%. The PAH emulsion is composed of large particles composed of the surface layer of hydroxyl-rich polymer _P2 and the surface layer of small particles composed of carboxylate-rich polymer _P1 . Compared with conventional hydroxyacrylate emulsions, PAH latex particles have smaller average particle size and wider particle size distribution. PAH is used to prepare waterborne two-component polyurethane wood coatings. The coating film has excellent water resistance and solvent resistance, high crosslink density and high hardness, good mechanical properties, scratch resistance and wear resistance; the coating structure is dense and glossy High, good overall performance, not only can be used in high-grade wood coatings, but also in automotive refinishing paints, metal anti-corrosion paints and other industrial protective paints.

The purpose of the present invention is achieved through the following technical solutions:

The preparation method of acrylate hybrid emulsion comprises the steps:

(1) Add water, emulsifier and buffering agent into the reaction kettle, stir at 70-85°C for 10-30 minutes, then add the mixture of alkyl methacrylate, alkyl acrylate and alkacrylic acid dropwise at a uniform speed , drop the aqueous solution of initiator simultaneously, drop in 10～30 minutes, after the emulsion is blue phase, keep warm for 15～45 minutes, obtain seed emulsion, the parts by weight of raw materials are as follows:

45-55 parts of water

Emulsifier 0.2～2 parts

Buffer 0.1～0.5 parts

Alkyl methacrylate 1-5 parts

Alkyl Acrylate 1~5 parts

Alkylacrylic acid 0.05～0.25 parts

Initiator 0.01～0.05 parts;

(2) Keeping the temperature of the reaction system at 75-85°C, add alkyl methacrylate, alkyl acrylate, alkacrylic acid and hydroxyalkyl methacrylate or hydroxyalkyl acrylate dropwise at a constant speed to the seed emulsion The mixture is added dropwise with the aqueous solution of initiator and neutralizer at the same time to adjust the pH of the reaction system to 7.5-9.0. After 1-3 hours of dropwise addition, it is kept at 75-85° C. for 30-90 minutes; the parts by weight of raw materials are as follows:

Alkyl methacrylate 10-25 parts

Alkyl Acrylate 2～5 parts

2-5 parts of hydroxyalkyl methacrylate or hydroxyalkyl acrylate

Alkyl acrylic acid 1~3 parts

Initiator 0.05～0.15 parts;

(3) in the reaction system, add dropwise the mixture of alkyl methacrylate, alkyl acrylate, functional amides and hydroxyalkyl methacrylate or hydroxyalkyl acrylate, and drop the aqueous solution of initiator simultaneously, After 1-3 hours of dropwise addition, keep the temperature at 75-85°C for 30-90 minutes, and cool down to below 60°C to obtain acrylate hybrid emulsion. The parts by weight of raw materials are as follows:

Alkyl methacrylate 2～10 parts

Alkyl Acrylate 2～10 parts

5-10 parts of hydroxyalkyl methacrylate or hydroxyalkyl acrylate

Functional amide 0～2 parts

Initiator 0.05-0.1 parts.

The number of carbon atoms in the alkyl group of the alkyl acrylate is 1-20; the number of carbon atoms in the alkyl group of the alkyl methacrylate is 1-20; the number of carbon atoms in the alkyl group of the hydroxyalkyl acrylate is 1-20; The number of carbon atoms in the alkyl group of the hydroxyalkyl methacrylate is 1-20; the number of carbon atoms in the alkyl group of the alkacrylic acid is 1-20.

The functional amides include acrylamide, diacetone acrylamide, N-methylolacrylamide, methacrylamide, N,N-dimethylacrylamide, ethylene urea ethoxy methacrylate, formazan tert-butylaminoethyl acrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate, tetrahydrofuryl methacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethyl One or more of acrylate or 1,6-hexanediol acrylate.

The alkyl acrylate includes more than one of methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, isobornyl acrylate, hexyl acrylate or isooctyl acrylate;

The alkyl methacrylate includes methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, isobornyl methacrylate, hexyl methacrylate or methacrylic acid More than one of isooctyl esters;

The hydroxyalkyl methacrylate includes more than one of -β-hydroxyethyl methacrylate or -β-hydroxypropyl methacrylate;

The hydroxyalkyl acrylate includes more than one of 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate or 6-hydroxyhexyl acrylate;

The alkacrylic acid includes more than one of methacrylic acid, acrylic acid, itaconic acid or octadecenoic acid;

Described emulsifying agent is the mixture of anionic surfactant and nonionic surfactant, and the weight ratio of anionic surfactant and nonionic surfactant is 1: 4～4: 1, and described anionic surfactant is dodecane Sodium phenyl sulfonate, sodium lauryl sulfate, disodium alkyl diphenyl ether sulfonate (DSB), disodium ethoxysulfosuccinate (A-102), sodium vinylsulfonate (SVS) Or one or a mixture of two or more in sodium alkyl amido vinyl sulfonate (DNS-86); the nonionic surfactant is CO-893 or CO of OP-10, TX-100, Rohdia company -One or a mixture of two or more of 897.

The initiator is a persulfate or a redox system, and the concentration of the aqueous solution of the initiator is 1% to 5% by weight.

Persulfate such as potassium persulfate or ammonium persulfate, redox system such as sodium bisulfite-potassium persulfate, hydrogen peroxide-ferrous chloride, potassium persulfate-ferrous chloride or cumene hydroperoxide- Ferrous chloride.

The buffering agent is sodium carbonate and/or sodium bicarbonate.

The neutralizer is an alkaline compound.

The neutralizing agent includes one or a mixture of two or more of ammonia water, triethylamine, N,N-dimethylethanolamine, AMP-95 or sodium hydroxide.

The number-average relative average molecular weight of the obtained acrylate hybrid emulsion is 10 ³ to 10 ⁶ , the molecular weight distribution is 1.0 to 50, the latex particle size is less than 300 nm, the solid content of the dispersion is 45 to 50%, and the hydroxyl value is 15 to 120 mgKOH/g. Among them, the glass transition temperature of the acrylate polymer is 20-80°C.

Another object of the present invention is to apply the acrylate hybrid emulsion of the present invention to prepare waterborne two-component polyurethane coatings.

Add the wetting agent, co-solvent, defoamer and thickener into the stirring tank, disperse for 10-30 minutes, then slowly add the acrylate hybrid emulsion into the stirring tank, and stir at medium speed Stir for 30-60 minutes, adjust the pH of the coating with ammonia water to 8.0-9.0, filter the material, then add a hydrophilic modified polyisocyanate curing agent to the filtered acrylate hybrid emulsion, and stir rapidly for 5-20 minutes , add water to dilute to the specified viscosity of 30-200cps, stand and filter to obtain high-performance water-based two-component polyurethane coatings;

Described polyisocyanate solidifying agent comprises hexamethylene diisocyanate (HDI), trimer of isophorone diisocyanate (IPDI) and unmodified HDI of sulfonate, carboxylate and alkoxyl hydrophilic modification And one or more mixtures of IPDI trimer.

The wetting agent is one or more mixtures of TEGO-245, TEGO-500 of TEGO Company or BYK-346 of BYK Company; the co-solvent is ethylene glycol ethyl ether, ethylene glycol butyl ether, One or more mixtures of ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol methyl ether acetate or dipropylene glycol butyl ether acetate; the defoamer is TEGO’s One or more mixtures of TEGO-800, TEGO-805, TEGO-810, TEGO-815, TEGO-825, BYK's BYK-019 or BYK-020; the thickener is alkali-swellable acrylate or One or more mixtures of polyurethane associative thickeners.

The preparation method of the water-based two-component polyurethane coating is characterized in that the weight ratio of the hydroxyl resin to the curing agent is 1:1-4:1.

The coating layer of the water-based two-component polyurethane wood coating has excellent water resistance and solvent resistance, high crosslink density and high hardness, good mechanical properties, scratch resistance and wear resistance; the coating structure is dense and the gloss is high , Good overall performance. It can be used not only in high-grade wood coatings, but also in automotive refinishing paints, metal anti-corrosion paints and other industrial protective paints.

Basic principle of the present invention:

The coating film performance of waterborne two-component polyurethane coatings is determined by the crosslinking density of the coating film (physical mechanical and chemical properties of the coating film) and the compatibility between components (the appearance and decorative properties of the coating film). The crosslinking density of the coating film is determined by the concentration of OH groups and the reaction rate and degree of NCO and OH; the compatibility is related to the structure, particle structure and shape of the waterborne hydroxyl resin, the emulsifying ability of the curing agent and the content of the emulsifier. Using the seed emulsion polymerization process, the seeds are hydrophobic polymers. After the seed emulsion is synthesized, the acrylate monomer mixture containing COOH groups is added dropwise, and then an appropriate amount of neutralizer is added dropwise to synthesize latex particles P with self-emulsifying ability. ₁ , the surface of P ₁ is covered with carboxylate, and the pH value is controlled to be slightly greater than 7. Then, a mixture of acrylate monomers rich in OH groups is added dropwise into the same system to polymerize to form new latex particles P ₂ , and the surface layer of the latex particles P ₂ is covered by OH groups. Since latex particle _P1 has the ability to emulsify latex particle _P2 , the polymerization stability of latex particle _P2 with high hydroxyl content can be improved.

This process first synthesizes an acrylate polymer containing a large amount of carboxylate, which has strong hydrophilicity and can be used as a polymer emulsifier to stabilize the emulsion polymerization of polyacrylate in the later stage, which is equivalent to soap-free emulsion polymerization. Therefore, the amount of emulsifier and hydrophilic acrylate monomer can be greatly reduced, and the water resistance and appearance of the coating film can be improved; moreover, the OH group can be controlled in latex particles P ₁ and latex particles P ₂ according to design requirements The distribution of water-based two-component polyurethane film to adjust the degree of crosslinking and hardness. The acrylate hybrid emulsion system is composed of two different latex particles P ₁ and P ₂ , wherein the average particle size of P ₁ is much smaller than that of P ₂ . Since the acrylate hybrid emulsion is composed of latex particles P ₁ and P ₂ carrying two different functional groups (COOH group and OH group), the whole emulsion system presents a state of "large particles doped with small particles", resulting in The distribution of the emulsion becomes wider and the average particle size is smaller.

The acrylate hybrid emulsion prepared by the present invention is characterized by the following methods: the particle size and distribution of the emulsion are measured by a nanometer particle size analyzer (ZS Nano S); the emulsion polymer structure is measured by a Fourier transform infrared spectrometer (FTIR); the vitrification of the emulsion The temperature was measured with a differential scanning calorimeter (DSC); the minimum film-forming temperature was measured with a minimum film-forming temperature instrument; the latex particle morphology of the emulsion was measured with a transmission electron microscope (TEM).

The performance of the water-based two-component polyurethane coating film prepared by the present invention can be characterized by the following methods: the mechanical properties of the coating film are tested by an Instron electronic tensile testing machine; The hardness of the coating film is tested according to GB/T1730-93 with a pendulum hardness tester; the gloss of the coating film is tested with a 60° angle WGG60-E4 gloss meter and tested according to HG3828-2006; the test of chemical solvent resistance (MEK) is Scrub the surface of the coating film back and forth with MEK-saturated non-woven paper, and record the number of scrubbing times when the coating film has just been scratched; the adhesion is measured according to the cross-hatch method of GB/T9286-88; the curing film-forming process of 2K-WPU adopts Fourier The leaf infrared spectrometer was used for tracking analysis; the microstructure of the coating was characterized by atomic force microscopy (AFM).

Advantage and beneficial effect that the present invention has with respect to prior art:

(1) The distribution of the hydroxyl functional monomer of the present invention in the two kinds of latex particles is different, which strengthens the self-emulsification ability of the hydroxyl acrylate hybrid emulsion to the hydrophilic modified polyisocyanate curing agent, and improves the A component (hydrophilic modified polyisocyanate curing agent). Hardener) and B component (polyacrylate polyol) compatibility.

(2) The glass transition temperatures of the two latex particles of the present invention are different, forming a structure similar to a core/shell, and the emulsion of this structure has excellent low-temperature film-forming properties.

(3) The present invention adopts methods such as immediate neutralization and segmental dropwise addition of polar monomers (carboxyl monomers and hydroxyl monomers) in the polymerization process to realize the asymmetric distribution of polar monomers and improve the stability of polymerization .

(4) The present invention adopts a reasonable NCO/OH value, suppresses a large amount of side reactions in the film-forming process of the water-based two-component polyurethane coating, and avoids problems such as "foaming" and "pinholes" of the coating film, The appearance of the coating film is better.

(5) The present invention introduces crosslinkable groups such as hydroxyl, amino, N-methylol, glycidyl or epoxy, acetoethoxy, amido, alkyl siloxane, diacetone acrylamide etc. During the film-forming process of the emulsion, with the continuous volatilization of water, the pH value of the system decreases, relying on the chemical reaction between groups to obtain a coating film with a cross-linked structure, and improve the water resistance and solvent resistance of the coating film.

(6) The present invention synthesizes two kinds of latex particles with different shapes and functions, and the surface layers of the two kinds of latex particles are respectively covered by different functional groups, which strengthens the self-emulsifying ability of the acrylate hybrid emulsion.

(7) The present invention has designed the different distributions of functional carboxyl groups (-COOH) in two kinds of latex particles, and a part of latex particles acts as a polymer emulsifier in the emulsion polymerization process to ensure the high hydroxyl value acrylate hybrid emulsion. Polymerization is stable.

The present invention designs the distribution of monomers containing hydrophilic carboxyl groups (-COOH) in the process of emulsion polymerization to be different, and neutralizes carboxylic acids to form salts through timely high-temperature neutralization, which acts as a polymer emulsifier and can reduce emulsification dosage, improve the stability of emulsion polymerization.

The different distribution ratios of hydroxyl-containing acrylic functional monomers in the early stage and late stage of emulsion polymerization can increase the contact probability and reaction degree of NCO groups and OH groups in the film-forming process of water-based two-component polyurethane coatings, and can also increase the degree of reaction of hydroxyl groups. Compatibility with polyisocyanate curing agents.

(8) The polymer emulsion is non-toxic and non-flammable. There is no artificial addition of halogenated hydrocarbons, benzene, toluene, xylene, formaldehyde and its polymers, and heavy metals such as lead, cadmium, chromium, and mercury compounds. The content of total volatile organic compounds (TVOC) in the product is less than 50g/L, which fully meets the technical requirements for environmental labeling product certification and the water-based coating HJ/T201-2005 standard, which is a green product.

Description of drawings

Figure 1 is a TEM image of the acrylate hybrid emulsion prepared in Example 5 of the present invention.

Detailed ways

The following are specific examples of the invention, but are not limited to the examples.

Example 1

The formula of acrylate hybrid emulsion (PAH, hydroxyl value=99mgKOH/g) is shown in Table 1:

Table 1

Add 0.4 parts of emulsifier, 0.18 parts of buffer, and 46.3 parts of deionized water into the reactor, raise the temperature to 75°C, stir for 30 minutes, and dropwise add 0.1 parts of methacrylic acid, 1 part of butyl acrylate and 3 parts of methacrylic acid The mixed monomer of methyl ester, add dropwise the aqueous solution (weight fraction is 5%) that contains 0.02 part of initiator simultaneously, add dropwise in half an hour, treat that the emulsion is blue phase and stable half an hour, obtain seed emulsion, keep reaction system temperature at 80°C, then drop the first polar monomer mixture into the seed emulsion to prepare polymer latex particles P ₁ , the composition of the first polar monomer mixture is 20.5 parts of methyl methacrylate, 2.5 parts of acrylic acid Butyl ester, 1.4 parts of methacrylic acid and 2 parts of methacrylic acid-beta-hydroxyethyl ester, dropwise adding 0.1 part of initiator potassium persulfate aqueous solution and 1.0 part of neutralizer ( N,N-dimethylethanolamine), carry out high-temperature neutralization, pH=8.0, all dropwise in 3 hours. After the dropwise addition, continue to keep warm at 82°C for half an hour, then add the second polar monomer mixture dropwise at a constant speed in the emulsion to prepare polymer latex particles P ₂ , the composition of the second polar monomer mixture is 10 parts of formazan methyl acrylate, 2.5 parts of butyl acrylate, 0.8 parts of diacetone acrylamide, 0.2 parts of a solution of ethylene urea ethoxy methacrylate (50% by weight) and 7.5 parts of methacrylic acid -β-Hydroxyethyl ester, add 0.1 part of initiator aqueous solution dropwise at the same time, all of which are added dropwise in 3 hours, keep warm at 82°C for 1 hour, cool down to 55°C, add 0.4 part of adipic hydrazide aqueous solution and mix well , to obtain a translucent acrylate hybrid emulsion.

The prepared PAH emulsion has an average particle diameter of 105 nm, a molecular weight of 10 ⁵ , a viscosity of 1200 cps, pH=8.0, and a solid content of 51.5%.

Example 2

Using the acrylate hybrid emulsion prepared in Example 1, a waterborne two-component polyurethane coating (2K-WPU) formulation was prepared as shown in Table 2.

Table 2

The preparation method is as follows: firstly add raw materials No. 2-7 into the stirring tank, disperse with a high-speed disperser for 30 minutes, then slowly add the PAH emulsion into the stirring tank, stir at 700 rpm for 60 minutes, and adjust the pH of the coating with ammonia water Value, when pH=8.0, filter the material, then add hydrophilic modified HDI curing agent to the filtered PAH emulsion, stir rapidly for 20 minutes, add water to dilute to the specified viscosity of 200cps, stand and filter, and the prepared water-based Two-component polyurethane coating with the following properties:

Appearance: milky white slightly transparent liquid, without mechanical impurities; pH=8.0; solid content 33%, viscosity 200cps.

Wood coating film performance: Pencil hardness of coating film: 3H; water resistance: no obvious change after 48 hours of immersion in water; alcohol and alkali resistance: no change after 8 hours of immersion; adhesion: level 1; flexibility: level 2; anti-adhesion: Grade A; Gloss > 95%.

Example 3

The monomer composition is butyl acrylate, methyl methacrylate, methacrylic acid and β-hydroxyethyl methacrylate, and the formula of acrylate hybrid emulsion is shown in Table 3:

table 3

Add 0.75 parts of emulsifier, 0.2 parts of buffer, and 46.2 parts of deionized water into the reactor, raise the temperature to 75°C, stir for 30 minutes, and dropwise add 0.1 parts of methacrylic acid, 2 parts of butyl acrylate and 1 part of methacrylic acid Mixed monomers of methyl ester, add dropwise the aqueous solution (weight fraction is 5%) that contains 0.05 part of initiator (potassium persulfate) simultaneously, drop in half an hour, treat that emulsion is blue phase and stable 45 minutes, obtain seed emulsion, keep The temperature of the reaction system is 78°C, and then the first polar monomer mixture is added dropwise to the seed emulsion at a uniform speed to prepare polymer latex particles P ₁ , the composition of the monomer mixture is 10 parts of methyl methacrylate, 5 parts of butyl acrylate ester, 2 parts of methacrylic acid and 2 parts of methacrylic acid-beta-hydroxyethyl ester, dripping the aqueous solution containing 0.08 parts of initiator (potassium persulfate) and neutralizing agent ( Aqueous solution of ammonia water) was neutralized at high temperature, pH = 7.5, and the dropwise addition was completed in 1 hour. After the dropwise addition, the temperature was kept at 78°C for 90 minutes, and then the second polar monomer mixture was added dropwise in the emulsion at a uniform speed to prepare the polymer. Latex particle P ₂ , the composition of the monomer mixture is 2.5 parts of methyl methacrylate, 10 parts of butyl acrylate and 10 parts of β-hydroxyethyl methacrylate, while adding dropwise 0.12 parts of initiator ( Potassium persulfate) aqueous solution was added dropwise in 1 hour, and after being kept at 78° C. for 90 minutes, the temperature was lowered to 50° C. and filtered, and the translucent acrylate hybrid emulsion PAH was obtained in discharging.

The prepared PAH emulsion has an average particle diameter of 120nm, a molecular weight of 10 ⁵ , a viscosity of 600cps, pH=8.0, and a solid content of 48.6%.

Example 4

Using the acrylate hybrid emulsion prepared in Example 3, a waterborne two-component polyurethane coating (2K-WPU) formulation was prepared as shown in Table 4.

Table 4

The preparation method is as follows: firstly add raw materials No. 2-7 into the stirring tank, disperse with a high-speed disperser for 30 minutes, then slowly add the PAH emulsion into the stirring tank, stir at a medium speed for 30 minutes, adjust the pH value of the coating with ammonia water, When the pH value is qualified, filter the material, then add hydrophilic modified HDI curing agent to the filtered PAH emulsion, stir rapidly for 5 minutes, add water to dilute to the specified viscosity, and let it stand and filter. The prepared waterborne two-component polyurethane coating has the following properties:

Appearance: milky white slightly transparent liquid, without mechanical impurities; pH=9; solid content 35%, viscosity 280cps.

Wood coating film performance: Pencil hardness of coating film: 2H; water resistance: no obvious change after 48 hours of immersion in water; alcohol and alkali resistance: no change after 8 hours of immersion; adhesion: level 1; flexibility: level 2; anti-adhesion: Grade A; Gloss > 95%.

Example 5

The monomer composition is butyl acrylate, methacrylic acid and hydroxypropyl acrylate, and the formula of acrylate hybrid emulsion is shown in Table 5:

table 5

Add 0.86 parts of emulsifier, 0.15 parts of buffer, and 47.79 parts of deionized water into the reactor, raise the temperature to 82°C, stir for 30 minutes, and dropwise add 0.2 parts of methacrylic acid, 1 part of butyl acrylate and 2 parts of methacrylic acid Mixed monomers of methyl ester, dropwise add a solution containing 0.05 parts of initiator (ammonium persulfate) at the same time, and finish adding dropwise in 10 minutes. After the emulsion is in a blue phase and stabilizes for 15 minutes, a seed emulsion is obtained, and the temperature of the reaction system is kept at 83°C. Then drop the first section of polar monomer mixture into the seed emulsion to prepare polymer latex particles P ₁ , the composition of the monomer mixture is 15 parts of methyl methacrylate, 3.0 parts of butyl acrylate, 1.5 parts of methyl Acrylic acid and 3.2 parts of hydroxypropyl methacrylate, dropwise adding 0.1 part of initiator (ammonium persulfate) aqueous solution (5% by weight) and neutralizer (sodium hydroxide) while dripping the acrylate monomer mixture , carry out high-temperature neutralization, pH=9.0, dropwise addition within 2.5 hours. After the dropwise addition, keep the temperature at 85°C for 30 minutes, then add the second polar monomer mixture dropwise at a constant speed in the emulsion to prepare polymer latex particles P ₂ , the composition of the monomer mixture is 8.5 parts of methyl methacrylate, 8.5 parts of butyl acrylate and 7.5 parts of hydroxypropyl acrylate were added dropwise with 0.15% initiator aqueous solution at the same time, and the dropwise addition was completed within 2.5 hours. After the temperature was kept at 85°C for 30 minutes, the temperature was lowered to 55°C and the material was discharged to obtain a translucent Acrylate hybrid emulsion.

The prepared PAH emulsion has an average particle diameter of 158nm, a molecular weight of 2.2×10 ⁵ , a viscosity of 1000 cps, pH=8.0, and a solid content of 51.5%. Figure 1 is a TEM image of the acrylate hybrid emulsion prepared in Example 5 of the present invention.

Example 6

Using the acrylate hybrid emulsion prepared in Example 5, a waterborne two-component polyurethane coating (2K-WPU) formulation was prepared as shown in Table 6.

Table 6

The preparation method is as follows: firstly add raw materials No. 2-7 into the stirring tank, disperse with a high-speed disperser for 30 minutes, then slowly add the PAH emulsion into the stirring tank, stir at a medium speed for 60 minutes, adjust the pH value of the coating with ammonia water, When the pH value is qualified, filter and discharge, then add hydrophilic modified HDI curing agent to the filtered PAH emulsion, stir rapidly for 20 minutes, add water to dilute to the specified viscosity, and stand for filtration. The prepared waterborne two-component polyurethane coating has the following properties:

Appearance: milky white slightly transparent liquid, without mechanical impurities; pH=9; solid content 30%, viscosity 240cps.

Wood coating performance: Pencil hardness of the coating film: 2H; Water resistance: no significant change after 96 hours of immersion; Alcohol and alkali resistance: no change after 10 hours of immersion; Adhesion: Grade 1; Flexibility: Grade 1; Anti-adhesion: Grade A; Gloss > 95%.

performance comparison

The acrylate hybrid emulsion PAH of embodiment 1 and embodiment 3 prepares water-based two-component polyurethane coating according to the formula of embodiment 2 and performs performance comparison with solvent-based two-component polyurethane coating, and PAH prepares the comprehensive performance of water-borne two-component polyurethane coating The experimental data are listed in Table 7.

Table 7 shows that the acrylate hybrid emulsion PAH prepared by the method of the present invention is used to prepare water-based two-component polyurethane coatings. The overall performance is close to that of solvent-based two-component polyurethane coatings. It has excellent mechanical and physical and chemical properties, and can be widely used in high-grade Wood furniture paint, automotive paint, metal anti-corrosion and industrial protection and other fields. At the same time, the acrylate hybrid emulsion PAH can flexibly design the latex particle shape and the distribution of functional groups according to the performance requirements, reduce the amount of emulsifier used in emulsion polymerization, and ensure the stability of polymerization. This polymerization process has great advantages Strong practicability and easy to promote.

Table 7

Claims (9)

1. the preparation method of acrylate hybrid emulsion is characterized in that, comprises the steps: (1) Add water, emulsifier and buffering agent into the reaction kettle, stir at 70-85°C for 10-30 minutes, then add the mixture of alkyl methacrylate, alkyl acrylate and alkacrylic acid dropwise at a uniform speed , drop the aqueous solution of initiator simultaneously, drop in 10～30 minutes, after the emulsion is blue phase, keep warm for 15～45 minutes, obtain seed emulsion, the parts by weight of raw materials are as follows: 45-55 parts of water Emulsifier 0.2～2 parts Buffer 0.1～0.5 parts Alkyl methacrylate 1-5 parts Alkyl Acrylate 1-5 parts Alkylacrylic acid 0.05～0.25 parts Initiator 0.01～0.05 parts; (2) Keeping the temperature of the reaction system at 75-85°C, add alkyl methacrylate, alkyl acrylate, alkacrylic acid and hydroxyalkyl methacrylate or hydroxyalkyl acrylate dropwise at a constant speed to the seed emulsion The mixture is added dropwise with the aqueous solution of initiator and neutralizer at the same time to adjust the pH of the reaction system to 7.5-9.0. After 1-3 hours of dropwise addition, it is kept at 75-85° C. for 30-90 minutes; the parts by weight of raw materials are as follows: Alkyl methacrylate 10-25 parts Alkyl Acrylate 2～5 parts 2-5 parts of hydroxyalkyl methacrylate or hydroxyalkyl acrylate Alkyl acrylic acid 1~3 parts Initiator 0.05～0.15 parts; (3) in the reaction system, add dropwise the mixture of alkyl methacrylate, alkyl acrylate, functional amides and hydroxyalkyl methacrylate or hydroxyalkyl acrylate, and drop the aqueous solution of initiator simultaneously, After 1-3 hours of dropwise addition, keep the temperature at 75-85°C for 30-90 minutes, and cool down to below 60°C to obtain acrylate hybrid emulsion. The parts by weight of raw materials are as follows: Alkyl methacrylate 2～10 parts Alkyl Acrylate 2～10 parts Hydroxyalkyl methacrylate or hydroxyalkyl acrylate 5-10 parts Functional amide 0～2 parts Initiator 0.05-0.1 parts. 2. The preparation method according to claim 1, characterized in that, the number of carbon atoms in the alkyl group of the alkyl acrylate is 1 to 20; the number of carbon atoms in the alkyl group of the alkyl methacrylate is 1 to 20; The number of carbon atoms in the alkyl group of hydroxyalkyl acrylate is 1-20; the number of carbon atoms in the alkyl group of hydroxyalkyl methacrylate is 1-20; the number of carbon atoms in the alkyl group of alkacrylic acid is 1-20; The functional amides include acrylamide, diacetone acrylamide, N-methylolacrylamide, methacrylamide, N,N-dimethylacrylamide, ethylene urea ethoxy methacrylate, formazan tert-butylaminoethyl acrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate, tetrahydrofuryl methacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethyl One or more of acrylate or 1,6-hexanediol acrylate. 3. preparation method according to claim 2, is characterized in that, described alkyl acrylate comprises methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, isobornyl acrylate, hexyl acrylate or acrylic acid More than one of isooctyl esters; The alkyl methacrylate includes methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, isobornyl methacrylate, hexyl methacrylate or methacrylic acid More than one of isooctyl esters; The hydroxyalkyl methacrylate includes more than one of -β-hydroxyethyl methacrylate or -β-hydroxypropyl methacrylate; The hydroxyalkyl acrylate includes more than one of 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate or 6-hydroxyhexyl acrylate; The alkacrylic acid includes one or more of methacrylic acid or acrylic acid. 4. the preparation method of acrylate hybrid emulsion according to claim 1 is characterized in that, described emulsifying agent is the mixture of anionic surfactant and nonionic surfactant, anionic surfactant and nonionic surfactant The weight ratio is 1:4～4:1, and the anionic surfactant is sodium dodecylbenzenesulfonate, sodium lauryl sulfate, disodium salt of alkyl diphenyl ether sulfonate, ethoxysulfonate Disodium succinate, sodium vinyl sulfonate or sodium alkylamido vinyl sulfonate or a mixture of two or more; the nonionic surfactant is one of OP-10 or TX-100 one or a mixture of two. 5. the preparation method of acrylate hybrid emulsion according to claim 1 is characterized in that, described initiator is persulfate or redox system, and the concentration of the aqueous solution of described initiator is 1%～5% by weight . 6. the preparation method of acrylate hybrid emulsion according to claim 1, is characterized in that, described buffering agent is sodium carbonate and/or sodium bicarbonate. the 7. the preparation method of acrylate hybrid emulsion according to claim 1 is characterized in that, described neutralizing agent is basic compound. 8. the preparation method of acrylate hybrid emulsion according to claim 7, is characterized in that, described neutralizer comprises ammoniacal liquor, triethylamine, N, N-dimethylethanolamine, AMP-95 or sodium hydroxide one or a mixture of two or more. 9. the application of the acrylate hybrid emulsion that the preparation method described in one of claim 1-8 makes in the preparation waterborne two-component polyurethane woodware coating. the

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