Isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive and preparation method thereof

Abstract

The invention discloses a kind of isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive and preparation method thereof, relate to the field of adhesive preparation technology, comprise the following steps: S1: prepare amphiphilic hyperbranched skeleton macromonomer, the amphiphilic hyperbranched skeleton macromonomer contains carbon-carbon double bond functional group and functional group capable of reacting with hydroxyl group; S2: the amphiphilic hyperbranched skeleton macromonomer, buffer, deionized water and polymerization inhibitor are mixed, and then the first hard monomer, the second soft monomer, the third functional monomer and the fourth hard monomer are added in sequence to react, and an aqueous hyperbranched multi-block copolymer emulsion is prepared; S3: isocyanate is mixed with the aqueous hyperbranched multi-block copolymer emulsion to obtain an isocyanate-waterborne polymer composite emulsion adhesive. The adhesive prepared by the present invention can greatly improve the mechanical strength and water resistance of the adhesive, and can meet the adhesive needs of various occasions.

Description

Technical Field

[0001] The present invention relates to the field of adhesives, in particular to an isocyanate-aqueous hyperbranched multi-block copolymer composite emulsion adhesive and a preparation method thereof. Background Art

[0002] Polymer emulsion adhesives are water-based adhesives favored by consumers for their formaldehyde-free nature and room-temperature curing properties. However, their poor water resistance significantly limits their practical applications. Therefore, improving the water resistance of polymer emulsion adhesives is a hot topic in both academia and industry.

[0003] Increasing the amount of hydrophobic components and reducing the amount of hydrophilic components, such as reducing the amount of emulsifiers, stabilizers and other ingredients added, is an important method to improve the water resistance of latex adhesives. However, emulsifiers and stabilizers are important ingredients in the preparation process of latex adhesives. How to find a balance between improving the water resistance of latex adhesives and reducing the amount of emulsifiers and stabilizers is an important issue. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide an isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive and a preparation method thereof.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for preparing an isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive comprises the following steps:

[0007] S1: preparing an amphiphilic hyperbranched backbone macromonomer, wherein the amphiphilic hyperbranched backbone macromonomer contains a carbon-carbon double bond functional group and a functional group capable of reacting with a hydroxyl group;

[0008] S2: mixing an amphiphilic hyperbranched backbone macromonomer, a buffer, deionized water, and a polymerization inhibitor, and then sequentially adding a first hard monomer, a second soft monomer, a third functional monomer, and a fourth hard monomer to react to prepare an aqueous hyperbranched multi-block copolymer emulsion;

[0009] S3: mixing the isocyanate with the aqueous hyperbranched multi-block copolymer emulsion prepared in S2 to obtain an isocyanate-aqueous polymer composite emulsion adhesive.

[0010] As a preferred embodiment of the present invention, the preparation method of the amphiphilic hyperbranched skeleton macromonomer is as follows: polyvinyl alcohol is first dissolved in a solvent to prepare a polyvinyl alcohol solution, and then a bifunctional monomer, a catalyst and a polymerization inhibitor are respectively added to the polyvinyl alcohol solution, and the reaction is maintained at a certain temperature for a period of time until the non-carbon-carbon double bond functional groups of the bifunctional monomer are completely reacted to obtain a mixed solution. After cooling to room temperature, the mixed solution is added to ether for precipitation, and after multiple washing and drying, the product is obtained.

[0011] As a preferred embodiment of the present invention, the solvent is N,N-dimethylformamide.

[0012] As a preferred embodiment of the present invention, the bifunctional monomer is one or a mixture of acrylic acid, methacrylic acid, 2-isocyanate ethyl acrylate, acryloyl chloride, and maleic anhydride.

[0013] As a preferred embodiment of the present invention, the catalyst is one of p-diaminopyridine, aluminum chloride, zinc chloride, boric acid, boron trifluoride, and dibutyltin dilaurate;

[0014] The polymerization inhibitor is a mixture of one or more of hydroquinone, p-tert-butylcatechol, and 2,6-di-tert-butyl-p-methylphenol.

[0015] As a preferred embodiment of the present invention, in S2, the aqueous hyperbranched multi-block copolymer emulsion is specifically prepared as follows: the following parts are by weight:

[0016] 6 parts of an amphiphilic hyperbranched skeleton macromolecular monomer and 0.5-2 parts of a buffer are added to 100-150 parts of deionized water, heated to dissolve, cooled to 40°C after dissolution, 2 parts of a first hard monomer are added for pre-emulsification for 15 minutes, heated to 75°C, a portion of an initiator aqueous solution is added dropwise to initiate polymerization, and after blue light appears and reflux occurs, the remaining 8 parts of the first hard monomer are added dropwise and the reaction temperature is controlled at 75°C. After no reflux occurs, 20 parts of a second soft monomer are added and the reaction temperature is maintained at 70°C. After no reflux occurs, 0.5-2 parts of a third functional monomer are added and the reaction temperature is maintained at 80°C. After no reflux occurs, 10 parts of a fourth hard monomer are added and the reaction temperature is maintained at about 85°C. After no reflux occurs, the temperature is continued to be raised to 90°C and matured for 30 minutes; then the temperature is cooled to room temperature, a plasticizer is added and the material is discharged to obtain the product.

[0017] As a preferred embodiment of the present invention,

[0018] The buffer is sodium bicarbonate and / or sodium carbonate;

[0019] The first hard monomer is one or more of vinyl acetate, styrene, acrylonitrile, and methyl methacrylate;

[0020] The initiator is a mixture of one or more of ammonium persulfate, potassium persulfate, and sodium persulfate;

[0021] The second soft monomer is one or more of butyl acrylate, ethyl acrylate, and isooctyl acrylate;

[0022] The third functional monomer is one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and glycidyl methacrylate;

[0023] The fourth hard monomer is a mixture of one or more of acrylonitrile, methyl methacrylate, styrene, and vinyl acetate;

[0024] The plasticizer is a mixture of one or more of dimethyl phthalate, diethyl phthalate and dibutyl phthalate.

[0025] As a preferred embodiment of the present invention,

[0026] The isocyanate is a mixture of one or more of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0027] As a preferred embodiment of the present invention, the isocyanate accounts for 10-30% of the mass of the aqueous hyperbranched multi-block copolymer emulsion.

[0028] The beneficial effects of the present invention are:

[0029] (1) The present invention eliminates the need for emulsifiers and maintains the stability of the copolymer latex adhesive by constructing an amphiphilic hyperbranched skeleton macromolecular monomer. By constructing a hyperbranched multi-block molecular structure with alternating hard segments and soft segments, the water resistance and mechanical strength of the copolymer latex adhesive are enhanced on the one hand, and the glass transition temperature of the emulsion is controlled on the other hand, which is more conducive to operation at a lower temperature. Finally, the high reactivity of isocyanate is used to introduce high-strength, high-water-resistant urethane and urea groups, thereby further improving the mechanical and water-resistant properties of the adhesive.

[0030] (2) The amphiphilic hyperbranched skeleton macromolecular monomer constructed by the present invention has the following effects and advantages in the reaction system. First, after the hydrophobic part of the carbon-carbon double bond is introduced into the amphiphilic hyperbranched skeleton macromolecular monomer, the hydrophilic and lipophilic properties are better, and it can play a dual role of emulsification and stabilization of the latex. Compared with the traditional emulsion polymerization process, no additional protective colloid and emulsifier are used in this system; secondly, the amphiphilic hyperbranched skeleton macromolecular monomer uses the introduced branched active double bonds to act as a hyperbranched molecular skeleton on the one hand, and on the other hand, it forms a chemical bond with the latex particles by participating in the polymerization reaction, which has a synergistic promoting effect on stabilizing the emulsion; finally, the prepared hyperbranched multi-block copolymer based on polyvinyl alcohol has good structural advantages, which has an important promoting effect on improving the water resistance and other properties of the adhesive.

[0031] (3) In the present invention, after isocyanate is compounded with an aqueous hyperbranched multi-block copolymer emulsion, a chemical cross-linking reaction occurs between the isocyanate group and the hydroxyl group, water, etc., which, on the one hand, introduces a urethane group and a urea group with high mechanical strength and water resistance into the adhesive system, and on the other hand, reduces the hydrophilic group, which can greatly improve the mechanical strength and water resistance of the adhesive and meet the adhesive needs of various occasions. DETAILED DESCRIPTION

[0032] A method for preparing an isocyanate-aqueous polymer composite emulsion wood adhesive comprises the following steps:

[0033] S1: Construction of amphiphilic hyperbranched backbone macromonomer: At a certain temperature, polyvinyl alcohol is first dissolved in a solvent, and then a certain stoichiometric amount of a bifunctional monomer (one functional group is a carbon-carbon double bond, and the other functional group can react with a hydroxyl group), a catalyst, and an inhibitor are respectively added to the above solution. The temperature is maintained for a period of time until the non-carbon-carbon double bond functional groups of the bifunctional monomer react completely. After cooling to room temperature, the mixed solution is precipitated in ether. After multiple washing and drying, an amphiphilic hyperbranched backbone macromonomer is obtained.

[0034] S2: Preparation of aqueous hyperbranched multi-block copolymer emulsion: Taking hyperbranched vinyl acetate, butyl acrylate, acrylic acid, acrylonitrile tetrablock copolymer emulsion as an example, 100-150 parts of deionized water, 6 parts of amphiphilic hyperbranched skeleton macromonomer, and 0.5-2 parts of buffer are added to a reactor equipped with a condenser, a thermometer, a constant pressure dropping funnel, and a stirring device. Then, the temperature is slowly raised while stirring until the amphiphilic hyperbranched skeleton macromonomer and the buffer are completely dissolved. The temperature is then lowered to 40°C, and 2 parts of the first hard monomer vinyl acetate are added to the reactor for pre-emulsification for 15 minutes. After slowly raising the temperature to 75°C, a portion of the initiator aqueous solution is added dropwise to start initiation of polymerization. After the blue light appears and reflux occurs, the remaining 8 parts of vinyl acetate are added dropwise and the reaction temperature is controlled at about 75°C. After reflux stops, 20 parts of the second soft monomer butyl acrylate are added to the reactor at a certain dropwise rate and the reaction temperature is maintained at about 70°C. After reflux stops, 0.5-2 parts of the third functional monomer acrylic acid are added to the reactor at a certain dropwise rate and the reaction temperature is maintained at about 80°C. After reflux stops, 10 parts of the fourth hard monomer acrylonitrile are added to the reactor at a certain dropwise rate and the reaction temperature is maintained at about 85°C. After reflux stops, the temperature is continued to rise to 90°C and matured for 30 minutes. The temperature is then cooled to room temperature, a certain amount of plasticizer is added, and the mixture is discharged to obtain an aqueous hyperbranched multi-block copolymer emulsion.

[0035] S3: Preparation of isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive: Isocyanate and the waterborne hyperbranched multi-block copolymer composite emulsion prepared in S2 are compounded in a certain ratio to obtain an isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive.

[0036] The polyvinyl alcohol is specifically controlled in terms of polymerization degree (≥1700) and hydroxyl content (≥85%). More specifically, the fluorine can be a mixture of one or more of the fluorine numbers 1788, 1799, and 2099.

[0037] The solvent is N, N-dimethylformamide or other solvents that are easy to dissolve polyvinyl alcohol.

[0038] The bifunctional unit is one of acrylic acid, methacrylic acid, 2-isocyanate ethyl acrylate, acryloyl chloride, maleic anhydride, or a mixture of the above functional monomers.

[0039] The catalyst is one of p-diaminopyridine, aluminum chloride, zinc chloride, boric acid, boron trifluoride and dibutyltin dilaurate.

[0040] The polymerization inhibitor is one of hydroquinone, p-tert-butylcatechol, 2,6-di-tert-butyl-p-methylphenol, or a mixture of the above polymerization inhibitors.

[0041] The buffer is sodium bicarbonate, sodium carbonate or a mixture of sodium bicarbonate and sodium carbonate.

[0042] The first hard monomer is vinyl acetate, styrene, acrylonitrile, methyl methacrylate, etc.

[0043] The initiator is a mixture of one or more of ammonium persulfate, potassium persulfate and sodium persulfate.

[0044] The second soft monomer is butyl acrylate, ethyl acrylate, isooctyl acrylate, etc.

[0045] The third functional monomer is one of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and glycidyl methacrylate.

[0046] The fourth hard monomer is one or more of acrylonitrile, methyl methacrylate, styrene and vinyl acetate.

[0047] The monomer polymerization reaction proceeds smoothly as follows: a first hard monomer, a second soft monomer, a third functional monomer, and a fourth hard monomer.

[0048] The mass ratio of the polymerized monomers is: the first hard monomer: the second soft monomer: the third functional monomer: the fourth hard monomer is (3-5): (15-20): (0.2-0.8): (14-20).

[0049] The plasticizer is a mixture of one or more of dimethyl phthalate, diethyl phthalate and dibutyl phthalate.

[0050] The isocyanate is a mixture of one or more of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0051] The compounding ratio of the isocyanate and the aqueous polymer emulsion is: the isocyanate accounts for 10-30% by mass of the aqueous hyperbranched multi-block copolymer emulsion.

[0052] Reaction mechanism:

[0053] 1. Construction of amphiphilic hyperbranched macromonomers:

[0054] Example 1: Polyvinyl alcohol (PVA) and acrylic acid react, and the hydroxyl groups (OH-) on the polyvinyl alcohol react with the carboxyl groups (-COOH) on the acrylic acid to construct a hyperbranched macromonomer containing a hydrophobic group of C=C;

[0055] Example 2: Polyvinyl alcohol (PVA) and 2-isocyanatoethyl acrylate are reacted, and the hydroxyl group (OH-) on the polyvinyl alcohol reacts with the carboxyl group (-COOH) on the 2-isocyanatoethyl acrylate to construct a hyperbranched macromonomer containing a hydrophobic group of C=C;

[0056] 2. Emulsion polymerization process:

[0057] Hyperbranched macromonomers, wherein represents C=C, represents the PVA main chain;

[0058] Polymerization process:

[0059]

[0060] 3. Preparation process of emulsion adhesive:

[0061] The emulsion polymer and polyisocyanate undergo ester cross-linking reaction to prepare the adhesive.

[0062] The technical solution of the present invention is further described below with reference to specific embodiments.

[0063] The following parts are by weight.

[0064] Example 1

[0065] 1) Preparation of an amphiphilic hyperbranched backbone macromonomer: 20 g of polyvinyl alcohol 1788 was dissolved in 100 g of N,N-dimethylformamide. 3.6 g (0.05 mol) of acrylic acid, 0.1 g of boron trifluoride as a catalyst, and 0.05 g of hydroquinone as a polymerization inhibitor were then added to the solution. The mixture was reacted at 120° C. for 6 hours until the acrylic acid was completely reacted. After cooling to room temperature, the mixed solution was precipitated in diethyl ether, washed multiple times, and dried to obtain an amphiphilic hyperbranched backbone macromonomer.

[0066] 2) Preparation of aqueous hyperbranched multi-block copolymer emulsion: 100 g of deionized water, 6 g of amphiphilic hyperbranched backbone macromonomer, and 0.5 g of buffer were added to a reactor equipped with a condenser, a thermometer, a constant pressure dropping funnel, and a stirring device. The temperature was then slowly raised while stirring until the amphiphilic hyperbranched backbone macromonomer and the buffer were completely dissolved. The temperature was then lowered to 40° C. 2 g of the first hard monomer, vinyl acetate, was added to the reactor for pre-emulsification for 15 minutes. The temperature was slowly raised to 75° C., and a portion of the initiator, ammonium persulfate aqueous solution, was added dropwise to initiate polymerization. After blue light appeared and reflux was generated, the remaining 8 g of vinyl acetate was added dropwise and the reaction was controlled. The reaction temperature is about 75°C. After reflux stops, 20g of the second soft monomer butyl acrylate is added to the reactor at a certain drop rate (120mL / min) while maintaining the reaction temperature at about 70°C. After reflux stops, 0.5g of the third functional monomer acrylic acid is added to the reactor at a certain drop rate while maintaining the reaction temperature at about 80°C. After reflux stops, 10g of the fourth hard monomer acrylonitrile is added to the reactor at a certain drop rate (130mL / min) while maintaining the reaction temperature at about 85°C. After reflux stops, the temperature is further raised to 90°C and matured for 30 minutes. The temperature is then cooled to room temperature, and 5g of the plasticizer dibutyl phthalate is added to obtain an aqueous hyperbranched multi-block copolymer emulsion.

[0067] 3) Preparation of isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive: isocyanate and the waterborne hyperbranched multi-block copolymer emulsion prepared in step 2) are compounded in a mass ratio of 10:100 to obtain an isocyanate-waterborne polymer composite emulsion adhesive.

[0068] Example 2

[0069] 1) Preparation of an amphiphilic hyperbranched backbone macromonomer: 15 g of polyvinyl alcohol 1799 was dissolved in 100 g of N,N-dimethylformamide. 4.3 g (0.05 mol) of methacrylic acid, 0.1 g of diaminopyridine as a catalyst, and 0.05 g of p-tert-butylcatechol as a polymerization inhibitor were then added to the solution. The reaction was maintained at 140° C. for 8 hours until the methacrylic acid reacted completely. After cooling to room temperature, the mixed solution was precipitated in diethyl ether, washed multiple times, and dried to obtain an amphiphilic hyperbranched backbone macromonomer.

[0070] 2) Preparation of aqueous hyperbranched multi-block copolymer emulsion: 110 g of deionized water, 8 g of amphiphilic hyperbranched backbone macromonomer, and 0.7 g of buffer were added to a reactor equipped with a condenser, a thermometer, a constant pressure dropping funnel, and a stirring device. The mixture was then slowly heated while stirring until the amphiphilic hyperbranched backbone macromonomer and the buffer were completely dissolved. The mixture was cooled to 40° C., 4 g of the first hard monomer styrene was added to the reactor for pre-emulsification for 15 minutes, and the mixture was slowly heated to 80° C., and a portion of the initiator ammonium persulfate aqueous solution was added dropwise to initiate polymerization. After blue light appeared and reflux was generated, the remaining 6 g of styrene was added dropwise and the reaction temperature was controlled at 80° C. At about 80°C, after no reflux occurs, 25g of the second soft monomer ethyl acrylate is added to the reactor at a certain drop rate (120mL / min) and the reaction temperature is maintained at about 70°C. After no reflux occurs, 0.5g of the third functional monomer methacrylic acid is added to the reactor at a certain drop rate (130mL / min) and the reaction temperature is maintained at about 80°C. After no reflux occurs, 15g of the fourth hard monomer vinyl acetate is added to the reactor at a certain drop rate and the reaction temperature is maintained at about 75°C. After no reflux occurs, the temperature is continued to rise to 90°C and matured for 30 minutes. The temperature is then cooled to room temperature, and 8g of plasticizer dibutyl phthalate is added to obtain an aqueous hyperbranched multi-block copolymer emulsion.

[0071] 3) Preparation of isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive: isocyanate and the waterborne hyperbranched multi-block copolymer emulsion prepared in step 2) are compounded in a mass ratio of 15:100 to obtain an isocyanate-waterborne polymer composite emulsion adhesive.

[0072] Example 3

[0073] 1) Preparation of an amphiphilic hyperbranched backbone macromonomer: 8 g of polyvinyl alcohol 2099 was dissolved in 100 g of N,N-dimethylformamide. 1.55 g (0.01 mol) of 2-isocyanatoethyl acrylate, 0.1 g of dibutyltin dilaurate as a catalyst, and 0.05 g of p-tert-butylcatechol as a polymerization inhibitor were then added to the solution. The mixture was reacted at 80° C. for 4 hours until the isocyanate groups were completely reacted. After cooling to room temperature, the mixed solution was precipitated in ether, washed multiple times, and dried to obtain an amphiphilic hyperbranched backbone macromonomer.

[0074] 2) Preparation of aqueous hyperbranched multi-block copolymer emulsion: 120 g of deionized water, 6 g of amphiphilic hyperbranched backbone macromonomer, and 0.7 g of sodium bicarbonate as buffer were added to a reactor equipped with a condenser, a thermometer, a constant pressure dropping funnel, and a stirring device. The mixture was then slowly heated while stirring until the amphiphilic hyperbranched backbone macromonomer and the buffer were completely dissolved. The mixture was cooled to 40° C., 3 g of the first hard monomer methyl methacrylate was added to the reactor for pre-emulsification for 15 minutes, and the mixture was slowly heated to 80° C., and a portion of the initiator ammonium persulfate aqueous solution was added dropwise to initiate polymerization. After blue light appeared and reflux occurred, the remaining 7 g of methyl methacrylate was added dropwise and the mixture was controlled to be molten. The reaction temperature is about 80°C. After no reflux occurs, 25g of the second soft monomer isooctyl acrylate is added to the reactor at a certain drop rate (120mL / min) and the reaction temperature is maintained at about 75°C. After no reflux occurs, 0.5g of the third functional monomer hydroxyethyl acrylate is added to the reactor at a certain drop rate (120mL / min) and the reaction temperature is maintained at about 80°C. After no reflux occurs, 15g of the fourth hard monomer vinyl acetate is added to the reactor at a certain drop rate and the reaction temperature is maintained at about 75°C. After no reflux occurs, the temperature is continued to be raised to 90°C and matured for 30 minutes. The temperature is then cooled to room temperature, and 10g of plasticizer dibutyl phthalate is added to obtain an aqueous hyperbranched multi-block copolymer emulsion.

[0075] 3) Preparation of isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive: isocyanate and the waterborne hyperbranched multi-block copolymer emulsion prepared in step 2) are compounded in a mass ratio of 15:100 to obtain an isocyanate-waterborne polymer composite emulsion adhesive.

[0076] Example 4

[0077] This example further modified Example 3, specifically: 3) Preparation of an isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive: Isocyanate and the aqueous hyperbranched multi-block copolymer emulsion prepared in step 2) were compounded at a mass ratio of 15:100, and a dispersion liquid accounting for 1 wt% of the aqueous hyperbranched multi-block copolymer emulsion was added during compounding to obtain an isocyanate-waterborne polymer composite emulsion adhesive. The remaining steps were the same as in Example 3.

[0078] The dispersion is specifically prepared by uniformly dispersing 1 part by weight of nano hollow silica microspheres in 79 parts by weight of polyether polycarboxylic acid sodium sulfonate. The preparation method of the nano hollow silica microspheres is as follows: stirring cyanobacteria powder at a low speed, then adding it to ethanol, and then adding ammonia water and orthosilicates to coat the silica. The mixture is then dried at 80°C for 1 hour and calcined at 350°C to obtain the hollow silica microspheres.

[0079] Example 5

[0080] This example further modified Example 3, specifically: 3) Preparation of an isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive: Isocyanate and the aqueous hyperbranched multi-block copolymer emulsion prepared in step 2) were compounded in a mass ratio of 15:100, and a dispersion liquid accounting for 1.5 wt% of the aqueous hyperbranched multi-block copolymer emulsion was added during compounding to obtain an isocyanate-waterborne polymer composite emulsion adhesive. The remaining steps were the same as in Example 3.

[0081] The dispersion is specifically prepared by uniformly dispersing 1 part by weight of nano hollow silica microspheres in 85 parts by weight of polyether polycarboxylic acid sodium sulfonate. The preparation method of the nano hollow silica microspheres is as follows: stirring cyanobacteria powder at a low speed, then adding it to ethanol, and then adding ammonia water and orthosilicates to coat the silica. The mixture is then dried at 80°C for 1 hour and calcined at 350°C to obtain hollow silica microspheres.

[0082] Comparative Example 1 (no amphiphilic macromolecules)

[0083] 1) Add 120g of deionized water, 6g of polyvinyl alcohol, and 0.7g of sodium bicarbonate as a buffer to a reactor equipped with a condenser, a thermometer, a constant pressure dropping funnel, and a stirring device, then slowly heat up while stirring until completely dissolved, cool to 40°C, add 3g of the first hard monomer methyl methacrylate to the reactor for pre-emulsification for 15 minutes, slowly heat to 80°C, dropwise add part of the initiator ammonium persulfate aqueous solution to initiate polymerization, wait for blue light to appear and reflux to occur, start dropwise adding the remaining 7g of methyl methacrylate and control the reaction temperature at about 80°C, wait until reflux stops, and add 2 5g of the second soft monomer, isooctyl acrylate, was added to the reactor at a certain drop rate while maintaining the reaction temperature at about 75°C. After no reflux occurred, 0.5g of the third functional monomer, hydroxyethyl acrylate, was added to the reactor at a certain drop rate (150mL / min) while maintaining the reaction temperature at about 80°C. After no reflux occurred, 15g of the fourth hard monomer, vinyl acetate, was added to the reactor at a certain drop rate (120mL / min) while maintaining the reaction temperature at about 75°C. After no reflux occurred, the temperature was further raised to 90°C and matured for 30 minutes. The mixture was then cooled to room temperature and 10g of the plasticizer, dibutyl phthalate, was added to obtain an aqueous hyperbranched multi-block copolymer emulsion.

[0084] 3) Preparation of isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive: isocyanate and the waterborne hyperbranched multi-block copolymer emulsion prepared in step 2) are compounded in a mass ratio of 15:100 to obtain an isocyanate-waterborne polymer composite emulsion adhesive.

[0085] Comparative Example 2

[0086] Add 60 kg of water to the reactor, add 0.4 kg of polyvinyl alcohol 1799 and 0.2 kg of carboxymethyl cellulose, stir and heat to 90 ° C, keep warm for 1 hour, cool to room temperature, add 0.3 kg of composite emulsifier, 0.1 kg of N-hydroxymethyl acrylamide, and 0.5 kg of sodium bicarbonate to dissolve evenly.

[0087] 32 kg of vinyl acetate, 7 kg of butyl acrylate, 10 kg of ethyl acrylate, 0.5 kg of acrylic acid, and 0.3 kg of hydroxyethyl acrylate were mixed evenly, 20 wt% of the mixture was added to the reactor for pre-emulsification, the temperature was slowly raised to 80 ° C, 0.05 kg of initiator ammonium persulfate was added, and when a light blue color appeared in the reactor or there was no reflux at the condenser, the remaining mixed monomers and 0.2 kg of initiator ammonium persulfate were added dropwise. The addition time was controlled within 4.5 hours, and the temperature in the reactor was maintained at about 84 ° C.

[0088] The above examples and comparative examples were subjected to performance tests, and the test results are shown in the following table;

[0089] (1) Water resistance test

[0090] At room temperature, the adhesives of the above examples and comparative examples were applied to the surface of eucalyptus wood with a moisture content of 10% for gluing, with a glue amount of 300 g / m 2 , hold the pressure at 1 MPa for 1 hour and then let it stand for 12 hours to fully cure (hot pressing temperature), then boil the glued eucalyptus in boiling water for 3 hours.

[0091] After being taken out from the boiling water and dried, the samples were tested for shear strength Q4 and water resistance (no debonding was found in any of the samples).

[0092] (2) Mechanical strength test (shear strength)

[0093] Eucalyptus wood with a moisture content of 10% was sawn into rectangular boards of appropriate size, coated with adhesive (280g / m2), and covered with birch boards of the same size. The boards were pressurized to 1 MPa and the pressure was removed after 24 hours. The boards were left to stand naturally under normal pressure for 7 days, then sawn into standard specimen sizes. Tensile strength tests were then performed using a universal electronic tensile testing machine at a pulling speed of 50 mm / min. The tests were conducted according to the ED204 D3 standard. The EN 204D3 standard:

[0094] Placed at room temperature 20-25℃ and standard atmospheric pressure for seven days, the tensile strength of the specimen is ≥10Mpa (dry strength without immersion Q1);

[0095] Place under normal temperature 20-25℃ and standard atmospheric pressure for seven days, soak in water at 20±5℃ for four days ≥2Mpa (wet strength Q2);

[0096] Place at room temperature 20-25℃ and standard atmospheric pressure for seven days, soak in water at 20±5℃ for 4 days, place at standard atmospheric pressure for seven days≥8Mpa (dry strength Q3).

[0097] (3) Room temperature stability test conditions: After standing for 7 days and 30 days at room temperature of 25°C, filter with a 120-mesh filter to observe whether flocs appear.

[0098] Table 1 Performance test values ​​of embodiments and comparative examples

[0099]

[0100]

[0101] As can be seen from the above table, the glue of the present invention has stable and high water resistance and mechanical strength. The main reasons may be as follows: Analysis of Comparative Example 1 shows that by constructing an amphiphilic hyperbranched skeleton macromonomer, the addition of emulsifier is reduced and the stability of the copolymer latex glue is maintained. Analysis of Comparative Example 2 shows that by constructing a hyperbranched multi-block molecular structure with alternating hard segments and soft segments, the water resistance and mechanical strength of the copolymer latex glue are enhanced on the one hand, and the glass transition temperature of the emulsion can be controlled on the other hand, which is more conducive to subsequent operation at a lower temperature. Finally, the high reactivity of isocyanate is utilized to introduce high-strength, highly water-resistant urethane and urea groups, thereby further improving the mechanical and water resistance of the adhesive. In addition, the room temperature stability performance of Examples 4 and 5 is even better, which is probably due to the dispersion added in the examples. Since the hollow silica particles have an increased elastic force of collision when in motion, the dispersion performance is even better, making the adhesive system more stable. Furthermore, the selection of polyether long chains with steric hindrance effects and polyether polycarboxylic acid sodium sulfonate with strong polar groups that can provide electrostatic repulsion, synergistically with the hollow silica particles (reducing the agglomeration between particles), further reduces the possibility of stratification, makes the phase distribution more uniform, and thus improves its performance.

[0102] Under the premise that no conflict occurs, those skilled in the art may freely combine and superimpose the above-mentioned additional technical features.

[0103] The above descriptions are merely preferred embodiments of the present invention. Any technical solution that achieves the purpose of the present invention by substantially the same means shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing an isocyanate-waterborne hyperbranched multi-block copolymer composite emulsion adhesive, characterized in that: The following steps are involved: S1: preparing an amphiphilic hyperbranched backbone macromonomer; the preparation method of the amphiphilic hyperbranched backbone macromonomer is as follows: first dissolving polyvinyl alcohol in a solvent to prepare a polyvinyl alcohol solution, then adding a bifunctional monomer, a catalyst, and a polymerization inhibitor to the polyvinyl alcohol solution, maintaining a certain temperature for a period of time to react until the non-carbon-carbon double bond functional groups of the bifunctional monomer are completely reacted to obtain a mixed solution, cooling the mixed solution to room temperature, adding ether to precipitate the mixed solution, and washing and drying the mixed solution multiple times to obtain the product; S2: mixing an amphiphilic hyperbranched backbone macromonomer, a buffer, deionized water, and a polymerization inhibitor, and then sequentially adding a first hard monomer, a second soft monomer, a third functional monomer, and a fourth hard monomer to react to prepare an aqueous hyperbranched multi-block copolymer emulsion; S3: mixing the isocyanate with the aqueous hyperbranched multi-block copolymer emulsion prepared in S2 to obtain an isocyanate-aqueous polymer composite emulsion adhesive; The bifunctional monomer is one or a mixture of acrylic acid, methacrylic acid, 2-isocyanate ethyl acrylate, acryloyl chloride, and maleic anhydride.

2. The method for preparing an isocyanate-aqueous hyperbranched multi-block copolymer composite emulsion adhesive according to claim 1, wherein: The solvent is N,N-dimethylformamide.

3. The method for preparing an isocyanate-aqueous hyperbranched multi-block copolymer composite emulsion adhesive according to claim 1, wherein: The catalyst is one of p-diaminopyridine, aluminum chloride, zinc chloride, boric acid, boron trifluoride, and dibutyltin dilaurate; The polymerization inhibitor is a mixture of one or more of hydroquinone, p-tert-butylcatechol, and 2,6-di-tert-butyl-p-methylphenol.

4. The method for preparing an isocyanate-aqueous hyperbranched multi-block copolymer composite emulsion adhesive according to claim 1, wherein: In S2, the aqueous hyperbranched multi-block copolymer emulsion is specifically prepared as follows: the following parts are by weight: 6 parts of an amphiphilic hyperbranched skeleton macromolecular monomer and 0.5-2 parts of a buffer are added to 100-150 parts of deionized water, heated to dissolve, cooled to 40°C after dissolution, 2 parts of a first hard monomer are added for pre-emulsification for 15 minutes, heated to 75°C, a portion of an initiator aqueous solution is added dropwise to initiate polymerization, and after blue light appears and reflux occurs, the remaining 8 parts of the first hard monomer are added dropwise and the reaction temperature is controlled at 75°C. After no reflux occurs, 20 parts of a second soft monomer are added and the reaction temperature is maintained at 70°C. After no reflux occurs, 0.5-2 parts of a third functional monomer are added and the reaction temperature is maintained at 80°C. After no reflux occurs, 10 parts of a fourth hard monomer are added and the reaction temperature is maintained at about 85°C. After no reflux occurs, the temperature is continued to be raised to 90°C and matured for 30 minutes; then the temperature is cooled to room temperature, a plasticizer is added and the material is discharged to obtain the product.

5. The method for preparing an isocyanate-aqueous hyperbranched multi-block copolymer composite emulsion adhesive according to claim 4, wherein: The buffer is sodium bicarbonate and / or sodium carbonate; The first hard monomer is one or more of vinyl acetate, styrene, acrylonitrile, and methyl methacrylate; The initiator is a mixture of one or more of ammonium persulfate, potassium persulfate, and sodium persulfate; The second soft monomer is one or more of butyl acrylate, ethyl acrylate, and isooctyl acrylate; The third functional monomer is one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and glycidyl methacrylate; The fourth hard monomer is a mixture of one or more of acrylonitrile, methyl methacrylate, styrene, and vinyl acetate; The plasticizer is a mixture of one or more of dimethyl phthalate, diethyl phthalate and dibutyl phthalate.

6. The method for preparing an isocyanate-aqueous hyperbranched multi-block copolymer composite emulsion adhesive according to claim 1, wherein: The isocyanate is a mixture of one or more of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate.

7. The method for preparing an isocyanate-aqueous hyperbranched multi-block copolymer composite emulsion adhesive according to claim 1, characterized in that: The isocyanate accounts for 10-30% of the mass of the aqueous hyperbranched multi-block copolymer emulsion.

Images