WO2023207029A1 - Polyurethane microcapsule curing agent, adhesive agent, adhesive film, and preparation methods therefor - Google Patents

Abstract

A method for preparing a polyurethane microcapsule curing agent. The polyurethane microcapsule curing agent comprises a microcapsule structure, wherein the microcapsule structure comprises a wall material and a core material sealed in the wall material. The preparation method comprises the following steps: mixing an oil phase solution containing an isocyanate monomer and a catalyst with an aqueous phase solution containing an emulsifier, and emulsifying same to form an emulsion, wherein the aqueous phase solution constitutes an aqueous phase, and the oil phase solution forms liquid droplets; adding an amine solution to the emulsion, and mixing same to make amine react with the isocyanate monomer at the interface; heating the emulsion having the amine solution added therein to 50-80°C and maintaining same at the temperature for 1-8 min, wherein the isocyanate monomer inside the liquid droplets is reacted and converted into an isocyanate dimer and/or an isocyanate trimer, and the heating rate during heating is greater than or equal to 20°C/s; and cooling the thermally insulated system to 20-30°C, wherein the cooling rate during cooling is greater than or equal to 20°C/s.

Description

Polyurethane microcapsule curing agent, adhesive, adhesive film and respective preparation methods Technical field

The invention belongs to the technical fields of polyurethane curing agents and polyurethane materials, and specifically relates to a preparation method of polyurethane microcapsule curing agent, a polyurethane microcapsule curing agent prepared by the preparation method and the use of the polyurethane microcapsule curing agent in polyurethane materials such as adhesives ( Glue), coatings, adhesive films, etc.

Background technique

Curing agent, also known as hardener, curing agent or stabilizer, is a type of substance or mixture that promotes or controls the curing reaction. Curing agent is an indispensable additive for resin curing. Whether it is used as adhesive, coating, or castable, curing agent must be added, otherwise the resin cannot be cured.

In order to facilitate the use of coatings, adhesives, etc., single-component polyurethane material systems are used in many applications. The release of isocyanate is achieved by heating, allowing it to react with components containing active hydrogen to increase the cross-linking density, thereby achieving solidify. The above-mentioned one-component polyurethane material system contains a latent curing agent component that can function as a curing agent under certain conditions. The latent curing agent needs to be unsealed at a certain temperature, and then a cross-linking reaction occurs. However, at normal temperature Will not react.

In the prior art, TDI (toluene diisocyanate) dimer, MDI (diphenylmethane diisocyanate) dimer, IPDI (isophorone diisocyanate) dimer or IPDI trimer have been used to remove the surface. It is activated to form a microcapsule structure, and a stable suspension is made through protective colloids. This suspension can be added to the emulsion to make a one-component polyurethane material system that can be quickly unsealed. This method of using solid dimers and trimers as raw materials to form microcapsule structures is usually called a solid-state interstitial encapsulation scheme.

There are two main solid-state interstitial encapsulation solutions: spray drying granulation and mechanical grinding. The above two methods have the following problems: pyridine is used as a solvent in the process of spray drying and granulation. The smell of pyridine is very strong, and the particle size of the particles in the suspension is generally 15-60um. After a period of time, After storage, particles with larger particle sizes will sink irrecoverably to the bottom, causing complete failure of the product; particles made by mechanical grinding will release a certain amount of unreacted monomers due to the crushing of large particles during the grinding process. The monomer is wrapped in it during the crystallization process and is difficult to separate after granulation. After it is released, it will generate a certain amount of ineffective solid content components with the co-ground amine and water, which will affect the overall performance, and this process will produce a large number of bubbles. Processing and lowering the pH value of polyurethane dispersion. The pH value of the product will drop rapidly within a period of time after production is completed. Some emulsions that are more sensitive to pH will have problems such as immediate gelation and precipitation when used.

Microcapsule curing agent and polyurethane dispersion (PUD) are formulated into glue. After the glue is film-formed, the PUD is activated at high temperatures and will penetrate into the microcapsules through the wall material to cause cross-linking. However, the appearance of TDI dimer particles prepared using the above two methods is irregular, as shown in Figure 1 (TDI dimer particles prepared by spray drying granulation method) and Figure 2 (TDI prepared by mechanical grinding method). Dimer particles), the microcapsules formed after reacting with inactivated amines in water are still irregular, and the thickness of the microcapsule wall material is also inconsistent. Microcapsules made using the above two methods are greatly affected by the process batch. The shape and thickness of the wall material affect the speed and quantity of penetration, thereby affecting the cross-linking process and the performance of the final material.

The disclosure of the above background technology content is only used to assist in understanding the inventive concepts and technical solutions of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, In this case, the above background technology should not be used to evaluate the novelty and inventiveness of this application.

Contents of the invention

In view of this, in order to overcome the shortcomings of the prior art, the object of the present invention is to provide an improved preparation method of polyurethane microcapsule curing agent.

The invention also provides a polyurethane microcapsule curing agent prepared by the preparation method and its application. The polyurethane microcapsule curing agent avoids excessive reaction between highly active isocyanate and water during the production process, thereby reducing the generation of carbon dioxide. , which facilitates continuous production and avoids the rapid decline of pH, making it have good compatibility with many emulsions. The microcapsule particles produced through interfacial reaction have a uniform and smooth surface and a uniform wall material thickness. For microcapsules under heating, Polymerization has a more stable and controllable penetration speed and curing cross-linking speed.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A preparation method of polyurethane microcapsule curing agent. The polyurethane microcapsule curing agent includes a microcapsule structure. The microcapsule structure includes a wall material and a core material enclosed in the wall material. The preparation method includes the following step:

An oil phase solution containing isocyanate monomer and catalyst and an aqueous phase solution containing an emulsifier are mixed and emulsified to form an emulsion, wherein the aqueous phase solution constitutes a water phase (continuous phase), and the oil phase solution forms droplets (dispersed phase);

Adding an amine solution to the emulsion and mixing to cause an interfacial reaction between the amine and the isocyanate monomer at the interface to form the wall material of the microcapsule;

The emulsion after adding the amine solution is heated to 50-80°C and kept for 1-8 minutes, wherein the isocyanate monomer inside the droplets reacts and is converted into isocyanate dimer and/or isocyanate trimer, and the isocyanate Dimers and/or isocyanate trimers constitute the core material of the microcapsules, and the temperature rise rate during heating is greater than or equal to 20°C/s;

The system after insulation is cooled to 20-30°C, and the cooling rate during the cooling is greater than or equal to 20°C/s.

In some embodiments, the entire system is heated to 50-80°C within 1-10 seconds by controlling the heating rate to avoid water penetration during the long heating process.

Preferably, the preparation method includes the step of adding a thickener to the cooled system for thickening. The viscosity of the thickened system at 25°C is 1000-2000 cps.

Preferably, the preparation method includes the step of allowing the thickened system to stand for aging, and the aging involves keeping the thickened polyurethane microcapsule curing agent at 20 to 30°C for 12 to 36 hours. During the curing process, the remaining isocyanate monomers in the core material will be fully converted into dimers under the action of catalysts, forming microcapsules with isocyanate dimers inside and wall materials with a certain strength on the outside.

According to some preferred implementation aspects of the present invention, before mixing the oil phase solution and the water phase solution, the temperature of the oil phase solution is controlled to be 20-22°C. Put the isocyanate monomer and catalyst into the premix silo at about 20 to 22°C and mix them evenly. Too low a temperature will cause the isocyanate monomer to crystallize, which is not conducive to the formation of uniform droplets in the water phase, while too high a temperature will Converting the isocyanate monomer into a large number of dimer crystals early is also not conducive to the formation of uniform droplets.

According to some preferred implementation aspects of the present invention, when emulsifying and adding an amine solution for reaction, the temperature of the system is controlled to be 0 to 5°C. Using a low temperature of 0 to 5°C can greatly reduce the reaction speed between isocyanate monomer and water, reduce the generation of bubbles, make the emulsified particle size controllable, and the resulting micelle interface is smooth. In some embodiments of the present invention, the aqueous solution is formed by adding an emulsifier to ice water, and then the temperature of the aqueous solution is controlled to be 0-5°C.

According to some preferred implementation aspects of the present invention, during emulsification, the mass ratio of the emulsifier in the aqueous solution to the isocyanate monomer in the oil phase solution is 0.01% to 5%, and in some embodiments is preferably 0.1 %~2%.

According to some preferred implementation aspects of the present invention, the particle size of the microcapsules in the polyurethane microcapsule curing agent is 1 to 10 μm, preferably 5 μm, and the corresponding equipment rotation speed during emulsification is 1000 to 9000 rpm. The particle size is controlled by the amount of emulsifier and the speed of the emulsification equipment, that is, the particle size can be controlled during the reaction process. However, in the traditional method, since the isocyanate dimer is prepared first, the particle size cannot be controlled in the subsequent process. Adjust the size of the diameter.

According to some preferred implementation aspects of the present invention, the isocyanate monomer is an isocyanate having at least two isocyanate groups -NCO. Preferred is toluene diisocyanate TDI, such as T80, T100, etc. Diphenylmethane diisocyanate MDI can also be used as the core material to form microcapsules.

According to some preferred implementation aspects of the present invention, a tubular reactor is used to heat and cool the emulsion to achieve rapid heating and cooling. The front section of the tubular reactor is used to heat the emulsion in 1 to 10 seconds. The temperature is raised to the set temperature within 1 to 10 seconds, and the rear section of the tubular reactor is used to cool the emulsion to the set temperature within 1 to 10 seconds. The continuous production method using tubular reactors does not have stability problems between batches, and it heats up and cools down quickly.

According to some preferred implementation aspects of the present invention, the catalyst is selected from the group consisting of 4-dimethylaminopyridine, pyridine, tri-tert-butylphosphine, tributylphosphine, triethylenediamine, 2,4,6-tris(dimethyl Aminomethyl)phenol, bis(dimethylaminoethyl) ether, 1,8-diazabicyclo[5.4.0]undec-7-N-methylmorpholine, pentamethyldipropylene diamine, 1-methyl-4-(2-dimethylaminoethyl)piperazine, dimethylaminopyridine, 2,2'-dimorpholindiethyl ether, N,N-dimethylbenzylamine , N,N'-dimethylethanolamine, pentamethyldiethylenetriamine, or a combination of one or more. The molar ratio between catalyst and isocyanate monomer is 0.001~0.5%. Too little catalyst is not enough to produce crystallization in a short time through the tubular reactor and improve the structural strength of the microcapsules. Too much catalyst will lead to premature crystallization. Unable to emulsify.

According to some preferred implementation aspects of the present invention, the amine in the amine solution is selected from ammonia, urea, ethylenediamine, pentyldiamine, hexamethylenediamine, hydrazine hydrate, guanidine, adipic acid dihydrazide, polyetheramine , one or more combinations of isophorone diamine, 4,4'-diaminodicyclohexylmethane, and diethanolamine. The molar ratio between amine and isocyanate monomer in the amine solution is 6-12%. The mass percentage concentration of the amine solution is 5% to 35%, preferably about 10% to 30%.

The amine solution is the encapsulation component used to convert micelles into particles, causing interfacial reactions on the surface of the micelles to form uniform wall materials. At the same time, the temperature of the ice water inhibits the reaction between water and NCO, causing NCO to react mainly with amine. The amine and NCO react at the interface to form a thin layer of polyurea layer, which is the wall material, preventing moisture from entering the core material.

According to some preferred implementation aspects of the present invention, the emulsifier in the aqueous solution is a polyoxyethylene ether-based Span emulsifier and/or a polyoxyethylene ether-based Tween emulsifier.

According to some preferred implementation aspects of the present invention, a defoaming agent is added to the aqueous solution during the emulsification, and the defoaming agent is a silicone defoaming agent and/or a mineral oil defoaming agent.

According to some preferred implementation aspects of the present invention, the thickener is one or more selected from the group consisting of xanthan gum, guar gum, cellulose, polyurethane thickeners, polyacrylic acid thickeners, and polyvinylpyrrolidone. combination of species. The dosage of thickener is 0.01-1%, and the viscosity of the system after thickening is 1000-2000 cps at 25°C.

According to some preferred implementation aspects of the present invention, the preparation method further includes the step of adding a preservative into the system after thickening, and the preservative is an isothiazolinone fungicide, such as kason.

In the preferred embodiment of the present invention, by controlling the heating rate and cooling rate, the emulsion system containing particles is rapidly heated to 50-80°C within a few seconds and lasts for about 2 minutes. At this time, due to the rapid reaction speed of the aromatic monomer, the wall wall The material has a certain strength, and the isocyanate monomer has been partially converted into a dimer solid at this temperature. The entire microcapsule has a certain strength, and then quickly cools down to a safe temperature (room temperature is around 20~30°C) for 30 seconds. This avoids the penetration of water during the process and will not affect the isocyanate monomers and dimers in the core material.

In existing application scenarios, for example, the core material of pesticide and flavor microcapsules is liquid. In order to make the microcapsules reach a certain strength, the suspension is usually stirred at 40 to 50°C for 1 to 8 hours to form a solid wall material to prevent Adhesion, but in the application scenario of the present invention, such a long time of high temperature will cause a large amount of water to penetrate and react with the internal isocyanate monomer and dimer, and at the same time generate a large number of bubbles, lowering the pH of the system. Therefore, this In the invention, by raising the temperature to about 50 to 80°C in a very short period of time, part of the wall material is rapidly matured to a certain strength, and the core material is also converted into a large amount of solid dimers. At this time, the microcapsules already have certain strength, and then rapidly cools down to 20-30°C within a few seconds, and matures to fully convert the core material into dimers, thus preventing water from entering the core material and adhesion between microcapsules.

In some embodiments of the present invention, a tubular reactor may be used to perform continuous processing of heating and cooling of the emulsion. The tubular reactor can be divided into two sections. The front section realizes rapid temperature rise, and the latter section realizes cooling. The heating, cooling and holding time can be controlled through the length and distance of the tubular reactor. After cooling to normal temperature, the material is discharged, a thickening agent is added to the system to thicken and prevent settling, and then left to mature.

In the preparation process of the microcapsule curing agent, all raw materials used in the present invention are in liquid state. In some embodiments of the present invention, the preparation method specifically includes the following steps:

1) Put TDI and catalyst into the premix silo at about 20-22°C and mix them evenly to form a solution containing isocyanate monomer and catalyst, that is, an oil phase solution.

2) Add the emulsifier to the ice water to form an aqueous solution, which is the continuous phase. Add the oil phase solution dropwise into the aqueous solution to emulsify at high speed into droplets with controllable particle size and smooth interface, which is the dispersed phase.

3) Then add dropwise the amine solution of the capsule component, stir and mix evenly, so that the amine reacts with the isocyanate monomer on the surface of the droplet at the interface to form a uniform wall material.

4) The emulsion system obtained in step 3) is quickly heated to 50-80°C within a few seconds through a tubular reactor, lasting about 2 minutes, so that the wall material is rapidly matured, and the internal isocyanate monomer is converted into isocyanate dimer. , and then cool down quickly.

5) Finally, the temperature is lowered to normal temperature and the material is discharged, the system is thickened to prevent settling, and then matured so that the remaining TDI inside is fully converted into dimers under the action of the catalyst, thereby obtaining microcapsules and polyurethane microcapsule curing agent. The process is called the encapsulation scheme of the liquid continuous method.

Another object of the present invention is to provide a polyurethane microcapsule curing agent prepared by the above-mentioned preparation method. The polyurethane microcapsule curing agent includes an emulsion and microcapsules dispersed in the emulsion. The microcapsules include The inner part is a core material of isocyanate dimer and the outer part is a polyurea layer wall material formed by the reaction of amine and isocyanate; the mass proportion of the microcapsules in the polyurethane microcapsule curing agent is 35 to 45%. In some embodiments, an emulsion includes ingredients such as emulsifiers, thickeners, preservatives, and water. More specifically, in some embodiments of the present invention, in terms of mass percentage, the polyurethane microcapsule curing agent includes 35 to 45% of microcapsules; 0.1 to 2% of emulsifiers; 0.1 to 0.5% of thickeners; and preservatives. 0.1～0.5% part; 54%～65% water. Preferably, the polyurethane microcapsule curing agent includes 39.5% of microcapsules; 0.1% of emulsifier; 0.3% of thickener; 0.1% of preservative; and 60% of water.

Another object of the present invention is to provide an application of the above-mentioned microcapsule curing agent in the preparation of polyurethane materials, such as being configured into polyurethane glue (adhesive) or coatings, adhesive films and other products.

The invention provides a preparation method of polyurethane adhesive, which includes the following steps:

1) Prepare the polyurethane microcapsule curing agent according to the preparation method as mentioned above;

2) Add vinyl acetate-ethylene emulsion to the polyurethane dispersion, adjust the pH value to 6 to 8, add the polyurethane microcapsule curing agent, additives and water, and stir to obtain the polyurethane adhesive; the polyurethane adhesive The amount of microcapsule curing agent added is 3 to 20%. The mass ratio of polyurethane dispersion to vinyl acetate-ethylene emulsion is preferably 6:4.

According to some preferred implementation aspects of the present invention, the polyurethane dispersion is prepared by the following method: heating and dehydrating polyether polyol and/or polyester polyol, and adding a chain extender to perform chain extension;

Add diisocyanate and catalyst to react until the set isocyanate group content is reached to obtain an isocyanate-terminated prepolymer;

After adding solvent to dilute and cool down, add sodium ethylenediamine ethanesulfonate to extend the chain again;

After adding trishydroxymethylaminomethane for end-capping, adding water for dispersion, and removing the solvent, the polyurethane dispersion is obtained. The solvent may preferably be acetone.

In some embodiments of the present invention, the preparation method of the polyurethane dispersion specifically includes the following steps:

1) Put two polyester polyols with different molecular weights into the reactor, heat and dehydrate, then add the chain extender 1,4-butanediol (BDO) for chain extension, and cool to 60°C while stirring.

2) Add diisocyanate and catalyst and keep stirring at 80°C-90°C until the set isocyanate group NCO content is reached to obtain an isocyanate-terminated prepolymer; the set isocyanate group content is about 1.3%.

3) Add a solvent such as acetone to the system, dilute and cool to 50°C.

4) Add an aqueous solution of sodium ethylenediamine ethane sulfonate (AAS) and stir vigorously for 30 minutes to perform hydrophilic chain extension.

5) Add an aqueous solution of trishydroxymethylaminomethane (TRIS) to react the remaining isocyanate completely, and then distill the solvent acetone to obtain a water-based polyurethane dispersion.

Compared with polyurethane dispersions prepared by traditional processes, the preparation method of the polyurethane dispersion of the present invention uses trishydroxymethylaminomethane for end-capping, so that the prepared PUD molecular chain has three more hydroxyl groups at both ends, which is beneficial to Reacts with curing agent.

According to some preferred implementation aspects of the present invention, a multifunctional amine additive such as Dow's AMP95 is used to adjust the pH value.

According to some preferred implementation aspects of the present invention, the added auxiliary agent includes one or more of a wetting agent, a defoaming agent, and a thickening agent.

According to some preferred implementation aspects of the present invention, the viscosity of the polyurethane adhesive at 25°C is 1500-3000 mPa·s; the solid content is 35-60%.

The invention provides a polyurethane adhesive prepared by the above preparation method, including a polyurethane dispersion and a microcapsule curing agent; the mass ratio of the polyurethane dispersion and the microcapsule curing agent is 100:5-20. In some embodiments, the polyurethane adhesive accounts for 70 to 85% of the polyurethane dispersion, 7 to 12% of the microcapsule curing agent, and 10 to 18% of the additives and water.

The invention provides a method for preparing a polyurethane adhesive film, which includes the following steps: prepare a polyurethane adhesive according to the above preparation method; apply the polyurethane adhesive on a release paper, and obtain the polyurethane adhesive film after drying. The temperature during drying should be lower than 60°C, preferably lower than 55°C, to avoid activating the microcapsule curing agent and causing premature reaction.

The invention provides a polyurethane adhesive film prepared by the above preparation method.

Due to the implementation of the above technical solution, the present invention has the following advantages compared with the prior art: the preparation method of the polyurethane microcapsule curing agent in the present invention, the wall material formed by the interfacial reaction after the liquid raw material is emulsified is continuous and uniform, and the wall material is formed by rapid temperature rise. Then the temperature is quickly cooled down, allowing the wall material to mature quickly, avoiding water penetration and not affecting the isocyanate monomers and dimers in the core material; greatly increasing the effective content of isocyanate dimers inside the microcapsules, improving improve the efficiency of the cross-linking reaction.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a scanning electron microscope (SEM) photo of TDI dimer (ADDOLINK TT) used in the preparation process of existing commercially available microcapsule curing agents;

Figure 2 is a scanning electron microscope (SEM) photo of dimer particles produced using a mechanical grinding method;

Figure 3 is a scanning electron microscope (SEM) photo of the microcapsule particles in the polyurethane microcapsule curing agent prepared in Example 1-1 of the present invention;

Figure 4 is a schematic diagram of the process of preparing polyurethane microcapsule curing agent in Example 1 of the present invention;

Figure 5 is a schematic diagram of the principle of the experimental method in Experiment 1 and Experiment 4 of the present invention;

Figure 6 is a DSC test curve chart of the dry film obtained in Experiment 2 corresponding to Example 1 of the present invention;

Figure 7 is a DSC test curve chart of the dry film obtained in Experiment 2 corresponding to Example 2 of the present invention;

Figure 8 is a DSC test curve chart of the dry film obtained in Experiment 2 of the present invention corresponding to Example 2;

Figure 9 is the infrared test spectrum obtained in Experiment 3 of the present invention;

Figure 10 is a schematic diagram of the principle of the experimental method in Experiment 5 of the present invention;

In the attached picture, MDF board-1, adhesive film-2, PVC film-3, weight-4, base material-5, push-out hole-6, and stained object-7.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described implementation The examples are only part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of protection of the present invention.

Table 1 shows the Chinese ingredients or functions corresponding to the reagent abbreviations used in the examples and the manufacturer abbreviations:

Table 1 Description of some reagents

serial number	abbreviation	Ingredients or effects		Manufacturer abbreviation
1	TDI	Toluene diisocyanate		Covestro
2	IPDI	Isophorone diisocyanate		Covestro
3	HDI	Hexamethylene diisocyanate		Covestro
4	BL 2514	Latent curing agent (TDI dimer)	Covestro
5	AAS	Sodium ethylenediamine ethane sulfonate		Evonik
6	TBUP	Tributylphosphonium		Sigma
7	TRIS	Trishydroxymethylaminomethane	Sigma
8	BDO	1,4-butanediol	China and Thailand
9	T403	Polyoxypropylenetriamine	Huntsman
10	ALA	thickener	OMG
11	L75N	thickener	OMG
12	MB20	Organobismuth catalyst	Air Chemical Industry
13	DS2130	Dispersant	Oscar
14	UL5120	Silicone wetting agent	Oscar
15	F908	Silicone defoamer	Oscar
16	F8916	Silicone defoamer	Oscar
17	Polyester polyol I	2000 molecular weight	Oscar
18	Polyester Polyol II	1800 molecular weight	Oscar
19	NE580	NCO=20.5% water-based HDI curing agent	Oscar
20	Span 60	emulsifier	Haishihua
twenty one	VAE706	Vinyl acetate-ethylene emulsion	Wacker
twenty two	AMP95	Multifunctional amine additives	Dow

Example 1 Preparation of Microcapsule Curing Agent

The traditional method of preparing polyurethane microcapsule curing agent is to first make TDI into dimer solid, and then disperse it into water for deactivation. Figure 1 shows the appearance of commercially available dimer particles. Figure 2 shows the appearance of dimers made by grinding. It can be seen that the surface of this solid is different in size and extremely uneven. The product is generated after deactivation. The shape of the shell is uncontrollable, as shown by the permeability of water to the microcapsules and the permeability of heated polymers such as polyurethane dispersions to the microcapsules during actual use. The present invention uses a liquid continuous method to produce polyurethane microcapsule curing agent. The particle size of the obtained microcapsules is relatively controllable and the surface is smooth. As shown in Figure 3, the speed of water penetration into the wall material and the penetration of the heated polymer during use are Sex is controllable.

The interfacial polymerization method refers to emulsifying or dispersing the core material in a continuous phase in which the wall material is dissolved, and then forming microcapsules through monomer polymerization on the surface of the core material. Interfacial polymerization can be used to prepare microcapsules with smooth and continuous particle surfaces, thus solving the problem of irregular particles. Although this kind of encapsulation scheme exists in pesticides, flavors and other industries, the difference is that when the interfacial polymerization method is used in the existing technology, the residual isocyanate does not need to be considered during the encapsulation and maturation process, so it will take a long time ( Heating (basically longer than 1 hour) allows the wall material to reach a certain strength as quickly as possible to prevent adhesion between microcapsules. However, a large amount of isocyanate (isocyanate group-NCO) needs to be retained in the polyurethane microcapsule curing agent for subsequent cross-linking reactions. If the temperature exceeds 40°C for a long time, a large amount of water will penetrate into the microcapsules through the wall material. As a result, the internal active ingredients are greatly reduced. Therefore, heating and curing microcapsules to prevent adhesion and low-temperature storage to retain a large amount of isocyanate (dimer) form a contradiction. The existing implementation of the interfacial polymerization method cannot solve such a problem.

In order to solve the above problems and achieve the above objectives, the preparation method of the polyurethane microcapsule curing agent of the present invention adopts the following steps:

1) Put TDI and catalyst into the premix silo at about 20-22°C and mix them evenly to form a solution containing isocyanate monomer and catalyst, that is, an oil phase solution.

2) Add emulsifier to ice water to form an aqueous solution (control temperature is 0-5°C), add oil phase solution dropwise into the aqueous solution to emulsify at high speed into droplets with controllable particle size and smooth interface.

3) Then add dropwise the amine solution of the capsule component, stir and mix, so that the amine reacts with the isocyanate monomer on the surface of the droplet at the interface to form a uniform wall material.

4) The emulsion is quickly heated to 50-80°C within a few seconds through a tubular reactor, lasting about 2 minutes, so that the wall material is rapidly matured, and the internal isocyanate monomer is converted into isocyanate dimer, and then the temperature is quickly cooled.

5) Finally, the temperature is lowered to normal temperature and the material is discharged. The system is thickened to prevent settling, and then matured so that the remaining TDI inside is fully converted into dimers under the action of the catalyst, thereby obtaining microcapsules and polyurethane microcapsule curing agent.

Example 1-1

As shown in Figure 4, the preparation method of the polyurethane microcapsule curing agent in this embodiment adopts the following steps:

1) Prepare oil phase solution

Put 500kg TDI and 0.25kg tributylphosphine into the premix silo at 20°C and mix evenly to form a solution containing isocyanate monomer and catalyst, that is, an oil phase solution.

2) Prepare aqueous solution

Add 5kg of emulsifier and 0.5kg of defoaming agent to 500L of ice water, and mix evenly to form an aqueous solution containing the emulsifier, that is, an aqueous phase solution, and control its temperature to 1°C.

3) Emulsification

Pass the oil phase solution obtained in step 1) at a flow rate of 27.5kg/h and the aqueous phase solution obtained in step 2) at a flow rate of 30kg/h into an emulsification device (continuous high-speed emulsifier) for high-speed emulsification, so that the oil phase The solution formed an emulsion with controlled particle size and 47.8% solids content. The particle size of the droplets can be achieved by adding the amount of emulsifier and controlling the rotation speed of the equipment. Control the temperature of the system during the emulsification process to 1°C.

4) Prepare amine solution

Add 1.64kg polyetheramine to 17.5kg deionized water and stir to form a uniform amine solution with a concentration of 9.4%, which is the capsule component.

5) Interface reaction

Put the emulsification completed in step 3) into a continuous mixer at a flow rate of 57.5kg/h and the amine solution obtained in step 4) at a flow rate of 17.5kg/h, so that the diluted amine solution and isocyanate react on the droplet surface. The interface reacts to form a polyurea layer, the wall material. The temperature of the system during the interfacial reaction was controlled to 1°C.

6) Maturation of wall materials

The emulsion system is quickly heated to 80°C within 4 seconds at a heating rate of 20°C/s through a tubular reactor for 2 minutes to rapidly mature the wall material. At the same time, the TDI monomer in the core material is heated under the action of the catalyst and temperature. It is quickly converted into a dimer, and then rapidly cooled to 20°C within 2 seconds at a cooling rate of 30°C/s and continued for 30s.

7) Anti-settlement and anti-corrosion

Cool the temperature to 20°C and discharge the material at room temperature. Add 0.3% by mass of the thickener xanthan gum to the system to thicken and prevent sedimentation; add 0.1% (weight ratio) of the isothiazolinone fungicide of the entire system to the system. Such as Casson.

8) Maturation of core material

The system is left to mature at room temperature, and maintained at 25°C for 24 hours, so that the undimerized TDI in the core material is fully converted into dimer under the action of the catalyst, and microcapsules and polyurethane microcapsule curing agent are obtained. The solid content is 39.2% and the viscosity is 1580cps.

Example 1-2

Proceed with reference to Example 1-1. The difference from Example 1-1 is that in step 3) of this example, 3.28kg of amine is added to 17.5kg of deionized water, and other steps and parameters remain unchanged.

Example 1-3

Proceed with reference to Example 1-1. The difference from Example 1-1 is that in step 1) of this example, 2.2kg of catalyst 4-dimethylaminopyridine is added to 500kg of TDI, and other parameters remain unchanged.

Comparative example 1-1

The difference between this comparative example and Example 1-1 is that 100% concentration of amine is used directly during the interfacial reaction (encapsulation), and no diluted amine solution is used, which results in a large amount of agglomeration and precipitation during the reaction and the inability to form a stable Microcapsule dispersion.

Comparative Example 1-2

The difference between this comparative example and Example 1-1 is that the wall material is aged by stirring at 50°C for 6 hours. Other steps and parameters are basically consistent with Example 1-1. During the curing process of the wall material, a large number of bubbles were generated, and a small amount of agglomeration and precipitation were formed. After filtering the precipitation, the dispersion viscosity was 4530 cps and the solid content was 35.8%.

Comparative Example 1-3

The difference between this comparative example and Example 1-1 is that no thickener was added to the system for anti-settling treatment. Other steps and parameters are basically consistent with Example 1-1. The dispersant has a viscosity of 320 cps and a solid content of 39.4%. After two days, there is a large amount of precipitation in the system. It can return to the initial state after stirring, but it will soon settle down. After a week, it will form a hard lump and cannot be restored to the initial state after stirring.

Example 2-1 Preparation of thermosetting one-component polyurethane adhesive

The preparation method of the thermosetting one-component polyurethane adhesive in this embodiment specifically includes the following steps:

1) Preparation of microcapsule curing agent

Add 500g TDI monomer and 0.05g tributylphosphorus to the container, keep the temperature between 20 and 25°C, stir evenly to form an oil phase solution; add 8g Span 60 to 828g ice water, stir evenly to form a water phase Solution; Slowly drop the above oil phase solution into the water phase solution, and disperse at high speed for half an hour to form a stable emulsion.

Slowly add 100g of 30% concentration polyetheramine aqueous solution into the emulsion, stir for half an hour, and then send it into the tubular reactor. The temperature will quickly rise to 80°C within 3 seconds, and then quickly drop to 25°C within 2 seconds after maintaining for 2 minutes. Keep it for 30 seconds and then discharge it into a mixing container. Add 20g DS2130 dispersant, 2g F908 defoamer, and 2g ALA thickener while stirring. After aging for 36 hours, microcapsule curing agent A is obtained. The viscosity at 25°C is 1540mPa· s, solid content 39%, microcapsule particle size D ₅₀ is about 5um.

2) Preparation of water-based polyurethane dispersion

Put 500g polyester polyol I and 50g polyester polyol II into the reactor, heat to 115°C for dehydration for 1 hour, then add 2.5g BDO, and cool to 60°C while stirring. Then add 42g HDI, 28g IPDI, 3g MB20 and keep stirring at 80℃-90℃ until an isocyanate content of 1.28% is reached. Add 850g acetone, and cool the system temperature to 50°C.

Dilute 7.0g AAS in 55g water, then add it to the system and stir for 30 minutes; then dissolve 8g TRIS in 555g aqueous solution and add it to the system for dispersion. Finally, acetone is distilled off to obtain aqueous polyurethane dispersion B. The melting point of the obtained polyurethane dispersion solid was 44.12°C, the solid content was 49.2% by weight, and the viscosity at 25°C was 1290 mPa·s.

3) Preparation of polyurethane adhesive

Add 300g water-based polyurethane dispersion B and 200g VAE706 to the container, use AMP95 to adjust the pH value to about 7, then add 35g microcapsule curing agent A, 0.5g wetting agent UL5120, 0.5g defoaming agent F8916, and 50g water. After stirring for half an hour, add 0.5g of thickener L75N to obtain a finished polyurethane adhesive with a viscosity of 2130 mPa·s at 25°C and a solid content of 45%.

Example 2-2:

On the basis of Example 2-1, the dosage of microcapsule curing agent A was increased from 35g to 50g, while the others remained unchanged.

Example 2-3

On the basis of Example 2-1, the dosage of microcapsule curing agent A was increased from 35g to 100g, while the others remained unchanged.

Comparative example 2-1

On the basis of Example 2-1, 35g of microcapsule curing agent A was replaced with 35g of Covestro Dispercoll XP BL 2514, and the others remained unchanged.

Comparative Example 2-2

On the basis of Example 2-1, 35g of microcapsule curing agent A was replaced with 50g of Covestro Dispercoll XP BL 2514, and the others remained unchanged.

Comparative Example 2-3

On the basis of Example 2-1, 35g of microcapsule curing agent A was replaced with 100g of Covestro Dispercoll XP BL 2514, and the others remained unchanged.

Comparative Example 2-4

On the basis of Example 2-1, the added amount of Span 60 is increased to 18g, and other conditions remain unchanged. Microcapsule curing agent B can be obtained, with a solid content of 39%, a viscosity of 4130mPa·s, and a particle size D ₅₀ <1um. .

Comparative Example 2-5

On the basis of Example 2-1, 35 g of microcapsule curing agent A was replaced with 35 g of microcapsule curing agent B, and the others remained unchanged.

Comparative Example 2-6

On the basis of Example 2-1, 35 g of microcapsule curing agent A was replaced with 50 g of microcapsule curing agent B, and the others remained unchanged.

Comparative Example 2-7

On the basis of Example 2-1, 35 g of microcapsule curing agent A was replaced with 100 g of microcapsule curing agent B, and the others remained unchanged.

Comparative Example 2-8

On the basis of Example 2-1, 35g of microcapsule curing agent A was replaced with 35g of NE580 curing agent, and the others remained unchanged.

Comparative Example 2-9

On the basis of Example 2-1, no microcapsule curing agent A or microcapsule curing agent B is added, and the others remain unchanged.

Example 3 and Comparative Example 3 Polyurethane Adhesive Film

The glue prepared in Example 2 and Comparative Example 2 is coated on the release paper (film) by roller coating or slit coating, and dried through a variable temperature drying tunnel to form a film to form Example 3 and Comparative Example 3. The drying temperature should be lower than 55℃ to prevent the microcapsule curing agent from being activated.

Tests and Results

1) Scanning electron microscope (SEM)

Scanning electron microscopy (SEM) was performed on the raw materials of commercially available microcapsule curing agent products (TDI dimer, ADDOLINK TT), the dimer particles obtained through the grinding scheme, and the microcapsule curing agent prepared in Example 1-1. After testing, the scanned pictures obtained are shown in Figure 1, Figure 2 and Figure 3 respectively.

It can be seen from Figure 1 and Figure 2 that the TDI dimer solids have different sizes and the surface is extremely uneven. The shape of the shell of the product generated after deactivation is uncontrollable, which is manifested in the permeability to water and the permeability of the PUD in the later stage. They are also uncontrollable. The microcapsules shown in Figure 3 have a relatively controllable particle size and a smooth surface. The speed at which water penetrates the wall material and the permeability of the polymer during use are controllable. Figure 3 shows the pass

The diameter of the microcapsules prepared in Example 1-1 is about 5um.

2)Related tests

experiment one

The microcapsule curing agent prepared in Example 1-1, Example 1-2, Example 1-3 and Comparative Example 1-2 was made into glue according to the same formula, and scraped onto MDF board 1 using a 50um preparer. The gluing area is 50*200mm. After drying, the adhesive film 2 is obtained. PVC film 3 (45 filaments) is attached to the adhesive film 2 and a 180° peeling test is performed. After hot pressing at 100°C for 2 minutes, immediately hang the 10N weight 4 and immediately put it into the oven to observe the peeling distance (within 5 minutes) of the weight at different temperatures (70~90°C), as shown in Figure 5 shown, where 70°C, 80°C, and 90°C are independent experiments. The test results (unit: cm) are shown in Table 2:

Table 2 Test results

​	Example 1-1	Example 1-2	Example 1-3	Comparative Example 1-2
70℃	<1	<1	<1	12
80℃	2	5	5	20
90℃	3	7	8	20

It can be seen from the experimental results in Table 2 that after hot pressing at 100°C for 2 minutes, Examples 1-1, 1-2, and 1-3 showed higher initial temperature resistance at 70°C, indicating that PUD and isocyanate have A certain degree of reaction has occurred to increase the molecular weight, and the reaction efficiency is high. However, the degree of cross-linking of Comparative Examples 1-2 is lower than that of the Examples. This represents the polyurethane microcapsule curing agent prepared in the Examples at a lower temperature and in a shorter time. Unsealing and cross-linking in the traditional sense can be achieved within a short period of time. Traditional curing agents may need to react at 120°C for 1 hour. Moreover, the peeling effect of the embodiment at 80°C and 90°C is much better than that of the comparative example.

Experiment 2

The polyurethane microcapsule curing agent prepared in Example 1-1, Example 1-2 and Comparative Example 1-2 was prepared according to the same formula to obtain glue, and was coated on the release paper respectively to make a glue with a thickness of 50um. Dry film, use DSC to test the dry film sample, and the obtained spectra are shown in Figures 6-8.

From Figure 6-8, it can be seen that the enthalpies of the DSC test curves of the dry films corresponding to Example 1-1, Example 1-2 and Comparative Example 1-2 are 22.616J, 23.723J, and 12.093J respectively, that is, the comparative example The enthalpy of the DSC test curve of 1-2 is much smaller than that of Example 1-1 and Example 1-2, indicating that the reaction efficiency between the polyurethane microcapsule curing agent prepared in the Example and the PUD is greater than that of Comparative Example 1-2.

Experiment 3

The three dry films produced in Experiment 2 were subjected to infrared testing, and the results are shown in Figure 9.

It can be seen from the infrared spectrum of Figure 9 that in the 2240-2280cm ^-1 region, the peaks of Examples 1-1 and 1-2 are much larger than those of Comparative Example 1-2. The 2240-2280cm ^-1 region corresponds to -N=C= The stretching vibration peak of O indicates that the curing agent prepared in Example 1-1 and Example 1-2 contains more effective isocyanate components. The PUD polymer activated at a temperature of 70 to 100°C will penetrate into the microcapsules through the wall material of the microcapsules and react with these wrapped isocyanates. The more effective isocyanate the curing agent contains, the more efficient the reaction will be.

Experiment 4

As shown in Figure 5, an initial temperature resistance test was performed on some of the polyurethane adhesives in the above-mentioned Example 2 (2-1 to 2-3) and Comparative Example 2 (2-1 to 2-9):

Use a preparer to scrape the polyurethane adhesive onto the MDF board 1 to form an adhesive layer with a wet film thickness of 50um (width 5cm, length 20cm), and then place it in an oven at room temperature or below 40°C to dry until it is no longer sticky, forming Adhesive film 2, and then cover the top of the adhesive film 2 with PVC film 3 with a thickness of 35mm, and perform a 180° peeling test. Use a hot press machine to heat press at 60°C for 2 minutes or 80°C for 2 minutes. Then immediately put the workpiece into an oven at 80°C, hang a 1kg weight 4, and observe the displacement distance of the PVC film (5 minutes Inside). The following are the initial heat resistance test displacement results (cm):

Table 3 Test results

It can be seen from the experiment and the results in Table 3 above that the effect of the embodiment is obviously better than that of the comparative example. And microcapsule curing agents with a particle size of about 1 to 5um are more suitable, although the microcapsules in Comparative Examples 2-5 to 2-7 have smaller particle sizes (D ₅₀ <1um) and larger specific surface areas. , but because the wall material takes up too much isocyanate, the ineffective solid content is high and the effective isocyanate content is low, resulting in poor actual cross-linking effect. Comparative Example 2-9, which did not add any curing agent, was completely peeled off under the initial temperature resistance test conditions, while Comparative Example 2-8, which added a two-component curing agent (NE580), failed to peel off in a short time. A cross-linking reaction occurs, so the initial temperature resistance is not improved.

Experiment 5

As shown in Figure 10, the polyurethane adhesive film prepared in Example 3 and Comparative Example 3 was subjected to a push-out test: the adhesive film 2 was sandwiched between the base material 5 (size 4*4cm) and the adhered material 7 (diameter 2.1 cm), hot press at 80°C for 120 to 240 seconds, use a stick-shaped object to move to the ejection hole 6 (diameter: 0.9cm) at a speed of V=10mm/min, push it out, and test the impact of the adherend when it falls. The maximum pressure, converted into pressure (MPa), is the derived value. Test substrate 5 is 304 stainless steel treated with primer (such as silane, primer, UPUV, etc.), and the adherends are PC, PET, PI, fabric and other materials. The following are the results of the rollout test (MPa):

Table 4 Test results

Through experiments and the data in Table 4 above, the effect of the embodiment is obviously better than that of the comparative example. Corresponding to the results of Experiment 4, microcapsule curing agents with a particle size of about 1 to 5um are more suitable. Smaller particle sizes (D ₅₀ <1um) have a larger specific surface area, but the wall material takes up too much The ineffective solid content of isocyanate is relatively high, resulting in poor actual cross-linking effect and poor results in the launch test.

Since the cross-linking efficiency is directly proportional to the specific surface area of the latent curing agent within a certain range, the emulsion particles (15-60 μm) in the prior art are relatively large, resulting in a relatively large amount of latent curing agent added, and excessive latent curing The agent is equivalent to a solid filler and affects the final performance of the film. In the preparation method of the polyurethane microcapsule curing agent of the present invention, the particle size of the microcapsules is controllable (1-5 μm), which prevents the emulsion from settling too quickly. Even if some sedimentation occurs after long-term storage, simple stirring can It can be restored to the normal state again; the wall material formed by the interfacial reaction after emulsification of the liquid raw materials is continuous and uniform, so that the penetration ability of the latent curing agent of the PUD after activation is stable, and there is no problem of releasing a large amount of carbon dioxide in the later period; and the continuous production method is not There are batch stability issues. On the other hand, the existing PUD has a relatively large molecular weight, a small number of terminal hydroxyl groups or amine groups, and a small number that can react with the latent curing agent. When preparing the polyurethane dispersion, the present invention introduces TRIS without reducing the molecular weight. Under the premise, the hydroxyl content is increased, which is more conducive to the reaction with the microcapsule curing agent and improves the cross-linking density and efficiency.

The above embodiments are only for illustrating the technical concepts and characteristics of the present invention. Their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly. They cannot thereby limit the scope of protection of the present invention. Equivalent changes or modifications in spirit shall be included in the protection scope of the present invention.

Claims (37)

1. A method for preparing a polyurethane microcapsule curing agent. The polyurethane microcapsule curing agent includes a microcapsule structure, characterized in that the microcapsule structure includes a wall material and a core material enclosed in the wall material, and the The preparation method includes the following steps:

   Mixing and emulsifying an oil phase solution containing isocyanate monomer and catalyst with an aqueous phase solution containing an emulsifier to form an emulsion, wherein the oil phase solution forms droplets dispersed in the aqueous phase solution;

   Adding an amine solution to the emulsion and mixing, causing an interfacial reaction between the amine and the isocyanate monomer at the interface of the droplets to form the wall material of the microcapsule;

   The emulsion after adding the amine solution is heated to 50-80°C within 1-10 seconds and kept at the temperature for 1-8 minutes, where the isocyanate monomer inside the droplets reacts and is converted into isocyanate dimer and/or isocyanate trimer. Body, the isocyanate dimer and/or isocyanate trimer constitutes the core material of the microcapsule;

   The heat-insulated system is cooled to 20-30°C within 1-10 seconds and discharged.
2. The preparation method according to claim 1, characterized in that the heating rate during heating is greater than or equal to 20°C/s; the temperature cooling rate during cooling is greater than or equal to 20°C/s.
3. The preparation method according to claim 1, characterized in that the preparation method includes the step of adding a thickener to the cooled system for thickening, and the viscosity of the thickened system at 25°C is 1000-2000 cps ; and/or include the step of keeping the cooled system at 20-30°C for 12-36 hours.
4. The preparation method according to claim 1 or 3, characterized in that the preparation method includes first adding a thickening agent to the cooled system for thickening, and then placing the cooled system at 20-30°C for insulation. 12～36h.
5. The preparation method according to claim 1, characterized in that, before mixing the oil phase solution and the water phase solution, the temperature of the oil phase solution is controlled to 20-22°C.
6. The preparation method according to claim 1, characterized in that controlling emulsification and adding amine solution for reaction are performed at 0 to 5°C.
7. The preparation method according to claim 1 or 6, characterized in that the aqueous phase solution is formed by adding an emulsifier to ice water.
8. The preparation method according to claim 1, characterized in that the mass ratio of the emulsifier in the aqueous solution to the isocyanate monomer in the oil phase solution is 0.01% to 5%.
9. The preparation method according to claim 1, characterized in that the mass percentage concentration of the amine solution is 5 to 35%.
10. The preparation method according to claim 1, characterized in that the particle size of the microcapsules in the polyurethane microcapsule curing agent is 1 to 10 μm.
11. The preparation method according to claim 1, characterized in that the isocyanate monomer is an isocyanate having at least two isocyanate groups.
12. The preparation method according to claim 1 or 11, characterized in that the isocyanate monomer is toluene diisocyanate and/or diphenylmethane diisocyanate.
13. The preparation method according to claim 1, characterized in that a tubular reactor is used to heat and cool the emulsion, and the front section of the tubular reactor is used to heat the emulsion within 1 to 10 seconds. to the set temperature, the rear section of the tubular reactor is used to cool the emulsion to the set temperature within 1 to 10 seconds.
14. The preparation method according to claim 1, characterized in that the corresponding equipment rotation speed during the emulsification is 1000-9000 rpm.
15. The preparation method according to claim 1, characterized in that the catalyst is selected from the group consisting of 4-dimethylaminopyridine, pyridine, tri-tert-butylphosphine, tributylphosphine, triethylenediamine, 2,4,6 -Tris(dimethylaminomethyl)phenol, bis(dimethylaminoethyl)ether, 1,8-diazabicyclo[5.4.0]undec-7-N-methylmorpholine, penta Methyldipropylenediamine, 1-methyl-4-(2-dimethylaminoethyl)piperazine, dimethylaminopyridine, 2,2'-dimorpholindiethyl ether, N,N- One or a combination of one or more of dimethylbenzylamine, N,N'-dimethylethanolamine, and pentamethyldiethylenetriamine.
16. The preparation method according to claim 1, characterized in that the molar ratio between the catalyst and isocyanate monomer is 0.001 to 0.5%.
17. The preparation method according to claim 1, characterized in that the amine in the amine solution is selected from ammonia, urea, ethylenediamine, pentanediamine, hexamethylenediamine, hydrazine hydrate, guanidine, adipic acid diamide One or a combination of more of hydrazine, polyetheramine, isophoronediamine, 4,4'-diaminodicyclohexylmethane, and diethanolamine.
18. The preparation method according to claim 1 or 17, characterized in that the mass percentage concentration of the amine solution is 5 to 35%.
19. The preparation method according to claim 1 or 17, characterized in that the molar ratio between the amine and the isocyanate monomer in the amine solution is 6-12%.
20. The preparation method according to claim 1, characterized in that the emulsifier in the aqueous solution is a polyoxyethylene ether-based Span emulsifier and/or a polyoxyethylene ether-based Tween emulsifier.
21. The preparation method according to claim 3, characterized in that the thickener is selected from xanthan gum, guar gum, cellulose, polyurethane thickeners, polyacrylic acid thickeners, and polyvinylpyrrolidone. one or a combination of more.
22. The preparation method according to claim 1, characterized in that, during the emulsification, a defoaming agent is added to the aqueous solution, and the defoaming agent is a silicone defoaming agent and/or a mineral oil defoaming agent. agent.
23. The preparation method according to claim 1 or 22, characterized in that the preparation method includes the step of adding a preservative to the system, and the preservative is an isothiazolinone fungicide.
24. A method for preparing polyurethane microcapsule curing agent, which is characterized in that it includes the following steps:

    Mix the isocyanate monomer and the catalyst uniformly to form a first solution, add the first solution to the second solution containing the emulsifier for emulsification, so that the first solution forms dispersed droplets; add the amine solution and mix ;Raise the temperature of the system to 50~80℃ within 1~10s and keep it for 1~8min; then cool down to 20~30℃ within 1~10s.
25. A polyurethane microcapsule curing agent prepared by the preparation method according to any one of claims 1 to 24, characterized in that the polyurethane microcapsule curing agent includes an emulsion and microcapsules dispersed in the emulsion, so The microcapsules include an internal core material of isocyanate dimer and/or isocyanate trimer and an external wall material formed by the reaction of amine and isocyanate monomer; the mass proportion of the microcapsules in the polyurethane microcapsule curing agent It is 35~45%.
26. The preparation method according to claim 25, characterized in that, in terms of mass percentage, the polyurethane microcapsule curing agent includes 35 to 45% of microcapsules; 0.1 to 2% of emulsifier; and 0.1 to 0.5% of thickener. parts; 0.1-0.5% parts of preservatives; 54-65% parts of water.
27. Application of the polyurethane microcapsule curing agent as claimed in claim 25 or 26 in the preparation of polyurethane materials.
28. A method for preparing polyurethane adhesive, which is characterized by comprising the following steps:

    1) Prepare the polyurethane microcapsule curing agent according to the preparation method according to any one of claims 1-24;

    2) Add vinyl acetate-ethylene emulsion to the polyurethane dispersion, adjust the pH value to 6 to 8, add the polyurethane microcapsule curing agent, additives and water, and stir to obtain the polyurethane adhesive; the polyurethane adhesive The amount of microcapsule curing agent added is 3 to 20%.
29. The preparation method according to claim 28, characterized in that in step 2), a multifunctional amine additive is used to adjust the pH value.
30. The preparation method according to claim 28, wherein the auxiliary agent includes one or more of a wetting agent, a defoaming agent, and a thickening agent.
31. The preparation method according to claim 28, characterized in that the viscosity of the polyurethane adhesive at 25°C is 1500-3000 mPa·s; the solid content is 35-60%.
32. The preparation method according to claim 28, characterized in that the polyurethane dispersion is prepared by the following method: heating and dehydrating polyether polyol and/or polyester polyol, and adding a chain extender to extend the chain;

    Add diisocyanate and catalyst to react until the set isocyanate group content is reached;

    After adding solvent to dilute and cool down, add sodium ethylenediamine ethanesulfonate to extend the chain again;

    After adding trishydroxymethylaminomethane for end-capping reaction, water is added for dispersion, and the polyurethane dispersion is obtained after removing the solvent.
33. A polyurethane adhesive, characterized in that the polyurethane adhesive is prepared by the preparation method described in any one of claims 27-31, and the polyurethane adhesive includes a polyurethane dispersion and a microcapsule curing agent; the polyurethane dispersion The mass ratio to microcapsule curing agent is 100:5~20.
34. The polyurethane adhesive according to claim 33, characterized in that, in terms of mass percentage, the polyurethane adhesive contains 70 to 85% of polyurethane dispersion, 7 to 12% of microcapsule curing agent, and 10 to 18% of auxiliary agents and water.
35. A method for preparing a polyurethane adhesive film, which is characterized by: comprising the following steps: preparing a polyurethane adhesive according to the preparation method described in any one of claims 28-32; coating the polyurethane adhesive on release paper and drying Finally, the polyurethane film is obtained.
36. The preparation method according to claim 35, characterized in that the temperature during drying is lower than 60°C.
37. A polyurethane adhesive film, characterized in that the polyurethane adhesive film is prepared by the preparation method described in claim 35 or 36.

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