CN116510636A - A kind of polyurethane microcapsule curing agent and its application - Google Patents

Abstract

The invention discloses a curing agent for polyurethane microcapsules. The curing agent for polyurethane microcapsules comprises an emulsion and microcapsules dispersed in the emulsion. The mass ratio of the microcapsules to the curing agent for polyurethane microcapsules is 35-35. 45%; the microcapsules include a wall material and a core material enclosed in the wall material; the core material is an isocyanate dimer and/or an isocyanate trimer formed after the reaction of an isocyanate monomer and a catalyst; the The wall material is formed by the reaction of amine and isocyanate monomer. The polyurethane microcapsule curing agent in the present invention has a microcapsule structure, and the wall material formed by the interface reaction after the emulsification of the liquid raw material is continuous and uniform, and the wall material is rapidly matured by rapid temperature rise and then rapidly cooled, avoiding the penetration of water, It will not affect the isocyanate monomer and dimer in the core material; the effective content of the isocyanate dimer inside the microcapsule is greatly increased, and the efficiency of the crosslinking reaction is improved.

Description

A kind of polyurethane microcapsule curing agent and its application

This application is a divisional application of an invention patent application with an application date of April 25, 2022, an application number of 2022104413173, and an invention title of "polyurethane microcapsule curing agent, adhesive, adhesive film and their respective preparation methods".

technical field

The invention belongs to the technical field of polyurethane curing agents and polyurethane materials, and in particular relates to a polyurethane microcapsule curing agent and the application of the polyurethane microcapsule curing agent in polyurethane materials such as adhesives (glue), coatings, film and the like.

Background technique

Curing agent, also known as hardening agent, curing agent or stabilizer, is a kind of substance or mixture that promotes or controls the curing reaction. Curing agent is an essential additive for resin curing. No matter 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., a one-component polyurethane material system is used in many applications, and the isocyanate is released by heating, so that it reacts with the active hydrogen-containing component to increase the cross-linking density. solidify. The above-mentioned one-component polyurethane material system contains a latent curing agent component that can only function as a curing agent under certain conditions. won't respond.

The use of TDI (toluene diisocyanate) dimer, MDI (diphenylmethane diisocyanate) dimer, IPDI (isophorone diisocyanate) dimer or IPDI trimer surface removal has appeared in the prior art. Activated to form a microcapsule structure, a stable suspension is made through a protective colloid, and this suspension is added to the emulsion to make a one-component polyurethane material system that can be quickly unblocked. Generally, this method of using solid dimers and trimers as raw materials to form microcapsule structures is called solid-state interstitial encapsulation scheme.

There are mainly two types of solid-state interstitial encapsulation solutions in the prior art: spray-drying granulation and mechanical grinding. The above two methods have the following problems: use pyridine as a solvent in the process of spray drying and granulation, the smell of pyridine is very large, and the particle size of the particles in the suspension is generally 15-60um. After storage, the particles with larger particle size will sink to the bottom irreversibly, so that the product is completely ineffective; the particles made by mechanical grinding will release a certain amount of unreacted monomer due to the crushing of large particles during the grinding process. The monomer is wrapped in it during the crystallization process, and it is difficult to separate after granulation. After it is released, it will form a certain amount of invalid solid content components with the co-ground amine and water, which will affect the overall performance, and this process will produce a lot of air bubbles. Processing and lowering the pH value of the polyurethane dispersion, the pH value of the product will drop rapidly within a period of time after the production is completed, and some emulsions that are more sensitive to pH will immediately gel and precipitate when used.

The microcapsule curing agent and polyurethane dispersion (PUD) are formulated into glue. After the glue is formed into a film, the PUD is activated at high temperature and penetrates into the microcapsules through the wall material for cross-linking. But the appearance of the TDI dimer particle that uses above-mentioned two kinds of schemes to make is all irregular, as Fig. 1 (the TDI dimer particle that the spray-drying granulation method prepares) and Fig. 2 (the TDI that the mechanical milling method prepares dimer particles), the microcapsules formed after they reacted with the inactivated amine in water are still irregular, and the thickness of the microcapsule wall material is also inconsistent. The microcapsules made by the above two schemes are greatly affected by the process batch, and the shape and thickness of the wall material affect the speed and quantity of penetration, thus affecting the crosslinking process and the performance of the final material.

The disclosure of the above background technical content is only used to assist in understanding the inventive concepts and technical solutions of the present invention, and it does not necessarily belong to the prior art of this patent application. There is no clear evidence that the above content has been disclosed on the filing date of this patent application. Under the circumstances, 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 defective of prior art, the object of the present invention is to provide a kind of improved polyurethane microcapsule curing agent and application thereof.

The present invention also provides a preparation method of the polyurethane microcapsule curing agent, 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 and facilitating continuous production , and avoid the rapid drop of pH, so that it has better compatibility with many emulsions, the surface of the microcapsule particles prepared by interfacial reaction is uniform and smooth, and the thickness of the wall material is uniform, which is more stable and reliable for polymerization under heating Controlled penetration speed and curing crosslinking speed.

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

A kind of preparation method of polyurethane microcapsule curing agent, described polyurethane microcapsule curing agent comprises microcapsule structure, and described microcapsule structure comprises wall material and the core material that is enclosed in described wall material, and described preparation method comprises as follows step:

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

adding an amine solution to the emulsion and mixing, so that the amine reacts with the isocyanate monomer at the interface to form the wall material of the microcapsule;

Heat the emulsion after adding the amine solution to 50-80°C and keep it warm for 1-8 minutes, wherein the isocyanate monomer inside the droplet reacts and transforms into isocyanate dimer and/or isocyanate trimer, and the isocyanate Dimer and/or isocyanate trimer constitute the core material of the microcapsules, and the heating rate during heating is greater than or equal to 20°C/s;

The temperature of the system after the heat preservation is lowered to 20-30° C., and the cooling rate during the cooling is greater than or equal to 20° C./s.

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

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

Preferably, the preparation method includes the step of standing and curing the thickened system, and the curing is to keep the thickened polyurethane microcapsule curing agent at 20-30° C. for 12-36 hours. During the curing process, the remaining isocyanate monomers in the core material will be fully converted into dimers under the action of the catalyst, 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 premixing silo for uniform mixing at about 20-22°C. If the temperature is too low, the crystallization of the isocyanate monomer will not be conducive to the formation of uniform droplets in the water phase, and if the temperature is too high. The early transformation of isocyanate monomer into a large number of dimer crystals 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 0-5°C. Using a low temperature of 0-5°C can greatly reduce the reaction speed of the isocyanate monomer and water, reduce the generation of bubbles, make the emulsified particle size controllable, and obtain a smooth interface of micelles. In some embodiments of the present invention, the aqueous phase solution is formed by adding an emulsifier into ice water, and then controlling the temperature of the aqueous phase solution 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 phase solution to the isocyanate monomer in the oil phase solution is 0.01% to 5%, preferably 0.1% in some embodiments %~2%.

According to some preferred implementation aspects of the present invention, the particle size of the microcapsules in the polyurethane microcapsule curing agent is 1-10 μm, preferably 5 μm, and the corresponding equipment speed during emulsification is 1000-9000 rpm. The size of the particle size is controlled by the amount of emulsifier and the speed of the emulsification equipment, that is, the particle size can be adjusted during the reaction process, but the traditional method is unable to adjust the isocyanate dimer in the subsequent process because it first prepares the isocyanate dimer. The particle size is regulated.

According to some preferred implementation aspects of the present invention, the isocyanate monomer is an isocyanate having at least two isocyanate groups -NCO. It is preferably toluene diisocyanate TDI, such as T80, T100, etc., and 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 internal temperature is raised to the set temperature, and the latter part of the tubular reactor is used to cool the emulsion to the set temperature within 1-10s. There is no stability problem between batches in the continuous production method formed by the tubular reactor, and the temperature rises and falls rapidly.

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

According to some preferred implementation aspects of the present invention, the amine in the amine solution is selected from ammonia water, urea, ethylenediamine, pentamethylenediamine, hexamethylenediamine, hydrazine hydrate, guanidine, adipate dihydrazide, polyetheramine , isophoronediamine, 4,4'-diaminodicyclohexylmethane, diethanolamine or a combination of one or more. The molar ratio between amine and isocyanate monomer in the amine solution is 6-12%. The mass percent concentration of the amine solution is 5-35%, preferably about 10%-30%.

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

According to some preferred implementation aspects of the present invention, the emulsifier in the aqueous phase 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, an antifoaming agent is added to the aqueous phase solution during the emulsification, and the antifoaming agent is a silicone-based antifoaming agent and/or a mineral oil-based antifoaming agent.

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

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

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. The material has a certain strength, and at this temperature, the isocyanate monomer has been partially converted into a dimer solid, and the entire microcapsule has a certain strength, and then quickly cools down to a safe temperature (about 20-30°C at room temperature), avoiding The penetration of water during the process will not affect the isocyanate monomer and dimer 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 40-50°C for 1-8 hours to form a strong wall material to prevent However, in the application scenario of the present invention, such a long time of high temperature will cause a large amount of water to penetrate in and react with the internal isocyanate monomer and dimer, and generate a large number of air bubbles at the same time, reducing the pH of the system. Therefore, this In the invention, by raising the temperature to about 50-80°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 dimer. At this time, the microcapsules already have a certain strength. Strength, and then quickly cool down to 20-30°C within a few seconds, and then mature to fully convert the core material into a dimer, which not only prevents water from entering the core material but also avoids the adhesion between microcapsules.

In some embodiments of the present invention, a tubular reactor can be used to carry out the continuous treatment of raising and lowering the temperature of the above-mentioned emulsion. The tubular reactor can be divided into two sections, the front section realizes rapid temperature rise, and the rear section realizes cooling, and the length and distance of the tubular reactor can be used to control the heating, cooling and holding time. After cooling down to normal temperature, the material is discharged, and a thickener is added to the system for thickening and anti-sedimentation, followed by static aging.

In the preparation process of the microcapsule curing agent, all raw materials used in the present invention are liquid, and 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 evenly to form a solution containing isocyanate monomer and catalyst, that is, an oil phase solution.

2) adding the emulsifier into ice water to form a water phase solution, which is the continuous phase; adding the oil phase solution dropwise into the water phase 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 forming component, stir and mix evenly, so that the interface reaction between the amine and the isocyanate monomer on the surface of the droplet forms a uniform wall material.

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

5) Finally, cool down to normal temperature and discharge, thicken the system to prevent sedimentation, and then mature, so that the remaining TDI in the interior is fully converted into a dimer under the action of a catalyst, and then microcapsules and polyurethane microcapsule curing agents are obtained. 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, which includes emulsion and microcapsules dispersed in the emulsion, and the microcapsules include The inside is the core material of isocyanate dimer and the outside is the 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 35-45%. In some embodiments, the emulsion includes 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 35-45% parts of microcapsules; 0.1-2% parts of emulsifier; 0.1-0.5% parts of thickener; preservative 0.1-0.5% part; 54-65% part of 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 microcapsule curing agent as described above in the preparation of polyurethane materials, such as configuring products such as polyurethane glue (adhesive) or coatings and adhesive films.

The invention provides a kind of preparation method of polyurethane adhesive, comprises the steps:

1) prepare polyurethane microcapsule curing agent according to the above-mentioned preparation method;

2) Add vinyl acetate-ethylene emulsion to the polyurethane dispersion, adjust the pH value to 6-8, add the polyurethane microcapsule curing agent, auxiliary agent and water, and stir to obtain the polyurethane adhesive; the polyurethane adhesive The addition amount of the microcapsule curing agent in is 3～20%. 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 for chain extension;

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

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

After adding trihydroxymethylaminomethane for capping, adding water for dispersion, and removing the solvent to obtain the polyurethane dispersion. 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) to extend the chain, and cool down 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 solvent such as acetone to the system, dilute and cool to 50°C.

4) Add an aqueous solution of sodium ethylenediaminoethanesulfonate (AAS), and vigorously stir for 30 minutes to carry out hydrophilic chain extension.

5) adding an aqueous solution of trishydroxymethylaminomethane (TRIS) to completely react the remaining isocyanate, and then distill off the solvent acetone to obtain an aqueous polyurethane dispersion.

Compared with the polyurethane dispersion prepared by the traditional process, the preparation method of the polyurethane dispersion of the present invention adopts trishydroxymethylaminomethane to carry out capping, so that the two ends of the prepared PUD molecular chain have three more hydroxyl groups, which is beneficial to Reacts with curing agents.

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

According to some preferred implementation aspects of the present invention, the additives added include one or more of wetting agents, defoamers, and thickeners.

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, comprising a polyurethane dispersion and a microcapsule curing agent; the mass ratio of the polyurethane dispersion to the microcapsule curing agent is 100:5-20. In some embodiments, in the polyurethane adhesive, the polyurethane dispersion accounts for 70-85%, the microcapsule curing agent accounts for 7-12%, and the auxiliary agent and water account for 10-18%.

The invention provides a method for preparing a polyurethane adhesive film, comprising the following steps: preparing a polyurethane adhesive according to the above preparation method; coating the polyurethane adhesive on a release paper, and drying to obtain the polyurethane adhesive. The temperature during drying is lower than 60°C, preferably lower than 55°C, so as to prevent the microcapsule curing agent from being activated and reacting in advance.

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

Due to the implementation of the above technical solutions, the present invention has the following advantages compared with the prior art: the polyurethane microcapsule curing agent in the present invention has a microcapsule structure, and the wall material formed by the interface reaction after the emulsification of the liquid raw material is continuous and uniform. Rapid heating and then rapid cooling, so that the rapid aging of the wall material, avoiding the penetration of water, will not affect the isocyanate monomer and dimer in the core material; so that the effective content of the isocyanate dimer inside the microcapsule is greatly increased , improving the efficiency of the crosslinking reaction.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need 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 skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

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

Fig. 2 is the scanning electron microscope (SEM) picture of the dimer particle that uses mechanical milling method to make;

Fig. 3 is the scanning electron microscope (SEM) photograph of the microcapsule particle in the polyurethane microcapsule solidifying agent prepared in the embodiment of the present invention 1-1;

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

Fig. 5 is the principle schematic diagram of the experimental method in experiment one and experiment four of the present invention;

Fig. 6 is the DSC test curve atlas of the dry film that corresponding embodiment one obtains in experiment two of the present invention;

Fig. 7 is the DSC test curve atlas of the dry film that corresponding embodiment two obtains in experiment two of the present invention;

Fig. 8 is the DSC test curve atlas of the dry film that corresponding comparative example two obtains in experiment two of the present invention;

Fig. 9 is the infrared test spectrum that obtains in experiment three of the present invention;

Fig. 10 is a schematic diagram of the principle of the experimental method in experiment five of the present invention;

In the accompanying drawings, MDF board-1, adhesive film-2, PVC film-3, weight-4, base material-5, push-out hole-6, 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 drawings in the embodiments of the present invention. Obviously, the described implementation Examples are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

The following table 1 is the Chinese composition or effect corresponding to the abbreviation of some reagents adopted in the embodiment and the abbreviation of the manufacturer:

Table 1 Reagent Description

serial number abbreviation Composition or function Manufacturer abbreviation 1 TDI Toluene diisocyanate Covestro 2 IPDI Isophorone diisocyanate Covestro 3 HDI Hexamethylene diisocyanate Covestro 4 BL2514 Latent curing agent (TDI dimer) Covestro 5 AAS Sodium ethylenediamine ethanesulfonate Evonik 6 TBUP tributylphosphine Sigma 7 TRIS tris hydroxymethyl amino methane Sigma 8 BDO 1,4-Butanediol China and Thailand 9 T403 polyoxypropylene triamine Huntsman 10 ALA thickener OMG 11 L75N thickener OMG 12 MB20 Organic Bismuth Catalyst Air Chemicals 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 Sea petrochemical twenty one VAE706 Vinyl acetate-ethylene emulsion Wacker twenty two AMP95 Multifunctional amine additives Dow

The preparation of embodiment 1 microcapsule curing agent

The traditional method of preparing polyurethane microcapsule curing agent is to first make TDI into dimer solid, and then disperse it in water to deactivate. Figure 1 shows the appearance of commonly used dimer particles on the market, and Figure 2 shows the appearance of the dimer produced by the grinding method. It can be seen that the size of the solid is different and the surface is extremely rough. The shell shape of the product generated after deactivation It is uncontrollable, showing that the permeability of water to microcapsules and the permeability of heated polymers such as polyurethane dispersions to microcapsules in actual use are also uncontrollable. The present invention adopts liquid state continuous method to make polyurethane microcapsule curing agent, and the obtained microcapsule particle size is relatively controllable, and the surface is smooth, as shown in Fig. Sex is controllable.

The interfacial polymerization method means that the core material is emulsified or dispersed in a continuous phase in which the wall material is dissolved, and then microcapsules are formed on the surface of the core material through monomer polymerization. Microcapsules with smooth and continuous particle surfaces can be well prepared by the interfacial polymerization method, thereby solving the problem of irregular particles. Although this encapsulation scheme exists in industries such as pesticides and essences, the difference is that when the interfacial polymerization method is applied in the prior art, it is not necessary to consider the residue of isocyanate in the process of encapsulation and curing, so it will take a long time ( The heating time (basically longer than 1h) allows the wall material to reach a certain strength as soon as possible to prevent the adhesion between the microcapsules. However, a large amount of isocyanate (isocyanate group-NCO) needs to be retained in the polyurethane microcapsule curing agent for subsequent crosslinking 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. Lead to greatly reduce the internal active ingredients. Therefore, heating and ripening microcapsules to prevent adhesion and low temperature storage to retain a large amount of isocyanate (dimer) form a pair of contradictions, and the implementation of the existing interfacial polymerization method cannot solve such problems.

In order to solve the above problems and achieve the above object, 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 evenly to form a solution containing isocyanate monomer and catalyst, that is, an oil phase solution.

2) Add the emulsifier into ice water to form a water phase solution (control the temperature at 0-5°C), and add the oil phase solution dropwise into the water phase 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 forming component, stir and mix, so that the interface reaction between the amine and the isocyanate monomer on the surface of the droplet forms a uniform wall material.

4) Rapidly raise the temperature of the emulsion to 50-80°C within a few seconds through the tubular reactor for about 2 minutes, so that the wall material is rapidly matured, and at the same time, the internal isocyanate monomer is converted into isocyanate dimer, and then the temperature is rapidly lowered.

5) Finally, cool down to normal temperature and discharge, thicken the system to prevent sedimentation, and then mature, so that the remaining TDI in the interior can be fully converted into dimers under the action of a catalyst, and then microcapsules and polyurethane microcapsule curing agents can be obtained.

Example 1-1

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

1) Preparation of oil phase solution

Put 500kg of TDI and 0.25kg of 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 the aqueous phase solution

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

3) emulsification

The oil phase solution obtained in step 1) is passed into the emulsification device (continuous high-speed emulsifier) at a flow rate of 27.5kg/h and the water phase solution obtained in step 2) together with a flow rate of 30kg/h 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 rotational speed of the equipment. Control the temperature of the system during the emulsification process to 1°C.

4) Preparation of amine solution

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

5) Interface reaction

The emulsified emulsion in step 3) enters the 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 are formed on the droplet surface The interface reaction forms a layer of polyurea, that is, the wall material. The temperature of the system during the interfacial reaction was controlled at 1 °C.

6) Mature of wall material

The emulsion system is rapidly heated to 80°C within 4s at a heating rate of 20°C/s through a tubular reactor for 2 minutes, so that the wall material is rapidly matured, and at the same time, the TDI monomer in the core material is under the action of catalyst and temperature Rapidly transform into dimer, and then rapidly cool down to 20°C within 2 seconds at a cooling rate of 30°C/s, and last for 30s.

7) Anti-settling and anti-corrosion

Cool down to 20°C and discharge at room temperature, add 0.3% by mass of thickener xanthan gum to the system for thickening and anti-sedimentation; Such as Casson.

8) Mature of core material

Put the system at room temperature for static aging, and keep it at 25°C for 24 hours, so that the TDI that has not been dimerized in the core material can be fully converted into a dimer under the action of a catalyst, and microcapsules and polyurethane microcapsule curing agent are obtained. The solid content is 39.2%, and the viscosity is 1580 cps.

Example 1-2

Referring to Example 1-1, the difference from Example 1-1 is that in step 3) of this example, 3.28 kg of amine was added to 17.5 kg of deionized water, and other steps and parameters remained unchanged.

Example 1-3

Carry out 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 directly used during interfacial reaction (encapsulation), instead of diluted amine solution, which will cause a large amount of agglomeration and precipitation during the reaction, and cannot 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 matured by stirring at 50° C. for 6 hours. Other steps and parameters are basically the same as in Example 1-1. During the aging process of the wall material, a large number of air bubbles are generated, and a small amount of agglomeration precipitates are formed. After filtering the precipitate, the viscosity of the dispersion is 4530cps, and the solid content is 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-sedimentation treatment. Other steps and parameters are basically the same as in Example 1-1. Obtained dispersant viscosity 320cps, solid content 39.4% dispersion liquid, there is a large amount of precipitation in the system two days later, can recover to original state after stirring, but also can settle down soon, can form lump after a week, stirring can't restore initial state.

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

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

1) preparation of microcapsule curing agent

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

Slowly add 100g of 30% polyetheramine aqueous solution dropwise into the emulsion, stir for half an hour at the same time, send it into the tubular reactor, rapidly raise the temperature to 80°C within 3s, keep it for 2min, and quickly drop it to 25°C within 2s. Keep it for 30s and discharge it into a stirring container, add 20g DS2130 dispersant, 2g F908 defoamer, 2g ALA thickener while stirring, and prepare microcapsule curing agent A after aging for 36h. The viscosity at 25°C is 1540mPa. s, solid content 39%, microcapsule particle size D ₅₀ =5um.

2) Preparation of aqueous polyurethane dispersion

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

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

3) Preparation of polyurethane adhesive

Add 300g waterborne polyurethane dispersion B, 200g VAE706 into 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 defoamer F8916, 50g water, After stirring for half an hour, 0.5 g of thickener L75N was added 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 amount of microcapsule curing agent A was increased from 35g to 50g, and the others remained unchanged.

Example 2-3

On the basis of Example 2-1, the amount of microcapsule curing agent A was increased from 35g to 100g, and 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 BL2514, 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 BL2514, 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 XPBL 2514, and the others remained unchanged.

Comparative example 2-4

On the basis of Example 2-1, increase the amount of Span 60 added to 18g, and keep other conditions unchanged, to obtain microcapsule curing agent B with a solid content of 39%, a viscosity of 4130mPa·s, and a particle size of 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, 35g of microcapsule curing agent A was replaced with 50g 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 was added, and the others remained unchanged.

Embodiment 3 and comparative example 3 polyurethane film

The glue prepared in Example 2 and Comparative Example 2 was coated on the release paper (film) by roll coating or slit coating, and dried into a film through a variable temperature drying tunnel to form Example 3. and comparative example 3. The drying temperature is lower than 55°C to prevent the activation of the microcapsule curing agent.

Tests and Results

1) Scanning Electron Microscope (SEM)

Scanning electron microscope (SEM) is carried out to the raw material (TDI dimer, ADDOLINK TT) of commercially available microcapsule curing agent product, the dimer particle that obtains by milling scheme and the microcapsule curing agent that embodiment 1-1 prepares Test, the obtained scanned pictures are shown in Figure 1, Figure 2 and Figure 3 respectively.

From Figure 1 and Figure 2, it can be seen that the TDI dimer solids are of different sizes and the surface is extremely uneven. The shell shape of the product generated after deactivation is uncontrollable, showing the permeability to water and the permeability of PUD in the later stage. They are also uncontrollable. However, the microcapsules shown in Figure 3 have a relatively controllable particle size and a smooth surface, and the speed of water penetration into the wall material and the permeability of the polymer during use are controllable. Fig. 3 is the microcapsule prepared by Example 1-1, the diameter of the microcapsule is about 5um.

2) Related tests

experiment one

The microcapsule curing agent prepared by Example 1-1, Example 1-2, Example 1-3 and Comparative Example 1-2 is made into glue according to the same formula, and scraped on the MDF board 1 using a 50um preparer. The sizing area is 50*200mm, and the film 2 is obtained after drying, and the PVC film 3 (45 filaments) is pasted on the film 2, and a 180° peeling test is performed. After hot pressing at 100°C for 2 minutes, immediately hang a 10N weight 4, and immediately put it into an oven to observe the peeling distance (within 5 minutes) of the weight at different temperatures (70-90°C), as shown in Figure 5 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°C <1 <1 <1 12 80°C 2 5 5 20 90°C 3 7 8 20

From the experimental results in Table 2, it can be seen that after hot pressing at 100°C for 2 minutes, Examples 1-1, 1-2, and 1-3 showed high initial temperature resistance at 70°C, indicating that PUD and isocyanate have A certain degree of reaction has occurred and the molecular weight has been improved, and the reaction efficiency is high, while the degree of crosslinking of comparative examples 1-2 is lower than that of the examples, representing that the polyurethane microcapsule curing agent prepared by the examples is at a lower temperature and shorter Unblocking and crosslinking in the traditional sense can be achieved within a short time, and the traditional curing agent may need to react at 120°C for 1 hour. And the peeling effect of the example 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 glue formula to obtain glue, and coated on release paper respectively to make a thickness of 50um DSC is used to test the dry film sample, and the obtained spectra are shown in Figures 6-8.

From Figures 6-8, it can be seen that the enthalpy 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 examples 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 of the polyurethane microcapsule curing agent prepared in Example and PUD is greater than that of Comparative Example 1-2.

Experiment three

The three dry films prepared in Experiment 2 were tested by infrared, and the results are shown in Figure 9.

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

Experiment four

As shown in Figure 5, the initial temperature resistance test is carried out to some polyurethane adhesives in the above-mentioned embodiment 2 (2-1 to 2-3) and comparative example 2 (2-1 to 2-9):

Scrape-coat the polyurethane adhesive on the MDF board 1 using a preparer to form an adhesive layer (width 5cm, length 20cm) with a wet film thickness of 50um, and then place it in an oven at room temperature or below 40°C to dry until it does not stick to hands, forming Adhesive film 2, and then cover the top of the adhesive film 2 with a PVC film 3 with a thickness of 35 mm, and perform a 180° peel test. Use a hot press to 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 weight 4 weighing 1kg, and observe the displacement distance of the PVC film (5min Inside). The following are the displacement results (cm) of the initial heat resistance test:

Table 3 test results

As can be seen from the experiment and the results in Table 3 above, the effect of the embodiment is obviously better than that of the comparative example. And the microcapsule curing agent with a particle size of about 1-5um is more suitable, although the microcapsules in Comparative Examples 2-5-2-7 have smaller particle size (D ₅₀ <1um) and larger specific surface area , but because the wall material occupies too much isocyanate, the ineffective solid content is high, and the effective isocyanate content is low, resulting in poor actual crosslinking effect. And the result of Comparative Example 2-9 without adding any curing agent is all peeling off under the initial temperature resistance test conditions, and in the Comparative Example 2-8 that adds two-component curing agent (NE580), due to failure in a short time A cross-linking reaction occurs, so the initial temperature resistance does not improve.

Experiment five

As shown in Figure 10, the polyurethane adhesive films prepared in Example 3 and Comparative Example 3 were pushed out: the adhesive film 2 was clamped between the substrate 5 (the size was 4*4 cm) and the adhered material 7 (the diameter was 2.1 cm) cm), hot press at 80°C for 120-240s, move a stick-shaped object to the push-out hole 6 (0.9cm in diameter) at a speed of V=10mm/min, and push it out to test the impact of the adherend when it falls. The maximum pressure, converted into pressure (MPa), is the push-out value. The test substrate 5 is 304 stainless steel treated with primer (such as silane, primer, UPUV, etc.), and the adherend is PC, PET, PI, fabric and other materials. The following are the results of the launch 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. And corresponding to the results of Experiment 4, the microcapsule curing agent with a particle size of about 1-5um is more suitable, and the smaller particle size (D ₅₀ <1um) has a larger specific surface area, but the wall material takes up too much The isocyanate with high invalid solid content leads to poor actual crosslinking effect and poor test results.

Since the crosslinking efficiency is directly proportional to the specific surface area of the latent curing agent within a certain range, and the emulsion particles (15-60 μm) of the prior art are too 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 in the present invention, the particle size of the microcapsules is controllable (1-5 μm), which prevents the emulsion from settling too fast, and even if it is stored for a long time when part of the settling occurs, it can be easily stirred by simple stirring. It can return to the normal state again; the wall material formed by the interface reaction after the emulsification of the liquid raw material is continuous and uniform, so that the penetration ability of the PUD to the latent curing agent after activation is stable, and there is no problem of releasing a large amount of carbon dioxide in the later stage; 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 the number that can react with the latent curing agent is relatively small; when preparing polyurethane dispersions, 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 the crosslinking density and efficiency are improved.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention. Equivalent changes or modifications made in the spirit shall fall within the protection scope of the present invention.

Claims (14)

1. The polyurethane microcapsule curing agent is characterized by comprising emulsion and microcapsules dispersed in the emulsion, wherein the microcapsules account for 35-45% of the polyurethane microcapsule curing agent by mass;

the microcapsule comprises a wall material and a core material enclosed in the wall material; the core material is isocyanate dimer and/or isocyanate trimer formed after the reaction of isocyanate monomer and catalyst; the wall material is formed by reacting amine with isocyanate monomer.

2. The polyurethane microcapsule curing agent according to claim 1, wherein the molar ratio between the catalyst and the total amount of isocyanate monomers is 0.001 to 0.5%.

3. The polyurethane microcapsule curing agent according to claim 1, wherein the molar ratio between the amine and the total amount of isocyanate monomers is 6-12%.

4. The polyurethane microcapsule curing agent according to claim 1, wherein the particle size of the microcapsules in the polyurethane microcapsule curing agent is 1 to 10 μm.

5. The polyurethane microcapsule curing agent according to claim 1, wherein the emulsion comprises an emulsifier, a thickener, a preservative and water.

6. The polyurethane microcapsule curing agent according to claim 5, wherein the mass ratio between the emulsifier and the total amount of isocyanate monomers is 0.01% to 5%.

7. The polyurethane microcapsule curing agent according to claim 1 or 5, wherein the polyurethane microcapsule curing agent comprises 35-45% parts of microcapsules by mass percent; 0.1-2% of emulsifying agent; 0.1 to 0.5 percent of thickener; 0.1 to 0.5 percent of preservative; 54-65% of water.

8. The polyurethane microcapsule curing agent according to claim 7, wherein the catalyst is one or more selected from the group consisting of 4-dimethylaminopyridine, pyridine, tri-t-butylphosphine, tributylphosphine, triethylenediamine, 2,4, 6-tris (dimethylaminomethyl) phenol, bis (dimethylaminoethyl) ether, 1, 8-diazabicyclo [5.4.0] undec-7-N-methylmorpholine, pentamethyldipropylene diamine, 1-methyl-4- (2-dimethylaminoethyl) piperazine, dimethylaminopyridine, 2 '-dimorpholine diethyl ether, N-dimethylbenzylamine, N' -dimethylethanolamine, pentamethyldiethylenetriamine;

The amine is one or a combination of more selected from ammonia water, urea, ethylenediamine, pentylene diamine, hexamethylenediamine, hydrazine hydrate, guanidine, adipic dihydrazide, polyether amine, isophorone diamine, 4' -diamino dicyclohexylmethane and diethanolamine;

the emulsifier is span emulsifier of polyoxyethylene ether and/or tween emulsifier of polyoxyethylene ether;

the thickener is one or a combination of more selected from xanthan gum, guar gum, cellulose, polyurethane thickener, polyacrylic thickener and polyvinylpyrrolidone;

the preservative is isothiazolinone bactericides.

9. The polyurethane microcapsule curing agent according to claim 5, wherein the emulsion further comprises an antifoaming agent, which is a silicone-based antifoaming agent and/or a mineral oil-based antifoaming agent.

10. The polyurethane microcapsule curing agent according to claim 5, wherein the viscosity of the system after thickening by adding a thickener is 1000 to 2000cps at 25 ℃.

11. The polyurethane microcapsule curing agent according to claim 1, wherein the isocyanate monomer is an isocyanate having at least two isocyanate groups.

12. The polyurethane microcapsule curing agent according to claim 11, wherein the isocyanate monomer is toluene diisocyanate and/or diphenylmethane diisocyanate.

13. The polyurethane microcapsule curing agent according to claim 1, wherein the polyurethane microcapsule curing agent is prepared by the steps of:

mixing and emulsifying an oil phase solution containing isocyanate monomers and catalysts and an aqueous phase solution containing emulsifying agents to form emulsion; adding an amine solution into the emulsion and mixing the amine solution to enable amine and isocyanate monomers at an interface to undergo an interface reaction to form a wall material of the microcapsule;

heating the emulsion added with the amine solution to a set temperature within 1-10 s, wherein isocyanate monomers in the liquid drops react and are converted into isocyanate dimers and/or isocyanate trimers, and the isocyanate dimers and/or the isocyanate trimers form the core material of the microcapsule;

and then cooling the system after heat preservation to a set temperature within 1-10 s.

14. Use of a polyurethane microcapsule curing agent according to claims 1-13 for the preparation of polyurethane materials.