CN116510635A

CN116510635A - Preparation method of polyurethane microcapsule curing agent

Info

Publication number: CN116510635A
Application number: CN202310515012.7A
Authority: CN
Inventors: 龙伟
Original assignee: Jiangsu Osic Material Technology Co ltd
Current assignee: Jiangsu Osic Material Technology Co ltd
Priority date: 2022-04-25
Filing date: 2022-04-25
Publication date: 2023-08-01
Also published as: CN116510636A; WO2023207029A1; CN115025725A; CN115025725B; CN116535985A; CN116515441A; CN116515074A

Abstract

The invention discloses a preparation method of a polyurethane microcapsule curing agent, which comprises a microcapsule structure, wherein the microcapsule structure comprises a wall material and a core material sealed in the wall material, and the preparation method comprises the following steps: 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 oil phase droplets 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 cooling the system after heat preservation to a set temperature within 1-10 s.

Description

Preparation method of polyurethane microcapsule curing agent

The present application is a divisional application of the invention patent application with the application date of 2022, 4 and 25, the application number of 2022104413173 and the invention name of polyurethane microcapsule curing agent, adhesive film and respective preparation methods.

Technical Field

The invention belongs to the technical field of polyurethane curing agents and polyurethane materials, and particularly relates to a preparation method of a polyurethane microcapsule curing agent.

Background

Curing agents, also known as hardeners, curing agents or setting agents, are a class of substances or mixtures that enhance or control the curing reaction. The curing agent is an essential additive for curing the resin, and is added as an adhesive, a coating and a casting material, otherwise, the resin cannot be cured.

In order to facilitate the use of coatings, adhesives and the like, a single-component polyurethane material system is used in many application occasions, and the release of isocyanate is realized by heating, so that the isocyanate reacts with an active hydrogen-containing component to improve the crosslinking density, and further the curing is realized. The single-component polyurethane material system contains a latent curing agent component which can play a role of the curing agent under a certain condition, and the latent curing agent can be unsealed at a certain temperature so as to generate a crosslinking reaction, and can not react at normal temperature.

The prior art has shown that the use of surface deactivation of TDI (toluene diisocyanate) dimers, MDI (diphenylmethane diisocyanate) dimers, IPDI (isophorone diisocyanate) dimers or IPDI trimer to form microcapsule structures, the preparation of stable suspensions by protective colloids, and the addition of such suspensions to emulsions can produce rapidly deblocking one-component polyurethane material systems. Such a method of forming a microcapsule structure using a solid dimer, trimer as a raw material is generally called a solid state gap encapsulation scheme.

The solid gap type bag forming scheme in the prior art mainly comprises the following two steps: spray-drying granulation and mechanical milling. The two methods have the following problems: pyridine is used as a solvent in the spray drying granulation process, the smell of the pyridine is very large, the particle size of the prepared suspension is generally 15-60um, and after the suspension is stored for a period of time, unrecoverable bottoms appear on the particles with larger particle sizes, so that the product is completely ineffective; the particles produced by mechanical grinding release a certain amount of unreacted monomers due to the breaking of large particles in the grinding process, the monomers are wrapped in the particles in the crystallization process, the monomers are difficult to separate after granulation, a certain amount of invalid solid content components are generated by amine and water which are co-ground after release, so that the overall performance is influenced, a large amount of bubbles are generated in the process to influence the processing, the pH value of polyurethane dispersion is reduced, the pH value of the product is reduced more quickly in a period of time after the production is finished, and the problems of immediate gelation, precipitation and the like can occur when the emulsion which is sensitive to the pH value is used.

The microcapsule curing agent and polyurethane dispersoid (PUD) are prepared into glue, and after the glue is formed into a film, the PUD is activated at high temperature and can penetrate into the microcapsule through the wall material to crosslink. However, the TDI dimer particles produced using both of the above schemes are irregular in appearance, and as shown in FIG. 1 (TDI dimer particles produced by spray-drying granulation) and FIG. 2 (TDI dimer particles produced by mechanical milling), the microcapsules formed after they react with inactive amine in water are still irregular, and the microcapsule wall thickness is also inconsistent. The microcapsules prepared by the two schemes are greatly influenced by the process batch, and the shape and the thickness of the wall material influence the permeation speed and the quantity, thereby influencing the crosslinking process and the properties of the final material.

The foregoing background is only for the purpose of providing an understanding of the inventive concepts and technical aspects of the present invention and is not necessarily prior art to the present application and is not intended to be used to evaluate the novelty and creativity of the present application in the event that no clear evidence indicates that such is already disclosed at the filing date of the present application.

Disclosure of Invention

In view of the above, it is an object of the present invention to provide an improved method for preparing polyurethane microcapsule curing agent.

The invention also provides the polyurethane microcapsule curing agent prepared by the preparation method and application thereof, and the polyurethane microcapsule curing agent avoids excessive reaction of high-activity isocyanate and water in the production process, thereby reducing the generation of carbon dioxide, facilitating continuous production, avoiding rapid decrease of pH, leading the polyurethane microcapsule curing agent to have better compatibility with a plurality of emulsions, leading the microcapsule particles prepared by the interface reaction to have uniform and smooth surface and uniform wall thickness, and having more stable and controllable permeation speed and curing crosslinking speed for polymerization in a heating state.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

A method for preparing a polyurethane microcapsule curing agent, the polyurethane microcapsule curing agent comprises a microcapsule structure, the microcapsule structure comprises a wall material and a core material sealed in the wall material, and the method comprises the following steps:

mixing and emulsifying an oil phase solution containing isocyanate monomers and catalysts and an aqueous phase solution containing emulsifying agents to form an emulsion, wherein the aqueous phase solution forms an aqueous phase (continuous phase), and the oil phase solution forms liquid drops (dispersed phase);

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 50-80 ℃ and preserving heat for 1-8 min, wherein isocyanate monomers in the liquid drops react and are converted into isocyanate dimers and/or isocyanate trimers, the isocyanate dimers and/or the isocyanate trimers form the core material of the microcapsule, and the heating rate is greater than or equal to 20 ℃/s;

and cooling the system after heat preservation to 20-30 ℃, wherein the cooling rate during cooling is more than or equal to 20 ℃/s.

In some embodiments, the whole system is warmed to 50-80 ℃ within 1-10 seconds by controlling the warming rate, so as to avoid water penetration during long-time heating.

Preferably, the preparation method comprises the step of adding a thickener to the cooled system for thickening, wherein the viscosity of the thickened system is 1000-2000cps at 25 ℃.

Preferably, the preparation method comprises the step of standing and curing the thickened system, wherein the curing is to keep the temperature of the thickened polyurethane microcapsule curing agent at 20-30 ℃ for 12-36 h. In the curing process, the residual isocyanate monomer in the core material is fully converted into dimer under the action of a catalyst to form a microcapsule with the inside of the microcapsule being isocyanate dimer and the outer wall being a wall material with certain strength.

According to some preferred embodiments of the invention, the temperature of the oil phase solution is controlled to be 20-22 ℃ before the oil phase solution and the aqueous phase solution are mixed. The isocyanate monomer and the catalyst are put into a pre-mixing bin for uniform mixing at the temperature of about 20-22 ℃, the crystallization of the isocyanate monomer is unfavorable for forming uniform liquid drops in a water phase due to the excessively low temperature, and the crystallization of the isocyanate monomer is unfavorable for forming uniform liquid drops due to the excessively high temperature, so that the isocyanate monomer is converted into a large amount of dimer crystals in advance.

According to some preferred embodiments of the invention, the temperature of the system is controlled between 0 and 5 ℃ when emulsification and reaction with the addition of amine solution are carried out. The reaction speed of isocyanate monomer and water can be greatly reduced by adopting low temperature of 0-5 ℃, and the generation of bubbles is reduced, so that the emulsified particle size is controllable, and the obtained micelle interface is smooth. In some embodiments of the present invention, the aqueous phase solution is formed by adding an emulsifier to ice water, and the temperature of the aqueous phase solution is controlled to be 0-5 ℃.

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

According to some preferred embodiments 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 rotation speed during emulsification is 1000-9000 rpm. The particle size is controlled by the dosage of the emulsifier and the rotating speed of the emulsifying equipment, namely, the particle size can be regulated and controlled in the reaction process, and the traditional method is that the isocyanate dimer is prepared firstly, so that the particle size cannot be regulated and controlled in the subsequent process.

According to some preferred embodiments of the invention, the isocyanate monomer is an isocyanate having at least two isocyanate-NCO groups. Toluene diisocyanate TDI, such as T80, T100, etc., is preferred, and diphenylmethane diisocyanate MDI may be used as the core material to form the microcapsules.

According to some preferred embodiments of the invention, the heating and cooling of the emulsion is performed using a tubular reactor, the front section of which is used to heat the emulsion to a set temperature within 1-10 seconds and the rear section of which is used to cool the emulsion to a set temperature within 1-10 seconds, to achieve rapid heating and cooling. The continuous method formed by the tubular reactor has no stability problem among batches, and the temperature rise and the temperature drop are rapid.

According to some preferred embodiments of the present invention, the catalyst is one or more combinations 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 molar ratio between the catalyst and the isocyanate monomer is 0.001-0.5%, too little catalyst is insufficient to produce crystallization in a short time through the tubular reactor to increase the structural strength of the microcapsules, too much catalyst results in premature crystallization to emulsify.

According to some preferred embodiments of the invention, the amine in the amine solution is a combination of one or more selected from the group consisting of ammonia, urea, ethylenediamine, pentyldiamine, hexamethylenediamine, hydrazine hydrate, guanidine, adipic dihydrazide, polyetheramine, isophoronediamine, 4' -diaminodicyclohexylmethane, 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 5-35%, preferably about 10% -30%.

The amine solution is an encapsulated component for converting the micelle into particles, so that the surface of the micelle undergoes an interface reaction to form a uniform wall material. Meanwhile, the temperature of the ice water inhibits the reaction of the water and NCO, so that NCO mainly reacts with amine, and the amine and NCO react at the interface to form a thin polyurea layer, namely a wall material, so that moisture is prevented from entering the core material.

According to some preferred embodiments of the invention, the emulsifier in the aqueous solution is span emulsifier of polyoxyethylene ethers and/or tween emulsifier of polyoxyethylene ethers.

According to some preferred embodiments of the invention, an antifoaming agent is added to the aqueous phase solution at the time of emulsification, the antifoaming agent being a silicone-based antifoaming agent and/or a mineral oil-based antifoaming agent.

According to some preferred embodiments of the invention, the thickener is a combination of one or more selected from xanthan gum, guar gum, cellulose, polyurethane-based thickeners, polyacrylic-based thickeners, polyvinylpyrrolidone. The thickener is used in an amount of 0.01-1%, and the viscosity of the thickened system is 1000-2000cps at 25deg.C.

According to some preferred embodiments of the invention, the method of preparation further comprises the step of adding a preservative to the system after thickening, said preservative being an isothiazolinone fungicide, such as pinacolin.

In the preferred embodiment of the invention, the emulsion system containing particles is quickly heated to 50-80 ℃ for about 2min by controlling the heating rate and the cooling rate, at the moment, the wall material has a certain strength due to the rapid reaction speed of the aromatic monomer, the isocyanate monomer is partially converted into dimer solid at the temperature, the whole microcapsule has a certain strength, and then the temperature is quickly reduced to a safe temperature (about 20-30 ℃ at room temperature), so that the permeation of water in the process is avoided, and the isocyanate monomer and dimer in the core material are not influenced.

In the existing application scene, such as the core material of pesticide and essence microcapsule is liquid, in order to make the microcapsule reach a certain strength, the suspension is stirred for 1-8 h at 40-50 ℃ to form a firm wall material to prevent adhesion, but in the application scene of the invention, a large amount of water permeates into the microcapsule to react with internal isocyanate monomer and dimer and generate a large amount of bubbles at the same time, so that the pH of the system is reduced, therefore, the invention can quickly cure part of the wall material to reach a certain strength by raising the temperature to about 50-80 ℃ in a very short time, and the core material is also greatly converted into a solid dimer, at this time, the microcapsule has a certain strength, then is quickly cooled to 20-30 ℃ in a few seconds, and is cured to make the core material fully converted into a dimer, thus preventing water from entering the core material and avoiding adhesion between the microcapsules.

In some embodiments of the invention, a tubular reactor may be used in particular for continuous heating and cooling of the emulsion described above. The tubular reactor can be divided into two sections, the front section realizes rapid temperature rise, the rear section realizes temperature reduction, and the control of temperature rise, temperature reduction and heat preservation time can be realized through the length and the distance of the tubular reactor. Cooling to normal temperature, discharging, adding thickener into the system for thickening and preventing sedimentation, and standing for curing.

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

1) And (3) putting TDI and a catalyst into a pre-mixing bin at about 20-22 ℃ for uniform mixing to form a solution containing isocyanate monomers and the catalyst, namely an oil phase solution.

2) Adding an emulsifier into ice water to form an aqueous phase solution which is a continuous phase; the oil phase solution is added into the water phase solution in a dropwise manner to be emulsified into liquid drops with controllable particle size and smooth interfaces, which are dispersed phases.

3) Then the amine solution of the capsule component is added dropwise, and the mixture is stirred and mixed uniformly, so that the amine and isocyanate monomer on the surface of the liquid drop react at the interface to form a uniform wall material.

4) And 3) rapidly heating the emulsion system obtained in the step 3) to 50-80 ℃ in a few seconds through a tubular reactor for about 2 minutes to rapidly cure the wall material, simultaneously converting the isocyanate monomer in the wall material into an isocyanate dimer, and then rapidly cooling.

5) Finally, cooling to normal temperature for discharging, thickening and anti-sedimentation are carried out on the system, and then curing is carried out, so that the residual TDI inside is fully converted into dimer under the action of a catalyst, and microcapsules and polyurethane microcapsule curing agents are further obtained, and the whole process is called as a liquid continuous method encapsulation scheme.

The invention also aims to provide a polyurethane microcapsule curing agent prepared by the preparation method, which comprises an emulsion and microcapsules dispersed in the emulsion, wherein the microcapsules comprise a core material with an isocyanate dimer inside and a polyurea layer wall material with an amine outside and formed by reacting with isocyanate; the mass ratio of the microcapsule in the polyurethane microcapsule curing agent is 35-45%. In some embodiments, the emulsion includes an emulsifier, a thickener, a preservative, and water. More specifically, in some embodiments of the present invention, the polyurethane microcapsule curing agent comprises 35 to 45% parts by mass of microcapsules; 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. Preferably, the polyurethane microcapsule curing agent comprises 39.5% of microcapsules; 0.1% of an emulsifier; 0.3% of thickener; 0.1% of preservative; 60% of water.

It is still another object of the present invention to provide an application of the microcapsule curing agent in preparation of polyurethane materials, such as polyurethane glue (adhesive) or paint, adhesive film and the like.

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

1) Preparing a polyurethane microcapsule curing agent according to the preparation method;

2) Adding vinyl acetate-ethylene emulsion into polyurethane dispersoid, regulating the pH value to 6-8, adding the polyurethane microcapsule curing agent, auxiliary agent and water, and stirring to obtain the polyurethane adhesive; the addition amount of the microcapsule curing agent in the polyurethane adhesive is 3-20%. The mass ratio of polyurethane dispersion to vinyl acetate-ethylene emulsion is preferably 6:4.

according to some preferred embodiments of the invention, the polyurethane dispersion is prepared by: heating and dehydrating polyether polyol and/or polyester polyol, and adding a chain extender to carry out chain extension;

adding diisocyanate and a catalyst to react until the set isocyanate group content is reached, so as to obtain isocyanate terminated prepolymer;

adding solvent for dilution and cooling, and adding sodium ethylenediamine ethanesulfonate for chain extension again;

Adding trimethylol aminomethane for end capping, adding water for dispersion, and removing the solvent to obtain the polyurethane dispersoid. The solvent may preferably be acetone.

In some embodiments of the present invention, the method for preparing the polyurethane dispersion specifically comprises the steps of:

1) Two polyester polyols with different molecular weights are put into a reactor, heated and dehydrated, and then chain extender 1, 4-Butanediol (BDO) is added for chain extension, and the temperature is reduced to 60 ℃ while stirring.

2) Adding diisocyanate and a catalyst, and stirring at 80-90 ℃ until the set isocyanate group NCO content is reached to obtain isocyanate terminated prepolymer; the isocyanate group content was set to about 1.3%.

3) A solvent such as acetone is added to the system, diluted and cooled to 50 ℃.

4) An aqueous solution of sodium ethylenediamine-based ethanesulfonate (AAS) was added and vigorously stirred for 30 minutes, followed by hydrophilic chain extension.

5) Adding an aqueous solution of TRIS (hydroxymethyl) aminomethane (TRIS), reacting the residual isocyanate completely, and then distilling 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 adopts the trimethylol aminomethane for end capping, so that three hydroxyl groups are added at two ends of the prepared PUD molecular chain, and the polyurethane dispersion is favorable for reacting with a curing agent.

According to some preferred embodiments of the invention, the pH is adjusted using a multifunctional amine adjuvant such as Dow AMP 95.

According to some preferred embodiments of the invention, the auxiliary agents added include one or more of wetting agents, defoamers, thickeners.

According to some preferred embodiments of the invention, the polyurethane adhesive has a viscosity of 1500 to 3000 mPa-s at 25 ℃; the solid content is 35-60%.

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

The invention provides a preparation method of a polyurethane adhesive film, which comprises the following steps: the polyurethane adhesive is prepared according to the preparation method; and coating the polyurethane adhesive on release paper, and drying to obtain the polyurethane adhesive film. The temperature at the time of drying is lower than 60 ℃, preferably lower than 55 ℃, so as to avoid the activation of the microcapsule curing agent to react in advance.

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

Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages: according to the preparation method of the polyurethane microcapsule curing agent, the wall material formed by interface reaction after emulsification of the liquid raw materials is continuous and uniform, and the wall material is rapidly cured by rapid temperature rise and rapid temperature reduction, so that water penetration is avoided, and the isocyanate monomer and dimer in the core material are not influenced; the effective content of isocyanate dimer in the microcapsule is greatly improved, and the efficiency of the crosslinking reaction is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a Scanning Electron Microscope (SEM) photograph of TDI dimer (ADDOLINK TT) used in the preparation process of the existing commercial microcapsule curing agent;

FIG. 2 is a Scanning Electron Microscope (SEM) photograph of dimer particles prepared using a mechanical milling method;

FIG. 3 is a Scanning Electron Microscope (SEM) photograph of microcapsule particles in the polyurethane microcapsule curing agent prepared in example 1-1 of the present invention;

FIG. 4 is a schematic diagram of the process for preparing polyurethane microcapsule curing agent in example 1 of the present invention;

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

FIG. 6 is a DSC graph of a dry film obtained according to example I of experiment II of the present invention;

FIG. 7 is a DSC graph of a dry film obtained in accordance with example two of the present invention;

FIG. 8 is a DSC graph of dry film obtained in accordance with comparative example II in experiment II of the present invention;

FIG. 9 is an infrared test pattern obtained in experiment three of the present invention;

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

in the drawing, an MDF board-1, a glue film-2, a PVC film-3, weights-4, a base material-5, a push-out hole-6 and a dipped object-7.

Detailed Description

In order to make the technical solution of the present invention better understood by those skilled in the art, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

Table 1 below is a shorthand for the Chinese composition or effect corresponding to the partial reagent abbreviations used in the examples and the manufacturer:

table 1 section description of reagents

Sequence number	Abbreviations (abbreviations)	Composition or action	Manufacturer shorthand
				1	TDI	Toluene diisocyanate	Science creation
2	IPDI	Isophorone diisocyanate	Science creation
				3	HDI	Hexamethylene diisocyanate	Science creation
4	BL2514	Latent curing agent (TDI dimer)	Science creation
				5	AAS	Ethylenediamine sodium ethanesulfonate	Win wound
6	TBUP	Tributyl phosphorus	Sigma of
				7	TRIS	Trimethylolaminomethane	Sigma of
8	BDO	1, 4-butanediol	Zhongtai (Chinese character)
				9	T403	Polyoxypropylene triamines	Henschel
10	ALA	Thickening agent	OMG
				11	L75N	Thickening agent	OMG
12	MB20	Organobismuth catalysts	Air chemical industry
				13	DS2130	Dispersing agent	Ostima (Aosjia)
14	UL5120	Organosilicon wetting agent	Ostima (Aosjia)
				15	F908	Organosilicon defoamer	Ostima (Aosjia)
16	F8916	Organosilicon defoamer	Ostima (Aosjia)
				17	Polyester polyol I	2000 molecular weight	Ostima (Aosjia)
18	Polyester polyol II	1800 molecular weight	Ostima (Aosjia)
				19	NE580	Nco=20.5% aqueous HDI curative	Ostima (Aosjia)
20	Span 60	Emulsifying agent	Sea petrochemical industry
				21	VAE706	Vinyl acetate-ethylene emulsion	Wake (Wake)
22	AMP95	Multifunctional amine auxiliary agent	Ceramic' s

EXAMPLE 1 preparation of microcapsule curing agent

The traditional method for preparing polyurethane microcapsule curing agent is to prepare TDI into dimer solid first and then disperse the dimer solid into water for deactivation. The appearance of the dimer particles commonly used in the market is shown in FIG. 1, and the appearance of the dimer particles prepared by the grinding method is shown in FIG. 2, wherein the appearance of the dimer particles is not uniform in size and extremely uneven in surface, and the shape of the shell of the product obtained by deactivation is not controllable, and the permeability of water to the microcapsules and the permeability of the heated polymer such as polyurethane dispersion to the microcapsules in practical use are not controllable. The polyurethane microcapsule curing agent is prepared by adopting a liquid continuous method, the grain size of the obtained microcapsule is relatively controllable, the surface is smooth, and the speed of penetrating the wall material through water and the permeability of the heated polymer in the using process are controllable as shown in figure 3.

The interfacial polymerization method refers to emulsifying or dispersing a core material in a continuous phase in which a wall material is dissolved, and then forming microcapsules on the surface of the core material by polymerization of monomers. The microcapsule with smooth and continuous particle surface can be prepared by adopting an interfacial polymerization method, so that the problem of irregular particles is solved. Although the encapsulation scheme exists in industries such as pesticides, essence and the like, the difference is that when the interfacial polymerization method in the prior art is applied, isocyanate residues are not needed to be considered in the process of encapsulation curing, so that long-time (the duration is basically longer than 1 h) heating can lead the wall material to reach a certain strength as soon as possible so as to prevent adhesion among microcapsules. However, the polyurethane microcapsule curing agent needs to retain a large amount of isocyanate (isocyanate-NCO) for subsequent crosslinking reaction, and if the temperature exceeds 40 ℃ for a long time, a large amount of water permeates into the microcapsule through the wall material, resulting in a great reduction of the internal active ingredients. Therefore, the heating and curing of microcapsules prevents blocking and the preservation at low temperature to retain a large amount of isocyanate (dimer) forms a pair of contradictions, and the prior interfacial polymerization method embodiments cannot solve the problems.

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

2) Adding the emulsifier into ice water to form aqueous phase solution (controlling the temperature to be 0-5 ℃), and dripping the oil phase solution into the aqueous phase solution to emulsify at high speed into liquid drops with controllable particle size and smooth interfaces.

3) Then the amine solution of the capsule component is added dropwise, and the mixture is stirred and mixed so as to lead the amine to react with isocyanate monomer on the surface of the liquid drop at the interface to form uniform wall material.

4) The emulsion is heated to 50-80 ℃ in a few seconds by a tubular reactor, and the temperature is kept for about 2 minutes, so that the wall material is cured rapidly, and meanwhile, the isocyanate monomer in the emulsion is converted into isocyanate dimer, and then the temperature is reduced rapidly.

5) Finally, cooling to normal temperature for discharging, thickening and anti-sedimentation are carried out on the system, and then curing is carried out, so that the residual TDI inside is fully converted into dimer under the action of a catalyst, and the microcapsule and polyurethane microcapsule curing agent are obtained.

Example 1-1

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

1) Preparation of an oil phase solution

500kg of TDI and 0.25kg of tributylphosphine are charged into a pre-mixing bin at 20℃and mixed well to form a solution containing isocyanate monomer and catalyst, i.e. an oil phase solution.

2) Preparation of aqueous solutions

5kg of an emulsifier and 0.5kg of an antifoaming agent were added to 500L of ice water and mixed uniformly to form an aqueous solution containing the emulsifier, i.e., an aqueous phase solution, the temperature of which was controlled to 1 ℃.

3) Emulsification

And (3) introducing the oil phase solution obtained in the step (1) and the aqueous phase solution obtained in the step (2) into an emulsifying device (continuous high-speed emulsifying machine) at a flow rate of 27.5kg/h for high-speed emulsification, so that emulsion with controllable particle size and 47.8% of solid content is formed by the oil phase solution. The particle size of the droplets can be achieved by the amount of emulsifier added and controlling the rotational speed of the device. The temperature of the system in the emulsification process was controlled to be 1 ℃.

4) Preparation of amine solutions

1.64kg of polyetheramine was added to 17.5kg of deionized water and stirred to a uniform 9.4% strength amine solution to form the vesicle composition.

5) Interface reaction

Feeding the emulsion obtained in the step 3) into a continuous mixer at a flow rate of 57.5kg/h and the amine solution obtained in the step 4) at a flow rate of 17.5kg/h, and enabling the diluted amine solution and isocyanate to undergo interfacial reaction on the surface of the liquid drops to form a polyurea layer, namely a wall material. The temperature of the system in the interface reaction process is controlled to be 1 ℃.

6) Curing of wall material

The emulsion system is quickly heated to 80 ℃ within 4 seconds at a heating rate of 20 ℃/s through a tubular reactor for 2 minutes, so that the wall material is quickly cured, simultaneously, the TDI monomer in the core material is quickly converted into a dimer under the action of a catalyst and temperature, and then, the temperature is quickly reduced to 20 ℃ within 2 seconds at a cooling rate of 30 ℃/s, and the duration is 30 seconds.

7) Anti-sedimentation and anti-corrosion

Cooling to 20 ℃ and discharging at normal temperature, and adding 0.3 mass percent of thickener xanthan gum into the system to thicken and prevent sedimentation; 0.1% by weight of an isothiazolinone type bactericide such as pinocembrane of the whole system is added to the system.

8) Curing of core material

Standing and curing the system at normal temperature, and keeping the temperature at 25 ℃ for 24 hours, so that TDI which is not dimerized in the core material is fully converted into dimer under the action of a catalyst, and the microcapsule and polyurethane microcapsule curing agent is obtained, wherein the solid content is 39.2%, and the viscosity is 1580cps.

Examples 1 to 2

The procedure is as described in example 1-1, except that 3.28kg of amine is added to 17.5kg of deionized water in step 3) of this example, and the other steps and parameters are unchanged.

Examples 1 to 3

The procedure is carried out with reference to example 1-1, with the difference from example 1-1 that in step 1) of this example 2.2kg of catalyst 4-dimethylaminopyridine are added to 500kg of TDI, the other parameters being unchanged.

Comparative examples 1 to 1

This comparative example differs from example 1-1 in that: the interfacial reaction (encapsulation) uses 100% amine directly without the use of a dilute amine solution, resulting in a significant amount of agglomerated precipitate during the reaction and failure to form a stable microcapsule dispersion.

Comparative examples 1 to 2

This comparative example differs from example 1-1 in that: the wall material was ripened to stir at 50 ℃ for 6h. Other steps and parameters were substantially the same as in example 1-1. A large amount of bubbles are generated in the curing process of the wall material, a small amount of caking and precipitation are generated, and the dispersion liquid viscosity is 4530cps and the solid content is 35.8% after filtering and precipitation.

Comparative examples 1 to 3

This comparative example differs from example 1-1 in that: no thickener is added into the system for sedimentation prevention treatment. Other steps and parameters were substantially the same as in example 1-1. The obtained dispersing agent has the viscosity of 320cps and the solid content of 39.4%, a large amount of precipitates are in the system after two days, the system can be restored to the initial state after stirring, but the dispersing agent can be quickly settled down, hard lumps can be formed after one week, and the initial state can not be restored after stirring.

Example 2-1 preparation of thermosetting one-component polyurethane Adhesives

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

1) Preparation of microcapsule curing agent

Adding 500g of TDI monomer and 0.05g of tributyl phosphate into a container, keeping the temperature between 20 ℃ and 25 ℃ and uniformly stirring to form an oil phase solution; 8g span 60 is added into 828g ice water and stirred evenly to form aqueous phase solution; slowly dripping the oil phase solution into the water phase solution, and simultaneously dispersing at a high speed for half an hour to form stable emulsion.

Slowly dripping 100g of 30% concentration polyether amine aqueous solution into the emulsion, stirring for half an hour, feeding into a tubular reactor, quickly heating to 80 ℃ in 3s, quickly cooling to 25 ℃ in 2s after 2min, discharging to a stirring container after 30s, adding 20g of DS2130 dispersing agent, 2g of F908 defoamer and 2g of ALA thickener while stirring, curing for 36 hours to obtain microcapsule curing agent A, wherein the viscosity at 25 ℃ is 1540 mPa.s, the solid content is 39%, and the microcapsule particle size D ₅₀ ＝5um。

2) Preparation of aqueous polyurethane dispersions

500g of polyester polyol I and 50g of polyester polyol II were put into a reactor, heated to 115℃for dehydration for 1 hour, and 2.5g of BDO was added while cooling to 60℃with stirring. 42g of HDI, 28g of IPDI, 3g of MB20 are then added and stirring is maintained at 80℃to 90℃until an isocyanate content of 1.28% is reached. 850g of acetone were added and the system temperature was cooled to 50 ℃.

7.0g AAS was diluted in 55g water, then added to the system and stirred for 30min; then, 8g of TRIS was dissolved in 555g of an aqueous solution, and added to the system for dispersion, and finally acetone was distilled off to obtain an aqueous polyurethane dispersion B. The resulting polyurethane dispersion had a melting point of 44.12℃and a solids content of 49.2% by weight, and a viscosity of 1290 mPas at 25 ℃.

3) Preparation of polyurethane adhesive

300g of aqueous polyurethane dispersion B and 200g of VAE706 are added into a container, the pH value is adjusted to about 7 by using AMP95, then 35g of microcapsule curing agent A, 0.5g of wetting agent UL5120, 0.5g of defoamer F8916 and 50g of water are added, after half an hour of stirring, 0.5g of thickener L75N is added, and the finished polyurethane adhesive is prepared, wherein the viscosity at 25 ℃ is 2130 mPas and the solid content is 45%.

Example 2-2:

the amount of the microcapsule curing agent A was increased from 35g to 50g on the basis of example 2-1, the others remained unchanged.

Examples 2 to 3

The amount of the microcapsule curing agent A was increased from 35g to 100g based on example 2-1, and the others remained unchanged.

Comparative example 2-1

Based on example 2-1, 35g of microcapsule curing agent A was replaced with 35g of Colo Dispercoll XP BL 2514, the others remained unchanged.

Comparative examples 2 to 2

Based on example 2-1, 35g of microcapsule curing agent A was replaced with 50g of Colo Dispercoll XP BL 2514, the others remained unchanged.

Comparative examples 2 to 3

Based on example 2-1, 35g of microcapsule curing agent A was replaced with 100g of Colo Dispercoll XP BL 2514, the others remained unchanged.

Comparative examples 2 to 4

Based on example 2-1, the amount of span 60 added was increased to 18g, and the other conditions were kept unchanged, to obtain microcapsule curing agent B having a solid content of 39%, a viscosity of 4130 mPa.s, and a particle size D ₅₀ <1um。

Comparative examples 2 to 5

On the basis of example 2-1, 35g of microcapsule hardener A was replaced by 35g of microcapsule hardener B, the others remaining unchanged.

Comparative examples 2 to 6

On the basis of example 2-1, 35g of microcapsule hardener A was replaced by 50g of microcapsule hardener B, the others remaining unchanged.

Comparative examples 2 to 7

On the basis of example 2-1, 35g of microcapsule hardener A was replaced by 100g of microcapsule hardener B, the others remaining unchanged.

Comparative examples 2 to 8

35g of microcapsule curing agent A was replaced by 35g of NE580 curing agent on the basis of example 2-1, the others remaining unchanged.

Comparative examples 2 to 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.

Example 3 and comparative example 3 polyurethane film

The glue prepared in example 2 and comparative example 2 was coated on release paper (film) by roll coating or slot coating, and dried to form a film by a variable temperature drying tunnel, thus forming example 3 and comparative example 3. The drying temperature is lower than 55 ℃ to prevent activation of the microcapsule curing agent.

Testing and results

1) Scanning Electron Microscope (SEM)

Scanning Electron Microscope (SEM) tests were performed on the raw material of a commercially available microcapsule curing agent product (TDI dimer, addline TT), dimer particles obtained by a milling scheme, and the microcapsule curing agent prepared in example 1-1, and the obtained scanned pictures are shown in fig. 1, 2, and 3, respectively.

It can be seen from FIGS. 1 and 2 that TDI dimer is not uniform in solid size and has an extremely uneven surface, and that the shape of the shell of the product produced after deactivation is not controllable, and that the permeability to moisture and the permeability of the post-PUD are both not controllable. The microcapsule shown in fig. 3 has relatively controllable particle size, smooth surface, and controllable permeation rate of water to the wall material and polymer permeability during use. FIG. 3 shows the microcapsule prepared in example 1-1, the microcapsule diameter being about 5um.

2) Correlation test

Experiment one

The microcapsule curing agents prepared in examples 1-1, 1-2, 1-3 and comparative examples 1-2 were prepared into glue according to the same formulation, the glue was scraped on the MDF board 1 using a 50um preparation machine, the glue area was 50 x 200mm, the glue film 2 was obtained after air drying, the PVC film 3 (45 filaments) was attached to the glue film 2, and 180 ° peeling test was performed. After hot pressing at 100deg.C for 2min, 10N weights 4 were hung immediately, and the weights were placed in an oven to observe the separation distances (within 5 min) of the weights at different temperatures (70-90deg.C), as shown in FIG. 5, wherein 70deg.C, 80deg.C, and 90deg.C are independent experiments. The test results (units: cm) are shown in Table 2:

table 2 test results

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

As can be seen from the experimental results in Table 2, examples 1-1, 1-2 and 1-3 show higher initial temperature resistance at 70 ℃ after hot pressing at 100 ℃ for 2min, which means that PUD and isocyanate have reacted to some extent to increase molecular weight, reaction efficiency is high, and comparative examples 1-2 have lower crosslinking degree than examples, which means that the polyurethane microcapsule curing agent prepared in the examples can realize deblocking and crosslinking in the conventional sense at lower temperature and shorter time, and the conventional curing agent may need to react for 1h at 120 ℃. And the peeling effect of the examples at 80 ℃ and 90 ℃ is far better than that of the comparative examples.

Experiment two

The polyurethane microcapsule curing agents prepared in examples 1-1, 1-2 and comparative examples 1-2 were prepared into glues according to the same glue formulation, and coated on release papers to prepare dry films with a thickness of 50um, and the dry film samples were tested by DSC, and the obtained patterns are shown in FIGS. 6-8, respectively.

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

Experiment three

The three dry films prepared in experiment two were respectively subjected to infrared test, and the results are shown in fig. 9.

The infrared spectrum of FIG. 9 can be used to see 2240-2280 cm ^-1 The peak values of examples 1-1, 1-2 are much larger than those of comparative example 1-2. 2240 to 2280cm ^-1 The region corresponds to the stretching vibration peak of-n=c=o, indicating that the curing agents prepared in examples 1-1 and 1-2 contain more effective isocyanate component. The PUD polymer activated at a temperature of 70-100 ℃ penetrates into the microcapsules through the wall material of the microcapsules and reacts with these encapsulated isocyanates. The more effective isocyanate is contained in the curing agent, the more efficient the reaction.

Experiment four

As shown in fig. 5, initial temperature resistance tests were performed on a part of the polyurethane adhesives in the above-described examples 2 (2-1 to 2-3) and comparative examples 2 (2-1 to 2-9):

the polyurethane adhesive was knife coated on an MDF board 1 using a preparation machine to form a wet film thickness of 50um of adhesive layer (width 5cm, length 20 cm), then placed in an oven at room temperature or below 40 ℃ to dry to a non-stick hand, to form an adhesive film 2, and then a PVC film 3 with a thickness of 35 filaments was covered over the adhesive film 2 for 180 DEG peel test. Pressing by using a hot press machine at 60 ℃ for 2min or at 80 ℃ for 2min, then immediately placing the workpiece into an oven at 80 ℃, hanging a weight 4 with a weight of 1kg, and observing the displacement distance (within 5 min) of the PVC film. The following is the initial heat resistance test shift result (cm):

table 3 test results

It can be seen from the experiment and the results of table 3 above that the effect of the examples is significantly better than that of the comparative examples. And a microcapsule curing agent having a particle diameter of about 1 to 5 μm is preferable, although the microcapsules of comparative examples 2 to 5 to 2 to 7 have a smaller particle diameter (D ₅₀ <1 um), but the wall material occupies too much isocyanate, so that the ineffective solid content is higher, and the effective isocyanate content is lower, so that the actual crosslinking effect is poor. And the results of comparative examples 2 to 9 without any curing agent added thereto were all peeled off under the initial temperature resistance test conditions, whereas in comparative examples 2 to 8 with the two-component curing agent (NE 580) added thereto, the initial temperature resistance was not improved since the crosslinking reaction did not occur in a short period of time.

Experiment five

As shown in fig. 10, push-out test was performed on the polyurethane films prepared in example 3 and comparative example 3: the adhesive film 2 was sandwiched between a base material 5 (size 4 x 4 cm) and an adherend 7 (diameter 2.1 cm), hot-pressed at 80 ℃ for 120 to 240s, and pushed out by moving a rod-like object toward a push-out hole 6 (diameter 0.9 cm) at a speed of v=10 mm/min, and the maximum pressure applied when the adherend was dropped was measured and converted into a pressure (MPa), which was a push-out value. The test substrate 5 was 304 stainless steel treated with primer (e.g., silane, primer, UPUV, etc.), and the adherend was PC, PET, PI, fabric, etc. The following are the results of push-out tests (MPa):

table 4 test results

The effect of the examples was significantly better than the comparative examples by the experiments and the data of table 4 above. And, according to the results of experiment four, a microcapsule curing agent having a particle diameter of about 1 to 5 μm was more suitable, and the particle diameter (D ₅₀ <1 um) has larger specific surface area, but the wall material occupies excessive isocyanate, the ineffective solid content is higher, the actual crosslinking effect is poor, and the result of the push-out test is poor.

Because the cross-linking efficiency and the specific surface area of the latent curing agent are in a proportional relationship in a certain range, emulsion particles (15-60 mu m) in the prior art are larger, so that the addition amount of the latent curing agent is larger, and the excessive latent curing agent is equivalent to solid filler, so that the final performance of the adhesive film is influenced. According to the preparation method of the polyurethane microcapsule curing agent, the particle size of the microcapsule is controllable (1-5 mu m), so that the emulsion is prevented from sedimentation too fast, and even if the emulsion is stored for a long time and has partial sedimentation, the emulsion can be restored to a normal state through simple stirring; the wall material formed by the interfacial reaction after the emulsification of the liquid raw material is continuous and uniform, so that the infiltration capacity of the PUD to the latent curing agent after the activation is stable, and the problem of releasing a large amount of carbon dioxide in the later period does not exist; and the continuous method production has no batch stability problem. On the other hand, the existing PUD has larger molecular weight, smaller number of terminal hydroxyl groups or amine groups and smaller number of reactions with the latent curing agent; when the polyurethane dispersoid is prepared, the TRIS is introduced, so that the hydroxyl content is improved on the premise of not reducing the molecular weight, the reaction with the microcapsule curing agent is facilitated, and the crosslinking density and the crosslinking efficiency are improved.

The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the present invention and to implement the same, but are not intended to limit the scope of the present invention, and all equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of the present invention.

Claims

1. The preparation method of the polyurethane microcapsule curing agent comprises a microcapsule structure, and is characterized in that the microcapsule structure comprises a wall material and a core material sealed in the wall material, and the preparation method comprises the following steps:

mixing and emulsifying an oil phase solution containing isocyanate monomers and catalysts and an aqueous phase solution containing emulsifying agents to form emulsion;

heating the emulsion added with the amine solution to a set temperature within 1-10 s, wherein isocyanate monomers in the oil phase droplets 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 cooling the system after heat preservation to a set temperature within 1-10 s.

2. The method according to claim 1, wherein the heating and cooling of the emulsion is performed by using a tubular reactor, a front stage of the tubular reactor is used for heating the emulsion to a set temperature within 1 to 10 seconds, and a rear stage of the tubular reactor is used for cooling the emulsion to a set temperature within 1 to 10 seconds.

3. The preparation method according to claim 1 or 2, wherein the set temperature at the time of heating is 50 to 80 ℃, and the temperature is kept for 1 to 8 minutes after the temperature is raised to 50 to 80 ℃; the set temperature is 20-30 ℃ when the temperature is reduced.

4. The method according to claim 1 or 2, wherein the heating rate is 20 ℃/s or more and the cooling rate is 20 ℃/s or more.

5. The preparation method according to claim 1, wherein the mass ratio between the emulsifier and the isocyanate monomer in the aqueous phase solution is 0.01% to 5%.

6. The method according to claim 5, wherein the mass ratio between the emulsifier and the isocyanate monomer in the aqueous solution is 0.1% to 2%.

7. The process according to claim 5, wherein the rotation speed of the equipment is 1000 to 9000rpm.

8. The method according to claim 1, 5 or 7, wherein the particle size of the microcapsules in the polyurethane microcapsule curing agent is 1 to 10 μm.

9. The preparation method according to claim 1, wherein the preparation method comprises a step of adding a thickener to the cooled system for thickening, and the thickened system has a viscosity of 1000-2000cps at 25 ℃; and/or the step of placing the cooled system at 20-30 ℃ for 12-36 h.

10. The preparation method according to claim 9, wherein the preparation method comprises adding a thickener to the cooled system for thickening, and then placing the cooled system at 20-30 ℃ for 12-36 h.

11. The method according to claim 1, wherein the temperature of the oil phase solution is controlled to 20 to 22 ℃ before the oil phase solution and the aqueous phase solution are mixed.

12. The method according to claim 1, wherein the reaction is carried out at 0 to 5 ℃ by controlling emulsification and adding an amine solution.

13. The method of claim 12, wherein the aqueous solution is formed by adding an emulsifier to ice water.

14. The preparation method according to claim 1, wherein the mass percentage concentration of the amine solution is 5-35%.

15. The preparation method of claim 1, wherein the polyurethane microcapsule curing agent comprises 35-45% 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.