Low-viscosity adhesive for hot pressing process and preparation method thereof

Abstract

The present invention relates to the field of C09J175 / 04, and specifically relates to a low-viscosity adhesive for hot pressing process and a preparation method thereof. The adhesive comprises a main agent and an isocyanate curing agent, wherein the weight ratio of the main agent to the isocyanate curing agent is 100:(20-30); the raw materials for preparing the main agent comprise, by weight, at least 60-90 parts of a polyol composition, 3-6 parts of a small molecule chain extender, 40-60 parts of an inorganic filler, and 10-20 parts of a functional additive. By adopting a specific polyol composition and coordinating the raw materials in the system, rapid curing is achieved while ensuring the bonding performance and mechanical properties of the adhesive. The adhesive is suitable for semi-automatic and fully automatic line hot pressing process production, improves production efficiency, and has excellent pouring and spraying effects, thus having important practical application value.

Description

Technical Field

[0001] The present invention relates to the field of C09J175 / 04, and in particular to a low-viscosity adhesive for hot pressing process and a preparation method thereof. Background Art

[0002] Polyurethane adhesives contain a high number of highly polar urethane and isocyanate groups in their structure, resulting in high adhesion and bonding strength to a wide range of materials. They also possess excellent shear strength and impact resistance, making them suitable for a variety of structural bonding applications. The bonding and mechanical properties of polyurethane adhesives vary significantly depending on the raw material formulation, resulting in a wide variety of polyurethane adhesives available on the market with varying performance characteristics suitable for different applications.

[0003] In the field of panel processing, due to the high efficiency and low cost of hot pressing, hot pressing places higher overall requirements on adhesives than cold pressing. The content of hard and soft segments in the polyurethane adhesive structure affects the overall performance of the polyurethane. Chinese Patent CN 105820308 A discloses a method for preparing and applying a moisture-reactive polyurethane hot-melt adhesive for composite flooring. Using polyester polyol, diisocyanate, and chain extender as base materials, the adhesive achieves high cohesion and good initial tack. However, the adhesive fails to meet the practical application requirements of rapid curing in hot pressing, limiting its application in continuous production. Chinese Patent CN 113861919 A ​​discloses a polyurethane adhesive composition, a polyurethane adhesive, a polyurethane adhesive tape, and a method for preparing the tape. By controlling the polyurethane adhesive formulation, the resulting polyurethane adhesive exhibits good room temperature adhesion and high temperature resistance. However, the adhesive system suffers from a high viscosity, which fails to meet the practical application requirements of machine coating and spraying. In view of the above-mentioned defects of polyurethane adhesives in the application field of hot pressing process, how to make the provided polyurethane adhesive have a lower viscosity to meet the operating requirements of machine coating and spraying while ensuring the bonding performance and mechanical properties of the adhesive is an urgent problem to be solved in this field.

[0004] Therefore, the present invention provides a low-viscosity adhesive for hot pressing process. By adopting a specific polyol composition and coordinating the various raw materials in the system, rapid curing is achieved while ensuring the bonding performance and mechanical properties of the adhesive. The adhesive is suitable for semi-automatic and fully automatic line hot pressing process production, improves production efficiency, and has excellent spraying and spraying effects. Summary of the Invention

[0005] In one aspect, the present invention provides a low-viscosity adhesive for hot pressing, comprising a main agent and an isocyanate curing agent, wherein the weight ratio of the main agent to the isocyanate curing agent is 100:(20-30); the raw materials for preparing the main agent include, by weight, at least: 60-90 parts of a polyol composition, 3-6 parts of a small molecule chain extender, 40-60 parts of an inorganic filler, and 10-20 parts of a functional additive;

[0006] As a preferred technical solution, the polyol composition comprises at least two of polycaprolactone polyol, polybutylene adipate, polyethylene glycol adipate, polyhexanediol adipate, and polyneopentyl isophthalate; preferably, the polyol composition comprises polycaprolactone polyol and polybutylene adipate; preferably, the polycaprolactone polyol is a combination of difunctional polycaprolactone polyol and trifunctional polycaprolactone polyol, and the mass ratio of the difunctional polycaprolactone polyol to the trifunctional polycaprolactone polyol is (1-3): (2-4); preferably, the hydroxyl value of the difunctional polycaprolactone polyol is 112-204 mgKOH / g, and the hydroxyl value of the trifunctional polycaprolactone polyol is 80-90 mgKOH / g. g; further preferably, the hydroxyl value of the difunctional polycaprolactone polyol is 204 mgKOH / g, and the hydroxyl value of the trifunctional polycaprolactone polyol is 84 mgKOH / g; the inventors found in the course of exploration that the use of a difunctional polycaprolactone polyol having a hydroxyl value of 112-204 mgKOH / g in combination with a trifunctional polycaprolactone polyol having a hydroxyl value of 80-90 mgKOH / g, especially when the mass ratio of the difunctional polycaprolactone polyol to the trifunctional polycaprolactone polyol is (1-3): (2-4), improves the reaction consistency of polybutylene adipate and 4,4-diphenylmethane diisocyanate in the system, the density of the urethane generated by the reaction is higher, the curing effect is enhanced, and wrinkles and breaks in the cured film are avoided. The inventors speculate that the reason may be that, at this mass ratio, the trifunctional polycaprolactone polyol with a hydroxyl value of 80-90 mgKOH / g and the difunctional polycaprolactone polyol can exert a synergistic effect to the greatest extent, which helps to balance the molecular forces in the hard segment structure of the low-viscosity adhesive, reduce the viscosity of the system, and at the same time promote the reaction between polybutylene adipate and 4,4-diphenylmethane diisocyanate in the system, reduce the difficulty of production and processing and improve the curing efficiency.

[0007] The model of the difunctional polycaprolactone polyol is CAPA®2054, and the model of the trifunctional polycaprolactone polyol is CAPA®3201, both of which were purchased from Guangzhou Haoyi New Materials Technology Co., Ltd.

[0008] As a preferred technical solution, the polyol composition further comprises trifunctional castor oil polyol; preferably, the water content of the trifunctional castor oil polyol is less than 0.05wt%; preferably, the trifunctional castor oil polyol comprises trifunctional castor oil polyol A having a viscosity (25°C) of 430-490mPa.s and trifunctional castor oil polyol B having a viscosity (25°C) of 800-1300mPa.s; preferably, the mass ratio of the trifunctional castor oil polyol A to the trifunctional castor oil polyol B is (1-2): (3-5); during the hot pressing process, under high-frequency hot pressing, the trifunctional castor oil polyol Moisture in the adhesive film may cause bulging and degumming in the low-viscosity adhesive film, which cannot meet the processing requirements of the hot pressing process. During the research process, the inventors found that when the moisture content of the trifunctional castor oil polyol is controlled to be less than 0.05wt%, especially when a trifunctional castor oil polyol A with a viscosity (25°C) of 430-490mPa.s and a trifunctional castor oil polyol B with a viscosity (25°C) of 800-1300mPa.s in a mass ratio of (1-2): (3-5) are used, the hardness and bonding properties of the low-viscosity adhesive are balanced, the stability and fluidity of the adhesive system are effectively improved, and the comprehensive performance and product quality of the low-viscosity adhesive are guaranteed.

[0009] The trifunctional castor oil polyol A is of model URIC H-57, and the trifunctional castor oil polyol B is of model URIC H-870, both of which were purchased from Beijing Senchang Taihe Technology Co., Ltd.

[0010] As a preferred technical solution, the mass ratio of the polycaprolactone polyol, polybutylene adipate, and trifunctional castor oil polyol is (1-2): (0.8-1.2): (4-6); the use of trifunctional polycaprolactone polyol causes a certain degree of chemical crosslinking of the polymer, shortening the curing time of the adhesive; however, the introduction of trifunctional polycaprolactone polyol will affect the microphase separation of the soft segment and the hard segment in the polyurethane structure to a certain extent, affecting the bonding performance and mechanical properties of the adhesive; the inventors found in the process of exploration that by controlling the mass ratio of polycaprolactone polyol, polybutylene adipate, and trifunctional castor oil polyol in the system to (1-2): (0.8-1.2): (4-6), The viscosity and adhesion properties of the adhesive system are balanced, allowing the provided low-viscosity adhesive to cure rapidly during a hot pressing process, meeting the operational requirements of pouring and spraying. The inventors analyzed that this may be due to the influence of the active groups in the trifunctional castor oil polyol. Trifunctional castor oil polyol A with a viscosity (25°C) of 430-490 mPa.s and trifunctional castor oil polyol B with a viscosity (25°C) of 800-1300 mPa.s react with 4,4-diphenylmethane diisocyanate and cure rapidly, giving the provided low-viscosity adhesive greater polarity. The intermolecular forces between the soft chain segments in the adhesive structure are strong, resulting in high cohesive strength, thereby ensuring the adhesive's bonding strength, thermal oxidation resistance, and mechanical strength.

[0011] As a preferred technical solution, the small molecule chain extender is at least one of 1,4-butanediol and 1,6-hexanediol;

[0012] As a preferred technical solution, the inorganic filler is selected from at least one of silicon micropowder, talc, calcium carbonate, and titanium dioxide; preferably, the inorganic filler is silicon micropowder and calcium carbonate, and preferably, the mass ratio of the silicon micropowder to calcium carbonate is (4-6): (2-4); preferably, the particle size of the silicon micropowder is 2-4 μm, and the particle size of the calcium carbonate is 0.8-1.2 μm;

[0013] In order to make the provided adhesive meet the actual operation requirements of machine coating and spraying during the hot pressing process, based on the system of the present invention, silicon micropowder and calcium carbonate with a mass ratio of (4-6): (2-4) are introduced to effectively toughen and reinforce the polymer system and improve the processing performance of the polymer system. However, the inventors found in the process of exploration that the particle size of silicon micropowder and calcium carbonate is too small, and the nano-level inorganic nanoparticles tend to aggregate under the influence of strong surface activation energy, causing the inorganic particles to agglomerate, which cannot effectively improve the rheological properties of the adhesive system and may also cause the stability of the adhesive system to decrease, and defects exist after the adhesive is cured. The inventors control the introduction of silicon micropowder with a particle size of 2-4μm and calcium carbonate with a synergistic particle size of 0.8-1.2μm into the system. While not affecting the curing reaction of the system, the rheological properties of the system are effectively improved, the phenomenon of reduced system stability caused by particle agglomeration is avoided, precipitation and stratification phenomena are effectively reduced and eliminated, and the spraying and coating effects are good. It is suitable for semi-automatic and fully automatic line hot pressing process production and manufacturing, thereby improving production efficiency.

[0014] The silicon micropowder and calcium carbonate were purchased from Guangzhou Xinxi Metallurgical Chemical Co., Ltd.

[0015] As a preferred technical solution, the functional additives include at least a dispersant, an adhesion promoter, and a viscosity reducer; preferably, the mass ratio of the dispersant, adhesion promoter, and viscosity reducer is (1-3): (2-5): (8-12);

[0016] Preferably, the dispersant is an unsaturated carboxylic acid dispersant; preferably, the unsaturated carboxylic acid dispersant is Efka 5065 or Efka 5066, which achieves uniform dispersion and stable compatibility of the raw materials in the system, contributing to the stability of the low-viscosity adhesive system. The Efka 5065 and Efka 5066 were purchased from Guangzhou Haoyi New Materials Technology Co., Ltd.

[0017] Preferably, the adhesion promoter is benzylmethoxydimethylsilane; based on the system of the present invention, by introducing benzylmethoxydimethylsilane, conjugation occurs with the aromatic ring structure in the polymethylene polyphenyl polyisocyanate and 4,4-diphenylmethane diisocyanate structures in the system during the curing reaction, synergistically fixing the elastic chain segments of the polyurethane and improving the adhesion performance of the low-viscosity adhesive. The benzylmethoxydimethylsilane was purchased from Shanghai Bangao Chemical Co., Ltd.

[0018] Preferably, the viscosity reducing agent is a combination of 2,2,4-triethyl-1,3-pentanediol diisobutyrate and triethylene glycol monobutyl ether, and the mass ratio of the 2,2,4-triethyl-1,3-pentanediol diisobutyrate and triethylene glycol monobutyl ether is (4-6): (3-5). Based on the system of the present invention, the combination of 2,2,4-triethyl-1,3-pentanediol diisobutyrate and triethylene glycol monobutyl ether is used as the viscosity reducing agent, and in particular, their mass ratio is controlled to be (4-6): (3-5). While not affecting the adhesion performance of the adhesive, the viscosity of the adhesive system is synergistically reduced and the viscosity of the system is maintained stable, thereby promoting the curing reaction progress of the polyol composition and isocyanate in the system, reducing the curing reaction time, and improving production efficiency.

[0019] Another aspect of the present invention provides a method for preparing a low-viscosity adhesive for a hot pressing process. The method comprises the following steps: adding a polyol composition by weight into a reaction kettle, stirring and mixing for 10-15 minutes, adding an inorganic filler, a functional additive, and a small molecule chain extender, heating the mixture to 90-100° C., and vacuum dehydrating the mixture until the moisture content is ≤0.05% to obtain a main agent. When the main agent is used, an isocyanate curing agent is added by weight and mixed evenly.

[0020] As a preferred technical solution, the isocyanate curing agent is selected from one or a combination of toluene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, p-xylylene diisocyanate, methylcyclohexylmethane diisocyanate, dicyclohexylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate; preferably, the isocyanate curing agent is a combination of 4,4-diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate; the mass ratio of 4,4-diphenylmethane diisocyanate to polymethylene polyphenyl polyisocyanate is (15-20): (5-10).

[0021] Beneficial effects

[0022] 1. The present invention provides a low-viscosity adhesive for hot pressing process. By adopting a specific polyol composition and coordinating the various raw materials in the system, rapid curing is achieved while ensuring the bonding performance and mechanical properties of the adhesive. The adhesive is suitable for semi-automatic and fully automatic line hot pressing process production, improving production efficiency and having excellent spraying and spraying effects.

[0023] 2. Use difunctional polycaprolactone polyol with a hydroxyl value of 112-204 mgKOH / g in combination with trifunctional polycaprolactone polyol with a hydroxyl value of 80-90 mgKOH / g, especially when the mass ratio of difunctional polycaprolactone polyol to trifunctional polycaprolactone polyol is (1-3): (2-4), to improve the reaction consistency of polybutylene adipate and 4,4-diphenylmethane diisocyanate in the system, the density of the reacted urethane is higher, the curing effect is enhanced, and wrinkles and breaks in the cured film are avoided.

[0024] 3. In the present invention, by controlling the moisture content of the trifunctional castor oil polyol to less than 0.05wt%, in particular, by using trifunctional castor oil polyol A having a viscosity (25°C) of 430-490mPa.s and trifunctional castor oil polyol B having a viscosity (25°C) of 800-1300mPa.s in a mass ratio of (1-2): (3-5), the hardness and bonding properties of the low-viscosity adhesive are balanced, the stability and fluidity of the adhesive system are effectively improved, and the comprehensive performance and product quality of the low-viscosity adhesive are guaranteed.

[0025] 4. The present invention adopts an inorganic filler in combination with a viscosity reducing agent to effectively toughen and strengthen the low-viscosity adhesive while reducing the viscosity of the system and maintaining the stability of the viscosity of the system, thereby promoting the curing reaction progress of the polyol composition and isocyanate in the system, meeting the needs of spraying and pouring, being suitable for semi-automatic and fully automatic line hot pressing process production and manufacturing, and improving production efficiency.

[0026] 5. By controlling the mass ratio of polycaprolactone polyol, polybutylene adipate, and trifunctional castor oil polyol in the system to (1-2): (0.8-1.2): (4-6), the viscosity and adhesion properties of the adhesive system are balanced, so that the low-viscosity adhesive provided can be quickly cured in the hot pressing process, meeting the operational requirements of pouring and spraying. DETAILED DESCRIPTION

[0027] Example 1

[0028] Example 1 of the present invention provides a low-viscosity adhesive for hot pressing, comprising a main agent and an isocyanate curing agent, wherein the weight ratio of the main agent to the isocyanate curing agent is 100:30; the raw materials for preparing the main agent include, by weight, 80 parts of a polyol composition, 5 parts of a small molecule chain extender, 50 parts of an inorganic filler, and 15 parts of a functional additive;

[0029] The polyol composition includes polycaprolactone polyol and polybutylene adipate; the polycaprolactone polyol is a combination of difunctional polycaprolactone polyol and trifunctional polycaprolactone polyol, and the mass ratio of the difunctional polycaprolactone polyol to the trifunctional polycaprolactone polyol is 2:3; the hydroxyl value of the difunctional polycaprolactone polyol is 204 mgKOH / g, and the hydroxyl value of the trifunctional polycaprolactone polyol is 84 mgKOH / g.

[0030] The model of the difunctional polycaprolactone polyol is CAPA®2054, and the model of the trifunctional polycaprolactone polyol is CAPA®3201, both of which were purchased from Guangzhou Haoyi New Materials Technology Co., Ltd.

[0031] The polyol composition also includes trifunctional castor oil polyol; the moisture content of the trifunctional castor oil polyol is less than 0.05wt%; preferably, the trifunctional castor oil polyol includes trifunctional castor oil polyol A and trifunctional castor oil polyol B; the mass ratio of the trifunctional castor oil polyol A to the trifunctional castor oil polyol B is 1.5:4.

[0032] The trifunctional castor oil polyol A is of model URIC H-57, and the trifunctional castor oil polyol B is of model URIC H-870, both of which were purchased from Beijing Senchang Taihe Technology Co., Ltd.

[0033] The mass ratio of the polycaprolactone polyol, polybutylene adipate and trifunctional castor oil polyol is 1.5:1:5.

[0034] The small molecule chain extender is 1,6-hexanediol;

[0035] The inorganic filler is silicon micropowder and calcium carbonate, the mass ratio of the silicon micropowder to the calcium carbonate is 5:3; the average particle size of the silicon micropowder is 3 μm, and the average particle size of the calcium carbonate is 1 μm;

[0036] The silicon micropowder and calcium carbonate were purchased from Guangzhou Xinxi Metallurgical Chemical Co., Ltd.

[0037] The functional additives include a dispersant, an adhesion promoter, and a viscosity reducer; the mass ratio of the dispersant, adhesion promoter, and viscosity reducer is 2:3:10;

[0038] The dispersant is an unsaturated carboxylic acid dispersant, and the unsaturated carboxylic acid dispersant is Efka 5065. The Efka 5065 is purchased from Guangzhou Haoyi New Materials Technology Co., Ltd.

[0039] The adhesion promoter is benzylmethoxydimethylsilane, which is purchased from Shanghai Bangao Chemical Co., Ltd.

[0040] The viscosity reducing agent is a combination of 2,2,4-triethyl-1,3-pentanediol diisobutyrate and triethylene glycol monobutyl ether, and the mass ratio of the 2,2,4-triethyl-1,3-pentanediol diisobutyrate to triethylene glycol monobutyl ether is 5:4.

[0041] The isocyanate curing agent is a combination of 4,4-diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate; the mass ratio of the 4,4-diphenylmethane diisocyanate to the polymethylene polyphenyl polyisocyanate is 2:1.

[0042] On the other hand, Example 1 of the present invention provides a method for preparing a low-viscosity adhesive for a hot pressing process. The polyol composition is put into a reactor by weight, stirred and mixed for 15 minutes, and then an inorganic filler, a functional additive, and a small molecule chain extender are added. The temperature is raised to 100°C, and vacuum dehydration is performed until the moisture mass fraction in the material is ≤0.05% to obtain a main agent. When used, an isocyanate curing agent is added by weight and mixed evenly.

[0043] Example 2

[0044] Example 2 of the present invention provides, on the one hand, a low-viscosity adhesive for hot pressing, comprising a main agent and an isocyanate curing agent, wherein the weight ratio of the main agent to the isocyanate curing agent is 100:30; the raw materials for preparing the main agent include, by weight, 90 parts of a polyol composition, 6 parts of a small molecule chain extender, 55 parts of an inorganic filler, and 18 parts of a functional additive;

[0045] The polyol composition includes polycaprolactone polyol and polybutylene adipate; the polycaprolactone polyol is a combination of difunctional polycaprolactone polyol and trifunctional polycaprolactone polyol, and the mass ratio of the difunctional polycaprolactone polyol to the trifunctional polycaprolactone polyol is 3:4; the hydroxyl value of the difunctional polycaprolactone polyol is 204 mgKOH / g, and the hydroxyl value of the trifunctional polycaprolactone polyol is 84 mgKOH / g.

[0046] The model of the difunctional polycaprolactone polyol is CAPA®2054, and the model of the trifunctional polycaprolactone polyol is CAPA®3201, both of which were purchased from Guangzhou Haoyi New Materials Technology Co., Ltd.

[0047] The polyol composition also includes trifunctional castor oil polyol; the moisture content of the trifunctional castor oil polyol is less than 0.05wt%; preferably, the trifunctional castor oil polyol includes trifunctional castor oil polyol A and trifunctional castor oil polyol B; the mass ratio of the trifunctional castor oil polyol A to the trifunctional castor oil polyol B is 2:5.

[0048] The trifunctional castor oil polyol A is of model URIC H-57, and the trifunctional castor oil polyol B is of model URIC H-870, both of which were purchased from Beijing Senchang Taihe Technology Co., Ltd.

[0049] The mass ratio of the polycaprolactone polyol, polybutylene adipate and trifunctional castor oil polyol is 2:1.2:6.

[0050] The small molecule chain extender is 1,4-butanediol;

[0051] The inorganic filler is silicon micropowder and calcium carbonate, the mass ratio of the silicon micropowder to the calcium carbonate is 6:4; the average particle size of the silicon micropowder is 3 μm, and the average particle size of the calcium carbonate is 1 μm;

[0052] The silicon micropowder and calcium carbonate were purchased from Guangzhou Xinxi Metallurgical Chemical Co., Ltd.

[0053] The functional additives include a dispersant, an adhesion promoter, and a viscosity reducer; the mass ratio of the dispersant, adhesion promoter, and viscosity reducer is 3:5:10;

[0054] The dispersant is an unsaturated carboxylic acid dispersant, and the unsaturated carboxylic acid dispersant is Efka 5066. The Efka 5066 is purchased from Guangzhou Haoyi New Materials Technology Co., Ltd.

[0055] The adhesion promoter is benzylmethoxydimethylsilane, which is purchased from Shanghai Bangao Chemical Co., Ltd.

[0056] The viscosity reducing agent is a combination of 2,2,4-triethyl-1,3-pentanediol diisobutyrate and triethylene glycol monobutyl ether, and the mass ratio of the 2,2,4-triethyl-1,3-pentanediol diisobutyrate to triethylene glycol monobutyl ether is 6:5.

[0057] The isocyanate curing agent is a combination of 4,4-diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate; the mass ratio of the 4,4-diphenylmethane diisocyanate to the polymethylene polyphenyl polyisocyanate is 2:1.

[0058] On the other hand, Example 2 of the present invention provides a method for preparing a low-viscosity adhesive for a hot pressing process. The polyol composition is put into a reactor by weight, stirred and mixed for 15 minutes, and then an inorganic filler, a functional additive, and a small molecule chain extender are added. The temperature is raised to 100°C, and vacuum dehydration is performed until the moisture mass fraction in the material is ≤0.05% to obtain a main agent. When used, an isocyanate curing agent is added by weight and mixed evenly.

[0059] Example 3

[0060] Example 3 of the present invention provides, on the one hand, a low-viscosity adhesive for hot pressing process, including a main agent and an isocyanate curing agent, the weight ratio of the main agent to the isocyanate curing agent is 100:30; in parts by weight, the raw materials for preparing the main agent include: 70 parts of a polyol composition, 3 parts of a small molecule chain extender, 40 parts of an inorganic filler, and 12 parts of a functional additive.

[0061] The polyol composition includes polycaprolactone polyol and polybutylene adipate; the polycaprolactone polyol is a combination of difunctional polycaprolactone polyol and trifunctional polycaprolactone polyol, and the mass ratio of the difunctional polycaprolactone polyol to the trifunctional polycaprolactone polyol is 1:2; the hydroxyl value of the difunctional polycaprolactone polyol is 204 mgKOH / g, and the hydroxyl value of the trifunctional polycaprolactone polyol is 84 mgKOH / g.

[0062] The model of the difunctional polycaprolactone polyol is CAPA®2054, and the model of the trifunctional polycaprolactone polyol is CAPA®3201, both of which were purchased from Guangzhou Haoyi New Materials Technology Co., Ltd.

[0063] The polyol composition also includes trifunctional castor oil polyol; the moisture content of the trifunctional castor oil polyol is less than 0.05wt%; preferably, the trifunctional castor oil polyol includes trifunctional castor oil polyol A and trifunctional castor oil polyol B; the mass ratio of the trifunctional castor oil polyol A to the trifunctional castor oil polyol B is 1:3.

[0064] The trifunctional castor oil polyol A is of model URIC H-57, and the trifunctional castor oil polyol B is of model URIC H-870, both of which were purchased from Beijing Senchang Taihe Technology Co., Ltd.

[0065] The mass ratio of the polycaprolactone polyol, polybutylene adipate and trifunctional castor oil polyol is 1:0.8:4.

[0066] The small molecule chain extender is 1,6-hexanediol;

[0067] The inorganic filler is silicon micropowder and calcium carbonate, the mass ratio of the silicon micropowder to the calcium carbonate is 4:2; the average particle size of the silicon micropowder is 3 μm, and the average particle size of the calcium carbonate is 1 μm;

[0068] The silicon micropowder and calcium carbonate were purchased from Guangzhou Xinxi Metallurgical Chemical Co., Ltd.

[0069] The functional additives include a dispersant, an adhesion promoter, and a viscosity reducer; the mass ratio of the dispersant, adhesion promoter, and viscosity reducer is 1:3:8;

[0070] The dispersant is an unsaturated carboxylic acid dispersant, and the unsaturated carboxylic acid dispersant is Efka 5065. The Efka 5065 is purchased from Guangzhou Haoyi New Materials Technology Co., Ltd.

[0071] The adhesion promoter is benzylmethoxydimethylsilane, which is purchased from Shanghai Bangao Chemical Co., Ltd.

[0072] The viscosity reducing agent is a combination of 2,2,4-triethyl-1,3-pentanediol diisobutyrate and triethylene glycol monobutyl ether, and the mass ratio of the 2,2,4-triethyl-1,3-pentanediol diisobutyrate to triethylene glycol monobutyl ether is 4:3.

[0073] The isocyanate curing agent is a combination of 4,4-diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate; the mass ratio of the 4,4-diphenylmethane diisocyanate to the polymethylene polyphenyl polyisocyanate is 2:1.

[0074] On the other hand, Example 3 of the present invention provides a method for preparing a low-viscosity adhesive for a hot pressing process. The polyol composition is put into a reactor by weight, stirred and mixed for 15 minutes, and then an inorganic filler, a functional additive, and a small molecule chain extender are added. The temperature is raised to 100°C, and vacuum dehydration is performed until the moisture mass fraction in the material is ≤0.05% to obtain a main agent. When used, an isocyanate curing agent is added by weight and mixed evenly.

[0075] Comparative Example 1

[0076] Comparative Example 1 of the present invention provides a low-viscosity adhesive for hot pressing process, and its specific implementation is the same as that of Example 1, except that the raw materials for preparing the low-viscosity adhesive for hot pressing process do not include polybutylene adipate.

[0077] Comparative Example 2

[0078] Comparative Example 2 of the present invention provides a low-viscosity adhesive for hot pressing process, and its specific implementation is the same as that of Example 1, except that the polyol composition does not include trifunctional castor oil polyol.

[0079] Comparative Example 3

[0080] Comparative Example 3 of the present invention provides a low-viscosity adhesive for hot pressing process, and its specific implementation method is the same as Example 1, except that the inorganic filler is talcum powder, and the particle size of the talcum powder is 325 mesh, which is purchased from West Asia Chemical Technology (Shandong) Co., Ltd.

[0081] Comparative Example 4

[0082] Comparative Example 4 of the present invention provides a low-viscosity adhesive for hot pressing process, and its specific implementation is the same as that of Example 1, except that the polyol composition does not include polycaprolactone polyol.

[0083] Comparative Example 5

[0084] Comparative Example 5 of the present invention provides a low-viscosity adhesive for hot pressing process, and its specific implementation is the same as that of Example 1, except that the viscosity reducing agent is triethylene glycol monobutyl ether.

[0085] Performance testing methods

[0086] Aluminum alloy was used as the bonding specimen. The surface of the aluminum alloy was polished with 0# sandpaper, and the surface grease was removed by ultrasonic cleaning with acetone for 15 minutes. The surface was treated by FPL oxidation method, then rinsed with deionized water, and placed in a 60℃ forced air drying oven for use.

[0087] 1. Curing time

[0088] The low-viscosity adhesive obtained in the examples and comparative examples was sprayed onto the surface of the aluminum alloy specimen after the above treatment. The temperature was controlled at 60° C. and the curing time of the low-viscosity adhesive was recorded. The results are shown in Table 1.

[0089] 2. Tensile shear strength test

[0090] The tensile shear strength of the low-viscosity adhesives obtained in the Examples and Comparative Examples was tested according to the GB / T 7124-2008 method. A tensile shear strength of 8-9 MPa (inclusive) was rated as "excellent," a tensile shear strength of 6-8 MPa (inclusive) was rated as "good," and a tensile shear strength of less than 6 MPa was rated as "poor." The results are shown in Table 1.

[0091] 3. Plane tensile strength test

[0092] The low-viscosity adhesives obtained in the examples and comparative examples were tested for planar tensile strength according to the GB / T528 method. A planar tensile strength of 1.8-2.2 MPa (including 1.8 MPa) was rated as "excellent," a tensile shear strength of 1.5-1.8 MPa (including 1.5 MPa) was rated as "good," and a tensile shear strength of less than 1.5 MPa was rated as "poor." The results are shown in Table 1.

[0093]

Claims

1. A low viscosity adhesive for hot pressing process, characterized in that: The invention comprises a main agent and an isocyanate curing agent, wherein the weight ratio of the main agent to the isocyanate curing agent is 100:(20-30); The raw materials for preparing the main agent include at least 60-90 parts of a polyol composition, 3-6 parts of a small molecule chain extender, 40-60 parts of an inorganic filler, and 10-20 parts of a functional additive, calculated by weight. The polyol composition includes polycaprolactone polyol and polybutylene adipate; the polycaprolactone polyol includes a difunctional polycaprolactone polyol having a hydroxyl value of 112-204 mgKOH / g and a trifunctional polycaprolactone polyol having a hydroxyl value of 80-90 mgKOH / g, so the mass ratio of the difunctional polycaprolactone polyol to the trifunctional polycaprolactone polyol is (1-3):(2-4); the polyol composition also includes a trifunctional castor oil polyol, and the water content of the trifunctional castor oil polyol is less than 0.05wt%; the trifunctional castor oil polyol includes a mass ratio of (1-2): : (3-5) trifunctional castor oil polyol A having a viscosity of 430-490 mPa.s tested at 25°C and trifunctional castor oil polyol B having a viscosity of 800-1300 mPa.s tested at 25°C; the mass ratio of the polycaprolactone polyol, polybutylene adipate, and trifunctional castor oil polyol is (1-2): (0.8-1.2): (4-6); the inorganic filler is silica powder and calcium carbonate, and the mass ratio of the silica powder to calcium carbonate is (4-6): (2-4); the particle size of the silica powder is 2-4 μm, and the particle size of the calcium carbonate is 0.8-1.2 μm.

2. The low-viscosity adhesive for hot pressing process according to claim 1, characterized in that: The small molecule chain extender is at least one of 1,4-butanediol and 1,6-hexanediol.

3. The low-viscosity adhesive for hot pressing process according to claim 1, characterized in that: The functional additives at least include a dispersant, an adhesion promoter, and a viscosity reducer.

4. The low-viscosity adhesive for hot pressing process according to claim 3, characterized in that: The viscosity reducing agent is a combination of 2,2,4-triethyl-1,3-pentanediol diisobutyrate and triethylene glycol monobutyl ether.

5. A method for preparing a low-viscosity adhesive for hot pressing according to any one of claims 1 to 4, characterized in that: The polyol composition is put into a reactor by weight, stirred and mixed for 10-15 minutes, and then an inorganic filler, a functional additive, and a small molecule chain extender are added. The temperature is raised to 90-100°C, and vacuum dehydration is performed until the moisture mass fraction in the material is ≤0.05% to obtain the main agent. When used, the isocyanate curing agent is added by weight and mixed evenly.

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