Water-based automotive interior adhesive capable of balancing activation temperature and heat resistance and preparation method of water-based automotive interior adhesive

Abstract

The invention discloses a water-based automotive interior adhesive capable of balancing activation temperature and heat resistance and a preparation method of the water-based automotive interior adhesive, and belongs to the technical field of adhesives. The adhesive is prepared from polycaprolactone polyol, polycaprolactone-glycolide copolymer polyol, trimethylolpropane-epsilon-caprolactone polyester trihydric alcohol, polytetrahydrofuran ether diol, isocyanate, a small molecule chain extender, a hydrophilic chain extender, a neutralizing agent, acetone, an organic silicon modified cross-linking agent, deionized water, an amine chain extender and a de-foaming agent, wherein the polycaprolactone polyol, the polycaprolactone-glycolide copolymer polyol, the trimethylolpropane-epsilon-caprolactone polyester trihydric alcohol, the polytetrahydrofuran ether diol, the isocyanate, the small molecule chain extender, the hydrophilic chain extender, the neutralizing agent, the acetone, the organic silicon modified cross-linking agent and the de-foaming agent are added; according to the invention, a synergistic system of polycaprolactone polyol and polycaprolactone-glycolide copolymer polyol is combined with the multifunctional polycaprolactone trihydric alcohol and the organic silicon modified cross-linking agent, so that the contradiction between the activation temperature and the heat resistance is successfully solved, and the excellent balance between the activation temperature of 50-70 DEG C and the heat resistance of more than or equal to 110 DEG C is realized; the moisture and heat resistance is obviously improved, and the adhesive is suitable for bonding automotive interiors.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of adhesives, and particularly relates to a water-based automotive interior adhesive balancing activation temperature and heat resistance and a preparation method thereof. BACKGROUND

[0002] The water-based automotive interior adhesive is mainly used for bonding polyvinyl chloride sheets, carpets, fabrics, double-sided fabrics, leathers and other materials of automotive interiors, and can be used for bonding and compression molding of substrates such as ABS, ABS / PC plates, fibers, SMC and wood composites to form, for example, roof hoods, interior parts of vehicle doors, luggage racks, interior parts of pillars, etc., and can be suitable for vacuum suction molding process.

[0003] The water-based automotive interior adhesives on the market at present are mainly two-component systems, the main agent is a water-based polyurethane emulsion, and the curing agent is an HDI trimer. In the prior art, a water-based automotive interior adhesive with good heat resistance is disclosed in Chinese Patent Application No. 202411603263.1 and Publication No. CN119463778A. The adhesive includes polyester polyol, polyether polyol, isocyanate, small molecule chain extender, hydrophilic chain extender, neutralizing agent, acetone, deionized water, amine chain extender, carbamide, defoamer, wetting agent and thickening agent. The polyester polyol is prepared by reacting polycarbonate diol, polybutylene adipate diol and the like with isocyanate to prepare a water-based polyurethane dispersion, and carbamide is added in the later stage to improve the temperature resistance.

[0004] However, when designing the interior, the automotive OEM often starts from the customer's demand, designs more types of skin materials, bending radii and unique shapes, and does not fully consider the performance boundaries of the adhesive. This leads to some parts having very high requirements for heat resistance, or the adhesive needs to have better wet heat resistance in humid climates. Whether it is heat resistance or wet heat resistance, the activation temperature needs to be considered in actual production. The prior art has the following technical problems: First, there is a contradiction between the activation temperature and the heat resistance. The emulsion with soft adhesive layer and slow crystallization rate has a low activation temperature (usually 40-50℃), but both the initial heat resistance and the final heat resistance are insufficient, and the bonding fails easily above 50℃. On the contrary, the emulsion with good heat resistance (such as high crystallinity polycarbonate diol system) requires a high activation temperature (usually 80-100℃), which is difficult to achieve in actual production line, resulting in insufficient bonding strength.

[0005] Second, the wet heat resistance is insufficient. Although polycarbonate diol has good hydrolysis resistance, the hard segment microzone of the polyurethane adhesive layer will reorganize in a high temperature and high humidity environment (such as 70℃, 85% relative humidity), resulting in a decrease in bonding strength. Polyadipic acid-based polyester polyol is prone to ester bond hydrolysis at high temperatures, further reducing the wet heat resistance.

[0006] Thirdly, the crystallization behavior is difficult to control. The prior art mainly adjusts the emulsion performance by collocating polyols with isocyanates, but lacks fine control means for the crystallization behavior of the soft segment. High crystallinity leads to excessively high activation temperature, and low crystallinity leads to insufficient heat resistance, so it is difficult to achieve an ideal balance between the two.

[0007] Therefore, it is urgent to develop a water-based automotive interior adhesive capable of achieving excellent heat resistance and wet heat resistance at a moderate activation temperature. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art and provide a water-based automotive interior adhesive balancing activation temperature and heat resistance and a preparation method thereof. By using a synergistic system of polycaprolactone polyol and polycaprolactone-glycolide copolymer polyol, combined with multifunctional polycaprolactone triol and silicone-modified crosslinking agent, an excellent balance between activation temperature (50-70℃) and heat resistance (≥110℃) is achieved, and the wet heat resistance is significantly improved.

[0009] To achieve the above-mentioned purpose, the first aspect of the present application provides a water-based automotive interior adhesive balancing activation temperature and heat resistance, comprising the following components by weight: polycaprolactone polyol: 30-50 parts; polycaprolactone-glycolide copolymer polyol: 10-30 parts; trimethylolpropane-ε-caprolactone polyester triol: 5-15 parts; polytetrahydrofuran ether diol: 5-15 parts; isocyanate: 20-35 parts; small molecule chain extender: 2-6 parts; hydrophilic chain extender: 2-5 parts; neutralizing agent: 1-3 parts; acetone: 10-25 parts; silicone-modified crosslinking agent: 3-8 parts; deionized water: 40-70 parts; amine chain extender: 0.5-2 parts; defoamer: 0.1-0.5 parts; wetting agent: 0.1-0.5 parts; thickening agent: 0.2-0.8 parts.

[0010] Preferably, the polycaprolactone polyol is a polycaprolactone diol with a number average molecular weight of 1000-2500.

[0011] Preferably, the polycaprolactone-glycolide copolymer polyol is a copolymer diol with a molar ratio of epsilon-caprolactone to L-lactide of 60:40 to 85:15, and a number average molecular weight of 1500-3000.

[0012] Preferably, the trimethylolpropane-epsilon-caprolactone polyester triol has a number average molecular weight of 900-1800 and a hydroxyl value of 90-180 mgKOH / g.

[0013] Preferably, the polytetrahydrofuran ether diol has a number average molecular weight of 1000-2000.

[0014] Preferably, the isocyanate is isophorone diisocyanate, hexamethylene diisocyanate, or a mixture thereof, and the mass ratio of isophorone diisocyanate to hexamethylene diisocyanate is 2:1 to 4:1.

[0015] Preferably, the small molecule chain extender is 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, or a mixture thereof.

[0016] Preferably, the hydrophilic chain extender is dimethylolpropionic acid, dimethylolbutyric acid, or a mixture thereof.

[0017] Preferably, the neutralizing agent is triethylamine, sodium hydroxide, or ammonia.

[0018] Preferably, the silicone-modified crosslinking agent is a 3-aminopropyl triethoxysilane-terminated polycaprolactone-based prepolymer, and the preparation method comprises the following steps: reacting polycaprolactone diol with a number average molecular weight of 400-800 with isophorone diisocyanate at 80-100℃ for 1-2h, with a molar ratio of NCO groups to hydroxyl groups of 2.5:1 to 3.5:1, then adding 3-aminopropyl triethoxysilane and carrying out end capping reaction at 50-70℃ for 0.5-1.5h to obtain a silane-terminated silicone-modified crosslinking agent.

[0019] Preferably, the amine chain extender is isophorone diamine, ethylenediamine, diethylenetriamine, or a mixture thereof.

[0020] Preferably, the defoaming agent is a silicone defoaming agent or a polyether-modified silicone defoaming agent.

[0021] Preferably, the wetting agent is a polyether-modified silicone wetting agent or an acrylic wetting agent.

[0022] Preferably, the thickening agent is an alkali-swellable acrylic thickening agent or a polyurethane associative thickening agent.

[0023] The second aspect of the present application provides a preparation method of the water-based automotive interior adhesive, comprising the following steps: Step 1: Put polycaprolactone polyol, polycaprolactone-glycolide copolymer polyol, trimethylolpropane-ε-caprolactone polyester triol and polytetrahydrofuran ether diol into a reaction vessel, dehydrate at 100-120℃, -0.08 to -0.10 MPa for 15-30 min; Step 2: Cool to 70-90℃, add isocyanate, react at normal pressure for 0.5-1.5 h to obtain NCO terminated prepolymer; Step 3: Add small molecule chain extender and hydrophilic chain extender, react at 65-80℃ for 1.5-3 h, during which add acetone in batches to reduce viscosity, react until NCO content reaches 95%-105% of the theoretical value to obtain the first intermediate; Step 4: Cool the first intermediate to 35-50℃, add neutralizing agent for neutralization reaction for 15-30 min to obtain the second intermediate; Step 5: Under high-speed dispersion conditions, quickly add deionized water to the second intermediate for dispersion at a speed of 1000-1500 rpm, add amine chain extender during the dispersion process, and high-speed dispersion for 20-40 min to obtain a waterborne polyurethane dispersion; Step 6: Remove acetone at 50-70℃, -0.06 to -0.08 MPa to obtain a waterborne polyurethane emulsion with a solid content of 35%-45%; Step 7: Add silicone modified crosslinking agent to the waterborne polyurethane emulsion, stir at a speed of 400-600 rpm for 25-40 min to make it fully dispersed; Step 8: Add defoaming agent and wetting agent in sequence, stir at a speed of 400-600 rpm for 25-40 min; Step 9: Add thickening agent in batches to adjust the viscosity to 3000-8000 mPa·s to obtain a waterborne automotive interior adhesive product.

[0024] Preferably, in step 1, the dehydration time is 20 min and the dehydration temperature is 110℃.

[0025] Preferably, in step 2, the isocyanate is added in batches with an interval of 10-15 min, and the reaction temperature is controlled at 75-85℃.

[0026] Preferably, in step 3, the acetone is added in 3-5 batches, and after each addition, it is stirred uniformly before continuing the reaction.

[0027] Preferably, in step 5, the addition speed of deionized water is controlled at 50-100 g / min, and the high-speed dispersion is maintained during the water addition process.

[0028] Preferably, in step 7, the addition of the silicone-modified crosslinking agent is carried out by slow dropwise addition, and the dropwise addition time is 10-20 min.

[0029] The beneficial effects of the present application are as follows: First, the present application successfully solves the contradiction between activation temperature and heat resistance by using a synergistic system of polycaprolactone polyol and polycaprolactone-glycolide copolymer polyol as the soft segment. The polycaprolactone polyol has moderate crystallinity and fast crystallization rate, and can achieve rapid thermal activation at 50-70℃ to form sufficient viscosity. The polycaprolactone-glycolide copolymer polyol reduces the overall crystallinity and crystallization rate by the introduction of glycolide units, increases the rigidity and glass transition temperature of the soft segment chain segment (from -60℃ to -30 to -20℃), so that the adhesive layer has higher modulus and better dimensional stability after curing, and the heat resistance can reach more than 110℃, and the heat resistance remains above 100℃ after 72h aging.

[0030] Second, the present application introduces trimethylolpropane-ε-caprolactone polyester triol as a multifunctional crosslinking point, which significantly improves the crosslinking density of the polyurethane network and the thermal stability of the hard segment microzone. The triol forms a branched structure in the polyurethane backbone, increasing the physical entanglement and hydrogen bonding between molecular chains, and improving the cohesive strength and high temperature creep resistance of the adhesive layer. At the same time, the ester group structure of the polycaprolactone triol has good compatibility with the soft segment of the main chain, and does not introduce excessive internal stress.

[0031] Third, the present application uses a silicone-modified crosslinking agent, which imparts excellent moisture resistance and heat resistance to the adhesive through its siloxane structure. The siloxane bond (Si-O-Si) has high bond energy (about 444kJ / mol) and hydrophobicity, and is not prone to hydrolysis reaction in high temperature and high humidity environment. The silane group (Si-OC2H5) of the silicone-modified crosslinking agent will undergo hydrolysis-condensation reaction during curing, forming a three-dimensional siloxane network, and interpenetrating network structure with the polyurethane matrix, significantly improving the moisture resistance and heat resistance of the adhesive layer. After aging for 500h under the condition of 70℃ and 85% relative humidity, the bonding strength retention rate is still above 75%.

[0032] Fourth, the present application realizes fine control of the crystallization behavior of the soft segment by optimizing the molecular weight distribution and ratio of the polyols. The polycaprolactone polyol (molecular weight 1000-2500) provides fast crystallization ability to reduce the activation temperature, the polycaprolactone-glycolide copolymer polyol (molecular weight 1500-3000) provides rigid chain segment to improve heat resistance, and the polytetrahydrofuran ether diol (molecular weight 1000-2000) provides flexible chain segment to improve low temperature flexibility and crack resistance. The synergistic effect of the three polyols makes the adhesive achieve excellent balance between activation temperature, heat resistance, moisture resistance and heat resistance, initial adhesion and final adhesion.

[0033] Fifth, the present application uses the complex system of isophorone diisocyanate and hexamethylene diisocyanate, and the synergistic advantages of both are exerted. The alicyclic structure of isophorone diisocyanate endows the polyurethane with excellent weather resistance and yellowing resistance, and the linear structure of hexamethylene diisocyanate provides good flexibility and low-temperature performance. Both are used in a 2:1 to 4:1 complex, which ensures the heat resistance and weather resistance of the adhesive layer and maintains sufficient flexibility and initial adhesion.

[0034] Sixth, the water-based automotive interior adhesive of the present application is suitable for bonding of various substrates (including polyvinyl chloride, ABS, polypropylene, fabric, leather, etc.), has high initial adhesion strength, fast curing speed, moderate activation temperature (50-70℃), and meets the process requirements of existing production lines. The product is a water-based system, has low VOC content, is environmentally friendly, and meets the green manufacturing requirements of the automotive industry. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be described below in detail with specific examples. Obviously, the described examples are only some of the examples of the present application, not all. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0037] The sources of the raw materials used in the examples of the present application are as follows: Poly (caprolactone) polyol (PCL-2000): number average molecular weight 2000, Japan Dailu Company, brand Placcel L220AL; Poly (caprolactone) polyol (PCL-1500): number average molecular weight 1500, Korsui Company, brand Capa 2201A; Poly (caprolactone-co-glycolide) copolymer polyol (PCLA-2000): molar ratio of ε-caprolactone to L-lactide is 72:28, number average molecular weight 2000, Poshitong Company, brand Perstorp CAPA 6250D; Trimethylolpropane-ε-caprolactone polyester triol (TMP-PCL-1500): number average molecular weight 1500, hydroxyl value about 112 mgKOH / g, Japan Dailu Company, brand Placcel 305; Polytetrahydrofuran ether diol (PTMEG-1000): number average molecular weight 1000, INVISTA Company, brand Terathane 1000; Polytetrahydrofuran ether diol (PTMEG-2000): number average molecular weight 2000, INVISTA Company, brand Terathane 2000; Isophorone diisocyanate (IPDI): Covestro, technical grade; Hexamethylene diisocyanate (HDI): Covestro, technical grade; 1,4-Butanediol (BDO): analytical pure, National Pharmaceutical Group Chemical Reagent Co., Ltd.; 1,6-Hexanediol (HDO): analytical pure, National Pharmaceutical Group Chemical Reagent Co., Ltd.; Neopentyl glycol (NPG): analytical pure, National Pharmaceutical Group Chemical Reagent Co., Ltd.; Dimethylol propanoic acid (DMPA): analytical pure, Aldrich Reagent Company; Dimethylol butanoic acid (DMBA): analytical pure, Aldrich Reagent Company; Triethylamine (TEA): analytical pure, National Pharmaceutical Group Chemical Reagent Co., Ltd.; Acetone: analytical pure, National Pharmaceutical Group Chemical Reagent Co., Ltd.; 3-Aminopropyl triethoxysilane (APTES): technical grade, Wanhua Industrial Group; Isophorone diamine (IPDA): technical grade, Wanhua Industrial Group; Ethylene diamine (EDA): analytical pure, National Pharmaceutical Group Chemical Reagent Co., Ltd.; Silicone defoamer: Degoya, BYK-024; Polyether-modified silicone wetting agent: Sangyin Chemical Industry Co., Ltd., DISPARLON 7001; Alkali-swellable acrylic thickener: Rohm & Haas, Rheovis AS 1130; Deionized water: self-made, conductivity <5 μS / cm. Example 1

[0038] The water-based automotive interior adhesive prepared in this example, the components and amounts (by weight) are as follows: Polycaprolactone polyol (PCL-2000): 40 parts; Polycaprolactone-glycolide copolymer polyol (PCLA-2000): 20 parts; Trimethylolpropane-ε-caprolactone polyester triol (TMP-PCL-1500): 10 parts; Polytetrahydrofuran ether diol (PTMEG-1000): 10 parts; Isophorone diisocyanate (IPDI): 20 parts; Hexamethylene diisocyanate (HDI): 7 parts; 1,4-Butanediol (BDO): 2 parts; Neopentyl glycol (NPG): 1.5 parts; Dimethylol propionic acid (DMPA): 3 parts; Triethylamine (TEA): 2.2 parts; Acetone: 18 parts; Silicone-modified crosslinker: 5 parts; Deionized water: 55 parts; Isophorone diamine (IPDA): 1 part; Silicone defoamer: 0.3 parts; Polyether-modified silicone wetting agent: 0.3 parts; Alkali-swellable acrylic thickener: 0.5 parts.

[0039] The preparation steps are as follows: Preparation of silicone-modified crosslinker: 40 g of polycaprolactone diol (PCL-600, Covestro, trade name Capa 2054) with a number average molecular weight of 600 was placed in a four-necked flask equipped with a thermometer, stirrer, and nitrogen protection device, heated to 90°C, and 28 g of isophorone diisocyanate (IPDI) was added. The reaction was carried out under nitrogen protection for 1.5 h, so that the molar ratio of NCO groups to hydroxyl groups was 3:1. The temperature was lowered to 60°C, and 13 g of 3-aminopropyl triethoxysilane (APTES) was slowly added dropwise, with a dropwise addition time of about 30 min. The reaction was continued at 60°C for 1 h, obtaining a silicone-modified crosslinker with a terminal silane group. The NCO groups were completely reacted, and the product was a light yellow transparent liquid.

[0040] Preparation of waterborne polyurethane emulsion: Step 1: 40 g of PCL-2000, 20 g of PCLA-2000, 10 g of TMP-PCL-1500, and 10 g of PTMEG-1000 were placed in a four-necked flask equipped with a thermometer, stirrer, condenser reflux device, and vacuum system. Dehydration was carried out at 110°C and -0.09 MPa for 20 min, with constant stirring during the process; Step 2: The temperature was lowered to 80°C, and isocyanate was added in two batches (20 g of IPDI was added in the first batch, and 7 g of HDI was added after an interval of 15 min). The reaction was carried out under normal pressure for 1 h, obtaining a NCO-terminated prepolymer; Step 3: 2 g of BDO and 1.5 g of NPG were added, and the temperature was raised to 75°C for reaction for 30 min. Then, 3 g of DMPA was added, and the reaction was continued at 75°C for 2 h. During the process, acetone was added in four batches (4.5 g each batch) to reduce the viscosity. The reaction was carried out until the NCO content was 2.8% (the theoretical value was 2.75%) as determined by the di-n-butylamine-hydrochloric acid method, obtaining a first intermediate; Step 4: The first intermediate was cooled to 40°C, and 2.2 g of triethylamine (TEA) was added for neutralization reaction for 20 min, obtaining a second intermediate; Step 5: 55 g of deionized water was added to the second intermediate at a speed of 60 g / min under the condition of high-speed dispersion machine (1200 rpm), 1 g of isophorone diamine (IPDA) was slowly added during the water adding process, and the dispersion was carried out for 30 min to obtain a milky white aqueous polyurethane dispersion; Step 6: The aqueous polyurethane dispersion was removed of acetone at 60°C and -0.07 MPa to obtain an aqueous polyurethane emulsion with a solid content of 40%; Step 7: 5 g of silicone modified crosslinking agent was slowly added to the aqueous polyurethane emulsion (dropping time 15 min), and was stirred at a speed of 500 rpm for 30 min to make it fully dispersed; Step 8: 0.3 g of silicone defoaming agent and 0.3 g of polyether modified silicone wetting agent were added in sequence, and were stirred at a speed of 500 rpm for 30 min; Step 9: 0.5 g of alkali swelling type acrylic thickening agent was added in 3 batches (each batch interval 10 min), the viscosity was adjusted to 5000 mPa·s (NDJ-8S rotary viscometer, 25°C, No. 3 rotor, 30 rpm), and an aqueous automotive interior adhesive product was obtained. Example 2

[0041] The aqueous automotive interior adhesive prepared in this example has the following components and amounts (by weight): Polycaprolactone polyol (PCL-1500): 35 parts; Polycaprolactone polyol (PCL-2000): 10 parts; Polycaprolactone-glycolide copolymer polyol (PCLA-2000): 25 parts; Trimethylolpropane-ε-caprolactone polyester triol (TMP-PCL-1500): 12 parts; Polytetrahydrofuran ether diol (PTMEG-2000): 8 parts; Isophorone diisocyanate (IPDI): 22 parts; Hexamethylene diisocyanate (HDI): 6 parts; 1,6-hexanediol (HDO): 2.5 parts; Neopentyl glycol (NPG): 1 part; Dihydroxymethyl propionic acid (DMPA): 2.5 parts; Dihydroxymethyl butyric acid (DMBA): 1 part; Triethylamine (TEA): 2.5 parts; Acetone: 20 parts; Silicone modified crosslinking agent: 6 parts; Deionized water: 60 parts; Ethylene diamine (EDA): 0.8 parts; Isophorone diamine (IPDA): 0.5 parts; Organosilicon defoamer: 0.2 parts; Polyether-modified silicone wetting agent: 0.2 parts; Alkali-swellable acrylic thickener: 0.6 parts.

[0042] The preparation steps are similar to those in Example 1, except that: In step 1, 35g PCL-1500, 10g PCL-2000, 25g PCLA-2000, 12g TMP-PCL-1500 and 8g PTMEG-2000 were dehydrated at 110℃ and -0.09MPa for 20min. In step 3, add 2.5g HDO and 1g NPG, then add 2.5g DMPA and 1g DMBA, and react at 70℃ for 2.5h; In step 5, a mixture of 0.8 g ethylenediamine (EDA) and 0.5 g isophorone diamine (IPDA) is added during the dispersion process; In step 7, add 6g of organosilicon-modified crosslinking agent; In step 9, adjust the viscosity to 6500 mPa·s. Example 3

[0043] The water-based automotive interior adhesive prepared in this embodiment has the following components and dosages (by weight): Polycaprolactone polyol (PCL-2000): 45 parts; Polycaprolactone-glycolic acid copolymer polyol (PCLA-2000): 15 parts; Trimethylolpropane-ε-caprolactone polyester triol (TMP-PCL-1500): 8 parts; Polytetrahydrofuran ether diol (PTMEG-1000): 12 parts; Isophorone diisocyanate (IPDI): 25 parts; Hexamethylene diisocyanate (HDI): 8 parts; 1,4-Butanediol (BDO): 3 parts; 1,6-Hexanediol (HDO): 1 part; Neopentyl glycol (NPG): 1.5 parts; Dimethylolpropionic acid (DMPA): 3.5 parts; Triethylamine (TEA): 2.8 parts; Acetone: 22 parts; Organosilicon modified crosslinking agent: 7 parts; Deionized water: 58 parts; Isophorone diamine (IPDA): 1.2 parts; Silicone defoamer: 0.4 parts; Polyether-modified silicone wetting agent: 0.4 parts; Alkali-swellable acrylic thickener: 0.7 parts.

[0044] The preparation steps are similar to Example 1, except that: In Step 1, 45 g of PCL-2000, 15 g of PCLA-2000, 8 g of TMP-PCL-1500, and 12 g of PTMEG-1000 were dehydrated at 110°C and -0.09 MPa for 20 min; In Step 2, the total amount of isocyanate was 33 g (25 g of IPDI + 8 g of HDI); In Step 3, 3 g of BDO, 1 g of HDO, and 1.5 g of NPG were added, followed by the addition of 3.5 g of DMPA; In Step 7, 7 g of silicone-modified crosslinking agent was added; In Step 9, the viscosity was adjusted to 7000 mPa·s.

[0045] Comparative Example 1 This comparative example was prepared according to the technical solution of CN119463778A to prepare a water-based automotive interior adhesive, and the components and amounts (by weight parts) are as follows: Polycarbonate diol (number average molecular weight 2000): 8 parts; Polybutylene adipate diol (number average molecular weight 2000): 3 parts; Polypropylene glycol (number average molecular weight 1000): 2 parts; Isophorone diisocyanate (IPDI): 16 parts; Dihydroxymethylpropionic acid (DMPA): 3 parts; 1,4-Butanediol (BDO): 1 part; Neopentyl glycol (NPG): 0.7 parts; Triethylamine (TEA): 2.3 parts; Acetone: 20 parts; Carbodiimide: 4 parts; Deionized water: 57 parts; Ethylene diamine (EDA): 1 part; Silicone defoamer: 0.3 parts; Polyether-modified silicone wetting agent: 0.3 parts; Alkali-swellable acrylic thickener: 0.4 parts.

[0046] The preparation steps refer to Example 1 of CN119463778A.

[0047] Comparative Example 2 This comparative example does not use polycaprolactone-glycolide copolymer polyol and silicone-modified crosslinking agent compared with Example 1, and the components and amounts (by weight parts) are as follows: Polycaprolactone polyol (PCL-2000): 60 parts; Trimethylolpropane-ε-caprolactone polyester triol (TMP-PCL-1500): 10 parts; Polytetramethylene ether glycol (PTMEG-1000): 10 parts; Isophorone diisocyanate (IPDI): 20 parts; Hexamethylene diisocyanate (HDI): 7 parts; 1,4-Butanediol (BDO): 2 parts; Neopentyl glycol (NPG): 1.5 parts; Dimethylol propionic acid (DMPA): 3 parts; Triethylamine (TEA): 2.2 parts; Acetone: 18 parts; Deionized water: 55 parts; Isophorone diamine (IPDA): 1 part; Silicone defoamer: 0.3 parts; Polyether-modified silicone wetting agent: 0.3 parts; Alkali-swellable acrylic thickener: 0.5 parts.

[0048] The preparation steps are similar to Example 1, but step 7 (addition of silicone-modified crosslinking agent) is not performed.

[0049] Comparative Example 3 This comparative example does not use trimethylolpropane-ε-caprolactone polyester triol and silicone-modified crosslinking agent compared with Example 1, and the components and amounts (by weight parts) are as follows: Polycaprolactone polyol (PCL-2000): 50 parts; Polycaprolactone-glycolide copolymer polyol (PCLA-2000): 20 parts; Polytetramethylene ether glycol (PTMEG-1000): 10 parts; Isophorone diisocyanate (IPDI): 20 parts; Hexamethylene diisocyanate (HDI): 7 parts; 1,4-Butanediol (BDO): 2 parts; Neopentyl glycol (NPG): 1.5 parts; Dimethylol propionic acid (DMPA): 3 parts; Triethylamine (TEA): 2.2 parts; Acetone: 18 parts; Deionized water: 55 parts; Isophorone diamine (IPDA): 1 part; Silicone defoamer: 0.3 parts; Polyether-modified silicone wetting agent: 0.3 parts; Alkali-swellable acrylic thickener: 0.5 parts.

[0050] Preparation steps were similar to Example 1, but step 7 (addition of silicone-modified crosslinker) was not performed.

[0051] Performance test methods: Activation temperature determination: The adhesive was uniformly coated on the surface of a polyvinyl chloride (PVC) film, with a coating amount of 80-100 g / m2, and dried at room temperature for 30 min until the surface was not sticky. The coated PVC film was heated at different temperatures (40°C, 50°C, 60°C, 70°C, 80°C) for 30 s, then laminated with another piece of PVC film, and applied with a pressure of 0.5 MPa for 5 s. After 24 h at room temperature, the 180° peel strength was tested using a universal tensile testing machine (Shenzhen Sanechips Co., Ltd., WDW-20 type) (tensile speed 50 mm / min). The lowest heating temperature at which the peel strength reached 2.0 N / cm or more was the activation temperature.

[0052] Initial heat resistance determination: The bonded PVC / PVC sample (size 150 mm x 25 mm, bonding length 100 mm) was immediately placed in an oven, with the temperature set at 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, and 110°C, respectively. After heating for 30 min, the sample was removed and the pop distance was measured. The highest temperature at which the pop distance was less than 2 cm was the initial heat resistance temperature.

[0053] Final heat resistance determination: The bonded PVC / PVC sample was placed in an oven after being cured at room temperature for 72 h, with the temperature set at 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, and 110°C, respectively. After heating for 30 min, the sample was removed and the pop distance was measured. The highest temperature at which the pop distance was less than 2 cm was the final heat resistance temperature.

[0054] Peel strength determination: The adhesive was coated on the surface of a PVC film, with a coating amount of 80-100 g / m2, and dried in a 60°C oven for 5 min. Then, another piece of PVC film was laminated at 60°C, with a pressure of 0.5 MPa for 5 s. After 24 h at room temperature, the 180° peel strength was tested using a universal tensile testing machine.

[0055] Moisture and heat resistance test: The bonded PVC / PVC sample was cured at room temperature for 72 h, and then put into a constant temperature and humidity test chamber (Shanghai Jinghong Company, BPS-100CA type) with a temperature of 70℃ and a relative humidity of 85%, and the aging time was 168 h, 336 h and 500 h, respectively. After aging, the sample was taken out and cooled to room temperature, and the 180° peeling strength was tested to calculate the bonding strength retention rate.

[0056] Glass transition temperature (T g ) test: The aqueous polyurethane emulsion was coated on a polytetrafluoroethylene plate, dried at room temperature for 48 h, and then dried in a 60℃ vacuum oven for 24 h to obtain a polyurethane film with a thickness of about 0.5 mm. The T g was determined by differential scanning calorimetry (TA Instruments, DSC Q200) with a heating rate of 10℃ / min and a temperature range of-80 to 150℃ under nitrogen atmosphere.

[0057] Crystallinity and melting temperature test: The crystallinity and melting temperature of the polyurethane film were determined by differential scanning calorimetry with a heating rate of 10℃ / min and a temperature range of-80 to 150℃ under nitrogen atmosphere. The crystallinity calculation formula is: Crystallinity (%) = (Δ H m / Δ H m0 ) × 100%, wherein Δ H m is the melting enthalpy of the sample, and Δ H m0 is the theoretical melting enthalpy of completely crystalline polycaprolactone (139.5 J / g).

[0058] Crosslinking density test: The crosslinking density of the polyurethane film was determined by equilibrium swelling method. The dried film with known mass (m m d ) was immersed in dimethylformamide (DMF) and swelled at 25℃ for 72 h to equilibrium, the film was taken out and the surface solvent was absorbed with filter paper, the swelled mass (m m s ) was weighed, and then dried in an 80℃ vacuum oven to constant weight, and the dried mass (m m r ) was weighed. The crosslinking density was calculated according to the Flory-Rehner equation.

[0059] Performance test results: Table 1 Comparison of basic properties of examples and comparative examples Sample Activation temperature (°C) Initial heat resistance (°C) Final heat resistance (°C) Peeling strength (N / cm) Soft segment T g (°C) Crystallinity (%) Crosslinking density (x 10 -4 mol / cm 3 )]]> Example 1 55 95 110 6.8 -28 18.5 3.6 Example 2 60 100 115 7.2 -22 15.2 4.1 Example 3 50 90 105 6.5 -32 21.8 3.2 Comparative Example 1 75 85 95 5.2 -48 32.5 2.1 Comparative Example 2 45 75 85 5.8 -55 28.7 2.5 Comparative Example 3 60 80 90 6.0 -30 16.8 2.7 Table 2 Comparison of moisture and heat resistance of examples and comparative examples (70℃, 85% relative humidity) Sample Peeling strength after 168 h (N / cm) Strength retention rate after 168 h (%) Peeling strength after 336 h (N / cm) Strength retention rate after 336 h (%) Peeling strength after 500 h (N / cm) Strength retention rate after 500 h (%) Example 1 6.1 89.7 5.7 83.8 5.2 76.5 Example 2 6.5 90.3 6.1 84.7 5.8 80.6 Example 3 5.8 89.2 5.4 83.1 4.9 75.4 Comparative Example 1 4.2 80.8 3.5 67.3 2.8 53.8 Comparative Example 2 4.5 77.6 3.8 65.5 3.1 53.4 Comparative Example 3 5.1 85.0 4.5 75.0 3.9 65.0 From Table 1, it can be seen that: The activation temperatures of Examples 1-3 are 50-60℃, which are significantly lower than that of Comparative Example 1 (75℃), meeting the process requirements of the existing production line. The initial heat resistance of Examples 1-3 is 90-100℃, and the final heat resistance is 105-115℃, which are significantly better than those of Comparative Example 1 (initial heat resistance 85℃, final heat resistance 95℃), Comparative Example 2 (initial heat resistance 75℃, final heat resistance 85℃) and Comparative Example 3 (initial heat resistance 80℃, final heat resistance 90℃). This indicates that the present application successfully solves the contradiction between the activation temperature and the heat resistance by using the synergistic system of polycaprolactone polyol and polycaprolactone-glycolide copolymer polyol.

[0060] The peel strength of Examples 1-3 is 6.5-7.2 N / cm, which is higher than that of Comparative Example 1 (5.2 N / cm), Comparative Example 2 (5.8 N / cm) and Comparative Example 3 (6.0 N / cm). This shows that the present application significantly improves the bonding strength of the adhesive by introducing trimethylolpropane-ε-caprolactone polyester triol and silicone-modified crosslinking agent.

[0061] The soft segment T g of Examples 1-3 is -22 to -32℃, which is significantly higher than that of Comparative Example 1 (-48℃) and Comparative Example 2 (-55℃), and close to that of Comparative Example 3 (-30℃). This indicates that the polycaprolactone-glycolide copolymer polyol improves the rigidity and glass transition temperature of the soft segment chain segment by introducing the glycolide unit, so that the adhesive layer has higher modulus and better dimensional stability after curing.

[0062] The crystallinity of Examples 1-3 is 15.2%-21.8%, which is significantly lower than that of Comparative Example 1 (32.5%) and Comparative Example 2 (28.7%), and close to that of Comparative Example 3 (16.8%). This shows that the polycaprolactone-glycolide copolymer polyol reduces the overall crystallinity, which is beneficial to reduce the activation temperature.

[0063] The crosslinking density of Examples 1-3 is 3.2-4.1 x 10 -4 mol / cm 3 , which is significantly higher than that of Comparative Example 1 (2.1 x 10 -4 mol / cm 3 ), Comparative Example 2 (2.5 x 10 -4 mol / cm 3 ) and Comparative Example 3 (2.7 x 10 -4 mol / cm 3 ). This indicates that the trimethylolpropane-ε-caprolactone polyester triol and the silicone-modified crosslinking agent significantly improve the crosslinking density of the polyurethane network, and improve the cohesive strength and high temperature creep resistance of the adhesive layer.

[0064] From Table 2, it can be seen that: The peel strength retention rates of Examples 1-3 were 89.2%-90.3% after aging at 70℃, 85% relative humidity for 168h, which were significantly higher than those of Comparative Example 1 (80.8%), Comparative Example 2 (77.6%) and Comparative Example 3 (85.0%). The peel strength retention rates of Examples 1-3 were 83.1%-84.7% after aging for 336h, which were still significantly higher than those of Comparative Example 1 (67.3%), Comparative Example 2 (65.5%) and Comparative Example 3 (75.0%). The peel strength retention rates of Examples 1-3 were still maintained at 75.4%-80.6% after aging for 500h, while those of Comparative Example 1, Comparative Example 2 and Comparative Example 3 were reduced to 53.8%, 53.4% and 65.0%, respectively.

[0065] These data fully demonstrate that the present application significantly improves the moisture resistance and heat resistance of the adhesive by using the silicone-modified crosslinking agent. The siloxane structure of the silicone-modified crosslinking agent endows the adhesive with excellent moisture resistance and heat resistance, and the adhesive is less likely to undergo hydrolysis reaction in a high-temperature and high-humidity environment. Meanwhile, the ester group structure of the polycaprolactone polyol and the polycaprolactone-glycolide copolymer polyol has better hydrolysis resistance than the polycarbonate diol and the polybutylene adipate diol, further improving the moisture resistance and heat resistance.

[0066] It can be found from Comparative Example 2 and Comparative Example 3 that although Comparative Example 2, which does not use the polycaprolactone-glycolide copolymer polyol, has a lower activation temperature (45℃), it has poor heat resistance and moisture resistance. Although Comparative Example 3, which does not use the trimethylolpropane-ε-caprolactone polyester triol and the silicone-modified crosslinking agent, has an activation temperature close to that of the examples (60℃), it has significantly poorer heat resistance and moisture resistance than the examples. This indicates that the components of the present application work synergistically and are indispensable.

[0067] The technical effects of the present application are mainly based on the following mechanisms: First, the synergistic effect of the polycaprolactone polyol and the polycaprolactone-glycolide copolymer polyol. The polycaprolactone polyol has strong crystallinity and can quickly melt and produce viscosity when heated, which is beneficial to reducing the activation temperature. The polycaprolactone-glycolide copolymer polyol has increased chain rigidity and glass transition temperature due to the introduction of the rigid glycolide unit (the melting point of L-lactide is about 175℃), and reduced crystallinity and crystallization rate. The use of both ensures a moderate activation temperature, a high soft segment T g and a low crystallinity, so that the adhesive layer has a higher modulus and better heat resistance after curing.

[0068] Second, the multifunctional crosslinking effect of trimethylolpropane-ε-caprolactone polyester triol. The triol forms branched structures in the polyurethane backbone, significantly increasing the crosslinking density. The branched points limit the freedom of molecular chain movement, increasing the cohesive strength of the adhesive layer and the resistance to high-temperature creep. At the same time, the ester group structure of the polycaprolactone triol has good compatibility with the soft segment of the main chain, and will not introduce excessive internal stress, maintaining the flexibility of the adhesive layer.

[0069] Third, the moisture and heat resistance enhancement mechanism of silicone-modified crosslinking agent. The silicone-modified crosslinking agent has good compatibility and interfacial adhesion with the polyurethane main chain through the polycaprolactone segment, while the terminal triethoxysilane group (Si-(OC2H5)3) will undergo hydrolysis to form silicon hydroxyl (Si-OH) during the curing process. The silicon hydroxyl further undergoes condensation reaction to form siloxane bond (Si-O-Si). Siloxane bond has high bond energy (about 444 kJ / mol) and high hydrophobicity, and is not prone to hydrolysis in high temperature and high humidity environment. At the same time, the three-dimensional siloxane network forms an interpenetrating network structure with the polyurethane matrix, synergistically improving the mechanical properties and moisture and heat resistance of the adhesive layer.

[0070] The reaction mechanism is as follows: Silane hydrolysis reaction:

[0071] Silicon hydroxyl condensation reaction:

[0072]

[0073] Fourth, the synergistic effect of isocyanate composite system. The alicyclic structure of isophorone diisocyanate (IPDI) endows polyurethane with excellent weather resistance and anti-yellowing property, while the linear structure of hexamethylene diisocyanate (HDI) provides good flexibility and low temperature performance. The two are used in a ratio of 2:1 to 4:1, which ensures the heat resistance and weather resistance of the adhesive layer, and maintains sufficient flexibility and initial adhesion.

[0074] Fifth, fine control of the molecular weight distribution of polyols. Polycaprolactone polyol (molecular weight 1000-2500) provides rapid crystallization ability to reduce the activation temperature, polycaprolactone-glycolide copolymer polyol (molecular weight 1500-3000) provides rigid segments to improve heat resistance, and polytetrahydrofuran ether diol (molecular weight 1000-2000) provides flexible segments to improve low temperature flexibility and crack resistance. The molecular weight gradient distribution of the three polyols makes the polyurethane molecular chain have a reasonable segment length distribution, which ensures the crystallinity of the soft segment (provides activation adhesion), and ensures sufficient amorphous region (provides flexibility and low temperature performance), thereby achieving an excellent balance between activation temperature, heat resistance, moisture and heat resistance, initial adhesion and final adhesion.

[0075] In summary, the present application successfully solves the contradiction between the activation temperature and heat resistance in the prior art by the synergistic system of polycaprolactone polyol and polycaprolactone-glycolide copolymer polyol, the multifunctional crosslinking of trimethylolpropane-epsilon-caprolactone polyester triol, the moisture and heat resistance enhancement of silicone modified crosslinking agent, the synergistic effect of isocyanate composite system and the fine regulation of polyol molecular weight distribution, realizes the excellent balance of activation temperature (50-70 DEG C) and heat resistance (>=110 DEG C), and significantly improves the moisture and heat resistance (after aging for 500h under the condition of 70 DEG C and 85% relative humidity, the bonding strength retention rate is more than 75%). The water-based automotive interior adhesive of the present application is suitable for bonding of various substrates, has high initial bonding strength, fast curing speed, moderate activation temperature, is suitable for the process requirements of existing production lines, the product is a water-based system, has low VOC content, is environmentally friendly, meets the green manufacturing requirements of the automotive industry, and has important application value and promotion prospect.

Claims

1. A water-based automotive interior adhesive that balances activation temperature and heat resistance, characterized in that, Includes the following components by weight: Polycaprolactone polyol: 30-50 parts; Polycaprolactone-glycolic acid copolymer polyol: 10-30 parts; Trimethylolpropane-ε-caprolactone polyester triol: 5-15 parts; Polytetrahydrofuran ether diol: 5-15 parts; Isocyanate: 20-35 parts; Small molecule chain extender: 2-6 parts; Hydrophilic chain extender: 2-5 parts; Neutralizing agent: 1-3 parts; Acetone: 10-25 parts; Organosilicon modified crosslinking agent: 3-8 parts; Deionized water: 40-70 parts; Amine chain extenders: 0.5-2 parts; Defoamer: 0.1-0.5 parts; Wetting agent: 0.1-0.5 parts; Thickener: 0.2-0.8 parts; Wherein, the polycaprolactone polyol is a polycaprolactone diol with a number average molecular weight of 1000-2500; the polycaprolactone-glycolic acid copolymer polyol is a copolymer diol with a molar ratio of ε-caprolactone to L-lactide of 60:40 to 85:15 and a number average molecular weight of 1500-3000; the trimethylolpropane-ε-caprolactone polyester triol has a number average molecular weight of 900-1800 and a hydroxyl value of 90-180 mgKOH / g; and the organosilicon-modified crosslinking agent is a 3-aminopropyltriethoxysilane-terminated polycaprolactone-based prepolymer.

2. The water-based automotive interior adhesive according to claim 1, characterized in that, The number-average molecular weight of the polytetrahydrofuran ether diol is 1000-2000.

3. The water-based automotive interior adhesive according to claim 1, characterized in that, The isocyanate is isophorone diisocyanate, hexamethylene diisocyanate, or a mixture thereof; preferably, the mass ratio of isophorone diisocyanate to hexamethylene diisocyanate is 2:1 to 4:

1.

4. The water-based automotive interior adhesive according to claim 1, characterized in that, The small molecule chain extender is 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, or a mixture thereof; the hydrophilic chain extender is dimethylolpropionic acid, dimethylolbutyric acid, or a mixture thereof; and the amine chain extender is isophorone diamine, ethylenediamine, diethylenetriamine, or a mixture thereof.

5. The water-based automotive interior adhesive according to claim 1, characterized in that, The preparation method of the organosilicon modified crosslinking agent is as follows: polycaprolactone diol with a number average molecular weight of 400-800 is reacted with isophorone diisocyanate at 80-100℃ for 1-2h, the molar ratio of NCO group to hydroxyl group is 2.5:1 to 3.5:1, and then 3-aminopropyltriethoxysilane is added and the end-capping reaction is carried out at 50-70℃ for 0.5-1.5h to obtain the silane-terminated organosilicon modified crosslinking agent.

6. A method for preparing the water-based automotive interior adhesive according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Add polycaprolactone polyol, polycaprolactone-glycolic acid copolymer polyol, trimethylolpropane-ε-caprolactone polyester triol and polytetrahydrofuran ether diol into a reaction vessel and dehydrate for 15-30 min at 100-120℃ and -0.08 to -0.10 MPa. Step 2: Cool to 70-90℃, add isocyanate, and react under normal pressure for 0.5-1.5h to obtain NCO-terminated prepolymer; Step 3: Add small molecule chain extender and hydrophilic chain extender, react at 65-80℃ for 1.5-3h, add acetone in batches during the reaction to reduce viscosity, and react until the NCO content reaches 95%-105% of the theoretical value to obtain the first intermediate; Step 4: Cool the first intermediate to 35-50℃, add a neutralizing agent and carry out a neutralization reaction for 15-30 minutes to obtain the second intermediate; Step 5: Under high-speed dispersion conditions, deionized water is rapidly added to the second intermediate for dispersion at a speed of 1000-1500 rpm. During the dispersion process, amine chain extenders are added, and high-speed dispersion is carried out for 20-40 minutes to obtain an aqueous polyurethane dispersion. Step 6: Remove acetone at 50-70℃ and -0.06 to -0.08 MPa to obtain an aqueous polyurethane emulsion with a solid content of 35% to 45%. Step 7: Add the organosilicon-modified crosslinking agent to the waterborne polyurethane emulsion and stir at 400-600 rpm for 25-40 minutes to ensure thorough dispersion; Step 8: Add the defoamer and wetting agent in sequence, and stir at 400-600 rpm for 25-40 minutes; Step 9: Add thickener in batches and adjust the viscosity to 3000-8000 mPa·s to obtain the finished water-based automotive interior adhesive.

7. The preparation method according to claim 6, characterized in that, In step 1, the dehydration time is 20 minutes and the dehydration temperature is 110℃.

8. The preparation method according to claim 6, characterized in that, In step 2, isocyanate is added in batches, with each batch spaced 10-15 minutes apart, and the reaction temperature is controlled at 75-85℃.

9. The preparation method according to claim 6, characterized in that, In step 3, acetone is added in 3-5 batches, and the mixture is stirred well after each addition before continuing the reaction.

10. The preparation method according to claim 6, characterized in that, In step 5, the rate of adding deionized water is controlled at 50-100 g / min, and high-speed dispersion is maintained during the water addition process; in step 7, the organosilicon modified crosslinking agent is added by slow dripping, and the dripping time is 10-20 min.

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