High-bonding-strength fast-curing solvent-free polyurethane adhesive and preparation method thereof

Abstract

The invention relates to a high-bonding-strength fast-curing solvent-free polyurethane adhesive and a preparation method thereof. The high-bonding-strength fast-curing solvent-free polyurethane adhesive comprises a component A and a component B, the component A is prepared from the following components in percentage by mass: 5 to 15 percent of first polyester polyol, 20 to 30 percent of first polyether polyol and the balance of polyisocyanate; the component B is prepared from the following components in percentage by mass: 5 to 10 percent of second polyether polyol, 10 to 15 percent of cellulose-based polyether polyol, 0.3 to 1.2 percent of silane coupling agent and the balance of second polyester polyol. The invention develops a solvent-free polyurethane adhesive which has the advantages of high bonding strength, rapid curing, broad-spectrum applicability, environmental protection and no toxicity.

Description

Technical Field

[0001] This application relates to the field of adhesive technology, and in particular to a solvent-free polyurethane adhesive with high bonding strength and rapid curing, and its preparation method. Background Technology

[0002] With increasingly stringent environmental regulations and the popularization of green manufacturing concepts, solvent-free two-component polyurethane adhesives are gradually replacing traditional solvent-based products and becoming the mainstream choice in the flexible packaging composite industry due to their advantages such as not containing volatile organic solvents and being safe and environmentally friendly.

[0003] However, existing solvent-free adhesives still face many technical bottlenecks, making it difficult to meet the rapidly evolving packaging demands.

[0004] Firstly, regarding curing performance, traditional solvent-free adhesives typically require curing in a medium-to-high temperature environment above 40-50°C for 24-72 hours, which not only consumes a lot of energy but also prolongs the production cycle. For small and medium-sized enterprises lacking curing chamber equipment or in high-temperature regions (such as Southeast Asia), these harsh conditions severely restrict production efficiency.

[0005] Secondly, insufficient bonding strength has been a long-standing pain point in the industry. In severe cases, the adhesive is prone to a decrease in interlayer peel strength, leading to quality accidents such as broken packaging bags and leakage.

[0006] Furthermore, poor versatility limits the application scenarios of adhesives. Flexible packaging materials are diverse (such as PET, OPP, PA, aluminum foil, metallized film, etc.), and different structures require matching special adhesive formulations, leading to frequent model changes by manufacturers, which increases operational complexity and costs.

[0007] To address these issues, the industry has attempted to optimize performance by modifying polyester polyols and adding silane coupling agents, but these approaches often come at the expense of other factors. For instance, increasing the curing speed sacrifices adhesive strength, while enhancing heat resistance leads to a decrease in elasticity. Summary of the Invention

[0008] This application provides a solvent-free polyurethane adhesive with high bonding strength and rapid curing, and a preparation method thereof, which has the advantages of high bonding strength and rapid curing.

[0009] In a first aspect, embodiments of this application provide a solvent-free polyurethane adhesive with high bonding strength and rapid curing, comprising component A and component B; By mass fraction, component A comprises 5-15% of a first polyester polyol, 20-30% of a first polyether polyol, and the balance being a polyisocyanate. By mass fraction, component B comprises 5-10% of a second polyether polyol, 10-15% of a cellulose-based polyether polyol, 0.3-1.2% of a silane coupling agent, and the balance being a second polyester polyol.

[0010] In conjunction with the first aspect, in one embodiment, the number-average molecular weight of the first polyether polyol of component A is 400 to 1000; And / or, the first polyether polyol of component A has a functionality of 2; And / or, the polyisocyanate of component A includes one or more of the following: a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and isophorone diisocyanate. And / or, the molar ratio of functional group -NCO in component A to functional group -OH in component B is 1.5 to 2.0:1.

[0011] In conjunction with the first aspect, in one embodiment, the first polyester polyol of component A is prepared by reacting a bio-based dimer acid or a hydrogenated dimer acid, a small molecule polyacid, and a small molecule polyol.

[0012] In conjunction with the first aspect, in one embodiment, the small molecule polyacid includes one or more of isophthalic acid, phthalic acid, terephthalic acid, adipic acid, sebacic acid, and azelaic acid; And / or, the small molecule polyols include one or more of diethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, trimethylolpropane, and glycerol. And / or, weigh the raw materials for the first polyester polyol, which, by mass fraction, include 7-18% bio-based dimer acid or hydrogenated dimer acid, 42-45% small molecule polyacid, and the balance small molecule polyol. In an inert gas environment, add 7-18% bio-based dimer acid or hydrogenated dimer acid, 42-45% small molecule polyacid, and the balance small molecule polyol into a reactor equipped with a distillation column. Dehydrate at 140-160°C, and control the top temperature of the distillation column at 98-103°C for 1-2 hours. Then react at 160-210°C for 3-6 hours, add 10-40 ppm of catalyst, raise the temperature to 220-240°C, and de-alcoholize under vacuum for 2-5 hours to obtain the first polyester polyol. The catalyst includes one or a combination of two of isopropyl titanate, tetrabutyl titanate, and organotin compounds. And / or, the hydroxyl value of the first polyester polyol is 170-200 mgKOH / g, and the acid value is ≤ 0.5 mgKOH / g.

[0013] In conjunction with the first aspect, in one embodiment, the number-average molecular weight of the second polyether polyol of component B is 400 to 1000; And / or, the second polyether polyol of component B has a functionality of 3; And / or, the silane coupling agent of component B is at least one of KH-540, KH-550, KH-560, and KH-570.

[0014] In conjunction with the first aspect, in one embodiment, the second polyester polyol of component B is prepared by first alcoholystolysing castor oil and a small molecule polyol to obtain alcoholystolysed castor oil, and then reacting it with a small molecule dicarboxylic acid.

[0015] In conjunction with the first aspect, in one embodiment, the small molecule polyacid includes one or more of isophthalic acid, phthalic acid, terephthalic acid, adipic acid, sebacic acid, and azelaic acid; And / or, the small molecule polyols include one or more of diethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, trimethylolpropane, and glycerol. And / or, in an inert gas environment, 90-95% castor oil and 5-10% small molecule polyol by mass are added to a reactor, followed by 10-20 ppm catalyst. The mixture is stirred and heated to 215-220°C and held for 2-3 hours. The temperature is then gradually lowered to 140-150°C to obtain the castor oil alcoholysis product. In an inert gas environment, 5-8% of the castor oil alcoholysis product by mass, 50-52% small molecule polyacid, and the balance of small molecule polyol are added to a reactor equipped with a distillation column. Dehydration is carried out at 140-160°C, with the top temperature of the distillation column controlled at 98-103°C for 1-2 hours. The reaction is then carried out at 160-210°C for 3-6 hours, followed by the addition of 10-40 ppm catalyst. The temperature is raised to 220-240°C, and the mixture is subjected to vacuum dehydration for 2-5 hours. h, to obtain the second polyester polyol, wherein the catalyst comprises one or a combination of two of isopropyl titanate, tetrabutyl titanate or organotin; And / or, the second polyester polyol has a hydroxyl value of 180–220 mgKOH / g and an acid value of ≤ 0.5 mgKOH / g.

[0016] In conjunction with the first aspect, in one embodiment, the cellulose-based polyether polyol of component B is prepared by an etherification reaction of sodium cellulose and propylene oxide.

[0017] In conjunction with the first aspect, in one embodiment, sodium cellulose and propylene oxide are mixed in an organic solvent at a mass ratio of 5–8:1, and a ring-opening addition reaction is carried out at 70–130°C for 2–8 h, followed by a holding time of 1–2 h to obtain liquid sodium cellulose polyether; the liquid sodium cellulose polyether is then mixed with a 30–40% phosphoric acid solution and subjected to a neutralization reaction to obtain the cellulose-based polyether polyol, wherein the organic solvent is selected from diethoxymethane, dipropoxymethane, dibutoxymethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, toluene, xylene, or 1,4-dioxane; And / or, the hydroxyl value of the cellulose-based polyether polyol is 275–300 mgKOH / g.

[0018] Secondly, embodiments of this application provide a method for preparing a solvent-free polyurethane adhesive with high bonding strength and rapid curing as described above, comprising: After the first polyester polyol and the first polyether polyol are mixed evenly, polyisocyanate is added and reacted at 70-90℃ for 3-4 h to obtain component A. The second polyether polyol, the second polyester polyol, and the cellulose-based polyether polyol were stirred evenly at 40–50°C and kept at this temperature for 2–3 h. Then, a silane coupling agent was added and mixed evenly to obtain component B. Mixing components A and B yields a solvent-free polyurethane adhesive with high bonding strength and rapid curing.

[0019] The beneficial effects of the technical solution provided in this application include: This application provides a solvent-free polyurethane adhesive with high bonding strength and rapid curing, and its preparation method. The abundant secondary hydroxyl groups in the cellulose-based polyether polyol of component B react with the -NCO groups of the polyisocyanate in component A to form a three-dimensional network structure, effectively improving the crosslinking degree, mechanical properties, and adhesion of the polyurethane. Furthermore, thanks to the lower reactivity of the secondary hydroxyl groups, the reaction process is more stable in the early stages, thus significantly extending the adhesive's shelf life and workability. The addition of a first polyether polyol and / or a second polyether polyol with lower molecular weight allows for chain extension by the small molecules and NCO groups, pre-constructing a partial network structure. This advances and accelerates the entire curing and crosslinking process, shortening the curing time required to reach the final usable strength. Therefore, this application combines the advantages of high bonding strength and rapid curing. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart illustrating the preparation method of the high-bonding-strength, fast-curing solvent-free polyurethane adhesive provided in this application embodiment. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] This application provides a solvent-free polyurethane adhesive with high bonding strength and rapid curing, comprising component A and component B.

[0024] By mass fraction, component A comprises 5-15% of a first polyester polyol, 20-30% of a first polyether polyol, and the balance being a polyisocyanate.

[0025] By mass fraction, component B comprises 5-10% of a second polyether polyol, 10-15% of a cellulose-based polyether polyol, 0.3-1.2% of a silane coupling agent, and the balance being a second polyester polyol.

[0026] The first polyester polyol in component A is a bio-based polyester polyol, synthesized through bio-based dimer acid or hydrogenated dimer acid and small molecule polyacids and small molecule polyols. Because the small molecule alcohol raw materials in the bio-based polyester polyol (such as 2-methyl-1,3-propanediol and trimethylolpropane) contain side group structures, and the dimer acid contains flexible bio-based long chains, the combined effect of these two factors improves the compatibility between adhesive components and makes the microstructure more compact. At the same time, the side group structure also improves the wettability of the adhesive to the film material, thereby significantly improving the bonding strength.

[0027] The abundant secondary hydroxyl groups in the cellulose-based polyether polyol of component B can react with the -NCO groups of the polyisocyanate in component A to form a three-dimensional network structure, which effectively improves the crosslinking degree, mechanical properties and adhesion of polyurethane. Moreover, thanks to the low reactivity of the secondary hydroxyl groups, the reaction process is more stable in the early stage, thus significantly extending the shelf life and working time of the adhesive.

[0028] By adding a first polyether polyol and / or a second polyether polyol with a lower molecular weight, the small molecules are extended with NCO, and a partial network structure is pre-constructed. The entire curing and crosslinking process is advanced and accelerated, which can shorten the curing time required to reach the final service strength.

[0029] Preferably, the number-average molecular weight of the first polyether polyol in component A is 400-1000. The first polyether polyol can be purchased from Shandong Lanxing Dongda Chemical Co., Ltd., specifically DL-400 or DL-1000D.

[0030] Preferably, the first polyether polyol of component A has a functionality of 2.

[0031] Preferably, the polyisocyanate of component A includes one or more of the following: a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and isophorone diisocyanate.

[0032] Preferably, the molar ratio of the functional group -NCO in component A to the functional group -OH in component B is 1.5 to 2.0:1.

[0033] Preferably, the first polyester polyol of component A is prepared by reacting bio-based dimer acid or hydrogenated dimer acid, small molecule polyacid, and small molecule polyol. Specifically, the raw materials for the first polyester polyol are weighed out. By mass fraction, the raw materials include 7-18% bio-based dimer acid or hydrogenated dimer acid, 42-45% small molecule polyacid, and the balance small molecule polyol. In an inert gas environment, 7-18% bio-based dimer acid or hydrogenated dimer acid, 42-45% small molecule polyacid, and the balance small molecule polyol are added to a reactor equipped with a distillation column. Dehydration is carried out at 140-160°C, and the temperature at the top of the distillation column is controlled at 98-103°C for 1-2 hours. Then, the reaction is carried out at 160-210°C for 3-6 hours. 10-40 ppm of catalyst is added, the temperature is raised to 220-240°C, and the alcohol is removed under vacuum for 2-5 hours to obtain the first polyester polyol. The hydroxyl value of the first polyester polyol is 170-200 mgKOH / g, and the acid value is ≤ 0.5 mgKOH / g.

[0034] Preferably, the small molecule polyacid includes one or more of isophthalic acid, phthalic acid, terephthalic acid, adipic acid, sebacic acid, and azelaic acid.

[0035] Preferably, the small molecule polyol includes one or more of diethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, trimethylolpropane, and glycerol.

[0036] Preferably, the catalyst comprises one or a combination of two of isopropyl titanate, tetrabutyl titanate, and organotin compounds.

[0037] Preferably, the number-average molecular weight of the second polyether polyol in component B is 400-1000, and the second polyether polyol can be purchased from Guangzhou Yinghong Chemical Co., Ltd. as N-307 or N-310.

[0038] Preferably, the second polyether polyol of component B has a functionality of 3.

[0039] Preferably, the silane coupling agent of component B is at least one of KH-540, KH-550, KH-560, and KH-570.

[0040] Preferably, the second polyester polyol of component B is prepared by first alcoholystolysis of castor oil and small molecule polyol to obtain alcoholystolytic castor oil, and then reacting it with a small molecule dicarboxylic acid. Specifically, in an inert gas environment, 90-95% castor oil and 5-10% small molecule polyol by mass are added to a reactor, followed by 10-20 ppm of catalyst. The mixture is stirred and heated to 215-220°C and held for 2-3 hours. The temperature is then gradually lowered to 140-150°C to obtain the castor oil alcoholysis product. In an inert gas environment, 5-8% of the castor oil alcoholysis product by mass, 50-52% of the small molecule polyacid, and the remainder of the small molecule polyol are added to a reactor equipped with a distillation column. Dehydration is carried out at 140-160°C, with the top temperature of the distillation column controlled at 98-103°C for 1-2 hours. The reaction is then carried out at 160-210°C for 3-6 hours. 10-40 ppm of catalyst is then added, and the temperature is raised to 220-240°C. The mixture is then vacuum-treated for 2-5 hours to obtain the second polyester polyol, which has a hydroxyl value of 180-220. mgKOH / g, acid value ≤ 0.5 mgKOH / g.

[0041] Preferably, the small molecule polyacid includes one or more of isophthalic acid, phthalic acid, terephthalic acid, adipic acid, sebacic acid, and azelaic acid.

[0042] Preferably, the small molecule polyol includes one or more of diethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, trimethylolpropane, and glycerol.

[0043] Preferably, the catalyst comprises one or a combination of two of isopropyl titanate, tetrabutyl titanate, or organotin compounds; Preferably, the cellulose-based polyether polyol of component B is prepared by an etherification reaction of sodium cellulose and propylene oxide. Specifically, sodium cellulose and propylene oxide are mixed in an organic solvent at a mass ratio of 5–8:1, and a ring-opening addition reaction is carried out at 70–130°C for 2–8 h, followed by a holding time of 1–2 h to obtain liquid sodium cellulose polyether; the liquid sodium cellulose polyether is then mixed with a 30–40% phosphoric acid solution and neutralized to obtain the cellulose-based polyether polyol. The organic solvent is selected from diethoxymethane, dipropoxymethane, dibutoxymethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, toluene, xylene, or 1,4-dioxane.

[0044] Preferably, the hydroxyl value of the cellulose-based polyether polyol is 275–300 mgKOH / g.

[0045] See Figure 1 As shown in the embodiments of this application, a method for preparing a solvent-free polyurethane adhesive with high bonding strength and rapid curing is also provided, comprising: 101: Mix the first polyester polyol and the first polyether polyol evenly, then add the polyisocyanate and react at 70-90°C for 3-4 h to obtain component A.

[0046] 102: Stir the second polyether polyol, the second polyester polyol, and the cellulose-based polyether polyol at 40-50°C until homogeneous, keep warm for 2-3 hours, add the silane coupling agent, mix evenly, and obtain component B.

[0047] 103: Mix component A and component B with a molar ratio of -NCO functional group in component A to -OH functional group in component B of 1.5 to 2.0:1 to obtain a solvent-free polyurethane adhesive with high bonding strength and fast curing.

[0048] The present application is further described below with reference to specific embodiments.

[0049] Example 1 This embodiment provides a high-bonding-strength, fast-curing two-component solvent-free polyurethane adhesive. The preparation method of this adhesive is as follows (the amount of each component is by mass): (1) First, 31% adipic acid, 8% isophthalic acid, 3% terephthalic acid, 18% bio-based dimer acid, 11% diethylene glycol, 12% 1,2-propanediol, 14% 2-methyl-1,3-propanediol and 3% trimethylolpropane were added to a reactor with a distillation column. Dehydration was carried out at 140°C, and the temperature at the top of the distillation column was controlled at 103°C for 2 hours. Then, the reaction was carried out at 160°C for 6 hours. 40ppm of tetrabutyl titanate catalyst was added, the temperature was raised to 220°C, and the alcohol was removed under vacuum for 2 hours to obtain the first polyester polyol with a hydroxyl value of 193mgKOH / g.

[0050] (2) In an inert gas environment, 10% diethylene glycol, 90% castor oil, and 20 ppm tetrabutyl titanate catalyst were added to a reactor and stirred and heated to 220°C for 3 hours. The temperature was gradually lowered to 140°C to obtain castor oil alcoholysis product. Then, 5% castor oil alcoholysis product, 50% adipic acid, 15% diethylene glycol, and 30% 1,2-propanediol were added to a reactor with a distillation column. Dehydration was carried out at 140°C, and the temperature at the top of the distillation column was controlled at 103°C for 2 hours. Then, the reaction was carried out at 180°C for 5 hours. 10 ppm catalyst was added, the temperature was raised to 220°C, and the alcohol was removed under vacuum for 5 hours to obtain the second polyester polyol with a hydroxyl value of 215 mg KOH / g and an acid value ≤0.5 mg KOH / g.

[0051] (3) Sodium cellulose and toluene were added to a high-pressure reactor. After nitrogen purging three times, the stirrer was turned on and the temperature was slowly raised to 70°C. Then, propylene oxide (PO) was continuously introduced over 4 hours. The mass ratio of sodium cellulose to propylene oxide was 5:1. The reaction temperature was controlled at 110°C. After the PO was added, the reaction pressure was lower than 0.4 MPa. The reaction was kept at this temperature for 1 hour. At this time, the reaction pressure no longer decreased. After the temperature dropped to room temperature, the pressure was released and the material was discharged. The reaction solution was neutralized with 30% phosphoric acid. Activated clay and magnesium silicate were added for adsorption. Toluene was recovered under vacuum to obtain cellulose-based polyether polyol. The appearance was a low-viscosity reddish-brown liquid with a hydroxyl value of 280.3 mg KOH / g.

[0052] (4) Preparation method of component A: Mix 15% of the first polyester polyol and 20% of the first polyether polyol with a functionality of 2 and a molecular weight of 400 evenly, then add 65% of the mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, and react at 80°C for 4 hours to obtain the NCO-terminated polyurethane prepolymer, which is component A isocyanate-based component.

[0053] (5) Preparation method of component B: 84.7% of the second polyester polyol, 5% of the second polyether polyol with a functionality of 3 and a molecular weight of 1000, and 10% of the cellulose-based polyether polyol are stirred evenly at 50°C and kept at the temperature for 3 hours. Then, 0.3% of KH-550 silane coupling agent is added to obtain the hydroxyl component of component B.

[0054] Example 2 This embodiment provides a high-bonding-strength, fast-curing two-component solvent-free polyurethane adhesive. The preparation method of this adhesive is as follows (the amount of each component is by mass): (1) First, 30% azelaic acid, 15% isophthalic acid, 17% hydrogenated dimer acid, 14% diethylene glycol, 20% 2-methyl-1,3-propanediol and 4% glycerol were added to a reactor with a distillation column. Dehydration was carried out at 160°C, and the temperature at the top of the distillation column was controlled at 98°C for 4 hours. Then, the reaction was carried out at 200°C for 6 hours. 20 ppm of tetrabutyl titanate catalyst was added, the temperature was raised to 220°C, and the alcohol was removed under vacuum for 2 hours to obtain the first polyester polyol with a hydroxyl value of 174.5 mg KOH / g.

[0055] (2) In an inert gas environment, 5% glycerol, 95% castor oil, and 20 ppm tetrabutyl titanate catalyst were added to a reactor and stirred and heated to 220°C for 2 hours. The temperature was gradually lowered to 150°C to obtain castor oil alcoholysis product. Then, 8% castor oil alcoholysis product, 52% adipic acid, 15% diethylene glycol, 15% 1,2-propanediol, and 10% glycerol were added to a reactor with a distillation column. Dehydration was carried out at 150°C, and the temperature at the top of the distillation column was controlled at 100°C for 3 hours. Then, the reaction was carried out at 180°C for 5 hours. 20 ppm catalyst was added, the temperature was raised to 220°C, and the alcohol was removed under vacuum for 4 hours to obtain the second polyester polyol with a hydroxyl value of 206.3 mg KOH / g and an acid value ≤0.5 mg KOH / g.

[0056] (3) Sodium cellulose and toluene were added to a high-pressure reactor. After nitrogen purging three times, the stirrer was turned on and the temperature was slowly raised to 80°C. Then, propylene oxide (PO) was continuously introduced over 4 hours. The mass ratio of sodium cellulose to propylene oxide was 8:1. The reaction temperature was controlled at 130°C. After the PO was added, the reaction pressure was lower than 0.5 MPa. The reaction was kept at this temperature for 2 hours. At this time, the reaction pressure no longer decreased. After the temperature dropped to room temperature, the pressure was released and the material was discharged. The reaction solution was neutralized with 30% phosphoric acid. Activated clay and magnesium silicate were added for adsorption. Toluene was recovered under vacuum to obtain cellulose-based polyether polyol. The appearance was a low-viscosity reddish-brown liquid with a hydroxyl value of 290.3 mg KOH / g.

[0057] (4) Preparation method of component A: Mix 5% of the first polyester polyol and 30% of the first polyether polyol with a functionality of 2 and a molecular weight of 1000 evenly, then add 65% of diphenylmethane diisocyanate, and react at 70°C for 5 hours to obtain the NCO-terminated polyurethane prepolymer, namely the isocyanate-based component of component A. (5) Preparation method of component B: 78.8% of the second polyester polyol, 10% of the second polyether polyol with a functionality of 3 and a molecular weight of 1000, and 10% of the cellulose-based polyether polyol are stirred evenly at 40°C and kept at the temperature for 2 hours. Then, 1.2% of KH-560 silane coupling agent is added to obtain the hydroxyl component of component B.

[0058] Example 3 This embodiment provides a high-bonding-strength, fast-curing two-component solvent-free polyurethane adhesive. The preparation method of this adhesive is as follows (the amount of each component is by mass): (1) First, 10% adipic acid, 22% azelaic acid, 9% isophthalic acid, 4% terephthalic acid, 10% bio-based dimer acid, 7% hydrogenated dimer acid, 9% diethylene glycol, 20% 2-methyl-1,3-propanediol, 3% 1,4-butanediol, and 4% glycerol were added to a reactor with a distillation column. Dehydration was carried out at 160°C, and the temperature at the top of the distillation column was controlled at 98°C for 4 hours. Then, the reaction was carried out at 200°C for 6 hours. 20 ppm of tetrabutyl titanate catalyst was added, the temperature was raised to 220°C, and the alcohol was removed under vacuum for 2 hours to obtain the first polyester polyol with a hydroxyl value of 192.5 mg KOH / g.

[0059] (2) In an inert gas environment, 10% of 1,4-butanediol, 90% of castor oil, and 20 ppm of tetrabutyl titanate catalyst were added to a reactor and stirred and heated to 200°C for 2 hours. The temperature was gradually lowered to 150°C to obtain castor oil alcoholysis product. Then, 8% of castor oil alcoholysis product, 50% adipic acid, 12% diethylene glycol, and 30% 1,2-propanediol were added to a reactor with a distillation column. Dehydration was carried out at 150°C, and the temperature at the top of the distillation column was controlled at 100°C for 3 hours. Then, the reaction was carried out at 180°C for 5 hours. 20 ppm of catalyst was added, the temperature was raised to 220°C, and the alcohol was removed under vacuum for 4 hours to obtain the second polyester polyol with a hydroxyl value of 202 mg KOH / g and an acid value ≤0.5 mg KOH / g.

[0060] (3) Sodium cellulose and toluene were added to a high-pressure reactor. After nitrogen purging three times, the stirrer was turned on and the temperature was slowly raised to 80°C. Then, propylene oxide (PO) was continuously introduced over 5 hours. The mass ratio of sodium cellulose to propylene oxide was 7:1. The reaction temperature was controlled at 110°C. After the PO was added, the reaction pressure was lower than 0.4 MPa. The reaction was kept at this temperature for 2 hours. At this time, the reaction pressure no longer decreased. After the temperature dropped to room temperature, the pressure was released and the material was discharged. The reaction solution was neutralized with 40% phosphoric acid. Activated clay and magnesium silicate were added for adsorption. Toluene was recovered under vacuum to obtain cellulose-based polyether polyol. The appearance was a low-viscosity reddish-brown liquid with a hydroxyl value of 283.3 mg KOH / g.

[0061] (4) Preparation method of component A: Mix 15% of the first polyester polyol, 25% of the first polyether polyol with a functionality of 2 and a molecular weight of 1000 evenly, and then add 60% of diphenylmethane diisocyanate. React at 80°C for 4 hours to obtain the NCO-terminated polyurethane prepolymer, which is component A isocyanate-based component. (5) Preparation method of component B: 75% of the second polyester polyol, 9% of the second polyether polyol with a functionality of 3 and a molecular weight of 700, and 15% of the cellulose-based polyether polyol are stirred evenly at 40°C and kept at the temperature for 2 hours. Then, 1% of KH-570 silane coupling agent is added to obtain the hydroxyl component of component B.

[0062] Comparative Example 1 The only difference from Example 1 is that component A does not contain the first polyether polyol, but is made up with polyisocyanate.

[0063] Comparative Example 2 The only difference from Example 1 is that component B does not contain the second polyether polyol, but is supplemented with the second polyester polyol.

[0064] Comparative Example 3 The only difference from Example 1 is that: component A does not contain the first polyether polyol, but is made up with polyisocyanate; and component B does not contain the second polyether polyol, but is made up with the second polyester polyol.

[0065] Viscosity was measured according to the plate rotation viscometer method in GB / T 2794-2022.

[0066] Peel strength shall be measured in accordance with GB / T 2791-1995.

[0067] The two-component polyurethane adhesives of Examples 1 to 3 and Comparative Examples 1 to 3 were mixed according to the R values ​​of components A and B in Table 1 to form a coating adhesive. This coating was then used to coat the inner layers of OPP / VMPET / CPP and PET / Al / CPP (only the inner layer was evaluated under the same conditions; the outer layer was a dry coating). The coatings were cured at 40°C for 16 hours. The appearance of the outer layer was observed, the peel strength of the inner layer was tested, and the stickiness was determined by touch. The test results are shown in Table 1 below.

[0068] Table 1

[0069] As can be seen from Table 1, compared with Comparative Examples 1 to 3, the outer layer of the OPP / VMPET / CPP composites of solvent-free two-component polyurethane adhesives in Examples 1 to 3 has a better appearance, with no bubbles or white spots, and the curing speed and inner layer peel strength are better than those of the comparative examples.

[0070] In summary, the solvent-free two-component polyurethane adhesive of this application is suitable for flexible packaging materials with different structures, has strong versatility for inner and outer layers, has a good appearance when applied to flexible packaging materials, has a fast curing speed, and has high and stable peel strength after curing. It can effectively overcome the industry pain point that fast curing speed and high strength cannot be achieved at the same time.

[0071] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A high adhesive strength quick curing solventless polyurethane adhesive, characterized by, (1) a polyol component comprising a polyol having a hydroxyl group and a polyisocyanate compound, (2) a chain extender, (3) a curing catalyst, and (4) a blowing agent. It comprises A component and B component; The A component comprises 5-15% first polyester polyol, 20-30% first polyether polyol and the rest polyisocyanate by mass fraction; The B component comprises 5-10% second polyether polyol, 10-15% cellulose-based polyether polyol, 0.3-1.2% silane coupling agent and the rest second polyester polyol by mass fraction. 2.The high-bond-strength fast-curing solvent-free polyurethane adhesive of claim 1, wherein: The first polyether polyol of the A component has a number average molecular weight of 400-1000; And / or, the first polyether polyol of the A component has a functionality of 2; And / or, the polyisocyanate of the A component comprises one or more of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate mixture, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, isophorone diisocyanate; And / or, the molar ratio of functional groups -NCO in the A component and functional groups -OH in the B component is 1.5-2.0:

1. 3.The high-bond-strength fast-curing solvent-free polyurethane adhesive of claim 1, wherein: The first polyester polyol of the A component is prepared by reacting bio-based dimer acid or hydrogenated dimer acid, small molecule polyacid and small molecule polyol. 4.The high-bond-strength fast-curing solvent-free polyurethane adhesive of claim 3, wherein: The small molecule polyacid comprises one or more of isophthalic acid, phthalic acid, terephthalic acid, adipic acid, sebacic acid and azelaic acid; And / or, the small molecule polyol comprises one or more of diethylene glycol, 1, 2-propanediol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol and 2-methyl-1, 3-propanediol; And / or, the raw materials for the first polyester polyol are weighed, which comprise 7-18% bio-based dimer acid or hydrogenated dimer acid, 42-45% small molecule polyacid and the rest small molecule polyol by mass fraction, and the 7-18% bio-based dimer acid or hydrogenated dimer acid, 42-45% small molecule polyacid and the rest small molecule polyol are put into a reaction kettle with a distillation column in an inert gas environment, dehydration is carried out at 140-160℃, the distillation column top temperature is controlled at 98-103℃ for 1-2 h, then reaction is carried out at 160-210℃ for 3-6 h, 10-40 ppm of catalyst is added, the temperature is raised to 220-240℃, and vacuum dealcoholization is carried out for 2-5 h, to obtain the first polyester polyol, and the catalyst comprises one or a combination of isopropyl titanate, tetrabutyl titanate and organotin; And / or, the first polyester polyol has a hydroxyl value of 170-200 mgKOH / g and an acid value of ≤0.5 mgKOH / g. 5.The high-bond-strength fast-curing solvent-free polyurethane adhesive of claim 1, wherein: The second polyether polyol of the B component has a number average molecular weight of 400-1000; And / or, the second polyether polyol of component B has a functionality of 3; And / or, the silane coupling agent of component B is at least one of KH-540, KH-550, KH-560, and KH-570.

6. The solvent-free polyurethane adhesive with high bonding strength and rapid curing as described in claim 1, characterized in that: The second polyester polyol of component B is prepared by first alcoholystolysing castor oil and small molecule polyol to obtain alcoholystolysed castor oil, and then reacting it with a small molecule dicarboxylic acid.

7. The solvent-free polyurethane adhesive with high bonding strength and rapid curing as described in claim 6, characterized in that: The small molecule polyacids include one or more of isophthalic acid, phthalic acid, terephthalic acid, adipic acid, sebacic acid, and azelaic acid; And / or, the small molecule polyols include one or more of diethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, trimethylolpropane, and glycerol. And / or, in an inert gas environment, 90-95% castor oil and 5-10% small molecule polyol by mass are added to a reactor, followed by 10-20 ppm of catalyst. The mixture is stirred and heated to 215-220°C and held for 2-3 hours. The temperature is then gradually lowered to 140-150°C to obtain the castor oil alcoholysis product. In an inert gas environment, 5-8% of the castor oil alcoholysis product by mass, 50-52% of small molecule polyacid, and the balance of small molecule polyol are added to a reactor equipped with a distillation column. Dehydration is carried out at 140-160°C, with the top temperature of the distillation column controlled at 98-103°C for 1-2 hours. The reaction is then carried out at 160-210°C for 3-6 hours, followed by the addition of 10-40 ppm of catalyst. The temperature is raised to 220-240°C, and the mixture is subjected to vacuum dehydration for 2-5 hours. h, to obtain the second polyester polyol, wherein the catalyst comprises one or a combination of two of isopropyl titanate, tetrabutyl titanate or organotin; And / or, the second polyester polyol has a hydroxyl value of 180–220 mgKOH / g and an acid value of ≤ 0.5 mgKOH / g.

8. The solvent-free polyurethane adhesive with high bonding strength and rapid curing as described in claim 1, characterized in that: The cellulose-based polyether polyol of component B is prepared by etherification reaction of sodium cellulose and propylene oxide.

9. The solvent-free polyurethane adhesive with high bonding strength and rapid curing as described in claim 8, characterized in that: Sodium cellulose and propylene oxide are mixed in an organic solvent at a mass ratio of 5–8:1, and a ring-opening addition reaction is carried out at 70–130°C for 2–8 h, followed by a holding time of 1–2 h to obtain liquid sodium cellulose polyether. The liquid sodium cellulose polyether is then mixed with a 30–40% phosphoric acid solution and neutralized to obtain the cellulose-based polyether polyol. The organic solvent is selected from diethoxymethane, dipropoxymethane, dibutoxymethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, toluene, xylene, or 1,4-dioxane. And / or, the hydroxyl value of the cellulose-based polyether polyol is 275–300 mgKOH / g.

10. A process for preparing a high adhesive strength fast curing solventless polyurethane adhesive as claimed in any one of claims 1 to 9, characterized by, It includes: After the first polyester polyol and the first polyether polyol are mixed evenly, polyisocyanate is added and reacted at 70-90℃ for 3-4 h to obtain component A. The second polyether polyol, the second polyester polyol, and the cellulose-based polyether polyol were stirred evenly at 40–50°C and kept at this temperature for 2–3 h. Then, a silane coupling agent was added and mixed evenly to obtain component B. Mixing components A and B yields a solvent-free polyurethane adhesive with high bonding strength and rapid curing.

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