Environment-friendly polyurethane adhesive and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane adhesives, in particular to an environment-friendly polyurethane adhesive and a preparation method thereof. The polyurethane adhesive disclosed by the invention is prepared from the following raw materials in parts by weight: 45 to 65 parts of polyethylene glycol, 28 to 35 parts of isophorone diisocyanate, 7 to 13 parts of modified chain extender, 3 to 6 parts of propylene glycol, 0.1 to 0.3 part of dibutyltin dilaurate, 0.1 to 0.5 part of antioxidant, 8 to 12 parts of inorganic filler, 1 to 3 parts of silane coupling agent, 1 to 3 parts of defoaming agent and 30 to 60 parts of deionized water. The adhesive has the advantages of being environmentally friendly, short in curing time, good in water resistance, good in heat resistance, high in bonding strength and the like, and can be widely applied to various materials such as metal, plastic and rubber.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane adhesives, and particularly relates to an environmentally friendly polyurethane adhesive and a preparation method thereof. Background Art

[0002] In recent years, with the continuous development of society, people's awareness of environmental protection has been continuously enhanced, and some environmentally friendly materials have begun to receive more extensive attention. Adhesives are widely used in people's daily lives. Among them, waterborne polyurethane adhesives have good applications in construction, metal, plastic, rubber, etc. due to their environmental protection, good flexibility, good wear resistance, and chemical resistance.

[0003] However, traditional polyurethane adhesives contain a large amount of volatile organic compounds in both the production process and the resulting products, which are harmful to the human body when inhaled for a long time and do not conform to the concept of environmental protection. At present, in the field of adhesives, non-toxic, harmless and high-performance waterborne polyurethane (WPU) has gradually replaced traditional solvent-based polyurethane (PU) and become a research hotspot material, and is widely used in packaging industry, construction, furniture manufacturing and decoration and other fields. At present, waterborne polyurethane as the main adhesive has the following defects: long curing time, low bonding strength, poor water resistance and poor heat resistance. Therefore, it is necessary to develop an adhesive that is environmentally friendly, has a short curing time, good water resistance, good heat resistance and high bonding strength to meet the actual application requirements. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides an environmentally friendly polyurethane adhesive and a preparation method thereof.

[0005] The object of the present invention can be achieved by the following technical solutions: An environmentally friendly polyurethane adhesive, comprising the following raw materials in parts by weight: 45 - 65 parts of polyethylene glycol, 28 - 35 parts of isophorone diisocyanate, 7 - 13 parts of modified chain extender, 3 - 6 parts of propylene glycol, 0.1 - 0.3 parts of dibutyltin dilaurate, 0.1 - 0.5 parts of antioxidant, 8 - 12 parts of inorganic filler, 1 - 3 parts of silane coupling agent, 1 - 3 parts of defoaming agent, and 30 - 60 parts of deionized water; Further, the antioxidant is one of antioxidant 168 or antioxidant 1076; Further, the silane coupling agent is one of KH550 or KH560; Further, the defoaming agent is pentaerythritol stearate; The modified chain extender is prepared by the following steps: Step A1: Mix diethylenetriamine, sodium hydroxide and acetone and stir evenly, add p-phenylene diisocyanate, and raise the temperature to 35 - 45 °C for reaction for 3 - 5 h, then filter and dry to obtain an amino-terminated compound; Furthermore, in step A1, the dosage ratio of diethylenetriamine, sodium hydroxide, p-phenylene diisocyanate and acetone is 0.02 - 0.04 mol : 0.05 - 0.1 g : 0.01 - 0.02 mol : 200 mL; In the reaction of active hydrogen in step A1, the amino group has a very high reaction activity. The reaction between isocyanate and amino group can occur at a relatively low temperature. Diethylenetriamine, as a compound containing amino group, reacts with isocyanate to form substituted urea. By introducing the urea group, the material has high elasticity and impact resistance and is not easily brittle. The amino group in the amino-terminated compound containing urea group serves as the reaction site, providing conditions for the subsequent formation of amide bonds; Step A2: Add concentrated hydrochloric acid to deionized water and stir evenly. Slowly dropwise add the mixed solution of γ-chloropropylmethyldiethoxysilane, dimethyldimethoxysilane and ether. After dropping is completed in 30 min, stir and react at room temperature for 1.5 - 2.5 h, then raise the temperature to 40 °C and react for 2 - 3 h. Let it stand, collect the organic layer, extract, wash until neutral, dry, and rotary evaporate to obtain chlorosiloxane; Furthermore, in step A2, the dosage ratio of deionized water, concentrated hydrochloric acid, γ-chloropropylmethyldiethoxysilane, dimethyldimethoxysilane and ether is 100 mL : 0.01 - 0.02 mL : 0.01 - 0.03 mol : 0.05 - 0.1 mol : 100 mL; Step A3: Mix p-cyanobenzoic acid, triethylamine and N,N-dimethylformamide and stir evenly. Raise the temperature to 120 - 130 °C, add tetrabutylammonium bromide and stir for 30 - 60 min. Dropwise add all the chlorosiloxane obtained in step A2, and react at 140 - 150 °C for 8 - 10 h. Filter and rotary evaporate. Sequentially add deionized water and 48 wt% sulfuric acid, and reflux and react at 70 - 90 °C for 1 - 2 h. Wash until neutral, perform secondary rotary evaporation and drying to obtain carboxyl siloxane; Furthermore, in step A3, the dosage ratio of p-cyanobenzoic acid, triethylamine, N,N-dimethylformamide, tetrabutylammonium bromide, deionized water and 48 wt% sulfuric acid is 0.011 - 0.022 mol : 0.5 - 1.5 g : 100 mL : 0.08 - 0.24 g : 100 mL : 10 - 15 mL; In step A3, in the presence of triethylamine as an acid-binding agent, the chlorosiloxane reacts with p-cyanobenzoic acid under the catalysis of tetrabutylammonium bromide, and then the cyano group is hydrolyzed to carboxyl group under acidic conditions to obtain carboxyl siloxane. The product contains a siloxane structure and an aromatic ester group, laying a foundation for the subsequent formation of water resistance and heat resistance; Step A4: Stir the amino compound evenly in N,N-dimethylformamide, add concentrated sulfuric acid and carboxyl-functionalized siloxane, and heat up to 120 °C for reflux reaction for 3 - 5 h. Then heat up to 140 °C for reflux reaction for 2 h. Add deionized water, and cool down to 50 - 60 °C. Dropwise add epichlorohydrin at a titration rate of 10 drops / min, and continuously stir for 20 - 40 min. Then adjust the pH value to 3 - 4, perform vacuum distillation, purification, and drying to obtain the modified chain extender. Further, in Step A4, the molar ratio of the amino compound, the carboxyl group in the carboxyl-functionalized siloxane in Step A3, and epichlorohydrin is 1:2 - 2.02:2.5 - 3. Further, the concentrated sulfuric acid in Step A4 is 0.001 - 0.005 wt% of the total mass of the amino compound and the carboxyl-functionalized siloxane. In Step A4, the amino group in the amino compound reacts with the carboxyl group in the carboxyl-functionalized siloxane to form an amide structure. Then, the secondary amine in the amino compound reacts with epichlorohydrin to produce an alkylatable secondary amino group. These groups will alkylate themselves to form a nitrogen heterocyclic structure containing hydroxyl and quaternary ammonium salts. The nitrogen heterocyclic structure has high polarity and cohesive energy density, which can improve the adhesion strength by enhancing the intermolecular interaction force. The quaternary ammonium salt structure can also act as a catalytically active functional group to promote the curing rate, shorten the curing time, thereby improving the adhesion strength and curing rate of the material and increasing the stability of the finished product.

[0006] The inorganic filler is prepared by the following steps: Step B1: Mix the template agent P123 (number average molecular weight of 6500) and ethanol evenly, add 0.005 - 0.01 mol / L nitric acid and mix well, then add aluminum isopropoxide and disperse it evenly by ultrasonic treatment. Then place it in an oven at 80 - 100 °C for drying for 48 h. Grind it into powder and calcine it at 500 - 700 °C for 4 - 6 h. Cool it to room temperature, press it into tablets, grind it, and sieve it to obtain mesoporous alumina. Further, in Step B1, the dosage ratio of the template agent P123, ethanol, nitric acid, and aluminum isopropoxide is 1 g:50 mL:0.1 mL:1 - 5 g. In the adhesive, mesoporous alumina can utilize its mesoporous structure to adjust the shrinkage rate during the curing process, reduce the difference in thermal expansion coefficients between the adhesive and the adherend, thereby preventing the cracking or damage of the adhesive layer and significantly improving the shear strength at high temperatures. Step B2: Disperse the mesoporous alumina evenly in deionized water by ultrasonic treatment and label it as Solution 1. Stir the pyrrole monomer evenly in a mixed solution of ethanol and deionized water, then pour it into Solution 1, stir it in an ice-water bath for 1 h, and then add an aqueous solution of ammonium persulfate and react for 24 h. Centrifuge, wash, and dry to obtain the inorganic filler. Further, in step B2, the dosage ratio of pyrrole monomer, ethanol, deionized water, solution 1 and ammonium persulfate aqueous solution is 0.05 - 0.15 mol: 70 mL: 70 mL: 100 mL: 100 mL; Further, in solution 1 described in step B2, the dosage ratio of mesoporous alumina and deionized water is 1 - 2 g: 100 mL; Further, in the ammonium persulfate aqueous solution described in step B2, the dosage ratio of ammonium persulfate and deionized water is 0.05 - 0.15 mol: 100 mL; The polypyrrole coated on the surface of mesoporous alumina contains a nitrogen heterocyclic structure, which can interact with the molecules on the material surface to form a firm connection. This interaction not only enhances the adhesion of the adhesive, but also improves the stability and durability of the adhesive. The preparation method of this environmentally friendly polyurethane adhesive includes the following steps: Step S1: Weigh the raw materials by weight. Add polyethylene glycol (number average molecular weight of 3000), isophorone diisocyanate, dibutyltin dilaurate and propylene glycol into the reactor, and react at 60 - 80 °C for 1.5 - 2.5 h to obtain a polyurethane prepolymer; Step S2: Add a modified chain extender to the polyurethane prepolymer, stir and react at 70 - 90 °C for 2 - 3 h, then add an antioxidant, inorganic filler, silane coupling agent, defoaming agent and deionized water and stir for 0.5 - 1.5 h to obtain the environmentally friendly polyurethane adhesive.

[0007] Advantages of the present invention: In the environmentally friendly polyurethane adhesive of the present invention, a modified chain extender is introduced, which improves its heat resistance, water resistance and bonding strength, and shortens its curing time. This is because the modified chain extender introduces a urea group and an organosilicon segment, and the two work together to improve the heat resistance and water resistance of the adhesive; in addition, the modified chain extender also introduces a heterocyclic group and a quaternary ammonium salt structure. The heterocyclic group has high polarity and cohesive energy density, and improves the bonding strength by enhancing the intermolecular interaction force. The quaternary ammonium salt, as a catalytically active functional group, promotes the curing rate, shortens the curing time, and thus improves the bonding strength and curing rate of the material.

[0008] The inorganic filler is prepared by coating polypyrrole on the surface of alumina as the matrix. After introducing the matrix, it can improve the bonding strength of the adhesive and reduce the curing shrinkage rate of the adhesive. Specific embodiments

[0009] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0010] Example 1: The modified chain extender is prepared through the following steps: Step A1: Mix 0.02 mol of diethylenetriamine, 0.05 g of sodium hydroxide, and 200 mL of acetone evenly by stirring, add 0.01 mol of p-phenylene diisocyanate, and raise the temperature to 35 °C for reaction for 3 h. Then perform suction filtration and drying to obtain the amino-terminated compound. Step A2: Add 0.01 mL of concentrated hydrochloric acid to 100 mL of deionized water and stir evenly. Slowly dropwise add a mixture of 0.01 mol of γ-chloropropylmethyldiethoxysilane, 0.05 mol of dimethyldimethoxysilane, and 100 mL of diethyl ether. After the dropping is completed in 30 min, stir and react at room temperature for 1.5 h, then raise the temperature to 40 °C for reaction for 2 h. Let it stand, collect the organic layer, perform extraction, wash until neutral, dry, and rotary evaporate to obtain the chlorosiloxane. Step A3: Mix 0.011 mol of p-cyanobenzoic acid, 0.5 g of triethylamine, and 100 mL of N,N-dimethylformamide evenly by stirring, raise the temperature to 120 °C, add 0.08 g of tetrabutylammonium bromide and stir for 30 min. Dropwise add all of the chlorosiloxane obtained in Step A2, and react at 140 °C for 8 h. Filter and rotary evaporate, successively add 100 mL of deionized water and 10 mL of 48 wt% sulfuric acid, and reflux and react at 70 °C for 1 h. Wash until neutral, perform secondary rotary evaporation and drying to obtain the carboxyl-functionalized siloxane. Step A4: Stir the amino-terminated compound evenly in N,N-dimethylformamide, add sulfuric acid and the carboxyl-functionalized siloxane, and raise the temperature to 120 °C for reflux reaction for 3 h, then raise the temperature to 140 °C for reflux reaction for 2 h. Add deionized water, and cool down to 50 °C. Dropwise add epichlorohydrin at a dropping rate of 10 drops / min, continuously stir for 20 min, then adjust the pH value to 3, perform vacuum distillation, purification, and drying to obtain the modified chain extender. The molar ratio of the amino-terminated compound, the carboxyl group in the carboxyl-functionalized siloxane obtained in Step A3, and epichlorohydrin is 1:2:2.5, and the sulfuric acid is 0.001 wt% of the total mass of the amino-terminated compound and the carboxyl-functionalized siloxane.

[0011] The inorganic filler is prepared through the following steps: Step B1: Mix 1 g of template agent P123 (number-average molecular weight of 6,500) and 50 mL of ethanol uniformly, add 0.1 mL of 0.005 mol / L nitric acid and mix well, then add 1 g of aluminum isopropoxide and disperse it evenly by ultrasonic treatment. Then place it in an oven at 80 °C for drying for 48 h. After grinding into powder, calcine it at 500 °C for 4 h. Cool it to room temperature, press it into tablets, grind it, and sieve it to obtain mesoporous alumina; Step B2: Disperse 1 g of mesoporous alumina evenly in 100 mL of deionized water by ultrasonic treatment, denoted as solution 1; Stir 0.05 mol of pyrrole monomer evenly in a mixed solution of 70 mL of ethanol and 70 mL of deionized water, then pour it into 100 mL of solution 1, stir it in an ice-water bath for 1 h, then add 100 mL of ammonium persulfate aqueous solution and react for 24 h. Centrifuge, wash, and dry to obtain the inorganic filler. The dosage ratio of ammonium persulfate to deionized water in the ammonium persulfate aqueous solution is 0.05 mol:100 mL.

[0012] Example 2: The modified chain extender is prepared through the following steps: Step A1: Mix 0.03 mol of diethylenetriamine, 0.075 g of sodium hydroxide, and 200 mL of acetone evenly by stirring, add 0.015 mol of p-phenylene diisocyanate, and raise the temperature to 40 °C for reaction for 4 h. Filter by suction and dry to obtain the amino-terminated compound; Step A2: Add 0.015 mL of concentrated hydrochloric acid to 100 mL of deionized water and stir evenly. Slowly dropwise add a mixed solution of 0.02 mol of γ-chloropropylmethyldiethoxysilane, 0.075 mol of dimethyldimethoxysilane, and 100 mL of ether. After the dropping is completed in 30 min, stir and react at room temperature for 2 h, then raise the temperature to 40 °C for reaction for 2.5 h. Let it stand, collect the organic layer, extract, wash until neutral, dry, and rotary evaporate to obtain the chlorosiloxane; Step A3: Mix 0.016 mol of p-cyanobenzoic acid, 1 g of triethylamine, and 100 mL of N,N-dimethylformamide evenly by stirring, raise the temperature to 125 °C, add 0.16 g of tetrabutylammonium bromide and stir for 45 min. Dropwise add all of the chlorosiloxane obtained in Step A2, and react at 145 °C for 9 h. Filter and rotary evaporate. Sequentially add 100 mL of deionized water and 12 mL of 48 wt% sulfuric acid, and reflux and react at 80 °C for 1.5 h. Wash until neutral, rotary evaporate twice, and dry to obtain the carboxyl-functionalized siloxane; Step A4: Stir the amino compound evenly in N,N-dimethylformamide, add concentrated sulfuric acid and carboxyl silicone, heat up to 120 °C and reflux for 4 h, then heat up to 140 °C and reflux for 2 h. Add deionized water, cool down to 55 °C, and dropwise add epichlorohydrin at a dropping rate of 10 drops / min, continuously stir for 30 min, then adjust the pH value to 3.5, carry out vacuum distillation, purification and drying to obtain the modified chain extender. The molar ratio of the amino compound, the carboxyl group in the carboxyl silicone in Step A3 and epichlorohydrin is 1:2.01:2.7, and the concentrated sulfuric acid is 0.003 wt% of the total mass of the amino compound and carboxyl silicone.

[0013] The inorganic filler is prepared by the following steps: Step B1: Mix 1 g of template agent P123 (number average molecular weight of 6500) and 50 mL of ethanol evenly, add 0.1 mL of 0.0075 mol / L nitric acid and mix well, then add 3 g of aluminum isopropoxide and disperse evenly by ultrasonic wave. Then place it at 90 °C and dry for 48 h, grind it into powder, calcine it at 600 °C for 5 h, cool it to room temperature, press it into tablets, grind it and sieve it to obtain mesoporous alumina; Step B2: Ultrasonically disperse 1.5 g of mesoporous alumina evenly in 100 mL of deionized water and label it as Solution 1; Stir 0.1 mol of pyrrole monomer evenly in a mixture of 70 mL of ethanol and 70 mL of deionized water, then pour it into 100 mL of Solution 1, stir it in an ice-water bath for 1 h, then add 100 mL of ammonium persulfate aqueous solution and react for 24 h, centrifuge, wash and dry to obtain the inorganic filler. The dosage ratio of ammonium persulfate and deionized water in the ammonium persulfate aqueous solution is 0.1 mol:100 mL.

[0014] Example 3: The modified chain extender is prepared by the following steps: Step A1: Mix 0.04 mol of diethylenetriamine, 0.1 g of sodium hydroxide and 200 mL of acetone evenly, add 0.02 mol of p-phenylene diisocyanate, heat up to 45 °C and react for 5 h, carry out suction filtration and drying to obtain the amino compound; Step A2: Add 0.02 mL of concentrated hydrochloric acid to 100 mL of deionized water and stir evenly. Slowly dropwise add a mixture of 0.03 mol of γ-chloropropylmethyldiethoxysilane, 0.1 mol of dimethyldimethoxysilane and 100 mL of ether. After the dropping is completed in 30 min, stir and react at room temperature for 2.5 h, heat up to 40 °C and react for 3 h, let it stand, collect the organic layer, extract, wash until neutral, dry and rotary evaporate to obtain the chlorosilicone; Step A3, 0.022 mol of p-cyanobenzoic acid, 1.5 g of triethylamine and 100 mL of N, N-dimethylformamide were mixed and stirred uniformly, the temperature was raised to 130°C, 0.24 g of tetra-n-butylammonium bromide was added and stirred for 60 min, all the chlorosiloxanes in step A2 were added dropwise, and the mixture was reacted at 150°C for 10 h, filtered and rotary evaporated, 100 mL of deionized water and 15 mL of 48 wt% concentrated sulfuric acid were added in sequence, and the mixture was refluxed at 90°C for 2 h, washed until neutral, rotary evaporated twice, and dried to obtain carboxylsiloxane; Step A4, stir the terminal amino compound in N, N-dimethylformamide, add concentrated sulfuric acid and carboxyl siloxane, and heat to 120 ° C and reflux for 5 hours, then heat to 140 ° C and reflux for 2 hours, add deionized water, and cool to 60 ° C, add epichlorohydrin at a titration rate of 10 drops / min, continue stirring for 40 minutes, adjust the pH value to 4, distill under reduced pressure, purify and dry to obtain a modified chain extender, the molar ratio of carboxyl and epichlorohydrin in the terminal amino compound and the carboxyl siloxane in step A3 is 1:2.02:3, and the concentrated sulfuric acid is 0.005wt% of the total mass of the terminal amino compound and the carboxyl siloxane.

[0015] The inorganic filler is prepared by the following steps: Step B1, 1g of template P123 (number average molecular weight is 6500) and 50mL of ethanol are mixed evenly, 0.1mL of 0.01mol / L of nitric acid is added and mixed evenly, and then 5g of aluminum isopropoxide is added and ultrasonically dispersed evenly, and then dried at 100°C for 48h, ground into powder, and calcined at 700°C for 6h, cooled to room temperature, pressed into tablets, ground, and sieved to obtain mesoporous alumina; Step B2, 2g of mesoporous alumina is uniformly dispersed in 100mL of deionized water by ultrasonication, which is recorded as solution 1; 0.15mol of pyrrole monomer is uniformly stirred in a mixture of 70mL of ethanol and 70mL of deionized water, and then 100mL of solution 1 is poured into it, and the mixture is stirred for 1h in an ice water bath, and then 100mL of ammonium persulfate aqueous solution is added to react for 24h, centrifuged, washed, and dried to obtain an inorganic filler, and the amount ratio of ammonium persulfate to deionized water in the ammonium persulfate aqueous solution is 0.15mol:100mL.

[0016] Example 4: A method for preparing an environmentally friendly polyurethane adhesive comprises the following steps: Step S1, weighing raw materials by weight, adding 45 parts of polyethylene glycol, 28 parts of isophorone diisocyanate, 0.1 parts of dibutyltin dilaurate and 3 parts of propylene glycol into a reactor, reacting at 60° C. for 1.5 hours to obtain a polyurethane prepolymer; Step S2: Add 7 parts of the modified chain extender prepared in Example 1 to the polyurethane prepolymer, stir and react at 70 °C for 2 h, then add 0.1 part of antioxidant 168, 8 parts of the inorganic filler prepared in Example 1, 1 part of silane coupling agent KH550, 1 part of pentaerythritol stearate, and 30 parts of deionized water, and stir for 0.5 h to obtain the environmentally friendly polyurethane adhesive.

[0017] Example 5: A preparation method of an environmentally friendly polyurethane adhesive comprises the following steps: Step S1: Weigh the raw materials by weight parts. Add 55 parts of polyethylene glycol, 32 parts of isophorone diisocyanate, 0.2 part of dibutyltin dilaurate, and 5 parts of propylene glycol to a reactor, and react at 70 °C for 2 h to obtain a polyurethane prepolymer. Step S2: Add 10 parts of the modified chain extender prepared in Example 2 to the polyurethane prepolymer, stir and react at 80 °C for 2.5 h, then add 0.3 part of antioxidant 1076, 10 parts of the inorganic filler prepared in Example 2, 2 parts of silane coupling agent KH560, 2 parts of pentaerythritol stearate, and 45 parts of deionized water, and stir for 1 h to obtain the environmentally friendly polyurethane adhesive.

[0018] Example 6: A preparation method of an environmentally friendly polyurethane adhesive comprises the following steps: Step S1: Weigh the raw materials by weight parts. Add 65 parts of polyethylene glycol, 35 parts of isophorone diisocyanate, 0.3 part of dibutyltin dilaurate, and 6 parts of propylene glycol to a reactor, and react at 80 °C for 2.5 h to obtain a polyurethane prepolymer. Step S2: Add 13 parts of the modified chain extender prepared in Example 3 to the polyurethane prepolymer, stir and react at 90 °C for 3 h, then add 0.5 part of antioxidant 1076, 12 parts of the inorganic filler prepared in Example 3, 3 parts of silane coupling agent KH560, 3 parts of pentaerythritol stearate, and 60 parts of deionized water, and stir for 1.5 h to obtain the environmentally friendly polyurethane adhesive.

[0019] Comparative Example 1: This comparative example is an environmentally friendly polyurethane adhesive. The difference from Example 6 is that 1,4-butanediol is used instead of the modified chain extender prepared in Example 3, and the rest are the same.

[0020] Comparative Example 2: This comparative example is an environmentally friendly polyurethane adhesive. The difference from Example 6 is that alumina is used instead of the inorganic filler prepared in Example 3, and the rest are the same.

[0021] Comparative Example 3: This comparative example is an environmentally friendly polyurethane adhesive. The difference from Example 6 is that 1,4-butanediol is used instead of the modified chain extender prepared in Example 3, and alumina is used instead of the inorganic filler prepared in Example 3, and the rest are the same.

[0022] The environmentally friendly polyurethane adhesives prepared in Examples 4 - 6 and Comparative Examples 1 - 3 were coated on PC boards with a coater, cured into films with a film thickness of 0.2 mm, and then their properties were tested; Shear strength test: The shear strength of the film after 7 days was tested according to GB / T 7124-2008 "Determination of Tensile Shear Strength of Adhesives", and the test speed was 5 mm / min; Heat resistance test: The specimens coated with the film were placed in an environment of 70 °C and 50% RH for 7 days, and whether the film bubbled was observed; Water resistance test: The specimens coated with the film were placed in water at room temperature, and the time when the film bubbled was observed; The test results are shown in Table 1: Table 1: Performance test results

[0023] As can be seen from Table 1, the environmentally friendly polyurethane adhesive prepared by the present invention has excellent heat resistance, water resistance and relatively high shear strength, indicating that the adhesive still has excellent bonding performance in high-temperature and high-humidity environments, and also has a short curing time.

[0024] The above content is only an example and explanation of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. An environmentally friendly polyurethane adhesive, characterized in that: The invention comprises the following raw materials in parts by weight: 45-65 parts of polyethylene glycol, 28-35 parts of isophorone diisocyanate, 7-13 parts of modified chain extender, 3-6 parts of propylene glycol, 0.1-0.3 parts of dibutyltin dilaurate, 0.1-0.5 parts of antioxidant, 8-12 parts of inorganic filler, 1-3 parts of silane coupling agent, 1-3 parts of defoamer, and 30-60 parts of deionized water; The modified chain extender is prepared by reacting an amino terminal compound with a carboxyl siloxane and then reacting with epichlorohydrin, the carboxyl siloxane is prepared by reacting p-cyanobenzoic acid with a chlorine-containing siloxane and then hydrolyzing it, the chlorine-containing siloxane is prepared by hydrolyzing and condensing γ-chloropropylmethyldiethoxysilane and dimethyldimethoxysilane, and the amino terminal compound is prepared by reacting diethylenetriamine with p-phenylene diisocyanate; The inorganic filler is made of polypyrrole-coated mesoporous alumina.

2. The environmentally friendly polyurethane adhesive according to claim 1, characterized in that: The modified chain extender is prepared by the following steps: Step A1, diethylenetriamine, sodium hydroxide and acetone are mixed and stirred evenly, p-phenylene diisocyanate is added, and the temperature is raised to 35-45° C. to react for 3-5 hours, and then filtered and dried to obtain a terminal amino compound; Step A2, add concentrated hydrochloric acid to deionized water and stir evenly, slowly dropwise add a mixture of γ-chloropropylmethyldiethoxysilane, dimethyldimethoxysilane and ether, after 30 minutes of dropwise addition, stir and react at room temperature for 1.5-2.5 hours, heat to 40°C and react for 2-3 hours, let stand, collect the organic layer, extract, wash to neutrality, dry, and rotary evaporate to obtain chlorine-containing siloxane; Step A3, p-cyanobenzoic acid, triethylamine and N,N-dimethylformamide are mixed and stirred uniformly, the temperature is raised to 120-130°C, tetra-n-butylammonium bromide is added and stirred for 30-60 minutes, all the chlorine-containing siloxanes in step A2 are added dropwise, and the mixture is reacted at 140-150°C for 8-10 hours, filtered, and rotary evaporated, deionized water and 48wt% concentrated sulfuric acid are added in sequence, and the mixture is refluxed at 70-90°C for 1-2 hours, washed until neutral, rotary evaporated twice, and dried to obtain carboxyl siloxane; Step A4, the terminal amino compound is stirred evenly in N, N-dimethylformamide, concentrated sulfuric acid and carboxyl siloxane are added, and the temperature is raised to 120°C for reflux reaction for 3-5h, and then the temperature is raised to 140°C for reflux reaction for 2h, deionized water is added, and the temperature is lowered to 50-60°C, epichlorohydrin is added dropwise at a titration rate of 10 drops / min, and stirring is continued for 20-40min, and the pH value is adjusted to 3-4, and vacuum distillation is performed, purified, and dried to obtain a modified chain extender.

3. The environmentally friendly polyurethane adhesive according to claim 2, characterized in that: In step A1, the usage ratio of diethylenetriamine, sodium hydroxide, p-phenylene diisocyanate and acetone is 0.02-0.04 mol: 0.05-0.1 g: 0.01-0.02 mol: 200 mL.

4. The environmentally friendly polyurethane adhesive according to claim 2, characterized in that: In step A2, the usage ratio of deionized water, concentrated hydrochloric acid, γ-chloropropylmethyldiethoxysilane, dimethyldimethoxysilane and diethyl ether is 100 mL: 0.01-0.02 mL: 0.01-0.03 mol: 0.05-0.1 mol: 100 mL.

5. The environmentally friendly polyurethane adhesive according to claim 2, characterized in that: In step A3, the dosage ratio of p-cyanobenzoic acid, triethylamine, N,N-dimethylformamide, tetra-n-butylammonium bromide, deionized water and 48wt% concentrated sulfuric acid is 0.011-0.022mol:0.5-1.5g:100mL:0.08-0.24g:100mL:10-15mL.

6. The environmentally friendly polyurethane adhesive according to claim 2, characterized in that: In step A4, the molar ratio of the terminal amino compound, the carboxyl group in the carboxyl siloxane of step A3 and epichlorohydrin is 1:2-2.02:2.5-3, and the concentrated sulfuric acid is 0.001-0.005wt% of the total mass of the terminal amino compound and the carboxyl siloxane.

7. The environmentally friendly polyurethane adhesive according to claim 1, characterized in that: The inorganic filler is prepared by the following steps: Step B1, mix the template P123 and ethanol evenly, add 0.005-0.01 mol / L nitric acid and mix evenly, then add aluminum isopropoxide and disperse evenly by ultrasonication, then dry at 80-100°C for 48h, grind into powder, calcine at 500-700°C for 4-6h, cool to room temperature, press into tablets, grind, and sieve to obtain mesoporous alumina; Step B2, ultrasonically disperse the mesoporous alumina in deionized water, recorded as solution 1; stir the pyrrole monomer in a mixture of ethanol and deionized water, then pour into solution 1, stir for 1 hour in an ice water bath, then add ammonium persulfate aqueous solution to react for 24 hours, centrifuge, wash and dry to obtain an inorganic filler.

8. The environmentally friendly polyurethane adhesive according to claim 7, characterized in that: In step B1, the usage ratio of template P123, ethanol, nitric acid and aluminum isopropoxide is 1 g:50 mL:0.1 mL:1-5 g.

9. The environmentally friendly polyurethane adhesive according to claim 7, characterized in that: In step B2, the dosage ratio of pyrrole monomer, ethanol, deionized water, solution 1 and ammonium persulfate aqueous solution is 0.05-0.15 mol:70 mL:70 mL:100 mL:100 mL, the dosage ratio of mesoporous alumina and deionized water in the solution 1 is 1-2 g:100 mL, and the dosage ratio of ammonium persulfate and deionized water in the ammonium persulfate aqueous solution is 0.05-0.15 mol:100 mL.

10. A method for preparing the environmentally friendly polyurethane adhesive according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: Step S1, weighing raw materials by weight, adding polyethylene glycol, isophorone diisocyanate, dibutyltin dilaurate and propylene glycol into a reactor, reacting at 60-80° C. for 1.5-2.5 hours to obtain a polyurethane prepolymer; Step S2, adding a modified chain extender to the polyurethane prepolymer, stirring and reacting at 70-90° C. for 2-3 hours, then adding an antioxidant, an inorganic filler, a silane coupling agent, a defoamer and deionized water and stirring for 0.5-1.5 hours to obtain an environmentally friendly polyurethane adhesive.

Images