Degradable polyurethane hot melt pressure sensitive adhesive and preparation method and application thereof

Abstract

The application belongs to the field of hot melt pressure sensitive adhesive, and discloses a preparation method of degradable polyurethane hot melt pressure sensitive adhesive. The degradable polyurethane hot melt pressure sensitive adhesive is prepared by mixing degradable soybean oil-based polyol, polycaprolactone / propylene lactone block copolymer, diisocyanate, tackifying resin, stannous octoate, organic solvent, plasticizer, lubricant and antioxidant according to certain proportions. The polyurethane hot melt pressure sensitive adhesive prepared by the method has the advantage of degradability, and in the preparation process, it is surprisingly found that the combination of soybean oil-based polyol, polycaprolactone / propylene lactone block copolymer and diisocyanate has a synergistic effect on the tackiness and peeling strength of the polyurethane hot melt pressure sensitive adhesive. In addition, the application also discloses the degradable polyurethane hot melt pressure sensitive adhesive and its application.

Description

Technical Field

[0001] This invention relates to the field of hot melt pressure-sensitive adhesives, and more particularly to a biodegradable polyurethane hot melt pressure-sensitive adhesive, its preparation method, and its application. Background Technology

[0002] Hot melt pressure-sensitive adhesives are adhesives based on viscoelastic polymers, possessing both hot melt and pressure-sensitive properties. They are applied in a molten state, and after cooling and curing, they can quickly bond under relatively low pressure and are easily peeled off without contaminating the surfaces of the adhered objects. They are widely used in packaging, labeling, hygiene products, medical supplies, textiles, and specialty adhesives. Currently, the polymer matrix for preparing hot melt pressure-sensitive adhesives is mainly petroleum-based synthetic polymers, commonly including acrylate copolymers, styrene block copolymers, ethylene-vinyl acetate copolymers, polyisoprene, polybutadiene synthetic rubbers, and polyurethane elastomers. These materials are all petroleum-based and difficult to biodegrade in the environment, seriously impacting environmental protection. Therefore, it is particularly necessary to find biomass raw materials that can replace petroleum resources and have excellent performance to develop environmentally friendly, biodegradable, and recyclable hot melt adhesive materials.

[0003] Meanwhile, ordinary hot melt pressure-sensitive adhesives often have low peel strength and cannot provide good adhesion in certain special situations. In contrast, polyurethane hot melt adhesives have excellent initial tack, initial peel strength, and final peel strength. Polyurethane is a reaction product of diols or polyols with diisocyanates or polyisocyanates. Because of its good elasticity, strength, and biodegradability, thermoplastic polyurethane hot melt adhesives are a type of polyurethane that is plasticized by heating and soluble in solvents. Its molecular structure is a linear straight chain, and the main chain contains urethane groups (-NHCOO-) or isocyanate groups (-NCO-), which have strong polarity and chemical reactivity. It has excellent chemical adhesion to materials containing active hydrogen, porous materials such as foam plastics, wood, leather, fabrics, paper, and ceramics, as well as smooth materials such as metals, glass, rubber, and plastics, resulting in a strong bond.

[0004] Chinese Patent 201610492663.9 discloses a method for preparing acrylate-modified waterborne polyurethane from soybean oil-based polyols. This method uses soybean oil-based polyols and polyisocyanates to prepare soybean oil-based polyurethanes, and then uses acrylate monomers to copolymerize and graft them onto the polyurethane backbone through double bonds to form a network structure, thereby synthesizing a soybean oil-based acrylate-modified waterborne polyurethane product.

[0005] This scheme uses two soybean oil-based polyols as raw materials to synthesize waterborne polyurethane. These two polyols are made from widely available green resource epoxidized soybean oil, which can yield hydroxyl values ​​of 50-130 mgKOH / g. The resulting waterborne polyurethane has advantages such as being non-flammable, having low odor, not polluting the environment, and being easy to process. It not only meets the requirements of green chemical sustainable development, but also the waterborne polyurethane is easy to degrade.

[0006] Liu Hairong published a paper titled "Research on the Synthesis of Polycaprolactone-Laminate Type Biodegradable Polyurethane Materials." The paper describes the preparation of polycaprolactone-lactide copolymers via ring-opening polymerization and the selection of aliphatic adipisocyanate to synthesize biodegradable polyurethane materials. The effects of reaction temperature, feeding method, and different chain extenders on the target product were investigated during the synthesis process. The final synthesized polyurethane material was also characterized.

[0007] This method prepares biodegradable polyurethane materials using biodegradable polycaprolactone lactide copolymer and hexamethylene diisocyanate, which are green and environmentally friendly.

[0008] The problem this solution needs to solve is: how to provide a hot melt pressure-sensitive adhesive that is both degradable and has high peel strength and tack. Summary of the Invention

[0009] The purpose of this invention is to provide a biodegradable polyurethane hot melt pressure-sensitive adhesive, which is prepared by biodegradable soybean oil-based polyol, polycaprolactone / lactide block copolymer, and diisocyanate. Furthermore, by adding modified soybean oil-based polyol as the soft segment of the polymer to the biodegradable copolymer matrix, the performance of the biodegradable polyurethane pressure-sensitive adhesive is improved, thereby increasing the initial tack, initial peel strength, and final peel strength of the hot melt pressure-sensitive adhesive.

[0010] Unless otherwise specified in this invention: nM represents nanomoles per liter, μM represents micromoles per liter, mM represents millimoles per liter, and M represents moles per liter;

[0011] A method for preparing a biodegradable polyurethane hot melt pressure-sensitive adhesive includes the following steps:

[0012] Step 1: Mix soybean oil-based polyol, polycaprolactone / lactide block copolymer, and tackifying resin, and remove water under reduced pressure to obtain the primary product;

[0013] Step 2: Cool the primary product obtained in Step 1 to below 70°C, add diisocyanate, stannous octoate, and organic solvent, and heat to react to obtain a polyurethane prepolymer with terminal -NCO groups.

[0014] Step 3: After cooling the polyurethane prepolymer obtained in Step 2 to 60-70℃, add plasticizer, lubricant, and antioxidant, stir, remove solvent under reduced pressure, and discharge to obtain crude product;

[0015] Step 4: Transfer the crude product obtained in Step 3 to a vacuum drying oven and vacuum dry it at 80℃-100℃ for 20-28 hours to obtain a biodegradable polyurethane hot melt pressure-sensitive adhesive.

[0016] The polycaprolactone / lactide block copolymer comprises 10-25 parts by weight, soybean oil-based polyol comprises 15-22 parts by weight, diisocyanate comprises 38-46 parts by weight, tackifying resin comprises 15-30 parts by weight, stannous octoate comprises 1.5-2.5 parts by weight, plasticizer comprises 10-20 parts by weight, lubricant comprises 5-15 parts by weight, antioxidant comprises 1-2 parts by weight, and organic solvent comprises 30-45 parts by weight.

[0017] Preferably, the polycaprolactone / lactide block copolymer comprises 15-20 parts by weight, soybean oil-based polyol comprises 17-20 parts by weight, diisocyanate comprises 40-46 parts by weight, tackifying resin comprises 15-30 parts by weight, stannous octoate comprises 1.5-2.5 parts by weight, plasticizer comprises 10-20 parts by weight, lubricant comprises 5-15 parts by weight, antioxidant comprises 1-2 parts by weight, and organic solvent comprises 30-45 parts by weight.

[0018] More preferably, the mass fraction of the polycaprolactone / lactide block copolymer includes, but is not limited to, 15, 16, 17, 18, 19, and 20 parts.

[0019] The soybean oil-based polyols are available in parts by weight, including but not limited to 17, 18, 19, and 20.

[0020] The mass fractions of the diisocyanate include, but are not limited to, 40, 41, 42, 43, 44, 45, and 46 parts.

[0021] The tackifying resin is available in parts by weight, including but not limited to 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30 parts.

[0022] The mass fractions of stannous octoate include, but are not limited to, 1.5, 2.0, and 2.5 parts.

[0023] The plasticizer is available in parts by weight, including but not limited to 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 parts.

[0024] The mass fractions of the lubricant include, but are not limited to, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 parts;

[0025] The antioxidant is present in parts by weight, including but not limited to 1, 1.5, or 2 parts.

[0026] The organic solvents include, but are not limited to, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40 parts.

[0027] Preferably, the diisocyanate is selected from at least one of toluene diisocyanate, 1,6-hexane diisocyanate, 4,4′-diphenylmethane, diisocyanate, and isoflurone diisocyanate.

[0028] Preferably, the tackifying resin is selected from at least one of the following: rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, esterified rosin, maleic acid rosin, α-terpene resin, β-terpene resin, and terpene phenolic resin.

[0029] Preferably, the plasticizer is selected from at least one of phthalate plasticizers, aliphatic diester plasticizers, polyphenolic ester plasticizers, benzoate plasticizers, polyol ester plasticizers, chlorinated hydrocarbon plasticizers, epoxy plasticizers, and polyester plasticizers.

[0030] Preferably, the lubricant is selected from at least one of polyethylene wax, polypropylene wax, silica, and talc.

[0031] Preferably, the antioxidant is selected from at least one of antioxidant 1010 and antioxidant 268;

[0032] The organic solvent is selected from at least one of ethyl acetate, butanone, and acetone.

[0033] Preferably, step 1 specifically involves: mixing soybean oil-based polyol, polycaprolactone / lactide block copolymer, and tackifying resin, then adding the mixture to a four-necked flask equipped with a thermometer, a stirring device, and a condenser, heating it to the point of melting, and then stirring. The mixture is then melted and dehydrated under reduced pressure at 100-120°C for 1-2 hours.

[0034] Step 2 specifically involves cooling the mixture in the four-necked flask from step 1 to below 70°C, adding diisocyanate, stannous octoate, and organic solvent, and reacting at 60°C-90°C for 4-6 hours to obtain a polyurethane prepolymer with terminal -NCO groups.

[0035] Step 3 specifically involves: cooling the polyurethane prepolymer obtained in step 2 to 60-70°C in a four-necked flask, adding plasticizer, lubricant and antioxidant, stirring, removing solvent under reduced pressure, and discharging to obtain the crude product.

[0036] Step 4 specifically involves transferring the crude product obtained in step 3 to a vacuum drying oven and vacuum drying it at 80℃-100℃ for 20-28 hours to obtain a biodegradable polyurethane hot melt pressure-sensitive adhesive.

[0037] It should be noted and understood that the decompression time and temperature in step 1, and the drying time and temperature in step 4, have no essential impact on this scheme. The selection of the decompression time, temperature, drying time, and temperature is all for the purpose of drying the crude product. In actual operation, the operator can make adjustments according to the actual situation.

[0038] In addition, a biodegradable polyurethane hot melt pressure-sensitive adhesive is also disclosed, which is prepared by the above-mentioned method for preparing biodegradable polyurethane hot melt pressure-sensitive adhesive.

[0039] Preferably, the biodegradable polyurethane hot melt pressure-sensitive adhesive is used as an active ingredient in leather product adhesives.

[0040] The beneficial effects of the present invention are as follows: The present invention is prepared by biodegradable soybean oil-based polyol, polycaprolactone / lactide block copolymer and diisocyanate. Furthermore, by adding modified soybean oil-based polyol as the soft segment of the polymer to the biodegradable copolymer matrix, the performance of the biodegradable polyurethane pressure-sensitive adhesive is improved, thereby improving the initial tack, initial peel strength and final peel strength of the hot melt pressure-sensitive adhesive. Detailed Implementation

[0041] The present invention will now be clearly and completely described in conjunction with its embodiments. In the description of the present invention, it should be noted that, where no specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed; and where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased commercially.

[0042] Preparation of soybean oil-based polyol: The soybean oil-based polyol is prepared by ring-opening reaction using methanol as the ring-opening reagent and tetrafluoroboric acid as the catalyst, with a molar ratio of epoxy group to methanol of 1:1. Epoxidized soybean oil is added to a mixture of boiled methanol and tetrafluoroboric acid, and the mixture is refluxed for 1 hour. After the reaction is completed, heating is stopped, the mixture is cooled to room temperature, and concentrated ammonia water is added dropwise to neutralize it. After washing with water, the mixture is distilled under reduced pressure and filtered to obtain a light yellow transparent liquid soybean oil-based polyol.

[0043] Example 1

[0044] Step 1: Mix 15g soybean oil-based polyol, 10g polycaprolactone / lactide block copolymer and 15g rosin. After mixing, add the mixture to a four-necked flask equipped with a thermometer, a stirring device and a condenser. Heat to melt and start stirring. Melt at 120℃ and introduce nitrogen gas. Remove water under reduced pressure for 2 hours.

[0045] Step 2: Cool the mixture in the four-necked flask from Step 1 to 65°C, add 38.3g of isophorone diisocyanate, 1.5g of stannous octoate and 30g of butanone, and react at 80°C for 5 hours to obtain a polyurethane prepolymer with terminal -NCO groups.

[0046] Step 3: After cooling the polyurethane prepolymer obtained in Step 2 to 70°C in a four-necked flask, add 10g phthalate, 5g polyethylene wax, and 1.0g antioxidant 1010. After stirring, remove the solvent under reduced pressure and discharge to obtain the crude product.

[0047] Step 4: Transfer the crude product obtained in Step 3 to a vacuum drying oven and dry it at 80°C and 0.1 MPa vacuum for 24 hours to obtain biodegradable polyurethane hot melt pressure-sensitive adhesive.

[0048] Example 2

[0049] Step 1: Mix 18g of soybean oil-based polyol, 15g of polycaprolactone / lactide block copolymer, and 20g of maleic acid rosin. After mixing, add the mixture to a four-necked flask equipped with a thermometer, a stirring device, and a condenser. Heat the mixture to the point of melting and start stirring. Melt the mixture at 120°C and introduce nitrogen gas. Remove water under reduced pressure for 1.5 hours.

[0050] Step 2: Cool the mixture in the four-necked flask from Step 1 to 65°C, add 40.5g toluene diisocyanate, 1.8g stannous octoate and 35g acetone, and react at 85°C for 4 hours to obtain a polyurethane prepolymer with terminal -NCO groups.

[0051] Step 3: After cooling the polyurethane prepolymer obtained in Step 2 to 70°C in a four-necked flask, add 13g phthalate, 7g polyethylene wax and 1.2g antioxidant 1010, stir, remove solvent under reduced pressure, and discharge to obtain crude product.

[0052] Step 4: Transfer the crude product obtained in Step 3 to a vacuum drying oven and dry it at 90°C and 0.1 MPa vacuum for 24 hours to obtain biodegradable polyurethane hot melt pressure-sensitive adhesive.

[0053] Example 3

[0054] Step 1: Mix 20g of soybean oil-based polyol, 20g of polycaprolactone / lactide block copolymer, and 25g of α-terpene resin. After mixing, add the mixture to a four-necked flask equipped with a thermometer, a stirring device, and a condenser. Heat the mixture to melt and start stirring. Melt the mixture at 120°C and introduce nitrogen gas. Remove water under reduced pressure for 1.5 hours.

[0055] Step 2: Cool the mixture in the four-necked flask from Step 1 to 70°C, add 42.8g of 1,6-hexanediisocyanate, 2.0g of stannous octoate and 40g of butanone, and react at 85°C for 4 hours to obtain a polyurethane prepolymer with terminal -NCO groups.

[0056] Step 3: After cooling the polyurethane prepolymer obtained in Step 2 to 70°C in a four-necked flask, add 15g phthalate, 9g silica and 1.5g antioxidant 268, stir, remove solvent under reduced pressure, and discharge to obtain crude product.

[0057] Step 4: Transfer the crude product obtained in Step 3 to a vacuum drying oven and dry it at 100°C and 0.1 MPa vacuum for 24 hours to obtain biodegradable polyurethane hot melt pressure-sensitive adhesive.

[0058] Example 4

[0059] Step 1: Mix 22g soybean oil-based polyol, 25g polycaprolactone / lactide block copolymer, and 30g terpene phenolic resin. After mixing, add the mixture to a four-necked flask equipped with a thermometer, a stirring device, and a condenser. Heat the mixture to the point of melting and start stirring. Melt the mixture at 120°C and introduce nitrogen gas. Remove water under reduced pressure for 1.5 hours.

[0060] Step 2: Cool the mixture in the four-necked flask from Step 1 to 70°C, add 45.8g of 4,4′-diphenylmethane, 2.2g of stannous octoate and 45g of ethyl acetate, and react at 90°C for 3 hours to obtain a polyurethane prepolymer with terminal -NCO groups.

[0061] Step 3: After cooling the polyurethane prepolymer obtained in Step 2 to 70°C in a four-necked flask, add 18g of phthalate, 12g of polyethylene wax and 1.8g of antioxidant 268, stir, remove solvent under reduced pressure, and discharge to obtain crude product.

[0062] Step 4: Transfer the crude product obtained in Step 3 to a vacuum drying oven and dry it at 100°C and 0.1 MPa vacuum for 24 hours to obtain biodegradable polyurethane hot melt pressure-sensitive adhesive.

[0063] Example 5

[0064] Step 1: Mix 22g of soybean oil-based polyol, 26g of polycaprolactone / lactide block copolymer, and 31g of terpene phenolic resin. After mixing, add the mixture to a four-necked flask equipped with a thermometer, a stirring device, and a condenser. Heat the mixture to the point of melting and start stirring. Melt the mixture at 120°C and introduce nitrogen gas. Remove water under reduced pressure for 1.5 hours.

[0065] Step 2: Cool the mixture in the four-necked flask from Step 1 to 70°C, add 45.8g of 4,4′-diphenylmethane, 2.2g of stannous octoate, and 39.8g of ethyl acetate, and react at 90°C for 3 hours to obtain a polyurethane prepolymer with terminal -NCO groups.

[0066] Step 3: After cooling the polyurethane prepolymer obtained in Step 2 to 70°C in a four-necked flask, add 18g of phthalate, 12g of polyethylene wax and 1.8g of antioxidant 268, stir, remove solvent under reduced pressure, and discharge to obtain crude product.

[0067] Step 4: Transfer the crude product obtained in Step 3 to a vacuum drying oven and dry it at 100°C and 0.1 MPa vacuum for 24 hours to obtain biodegradable polyurethane hot melt pressure-sensitive adhesive.

[0068] Comparative Example 1

[0069] This is essentially the same as Example 2, except that castor oil-based polyols are used instead of soybean oil-based polyols.

[0070] Comparative Example 2

[0071] The process is basically the same as in Example 2, except that in step 1, 15g of polycaprolactone / lactide block copolymer and 20g of maleic acid rosin are mixed and then added to a four-necked flask equipped with a thermometer, a stirring device and a condenser. The mixture is heated to the point of melting and then stirred. Nitrogen gas is introduced at 120°C and the mixture is dehydrated under reduced pressure for 1.5 hours.

[0072] Comparative Example 3

[0073] The process is basically the same as in Example 2, except that in step 1, 33g of polycaprolactone / lactide block copolymer and 20g of maleic acid rosin are mixed and then added to a four-necked flask equipped with a thermometer, a stirring device and a condenser. The mixture is heated to the point of melting and then stirred. Nitrogen gas is introduced at 120°C and the mixture is dehydrated under reduced pressure for 1.5 hours.

[0074] Comparative Example 4

[0075] The process is basically the same as in Example 2, except that in step 1, 18g of soybean oil-based polyol and 20g of maleic acid-modified rosin are mixed and then added to a four-necked flask equipped with a thermometer, a stirring device and a condenser. The mixture is heated to the point of melting and then stirred. Nitrogen gas is introduced at 120°C and the mixture is dehydrated under reduced pressure for 1.5 hours.

[0076] Comparative Example 5

[0077] The process is basically the same as in Example 2, except that in step 1, 33g of soybean oil-based polyol and 20g of maleic acid rosin are mixed and then added to a four-necked flask equipped with a thermometer, a stirring device and a condenser. The mixture is heated to the point of melting and then stirred. Nitrogen gas is introduced at 120°C and the mixture is dehydrated under reduced pressure for 1.5 hours.

[0078] Table 1. Adhesive properties of polyurethane hot melt pressure-sensitive adhesives obtained in Examples 1-4

[0079] Group <![CDATA[T g (℃)]]> Initial adhesion mark (#) Tackiness (h) Peel strength (N / 10mm) Example 1 -30 7 235 4.2 Example 2 -34 10 280 4.8 Example 3 -35 12 250 5.2 Example 4 -38 15 245 5.4 Example 5 -33 9 230 4.6 Comparative Example 1 -30 6 230 4.1 Comparative Example 2 -28 5 210 3.6 Comparative Example 3 -29 6 220 3.9 Comparative Example 4 -27 5 205 3.5 Comparative Example 5 -29 5 215 3.8

[0080] Results analysis:

[0081] 1. As can be seen from Examples 1-5, there is no obvious correlation between the peel strength and tack of polyurethane hot melt pressure-sensitive adhesive. However, tack is positively correlated with the initial tack number. The peel strength increases continuously with the increase of the initial tack number. At the same time, the peel strength, initial tack number and peel temperature are negatively correlated. The peel strength and initial tack number increase as the peel temperature decreases.

[0082] Furthermore, as the proportion of polycaprolactone / lactide block copolymer and tackifying resin in Examples 1-5 continued to increase, the proportion of diisocyanate continued to decrease, and the tackiness showed a trend of first increasing and then decreasing, reaching its peak in Example 2.

[0083] Meanwhile, as the proportions of polycaprolactone / lactide block copolymer and tackifying resin continued to increase in Examples 1-5, the proportion of diisocyanate continued to decrease, and the peel strength showed a trend of first increasing and then decreasing. In Example 4, the peel strength increased to its peak value.

[0084] 2. As can be seen from Example 2 and Comparative Example 1, when castor oil-based polyol is used instead of soybean oil-based polyol, the tackiness and peel strength decrease to a certain extent, while the initial tack and peel temperature also decrease to a certain extent, but the decrease is not significant.

[0085] 3. As can be seen from Example 2 and Comparative Examples 2-3, when the polyurethane hot melt pressure-sensitive adhesive lacks soybean oil-based polyol, both the tack and peel strength decrease to a certain extent. At the same time, it can be observed that when the total amount of each component of the polyurethane remains unchanged, the decrease in tack and peel strength is relatively small.

[0086] 4. As can be seen from Example 2 and Comparative Examples 4-5, when the polyurethane hot melt pressure-sensitive adhesive lacks polycaprolactone / lactide block copolymer, both the tack and peel strength decrease to a certain extent. At the same time, it can be observed that when the total amount of each component of the polyurethane remains unchanged, the decrease in tack and peel strength is relatively small.

Claims

1. A process for the preparation of a degradable polyurethane hot-melt pressure sensitive adhesive, characterized in that, It comprises the following steps: Step 1: soybean oil based polyol, polycaprolactone / lactide block copolymer, tackifying resin are mixed, and water is removed under reduced pressure to obtain a first product; Step 2: the first product prepared in step 1 is cooled to below 70 DEG C, diisocyanate, stannous octoate, organic solvent are added, and heated to obtain a polyurethane prepolymer with terminal -NCO groups; Step 3: the polyurethane prepolymer prepared in step 2 is cooled to 60-70 DEG C, plasticizer, lubricant, antioxidant are added, stirred, and then the solvent is removed under reduced pressure to obtain a crude product; Step 4: the crude product prepared in step 3 is moved to a vacuum drying oven and dried at 80-100 DEG C for 20-28 hours to obtain a degradable polyurethane hot melt pressure sensitive adhesive; The mass fraction of the polycaprolactone / lactide block copolymer is 10-25 parts, the mass fraction of the soybean oil based polyol is 15-22 parts, the mass fraction of the diisocyanate is 38-46 parts, the mass fraction of the tackifying resin is 15-30 parts, the mass fraction of the stannous octoate is 1.5-2.5 parts, the mass fraction of the plasticizer is 10-20 parts, the mass fraction of the lubricant is 5-15 parts, the mass fraction of the antioxidant is 1-2 parts, and the mass fraction of the organic solvent is 30-45 parts. The diisocyanate is at least one selected from toluene diisocyanate, 1,6-hexane diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate.

2. The method for preparing the biodegradable polyurethane hot-melt pressure-sensitive adhesive according to claim 1, characterized in that, The mass fraction of the polycaprolactone / lactide block copolymer is 15-20 parts, the mass fraction of the soybean oil based polyol is 17-20 parts, the mass fraction of the diisocyanate is 40-46 parts, the mass fraction of the tackifying resin is 15-30 parts, the mass fraction of the stannous octoate is 1.5-2.5 parts, the mass fraction of the plasticizer is 10-20 parts, the mass fraction of the lubricant is 5-15 parts, the mass fraction of the antioxidant is 1-2 parts, and the mass fraction of the organic solvent is 30-45 parts.

3. The method for preparing the biodegradable polyurethane hot-melt pressure-sensitive adhesive according to claim 1, characterized in that, The tackifying resin is at least one selected from aliphatic rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, esterified rosin, maleated rosin, alpha-terpene resin, beta-terpene resin, terpene phenolic resin.

4. The method for preparing the biodegradable polyurethane hot-melt pressure-sensitive adhesive according to claim 1, characterized in that, The plasticizer is at least one selected from phthalate plasticizers, aliphatic dibasic acid ester plasticizers, benzenepolyacid ester plasticizers, benzoate plasticizers, polyhydric alcohol ester plasticizers, chlorinated hydrocarbon plasticizers, epoxy plasticizers, polyester plasticizers.

5. The method for preparing the biodegradable polyurethane hot-melt pressure-sensitive adhesive according to claim 1, characterized in that, The lubricant is at least one selected from polyethylene wax, polypropylene wax, silica, talc.

6. The method for preparing the biodegradable polyurethane hot-melt pressure-sensitive adhesive according to claim 1, characterized in that, The antioxidant is at least one selected from antioxidant 1010, antioxidant 268. The organic solvent is at least one selected from ethyl acetate, butanone, acetone.

7. The method for preparing the biodegradable polyurethane hot-melt pressure-sensitive adhesive according to claim 1, characterized in that, The step 1 is specifically: soybean oil based polyol, polycaprolactone / lactide block copolymer, tackifying resin are mixed, and then added into a four-necked flask equipped with a thermometer, stirring device and condenser tube, heated to melt, and then stirred at 100-120 DEG C for 1-2 hours to remove water under reduced pressure. The step 2 is specifically: cooling the mixture in the four-necked flask in step 1 to below 70 DEG C, adding diisocyanate, stannous octoate, organic solvent, and reacting at 60-90 DEG C for 4-6 hours to obtain polyurethane prepolymer with terminal -NCO group; The step 3 is specifically: cooling the polyurethane prepolymer obtained in step 2 to 60-70 DEG C in the four-necked flask, adding plasticizer, lubricant and antioxidant, stirring, removing solvent under reduced pressure, and discharging to obtain crude product; The step 4 is specifically: moving the crude product obtained in step 3 to a vacuum drying oven, drying at 80-100 DEG C under vacuum for 20-28 hours to obtain degradable polyurethane hot-melt pressure-sensitive adhesive.

8. A degradable polyurethane hot melt pressure sensitive adhesive characterized in that, The degradable polyurethane hot-melt pressure-sensitive adhesive is prepared by the method of any one of claims 1-7.

9. The degradable polyurethane hot-melt pressure sensitive adhesive according to claim 8, characterized in that, Active ingredient for use as adhesive for leather products.