High-performance polyurethane hot melt adhesive for edge sealing and preparation method thereof

Abstract

The application relates to the technical field of hot melt adhesives, in particular to high-performance edge-sealing polyurethane hot melt adhesive and a preparation method thereof. Raw materials are as follows in mass fractions: 5-10 parts of macromolecular resin, 2-8 parts of modified petroleum resin, 10-20 parts of polycaprolactone polyol, 10-20 parts of polycarbonate diol, 15-20 parts of polylactic acid polyol, 15-20 parts of polyester polyol, 5-15 parts of calcium powder, 0.005-0.02 parts of H3PO4, 8-15 parts of isocyanate b, 10-20 parts of prepolymer A and 5-10 parts of premix B. The high-performance edge-sealing polyurethane hot melt adhesive has the characteristics of slow curing and high initial adhesion, can obtain zero glue lines, has a beautiful surface, provides a clean surface appearance, is easy to use, has less glue coating, is easy to maintain, does not need cleaning during weekend shutdown, can be applied with low viscosity, and ensures low energy consumption.

Description

Technical Field

[0001] This invention relates to the field of hot melt adhesive technology, specifically to a high-performance polyurethane hot melt adhesive for edge sealing and its preparation method. Background Technology

[0002] To increase the structural strength of the edges of panel furniture and prevent damage such as warping from water and peeling from external forces, a layer of attractive wood veneer and PVC strips is often glued to the edges, serving both aesthetic and protective purposes. Traditional edge banding adhesives, mainly white glue and latex, are gradually being phased out due to their strong odor, presence of harmful substances like benzene, and tendency to peel off, affecting quality. Currently, the mainstream edge banding products for panel furniture are EVA hot melt adhesive and PUR hot melt adhesive. EVA edge banding adhesive uses ethylene-vinyl acetate, a physical adhesive that cures upon cooling and can be remelted upon heating, making it reversible. However, it has relatively poor rigidity, is not water-resistant, produces thick glue lines, is prone to mold and blackening, and has low peel strength. PUR edge banding adhesive, belonging to the polyurethane family, undergoes rapid physical curing to achieve high initial strength, followed by gradual moisture curing, a reaction that is irreversible. PUR edge banding adhesive boasts high bonding strength and excellent resistance to high and low temperatures, water vapor, paint, chemical corrosion, and aging. Compared to EVA edge banding adhesive, it produces finer adhesive lines, is less prone to mold growth, has better handling properties, and better meets environmental protection requirements. Its drawback is the need for specialized melting equipment, a limitation that granular PUR products overcome, eliminating the need for customers to modify their production equipment. From a cost-effectiveness perspective, based on the production cost of 18mm thick boards, the cost per square meter using EVA and PUR edge banding adhesives is roughly equivalent; however, considering product quality, stability, and production efficiency, PUR edge banding adhesive is more suitable.

[0003] Polyurethane hot melt adhesive (PUR) is heated and melted into a fluid, which is then applied to the surface of the substrate to bond the two objects together. After cooling, an adhesive bond is formed. Subsequently, the moisture in the air or trace amounts of moisture in the substrate and other compounds containing active hydrogen react with the -NCO groups to extend the chain, generating a cross-linked network structure and a polymer with high cohesive strength, which further enhances the adhesive strength and significantly improves the heat resistance.

[0004] With increasing environmental awareness, environmentally friendly adhesives are the current and future development trend. The polyurethane hot melt adhesive (PUR) industry is green and environmentally friendly, aligning with national policies and poised for continued rapid growth. However, while existing PUR edge banding adhesives on the market meet basic customer needs, they still have several shortcomings that require improvement: such as higher production strength for continuous production; meeting environmental requirements for low carbon footprint, low free isocyanate content, and low odor; and meeting human-centered requirements such as being unrestricted by equipment, easy to use, and eliminating the need for weekend overtime work. Summary of the Invention

[0005] To address the aforementioned needs in the prior art, this invention provides a high-performance polyurethane hot melt adhesive for edge sealing and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A high-performance polyurethane hot melt adhesive for edge sealing, characterized in that the raw materials, by weight parts, comprise:

[0008]

[0009] The prepolymer A is prepared from polyether polyol, special polyether, isocyanate a, dehydrating agent and stabilizer, wherein the mass ratio of polyether polyol, special polyether, isocyanate a, dehydrating agent and stabilizer is 6:1:2.5:0.1:0.4;

[0010] The premix B is composed of an adhesion promoter, a silane coupling agent, and a capping agent, wherein the mass ratio of the adhesion promoter, the silane coupling agent, and the capping agent is 1:3:6.

[0011] The macromolecular resin is any one of Mitsubishi 2598, Mitsubishi 2595, Kemao SK1000W, Lexin WH103, Sutlin C395, and Shuyu SY349.

[0012] The modified petroleum resin is one or more of the following: Hisense TK100, TA100, TN85, TN110, and Kemao KL100w.

[0013] The polycaprolactone polyol is one or more of Pastor PCL1800, PCL2000, and PCL2200.

[0014] The polycarbonate diol is one of PCDL351, PCDL2200, and PCDL3000.

[0015] The polylactic acid polyol is one or more of Tongbang PLA1000 and PLA2000;

[0016] The polyester polyol is one or more of Dynacoll 7361, 7380, 7381, and 7390.

[0017] Wherein, isocyanate a is one or more of Wanhua HDI, TDI, MDI100, MDI50, HMDI, and IPDI; and isocyanate b is one or more of Wanhua HDI, TDI, MDI100, MDI50, HMDI, and IPDI.

[0018] The polyether polyol is one or more of PPG1000, PPG2000, PPG4000, and PPG400; the special polyether is one or more of PEG2000, PTXG2000, and PTMEG2000.

[0019] The silane coupling agent is one or more of Sipro A1100, KH550, and A171.

[0020] The dehydrating agent is WD51; the stabilizer is Bayer EX10.

[0021] The adhesion promoter is Wacker E22; the end-capping agent is Bayer PV15.

[0022] The preparation method of the high-performance polyurethane hot melt adhesive for edge sealing according to the present invention includes the following steps:

[0023] (1) Preparation of prepolymer A

[0024] Add polyether polyol, special polyether, dehydrating agent and stabilizer to the reactor in proportion, stir and heat to 120°C, control the temperature and evacuate for 2 hours, then cool down to 70°C, add isocyanate a, control the temperature at 75-80°C, and react for 2 hours; after the time is up, discharge the material, seal and pack it with nitrogen gas for later use.

[0025] (2) Preparation of premix B

[0026] In the reaction vessel, add the adhesion promoter, silane coupling agent and end-capping agent directly in proportion, stir thoroughly, seal and pack with nitrogen gas, and set aside for later use;

[0027] (3) Add macromolecular resin, modified petroleum resin, phosphoric acid, polyester polyol, polycarbonate diol, polycaprolactone polyol, polylactic acid polyol, calcium 1, and prepolymer A to the reactor. Stir and mix evenly at 120-150°C. Heat and stir, maintain 120-150°C and vacuum for 1.5-2.5 hours. Then lower the temperature to 105-110°C, add isocyanate b, control the temperature at 118-120°C for 120 minutes, lower the temperature to 80°C, add premix B, react for 20-30 minutes, raise the temperature to 140-150°C, turn off the stirring, and discharge the material after 10-15 minutes. Seal the package with nitrogen gas, granulate underwater the next day, and vacuum package.

[0028] The high-performance polyurethane hot melt adhesive for edge sealing of this invention adopts a unique formula and process design. After customer construction, the strength of the adhesive far exceeds that of existing products on the market, and it can be safely grooved and drilled. It still has high strength after high and low temperature thermal cycling. It has excellent water resistance and the edge sealing tape does not bounce after being soaked in water.

[0029] The method of this invention fulfills the commitment to reducing carbon dioxide emissions, supporting a circular and environmentally friendly economy, and improving green and safe application standards. It is formaldehyde-free, has zero emissions, and produces biodegradable solid waste. In addition, by end-capped thermally activated isocyanate prepolymers, it can reduce harmful isocyanate-containing fumes by up to 90%, in compliance with European safety standard (EC) No 1272 / 2008 (CLP).

[0030] This invention, from a human-centered perspective, transforms traditional block PUR products into granules, eliminating the need for customers to modify their equipment. The product also requires no cleaning for at least three days after use, facilitating material feeding. After production, the equipment is easy to maintain, and there is no need for cleaning during weekend shutdowns, greatly simplifying the work and life of workshop workers.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] (1) The present invention adopts a unique formula design, selects special raw materials and proportions, which greatly improves the initial bonding strength of the edge sealing adhesive and meets the requirement that the thick edge sealing tape does not rebound; the high and low temperature resistance and moisture resistance are also significantly improved.

[0033] (2) The present invention selects polycaprolactone, polycarbonate diol and polylactic acid polyol, which improves the weather resistance, high temperature cooking performance and substrate adhesion of the adhesive, and also meets the environmental protection requirements of material degradability.

[0034] (3) The high-performance polyurethane hot melt adhesive for edge sealing of the present invention has the characteristics of slow curing and high initial tack, which can achieve zero glue lines, beautiful surface and provide a clean surface appearance.

[0035] (4) The high-performance polyurethane hot melt adhesive for edge sealing of the present invention is easy to use, requires less adhesive, is easy to maintain, does not require cleaning during weekend shutdowns, can be applied at low viscosity, and ensures low energy consumption. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The reaction time of each step in this invention is determined according to the actual progress of the reaction. During the reaction, the degree of reaction is judged by sampling the reactants, and the reaction is stopped when the requirements are met.

[0038] Example 1

[0039] A high-performance polyurethane hot melt adhesive for edge sealing has the following formulation:

[0040] 1 Macromolecular resin SY349 5 2 Modified petroleum resin TK100 3 3 Phosphoric acid 0.005 4 Polyester polyol 7381 15 5 Polycarbonate diol PCDL3000 20 6 Polycaprolactone polyol PCL2200 15 7 Polylactic acid polyol PLA2000 20 8 Calcium powder 12 9 Prepolymer A 18 10 HMDI isocyanate 12 11 Premix B 7

[0041] The specific preparation method is as follows:

[0042] (1) Preparation of prepolymer A

[0043] The mass ratio of polyether polyol, special polyether, isocyanate a, dehydrating agent and stabilizer is 6:1:2.5:0.1:0.4.

[0044] In a reactor, first add polyether polyol PPG2000, special polyether PTXG2000, dehydrating agent WD51, and stabilizer EX10 in the above proportions. Stir and heat to 120°C, maintain temperature under vacuum for two hours, then cool to 70°C. Next, add isocyanate MDI 100, maintain temperature at 75-80°C, and react for 2 hours. After the time is up, discharge the material, seal it, purge with nitrogen, and package it for later use.

[0045] (2) Preparation of premix B

[0046] In the reaction vessel, add adhesion promoter E22, coupling agent A171 and end-capping agent PV15 directly in a mass ratio of 1:3:6. Stir thoroughly, seal and package with nitrogen gas, and set aside for later use.

[0047] (3) Add 5 parts of macromolecular resin SY349 and 3 parts of modified petroleum resin TK100, 0.005 parts of phosphoric acid, 15 parts of polyester polyol 7381, 20 parts of polycarbonate diol PCDL3000, 15 parts of polycaprolactone polyol PCL2200, 20 parts of polylactic acid polyol PLA2000, 12 parts of calcium powder, and 18 parts of prepolymer A to the reactor. Stir and mix evenly at 120-150℃, heat and stir, maintain 120-150℃ and vacuum for 1.5-2.5h, then lower to 105-110℃, add 12 parts of isocyanate HMDI, control the temperature at 118-120℃ for 120min, lower to 80℃, add 7 parts of premix B, react for 20-30min, raise the temperature to 140-150℃, turn off the stirring, and discharge the material after 10-15min. The product is sealed in nitrogen gas, granulated underwater the next day, and then vacuum-packed.

[0048] Performance testing:

[0049] The high-performance polyurethane hot melt adhesive for edge banding prepared in Example 1 was tested under harsh conditions, using 2mm PVC edge banding strips to bond particleboard and plywood (adhesive application rate of 100g / m²). 2(The glue tank temperature is 150℃). Using a small PUR edge banding machine, the glue is directly applied to the equipment, and the initial strength is tested first. The specific experimental method is as follows: Using a small PUR edge banding machine, hot melt adhesive granules are placed into the glue tank. The board and edge banding strip are prepared. The equipment is operated to bond the board and the edge banding strip. Immediately after bonding, the edge banding strip is clamped with the clamp of a handheld digital tensile tester, and a 90° peel strength test is performed. The value is recorded, which is the initial strength.

[0050] After curing for 12 hours, the board was soaked in water for 7 hours, and the hydrolysis resistance was characterized by observing the changes in the board and the edge banding. After curing for 48 hours, the board was kept at -20℃ for 2 hours and then at -60℃ for 2 hours, for a total of 4 cycles. The low temperature resistance was characterized by testing the change in peel strength using a handheld digital tensile tester.

[0051] Initial strength of the lower line / N 65.4 68.2 Does it swell after soaking in water? no no Does the edge banding rebound after being soaked in water? no no Peel strength at room temperature / N 166.6 164.5 Peel strength under low temperature cycling / N 158.1 152.5

[0052] As shown in the table, the high-performance polyurethane hot melt adhesive for edge banding prepared in Example 1 is a high-strength woodworking adhesive with excellent hydrolysis resistance and low-temperature resistance. The edge banding tape did not spring back immediately after the board came off the edge banding machine, indicating extremely high initial strength. Even after soaking in water, the edge banding tape did not spring back, demonstrating excellent hydrolysis resistance. Under low-temperature conditions, the strength did not decrease significantly and remained at a high level, indicating that this high-performance polyurethane hot melt adhesive for edge banding is fully adaptable to harsh low-temperature environments.

[0053] Example 2

[0054] A high-performance polyurethane hot melt adhesive for edge sealing has the following formulation:

[0055] 1 Macromolecular resin C395 5 2 Modified petroleum resin TN110 3 3 Phosphoric acid 0.01 4 Polyester polyol 7390 15 5 Polycarbonate diol PCDL3000 20 6 Polycaprolactone polyol PCL2200 12 7 Polylactic acid polyol PLA2000 15 8 Calcium powder 12 9 Prepolymer A 18 10 MDI50 isocyanate 10 11 Premix B 6

[0056] The specific preparation method is as follows:

[0057] (1) Preparation of prepolymer A

[0058] The mass ratio of polyether polyol, special polyether, isocyanate a, dehydrating agent and stabilizer is 6:1:2.5:0.1:0.4.

[0059] Add polyether PPG2000, PTXG2000, dehydrating agent WD51, and stabilizer EX10 to the reactor according to the proportions in the above formula. Stir and heat to 120°C, maintain the temperature under vacuum for two hours, then cool to 70°C, add isocyanate MDI100, maintain the temperature at 75-80°C, and react for 2 hours. After the time is up, discharge the material, seal it, purge it with nitrogen, and package it for later use.

[0060] (2) Preparation of premix B

[0061] In the reaction vessel, add adhesion promoter E22, coupling agent A171 and end-capping agent PV15 directly in a mass ratio of 1:3:6. Stir thoroughly, seal and package with nitrogen gas, and set aside for later use.

[0062] (3) Add 5 parts of macromolecular resin C395 and 3 parts of modified petroleum resin TN110, 0.01 parts of phosphoric acid, 15 parts of polyester polyol 7390, 20 parts of polycarbonate diol PCDL3000, 12 parts of polycaprolactone polyol PCL2200, 15 parts of polylactic acid polyol PLA2000, 12 parts of calcium powder, and 18 parts of prepolymer A to the reactor. Stir and mix evenly at 120-150℃, heat and stir, maintain 120-150℃ and vacuum for 1.5-2.5h, then lower to 105-110℃, add 11 parts of isocyanate MDI 50, control the temperature at 118-120℃ for 120min, lower to 80℃, add 6 parts of premix B, react for 20-30min, raise the temperature to 140-150℃, turn off the stirring, and discharge the material after 10-15min. The product is sealed in nitrogen gas, granulated underwater the next day, and then vacuum-packed.

[0063] Performance testing:

[0064] (1) Referring to the American Society of Engineering ASTM D2295-72 (1983) standard for testing the heat resistance of adhesives, the prepared high-performance polyurethane hot melt adhesive for edge banding was placed in an oven at 150°C for 5 hours to conduct bonding tests between plywood and PVC edge banding strips, and the changes in initial peel strength and 24-hour peel strength were observed. The competing product selected was German Adhesive King 607.41.

[0065] 5min peel force / N 65.4 61.2 52.1 48.6 24h peel force / N 152.2 158.9 132.4 128.2

[0066] The results in the table show that the bonding strength decreases slightly after 5 hours at 150℃, but this does not affect the performance. Compared with competing products, the strength is significantly greater, indicating that the high-performance polyurethane hot melt adhesive for edge sealing prepared by this invention has excellent heat resistance.

[0067] (2) Comparison of other performance aspects

[0068] (No-cleaning performance: At 23℃ and 50% humidity, after 3 days (72 hours), remelt and observe whether a skin forms.)

[0069] odor none have Appearance Pale yellow granules at room temperature Pale yellow lumps at room temperature Is there a crust? no yes Is it biodegradable? yes no

[0070] This invention transforms traditional PUR adhesive blocks into granules, greatly facilitating customer production. No equipment modification is required, and worker operation is simple and convenient. The product is odorless, making it highly environmentally friendly and safe. Even after three days of use following production, no skinning occurs, eliminating the need for customers to clean the glue tank and reducing the need for weekend overtime. Therefore, the high-performance polyurethane hot melt adhesive for edge sealing prepared by this invention is a highly desirable and environmentally friendly product.

[0071] Example 3

[0072] A high-performance polyurethane hot melt adhesive for edge sealing has the following formulation:

[0073]

[0074]

[0075] The specific preparation method is as follows:

[0076] (1) Preparation of prepolymer A

[0077] The mass ratio of polyether polyol, special polyether, isocyanate a, dehydrating agent and stabilizer is 6:1:2.5:0.1:0.4.

[0078] Add polyether PPG2000, PTXG2000, dehydrating agent WD51, and stabilizer EX10 to the reactor according to the proportions in the above formula. Stir and heat to 120°C, maintain the temperature under vacuum for two hours, then cool to 70°C, add isocyanate MDI100, maintain the temperature at 75-80°C, and react for 2 hours. After the time is up, discharge the material, seal it, purge it with nitrogen, and package it for later use.

[0079] (2) Preparation of premix B

[0080] In the reaction vessel, add adhesion promoter E22, coupling agent A171 and end-capping agent PV15 directly in a mass ratio of 1:3:6. Stir thoroughly, seal and package with nitrogen gas, and set aside for later use.

[0081] (3) Add 8 parts of macromolecular resin SY349, 5 parts of petroleum resin TK100, 0.01 parts of phosphoric acid, 17 parts of polyester polyol 7381, 15 parts of polycarbonate diol PCDL3000, 15 parts of polycaprolactone polyol PCL2200, 15 parts of polylactic acid polyol PLA2000, 10 parts of calcium powder, and 15 parts of prepolymer A to a reactor. Stir and mix evenly at 120-150℃, heat and stir, maintain at 120-150℃ and vacuum for 1.5-2.5 hours, then lower to 105-110℃, add 10 parts of isocyanate HMDI, control the temperature at 118-120℃ for 120 minutes, lower to 80℃, add 6 parts of premix B, react for 20-30 minutes, raise the temperature to 140-150℃, turn off the stirring, and discharge after 10-15 minutes. Seal with nitrogen and package well. Granulate underwater the next day and vacuum package.

[0082] Performance testing:

[0083] (1) Referring to the American Society of Engineering ASTM D2295-72 (1983) standard for testing the heat resistance of adhesives, the prepared high-performance polyurethane hot melt adhesive for edge banding was placed in an oven at 150°C for 5 hours to conduct a bonding test between plywood and PVC edge banding strips, and the changes in initial peel strength and 24-hour peel strength were observed.

[0084]

[0085]

[0086] The results in the table show that the preferred solution has better mechanical properties than Examples 1 and 2.

[0087] (2) Comparison of other performance aspects

[0088] (No-cleaning performance: At 23℃ and 50% humidity, after 3 days (72 hours), remelt and observe whether a skin forms.)

[0089] odor none Appearance Pale yellow granules at room temperature Is there a crust? no Is it biodegradable? yes

[0090] The test results show that the preferred solution has superior cleaning-free performance.

[0091] It should be understood that the technical solutions obtained by proportionally increasing or decreasing the amount of reagents or raw materials used in the above embodiments (including the selection of chain extenders and auxiliaries, such as adding defoamers, antioxidants, anti-aging agents, etc.) are essentially the same as the above embodiments.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-performance polyurethane hot melt adhesive for edge sealing, characterized in that, Raw materials, by mass parts, include: 5-10 parts of macromolecular resin 2-8 parts of modified petroleum resin 10-20 parts of polycaprolactone polyol 10-20 parts of polycarbonate diol 15-20 parts of polylactic acid polyol 15-20 parts of polyester polyol 5-15 parts calcium powder Phosphoric acid (H3PO4) 0.005~0.02 parts Isocyanate b 8-15 parts Prepolymer A 10-20 parts Premix B: 5-10 parts; The prepolymer A is prepared from polyether polyol, special polyether, isocyanate a, dehydrating agent and stabilizer, wherein the mass ratio of polyether polyol, special polyether, isocyanate a, dehydrating agent and stabilizer is 6:1:2.5:0.1:0.4; The premix B is composed of an adhesion promoter, a silane coupling agent, and a capping agent, wherein the mass ratio of the adhesion promoter, the silane coupling agent, and the capping agent is 1:3:

6. The polycaprolactone polyol is one or more of Pastor's PCL1800, PCL2000, and PCL2200; The polycarbonate diol is one of PCDL351, PCDL2200, and PCDL3000 from Dazhi. The polylactic acid polyol is one or more of Tongbang PLA1000 and PLA2000; The polyester polyol is one or more of Dynacoll 7361, 7380, 7381, and 7390; The macromolecular resin is any one of Mitsubishi 2598, Mitsubishi 2595, Kemao SK1000W, Lexin WH103, Sutlin C395, and Shuyu SY349; The modified petroleum resin is one or more of the following: Hisense's TK100, TA100, TN85, TN110, and Kemao's KL100w; The isocyanate a is one or more of Wanhua HDI, TDI, MDI100, MDI50, HMDI, and IPDI; the isocyanate b is one or more of HDI, TDI, MDI100, MDI50, HMDI, and IPDI. The polyether polyol is one or more of PPG1000, PPG2000, PPG4000, and PPG400; the special polyether is one or more of PEG2000, PTXG2000, and PTMEG2000.

2. The high-performance polyurethane hot melt adhesive for edge sealing according to claim 1, characterized in that: The silane coupling agent is one or more of Sipro's A1100, KH550, and A171.

3. The high-performance polyurethane hot melt adhesive for edge sealing according to claim 1, characterized in that: The dehydrating agent is WD51 from Foch Chemical; the stabilizer is EX10 from BASF.

4. The high-performance polyurethane hot melt adhesive for edge sealing according to claim 1, characterized in that: The adhesion promoter is Wacker E22; the end-capping agent is Bayer PV15.

5. The method for preparing the high-performance polyurethane hot melt adhesive for edge sealing according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Preparation of prepolymer A Add polyether polyol, special polyether, dehydrating agent and stabilizer to the reactor in proportion, stir and heat to 120°C, control the temperature and evacuate for 2 hours, then cool down to 70°C, add isocyanate a, control the temperature at 75~80°C and react for 2 hours; after the time is up, discharge the material, seal and pack it with nitrogen gas for later use. (2) Preparation of premix B In the reaction vessel, add the adhesion promoter, silane coupling agent and end-capping agent directly in proportion, stir thoroughly, seal and pack with nitrogen gas, and set aside for later use; (3) Add macromolecular resin, modified petroleum resin, phosphoric acid, polyester polyol, polycarbonate diol, polycaprolactone polyol, polylactic acid polyol, calcium powder, and prepolymer A to the reactor. Stir and mix evenly at 120~150℃, heat and stir, maintain 120~150℃ and vacuum for 1.5~2.5h, then lower to 105~110℃, add isocyanate b, control the temperature at 118~120℃ for 120min, lower to 80℃, add premix B, react for 20~30min, raise the temperature to 140~150℃, turn off stirring, discharge after 10~15min, seal with nitrogen, granulate underwater the next day, and vacuum package.

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