Polyurethane hot melt adhesive for suede composite board and preparation method of polyurethane hot melt adhesive

Abstract

The invention relates to the field of novel adhesives, and particularly provides a polyurethane hot melt adhesive for a suede composite board and a preparation method of the polyurethane hot melt adhesive for the suede composite board. Liquid polyester polyol, amorphous polyester polyol and crystalline polyester polyol are compounded to improve indexes such as surface adhesion, mechanical strength and heat resistance of a system; meanwhile, the opening time is adjusted through the proportion of the crystalline polyester polyol; the finally obtained polyurethane hot melt adhesive product has good open time and viscosity, the bonding strength is improved, and the thermal stability is obviously improved.

Description

Technical Field

[0001] The present invention relates to the field of adhesive preparation, and particularly to a polyurethane hot melt adhesive for suede composite boards and a preparation method thereof. Background Art

[0002] PUR (Polyurethane Reactive), fully known as moisture-curing reactive polyurethane hot melt adhesive in Chinese, mainly consists of terminal isocyanate polyurethane prepolymer. Due to the adjustable adhesiveness and toughness (elasticity) of PUR, it has the characteristics of low cost, rapid curing, and excellent adhesive strength, heat resistance, chemical corrosion resistance, and aging resistance. Therefore, PUR has different applications in multiple industrial fields, including automobiles, electronics, medical treatment, furniture, packaging, etc.

[0003] PUR can meet such diverse applications because they are suitable for a series of substrates, including composite materials, paper, rubber, plastics, ceramics, metals, glass, and wood, etc.; these PURs are usually coated by extrusion, rolling, or spraying techniques because the high melt viscosity of the adhesive makes it an ideal solution for the applications it is used in. PUR not only meets industrial uses but also can be used for home repair applications, thus meeting the needs of almost all B2B and B2C end-users.

[0004] Nowadays, PUR is widely used in the automotive field and gradually replaces the previous solvent-based adhesives. However, the existing PUR for bonding PHC boards and suede has a low initial adhesion force and cannot meet the requirements of the existing production process. Therefore, there is an urgent need to develop a PUR with high initial adhesion force for bonding PHC boards and suede. Summary of the Invention

[0005] The technical problem to be solved by the present invention is as follows: This PUR is a spraying product, which requires excellent fluidity at high temperatures and good thermal stability; secondly, since the substrates are PHC boards and suede, excellent initial adhesion force is required; due to the operation requiring time, the open time should not be too short. To balance the viscosity and initial adhesion force while maintaining a relatively long open time and improve the thermal stability of the polyurethane hot melt adhesive, the inventors provide a polyurethane hot melt adhesive for suede composite boards and a preparation method thereof. By using a compounding method of liquid polyester polyol, amorphous polyester polyol, and crystalline polyester polyol, the surface adhesion, mechanical strength, heat resistance, and other indicators of the system are improved. At the same time, the open time is adjusted by the proportion of crystalline polyester polyol; the finally obtained polyurethane hot melt adhesive product has both good open time and viscosity, while improving the adhesive strength and significantly enhancing the thermal stability performance.

[0006] The specific technical solution of the present invention is as follows: A polyurethane hot melt adhesive for suede composite board, by weight, its raw materials include 10-20 parts of polyester polyol, 50-60 parts of polyether polyol, 2-5 parts of functional resin, 20-30 parts of isocyanate, and 0.01-0.05 parts of antioxidant.

[0007] Preferably, the polyester polyol is used in a compound of a first polyester polyol, a second polyester polyol, and a third polyester polyol; the functional resin is one or a compound of two of a first functional resin and a second functional resin.

[0008] Furthermore, by weight, there are 2-7 parts of the first polyester polyol, 2-7 parts of the second polyester polyol, and 5-10 parts of the third polyester polyol; the first polyester polyol is a liquid polyester polyol with a molecular weight of 2000; the second polyester polyol is an amorphous polyester polyol with a molecular weight of 2000-3000; the third polyester polyol is a crystalline polyester polyol with a molecular weight of 3500-5000.

[0009] More preferably, the first polyester polyol is selected from one or several of T-24 of Huada Chemistry, HDPOL-5520M, HDPOL-9520, and HDPOL-6315 of Huide Technology; the second polyester polyol is selected from one or several of Dynacoll7130 of Evonik, CJPOL-2020, CJPOL-520 of Fujian Chengjie High Polymer, and HDPOL-2430 of Huide Technology; the third polyester polyol is selected from one or several of Dynacoll 7380 of Evonik, HDPOL-338 of Huide Technology, XCP-254, XCP-2200NH, and XCP-3000H of Asahi Kasei Chemicals.

[0010] The three polyester polyols need to be used simultaneously. The first polyester polyol can increase the surface adhesion of the polyurethane, the second polyester polyol can increase the mechanical strength of the polyurethane, the third polyester polyol can reduce the open time of the polyurethane system while increasing the mechanical strength of the polyurethane, and with the addition of the three polyester polyols, the chemical resistance and heat resistance of the system will be greatly improved; in particular, the first polyester polyol can make the first functional resin disperse more stably in the system and reduce the influence of the first functional resin on the viscosity of the system. The second polyester polyol and the third polyester polyol have excellent compatibility with the polyether polyol, thus ensuring the stability of the main body of the formulation.

[0011] Preferably, the polyether polyol is polyethylene glycol with a molecular weight of 400 - 2000, more preferably 400 - 1000; in some embodiments of the present invention, polyethylene glycol with a molecular weight of 400 and / or polyethylene glycol with a molecular weight of 1000 is selected as the polyether polyol; further, the polyethylene glycol with a molecular weight of 400 is CHE-204 from Changhua Chemical, and the polyethylene glycol with a molecular weight of 1000 is CHE-210 from Changhua Chemical.

[0012] The above two polyether polyols can be used alone or together. The addition of polyether polyols can improve the flexibility, water resistance and low temperature resistance of the system. In particular, the molecular weight and the length of the molecular chain of the system are determined by the ratio of polyethylene glycol with a molecular weight of 400 and polyethylene glycol with a molecular weight of 1000. After testing, the mass ratio of polyethylene glycol with a molecular weight of 400 to polyethylene glycol with a molecular weight of 1000 of 4:23 is the most suitable in this system. And in this system, as the proportion of polyethylene glycol with a molecular weight of 400 increases, the chain length of the molecular chain will become shorter; in particular, the compatibility of polyether polyols with pure monomer resin is excellent, thus ensuring the stability of the formulation.

[0013] Preferably, the first functional resin in the functional resin is a hot-melt copolyester with a molecular weight of 15000 - 25000, and the second functional resin is a pure monomer resin.

[0014] For the two functional resins, by weight, the first functional resin is 1 - 4 parts, and the second functional resin is 1 - 4 parts; among them, the first functional resin greatly improves the mechanical strength, toughness and initial adhesion of the system. In particular, the compatibility of the first functional resin with the first polyester polyol is excellent, and the second functional resin has obvious effects on improving the wettability and permeability of the system and reducing the viscosity of the system.

[0015] As a further preference, the first functional resin is selected from one or more of HS260, HS270, HS560, HS170, HS171, 50293C of Hanhai New Materials; the second functional resin is poly(α-methylstyrene), and is selected from one or more of Kristalex 3085, Kristalex 3100, Kristalex 3105, Kristalex 3115, Kristalex 1120, Kristalex 5140 of Eastman.

[0016] Preferably, the antioxidant is a phenolic antioxidant, and is selected from one or more of C1010 and C1035 of BASF.

[0017] Preferably, the isocyanate is a diisocyanate, specifically selected from one or more of diphenylmethane diisocyanate, isophorone diisocyanate, and toluene diisocyanate.

[0018] In addition, the inventor also provides a method for preparing the polyurethane hot melt adhesive for suede composite board, which includes the following steps: (1) Add polyester polyol, polyether polyol, functional resin, and antioxidant into the reaction kettle, heat up to 140 - 150 °C, start vacuum pumping, keep the system pressure at -0.096 to -0.1 MPa, turn on the stirrer, keep the rotation speed at 400 - 500 r / min, and stir for 2 - 2.5 h until all raw materials are evenly mixed; The reaction kettle should be wiped clean before use and ensure there are no foreign objects.

[0019] (2) After the mixture is evenly mixed, cool the system to 100 - 105 °C, stop vacuum pumping, add isocyanate, then continue in a vacuum state, keep the system pressure at -0.096 to -0.1 MPa, keep the rotation speed at 150 - 200 r / min, react for at least 2 h. After reacting for 2 h, take a sample to test the viscosity. React until the viscosity reaches 4500 - 6500 CPS / 120 °C. After meeting the requirements, it can be discharged. Since the viscosity test is convenient and rapid, the discharge time of product production can be confirmed in time. Therefore, the viscosity test data is used as the sign to terminate the reaction.

[0020] The polyurethane hot melt adhesive for suede composite board provided by the present invention can be used for the composite between suede and board, and has obtained the following beneficial effects: The method of compounding liquid polyester polyol, amorphous polyester polyol, and crystalline polyester polyol is adopted to improve indexes such as surface adhesion, mechanical strength, and heat resistance of the system, and at the same time, the open time is adjusted by the proportion of crystalline polyester polyol.

[0021] The method of blending polyether polyols with different molecular weights is adopted to adjust the molecular weight and the length of the molecular chain while ensuring flexibility, water resistance, and low-temperature resistance, and further improve its bonding performance.

[0022] Functional resin is added. The first functional resin is a crystalline high-molecular-weight saturated polyester, which can keep the PUR at a relatively low viscosity under the condition of low NCO residue, which is beneficial for the subsequent spraying use of the product. In particular, the first functional resin has excellent compatibility with the first polyester polyol, solving the problem of shortened product shelf life caused by the precipitation of floccules in some systems. In particular, the NCO residue of this formula is 1.3 - 1.5%, which is extremely low compared with the same type of formula. It is relatively difficult to keep a low viscosity under this condition, but the addition of the first functional resin well solves the problem of high viscosity.

[0023] Functional resins are added, where the second functional resin replaces the terpene resin and hydrogenated terpene resin in the traditional formulation system, and the compatibility with polyester polyol and polyether polyol is improved to varying degrees. The problem of flocculation precipitation during the dissolution process in some systems is solved, and the effect on improving the bonding strength is obvious; in particular, the molecular weight of the monomer resin is relatively small, which improves the wetting and leveling properties of the system, so it is significantly helpful for reducing the viscosity of the system; in particular, the monomer resin has good compatibility with SBS, SIS, styrene-butadiene rubber, cis-butadiene rubber, natural rubber, nitrile rubber, chloroprene rubber, butyl rubber, ABS, CPVC, PVC, PS, EVA, POM, HIPS, etc. Therefore, the adaptability of this formulation is extremely wide, and it can be compatible with the bonding of most composite boards and suede surfaces.

[0024] No catalyst is added, effectively reducing the formation rate of skinning, delaying the aging of the product, ensuring the stability of the product in the later stage, and extending the shelf life of the product.

[0025] No defoaming agent is added, effectively preventing problems such as strength reduction and delamination caused by the migration of additives in the colloid in the later stage of the product.

[0026] The polyurethane hot melt adhesive product of the present invention has both good open time and viscosity, while improving the bonding strength and significantly improving the thermal stability performance. Specific embodiments

[0027] The technical solutions of the present invention will be further described below in conjunction with specific embodiments. These embodiments are only used to more specifically illustrate the technical solutions of the present invention and should not be construed as limiting the protection scope of the present invention.

[0028] The used T-24 is purchased from Huada Chemical Group Co., Ltd., Dynacoll 7130 is purchased from Evonik Industries AG, XCP-254 is purchased from Asahi Kasei Chemicals (Suzhou) Co., Ltd., CHE-204 and CHE-210 are purchased from Changhua Chemical, HS170 is purchased from Suzhou Hanhai New Materials Co., Ltd., Kristalex 3100 is purchased from Eastman Chemical Company, and C1035 is purchased from BASF SE; except for the reagents and substances used in the following examples, if not otherwise specified, they are all general commercially available products.

[0029] The test methods for each performance index in the experiment are as follows: 1) The viscosity test refers to the GB / T 2794-1995 standard, and the data is obtained by using a cone-plate viscometer under the condition of 120 °C.

[0030] 2) For the open time test, referring to the standard of GB / T 1728-1979, heat the colloid to 120 °C, apply it onto a plane with a film applicator of 30-mil thickness, start timing, and stop timing when the hot melt adhesive cools down and there is no stickiness felt when gently touching the surface with a finger. This time is the open time.

[0031] 3) For the initial adhesion force at 5 minutes and the final adhesion force at 48 hours test, referring to the standard of GB / T 7124-2008, cut the PVC leather into strips with a length of 25 cm and a width of 2.5 cm, prepare 2 strips for use, wipe the surface clean with alcohol, heat the colloid to 120 °C, apply it onto one PVC strip with a film applicator of 20-mil thickness, then bond the 2 PVC strips together, and test the peel force at 5 minutes and 48 hours on a tensile testing machine.

[0032] 4) For the heat aging, referring to the standard of GB / T 19250-2013, heat the colloid to 120 °C, expose it on a heating platform at 120 °C for 2 hours, and observe whether it draws filaments.

[0033] 5) For the damp heat aging, referring to the standard of GB / T 2423.3-2016, after the damp heat aging, measure the peel force after the damp heat aging according to the standard of GB / T 7124-2008, and characterize the damp heat aging performance of the sample by the magnitude of the peel force. Specifically, cut the suede and PHC board into strips with a length of 25 cm and a width of 2.5 cm, heat the colloid to 120 °C, apply it onto the suede with a film applicator of 20-mil thickness, then bond the suede and the PHC board together to prepare a test sample, put it into an incubator at 90 °C for 168 hours, take it out and restore it to room temperature, and test the peel force on a tensile testing machine.

[0034] 6) For the low temperature resistance test, referring to the standard of GB / T 2423.3-2016, after the low temperature resistance test, measure the peel force after the low temperature resistance test according to the standard of GB / T 7124-2008, and characterize the low temperature resistance performance of the sample by the magnitude of the peel force. Specifically, cut the suede and PHC board into strips with a length of 25 cm and a width of 2.5 cm, heat the colloid to 120 °C, apply it onto the suede with a film applicator of 20-mil thickness, then bond the suede and the PHC board together to prepare a test sample, put it into a refrigerator at -5 °C for 168 hours, take it out and restore it to room temperature, and test the peel force on a tensile testing machine.

[0035] 7) The measurement of the NCO residue content uses the traditional chemical method of toluene - di-n-butylamine titration method. Utilize the reaction of the isocyanate group with excessive di-n-butylamine to produce urea, and then titrate the excessive di-n-butylamine with hydrochloric acid to quantitatively calculate the content of the isocyanate group.

[0036] Preparation of standard solution: a) Bromocresol green indicator: Dissolve 0.1 g of bromocresol green in 100 mL of 20% (v / v) ethanol; b) 0.1 mol / L di-n-butylamine-toluene solution: Dissolve 12.9 g of di-n-butylamine in toluene, transfer it to a 1000 mL volumetric flask, and dilute to the mark with toluene. Shake well.

[0037] Experimental procedure: Weigh accurately 1.0000 g of the sample into a dry conical flask, add 25 mL of toluene to dissolve the sample, accurately add 25.00 mL of di-n-butylamine-toluene solution, stopper the flask, shake well, and let it stand for 15 min. Then, add 100 mL of isopropanol and 5 drops of bromocresol green indicator, and titrate with 0.1 mol / L HCl standard solution to the end point (from blue to yellow). Conduct a blank experiment simultaneously.

[0038] Calculation formula:

[0039] V0 —— Volume of HCl standard solution consumed in the blank, (ml); V —— Volume of HCl standard solution consumed by the sample, (ml); c —— Concentration of HCl standard solution, (mol / L); m —— Mass of the sample, (g).

[0040] Example 1 A polyurethane hot melt adhesive for suede composite board is prepared by the following method: Wipe the reaction kettle clean to ensure no foreign matters. Add 4 g of the first polyester polyol T-24, 6 g of the second polyester polyol Dynacoll 7130, 9 g of the third polyester polyol XCP-254, 8 g of polyether polyol CHE-204 with a molecular weight of 400, 46 g of polyether polyol CHE-210 with a molecular weight of 1000, 3 g of the first functional resin HS170, 2 g of the second functional resin Kristalex 3100, and 0.05 g of antioxidant C1035 into the reaction kettle. Heat up to 150 °C, start to evacuate, maintain a pressure of -0.1 MPa, turn on the stirrer, maintain a rotation speed of 400 r / min, stir for 2 h, take a sample to observe and confirm whether the raw materials are mixed evenly. When sampling, relieve the pressure of the reaction kettle, pick out 1 g of the sample with a glass rod, smear it on a smooth glass plate, and observe whether there are particles in the sample. If there are no particles, the sample is mixed evenly and the next step can be carried out.

[0041] 2) Cool the above system to 105 °C, stop evacuating, add 22 g of 4,4'-diphenylmethane diisocyanate, then continue to evacuate, maintain a pressure of -0.1 MPa, maintain a rotation speed of 150 r / min, react for at least 2 h, and take a sample to test the viscosity.

[0042] 3) Sampling for viscosity measurement starts at 2 h, and the reaction is terminated for discharging when the viscosity measured at 120 °C is between 4500 - 6500 CPS. If the viscosity does not meet the requirement, the reaction continues, and the viscosity is measured every half hour until the viscosity meets the requirement for discharging.

[0043] In this example, the test already met the standard after 2 h of reaction, and there was no need to continue the reaction.

[0044] The performance test results are shown in Table 1: Table 1 Performance Test Results of the Polyurethane Hot Melt Adhesive in Example 1 Project Remarks Index Reaction duration h 2 Viscosity CPS / 120℃ 5100 Open time min 13 Initial adhesion after 5 minutes N / 2.5cm 5.4 Final adhesion after 48 hours N / 2.5cm 29.7 Thermal aging Whether it is wire-drawing in an open environment at 120℃ for 2 hours No Humid heat aging N / 2.5cm 26.6 Low temperature resistance N / 2.5cm 31.5 NCO residue Free isocyanate content in polyurethane % 1.33 。

[0045] Example 2 A polyurethane hot melt adhesive for suede composite board is prepared by the following method: 1) Wipe the reaction kettle clean to ensure there are no foreign objects. Add 5 g of the first polyester polyol T - 24, 5 g of the second polyester polyol Dynacoll 7130, 7 g of the third polyester polyol XCP - 254, 58 g of the polyether polyol CHE - 210 with a molecular weight of 1000, 3 g of the first functional resin HS170, 2 g of the second functional resin Kristalex 3100, and 0.05 g of antioxidant C1035 into the reaction kettle. Heat up to 150 °C, start vacuum pumping, maintain a pressure of - 0.1 MPa, turn on the stirrer, maintain a rotation speed of 400 r / min, stir for 2 h, sample to observe and confirm whether the raw materials are mixed evenly. When sampling, relieve the pressure of the reaction kettle, pick out 1 g of the sample with a glass rod, smear it on a smooth glass plate, and observe whether there are particles in the sample. If there are no particles, the sample is mixed evenly and the next step can be carried out.

[0046] 2) Cool the above system to 105 °C, stop vacuum pumping, add 20 g of 4,4'-diphenylmethane diisocyanate, and then maintain the vacuum state, maintain a pressure of - 0.1 MPa, maintain a rotation speed of 150 r / min, and react for at least 2 h, sampling to test the viscosity.

[0047] 3) Sampling for viscosity measurement starts at 2 h, and the reaction is terminated for discharging when the viscosity measured at 120 °C is between 4500 - 6500 CPS. If the viscosity does not meet the requirement, the reaction continues, and the viscosity is measured every half hour until the viscosity meets the requirement for discharging.

[0048] In this example, the test already met the standard after 2 h of reaction, and there was no need to continue the reaction.

[0049] The performance test results are shown in Table 2: Table 2 Performance Test Results of the Polyurethane Hot Melt Adhesive in Example 2 Project Remarks Index Reaction duration h 2 Viscosity CPS / 120℃ 5700 Open time min 15 Initial adhesion after 5 minutes N / 2.5cm 2.3 Final adhesion after 48 hours N / 2.5cm 28.6 Thermal aging Whether it is wire-drawing in an open environment at 120℃ for 2 hours No Humid heat aging N / 2.5cm 26.7 Low temperature resistance N / 2.5cm 25.2 NCO residue Free isocyanate content in polyurethane % 1.35 。

[0050] Comparative Example 1 A polyurethane hot melt adhesive for suede composite board was prepared by the following method: 1) Wipe the reaction kettle clean to ensure no foreign matter. Add 5 g of the second polyester polyol Dynacoll 7130, 10 g of the third polyester polyol XCP-254, 8 g of the polyether polyol CHE-204 with a molecular weight of 400, 46 g of the polyether polyol CHE-210 with a molecular weight of 1000, 3 g of the first functional resin HS170, 2 g of the second functional resin Kristalex 3100, and 0.05 g of antioxidant C1035 into the reaction kettle. Heat up to 150 °C, start vacuum pumping, maintain a pressure of -0.1 MPa, turn on the stirrer, maintain a rotation speed of 400 r / min, stir for 2 h, take a sample to observe and confirm whether the raw materials are mixed evenly. When sampling, relieve the pressure of the reaction kettle, pick out 1 g of the sample with a glass rod, smear it on a smooth glass plate, and observe whether there are particles in the sample. If there are no particles, the sample is mixed evenly and the next step can be carried out.

[0051] 2) Cool the above system to 105 °C, stop vacuum pumping, add 21.5 g of 4,4'-diphenylmethane diisocyanate, and then maintain the vacuum state, maintain a pressure of -0.1 MPa, maintain a rotation speed of 150 r / min, and react for at least 2 h. Take a sample to test the viscosity.

[0052] 3) Start sampling to measure the viscosity at 2 h. Terminate the reaction and discharge the material when the viscosity is measured at 4500 - 6500 CPS at 120 °C. If the viscosity does not meet the requirement, continue the reaction, measure the viscosity every half hour until the viscosity meets the requirement and then discharge the material.

[0053] In this comparative example, the test already met the standard after reacting for 2 h, and there was no need to continue the reaction.

[0054] The performance test results are shown in Table 3: Table 3 Performance test results of the polyurethane hot melt adhesive in Comparative Example 1 Project Remarks Index Reaction duration h 2 Viscosity CPS / 120℃ 5900 Open time min 10 Initial adhesion after 5 minutes N / 2.5cm 6.2 Final adhesion after 48 hours N / 2.5cm 25.4 Thermal aging Whether it is wire-drawing in an open environment at 120℃ for 2 hours No Humid heat aging N / 2.5cm 21.2 Low temperature resistance N / 2.5cm 24.0 NCO residue Free isocyanate content in polyurethane % 1.37 。

[0055] Comparative Example 2 A polyurethane hot melt adhesive for suede composite board was prepared by the following method: Wipe the reaction kettle clean to ensure there are no foreign objects. Add 4 g of the first polyester polyol T-24, 6 g of the second polyester polyol Dynacoll 7130, 9 g of the third polyester polyol XCP-254, 8 g of polyether polyol CHE-204 with a molecular weight of 400, 46 g of polyether polyol CHE-210 with a molecular weight of 1000, 3 g of the first functional resin HS170, 2 g of hydrogenated terpene resin BT35DX, and 0.05 g of antioxidant C1035 into the reaction kettle. Heat up to 150 °C, start vacuum pumping, maintain a pressure of -0.1 MPa, turn on the stirring, maintain a rotation speed of 400 r / min, stir for 2 h, take a sample to observe and confirm whether the raw materials are evenly mixed. When sampling, relieve the pressure of the reaction kettle, pick out 1 g of the sample with a glass rod, smear it on a smooth glass plate, and observe whether there are particles in the sample. When observing the sample, a large number of white, loose flocculent particulate matters are found, and they still exist when the stirring time is extended to 3 h and do not redissolve into the system, so the reaction cannot continue, and thus the reaction stops and proceeds to the next step.

[0056] Comparative Example 3 A polyurethane hot melt adhesive for suede composite board is prepared by the following method: Steps 1) and 2) are carried out in the same way as in Example 1.

[0057] 3) Start sampling to measure the viscosity at 2 h, terminate the reaction and discharge the material when the viscosity is measured at 4500 - 6500 CPS at 120 °C. If the viscosity does not meet the requirement, continue the reaction, measure the viscosity every half hour until the viscosity meets the requirement and then discharge the material.

[0058] In this comparative example, the test already meets the standard after reacting for 2 h, and there is no need to continue the reaction.

[0059] 4) After the viscosity meets the requirement, add 0.5 g of DMDEE catalyst, maintain a rotation speed of 150 r / min, maintain at 105 °C, and stir for 10 minutes to discharge the material.

[0060] The performance test results are shown in Table 4: Table 4 Performance test results of the polyurethane hot melt adhesive in Comparative Example 3 Project Remarks Index Reaction duration h 2 Viscosity CPS / 120℃ 6700 Open time min 8 Initial adhesion after 5 minutes N / 2.5cm 5.9 Final adhesion after 48 hours N / 2.5cm 30.2 Thermal aging Whether it is wire-drawing in an open environment at 120℃ for 2 hours Yes Humid heat aging N / 2.5cm 33.1 Low temperature resistance N / 2.5cm 27.7 NCO residue Free isocyanate content in polyurethane % 1.32 Especially, due to the addition of the catalyst, the reaction is more rapid, resulting in the viscosity of the system reaching 6700 after adding the catalyst, exceeding the specified viscosity range.

[0061] Comparative Example 4 A polyurethane hot melt adhesive for suede composite board is prepared by the following method: Steps 1) and 2) are carried out in the same way as in Example 1, except that 0.5 g of defoamer YCK-630 is also added to the raw materials added in step 1) of this comparative example.

[0062] 3) Sampling for viscosity measurement starts at 2 h, and the reaction is terminated and the product is discharged when the viscosity measured at 120 °C is between 4500 - 6500 CPS. If the viscosity does not meet the requirement, the reaction continues, and the viscosity is measured every half hour until the viscosity meets the requirement and then the product is discharged.

[0063] In this comparative example, the test after 2 h of reaction already met the standard, and there was no need to continue the reaction.

[0064] The performance test results are as follows: Table 5 Performance test results of the polyurethane hot melt adhesive in Comparative Example 4 Project Remarks Index Reaction duration h 2 Viscosity CPS / 120℃ 5100 Open time min 13 Initial adhesion after 5 minutes N / 2.5cm 5.5 Final adhesion after 48 hours N / 2.5cm 31.1 Thermal aging Whether it is wire-drawing in an open environment at 120℃ for 2 hours No Humid heat aging N / 2.5cm 20.4 Low temperature resistance N / 2.5cm 19.6 NCO residue Free isocyanate content in polyurethane % 1.34 ; Through the comparison between Example 1 and Comparative Example 1, it can be clearly seen that after the first polyester polyol, the second polyester polyol, and the third polyester polyol are compounded, the effect of improving the adhesion is higher than that of the compounding of the second polyester polyol and the third polyester polyol. Because the first polyester polyol and the first functional resin have similar unit structures and similar polarities, there is a synergistic effect on the improvement of adhesion, making the product performance higher than that of only using the second polyester polyol and the third polyester polyol in compounding.

[0065] Through the comparison between Example 1 and Example 2, it can be clearly seen that the adhesion of choosing a single polyether polyol is lower than the bonding strength of adjusting the overall molecular weight by using a combined polyether polyol. The ratio in Example 1 is a more suitable ratio obtained through multiple experiments.

[0066] Through the comparison between Example 1 and Comparative Example 2, it can be clearly seen that the hydrogenated terpene resin is not stable in the system, while the monomer resin has good compatibility with various materials in the system. Therefore, it is necessary to replace the hydrogenated terpene resin with a functional resin.

[0067] Through the comparison between Example 1 and Comparative Example 3, it can be clearly seen that although the adhesion is improved after adding the catalyst, the heat aging performance becomes extremely poor, which may cause problems in large-scale production. Therefore, no catalyst is added in this scheme.

[0068] Through the comparison between Example 1 and Comparative Example 4, it can be clearly seen that although the adhesion strength is improved in the short term after adding the defoamer, the strength attenuation of the 168-hour damp heat aging and low-temperature resistance is too serious. Therefore, no defoamer is added in this scheme.

[0069] The sample prepared by the present invention is a colorless, transparent, slightly white, and highly fluid liquid at 120°C. In the formulation of the present invention, most of the additives are removed from the formulation to prevent the influence on the initial adhesion due to later migration, aging, etc. and to ensure the stability of the PUR. Secondly, a special functional resin is introduced to make the compatibility of the system better, the viscosity lower, and the adhesion stronger, so that the PUR can maintain a lower viscosity under the condition of low NCO residue, which is beneficial to the subsequent spraying use of the product.

[0070] The PUR prepared by the present invention has a viscosity of 4500 - 6500 CPS / 120°C, an open time of 10 - 15 minutes, which is basically similar to the same type of products on the market. The final adhesion force is about 30 N, and the bonding strength is slightly better than that of the same type of products. Moreover, compared with the same type of products, the PUR prepared by the present invention has better thermal stability and more excellent thermal aging performance, and has better performance in high-temperature spraying use.

[0071] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any equivalent replacement, modification, etc. made by those skilled in the art without any creative work within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A polyurethane hot melt adhesive for suede composite panels, characterized in that: By weight, the raw materials include 10-20 parts of polyester polyol, 50-60 parts of polyether polyol, 2-5 parts of functional resin, 20-30 parts of isocyanate, and 0.01-0.05 parts of antioxidant; The polyester polyol is a composite of a first polyester polyol, a second polyester polyol and a third polyester polyol, wherein the first polyester polyol is a liquid polyester polyol with a molecular weight of 2000; the second polyester polyol is an amorphous polyester polyol with a molecular weight of 2000-3000; and the third polyester polyol is a crystalline polyester polyol with a molecular weight of 3500-5000.

2. The polyurethane hot melt adhesive according to claim 1, characterized in that: The polyester polyol comprises 2-7 parts of a first polyester polyol, 2-7 parts of a second polyester polyol, and 5-10 parts of a third polyester polyol.

3. The polyurethane hot melt adhesive according to claim 1, characterized in that: The first polyester polyol is selected from one or more of T-24 of Huada Chemical, HDPOL-5520M, HDPOL-9520, and HDPOL-6315 of Huide Technology; The second polyester polyol is selected from one or more of Dynacoll 7130 of Evonik, CJPOL-2020, CJPOL-520 of Fujian Chengjie Polymer, and HDPOL-2430 of Huide Technology; The third polyester polyol is selected from one or more of Dynacoll 7380 of Evonik, HDPOL-338 of Huide Technology, XCP-254, XCP-2200NH and XCP-3000H of Asahikawa Chemical.

4. The polyurethane hot melt adhesive according to claim 1, characterized in that: The polyether polyol is polyethylene glycol, and its molecular weight is 400-2000.

5. The polyurethane hot melt adhesive according to claim 1 or 4, characterized in that: The polyether polyol is selected from polyethylene glycol with a molecular weight of 400 and / or polyethylene glycol with a molecular weight of 1000.

6. The polyurethane hot melt adhesive according to claim 5, characterized in that: The polyethylene glycol with a molecular weight of 400 is CHE-204 produced by Changhua Chemical, and the polyethylene glycol with a molecular weight of 1000 is CHE-210 produced by Changhua Chemical; the mass ratio of the polyethylene glycol with a molecular weight of 400 to the polyethylene glycol with a molecular weight of 1000 is 4:

23.

7. The polyurethane hot melt adhesive according to claim 1, characterized in that: The functional resin is one or a combination of a first functional resin and a second functional resin, wherein the first functional resin is a hot-melt copolyester with a molecular weight of 15,000-25,000, and the second functional resin is a pure monomer resin; The functional resin comprises 1-4 parts of a first functional resin and 1-4 parts of a second functional resin.

8. The polyurethane hot melt adhesive according to claim 7, characterized in that: The first functional resin is selected from one or more of HS260, HS270, HS560, HS170, HS171 of Hanhai New Materials, and 50293C of Changxing Technology; the second functional resin is poly-α-methylstyrene, selected from one or more of Kristalex 3085, Kristalex 3100, Kristalex3105, Kristalex 3115, Kristalex 1120, and Kristalex 5140 of Eastman.

9. The polyurethane hot melt adhesive according to claim 1, characterized in that: The antioxidant is a phenolic antioxidant, selected from one or more of BASF's C1010 and C1035; The isocyanate is a diisocyanate, selected from one or more of diphenylmethane diisocyanate, isophorone diisocyanate and toluene diisocyanate.

10. A method for preparing the polyurethane hot melt adhesive for suede composite board material according to claim 1, characterized in that: The following steps are involved: (1) Add polyester polyol, polyether polyol, functional resin and antioxidant into the reaction kettle, raise the temperature to 140-150°C, start vacuuming, maintain the system pressure at -0.096 to -0.1MPa, start stirring, maintain the speed at 400-500 r / min, stir for 2-2.5h, until all the raw materials are evenly mixed; (2) After mixing evenly, the system is cooled to 100-105°C, the vacuum is stopped, isocyanate is added, and the vacuum is continued. The system pressure is maintained at -0.096 to -0.1MPa, and the rotation speed is maintained at 150-200 r / min. The reaction is carried out for at least 2 hours. After 2 hours of reaction, samples are taken for viscosity testing. The material can be discharged when the viscosity reaches 4500-6500 CPS / 120°C.

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