Dispensing non-wire-drawing PUR hot melt adhesive and preparation method thereof

Abstract

This invention specifically relates to a non-stringing PUR hot melt adhesive and its preparation method. The non-stringing PUR hot melt adhesive comprises the following raw materials in parts by weight: 40-60 parts of polyether polyol, 10-20 parts of crystalline polyester polyol, 12-30 parts of isocyanate, 20-30 parts of thermoplastic tackifying resin, 3-6 parts of maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, 2-4 parts of TPU, 1.5-4 parts of nano-silica, 0.2-0.8 parts of catalyst, 0.1-0.5 parts of defoamer, 0.2-0.6 parts of antioxidant, and 0.5-1.5 parts of silane coupling agent. The PUR hot melt adhesive prepared by this invention has the characteristics of low viscosity, non-stringing during dispensing, and good adhesive strength and mechanical properties, making it suitable for precision dispensing. The preparation method of the PUR hot melt adhesive is stable, easy to operate and control, has high production efficiency, and is conducive to large-scale production.

Description

Technical Field

[0001] This invention relates to the field of hot melt adhesive technology, specifically to a non-stringing PUR hot melt adhesive and its preparation method. Background Technology

[0002] Polyurethane reactive hot melt adhesive (PUR hot melt adhesive) is a high-performance adhesive material widely used in the production processes of mobile phones, wearable devices, and tablet computer frames. It possesses excellent adhesion, weather resistance, solvent resistance, and high and low temperature performance. However, in actual application, PUR hot melt adhesive often exhibits stringing, primarily due to factors such as the viscosity, cohesive strength, shrinkage, and rheological properties of the molten adhesive. Current technologies often employ methods such as increasing equipment temperature, reducing adhesive viscosity, or wiping the dispensing nozzle after each application to prevent stringing and contamination of structural components. These methods often require precise control in practical applications and may not completely eliminate stringing, complicating the process, reducing production efficiency and quality, and affecting process stability and equipment aging. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of the prior art by providing a non-stringing PUR hot melt adhesive and its preparation method. The hot melt adhesive has good adhesive and mechanical properties and can effectively solve the stringing problem of PUR hot melt adhesive during use, thereby improving production efficiency and product quality. The preparation method of the PUR hot melt adhesive is easy to operate, has high production efficiency, and is conducive to large-scale production.

[0004] The objective of this invention is achieved through the following technical solution, comprising the following raw materials in parts by weight: 40-60 parts polyether polyol, 10-20 parts crystalline polyester polyol, 12-30 parts isocyanate, 20-30 parts thermoplastic tackifying resin, 3-6 parts maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, 2-4 parts TPU, 1.5-4 parts nano-silica, 0.2-0.8 parts catalyst, 0.1-0.5 parts defoamer, 0.2-0.6 parts antioxidant, and 0.5-1.5 parts silane coupling agent.

[0005] Furthermore, the polyether polyol is at least one of polypropylene glycol and polytetrahydrofuran ether glycol.

[0006] Furthermore, the polypropylene oxide diol has a weight-average molecular weight of 400-2000, and the polytetrahydrofuran ether diol has a weight-average molecular weight of 500-2000.

[0007] Furthermore, the polypropylene oxide diol has a weight-average molecular weight of 400-1000, and the polytetrahydrofuran ether diol has a weight-average molecular weight of 500-1000.

[0008] Furthermore, the crystalline polyester polyol is at least one selected from polybutylene adipate diol, polyethylene adipate diol, and 1,6-hexanediol polycarbonate diol. The crystalline polyester polyol has a weight-average molecular weight of 600-3000 and a melting point of 40-80°C.

[0009] Furthermore, the isocyanate monomer is at least one selected from toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoflurane diisocyanate, dicyclohexylmethane diisocyanate, and carbodiimide-modified 4,4'-diphenylmethane diisocyanate.

[0010] Furthermore, the thermoplastic tackifying resin is at least one selected from rosin resin, methyl styrene oligomer, petroleum resin, terpene-styrene resin, polyethylene terephthalate, and ethylene-vinyl acetate copolymer resin. This invention helps improve the adhesive properties of the adhesive by adding an appropriate proportion of tackifying resin to the PUR hot melt adhesive system. The softening point of the thermoplastic tackifying resin is 60-120℃.

[0011] Furthermore, the silane coupling agent is at least one selected from γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. This invention, by employing maleic anhydride-grafted acrylonitrile-butadiene-styrene and silane coupling agents, helps to improve the mechanical properties and adhesive strength of hot melt adhesives.

[0012] Furthermore, the antioxidant is at least one selected from antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 626, and antioxidant DSTDP. By employing the above-mentioned antioxidants, this invention can effectively prevent the hot melt adhesive from degrading due to oxidation during storage and use, thus helping to improve product stability and extend its service life.

[0013] Furthermore, the catalyst is at least one selected from bismorpholino diethyl ether and dibutyltin dilaurate. By employing the above-mentioned catalyst in the hot melt adhesive reaction system, this invention can effectively control the reaction rate of the system, shorten the open time, and enable the reaction system to quickly form a stable structure after curing.

[0014] This invention combines polyether polyol, crystalline polyester polyol, and isocyanate, and blends them with thermoplastic tackifying resin, maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, TPU (polyurethane elastomer), nano silica, and other raw materials. By carefully designing the dosage of each raw material, the low cohesive strength, high crystallization shrinkage, and low modulus of the PUR hot melt adhesive are controlled. The resulting PUR hot melt adhesive has the characteristics of smooth dispensing and no stringing, while also having good adhesive strength and heat resistance, making it suitable for precision dispensing. The invention employs low-molecular-weight polyether polyols to provide soft chain segments, reducing molecular chain length and entanglement, and lowering melt cohesion. The use of crystalline polyester polyols to provide highly crystalline materials, combined with nano-silica, improves shrinkage uniformity, resulting in better shrinkage performance of the adhesive. A small amount of adhesive remaining at the dispensing nozzle shrinks instantly, reducing adhesive residue at the nozzle tip and effectively minimizing the need for traditional wiping processes. The use of isocyanate to control the NCO / OH ratio ensures appropriate cross-linking, balancing modulus and bond strength. Adding an appropriate proportion of tackifying resin enhances the adhesive's bonding performance. Furthermore, by grafting maleic anhydride-acrylonitrile-butadiene-styrene copolymer with TPU, nano-silica, and other raw materials, the invention achieves excellent compatibility, improving the mechanical properties and bond strength of the adhesive, suppressing stringing, and effectively improving dispensing smoothness.

[0015] The present invention also provides a method for preparing the above-mentioned non-stringing PUR hot melt adhesive, comprising the following steps:

[0016] (1) Add polyether polyol and crystalline polyester polyol to a reaction vessel, stir evenly at 115-125℃, then add thermoplastic tackifying resin and stir evenly to obtain mixture one.

[0017] (2) Maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer was added to mixture one and sheared and dispersed at 125-135℃. Then nano-silica was added and sheared and dispersed to obtain mixture two.

[0018] (3) Reduce the temperature inside the reaction vessel to 75-85℃, add isocyanate to mixture two and stir until the -NCO content of the system reaches 95% of the theoretical value, and obtain mixture three;

[0019] (4) Reduce the temperature inside the reaction vessel to 65-74℃, add antioxidant, defoamer and silane coupling agent to mixture three and stir evenly, then add catalyst and stir evenly to obtain mixture four;

[0020] (5) The mixture is degassed under vacuum and then cooled to 50-60°C. It is then granulated by an extruder and discharged to obtain a non-stringing PUR hot melt adhesive.

[0021] The polyether polyol and crystalline polyester polyol described in this invention are both preheated and dried; the maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer is preheated at 60-70°C for 20-40 minutes.

[0022] Furthermore, in step (1), polyether polyol and crystalline polyester polyol are added to the reaction vessel and stirred at 115-125°C for 10-20 minutes at a stirring speed of 300-400 rpm. Then, thermoplastic tackifying resin is added and stirred for 30-40 minutes at a stirring speed of 400-500 rpm.

[0023] Further, in step (2), maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer is added to mixture one and subjected to high-speed shear dispersion at 125-135℃ for 20-30 min at a shear dispersion speed of 1000-1300 rpm; then nano silica is added and subjected to high-speed shear dispersion for 20-30 min at a shear dispersion speed of 1000-1300 rpm to obtain mixture two.

[0024] Furthermore, in step (3), isocyanate is slowly added dropwise to mixture two over a period of 30-50 minutes while stirring at a speed of 300-500 rpm.

[0025] Further, in step (4), antioxidants and defoamers are added to mixture three and stirred for 5-10 minutes at a stirring speed of 400-600 rpm. Then, silane coupling agent is added and stirred for 5-10 minutes at a stirring speed of 400-600 rpm. Then, catalyst is added and stirred for 4-8 minutes at a stirring speed of 400-600 rpm to obtain mixture four.

[0026] Furthermore, in step (5), the vacuum degree of vacuum degassing is -0.07 to -0.09 MPa, and the degassing time is 20-40 min until no bubbles escape.

[0027] This invention utilizes the above-mentioned amounts of raw materials and steps, and controls the process parameters of each step to ensure that the raw materials are evenly dispersed and well-matched. The process is stable, easy to operate, and has high production efficiency. The resulting hot melt adhesive has good bonding strength and heat resistance, and reduces the phenomenon of glue stringing.

[0028] The beneficial effects of this invention are as follows: This invention combines polyether polyol, crystalline polyester polyol, and isocyanate, and blends them with thermoplastic tackifying resin, TPU, maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, etc., to prepare a PUR hot melt adhesive with low viscosity, no stringing during dispensing, smooth dispensing, and good adhesive strength and mechanical properties, making it suitable for precision dispensing. The preparation method of the PUR hot melt adhesive is stable, easy to operate and control, has high production efficiency, and is conducive to large-scale production. Detailed Implementation

[0029] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0030] In some embodiments of the present invention, a non-stringy PUR hot melt adhesive comprises the following raw materials in parts by weight: 40-60 parts of polyether polyol, 10-20 parts of crystalline polyester polyol, 12-30 parts of isocyanate, 20-30 parts of thermoplastic tackifying resin, 3-6 parts of maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, 2-4 parts of TPU, 1.5-4 parts of nano-silica, 0.2-0.8 parts of catalyst, 0.1-0.5 parts of defoamer, 0.2-0.6 parts of antioxidant, and 0.5-1.5 parts of silane coupling agent. The particle size of the nano-silica is 30-60 nm.

[0031] In some embodiments of the present invention, the polyether polyol is at least one of polypropylene oxide diol and polytetrahydrofuran ether diol. The polypropylene oxide diol has a weight-average molecular weight of 400-2000, and the polytetrahydrofuran ether diol has a weight-average molecular weight of 500-2000.

[0032] In some embodiments of the present invention, the polyether polyol is composed of polypropylene glycol and polytetrahydrofuran ether glycol in a mass ratio of 1-3:1.

[0033] In some embodiments of the present invention, the polypropylene oxide diol has a weight-average molecular weight of 400-1000, and the polytetrahydrofuran ether diol has a weight-average molecular weight of 500-1000.

[0034] In some embodiments of the present invention, the crystalline polyester polyol is at least one selected from polybutylene adipate diol, polyethylene adipate diol, and 1,6-hexanediol polycarbonate diol. The crystalline polyester polyol has a weight-average molecular weight of 600-3000 and a melting point of 40-80°C.

[0035] In some embodiments of the present invention, the crystalline polyester polyol is composed of polybutylene adipate diol and poly(1,6-hexanediol carbonate) diol in a mass ratio of 2-5:1.

[0036] In some embodiments of the present invention, the isocyanate monomer is at least one selected from toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoflurane diisocyanate, dicyclohexylmethane diisocyanate, and carbodiimide-modified 4,4'-diphenylmethane diisocyanate.

[0037] In some embodiments of the present invention, the isocyanate monomer is composed of toluene diisocyanate and hexamethylene diisocyanate in a weight ratio of 1-2:1.

[0038] In some embodiments of the present invention, the thermoplastic tackifying resin is at least one selected from rosin resin, methylstyrene oligomer, petroleum resin, terpene-styrene resin, polyethylene terephthalate, and ethylene-vinyl acetate copolymer resin. The softening point of the thermoplastic tackifying resin is 60-120°C.

[0039] In some embodiments of the present invention, the thermoplastic tackifying resin is composed of rosin resin, terpene-styrene resin, and petroleum resin in a weight ratio of 1-2:1-2:1.

[0040] In some embodiments of the present invention, the silane coupling agent is at least one selected from γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0041] In some embodiments of the present invention, the antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 626 and antioxidant DSTDP.

[0042] In some embodiments of the present invention, the catalyst is at least one of bismorpholino diethyl ether and dibutyltin dilaurate.

[0043] In some embodiments of the present invention, a method for preparing the above-mentioned non-stringing PUR hot melt adhesive is provided, comprising the following steps:

[0044] (1) Add polyether polyol and crystalline polyester polyol to the reaction vessel, stir at 115-125℃ for 10-20 min at a stirring speed of 300-400 rpm, then add thermoplastic tackifying resin and stir for 30-40 min at a stirring speed of 400-500 rpm.

[0045] (2) Add maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer to mixture one, and perform high-speed shear dispersion at 125-135℃ for 20-30 min, with a shear dispersion speed of 1000-1300 rpm; then add nano silica and perform high-speed shear dispersion for 20-30 min, with a shear dispersion speed of 1000-1300 rpm to obtain mixture two;

[0046] (3) Reduce the temperature inside the reaction vessel to 75-85℃, add isocyanate to mixture two and stir until the -NCO content of the system reaches 95% of the theoretical value, and obtain mixture three;

[0047] (4) Reduce the temperature inside the reaction vessel to 65-74℃, add antioxidant, defoamer and silane coupling agent to mixture three and stir evenly, then add catalyst and stir evenly to obtain mixture four;

[0048] (5) Degas the mixture under vacuum and then cool it to 50-60°C. Granulate it using an extruder and discharge it to obtain a non-stringing PUR hot melt adhesive. Pack the obtained PUR hot melt adhesive into a sealed container for later use.

[0049] In some embodiments of the present invention, the polyether polyol and the crystalline polyester polyol are both preheated and dried. The maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer is preheated at 60-70°C for 20-40 minutes.

[0050] In some embodiments of the present invention, in step (3), isocyanate is slowly added dropwise to mixture two over a period of 30-50 minutes while being stirred at a speed of 300-500 rpm.

[0051] In some embodiments of the present invention, in step (4), after adding the silane coupling agent, the mixture is stirred for 5-10 minutes, and then the catalyst is added and stirred for 4-8 minutes at a stirring speed of 400-600 rpm to obtain mixture four.

[0052] In some embodiments of the present invention, in step (5), the vacuum degree of vacuum degassing is -0.07 to -0.09 MPa, the degassing time is 20-40 min, until no bubbles escape.

[0053] The polyether polyol and crystalline polyester polyol described in this invention are both preheated and dried; the maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer is preheated at 60-70°C for 20-40 minutes.

[0054] Example 1

[0055] This embodiment provides a non-stringy PUR hot melt adhesive, comprising the following raw materials in parts by weight: 50 parts polyether polyol, 13 parts crystalline polyester polyol, 14 parts isocyanate, 24 parts thermoplastic tackifying resin, 5 parts maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, 3 parts TPU, 2 parts nano silica, 0.6 parts catalyst, 0.3 parts defoamer, 0.4 parts antioxidant, and 1 part silane coupling agent. The nano silica has a particle size of 30-60 nm. The TPU used is BASF TPU1185A. The maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer is Shengli New Materials M400A ABS-g-MAH.

[0056] Furthermore, the polyether polyol is composed of polypropylene oxide diol and polytetrahydrofuran ether diol in a mass ratio of 2:1. The polypropylene oxide diol is Jiangsu Haian County Petrochemical PPG-600; the polytetrahydrofuran ether diol is BASF PolyTHF 1000.

[0057] Furthermore, the crystalline polyester polyol is composed of polybutylene adipate diol and poly(1,6-hexanediol carbonate) diol in a mass ratio of 3:1. The molecular weight of the polybutylene adipate diol is 800; the poly(1,6-hexanediol carbonate) diol is Ube UH-CARB200.

[0058] Furthermore, the isocyanate monomer is composed of toluene diisocyanate and hexamethylene diisocyanate in a weight ratio of 3:2, which improves the thermal stability of the hard segment.

[0059] Furthermore, the thermoplastic tackifying resin is composed of rosin resin, terpene-styrene resin, and petroleum resin in a weight ratio of 2:2:1. The rosin resin is pentaerythritol rosin ester P-100; the petroleum resin is C5 petroleum resin PR-80; and the terpene-styrene resin is terpene-styrene resin TR-80.

[0060] Furthermore, the silane coupling agent is composed of γ-mercaptopropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane in a weight ratio of 1:1.

[0061] Furthermore, the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 7:3. The catalyst is composed of bismorpholino diethyl ether and dibutyltin dilaurate in a weight ratio of 3:2. The defoamer is BYK-1790.

[0062] This embodiment also provides a method for preparing the above-mentioned non-stringing PUR hot melt adhesive, including the following steps:

[0063] (1) Add polyether polyol and crystalline polyester polyol to the reaction vessel, stir at 120°C for 15 min at a stirring speed of 300 rpm, then add thermoplastic tackifying resin and stir for 30 min at a stirring speed of 400 rpm.

[0064] (2) Maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer was added to mixture one and high-speed shear dispersion was carried out at 130°C for 25 min at a shear dispersion speed of 1100 rpm; then nano silica was added and high-speed shear dispersion was carried out for 25 min at a shear dispersion speed of 1100 rpm to obtain mixture two.

[0065] (3) Reduce the temperature inside the reaction vessel to 80°C, add isocyanate to mixture two and stir until the -NCO content of the system reaches 95% of the theoretical value, and obtain mixture three;

[0066] (4) Reduce the temperature inside the reaction vessel to 70°C, add antioxidant, defoamer and silane coupling agent to mixture three and stir evenly, then add catalyst and stir evenly to obtain mixture four;

[0067] (5) The mixture is degassed under vacuum and then cooled to 50°C. It is then granulated by a twin-screw extruder and discharged to obtain non-stringing PUR hot melt adhesive granules with a particle diameter of 3-5 mm. The obtained PUR hot melt adhesive is then placed in a sealed container for later use.

[0068] In this embodiment, both the polyether polyol and the crystalline polyester polyol were preheated and dried. The maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer was preheated at 60°C for 30 minutes.

[0069] Furthermore, in step (3), isocyanate is slowly added dropwise to mixture two over a period of 35 minutes while stirring at a speed of 400 rpm.

[0070] Furthermore, in step (4), antioxidants and defoamers are added to mixture three and stirred for 8 minutes at a stirring speed of 500 rpm. Silane coupling agent is added and stirred for 7 minutes. Catalyst is then added and stirred for 5 minutes at a stirring speed of 500 rpm to obtain mixture four.

[0071] Furthermore, in step (5), the vacuum degree of vacuum degassing is -0.09MPa, the degassing time is 20min, until no bubbles escape.

[0072] Example 2

[0073] This embodiment provides a non-stringing PUR hot melt adhesive, comprising the following raw materials in parts by weight: 45 parts polyether polyol, 10 parts crystalline polyester polyol, 12.5 parts isocyanate, 22 parts thermoplastic tackifying resin, 3 parts maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, 2 parts TPU, 1.5 parts nano silica, 0.4 parts catalyst, 0.2 parts defoamer, 0.3 parts antioxidant, and 0.8 parts silane coupling agent.

[0074] Furthermore, the polyether polyol is composed of polypropylene glycol and polytetrahydrofuran ether glycol in a weight ratio of 3:2.

[0075] Furthermore, the crystalline polyester polyol is composed of polybutylene adipate diol and poly(1,6-hexanediol carbonate) diol in a mass ratio of 3:1.

[0076] Furthermore, the thermoplastic tackifying resin is composed of rosin resin, terpene-styrene resin, and petroleum resin in a weight ratio of 2:1.5:1.

[0077] Furthermore, the silane coupling agent is γ-mercaptopropyltrimethoxysilane. The antioxidant is composed of antioxidant 1010 and antioxidant DSTDP in a weight ratio of 7:3. The catalyst is composed of bismorpholino diethyl ether and dibutyltin dilaurate in a weight ratio of 2:1. The defoamer is BYK-1790.

[0078] This embodiment also provides a method for preparing the above-mentioned non-stringing PUR hot melt adhesive, including the following steps:

[0079] (1) Add polyether polyol and crystalline polyester polyol to the reaction vessel, stir at 115°C for 20 min at a stirring speed of 400 rpm, then add thermoplastic tackifying resin and stir for 30 min at a stirring speed of 400 rpm.

[0080] (2) Maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer was added to mixture one and high-speed shear dispersion was carried out at 125°C for 20 min at a shear dispersion speed of 1200 rpm; then nano silica was added and high-speed shear dispersion was carried out for 20 min at a shear dispersion speed of 1200 rpm to obtain mixture two.

[0081] (3) Reduce the temperature inside the reaction vessel to 75°C, add isocyanate to mixture two and stir until the -NCO content of the system reaches 95% of the theoretical value, and obtain mixture three;

[0082] (4) Reduce the temperature inside the reaction vessel to 65°C, add antioxidant, defoamer and silane coupling agent to mixture three and stir evenly, then add catalyst and stir evenly to obtain mixture four;

[0083] (5) The mixture is degassed under vacuum and then cooled to 50-60°C. It is then granulated by an extruder and discharged to obtain a non-stringing PUR hot melt adhesive.

[0084] Furthermore, in step (3), isocyanate is slowly added dropwise to mixture two over a period of 40 minutes while stirring at a speed of 400 rpm.

[0085] The rest of this embodiment is the same as that in Embodiment 1.

[0086] Example 3

[0087] This embodiment provides a non-stringy PUR hot melt adhesive, comprising the following raw materials in parts by weight: 55 parts polyether polyol, 16 parts crystalline polyester polyol, 16 parts isocyanate, 26 parts thermoplastic tackifying resin, 5 parts maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, 3.5 parts TPU, 2.5 parts nano silica, 0.6 parts catalyst, 0.4 parts defoamer, 0.3 parts antioxidant, and 1.5 parts silane coupling agent.

[0088] Furthermore, the polyether polyol is composed of polypropylene oxide diol and polytetrahydrofuran ether diol in a mass ratio of 2:1. The polypropylene oxide diol is Hengyu Chemical PPG-600; the polytetrahydrofuran ether diol is BASF PolyTHF 1000.

[0089] Furthermore, the crystalline polyester polyol is composed of polybutylene adipate diol and poly(1,6-hexanediol carbonate) diol in a mass ratio of 4:1.

[0090] Furthermore, the isocyanate monomer is composed of toluene diisocyanate and hexamethylene diisocyanate in a weight ratio of 3:2.

[0091] Furthermore, the thermoplastic tackifying resin is composed of rosin resin, terpene-styrene resin, and petroleum resin in a weight ratio of 2:2:1.

[0092] Furthermore, the silane coupling agent is composed of γ-mercaptopropyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane in a weight ratio of 2:1.

[0093] Furthermore, the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 7:3. The catalyst is composed of bismorpholino diethyl ether and dibutyltin dilaurate in a weight ratio of 3:2. The defoamer is BYK-1790.

[0094] This embodiment also provides a method for preparing the above-mentioned non-stringing PUR hot melt adhesive, including the following steps:

[0095] (1) Add polyether polyol and crystalline polyester polyol to the reaction vessel, stir at 125°C for 10 min at a stirring speed of 400 rpm, then add thermoplastic tackifying resin and stir for 35 min at a stirring speed of 400 rpm.

[0096] (2) Maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer was added to mixture one and high-speed shear dispersion was carried out at 135℃ for 20 min at a shear dispersion speed of 1100 rpm; then nano silica was added and high-speed shear dispersion was carried out for 20 min at a shear dispersion speed of 1100 rpm to obtain mixture two.

[0097] (3) Reduce the temperature inside the reaction vessel to 80°C, add isocyanate to mixture two and stir until the -NCO content of the system reaches 95% of the theoretical value, and obtain mixture three;

[0098] (4) Reduce the temperature inside the reaction vessel to 72°C, add antioxidant, defoamer and silane coupling agent to mixture three and stir evenly, then add catalyst and stir evenly to obtain mixture four;

[0099] (5) The mixture is degassed under vacuum and then cooled to 60°C. It is then granulated by a twin-screw extruder and discharged to obtain non-stringing PUR hot melt adhesive granules with a particle diameter of 3-5 mm. The obtained PUR hot melt adhesive is then placed in a sealed container for later use.

[0100] Furthermore, in step (3), isocyanate is slowly added dropwise to mixture two over a period of 45 minutes while stirring at a speed of 400 rpm.

[0101] Furthermore, in step (5), the vacuum degree of vacuum degassing is -0.09MPa, the degassing time is 25min, until no bubbles escape.

[0102] The rest of this embodiment is the same as that in Embodiment 1.

[0103] Example 4

[0104] This embodiment provides a non-stringing PUR hot melt adhesive, comprising the following raw materials in parts by weight: 50 parts polyether polyol, 15 parts crystalline polyester polyol, 22.7 parts isocyanate, 24 parts thermoplastic tackifying resin, 5 parts maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, 3 parts TPU, 2 parts nano silica, 0.6 parts catalyst, 0.3 parts defoamer, 0.4 parts antioxidant, and 1 part silane coupling agent.

[0105] Furthermore, the polyether polyol is composed of polypropylene oxide diol and polytetrahydrofuran ether diol in a mass ratio of 2:1.5. The polypropylene oxide diol is Jiangsu Haian County Petrochemical PPG-400; the polytetrahydrofuran ether diol is BASF PolyTHF 1000.

[0106] Furthermore, the crystalline polyester polyol is composed of polybutylene adipate diol and poly(1,6-hexanediol carbonate) diol in a mass ratio of 4:1.

[0107] Furthermore, the isocyanate monomer is composed of toluene diisocyanate and hexamethylene diisocyanate in a weight ratio of 3:2.

[0108] Furthermore, the thermoplastic tackifying resin is composed of rosin resin, terpene-styrene resin, and petroleum resin in a weight ratio of 2:2:1. The rosin resin is pentaerythritol rosin ester P-100; the petroleum resin is C5 petroleum resin PR-80; and the terpene-styrene resin is terpene-styrene resin TR-80.

[0109] Furthermore, the silane coupling agent is composed of γ-mercaptopropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane in a weight ratio of 1:1.

[0110] Furthermore, the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 7:3. The catalyst is composed of bismorpholino diethyl ether and dibutyltin dilaurate in a weight ratio of 3:2. The defoamer is BYK-1790.

[0111] This embodiment also provides a method for preparing the above-mentioned non-stringing PUR hot melt adhesive, including the following steps:

[0112] (1) Add polyether polyol and crystalline polyester polyol to the reaction vessel, stir at 120°C for 15 min at a stirring speed of 300 rpm, then add thermoplastic tackifying resin and stir for 30 min at a stirring speed of 400 rpm.

[0113] (2) Maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer was added to mixture one and high-speed shear dispersion was carried out at 130°C for 25 min at a shear dispersion speed of 1100 rpm; then nano silica was added and high-speed shear dispersion was carried out for 25 min at a shear dispersion speed of 1100 rpm to obtain mixture two.

[0114] (3) Reduce the temperature inside the reaction vessel to 80°C, add isocyanate to mixture two and stir until the -NCO content of the system reaches 95% of the theoretical value, and obtain mixture three;

[0115] (4) Reduce the temperature inside the reaction vessel to 70°C, add antioxidant, defoamer and silane coupling agent to mixture three and stir evenly, then add catalyst and stir evenly to obtain mixture four;

[0116] (5) The mixture is degassed under vacuum and then cooled to 50°C. It is then granulated by a twin-screw extruder and discharged to obtain non-stringing PUR hot melt adhesive granules with a particle diameter of 3-5 mm. The obtained PUR hot melt adhesive is then placed in a sealed container for later use.

[0117] The rest of this embodiment is the same as that in Embodiment 1.

[0118] The performance of the PUR hot melt adhesives prepared in Examples 1-4 was tested, and the test results are shown in the table below:

[0119]

[0120] The melt viscosity was determined according to HG / T3660-1999: the prepared PUR hot melt adhesive was placed in an oven at 120℃ and heated for 30 minutes. After the PUR hot melt adhesive was completely melted, it was quickly poured into the sleeve of a rotational viscometer and held for 10 minutes before the melt viscosity was measured. The stringing resistance was determined using the following method: a pneumatic dispensing valve was used with a dispensing head distance of 5 mm. At a glue temperature of 120℃, the needle was pulled back at a fixed speed of 10 mm / s, and the stringing length was observed. The open time was determined according to IPC-TM-6502.4.45: the surface tack disappearance time was tested with a probe every 30 seconds after coating. Shear strength was determined according to ASTM D1002, using PUR hot melt adhesive to bond aluminum plates together with a thickness of 0.15 mm. A single-overlap structure was used. The aluminum plate dimensions were 100 mm × 25 mm × 1.6 mm. A universal testing machine was used for treatment at a loading rate of 1.3 mm / min and a temperature of 25 °C. High-temperature shear strength was tested after treatment at 70 °C for 10 min. Elongation at break was determined according to ASTM D412, using a dumbbell-shaped adhesive film with a thickness of 2 mm and a tensile rate of 500 mm / min.

[0121] In summary, the non-stringing PUR hot melt adhesive of the present invention combines polyether polyol, crystalline polyester polyol, isocyanate, and thermoplastic tackifying resin, and further combines them with maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, TPU, nano silica, and silane coupling agent. The synergistic effect of each raw material satisfies the dispensing fluidity requirements, resulting in smooth dispensing and reducing stringing. It also has good adhesive strength, mechanical properties, and reliability.

[0122] The specific embodiments described above are further illustrations of the technical solution and beneficial effects of the present invention, and are not intended to limit the implementation methods. For those skilled in the art, any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A non-stringing PUR hot melt adhesive, characterized in that: The raw materials include the following parts by weight: 40-60 parts of polyether polyol, 10-20 parts of crystalline polyester polyol, 12-30 parts of isocyanate, 20-30 parts of thermoplastic tackifying resin, 3-6 parts of maleic anhydride-grafted acrylonitrile-butadiene-styrene copolymer, 2-4 parts of polyurethane elastomer, 1.5-4 parts of nano silica, 0.2-0.8 parts of catalyst, 0.1-0.5 parts of defoamer, 0.2-0.6 parts of antioxidant, and 0.5-1.5 parts of silane coupling agent; The polyether polyol is at least one of polypropylene oxide diol and polytetrahydrofuran ether diol; the crystalline polyester polyol is at least one of polybutylene adipate diol, polyethylene adipate diol and poly(1,6-hexanediol carbonate) diol. The polyoxypropylene glycol has a weight-average molecular weight of 400-2000, and the polytetrahydrofuran ether glycol has a weight-average molecular weight of 500-2000. The isocyanate is at least one selected from toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and carbodiimide-modified 4,4'-diphenylmethane diisocyanate.

2. The non-stringing PUR hot melt adhesive according to claim 1, characterized in that: The thermoplastic tackifying resin is at least one of rosin resin, methylstyrene oligomer, petroleum resin, and terpene-styrene resin.

3. The non-stringing PUR hot melt adhesive according to claim 1, characterized in that: The silane coupling agent is at least one of γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

4. The non-stringing PUR hot melt adhesive according to claim 1, characterized in that: The antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 626, and antioxidant DSTDP.

5. The non-stringing PUR hot melt adhesive according to claim 1, characterized in that: The catalyst is at least one of bismorpholino diethyl ether and dibutyltin dilaurate.

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