Single-component polyurethane liquid glue and preparation method thereof

Abstract

The invention discloses a single-component polyurethane liquid glue which comprises a hydroxyl-terminated polyurethane prepolymer, polyol and isocyanate, and the molar ratio of an isocyanate group to a hydroxyl group is (1.01-5): 1; the hydroxyl-terminated polyurethane prepolymer comprises aliphatic or / and alicyclic isocyanate and polyol, and the molar ratio of an isocyanate group to a hydroxyl group is (0.5-0.99): 1. The preparation method comprises the following steps: firstly, synthesizing a hydroxyl-terminated polyurethane prepolymer, and then taking the hydroxyl-terminated polyurethane prepolymer as a main material to react with a small part of polyhydric alcohols and isocyanate. The polyurethane liquid adhesive synthesized by the two-step method has the performance advantages of high initial adhesion and low hardness, meets the process requirement of normal-temperature coating, can replace an adhesive film product and a hot melt adhesive product, and is applied to composite bonding of fabrics in the textile industry.

Description

Technical Field

[0001] The invention relates to the technical field of glue for textile fabric compounding, in particular to a single-component polyurethane liquid glue and a preparation method thereof. Background Art

[0002] Today, the apparel industry is constantly evolving and innovating, pursuing the perfect combination of fashion and functionality. Hot-melt adhesive film, a new adhesive product, is finding increasing application in the apparel industry, for example in multi-layer fabric lamination applications such as underwear, swim trunks, shapewear, and yoga wear. It not only replaces traditional sewing processes but also achieves seamless, traceless production, revolutionizing the apparel industry. Common hot-melt adhesive films include thermoplastic polyurethane (TPU) films and copolyester films. They are activated by applying high temperatures (typically around 140°C) and pressure (5 kgf), and then bonded after cooling. However, with the increasing diversity of fabrics, the activation and lamination methods for hot-melt adhesive films are limited for heat-sensitive fabrics and high-end, skin-friendly, and soft fabrics. Furthermore, during the preparation process, heat-activated adhesive films are typically coated on a release paper, which must be removed before use. This complicates the process. For apparel manufacturers, the accompanying release paper backing also increases material costs.

[0003] In textile fabric lamination applications, new bonding processes that replace adhesive films with coatable adhesives are gaining popularity. Patent CN109651998 A provides a low-viscosity, one-component, solvent-free polyurethane adhesive, its preparation method, and applications. This approach utilizes a step-by-step synthesis process: an isocyanate is first reacted with polyether polyols, polyester polyols, and hydroxy acrylates to produce an isocyanate-terminated polyurethane prepolymer, which is then reacted with a polyisocyanate to form the polyurethane adhesive. The resulting polyurethane exhibits excellent adhesion, is VOC-free, pollution-free, easy to coat, and cost-effective. Its primary application is laminating paper with plastic films or metal foils. However, the use of multifunctional isocyanate polymers or trimers in the synthesis process can lead to storage stability issues, such as crosslinking and gelation. Furthermore, the use of a high amount of multifunctional isocyanate increases crosslinking within the formulation, potentially affecting the adhesive's resilience, potentially limiting its application in applications requiring high resilience, such as fabric-to-fabric lamination.

[0004] Patent CN119552616A discloses a low-viscosity, high-initial-tack, single-component, moisture-curing polyurethane hot melt adhesive and its preparation method. This method primarily utilizes the design of raw materials and proportions, particularly specific liquid polyester polyols, to construct a low-viscosity system. This allows the PUR hot melt adhesive produced by the invention to be operated at relatively low temperatures while exhibiting high initial bonding strength and excellent final adhesion, making it particularly suitable for low-temperature lamination of heat-sensitive / thick substrates. Because the formulation of this solution contains an amorphous polyol with a glass transition temperature higher than room temperature and a tackifying resin that requires heating to melt, the final application process of the adhesive requires heating, and the viscosity index is primarily provided at 100°C. The adhesive's state at, for example, room temperature or low temperatures of 40-60°C is not addressed, and the issues of normal-temperature coating and construction are not addressed or addressed.

[0005] Based on this, it is necessary to develop a one-component polyurethane liquid adhesive with high initial adhesion and can be coated at room temperature. Summary of the Invention

[0006] We propose a one-component polyurethane liquid adhesive to address the issues raised in the above-mentioned background technology. The glue does not contain solvents or water, is fluid at room temperature of 23°C, and has a certain initial adhesion. It can be applied at room temperature and can meet the bonding needs of various complex shapes and surfaces, whether flat or curved, soft or hard materials. This one-component polyurethane liquid adhesive mainly relies on moisture in the air to complete the final cross-linking and curing. After curing, it is irreversible and can provide a strong and long-lasting bonding effect. It also has the advantages of a high degree of automation, flexible design, and good breathability. This product can not only be applied to traditional fields such as clothing, footwear, and automotive interiors, but can also be expanded to more emerging fields such as smart homes and wearable devices, providing innovative and efficient bonding solutions for these fields.

[0007] The present invention mainly prepares a solvent-free, odorless polyurethane glue with high initial tack by a two-step polymerization method using conventional polyether polyol or liquid polyol and different isocyanates, abandoning the conventional method of adding chain extenders, adding solid tackifying resins or designing hot melt adhesive water to improve the initial tack of the glue; in the final state, the glue of this solution has fluidity at room temperature and has the advantage of being coated at low temperatures; in terms of performance, the glue of this solution can achieve high softness and is more suitable for use on textiles.

[0008] The technical solutions of the present invention are as follows:

[0009] The first aspect of the present invention provides a one-component polyurethane liquid adhesive, which includes a hydroxyl-terminated polyurethane prepolymer, a polyol, and an isocyanate. The molar ratio of the isocyanate group to the hydroxyl group in the raw materials is (1.01-5):1, the preferred molar ratio is (1.1-3):1, and the more preferred molar ratio is (1.4-2.5):1.

[0010] The hydroxyl-terminated polyurethane prepolymer includes aliphatic and / or alicyclic isocyanates and polyols. The molar ratio of isocyanate groups to hydroxyl groups in the raw materials is (0.5-0.99):1, the preferred molar ratio is (0.55-0.99):1, and the more preferred molar ratio is (0.75-0.95):1.

[0011] Preferably, in the one-component polyurethane liquid glue, the weight ratio of the hydroxyl-terminated polyurethane prepolymer, polyol, and isocyanate is: (71-157): (5-30): (2-70); the preferred weight ratio is (80-135): (10-30): (5-55), and the more preferred weight ratio is (85-120): (15-30): (8-40).

[0012] In the hydroxyl-terminated polyurethane prepolymer, the weight ratio of polyol to aliphatic or / and alicyclic isocyanate is: (70-100): (1-61); the preferred weight ratio is (75-95): (5-50), and the more preferred weight ratio is (80-90): (7-35).

[0013] Preferably, the polyol is one or more polyols, and the viscosity of any polyol constituting the polyol is less than or equal to 100,000 cps / 25°C.

[0014] Polyols meeting the above viscosity range include polyether polyols and / or liquid non-crystalline polyester polyols. The polyether polyols may be polypropylene oxide ether glycol, polyethylene oxide ether glycol, or polytetramethylene oxide ether glycol, with a weight-average molecular weight of 200-6000, preferably 400-4000. Using low-molecular-weight polyether polyols, such as those with a molecular weight of 200-600, the resulting polyurethane liquid adhesive generally achieves higher initial tack, while using higher-molecular-weight polyols, such as those with a molecular weight of 2000-6000, results in better softness. This is because low-molecular-weight polyether polyols can act like chain extenders, promoting the chemical crosslinking effect during the polymerization process; high-molecular-weight polyether polyols have a higher density of ether oxygen bonds and a relatively flexible molecular chain, resulting in a relatively soft adhesive. Examples of commercial polyether polyols include, but are not limited to, D204 from Jiahua Chemical, 2120 and 2110TB from Dow Chemical, and PPG-6000 from Kukdo Chemical.

[0015] The liquid non-crystalline polyester polyol meeting the above viscosity range can be copolymerized by at least one small molecule dibasic acid and at least one small molecule diol. The small molecule dibasic acid can be succinic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, cyclohexanoic acid, phthalic acid, terephthalic acid, isophthalic acid; and ethylene glycol, butanediol, hexanediol, diethylene glycol, neopentyl glycol, 2-methyl-1,3-propanediol, 1,5-pentanediol. Examples of commercialized liquid non-crystalline polyester polyols include, but are not limited to, XCP-2000PM, XCP-1000PM, XCP-2000M, XCP-1000M from Asahikawa Chemical, HDPOL-5520 from Shanghai Huide, and Dynacoll 7250, Dynacoll 7230, and Dynacoll 7210 from Evonik Chemical of Germany. In addition, the liquid non-crystalline polyester polyol may also be a liquid dimer acid polyester polyol, commercially available under the trade names Priplast 1838 and Priplast 3238. In a one-component polyurethane liquid adhesive, the use of liquid polyester polyol can provide higher material bonding performance and reduce the adhesive's permeability on flexible fabrics, thereby achieving an ideal bonding effect.

[0016] Preferably, the isocyanate used to synthesize the one-component polyurethane liquid adhesive includes one or more of aliphatic isocyanates, alicyclic isocyanates, and aromatic isocyanates. Aliphatic isocyanates include hexamethylene diisocyanate (HDI) and 1,5-pentamethylene diisocyanate; alicyclic isocyanates include isophorone diisocyanate (IPDI) and dicyclohexylmethane diisocyanate; aromatic isocyanates include 4,4'-diphenylmethane diisocyanate (MDI), a 50 / 50 mixture of 4,4'-diphenylmethane diisocyanate and 2,4-diphenylmethane diisocyanate (MDI-50), and carbodiimide-modified MDI (liquefied MDI). Aromatic isocyanates are preferred, and MDI-50 is more preferred. When synthesizing hydroxyl-terminated polyurethane prepolymers, aliphatic isocyanates or alicyclic isocyanates are used. The advantage is that the synthesized prepolymers have high viscosity and flexibility, making them more convenient to use as the main material, while also being able to control the softness of the final glue.

[0017] Preferably, the one-component polyurethane liquid glue further comprises a liquid tackifying resin, and the weight ratio of the liquid tackifying resin to the hydroxyl-terminated polyurethane prepolymer is (0-20): (71-157). The liquid tackifying resin can be a liquid modified resin, and the commercial brand can be Guangdong Kemao Linchan Chemical Co., Ltd. KL1300; can be liquid acrylic resin, commercial brands include but not limited to BASF UV 3532. The selection principle of liquid tackifier is non-toxic, non-irritating odor, and good compatibility with polyurethane glue. Its function is to improve the initial adhesion of polyurethane liquid glue without affecting the final glue coating effect.

[0018] Preferably, the one-component polyurethane liquid adhesive further comprises an additive, which is one or more of a defoamer, an antioxidant, a fluorescent agent, a catalyst, a water scavenger, and a thixotropic agent. Defoamers are preferably acrylate defoamers, commercially available examples of which include but are not limited to BYK-A535 from BYK Chemical, BASF Efka FL3741, and Efka FL3741. 4016. The function of antioxidants is to prevent yellowing caused by the benzene ring structure in polyurethane glue. Commercial examples include but are not limited to antioxidant 1010 and antioxidant 1076. The function of fluorescent agents is to facilitate the identification of the uniformity of glue after coating. Commercial examples include but are not limited to BASF. UVITEX 0B, fluorescent brightener 0B from Shanghai Lianzhi Chemical Co., Ltd. The main function of a dehumidifier is to react and remove trace moisture from the hot melt adhesive, improving its stability. Optional dehumidifiers include, but are not limited to, p-toluenesulfonyl isocyanate (PTSI), 3-isocyanatepropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane, with PTSI being preferred. The purpose of using a catalyst is to increase the reaction efficiency between polyols and aliphatic or alicyclic isocyanates and shorten the reaction time. Commercially available examples include, but are not limited to, dibutyltin dilaurate, stannous octoate, and organobismuth catalysts. 8108, 8226. The thixotropic agent is mainly fumed silica, and commercial brands include but are not limited to Cabot's TS720 and Evonik's AEROSIL R974.

[0019] Preferably, the one-component polyurethane liquid adhesive further comprises a powder filler, wherein the powder filler is one or more of talc, titanium dioxide, high clay, bentonite, attapulgite, calcium carbonate, silica, graphite, and carbon black. The addition of the powder filler can shorten the adhesive's dry time, reduce its permeability, or impart color to the adhesive. The particle size of the added filler is greater than or equal to 2000 mesh, so as not to affect the coating effect.

[0020] Preferably, the one-component polyurethane liquid adhesive has a viscosity in the range of 2,000-100,000 mPa·s at 25°C, as measured using a Brookfield DV-2T viscometer using a No. 28 spindle in accordance with ASTM D3236. The adhesive viscosity is preferably in the range of 5,000-100,000 mPa·s, and more preferably in the range of 20,000-80,000 mPa·s.

[0021] Preferably, the hardness of the one-component polyurethane liquid adhesive after complete curing is in the range of HA40-HA80. The hardness is measured by a Shore A durometer according to ASTM D2240, and the preferred hardness value is Shore HA50-HA70.

[0022] Preferably, the one-component polyurethane liquid adhesive exhibits an initial tack greater than 1.5 N / cm when cured, as measured in accordance with ASTM D2724-1987. The substrate used in the initial tack test conducted in the present invention is spandex cloth.

[0023] A second aspect of the present invention provides a method for preparing a one-component polyurethane liquid adhesive, comprising the following steps:

[0024] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0025] (1) adding polyol, then melting and mixing until uniform, and vacuum dehydrating;

[0026] (2) Add aliphatic or alicyclic isocyanate and react at 60-120°C under vacuum conditions. Take a sample to determine the NCO content. If it is 0, terminate the reaction.

[0027] S2: Preparation of one-component polyurethane liquid glue

[0028] (3) adding a hydroxyl-terminated polyurethane prepolymer and a polyol, melting and mixing them until uniform, and vacuum dehydrating;

[0029] (4) Add isocyanate and react at 60-120°C under vacuum conditions. Take a sample to determine the NCO value. If the NCO content is less than or equal to the theoretical value, the reaction is complete.

[0030] The theoretical value of NCO content in the above reaction process is defined as follows: in the preparation process of the polyurethane prepolymer, the mass proportion of the remaining NCO in the synthesized polyurethane prepolymer composition after the copolymerization reaction of isocyanate and hydroxyl groups in a molar ratio of 1:1 is calculated based on the feed amounts of the isocyanate component and the polyol component, and is expressed as a percentage. It can be measured with reference to the standard method of HGT2409-1992.

[0031] Preferably, in the method for preparing the one-component polyurethane liquid adhesive, in step S1, the molar ratio of the NCO group in the aliphatic or alicyclic isocyanate to the OH group in the polyol is (0.5-0.99):1;

[0032] The molar ratio of the NCO groups in the aliphatic or / and alicyclic isocyanate in step (2) and the isocyanate in step (4) to the 0H groups in the polyol in step (1) and step (3) is (1.01-5):1.

[0033] Preferably, a curing accelerator is added in step (4), and the curing accelerator is one or more of bis(2,2-morpholinoethyl) ether (DMDEE), N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N,N,N',N'-tetramethylalkylenediamine; the amount of the curing accelerator is 0.01-2% of the amount of raw material added, and the preferred addition amount is 0.05-0.1%.

[0034] A third aspect of the present invention provides a laminate comprising:

[0035] (1) a first substrate comprising spandex or nylon, and

[0036] (2) a second substrate of the same type or a different type relative to the first substrate;

[0037] The second substrate is adhered to one side of the first substrate, and a one-component polyurethane liquid glue that is fluid at room temperature is applied to one side of the first substrate; the one-component polyurethane liquid glue comprises a hydroxyl-terminated polyurethane prepolymer, a polyol, and an isocyanate, and the molar ratio of the isocyanate group to the hydroxyl group is (1.01-5):1; the hydroxyl-terminated polyurethane prepolymer comprises a polyol and an aliphatic or / and alicyclic isocyanate, and the molar ratio of the isocyanate group to the hydroxyl group is (0.5-0.99):1.

[0038] The fourth aspect of the present invention provides an adhesive film for spandex or nylon fabrics, which can be composed of a one-component polyurethane liquid glue, wherein the one-component polyurethane liquid glue includes a hydroxyl-terminated polyurethane prepolymer, a polyol, and an isocyanate, and the molar ratio of the isocyanate group to the hydroxyl group is (1.01-5):1; the hydroxyl-terminated polyurethane prepolymer includes a polyol and an aliphatic or / and alicyclic isocyanate, and the molar ratio of the isocyanate group to the hydroxyl group is (0.5-0.99):1.

[0039] The fifth aspect of the present invention provides a use of the one-component polyurethane liquid glue, the laminate, and the spandex or nylon fabric adhesive film, which are used to prepare underwear, swimming trunks, shapewear or yoga clothes.

[0040] The present invention adopts a two-step process to synthesize a hydroxyl-terminated prepolymer and then synthesize a one-component polyurethane liquid adhesive. The entire reaction process is controllable and designable, avoiding the structural disorder and poor product stability problems of the one-step synthesis of high-molecular-weight polyurethane prepolymers. The viscosity of the resulting one-component polyurethane liquid adhesive is in the range of 2,000-100,000 cps at 25°C. The specific viscosity is adjustable, and different viscosities of the adhesive can be controlled according to different substrates and bonding structures. Room-temperature coating is possible, and the process is simple to use. The main beneficial effects include: first, the initial tack of the final adhesive is controlled by the synthesized hydroxyl-terminated polyurethane prepolymer. According to the ratio of NCO:OH=0.5-0.99, the synthesized polyurethane prepolymer has a high molecular weight, equivalent to a polyol raw material having a high initial tack. Second, using aliphatic and / or alicyclic isocyanates to synthesize hydroxyl-terminated polyurethane prepolymers can impart a certain degree of flexibility to the prepolymer. Compared to aromatic isocyanates, aliphatic and alicyclic isocyanates have lower crystallinity and lack rigid benzene rings in their molecular structures, resulting in flexible molecular chains or low-hindered, easily movable aliphatic ring-exchange structures. Third, the end-capping active groups of the one-component polyurethane liquid adhesive are preferably aromatic isocyanate NCO groups, which have higher reactivity than aliphatic NCO groups. Therefore, the curing speed is similar to that of conventional moisture-curing polyurethane hot melt adhesives and can be controlled by the amount of catalyst added. Therefore, it can replace hot melt adhesive films or polyurethane hot melt adhesives in practice. DETAILED DESCRIPTION

[0041] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0042] Example 1

[0043] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0044] (1) 20 parts of polyether polyol D204, 50 parts of polyether polyol 2110TB, 0.05 parts of defoamer BYK-A535, and 0.1 parts of antioxidant 1010 were added to a reactor; the temperature was raised to 120° C., and the mixture was mixed and stirred for at least 0.5 hours; then, negative pressure was turned on for dehydration, and a vacuum of -0.1 MPa was maintained for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0045] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 15.5 parts of HDI are added, and the reaction is carried out at 80-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content, and when the NCO% measured by titration is close to 0, the reaction is terminated; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0046] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.92:1.

[0047] S2: Preparation of one-component polyurethane liquid glue

[0048] (3) Add 10 parts of polyester polyol XCP-2000PM and 5 parts of polyester polyol Dynacoll 7250 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the water is removed under negative pressure at a vacuum degree of -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0049] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 18 parts of MDI-50 are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.06 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0050] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.54:1, and the theoretical isocyanate content NCO% in the final product was 4.08%.

[0051] Example 2

[0052] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0053] (1) 40 parts of polyether polyol 2110TB and 50 parts of polyether polyol 2120 were added to a reaction kettle; the temperature was raised to 120° C. and the mixture was mixed and stirred for at least 0.5 hours; then, negative pressure was applied to dehydrate the mixture and the vacuum was maintained at -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0054] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 90°C; 13 parts of IPDI are added, and the reaction is carried out at 90-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content, and when the NCO% measured by titration is close to 0, the reaction is terminated; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0055] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.9:1.

[0056] S2: Preparation of one-component polyurethane liquid glue

[0057] (3) Add 10 parts of polyether polyol D204, 15 parts of polyester polyol XCP-2000PM, 0.1 parts of defoamer FL3741, and 0.15 parts of antioxidant 1010 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the water is removed under negative pressure at a vacuum degree of -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0058] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 25 parts of MDI-50 are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.08 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0059] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.62:1, and the theoretical isocyanate content NCO% in the final product was 3.33%.

[0060] Example 3

[0061] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0062] (1) Add 100 parts of polyester polyol HDPOL-5520 to a reactor; heat to 120° C., mix and stir for at least 0.5 hours; then, start negative pressure extraction for dehydration, and maintain at a vacuum degree of -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0063] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 60°C; 0.01 parts of a catalyst dibutyltin dilaurate T-12 is added to the kettle and stirred for 10 minutes; 8 parts of HDI are added and reacted at 60-100°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content, and the reaction is terminated when the NCO% measured by titration is close to 0; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0064] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.95:1.

[0065] S2: Preparation of one-component polyurethane liquid glue

[0066] (3) Add 10 parts of polyether polyol 2120, 15 parts of polyester polyol Dynacoll 7230, 0.1 parts of defoamer FL3741, and 0.1 parts of antioxidant 1010 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the negative pressure is drawn under a vacuum degree of -0.1 MPa to remove moisture for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0067] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 70°C; 13 parts of HDI are added, and the reaction is carried out at 70-100°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.15 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0068] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.99:1, and the theoretical isocyanate content NCO% in the final product was 3.55%.

[0069] Example 4

[0070] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0071] (1) Add 60 parts of polyester polyol HDPOL-5520 and 30 parts of polyether polyol PPG-6000 to a reactor; heat to 120° C., mix and stir for at least 0.5 hours; then, turn on the negative pressure to dehydrate, and maintain the vacuum degree at -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0072] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 90°C; 8.5 parts of hydrogenated MDI are added and reacted at 90-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content. When the NCO% measured by titration is close to 0, the reaction is terminated; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0073] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.93:1.

[0074] S2: Preparation of one-component polyurethane liquid glue

[0075] (3) Add 10 parts of polyether polyol 2120, 15 parts of polyester polyol Dynacoll 7210, and 10 parts of liquid tackifying resin KL3100 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the negative pressure is drawn under a vacuum degree of -0.1 MPa to remove moisture for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0076] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 8 parts of MDI-50 are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.08 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0077] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.46:1, and the theoretical isocyanate content NCO% in the final product was 1.20%.

[0078] Example 5

[0079] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0080] (1) 80 parts of polyester polyol 2110TB and 0.05 parts of defoamer BYK-A535 were added to a reactor; the temperature was raised to 120° C. and the mixture was mixed and stirred for at least 0.5 hours; then, negative pressure was applied to dehydrate the mixture and the vacuum was maintained at -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0081] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 13 parts of HDI are added, and the reaction is carried out at 80-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content, and when the NCO% measured by titration is close to 0, the reaction is terminated; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0082] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.96:1.

[0083] S2: Preparation of one-component polyurethane liquid glue

[0084] (3) Add 25 parts of polyether polyol PPG-4000 and 15 parts of liquid tackifying resin KL3100 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the negative pressure is drawn under a vacuum degree of -0.1 MPa to remove moisture for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0085] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 22 parts of HDI are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.07 parts of curing accelerator N, N-dimethylcyclohexylamine are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0086] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.86:1, and the theoretical isocyanate content NCO% in the final product was 4.35%.

[0087] In order to compare the effects of the above embodiments, the following comparative examples are designed:

[0088] Comparative Example 1 (one-step method)

[0089] Preparation of one-component polyurethane liquid adhesive

[0090] (1) 80 parts of polyether polyol 2110TB, 25 parts of polyether polyol PPG-4000, 15 parts of liquid tackifying resin, and 0.05 parts of defoaming agent BYK-A535 were added to a reactor; the temperature was raised to 120° C., and the mixture was mixed and stirred for at least 0.5 hours; then, negative pressure was turned on for dehydration, and a vacuum of -0.1 MPa was maintained for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0091] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 35 parts of HDI are added, and the reaction is carried out at 80-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.07 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0092] During the entire reaction process, the molar ratio of isocyanate groups to hydroxyl groups was 1.86:1, and the theoretical isocyanate content NCO% in the final product was 4.35%.

[0093] Comparative Example 2

[0094] S1: Preparation of isocyanate NCO-terminated polyurethane prepolymer

[0095] (1) 40 parts of polyether polyol 2110TB and 50 parts of polyether polyol 2120 were added to a reaction kettle; the temperature was raised to 120° C. and the mixture was mixed and stirred for at least 0.5 hours; then, negative pressure was applied to dehydrate the mixture and the vacuum was maintained at -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0096] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 90°C; 16 parts of IPDI are added, and the reaction is carried out at 90-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content, and the reaction is terminated when the NCO% measured by titration is close to 0; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0097] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 1.11:1.

[0098] S2: Preparation of one-component polyurethane liquid glue

[0099] (3) Add 10 parts of polyether polyol D204, 15 parts of polyester polyol XCP-2000PM, 0.1 parts of defoamer FL3741, and 0.15 parts of antioxidant 1010 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the water is removed under negative pressure at a vacuum degree of -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0100] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 21.55 parts of MDI-50 are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.08 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0101] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.62:1, and the theoretical isocyanate content NCO% in the final product was 3.33%.

[0102] Comparative Example 3

[0103] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0104] (1) 40 parts of polyether polyol 2110TB and 50 parts of polyether polyol 2120 were added to a reaction kettle; the temperature was raised to 120° C. and the mixture was mixed and stirred for at least 0.5 hours; then, negative pressure was applied to dehydrate the mixture and the vacuum was maintained at -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0105] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 90°C; 13 parts of IPDI are added, and the reaction is carried out at 90-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content, and when the NCO% measured by titration is close to 0, the reaction is terminated; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0106] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.9:1.

[0107] S2: Preparation of one-component polyurethane liquid glue

[0108] (3) Add 10 parts of polyether polyol D204, 15 parts of polyester polyol XCP-2000NH (a polyester polyol copolymerized with adipic acid, neopentyl glycol, and hexanediol, with a molecular weight of 2000 and in a solid or paste form at room temperature), 0.1 parts of defoamer FL3741, and 0.15 parts of antioxidant 1010 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, and remove moisture under negative pressure at a vacuum degree of -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0109] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 25 parts of MDI-50 are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.08 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0110] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.62:1, and the theoretical isocyanate content NCO% in the final product was 3.33%.

[0111] Comparative Example 4

[0112] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0113] (1) 40 parts of polyether polyol 2110TB and 50 parts of polyether polyol PTMEG-2000 (polytetrahydrofuran diol with a molecular weight of 2000, solid or paste at room temperature) were added to a reaction kettle; the temperature was raised to 120° C. and mixed and stirred for at least 0.5 hour; thereafter, negative pressure was turned on for dehydration, and a vacuum of -0.1 MPa was maintained for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0114] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 90°C; 13 parts of IPDI are added, and the reaction is carried out at 90-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content, and when the NCO% measured by titration is close to 0, the reaction is terminated; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0115] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.9:1.

[0116] S2: Preparation of one-component polyurethane liquid glue

[0117] (3) Add 10 parts of polyether polyol D204, 15 parts of polyester polyol XCP-2000PM, 0.1 parts of defoamer FL3741, and 0.15 parts of antioxidant 1010 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the water is removed under negative pressure at a vacuum degree of -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0118] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 25 parts of MDI-50 are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.08 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0119] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.62:1, and the theoretical isocyanate content NCO% in the final product was 3.33%.

[0120] Comparative Example 5

[0121] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0122] (1) Add 60 parts of polyester polyol HDPOL-5520 and 30 parts of polyether polyol PPG-6000 to a reactor; heat to 120° C., mix and stir for at least 0.5 hours; then, turn on the negative pressure to dehydrate, and maintain the vacuum degree at -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0123] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 8.1 parts of hydrogenated MDI-50 are added, and the reaction is carried out at 80-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content, and the reaction is terminated when the NCO% measured by titration is close to 0; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0124] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.92:1.

[0125] S2: Preparation of one-component polyurethane liquid glue

[0126] (3) Add 10 parts of polyether polyol 2120, 15 parts of polyester polyol Dynacoll 7210, and 10 parts of liquid tackifying resin KL3100 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the negative pressure is drawn under a vacuum degree of -0.1 MPa to remove moisture for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0127] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 8 parts of MDI-50 are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.07 parts of a curing accelerator N,N-dimethylcyclohexylamine are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0128] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.46:1, and the theoretical isocyanate content NCO% in the final product was 1.20%.

[0129] Comparative Example 6

[0130] S1: Preparation of hydroxyl-terminated polyurethane prepolymer

[0131] (1) 20 parts of polyether polyol D204, 50 parts of polyether polyol 2110TB, 0.05 parts of defoamer BYK-A535, and 0.1 parts of antioxidant 1010 were added to a reactor; the temperature was raised to 120° C., and the mixture was mixed and stirred for at least 0.5 hours; then, negative pressure was turned on for dehydration, and a vacuum of -0.1 MPa was maintained for at least 1 hour to obtain a uniformly mixed and dehydrated polyol mixture;

[0132] (2) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 7 parts of HDI are added and reacted at 80-120°C for 2-3 hours, wherein the negative pressure degassing is maintained for at least 1 hour, and the vacuum degree of the negative pressure is maintained at -0.1 MPa; a sample is taken to determine the NCO content. When the NCO% measured by titration is close to 0, the reaction is terminated; stirring is stopped, and the synthesized hydroxyl-terminated polyurethane prepolymer is sealed and stored.

[0133] The molar ratio of isocyanate groups to hydroxyl groups in the S1 process is 0.41:1.

[0134] S2: Preparation of one-component polyurethane liquid glue

[0135] (3) Add 10 parts of polyester polyol XCP-2000PM and 5 parts of polyester polyol Dynacoll 7250 to the reactor of S1, control the material temperature to 120°C, mix and stir for 1.5-2 hours, wherein the water is removed under negative pressure at a vacuum degree of -0.1 MPa for at least 1 hour to obtain a uniformly mixed and dehydrated composition;

[0136] (4) Under the protection of a vacuum degree of -0.1 MPa, the material is cooled to 80°C; 30.5 parts of MDI-50 are added, and the reaction is carried out at 80-120°C for 1.5-2 hours, wherein the negative pressure degassing is maintained for at least 1 hour; 0.06 parts of a curing accelerator DMDEE are added, and the mixture is stirred and mixed under vacuum for 10 minutes; a sample is taken to determine the NCO content. If the value of NCO% is less than or equal to the theoretical value, it indicates that the reaction is complete. The material is discharged under the protection of nitrogen, and the product is sealed and stored, thus preparing a one-component polyurethane liquid adhesive.

[0137] During the entire reaction process of S1 and S2, the molar ratio of isocyanate groups to hydroxyl groups was 1.54:1, and the theoretical isocyanate content NCO% in the final product was 3.92%.

[0138] The polyurethane liquid adhesives of the embodiment and the comparative example were tested for performance in parallel, including viscosity index, Shore A hardness, glue state at room temperature, and initial tack. The data are compared as follows:

[0139] sample Viscosity / 25℃ Hardness / Shore A Glue state (at 25°C) Initial adhesion N / cm Example 1 78000mPa·s HA70 Uniform and transparent 2.8 Example 2 55000mPa·s HA58 Uniform and transparent 2.5 Example 3 42000mPa·s HA65 Uniform, milky white 1.7 Example 4 59000mPa·s HA55 Uniform, milky white and translucent 2.5 Example 5 36000mPa·s HA62 Uniform, milky white and translucent 2.1 Comparative Example 1 17000mPa·s HA50 Uniform, milky white and translucent 1 Comparative Example 2 / / Gel particles appear, not smooth / Comparative Example 3 / HA80 Semisolid, solid and liquid discontinuous, non-homogeneous / Comparative Example 4 / HA76 Paste solid, non-homogeneous / Comparative Example 5 / HA77 Sandy semi-solid, non-uniform / Comparative Example 6 27000mPa·s HA74 Uniform and transparent 0.8

[0140] The polyurethane adhesives synthesized in Comparative Examples 2-5 were heterogeneous at room temperature, exhibiting either gel particles or a coexistence of solid and liquid phases. Therefore, viscosity testing at room temperature, coating treatment, and initial tack testing were not possible. For Comparative Example 2, which contained gel particles, hardness data after curing could not be measured.

[0141] From the table above we can see that:

[0142] In Example 1, when synthesizing the hydroxyl-terminated polyurethane prepolymer, a large amount of polyether polyol D204 with a molecular weight of 400 was used. The low molecular weight polyether polyol played a role similar to that of a chain extender during the synthesis process. The viscosity of the finally synthesized polyurethane liquid glue was high, and at the same time, it showed a high initial tack of 2.8 N / cm. The low molecular weight polyether polyol with a higher content was closer to the hard segment in the synthesized glue molecular chain, so the hardness of the glue after curing was relatively high. Since the main raw material of the synthesis reaction was polyether polyol, the appearance of the glue was transparent.

[0143] Comparative Example 1 has the same formula composition as Example 1. Comparative Example 1 adopts a one-step synthesis method, and all polyols, liquid resins and isocyanates are mixed and reacted together. The viscosity and initial tack of the prepared polyurethane glue are significantly lower than those of Example 1. This is because in the one-step synthesis process, the isocyanate group is significantly more excessive than the hydroxyl group, and the molecular weight of the polyurethane prepolymer generated by the monomer copolymerization is low, so the final glue viscosity is low; while in the two-step synthesis process, in step S1, the hydroxyl group molar amount is controlled to be slightly higher than the isocyanate group molar amount, and a hydroxyl-terminated polyurethane prepolymer with a high molecular weight is preferentially synthesized. Then, in step S2, this part of the hydroxyl-terminated polyurethane prepolymer is used as the main material, and the chain growth reaction and NCO end-capping reaction are carried out again. The polyurethane liquid glue finally formed contains more high molecular weight polyurethane prepolymers, so its viscosity becomes higher, and the corresponding initial tack is also improved.

[0144] In step S1 of Comparative Example 2, an isocyanate-terminated polyurethane prepolymer is first synthesized. As an intermediate product, its active isocyanate groups can react with moisture in the environment due to poor sealing properties, resulting in impure intermediate products. Furthermore, in step S2, the isocyanate-terminated polyurethane prepolymer, similar to crosslinking sites, is further reacted with polyol and isocyanate monomers, easily forming gel particles or agglomerates containing a large amount of polyurethane prepolymer distributed in the glue.

[0145] Comparing Comparative Examples 3 and 4 with Example 2, it is found that regardless of whether a paste-like material at room temperature is used in the synthesis stage of the hydroxyl-containing polyurethane prepolymer (Comparative Example 4) or a solid material is used in the synthesis S2 stage of the polyurethane liquid glue (Comparative Example 3), the final synthesized glue is in a non-uniform liquid state at room temperature. For example, the glue is in a warm paste state, or the glue contains solid and liquid discontinuous phases, which makes it impossible to apply or coat the glue at room temperature. It still needs to be matched with heated coating equipment, thereby losing the application advantage of the polyurethane liquid glue.

[0146] In Comparative Example 5, aromatic isocyanate is used to synthesize a hydroxyl-containing polyurethane prepolymer in the S1 stage. Since aromatic isocyanate has a relatively rigid benzene ring structure and has a certain degree of crystallinity, the fluidity of the product is poor when synthesizing a higher molecular weight prepolymer. After the intermediate product continues to react with the isocyanate in the S2 stage, the final glue easily forms a partial solid. At room temperature, the glue as a whole appears non-liquid and sandy.

[0147] Comparative Example 6, referring to the formulation of Example 1, set the isocyanate to hydroxyl group ratio (NCO:OH) of the hydroxyl-terminated polyurethane prepolymer in stage S1 to 0.41. The NCO:OH ratio in the final polyurethane liquid adhesive remained unchanged at 1.54. Because the molecular weight of the synthesized hydroxyl-containing polyurethane prepolymer is relatively low, even when the same NCO:OH ratio is maintained throughout the entire process, the proportion of high-molecular-weight polymers in the resulting adhesive remains relatively low when used as the main material in the subsequent synthesis of the polyurethane liquid adhesive. The results showed that the viscosity of the adhesive in Comparative Example 6 was significantly reduced, as was its initial tack.

[0148] The above descriptions are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by utilizing the contents of the present invention specification under the inventive concept of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A one-component polyurethane liquid adhesive comprising a hydroxyl-terminated polyurethane prepolymer, a polyol, and an isocyanate, wherein the molar ratio of the isocyanate group to the hydroxyl group is (1.01-5):1; The hydroxyl-terminated polyurethane prepolymer comprises aliphatic or / and alicyclic isocyanate and polyol, and the molar ratio of isocyanate group to hydroxyl group is (0.5-0.99):

1.

2. The one-component polyurethane liquid glue according to claim 1, wherein: In the one-component polyurethane liquid adhesive, the weight ratio of the hydroxyl-terminated polyurethane prepolymer, the polyol, and the isocyanate is (71-157):(5-30):(2-70); In the hydroxyl-terminated polyurethane prepolymer, the weight ratio of polyol to aliphatic or / and alicyclic isocyanate is (70-100):(1-61).

3. The one-component polyurethane liquid glue according to claim 1, wherein: The polyol is one or more polyols, and the viscosity of any polyol constituting the polyol is less than or equal to 100,000 cps / 25°C.

4. The one-component polyurethane liquid glue according to claim 3, wherein: The polyol includes polyether polyol and / or liquid non-crystalline polyester polyol. The one-component polyurethane liquid adhesive according to claim 1 , wherein the isocyanate comprises one or more of aliphatic isocyanate, alicyclic isocyanate, and aromatic isocyanate.

6. The one-component polyurethane liquid adhesive according to claim 1, further comprising a liquid tackifying resin, wherein the weight ratio of the liquid tackifying resin to the hydroxyl-terminated polyurethane prepolymer is (0-20): (71-157). 7 . The one-component polyurethane liquid adhesive according to claim 1 , having a viscosity of 2000-100000 mPa·s at 25° C., as measured by a Brookfield DV-2T viscometer using a No. 28 spindle in accordance with ASTM D3236.

8. The one-component polyurethane liquid adhesive according to any one of claims 1 to 6, wherein the hardness of the one-component polyurethane liquid adhesive after complete curing is in the range of HA40-HA80, and the hardness is measured by a Shore A durometer according to ASTM D2240.

9. The one-component polyurethane liquid adhesive according to any one of claims 1 to 6, which exhibits an initial viscosity > 1.5 N / cm when cured, the initial viscosity being measured according to ASTM D2724-1987.

10. A method for preparing a one-component polyurethane liquid adhesive, comprising the following steps: S1: Preparation of hydroxyl-terminated polyurethane prepolymer (1) adding polyol, then melting and mixing until uniform, and vacuum dehydrating; (2) Add aliphatic or / and alicyclic isocyanate and react at 60-120°C under vacuum conditions. Take a sample to determine the NCO content. If it is 0, terminate the reaction. S2: Preparation of one-component polyurethane liquid glue (3) adding a hydroxyl-terminated polyurethane prepolymer and a polyol, melting and mixing them until uniform, and vacuum dehydrating; (4) Add isocyanate and react at 60-120°C under vacuum conditions. Take a sample to determine the NCO value. If the NCO content is less than or equal to the theoretical value, the reaction is complete.

11. The method for preparing a one-component polyurethane liquid adhesive according to claim 10, wherein in step S1, the molar ratio of the NCO group in the aliphatic or / and alicyclic isocyanate to the OH group in the polyol is (0.5-0.99):1; The molar ratio of the NCO groups in the aliphatic or / and alicyclic isocyanate in step (2) and the isocyanate in step (4) to the OH groups in the polyol in step (1) and step (3) is (1.01-5):

1.

12. The method for preparing a one-component polyurethane liquid adhesive according to claim 10, wherein a curing accelerator is added in step (4), and the curing accelerator is one or more of bis(2,2-morpholinoethyl) ether, N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, and N,N,N',N'-tetramethylalkylenediamine, and the amount of the curing accelerator is 0.01-2% of the amount of raw material added.

13. A laminate comprising: (1) a first substrate comprising spandex or nylon, and (2) A second substrate that is the same type or a different type than the first substrate. The second substrate is adhered to one side of the first substrate, and a one-component polyurethane liquid glue that is fluid at room temperature is applied to one side of the first substrate; the one-component polyurethane liquid glue includes a hydroxyl-terminated polyurethane prepolymer, a polyol, and an isocyanate, and the molar ratio of the isocyanate group to the hydroxyl group is (1.01-5):1; the hydroxyl-terminated polyurethane prepolymer includes an aliphatic or / and alicyclic isocyanate and a polyol, and the molar ratio of the isocyanate group to the hydroxyl group is (0.5-0.99):

1.

14. A spandex or nylon fabric adhesive film formed by coating a one-component polyurethane liquid adhesive, wherein the one-component polyurethane liquid adhesive comprises a hydroxyl-terminated polyurethane prepolymer, a polyol, and an isocyanate, wherein the molar ratio of the isocyanate group to the hydroxyl group is (1.01-5):1; The hydroxyl-terminated polyurethane prepolymer comprises aliphatic or / and alicyclic isocyanate and polyol, and the molar ratio of isocyanate group to hydroxyl group is (0.5-0.99):

1.

15. Use of the one-component polyurethane liquid adhesive according to any one of claims 1 to 6, the laminate according to claim 13, and the spandex or nylon fabric adhesive film according to claim 14 for preparing underwear, swimming trunks, body shapers, or yoga clothes.