Polyurethane adhesive and its preparation method and application

Abstract

The invention relates to a polyurethane adhesive and a preparation method and application thereof. The adhesive is composed of the following raw materials in percentage by weight: 35-65wt% of a composite polyether polyol, 14-25wt% of a polyisocyanate, 1-5wt% of a hydrophilic chain extender, 1-5wt% of a small molecule chain extender, 0.05-3wt% of a catalyst, 0.5-4wt% of a neutralizer, 1-7wt% of a capping agent, 1-8wt% of a silane coupling agent, 2-12wt% of mesoporous microspheres, 2-5% of isopropyl alcohol, 2-5wt% of butyl acetate and 0.2-4wt% of a defoamer, with the balance being water. The composite polyether polyol is a composition of a Mannich polyether polyol and a soft foam polyether polyol in a mass ratio of 1:(0.5-1). The adhesive can replace hot melt adhesive powder in clothing heat transfer printing, can improve the softness, air permeability, friction resistance and soaping color fastness of fabric heat transfer printing, and can significantly reduce the film-forming and curing temperature of the adhesive.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane adhesives, in particular to a polyurethane adhesive and a preparation method and application thereof. Background Art

[0002] In the field of apparel printing, there are three main techniques: traditional screen printing and knitting, as well as the emerging white ink heat transfer process. White ink heat transfer involves using a white ink heat transfer printer to directly print computer-generated designs onto PET film pre-coated with release agent and ink-absorbing coating. The color film is applied first, followed by the white ink. A powder shaker then applies hot melt adhesive powder, evenly covering the white ink pattern. The hot melt adhesive is then dried, and then a heat press is used to transfer the white ink to the fabric. The waste film is then removed, completing the heat transfer process. White ink heat transfer offers the following advantages: 1) Color freedom: With white ink heat transfer, artists can use KCMY color management software to create and freely utilize a variety of colors, making their work more vibrant and vibrant. 2) Diverse creative techniques: White ink heat transfer can be applied to a variety of materials, such as fabric, paper, and leather, achieving a variety of artistic effects and aesthetics. 3) Personalization: Designs and colors can be customized to your preferences. Whether it's a high-stretch jersey or a low-stretch promotional shirt, heat transfer can be used to print your design.

[0003] The heat transfer process has the above-mentioned unique advantages and is replacing traditional screen printing, water slurry printing and knitting. It is gradually being widely used and recognized by the garment printing industry, which has had a significant impact on the entire garment printing industry. The white ink heat transfer market is growing at an alarming rate.

[0004] In the white ink heat transfer process, hot melt adhesive powder is used to bond the design and base material. Using a powder shaker, the hot melt adhesive powder is evenly applied to the white ink layer printed on PET film. It is then baked at 160-180°C to melt into a film, which is then applied to the base fabric and heat-transferred at high temperatures to create the heat transfer. Hot melt adhesive powder provides excellent adhesion and water-based fastness.

[0005] However, the disadvantage of white ink heat transfer is that clothing printed on clothing has a heavy adhesive feel and poor breathability. If the full pattern covers a large area, it will appear stuffy and affect people's wearing comfort. In addition, the hot melt adhesive powder process requires high temperature to melt and combine with the pattern to achieve the desired bonding effect. The high temperature leads to high energy consumption during the production process. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a polyurethane adhesive with low curing temperature, softness after bonding, good air permeability and high adhesion, as well as a preparation method and application thereof.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides a polyurethane adhesive, which is made from the following raw materials in percentage by weight: 35-65 wt% of a composite polyether polyol, 14-25 wt% of a polyisocyanate, 1-5 wt% of a hydrophilic chain extender, 1-5 wt% of a small molecule chain extender, 0.05-3 wt% of a catalyst, 0.5-4 wt% of a neutralizing agent, 1-7 wt% of a capping agent, 1-8 wt% of a silane coupling agent, 2-12 wt% of mesoporous microspheres, 2-5% of isopropyl alcohol, 2-5 wt% of butyl acetate, and 0.2-4 wt% of a defoaming agent, with the balance being water;

[0009] The composite polyether polyol is a composition of a Mannich polyether polyol and a flexible foam polyether polyol in a mass ratio of 1:(0.5-1); the flexible foam polyether polyol is manufactured by Shandong Bluestar Dongda Co., Ltd., with a model number of 10LD28XM, a number average molecular weight of 4000, and a functionality of 2; the mesoporous microspheres are manufactured by Shanghai Zhenzhun Biotechnology Co., Ltd., with a model number of MS-10040.

[0010] Preferably, the silane coupling agent is β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0011] Preferably, the polyisocyanate is hydrogenated phenylmethane diisocyanate.

[0012] Preferably, the catalyst is bismuth neodecanoate.

[0013] Preferably, the hydrophilic chain extender is 2,2-dimethylolpropionic acid (DMPA) and / or 2,2-dimethylolbutanoic acid (DMBA).

[0014] Preferably, the small molecule chain extender is at least one of 1,4-butanediol, ethylene glycol, hexanediol, diethylene glycol, ethylenediamine, and diethylenetriamine.

[0015] Preferably, the blocking agent is methyl ethyl ketoxime.

[0016] Preferably, the neutralizing agent is triethylamine.

[0017] In a second aspect, the present invention provides a method for preparing the polyurethane adhesive according to the first aspect, comprising the following steps:

[0018] S1. Stirring the polyether polyol, hydrophilic chain extender, silane coupling agent and mesoporous microspheres in a nitrogen atmosphere, then adding the polyisocyanate and catalyst, stirring and reacting at 70-95° C. for 1-4 hours, and then cooling the reaction product to 60-70° C. for later use;

[0019] S2, adding a small molecule chain extender to the product obtained in S1, then stirring and reacting for 1-2 hours, and gradually heating to 85-90°C;

[0020] S3, adding the end-capping agent to the product obtained in S2, continuing to stir and react for 1-3 hours, then adding a neutralizing agent at room temperature, and adding water, butyl acetate and isopropyl alcohol for ultrasonic dispersion to obtain an aqueous polyurethane emulsion;

[0021] S4. Add a defoamer to the aqueous polyurethane emulsion prepared in S3, disperse and stir, and obtain the polyurethane adhesive.

[0022] Preferably, in step S1, the stirring speed is 500-600 rpm.

[0023] Preferably, in step S2, the stirring speed is 500-600 rpm, and the stirring time is 10-30 min.

[0024] Preferably, in step S3, the stirring speed is 500-600 rpm, the ultrasonic power is 200-250 W, and the ultrasonic time is 5-10 min.

[0025] Preferably, in step S4, the stirring speed is 500-600 rpm, and the stirring time is 10-30 min.

[0026] In a third aspect, the present invention provides use of the polyurethane adhesive described in the first aspect in preparing clothing heat transfer coating ink.

[0027] Adhesive of the present invention is waterborne polyurethane, and it has adopted Mannich polyether polyol and soft foam polyether polyol as polyether polyol, and both are composite and have good reactivity.Simultaneously, the flexible segment that soft foam polyether polyol provides can make whole system more easily deform under the external forces such as stretching, and the rigid structure (aromatic ring structure) of Mannich polyether polyol can play certain supporting role, prevent material from excessive deformation and lose intensity, Mannich polyether polyol and soft foam polyether polyol collaboratively form the cross-linked network with suitable flexibility, after this adhesive is joined in ink-jet and is applied to clothing heat transfer, its printing can not bring stiff feeling to clothes, overcome the problem that hot-melt powder and printing ink compound can make printing feel too poor, make to wear more comfortable.In addition, soft foam polyether polyol and Mannich polyether polyol two synergistic action, can make adhesive and ink, fabric form better interface bonding, reduce interface defect, improve sticking power, thus make fabric have good friction resistance and soaping resistance color fastness.

[0028] The use of butyl acetate and mesoporous microspheres in the present invention significantly improves the air permeability of printed products. This is because butyl acetate reduces the surface tension of the system during the foaming process, making it easier for bubbles to rupture and form an open-pore structure. Furthermore, butyl acetate has a boiling point of 126°C, which is higher than that of water but lower than the curing temperature of 130-140°C. Therefore, butyl acetate evaporates during the adhesive curing process, leaving tiny, breathable pores in the polyurethane film layer. This improves the air permeability and imparts good open porosity to the polyurethane, allowing air and moisture to circulate and enhancing user comfort. The mesoporous microspheres, through their mesoporous structure, further enhance the air permeability of the adhesive. Therefore, when the adhesive is formulated into ink, the air permeability of the printed product is significantly improved, making the printed product more breathable and comfortable. Isopropyl alcohol is used as a cosolvent to increase the solubility of butyl acetate in water. One end of the silane coupling agent reacts with hydroxyl groups on the surface of the mesoporous microspheres to form a covalent bond, while the other end reacts with organic groups in the polyurethane resin. This "bridging" effect can significantly improve the interfacial bonding strength between the filler and the polyurethane matrix.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The water-based polyurethane adhesive of the present invention uses Mannich polyether polyol and soft foam polyether polyol as polyether polyols, which synergistically form a cross-linked network with appropriate flexibility. After being applied to clothing heat transfer, the printing does not feel stiff, overcoming the problem of poor hand feel of hot melt powder and ink composites, making it comfortable to wear and improving the friction resistance and soap washing color fastness of the fabric. At the same time, the polyurethane adhesive of the present invention has an operating temperature between 130-140°C and a curing time of less than 3 minutes, which is significantly lower than the temperature at which hot melt adhesive powder melts to form a film (above 180°C), thus avoiding the effects of high temperature on fabrics and high energy consumption.

[0031] (2) The present invention uses butyl acetate and mesoporous microspheres to synergistically improve the air permeability of the polyurethane adhesive. After the adhesive of the present invention is made into ink, the adhesive has good open porosity, which is conducive to the circulation of air and moisture, thereby improving the comfort of use.

[0032] (3) The adhesive of the present invention can replace hot melt adhesive powder in clothing heat transfer printing, and can improve the softness, air permeability, friction resistance and soap washing color fastness of fabric heat transfer printing. At the same time, it can significantly reduce the film-forming and curing temperature of the adhesive. DETAILED DESCRIPTION

[0033] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0034] The sources of the raw materials and equipment used in the embodiments and comparative examples are as follows:

[0035] Mannich polyether polyol: manufactured by Jiahua Chemical (Shanghai) Co., Ltd., model number Purabiol RC5335, viscosity 900-1500 mPa·s / 25°C;

[0036] Soft foam polyether polyol: manufacturer is Shandong Bluestar Dongda Co., Ltd., model number is 10LD28XM, number average molecular weight is 4000, functionality is 2;

[0037] Mesoporous microspheres: molecular sieve, manufactured by Shanghai Zhenzhun Biotechnology Co., Ltd., model MS-10040, with a specific surface area of ​​350-450m 2 / g, pore size is 0.56-0.58nm, crystallinity: >95%, particle size is 100-300nm;

[0038] β-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane: Manufacturer: Hangzhou Jessica Chemical Co., Ltd., model number KH-1771;

[0039] Butyl acetate: manufacturer is Shanghai Yien Chemical Technology Co., Ltd., model number is R007184;

[0040] Bismuth neodecanoate: manufacturer: Shandong Lanyue New Material Technology Co., Ltd., model: LK-5;

[0041] Hydrogenated phenylmethane diisocyanate: manufacturer is Covestro, model number is Desmodur H12MDI;

[0042] 2,2-Dihydroxymethylpropionic acid: manufacturer: Shanghai Haohong Biopharmaceutical Technology Co., Ltd., model number 1033326;

[0043] 2,2-Dihydroxymethylbutyric acid: manufacturer: Shanghai Haohong Biopharmaceutical Technology Co., Ltd., model number 1014884;

[0044] 1,4-Butanediol: Manufacturer: Guangdong Wengjiang Chemical Reagent Co., Ltd., model number PB04152;

[0045] Ethylene glycol: manufacturer is Guangdong Wengjiang Chemical Reagent Co., Ltd., model number MB00660;

[0046] Triethylamine: manufacturer: Guangdong Wengjiang Chemical Reagent Co., Ltd., model number: GB00816;

[0047] Methyl ethyl ketone oxime: Honeywell, brand MEKO

[0048] Polyether silicone defoamer: manufactured by Germany Digo, model 825;

[0049] Unless otherwise specified, other materials and reagents used in the examples can be obtained from commercial sources.

[0050] Example 1

[0051] A polyurethane adhesive is prepared from the following raw materials in percentage by weight: 55 wt% of a composite polyether polyol, 20 wt% of a polyisocyanate, 3 wt% of a hydrophilic chain extender, 3 wt% of a small molecule chain extender, 1 wt% of a catalyst, 2 wt% of a neutralizing agent, 5 wt% of a capping agent, 6 wt% of a silane coupling agent, 10 wt% of mesoporous microspheres, 4% of isopropyl alcohol, 4 wt% of butyl acetate, and 3 wt% of a defoaming agent, with the balance being water; wherein the composite polyether polyol is a combination of a Mannich polyether polyol and a soft foam polyether polyol in a mass ratio of 1:0.8;

[0052] Wherein, the polyisocyanate is hydrogenated phenylmethane diisocyanate, the hydrophilic chain extender is 2,2-dihydroxymethylpropionic acid, the small molecule chain extender is 1,4-butanediol, the catalyst is bismuth neodecanoate, the neutralizer is triethylamine, the end-capping agent is methyl ethyl ketone oxime, the silane coupling agent is β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, the mesoporous microspheres are molecular sieves, and the defoamer is a polyether siloxane defoamer;

[0053] The preparation method of the polyurethane adhesive comprises the following steps:

[0054] S1. Stirring polyether polyol, hydrophilic chain extender, silane coupling agent and mesoporous microspheres at 550 rpm in a nitrogen atmosphere, then adding polyisocyanate and catalyst, stirring and reacting at 80° C. for 3 h, and then cooling the reaction product to 65° C. for later use;

[0055] S2, adding a small molecule chain extender to the product obtained in S1, then stirring at 550 rpm for 1.5 h and gradually heating to 85°C;

[0056] S3, adding the end-capping agent to the product obtained in S2, continuing the reaction for 2 hours, then adding a neutralizing agent at room temperature, and adding water, isopropyl alcohol and butyl acetate, and ultrasonically dispersing at a power of 200 W for 8 minutes to obtain an aqueous polyurethane emulsion;

[0057] S4. After adding a defoamer to the aqueous polyurethane emulsion prepared in S3, the mixture was dispersed and stirred at a rotation speed of 550 rpm for 20 minutes to obtain the polyurethane adhesive.

[0058] Example 2

[0059] A polyurethane adhesive is prepared from the following raw materials in percentage by weight: 35 wt% of a composite polyether polyol, 14 wt% of a polyisocyanate, 1 wt% of a hydrophilic chain extender, 1 wt% of a small molecule chain extender, 0.05 wt% of a catalyst, 0.5 wt% of a neutralizer, 1 wt% of a capping agent, 1 wt% of a silane coupling agent, 2 wt% of mesoporous microspheres, 2% of isopropyl alcohol, 2 wt% of butyl acetate, and 0.2 wt% of a defoamer, with the balance being water; wherein the composite polyether polyol is a combination of a Mannich polyether polyol and a soft foam polyether polyol in a mass ratio of 1:0.5;

[0060] Wherein, the polyisocyanate is hydrogenated phenylmethane diisocyanate, the hydrophilic chain extender is 2,2-dihydroxymethylbutyric acid, the small molecule chain extender is ethylene glycol, the catalyst is bismuth neodecanoate, the neutralizer is triethylamine, the end-capping agent is methyl ethyl ketone oxime, the silane coupling agent is β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, the mesoporous microspheres are molecular sieves, and the defoamer is a polyether siloxane defoamer;

[0061] The preparation method of the polyurethane adhesive comprises the following steps:

[0062] S1. Stirring polyether polyol, hydrophilic chain extender, silane coupling agent and mesoporous microspheres at 500 rpm in a nitrogen atmosphere, then adding polyisocyanate and catalyst, stirring and reacting at 70° C. for 4 h, and then cooling the reaction product to 60° C. for later use;

[0063] S2, adding a small molecule chain extender to the product obtained in S1, then stirring at 500 rpm for 1 h and gradually heating to 85°C;

[0064] S3, adding the end-capping agent to the product obtained in S2, continuing the reaction for 3 hours, then adding a neutralizing agent at room temperature, and adding water, isopropyl alcohol and butyl acetate, and ultrasonically dispersing the mixture at a power of 200 W for 10 minutes to obtain an aqueous polyurethane emulsion;

[0065] S4. Add a defoamer to the aqueous polyurethane emulsion prepared in S3, and disperse and stir at a rotation speed of 500 rpm for 30 minutes to obtain the polyurethane adhesive.

[0066] Example 3

[0067] A polyurethane adhesive is prepared from the following raw materials in percentage by weight: 65 wt% of a composite polyether polyol, 25 wt% of a polyisocyanate, 5 wt% of a hydrophilic chain extender, 5 wt% of a small molecule chain extender, 3 wt% of a catalyst, 4 wt% of a neutralizing agent, 7 wt% of a capping agent, 8 wt% of a silane coupling agent, 12 wt% of mesoporous microspheres, 5% of isopropyl alcohol, 5 wt% of butyl acetate, and 4 wt% of a defoaming agent, with the balance being water; wherein the composite polyether polyol is a composition of a Mannich polyether polyol and a soft foam polyether polyol in a mass ratio of 1:1;

[0068] Wherein, the polyisocyanate is hydrogenated phenylmethane diisocyanate, the hydrophilic chain extender is 2,2-dihydroxymethylbutyric acid, the small molecule chain extender is 1,4-butanediol, the catalyst is bismuth neodecanoate, the neutralizer is triethylamine, the end-capping agent is methyl ethyl ketone oxime, the silane coupling agent is β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, the mesoporous microspheres are molecular sieves, and the defoamer is a polyether siloxane defoamer;

[0069] The preparation method of the polyurethane adhesive comprises the following steps:

[0070] S1. Stirring polyether polyol, hydrophilic chain extender, silane coupling agent and mesoporous microspheres at 600 rpm in a nitrogen atmosphere, then adding polyisocyanate and catalyst, stirring and reacting at 95° C. for 1 h, and then cooling the reaction product to 70° C. for later use;

[0071] S2, adding a small molecule chain extender to the product obtained in S1, then stirring at 600 rpm for 1 h and gradually heating to 90°C;

[0072] S3, adding the end-capping agent to the product obtained in S2, continuing the reaction for 1 hour, then adding a neutralizing agent at room temperature, and adding water, isopropyl alcohol and butyl acetate, and ultrasonically dispersing at a power of 250 W for 5 minutes to obtain an aqueous polyurethane emulsion;

[0073] S4. Add a defoamer to the aqueous polyurethane emulsion prepared in S3, and disperse and stir at a rotation speed of 600 rpm for 10 minutes to obtain the polyurethane adhesive.

[0074] Comparative Example 1

[0075] The difference between Comparative Example 1 and Example 1 is that no Mannich polyether polyol is added, and the missing amount is made up by using soft foam polyether polyol.

[0076] Comparative Example 2

[0077] The difference between Comparative Example 2 and Example 1 is that no soft foam polyether polyol is added, and the missing amount is made up by using Mannich polyether polyol.

[0078] Comparative Example 3

[0079] The difference between Comparative Example 3 and Example 1 is that the total amount of the composite polyether polyol remains unchanged, and the mass ratio of the composition of the Mannich polyether polyol and the flexible foam polyether polyol is 0.8:1.

[0080] Comparative Example 4

[0081] The difference between Comparative Example 4 and Example 1 is that butyl acetate and mesoporous microspheres are not added.

[0082] Comparative Example 5

[0083] The difference between Comparative Example 5 and Example 1 is that butyl acetate is not added.

[0084] Comparative Example 6

[0085] The difference between Comparative Example 6 and Example 1 is that no mesoporous microspheres are added.

[0086] Performance Testing

[0087] The binders of Examples 1-3 and Comparative Examples 1-6 were prepared into coating inks, specifically as follows:

[0088] The coating ink includes the following raw materials in weight percentage: 30% binder of each group, 8% pigment, 35% humectant, 1.5% surfactant, 0.1% pH regulator, 0.1% preservative, and the balance is water; wherein the humectant is propylene glycol and ethylene glycol in a mass ratio of 1:1; the surfactant is Surfynol 104E; the pH regulator is triethanolamine; the preservative is isothiazolone; the pigment is a purple-red pigment, which is prepared by pre-dispersing a mixture of Pigment Red 254 and Pigment Red 202 in a vinyl copolymer carrier resin to form a solid magenta pigment, the manufacturer is BASF, and the model is Microlith 4330K.

[0089] Printing performance tests were conducted on coating inks prepared with the adhesives of Examples 1-3 and Comparative Examples 1-6. A Caishen Xingguang 3204SG inkjet printer with a Xingguang 1024 nozzle was used for the printing tests. The printing medium was 12A woven cotton fabric. After printing, the fabric was baked at 80°C for 8 minutes to obtain eight fabric swatches of Examples 1-3 and Comparative Examples 1-6.

[0090] 1. Color fastness test

[0091] The color fastness to washing with soap and soap was measured according to GB / T 3921-2008 “Textiles — Tests for color fastness — Color fastness to washing with soap and soap”, and the color fastness to rubbing was measured according to GB / T 3920-2008 “Textiles — Tests for color fastness — Color fastness to rubbing”, as shown in Table 1.

[0092] 2. Stiffness test

[0093] Cut a 20cm x 2.5cm fabric swatch from the printed pattern. Place it face-up on the stiffness tester platform, aligning one end of the swatch with the platform's front edge. Place a graduated pressure plate on the swatch, which will move the swatch forward synchronously at a speed of 0.3-0.5cm / s. When one end of the swatch just touches the test line, stop moving and record the length (cm). See Table 1 for details.

[0094] 3. Printing air permeability test

[0095] The air permeability (mm / s) of the fabric at the printed pattern was measured on a fully automatic air permeability meter according to GB / T 5453-1997 “Determination of Air Permeability of Textile Fabrics”. The test conditions were a hole area of ​​20 cm 2 , the pressure is 100Pa, see Table 1 for details.

[0096] 4. Curing time and temperature test

[0097] Components A and B of Examples 1-3 and Comparative Examples 1-6 were mixed to obtain adhesives. The curing time in the container, i.e., the operating time, was measured. Components A and B of each group were then re-adjusted and evenly applied to three panels at a coating weight of 0.03 g / cm². The panels were then placed in an oven and the curing temperature and curing time were measured. See Table 2 for details. The curing temperature here is equal to the film-forming, curing temperature of the adhesive.

[0098] Table 1 Test results of each group of fabric samples

[0099]

[0100] Note: Color fastness is typically graded into five levels, with level 1 indicating poor color fastness and level 5 indicating excellent color fastness. A higher level of color fastness for fabric prints indicates a more stable color, making it less likely to fade or bleed during wear and washing, thus preserving the appearance and quality of the garment. Normal fabrics generally require a color fastness of level 3 to 4 to meet wear requirements.

[0101] If the printed pattern has a high stiffness, it is not easily deformed when subjected to external force, so the elongation of the fabric swatch's droop contact detection line during the push process will be shorter. Conversely, if the fabric swatch has a low stiffness, it is more easily deformed, indicating that the print is more flexible, so the elongation of the fabric swatch's droop contact detection line during the push process will be longer.

[0102] Air permeability is an important indicator to measure the breathability of fabrics. It indicates the rate at which air flows vertically through a sample under specified sample area, pressure drop and time conditions. The higher the air permeability, the better the breathability.

[0103] Table 2 Curing time and curing temperature of each group of adhesives

[0104] Group / Performance Operation time / s Curing temperature / ℃ Curing time / s Example 1 152 130 170 Example 2 158 139 176 Example 3 155 136 174 Comparative Example 1 204 167 322 Comparative Example 2 202 168 326 Comparative Example 3 189 146 334 Comparative Example 4 179 150 216 Comparative Example 5 171 146 210 Comparative Example 6 174 148 204

[0105] As shown in Tables 1-2, combining Example 1 with Comparative Examples 1-2, the fabric sample of Example 1 has higher color fastness, indicating better adhesion of the ink to the fabric and better flexibility of the print. Furthermore, the curing temperature and time of the adhesive of Example 1 are both reduced. This may be because the polyether polyols compounded with the Mannich polyether polyol and the soft foam polyether polyol work synergistically, both having good compatibility with the prepolymer. The compounding of the two has good reactivity, thereby accelerating the curing process of the polyurethane. Effective curing reactions can also be carried out at temperatures of 130-140°C, eliminating the need for use at high temperatures above 180°C, thus avoiding damage to the fabric caused by high temperatures. At the same time, the compounding of the two also allows for better interface bonding between the adhesive and the ink and fabric, reducing defects and improving adhesion, resulting in good friction and soap-resistant color fastness to the fabric. It also improves the softness of the fabric heat transfer print and has little effect on the air permeability of the print.

[0106] Combining Example 1 with Comparative Example 3, it can be seen that when the total amount of composite polyether polyol is the same, the mass ratio of Mannich polyether polyol to soft foam polyether polyol is selected within the range of 1: (0.5-1), so that the adhesion, feel, air permeability, curing temperature and time of the print on the fabric are all at a better level.

[0107] Combining Example 1 with Comparative Examples 4-6, it can be seen that butyl acetate and mesoporous microspheres can improve the adhesion and feel of the print on the fabric to a certain extent and can reduce the curing temperature and time. Their effect on the air permeability of the print is greater. This may be because butyl acetate and mesoporous microspheres work together to improve the air permeability of polyurethane, significantly improving the air permeability of the print, making the printed product more breathable and comfortable.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polyurethane adhesive, characterized in that The invention is prepared from the following raw materials in percentage by weight: 35-65wt% of composite polyether polyol, 14-25wt% of polyisocyanate, 1-5wt% of hydrophilic chain extender, 1-5wt% of small molecule chain extender, 0.05-3wt% of catalyst, 0.5-4wt% of neutralizer, 1-7wt% of end-capping agent, 1-8wt% of silane coupling agent, 2-12wt% of mesoporous microspheres, 2-5% of isopropyl alcohol, 2-5wt% of butyl acetate and 0.2-4wt% of defoaming agent, and the balance is water; wherein the composite polyether polyol is a mixture of 1:(0.5-1) by weight. A composition of Mannich polyether polyol and soft foam polyether polyol; the manufacturer of the soft foam polyether polyol is Shandong Bluestar Dongda Co., Ltd., the model is 10LD28XM, the number average molecular weight is 4000, and the functionality is 2; the manufacturer of the mesoporous microspheres is Shanghai Zhenzhun Biotechnology Co., Ltd., the model is MS-10040; the small molecule chain extender is at least one of 1,4-butanediol, ethylene glycol, hexanediol, diethylene glycol, ethylenediamine, and diethylenetriamine; the hydrophilic chain extender is 2,2-dihydroxymethylpropionic acid and / or 2,2-dihydroxymethylbutyric acid.

2. The polyurethane adhesive according to claim 1, wherein The silane coupling agent is β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

3. The polyurethane adhesive according to claim 1, wherein The polyisocyanate is hydrogenated phenylmethane diisocyanate.

4. The polyurethane adhesive according to claim 1, wherein The catalyst is bismuth neodecanoate.

5. The polyurethane adhesive according to claim 1, wherein The neutralizing agent is triethylamine.

6. The polyurethane adhesive according to claim 1, wherein The blocking agent is methyl ethyl ketone oxime.

7. The method for preparing the polyurethane adhesive according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Stirring the polyether polyol, hydrophilic chain extender, silane coupling agent and mesoporous microspheres in a nitrogen atmosphere, then adding the polyisocyanate and catalyst, stirring and reacting at 70-95° C. for 1-4 hours, and then cooling the reaction product to 60-70° C. for later use; S2. Add a small molecule chain extender to the product obtained in S1, then stir and react for 1-2 hours, and gradually heat to 85-90°C; S3, adding the end-capping agent to the product obtained in S2, continuing to stir and react for 1-3 hours, then adding a neutralizing agent at room temperature, and adding water, butyl acetate and isopropyl alcohol for ultrasonic dispersion to obtain an aqueous polyurethane emulsion; S4. Add a defoamer to the aqueous polyurethane emulsion prepared in S3, disperse and stir, and obtain the polyurethane adhesive.

8. The method for preparing the polyurethane adhesive according to claim 7, wherein: In the step S1, the stirring speed is 500-600 rpm; in the step S2, the stirring speed is 500-600 rpm; in the step S3, the stirring speed is 500-600 rpm, the ultrasonic power is 200-250 W, and the ultrasonic time is 5-10 min; in the step S4, the stirring speed is 500-600 rpm, and the stirring time is 10-30 min.

9. Use of the polyurethane adhesive according to any one of claims 1 to 6 in preparing clothing heat transfer coating ink.

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