Recycled TPU (thermoplastic polyurethane) hot melt adhesive film with solid color effect and preparation method thereof

Abstract

The invention particularly relates to a recycled TPU (thermoplastic polyurethane) hot melt adhesive film with solid color effect and a preparation method thereof, the preparation method comprises the following steps: classifying and collecting TPU wastes according to different colors, cleaning and drying, then putting the TPU wastes into a crusher to crush the TPU wastes into small particles, and drying to obtain the TPU hot melt adhesive film with solid color effect. Uniformly mixing the small particles obtained in the step A1, a chain extender, a coloring agent, a dispersing agent and a photo-thermal stabilizer, performing melt extrusion through a double-screw extruder to obtain recycled TPU color master batches, uniformly mixing TPU hot melt colloidal particles, the recycled TPU color master batches, an antioxidant and an anti-yellowing agent under a heating condition to obtain a mixed melt, and performing tape casting, cooling and curing to obtain a solid adhesive film. A release film is attached to the surface of the solid adhesive film, and then the solid adhesive film is rolled to obtain the TPU hot melt adhesive film. The problems of whitening and color crossing of the hot melt adhesive film during application are solved by recycling the TPU waste, and the hot melt adhesive film has good adhesive property and photo-thermal aging resistance.

Description

Technical Field

[0001] The invention relates to the technical field of hot melt adhesive film preparation, and in particular to a recycled TPU hot melt adhesive film with a solid color effect. Background Art

[0002] With the widespread application of thermoplastic polyurethane (TPU) materials in many fields such as footwear, electronic accessories, and automotive interiors, the production of TPU consumes a large amount of petrochemical raw materials. At the same time, the amount of TPU waste is also increasing day by day. If these wastes are not properly handled, discarded or landfilled at will, they will cause irreparable and continuous pollution to the soil environment. Therefore, it is of great significance to recycle and reprocess TPU waste. On the one hand, the recycled TPU can be remade into various products, and the cost of the reprocessed products is lower, which can help companies reduce production costs; especially in some cost-sensitive fields, such as mid- and low-end footwear materials, ordinary packaging materials, etc., the price advantage of recycled and reprocessed products makes them more attractive. On the other hand, it can also effectively reduce the energy consumption and greenhouse gas emissions caused by the preparation of new materials, and promote sustainable development.

[0003] However, the current recycling of TPU waste faces many difficulties. First, TPU waste comes from a wide range of sources and has complex components. The performance of waste under different production processes and application scenarios varies greatly. It is mixed with impurities, residual additives and other problems, making it difficult to treat with unified standards. Second, there is a strong hydrogen bond between TPU molecular chains, which makes the waste have a high melting temperature and high viscosity during the recycling process, and is difficult to process, which poses great challenges to both equipment and processes. Third, after TPU waste is recycled and reprocessed, the performance stability of the product is lower than that of new materials, such as mechanical properties and aging resistance. How to improve the quality of recycled materials to meet diverse market needs is still a key issue that needs to be solved urgently.

[0004] TPU hot melt adhesive film is a type of TPU product with broad application market demand. With its good flexibility, initial adhesion, and low-temperature rapid curing properties, it can accurately meet most of the bonding needs of the application market. However, this type of product still has a lot of room for improvement in high temperature resistance and hydrolysis resistance. For example, when used in mesh bonding applications, it is easy to cause problems such as whitening or color bleeding of the hot melt adhesive film under high temperature hot pressing conditions. In response to this, the present invention proposes a solution for how to recycle and reprocess TPU waste, as well as improving the bonding performance and temperature resistance of the hot melt adhesive film. Summary of the invention

[0005] The purpose of the present invention is to solve the above-mentioned deficiencies in the prior art and to provide a recycled TPU hot melt adhesive film with a solid color effect and a preparation method thereof.

[0006] The purpose of the present invention is achieved by the following technical solution: A method for preparing a recycled TPU hot melt adhesive film with a solid color effect, comprising the following preparation steps:

[0007] A1. After collecting TPU waste by color, wash and dry it, and then put it into a crusher to break it into small particles;

[0008] A2, 30-50 parts of the product obtained in step A1, 2-5 parts of a chain extender, 0.5-3 parts of a colorant, 0.1-2 parts of a dispersant, and 0.5-2 parts of a light and heat stabilizer are mixed evenly, and then melt-extruded through a twin-screw extruder to obtain a recycled TPU masterbatch;

[0009] A3. 80-100 parts of TPU hot melt adhesive particles, 0.5-5 parts of recycled TPU masterbatch, 0.1-3 parts of antioxidant and 0.5-3 parts of anti-yellowing agent are mixed evenly under heating conditions to obtain a mixed melt, and then cast and solidified by cooling to obtain a solid adhesive film, and a release film is attached to the surface of the solid adhesive film and then rolled up to obtain the TPU hot melt adhesive film.

[0010] Furthermore, in step A2, the chain extender is a rosin-based chain extender containing terminal hydroxyl groups. In the present invention, the preparation method of the chain extender is specifically as follows: fully dissolving dimerized rosin in tetrahydrofuran, adding oxalyl chloride thereto and stirring for reaction for 4-6 hours, removing the solvent by rotary evaporation, then adding triethylamine and ethylene glycol thereto, heating to 50-55° C. for reaction for 5-6 hours, and then filtering, washing and drying to obtain the chain extender.

[0011] Furthermore, in step A2, the colorant is one or more of titanium dioxide, carbon black, ultramarine, phthalocyanine pigment, azo pigment, and quinacridone pigment.

[0012] Furthermore, in step A2, the dispersant is at least one of polyethylene wax, polyoxyethylene fatty acid ester, naphthalenesulfonate formaldehyde condensate, and polyether modified silicone.

[0013] Furthermore, in step A2, the preparation method of the light and heat stabilizer comprises the following steps: fully dispersing the hindered amine light stabilizer and nano titanium dioxide in a solvent, raising the temperature to 90-100°C under nitrogen protection, adding a titanate catalyst thereto and mixing evenly, keeping the temperature for reaction for 12-16 hours, and then centrifuging, washing and drying to obtain the light and heat stabilizer. The hindered amine light stabilizer is preferably light stabilizer 770, light stabilizer 622 or light stabilizer UV-292.

[0014] Furthermore, in step A3, the antioxidant is at least one of a phosphite antioxidant, a hindered phenol antioxidant, and a thioester antioxidant.

[0015] Furthermore, in step A3, the anti-yellowing agent is at least one of BIORICH BT2000, UVK-CLV, Chimassorb944FD, and Revonox U-5068L.

[0016] Furthermore, the preparation method of the TPU hot melt rubber particles includes the following steps: first vacuum dehydrating the polyester polyol, then controlling the temperature at 80-90°C, slowly dripping diisocyanate therein to carry out a prepolymerization reaction, and then adding a modified epoxy resin to continue the reaction for 1-2 hours, and then successively adding 1,4-butanediol and an organic tin catalyst to continue the reaction, testing its NCO conversion rate to reach the theoretical value and then stopping, and then transferring the obtained viscous liquid to an extruder for molding processing, and then cooling and granulating to obtain the TPU hot melt rubber particles.

[0017] Furthermore, the polyester polyol is compounded by polycaprolactone diol and polycarbonate diol in a mass ratio of 3-4:1, and the diisocyanate is compounded by hexamethylene diisocyanate and dicyclohexylmethane-4,4'-diisocyanate in a mass ratio of 2.5-3.5:1.

[0018] Furthermore, the preparation method of the modified epoxy resin is specifically as follows: epoxy resin E-51, silane coupling agent and dibutyltin dilaurate are uniformly mixed, and stirred for reaction at 55-58°C for 1-3h under a nitrogen atmosphere to obtain the modified epoxy resin. In the present invention, the modified epoxy resin prepared by the above method is rich in active groups such as epoxy groups, which can give the TPU hot melt adhesive better bonding strength, and has a significant effect on improving the toughness and strength of the TPU hot melt adhesive film.

[0019] The invention obtains a regenerated and recycled TPU hot melt adhesive film with a solid color effect through the preparation method.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention recycles TPU waste and processes it to make recycled TPU masterbatch, and then uses the recycled TPU masterbatch in the preparation of TPU hot melt adhesive film, which not only realizes the recycling of TPU waste and has good environmental protection, but also reduces the production cost of the hot melt adhesive film. The recycled TPU masterbatch has good dispersibility, can be evenly dispersed in the TPU system, has high coloring degree, and excellent processing performance;

[0022] (2) The present invention can improve the hardness, chemical resistance and thermal stability of TPU waste by adding a rosin-based chain extender containing terminal hydroxyl groups, and reduce the use of petroleum-based raw materials, making the recycling of TPU masterbatch more environmentally friendly;

[0023] (3) The present invention grafts hindered amine light stabilizers with nano-titanium dioxide to utilize the intermolecular force between the two to help improve the anti-ultraviolet effect of the light and heat stabilizer, and synergistically improve its light aging resistance and heat stability; at the same time, the dispersibility of nano-titanium dioxide in the TPU matrix is ​​significantly improved, and the agglomeration of nano-titanium dioxide is reduced, thereby making the light and heat stabilizer have better anti-ultraviolet aging and heat resistance.

[0024] (4) The present invention effectively improves the bonding performance, weather resistance and tensile strength of the TPU hot melt adhesive particles by cleverly mixing polyester polyols, diisocyanates and modified epoxy resins, so that the particles can meet the bonding requirements of applications and broaden the scope of market application. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0026] Example 1

[0027] This embodiment provides a method for preparing a recycled TPU hot melt adhesive film with a solid color effect, comprising the following preparation steps:

[0028] A1. After collecting TPU waste by color, wash and dry it, and then put it into a crusher to break it into small particles;

[0029] A2, 35 parts of the small particles obtained in step A1, 3 parts of a chain extender, 1 part of a colorant, 0.7 parts of a dispersant, and 1 part of a light and heat stabilizer are mixed evenly, and then melt-extruded through a twin-screw extruder to obtain a recycled TPU masterbatch;

[0030] A3. 80 parts of TPU hot melt adhesive particles, 1.5 parts of recycled TPU masterbatch, 1.2 parts of antioxidant and 1.5 parts of anti-yellowing agent are mixed evenly at 150° C. to obtain a mixed melt, and then a solid adhesive film is obtained by cast molding and cooling and solidification, and an OPP release film is attached to the surface of the solid adhesive film and then rolled up to obtain the TPU hot melt adhesive film.

[0031] Furthermore, in step A2, the chain extender is a rosin-based chain extender containing terminal hydroxyl groups. In the present invention, the preparation method of the chain extender is specifically as follows: fully dissolve dimerized rosin in tetrahydrofuran, add oxalyl chloride thereto, stir and react for 5 hours, remove the solvent by rotary evaporation, then add triethylamine and ethylene glycol thereto, heat to 52°C and react for 6 hours, and then filter, wash and dry to obtain the chain extender. The molar ratios of dimerized rosin, oxalyl chloride, triethylamine and ethylene glycol are 0.493:1:1:1 respectively.

[0032] Furthermore, in step A2, the colorant is carbon black.

[0033] Furthermore, in step A2, the dispersant is polyoxyethylene fatty acid ester.

[0034] Furthermore, in step A2, the preparation method of the photothermal stabilizer includes the following steps: fully dispersing hindered amine light stabilizer 662 and nano titanium dioxide in a solvent at a molar ratio of 1:1.7, raising the temperature to 90°C under nitrogen protection, adding 0.2wt% of titanate catalyst thereto and mixing evenly, keeping the temperature for reaction for 12h, and obtaining the photothermal stabilizer by centrifugation, washing and drying after the reaction.

[0035] Furthermore, in step A3, the antioxidant is compounded by antioxidant 1098 and antioxidant 168 in a mass ratio of 1:1.

[0036] Furthermore, in step A3, the anti-yellowing agent is UVK-CLV.

[0037] Furthermore, the preparation method of the TPU hot-melt rubber particles includes the following steps: first vacuum dehydrating the polyester polyol, then controlling the temperature at 80°C, slowly dripping diisocyanate therein to carry out a prepolymerization reaction, and then adding a modified epoxy resin to continue the reaction for 1 hour, and then successively adding 1,4-butanediol and dibutyltin dilaurate to continue the reaction, testing its NCO conversion rate to reach the theoretical value and then stopping, and then transferring the obtained viscous liquid to an extruder for molding and cooling and granulating, so as to obtain the TPU hot-melt rubber particles.

[0038] Furthermore, the polyester polyol is compounded with polycaprolactone diol and polycarbonate diol in a mass ratio of 3.5:1, and the diisocyanate is compounded with hexamethylene diisocyanate and dicyclohexylmethane-4,4'-diisocyanate in a mass ratio of 3:1. In the above system, the molar ratio of OH to NCO is 1:1, the molar ratio of polyester polyol to 1,4-butanediol is 1:1, and the amount of dibutyltin dilaurate is 0.1% of the total mass.

[0039] Furthermore, the preparation method of the modified epoxy resin is specifically as follows: epoxy resin E-51, silane coupling agent and dibutyltin dilaurate are uniformly mixed, and stirred for reaction at 55° C. for 2 hours under a nitrogen atmosphere to obtain the modified epoxy resin.

[0040] Example 2

[0041] This embodiment provides a method for preparing a recycled TPU hot melt adhesive film with a solid color effect, comprising the following preparation steps:

[0042] A1. After collecting TPU waste by color, wash and dry it, and then put it into a crusher to break it into small particles;

[0043] A2, 45 parts of the small particles obtained in step A1, 4 parts of the chain extender, 2 parts of the colorant, 1.5 parts of the dispersant, and 1.4 parts of the light and heat stabilizer are mixed evenly, and then melt-extruded through a twin-screw extruder to obtain a recycled TPU masterbatch;

[0044] A3. 90 parts of TPU hot melt adhesive particles, 3 parts of recycled TPU masterbatch, 2 parts of antioxidant and 2 parts of anti-yellowing agent are mixed evenly at 155°C to obtain a mixed melt, and then a solid adhesive film is obtained by cast molding and cooling and solidification, and an OPP release film is attached to the surface of the solid adhesive film and then rolled up to obtain the TPU hot melt adhesive film.

[0045] Furthermore, in step A2, the chain extender is a rosin-based chain extender containing terminal hydroxyl groups. In the present invention, the preparation method of the chain extender is specifically as follows: fully dissolve dimerized rosin in tetrahydrofuran, add oxalyl chloride thereto, stir and react for 5 hours, remove the solvent by rotary evaporation, then add triethylamine and ethylene glycol thereto, heat to 55°C and react for 5 hours, and then filter, wash and dry to obtain the chain extender. The molar ratios of dimerized rosin, oxalyl chloride, triethylamine and ethylene glycol are 0.5:1:1:1 respectively.

[0046] Furthermore, in step A2, the colorant is titanium dioxide.

[0047] Furthermore, in step A2, the dispersant is polyether-modified silicone.

[0048] Furthermore, in step A2, the preparation method of the photothermal stabilizer includes the following steps: fully dispersing hindered amine light stabilizer 770 and nano titanium dioxide in a solvent at a molar ratio of 1:2, raising the temperature to 95°C under nitrogen protection, adding 0.25wt% of titanate catalyst thereto and mixing evenly, keeping the temperature for reaction for 15h, and obtaining the photothermal stabilizer by centrifugation, washing and drying after the reaction.

[0049] Furthermore, in step A3, the antioxidant is compounded by antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2.

[0050] Furthermore, in step A3, the anti-yellowing agent is BIORICH BT2000.

[0051] Furthermore, the preparation method of the TPU hot-melt rubber particles includes the following steps: first vacuum dehydrating the polyester polyol, then controlling the temperature at 85°C, slowly dripping diisocyanate therein to carry out a prepolymerization reaction, and then adding a modified epoxy resin to continue the reaction for 2 hours, and then successively adding 1,4-butanediol and dibutyltin dilaurate to continue the reaction, testing its NCO conversion rate to reach the theoretical value and then stopping, and then transferring the obtained viscous liquid to an extruder for molding and cooling and granulating, so as to obtain the TPU hot-melt rubber particles.

[0052] Furthermore, the polyester polyol is compounded with polycaprolactone diol and polycarbonate diol in a mass ratio of 4:1, and the diisocyanate is compounded with hexamethylene diisocyanate and dicyclohexylmethane-4,4'-diisocyanate in a mass ratio of 3:1. In the above system, the molar ratio of OH to NCO is 1:1, the molar ratio of polyester polyol to 1,4-butanediol is 1:1, and the amount of dibutyltin dilaurate is 0.1% of the total mass.

[0053] Furthermore, the preparation method of the modified epoxy resin is specifically as follows: epoxy resin E-51, silane coupling agent KH550 and dibutyltin dilaurate are uniformly mixed, and stirred for reaction at 58° C. for 2 hours under a nitrogen atmosphere to obtain the modified epoxy resin.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that this comparative example provides a method for preparing a recycled TPU hot melt adhesive film with a solid color effect, comprising the following preparation steps:

[0056] A1. After collecting TPU waste by color, wash and dry it, and then put it into a crusher to break it into small particles;

[0057] A2. 80 parts of TPU hot melt adhesive particles, 1.5 parts of TPU waste small particles, 1.2 parts of antioxidants and 1.5 parts of anti-yellowing agents are mixed evenly at 150° C. to obtain a mixed melt, and then a solid adhesive film is obtained by cast molding and cooling and solidification, and an OPP release film is attached to the surface of the solid adhesive film and then rolled up to obtain the TPU hot melt adhesive film.

[0058] The remaining parameters of this comparative example are the same as those of Example 1 and will not be described again here.

[0059] Comparative Example 2

[0060] The difference between this comparative example and Example 1 is that in this comparative example, the chain extender is 1,4-butanediol, and the light stabilizer is a hindered amine light stabilizer.

[0061] Performance Testing

[0062] The performance tests and appearance evaluations of the TPU hot melt adhesive films prepared in Examples 1-2 and Comparative Examples 1-2 were conducted. Among them, the thickness of the TPU hot melt adhesive film was controlled at 0.05 mm, and the tensile strength and bonding strength of each TPU hot melt adhesive film were tested. The tensile strength was determined according to GB / T 7124-2008 Determination of the tensile shear strength of adhesives (rigid material to rigid material). The high-temperature bonding test method is: glue dots are placed on the substrate, the two substrates are cross-lapped and pressure-maintained, and after they are completely cured, they are placed in an oven at 80°C or 150°C, heated for 4 hours, the sample is taken out and placed at room temperature for 2 hours, and then tested on a tensile testing machine. The substrate selected is TPU film / TPU film, and the TPU film is a TPU film with model number ZD-135CM*85A from Guangdong Zhongding Technology Development Co., Ltd., with a thickness of 0.7 mm. The test results are shown in the following table:

[0063]

[0064] It can be seen from the data in the above table that the TPU hot melt adhesive film prepared by the preparation method of Examples 1-2 of the present invention has good tensile strength and bonding strength, and under high temperature treatment, the bonding strength of the TPU hot melt adhesive has no obvious downward trend, indicating that it has good temperature resistance and stability.

[0065] The above specific embodiments are further explanations of the technical solutions and beneficial effects of the present invention, and are not limitations of the implementation methods. For those skilled in the art, any obvious replacements that do not depart from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A method for preparing a recycled TPU hot melt adhesive film with a solid color effect, characterized in that: The method comprises the following preparation steps: A1. After collecting TPU waste by color, wash and dry it, and then put it into a crusher to break it into small particles; A2, the small particles obtained in step A1, the chain extender, the colorant, the dispersant, and the light and heat stabilizer are uniformly mixed, and then melt-extruded through a twin-screw extruder to obtain a recycled TPU masterbatch; A3, the TPU hot melt adhesive particles, the recycled TPU masterbatch, the antioxidant and the anti-yellowing agent are mixed evenly under heating conditions to obtain a mixed melt, and then cast and solidified by cooling to obtain a solid adhesive film, and a release film is attached to the surface of the solid adhesive film and then rolled up to obtain the TPU hot melt adhesive film.

2. The recycled TPU hot melt adhesive film with solid color effect and the preparation method thereof according to claim 1, characterized in that: In step A2, the chain extender is a rosin-based chain extender containing terminal hydroxyl groups.

3. The recycled TPU hot melt adhesive film with solid color effect and the preparation method thereof according to claim 1, characterized in that: In step A2, the colorant is one or more of titanium dioxide, carbon black, ultramarine, phthalocyanine pigment, azo pigment, and quinacridone pigment.

4. The recycled and recyclable TPU hot melt adhesive film with solid color effect and the preparation method thereof according to claim 1, characterized in that: In step A2, the dispersant is at least one of polyethylene wax, polyoxyethylene fatty acid ester, naphthalenesulfonate formaldehyde condensate, and polyether modified silicone.

5. The recycled TPU hot melt adhesive film with solid color effect and the preparation method thereof according to claim 1, characterized in that: In step A2, the preparation method of the light and heat stabilizer comprises the following steps: fully dispersing the hindered amine light stabilizer and nano titanium dioxide in a solvent, raising the temperature to 90-100° C. under nitrogen protection, adding a titanate catalyst thereto and mixing them evenly, keeping the temperature to react for 12-16 hours, and after the reaction is completed, centrifuging, washing and drying to obtain the light and heat stabilizer.

6. The recycled and solid color TPU hot melt adhesive film and the preparation method thereof according to claim 1, characterized in that: In step A3, the antioxidant is at least one of a phosphite antioxidant, a hindered phenol antioxidant, and a thioester antioxidant.

7. The recycled and solid color TPU hot melt adhesive film and the preparation method thereof according to claim 1, characterized in that: In step A3, the anti-yellowing agent is at least one of BIORICH BT2000, UVK-CLV, Chimassorb 944FD, and Revonox U-5068L.

8. The recycled and solid color TPU hot melt adhesive film and the preparation method thereof according to claim 1, characterized in that: The preparation method of the TPU hot melt rubber particles comprises the following steps: first vacuum dehydrating the polyester polyol, then controlling the temperature at 80-90°C, slowly dripping diisocyanate therein to carry out a prepolymerization reaction, then adding a modified epoxy resin to continue the reaction for 1-2 hours, then successively adding 1,4-butanediol and an organic tin catalyst to continue the reaction, testing its NCO conversion rate to reach the theoretical value and then stopping, then transferring the obtained viscous liquid to an extruder for molding processing, and then cooling and granulating to obtain the TPU hot melt rubber particles.

9. The recycled and solid color TPU hot melt adhesive film and the preparation method thereof according to claim 8, characterized in that: The polyester polyol is compounded by polycaprolactone diol and polycarbonate diol in a mass ratio of 3-4:1, and the diisocyanate is compounded by hexamethylene diisocyanate and dicyclohexylmethane-4,4'-diisocyanate in a mass ratio of 2.5-3.5:

1.

10. A recycled TPU hot melt adhesive film with solid color effect, characterized in that: The method is prepared according to any one of claims 1 to 9.

Images