Solvent-free foamed TPU (thermoplastic polyurethane) high-low temperature film and preparation method thereof

Abstract

The invention relates to the technical field of TPU, in particular to a solvent-free foamed TPU high-low temperature film and a preparation method thereof. The solvent-free foaming TPU high and low temperature film is prepared from the following raw materials in parts by weight: 25 to 35 parts of isocyanate, 50 to 60 parts of polyhydric alcohol, 8 to 12 parts of a composite chain extender, 0.02 to 0.1 part of a catalyst, 0.1 to 0.3 part of an antioxidant and 0.1 to 0.3 part of an ultraviolet absorbent, the composite chain extender is a mixture of micromolecular dihydric alcohol and a bio-based chain extender. The environment-friendly coating has the advantages of excellent environment-friendly performance, no chemical solvent residue, no VOC (volatile organic compound) pollution, avoidance of tail gas treatment in the preparation process, reduction of energy loss in production, and good mechanical property and temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of TPU technology, specifically to a solvent-free foamed TPU high and low temperature film and its preparation method. Background Technology

[0002] High and low temperature film is a double-layer (or multi-layer) composite film, mainly consisting of a high-temperature film layer with a higher melting point and a low-temperature film layer with a lower melting point. Utilizing the melting point difference between the two layers, a seamless bonding process combining hot-pressing and surface decoration is achieved. The high-temperature film layer provides protection and wear resistance, while the low-temperature film layer melts during the seamless hot-pressing process, effectively bonding the material to be processed with the high-temperature film layer, acting as a hot-melt adhesive. Due to its simplicity, softness, elasticity, three-dimensionality, and ease of use, high and low temperature film is widely used in the production and processing of various textile fabrics such as footwear, apparel, and bags. It is one of the preferred materials for many product categories, including fashion casual sports brands and sports equipment.

[0003] Thermoplastic polyurethane elastomer, also known as thermoplastic polyurethane rubber, abbreviated as TPU, is a type of (AB) n TPU is a block linear polymer, where A is a high molecular weight (1000~6000) polyester or polyether, and B is a diol containing 2~12 straight-chain carbon atoms. The chemical structure between the A and B segments is a diisocyanate. Thermoplastic polyurethane (TPU) rubber is cross-linked by intermolecular hydrogen bonds or by slight cross-linking between macromolecular chains. These two cross-linking structures are reversible with increasing or decreasing temperature. In the molten or solution state, the intermolecular forces weaken, but after cooling or solvent evaporation, strong intermolecular forces reconnect them, restoring the original solid properties. TPU has excellent abrasion resistance, ozone resistance, high strength, good elasticity, low temperature resistance, and good oil and chemical resistance. In the current TPU preparation technology, because molecules capable of forming multiple hydrogen bonds usually have high melting points, the polymerization reaction requires the use of large amounts of organic solvents (such as tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and N,N-dimethylamide (DMF)) to dissolve the monomers to facilitate the polymerization reaction. However, due to the use of a large amount of organic solvents, a large amount of volatile organic compounds (VCOs) are released into the atmosphere during the TPU curing process, causing huge pollution to the ecological environment and posing an impact and threat to human survival.

[0004] Therefore, the present invention provides a solvent-free foamed TPU high and low temperature film and its preparation method to solve the above-mentioned problems. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to overcome the problems existing in the prior art and provide a solvent-free foamed TPU high and low temperature film. This high and low temperature film has no chemical solvent residue, no VOC pollution, avoids the treatment of exhaust gas during the preparation process, reduces energy consumption in production, has excellent environmental performance, and also has good mechanical properties and temperature resistance characteristics.

[0006] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: A solvent-free foamed TPU high and low temperature film comprises the following raw materials in parts by weight: 25-35 parts isocyanate, 50-60 parts polyol, 8-12 parts composite chain extender, 0.02-0.1 parts catalyst, 0.1-0.3 parts antioxidant, and 0.1-0.3 parts ultraviolet absorber; wherein the composite chain extender is a mixture of small molecule diol and bio-based chain extender. This invention, by optimizing the ratio of isocyanate to polyol, achieves uniform foaming without relying on organic solvents, while maintaining the excellent low-temperature and high-temperature resistance of TPU. Furthermore, by selecting the composite chain extender, the small molecule diol can increase the crosslinking density of TPU and enhance its mechanical properties, while the bio-based chain extender can improve the environmental friendliness of the TPU polymerization reaction, reducing negative environmental impacts. Ultimately, it achieves a film with no chemical solvent residue, no VOC pollution, and certain mechanical and temperature resistance properties.

[0007] Preferably, the composite chain extender is a mixture of a small molecule diol and a bio-based chain extender in a weight ratio of 1-3:1. Adding an appropriate amount of bio-based chain extender can not only reduce carbon emissions but also improve the sustainability of TPU, while simultaneously imparting superior biodegradability to the material. However, excessive amounts of bio-based chain extender can lead to a decrease in the mechanical properties of TPU; therefore, its addition amount needs to be controlled.

[0008] Preferably, the isocyanate is selected from one or more of 1,5-pentanediisocyanate, L-lysine diisocyanate, and dimeric diisocyanate. 1,5-pentanediisocyanate has a structure and chemical properties similar to hexamethylene diisocyanate (a traditional petroleum-based isocyanate), but it has a lower carbon content and higher activity. Therefore, using it as the hard segment of TPU can effectively improve the crystallinity and mechanical properties of the material, while reducing reaction temperature and energy consumption. L-lysine diisocyanate degrades to produce L-lysine, an amino acid required by the human body. Using it as the hard segment of TPU can effectively avoid the biotoxicity problem of TPU degradation products, and it has excellent biocompatibility, giving TPU excellent biodegradability and biocompatibility. Dimeric diisocyanate has a thirty-six-carbon dimer fatty acid backbone and a cyclohexyl group, and can react with compounds having two or more active hydrogen atoms. Using it as the hard segment of TPU can improve the flexibility, low toxicity, and water resistance of TPU.

[0009] Preferably, the polyol is polypropylene carbonate diol. The main chain of polypropylene carbonate diol is primarily composed of alternating copolymerization of carbon dioxide and propylene oxide. It is a polyol containing both ester and ether bonds. Using it as the soft segment of TPU leverages its ester bonds to improve the mechanical and abrasion resistance of the TPU, while its ether bonds enhance its flexibility and water resistance. Furthermore, polypropylene carbonate diol can replace traditional petroleum-based polyester / polyether polyols, possessing low carbon footprint, sustainability, and biodegradability. Using it as a polyol effectively improves the biodegradability, mechanical properties, water resistance, and flame retardancy of TPU.

[0010] Preferably, the small molecule diol is selected from one or more of 1,4-butanediol, ethylene glycol, and hexanediol.

[0011] Preferably, the bio-based chain extender is vanillin diol with imine bonds. Vanillin diol with imine bonds has high reactivity due to the imine bonds it contains, enabling it to undergo hydrogen bonding with isocyanates and accumulate with the crystalline phase. This induces microphase separation between hard and soft segments, allowing the hard segments to disperse among the soft segments and form a glassy micro-region structure, thereby improving the mechanical strength and heat resistance of TPU.

[0012] Preferably, the preparation steps of the vanillin diol with imine bonds are as follows: (1) First, vanillin alcohol is dissolved in dichloromethane, and m-phenylenediamine is slowly added dropwise to the vanillin alcohol solution at 40-50℃; (2) Then, the temperature is heated to 55-60℃, and the reaction is refluxed for 6-8 hours to obtain the primary product; (3) Finally, the primary product is washed multiple times with dichloromethane, filtered, and dried to obtain vanillin diol with imine bonds. On the one hand, imine bonds can react with water and break under acidic conditions, and can also undergo metathesis reactions with compounds containing amino groups. That is to say, using it as a chain extender for TPU can give TPU degradable and recyclable properties, which is beneficial to environmental protection; on the other hand, its raw materials are all derived from bio-based resources, which helps to reduce dependence on petroleum-based raw materials and improve the sustainability of materials.

[0013] Preferably, the catalyst is selected from one or more of dibutyltin dilaurate, stannous octoate, and butyltin diacetate.

[0014] Preferably, the antioxidant is selected from one or more of antioxidant 1010, antioxidant 1024 and antioxidant 264.

[0015] Preferably, the ultraviolet absorber is selected from one or more of ultraviolet absorbers UV-P, UV-O, and UV-9.

[0016] A method for preparing the above-mentioned solvent-free foamed TPU high and low temperature film includes the following steps: S1. Add the isocyanate and polyol in parts by weight to the reaction vessel and react at 80-100℃ for 2-4 hours to obtain the prepolymer; S2. Then add the composite chain extender, catalyst, antioxidant and ultraviolet absorber to the reaction vessel and react at 100-120℃ for 3-5 hours. Then add the product to the twin-screw extruder and extrude and granulate at 160-220℃ to obtain TPU particles. S3. Then add TPU granules to the casting machine for melting, and then cast them into the coating machine. After coating, a semi-finished product is obtained. S4. Finally, the semi-finished product is laminated with TPU hot melt adhesive film to obtain solvent-free foamed TPU high and low temperature film.

[0017] Preferably, in step S3, TPU particles are added to a heating kettle for heating, and then cast into a foaming extruder. The TPU material melts under the conveying and shearing of the screw. The melt enters the normal pressure environment through the die head, and the pressure is released, which is the foaming process, to obtain a lightweight porous TPU base film. After passing through a shaping and cooling device, the porous TPU base film forms a stable TPU high-temperature film.

[0018] By employing a semi-prepolymer method, free isocyanate is used as a solvent during the chain extension stage to reduce the viscosity of the system. The resulting TPU exhibits superior cell structure uniformity and dimensional stability, while also improving the material's suitability under extreme temperature conditions.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The solvent-free foamed TPU high and low temperature film provided by this invention achieves uniform foaming without relying on organic solvents by optimizing the ratio of isocyanate to polyol, while maintaining the excellent low-temperature and high-temperature resistance of TPU. In addition, by selecting composite chain extenders, small molecule diols can increase the crosslinking density of TPU and enhance mechanical properties, while bio-based chain extenders can improve the environmental protection characteristics of TPU polymerization reaction and reduce the negative impact on the environment. Ultimately, it achieves no chemical solvent residue, no VOC pollution, avoids the treatment of exhaust gas during the preparation process, reduces energy consumption in production, and has certain mechanical properties and temperature resistance.

[0020] 2. The preparation method provided by this invention uses a semi-prepolymer method, and the raw materials used are all bio-based, which is green and environmentally friendly. The preparation process is simple and easy to operate, with no chemical solvent residue and no VOC pollution. Detailed Implementation

[0021] The present invention will now be described in detail with reference to specific embodiments. It should also be noted that, in order to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can also use other alternative methods to implement some well-known technologies.

[0022] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0023] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0024] Example 1 A solvent-free foamed TPU high and low temperature film comprises the following raw materials in parts by weight: 25 parts isocyanate, 500 parts polyol, 8 parts composite chain extender, 0.02 parts catalyst, 0.1 parts antioxidant and 0.1 parts ultraviolet absorber; wherein the composite chain extender is a mixture of small molecule diol and bio-based chain extender.

[0025] Preferably, the composite chain extender is a mixture of a small molecule diol and a bio-based chain extender in a weight ratio of 1:1, wherein the isocyanate is selected as 1,5-pentanediisocyanate, the polyol is selected as polypropylene carbonate diol, the small molecule diol is selected as 1,4-butanediol, and the bio-based chain extender is selected as vanillin diol with an imine bond.

[0026] Preferably, the preparation steps of the vanillin diol with imine bond are as follows: (1) first dissolve vanillin in dichloromethane, and slowly add m-phenylenediamine to the vanillin solution at 40°C; (2) then heat the temperature to 55°C, reflux for 6 hours to obtain the primary product; (3) finally wash the primary product with dichloromethane several times, filter and dry to obtain vanillin diol with imine bond.

[0027] Preferably, the catalyst is dibutyltin dilaurate, the antioxidant is antioxidant 1010, and the ultraviolet absorber is ultraviolet absorber UV-P.

[0028] A method for preparing the above-mentioned solvent-free foamed TPU high and low temperature film includes the following steps: S1. Add the isocyanate and polyol in parts by weight to the reaction vessel and react at 80°C for 2 hours to obtain the prepolymer. S2. Then add the composite chain extender, catalyst, antioxidant and ultraviolet absorber to the reaction vessel, react at 100°C for 3 hours, and then add the product to the twin-screw extruder and extrude and granulate at 160°C to obtain TPU particles. S3. Then add TPU granules to the casting machine for melting, and then cast them into the coating machine. After coating, a semi-finished product is obtained. S4. Finally, the semi-finished product is laminated with TPU hot melt adhesive film to obtain solvent-free foamed TPU high and low temperature film.

[0029] Example 2 A solvent-free foamed TPU high and low temperature film comprises the following raw materials in parts by weight: 35 parts isocyanate, 60 parts polyol, 12 parts composite chain extender, 0.1 parts catalyst, 0.3 parts antioxidant and 0.3 parts ultraviolet absorber; wherein the composite chain extender is a mixture of small molecule diol and bio-based chain extender.

[0030] Preferably, the composite chain extender is a mixture of a small molecule diol and a bio-based chain extender in a weight ratio of 3:1, wherein the isocyanate is selected from L-lysine diisocyanate, the polyol is selected from polypropylene carbonate diol, the small molecule diol is selected from ethylene glycol, and the bio-based chain extender is selected from vanillin diol with an imine bond.

[0031] Preferably, the preparation steps of the vanillin diol with imine bond are as follows: (1) Vanillin alcohol is first dissolved in dichloromethane, and m-phenylenediamine is slowly added dropwise to the vanillin alcohol solution at 50°C; (2) The temperature is then heated to 60°C, and the reaction is refluxed for 8 hours to obtain the primary product; (3) Finally, the primary product is washed with dichloromethane several times, filtered, and dried to obtain vanillin diol with imine bond.

[0032] Preferably, the catalyst is stannous octoate, the antioxidant is antioxidant 1024 and antioxidant 264, and the ultraviolet absorber is ultraviolet absorber UV-0.

[0033] A method for preparing the above-mentioned solvent-free foamed TPU high and low temperature film includes the following steps: S1. Add the isocyanate and polyol in parts by weight to the reaction vessel and react at 100°C for 4 hours to obtain the prepolymer. S2. Then add the composite chain extender, catalyst, antioxidant and ultraviolet absorber to the reaction vessel, react at 120°C for 5 hours, and then add the product to the twin-screw extruder and extrude and granulate at 220°C to obtain TPU particles. S3. Then add TPU granules to the casting machine for melting, and then cast them into the coating machine. After coating, a semi-finished product is obtained. S4. Finally, the semi-finished product is laminated with TPU hot melt adhesive film to obtain solvent-free foamed TPU high and low temperature film.

[0034] Example 3 A solvent-free foamed TPU high and low temperature film comprises the following raw materials in parts by weight: 30 parts isocyanate, 55 parts polyol, 10 parts composite chain extender, 0.06 parts catalyst, 0.2 parts antioxidant and 0.2 parts ultraviolet absorber; wherein the composite chain extender is a mixture of small molecule diol and bio-based chain extender.

[0035] Preferably, the composite chain extender is a mixture of a small molecule diol and a bio-based chain extender in a weight ratio of 2:1, wherein the isocyanate is selected as diisocyanate, the polyol is selected as polypropylene carbonate diol, the small molecule diol is selected as hexanediol, and the bio-based chain extender is selected as vanillin diol with an imine bond.

[0036] Preferably, the preparation steps of the vanillin diol with imine bond are as follows: (1) Vanillin alcohol is first dissolved in dichloromethane, and m-phenylenediamine is slowly added dropwise to the vanillin alcohol solution at 45°C; (2) The temperature is then heated to 58°C, and the reaction is refluxed for 7 hours to obtain the primary product; (3) Finally, the primary product is washed with dichloromethane several times, filtered, and dried to obtain vanillin diol with imine bond.

[0037] Preferably, the catalyst is butyltin diacetate, the antioxidant is antioxidant 264, and the ultraviolet absorber is ultraviolet absorber UV-9.

[0038] A method for preparing the above-mentioned solvent-free foamed TPU high and low temperature film includes the following steps: S1. Add the isocyanate and polyol in parts by weight to the reaction vessel and react at 90°C for 3 hours to obtain the prepolymer; S2. Then add the composite chain extender, catalyst, antioxidant and ultraviolet absorber to the reaction vessel, react at 110°C for 4 hours, and then add the product to the twin-screw extruder and extrude and granulate at 190°C to obtain TPU particles. S3. Then add TPU granules to the casting machine for melting, and then cast them into the coating machine. After coating, a semi-finished product is obtained. S4. Finally, the semi-finished product is laminated with TPU hot melt adhesive film to obtain solvent-free foamed TPU high and low temperature film.

[0039] Comparative Example 1 The difference between this comparative example and Example 3 is that an equal amount of 1,4-butanediol is used instead of vanillin diol with an imine bond.

[0040] Comparative Example 2 The difference between this comparative example and Example 3 is that an equal amount of vanillin diol with imine bonds is used instead of hexanediol.

[0041] Comparative Example 3 The difference between this comparative example and Example 3 is that an equal amount of polyether-ester block diol is used instead of polypropylene carbonate diol.

[0042] Performance testing: The solvent-free foamed TPU high and low temperature films prepared in Examples 1-3 and Comparative Examples 1-3 were tested respectively, and the test results are shown in the table below.

[0043]

[0044] As can be seen from the table above, the solvent-free foamed TPU high and low temperature films prepared in Examples 1-3 have excellent mechanical properties, hydrolysis resistance, and yellowing resistance. They are free of VOC pollution and chemical solvent residues, and their density is significantly reduced, ranging from 0.32 to 0.35 g / cm³. 3 The density is significantly lower than that of traditional TPU (1.1-1.2 g / cm³). 3 ).

[0045] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A solvent-free foamed TPU high-low temperature film, characterized by: The raw materials include the following weight parts: isocyanate 25-35 parts, polyol 50-60 parts, composite chain extender 8-12 parts, catalyst 0.02-0.1 part, antioxidant 0.1-0.3 part and ultraviolet absorber 0.1-0.3 part; the composite chain extender is a mixture of small molecule diol and bio-based chain extender.

2. The solvent-free foamed TPU high-low temperature film according to claim 1, characterized in that: The isocyanate is selected from one or more of 1,5-pentane diisocyanate, L-lysine diisocyanate and dimer diisocyanate.

3. The solvent-free foamed TPU high-low temperature film according to claim 1, characterized in that: The polyol is selected from polypropylene carbonate glycol.

4. The solvent-free foamed TPU high-low temperature film according to claim 1, characterized in that: The small molecule diol is selected from one or more of 1,4-butanediol, ethylene glycol and hexanediol.

5. The solvent-free foamed TPU high-low temperature film according to claim 1, characterized in that: The bio-based chain extender is selected from vanillin diol with imine bond.

6. The solvent-free foamed TPU high-low temperature film according to claim 5, characterized in that: The preparation steps of the vanillin diol with imine bond are as follows: (1) first, vanillyl alcohol is dissolved in dichloromethane, and m-xylene methylamine is slowly added to the vanillyl alcohol solution at 40-50 DEG C; (2) then heat the temperature to 55-60 DEG C, condense reflux reaction for 6-8 h, obtain the reaction primary product; (3) finally, the reaction primary product is washed with dichloromethane for several times, filtered and dried to obtain the vanillin diol with imine bond.

7. The solvent-free foamed TPU high-low temperature film according to claim 1, characterized in that: The catalyst is selected from one or more of dibutyl tin dilaurate, stannous octoate and butyl tin diacetate.

8. The solvent-free foamed TPU high-low temperature film according to claim 1, characterized in that: The antioxidant is selected from one or more of antioxidant 1010, antioxidant 1024 and antioxidant 264.

9. The solvent-free foamed TPU high-low temperature film according to claim 1, characterized in that: The ultraviolet absorber is selected from one or more of ultraviolet absorber UV-P, ultraviolet absorber UV-0 and ultraviolet absorber UV-9.

10. A process for the preparation of a solvent-free foamed TPU high-low temperature film as claimed in any one of claims 1 to 9, characterized in that: The method comprises the following steps: S1, the isocyanate and the polyol are added to the reaction container together, and the pre-polymer is obtained by reacting at 80-100 DEG C for 2-4 h; S2, the composite chain extender, catalyst, antioxidant and ultraviolet absorber are added to the reaction container, and the product is obtained by reacting at 100-120 DEG C for 3-5 h, and then the product is added to the double screw extruder and extruded and granulated at 160-220 DEG C to obtain TPU particles; S3, the TPU particles are added to the casting machine for melting, and then coated on the coating machine to obtain a semi-finished product through the coating process; S4, finally, the semi-finished product is compounded with the TPU hot melt adhesive film to obtain a solvent-free foaming TPU high-low temperature film.

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