Polyurethane resin, preparation method thereof and TPU car cover

Abstract

The application relates to the technical field of car film, in particular to a polyurethane resin, a preparation method thereof and a TPU car film. The raw material for synthesizing the resin comprises 200 parts of polyol, 8-20 parts of chain extender, 70-100 parts of isocyanate, 0.1-1 part of catalyst, 600-800 parts of solvent and 0.1-2 parts of additive; wherein the polyol comprises at least one of polycaprolactone polyol and polycarbonate polyol; the number average molecular weight of the polyol is 800-2000, and the hydroxyl value is 90-140 mgKOH / g; the solid content of the polyurethane resin is 20-40 wt%, and the viscosity at 25 DEG C is 60-90 million mPas. The TPU car film prepared from the specific polyurethane resin has excellent light transmittance, haze, weather resistance, adhesion and solvent resistance.

Description

Technical Field

[0001] This invention relates to the field of car wrap technology, specifically to a polyurethane resin, its preparation method, and a TPU car wrap. Background Technology

[0002] As a key product for personalized decoration and protection of automotive exteriors, car wrap performance relies on the synthesis process and film structure design of TPU resin. Currently, most car wraps on the market employ a multi-layer composite structure, typically including a pressure-sensitive adhesive layer, a TPU base layer, a color-changing layer, a PU transparent base layer, and a self-healing layer. This type of structure design has significant limitations: firstly, the color-changing layer and the PU transparent base layer are often formed by dissolving TPU particles, resulting in poor interlayer compatibility and a tendency for delamination, severely impacting product lifespan; secondly, the multi-layer structure leads to cumbersome production processes, with the particle dissolution step being time-consuming and labor-intensive, significantly increasing production costs and processing cycles. Existing TPU-related technologies for car wraps have significant shortcomings in terms of structural simplification, interlayer adhesion enhancement, and multi-functional integration. There is an urgent need to develop an integrated TPU resin that can replace the traditional color-changing layer and PU transparent base layer. By optimizing the synthesis formula and process, the production process can be simplified, costs reduced, and the interlayer adhesion, weather resistance, and optical properties of the product comprehensively improved.

[0003] Chinese invention patent application CN118725761A discloses a TPU color-changing car wrap film and its preparation method. This patent uses aliphatic TPU as the substrate and prepares it through a three-layer co-extrusion blown film or casting process by adding color powder / masterbatch, forming a composite structure of a pearlescent coating and a TPU base color layer, which to some extent optimizes the basic mechanical properties of the color-changing car wrap. However, this patent does not break through the traditional multi-layered, separated structural design. The composite of the color-changing layer and the base layer still relies on a physical co-extrusion process, failing to improve interlayer adhesion from the resin molecular structure design level, and cannot fundamentally solve the industry pain point of easy delamination between layers. Secondly, its core technology focuses on molding process optimization, without disclosing a targeted TPU resin synthesis formulation synergistic ratio design, making it difficult to achieve a multi-functional synergistic improvement in weather resistance, solvent resistance, and high adhesion. Thirdly, the processing still requires separate handling of the composite of the masterbatch and the substrate, failing to simplify the production process, and poor particle dispersion uniformity may also affect the product's optical performance and color stability. Summary of the Invention

[0004] The first aspect of this invention provides a polyurethane resin, comprising, by weight, the following raw materials: 200 parts polyol, 8-20 parts chain extender, 70-100 parts isocyanate, 0.1-1 parts catalyst, 600-800 parts solvent, and 0.1-2 parts additives; wherein the polyol has a number average molecular weight of 800-2000 and a hydroxyl value of 90-140 mgKOH / g; and the polyurethane resin has a solid content of 20-40 wt% and a viscosity of 60,000-90,000 mPa at 25°C. s.

[0005] This invention limits the polyol to include at least one of polycaprolactone polyol and polycarbonate polyol, and the number average molecular weight of the polyol is 800-2000 and the hydroxyl value is 90-140 mgKOH / g, which can meet the requirements for the use of TPU car wraps and improve the weather resistance and solvent resistance of TPU car wraps. At least one of polycaprolactone polyol and polycarbonate polyol is selected as the core raw material. Both are aliphatic polyols, and their molecular structures do not contain aromatic rings that are easily degraded by ultraviolet light. Their linear and regular carbon chain structure gives them excellent chemical stability, which improves the weather resistance of TPU car wraps from the source. At the same time, the number average molecular weight of the polyol is limited to 800-2000. This range can ensure that the TPU soft segments have suitable flexibility to adapt to the car wrap's application requirements, while avoiding the mechanical property degradation caused by incomplete reaction due to excessively large molecular weight or excessively small molecular weight. The hydroxyl value range of 90-140 mgKOH / g can accurately match the reaction equivalent of isocyanate and chain extender to form a polyurethane molecular network with moderate crosslinking density. The dense molecular structure can effectively block solvent molecules from penetrating, thereby significantly improving solvent resistance. Furthermore, the obtained polyurethane resin is applied to TPU car wraps. In terms of structural design, this invention abandons the multi-layer composite structure of traditional color-changing car wraps, retaining only a minimal combination of adhesive layer and TPU layer, reducing the number of interfaces between different materials. At the same time, the TPU soft segments formed by polyol have good molecular compatibility with adhesive layer and TPU substrate, and can strengthen interlayer bonding through van der Waals forces and hydrogen bonding. This completely solves the problem of easy delamination caused by poor interfacial compatibility between color-changing layer and PU transparent layer in traditional multi-layer structure, and achieves synergistic improvement in weather resistance, solvent resistance and interlayer stability.

[0006] Optionally, the polyol includes at least one of polycaprolactone polyol and polycarbonate polyol.

[0007] Optionally, the polyol has a number-average molecular weight of 800-1500 and a hydroxyl value of 100-130 mgKOH / g.

[0008] Optionally, the solid content of the polyurethane resin is 25-35 wt%.

[0009] The chain extender includes at least one of 1,4-butanediol, 1,3-propanediol, ethylene glycol, 1,6-hexanediol, neopentyl glycol, dimethylmercaptotoluene diamine, and polyurea depolymerization products.

[0010] The isocyanate includes at least one of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated toluene diisocyanate, m-phenylene dimethyl diisocyanate, 1,4-cyclohexane diisocyanate, and diphenylmethane diisocyanate.

[0011] The catalyst includes at least one of dibutyltin laurate, dibutyltin dimaleate, dibutyltin sulfate, organobismuth catalyst, zinc acetylacetonate, and stannous octoate.

[0012] The solvent includes at least one of N,N-dimethylformamide, butanone, acetone, tetrahydrofuran, ethyl acetate, cyclohexanone, isophorone, and methyl nylonate.

[0013] The additives include UV-resistant additives, including at least one of the following brands: A-770, UV-P, UV-327, UV-328, UV-531, and 2-hydroxy-4-methoxybenzophenone (UV-9).

[0014] The second aspect of the present invention provides a method for preparing polyurethane resin, comprising the following steps: adding a chain extender to a dehydrated polyol, then adding isocyanate, and mixing evenly to obtain a first mixture; adding a catalyst to the first mixture, reacting, adding a solvent to adjust the viscosity, and obtaining a second mixture; adding an additive to the second mixture and mixing evenly.

[0015] The dehydration includes vacuum dehydration, with a dehydration temperature of 110-140℃, a dehydration time of 1-3 hours, and a vacuum degree of -0.10MPa to -0.09MPa.

[0016] The reaction time is 2-5 hours.

[0017] A third aspect of the present invention provides a TPU car cover, comprising a laminated adhesive layer and a TPU layer, wherein the adhesive layer is composed of a prepared polyurethane resin.

[0018] The thickness of the adhesive layer is 80-200 μm.

[0019] The thickness of the adhesive layer is 100-150 μm.

[0020] The method for preparing the TPU car cover includes the following steps: coating a TPU layer with polyurethane resin and drying it to obtain the TPU car cover, wherein the dried polyurethane resin forms an adhesive layer.

[0021] Beneficial effects 1. This invention limits the polyol to include at least one of polycaprolactone polyol and polycarbonate polyol, and the number average molecular weight of the polyol is 800-2000, and the hydroxyl value is 90-140 mgKOH / g, which can meet the requirements for the use of TPU car wraps and improve the weather resistance and solvent resistance of TPU car wraps.

[0022] 2. The TPU car wrap of this invention consists only of an adhesive layer and a TPU layer, which solves the problem of easy delamination in color-changing adhesive layers in the industry.

[0023] 3. The TPU car wrap prepared by this invention has a haze ≤0.5 and a light transmittance ≥96%.

[0024] 4. The TPU car cover prepared by this invention has a tensile strength ≥82MPa.

[0025] 5. The TPU car wrap prepared by this invention, after 7 days of double 85 testing, showed no delamination when torn. Detailed Implementation

[0026] Example 1 A polyurethane resin, by weight, comprises the following raw materials: 200g of polyol (polycaprolactone polyol, Pastor Capa2101A, number average molecular weight of 1000, hydroxyl value of 112mgKOH / g), 10g of chain extender (1,4-butanediol), 81.492g of isocyanate (dicyclohexylmethane diisocyanate), 0.5g of catalyst (dibutyltin laurylate), 685g of solvent (342g of N,N-dimethylformamide + 343g of butanone), and 0.6g of additives (UV additives: 0.3gA-770 + 0.3gUV-P).

[0027] A method for preparing a polyurethane resin includes the following steps: A polyol is added to a reaction vessel and heated to 120°C. Under vacuum, the mixture is dehydrated for 2 hours with stirring at a vacuum degree of -0.10 MPa. The temperature is then lowered to 60°C. 10 g of 1,4-butanediol (chain extender) and 2 g of polycaprolactone polyol (Pastor Capa 3050) are added and stirred for 20 minutes until homogeneous. Then, 81.492 g of dicyclohexylmethane diisocyanate is added and stirred for 10 minutes. Next, 0.5 g of dibutyltin laurate is added and the mixture is reacted at 80-90°C for 3-4 hours. Depending on the viscosity, 342 g of N,N-dimethylformamide and 343 g of butanone are gradually added. Finally, 0.3 g of A-770 and 0.3 g of UV-P are added and stirred for 20 minutes. The mixture is then cooled to 50°C and discharged to obtain a polyurethane resin with a solid content of 30% and a viscosity of 70,000-80,000 at 25°C.

[0028] A TPU car cover comprises a laminated adhesive layer and a TPU layer, wherein the adhesive layer is composed of the aforementioned polyurethane resin; the thickness of the adhesive layer is 120 μm; the TPU car cover is formed by coating polyurethane resin onto TPU; the TPU layer is purchased from Zhejiang Kaiyang New Material Co., Ltd.

[0029] Example 2 A polyurethane resin, by weight, comprises the following raw materials: 200g of polyol (polycaprolactone polyol, Pastor Capa2101A, number average molecular weight of 1000, hydroxyl value of 112mgKOH / g; polycarbonate polyol, number average molecular weight of 1000, hydroxyl value of 110mgKOH / g), 10g of chain extender (1,4-butanediol), 81.492g of isocyanate (dicyclohexylmethane diisocyanate), 0.5g of catalyst (dibutyltin laurylate), 685g of solvent (342g N,N-dimethylformamide + 343g butanone), and 0.6g of additives (UV additives: 0.3g A-770 + 0.3g UV-P).

[0030] A method for preparing a polyurethane resin includes the following steps: 100g of Pastor Capa2101A and 100g of Ube UH100 are added to a reaction vessel and heated to 120°C. The mixture is then vacuum-dehydrated for 2 hours with stirring, at a vacuum degree of -0.10 MPa. The temperature is lowered to 60°C, and 10g of 1,4-butanediol and 2g of Pastor Capa3050 are added. The mixture is stirred for 20 minutes until homogeneous. Then, 83.987g of dicyclohexylmethane diisocyanate is added and stirred for 10 minutes. Next, 0.5g of dibutyltin laurylate is added, and the mixture is reacted at 80-90°C for 3-4 hours. Depending on the viscosity, 342g of N,N-dimethylformamide and 343g of butanone are gradually added. Finally, 0.3g of A-770 and 0.3g of UV-P are added, and the mixture is stirred for 20 minutes. The mixture is then cooled to 50°C and discharged to obtain a polyurethane resin with a solid content of 30% and a viscosity of 60,000-90,000 N / A at 25°C.

[0031] A TPU car cover comprises a laminated adhesive layer and a TPU layer, wherein the adhesive layer is composed of the aforementioned polyurethane resin; the thickness of the adhesive layer is 120 μm; the TPU car cover is formed by coating polyurethane resin onto TPU; the TPU layer is purchased from Zhejiang Kaiyang New Material Co., Ltd.

[0032] Example 3 A polyurethane resin, by weight, comprises the following raw materials: 200g of polyol (polycaprolactone polyol, Pastor Capa2101A, number average molecular weight of 1000, hydroxyl value of 112mgKOH / g; polycarbonate polyol, number average molecular weight of 1000, hydroxyl value of 110mgKOH / g), 10g of chain extender (1,4-butanediol), 81.492g of isocyanate (dicyclohexylmethane diisocyanate), 0.5g of catalyst (dibutyltin laurylate), 685g of solvent (342g N,N-dimethylformamide + 343g butanone), and 0.6g of additives (UV additives: 0.3g A-770 + 0.3g UV-P).

[0033] A method for preparing a polyurethane resin includes the following steps: 50g of Pastor Capa2101A and 150g of Ube UH100 (Japan) are added to a reaction vessel and heated to 120°C. The mixture is then vacuum-dehydrated for 2 hours with stirring, at a vacuum degree of -0.10 MPa. The temperature is lowered to 60°C, and 14g of 1,4-butanediol and 2g of Pastor Capa3050 are added. The mixture is stirred for 20 minutes until homogeneous. Then, 92.904g of dicyclohexylmethane diisocyanate is added, and the mixture is stirred for 10 minutes. Next, 0.5g of dibutyltin laurylate is added, and the mixture is reacted at 80-90°C for 3-4 hours. Depending on the viscosity, 342g of N,N-dimethylformamide and 343g of butanone are gradually added. Finally, 0.3g of A-770 and 0.3g of UV-P are added, and the mixture is stirred for 20 minutes. The mixture is then cooled to 50°C and discharged to obtain a polyurethane resin with a solid content of 30% and a viscosity of 60,000-90,000 N / A at 25°C.

[0034] A TPU car cover comprises a laminated adhesive layer and a TPU layer, wherein the adhesive layer is composed of the aforementioned polyurethane resin; the thickness of the adhesive layer is 120 μm; the TPU car cover is formed by coating polyurethane resin onto TPU; the TPU layer is purchased from Zhejiang Kaiyang New Material Co., Ltd.

[0035] Comparative Example 1 A method for preparing a polyurethane resin includes the following steps: 200g of polyol (polycaprolactone polyol, Asahikawa Chemical XCP-1024) is added to a reaction vessel and heated to 120℃. Under vacuum, the resin is dehydrated for 2 hours with stirring at a vacuum degree of -0.10MPa. The temperature is then lowered to 60℃, and 10g of 1,4-butanediol and 2g of Pastor Capa3050 are added. The mixture is stirred for 20 minutes until homogeneous. Then, 81.492g of dicyclohexylmethane diisocyanate is added and stirred for 10 minutes. Next, 0.5g of dibutyltin laurylate is added, and the mixture is reacted at 80-90℃ for 3-4 hours. Depending on the viscosity, 342g of N,N-dimethylformamide and 343g of butanone are gradually added. Finally, 0.3g of A-770 and 0.3g of UV-P are added, and the mixture is stirred for 20 minutes. The mixture is then cooled to 50℃ and discharged to obtain a polyurethane resin with a solid content of 30% and a viscosity of 60,000-90,000 at 25℃.

[0036] A TPU car cover comprises a TPU layer, an adhesive layer, and a transparent PU layer (from Zhejiang Kaiyang New Material Co., Ltd.) stacked sequentially. The adhesive layer is composed of the aforementioned polyurethane resin. The thickness of the adhesive layer is 120 μm. The preparation method of the TPU car cover includes the following steps: coating the TPU layer with polyurethane resin and drying it to obtain the TPU car cover. The dried polyurethane resin forms the adhesive layer. The TPU layer is purchased from Zhejiang Kaiyang New Material Co., Ltd.

[0037] Performance testing methods The TPU car wraps obtained in the examples and comparative examples were subjected to performance tests, and the test data are listed in Table 1.

[0038] Light transmittance, haze: Refer to GB / T 2410-2008 Elongation at break, tensile strength, tear strength: Refer to GB / T 528-2009 Weather resistance QUV: Refer to GB / T 23987.3-2025 Adhesion: Refer to GB / T 33049-2016 Performance test data Table 1

Claims

1. A polyurethane resin, characterized in that, The raw materials, by weight, include: 200 parts polyol, 8-20 parts chain extender, 70-100 parts isocyanate, 0.1-1 parts catalyst, 600-800 parts solvent, and 0.1-2 parts additives; the polyol includes at least one of polycaprolactone polyol and polycarbonate polyol; the number average molecular weight of the polyol is 800-2000, and the hydroxyl value is 90-140 mgKOH / g; the solid content of the polyurethane resin is 20-40 wt%, and the viscosity at 25°C is 60,000-90,000 mPa. s.

2. The polyurethane resin according to claim 1, characterized in that, The polyol has a number-average molecular weight of 800-1500 and a hydroxyl value of 100-130 mgKOH / g.

3. The polyurethane resin according to claim 2, characterized in that, The solid content of the polyurethane resin is 25-35 wt%.

4. The polyurethane resin according to claim 3, characterized in that, The chain extender includes at least one of 1,4-butanediol, 1,3-propanediol, ethylene glycol, 1,6-hexanediol, neopentyl glycol, dimethylmercaptotoluene diamine, neopentyl glycol, and polyurea depolymerization products.

5. The polyurethane resin according to claim 4, characterized in that, The isocyanate includes at least one of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated toluene diisocyanate, m-phenylene dimethyl diisocyanate, 1,4-cyclohexane diisocyanate, and diphenylmethane diisocyanate.

6. A method for preparing the polyurethane resin according to any one of claims 1-5, characterized in that, Includes the following steps: Chain extender is added to dehydrated polyol, then isocyanate is added and mixed evenly to obtain a first mixture; catalyst is added to the first mixture to react, solvent is added to adjust viscosity to obtain a second mixture; additives are added to the second mixture and mixed evenly.

7. The method for preparing the polyurethane resin according to claim 6, characterized in that, The dehydration includes vacuum dehydration, with a dehydration temperature of 110-140℃, a dehydration time of 1-3 hours, and a vacuum degree of -0.10~-0.09MPa.

8. A TPU car cover, characterized in that, It includes a laminated adhesive layer and a TPU layer, wherein the adhesive layer is composed of the polyurethane resin prepared according to claim 6 or 7.

9. The TPU car cover according to claim 8, characterized in that, The thickness of the adhesive layer is 80-200 μm.

10. The TPU car cover according to claim 9, characterized in that, The thickness of the adhesive layer is 100-150 μm.

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