Thermoplastic polyurethane resin applicable to preparation of automobile coating

Abstract

The invention discloses thermoplastic polyurethane resin suitable for preparing an automobile coating. The thermoplastic polyurethane resin is formed by carrying out polymerization reaction on a reaction mixture, and the reaction mixture comprises an isocyanate material, a polyol material and a chain extender. The chemical structure of the isocyanate material does not have a benzene ring. The isocyanate material is selected from at least one of a material group consisting of dicyclohexylmethane diisocyanate (H12MDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), and the isocyanate material is selected from at least one of a material group consisting of dicyclohexylmethane diisocyanate (H12MDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). The polyol material is selected from at least one of a material group consisting of polycaprolactone polyol and polyether polyol. The chain extender is a dihydric alcohol chain extender. Therefore, the problems that in the prior art, TPU materials are prone to yellowing over time, physical properties are reduced due to hydrolysis, crystal points are prone to being generated through film spraying processing, transparency is poor and the like are solved, and then the quality of automobile film coating can be effectively improved.

Description

Technical Field

[0001] The invention relates to a thermoplastic polyurethane resin, in particular to a thermoplastic polyurethane resin suitable for preparing automobile wrapping films. Background Art

[0002] Traditional TPU materials used in automotive wrapping are prone to yellowing over time and degradation of physical properties due to hydrolysis. In addition, the finished products of traditional TPU materials used in automotive wrapping are prone to crystal points and poor transparency after lamination, resulting in poor quality of automotive wrapping.

[0003] Therefore, the inventors felt that the above defects could be improved, so they devoted themselves to research and applied scientific principles, and finally proposed the present invention which has a reasonable design and effectively improves the above defects. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a thermoplastic polyurethane resin suitable for preparing automobile coatings in view of the deficiencies of the prior art.

[0005] In order to solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a thermoplastic polyurethane resin suitable for preparing an automobile film, which is formed by a reaction mixture through a polymerization reaction, wherein the reaction mixture comprises: an isocyanate material, the chemical structure of which does not have a benzene ring, and the isocyanate material is selected from dicyclohexylmethane diisocyanate (H 12 The invention discloses a novel polyol material, comprising: a polyol material selected from at least one of the material group consisting of polycaprolactone polyol and polyether polyol; and a chain extender, wherein the chain extender is a diol chain extender.

[0006] Preferably, the isocyanate material comprises a first isocyanate component and a second isocyanate component; wherein the first isocyanate component is dicyclohexylmethane diisocyanate (H 12 The second isocyanate component is at least one of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI).

[0007] Preferably, based on the total weight of the first isocyanate component and the second isocyanate component being 100%, a first weight percentage of the first isocyanate component is between 70% and 98%, and a second weight percentage of the second isocyanate component is between 2% and 30%.

[0008] Preferably, the polyol material is further limited to polycaprolactone polyol, which is formed by polymerization reaction of small molecule diol and caprolactone monomer; wherein the small molecule diol is a diol with carbon number C2 to C8.

[0009] Preferably, the small molecule diol is 1,6-hexanediol, and the number average molecular weight (Mn) of the polyol material is between 1,000 g / mol and 5,000 g / mol; wherein the chain extender is 1,4-butanediol (14BG).

[0010] Preferably, the NCO / OH equivalent ratio between the isocyanate group (—NCO) of the isocyanate material and the hydroxyl group (—OH) of the polyol material is between 0.998 and 1.015.

[0011] Preferably, the reaction mixture further comprises: an anti-hydrolysis agent and a chain terminator, the anti-hydrolysis agent is carbodiimide, and the chain terminator is a long-chain fatty alcohol having a carbon number of C12 to C18.

[0012] Preferably, the chain terminator is at least one selected from the group consisting of stearyl alcohol, lauryl alcohol, and oleic alcohol.

[0013] Preferably, based on 100 parts by weight of the total weight of the reaction mixture, the amount of the isocyanate material is between 20 and 60 parts by weight, the amount of the polyol material is between 20 and 60 parts by weight, the amount of the chain extender is between 5 and 20 parts by weight, the amount of the anti-hydrolysis agent is between 0.1 and 1 parts by weight, and the amount of the chain terminator is between 0.01 and 0.3 parts by weight.

[0014] Preferably, the thermoplastic polyurethane resin has a melt index of 1 to 5 g / 10 min / 200°C.

[0015] The beneficial effect of the present invention is that the thermoplastic polyurethane resin suitable for preparing automobile wrapping provided by the present invention can effectively improve the problems of TPU materials in the prior art such as yellowing over time, degradation of physical properties due to hydrolysis, easy generation of crystal points and poor transparency after lamination processing, etc. through "material selection and matching of isocyanate materials and polyol materials", thereby effectively improving the quality of automobile wrapping. DETAILED DESCRIPTION

[0016] The following specific embodiments are used to illustrate the embodiments disclosed in the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without deviating from the concept of the present invention. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention. It should be understood that although the terms "first", "second", "third" and the like may be used herein to describe various materials or parameters, these materials or parameters should not be limited by these terms. These terms are mainly used to distinguish one material from another material, or one parameter from another parameter. In addition, the term "or" used in this article may include any one or more combinations of the associated listed items depending on the actual situation.

[0017] [Thermoplastic polyurethane resin]

[0018] One of the purposes of the embodiments of the present invention is to provide a thermoplastic polyurethane resin (TPU resin), and in particular to provide a thermoplastic polyurethane resin suitable for preparing automobile wrapping films.

[0019] The thermoplastic polyurethane resin of the present invention is formed by a reaction mixture through a polymerization reaction, wherein the reaction mixture includes an isocyanate material, a polyol material, a chain extender, an anti-hydrolysis agent, and a chain terminator.

[0020] It should be noted that, in this embodiment, although the reaction mixture is not limited, a UV absorber, a photo-stabilizer, other auxiliary additive components (such as antioxidants, etc.), and / or other solvent components can be selectively added.

[0021] Based on 100 parts by weight of the total weight of the reaction mixture, the amount of the isocyanate material is between 20 parts by weight and 60 parts by weight, preferably between 25 parts by weight and 55 parts by weight, and particularly preferably between 30 parts by weight and 50 parts by weight. The amount of the polyol material is between 20 parts by weight and 60 parts by weight, preferably between 25 parts by weight and 55 parts by weight, and particularly preferably between 30 parts by weight and 50 parts by weight. The amount of the chain extender is between 5 parts by weight and 20 parts by weight, preferably between 7 parts by weight and 18 parts by weight, and particularly preferably between 9 parts by weight and 16 parts by weight, but the present invention is not limited thereto.

[0022] Further, the amount of the anti-hydrolysis agent is between 0.1 and 1 parts by weight, preferably between 0.2 and 0.9 parts by weight, and particularly preferably between 0.3 and 0.8 parts by weight. The amount of the chain terminator is between 0.01 and 0.3 parts by weight, and preferably between 0.05 and 0.2 parts by weight. The amount of the ultraviolet light absorber is between 0.1 and 0.5 parts by weight, and preferably between 0.2 and 0.5 parts by weight. The amount of the light stabilizer is between 0.1 and 0.5 parts by weight, and preferably between 0.2 and 0.5 parts by weight. The other auxiliary additive components and / or other solvent components are the remaining components, but the present invention is not limited thereto.

[0023] In terms of material selection, the isocyanate material is selected from dicyclohexylmethane diisocyanate (4,4'-diisocyanato dicyclohexylmethane, H 12 At least one of the material group consisting of MDI (also known as hydrogenated diphenylmethane diisocyanate), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI).

[0024] Dicyclohexylmethane diisocyanate (H 12 The chemical structure of MDI is as follows.

[0025]

[0026] The chemical structure of hexamethylene diisocyanate (HDI) is as follows.

[0027]

[0028] The chemical structure of isophorone diisocyanate (IPDI) is as follows.

[0029]

[0030] It is worth mentioning that the isocyanate materials (such as HDI, HDI, IPDI) used in the embodiments of the present invention do not have a benzene ring in their chemical structure.

[0031] More specifically, dicyclohexylmethane diisocyanate (H 12 The chemical structure of MDI has two cyclohexyl groups. The chemical structure of hexamethylene diisocyanate (HDI) has one hexamethylene group. And the chemical structure of isophorone diisocyanate (IPDI) has one cyclohexyl group. However, the chemical structures of the above-mentioned isocyanate materials do not have the so-called benzene ring (the carbon-carbon bond in the benzene ring is a bond between a single bond and a double bond). Furthermore, the isocyanate material selected by the embodiment of the present invention can at least effectively improve the problem that the thermoplastic polyurethane resin in the prior art is prone to yellowing over time.

[0032] In a preferred embodiment of the present invention, the isocyanate material can be selected from two isocyanates at the same time, so as to effectively improve the problem of yellowing of thermoplastic polyurethane resin over time and the generation of crystal points during lamination processing, and can also improve the scratch resistance and soft feel of the automobile film.

[0033] More specifically, the isocyanate material comprises: a first isocyanate component and a second isocyanate component. The first isocyanate component is dicyclohexylmethane diisocyanate (H 12 MDI), and the second isocyanate component is at least one of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI).

[0034] Based on the total weight of the first isocyanate component and the second isocyanate component being 100%, the first isocyanate component (H 12 The first weight percentage of MDI) is between 70% and 98%, preferably between 80% and 98%, and particularly preferably between 86.2% and 94%.

[0035] Furthermore, the second weight percentage of the second isocyanate component (HDI and / or IPDI) is between 2% and 30%, preferably between 2% and 20%, and particularly preferably between 6% and 13.8%. 12 The first isocyanate component is a polyisocyanate component, wherein the first isocyanate component (MDI) is the main isocyanate component, and the second isocyanate component (HDI and / or IPDI) is the isocyanate component added in a small amount.

[0036] It is worth mentioning that since the first isocyanate component (H 12 MDI) does not have a benzene ring, but has two symmetrically positioned cyclohexyl groups, so it can effectively improve the problems of yellowing over time and the generation of crystal points during the coating process in the prior art, and can maintain the physical properties required for automotive coating.

[0037] In addition, since the first isocyanate component (H 12 The molecular structure of the second isocyanate component (HDI and / or IPDI) is softer than the aromatic diisocyanate (such as MDI) commonly used in the prior art, so the scratch resistance of the final automobile film can be effectively improved. Furthermore, the second isocyanate component (HDI and / or IPDI) can also make the automobile film feel softer and have better scratch resistance.

[0038] Specifically, the polyol material in this embodiment is at least one selected from the group consisting of polycaprolactone (PCL) and polyether polyol, and is preferably polycaprolactone (PCL).

[0039] The polycaprolactone polyol is formed by polymerization of a low molecular diol and a caprolactone monomer, wherein the low molecular diol is a diol having a carbon number of C2 to C8.

[0040] In a preferred embodiment of the present invention, the small molecule diol is a diol with a carbon number of C6. That is, the small molecule diol is preferably 1,6-hexanediol.

[0041] Furthermore, the number average molecular weight (Mn) of the polyol material is between 1,000 g / mol and 5,000 g / mol, and preferably between 1,000 g / mol and 3,000 g / mol.

[0042] It is worth mentioning that, under the above material parameter conditions, the polycaprolactone polyol can make the final thermoplastic polyurethane resin (such as TPU particles) have better transparency, hydrolysis resistance, and processability.

[0043] Furthermore, the small molecule diol is preferably 1,6-hexanediol, which can make the TPU particles have better processability than other diols (such as 1,4-butanediol). The thermoplastic polyurethane resin of the embodiment of the present invention is synthesized using polycaprolactone polyol, which has better physical properties (such as light transmittance) than polyether polyol. In addition, the general polyester polyol has poor hydrolysis resistance, so it is not considered for use in the present invention.

[0044] It is worth mentioning that in some embodiments of the present invention, the NCO / OH equivalent ratio between the isocyanate group (-NCO) of the isocyanate material and the hydroxyl group (-OH) of the polyol material is preferably between 0.998 and 1.015, and particularly preferably between 1.012 and 1.015. Thus, the thermoplastic polyurethane resin (such as TPU pellets) finally formed can have a stable melt index change rate.

[0045] Furthermore, in some embodiments of the present invention, the material type of the chain extender is a diol chain extender, and the chain extender is preferably 1,4-butanediol (1,4-butanediol, 14BG). Furthermore, the amount of the chain extender is between 5 parts by weight and 20 parts by weight, preferably between 7 parts by weight and 18 parts by weight, and particularly preferably between 9 parts by weight and 16 parts by weight. The chain extender can effectively improve specific physical properties of the final polymer, such as hardness, heat resistance or hydrolysis resistance.

[0046] Furthermore, in some embodiments of the present invention, the material type of the anti-hydrolysis agent is preferably carbodiimide, and the amount of the anti-hydrolysis agent is between 0.1 parts by weight and 1 part by weight, preferably between 0.2 parts by weight and 0.9 parts by weight, and particularly preferably between 0.3 parts by weight and 0.8 parts by weight. The anti-hydrolysis agent can effectively improve the hydrolysis resistance of the final polymer.

[0047] Furthermore, in some embodiments of the present invention, the material type of the chain terminator is preferably a long-chain fatty alcohol (monohydric alcohol) having a carbon number of C12 to C18. For example, the chain terminator can be at least one of the material group consisting of stearyl alcohol (C18 long-chain fatty alcohol), lauryl alcohol (C12 long-chain fatty alcohol), and oleic alcohol (C18 long-chain unsaturated fatty alcohol), but the present invention is not limited thereto. In addition, the amount of the chain terminator is between 0.01 parts by weight and 0.3 parts by weight, and preferably between 0.05 parts by weight and 0.2 parts by weight. The chain terminator can adjust the melt index (MI) and molecular weight of the thermoplastic polyurethane resin (such as TPU pellets) finally formed.

[0048] It is worth mentioning that the melt index of the thermoplastic polyurethane resin is regulated to be between 1 and 5 g / 10 min / 200° C., preferably between 1.5 and 4 g / 10 min / 200° C., and particularly preferably between 1.6 and 3.1 g / 10 min / 200° C. The weight average molecular weight (Mw) of the thermoplastic polyurethane resin is between 120,000 and 280,000 g / mol, preferably between 150,000 and 250,000 g / mol, and particularly preferably between 185,000 and 223,000 g / mol.

[0049] It should be noted that the "melt index" in this embodiment refers to the weight of the thermoplastic polyurethane resin passing through the standard die every 10 minutes on the melt flow anemometer at a temperature of 200°C, and the unit is g / 10min / 200°C. The melt index represents the fluidity of the resin in the molten state. The larger the melt index, the smaller the molecular weight and the higher the fluidity.

[0050] In addition, the molecular weight (weight average molecular weight, Mw) of the thermoplastic polyurethane resin is obtained by analysis using gel permeation chromatography (GPC).

[0051] Furthermore, the ultraviolet absorber is used to enhance the anti-ultraviolet capability of the thermoplastic polyurethane resin finally formed (i.e., enhance the QUV grade). In some embodiments of the present invention, the ultraviolet absorber is at least one of the material groups selected from benzotriazoles, benzophenones, and triazines. In a specific application example, the ultraviolet absorber is UV-328 ultraviolet absorber (2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol), but the present invention is not limited thereto. It is worth mentioning that the UV-328 ultraviolet absorber belongs to the phenolic benzotriazole compound.

[0052] In addition, in some embodiments of the present invention, the light stabilizer is a low molecular weight hindered amine light stabilizer (HALS). For example, the light stabilizer is LS 770 hindered amine light stabilizer (bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate), but the present invention is not limited thereto.

[0053] According to the material selection and dosage ratio of each component in the above-mentioned thermoplastic polyurethane resin, the thermoplastic polyurethane resin (such as: TPU particles) has good performance in the following specific physical properties.

[0054] <Processability>: After the TPU pellets are coated by an extruder (T-die), the film has no coarse particles or crystal points. In other words, the thermoplastic polyurethane resin has good processability.

[0055] <Light transmittance>: The injection-molded test piece having a thickness of 2 mm has a visible light transmittance of not less than 90%. That is, the thermoplastic polyurethane resin has good light transmittance.

[0056] <Weather resistance>: The ΔE color difference value of the thermoformed test piece with a thickness of 0.2 mm after irradiation with QUV 340 nm light for 1000 hours is not greater than 5, and preferably not greater than 3. That is, the thermoplastic polyurethane resin has good weather resistance, that is, it has the characteristic of not being easy to yellow over time. The testing instrument can be a QUV ultraviolet weathering tester, and the testing method can be based on ASTMG154-16.

[0057] <Hydrolysis resistance>: A thermoformed test piece with a thickness of 0.2 mm is stored at a temperature of 60°C and a relative humidity of 90 RH% for 28 days, and the tensile strength of the test piece is maintained at not less than 80%. In other words, the thermoplastic polyurethane resin has good hydrolysis resistance.

[0058] [Method for producing thermoplastic polyurethane resin]

[0059] The above is a description of the characteristics of the thermoplastic polyurethane resin material according to the embodiment of the present invention. The following describes a method for manufacturing the thermoplastic polyurethane resin according to the embodiment of the present invention. The method includes step S110, step S120, and step S130, but the present invention is not limited thereto.

[0060] The step S110 is a mixing step, which includes adding isocyanate material, polyol material, chain extender, anti-hydrolysis agent, and other trace components such as UV absorber and photo-stabilizer into a mixer according to a predetermined amount range for mixing to form a reaction mixture.

[0061] The step S120 is a reaction step, which includes: introducing the reaction mixture into an extruder (such as a twin-screw extruder) to allow the isocyanate material and the polyol material to undergo a polymerization reaction, and introducing a chain terminator into the reaction mixture at the rear end of the extruder to terminate the polymerization reaction and form a thermoplastic polyurethane resin.

[0062] The extrusion temperature of the extruder may be, for example, between 150° C. and 250° C., so as to facilitate the polymerization reaction to proceed sufficiently, but the present invention is not limited thereto.

[0063] The step S130 is a pelletizing step, which includes pelletizing the thermoplastic polyurethane resin in an aqueous environment to form thermoplastic polyurethane resin in the form of pellets (ie, TPU pellets).

[0064] Wherein, based on the total weight of the reaction mixture being 100 parts by weight, the amount of the isocyanate material is between 20 parts by weight and 60 parts by weight, the amount of the polyol material is between 20 parts by weight and 60 parts by weight, the amount of the chain extender is between 5 parts by weight and 20 parts by weight, the amount of the anti-hydrolysis agent is between 0.1 parts by weight and 1 parts by weight, the amount of the chain terminator is between 0.01 parts by weight and 0.3 parts by weight, the amount of the ultraviolet light absorber is between 0.1 parts by weight and 0.5 parts by weight, and the amount of the light stabilizer is between 0.1 parts by weight and 0.5 parts by weight, but the present invention is not limited thereto.

[0065] [Experimental data test]

[0066] Hereinafter, please refer to Examples 1 to 4 and Comparative Examples 1 to 2 to explain the contents of the present invention in detail. However, the following examples are only used to help understand the present invention, and the scope of the present invention is not limited to these examples. The experimental conditions and test results of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1. Among them, Examples 1 to 4 are preferred embodiments of the present invention, and Comparative Examples 1 to 2 are control groups, which are used to prove that Examples 1 to 4 have better technical effects.

[0067] Example 1: 40 g of isocyanate (containing 94% H 12 MDI and 6% HDI), 39 grams of polyol (polycaprolactone polyol, Mn = 2,000g / mol), 11.4 grams of chain extender (14BG), 0.3 grams of anti-hydrolysis agent (carbodiimide), 0.1 grams of chain terminator (stearyl alcohol), 0.3 grams of ultraviolet absorber (UV328), and 0.3 grams of light stabilizer (LS770) are introduced into a twin-screw extruder for mixing and reaction. The chain terminator is introduced into the rear section of the twin-screw extruder to terminate the polymerization reaction and form a thermoplastic polyurethane resin, which is then pelletized to form TPU pellets. The NCO / OH equivalent ratio of isocyanate to polyol is 1.012, the weight average molecular weight (Mw) of the TPU pellets is 185,000 g / mol, and the melt index MI is 2.5g / 10min / 200℃.

[0068] Example 2: 40.2 g of isocyanate (containing 86.2% H 12 MDI and 13.8% HDI), 39.4 grams of polyol (polycaprolactone polyol, Mn = 2,000 g / mol), 11.5 grams of chain extender (14BG), 0.5 grams of anti-hydrolysis agent (carbodiimide), 0.1 grams of chain terminator (stearyl alcohol), 0.3 grams of ultraviolet absorber (UV328), and 0.3 grams of light stabilizer (LS770) are introduced into a twin-screw extruder for mixing and reaction. The chain terminator is introduced into the rear section of the twin-screw extruder to terminate the polymerization reaction and form a thermoplastic polyurethane resin, which is then pelletized to form TPU pellets. The NCO / OH equivalent ratio of isocyanate to polyol is 1.015, the weight average molecular weight (Mw) of the TPU pellets is 223,000 g / mol, and the melt index MI is 3.1 g / 10min / 200°C.

[0069] Example 3: 40.5 g of isocyanate (containing 91.4% H 12 MDI and 8.6% IPDI), 38.6 grams of polyol (polycaprolactone polyol, Mn = 2,000 g / mol), 11.3 grams of chain extender (14BG), 0.5 grams of anti-hydrolysis agent (carbodiimide), 0.1 grams of chain terminator (stearyl alcohol), 0.3 grams of ultraviolet absorber (UV328), and 0.3 grams of light stabilizer (LS770) are introduced into a twin-screw extruder for mixing and reaction. The chain terminator is introduced into the rear section of the twin-screw extruder to terminate the polymerization reaction and form a thermoplastic polyurethane resin, which is then pelletized to form TPU pellets. The NCO / OH equivalent ratio of isocyanate to polyol is 1.015, the weight average molecular weight (Mw) of the TPU pellets is 219,000 g / mol, and the melt index MI is 2.4 g / 10min / 200°C.

[0070] Example 4: 40.5 g of isocyanate (containing 91.4% H 12MDI and 8.6% IPDI), 38.9 grams of polyol (polycaprolactone polyol, Mn = 2,000 g / mol), 11.3 grams of chain extender (14BG), 0.5 grams of anti-hydrolysis agent (carbodiimide), 0.1 grams of chain terminator (stearyl alcohol), 0.3 grams of ultraviolet absorber (UV328), and 0.3 grams of light stabilizer (LS770) are introduced into a twin-screw extruder for mixing and reaction. The chain terminator is introduced into the rear section of the twin-screw extruder to terminate the polymerization reaction and form a thermoplastic polyurethane resin, which is then pelletized to form TPU pellets. The NCO / OH equivalent ratio of isocyanate to polyol is 1.015, the weight average molecular weight (Mw) of the TPU pellets is 206,000 g / mol, and the melt index MI is 1.6 g / 10min / 200°C.

[0071] Comparative Example 1: 40.8 g of isocyanate (containing 100% MDI), 48 g of polyol (polycaprolactone polyol, Mn=2,000 g / mol), 11.2 g of chain extender (14BG), 0.5 g of anti-hydrolysis agent (carbodiimide), 0.1 g of chain terminator (stearyl alcohol), 0.3 g of ultraviolet absorber (UV328), and 0.3 g of light stabilizer (LS770) are introduced into a twin-screw extruder for mixing and reaction. The chain terminator is introduced into the rear section of the twin-screw extruder to terminate the polymerization reaction and form a thermoplastic polyurethane resin, which is then pelletized to form TPU pellets. The NCO / OH equivalent ratio of isocyanate to polyol is 1.012, the weight average molecular weight (Mw) of the TPU pellets is 206,000 g / mol, and the melt index MI is 4.0 g / 10 min / 200°C.

[0072] Comparative Example 2: 47.7 grams of isocyanate (containing 100% MDI), 39.9 grams of polyol (polyether polyol, Mn = 1,800 g / mol), 12.4 grams of chain extender (14BG), 0.2 grams of anti-hydrolysis agent (carbodiimide), 0.1 grams of chain terminator (stearyl alcohol), 0.3 grams of ultraviolet absorber (UV328), and 0.3 grams of light stabilizer (LS770) are introduced into a twin-screw extruder for mixing and reaction. The chain terminator is introduced into the rear section of the twin-screw extruder to terminate the polymerization reaction and form a thermoplastic polyurethane resin, which is then pelletized to form TPU pellets. The NCO / OH equivalent ratio of isocyanate to polyol is 1.015, the weight average molecular weight (Mw) of the TPU pellets is 206,000 g / mol, and the melt index MI is 2.9 g / 10 min / 200°C.

[0073] Next, the thermoplastic polyurethane resins prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were tested for physical and chemical properties to obtain the physical and chemical properties of the thermoplastic polyurethane resins, such as processability (film appearance), visible light transmittance (%), color difference value (ΔE) of weatherability QUV test, and hydrolysis resistance (tensile strength maintenance rate %). The test method is described below, and the test results are summarized in Table 1 below.

[0074] <Processability>: After the TPU pellets are extruded by the extruder (T-die), observe whether there are coarse particles or crystal points on the film surface. If there are no coarse particles or crystal points on the film surface, it means that the TPU pellets have good processability.

[0075] <Transparency>: A TPU injection molded test piece having a thickness of 2 mm was tested for visible light transmittance using a transmittance meter, and its transmittance (%) was recorded.

[0076] <Weather resistance (QUV test)>: A 0.2 mm thick TPU hot press molded test piece was irradiated with QUV 340 nm light for 1000 hours, and the ΔE*ab (CIE color difference value) of the test piece was analyzed.

[0077] <Hydrolysis Resistance>: A 0.2 mm thick TPU thermoforming test piece was placed in an environment with a temperature of 60°C and a relative humidity of 90 RH% for 28 days, and the tensile strength maintenance rate (%) was measured.

[0078] [Table 1 Experimental conditions and test results]

[0079]

[0080]

[0081] [Test results discussion]

[0082] From the above experimental results, it can be seen that in Examples 1 to 4, after the TPU pellets of Examples 1 to 4 were coated by an extruder (T-die), the film appearance had no coarse particles or crystal points, and had good processability. The 2mm thick TPU injection molded sheet had a visible light transmittance of 91.5% to 92.1%, and had good light transmittance.

[0083] The 0.2mm thick TPU thermoforming test piece has a △E color difference value of 0.98 to 1.34 after 1000 hours of QUV 340nm light irradiation, which has good weather resistance, that is, it has the characteristic of not easily yellowing over time. The 0.2mm thick TPU thermoforming test piece was stored for 28 days under the environmental conditions of temperature 60℃ and relative humidity 90RH%, and the tensile strength maintenance rate of the test piece was between 80.3% and 82.3%, which has good hydrolysis resistance.

[0084] In general, the TPU particles of Examples 1 to 4 are H 12 MDI is its main isocyanate material and is combined with a small amount of HDI or IPDI and polycaprolactone polyol for synthesis, thereby achieving a light transmittance of more than 90% and having better weather resistance (yellowing resistance) and hydrolysis resistance.

[0085] The isocyanate material of the TPU particles of Comparative Examples 1-2 is all aromatic MDI, and the ΔE color difference value is between 20.6 and 26.4, which is poorer in weather resistance than Examples 1-4, and is prone to yellowing over time, and the hydrolysis resistance of Comparative Example 1 is also worse than that of Examples 1-4. Comparative Example 2 uses polyether polyol, which has a slightly lower light transmittance (less than 90%) than Examples 1-4.

[0086] [Beneficial Effects of Embodiments]

[0087] The beneficial effect of the embodiments of the present invention is that the thermoplastic polyurethane resin suitable for preparing automobile wrapping provided by the present invention can effectively improve the problems of TPU granule materials in the prior art, such as yellowing over time, degradation of physical properties due to hydrolysis, easy generation of crystal points and poor transparency after lamination processing, through "material selection and matching of isocyanate materials and polyol materials", thereby effectively improving the quality of automobile wrapping.

[0088] The contents disclosed above are only preferred feasible embodiments of the present invention, and are not intended to limit the scope of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention specification are included in the scope of the present invention.

Claims

1. A thermoplastic polyurethane resin suitable for preparing automobile coating, characterized in that: The thermoplastic polyurethane resin is formed by a reaction mixture through a polymerization reaction, wherein the reaction mixture includes: an isocyanate material having no benzene ring in its chemical structure, and the isocyanate material is at least one selected from the group consisting of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; A polyol material, which is at least one selected from the group consisting of polycaprolactone polyol and polyether polyol; and A chain extender, wherein the chain extender is a diol chain extender.

2. The thermoplastic polyurethane resin according to claim 1, characterized in that The isocyanate material comprises a first isocyanate component and a second isocyanate component; wherein the first isocyanate component is dicyclohexylmethane diisocyanate, and the second isocyanate component is at least one of hexamethylene diisocyanate and isophorone diisocyanate.

3. The thermoplastic polyurethane resin according to claim 2, characterized in that Based on the total weight of the first isocyanate component and the second isocyanate component being 100%, a first weight percentage of the first isocyanate component is between 70% and 98%, and a second weight percentage of the second isocyanate component is between 2% and 30%.

4. The thermoplastic polyurethane resin according to claim 1, characterized in that The polyol material is further limited to polycaprolactone polyol, which is formed by polymerization reaction of small molecule diol and caprolactone monomer; wherein the small molecule diol is a diol with carbon number C2 to C8.

5. The thermoplastic polyurethane resin according to claim 4, characterized in that The small molecule diol is 1,6-hexanediol, and the number average molecular weight of the polyol material is between 1,000 g / mol and 5,000 g / mol; wherein the chain extender is 1,4-butanediol.

6. The thermoplastic polyurethane resin according to claim 1, characterized in that The equivalent ratio of the isocyanate groups of the isocyanate material to the hydroxyl groups of the polyol material is between 0.998 and 1.

015.

7. The thermoplastic polyurethane resin according to claim 1, characterized in that The reaction mixture further comprises: an anti-hydrolysis agent and a chain terminator, wherein the anti-hydrolysis agent is carbodiimide, and the chain terminator is a long-chain fatty alcohol having a carbon number of C12 to C18.

8. The thermoplastic polyurethane resin according to claim 7, characterized in that The chain terminator is at least one selected from the group consisting of stearyl alcohol, lauryl alcohol, and oleic alcohol.

9. The thermoplastic polyurethane resin according to claim 7, characterized in that Based on 100 parts by weight of the total weight of the reaction mixture, the amount of the isocyanate material is between 20 parts by weight and 60 parts by weight, the amount of the polyol material is between 20 parts by weight and 60 parts by weight, the amount of the chain extender is between 5 parts by weight and 20 parts by weight, the amount of the anti-hydrolysis agent is between 0.1 parts by weight and 1 part by weight, and the amount of the chain terminator is between 0.01 parts by weight and 0.3 parts by weight.

10. The thermoplastic polyurethane resin according to any one of claims 1 to 9, characterized in that The thermoplastic polyurethane resin has a melt index of 1 to 5 g / 10 min / 200° C.

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