Thermoplastic composite and preparation method therefor

Abstract

Disclosed are a thermoplastic composite and a preparation method therefor, belonging to the technical field of polymer materials. By means of defining specific parameters of thermoplastic polyurethane and a hindered phenol antioxidant in the thermoplastic composite component, said two components in the thermoplastic composite can achieve high mutual melting. In this way, the thermoplastic composite not only can achieve long-term stability, but can also achieve the excellent effect of a performance retention rate greater than or equal to 80%, even in a severe thermo-oxidative aging test at a temperature of up to 120°C and a duration of up to 1000 h.

Description

A thermoplastic composite and a method for preparing the same Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a thermoplastic composite and a preparation method thereof. Background Art

[0002] Thermoplastic polyurethane (TPU) materials are widely used in various fields due to their excellent mechanical properties, chemical stability, and fatigue resistance. However, when TPU materials are used in industries such as automobiles and engineering machinery, they need to have sufficient long-term resistance to thermal oxidative aging to ensure their service life. After most existing TPU materials have been used for a period of time, the antioxidants contained in the TPU materials will precipitate to varying degrees, causing the TPU materials to be easily oxidized, which in turn leads to a decrease in their performance. When the temperature in the environment in which the TPU materials are used is high, the antioxidants will precipitate more rapidly, causing the performance of the TPU materials to deteriorate rapidly. Summary of the Invention

[0003] To address the shortcomings of the prior art, the present invention provides a thermoplastic composite. By defining specific parameters for the thermoplastic polyurethane and hindered phenolic antioxidant within the composite, a high degree of intermixing of the two components is achieved. This allows the composite to achieve not only long-term stability but also excellent performance retention of ≥80% even in rigorous thermal oxidative aging tests at temperatures up to 120°C for up to 1000 hours.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A thermoplastic composite comprising the following components in parts by weight:

[0006] 99.5-99.95 parts of thermoplastic polyurethane and 0.05-0.5 parts of hindered phenol antioxidant;

[0007] The number of repeating units of the soft segment polyester of the thermoplastic polyurethane is 3 to 14, and satisfies 2≤MA / MB≤6;

[0008] Wherein, MA is the melt flow index (MFI) of thermoplastic polyurethane at 200°C and 5 kg load according to the Chinese national standard GB / T 3682.2-2018, and MB is the melt flow index of thermoplastic polyester at 200°C and 2.16 kg load according to the Chinese national standard GB / T3682.2-2018;

[0009] The solubility of the hindered phenol antioxidant in tetrahydrofuran at 23°C is ≥50g / 100g and satisfies 17≤δ d ≤20, 1≤δ p ≤3,9.5≤δ h ≤11.5;

[0010] where δ d is the solubility parameter dispersion component of hindered phenolic antioxidants, δ p is the polar component of the solubility parameter of hindered phenol antioxidants, δ h is the hydrogen bonding component of the solubility parameter of hindered phenol antioxidants.

[0011] In the thermoplastic composite described herein, the inventors creatively discovered that the combination of thermoplastic polyurethane (TPU) and hindered phenolic antioxidants is closely related to the number of repeating units in the soft segment polyester of the TPU, as well as the fluidity and dispersion of the hindered phenolic antioxidant in the TPU. Because the soft segment polyester in the TPU has a low glass transition temperature and is in an amorphous state at room temperature, the hindered phenolic antioxidant easily migrates within the soft segment polyester. Only under the appropriate conditions (i.e., when the number of repeating units in the soft segment polyester is within a specific range) does the soft segment polyester of the TPU interact strongly with the hindered phenolic antioxidant, limiting its surface migration. Furthermore, the fluidity of the TPU is related to the ratio of the melt flow index (MA / MB) of the TPU under different load conditions, which in turn is related to the molecular weight polydispersity of the TPU. Therefore, after research, find that, when the ratio MA / MB of the number of repeating units and the melt flow index of thermoplastic polyurethane under different load conditions satisfies limiting conditions in the soft segment polyester of thermoplastic polyurethane, the soft segment polyester of thermoplastic polyurethane and hindered phenolic antioxidant produce larger interaction, thereby hindered phenolic antioxidant is separated out and plays good inhibitory action.Simultaneously, for hindered phenolic antioxidant, need strictly limit its intrinsic solubility and solubility parameter.Because the solubility of hindered phenolic antioxidant in tetrahydrofuran (THF) can reflect the solubility of hindered phenolic antioxidant in thermoplastic polyurethane, so this solubility is big more, and in the unit product (i.e. thermoplastic composite), soluble hindered phenolic antioxidant is many more.And when hindered phenolic antioxidant solubility parameter is limited in specific range, the compatibility of hindered phenolic antioxidant and thermoplastic polyurethane on thermodynamics is just good, and separating out possibility is low more. Therefore, when all of the aforementioned parameters are within the specified ranges of this invention, the compatibility and mixing stability of the hindered phenolic antioxidant in the thermoplastic polyurethane are significantly improved. This prevents precipitation of the hindered phenolic antioxidant under prolonged storage at room temperature and imparts excellent thermal oxidative stability to the thermoplastic composite. Furthermore, even after a rigorous thermal oxidative aging test at 120°C for 1000 hours, the thermoplastic composite maintains mechanical property retention exceeding 80%.

[0012] Preferably, the test method for the number of repeating units in the soft segment polyester of the thermoplastic polyurethane is 1 HNMR nuclear magnetic hydrogen spectrum analysis method, direct confirmation based on nuclear magnetic hydrogen spectrum.

[0013] Preferably, the solubility parameter of the hindered phenol antioxidant is determined by referring to the fourth revised edition of "Properties of Polymer" - DW van Krevelen, K. te Nijenhuis, and is determined according to the following formula: δ d =ΣF di / V;δ p =(ΣF pi ) 1 / 2 / V;δ h =(ΣE hi / V) 1 / 2

[0014] Among them F di is the group dispersion contribution, F pi is the polarity contribution of the group, E hi The specific test method for the solubility parameter of the hindered phenol antioxidant is as follows: first confirm the functional groups on the sample to be tested by infrared spectroscopy, and then determine the contribution of each functional group, F di 、F pi 、E hi and V, wherein the method for determining the contribution of each functional group can be found in Chapter 7 of "Properties of Polymer".

[0015] Preferably, the number of repeating units in the soft segment polyester of the thermoplastic polyurethane is any one of 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14, or a range of any two of them (including endpoints).

[0016] More preferably, the number of repeating units in the soft segment polyester of the thermoplastic polyurethane is 5 to 10.

[0017] Preferably, the value of MA / MB is any one of 2, 3, 4, 5, and 6, or a range of any two of them (including endpoints).

[0018] More preferably, the MA / MB satisfies: 3≤MA / MB≤5.

[0019] More preferably, the MA is 2-30 g / 10 min, and the MB is 1-5 g / 10 min.

[0020] When the number of repeating units in the soft segment polyester of the thermoplastic polyurethane and the melt flow index ratio MA / MB of the thermoplastic polyurethane under different loads are preferably within the above range, the overall flow stability of the thermoplastic polyurethane is better, the compatibility with the hindered phenol antioxidant is better, and the stability and long-term thermal oxidative aging resistance of the product are also better.

[0021] More preferably, the thermoplastic polyurethane is a polyester polyurethane elastomer.

[0022] More preferably, the preparation method of the thermoplastic polyurethane is as follows with reference to the second edition of Handbook of Polyurethane Elastomers, Chemical Industry Press:

[0023] Diphenylmethane diisocyanate, polyester polyol and 1,4-butanediol are mixed and dried, and then introduced into a screw extruder for reaction and extrusion at 160-210° C. The thermoplastic polyurethane is obtained after cooling, pelletizing and drying.

[0024] Preferably, the polyester polyol is at least one of polyethylene adipate polyol, polypropylene adipate polyol, polybutylene adipate polyol and polyhexylene adipate polyol.

[0025] More preferably, the polyester polyol is polybutylene adipate polyol.

[0026] More preferably, the polyester polyol has a hydroxyl value of 40 to 164 mgKOH / g.

[0027] The molecular weight of the polyester polyol is 400 to 5000 g / mol, preferably 1000 to 2000 g / mol.

[0028] Preferably, the molar ratio of the total hydroxyl content in the polyester polyol and 1,4-butanediol to the isocyanate group in diphenylmethane diisocyanate is (0.9-1.1):1.

[0029] More preferably, the mass ratio of the polyester polyol, diphenylmethane diisocyanate, and 1,4-butanediol is (23-289):(11-28):1.

[0030] It should be noted that the thermoplastic polyurethane described in the present invention is not limited to that prepared by the above-described method. Depending on actual needs, those skilled in the art may also prepare thermoplastic polyurethane using other preparation methods or commercially available products. Any similar product may be used as long as it meets the definition of thermoplastic polyurethane in the present invention and the resulting thermoplastic composite can achieve the same technical effects.

[0031] Preferably, the solubility of the hindered phenol antioxidant in tetrahydrofuran at 23° C. is 50 g / 100 g to 300 g / 100 g.

[0032] Preferably, the solubility parameter dispersion component δ of the hindered phenol antioxidant is d Any one of 17, 18, 19, and 20, or a range value of any two (including the endpoint values).

[0033] Preferably, the solubility parameter polar component δ of the hindered phenol antioxidant is p Any one of 1, 1.5, 2, 2.5, 3, or any two of the range values ​​(including the endpoint values).

[0034] Preferably, the solubility parameter hydrogen bond component δ of the hindered phenol antioxidant is hAny one of 9.5, 10, 10.5, 11, and 11.5, or any two of the range values ​​(including the endpoint values).

[0035] More preferably, the hindered phenol antioxidant is at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane.

[0036] More preferably, the hindered phenol antioxidant satisfies 17.5≤δ d ≤19.5, 1.3≤δ p ≤2.5, 10.0≤δ h ≤11.3.

[0037] When the hindered phenol antioxidant is selected within the above preferred range, not only can the most efficient compounding stability between the thermoplastic polyurethane and the hindered phenol antioxidant be achieved, but the prepared thermoplastic composite will also have the most excellent long-term heat-oxidative aging resistance, and the performance retention rate of the thermoplastic composite can reach more than 80%.

[0038] Preferably, the thermoplastic composite further comprises 0.1 to 10 parts of a functional additive;

[0039] More preferably, the functional additive includes at least one of a flame retardant, a light stabilizer, a colorant, a lubricant, an antistatic agent, a toughening agent, and a filler.

[0040] Without affecting the low precipitation properties of conventional antioxidants and the long-term thermal oxidative aging resistance of the thermoplastic composites of the present invention, those skilled in the art may introduce additional functional additives into the product according to actual product needs. For example, to impart flame retardancy to the product, 0.1 to 10 parts of a flame retardant may be introduced; to enhance light stability, 0.1 to 1 part of a light stabilizer may be introduced; to impart a different color to the product, 0.1 to 5 parts of a colorant may be introduced; to enhance processability, 0.1 to 5 parts of a lubricant may be introduced, etc.

[0041] Another object of the present invention is to provide a method for preparing the thermoplastic composite, comprising the following steps:

[0042] The components of the thermoplastic composite are mixed uniformly, and then melt-extruded in a screw extruder. After cooling, granulation and drying, the thermoplastic composite is obtained.

[0043] The preparation method of the thermoplastic composite of the present invention has simple operating steps and can realize industrial large-scale production.

[0044] Preferably, the temperature during the melt extrusion is 60-190° C., the residence time of the melt extrusion is 40-60 s, and the screw length-diameter ratio of the screw extruder is (36-60):1.

[0045] Another object of the present invention is to provide use of the thermoplastic composite in the preparation of automotive parts.

[0046] Preferably, the automobile parts include automobile wiring harnesses, automobile buckles, automobile dust covers and automobile cushions.

[0047] The thermoplastic composite of the present invention not only retains the excellent mechanical properties, chemical resistance, and fatigue resistance of thermoplastic polyurethane, but also exhibits excellent long-term resistance to thermal oxidative aging. Even after prolonged high-temperature treatment, the mechanical properties of the thermoplastic composite of the present invention remain high, and antioxidant precipitation in the thermoplastic composite is extremely low. Therefore, the thermoplastic composite of the present invention is highly suitable for the manufacture of automotive parts that require long-term high-temperature operation.

[0048] The present invention provides a thermoplastic composite that achieves high intermixing between the thermoplastic polyurethane and hindered phenolic antioxidant by defining specific parameters within the composite. This allows the composite to maintain long-term stability and, even in rigorous thermal oxidative aging tests at temperatures up to 120°C for 1000 hours, maintain a performance retention rate of ≥80%. DETAILED DESCRIPTION

[0049] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples. Its purpose is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention are all conventional common reagents and instruments unless otherwise specified.

[0050] Examples 1 to 14

[0051] Multiple embodiments of the thermoplastic composite of the present invention are provided, wherein the components and proportions of the thermoplastic composite in each embodiment are shown in Table 3.

[0052] A method for preparing the thermoplastic composite of the present invention is provided, comprising the following steps:

[0053] The components of the thermoplastic composite are mixed uniformly, and then melt-extruded in a screw extruder. After cooling, granulation and drying, the thermoplastic composite is obtained.

[0054] When the components are melt-extruded, the temperature zones of the screw extruder are set to 60°C in zone 1, 140°C in zone 2, 180°C in zone 3, 180°C in zone 4, 180°C in zone 5, 170°C in zone 6, 170°C in zone 7, 170°C in zone 8, 180°C in zone 9, and 190°C in zone 10; the screw speed is 200 rpm, the screw length-diameter ratio is 40:1, and the residence time of the material in the screw extruder is 40 to 60 seconds.

[0055] Comparative Examples 1 to 14

[0056] The difference between the comparative examples and the examples is only in the types and proportions of the components, as shown in Table 4.

[0057] The components used in each embodiment and comparative example are as follows:

[0058] The thermoplastic polyurethane 1 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 1 (hydroxyl value is 105 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are uniformly mixed in a mass ratio of 97:25:1, fed into a twin-screw extruder, reacted at 160-210° C., cooled, and granulated to obtain thermoplastic polyurethane 1.

[0059] The thermoplastic polyurethane 2 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 2 (hydroxyl value is 85 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are mixed uniformly in a mass ratio of 86:19:1, fed into a twin-screw extruder, reacted at 160-210°C, cooled, and granulated to obtain thermoplastic polyurethane 2.

[0060] The thermoplastic polyurethane 3 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 3 (hydroxyl value is 75 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are mixed uniformly in a mass ratio of 116:23:1, fed into a twin-screw extruder, reacted at 160-210°C, cooled, and granulated to obtain thermoplastic polyurethane 3.

[0061] The thermoplastic polyurethane 4 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 4 (hydroxyl value is 66 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are mixed uniformly in a mass ratio of 94:17:1, fed into a twin-screw extruder, reacted at 160-210°C, cooled, and granulated to obtain thermoplastic polyurethane 4.

[0062] The thermoplastic polyurethane 5 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 5 (hydroxyl value is 54 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are uniformly mixed in a mass ratio of 209:28:1, fed into a twin-screw extruder, reacted at 160-210° C., cooled, and granulated to obtain thermoplastic polyurethane 5.

[0063] The thermoplastic polyurethane 6 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 6 (hydroxyl value is 164 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are mixed uniformly in a mass ratio of 23:11:1, fed into a twin-screw extruder, reacted at 160-210°C, cooled, and granulated to obtain thermoplastic polyurethane 6.

[0064] The thermoplastic polyurethane 7 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 7 (hydroxyl value is 40 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are mixed uniformly in a mass ratio of 289:28:1, fed into a twin-screw extruder, reacted at 160-210°C, cooled, and granulated to obtain thermoplastic polyurethane 7.

[0065] The thermoplastic polyurethane 8 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 8 (hydroxyl value is 125 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are mixed uniformly in a mass ratio of 69:23:1, fed into a twin-screw extruder, reacted at 160-210°C, cooled, and granulated to obtain thermoplastic polyurethane 8.

[0066] The thermoplastic polyurethane 9 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 9 (hydroxyl value 45 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are uniformly mixed in a mass ratio of 138:17:1, fed into a twin-screw extruder, reacted at 160-210°C, cooled, and granulated to obtain thermoplastic polyurethane 9.

[0067] The thermoplastic polyurethane 10 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 10 (hydroxyl value 230 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are uniformly mixed in a mass ratio of 16:12:1, fed into a twin-screw extruder, reacted at 160-210° C., cooled, and granulated to obtain thermoplastic polyurethane 10.

[0068] The thermoplastic polyurethane 11 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 11 (hydroxyl value is 41 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are uniformly mixed in a mass ratio of 164:17:1, fed into a twin-screw extruder, reacted at 160-210° C., cooled, and granulated to obtain thermoplastic polyurethane 11.

[0069] The thermoplastic polyurethane 12 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 12 (hydroxyl value is 30 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are uniformly mixed in a mass ratio of 369:28:1, fed into a twin-screw extruder, reacted at 160-210° C., cooled, and granulated to obtain thermoplastic polyurethane 12.

[0070] The thermoplastic polyurethane 13 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 13 (hydroxyl value is 21 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are mixed uniformly in a mass ratio of 452:25:1, fed into a twin-screw extruder, reacted at 160-210° C., cooled, and granulated to obtain thermoplastic polyurethane 13.

[0071] The thermoplastic polyurethane 14 is a homemade polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 14 (hydroxyl value is 29 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are uniformly mixed in a mass ratio of 172:14:1, fed into a twin-screw extruder, reacted at 160-210° C., cooled, and granulated to obtain thermoplastic polyurethane 14.

[0072] The thermoplastic polyurethane 15 is a self-made polyester polyurethane elastomer, and the preparation method is as follows: polyester polyol 15 (hydroxyl value 42 mgKOH / g), diphenylmethane diisocyanate, and 1,4-butanediol are uniformly mixed in a mass ratio of 180:19:1, fed into a twin-screw extruder, reacted at 160-210° C., cooled, and granulated to obtain thermoplastic polyurethane 15.

[0073] The polyester polyols used as raw materials for preparing the thermoplastic polyurethanes were produced as follows: adipic acid and butanediol were added to a reactor and reacted at 140-190°C until the hydroxyl value reached the target value. Heating was then stopped to obtain the polyester polyols. Hydroxyl value testing was conducted in accordance with Chinese Chemical Industry Standard HG / T 2709-2022. All raw materials were dried before mixing.

[0074] The hindered phenol antioxidant 1 is 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane produced by Japan Aidi Co., Ltd.

[0075] The hindered phenol antioxidant 2 is triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] produced by Tianjin Li'anlong New Materials Co., Ltd., China.

[0076] The hindered phenol antioxidant 3 is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] produced by Tianjin Li'anlong New Materials Co., Ltd., China.

[0077] The hindered phenol antioxidant 4 is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate produced by Tianjin Li'anlong New Materials Co., Ltd., China.

[0078] The hindered phenol antioxidant 5 is bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazine produced by Tianjin Li'anlong New Materials Co., Ltd., China.

[0079] The hindered phenol antioxidant 6 is 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione produced by the Belgian Solvay Group.

[0080] The hindered phenol antioxidant 7 is 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid produced by Tianjin Li'anlong New Materials Co., Ltd., China.

[0081] The hindered phenol antioxidant 8 is 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene produced by Tianjin Li'anlong New Materials Co., Ltd., China.

[0082] The hindered phenol antioxidant 9 is N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine produced by Tianjin Li'anlong New Materials Co., Ltd., China.

[0083] The phosphite antioxidant is tris(2,4-di-tert-butylphenyl) phosphite produced by Tianjin Li'anlong New Materials Co., Ltd., China.

[0084] The lubricant is montan wax produced by Clariant Chemical Group of Switzerland.

[0085] The antistatic agent is PELESTAT-6500 produced by Sanyo Chemical Industries, Ltd. of Japan.

[0086] Unless otherwise specified, the components and raw materials used in the examples and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

[0087] The parameters of each thermoplastic polyurethane are shown in Table 1, and the parameters of each hindered phenol antioxidant are shown in Table 2.

[0088] Table 1 Related parameters of thermoplastic polyurethane 1-15

[0089] Table 2 Related parameters of hindered phenolic antioxidants 1-9

[0090] Table 3 Components and ratios of the thermoplastic composites of Examples 1-14

[0091] Table 4 Components and ratios of the products of Comparative Examples 1-14

[0092] In order to verify the performance of the thermoplastic composite of the present invention, the products prepared in each embodiment and comparative example were subjected to the following performance tests. The specific steps are as follows:

[0093] (1) Surface precipitation evaluation test: Each product was injection molded into a test piece of 100 × 100 × 2 mm and then left to stand for 6 months at 23°C and 50% relative humidity. After the third month and after the standing period, the surface of the test piece was observed using a Leica optical microscope to determine whether there was any precipitation of the antioxidant.

[0094] (2) Long-term heat and oxygen aging test: Each product was injection molded into a 100×100×2 mm test piece. The product was then cut into dumbbell shapes according to the Chinese national standard GB / T 528-2008 and subjected to initial tensile strength and elongation at break tests, recorded as TS0 and E0, respectively. After the test, the product was placed in an aging chamber at 120°C, which was open to the atmosphere, and allowed to stand for 1000 hours. After the standing period, the same tensile strength and elongation at break tests were performed on the above products, and recorded as TS1 and E1.

[0095] The tensile strength retention rate and elongation at break retention rate of the product after long-term aging and static storage are calculated using the following formula:

[0096] (a) Tensile strength retention La (%) = TS1 / TS0 × 100;

[0097] (b) Elongation at break retention Lb (%) = E1 / E0 × 100;

[0098] The test results are shown in Tables 5 and 6.

[0099] Table 5 Performance test results of thermoplastic composites of Examples 1-14

[0100] Table 6 Performance test results of the products of Comparative Examples 1-14

[0101] As can be seen from Tables 5 and 6, the thermoplastic composites of the present invention exhibit ideal component stability. Even after standing for up to six months, the thermoplastic composites of the present invention exhibit no precipitation of the antioxidant. Furthermore, the thermoplastic composites of the present invention exhibit excellent long-term thermal oxidation resistance, maintaining both tensile strength retention and elongation at break above 80% after treatment at 120°C for 1000 hours. In particular, in Examples 1-5, when the number of repeating units in the soft segment polyester of the thermoplastic polyurethane is 5-10 and / or the melt flow index ratio MA / MB of the thermoplastic polyurethane under different load conditions satisfies the following conditions: 3 ≤ MA / MB ≤ 5, the prepared thermoplastic composites exhibit even better long-term thermal oxidation resistance, with both tensile strength retention and elongation at break exceeding 85%. In contrast, the types of thermoplastic polyurethane and antioxidant in the comparative examples did not meet the requirements of the present invention. Some products experienced antioxidant precipitation within three months, while others did not experience antioxidant precipitation in the short term. However, the compatibility of the antioxidant and thermoplastic polyurethane in these products was poor, resulting in the inability to maintain both the tensile strength retention and elongation at break retention above 80% during long-term thermal oxidative aging testing. These experimental results indicate that the number of repeating units in the soft segment polyester of the thermoplastic polyurethane, the melt flow index ratio, and the solubility parameters of the hindered phenolic antioxidant directly affect the thermal oxidative aging stability and component compatibility of the product. Furthermore, in Comparative Example 12, a non-hindered phenolic antioxidant was introduced into the product, and the test results showed that the product failed to achieve the desired technical effect. In Comparative Example 13, due to the excessive addition of hindered phenolic antioxidant, even though the parameter limits of each component meet the requirements, the thermoplastic polyurethane cannot effectively carry the antioxidant component, so after the product is left standing for a long time, the antioxidant precipitates; and the product's resistance to heat and oxygen aging is not ideal.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A thermoplastic composite, characterized in that The composition comprises the following components in parts by weight: 99.5-99.95 parts of thermoplastic polyurethane and 0.05-0.5 parts of hindered phenol antioxidant; The number of repeating units of the soft segment polyester of the thermoplastic polyurethane is 3 to 14, and satisfies 2≤MA / MB≤6; Wherein, MA is the melt flow index (MFI) of thermoplastic polyurethane at 200°C and 5 kg load according to the Chinese national standard GB / T 3682.2-2018, and MB is the melt flow index of thermoplastic polyester at 200°C and 2.16 kg load according to the Chinese national standard GB / T3682.2-2018; The solubility of the hindered phenol antioxidant in tetrahydrofuran at 23°C is ≥50g / 100g and satisfies 17≤δ d ≤20, 1≤δ p ≤3,9.5≤δ h ≤11.5; where δ d is the solubility parameter dispersion component of hindered phenolic antioxidants, δ p is the polar component of the solubility parameter of hindered phenol antioxidants, δ h is the hydrogen bonding component of the solubility parameter of hindered phenol antioxidants.

2. The thermoplastic composite according to claim 1, characterized in that The number of repeating units of the soft segment polyester of the thermoplastic polyurethane is 5 to 10.

3. The thermoplastic composite according to claim 1 or 2, characterized in that The MA / MB satisfies: 3≤MA / MB≤5.

4. The thermoplastic composite according to any one of claims 1 to 3, characterized in that The MA is 2-30 g / 10 min, and the MB is 1-5 g / 10 min.

5. The thermoplastic composite according to any one of claims 1 to 4, characterized in that The thermoplastic polyurethane is a polyester polyurethane elastomer; preferably, the preparation method of the thermoplastic polyurethane is: After polyester polyol, diphenylmethane diisocyanate and 1,4-butanediol are dry-mixed, they are introduced into a screw extruder and extruded at 160-210° C., cooled and pelletized to obtain thermoplastic polyurethane.

6. The thermoplastic composite according to any one of claims 1 to 5, characterized in that The solubility of the hindered phenol antioxidant in tetrahydrofuran at 23° C. is 50 g / 100 g to 300 g / 100 g.

7. The thermoplastic composite according to any one of claims 1 to 6, characterized in that The hindered phenol antioxidant is at least one of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane; preferably, the hindered phenol antioxidant satisfies 17.5≤δ d ≤19.5, 1.3≤δ p ≤2.5, 10.0≤δ h ≤11.

3.

8. The method for preparing a thermoplastic composite according to any one of claims 1 to 7, wherein: The following steps are involved: The components of the thermoplastic composite are mixed uniformly, and then melt-extruded in a screw extruder. After cooling, granulation and drying, the thermoplastic composite is obtained.

9. Use of the thermoplastic composite according to any one of claims 1 to 7 in the preparation of automobile parts.

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