Flexible flame-retardant TPU-silicone rubber composite material and preparation method thereof

Abstract

The invention provides a flexible flame-retardant TPU (thermoplastic polyurethane)-silicone rubber composite material. The TPU-silicone rubber composite material is prepared from the following raw materials in parts by mass: 50 to 70 parts of modified TPU, 20 to 50 parts of silicone rubber, 5 to 10 parts of compatilizer, 0.5 to 1.0 part of antioxidant, 0.5 to 1.0 part of ultraviolet absorbent and 2 to 5 parts of filler, wherein the modified TPU is obtained by polymerizing diisocyanate and polyhydric alcohol containing silicon and phosphorus elements. The modified TPU master batch is obtained by designing phosphorus-containing polyol for polymerization, the flame retardance of a resin structure is improved, meanwhile, a silicon-containing structure is grafted, and the interface wettability and the blending stability with silicone rubber are improved; the TPU-silicone rubber composition is good in compatibility, excellent in weather resistance and heat resistance, flame-retardant, environment-friendly and good in processability; therefore, the application range of the material in the fields of cable sheaths, automobile parts, intelligent wearing and the like is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a flexible and flame-retardant TPU-silicone rubber composite material. Background Art

[0002] Thermoplastic polyurethane (TPU) is a polymer material that combines the elasticity of rubber with the processing properties of thermoplastics. It boasts excellent wear resistance, mechanical strength, and good processing adaptability, making it widely used in cable sheathing, electronic equipment coatings, sports equipment, and automotive parts. However, TPU has poor thermal stability at high temperatures, limited flexibility at low temperatures, and is prone to aging and hardening with long-term exposure to UV or ozone, limiting its application in high-reliability or extreme environments.

[0003] Silicone rubber is an elastic material with a polyorganosiloxane backbone. It exhibits excellent high and low temperature resistance (typically operating in temperatures ranging from -60°C to +200°C), weather resistance, and electrical insulation. It is commonly used in high-end applications such as aerospace, cables, medical treatment, and sealing. However, its weaknesses include high processing temperatures, inability to thermoform, relatively low mechanical strength, and high cost.

[0004] To combine the advantages of both materials, TPU and silicone rubber alloys have been gradually developed in recent years. These materials combine TPU and silicone rubber in a specific ratio through physical blending, chemical modification, or dynamic vulcanization. They aim to combine the mechanical strength and thermoplastic processing properties of TPU with the softness, temperature resistance, and excellent weather resistance of silicone rubber.

[0005] Currently, TPU and silicone rubber alloys have found initial application in products such as flexible cable sheaths, wearable devices, electronic connector coatings, automotive wire and cable, and medical flexible catheters. These materials can be formed through thermoplastic molding processes like injection molding and extrusion, while also offering enhanced flexibility, heat resistance, cold resistance, UV resistance, and surface tactile properties, demonstrating promising market prospects.

[0006] However, the existing TPU / silicone rubber alloy materials still have the following shortcomings:

[0007] Poor compatibility: TPU and silicone rubber differ greatly in molecular structure, polarity and interfacial tension. Direct blending often leads to phase separation of materials, resulting in problems such as decreased mechanical properties and interface delamination.

[0008] Poor processing stability: Some blending systems have uneven dispersion, silicone rubber precipitation, poor extrusion glossiness and other phenomena during the thermal processing process, affecting the appearance and dimensional stability of the finished product.

[0009] Flame retardancy and chemical resistance need to be improved: In applications with higher requirements such as wire and cable sheathing, alloy materials must meet flame retardancy levels such as UL 94V-0 and have better oil resistance and acid and alkali corrosion resistance.

[0010] Difficulty in cost control: Silicone rubber is relatively expensive. Improving its dispersion and utilization efficiency in the TPU matrix while ensuring its performance is an important direction for achieving material commercialization.

[0011] Therefore, there is still an urgent need to develop a TPU / silicone rubber alloy material with good compatibility, excellent weather and heat resistance, flame retardancy, environmental protection and good processing performance, so as to expand its application in cable sheaths, automotive parts and smart wearables. Summary of the Invention

[0012] Purpose of the Invention: This invention aims to overcome the difficulties of the prior art by providing a flexible, flame-retardant TPU-silicone rubber composite material and its preparation method. The TPU-silicone rubber composite material provided by the present invention exhibits good compatibility, excellent weather and heat resistance, flame retardancy, environmental friendliness, good processability, and cost-effectiveness.

[0013] The technical solution of the present invention:

[0014] In a first aspect, the present invention provides a flexible and flame-retardant TPU-silicone rubber composite material. The raw materials of the TPU-silicone rubber composite material include, by weight:

[0015] Modified TPU 50-70 parts;

[0016] 20-50 parts of silicone rubber;

[0017] 5-10 parts of compatibilizer;

[0018] 0.5-1.0 parts of antioxidant;

[0019] 0.5-1.0 parts of UV absorber;

[0020] 2-5 parts of filler.

[0021] The modified TPU is obtained by polymerizing diisocyanate and polyol containing silicon and phosphorus elements.

[0022] In some embodiments, the method for preparing the polyol containing silicon and phosphorus elements comprises the following steps:

[0023] Step 1: Add triethyl phosphate to a reactor, gradually add phosphorus pentoxide under nitrogen protection, and heat to react to obtain a viscous liquid;

[0024] Step 2: After the reaction solution is cooled, add phosphoric acid aqueous solution dropwise, and keep the temperature to react after the reaction is completed to obtain a reaction product;

[0025] Step 3: Add epoxy silane dropwise to the reaction product obtained in step 2. After the addition is completed, transfer the liquid to a high-pressure reactor, pressurize and heat the reactor for reaction. After the reaction is completed, post-process the reactor to obtain a polyol containing silicon and phosphorus elements.

[0026] In some embodiments, the molar ratio of triethyl phosphate to phosphorus pentoxide is 1:0.8-1.

[0027] In some embodiments, the reaction temperature in step 1 is 80-100° C., and the reaction time is 4-6 h.

[0028] In some embodiments, the reaction temperature in step 2 is 60-70° C., and the reaction time is 0.5-2 h.

[0029] In some embodiments, the reaction temperature in step 3 is 60-80° C., the reaction time is 1-3 h, and the reaction pressure is 0.5 MPa.

[0030] In some embodiments, the epoxy silane is selected from one of γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane.

[0031] Step 1 is to carry out a polymerization reaction between triethyl phosphate and phosphorus pentoxide to prepare a mixed polyethyl phosphate; step 2 is to add a phosphoric acid aqueous solution to the mixed polyethyl phosphate to convert the mixed polyethyl phosphate into a short-chain -P(O)OH-containing mixture; step 3 is to carry out a self-catalytic ring-opening reaction between epoxy silane and -P(O)OH to form a polyol containing silicon and phosphorus.

[0032] Silicon and phosphorus-containing polyols themselves have poor carbon-forming properties. The product has a high phosphorus content. The product formed can generate phosphoric acid after thermal decomposition or dehydrate to form polyphosphoric acid that covers the surface of the polymer material to achieve the purpose of condensed phase flame retardancy.

[0033] In some embodiments, the diisocyanate is selected from one or more combinations of 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0034] In some embodiments, the silicone rubber is selected from one or more combinations of hydroxy silicone rubber, dimethyl silicone rubber, methyl vinyl silicone rubber, methyl vinyl phenyl silicone rubber, methyl phenyl silicone rubber, and fluorosilicone rubber.

[0035] In some embodiments, the compatibilizer is selected from one or more combinations of polyethylene grafted with maleic anhydride, EPDM rubber grafted with maleic anhydride, and polyolefin elastomer grafted with maleic anhydride.

[0036] In some embodiments, the antioxidant is selected from one or more combinations of antioxidant 168, antioxidant 1076, antioxidant 1010, or antioxidant 164.

[0037] In some embodiments, the ultraviolet absorber is selected from one or more combinations of ultraviolet absorber UV-P, ultraviolet absorber UV-O, ultraviolet absorber UV-9, and ultraviolet absorber UV-531.

[0038] In some embodiments, the filler is selected from one or more combinations of alumina, mica powder, and talc powder.

[0039] In a second aspect, the present invention provides a method for preparing the TPU-silicone rubber composite material, specifically comprising: mixing the components according to the formula at a rotation speed of 2000-2500 rpm for 10-15 minutes to obtain a mixture, and melt-extruding the mixture to obtain a TPU-silicone rubber composite material.

[0040] Beneficial effects:

[0041] 1. This application prepares a TPU-silicone rubber composition, which has good compatibility, excellent weather and heat resistance, flame retardancy, environmental protection and good processing performance, so as to expand its application range in cable sheathing, automotive parts and smart wearables.

[0042] 2. This application improves the flame retardancy of the resin structure by modifying the TPU structure and polymerizing it by designing phosphorus-containing polyols, while grafting silicon-containing structures to improve the interface wettability and blending stability with silicone rubber. DETAILED DESCRIPTION

[0043] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are illustrative of the present invention and are intended only to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention.

[0044] Unless otherwise specified, all chemical reagents used in this invention were of commercially available analytical grade. Methylphenyl silicone rubber was purchased from Zhejiang Quzhou Zhengbang Organic Silicone Co., Ltd.; methylvinyl silicone rubber was purchased from Jiangsu Yak Chemical Co., Ltd.; fluorosilicone rubber was purchased from Shin-Etsu Chemical Co., Ltd., Japan, product designation FE-361-U. Polyethylene-grafted maleic anhydride was purchased from Shanghai Jingzhengfeng Chemical Additives Co., Ltd., model GR202; mica powder was purchased from Shenzhen Haiyang Powder Technology Co., Ltd., model HY-HM1; commercial TPU was purchased from BASF, model 45A; and flame retardant FR191 was purchased from Bailing Biotech.

[0045] Preparation of polyols containing silicon and phosphorus

[0046] Step 1: Add 10 mmol of triethyl phosphate to the reactor, and gradually add 8.5 mmol of phosphorus pentoxide under nitrogen protection, heat to 90°C, and react for 5 hours to obtain a viscous liquid;

[0047] Step 2: After the reaction solution obtained in step 1 is cooled to 60° C., 0.05 g of a phosphoric acid aqueous solution (mass fraction 85%) is added dropwise. After the addition is completed, the mixture is kept at 60° C. for 1 h to obtain a reaction product;

[0048] Step 3: After the reaction solution from Step 2 was cooled to 15°C, 10 mmol of γ-glycidoxypropyltrimethoxysilane was added dropwise. After the addition was complete, the solution was transferred to a high-pressure reactor and reacted at 0.5 MPa and 70°C for 1.5 hours. After completion of the reaction, post-processing was performed to obtain a polyol containing silicon and phosphorus. Testing revealed a hydroxyl value of 135 mgKOH / g and a phosphorus content of 16.3%.

[0049] Preparation of modified TPU

[0050] In a dry three-necked flask, add 100g of the silicon- and phosphorus-containing polyol prepared above, heat to 70°C and stir evenly, add 53.3g of IPDI dropwise while maintaining stirring; add 0.03g of DBTDL dropwise and continue stirring; raise the temperature to 90°C and maintain the reaction for 3 hours; cool and cut into pellets to obtain the modified TPU masterbatch.

[0051] Example

[0052] The modified TPU masterbatch, silicone rubber, compatibilizer, antioxidant, UV absorber, and filler were weighed according to Table 1, and the above components were added to a high-speed mixer and mixed at a speed of 2000 rpm for 15 minutes to obtain a mixture. The mixture was then fed into a twin-screw extruder for melt extrusion to obtain a TPU-silicone rubber composite material.

[0053] Table 1 Example formula table

[0054]

[0055]

[0056] Comparative Example

[0057] The raw materials of each component were weighed according to Table 2, and added to a high-speed mixer, and mixed at a speed of 2000 rpm for 15 minutes to obtain a mixture; the mixture was then sent to a twin-screw extruder for melt extrusion to obtain a composite material.

[0058] Table 1 Comparative Example Formula

[0059]

[0060] Effect embodiment

[0061] The effects of the composite materials of the embodiment and comparative example are verified in terms of the following performances. The test results are shown in Table 3.

[0062] 1. Softness test: elastic modulus test was conducted according to ASTM D790-03, test conditions were 25℃±2℃, and elastic modulus standard was 2.5-4.2Mpa.

[0063] 2. Tensile strength: The tensile strength is tested using a tensile testing machine. According to the GB12706.1-2008 standard, the tensile strength standard for low-smoke halogen-free cables is 9.0 MPa, which exceeds the standard requirement and demonstrates excellent tensile strength.

[0064] 3. Flame retardant performance: Flame retardant performance test is carried out with reference to standard GBT 2408-2008.

[0065] 4. Abrasion test: This test simulates the friction between the wire and other objects during installation to determine if the wire will be damaged. The test involves repeatedly scraping the wire 10,000 times on an abrasion tester to check if the wire sheath is worn through.

[0066] Table 3 Test results

[0067]

[0068] As can be seen from Table 3, the TPU-silicone rubber composite materials prepared in Examples 1-3 of the present application have good softness, tensile strength, flame retardancy, and wear resistance. This indicates that the modified TPU prepared in this application, when added to the rubber material, imparts good compatibility to the rubber material, enabling uniform mixing and compounding with the silicone rubber. This results in the prepared rubber material having high mechanical properties and flexibility, facilitating subsequent application in cable materials.

[0069] Examples 4-5 changed the type of silicone rubber. As can be seen from Table 3, compared with Example 1, the various data of Examples 4-5 have changed to varying degrees, indicating that the type of silicone rubber and the composite effect of modified TPU are different. The use of methylphenyl silicone rubber is more conducive to improving the performance of the composite material.

[0070] In Comparative Example 1, no modified TPU masterbatch was added, and commercially available ordinary TPU masterbatch was used. As shown in Table 3, compared with Example 2, the modified TPU of the present application can effectively improve the flame retardancy of the composite material.

[0071] Comparative Example 2 does not incorporate modified TPU masterbatch, but instead uses commercially available conventional TPU masterbatch, and increases the amount of silicone rubber used. Table 3 shows that, compared with Example 2 and Comparative Example 1, increasing the amount of silicone rubber improves the flexibility of the composite material provided by Comparative Example 2. However, the excessive use of silicone rubber increases costs, reduces mechanical strength, and decreases wear resistance.

[0072] As can be seen from Comparative Example 3, the TPU-silicone rubber composite material provided by the present invention can eliminate the need for flame retardants, thereby further reducing costs.

[0073] The present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A flexible and flame-retardant TPU-silicone rubber composite material, characterized in that: The raw materials of the TPU-silicone rubber composite material include, by mass: Modified TPU 50-70 parts; 20-50 parts of silicone rubber; 5-10 parts of compatibilizer; 0.5-1.0 parts of antioxidant; 0.5-1.0 parts of UV absorber; 2-5 parts of filler; The modified TPU is obtained by polymerizing diisocyanate and polyol containing silicon and phosphorus elements.

2. The TPU-silicone rubber composite material according to claim 1, characterized in that: The preparation method of the polyol containing silicon and phosphorus elements comprises the following steps: Step 1: Add triethyl phosphate to a reactor, gradually add phosphorus pentoxide under nitrogen protection, and heat to react to obtain a viscous liquid; Step 2: After the reaction solution is cooled, add phosphoric acid aqueous solution dropwise, and keep the temperature to react after the reaction is completed to obtain a reaction product; Step 3: Add epoxy silane dropwise to the reaction product obtained in step 2. After the addition is completed, transfer the liquid to a high-pressure reactor, pressurize and heat the reactor for reaction. After the reaction is completed, post-process the reactor to obtain a polyol containing silicon and phosphorus elements.

3. The TPU-silicone rubber composite material according to claim 2, characterized in that: The molar ratio of triethyl phosphate to phosphorus pentoxide is 1:0.8-1.

4. The TPU-silicone rubber composite material according to claim 2, characterized in that: The reaction temperature in step 1 is 80-100° C., the reaction time is 4-6 h, the reaction temperature in step 2 is 60-70° C., the reaction time is 0.5-2 h, the reaction temperature in step 3 is 60-80° C., the reaction time is 1-3 h, and the reaction pressure is 0.5 MPa.

5. The TPU-silicone rubber composite material according to claim 2, characterized in that: The epoxy silane is selected from one of γ-glycidyloxypropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane.

6. The TPU-silicone rubber composite material according to claim 1, characterized in that: The silicone rubber is selected from one or more combinations of hydroxy silicone rubber, dimethyl silicone rubber, methyl vinyl silicone rubber, methyl vinyl phenyl silicone rubber, methyl phenyl silicone rubber, and fluorosilicone rubber.

7. The TPU-silicone rubber composite material according to claim 1, characterized in that: The diisocyanate is selected from one or more combinations of 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

8. The TPU-silicone rubber composite material according to claim 1, characterized in that: The compatibilizer is selected from one or more combinations of polyethylene grafted with maleic anhydride, EPDM rubber grafted with maleic anhydride, and polyolefin elastomer grafted with maleic anhydride; the antioxidant is selected from one or more combinations of antioxidant 168, antioxidant 1076, antioxidant 1010, or antioxidant 164.

9. The TPU-silicone rubber composite material according to claim 1, characterized in that: The ultraviolet absorber is selected from one or more combinations of ultraviolet absorber UV-P, ultraviolet absorber UV-O, ultraviolet absorber UV-9, and ultraviolet absorber UV-531; the filler is selected from one or more combinations of aluminum oxide, mica powder, and talc powder.

10. The method for preparing the TPU-silicone rubber composite material according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: mixing the components according to the formula at a rotation speed of 2000-2500 rpm for 10-15 minutes to obtain a mixture material; and melt-extruding the mixture material to obtain a TPU-silicone rubber composite material.

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