Polyethylene composite material and production process thereof

Abstract

The invention discloses a polyethylene composite material and a production process thereof, and belongs to the technical field of polyethylene composites.The polyethylene composite material comprises, by weight, 15-20 parts of low-melting-point resin, 30-45 parts of silane coupling agent modified ultra-high molecular weight polyethylene and 7-13 parts of silane coupling agent modified organic filler. According to the polyethylene composite material, the heat resistance of the organic filler is improved, and the dispersity of the organic filler in polyethylene is improved, so that the viscosity is reduced, and the creep resistance of the polyethylene composite material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene composite materials, and particularly relates to polyethylene composite materials and their production processes. Background Art

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fibers have the advantages of low density, high strength, high specific strength and specific modulus, good bending and friction resistance, and excellent chemical stability. However, they have the disadvantages of low melting point, poor creep resistance and poor surface adhesion performance. Their advantages are more obvious under the use conditions of non-high temperature and non-long-time stretching. The force between polyethylene molecular chains is weak, and the molecular chains are highly oriented. Under long-term stress, the molecular chains are prone to slip, resulting in insufficient creep resistance.

[0003] Ultra-high molecular weight polyethylene fibers have certain deficiencies, which are mainly reflected in the following three points. First, due to the high crystallinity and non-polarity on the surface of ultra-high molecular weight polyethylene fibers, their adhesion to resins is poor, the interfacial bonding force is insufficient, and interfacial fracture and debonding are prone to occur under stress, resulting in a decrease in the mechanical properties of the composite material. Second, the melting point of polyethylene materials is relatively low, only around 130°C, and the thermal aging rate of ultra-high molecular weight polyethylene fibers under tensile conditions is relatively fast. Therefore, their maximum service temperature is generally between 80 and 100°C, which limits their application in high-temperature environments. Third, the main chain of the structure of ultra-high molecular weight polyethylene fibers does not contain side groups, the force between molecular chains is weak, and the molecular chains are highly oriented. Under long-term stress, the molecular chains are prone to slip between each other, resulting in elongation under stress and insufficient creep resistance.

[0004] Inorganic fillers for filling ultra-high molecular weight polyethylene include calcium carbonate, talcum powder, kaolin, barium sulfate, calcium silicate, silicon dioxide, etc. Calcium carbonate-filled ultra-high molecular weight polyethylene composites can reduce the cost of products, improve rigidity, heat resistance and dimensional stability. However, the interfacial adhesion between the inorganic filler calcium carbonate and the non-polar polymer ultra-high molecular weight polyethylene is poor, resulting in a decrease in the mechanical properties and flow properties of the material, and the energy is much lower than that of the original polyethylene. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, one of the purposes of the present invention is to provide a polyethylene composite material, which does not contain inorganic fillers, improves the heat resistance of organic fillers, improves the dispersion of organic fillers in polyethylene, thereby reducing viscosity and improving the creep resistance of the polyethylene composite material.

[0006] Another purpose of the present invention is to provide a production process for polyethylene composite materials, which has a simple preparation process and low production cost.

[0007] One of the purposes of the present invention is achieved by adopting the following technical solutions: A polyethylene composite material, by weight, comprises 15-20 parts of a low melting point resin, 30-45 parts of ultra-high molecular weight polyethylene modified with a silane coupling agent, and 7-13 parts of an organic filler modified with a silane coupling agent.

[0008] Further, by weight, it comprises 15 parts of a low melting point resin, 42 parts of ultra-high molecular weight polyethylene modified with a silane coupling agent, and 10 parts of an organic filler modified with a silane coupling agent.

[0009] Further, the low melting point resin is one or two of polyethylene glycol and polyamide.

[0010] Further, the preparation method of the ultra-high molecular weight polyethylene modified with a silane coupling agent is as follows: treating the ultra-high molecular weight polyethylene with a potassium dichromate-sulfuric acid system strong oxidant can effectively introduce polar groups. The oxidation conditions are: the mass ratio of potassium chromate, water and concentrated sulfuric acid is usually 5:8:10, the optimal treatment temperature is usually 45-60 °C, and the appropriate oxidation time is about 45 minutes. Then, it is modified with a silane coupling agent to obtain the ultra-high molecular weight polyethylene modified with a silane coupling agent.

[0011] Further, the organic filler modified with a silane coupling agent is one or two of a polyimide resin modified with a silane coupling agent and a SAM-I modified with a silane coupling agent.

[0012] The second object of the present invention is achieved by the following technical solution: A production process of a polyethylene composite material, comprising the following steps: S1. Mix and melt the low melting point resin, the ultra-high molecular weight polyethylene modified with a silane coupling agent, and the organic filler modified with a silane coupling agent to obtain an ultra-high molecular weight polyethylene fiber spinning solution; S2. Subject the ultra-high molecular weight polyethylene fiber spinning solution to extrusion spinning and volatilization of excess solution in sequence to form a dry state raw fiber; S3. Stretch the dry state raw fiber to obtain the polyethylene composite material.

[0013] Further, the temperature of the mixing and melting is 120-200 °C.

[0014] Further, the equipment for extrusion spinning comprises a spinning box and a spinneret plate. The temperature of the extrusion spinning is 130-250 °C; the temperature for volatilization of excess solution is 150-300 °C. Compared with the prior art, the beneficial effects of the present invention are as follows: The polyethylene composite provided by the present invention has a low melting point resin that can be melted at a relatively low temperature. After being blended with ultra-high molecular weight polyethylene, it will be dispersed in the ultra-high molecular weight polyethylene melt, where it acts as a "lubricant" in the ultra-high molecular weight polyethylene melt, reducing the friction between the ultra-high molecular weight polyethylene molecular chains; its melt viscosity is also relatively low, which means they are more likely to flow and require less energy during processing, reducing the shear force and pressure required during the processing of ultra-high molecular weight polyethylene. The blend system does not need to be heated to a very high temperature like pure ultra-high molecular weight polyethylene to reach a processable state, which not only reduces energy consumption but also reduces the risk of aging or degradation that ultra-high molecular weight polyethylene may undergo at high temperatures. Siloxane coupling agents (such as triethoxysilane) will undergo hydrolysis reactions in the presence of water to generate silanols (Si-OH) and alcohols (ROH). The generated silanols (Si-OH) can undergo condensation reactions through their own silanol groups to form silicon-oxygen bonds and release water molecules, forming silicon-oxygen bonds (Si-O-Si) or forming silicon-oxygen bonds (Si-O-C) with the hydroxyl groups on the surface of ultra-high molecular weight polyethylene. Finally, long side chains are formed on the ultra-high molecular weight polyethylene to form a highly oriented and dense structure. The silane coupling agent can enter the interior of the ultra-high molecular weight polyethylene fiber between the molecular chains and be evenly dispersed, crosslinking between the molecular chains inside the ultra-high molecular weight polyethylene fiber during the hot stretching process, which can better improve the force between the molecular chains of the ultra-high molecular weight polyethylene fiber and reduce the slippage between the molecular chains under stress, and has a more obvious improvement effect on the anti-creep performance of the ultra-high molecular weight polyethylene fiber. The silane coupling agent modifies the organic filler, and the interfacial compatibility between the organic filler and the ultra-high molecular weight polyethylene matrix is good, forming a good interfacial bond, improving the dispersion of the organic filler in the matrix, thereby reducing the viscosity and increasing the molding efficiency.

[0015] For the ultra-high molecular weight polyethylene composite provided by the present invention, the Tg of polyimide is usually above 300 °C. By compounding polyimide with ultra-high molecular weight polyethylene, the thermal stability of the ultra-high molecular weight polyethylene composite can be effectively improved, enabling it to be used at higher temperatures, and the addition of polyimide can enhance the mechanical properties of the ultra-high molecular weight polyethylene material, such as tensile strength and modulus; while adding a heat-resistant modifier, such as SAM-I (a terpolymer of styrene, acrylonitrile, and N-phenyl maleimide), to ultra-high molecular weight polyethylene can improve the heat resistance of the ultra-high molecular weight polyethylene composite, and the addition of SAM-I can make up for the possible decline in the processing performance of ultra-high molecular weight polyethylene caused by the polyimide resin. Detailed implementation manners

[0016] The following combines specific embodiments to further describe the present invention. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments.

[0017] The ultra-high molecular weight polyethylene particles used as the matrix in the composite material were purchased from Daqing Petrochemical Company, China. The solid density of these particles is 935 kg / m3, and the molecular weight is usually above 1.5 million. Due to its extremely high molecular weight, the melt flow index of UHMWPE is usually very low, even difficult to measure, less than 0.01 g / 10 min.

[0018] The silane coupling agent KH-570, CAS No.: 2530-85-0, was purchased from Quzhou Ruierfeng Chemical Co., Ltd.

[0019] Polyethylene glycol, CAS No.: 25322-68-3, was purchased from Aladdin Chemistry.

[0020] The low melting point polyamide, CAS No.: 5892-11-5, was purchased from Shanghai Merck Chemical Technology Co., Ltd.

[0021] Polyimide, 26023-21-2, was purchased from Hubei Qifei Pharmaceutical Chemical Co., Ltd.

[0022] The food quality physical property analyzer JC510-XL500 was purchased from Beijing Jiashengxingye Technology Co., Ltd.

[0023] Polyethylene glycol (PEG): Polyethylene glycol is a common low melting point polymer, and its melting point is usually between 30°C and 60°C.

[0024] Low melting point polyamide: The melting points of these materials are usually lower than the processing temperature of traditional polyethylene (the processing temperature of polyethylene is usually between 180°C and 220°C).

[0025] These low melting point resins can be melted at a lower temperature and will be dispersed in the polyethylene melt. It will act as a "lubricant" in the polyethylene melt, reducing the friction between polyethylene molecular chains; its melt viscosity is also relatively low, which means it is easier to flow and requires less energy during processing, reducing the shear force and pressure required during processing. The blend system does not need to be heated to a very high temperature like pure polyethylene to reach a processable state, which not only reduces energy consumption but also reduces the risk of aging or degradation of polyethylene at high temperatures. Examples

[0026] The polyethylene composite material provided in this example includes 15 parts of low melting point resin polyethylene glycol, 42 parts of ultra-high molecular weight polyethylene modified with silane coupling agent, and 10 parts of silane coupling agent modified organic filler SAM-I.

[0027] The silane coupling agent in this example is silane coupling agent KH-570.

[0028] In this embodiment, the preparation method of the ultra-high molecular weight polyethylene modified by a silane coupling agent is as follows: Treating the ultra-high molecular weight polyethylene with a strong oxidant of a potassium dichromate-sulfuric acid system can effectively introduce polar groups. The oxidation conditions are as follows: The mass ratio of potassium chromate, water and concentrated sulfuric acid is usually 5:8:10. The optimal treatment temperature is usually 45 - 60 °C, and the appropriate oxidation time is about 45 minutes. Then, it is modified by a silane coupling agent to obtain the ultra-high molecular weight polyethylene modified by a silane coupling agent.

[0029] During the mixing process of potassium dichromate and concentrated sulfuric acid, nascent oxygen (O) is generated. This active oxygen has a strong oxidizing effect on the surface of polyethylene. These active oxygen will react with the carbon-hydrogen bonds on the surface of polyethylene to form polar groups such as hydroxyl (-OH), carbonyl (-C=O) and carboxyl (-COOH). The mass ratio of potassium chromate, water and concentrated sulfuric acid is usually 5:8:10. The optimal treatment temperature is usually 45 - 60 °C, and the appropriate oxidation time is about 45 minutes.

[0030] This embodiment also provides a production process for a polyethylene composite material, including the following steps: S1. Mix and melt a low-melting-point resin, the ultra-high molecular weight polyethylene modified by a silane coupling agent, and an organically filled material modified by a silane coupling agent at a temperature of 150 °C to obtain an ultra-high molecular weight polyethylene fiber spinning solution. S2. Sequentially subject the ultra-high molecular weight polyethylene fiber spinning solution to extrusion spinning and volatilization of the excess solution. The equipment for extrusion spinning includes a spinning box and a spinneret. The temperature for extrusion spinning is 130 - 250 °C; the temperature for volatilization of the excess solution is 165 °C to form a dry-state raw fiber. S3. Stretch the dry-state raw fiber to obtain a polyethylene composite material. Example

[0031] The polyethylene composite material provided in this embodiment includes 18 parts of a low-melting-point resin polyamide, 30 parts of the ultra-high molecular weight polyethylene modified by a silane coupling agent, and 7 parts of an organically filled material modified by a silane coupling agent, polyimide resin.

[0032] The silane coupling agent in this embodiment is the silane coupling agent KH-570.

[0033] This embodiment also provides a production process for a polyethylene composite material, including the following steps: S1. Mix and melt a low-melting-point resin, the ultra-high molecular weight polyethylene modified by a silane coupling agent, and an organically filled material modified by a silane coupling agent at a temperature of 120 °C to obtain an ultra-high molecular weight polyethylene fiber spinning solution. S2. The ultra-high molecular weight polyethylene fiber spinning solution is successively subjected to extrusion spinning and volatilization of the excess solution. The equipment for extrusion spinning includes a spinning box and a spinneret plate. The temperature for extrusion spinning is 130 - 250 °C; the temperature for volatilization of the excess solution is 300 °C to form a dry-state raw fiber. S3. The dry-state raw fiber is stretched to obtain a polyethylene composite material. Example

[0034] The polyethylene composite material provided in this example includes 20 parts of a low-melting-point resin, 45 parts of ultra-high molecular weight polyethylene modified with a silane coupling agent, and 13 parts of a polyimide resin which is an organic filler modified with a silane coupling agent.

[0035] The silane coupling agent in this example is silane coupling agent KH-570.

[0036] This example also provides a production process for the polyethylene composite material, including the following steps: S1. The low-melting-point resin, ultra-high molecular weight polyethylene modified with a silane coupling agent, and the organic filler modified with a silane coupling agent are mixed and melted at a temperature of 200 °C to obtain an ultra-high molecular weight polyethylene fiber spinning solution. S2. The ultra-high molecular weight polyethylene fiber spinning solution is successively subjected to extrusion spinning and volatilization of the excess solution. The equipment for extrusion spinning includes a spinning box and a spinneret plate. The temperature for extrusion spinning is 130 - 250 °C; the temperature for volatilization of the excess solution is 150 °C to form a dry-state raw fiber. S3. The dry-state raw fiber is stretched to obtain a polyethylene composite material.

[0037] Comparative Example 1 Different from Example 1, the polyethylene composite material provided in this comparative example includes 42 parts of ultra-high molecular weight polyethylene modified with a silane coupling agent and 10 parts of SAM-I which is an organic filler modified with a silane coupling agent.

[0038] Comparative Example 2 Different from Example 1, the production process of the polyethylene composite material provided in this comparative example includes 15 parts of polyethylene glycol which is a low-melting-point resin, 42 parts of ultra-high molecular weight polyethylene, and 10 parts of SAM-I which is an organic filler modified with a silane coupling agent.

[0039] Comparative Example 3 Different from Example 1, the polyethylene composite material provided in this comparative example includes 15 parts of polyethylene glycol which is a low-melting-point resin, 42 parts of ultra-high molecular weight polyethylene modified with a silane coupling agent, and 10 parts of wood flour fiber which is an organic filler modified with a silane coupling agent.

[0040] Wood flour fiber is an organic filler with low heat resistance.

[0041] Experimental Example This experimental example tested the melt viscosity, heat resistance, and creep elongation rate of the polyethylene composites obtained in Examples 1-3 and Comparative Examples 1-3, where: The pretreated sample was added to the barrel of the melt flow rate instrument and compacted. It was heated to the set temperature of 80 °C, and after the sample was completely melted, it was preheated for 8 minutes. The selected load weight was added, and the load was selected as 2160 grams (21.18 N) to start extruding the material. The melt mass passing through the capillary was measured at regular time intervals (usually 10 minutes), and the melt mass passing through the capillary per unit time (10 minutes) was calculated, which was the MFI value. The melt index (MFI) was calculated, and this value was inversely proportional to the melt viscosity. Result analysis: The higher the melt index (MFI), the lower the melt viscosity of the material and the better the fluidity, to evaluate the melt viscosity characteristics of the polyethylene composite.

[0042] Test of heat resistance: After the specimen was aged in an air environment of an oven at 115 °C for 100 hours, the breaking strength and breaking elongation rate of the polyethylene composites obtained in Examples 1-3 and Comparative Examples 1-2 were tested according to GBT19975-2005.

[0043] Test of creep elongation rate: It was carried out according to the tensile creep test method specified in the test method for tensile properties of high-strength chemical fiber filaments GBT 19975-2005, where the load was 50% of the fiber breaking load and the test temperature was 70 °C. The test results are shown in Table 1.

[0044] Table 1

[0045] As can be seen from the measurement results in Table 1, when compared with Comparative Example 1, the melt index (MFI) of the sample of the polyethylene composite provided in Example 1 is significantly higher than that of Comparative Example 1, indicating that the low melting point resin can be melted at a lower temperature. After being blended with ultra-high molecular weight polyethylene, it will be dispersed in the ultra-high molecular weight polyethylene melt and play the role of a "lubricant" in the ultra-high molecular weight polyethylene melt, reducing the friction between the ultra-high molecular weight polyethylene molecular chains; its melt viscosity is also relatively low, which means that they are more likely to flow and require less energy during processing; when compared with Comparative Example 2, the creep elongation rate of the sample of the polyethylene composite provided in Example 1 is significantly lower than that of Comparative Example 2, indicating that the ultra-high molecular weight polyethylene modified by the silane coupling agent in the present invention forms long side chains on the ultra-high molecular weight polyethylene to form a highly oriented dense structure. The silane coupling agent can enter the interior of the ultra-high molecular weight polyethylene fiber and be evenly dispersed between the molecular chains. During the hot stretching process, cross-linking occurs between the molecular chains inside the ultra-high molecular weight polyethylene fiber, which can better improve the force between the molecular chains of the ultra-high molecular weight polyethylene fiber and reduce the slippage between the molecular chains under stress, and the improvement effect on the anti-creep performance of the ultra-high molecular weight polyethylene fiber is more obvious; when compared with Comparative Example 3, the fracture strength, fracture elongation rate, and heat resistance of the sample of the polyethylene composite provided in Example 1 are significantly higher than those of Comparative Example 3, indicating that by compounding polyimide with ultra-high molecular weight polyethylene in the present invention, the thermal stability of the ultra-high molecular weight polyethylene composite can be effectively improved, enabling it to be used at a higher temperature; and by adding a heat-resistant modifier, such as SAM-I, to the ultra-high molecular weight polyethylene, the heat resistance of the ultra-high molecular weight polyethylene composite is improved.

[0046] The above embodiments are only the preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A polyethylene composite material, characterized in that: In parts by weight, the invention comprises 15-20 parts of a low melting point resin, 30-45 parts of an ultra-high molecular weight polyethylene modified by a silane coupling agent, and 7-13 parts of an organic filler modified by a silane coupling agent.

2. The polyethylene composite material according to claim 1, characterized in that: In parts by weight, the composition comprises 15 parts of low melting point resin, 42 parts of ultra-high molecular weight polyethylene modified by a silane coupling agent, and 10 parts of an organic filler modified by a silane coupling agent.

3. The polyethylene composite material according to claim 1, characterized in that: The low melting point resin is one or both of polyethylene glycol and polyamide.

4. The polyethylene composite material according to claim 1, characterized in that: The preparation method of the ultra-high molecular weight polyethylene modified by a silane coupling agent is as follows: treating the ultra-high molecular weight polyethylene with a strong oxidant of a potassium dichromate-sulfuric acid system can effectively introduce polar groups, and the oxidation conditions are: the mass ratio of potassium chromate, water and concentrated sulfuric acid is usually 5:8:10, the optimal treatment temperature is usually 45-60°C, the suitable oxidation time is about 45 minutes, and then modified with a silane coupling agent to obtain the ultra-high molecular weight polyethylene modified by a silane coupling agent.

5. The polyethylene composite material according to claim 1, characterized in that: The silane coupling agent modified organic filler is one or both of silane coupling agent modified polyimide resin and silane coupling agent modified SAM-I.

6. The polyethylene composite material production process according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, mixing and melting the low melting point resin, the ultra-high molecular weight polyethylene modified by the silane coupling agent, and the silane coupling agent modified organic filler to obtain an ultra-high molecular weight polyethylene fiber spinning solution; S2, subjecting the ultra-high molecular weight polyethylene fiber spinning solution to extrusion spinning and volatilization of excess solution in sequence to form dry raw fibers; S3, stretching the dry raw silk to obtain the polyethylene composite material.

7. The polyethylene composite material production process according to claim 6, characterized in that: The temperature of the mixed melting is 120-200°C.

8. The polyethylene composite material production process according to claim 6, characterized in that: The extrusion spinning equipment comprises a spinning box and a spinneret, the extrusion spinning temperature is 130-250°C, and the temperature at which the excess solution evaporates is 150-300°C.

Images