Weather-resistant medium-density polyethylene cable sheath material and preparation method thereof

Abstract

The invention discloses a weather-resistant medium-density polyethylene cable sheath material and a preparation method thereof. The cable sheath material comprises the following raw materials in parts by weight: 45-55 parts of high-density polyethylene, 30-40 parts of linear low-density polyethylene, 3-5 parts of metal organic framework composite resin, 1-3 parts of a compatilizer, 0-2 parts of a high-molecular-weight hindered amine light stabilizer, 0.5-2 parts of a lubricant, 0.4-0.6 part of a nano inorganic screening agent, 0.3-0.6 part of an ultraviolet light absorber, 0.5-1.5 parts of calcium carbonate and 0-3 parts of a coloring agent. Wherein the nano inorganic screening agent is layered double hydroxide. The sheath material can adapt to environment and climate changes of different areas, the mechanical performance is guaranteed, meanwhile, the appearance and the main performance of a product are stable, the weather resistance is excellent, and the problems of sheath color spots, color fading, cracking and the like can be avoided.

Description

Technical Field

[0001] The present invention relates to the field of polymer material processing, and particularly relates to a weather-resistant medium-density polyethylene cable sheath material. Background Art

[0002] Polyethylene materials have the characteristics of low-temperature resistance, good chemical stability, low water absorption, and excellent electrical properties, so they are widely used in the communication and power cable industries. With the modernization and popularization of optical communication and power transmission, for the convenience of engineering installation and maintenance, each cable needs to be distinguished by different colors. Although polyethylene sheaths of different colors meet the above requirements, due to the mismatch of systems such as antioxidants and ultraviolet absorbers, they are extremely vulnerable to environmental factors such as light, ultraviolet rays, and acidity, resulting in fading and even cracking, seriously affecting signal and power transmission, and even causing safety accidents. The environments and climates of different countries and regions vary greatly, and the impact on the performance of polyethylene is quite different. For example, in areas with strong sunlight, the ultraviolet radiation is intense. If the ultraviolet absorber in the sheath material is insufficient or has poor performance, ultraviolet rays will accelerate the aging of the material, causing the sheath to fade, become brittle, and then crack. In areas with frequent acid rain, acidic substances in the air will react chemically with the sheath material, destroying the material structure, and also causing fading and performance degradation. In the research and production process of traditional polyethylene sheath materials, the selection and use of colorants are often mainly concerned to meet the requirements of different color identifications, but the research on weather resistance is relatively insufficient. This results in unstable performance of the sheath material under different climate conditions, restricting the application range and service life of optical and power cables in different climate regions. Summary of the Invention

[0003] To solve the above technical problems, the purpose of the present invention is to provide a weather-resistant medium-density polyethylene cable sheath material and its preparation method; this sheath material can adapt to the environmental and climate changes in different regions, while ensuring mechanical properties, the appearance and main performance of the product are stable, and it has excellent weather resistance, and can avoid problems such as sheath color spots, fading, and cracking.

[0004] To achieve the above technical purpose and reach the above technical effect, the present invention is realized through the following technical solutions:

[0005] On the one hand, the present invention provides a weather-resistant medium-density polyethylene cable sheath material, which includes the following raw materials according to weight ratio: 45-55 parts of high-density polyethylene, 30-40 parts of linear low-density polyethylene, 3-5 parts of metal-organic framework composite resin, 1-3 parts of compatibilizer, 0-2 parts of high-molecular-weight hindered amine light stabilizer, 0.5-2 parts of lubricant, 0.4-0.6 parts of nano-inorganic shielding agent, 0.3-0.6 parts of ultraviolet absorber, 0.5-1.5 parts of calcium carbonate, 0-3 parts of colorant; wherein, the nano-inorganic shielding agent is layered double hydroxide.

[0006] Further, the metal-organic framework composite resin is formed by compounding a metal-organic framework with polyethylene.

[0007] Further, the preparation method of the metal-organic framework composite resin is as follows:

[0008] A certain amount of MOF powder and polyethylene particles or powder are stirred and mixed evenly; the evenly mixed MOF / polyethylene mixture is melt-blended and extruded to obtain the metal-organic framework composite resin.

[0009] Preferably, the compatibilizer is maleic anhydride grafted polyethylene.

[0010] Preferably, the lubricant is selected from at least one of stearic acid, calcium stearate, zinc stearate, magnesium stearate, and polyethylene wax.

[0011] Preferably, the ultraviolet absorber is selected from at least one of titanium dioxide, zinc oxide, benzotriazole ultraviolet absorbers, and benzophenone ultraviolet absorbers.

[0012] Preferably, the colorant is selected from one of carbon black, titanium dioxide, phthalocyanine pigments, and azo pigments.

[0013] On the other hand, the present invention provides a preparation method of a weather-resistant medium-density polyethylene cable sheath material, which includes the following steps:

[0014] (1) Mix high-density polyethylene, linear low-density polyethylene, metal-organic framework composite resin, compatibilizer, high molecular weight hindered amine light stabilizer, lubricant, nano-inorganic shielding agent, ultraviolet absorber, calcium carbonate, and colorant in a mixer according to the weight ratio;

[0015] (2) The mixed material obtained in step (1) is kneaded and extruded into pellets by a twin-screw extruder, and then cooled by water, dried, screened, and packaged into finished products.

[0016] Further, the mixing temperature in step (1) is 50-60°C, and the rotation speed of the mixer is 1000-3000 r / min.

[0017] Further, in step (2), the temperature range of the twin-screw extruder is 150-220°C.

[0018] The beneficial effects of the present invention are:

[0019] (1) The sheath material matrix of the present invention uses high-density polyethylene and linear low-density polyethylene. The high-density polyethylene has a relatively high crystallinity, the molecular chains are arranged more closely, and it has relatively good weather resistance.

[0020] (2) The sheath material of the present invention contains a metal-organic framework (MOF) composite resin and a layered double hydroxide (LDH), and has the following technical effects:

[0021] Reflection and scattering effect of LDH: LDH has a layered structure and a relatively high refractive index, which can effectively reflect and scatter ultraviolet rays, reduce the direct penetration and damage of ultraviolet rays to the sheath material, and thus reduce the occurrence probability of photodegradation reactions; moreover, metal ions (such as Mg 2+ , Al 3+ ) and interlayer anions (such as CO3 2- , NO3 - ) in LDH can absorb part of the ultraviolet light through electron transition and release it as heat energy;

[0022] Free radical absorption effect of MOF: Ultraviolet irradiation will cause polymer molecules in the material to generate free radicals, and these free radicals further initiate chain reactions, resulting in the breaking, crosslinking or degradation of the polymer molecular chains, thereby degrading the performance of the material and causing phenomena such as fading and cracking. The MOF material has a highly ordered porous structure and a large specific surface area, and its pores can provide adsorption sites for free radicals, capture free radicals by physical adsorption or chemical adsorption, reduce the diffusion and propagation of free radicals in the sheath material, and thus inhibit the photooxidative degradation reaction initiated by free radicals and improve the weather resistance of the material. Some metal nodes or organic ligands in MOF also have specific chemical properties and can react with free radicals to make them inactivated.

[0023] Endothermic decomposition effect of LDH: When the ambient temperature rises, LDH will undergo a decomposition reaction, absorb a large amount of heat energy, thereby playing a certain cooling role, slowing down the rise of the sheath material temperature, and reducing the thermal aging rate;

[0024] Heat insulation and protection effect of MOF: The porous structure of MOF can form tiny heat insulation layers inside the sheath material, hinder the conduction of heat, and reduce the temperature inside the sheath material. At the same time, MOF can form carbon residues with better stability at high temperatures, further enhancing the thermal stability of the material;

[0025] The endothermic decomposition of LDH and the heat insulation and protection of MOF cooperate with each other to jointly inhibit the rise of the sheath material temperature, reduce the damage of high temperature to the material performance, and improve the stability and service life of the sheath material in high temperature environments.

[0026] Water absorption and swelling effect of LDH: LDH has a certain water absorption capacity and can adsorb a certain amount of water to prevent further penetration of water into the sheath material. At the same time, LDH will swell after absorbing water, filling the micro-pores inside the sheath material and improving the density of the material. The porous structure of MOF can also adsorb an appropriate amount of water to adjust the humidity inside the sheath material. In a humid environment, MOF can adsorb excess water to prevent the performance of the sheath material from deteriorating due to excessive water absorption. In a dry environment, MOF can release the adsorbed water to maintain the humidity balance inside the sheath material. The combined action of LDH and MOF can not only effectively prevent the intrusion of water but also adjust the humidity inside the sheath material, keep the internal environment of the material stable, and improve the water absorption stability and dimensional stability of the sheath material.

[0027] (3) The sheath material of the present invention can adopt a composite synergistic system formed by combining a high molecular weight hindered amine light stabilizer (HALS) and an ultraviolet absorber (UVA). HALS captures free radicals, and UVA absorbs ultraviolet rays, synergistically prolonging the life of the material and improving its weather resistance. Specific embodiments

[0028] The technical solutions in the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0029] The present invention provides a weather-resistant medium-density polyethylene cable sheath material, which includes the following raw materials according to weight ratio: 45-55 parts of high-density polyethylene, 30-40 parts of linear low-density polyethylene, 3-5 parts of metal-organic framework composite resin, 1-3 parts of compatibilizer, 0-2 parts of high molecular weight hindered amine light stabilizer, 0.5-2 parts of lubricant, 0.4-0.6 parts of nano-inorganic shielding agent, 0.3-0.6 parts of ultraviolet absorber, 0.5-1.5 parts of calcium carbonate, and 0-3 parts of colorant; wherein, the nano-inorganic shielding agent is layered double hydroxide.

[0030] Among them, the metal-organic framework composite resin is composed of a metal-organic framework and polyethylene. Specifically, the preparation method of the metal-organic framework composite resin is as follows:

[0031] (1) Prepare MOF powder

[0032] Weigh 0.5 g of aluminum nitrate nonahydrate and 0.69 g of terephthalic acid, add 10 mL of dimethylformamide (DMF), and stir magnetically for 2 hours until completely dissolved. Transfer the solution into a stainless-steel reactor lined with polytetrafluoroethylene, and control the loading amount within 60%-70% of the inner liner volume. Place the reactor in an oven, heat it to 100 °C at a rate of 3 °C / min and hold for 24 hours. During the reaction, relieve the pressure regularly to control the pressure below 0.8 MPa. After the reaction, cool it naturally to room temperature, take out the mixture, and collect the solid precipitate by centrifugation. Wash the precipitate with deionized water and ethanol to remove impurities. Finally, place the precipitate in a vacuum drying oven and dry it at 60 °C for 16 hours to obtain MOF.

[0033] Mix a certain amount of MOF powder with polyethylene particles or powder evenly by stirring, and the mass ratio of MOF powder to polyethylene is 1:10 - 30; melt-blend and extrude the evenly mixed MOF / polyethylene mixture at 140 °C - 160 °C to prepare a metal-organic framework composite resin.

[0034] Among them, the compatibilizer is preferably maleic anhydride grafted polyethylene.

[0035] Among them, the lubricant is selected from at least one of stearic acid, calcium stearate, zinc stearate, magnesium stearate, and polyethylene wax.

[0036] Among them, the ultraviolet absorber is selected from at least one of titanium dioxide, zinc oxide, benzotriazole ultraviolet absorbers, and benzophenone ultraviolet absorbers.

[0037] Among them, the colorant is selected from one of carbon black, titanium dioxide, phthalocyanine pigments, and azo pigments.

[0038] The preparation method of the weather-resistant medium-density polyethylene cable sheath material includes the following steps:

[0039] (1) Mix high-density polyethylene, linear low-density polyethylene, metal-organic framework composite resin, compatibilizer, high-molecular-weight hindered amine light stabilizer, lubricant, nano-inorganic shielding agent, ultraviolet absorber, calcium carbonate, and colorant in a mixer according to the weight ratio; the mixing temperature is 50 - 60 °C, and the rotation speed of the mixer is 1000 - 3000 r / min;

[0040] (2) Knead and extrude the mixed material obtained in step (1) through a twin-screw extruder to granulate, and then cool it with water, dry it, screen it, and package it into finished products. Among them, the temperature range of the twin-screw extruder is 150 - 220 °C.

[0041] The following further elaborates on the present invention through specific examples.

[0042] Prepare the sheath materials of the examples and comparative examples according to the component weight ratios (parts) in Table 1 below and the above preparation method.

[0043] Table 1

[0044]

[0045] In Table 1, high-density polyethylene: tensile strength ≥ 35 Mpa, elongation at break ≥ 800%; the metal-organic framework (MOF) composite resin is the MOF / polyethylene composite resin prepared by the above method (the mass ratio of MOF powder to polyethylene is 1:10); the compatibilizer is maleic anhydride-grafted metallocene polyethylene, tensile strength ≥ 20 Mpa, elongation at break ≥ 700%; the high molecular weight hindered amine light stabilizer (HALS) model is XT 55; the ultraviolet light absorber model is UV-531; the nano-inorganic shielding agent is layered double hydroxides (LDH); the colorant is phthalocyanine blue masterbatch.

[0046] Performance test

[0047] Sample preparation: First, weigh the raw materials according to the ratio, and after preliminary mixing manually, put them into an open mill and knead at 160 °C. The sample sheet is smooth on the surface and has uniform stretching, and then take out the sheet. Preheat in a flat vulcanizing machine with a pressure of 18 ± 1 MPa for 5 min, apply pressure at 170 ± 5 °C for 5 min, and cool and apply pressure for 5 min to obtain the sample sheet. Finally, conduct tests according to the test items. The performance test results are shown in Table 2.

[0048] Table 2

[0049] Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Density (g / cm 3 )]]> 0.950 0.951 0.952 0.945 0.947 0.949 *Tensile strength (MPa) 28.1 28.5 28.3 24.5 24.3 24.2 *Elongation at break (%) 870 880 910 780 759 762 *Color difference △E 0.78 0.68 0.58 3.95 4.83 4.85 *Rate of change of tensile strength (%) 5.7 4.5 3.8 10.1 17.9 18.1 *Rate of change of elongation at break (%) 1.2 1.1 0.9 11.2 12.2 14.3

[0050] Note: The performance test data marked with * are after artificial weathering, according to the artificial weathering test method in Appendix A of GB / T 12527-2008 (xenon lamp method, 1008 hours).

[0051] As can be seen from Table 2 above, compared with the comparative example, the sheath material of the embodiment of the present invention has better weather resistance.

[0052] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

[0053] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A weather-resistant medium-density polyethylene cable sheath material, characterized in that, It comprises the following raw materials according to weight ratio: 45-55 parts of high-density polyethylene, 30-40 parts of linear low-density polyethylene, 3-5 parts of metal-organic framework composite resin, 1-3 parts of compatibilizer, 0-2 parts of high molecular weight hindered amine light stabilizer, 0.5-2 parts of lubricant, 0.4-0.6 parts of nano-inorganic shielding agent, 0.3-0.6 parts of ultraviolet absorber, 0.5-1.5 parts of calcium carbonate, 0-3 parts of colorant; wherein, the nano-inorganic shielding agent is layered double hydroxide.

2. The weather-resistant medium-density polyethylene cable sheath material according to claim 1, wherein The metal-organic framework composite resin is composed of a metal-organic framework and polyethylene.

3. The weather-resistant medium-density polyethylene cable sheath material according to claim 2, wherein, The preparation method of the metal-organic framework composite resin is as follows: Mix a certain amount of MOF powder with polyethylene particles or powder evenly by stirring; extrude the uniformly mixed MOF / polyethylene mixture by melt blending to obtain the metal-organic framework composite resin.

4. The weather-resistant medium-density polyethylene cable sheath material according to claim 1, characterized in that, The compatibilizer is maleic anhydride grafted polyethylene.

5. The weather-resistant medium-density polyethylene cable sheath material according to claim 1, characterized in that The lubricant is selected from at least one of stearic acid, calcium stearate, zinc stearate, magnesium stearate, and polyethylene wax.

6. The weather-resistant medium-density polyethylene cable sheath material according to claim 1, wherein, The ultraviolet absorber is selected from at least one of titanium dioxide, zinc oxide, benzotriazole ultraviolet absorbers, and benzophenone ultraviolet absorbers.

7. A weather-resistant medium-density polyethylene cable sheath material according to claim 1, characterized in that, The colorant is selected from one of carbon black, titanium dioxide, phthalocyanine pigments, and azo pigments.

8. A preparation method of a weather-resistant medium-density polyethylene cable sheath material, characterized in that, It includes the following steps: (1) Mix high-density polyethylene, linear low-density polyethylene, metal-organic framework composite resin, compatibilizer, high molecular weight hindered amine light stabilizer, lubricant, nano-inorganic shielding agent, ultraviolet absorber, calcium carbonate, and colorant in a mixer according to the weight ratio. (2) Knead and extrude the mixed material obtained in step (1) by a twin-screw extruder to granulate, and then cool with water, dry, screen, and package the finished product.

9. The preparation method of a weather-resistant medium-density polyethylene cable sheath material according to claim 8, characterized in that, The mixing temperature in step (1) is 50-60 °C, and the rotation speed of the mixer is 1000-3000 r / min.

10. The preparation method of a weather-resistant medium-density polyethylene cable sheath material according to claim 8, characterized in that, In step (2), the temperature range of the twin-screw extruder is 150-220 °C.

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