Halogen-free polyolefin sheath material with high flame retardance and low friction coefficient, and preparation and application thereof

Abstract

The present application relates to high flame-retardant low friction coefficient halogen-free polyolefin sheath material and its preparation and application, belong to sheath material technical field. High flame-retardant low friction coefficient halogen-free polyolefin sheath material of the present application uses ethylene-vinyl acetate copolymer, ethylene-octene copolymer, ethylene-propylene rubber, polyethylene, modified polyolefin resin as matrix material, uses hydrogenated aluminum hydroxide, magnesium hydroxide, flame-retardant synergist and the like as flame-retardant filler, adds lubricant, antioxidant, black mother and the like auxiliary agent after plasticizing mixing and is formed into granules. The oxygen index of the sheath material is far more than the oxygen index standard of sheath material in national standard GB / T 32129-2015 ≥ 30%, and also higher than the oxygen index 38% of the high flame-retardant halogen-free sheath material on sale;And dynamic friction coefficient is less than 0.45 μs, far less than 0.8 μs-2.0 μs of the product on sale.

Description

Technical Field

[0001] This invention relates to the field of sheathing materials, and in particular to halogen-free polyolefin sheathing materials with high flame retardancy and low coefficient of friction, as well as their preparation and application. Background Technology

[0002] Air-blown microfiber cables are used in core networks, metropolitan area networks (MANs), access networks, backbone networks, local area networks (LANs), FTTx networks, data centers, 5G, and more. They are optical cables that can be installed into microducts using the air-blowing method. Air-blown microfiber cables boast a small size, light weight, and a perfect cable structure, offering high fiber density, low cost, and flexibility. They can be upgraded to the latest fiber optic technologies after initial installation. A typical air-blown microfiber cable system has a main conduit-microconduit-microfiber cable structure. The main conduit can be inserted into concrete pipe holes or used for new route construction.

[0003] Due to the unique air-blowing conduit installation process of air-blown micro-cables, there are comprehensive requirements for halogen-free, low-smoke, flame-retardant polyolefin sheathing materials, demanding both low friction coefficients and high flame-retardant performance. Conventional halogen-free, low-smoke, flame-retardant polyolefin sheathing materials use EVA, POE, polyethylene, and modified polyethylene as matrix materials, filled with inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide. Depending on different flame-retardant and cost requirements, a certain amount of calcium carbonate may even be added as a filler. Additives such as silicone masterbatch, black masterbatch, and polyethylene wax are added, and the mixture is granulated after plasticizing. Conventional halogen-free, low-smoke, flame-retardant polyolefin sheathing materials generally have limited flame-retardant properties, only ensuring that air-blown microcables pass the IEC 60332-1 single-strand burning test and the IEC 60332-3 bundled burning test, but cannot meet the higher flammability ratings of the CPR-B2ca and CCa burning tests. Furthermore, conventional sheathing materials with conventional lubricants and lubrication systems have a high coefficient of dynamic friction, which cannot meet the low coefficient of friction requirement for the optical cable surface in air-blown microcables. Therefore, conventional halogen-free, flame-retardant polyolefin sheathing materials cannot meet the requirements of air-blown microcables.

[0004] In the existing technology, the flame retardant properties of halogen-free low-smoke flame-retardant polyolefin sheathing materials are generally not good enough to meet the CPR-B2ca flammability rating requirements for air-blown microcables. At the same time, the surface smoothness of the optical cable is not high and the coefficient of friction is large, which cannot meet the construction requirements for air-blown microcables through conduits.

[0005] Therefore, the technical solution of this invention mainly solves the above two problems, so that the air-blown microcable can meet the flammability requirements of CPR-B2ca and at the same time have a low coefficient of friction to meet the construction requirements. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a high flame-retardant, low-friction coefficient halogen-free polyolefin sheathing material, its preparation, and its application. This invention utilizes EVA with a higher VA content as the matrix material to improve the product's mechanical and flame-retardant properties. Simultaneously, it adds a fibrous flame-retardant charring synergist combined with inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide, giving the product high flame-retardant characteristics and ensuring that the cable meets the CPR-B2ca flammability rating. Furthermore, it incorporates a special organosilicon-based and polyester-based composite lubricating system, resulting in a smooth cable surface and low friction coefficient, meeting the construction requirements for air-blown micro-cable conduit installation.

[0007] This invention is achieved through the following technical solution:

[0008] The first objective of this invention is to provide a halogen-free polyolefin sheathing material with high flame retardancy and low coefficient of friction, wherein the halogen-free polyolefin sheathing material comprises the following components by weight:

[0009]

[0010] In one embodiment of the present invention, the VA content of the ethylene-vinyl acetate copolymer is 27wt% to 34wt%.

[0011] In one embodiment of the present invention, the ethylene-vinyl acetate copolymer with a VA content of 27wt% to 29wt% is 10 to 30 parts; the ethylene-vinyl acetate copolymer with a VA content of 32wt% to 34wt% is 20 to 40 parts.

[0012] In one embodiment of the present invention, the modified polyolefin resin is selected from maleic anhydride-grafted ethylene-butene copolymer and / or maleic anhydride-grafted metallocene polyethylene, with a grafting rate ≥0.8%.

[0013] In one embodiment of the present invention, the inorganic flame retardant is selected from one or more of magnesium hydroxide, aluminum hydroxide, and silicon-based inorganic compounds.

[0014] In one embodiment of the present invention, the ethylene-butene copolymer has a melt index of 0.3 g / 10 min to 0.7 g / 10 min and a Vicat softening point of ≤55°C.

[0015] In one embodiment of the present invention, the antioxidant is selected from one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dilauryl thiodipropionate, 2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 4,4'-thiobis(6-tert-butyl-3-methylphenol).

[0016] In one embodiment of the present invention, the polyester lubricant is selected from oleamide and / or erucamide.

[0017] A second objective of this invention is to provide a method for preparing the aforementioned high flame retardant and low friction coefficient halogen-free polyolefin sheathing material, characterized by comprising the following steps:

[0018] (1) Ethylene-vinyl acetate copolymer, ethylene-butene copolymer, EPDM rubber, polyethylene, modified polyolefin resin, inorganic flame retardant, flame retardant synergist, silicone masterbatch, polyester lubricant, antioxidant, polyethylene wax and black masterbatch are plasticized and mixed in an internal mixer.

[0019] (2) The mixture obtained in step (1) is processed by twin-screw extrusion and then granulated by single-screw extrusion to obtain the high flame retardant and low friction coefficient halogen-free polyolefin sheath material.

[0020] A third objective of this invention is to provide the application of the aforementioned high flame retardant, low friction coefficient halogen-free polyolefin sheathing material in the preparation of B2ca grade air-blown microcables.

[0021] In one embodiment of the present invention, the composition comprises the following components in parts by weight:

[0022]

[0023]

[0024] In one embodiment of the present invention, the ethylene-vinyl acetate copolymer is an ethylene-vinyl acetate copolymer with a VA content of 27wt% to 29wt%; wherein the VA content is 28±1%, the weight is 2.16Kg, and the melt index at 190℃ is 4.5±0.5g / 10min.

[0025] In one embodiment of the present invention, the ethylene-vinyl acetate copolymer is an ethylene-vinyl acetate copolymer with a VA content of 32wt% to 34wt%; wherein the VA content is 33±1%, 2.16Kg, and the melt index at 190℃ is 3.0±1g / 10min.

[0026] In one embodiment of the present invention, the EPDM rubber has a Mooney viscosity of 20±5MU and an ethylene content of 70.5±1wt%.

[0027] In one embodiment of the present invention, the polyethylene resin has a melt index of 0.5 g / 10 min to 4.5 g / 10 min and a melt index of 105 °C to 125 °C.

[0028] In one embodiment of the present invention, the amount of aluminum hydroxide added is 0 to 230 parts, preferably 100 to 130 parts; the amount of magnesium hydroxide added is 0 to 230 parts, preferably 100 to 130 parts.

[0029] Among them, aluminum hydroxide: the D50 of domestically produced aluminum hydroxide is 1.6~2.2μm, and the D97≤7μm;

[0030] Magnesium hydroxide: Chemically produced magnesium hydroxide, D50 is 1.3-1.7μm, D97≤7μm.

[0031] In one embodiment of the present invention, the flame retardant charring synergist is a silicate compound with a needle-like structure, which has a very effective anti-dripping effect and is a white or pale yellow powder; preferably, the aspect ratio is 2 to 3:1.

[0032] In one embodiment of the present invention, the carbon black content of the black masterbatch is 45±2%.

[0033] In one embodiment of the present invention, the silicone masterbatch has a silicone content of 70±5% and a melt index of ≥5g / 10min.

[0034] In one embodiment of the present invention, the polyethylene wax has a melting point ≥105°C.

[0035] The technical solution of the present invention has the following advantages compared with the prior art:

[0036] This invention provides a halogen-free polyolefin sheath material for B2ca grade air-blown microcables, its preparation method, and its application. Its oxygen index is much higher than the requirement of ≥30% for the oxygen index of sheath material in the national standard GB / T 32129-2015, and it is also higher than the oxygen index of 38% of commercially available high flame-retardant halogen-free sheath materials; the dynamic friction coefficient is <0.45μs, which is much lower than the 0.8μs to 2.0μs of commercially available products. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0038] Unless otherwise specified, the experimental materials used in the following examples can be obtained through regular market purchases.

[0039] Example 1

[0040] This embodiment provides a halogen-free polyolefin sheathing material with high flame retardancy and low coefficient of friction, comprising the following components by weight:

[0041]

[0042]

[0043] The modified polyolefin is selected from maleic anhydride-grafted ethylene-butene copolymers with a grafting rate ≥0.8% and maleic anhydride-grafted metallocene polyethylene. The flame retardant charring synergist was purchased from Shanghai Zhuangjing Chemical Co., Ltd., model CLay20.

[0044] The preparation method of the high flame retardant and low friction coefficient halogen-free polyolefin sheath material in this embodiment is as follows:

[0045] The production process involves plasticizing and mixing the above components using an internal mixer; processing them through twin-screw extrusion; granulating them through single-screw extrusion; and then air-cooling and packaging the finished product.

[0046] All properties of the high flame retardant and low friction coefficient halogen-free polyolefin sheathing material in this embodiment meet the B2ca standard.

[0047] Example 2

[0048] This embodiment provides a halogen-free polyolefin sheathing material with high flame retardancy and low coefficient of friction, comprising the following components by weight:

[0049]

[0050]

[0051] The modified polyolefin is selected from maleic anhydride-grafted ethylene-butene copolymers with a grafting rate ≥0.8% and maleic anhydride-grafted metallocene polyethylene. The flame retardant charring synergist was purchased from Shanghai Zhuangjing Chemical Co., Ltd., model CLay20.

[0052] The preparation method of the high flame retardant and low friction coefficient halogen-free polyolefin sheath material in this embodiment is as follows:

[0053] The production process involves plasticizing and mixing the above components using an internal mixer; processing them through twin-screw extrusion; granulating them through single-screw extrusion; and then air-cooling and packaging the finished product.

[0054] All properties of the high flame retardant and low friction coefficient halogen-free polyolefin sheathing material in this embodiment meet the B2ca standard.

[0055] Example 3

[0056] This embodiment provides a halogen-free polyolefin sheathing material with high flame retardancy and low coefficient of friction, comprising the following components by weight:

[0057]

[0058]

[0059] The modified polyolefin is selected from maleic anhydride-grafted ethylene-butene copolymers with a grafting rate ≥0.8% and maleic anhydride-grafted metallocene polyethylene. The flame retardant charring synergist was purchased from Shanghai Zhuangjing Chemical Co., Ltd., model CLay20.

[0060] The preparation method of the high flame retardant and low friction coefficient halogen-free polyolefin sheath material in this embodiment is as follows:

[0061] The production process involves plasticizing and mixing the above components using an internal mixer; processing them through twin-screw extrusion; granulating them through single-screw extrusion; and then air-cooling and packaging the finished product.

[0062] All properties of the high flame retardant and low friction coefficient halogen-free polyolefin sheathing material in this embodiment meet the B2ca standard.

[0063] Example 4

[0064] This embodiment provides a halogen-free polyolefin sheathing material with high flame retardancy and low coefficient of friction, comprising the following components by weight:

[0065]

[0066]

[0067] The modified polyolefin is selected from maleic anhydride-grafted ethylene-butene copolymers with a grafting rate ≥0.8% and maleic anhydride-grafted metallocene polyethylene. The flame retardant charring synergist was purchased from Shanghai Zhuangjing Chemical Co., Ltd., model CLay20.

[0068] The preparation method of the high flame retardant and low friction coefficient halogen-free polyolefin sheath material in this embodiment is as follows:

[0069] The production process involves plasticizing and mixing the above components using an internal mixer; processing them through twin-screw extrusion; granulating them through single-screw extrusion; and then air-cooling and packaging the finished product.

[0070] All properties of the high flame retardant and low friction coefficient halogen-free polyolefin sheathing material in this embodiment meet the B2ca standard.

[0071] Comparative Example 1

[0072] The composition of the halogen-free polyolefin sheath material in this comparative example is similar to that in Example 1, except that no polyester lubricant is added.

[0073] Comparative Example 2

[0074] The composition of the halogen-free polyolefin sheath material in this comparative example is similar to that in Example 1, except that no flame retardant charring synergist is added.

[0075] Comparative Example 3

[0076] The composition of the halogen-free polyolefin sheath material in this comparative example is similar to that in Example 1, except that silicone masterbatch is used instead of polyester lubricant.

[0077] Comparative Example 4

[0078] The composition of the halogen-free polyolefin sheath material in this comparative example is similar to that in Example 1, except that commercially available diatomaceous earth is used instead of the flame retardant charring synergist.

[0079] Test case

[0080] To compare and illustrate the halogen-free polyolefin sheath materials prepared in the embodiments of the present invention and the comparative examples, performance tests were conducted on their tensile strength, elongation at break, oxygen index, coefficient of dynamic friction, and cable flammability rating. The comparison results are shown in Table 1.

[0081] Table 1. Performance comparison of halogen-free polyolefin sheathing materials in different embodiments and comparative examples.

[0082]

[0083] As can be clearly seen from the data in Table 1, compared with Example 1, the halogen-free polyolefin sheath material prepared in Example 2 showed a significant decrease in dynamic friction coefficient, peak heat release rate, and total heat release. This indicates that within a certain range, the greater the amount of polyester lubricant and flame-retardant charring synergist added, the more helpful it is in reducing the dynamic friction coefficient, peak heat release rate, and total heat release. However, excessive addition will weaken the effect and affect other performance indicators.

[0084] The halogen-free polyolefin sheath material prepared in Comparative Example 1 was unqualified because the dynamic friction coefficient reached 0.56 μs due to the lack of polyester lubricant.

[0085] The halogen-free polyolefin sheath material prepared in Comparative Example 2 had significantly reduced flame retardant performance and oxygen index due to the absence of flame retardant charring synergists. The combustion indicators after cabling were unqualified, including charring height, peak heat release rate, and total heat release. This indicates that flame retardant charring synergists play a decisive role in flame retardant performance.

[0086] The friction coefficient of the halogen-free polyolefin sheath material prepared in Comparative Example 3 was 0.52 μs, which was higher than that of Example 1 (0.43 μs); indicating that the silicone masterbatch was not as effective as the polyester lubricant in reducing the friction coefficient.

[0087] The use of diatomaceous earth in the halogen-free polyolefin sheath material prepared in Comparative Example 4 resulted in unqualified peak heat release rate and total heat release, indicating that the flame retardant performance of other commercially available charring agents is not as good as that of the flame retardant charring synergist used in the project.

[0088] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A halogen-free polyolefin sheathing material with high flame retardancy and low coefficient of friction, characterized in that, The halogen-free polyolefin sheath material comprises the following components in parts by weight: 30 to 70 parts of ethylene-vinyl acetate copolymer; 10 to 30 parts of ethylene-butene copolymer; 5 to 20 parts of EPDM rubber; 5 to 15 parts of polyethylene; 10 to 20 parts of modified polyolefin resin; 200-230 parts of inorganic flame retardant; 5 to 15 parts of flame retardant charring synergist; 1 to 5 parts of silicone masterbatch; 0.5 to 2 parts of oleamide and / or erucamide; Antioxidant 2 to 5 parts; Polyethylene wax 0.5 to 1.5 parts; 2 to 5 portions of black mother-of-pearl; The ethylene-vinyl acetate copolymer is 10 to 30 parts of ethylene-vinyl acetate copolymer with a VA content of 27wt% to 29wt% and 20 to 40 parts of ethylene-vinyl acetate copolymer with a VA content of 32wt% to 34wt%. The flame retardant charring synergist was purchased from Shanghai Zhuangjing Chemical Co., Ltd., and the model is CLay20. The inorganic flame retardant is magnesium hydroxide and aluminum hydroxide; The silicone masterbatch contains 70±5% silicone.

2. The halogen-free polyolefin sheathing material according to claim 1, characterized in that, The modified polyolefin resin is selected from maleic anhydride-grafted ethylene-butene copolymer and / or maleic anhydride-grafted metallocene polyethylene, with a grafting rate ≥0.8%.

3. The halogen-free polyolefin sheathing material according to claim 1, characterized in that, The ethylene-butene copolymer has a melt index of 0.3 g / 10 min to 0.7 g / 10 min and a Vicat softening point of ≤55℃.

4. The halogen-free polyolefin sheathing material according to claim 1, characterized in that, The antioxidant is selected from one or more of the following: tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ester, dilauryl thiodipropionate, 2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate ethyl ester], and 4,4'-thiobis(6-tert-butyl-3-methylphenol].

5. The method for preparing the high flame retardant and low friction coefficient halogen-free polyolefin sheath material according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Ethylene-vinyl acetate copolymer, ethylene-butene copolymer, EPDM rubber, polyethylene, modified polyolefin resin, inorganic flame retardant, flame retardant synergist, silicone masterbatch, oleamide and / or erucamide, antioxidant, polyethylene wax and black masterbatch are plasticized and mixed in an internal mixer. (2) The mixture obtained in step (1) is processed by twin-screw extrusion and then granulated by single-screw extrusion to obtain the high flame retardant and low friction coefficient halogen-free polyolefin sheath material.

6. The application of the high flame retardant and low friction coefficient halogen-free polyolefin sheath material according to any one of claims 1 to 4 in the preparation of B2ca grade air-blown microcables.

Images