Long-life flexible crosslinked polyolefin material, method of making and use

Abstract

The application discloses a long-life soft cross-linked polyolefin material and a preparation method and application thereof, and belongs to the technical field of polyolefin materials, and has the technical scheme as follows: a long-life soft cross-linked polyolefin material, which comprises grafted A components and catalytic B components in a weight ratio of 90-95:5-10, and the total amount of the grafted A components and the B components is 100; the raw materials of the grafted A components include, in weight parts, VLLDPE 15-40 parts, rubber 30-50 parts, ethylene-octene copolymer 30-45 parts, silane cross-linking agent 2-8 parts, initiator 0.5-1.5 parts, lubricant 0.5-2 parts, first antioxidant 1-4 parts and metal oxide 0.5-3 parts; and the raw materials of the catalytic B components include, in weight parts, ethylene-vinyl acetate copolymer 100 parts, second antioxidant 3-7 parts, third antioxidant 5-12 parts and catalyst 5-10 parts, so that the effect of improving the aging resistance of cross-linked polyolefin is achieved.

Description

Technical Field

[0001] This invention relates to the field of polyolefin materials technology, and in particular to a long-life, flexible, cross-linked polyolefin material, its preparation method, and its application. Background Technology

[0002] Cross-linked polyolefin materials are widely used in cable sheathing and other fields due to their excellent electrical, heat resistance, and mechanical properties. However, traditional cross-linked polyolefin materials are prone to hardening and embrittlement during long-term use, affecting their service life and performance. Currently, to improve the flexibility of cross-linked polyolefin materials, they are usually blended with rubber, and plasticizers are added to the rubber to reduce the hardness of the cross-linked polyolefin. However, this method leads to a decrease in the electrical properties of the cross-linked polyolefin material, and the plasticizer is prone to migration, affecting the long-term stability of the cross-linked polyolefin material. In addition, because of the presence of unsaturated bonds in rubber, it is susceptible to attack by oxygen free radicals under high-temperature conditions, affecting the service life of the cross-linked polyolefin material. Summary of the Invention

[0003] To improve the aging resistance of cross-linked polyolefins, this invention provides a long-life, flexible cross-linked polyolefin material, its preparation method, and its application.

[0004] The first aspect of the present invention is to provide a long-life flexible cross-linked polyolefin material, which adopts the following technical solution: a long-life flexible cross-linked polyolefin material, comprising a grafted A component and a catalytic B component in a weight ratio of 90-95:5-10, wherein the total amount of the grafted A component and the B component is 100.

[0005] The grafted component A raw material comprises, by weight: 15-40 parts VLLDPE, 30-50 parts rubber, 30-45 parts ethylene-octene copolymer, 2-8 parts silane crosslinking agent, 0.5-1.5 parts initiator, 0.5-2 parts lubricant, 1-4 parts primary antioxidant, and 0.5-3 parts metal oxide.

[0006] The catalyst component B raw material comprises, by weight: 100 parts of ethylene-vinyl acetate copolymer, 3-7 parts of second antioxidant, 5-12 parts of third antioxidant, and 5-10 parts of catalyst.

[0007] Preferably, the grafted component A raw material comprises, by weight: 20-30 parts VLLDPE, 35-45 parts rubber, 35-45 parts ethylene-octene copolymer, 3-6 parts silane crosslinking agent, 0.5-1.5 parts initiator, 0.5-2 parts lubricant, 1-4 parts first antioxidant, and 0.5-3 parts metal oxide;

[0008] The catalyst component B raw material comprises, by weight, 100 parts of ethylene-vinyl acetate copolymer, 4-7 parts of second antioxidant, 6-10 parts of third antioxidant, and 5-10 parts of catalyst.

[0009] Preferably, the rubber includes one or both of EVM rubber and HNBR rubber.

[0010] Preferably, the weight ratio of the EVM rubber to the HNBR rubber is 1:(1-2).

[0011] Preferably, the silane crosslinking agent comprises methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:(1-3).

[0012] Preferably, the metal oxide is zinc oxide.

[0013] Preferably, the first antioxidant is antioxidant 1010.

[0014] Preferably, the second antioxidant is allylphenol, and the third antioxidant is 2-methoxy-4-allylphenol.

[0015] A second aspect of the present invention provides a method for preparing a long-life, flexible, cross-linked polyolefin material, comprising the following preparation steps: preparing a grafted A component by mixing the raw materials uniformly according to the formula ratio, compounding and granulating, and then drying to obtain the grafted A component; preparing a catalytic B component by mixing the raw materials uniformly according to the formula ratio, extruding the mixture through a twin-screw extruder, granulating, and drying to obtain the catalytic B component; and mixing the grafted A component and the catalytic B component in a weight ratio to obtain the cross-linked polyolefin material.

[0016] A third aspect of the present invention is to provide an application of a long-life, flexible, cross-linked polyolefin material, wherein the cross-linked polyolefin is used to prepare cable materials and wire materials.

[0017] In summary, the present invention has the following beneficial effects:

[0018] VLLDPE is a type of ultra-low density polyethylene with moderate branching, containing a large number of short branches and numerous tertiary carbon atoms on its main chain. This gives VLLDPE high reactivity with silane crosslinking agents and ethylene-octene copolymers. The molecular chains are connected by Si-O-Si crosslinking bonds, and the octene side chains provided by the ethylene-octene copolymer act as active sites for the crosslinking reaction, increasing the length of the molecular chains between the crosslinking points in the crosslinking network. This facilitates relative slippage of molecular chain segments during stretching, increasing the material's ductility and elongation at break. In addition, when the rubber used is one or a mixture of two of EVM rubber and HNBR rubber, its combination with ethylene-octene copolymers and ethylene-vinyl acetate copolymers raises the upper limit of the service temperature of the crosslinked polyolefin material, thereby improving its aging resistance. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the embodiments.

[0020] The raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0021] In the embodiments and comparative examples of this application, dicumyl peroxide is used as the initiator.

[0022] The catalyst used is dibutyltin dilaurate;

[0023] The lubricant used is silicone;

[0024] VLLDPE has a melt index of 1.0 g / 10 min and a density of 0.888 g / cm³. 3 Purchased from DuPont Dow.

[0025] Example 1

[0026] A method for preparing a long-life, flexible, cross-linked polyolefin material includes the following steps:

[0027] S1. Preparation of grafted component: 15 kg of VLLDPE, 30 kg of EVM rubber, 30 kg of ethylene-octene copolymer, 2 kg of silane crosslinking agent, 0.5 kg of dicumyl peroxide, 0.5 kg of silicone, 1 kg of antioxidant 1010, and 0.5 kg of zinc oxide are mixed in a mixer, granulated, dehydrated, and dried to obtain grafted component A; wherein the silane crosslinking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1;

[0028] S2. Preparation of the catalytic component: 100 kg of ethylene-vinyl acetate copolymer, 3-7 kg of allylphenol, 5-12 kg of 2-methoxy-4-allylphenol, and 5-10 kg of dibutyltin dilaurate are mixed evenly and then extruded and granulated by a twin-screw extruder to obtain catalytic component B. The temperature of the feeding section of the twin-screw extruder is 120-130℃, the temperature of the compression section is 135-155℃, the temperature of the homogenization section is 160-175℃, and the temperature of the die head is 165-185℃.

[0029] S3. Mix 90 kg of grafted component A and 10 kg of catalyst component B in a total volume of 100 kg and package to obtain cross-linked polyolefin material.

[0030] Example 2

[0031] A method for preparing a long-life, flexible, cross-linked polyolefin material includes the following steps:

[0032] S1. Preparation of grafted component: 20 kg of VLLDPE, 35 kg of EVM rubber, 35 kg of ethylene-octene copolymer, 3 kg of silane crosslinking agent, 0.6 kg of dicumyl peroxide, 0.7 kg of silicone, 1 kg of antioxidant 1010, and 1 kg of zinc oxide are mixed in a mixer, granulated, dehydrated, and dried to obtain grafted component A; wherein the silane crosslinking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1;

[0033] S2. Preparation of the catalytic component: 100 kg of ethylene-vinyl acetate copolymer, 4 kg of allylphenol, 6 kg of 2-methoxy-4-allylphenol, and 6 kg of dibutyltin dilaurate are mixed evenly and then extruded and granulated by a twin-screw extruder to obtain catalytic component B. The temperature of the feeding section of the twin-screw extruder is 120-130℃, the temperature of the compression section is 135-155℃, the temperature of the homogenization section is 160-175℃, and the temperature of the die head is 165-185℃.

[0034] S3. Mix 95kg of grafted component A and 5kg of catalytic component B in a total volume of 100kg and package to obtain cross-linked polyolefin material.

[0035] Example 3

[0036] A method for preparing a long-life, flexible, cross-linked polyolefin material includes the following steps:

[0037] S1. Preparation of grafted components: 25 kg of VLLDPE, 40 kg of EVM rubber, 40 kg of ethylene-octene copolymer, 5 kg of silane crosslinking agent, 1.0 kg of dicumyl peroxide, 1.2 kg of silicone, 3 kg of antioxidant 1010, and 2 kg of zinc oxide are mixed in a mixer, granulated, dehydrated, and dried to obtain grafted component A; wherein the silane crosslinking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1;

[0038] S2. Preparation of the catalytic component: 100 kg of ethylene-vinyl acetate copolymer, 5 kg of allylphenol, 8 kg of 2-methoxy-4-allylphenol, and 7 kg of dibutyltin dilaurate are mixed evenly and then extruded and granulated by a twin-screw extruder to obtain catalytic component B. The temperature of the feeding section of the twin-screw extruder is 120-130℃, the temperature of the compression section is 135-155℃, the temperature of the homogenization section is 160-175℃, and the temperature of the die head is 165-185℃.

[0039] S3. Mix 90 kg of grafted component A and 10 kg of catalyst component B in a total volume of 100 kg and package to obtain cross-linked polyolefin material.

[0040] Example 4

[0041] A method for preparing a long-life, flexible, cross-linked polyolefin material includes the following steps:

[0042] S1. Preparation of grafted components: 30 kg of VLLDPE, 45 kg of EVM rubber, 42 kg of ethylene-octene copolymer, 6 kg of silane crosslinking agent, 1 kg of dicumyl peroxide, 1.5 kg of silicone, 3 kg of antioxidant 1010, and 2.5 kg of zinc oxide are mixed in a mixer, granulated, dehydrated, and dried to obtain grafted component A; wherein the silane crosslinking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1.

[0043] S2. Preparation of the catalytic component: 100 kg of ethylene-vinyl acetate copolymer, 6 kg of allylphenol, 10 kg of 2-methoxy-4-allylphenol, and 8 kg of dibutyltin dilaurate are mixed evenly and then extruded and granulated by a twin-screw extruder to obtain catalytic component B. The temperature of the feeding section of the twin-screw extruder is 120-130℃, the temperature of the compression section is 135-155℃, the temperature of the homogenization section is 160-175℃, and the temperature of the die head is 165-185℃.

[0044] S3. Mix 90 kg of grafted component A and 10 kg of catalyst component B in a total volume of 100 kg and package to obtain cross-linked polyolefin material.

[0045] Example 5

[0046] A method for preparing a long-life, flexible, cross-linked polyolefin material includes the following steps:

[0047] S1. Preparation of grafted component: 40 kg of VLLDPE, 50 kg of EVM rubber, 45 kg of ethylene-octene copolymer, 8 kg of silane crosslinking agent, 1.5 kg of dicumyl peroxide, 2 kg of silicone, 4 kg of antioxidant 1010, and 3 kg of zinc oxide are mixed in a mixer, then granulated, dehydrated, and dried to obtain grafted component A; wherein the silane crosslinking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1;

[0048] S2. Preparation of the catalytic component: 100 kg of ethylene-vinyl acetate copolymer, 7 kg of allylphenol, 12 kg of 2-methoxy-4-allylphenol, and 10 kg of dibutyltin dilaurate are mixed evenly and then extruded and granulated by a twin-screw extruder to obtain catalytic component B. The temperature of the feeding section of the twin-screw extruder is 120-130℃, the temperature of the compression section is 135-155℃, the temperature of the homogenization section is 160-175℃, and the temperature of the die head is 165-185℃.

[0049] S3. Mix 90 kg of grafted component A and 10 kg of catalyst component B in a total volume of 100 kg and package to obtain cross-linked polyolefin material.

[0050] Example 6

[0051] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 3 in that the silane cross-linking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:2, i.e., the content of methyltrimethoxysilane is 1.67 kg and vinyltrimethoxysilane is 3.33 kg, while the rest is the same as in Example 3.

[0052] Example 7

[0053] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 3 in that the silane cross-linking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:3, i.e., the content of methyltrimethoxysilane is 1.25 kg and vinyltrimethoxysilane is 3.75 kg, while the rest is the same as in Example 3.

[0054] Example 8

[0055] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 3 in that only vinyltrimethoxysilane is used as the silane cross-linking agent, while all other components are the same as in Example 3.

[0056] Example 9

[0057] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 3 in that only methyltrimethoxysilane is used as the silane cross-linking agent, while the others are the same as in Example 3.

[0058] Example 10

[0059] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 3 in that the silane cross-linking agent includes γ-aminopropyltriethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1, while the rest are the same as in Example 3.

[0060] Example 11

[0061] A method for preparing a long-life, soft, cross-linked polyolefin material, which differs from Example 3 in that the rubber used is HNBR rubber, while all other aspects are the same as in Example 3.

[0062] Example 12

[0063] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 3 in that the rubber used is a mixture of EVM rubber and HNBR rubber, with a weight ratio of 1:1, i.e., 20 kg of EVM rubber and 20 kg of HNBR rubber. All other aspects are the same as in Example 3.

[0064] Comparative Example 12

[0065] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 3 in that the rubber used is a mixture of EPDM rubber and HNBR rubber, with a weight ratio of EPDM rubber to HNBR rubber of 1:1, i.e., 20 kg of EPDM rubber and 20 kg of HNBR rubber. All other aspects are the same as in Example 3.

[0066] Example 13

[0067] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 3 in that the rubber used is a mixture of EVM rubber and HNBR rubber, with a weight ratio of 1:2, i.e., 13.3 kg of EVM rubber and 26.7 kg of HNBR rubber. All other aspects are the same as in Example 3.

[0068] Comparative Example 1

[0069] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 12 in that an equal amount of LLDPE is used instead of VLLDPE, wherein the LLDPE has a melt index of 1.7-2.3 g / 10 min and a density of 0.918-0.922 g / cm³. 3 Everything else is the same as in Example 12.

[0070] Comparative Example 2

[0071] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 12 in that the grafted component A contains 10 kg of VLLDPE, 25 kg of rubber, 25 kg of ethylene-octene copolymer, and 1 kg of silane crosslinking agent. The rubber is a mixture of EVM rubber and HNBR rubber in a weight ratio of 1:1. The silane crosslinking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1. All other components are the same as in Example 12.

[0072] Comparative Example 3

[0073] A method for preparing a long-life, flexible, cross-linked polyolefin material differs from Example 12 in that the grafted component A contains 45 kg of VLLDPE, 55 kg of rubber, 50 kg of ethylene-octene copolymer, 10 kg of silane crosslinking agent, and 2 kg of dicumyl peroxide. The rubber is a mixture of EVM rubber and HNBR rubber in a weight ratio of 1:1. The silane crosslinking agent includes methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1. All other components are the same as in Example 12.

[0074] Performance testing

[0075] The cross-linked polyolefin cable materials obtained in the above examples, comparative examples, and comparative examples were made into test samples with a thickness of 1 mm. These samples were then naturally placed at 25°C and 65% relative humidity for 120 hours. Their thermal life performance, hardness, tensile strength, and elongation at break were then tested. The thermal life of the cable insulation and sheath was evaluated using the methods of GB / T 11026.1-2016 and GB / T 11026.2-2012. The performance used for life determination was the elongation at break retention rate, with an endpoint of 50%. The tensile strength and elongation at break were tested according to the relevant provisions in GB / T1040. The test results are shown in Table 1.

[0076] Table 1. Performance test results of cross-linked polyolefins as cable materials

[0077]

[0078]

[0079] From the table above, we can see that:

[0080] After varying the content of each raw material in the grafted A component and the catalytic B component in Examples 1-5 of this application, the cross-linked polyolefin materials obtained in Examples 1-5 have a hardness of 78-82 Shore A and an elongation at break of ≥440%, indicating that the cross-linked polyolefin materials obtained in Examples 1-5 of this application have good softness. Moreover, after undergoing an air heat aging test at 180℃ for 168h, the elongation at break of the cross-linked polyolefin materials in Examples 1-5 of this application is still ≥410%, and the tensile strength is greater than 15MPa. Therefore, the cross-linked polyolefin materials obtained in Examples 1-5 of this application have good aging resistance and a long service life.

[0081] Compared with Example 3, when the weight ratio of methyltrimethoxysilane and vinyltrimethoxysilane was changed from 1:1 to 1:2 or 1:3, the tensile strength and elongation at break of the cross-linked polyolefin materials obtained in Examples 6-7 were higher than those in Example 3. It can be seen that when the weight ratio of methyltrimethoxysilane and vinyltrimethoxysilane is in the range of 1:1-3, the aging resistance and mechanical properties of cross-linked polyolefin materials can be effectively improved.

[0082] Compared with Example 3, when only vinyltrimethoxysilane or methyltrimethoxysilane was used as the silane crosslinking agent, the hardness of the crosslinked polyolefin materials obtained in Examples 8-9 increased and the elongation at break decreased. It can be seen that the softness of the crosslinked polyolefin material decreased. Furthermore, after an air heat aging test at 180°C for 168 hours, the elongation at break and tensile strength of the crosslinked polyolefin materials obtained in Examples 8-9 were significantly reduced compared with those in Example 3. This further illustrates that when a mixture of vinyltrimethoxysilane and methyltrimethoxysilane is used as the silane crosslinking agent, the resulting crosslinked polyolefin material is not only softer but also has better aging resistance and a longer service life.

[0083] Compared with Example 3, when the silane crosslinking agent is a mixture of γ-aminopropyltriethoxysilane and vinyltrimethoxysilane, the hardness of the crosslinked polyolefin material obtained in Example 10 is higher than that in Example 3, while the tensile strength and elongation at break are lower. After the aging resistance test, the retention rate of elongation at break and tensile strength is also significantly lower than that in Example 3. It can be seen that when the content and type of other raw materials remain unchanged, using a mixture of methyltrimethoxysilane and vinyltrimethoxysilane as the silane crosslinking agent can effectively improve the softness and aging resistance of the crosslinked polyolefin material.

[0084] Compared with Example 3, when the rubber usage is the same, the cross-linked polyolefin materials obtained in Examples 12-13 have lower hardness and higher elongation at break when the rubber is a mixture of EVM rubber and HNBR rubber. That is, the softness of the cross-linked polyolefins obtained in Examples 12-13 is improved compared with that in Example 3. After the aging resistance test, the cross-linked polyolefin materials obtained in Examples 12-13 also have excellent aging resistance. It can be seen that when the rubber is a mixture of EVM rubber and HNBR rubber, the performance of the cross-linked polyolefins obtained is better than that of using EVM rubber or HNBR rubber alone.

[0085] Compared with Example 12, when EPDM rubber was used instead of EVM rubber, the softness and aging resistance of the cross-linked polyolefin material obtained in Comparative Example 12 were reduced. It can be seen that the combined use of EVM rubber and HNBR rubber can effectively improve the softness and aging resistance of cross-linked polyolefin materials.

[0086] Compared with Example 12, when an equal amount of LLDPE was used to replace VLLDPE, the softness, mechanical properties and aging resistance of the cross-linked polyolefin material obtained in Comparative Example 1 were all reduced compared with Example 12. It can be seen that by selecting VLLDPE as the matrix resin, the softness and aging resistance of the cross-linked polyolefin material can be effectively guaranteed.

[0087] Compared with Example 12, when the content of VLLDPE, rubber, ethylene-octene copolymer and silane crosslinking agent in Comparative Example 2 was lower than the limit of this application, the hardness of the crosslinked polyolefin material obtained in Comparative Example 2 increased. It can be seen that the softness of the crosslinked polyolefin material decreased. Moreover, after the aging resistance test, the elongation at break and tensile strength retention rate of the crosslinked polyolefin material decreased rapidly, and the aging resistance performance decreased.

[0088] Compared with Example 3, when the content of VLLDPE, rubber, ethylene-octene copolymer and silane crosslinking agent in Comparative Example 3 exceeded the limits of this application, the hardness of the crosslinked polyolefin material obtained in Comparative Example 3 decreased, making it easier to deform. The crosslinked polyolefin material had better softness. However, after the aging resistance test, the elongation at break and tensile strength of the crosslinked polyolefin material in Comparative Example 3 decreased rapidly. It can be seen that the aging resistance in Comparative Example 3 was greatly reduced. This further illustrates that when the components in this application are within the limits of this application, the crosslinked polyolefin material has good softness and aging resistance.

[0089] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A long life, flexible crosslinked polyolefin material characterized by: The grafting A component and the catalyzing B component are in a weight ratio of 90:10, and the total amount of the grafting A component and the B component is 100; The raw materials of the grafting A component include, by weight, VLLDPE 25 parts, rubber 40 parts, ethylene-octene copolymer 40 parts, silane crosslinking agent 5 parts, dicumyl peroxide 1 part, silicone 1.2 parts, first antioxidant 3 parts, and zinc oxide 2 parts, wherein the rubber is composed of EVM rubber and HNBR rubber in a weight ratio of 1:1, and the silane crosslinking agent is composed of methyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 1:1; The raw materials of the catalyzing B component include, by weight, ethylene-vinyl acetate copolymer 100 parts, second antioxidant 5 parts, third antioxidant 8 parts, and dibutyltin dilaurate 7 parts; The first antioxidant is antioxidant 1010, the second antioxidant is allyl phenol, and the third antioxidant is 2-methoxy-4-allyl phenol.

2. A process for the production of long-life, flexible crosslinked polyolefin materials as claimed in claim 1, characterized in that, The preparation steps include: preparing the grafting A component, uniformly mixing the raw materials according to the formula ratio, mixing and granulating, and then drying to obtain the grafting A component; preparing the catalyzing B component, uniformly mixing the raw materials according to the formula ratio, extruding through a double-screw extruder, granulating, and then drying to obtain the catalyzing B component, and mixing the grafting A component and the catalyzing B component according to the weight ratio to obtain the crosslinked polyolefin material.

3. Use of a long-life, flexible crosslinked polyolefin material as claimed in claim 2, characterized in that: The crosslinked polyolefin is used for preparing cable material and wire cable material.

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