阅读说明：本技术 一种硅烷交联型阻燃半导电聚烯烃护套材料及其制备方法和应用 (Silane cross-linked flame-retardant semiconductive polyolefin sheath material and preparation method and application thereof ) 是由 钱其琨 涂必冬 张丽本 沈永健 于 2019-10-16 设计创作，主要内容包括：本发明公开了一种硅烷交联型阻燃半导电聚烯烃护套材料及其制备方法和应用,其原料包括A、B料,A料包括：线性低密度聚乙烯、乙烯-醋酸乙烯共聚物、乙烯-辛烯共聚物、阻燃剂、导电炭黑、含有乙烯基的硅烷、引发剂和抗预交联剂,B料包括：线性低密度聚乙烯和水解催化剂；抗预交联剂由2-乙烯基-1H-苯并咪唑与3-苯丙酸-2-甲基-2-丙烯酯共聚反应制成；制备：制成硅烷接枝的A料,然后与B料按配方混合挤出成型后水煮交联,制成；以及一种含有上述材料的煤矿瓦斯外排管；本发明的护套材料不仅具有良好的导电性、阻燃性,且兼具优异的机械力学性能、耐高温性能、使用寿命长等特性。(The invention discloses a silane cross-linked flame-retardant semiconductive polyolefin sheath material and a preparation method and application thereof, wherein the raw materials comprise A, B materials, and A material comprises: linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-octene copolymer, flame retardant, conductive carbon black, vinyl-containing silane, initiator and anti-pre-crosslinking agent, the B material comprises: linear low density polyethylene and a hydrolysis catalyst; the anti-pre-crosslinking agent is prepared by copolymerization reaction of 2-vinyl-1H-benzimidazole and 3-phenylpropionic acid-2-methyl-2-propenyl ester; preparation: preparing a silane grafted material A, mixing the silane grafted material A with a material B according to a formula, extruding, forming, and then boiling in water for crosslinking to prepare the material A; and a coal mine gas external discharge pipe containing the material; the sheath material disclosed by the invention not only has good conductivity and flame retardance, but also has the characteristics of excellent mechanical property, high temperature resistance, long service life and the like.)

1. The silane cross-linked flame-retardant semiconductive polyolefin sheath material is characterized in that the sheath material comprises a material A and a material B, wherein the material A comprises the following components: the material B comprises the following raw materials of linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-octene copolymer, flame retardant, conductive carbon black, silane containing vinyl, initiator and anti-pre-crosslinking agent: linear low density polyethylene and a hydrolysis catalyst; wherein the anti-pre-crosslinking agent is prepared by copolymerization of 2-vinyl-1H-benzimidazole shown in formula (I) and 3-phenylpropionic acid-2-methyl-2-propenyl ester shown in formula (II), and the molecular weight of the anti-pre-crosslinking agent is 1000-15000;

2. the silane crosslinked flame-retardant semiconductive polyolefin sheath material according to claim 1, wherein the feeding molar ratio of the 2-vinyl-1H-benzimidazole of formula (I) to the 3-phenylpropionic acid-2-methyl-2-propenyl ester of formula (II) is 1: 0.95-1.05.

3. The silane-crosslinked flame-retardant semiconductive polyolefin sheathing compound according to claim 1, wherein said copolymerization is carried out in the presence of azobisisoheptonitrile in an organic solvent in an anhydrous environment under reflux, and the amount of said initiator is 0.1 to 2% of the total charge of said 2-vinyl-1H-benzimidazole of formula (i) and said 2-methyl-2-propenyl-3-phenylpropionate of formula (ii).

4. The silane cross-linked flame-retardant semiconductive polyolefin sheath material according to claim 1, wherein the sheath material is prepared by mixing, extruding and water boiling and cross-linking a material A and a material B, and the feeding mass ratio of the material A to the material B is 4-6: 1.

5. The silane cross-linking type flame-retardant semiconductive polyolefin sheath material according to claim 1 or 4, wherein the material A comprises, by mass, 10-40 parts of linear low-density polyethylene, 30-70 parts of ethylene-vinyl acetate copolymer, 10-40 parts of ethylene-octene copolymer, 20-50 parts of flame retardant, 40-80 parts of conductive carbon black, 1-10 parts of vinyl-containing silane, 0.1-1 part of initiator and 1-10 parts of anti-pre-crosslinking agent; also optionally comprises 1-4 parts of antioxidant, 1-10 parts of lubricant and 1-10 parts of dispersant;

in the raw materials of the material B, by mass, 90-110 parts of linear low-density polyethylene and 15-25 parts of hydrolysis catalyst are used.

6. The silane crosslinked flame retardant semiconductive polyolefin sheath material according to claim 1 or 5, wherein the linear low density polyethylene has a melt index of 1 to 20g/10 min; and/or the ethylene-vinyl acetate copolymer has a melt index of 0.2-20g/10min, wherein the content of vinyl acetate is 15-30%; and/or the ethylene-octene copolymer has a melt index of 1-20g/10 min.

7. The silane cross-linked flame retardant semiconductive polyolefin sheathing material according to claim 5, wherein said flame retardant is a combination of one or more selected from pentaerythritol, dipentaerythritol, tripentaerythritol, ammonium polyphosphate, melamine cyanurate, red phosphorus, aluminum hypophosphite, diethyl aluminum hypophosphite, montmorillonite and china clay; the conductive carbon black is VXC200 of Cabot corporation; the silane containing vinyl is one or more of vinyl trimethoxy silane, vinyl triethoxy silane and vinyl-tri (2-methoxyethoxy) silane; the initiator is dicumyl peroxide and/or dibenzoyl peroxide; the antioxidant is one or more of 4,4 '-thiobis (5-methyl-2-tert-butylphenol), pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], tris [2, 4-di-tert-butylphenyl ] phosphite, N-octadecyl beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, N' -bis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl ] hydrazine and dilauryl thiodipropionate; the lubricant is one or more of polyethylene wax, oxidized polyethylene wax, erucamide, ethylene bis stearamide, stearic acid and zinc stearate; the dispersing agent is one or more of amide dispersing agents TAS-2A, EBS and BYK 9076; the hydrolysis catalyst is butyltin dilaurate.

8. The silane cross-linked flame-retardant semiconductive polyolefin sheath material according to claim 1, wherein the material A is prepared by the following method: mixing linear low-density polyethylene, ethylene-vinyl acetate copolymer and ethylene-octene copolymer to obtain a resin base material, mixing silane containing vinyl, an initiator and an anti-pre-crosslinking agent to obtain a silane grafting solution, then mixing the rest raw materials of the material A to obtain an auxiliary material, feeding the auxiliary material through a screw extruder, and carrying out melt co-extrusion grafting to obtain the modified polyethylene material; wherein the silane grafting solution is injected at the tail end of the screw extruder.

9. A method for preparing the silane crosslinked flame retardant semiconductive polyolefin sheathing material according to any one of claims 1 to 8, comprising the steps of:

preparing a material A: mixing linear low-density polyethylene, ethylene-vinyl acetate copolymer and ethylene-octene copolymer to obtain a resin base material, mixing silane containing vinyl, an initiator and an anti-pre-crosslinking agent to obtain a silane grafting solution, then mixing the rest raw materials of the material A to obtain an auxiliary material, feeding the auxiliary material through a screw extruder, and carrying out melt co-extrusion grafting to obtain the modified polyethylene material; wherein the silane grafting solution is injected at the tail end of the screw extruder;

preparing a material B: mixing the raw materials of the material B according to a formula, banburying, extruding and forming to obtain the material B;

and mixing the prepared material A and the material B according to a formula, and performing extrusion molding and water boiling crosslinking to prepare the silane crosslinking type flame-retardant semiconductive polyolefin sheath material.

10. A coal mine gas external drainage pipe, which comprises an external drainage pipe body and is characterized in that the coal mine gas external drainage pipe further comprises a sheath coated on the external drainage pipe body, and the sheath is made of the silane cross-linked flame-retardant semiconductive polyolefin sheath material according to any one of claims 1 to 8.

Technical Field

The invention belongs to the field of coal mines, particularly relates to a material for a coal mine gas pipe, and particularly relates to a silane cross-linked flame-retardant semiconductive polyolefin sheath material and a preparation method and application thereof.

Background

In coal mine production, mine operation is very dangerous, one of the main dangerous sources is produced gas, so the gas needs to be discharged, however, in the drainage process, because the substance flowing in the drainage pipeline is mainly the main body of gas and is mixed with a certain amount of dust, and when the gas flow with solid dust flows at a certain speed in the pipeline (most of the polyolefin plastic pipes used at present are widely applied due to the characteristics of light weight, corrosion resistance, aging resistance, easy installation and the like), the gas and the solid dust frequently rub and collide with the pipe wall, so strong static electricity is generated, even a spark discharge phenomenon is also accompanied, the energy of the discharge spark is enough to ignite the gas, so fire or gas explosion is easy to cause mine accidents, although some improvements are made on the drainage pipeline in the market at present, for example, by adding an antistatic agent to reduce the possibility of static electricity generation, but the effect is not ideal and there is a great potential safety risk.

At present, there is a scheme of adding conductive carbon black to achieve that the volume resistivity of a material is less than 100 Ω · cm and static electricity can be rapidly derived, but basically, a thermoplastic polyolefin sheath material, for example, chinese patent CN109082002A, discloses a flame-retardant semiconductive sheath material for a coal mine gas pipe, and a preparation method and an application thereof, although this patent achieves excellent conductivity and flame retardance of the sheath material, there are certain defects in high temperature resistance and service life, in the prior art, a crosslinking mode is usually adopted to obtain a crosslinked polyolefin material, for example, a silane crosslinking mode, so as to raise the working service temperature of the polyolefin material, however, this mode is easy to generate a pre-crosslinking phenomenon in the processes of extrusion, mixing or storage, and the reason thereof mainly includes: the nitrogen-phosphorus flame retardant is easy to absorb moisture, and resin materials or other raw materials contain bound water or free water and the like, so that the mechanical property of the product is influenced, the extruded surface of the product is rough, the quality and the processing property of the product are seriously influenced, even the product can be scrapped, and the application of the nitrogen-phosphorus flame retardant in a high-strength environment is particularly not facilitated.

In view of the above-mentioned problem of pre-crosslinking of the crosslinked polyolefin material, it is a common practice in the prior art to add an anti-pre-crosslinking agent, which commonly includes long-chain silanes or substituted silanes, such as hexadecyl trimethoxy silane or 3-thio octanoyl-1-propyl triethoxy silane, to make the product waterproof by virtue of their easy hydrolytic condensation; however, practical studies find that these anti-pre-crosslinking agents can achieve a certain anti-pre-crosslinking effect, but for flame-retardant semiconductive polyolefin sheath materials containing a large amount of conductive carbon black for coal mines, the existing anti-pre-crosslinking agents are difficult to achieve anti-pre-crosslinking, and meanwhile, the materials have excellent mechanical properties and flame-retardant conductivity, and are difficult to meet coal mine operation with extremely high safety requirements.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects in the prior art, and provide a novel silane crosslinking type flame-retardant semiconductive polyolefin sheath material which not only has good conductivity and flame retardance, but also has the characteristics of excellent mechanical property, high temperature resistance, long service life and the like.

The invention also provides a preparation method of the silane crosslinking type flame-retardant semiconductive polyolefin sheath material.

The invention also provides the application of the silane cross-linked flame-retardant semiconductive polyolefin sheath material in a coal mine gas external drainage pipe.

In order to solve the technical problems, the invention adopts a technical scheme as follows:

the silane cross-linked flame-retardant semiconductive polyolefin sheath material comprises a material A and a material B, wherein the material A comprises the following components: the material B comprises the following raw materials of linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-octene copolymer, flame retardant, conductive carbon black, silane containing vinyl, initiator and anti-pre-crosslinking agent: linear low density polyethylene and a hydrolysis catalyst; wherein the anti-pre-crosslinking agent is prepared by copolymerization of 2-vinyl-1H-benzimidazole shown in formula (I) and 3-phenylpropionic acid-2-methyl-2-propenyl ester shown in formula (II), and the molecular weight of the anti-pre-crosslinking agent is 1000-15000;

according to some preferred aspects of the invention, the molar ratio of the 2-vinyl-1H-benzimidazole of formula (I) to the 3-phenylpropanoic acid-2-methyl-2-propenyl ester of formula (II) is 1: 0.95-1.05.

According to some preferred aspects of the invention, the copolymerization is carried out in the presence of azobisisoheptonitrile in an organic solvent under anhydrous conditions at reflux, and the amount of the initiator is 0.1-2% of the total charge of the 2-vinyl-1H-benzimidazole of formula (I) and the 2-methyl-2-propenyl-3-phenylpropionate of formula (II).

According to some particular aspects of the invention, the organic solvent may be tetrahydrofuran.

In some preferred embodiments of the present invention, the anti-precrosslinking agent is prepared by: mixing 2-vinyl-1H-benzimidazole shown in formula (I) and 3-phenylpropionic acid-2-methyl-2-propenyl ester shown in formula (II), adding Azobisisoheptonitrile (AVBN) and anhydrous Tetrahydrofuran (THF), reacting under reflux, concentrating under reduced pressure after the reaction is finished to remove tetrahydrofuran, stirring and cleaning residues by using methanol, and then drying in vacuum to obtain the compound.

According to some preferred aspects of the invention, the sheath material is prepared by mixing, extruding and water boiling and crosslinking a material A and a material B, wherein the feeding mass ratio of the material A to the material B is 4-6: 1. According to some specific and preferred aspects of the invention, the temperature of the poaching cross-linking is 88 to 92 ℃.

According to some preferred aspects of the invention, the raw materials of the material A comprise, by mass, 10-40 parts of linear low density polyethylene, 30-70 parts of ethylene-vinyl acetate copolymer, 10-40 parts of ethylene-octene copolymer, 20-50 parts of flame retardant, 40-80 parts of conductive carbon black, 1-10 parts of silane containing vinyl, 0.1-1 part of initiator and 1-10 parts of anti-pre-crosslinking agent; also optionally comprises 1-4 parts of antioxidant, 1-10 parts of lubricant and 1-10 parts of dispersant;

in the raw materials of the material B, by mass, 90-110 parts of linear low-density polyethylene and 15-25 parts of hydrolysis catalyst are used.

According to some preferred aspects of the present invention, the linear low density polyethylene has a melt index of 1 to 20g/10 min.

According to some preferred aspects of the present invention, the ethylene-vinyl acetate copolymer has a melt index of 0.2 to 20g/10min, wherein the vinyl acetate content is 15 to 30%.

According to some preferred aspects of the present invention, the ethylene-octene copolymer has a melt index of 1 to 20g/10 min.

According to some specific aspects of the invention, the flame retardant is a combination of one or more selected from pentaerythritol, dipentaerythritol, tripentaerythritol, ammonium polyphosphate, melamine cyanurate, red phosphorus, aluminum hypophosphite, diethyl aluminum hypophosphite, montmorillonite, and china clay. According to some preferred aspects of the present invention, the flame retardant is composed of a combination of one or more of pentaerythritol and its derivatives, the ammonium polyphosphate and the melamine cyanurate, the mass ratio of the ammonium polyphosphate and the melamine cyanurate in the combination of one or more of pentaerythritol and its derivatives is 1: 3-10: 2-6, and the pentaerythritol derivatives are dipentaerythritol and/or tripentaerythritol.

According to some specific aspects of the invention, the conductive carbon black is VXC200 of cabot corporation.

According to some specific aspects of the invention, the vinyl-containing silane is a combination of one or more selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, and vinyl-tris (2-methoxyethoxy) silane.

According to some particular aspects of the invention, the initiator is dicumyl peroxide and/or dibenzoyl peroxide.

According to some specific aspects of the invention, the antioxidant is a combination of one or more selected from the group consisting of 4,4 '-thiobis (5-methyl-2-tert-butylphenol), pentaerythrityl tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], tris [2, 4-di-tert-butylphenyl ] phosphite, N-octadecyl beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, N' -bis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl ] hydrazine, and dilauryl thiodipropionate.

According to some specific aspects of the invention, the lubricant is a combination of one or more selected from the group consisting of polyethylene wax, oxidized polyethylene wax, erucamide, ethylene bis stearamide, stearic acid, and zinc stearate.

According to some specific aspects of the present invention, the dispersant is selected from the group consisting of one or more of amide dispersants TAS-2A, EBS and BYK 9076.

According to some specific aspects of the invention, the hydrolysis catalyst is butyltin dilaurate.

According to some preferred and specific aspects of the present invention, the material a is prepared by: mixing linear low-density polyethylene, ethylene-vinyl acetate copolymer and ethylene-octene copolymer to obtain a resin base material, mixing silane containing vinyl, an initiator and an anti-pre-crosslinking agent to obtain a silane grafting solution, then mixing the rest raw materials of the material A to obtain an auxiliary material, feeding the auxiliary material through a screw extruder, and carrying out melt co-extrusion grafting to obtain the modified polyethylene material; wherein the silane grafting solution is injected at the tail end of the screw extruder.

The invention provides another technical scheme that: the preparation method of the silane cross-linked flame-retardant semiconductive polyolefin sheath material comprises the following steps:

preparing a material A: mixing linear low-density polyethylene, ethylene-vinyl acetate copolymer and ethylene-octene copolymer to obtain a resin base material, mixing silane containing vinyl, an initiator and an anti-pre-crosslinking agent to obtain a silane grafting solution, then mixing the rest raw materials of the material A to obtain an auxiliary material, feeding the auxiliary material through a screw extruder, and carrying out melt co-extrusion grafting to obtain the modified polyethylene material; wherein the silane grafting solution is injected at the tail end of the screw extruder;

preparing a material B: mixing the raw materials of the material B according to a formula, banburying, extruding and forming to obtain the material B;

and mixing the prepared material A and the material B according to a formula, and performing extrusion molding and water boiling crosslinking to prepare the silane crosslinking type flame-retardant semiconductive polyolefin sheath material.

According to some preferred aspects of the invention, in the process of preparing the material A, the screw extruder adopts a compound single-screw buss machine, the length-diameter ratio is more than or equal to 40: 1, the process temperature of the melting section is 140-.

The invention provides another technical scheme that: the utility model provides a colliery gas calandria, is including arranging the tub body outward, colliery gas calandria still includes the cladding and is in sheath on the calandria body outward, the sheath is by the aforesaid silane cross-linked type flame retardant semi-conductive polyolefin sheath material make.

According to the invention, the "melt index" is determined according to ASTM D1238 at 190 ℃ under a test load of 2.16 Kg.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages:

the silane crosslinking type flame-retardant semiconductive polyolefin sheath material disclosed by the invention adopts a specific anti-pre-crosslinking agent, so that the flame-retardant semiconductive polyolefin sheath material highly filled with conductive carbon black can have good conductivity (the volume resistivity can be less than 50 omega cm) and flame retardance (the flame-retardant grade reaches V-0 grade), has the characteristics of excellent mechanical property, high temperature resistance, long service life and the like, is smooth in extrusion surface, and greatly widens the application of the crosslinking type polyolefin sheath material in the coal mine industry.

Detailed Description

The above-described scheme is further illustrated below with reference to specific examples; it is to be understood that these embodiments are provided to illustrate the general principles, essential features and advantages of the present invention, and the present invention is not limited in scope by the following embodiments; the implementation conditions used in the examples can be further adjusted according to specific requirements, and the implementation conditions not indicated are generally the conditions in routine experiments.

Not specifically illustrated in the following examples, all starting materials are commercially available or prepared by methods conventional in the art. In the following, the linear low density polyethylene is purchased from DuPont Dow, and the melt index is 2g/10 min; the ethylene-vinyl acetate copolymer is purchased from Yangzi petrochemical Basff, the melt index is 2.7g/10min, and the content of vinyl acetate is 18%; ethylene-octene copolymers were purchased from mitsui chemistry with a melt index of 3.6g/10 min; conductive carbon black was purchased from VXC200 of cabot corporation; the ammonium polyphosphate is purchased from shouguanpu chemical industry, and the melamine cyanurate is purchased from Weifang Dakang chemical industry; the rest antioxidants and lubricants are commercial industrial products.

The anti-precrosslinking agents used in the following were prepared by the following method: mixing 5mol of 2-vinyl-1H-benzimidazole shown in formula (I) and 5mol of 3-phenylpropionic acid-2-methyl-2-propenyl ester shown in formula (II), adding 2.5g of Azodiisoheptanonitrile (AVBN) and 10L of anhydrous Tetrahydrofuran (THF), reacting for 24 hours under reflux, concentrating under reduced pressure after the reaction is finished to remove the tetrahydrofuran, stirring and cleaning the residue with methanol, and then drying in vacuum to prepare the anti-precrosslinking agent shown in formula (III), wherein the reaction route is as follows:

the molar percentage of 2-vinyl-1H-benzimidazole of formula (I) in the anti-precrosslinking agent of formula (III) was found to be about 50%, and the number average molecular weight was found to be about 1700 after several measurements.