Double insulation self-limiting temperature heating cable

Abstract

The present invention relates to a double-insulated self-limiting temperature heating belt, which belongs to the technical field of electric heating elements, including a metal wire core, two parallel metal wire cores are covered with a PTC material layer on the outside, and the outside of the PTC material layer is sequentially coated with an inner insulating layer and a flame-retardant outer insulating layer; the PTC material layer is made of a polymer-based PTC material; the polymer-based PTC material includes the following raw materials by weight: 70-80 parts of polyethylene material, 7-8 parts of modified graphene, 0.03 parts of stabilizer, 30 parts of carbon black and 10-12 parts of compatibilizer; in order to improve the stability of the material, a modified graphene is prepared in the present invention, adsorbed on the surface of graphene, graphene is prevented from agglomerating, and the two-dimensional sheet structure of the modified graphene is maintained. Because graphene has a two-dimensional sheet structure, the migration of conductive particles such as carbon black can be limited, and the stability is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electric heating elements, and in particular relates to a double-insulated self-limiting temperature heating belt. Background Art

[0002] Self-limiting temperature heating belt has become a relatively good choice. It is a strip electric heater that uses a conductive polymer composite material with a positive temperature coefficient of resistivity (PTC) as a heating element. Its characteristics are: it can automatically limit the temperature during heating and can automatically adjust the output power according to the temperature of the heated system without adding other equipment. Electric heating and heat tracing technology are increasingly widely used. Self-limiting temperature electric heating belts with positive temperature coefficient characteristics are widely used in the heat tracing and insulation system of liquid transportation pipelines due to their unique self-limiting temperature characteristics.

[0003] The crystallization behavior of existing PTC polymer heating material products used for self-limiting temperature electric heating belts is unstable and imperfect, and there is residual thermal stress inside the PTC heating material, which will make the resistance of the PTC heating material unstable, the temperature rise and fall uneven, the PTC characteristics unstable, the repeatability of the PTC characteristics decreased, and the service life of the material shortened. Summary of the invention

[0004] In order to solve the technical problems mentioned in the background technology, the present invention provides a double-insulated self-limiting temperature heating belt.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The double-insulated self-limiting temperature heating tape includes a metal wire core. The outer sides of two parallel metal wire cores are covered with a PTC material layer. The outer sides of the PTC material layer are sequentially coated with an inner insulation layer and a flame-retardant outer insulation layer. The two insulation layers ensure good insulation performance as a whole and improve the safety performance of the product.

[0007] The PTC material layer is made of a polymer-based PTC material; the polymer-based PTC material comprises the following raw materials in parts by weight: 70-80 parts of polyethylene material, 7-8 parts of modified graphene, 0.03 parts of stabilizer, 30 parts of carbon black and 10-12 parts of compatibilizer;

[0008] The modified graphene is prepared by the following steps:

[0009] Step 1: Mix graphene and water, stir and disperse in an ice-water bath, then add ferric chloride solution and pyrrole, and continue stirring for 10-12 hours. After the stirring is completed, wash with water, centrifuge, and detect with silver nitrate solution until there is no white precipitate, and vacuum dry at 80°C to constant weight to obtain a pre-modified material;

[0010] Step 2: Add the pre-modified material and the branched modifier into chloroform, and disperse them by ultrasonication for 48 hours. After the ultrasonication, centrifuge at 4000r / min for 30 minutes, and vacuum dry to constant weight at 80°C to obtain modified graphene. The mechanical properties are improved by replacing part of the carbon black with modified graphene and adding a certain proportion of metallocene materials.

[0011] Furthermore, in step one, the ratio of graphene to water is 1 g:10 mL; the concentration of the ferric chloride solution is 1 mol / L, and the molar ratio of FeCl3 to pyrrole in the ferric chloride solution is 2.3:1; the ratio of pyrrole to graphene is 0.5 mL:1 g; and in step two, the ratio of the pre-modified material, the branched modifier and chloroform is 2 g:1 g:50 mL.

[0012] Further, the branched modifier is prepared by the following steps:

[0013] Ethylene was introduced into the reactor, dichloromethane was added, the temperature was controlled at 25°C, stirred for 20 minutes, nitrogen was introduced for protection, styrene and 1,4-butanediol diacrylate were added, Pd-diimine catalyst was added, the reaction was carried out in the dark for 24 hours, and after the reaction was completed, the dichloromethane was removed by vacuum concentration to obtain a branched modifier. The amount ratio of dichloromethane, styrene, 1,4-butanediol diacrylate and catalyst was 40mL: 1g: 4g: 0.5g.

[0014] Furthermore, the polyethylene material is a mixture of metallocene polyethylene and high-density polyethylene in a mass ratio of 1:10. The mechanical strength of the material is improved by adding metallocene polyethylene.

[0015] Furthermore, the stabilizer is a mixture of a hindered phenol antioxidant and a benzotriazole light stabilizer in a mass ratio of 1:2.

[0016] Furthermore, the compatibilizer is one of maleic anhydride grafted polyethylene, acrylate grafted polyethylene or ethylene-vinyl acetate copolymer.

[0017] Furthermore, the polymer-based PTC material is prepared by the following steps:

[0018] According to the ratio, the polyethylene material, the modified graphene, the stabilizer, the carbon black and the compatibilizer are uniformly mixed, and kneaded at a temperature of 180° C. for 5-7 minutes to obtain a polymer-based PTC material.

[0019] Beneficial effects of the present invention:

[0020] In order to improve the stability of the material, a modified graphene is prepared in the present invention. The preparation process of the modified graphene goes through two steps. First, the modified graphene is treated with a conductive polymer polypyrrole to make up for its surface defects and improve the conductive stability. Then, a branching modifier is used to maintain the shape. The branching modifier is a hyperbranched polymer with the characteristics of low viscosity, no chain entanglement, etc. The branching modifier is added to react with the graphene in a π-π manner and adsorb on the surface of the graphene to prevent the graphene from agglomerating and maintain the two-dimensional sheet structure of the modified graphene.

[0021] Modified graphene can not only improve the room temperature conductivity of polymer-based PTC materials, but also replace part of the carbon black with modified graphene. Since graphene has a two-dimensional layer structure, it can limit the migration of conductive particles such as carbon black. Usually, the conductivity of graphene will be further reduced after the surface of graphene is modified. In the present invention, the conductive polymer polypyrrole is introduced to compensate for the problem of reduced conductivity caused by modification. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The double-insulated self-limiting temperature heating belt comprises a metal core, two parallel metal cores are covered with a PTC material layer on the outside, and the outer side of the PTC material layer is sequentially coated with an inner insulation layer and a flame-retardant outer insulation layer. The PTC material layer is made of a polymer-based PTC material.

[0024] Example 1

[0025] Preparation of modified graphene:

[0026] Step 1: Mix graphene and water, stir and disperse in an ice-water bath, then add ferric chloride solution and pyrrole, continue stirring for 10 hours, wash with water, centrifuge, detect with silver nitrate solution until there is no white precipitate, and vacuum dry to constant weight at 80°C to obtain a pre-modified material; the amount ratio of graphene to water is 1g:10mL; the concentration of ferric chloride solution is 1mol / L, and the molar ratio of FeCl3 to pyrrole in the ferric chloride solution is 2.3:1; the amount ratio of pyrrole to graphene is 0.5mL:1g;

[0027] Step 2: introduce ethylene into a reaction kettle, add dichloromethane, control the temperature to 25°C, stir for 20 minutes, introduce nitrogen protection, add styrene and 1,4-butanediol diacrylate, add Pd-diimine catalyst, react in the dark for 24 hours, and after the reaction is completed, remove dichloromethane by vacuum concentration to obtain a branched modifier; wherein the amount ratio of dichloromethane, styrene, 1,4-butanediol diacrylate and catalyst is 40mL:1g:4g:0.5g;

[0028] The pre-modified material and the branched modifier were added to chloroform, and ultrasonically dispersed for 48 hours. After the ultrasonication, the graphene was centrifuged at 4000 r / min for 30 minutes, and vacuum dried at 80°C to constant weight to obtain modified graphene. The amount ratio of the pre-modified material, the branched modifier and the chloroform was 2g:1g:50mL.

[0029] Example 2

[0030] Preparation of modified graphene:

[0031] Step 1: Mix graphene and water, stir and disperse in an ice-water bath, then add ferric chloride solution and pyrrole, continue stirring for 12 hours, wash with water, centrifuge, detect with silver nitrate solution until there is no white precipitate, and vacuum dry to constant weight at 80°C to obtain a pre-modified material; the amount ratio of graphene to water is 1g:10mL; the concentration of ferric chloride solution is 1mol / L, and the molar ratio of FeCl3 to pyrrole in the ferric chloride solution is 2.3:1; the amount ratio of pyrrole to graphene is 0.5mL:1g;

[0032] Step 2: introduce ethylene into a reaction kettle, add dichloromethane, control the temperature to 25°C, stir for 20 minutes, introduce nitrogen protection, add styrene and 1,4-butanediol diacrylate, add Pd-diimine catalyst, react in the dark for 24 hours, and after the reaction is completed, remove dichloromethane by vacuum concentration to obtain a branched modifier; wherein the amount ratio of dichloromethane, styrene, 1,4-butanediol diacrylate and catalyst is 40mL:1g:4g:0.5g;

[0033] The pre-modified material and the branched modifier were added to chloroform, and ultrasonically dispersed for 48 hours. After the ultrasonication, the graphene was centrifuged at 4000 r / min for 30 minutes, and vacuum dried at 80°C to constant weight to obtain modified graphene. The amount ratio of the pre-modified material, the branched modifier and the chloroform was 2g:1g:50mL.

[0034] Comparative Example 1

[0035] Compared with Example 2, step 2 is not performed, and the remaining raw materials and preparation process remain the same as Example 2.

[0036] Example 3

[0037] Preparation of polymer-based PTC materials:

[0038] According to weight parts, 70 parts of polyethylene material, 7 parts of modified graphene prepared in Example 1, 0.03 parts of stabilizer, 30 parts of carbon black and 10 parts of compatibilizer were mixed evenly, and kneaded for 5 minutes at a temperature of 180°C to obtain a polymer-based PTC material. The compatibilizer is maleic anhydride grafted polyethylene, wherein the polyethylene material is a mixture of metallocene polyethylene and high-density polyethylene in a mass ratio of 1:10. The stabilizer is a mixture of hindered phenol antioxidant and benzotriazole light stabilizer in a mass ratio of 1:2.

[0039] Example 4

[0040] Preparation of polymer-based PTC materials:

[0041] According to weight parts, 75 parts of polyethylene material, 7.5 parts of modified graphene prepared in Example 2, 0.03 parts of stabilizer, 30 parts of carbon black and 11 parts of compatibilizer were mixed evenly, and kneaded for 7 minutes at a temperature of 180°C to obtain a polymer-based PTC material. The compatibilizer is acrylate grafted polyethylene, wherein the polyethylene material is a mixture of metallocene polyethylene and high-density polyethylene in a mass ratio of 1:10. The stabilizer is a mixture of hindered phenol antioxidant and benzotriazole light stabilizer in a mass ratio of 1:2.

[0042] Example 5

[0043] Preparation of polymer-based PTC materials:

[0044] According to weight parts, 80 parts of polyethylene material, 8 parts of modified graphene prepared in Example 2, 0.03 parts of stabilizer, 30 parts of carbon black and 12 parts of compatibilizer are mixed evenly, and kneaded at a temperature of 180°C for 5-7 minutes to obtain a polymer-based PTC material. The compatibilizer is ethylene-vinyl acetate copolymer; wherein the polyethylene material is a mixture of metallocene polyethylene and high-density polyethylene in a mass ratio of 1:10. The stabilizer is a mixture of hindered phenol antioxidant and benzotriazole light stabilizer in a mass ratio of 1:2.

[0045] Comparative Example 2

[0046] Compared with Example 4, the modified graphene is replaced with the sample prepared in Comparative Example 1, and the remaining raw materials and preparation process remain the same as those in Example 2.

[0047] Comparative Example 3

[0048] Compared with Example 4, the modified graphene is replaced with unmodified graphene, and the remaining raw materials and preparation process remain the same as those in Example 2.

[0049] The samples prepared in Examples 3 to 5 and Comparative Examples 2 to 3 were tested, PTC strength = Log (peak resistivity / room temperature resistivity), and the test results are shown in Table 1 below:

[0050] Table 1

[0051] Example 3 Example 4 Example 5 Comparative Example 2 Comparative Example 3 Room temperature resistivity / (Ω·cm) 2.5 2.2 2.1 3.8 4.9 PTC Strength 7.2 7.2 7.2 6.1 5.8

[0052] It can be seen from the test data that the polymer-based PTC material prepared by the present invention has good stability, low room temperature resistivity, good conductivity, higher PTC strength than the comparative example, and better safety.

[0053] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0054] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. Double insulation type self-limiting temperature heating belt, characterized by: It comprises a metal wire core, two parallel metal wire cores are covered with a PTC material layer on the outside, and the outer side of the PTC material layer is sequentially covered with an inner insulating layer and a flame-retardant outer insulating layer; The PTC material layer is made of a polymer-based PTC material; the polymer-based PTC material comprises the following raw materials in parts by weight: 70-80 parts of polyethylene material, 7-8 parts of modified graphene, 0.03 parts of stabilizer, 30 parts of carbon black and 10-12 parts of compatibilizer; The modified graphene is prepared by the following steps: Step 1: Mix graphene and water, stir and disperse in an ice-water bath, then add ferric chloride solution and pyrrole, and continue stirring for 10-12 hours. After the stirring is completed, wash with water, centrifuge, and detect with silver nitrate solution until there is no white precipitate, and vacuum dry at 80°C to constant weight to obtain a pre-modified material; Step 2: adding the pre-modified material and the branched modifier into chloroform, ultrasonically dispersing for 48 hours, centrifuging at 4000 r / min for 30 minutes after the end of the ultrasonication, and vacuum drying at 80°C to constant weight to obtain modified graphene; The branched modifier is prepared by the following steps: Ethylene was introduced into the reactor, and dichloromethane was added. The temperature was controlled at 25°C, stirred for 20 minutes, and nitrogen was introduced for protection. Styrene and 1,4-butanediol diacrylate were added, and a catalyst was added. The reaction was protected from light for 24 hours. After the reaction was completed, the dichloromethane was removed by vacuum concentration to obtain a branched modifier.

2. The double-insulated self-limiting temperature heating belt according to claim 1 is characterized in that: The polyethylene material is a mixture of metallocene polyethylene and high-density polyethylene in a mass ratio of 1:

10.

3. The double-insulated self-limiting temperature heating belt according to claim 1 is characterized in that: The stabilizer is a mixture of hindered phenol antioxidant and benzotriazole light stabilizer in a ratio of 1:2 by mass.

4. The double-insulated self-limiting temperature heating belt according to claim 1 is characterized in that: The compatibilizer is one of maleic anhydride grafted polyethylene, acrylate grafted polyethylene or ethylene-vinyl acetate copolymer.

5. The double-insulated self-limiting temperature heating belt according to claim 1 is characterized in that: The polymer-based PTC material is prepared by the following steps: The polyethylene material, modified graphene, stabilizer, carbon black and compatibilizer are uniformly mixed, and kneaded at a temperature of 180° C. for 5-7 minutes to obtain a polymer-based PTC material.