Low-smoke halogen-free flame-retardant polyolefin insulation material for high-voltage cable in vehicle and preparation method thereof

Abstract

A low-smoke halogen-free flame-retardant polyolefin insulation material for high-voltage cables in vehicles, raw materials including, by mass fraction: SEBS 30-50 parts, ethylene-propylene-butene block copolymer elastomer 30-50 parts, polyethylene grafted maleic anhydride compatibilizer 10-20 parts, color master batch 3-5 parts, antioxidant 1.5-2.5 parts, aluminum hydroxide 110-130 parts, phosphorus-containing silane 1.5-3 parts, crosslinking agent 1-2 parts, silicone master batch 3-5 parts. SEBS is oil-free granular; aluminum hydroxide is in powder form and is modified by phosphorus-containing silane; the crosslinking agent is a multifunctional crosslinking sensitizer with not less than 2 functional groups. The preparation method of the insulation material includes the following steps: S1, modifying the aluminum hydroxide powder with phosphorus-containing silane; S2, uniformly mixing the base resin; S3, granulating by using a large-length-ratio double-screw extruder; S4, granulating the material obtained in step S3, the material obtained in step S1 and other raw materials by using a mixing mill and a two-stage production process to obtain the finished product.

Description

TECHNICAL FIELD

[0001] The low-smoke halogen-free flame-retardant polyolefin insulation material for high-voltage cables in vehicles provided by the application is applied to the field of new energy electric vehicles and has excellent oil resistance, flame retardance, softness and tear resistance. BACKGROUND

[0002] At present, new energy electric vehicles are developing rapidly all over the world, and people have higher requirements for electric vehicles, such as higher endurance, faster acceleration and faster charging speed, etc., which puts forward higher requirements for automobile supporting components. However, there are many problems, and quality problems have occurred repeatedly. In addition, consumers have higher requirements for the endurance and speed of electric vehicles, and the implementation of these requirements cannot be separated from the support of high-quality and high-performance electric wires and cables inside electric vehicles. At present, new energy vehicles are mainly divided into pure electric and oil-electric hybrid, and the electric wires and cables connecting various components inside the vehicle need to have higher performance, need to prevent the decline of the electrical properties of the material insulation after the electric wires and cables crack and are immersed in chemical reagents, thereby causing a short circuit and fire. In order to reduce the incidence of fire and the mortality rate when fire occurs, higher requirements are also put forward for the flame retardance of the cable. In addition, the higher endurance requirement of new energy electric vehicles means that the installed capacity of the electric vehicle is increased, the space occupied by the battery is larger, and the installation space of the high-voltage wire harness is further reduced, and higher requirements are also put forward for the softness of the overall material.

[0003] Defects and deficiencies of the prior art:

[0004] 1. Chinese patent application CN 117659558A proposes a low-smoke halogen-free high-flame-retardant cable material for high-voltage wires in new energy vehicles and a preparation method thereof. The material for high-voltage soft cables in vehicles is used to improve the oil resistance and softness of the material. An oil-resistant modified resin is selected, which contains polyphenyl ether material. Since the melting point of polyphenyl ether is relatively high, aluminum hydroxide is added as a flame retardant in this scheme. According to the literature and actual use experience, the extrusion processing temperature is higher than 200℃, and aluminum hydroxide starts to dehydrate, which will seriously affect the extrusion processing of the material, cause pores, and lead to the decline of the mechanical properties and electrical properties of the material. The melting point of polyphenyl ether is higher than 200℃, and it is difficult to disperse uniformly at a temperature lower than the melting point, which can easily cause cracking of the material later. In order to improve the softness of the material while considering the flame retardance, water magnesium hydroxide and aluminum hydroxide / secondary aluminum phosphate are used as the main flame retardants, and graphite carbon black and carbonization agent are also introduced to meet the relevant flame retardance requirements and softness. Secondary aluminum phosphate is acidic and can react with alkaline water magnesium hydroxide, which can affect the extrusion processing. In addition, the introduction of carbonization agent can cause the volume resistivity of the material insulation to decrease.

[0005] 2. Chinese patent CN 109251399B proposes a soft low-smoke halogen-free high-flame-retardant oil-resistant cable material for high-voltage lines in vehicles and a preparation method thereof. The oil-resistant material for high-voltage lines in vehicles, wherein the halogen-free flame retardant is a blend of aluminum diethyl phosphinate and aluminum hydroxide in a weight ratio of 3:1; the flame-retardant synergist is a silane coupling agent coated melamine polyphosphate. Aluminum diethyl phosphinate is prone to hydrolysis, which can cause a decrease in the insulation resistance of the material, resulting in a decrease in the protective effect of the cable and inability to operate safely for a long time. To improve the softness of the material, at least one of the plasticizers, trimethylolpropane, diethylene glycol dibenzoate, and acetyl citric acid tri-n-butyl ester, is added. Although the introduction of plasticizers improves the softness of the material, it can significantly reduce the tear resistance of the material, resulting in a risk of cable cracking. The presence of plasticizers, especially those containing benzene, can easily produce volatile odors, which do not meet the requirements. SUMMARY

[0006] The present application adopts non-oil-filled SEBS, ethylene-propylene-butene block copolymer elastomer and polyethylene grafted maleic anhydride compatibilizer as the base resin, wherein:

[0007] SEBS has excellent electrical properties and softness. Generally, SEBS needs to be filled with oil to improve the softness, extrusion processing performance, etc. of the material, but the drawbacks brought by oil filling are also very obvious, which can affect the flame retardant properties, tear resistance and crack resistance of the material. This formula uses non-oil-filled SEBS, and overcomes the shortcomings of the material's softness, extrusion processing performance, etc. caused by non-oil filling when designing other components.

[0008] The ethylene-propylene-butene terblock copolymer elastomer has a relatively low hardness due to its structural characteristics, etc. Compared with the EVA and EVM introduced in the prior art for oil resistance, this elastomer has excellent electrical properties, and its high melting point allows it to withstand related solvents at a certain temperature.

[0009] Polyethylene grafted maleic anhydride as a compatibilizer, polyethylene has excellent electrical properties.

[0010] In the present application, low-melt-index high-density polyethylene is selected as the compatibilizer base resin. The high-density polyethylene has high density and significantly improved chemical solvent resistance. By utilizing the characteristics of high crystallinity and large molecular weight of high-density polyethylene, the mechanical and tear resistance are improved while meeting the chemical solvent resistance.

[0011] Compared with the scheme of modifying the powder by using the conventional silane coupling agent, the phosphorus-containing silane forms phosphorus-containing radicals in the combustion process, which can quench the radicals and terminate the combustion reaction, thereby improving the flame retardant performance of the material.

[0012] In addition, for the irradiation crosslinked material, the 5 or 6 functional group crosslinking sensitizer is used in the application to replace the conventional 2 functional group sensitizer (such as TAIC, TAC, TMPTMA, etc.), and the increase of the functional groups of the sensitizer can significantly improve the irradiation crosslinking efficiency of the material, ensure the crosslinking degree of the material under the compatible irradiation dose, and reduce the damage of the irradiation rays to the main chain of the base resin, which can reduce the decrease of the tear resistance caused by the irradiation and reduce the influence of the irradiation on the flame retardant performance.

[0013] Advantages of the application:

[0014] The soft high-melting-point elastomer is blended with the polyethylene resin with high crystallinity to replace the low-melting-point polar polymer EVA and EVM in the conventional scheme, so that the problem of chemical solvent resistance of the automobile cable material is solved, the influence of the polar resin on the electrical performance of the insulating material is reduced, and the problems of electric leakage and short circuit caused by the decrease of the insulating performance are avoided.

[0015] The phosphorus-based silane is used to modify the aluminum hydroxide, and compared with the conventional non-phosphorus-based silane such as vinyl silane, the phosphorus-based silane can have excellent flame retardant charring property with a better flame retardant dosage, and further improve the softness of the material. In addition, compared with the conventional magnesium hydroxide / water magnesium carbonate / aluminum hydroxide flame retardant system, in order to meet the softness of the material, it is generally necessary to additionally introduce a flame retardant synergist, such as aluminum hypophosphite and a carbonizing agent. The aluminum hypophosphite is easy to absorb moisture, and the acidic characteristics also affect the extrusion process. The commercialized carbonizing agent is generally modified by intercalating a large amount of organic solvent, which is extremely easy to dilute and affects the electrical insulation performance of the material. The volatilization of the organic solvent during the use of the material in a high-temperature environment will accelerate the aging of the material and affect the service life.

[0016] In order to further improve the softness of the material and improve the tear resistance, the poly-carbon-silane and the aluminum hydroxide are introduced as the flame retardant synergist under the condition of low flame retardant filling. At the same time, for the irradiation type material, the 5 or 6 functional group crosslinking sensitizer is used to replace the conventional 2 functional group crosslinking sensitizer, so as to improve the crosslinking efficiency and crosslinking density and improve the tear resistance and flame retardant performance of the material.

[0017] A preparation method of a low-smoke halogen-free flame-retardant polyolefin insulating material for an in-vehicle high-voltage cable, first, the raw materials are weighed according to the formula, and then prepared according to the following steps:

[0018] S1, using phosphorus-containing silane to modify aluminum hydroxide powder, surface treatment.

[0019] S2, the base resin is discharged to the high mixer and mixed uniformly.

[0020] S3, using a large length ratio double screw extruder to blend and granulate the material obtained in step S2.

[0021] S4, the material obtained in step S3, the material prepared in step S1 and other raw materials are jointly put into an internal mixer, and a double-stage production granulation process is used to prepare the finished material.

[0022] In step S1, the aluminum hydroxide powder is preheated to 80-90℃, and the powder is fully stirred, and the phosphorus-containing silane aerosol is sprayed onto the surface of the powder during the stirring process.

[0023] In step S3, the length ratio of the double screw extruder is greater than or equal to 52, and the base resin is mixed and granulated in advance by using a large length ratio double screw, so that the mixture forms a nearly homogeneous system under the action of a longer and sufficient shear, and the good dispersibility makes the performance of the material more excellent. DETAILED DESCRIPTION

[0024] The application will be further described below in combination with specific examples.

[0025] (1) Formula composition

[0026] According to the mass fraction, including

[0027] SEBS 30-50 parts,

[0028] Ethylene-propylene-butene block copolymer elastomer 30-50 parts,

[0029] Polyethylene grafted maleic anhydride compatibilizer 10-20 parts,

[0030] Color master batch 3-5 parts,

[0031] Antioxidant 1.5-2.5 parts,

[0032] Aluminum hydroxide 110-130 parts,

[0033] Silane 1.5-3 parts,

[0034] Polycarbosilane 3-5 parts,

[0035] Crosslinking agent 1-2 parts,

[0036] Silicone master batch 3-5 parts.

[0037] Among them:

[0038] SEBS is non-oil-filled granular.

[0039] The polyethylene base material for polyethylene grafted maleic anhydride compatibilizer is high-density polyethylene.

[0040] The antioxidant is antioxidant B255 (tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester) or B900 (tris(2,4-di-tert-butylphenyl) phosphite) commercially available from BASF, B225 is a compound of antioxidant 1010 and antioxidant 168 in a ratio of 1:1, and B900 is a compound of antioxidant 1076 and antioxidant 168 in a ratio of 1:4.

[0041] The silane is a phosphorus-containing silane (such as 3-(trihydroxysilyl) propyl methyl phosphate or tris(trimethylsilyl) phosphate).

[0042] The crosslinking agent is a 5-functional structure (such as bis-pentaerythritol pentaacrylate DPEPA) or a 6-functional structure (such as bis-pentaerythritol hexaacrylate DPHA).

[0043] (2) Preparation of insulating material according to the formula

[0044] First, the aluminum hydroxide is modified and surface treated using a phosphorus-containing silane.

[0045] The aluminum hydroxide powder is preheated to 80-90°C, and the powder is stirred at a stirring speed of 600-800 rpm. During the stirring process, the phosphorus-containing silane is converted into an aerosol through an atomizing device, and sprayed onto the surface of the powder. The spraying and stirring time is 30-50 min.

[0046] Then, the base resin (non-oil-filled SEBS, ethylene-propylene-butene block elastomer, and polyethylene grafted maleic anhydride compatibilizer as the base resin) is weighed according to the formula ratio and discharged into a high-speed mixer. After mixing uniformly, the base resin is blended and pelletized by a large-length-diameter ratio twin screw to improve the compatibility and dispersibility of the polymer components.

[0047] The temperature settings of each zone of the twin screw extruder are as follows: barrel zone one: 120±5°C, barrel zone two: 140±5°C, barrel zone three: 150±5°C, barrel zone four: 160±5°C, barrel zone five: 170±5°C, barrel zone six: 180±5°C, barrel zone seven: 185±5°C, barrel zone eight: 190±5°C, barrel zone nine: 190±5°C, and die head: 190±5°C.

[0048] Next, the material prepared by the twin screw blending is weighed according to the ratio, and the modified powder (aluminum hydroxide) and its raw material are weighed and put into an internal mixer. The internal mixing and double-stage production pelletization process is used to prepare the finished product.

[0049] In the internal mixing and double-stage production pelletization process:

[0050] The temperature of the internal mixer is 150-160℃, the mixing time is 10-20min, the discharge temperature is controlled at 150-160℃, and after the mixing is completed, the double-cone feeding is carried out, and the feeding temperature is 80-90℃;

[0051] The temperature of each zone of the double-screw mixer is: zone 1 90-100℃, zone 2 90-100℃, zone 3 90-100℃, zone 4 80-90℃, zone 5 80-90℃, zone 6 80-90℃, and zone 7 80-90℃, and the rotation speed of the double screw is 180-230rpm;

[0052] The temperature of each zone of the single-screw extruder is: zone 1 95-105℃, zone 2 105-115℃, zone 3 115-125℃, zone 4 120-130℃, and zone 5 125-130℃, and the rotation speed of the single screw is 80-100rpm.

[0053] (3) Example

[0054] In this example, a low-smoke halogen-free flame-retardant polyolefin insulation material for high-voltage cables in vehicles is provided, and the raw materials for preparing the same include the following components in parts by weight:

[0055] Example 1

[0056]

[0057]

[0058] Example 2

[0059]

[0060] Example 3

[0061]

[0062] Example 4

[0063]

[0064] Example 5

[0065]

[0066]

[0067] Example 6

[0068]

[0069] Comparative Example 1

[0070] The only difference from Example 1 is that the ethylene-propylene-butene block copolymer elastomer is replaced by POE (ethylene-butene).

[0071] Comparative Example 2

[0072] The only difference from Example 1 is that the silane is replaced by vinyltris(β-methoxyethoxy)silane (A-172).

[0073] Comparative Example 3

[0074] The only difference from Example 1 is that the polycarbosilane is replaced by a carbon former.

[0075] Comparative Example 4

[0076] The only difference from Example 1 is that the high-density polyethylene grafted maleic anhydride compatibilizer is replaced by a commonly used LLDPE-g-MAH compatibilizer.

[0077] The formulations of each example and comparative example are as follows:

[0078]

[0079]

[0080]

[0081] The test results of each example and comparative example are as follows, and the reference test standards are as follows:

[0082] GB / T 1040.3-2006 Determination of tensile properties of plastics - Part 3: test conditions for films and sheets;

[0083] GB / T 1408.1-2016 Test methods of electrical strength of insulating materials - Part 1: test at power frequency;

[0084] GB / T 2411-2008 Plastics and ebonite - Determination of indentation hardness (Shore hardness) by durometer;

[0085] GB / T 2951.12-2008 General test methods for cable and optical cable insulating and sheathing materials - Part 12: general test methods - thermal ageing test methods;

[0086] GB / T 2951.14-2008 General test methods for cable and optical cable insulating and sheathing materials - Part 14: general test methods - low temperature tests;

[0087] GB / T 5470-2008 Test method of impact embrittlement temperature of plastics insulation;

[0088] GB / T 17650.1-1998 Test methods for gases evolved during the combustion of materials from cables or optical cables Part 1: determination of halogen acid gas total amount;

[0089] GB / T 17650.2-1998 Test methods for gases evolved during the combustion of materials from cables or optical cables Part 2: determination of gas acidity by measurement of pH value and electrical conductivity;

[0090] GB / T 25085-2010 Road vehicles - Single-core electrical wires of 60 V and 600 V;

[0091] GB / T 31838.2-2019 Dielectric and resistive properties Part 2: resistive properties (DC method) Volume resistance and volume resistivity.

[0092]

[0093]

[0094] In the present application, high melting point elastomer is selected to replace traditional EVA and EVM, the elastomer has excellent electrical properties, and its high melting point enables it to withstand related solvents at a certain temperature.

[0095] Low-melting-point high-density polyethylene is selected as the compatibilizer matrix resin, the polyethylene has high density and significantly improved chemical solvent resistance, and the high crystallinity and large molecular weight of the high-density polyethylene meet the requirements of chemical solvent resistance while improving the mechanical and tear resistance.

[0096] The superfine aluminum hydroxide is modified by phosphorus-containing silane (phosphorus-based silane), compared with the conventional silane coupling agent modification powder scheme, the phosphorus-containing silane forms phosphorus-containing free radicals during combustion, which can quench free radicals and terminate the combustion reaction, thereby improving the flame retardant performance of the material.

[0097] On this basis, polycarbosilane is further introduced as a synergistic flame retardant to further improve the flame retardant performance of the material, so that the material can meet the relevant flame retardant requirements under the premise of lower flame retardant filling, and the influence and degradation of the material's softness and tear resistance are reduced.

[0098] In addition, for the irradiation crosslinked material, the 5-functional group and 6-functional group crosslinking sensitizer is used in the application to replace the traditional 2-functional group sensitizer (such as TAIC, TAC, TMPTMA, etc.), the increase of the functional groups of the sensitizer can significantly improve the irradiation crosslinking efficiency of the material, ensure the crosslinking degree of the material under the compatible irradiation dose, and reduce the damage of the irradiation rays to the main chain of the matrix resin, which can reduce the decrease of the tear resistance caused by the irradiation on one hand, and can reduce the influence of the irradiation on the flame retardant performance on the other hand.

Claims

1. A low-smoke, halogen-free, flame-retardant polyolefin insulation material for high-voltage cables inside vehicles, characterized in that... Raw materials include, by mass fraction: SEBS 30-50 parts, Ethylene-propylene-butene block copolymer elastomer 30-50 parts, Polyethylene grafted maleic anhydride compatibilizer 10-20 parts, Color masterbatch 3-5 parts, Antioxidant 1.5-2.5 parts, Aluminum hydroxide 110-130 parts, Phosphorus-containing silane 1.5-3 parts, Crosslinking agent 1-2 parts, Silicone masterbatch 3-5 parts, Polycarbosilane 3-5 parts; Among them: SEBS, ethylene-propylene-butene block copolymer elastomer and polyethylene grafted maleic anhydride compatibilizer as matrix resin; SEBS is not oil-filled granular; The aluminum hydroxide is in powder form and is modified by phosphorus-containing silane; The crosslinking agent is a multifunctional crosslinking sensitizer, and the functional groups are not less than 2; The polyethylene grafted maleic anhydride compatibilizer is a high-density polyethylene grafted maleic anhydride compatibilizer, and the polyethylene base material is high-density polyethylene.

2. The low smoke zero halogen flame retardant polyolefin insulation compound for in-vehicle high voltage cable according to claim 1, characterized by The crosslinking agent is a 5-functional group structure crosslinking sensitizer, or a 6-functional group structure crosslinking sensitizer.

3. The low-smoke halogen-free flame-retardant polyolefin insulation material for in-vehicle high-voltage cables according to claim 1, characterized in that the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a ratio of 1:1, or a compound of antioxidant 1076 and antioxidant 168 in a ratio of 1:

4.

4. The low smoke zero halogen flame retardant polyolefin insulation compound for in-vehicle high voltage cable according to claim 1, characterized in that The phosphorus-containing silane is 3-(trihydroxysilyl)propyl methyl phosphate or tris(trimethylsilyl) phosphate.

5. A preparation method of the low-smoke halogen-free flame-retardant polyolefin insulation material for in-vehicle high-voltage cables according to any one of claims 1-4, characterized in that first, the raw materials are weighed according to the formula, and then prepared according to the following steps: S1, the aluminum hydroxide powder is modified and surface treated using phosphorus-containing silane; S2, the matrix resin is discharged into a high-speed mixer and mixed uniformly; S3, the material obtained in step S2 is blended and granulated using a large-length-diameter ratio twin-screw extruder; S4, the material obtained in step S3, the material prepared in step S1, and other raw materials are jointly fed into a banbury mixer, and a banbury plus double-stage production granulation process is adopted to prepare the finished product.

6. The preparation method according to claim 5, characterized in that in step S1, the aluminum hydroxide powder is preheated to 80-90°C, and the powder is stirred thoroughly, and the phosphorus-containing silane aerosol is sprayed onto the surface of the powder during the stirring process.

7. The method of claim 5 wherein In step S3, the temperature settings of the twin-screw extruder are as follows: barrel zone one: 120±5°C, barrel zone two: 140±5°C, barrel zone three: 150±5°C, barrel zone four: 160±5°C, barrel zone five: 170±5°C, barrel zone six: 180±5°C, barrel zone seven: 185±5°C, barrel zone eight: 190±5°C, barrel zone nine: 190±5°C, and die head: 190±5°C.

8. The method of claim 5 wherein In the banbury plus double-stage production granulation process of step S4: The temperature of the banbury is 150-160°C, the banbury time is 10-20 min, the discharge temperature is controlled at 150-160°C, and after the banbury is completed, double-cone feeding is carried out at a feeding temperature of 80-90°C; The temperature of each zone of the double screw mixing is: first zone 90-100℃, second zone 90-100℃, third zone 90-100℃, fourth zone 80-90℃, fifth zone 80-90℃, sixth zone 80-90℃, seventh zone 80-90℃, and the rotation speed of the double screw is 180-230rpm; The temperature of each zone of the single screw extrusion is: first zone 95-105℃, second zone 105-115℃, third zone 115-125℃, fourth zone 120-130℃, fifth zone 125-130℃, and the rotation speed of the single screw is 80-100rpm.

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