EBA material for cable shielding material and preparation method thereof

Abstract

The invention provides an EBA material for a cable shielding material and a preparation method of the EBA material. The EBA material is prepared by taking an ethylene-butyl acrylate copolymer as matrix resin, adding a plurality of modifiers and assistants and carrying out blending modification. The EBA cable shielding material prepared by the invention has excellent heat resistance, chemical corrosion resistance, good electrical insulation property and mechanical property and good processability, can effectively improve the shielding effect and prolong the service life of a cable, is suitable for manufacturing shielding layers of various cables, and has a wide market application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of cable material manufacturing, and in particular to an EBA cable shielding material and a preparation method thereof. Background Art

[0002] Traditional cable shielding materials are primarily based on metals such as copper and aluminum. However, these materials have drawbacks such as heavy weight, high cost, and susceptibility to corrosion. With the development of the cable industry, the requirements for cable shielding materials are becoming increasingly stringent. Ethylene-vinyl acetate copolymer (EVA) and other materials have gradually gained a significant share of the base resin market for cable shielding materials due to their excellent polarity, processability, compatibility with carbon black, and low cost.

[0003] However, existing cable materials still face some challenges when used for cable shielding. For example, their tensile strength and environmental stress cracking resistance cannot fully meet the requirements of cable shielding materials in complex operating environments. In addition, most cable shielding materials lack heat resistance and long-term stability under high-voltage conditions, necessitating the development of high-performance alternative matrices.

[0004] Ethylene butyl acrylate (EBA), a thermoplastic elastomer, has excellent low-temperature toughness, high-temperature resistance, and processability, and holds great promise for cable shielding applications. Therefore, developing an EBA composition for cable shielding that overcomes these shortcomings is of great significance. Summary of the Invention

[0005] The present invention aims to provide an EBA material for cable shielding and its preparation method. This material, based on ethylene-butyl acrylate copolymer (EBA) as the base resin and supplemented with conductive fillers, dispersants, and functional additives, addresses the problems of traditional shielding materials, such as poor heat resistance, complex processing, and severe black contamination. This material exhibits excellent heat resistance, mechanical properties, and processing performance, effectively meeting the application requirements of cable shielding materials in various complex environments.

[0006] The invention provides an EBA material for cable shielding material, which comprises the following raw materials in proportion by weight: 5 to 20 parts of conductive filler, 0 to 10 parts of dispersant, 100 parts of ethylene-butyl acrylate copolymer (EBA), 0 to 3 parts of cross-linking agent, 0 to 5 parts of lubricant, and 0 to 2 parts of antioxidant.

[0007] Furthermore, the butyl acrylate content of the ethylene-butyl acrylate copolymer is 10-25 wt%, the melt index is 2.0-10.0 g / 10 min (190° C. / 2.16 kg), the melting point is 85-100° C., the weight average molecular weight is 50,000-100,000, and the molecular weight distribution index is ≤5.

[0008] Furthermore, the melting point T of the ethylene-butyl acrylate copolymer is m And the butyl acrylate content X BA Complies with the following formula: 108-T m =k*X BA , 0.65≤k≤0.95, T m The unit is ℃, X BA The unit is wt%, X BA The value is 10 to 25. The ethylene-butyl acrylate copolymer is produced by an autoclave process, wherein the reaction temperature is 120 to 280°C, the reaction pressure is 1000 to 2800 bar, the mass flow ratio of BA to ethylene is 0.1 to 0.3, and the average residence time of the materials in the reactor is 0.005 to 0.2 h. The preferred reaction temperature is 160 to 260°C, the reaction pressure is 1500 to 2600 bar, and the reaction residence time is 0.01 to 0.08 h. The mass flow ratio of BA to ethylene refers to the ratio of the flow rate of newly added butyl acrylate to the flow rate of newly added ethylene to the reaction system.

[0009] Furthermore, the present invention also provides a method for preparing the EBA material for cable shielding material, which comprises:

[0010] S1. Add the conductive filler and dispersant into the mixer and mix for 5 to 8 minutes;

[0011] S2, adding ethylene-butyl acrylate copolymer (EBA), a crosslinking agent, a lubricant and an antioxidant to the material in S1 in sequence, and mixing for another 8 to 12 minutes;

[0012] S3. Transfer the mixed materials in S2 into a twin-screw extruder, and obtain EBA cable shielding material by extrusion and pelletizing.

[0013] Furthermore, the mixing temperature of S1 and S2 is 90°C to 120°C, and the rotation speed is 60 rpm to 90 rpm. Furthermore, the mixing temperature of S2 is at least 5°C higher than the DSC melting point of the ethylene-butyl acrylate copolymer, preferably at least 10°C higher.

[0014] In the present invention, EBA resin (ethylene-butyl acrylate copolymer) is used as a matrix material to provide basic physical properties and processing properties for the EBA cable shielding material; the addition of conductive fillers significantly improves the conductivity and electromagnetic shielding effectiveness of the composition; the antioxidant can effectively prevent the performance degradation of the composition due to oxidation during processing and use, thereby extending the service life; the lubricant improves the processing fluidity of the composition, allowing the components to be uniformly dispersed and melt-blended during processing; the plasticizer enhances the flexibility and low-temperature performance of the composition, ensuring that the cable shielding material can maintain good mechanical properties under different temperature environments.

[0015] The present invention also provides a method for preparing the aforementioned EBA material, comprising uniformly mixing the components in a suitable proportion, melt-blending them in a twin-screw extruder at high temperature, and extruding and granulating them to produce EBA granules for cable shielding. This method is simple and easy to implement, ensuring that the components are fully dispersed and melt-blended, thereby producing an EBA material with stable performance.

[0016] Compared with the existing technology, the EBA material for cable shielding materials of the present invention has significant advantages in mechanical properties and processing performance, and can effectively solve the shortcomings of existing materials in cable shielding applications, providing a new material with excellent performance and broad application prospects in the field of cable shielding materials. DETAILED DESCRIPTION

[0017] The present invention will be further described and illustrated below in conjunction with specific embodiments. The embodiments are merely illustrative of the present disclosure and do not limit its scope. The technical features of the various embodiments of the present invention may be combined accordingly, provided that there is no conflict between them.

[0018] To address the problems of poor mechanical properties and complex processing of traditional shielding materials, this invention provides an EBA material for cable shielding. Its components include a conductive filler, a dispersant, ethylene-butyl acrylate copolymer (EBA), a crosslinker, a lubricant, and an antioxidant. The formula, by weight, is: 5-20 parts conductive filler, 0-10 parts dispersant, 100 parts ethylene-butyl acrylate copolymer (EBA), 0-3 parts crosslinker, 0-5 parts lubricant, and 0-2 parts antioxidant.

[0019] Among them, according to a preferred embodiment of the present invention, the ethylene-butyl acrylate copolymer (EBA matrix) meets the following requirements: butyl acrylate content is 10-25wt%, melt index is 2.0-10.0g / 10min (190℃ / 2.16Kg), melting point is 80-100℃, weight average molecular weight is 50,000-100,000, and molecular weight distribution is ≤5.

[0020] The melting point T of the ethylene-butyl acrylate copolymer of the present invention is m And the butyl acrylate content X BA Complies with the following formula: 108-T m =k*X BA , 0.65≤k≤0.95, T m The unit is ℃, X BA The unit is wt%, X BAThe value is 10 to 25. By controlling the BA content and melting point in the ethylene-butyl acrylate copolymer matrix resin, that is, the uniformity of the BA unit distribution (reflected by the k value), the thermal stability of the cable shielding material and the dispersion stability of the conductive filler in the EBA matrix can be guaranteed. If the k value is high, the difference in the local entanglement degree of the molecular chain may cause filler migration. The original reason is that the molecular chain structure of conventional EBA is not regular enough; if the k value is low, not only will the melt be unstable during the cable processing due to the lower melting temperature of the EBA matrix, but the thermal decomposition temperature will also be lowered, affecting the cable processing temperature and processing efficiency. Therefore, the present invention strictly controls the k value through the polymerization process to achieve orderly arrangement of the molecular chains.

[0021] The ethylene-butyl acrylate copolymer of the present invention is produced by an autoclave process, wherein the reaction temperature is 120-280°C, the reaction pressure is 1000-2800 bar, the mass flow ratio of BA to ethylene is 0.1-0.3, and the average residence time of the materials in the reactor is 0.005-0.2 h. Preferably, the reaction temperature is 160-260°C, the reaction pressure is 1500-2600 bar, and the reaction residence time is 0.01-0.08. In some preferred laboratory-scale autoclave production of ethylene-butyl acrylate copolymer, the ethylene flow rate is 0.8-1 kg / h and the BA flow rate is 0.15 kg / h. In some preferred industrial-scale equipment, the ethylene flow rate is 2-50 t / h and the BA flow rate is 0.2-5.5 t / h. In the tubular process for producing ethylene-butyl acrylate copolymer in an ethylene-preferred industrial-scale plant, the ethylene flow rate is 10-150 t / h, and the BA flow rate is 0.2-10 t / h. The terms "ethylene flow rate" and "BA flow rate" herein refer to fresh feed, which enters the reactor together with unreacted recycled material from the reactor outlet. It can be assumed that almost all of the fresh feed is polymerized into the ethylene-butyl acrylate copolymer, meaning that the ethylene flow rate and BA flow rate are approximately equal to the ethylene-butyl acrylate copolymer yield.

[0022] According to a preferred embodiment of the present invention, the conductive filler may be one or more of conductive carbon black and nanomaterials; wherein the nanomaterials may be one or more of carbon nanotubes and graphene.

[0023] According to a preferred embodiment of the present invention, the dispersant is polyvinylpyrrolidone (PVP).

[0024] According to a preferred embodiment of the present invention, the cross-linking agent is an organic peroxide with a self-accelerating decomposition temperature ≥70°C, including one or more of di-tert-butyl peroxide (DTBP), tert-butyl isopropyl peroxide (TBCP), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (bis-25), bis(tert-butylperoxyisopropyl)benzene (BIPB), and diisopropyl peroxide (DCP).

[0025] According to a preferred embodiment of the present invention, the lubricant is a high molecular weight polysiloxane, such as E525, P121, etc.

[0026] According to a preferred embodiment of the present invention, the antioxidant is a hindered phenol antioxidant, including one or more of antioxidant 300, antioxidant 1010 and antioxidant 168.

[0027] Example 1:

[0028] An EBA material for cable shielding material comprises the following raw materials in the following proportions by weight: 10 parts of conductive filler, 5 parts of dispersant, 100 parts of ethylene-butyl acrylate copolymer (EBA), 2 parts of crosslinking agent, 2 parts of lubricant, and 1 part of antioxidant.

[0029] In this example, the conductive filler is a mixture of conductive carbon black and graphene, with a mass ratio of 1:1. The conductive carbon black has a purity of ≥99.9%, a fiber diameter of 150-300 nm, a length of 10-20 μm, and a resistivity of ≤0.015 Ω·m. The graphene has a carbon content of ≥99.9% and an average thickness of ≤5 nm. The dispersant is polyvinyl pyrrolidone K90, with a K value of 88-96, a white powder appearance, a melting point of approximately 165°C, and a density of 1.69 g / cm3. 3 Ethylene-butyl acrylate copolymer was prepared by an autoclave method, with a reaction temperature of 170°C, a reaction pressure of 1800 bar, an ethylene flow rate of 0.8 kg / h, a BA flow rate of 0.15 kg / h, and a residence time of the reaction materials in the reactor of 0.05 h. The butyl acrylate content was 20 wt%, the melt index was 5.5 g / 10 min (190°C / 2.16 kg), the melting point was 92°C, the weight-average molecular weight was 75,000, and the molecular weight distribution was 2.85. The crosslinking agent was dicumyl peroxide (DCP), which appeared as a white crystalline powder with a density of 1.02 g / cm 3 The lubricant is lubricant E525, which is a white powder. The antioxidant is antioxidant 1010, which has a melting point of 110-125°C and a density of 1.15 g / cm 3 .

[0030] The following methods are used to describe the analysis and testing of various indicators of EBA matrix and EBA materials:

[0031] 1. Differential Scanning Calorimetry (DSC)

[0032] Equipment: TAQ1000 DSC (equipped with RCS cooling system), nitrogen flow rate 50 mL / min.

[0033] Sample preparation: 5-10 mg of sample was pressed into a thin film and sealed in an aluminum crucible.

[0034] Test procedure:

[0035] The temperature was raised to 150°C at 10°C / min and kept constant for 3 minutes to eliminate the thermal history; the temperature was lowered to -80°C at 10°C / min and the crystallization temperature (Tc) was recorded; the temperature was raised again to 150°C at 10°C / min and the melting temperature (Tm) was recorded.

[0036] GPC testing

[0037] The equipment used was a high-temperature GPC instrument (Polymer Laboratories PL220) with an IR5 infrared detector. The solvent was 1,2,4-trichlorobenzene (containing 200 ppm BHT antioxidant); the flow rate was 1.0 mL / min, and the temperature was 150°C. The chromatographic column was a 3×PLgel 10 μm MIXED-B LS column. Reported parameters: number average molecular weight (M n ), weight average molecular weight (M w ), molecular weight distribution (M w / M n ).

[0038] Melt Index (MI)

[0039] Standard: ASTM D1238 (190°C / 2.16kg).

[0040] Equipment: Melt index meter.

[0041] step:

[0042] Preheat the barrel to 190°C; add the sample and pre-melt for 5 minutes; apply a 2.16 kg weight, cut every 30 seconds, and take the average of 5 cuts. The unit is g / 10 min.

[0043] Tensile properties test

[0044] Standard: GB / T1040.1-2018

[0045] Specimen: dumbbell-shaped specimen, thickness 2 mm.

[0046] Tensile rate: 50 mm / min.

[0047] The following method is used to describe the EBA material preparation:

[0048] Add the conductive filler and dispersant to a mixer and mix at 105°C for 8 minutes. Add EBA, dispersant, crosslinker, lubricant, and antioxidant in sequence, raise the temperature to 120°C, and mix for another 10 minutes. Transfer the mixed materials to a screw extruder for extrusion and pelletization to obtain EBA cable shielding compound.

[0049] Examples 1 to 3 of the present invention and Comparative Examples 4 to 6 all employed the same processing technology, but used different base resins. Example 2 was prepared using an autoclave method, with a reaction temperature of 170°C, a reaction pressure of 1700 bar, an ethylene flow rate of 1 kg / h, a BA flow rate of 0.15 kg / h, and a reaction time of 0.45 h. Example 3 was prepared using an autoclave method, with a reaction temperature of 180°C, a reaction pressure of 1700 bar, an ethylene flow rate of 0.9 kg / h, a BA flow rate of 0.15 kg / h, and a reaction time of 0.6 h.

[0050] The EVA matrix resin (ethylene-vinyl acetate copolymer) used in Comparative Example 4 was the commercially available E156W. The EBA matrix resins used in Comparative Examples 5 and 6 were the commercially available 35BA40 and E2770. The EBA matrix resin specifications used in the Examples and Comparative Examples are shown in Table 1; the synthetic EBA material formula and composition are shown in Table 2; and their performance indicators are shown in Table 3.

[0051] Table 1: EBA matrix resin performance indicators

[0052]

[0053] Table 2: Synthetic EBA material formula and composition

[0054]

[0055] Table 3: EBA material performance indicators

[0056]

[0057]

[0058] As can be seen from Tables 1 to 3, the thermal decomposition temperature of the cable material prepared with EBA as the matrix is ​​much higher than that of the cable material obtained using commercially available EVA matrix resin. When the k value is between 0.65 and 0.95, the BA units are evenly distributed in the molecular chain, forming crystalline regions of uniform size and dense arrangement. As shown in Table 3, the melting point and thermal decomposition temperature of this type of EBA matrix are significantly higher than those of Comparative Examples 2-3. This is because the perfect crystal structure requires higher energy to destroy, which directly improves the heat resistance of the material. In addition, the uniformity of the BA unit distribution (reflected by the k value) ensures the dispersion stability of the conductive filler in the matrix. If the k value is high (such as Comparative Example 2), the difference in the local entanglement degree of the molecular chain may cause filler migration. This shows that the molecular chain structure regularity of conventional EBA is insufficient, while the present invention strictly controls the k value through a specific polymerization process, achieving orderly arrangement of the molecular chain, which is the core prerequisite for improving performance.

[0059] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. Persons skilled in the art will readily appreciate that variations and modifications may be made without departing from the scope of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. An EBA material for cable shielding material, characterized in that: The invention comprises the following raw materials in proportion by weight: 5 to 20 parts of conductive filler, 0 to 10 parts of dispersant, 100 parts of ethylene-butyl acrylate copolymer (EBA), 0 to 3 parts of crosslinking agent, 0 to 5 parts of lubricant, and 0 to 2 parts of antioxidant; the butyl acrylate content of the ethylene-butyl acrylate copolymer is 10 to 25 wt%, the melt index thereof is 2.0 to 10.0 g / 10 min (190° C. / 2.16 kg), the melting point is 85 to 100° C., the weight average molecular weight is 50,000 to 100,000, and the molecular weight distribution index is ≤5.

2. The EBA material for cable shielding material according to claim 1, characterized in that: The ethylene-butyl acrylate copolymer meets the following conditions: (1) Melting point T of ethylene-butyl acrylate copolymer m And the butyl acrylate content X BA Complies with the following formula: 108-T m =k*X BA , 0.65≤k≤0.95, T m The unit is ℃, X BA The unit is wt%, X BA The value is 10 to 25. (2) Ethylene-butyl acrylate copolymer is produced by an autoclave method, wherein the reaction temperature is 120-280°C, the reaction pressure is 1000-2800 bar, the mass flow rate ratio of BA to ethylene is 0.1-0.3, and the average residence time of the materials in the reactor is 0.005-0.2 h; preferably, the reaction temperature is 160-260°C, the reaction pressure is 1500-2600 bar, and the reaction residence time is 0.01-0.08 h.

3. The EBA material for cable shielding material according to claim 1, characterized in that: The conductive filler is one or more of conductive carbon black and nanomaterials; wherein the nanomaterials are one or more of carbon nanotubes and graphene.

4. The EBA material for cable shielding material according to claim 1, characterized in that: The dispersant is polyvinylpyrrolidone (PVP).

5. The EBA material for cable shielding material according to claim 1, characterized in that: The cross-linking agent is an organic peroxide with a self-accelerating decomposition temperature of ≥70°C, including one or more of di-tert-butyl peroxide (DTBP), tert-butyl isopropyl peroxide (TBCP), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (bis-25), bis(tert-butylperoxyisopropyl)benzene (BIPB), and diisopropylbenzene peroxide (DCP).

6. The EBA material for cable shielding material according to claim 1, characterized in that: The lubricant is high molecular weight polysiloxane.

7. The EBA material for cable shielding material according to claim 1, characterized in that: The antioxidant is a hindered phenol antioxidant, including one or more of antioxidant 300, antioxidant 1010 and antioxidant 168.

8. A method for preparing the EBA material for cable shielding material according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Add the conductive filler and dispersant into the mixer and mix for 5 to 8 minutes; S2, adding ethylene-butyl acrylate copolymer (EBA), a crosslinking agent, a lubricant and an antioxidant to the material in S1 in sequence, and mixing for another 8 to 12 minutes; S3. Transfer the mixed materials in S2 into a twin-screw extruder, and obtain EBA cable shielding material by extrusion and pelletizing.

9. The preparation method according to claim 8, characterized in that The mixing temperature of S1 and S2 is 90°C to 120°C, and the rotation speed is 60rpm to 90rpm.

10. The preparation method according to claim 9, characterized in that The mixing temperature of S2 is at least 5°C higher than the DSC melting point of the ethylene-butyl acrylate copolymer, preferably at least 10°C higher.

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