PVC (polyvinyl chloride) base material for high-voltage cable insulating layer and preparation method of PVC base material

Abstract

The invention relates to a PVC base material for a high-voltage cable insulating layer and a preparation method of the PVC base material. The PVC base material comprises 15-20 parts of polyvinyl chloride; 25 to 30 parts of an ethylene-vinyl acetate copolymer; 40 parts of superfine calcium carbonate; 10-15 parts of a plasticizer; 0.5 to 1 part of a coupling agent; 1-2 parts of silicon fluorine rubber; 0.1 to 0.5 part of an antioxidant; 1 to 1.5 parts of a lubricant; and 0.1 to 0.5 part of a stabilizing agent. The high-voltage insulation performance of the PVC cable can be improved, the PVC cable is prevented from being broken down in a high-voltage state, meanwhile, the problem of insulation thermal aging of the cable is solved, the service life of the cable insulation layer is prolonged, and the loss of manpower and financial resources is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of cable materials, and in particular to a PVC substrate for a high-voltage cable insulation layer and a preparation method thereof. Background Art

[0002] The insulation layer of the cable plays the role of isolating the multi-core conductors and the conductors from the sheath, and ensures a certain electrical withstand voltage. Generally, the insulation layer should have a certain heat resistance and stable insulation quality.

[0003] The thickness of the insulation layer is related to the working voltage. Generally speaking, the higher the voltage level, the thicker the insulation layer, but it is not proportional. Because from the perspective of electric field strength, the thickness of the insulation layer can be thinner when the conductor cross-sectional area of ​​the cable of the same voltage level is large. For cables with lower voltage levels, especially oil-impregnated paper insulated cables with lower voltage levels, in order to ensure that the paper layer has a certain mechanical strength when the cable is bent, the thickness of the insulation layer is thickened as the conductor cross-sectional area increases.

[0004] The insulation layer materials are mainly oil-impregnated cable paper, plastic and rubber. According to the different materials used for the conductor insulation layer, cables are mainly divided into plastic insulated cables, rubber insulated cables and oil-impregnated paper insulated cables.

[0005] In power cables with extruded plastic insulation, commonly used plastics include polyvinyl chloride (PVC), polyethylene, and cross-linked polyethylene (XLPE). Among them, PVC is still widely used in low-voltage cables due to its convenient process, good comprehensive electromechanical properties, good flame retardant properties, and low cost. Polyethylene is widely used in cable insulation and outdoor cable sheaths due to its excellent electrical properties, moisture resistance, cold resistance, and moderate mechanical properties, while cross-linked polyethylene is widely used in the insulation of medium and high voltage cables due to its excellent electrical and mechanical properties. Polypropylene is often used in the insulation of communication cables and oil well cables due to its superior electrical properties, good high temperature resistance, and oil resistance. It is also the preferred insulation material for telephone and computer cords.

[0006] However, the existing PVC cables have poor high-voltage insulation performance and are prone to breakdown under high voltage conditions. At the same time, there are defects in cable insulation thermal aging, which makes it difficult to meet service life requirements.

[0007] Therefore, how to solve the above-mentioned deficiencies in the prior art has become a subject to be studied and solved by the present invention. Summary of the invention

[0008] The purpose of the present invention is to provide a PVC substrate for a high-voltage cable insulation layer and a preparation method thereof.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A PVC substrate for a high-voltage cable insulation layer comprises the following components in parts by weight:

[0011] 15-20 parts of polyvinyl chloride;

[0012] 25-30 parts of ethylene-vinyl acetate copolymer;

[0013] 40 parts of superfine calcium carbonate;

[0014] 10-15 parts of plasticizer;

[0015] Coupling agent 0.5-1 part;

[0016] 1-2 parts of silicone fluororubber;

[0017] 0.1-0.5 parts of antioxidant;

[0018] 1 to 1.5 parts of lubricant;

[0019] Stabilizer 0.1-0.5 parts.

[0020] In a further technical solution, the polyvinyl chloride is an amorphous polymer containing a small amount of crystalline structure, and the side group contains a polar group chlorine atom. The polyvinyl chloride has excellent electrical insulation properties and is widely used in low-voltage wires and cables.

[0021] In a further technical solution, the ethylene-vinyl acetate copolymer is formed by graft copolymerization of ethylene and vinyl acetate, the main chain contains a polar group acetate group, and the content of vinyl acetate is higher than 20%, thereby reducing the crystallinity and improving the flexibility and impact resistance. And because of the presence of vinyl acetate, the copolymer can have better tolerance and cross-linking, and has a high decomposition temperature of 230°C, so it can better assist polyvinyl chloride in this system and improve the insulation performance of the PVC substrate under high voltage.

[0022] In a further technical solution, the particle size of the ultrafine calcium carbonate is 0.02 to 0.1 μm. Ultrafine calcium carbonate has special quantum size effect, small size effect, and surface effect, which can make the material have better reinforcement and dispersibility, so it has obvious beneficial effects in increasing the volume of plastic products, reducing costs, improving stability, hardness and steelness, improving the processing performance of plastics, improving its heat resistance, improving the astigmatism, scratch resistance, smoothness of plastics, and toughening effect on notch impact strength and viscosity during mixing.

[0023] In a further technical solution, the plasticizer is selected from any one of phthalates, aliphatic dibasic acid esters, phosphates, epoxy compounds, polyesters, and alkylbenzene sulfonates to improve the hardness and strength of the material. In order to increase the plasticity and strength of the PVC substrate, phthalates can be added. The main function of the plasticizer is to weaken the secondary bonds between resin molecules, increase the mobility of resin molecular bonds, reduce the crystallinity of resin molecules, increase the plasticity of resin molecules, enhance their flexibility, and facilitate processing.

[0024] A further technical solution is that the coupling agent is propyl dioleate acyloxy titanate. The biggest feature of the molecular structure of the coupling agent is that it contains two groups with different chemical properties in the molecule, one is an inorganic-philic group, which is easy to react chemically with the surface of inorganic substances; the other is an organic-philic group, which can react chemically with synthetic resins or other polymers or generate hydrogen bonds and dissolve therein, so as to improve the interface between inorganic and organic substances, thereby greatly improving the performance of the composite material.

[0025] According to a further technical solution, the main chain of the silicone-fluororubber contains silicon-oxygen bonds, and the side groups contain fluorine atoms.

[0026] In a further technical solution, the antioxidant is a mixture of one or more of tris[2,4-di-tert-butylphenyl phosphite, bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, and pentaerythritol tetrakis(3-laurylthiopropionate). It is used to improve the anti-aging performance of the wire in later use.

[0027] In a further technical solution, the stabilizer is a mixture of one or more of 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, so as to improve the anti-aging performance of the wire in later use.

[0028] In a further technical solution, the lubricant is polyethylene wax or silicone masterbatch. On the one hand, it can reduce the generation of eye mold residue during extrusion, and on the other hand, it can improve the surface effect of the finished wire in the later stage, making it smoother and more wear-resistant.

[0029] Furthermore, the present invention also discloses a method for preparing a PVC substrate for a high-voltage cable insulation layer, the steps comprising:

[0030] Step 1: Prepare ingredients according to the following weight proportions: 15-20 parts of polyvinyl chloride; 25-30 parts of ethylene-vinyl acetate copolymer; 40 parts of ultrafine calcium carbonate; 10-15 parts of plasticizer; 0.5-1 part of coupling agent; 1-2 parts of silicone fluororubber; 0.1-0.5 parts of antioxidant; 1-1.5 parts of lubricant; 0.1-0.5 parts of stabilizer;

[0031] Step 2: placing the polyvinyl chloride resin and the plasticizer (DOP) in a high-speed mixer, stirring at 80-90° C. at a speed of 40 Hz for 5-10 min to obtain a first mixture;

[0032] The ultrafine calcium carbonate and the coupling agent (KR-TTS) are placed in a high-speed mixer, and stirred at 80 to 90° C. and 25 Hz for 20 to 30 minutes to obtain a second mixture;

[0033] The silicone fluororubber is placed in a crusher for crushing and kneading to obtain a silicone fluororubber powder with a particle size of less than 300 μm;

[0034] Step 3: Place the first mixture, the second mixture, the silicone fluororubber powder, the ethylene-vinyl acetate copolymer and various additives in a high-speed mixer and stir at a speed of 60 Hz for 5 to 10 minutes to disperse them evenly to obtain a mixed material;

[0035] The fourth step is to extrude the mixed material through a twin-screw extruder, the L / D ratio of the extruder is 20:1, the extrusion temperature is 165-185° C., and the screw speed is 60-80 r / min.

[0036] The terms “include,” “including,” “have,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] The terms used herein generally have the ordinary meanings of each term used in the art, in the context of the present invention, and in the specific context, unless otherwise noted. Certain terms used to describe the present invention will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art regarding the description of the present invention.

[0038] The working principle and advantages of the present invention are as follows:

[0039] The existing PVC wires are difficult to extrude due to their small melt index and poor fluidity. At the same time, the processability and insulation performance lead to low tensile strength and elasticity, as well as reduced insulation performance under high voltage. The present invention provides a PVC substrate for the insulation layer of a high-voltage cable. By modifying ultrafine calcium carbonate with a coupling agent, the volume of the plastic product is increased, the cost is reduced, the stability, hardness and rigidity are improved, the processing performance of the plastic is improved, the heat resistance is improved, and the astigmatism, scratch resistance, smoothness of the plastic, the toughening effect on the notch impact strength, and the viscosity during the mixing process are significantly improved;

[0040] By pre-blending polyvinyl chloride resin with plasticizer, the plasticizer increases the plasticity of the PVC substrate and improves its strength, weakens the secondary bonds between PVC resin molecules, increases the mobility of resin molecular bonds, reduces the crystallinity of resin molecules, increases the plasticity of resin molecules, enhances its flexibility, and makes it easier to process;

[0041] By introducing ethylene-vinyl acetate copolymer into the system, the crystallinity is reduced, and the flexibility and impact resistance are improved. Because the copolymer contains vinyl acetate, the copolymer has better tolerance and cross-linking, and the copolymer has a high decomposition temperature of 230°C. Therefore, it can better assist polyvinyl chloride in the system and improve the insulation performance of PVC substrate under high voltage;

[0042] By adding various antioxidants and stabilizer additives, it can prevent the heat resistance and high-voltage insulation of the wire from being greatly reduced due to factors such as thermal aging when the wire is used for a long time in the natural environment;

[0043] By adding high-temperature resistant silicone-fluorine auxiliary materials, hard materials and plastic components and adopting co-extrusion for modification, the homogeneity of the material and its fusion with PVC are improved, so as to improve the hardness and tensile strength of the sheath. Under the premise of achieving smooth winding, the elasticity of the material itself is increased, which makes it easier to control the cutting force and the end clamping force, ensure the quality of the joint and improve the success rate of the connection.

[0044] Compared with the prior art, the PVC-based material for a high-voltage cable insulation layer and the preparation method thereof of the present invention have the following beneficial effects:

[0045] 1. The present invention adopts the method of coupling agent modification of calcium carbonate, which increases the volume of plastic products, reduces costs, improves stability, hardness and rigidity, improves the processing performance of plastics, improves heat resistance, and has obvious beneficial effects on improving the astigmatism, scratch resistance, smoothness and toughening effect of notch impact strength of plastics and viscosity during mixing.

[0046] Second, the present invention adds ethylene-vinyl acetate copolymer, which reduces crystallinity, improves flexibility and impact resistance. Compared with the same industry, the copolymer contains vinyl acetate, which can make the copolymer have better tolerance and cross-linking, and the copolymer has a high decomposition temperature of 230°C, so it can better assist polyvinyl chloride in the system and improve the insulation performance of PVC substrate under high voltage. Finally, various antioxidants and stabilizer additives are added to prevent the heat resistance and high-voltage insulation of the wire from being greatly reduced due to factors such as thermal aging when the wire is used for a long time in the natural environment.

[0047] 3. The present invention adopts the method of pre-blending plasticizer with polyvinyl chloride to increase the plasticity and strength of the PVC substrate, weaken the secondary bonds between PVC resin molecules, increase the mobility of resin molecular bonds, reduce the crystallinity of resin molecules, increase the plasticity of resin molecules, enhance its flexibility, and facilitate processing.

[0048] Fourth, compared with the simple use of titanate cross-linking, the addition of silicone fluororubber in the present invention can optimize and improve the toughness and tensile strength of the material, while also improving the power transmission and current interception capabilities and the wear resistance.

[0049] In summary: the present invention improves the processing performance of PVC wire through the above modification, improves its heat resistance, improves the astigmatism, scratch resistance and smoothness of PVC, and has obvious effects on the toughening effect of notch impact strength and viscosity during mixing; the crystallinity is reduced, the flexibility and impact resistance are improved, and the copolymer has better tolerance and cross-linking due to the presence of vinyl acetate in the copolymer, and the copolymer has a high decomposition temperature of 230°C, so it can better assist polyvinyl chloride in the system and improve the insulation performance of PVC substrate under high voltage. Finally, various antioxidants and stabilizer additives are added to prevent the heat resistance and high-voltage insulation of the wire from being greatly reduced due to factors such as thermal aging when the wire is used for a long time in the natural environment in the later stage. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with embodiments:

[0051] The present invention will be described in detail below. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the techniques taught by the present invention without departing from the spirit and scope of the present invention.

[0052] The terms used herein are only for describing specific embodiments and are not intended to be limiting of the present invention. Singular forms such as "a", "this", "here", "this" and "the" as used herein also include plural forms.

[0053] Embodiments 1 to 6:

[0054] A PVC substrate for a high-voltage cable insulation layer is prepared by using different proportions of the following raw materials: 15-20 parts of polyvinyl chloride, 25-30 parts of ethylene-vinyl acetate copolymer, 40 parts of ultrafine calcium carbonate, 10-15 parts of plasticizer, 0.5-1 part of coupling agent, 1-2 parts of silicone fluororubber, 0.1-0.5 part of antioxidant, 1-1.5 parts of lubricant and 0.1-0.5 part of stabilizer.

[0055] The specific steps of the manufacturing process of the above embodiment are as follows:

[0056] Prepare the materials and mix them according to the following mass components: 15-20 parts of polyvinyl chloride, 25-30 parts of ethylene-vinyl acetate copolymer, 40 parts of ultrafine calcium carbonate, 10-15 parts of plasticizer, 0.5-1 part of coupling agent, 1-2 parts of silicone fluororubber, 0.1-0.5 parts of antioxidant, 1-1.5 parts of lubricant, and 0.1-0.5 parts of stabilizer.

[0057] Blending: Place 15-20 parts of polyvinyl chloride resin and 10-15 parts of plasticizer (DOP) in a high-speed mixer, stir thoroughly at 80-90°C for 5-10 minutes and then pour out.

[0058] Modify and stir, place the ultrafine calcium carbonate and coupling agent (KR-TTS) in a high-speed mixer, and stir thoroughly at 80-90°C for 20-30 minutes.

[0059] 1-2 parts of silicone fluororubber are placed in a crusher for crushing and kneading to obtain uniform powder less than 300um.

[0060] Stirring, place the mixture stirred in the second step, ethylene-vinyl acetate copolymer and various additives together in the mixer in the third step, and stir them fully for 5 to 10 minutes to make them evenly dispersed.

[0061] Extrusion granulation: extrude the stirred material on a twin-screw extruder with an L / D ratio of 20:1, a barrel temperature of 165-185°C, and a screw speed of 60-80 r / min.

[0062] Comparative Examples 1 and 2 were prepared by referring to the preparation method of the above embodiment.

[0063] The component tables of Examples 1 to 6 and Comparative Examples 1 and 2 are shown in Table 1.

[0064]

[0065] Table 1

[0066] As can be seen from Table 1, the wires prepared in Examples 1 to 6 have a thickness of 2 mm, a Shore hardness of 90 to 95 A, a tensile strength of 45 to 47 Map, an elongation of 100 to 200%, a heat shrinkage rate of <1, and a temperature resistance level of -40 to 125°C.

[0067] The wires prepared in Examples 1 to 6 have high hardness, are not easily deformed by force during cutting and terminal clamping, and are easy to grasp the cutting force and terminal clamping force, reducing the number of repeated cutting or repeated joints, saving construction costs; in addition, the wire joints are not easily deformed, and when the insulating layer ends are clamped, the internal copper wires will not be greatly squeezed, the performance of the wires will not be damaged, and the success rate of connection will be improved. In addition, the wires have high strength, and are very wear-resistant, high-temperature-resistant, water-proof, anti-corrosive, insect-proof, and rodent-proof, and have a longer service life. The wires have high hardness, high tensile strength, better protection, and are suitable for use in various electronic devices.

[0068] Embodiments 1 to 6 mainly adjust the ratio of components between the schemes, and adjust the hardness, electrical insulation, strength and elongation of the wire, but the overall direction is consistent, which is to improve the later performance of the wire and the smoothness of extrusion processing under the premise of better appearance effect.

[0069] Comparative Examples 1 and 2 lack some key components of the present invention. Among them, Comparative Example 1 lacks silicone fluororubber, so its tensile strength and elongation at break are significantly reduced, and the wire surface is prone to scratches during the friction and dragging of the wire, and it is not wear-resistant, lacking the toughness, tensile resistance, and wear resistance of silicone fluororubber itself. Comparative Example 2 lacks the coupling agent modification processing, resulting in poor stickiness of the dough during mixing and extrusion, dryness, and glue breakage, and continuous pellets appearing when pelletizing on the die surface, affecting the entire plasticization process, so the tensile strength and elongation at break also decline significantly.

[0070] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A PVC substrate for a high voltage cable insulation layer, characterized in that: The composition comprises the following parts by weight: 15-20 parts of polyvinyl chloride; 25-30 parts of ethylene-vinyl acetate copolymer; 40 parts of superfine calcium carbonate; Plasticizer 10~15 parts; Coupling agent 0.5~1 part; 1~2 parts of silicone fluororubber; Antioxidant 0.1~0.5 parts; 1~1.5 parts of lubricant; Stabilizer 0.1~0.5 parts.

2. The PVC substrate for a high-voltage cable insulation layer according to claim 1, characterized in that: The polyvinyl chloride is an amorphous polymer containing a small amount of crystalline structure, and the side group contains a polar group chlorine atom.

3. The PVC substrate for a high voltage cable insulation layer according to claim 1, characterized in that: The ethylene-vinyl acetate copolymer is formed by graft copolymerization of ethylene and vinyl acetate, and the content of vinyl acetate is higher than 20%.

4. The PVC substrate for a high-voltage cable insulation layer according to claim 1, characterized in that: The particle size of the ultrafine calcium carbonate is 0.02-0.1 μm.

5. The PVC substrate for high voltage cable insulation layer according to claim 1, characterized in that: The plasticizer is selected from any one of phthalates, aliphatic dibasic acid esters, phosphates, epoxy compounds, polyesters, and alkylbenzene sulfonates.

6. The PVC substrate for a high voltage cable insulation layer according to claim 1, characterized in that: The coupling agent is propyl dioleyl titanate.

7. The PVC substrate for high voltage cable insulation layer according to claim 1, characterized in that: The main chain of the silicone fluororubber contains silicon-oxygen bonds, and the side groups contain fluorine atoms.

8. The PVC substrate for high voltage cable insulation layer according to claim 1, characterized in that: The antioxidant is a mixture of one or more of tris[2,4-di-tert-butylphenyl phosphite, bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine, and pentaerythritol tetrakis(3-laurylthiopropionate).

9. The PVC substrate for a high voltage cable insulation layer according to claim 1, characterized in that: The stabilizer is a mixture of one or more of 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole.

10. The PVC substrate for high voltage cable insulation layer according to claim 1, characterized in that: The lubricant is polyethylene wax or silicone masterbatch.

11. A method for preparing a PVC substrate for a high-voltage cable insulation layer, for preparing a PVC substrate for a high-voltage cable insulation layer according to any one of claims 1 to 10, characterized in that: The steps of the preparation method include: Step 1: Prepare the ingredients according to the following weight proportions: 15-20 parts of polyvinyl chloride; 25-30 parts of ethylene-vinyl acetate copolymer; 40 parts of ultrafine calcium carbonate; 10-15 parts of plasticizer; 0.5-1 parts of coupling agent; 1-2 parts of silicone fluororubber; 0.1-0.5 parts of antioxidant; 1-1.5 parts of lubricant; 0.1-0.5 parts of stabilizer; Step 2: placing the polyvinyl chloride resin and the plasticizer in a high-speed mixer, stirring at 80-90° C. and 40 Hz for 5-10 min to obtain a first mixture; placing the ultrafine calcium carbonate and the coupling agent in a high-speed mixer, and stirring at 80-90° C. and 25 Hz for 20-30 min to obtain a second mixture; The silicone fluororubber is placed in a crusher for crushing and kneading to obtain a silicone fluororubber powder with a particle size of less than 300 μm; Step 3: Place the first mixture, the second mixture, the silicone fluororubber powder, the ethylene-vinyl acetate copolymer and various additives in a high-speed mixer and stir at a speed of 60 Hz for 5 to 10 minutes to disperse them evenly to obtain a mixed material; The fourth step is to extrude the mixed material through a twin-screw extruder, the L / D ratio of the extruder is 20:1, the extrusion temperature is 165-185°C, and the screw speed is 60-80r / min.

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