Temperature-resistant thermoplastic elastomer cable insulation material and preparation method thereof

Abstract

The invention discloses a temperature-resistant thermoplastic elastomer cable insulation material and a preparation method thereof, relates to the field of cable insulation materials, and aims to solve the problems that in the prior art, special equipment is needed for dynamic vulcanization, rubber and plastic combination can cause reduction of softness and plastic processing performance, and the rated working temperature is relatively low. Hydrogenated nitrile rubber and PA12 are used as rubber and plastic base materials, the rated working temperature of a mixture can reach 125 DEG C, a composite vulcanizing agent formed by combining a vulcanizing agent and an accelerant is adopted for accelerating vulcanization, the crosslinking degree is obviously improved, the mobility of the mixture is guaranteed, a dynamic vulcanization process is adopted in the vulcanization process, special crosslinking equipment or vulcanization equipment does not need to be used, and the production cost is reduced. The PIBSA is used for enhancing rubber and plastic combination, and the plasticizer is added for enhancing the plastic processing performance.

Description

Technical Field

[0001] The invention relates to the technical field of cable insulation materials, in particular to a temperature-resistant thermoplastic elastomer cable insulation material and a preparation method thereof. Background Art

[0002] At present, the insulation materials of electric vehicle cables are mainly cross-linked polyolefin or rubber materials. The heat resistance of cross-linked polyolefin can reach up to D grade (cable rated temperature 150℃), but its flexibility cannot meet the needs. Although rubber materials have good flexibility, they usually have poor temperature resistance.

[0003] Thermoplastic elastomers (TPE) have the characteristics of both rubber and thermoplastic materials, and are receiving more and more attention in the insulation materials of cables. If you want to obtain high-performance thermoplastic elastomers that can be used in electric vehicles, the ideal form of the blend is that the rubber phase is dispersed in the form of fine particles in the continuous plastic phase, and the rubber phase is cross-linked to provide good elasticity and softness. In addition, this form should remain unchanged during the processing. Based on the above requirements, this type of elastomer cannot be prepared by ordinary methods such as solution blending, latex blending, etc., but should be prepared by dynamic vulcanization. This special thermoplastic elastomer.

[0004] The cross-linking or vulcanization process is the main way to improve the temperature resistance of cable materials, but the existing technology requires the use of special cross-linking or vulcanization equipment; and in the dynamic vulcanization process of the existing technology, with the increase of cross-linking degree and mixing with nylon, the softness and plastic processing properties of TPV will decrease, which is not conducive to extrusion processing. Summary of the invention

[0005] The present invention aims to provide a temperature-resistant thermoplastic elastomer cable insulation material and a preparation method thereof, which can have the properties of both rubber and thermoplastic materials, can reach a rated temperature of 125°C, and has good heat aging resistance and mechanical strength.

[0006] In order to achieve the above object, the present invention first discloses a temperature-resistant thermoplastic elastomer cable insulation material, and the technical scheme adopted is that the proportion by weight is as follows: 90~110 parts of rubber and plastic base material; Additives: DCP + HVA-2 3~5 parts, antioxidant 0.2~0.4 parts, compatibilizer 1~2 parts; The rubber-plastic base material contains PA12; the compatibilizer is PIBSA (polyisobutylene succinic anhydride).

[0007] PA12 is a very good electrical insulator and its insulation performance will not be affected by moisture. It has good impact resistance and chemical stability. In addition to its advantages of high strength, good toughness, oil resistance, wear resistance, and aging resistance, PA12 is also light, easy to process, and has a thermal decomposition temperature greater than 350°C.

[0008] As a preferred technical solution of the present invention, the rubber-plastic base material also contains nitrile rubber (NBR), and the rubber-plastic ratio is (60-70): (30-40). NBR and PA12 both have polar groups, and the surface energies of the two are matched, so they have good blending compatibility. The thermoplastic elastomer prepared by the dynamic vulcanization process has a special phase structure, and its microstructure is different from that of the thermoplastic elastomer prepared by the polymer synthesis method. Among them, the plastic continuous phase with a small mass fraction is dispersed with vulcanized rubber particles with a large mass fraction. The principle of microscopic phase formation is that when rubber and plastic are blended, the rubber undergoes dynamic vulcanization under high temperature and high shear, so its viscosity and cohesion are very large, while the viscosity of the resin in the molten state is low. In this way, even if the rubber-plastic ratio is high, the system can still form a blend with rubber particles as the dispersed phase and resin as the continuous phase, which has high tensile strength, good wear resistance and excellent solvent resistance, and also has the properties of high elasticity, easy processing and repeated processing.

[0009] As a preferred technical solution of the present invention, the nitrile rubber is AN 31% hydrogenated nitrile rubber.

[0010] As a preferred technical solution of the present invention, the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (ie, antioxidant 1010).

[0011] As a preferred technical solution of the present invention, the auxiliary agent also includes 2 to 3 parts by weight of a plasticizer, and the plasticizer is dioctyl phthalate (DOP).

[0012] As a preferred technical solution of the present invention, the auxiliary agent also includes 1 to 2 parts by mass of ZnO. Zinc oxide can accelerate the vulcanization speed, improve the degree of crosslinking, enhance the hardness and wear resistance of rubber, and make the insulating material have better physical and mechanical properties, such as tear resistance, wear resistance and elasticity.

[0013] The present invention also discloses a method for preparing the above-mentioned temperature-resistant thermoplastic elastomer cable insulation material, and the technical scheme adopted is that the method comprises the following steps: Step 1, after the extruder is preheated, the rubber and plastic base material is added to the first feeding port of the extruder, and the main engine screw drive motor is started at the same time, and the speed of the main engine screw is gradually increased; Step 2: When the main engine screw reaches the speed At the same time, the auxiliary agent is added to the second feeding port, and the speed of the main screw is increased to ; Step 3: After the extruder current meter is stable, increase the speed of the main screw to ; After stabilization for 5 minutes, the material is extruded.

[0014] In the above main engine screw speed, .

[0015] As a preferred technical solution of the present invention, in the step 1, after the extruder is preheated at 160°C for 3 hours, the temperatures of the feeding section, the melting section, and the section from homogenization to the die are respectively heated to 175°C, 180°C, 195°C, 210°C, 215°C, 200°C, and 190°C and maintained for 1 hour.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention adopts the composite form of vulcanizer and accelerator to make the swelling ratio of the rubber-plastic base material reach 0.24, the rubber cross-linking degree is significantly improved, and the mechanical properties and heat resistance of the mixture are effectively improved; by adding an appropriate amount of PIBSA, the maleic anhydride grafted on the PIBSA has anhydride group that can react with the terminal amino group of the TPE plastic phase matrix to produce an integrated branch chain, so that the bonding of rubber and plastic is enhanced, and the cross-linking degree and tensile strength of the rubber-plastic mixture are significantly improved. PA12 in the rubber-plastic base material has good heat resistance itself, so that the working temperature of the mixture meets the requirement of 125°C.

[0017] Furthermore, the vulcanizer is DCP and the accelerator is HVA-2. During the vulcanization process, DCP is first vulcanized with NBR, which triggers the vulcanization of HVA-2 and NBR, and at the same time chemically combines with PA12. NBR and PA12 form a dual-continuous phase structure, which is beneficial to interface compatibility and ensures the fluidity of the mixture. At the same time, the composite form of the vulcanizer and the accelerator can ensure that the degree of crosslinking reaches a sufficiently high level, so that the insulating material has a certain softness and can meet the extrusion requirements. The dynamic vulcanization process in the preparation process does not require the use of special crosslinking equipment or vulcanization equipment; the added plasticizer can increase the plasticity of the insulating material, enhance its flexibility, and facilitate processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a comparison chart of the effects of different vulcanizers on the volume swelling rate of dynamically vulcanized thermoplastic elastomers; Figure 2 This is a comparison chart of the effects of different vulcanizers on the tensile strength of dynamically vulcanized thermoplastic elastomers; Figure 3 This is a comparison chart of the effects of different vulcanizers on the elongation at break of dynamically vulcanized thermoplastic elastomers; Figure 4This is a comparison chart of the effects of different NBR types and different rubber-plastic ratios on the tensile strength of dynamically vulcanized thermoplastic elastomers; Figure 5 This is a comparison chart of the effects of different NBR types and different rubber-plastic ratios on the elongation at break of dynamically vulcanized thermoplastic elastomers; Figure 6 This is a comparison chart of the effects of different plasticizers on the hardness of dynamically vulcanized thermoplastic elastomers; Figure 7 This is a comparison chart of the effects of different plasticizers on the tensile strength of dynamically vulcanized thermoplastic elastomers; Figure 8 This is a comparison chart of the effects of different phase solvents on the hardness of dynamically vulcanized thermoplastic elastomers; Fig. 9 This is a comparison chart of the effects of different phase solvents on the elongation at break of dynamically vulcanized thermoplastic elastomers. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention are described clearly and completely below. 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. Example 1

[0020] The present invention discloses a heat-resistant thermoplastic elastomer cable insulation material, and the technical scheme adopted is that the proportion by weight is as follows: Rubber-plastic base material: HNBR (AN33%) 64 parts, PA12 36 parts; Additives: DCP+HVA-2 3.6 parts, antioxidant 1010 0.3 parts, ZnO 1.3 parts, PIBSA 1.6 parts, DOP 2.7 parts.

[0021] Among them, the usage ratio of DCP and HVA-2 is 0.7:2.9.

[0022] This embodiment also discloses a method for preparing the above-mentioned temperature-resistant thermoplastic elastomer cable insulation material, and the technical solution adopted is, comprising the following steps: Step 1, preheating the twin-screw extruder at 160°C for 3 hours, and then heating the temperature of each section of the feed, melting, and homogenization to the die to 175°C, 180°C, 195°C, 210°C, 215°C, 200°C, and 190°C respectively and maintaining for 1 hour; Step 2, adding the rubber and plastic base material into the first feeding port according to the weight ratio, and starting the main engine screw drive motor at the same time, and gradually increasing the speed of the main engine screw; Step 3, when the speed of the main engine screw reaches 40 rpm, each additive is added at the second feeding port, and the speed of the main engine screw is increased to 85 rpm; Step 4: After the ammeter reading of the twin-screw extruder is stable, adjust the speed of the main screw to 175 rpm and maintain it; after stabilization for 5 minutes, the extruded mixture can be regarded as a mixed insulating material.

[0023] When testing the properties of the rubber compound, the extruded material can be cooled and placed on a flat press, hot pressed at 185°C for 10 minutes to form a sheet, and then cut into the required shape for testing.

[0024] Comparative Example 1: Rubber cable material.

[0025] Comparative Example 2: Existing TPE.

[0026] The rated working temperature (°C), production equipment and main performance of Example 1, Comparative Example 1 and Comparative Example 2 were compared, wherein the main performances included tensile strength (MPa), elongation at break (%) and hardness (Shore A) before and after heat aging. The comparison results are as follows:

[0027] Through the above comparison, it can be seen that although Comparative Example 1 has a higher rated operating temperature and a higher tensile strength before aging, its production equipment is complex, the investment is large, and its hardness is high, and its performance decays seriously after aging; although Comparative Example 2 reduces the equipment investment cost, its rated operating temperature is only up to 100°C at most, the heat resistance is low, and its elongation at break is seriously decayed after aging; Example 1 uses a dynamic vulcanization (TPV) thermoplastic elastomer prepared by a composite vulcanizing agent, and the operating temperature can reach 125°C. No vulcanization processing equipment is required, and ordinary extruders can achieve continuous cable production, thereby improving production efficiency and reducing equipment investment; and Example 1 has better elongation at break and heat aging resistance than Comparative Examples 1 and 2. Although its tensile strength is lower than that of Comparative Examples 1 and 2, it is still much higher than the standard requirement of 10MPa, and as the cable ages, the performance decay of Example 1 is smaller, which is an ideal temperature-resistant and soft cable material for electric vehicles. Example 2

[0028] The difference between this embodiment and embodiment 1 is that: The proportions by weight are as follows: Rubber-plastic base material: HNBR (AN33%) 70 parts, PA12 30 parts; Additives: 3 parts of DCP+HVA-2, 0.4 parts of antioxidant 1010, 1 part of ZnO, 1 part of PIBSA, and 2 parts of DOP. Example 3

[0029] The difference between this embodiment and embodiment 1 is that: The proportions by weight are as follows: Rubber-plastic base material: HNBR (AN33%) 60 parts, PA12 40 parts; Additives: DCP+HVA-2 5 parts, antioxidant 1010 0.2 parts, ZnO 2 parts, PIBSA 2 parts, DOP 3 parts.

[0030] In order to determine the influence of different vulcanizing agents on the final heat-resistant thermoplastic elastomer cable insulation material, a comparative test of different vulcanizing agents was carried out. The sample preparation method was the heat-resistant thermoplastic elastomer cable insulation material preparation method disclosed in Example 1. The sample formula of the comparative test was as follows:

[0031] In the composition of the above samples, the vulcanizing agents are ①SP1045 vulcanizing resin, ②4,4′-dithiodimorpholine (DTDM) and ③DCP+HVA-2 as vulcanizing agents, and 6 groups of formulas of each vulcanizing agent are combined to prepare a total of 18 samples for testing volume swelling rate, tensile strength and elongation at break. The test results are as follows: Figures 1 to 3 As shown in the figure, the test results show that the use of DCP+HVA-2 as a vulcanizing agent can make the dynamically vulcanized thermoplastic elastomer have a lower volume swelling rate, higher tensile strength and higher elongation at break than SP1045 and DTDM.

[0032] In order to determine the influence of different HNBR varieties and HNBR / PA rubber-plastic ratios on the final heat-resistant thermoplastic elastomer cable insulation material, a comparative test of different NBR varieties and NBR / PA rubber-plastic ratios was conducted. The sample preparation method is the heat-resistant thermoplastic elastomer cable insulation material preparation method disclosed in Example 1. The sample formula of the comparative test is as follows:

[0033] Among them, hydrogenated NBR selected HNBR1704, HNBR2707, HNBR3604 and HNBR3606, and 24 samples were prepared with six groups of formulas for tensile strength and elongation at break tests. The tensile strength test results are as follows: Figure 4 The test results of elongation at break are shown in Figure 5As shown in the figure, the test results show that the performance of HNBR3606 nitrile rubber is better than that of HNBR1704, HNBR2707 and HNBR3604. The comparison of rubber-plastic ratio shows that with the decrease of rubber content and the increase of plastic content, the tensile strength and elongation at break both show an upward trend. However, the increase of plastic content will lead to the decrease of elasticity and flexibility of cable insulation material, affecting the flexibility of the final insulated cable.

[0034] In order to explore the influence of different plasticizers on the final heat-resistant thermoplastic elastomer cable insulation material, a comparative test of different plasticizers was carried out. The sample preparation method was the heat-resistant thermoplastic elastomer cable insulation material preparation method disclosed in Example 1. The sample formula of the comparative test was as follows:

[0035] Three different plasticizers were selected: tricresyl phosphate (TCP), dioctyl phthalate (DOP), and dibutyl phthalate (DBP). A total of 18 samples were prepared with the above six formulations for hardness and tensile strength tests. The hardness test results are shown in the figure. Figure 6 The test results of tensile strength are shown in Figure 7 As shown in the figure, the test results show that the hardness of the heat-resistant thermoplastic elastomer cable insulation material samples using DOP is always higher than that of the heat-resistant thermoplastic elastomer cable insulation material samples using TCP and DBP. With the increase of the amount of plasticizer, the hardness of the heat-resistant thermoplastic elastomer cable insulation material shows a downward trend, while the tensile strength shows a trend of first increasing and then decreasing. When the amount of plasticizer is 2~3 parts by weight, the tensile strength is the highest, and the tensile strength of the DOP sample is better than that of the TCP and DBP samples. Therefore, combined with the test results of hardness and tensile strength, it is better to use 2~3 parts by weight of DOP as a plasticizer.

[0036] In order to explore the influence of different plasticizers on the final heat-resistant thermoplastic elastomer cable insulation material, a comparative test of different plasticizers was carried out. The sample preparation method was the heat-resistant thermoplastic elastomer cable insulation material preparation method disclosed in Example 1. The sample formula of the comparative test was as follows:

[0037] The solvents used were ABS-g-MAH, PIBSA and KH-550. Combining the above six formulas, 18 groups of samples were prepared for hardness and elongation at break tests. The hardness test results are as follows: Figure 8 As shown in the test results, it can be seen that with the increase of the amount of solvent, the hardness of the sample shows an upward trend, and too high hardness will lead to a decrease in the flexibility of the cable insulation material. Fig. 9The elongation at break test results shown in the figure show that with the increase in the amount of solvent, the elongation at break shows an upward trend, and the elongation at break of PIBSA samples is generally better than that of ABS-g-MAH and KH-550. Figure 8 , Fig. 9 As shown in the variation trend, a higher elongation at break can be obtained when PIBSA is used as a phase solvent, and when the dosage is 1.5 to 2 parts by weight, not only the elongation at break is greatly improved, but also the hardness increases more slowly. Therefore, it is better to select 1.5 to 2 parts by weight of PIBSA as a phase solvent.

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A temperature-resistant thermoplastic elastomer cable insulation material, characterized in that: The proportions by weight are as follows: 90~110 parts of rubber and plastic base material; Additives: DCP + HVA-2 3~5 parts, antioxidant 0.2~0.4 parts, compatibilizer 1~2 parts; The rubber-plastic base material contains PA12; the compatibilizer is PIBSA.

2. The heat-resistant thermoplastic elastomer cable insulation material according to claim 1, characterized in that: The rubber-plastic base material also contains nitrile rubber, and the rubber-plastic ratio is (60-70): (30-40).

3. The heat-resistant thermoplastic elastomer cable insulation material according to claim 2, characterized in that: The nitrile rubber is AN 31% hydrogenated nitrile rubber.

4. The heat-resistant thermoplastic elastomer cable insulation material according to claim 1, characterized in that: The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

5. The heat-resistant thermoplastic elastomer cable insulation material according to claim 1, characterized in that: The auxiliary agent also includes 2 to 3 parts by weight of a plasticizer, and the plasticizer is dioctyl phthalate.

6. The heat-resistant thermoplastic elastomer cable insulation material according to claim 1, characterized in that: The auxiliary agent also includes 1 to 2 parts by mass of ZnO.

7. A method for preparing a heat-resistant thermoplastic elastomer cable insulation material as claimed in claim 1, characterized in that: The following steps are involved: Step 1, after the extruder is preheated, the rubber and plastic base material is added to the first feeding port of the extruder, and the main engine screw drive motor is started at the same time, and the speed of the main engine screw is gradually increased; Step 2: When the main engine screw speed reaches At the same time, the auxiliary agent is added to the second feeding port, and the speed of the main screw is increased to ; Step 3: After the extruder current meter is stable, increase the speed of the main screw to ; After stabilization for 5 minutes, the material is extruded; In the above main engine screw speed, .

8. The method for preparing a heat-resistant thermoplastic elastomer cable insulation material according to claim 7, characterized in that: In the step 1, after preheating the extruder at 160° C. for 3 hours, the temperatures of the feeding section, melting section, and homogenization section to the die are respectively heated to 175° C., 180° C., 195° C., 210° C., 215° C., 200° C., and 190° C. and maintained for 1 hour before adding the rubber-plastic base material.

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