Sheath material for high-flexibility robot cable and preparation method of sheath material

Abstract

The invention discloses a sheath material for a high-flexibility robot cable, and the sheath material comprises the following components in parts by mass: 100 parts of polyvinyl chloride resin; 15-20 parts of nitrile rubber; 50 to 70 parts of trioctyl trimellitate; 6 to 10 parts of epoxidized soybean oil; 10 to 20 parts of gas phase method nanometer white carbon black; 5-10 parts of a composite stabilizer; 10 to 15 parts of an environment-friendly flame retardant Sb2O3; 5 to 10 parts of a phosphorus-nitrogen intumescent flame retardant; 5 to 10 parts of flame-retardant graphite; 0.3 to 0.5 part of an antioxidant; 0.3 to 0.5 part of an ultraviolet light absorber; 0.4 to 0.6 part of a light stabilizer; 0.4 to 0.6 part of PE (Poly Ethylene) wax; the invention has the following beneficial effects: nitrile butadiene rubber (NBR) and PVC are blended to form a sea-island phase structure, so the brittleness resistance, oil resistance and low temperature resistance of the material are significantly improved, and the material is suitable for high-frequency motion scenes of robots; the addition of the gas-phase nano white carbon black enhances the reinforcing effect, the tensile strength before aging reaches 2.52 kgf / cm < 2 >, and the elongation at break is 350%, which far exceeds the industrial standard.

Description

Technical Field

[0001] The present invention relates to a flexible cable material, and in particular to a sheathing material for a highly flexible robot cable and a preparation method thereof. Background Art

[0002] As an important component for transmitting power and control signals, the flexible cable for industrial robots must have performance suitable for the operation of industrial robots to meet the usage requirements. The technical requirements for flexible cables for industrial robots are different from those of ordinary flexible cables, which are determined by factors such as the usage environment, special movement mode, and working intensity of industrial robots.

[0003] PVC resin has excellent comprehensive performance and low price, so it has been favored by people since its inception. However, the disadvantages that PVC is prone to decomposition when heated, has poor toughness, and poor high and low temperature resistance also greatly limit its development in robot cables.

[0004] At present, the main solution is to blend PVC with other elastomers to make up for its performance deficiencies. However, although the blended materials meet the requirements in terms of usage performance, due to the lack of selection of blended materials and blending process, the compatibility of the blended materials is poor, the surface is rough during cable extrusion, and at the same time, due to the melting point difference of the blended materials, phenomena such as bumps and pits appear on the surface, and due to poor plasticization of the blended materials, the surface of the wire in the robot cable cracks during long-term movement; when used outdoors, since the PVC material itself is not resistant to light aging, the surface cracks after long-term ultraviolet irradiation, and the service life of the cable is greatly reduced. When the robot cable is used in a low-temperature environment, due to the poor low-temperature performance of the PVC material, the outer sheath of the cable cracks or even breaks.

[0005] Therefore, it is necessary to develop a sheathing material for a highly flexible robot cable and a preparation method thereof. After searching, no technical solution identical to the present invention has been found. Summary of the Invention

[0006] The main technical problem to be solved by the present invention is to provide a sheathing material for a highly flexible robot cable and a preparation method thereof, so as to solve one or more of the above-mentioned existing technical problems.

[0007] To solve the above technical problems, a technical solution adopted by the present invention is: a sheathing material for a highly flexible robot cable, and its innovation lies in: by mass parts, it includes the following components: 100 parts of polyvinyl chloride (PVC) resin; 15-20 parts of nitrile rubber (NBR); 50-70 parts of trioctyl trimellitate (TOTM); 6-10 parts of epoxy soybean oil; 10-20 parts of fumed nano-silica; 5-10 parts of composite stabilizer; 10-15 parts of environmentally friendly flame retardant Sb2O3; 5-10 parts of phosphorus-nitrogen intumescent flame retardant; 5-10 parts of flame retardant graphite; 0.3-0.5 parts of antioxidant; 0.3-0.5 parts of ultraviolet absorber; 0.4-0.6 parts of light stabilizer; 0.4-0.6 parts of PE wax;

[0008] Among them, the nitrile rubber is blended with PVC to form a sea-island phase structure, the flame retardant graphite and the phosphorus-nitrogen intumescent flame retardant act synergistically to form a honeycomb carbon isolation layer, the combination of TOTM and epoxy soybean oil provides heat resistance and low volatility, and the temperature resistance grade of the sheathing material reaches above 105°C, and the double-screw extrusion process is used to ensure uniform plasticization of the material.

[0009] In some embodiments, the composite stabilizer is a calcium-zinc composite stabilizer.

[0010] In some embodiments, the particle size of the flame retardant graphite is 1-5 μm, and the weight ratio with the phosphorus-nitrogen intumescent flame retardant is 1:1-2:1.

[0011] In some embodiments, the number of cracks in the sheathing material during the low-temperature impact embrittlement test at -40°C is 0 / 30, and the 3D torsion times of the finished cable are ≥18 million times.

[0012] In some embodiments, the heat loss of the sheathing material is ≤0.5 mg / cm 2 。

[0013] A preparation method of a sheathing material for a highly flexible robot cable, characterized by including the following steps:

[0014] (1) Premixing: Add PVC resin, TOTM, epoxy soybean oil, fumed nano-silica, composite stabilizer, and antioxidant into a high-speed mixer, and mix at a temperature of 70-80°C and a rotation speed of 800-1000 rpm for 4-6 minutes; then add environmentally friendly flame retardant Sb2O3, phosphorus-nitrogen intumescent flame retardant, flame retardant graphite, ultraviolet absorber, light stabilizer, and PE wax, and continue to mix for 6-12 minutes;

[0015] (2) Kneading: Add the mixture obtained in step (1) into a kneader, knead at 120°C for 2-3 minutes, then add nitrile rubber, raise the temperature to 135°C and knead for 4-6 minutes to fully fuse the nitrile rubber and PVC and form chemical bonds;

[0016] (3) Twin-screw extrusion: The kneaded material is extruded through a twin-screw extruder with a length-diameter ratio of 40:1. The temperatures of each temperature zone are 170 °C, 180 °C, 190 °C, 190 °C, 195 °C, 195 °C, 200 °C, 200 °C, 195 °C, and 190 °C in sequence. The vacuum degree is controlled at -0.08 MPa to suck out volatile gases.

[0017] (4) Single-screw plasticization: The rubber compound after twin-screw extrusion is further plasticized through a single-screw extruder. The temperatures of each zone are 140 - 150 °C in zone 1, 160 - 170 °C in zone 2, and 180 - 190 °C in zone 3, and finally granulated and encapsulated.

[0018] In some embodiments, the vacuum suction pressure of the twin-screw extruder is -0.08 to -0.10 MPa, and the vacuum suction continues until the material is completely extruded.

[0019] In some embodiments, the antioxidant, ultraviolet absorber, and light stabilizer described in step (1) are added within the last 6 minutes of the premixing stage.

[0020] In some embodiments, the temperature gradient of each zone of the single-screw extruder is 10 - 20 °C / zone, and the extrusion pressure is 5 - 10 MPa.

[0021] In some embodiments, the combined process of the twin-screw extruder and the single-screw extruder makes the surface roughness of the cable ≤ 0.1 μm, and there are no pockmarks and bump defects.

[0022] The beneficial effects of the present invention are as follows: Excellent flexibility and mechanical properties: Through the blending of nitrile rubber (NBR) and PVC, a "sea-island phase structure" is formed, significantly improving the anti-brittleness, oil resistance, and low-temperature resistance of the material (the number of ruptures in the -40 °C impact test is 0 / 30), and it is suitable for high-frequency motion scenarios of robots.

[0023] The addition of fumed nano-silica enhances the reinforcing effect. The tensile strength before aging reaches 2.52 kgf / cm 2 , and the elongation at break is 350%, far exceeding the industry standard (UL1581).

[0024] Efficient flame retardancy and thermal stability: The synergistic effect of the environmental-friendly flame retardant Sb2O3, phosphorus-nitrogen intumescent flame retardant, and flame-retardant graphite forms a honeycomb-like carbon isolation layer, and the flame retardancy reaches V-0 level (UL94), effectively preventing dripping and flame spread.

[0025] The combination of TOTM and epoxidized soybean oil provides low volatility and heat resistance. With the cooperation of a composite stabilizer (such as calcium-zinc stabilizer), the temperature resistance grade is increased to 105 °C, and the temperature at which the weight loss is 5% reaches 303.1 °C (verified by TG curve).

[0026] Long - term durability and environmental adaptability: Excellent anti - aging performance (tensile strength retention rate ≥ 82% after aging at 136℃ for 168h), and no surface cracks after 720 - hour UV test, suitable for outdoor complex environments.

[0027] Outstanding oil - resistance performance (tensile strength retention rate ≥ 78% after 96h in IRM902 oil), meeting the working condition requirements of industrial robots in long - term contact with oil stains.

[0028] Optimized preparation process and surface quality: Twin - screw + single - screw combined extrusion process (length - diameter ratio 40:1, vacuum suction - 0.08MPa), ensuring uniform plasticization of materials, eliminating defects such as pitting and lumps (SEM shows smooth cross - section, roughness ≤ 0.1μm).

[0029] Precise control of process parameters (such as internal mixer temperature 135℃, gradient temperature zone design), improving production efficiency and product consistency.

[0030] Environmental protection and safety: Using low - toxicity plasticizers (TOTM, ESO) and environmentally friendly flame retardants (Sb2O3), reducing environmental pollution and harm to the human body.

[0031] Heating loss ≤ 0.5mg / cm 2 (GB / T 2951 standard), indicating extremely low volatile substances during the material processing.

[0032] Comprehensive performance verification and industrial practicability: The finished cable passes the 3D torsion test ≥ 18 million times (2PfG2577 standard), verifying its ultra - long life under dynamic load.

[0033] The data of the examples cover the basic formula, flame - retardant optimization and high - temperature - resistant scenarios, and the technical solution has wide applicability and industrialization potential. Brief Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings, where:

[0035] Figure 1 is the TG curve of the comparative example of a sheath material for a highly flexible robot cable and its preparation method of the present invention and ordinary PVC cable material.

[0036] Figure 2 is the surface view and the display view under the microscope of the sheath material extruded by the twin - screw of a sheath material for a highly flexible robot cable and its preparation method of the present invention. Detailed implementation mode

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] Embodiment 1: Basic formula and preparation process

[0039] Formula composition (by mass parts):

[0040] PVC resin: 100 parts

[0041] Nitrile rubber (NBR): 15 parts

[0042] Trioctyl trimellitate (TOTM): 50 parts

[0043] Epoxidized soybean oil (ESO): 6 parts

[0044] Fumed nano-silica: 10 parts

[0045] Calcium-zinc composite stabilizer: 5 parts

[0046] Environmentally friendly flame retardant Sb2O3: 10 parts

[0047] Phosphorus-nitrogen intumescent flame retardant: 5 parts

[0048] Flame retardant graphite (particle size 1-5 μm): 5 parts

[0049] Antioxidant: 0.3 parts

[0050] Ultraviolet absorber: 0.3 parts

[0051] Light stabilizer: 0.4 parts

[0052] PE wax: 0.4 parts

[0053] Preparation steps:

[0054] Pre-mixing

[0055] Add PVC resin, TOTM, ESO, fumed nano-silica, calcium-zinc composite stabilizer, and antioxidant to a high-speed mixer, and mix at 75 °C and 900 rpm for 5 minutes; add Sb2O3, phosphorus-nitrogen flame retardant, flame retardant graphite, ultraviolet absorber, light stabilizer, and PE wax, and continue to mix for 8 minutes.

[0056] Internal mixing

[0057] The mixture is transferred to an internal mixer and kneaded at 120°C for 2.5 minutes; nitrile rubber is added, and the temperature is raised to 135°C and kneaded for 5 minutes to form a sea-island phase structure.

[0058] Twin-screw extrusion

[0059] A twin-screw extruder with a length-diameter ratio of 40:1 is used, and the temperatures of each temperature zone are 170°C, 180°C, 190°C, 190°C, 195°C, 195°C, 200°C, 200°C, 195°C, 190°C in sequence, and the vacuum degree is -0.08 MPa to suck out volatile gases.

[0060] Single-screw plasticization

[0061] The extruded material is plasticized and pelletized by a single-screw extruder (zone 1 at 145°C, zone 2 at 165°C, zone 3 at 185°C).

[0062] Performance testing and results

[0063] Mechanical properties (see Table 1): Tensile strength before aging is 2.52 kgf / cm 2 , and the elongation at break is 350%;

[0064] Aging resistance (136°C × 168 h): Tensile strength retention rate is 82%, and elongation at break retention rate is 71%; Low-temperature performance (-40°C impact test): Number of ruptures is 0 / 30;

[0065] Surface quality (see Figure 2 ): The surface is smooth after twin-screw extrusion, and SEM shows no burrs on the cross-section.

[0066] Example 2: Optimize the flame-retardant performance formula

[0067] Formula adjustment

[0068] Phosphorus-nitrogen flame retardant: 8 parts, flame-retardant graphite: 9 parts (weight ratio to phosphorus-nitrogen flame retardant is 1:0.89)

[0069] The remaining components are the same as in Example 1.

[0070] Process optimization

[0071] Vacuum suction pressure: -0.09 MPa, lasting until extrusion is completed;

[0072] Timing of adding antioxidant: Add it in the last 6 minutes of premixing.

[0073] The rest is the same as in Example 1.

[0074] Performance testing and results

[0075] Flame retardancy (UL94 test): Reaches V-0 level, and a honeycomb-like carbon layer is formed after combustion;

[0076] Oil resistance (IRM902 oil at 100 °C for 96 h): Tensile strength retention rate is 89%;

[0077] Thermal stability (TG curve shown in Figure 1 ): Temperature at 5% weight loss increased to 303.1 °C.

[0078] Example 3: High temperature resistance and long life formula

[0079] Formulation adjustment

[0080] TOTM: 70 parts

[0081] Epoxidized soybean oil: 10 parts

[0082] Nitrile rubber: 20 parts

[0083] Flame retardant graphite: 10 parts (weight ratio with phosphorus-nitrogen flame retardant is 1:1)

[0084] The remaining components are the same as in Example 1.

[0085] Process optimization

[0086] Single screw temperature gradient: Zone 1 at 150 °C, Zone 2 at 170 °C, Zone 3 at 190 °C (gradient 20 °C / zone);

[0087] Extrusion pressure: 8 MPa.

[0088] The remaining components are the same as in Example 1.

[0089] Performance test and results

[0090] Temperature resistance grade: No decomposition during long-term use at 105 °C;

[0091] Cable life (3D torsion test): 23 million times (see Table 1);

[0092] Surface finish (shown in Figure 2 ): Roughness ≤ 0.1 μm, no pitting;

[0093] Heating loss: 0.14 mg / cm 2 (superior to GB / T 2951 standard).

[0094] Summary of technical effects

[0095] Example 1 verifies the feasibility of the basic formulation and meets the basic requirements of flexible cables;

[0096] Example 2 significantly improves flame retardancy and oil resistance by optimizing the proportion of flame retardants and the process;

[0097] Example 3 demonstrates the industrial potential of the high temperature resistant and long lifespan sheath material, and the data supports the performance limits in the claims (such as heating loss ≤ 0.5mg / cm 2 ).

[0098]

[0099]

[0100] Table 1

[0101] The technical solution has the following advantages:

[0102] Excellent flexibility and mechanical properties: By blending nitrile rubber (NBR) and PVC, a "sea-island phase structure" is formed, significantly improving the anti-brittleness, oil resistance and low temperature resistance of the material (the number of ruptures in the -40°C impact test is 0 / 30), suitable for high-frequency motion scenarios of robots.

[0103] The addition of fumed nano-silica enhances the reinforcing effect. The tensile strength before aging reaches 2.52kgf / cm 2 , and the elongation at break is 350%, far exceeding the industry standard (UL1581).

[0104] High-efficiency flame retardancy and thermal stability: The synergistic effect of the environmental-friendly flame retardant Sb2O3, phosphorus-nitrogen intumescent flame retardant and flame retardant graphite forms a honeycomb-like carbon isolation layer, and the flame retardancy reaches V-0 level (UL94), effectively preventing melt dripping and flame spread.

[0105] The combination of TOTM and epoxidized soybean oil provides low volatility and heat resistance. With the cooperation of compound stabilizers (such as calcium-zinc stabilizers), the temperature resistance grade is increased to 105°C, and the temperature at 5% weight loss reaches 303.1°C (verified by TG curve).

[0106] Long-term durability and environmental adaptability: Excellent aging resistance (tensile strength retention rate ≥ 82% after aging at 136°C for 168h), and no surface cracks after 720 hours of UV test, suitable for outdoor complex environments.

[0107] Outstanding oil resistance (tensile strength retention rate ≥ 78% after 96h in IRM902 oil), meeting the working conditions requirements of industrial robots in long-term contact with oil stains.

[0108] Optimized preparation process and surface quality: The combined extrusion process of twin-screw + single-screw (length-diameter ratio 40:1, vacuum suction -0.08MPa) ensures uniform plasticization of the material, eliminating defects such as pitting and lumps (SEM shows a smooth cross-section, roughness ≤ 0.1μm).

[0109] Precise control of process parameters (such as internal mixer temperature 135°C, gradient temperature zone design), improving production efficiency and product consistency.

[0110] Environmental protection and safety: Low-toxicity plasticizers (TOTM, ESO) and environmentally friendly flame retardants (Sb2O3) are used to reduce environmental pollution and harm to the human body.

[0111] Heating loss ≤ 0.5mg / cm 2 (GB / T 2951 standard), indicating that the volatile substances in the material processing process are extremely low.

[0112] Comprehensive performance verification and industrial practicability: The finished cable passes the 3D torsion test ≥ 18 million times (2PfG2577 standard) to verify its ultra-long life under dynamic load.

[0113] The example data covers the basic formula, flame retardant optimization and high temperature resistance scenarios, and the technical solution has wide applicability and industrialization potential.

[0114] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A sheath material for a highly flexible robot cable, characterized in that: By mass parts, it includes the following components: 100 parts of polyvinyl chloride (PVC) resin; 15 - 20 parts of nitrile rubber (NBR); 50 - 70 parts of trioctyl trimellitate (TOTM); 6 - 10 parts of epoxidized soybean oil; 10 - 20 parts of fumed nano - silica; 5 - 10 parts of composite stabilizer; 10 - 15 parts of environmentally friendly flame retardant Sb2O3; 5 - 10 parts of phosphorus - nitrogen intumescent flame retardant; 5 - 10 parts of flame - retardant graphite; 0.3 - 0.5 parts of antioxidant; 0.3 - 0.5 parts of ultraviolet absorber; 0.4 - 0.6 parts of light stabilizer; 0.4 - 0.6 parts of PE wax; Among them, the nitrile rubber and PVC are blended to form a sea - island phase structure, the flame - retardant graphite and the phosphorus - nitrogen intumescent flame retardant act synergistically to form a honeycomb - like carbon isolation layer, the combination of TOTM and epoxidized soybean oil provides heat resistance and low volatility, and the temperature resistance grade of the sheath material reaches above 105°C, and the uniform plasticization of the material is ensured by a twin - screw extrusion process.

2. The sheath material for a highly flexible robot cable according to claim 1, wherein: The composite stabilizer is a calcium - zinc composite stabilizer.

3. The sheath material for a highly flexible robot cable according to claim 1, characterized in that: The particle size of the flame - retardant graphite is 1 - 5μm, and the weight ratio with the phosphorus - nitrogen intumescent flame retardant is 1:1 - 2:

1.

4. The sheath material for a highly flexible robot cable according to claim 1, characterized in that: The number of ruptures of the sheath material in the low - temperature impact embrittlement test at - 40°C is 0 / 30, and the 3D torsion times of the finished cable ≥ 18 million times.

5. The sheath material for a highly flexible robot cable according to claim 1, characterized in that: The heating loss of the sheath material ≤ 0.5 mg / cm 2 .

6. A preparation method of a sheath material for a highly flexible robot cable, characterized in that: It includes the following steps: (1) Premixing: Add PVC resin, TOTM, epoxidized soybean oil, fumed nano - silica, composite stabilizer, and antioxidant into a high - speed mixer, and mix at 70 - 80°C and a rotation speed of 800 - 1000 r / min for 4 - 6 minutes; then add environmentally friendly flame retardant Sb2O3, phosphorus - nitrogen intumescent flame retardant, flame - retardant graphite, ultraviolet absorber, light stabilizer, and PE wax, and continue to mix for 6 - 12 minutes; (2) Kneading: Add the mixture obtained in step (1) into a kneader, knead at 120°C for 2 - 3 minutes, then add nitrile rubber, raise the temperature to 135°C and knead for 4 - 6 minutes to make the nitrile rubber and PVC fully fuse and form chemical bonds; (3) Twin - screw extrusion: Extrude the kneaded material through a twin - screw extruder with a length - to - diameter ratio of 40:1, and the temperature of each temperature zone is 170°C, 180°C, 190°C, 190°C, 195°C, 195°C, 200°C, 200°C, 195°C, 190°C in sequence, and the vacuum degree is controlled at - 0.08 MPa to suck out volatile gases; (4) Single - screw plasticization: Further plasticize the rubber compound after twin - screw extrusion through a single - screw extruder, and the temperature of each zone is 140 - 150°C in zone 1, 160 - 170°C in zone 2, 180 - 190°C in zone 3, and finally granulate and package.

7. The preparation method of a sheath material for a highly flexible robot cable according to claim 6, characterized in that: The vacuum suction pressure of the twin - screw extruder is - 0.08 - - 0.10 MPa, and the vacuum suction continues until the material is completely extruded.

8. The preparation method of a sheath material for a highly flexible robot cable according to claim 6, characterized in that: In step (1), the antioxidant, ultraviolet absorber, and light stabilizer are added in the last 6 minutes of the premixing stage.

9. The preparation method of a sheath material for a highly flexible robot cable according to claim 6, characterized in that: The temperature gradient of each zone of the single - screw extruder is 10 - 20°C / zone, and the extrusion pressure is 5 - 10 MPa.

10. The preparation method of a sheath material for a highly flexible robot cable according to claim 6, characterized in that: The combined process of the twin-screw extruder and the single-screw extruder enables the surface roughness of the cable to be ≤ 0.1 μm, and there are no pitting and bump defects.

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