Processing method of fireproof rubber part for automobile wire harness

Abstract

The invention discloses a processing method of a fireproof rubber part for an automobile wire harness, and relates to the technical field of BB.The processing method comprises the following steps that natural rubber, chloroprene rubber and ethylene propylene diene monomer are put into an internal mixer according to the mass ratio of 2: 3: 1, and preliminary mixing is conducted for 5-8 minutes at the temperature of 50-60 DEG C; and then adding 5% of modified magnesium hydroxide, 3% of nanoscale antimony trioxide, 2% of silicone powder composite flame retardant, 1% of accelerant DM, 0, 5% of sulfur, 0, 8% of stearic acid and 1, 2% of zinc oxide based on the total mass. The fireproof performance is improved through the design of a composite flame-retardant system, natural rubber, chloroprene rubber and ethylene propylene diene monomer are compounded according to a specific proportion, and a composite flame retardant, which is coated with stearic acid on the surface of modified magnesium hydroxide, nano-scale antimony trioxide, silicone powder and the like, is added, so that the flame retardant is uniformly dispersed to form a physical barrier and chemical flame-retardant synergistic effect; the fire endurance and the self-extinguishing capability of the rubber part are obviously improved, and the fireproof requirement of the automobile wire harness is met.

Description

Technical Field

[0001] The invention relates to the technical field of automobile wiring harnesses, and in particular to a method for processing fireproof rubber parts for automobile wiring harnesses. Background Art

[0002] In the automotive wiring harness industry, the fire resistance and mechanical properties of rubber parts are crucial. Existing technologies face numerous challenges in the processing of rubber parts for automotive wiring harnesses, including a single flame retardant system, poor compatibility between the flame retardant and the rubber matrix, and easy agglomeration and precipitation, resulting in insufficient fire resistance and difficulty meeting high fire protection standards. Furthermore, insufficiently precise extrusion molding temperature control and a lack of effective temperature control and monitoring during the vulcanization process result in low product dimensional accuracy and poor mechanical properties. Furthermore, surface treatments struggle to effectively enhance the surface energy of rubber parts, leading to weak adhesion of the fire retardant coating.

[0003] To address these issues, the present invention provides a method for processing fire-resistant rubber parts for automotive wiring harnesses. This method utilizes a specific ratio of rubber compound and flame retardant to enhance the compatibility between the flame retardant and the rubber matrix, creating a synergistic flame-retardant effect. Furthermore, the molding and vulcanization process is optimized through segmented temperature control and precision molds. Radio frequency plasma treatment is used to enhance the surface energy of the rubber parts. Furthermore, a fire-resistant coating with a specific formulation and process is applied to enhance the fire resistance, mechanical properties, and coating adhesion of the rubber parts, meeting the safety requirements of automotive wiring harnesses. Summary of the Invention

[0004] The present invention provides a method for processing a fireproof rubber part for an automobile wiring harness, so as to solve the problems existing in the above-mentioned background technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for processing a fireproof rubber part for an automobile wiring harness comprises the following steps:

[0007] S1. Raw material pretreatment: natural rubber, chloroprene rubber, and EPDM rubber are put into an internal mixer at a mass ratio of 2:3:1, and preliminarily mixed at 50-60°C for 5-8 minutes; then, 5% of modified magnesium hydroxide, 3% of nano-antimony trioxide, 2% of silicone powder composite flame retardant, 1% of accelerator DM, 0.5% of sulfur, 0.8% of stearic acid, and 1.2% of zinc oxide are added, and the temperature is raised to 60-70°C and the mixing is continued for 15-20 minutes. During the mixing process, the rotor speed is maintained at 40-60 r / min to obtain a uniformly dispersed rubber mixture, wherein the modified magnesium hydroxide is a particle with a particle size of 5-10 μm with a surface coated with stearic acid;

[0008] S2. Extrusion molding: The mixed rubber is evenly conveyed to a co-rotating twin-screw extruder through a feeder. The screw diameter is 65 mm, the aspect ratio is 40:1, the conveying section temperature is set at 70-80°C, the melting section temperature is 80-90°C, the homogenization section temperature is 85-95°C, the die head temperature is 100-110°C, the screw speed is controlled at 30-40 r / min, and extrusion molding is performed through a precision mold. The mold flow channel adopts a streamlined design and the die compression ratio is 12-15. A rubber blank with a dimensional accuracy of ±0.05 mm is obtained;

[0009] S3. Vulcanization treatment: The rubber blank is placed in a flat vulcanizer with temperature gradient control. It is first preheated in the preheating zone at 100-110°C for 5-8 minutes, and then enters the vulcanization zone. The vulcanization zone adopts staged temperature rise control. The first stage is 140-145°C for 5 minutes, and the second stage is heated to 145-150°C for 5-10 minutes. The vulcanization pressure is maintained at 10-15MPa. During the vulcanization process, a circulating hot water system is used to control the mold temperature fluctuation to no more than ±1°C. After vulcanization is completed, it is cooled under pressure at a cooling rate of 5-8°C / minute.

[0010] S4. Surface treatment: Use radio frequency plasma treatment equipment to modify the surface of the vulcanized rubber parts. The treatment gas is a mixture of argon and oxygen with a volume ratio of 3:1. The treatment power is 100-150W and the treatment time is 3-5 minutes. During the treatment, the vacuum degree is maintained at 50-100Pa, so that oxygen-containing polar groups are formed on the surface of the rubber parts, and the surface energy is increased to 45-55mN / m.

[0011] S5. Fire retardant coating application: Apply the water-based intumescent fire retardant coating to the surface-treated rubber parts through high-pressure airless spraying equipment. The spraying pressure is 15-20 MPa, the spray gun movement speed is 300-400 mm / s, and the coating thickness is controlled at 0.2-0.3 mm. The water-based intumescent fire retardant coating is composed of the following raw materials in parts by weight: 30 parts of ammonium polyphosphate, 20 parts of pentaerythritol, 10 parts of melamine, 15 parts of silicone-modified acrylic emulsion, 5 parts of expandable graphite, 3 parts of titanium dioxide, 2 parts of dispersant, 1 part of defoaming agent and 20 parts of deionized water. After coating, dry it in a hot air circulation oven at 80-90°C for 2-3 hours to form a fire retardant coating with a three-dimensional network structure.

[0012] A further improvement of the technical solution of the present invention is that: in the raw material pretreatment step, the surface coating treatment method of the modified magnesium hydroxide is: adding stearic acid and magnesium hydroxide particles to an ethanol solution in a mass ratio of 1:10, stirring and reacting at 60°C for 2 hours, and then filtering and drying to obtain a modified magnesium hydroxide with a surface coated with stearic acid.

[0013] A further improvement of the technical solution of the present invention is that in the extrusion molding step, before the rubber mix is ​​conveyed to the twin-screw extruder, the rubber mix is ​​preheated at a temperature of 50-60° C. for 10-15 minutes.

[0014] A further improvement of the technical solution of the present invention is that in the vulcanization step, both the preheating zone and the vulcanization zone of the flat vulcanizer are provided with infrared temperature measuring devices to monitor the temperature of the rubber blank in real time.

[0015] A further improvement of the technical solution of the present invention is that in the vulcanization treatment step, during the pressure-maintaining cooling stage, liquid nitrogen is used to assist cooling, so that the cooling rate is increased to 10-12°C / minute.

[0016] A further improvement of the technical solution of the present invention is that: in the surface treatment step, before the radio frequency plasma treatment, the surface of the rubber part is first ultrasonically cleaned, the cleaning liquid is a mixed solution of acetone and water, the volume ratio is 1:1, and the cleaning time is 15-20 minutes.

[0017] A further improvement of the technical solution of the present invention is that in the fire retardant coating application step, before applying the water-based intumescent fire retardant coating, a layer of adhesion promoter is first sprayed on the surface of the rubber part, and the adhesion promoter is a polyurethane adhesion promoter.

[0018] A further improvement of the technical solution of the present invention is that: in the fire-retardant coating coating step, when preparing the water-based intumescent fire-retardant coating, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite, titanium dioxide, dispersant and defoamer are first added to deionized water, stirred at a speed of 800-1000 r / min for 30-40 minutes, and then the silicone-modified acrylic emulsion is added and stirring is continued for 15-20 minutes.

[0019] Due to the adoption of the above technical solution, the present invention has the following technical advancements compared to the prior art:

[0020] 1. The present invention provides a method for processing fireproof rubber parts for automotive wiring harnesses. The fireproof performance is improved by designing a composite flame retardant system. Natural rubber, chloroprene rubber, and EPDM rubber are compounded in a specific proportion, and modified magnesium hydroxide with a surface coated with stearic acid, nano-scale antimony trioxide, silicone powder and other composite flame retardants are added. The surface coating treatment enhances the compatibility with the rubber matrix, makes the flame retardant evenly dispersed, forms a physical barrier + chemical flame retardant synergistic effect, significantly improves the fire resistance limit and self-extinguishing ability of the rubber parts, and meets the fire protection requirements of automotive wiring harnesses.

[0021] 2. The present invention provides a method for processing fire-resistant rubber parts for automotive wiring harnesses, which achieves precise control in the molding and vulcanization processes to optimize performance. It adopts a co-rotating twin-screw extruder with segmented temperature control, a streamlined mold and preheating treatment, and a flat-plate vulcanizer to ensure uniform vulcanization through temperature gradient control, infrared temperature measurement and a circulating hot water system. Liquid nitrogen is used to assist cooling during the pressure-holding cooling stage to increase the rate, shorten the cycle, reduce thermal degradation of the molecular chain, and improve the mechanical properties and aging resistance of the product.

[0022] 3. The present invention provides a method for processing fire-resistant rubber parts for automotive wiring harnesses. The surface treatment and coating application processes enhance the comprehensive performance. After vulcanization, radio frequency plasma treatment is used to introduce oxygen-containing polar groups on the surface of the rubber parts to increase the surface energy. Ultrasonic cleaning is used to remove impurities, providing a highly active interface for the fire-resistant coating. The water-based intumescent fire-resistant coating adopts a specific formula and a high-pressure airless spray process, combined with an adhesion promoter. The resulting coating is resistant to bending and fire. The refined control of each process parameter and the linkage of equipment also improve production efficiency, shorten the cycle, and reduce the scrap rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention; DETAILED DESCRIPTION

[0024] The present invention is described in further detail below in conjunction with the embodiments:

[0025] Example 1

[0026] like Figure 1 The present invention provides a method for processing fire-resistant rubber parts for automotive wiring harnesses. 20 kg of natural rubber, 30 kg of chloroprene rubber, and 10 kg of EPDM rubber are placed in an internal mixer. The mixer temperature is set to 55°C, the mixer is started, and preliminary mixing is performed at a rotor speed of 50 r / min for 6 minutes. After preliminary mixing, 3 kg of modified magnesium hydroxide (5% of the total mass of 60 kg), 1.8 kg of nano-antimony trioxide (3% of the total mass), 1.2 kg of silicone powder composite flame retardant (2% of the total mass), 0.6 kg of DM accelerator (1% of the total mass), 0.3 kg of sulfur (0.5% of the total mass), 0.48 kg of stearic acid (0.8% of the total mass), and 0.72 kg of zinc oxide (1.2% of the total mass) are added to the internal mixer. The temperature is then raised to 65°C, and mixing is continued for 18 minutes, with the rotor speed maintained at 50 r / min, to obtain a uniformly dispersed rubber mixture. The modified magnesium hydroxide is prepared by the following method: adding stearic acid and magnesium hydroxide particles in a mass ratio of 1:10 to an ethanol solution, stirring and reacting at 60°C for 2 hours, and then filtering and drying to obtain particles with a particle size of 5-10 μm whose surface is coated with stearic acid.

[0027] Example 2

[0028] like Figure 1 As shown, the present invention provides a method for processing fireproof rubber parts for automotive wiring harnesses. Before the rubber mix is ​​conveyed to the twin-screw extruder, the rubber mix is ​​first placed in a preheating device and preheated at 55°C for 12 minutes. The preheated rubber mix is ​​then evenly conveyed to the co-rotating twin-screw extruder through a feeder. The twin-screw extruder has a screw diameter of 65mm and an aspect ratio of 40:1. The conveying section temperature is set to 75°C, the melting section temperature is 85°C, the homogenizing section temperature is 90°C, the die head temperature is 105°C, and the screw speed is controlled at 35r / min. Through precision mold extrusion molding, the mold runner adopts a streamlined design, and the die compression ratio is 13, and finally a rubber part embryo with a dimensional accuracy of ±0.05mm is obtained;

[0029] The rubber blank is placed in a flat-plate vulcanizer with temperature gradient control. It is first preheated in a 105°C preheating zone for 6 minutes. The preheating zone is equipped with an infrared temperature measuring device to monitor the temperature of the rubber blank in real time. It then enters the vulcanization zone, where the temperature is raised in stages. The first stage is maintained at 142°C for 5 minutes, and the second stage is heated to 147°C for 8 minutes. The vulcanization pressure is maintained at 12MPa. During the vulcanization process, a circulating hot water system is used to control the mold temperature fluctuation to no more than ±1°C. After vulcanization is completed, pressure-maintaining cooling is carried out, and liquid nitrogen is used to assist cooling, increasing the cooling rate to 11°C / minute.

[0030] Before the RF plasma treatment, the rubber parts were placed in a 1:1 volume ratio of acetone and water and cleaned in an ultrasonic cleaning device for 18 minutes. The vulcanized rubber parts were then surface-modified using an RF plasma treatment device. The treatment gas was a 3:1 volume ratio of argon and oxygen at a power of 120W for four minutes. During the treatment, the vacuum level was maintained at 75 Pa, forming oxygen-containing polar groups on the rubber parts' surfaces and increasing their surface energy to 50 mN / m.

[0031] Example 3

[0032] like Figure 1The present invention provides a method for processing fire-resistant rubber parts for automotive wiring harnesses. Prior to applying a water-based intumescent fire-retardant coating, a layer of polyurethane adhesion promoter is sprayed on the surface of the rubber part. The water-based intumescent fire-retardant coating is prepared as follows: 30 kg of ammonium polyphosphate, 20 kg of pentaerythritol, 10 kg of melamine, 5 kg of expandable graphite, 3 kg of titanium dioxide, 2 kg of dispersant, and 1 kg of defoamer are added to 20 kg of deionized water and stirred at 900 rpm for 35 minutes. Then, 15 kg of silicone-modified acrylic emulsion is added and stirred for a further 18 minutes. The prepared water-based intumescent fire-retardant coating is then applied to the surface-treated rubber part using a high-pressure airless sprayer. The spray pressure is 18 MPa, the spray gun travel speed is 350 mm / s, and the coating thickness is controlled to 0.25 mm. After application, the coating is dried in a hot air circulation oven at 85°C for 2.5 hours to form a fire-retardant coating with a three-dimensional network structure.

[0033] The above generally describes the present invention in detail. However, it is obvious to those skilled in the art that modifications or improvements may be made based on the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A method for processing fireproof rubber parts for automobile wiring harnesses, characterized in that: The following steps are involved: S1. Raw material pretreatment: natural rubber, chloroprene rubber, and EPDM rubber are put into an internal mixer at a mass ratio of 2:3:1, and preliminarily mixed at 50-60°C for 5-8 minutes; then, 5% of modified magnesium hydroxide, 3% of nano-antimony trioxide, 2% of silicone powder composite flame retardant, 1% of accelerator DM, 0.5% of sulfur, 0.8% of stearic acid, and 1.2% of zinc oxide are added, and the temperature is raised to 60-70°C and the mixing is continued for 15-20 minutes. During the mixing process, the rotor speed is maintained at 40-60 r / min to obtain a uniformly dispersed rubber mixture, wherein the modified magnesium hydroxide is a particle with a particle size of 5-10 μm with a surface coated with stearic acid; S2. Extrusion molding: The mixed rubber is evenly conveyed to a co-rotating twin-screw extruder through a feeder. The screw diameter is 65 mm, the aspect ratio is 40:1, the conveying section temperature is set at 70-80°C, the melting section temperature is 80-90°C, the homogenization section temperature is 85-95°C, the die head temperature is 100-110°C, the screw speed is controlled at 30-40 r / min, and extrusion molding is performed through a precision mold. The mold flow channel adopts a streamlined design and the die compression ratio is 12-15. A rubber blank with a dimensional accuracy of ±0.05 mm is obtained; S3. Vulcanization treatment: The rubber blank is placed in a flat vulcanizer with temperature gradient control. It is first preheated in the preheating zone at 100-110°C for 5-8 minutes, and then enters the vulcanization zone. The vulcanization zone adopts staged temperature rise control. The first stage is 140-145°C for 5 minutes, and the second stage is heated to 145-150°C for 5-10 minutes. The vulcanization pressure is maintained at 10-15MPa. During the vulcanization process, a circulating hot water system is used to control the mold temperature fluctuation to no more than ±1°C. After vulcanization is completed, it is cooled under pressure at a cooling rate of 5-8°C / minute. S4. Surface treatment: Use radio frequency plasma treatment equipment to modify the surface of the vulcanized rubber parts. The treatment gas is a mixture of argon and oxygen with a volume ratio of 3:

1. The treatment power is 100-150W and the treatment time is 3-5 minutes. During the treatment, the vacuum degree is maintained at 50-100Pa, so that oxygen-containing polar groups are formed on the surface of the rubber parts, and the surface energy is increased to 45-55mN / m. S5. Fire retardant coating application: Apply the water-based intumescent fire retardant coating to the surface-treated rubber parts through high-pressure airless spraying equipment. The spraying pressure is 15-20 MPa, the spray gun movement speed is 300-400 mm / s, and the coating thickness is controlled at 0.2-0.3 mm. The water-based intumescent fire retardant coating is composed of the following raw materials in parts by weight: 30 parts of ammonium polyphosphate, 20 parts of pentaerythritol, 10 parts of melamine, 15 parts of silicone-modified acrylic emulsion, 5 parts of expandable graphite, 3 parts of titanium dioxide, 2 parts of dispersant, 1 part of defoaming agent and 20 parts of deionized water. After coating, dry it in a hot air circulation oven at 80-90°C for 2-3 hours to form a fire retardant coating with a three-dimensional network structure.

2. The method for processing fireproof rubber parts for automobile wiring harnesses according to claim 1, characterized in that: In the raw material pretreatment step, the surface coating treatment method of the modified magnesium hydroxide is: adding stearic acid and magnesium hydroxide particles in a mass ratio of 1:10 to an ethanol solution, stirring and reacting at 60° C. for 2 hours, and then filtering and drying to obtain a modified magnesium hydroxide with a surface coated with stearic acid.

3. The method for processing a fireproof rubber part for an automobile wiring harness according to claim 1, characterized in that: In the extrusion molding step, the rubber mix is ​​preheated before being conveyed to the twin-screw extruder. The preheating temperature is 50-60° C. and the preheating time is 10-15 minutes.

4. The method for processing a fireproof rubber part for an automobile wiring harness according to claim 1, characterized in that: In the vulcanization step, both the preheating zone and the vulcanization zone of the flat vulcanizer are provided with infrared temperature measuring devices to monitor the temperature of the rubber blank in real time.

5. The method for processing a fireproof rubber part for an automobile wiring harness according to claim 1, characterized in that: In the vulcanization step, during the pressure-maintaining cooling stage, liquid nitrogen is used to assist cooling, so that the cooling rate is increased to 10-12° C. / minute.

6. The method for processing a fireproof rubber part for an automobile wiring harness according to claim 1, characterized in that: In the surface treatment step, before the radio frequency plasma treatment, the surface of the rubber part is firstly ultrasonically cleaned, the cleaning liquid is a mixed solution of acetone and water with a volume ratio of 1:1, and the cleaning time is 15-20 minutes.

7. The method for processing a fireproof rubber part for an automobile wiring harness according to claim 1, characterized in that: In the fire retardant coating application step, before applying the water-based intumescent fire retardant coating, a layer of adhesion promoter is sprayed on the surface of the rubber part, and the adhesion promoter is a polyurethane adhesion promoter.

8. The method for processing fireproof rubber parts for automobile wiring harnesses according to claim 1, characterized in that: In the fire-retardant coating coating step, when preparing the water-based intumescent fire-retardant coating, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite, titanium dioxide, a dispersant and a defoaming agent are first added to deionized water, stirred at a speed of 800-1000 r / min for 30-40 minutes, and then the silicone-modified acrylic emulsion is added, and stirring is continued for 15-20 minutes.

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