Thermal aging resistant EPDM dynamically vulcanized TPV, and preparation method and application thereof

Abstract

The invention discloses thermal aging-resistant EPDM (Ethylene-Propylene-Diene Monomer) dynamically-vulcanized TPV (Thermoplastic Vulcanizate) as well as a preparation method and application thereof. The preparation method comprises the following steps: feeding a master batch into a double Then feeding the COC resin into the double-screw extruder from the middle section for mixing; then carrying out homogenization; and finally, granulating to obtain the thermal aging-resistant EPDM dynamically vulcanized TPV. The master batch comprises polypropylene, EPDM, white oil, a filling agent, an auxiliary agent and a vulcanizing agent. The invention discloses a heat-aging-resistant EPDM (ethylene-propylene-diene monomer) dynamically-vulcanized TPV (thermoplastic vulcanizate) as well as a preparation method and application thereof from a material formula in combination with a preparation process, and the prepared product has excellent heat-aging resistance.

Description

Technical Field

[0001] The present invention belongs to advanced material technology and relates to a high-performance TPV, specifically a heat-aging-resistant EPDM dynamically vulcanized TPV and a preparation method and application thereof. Background Art

[0002] Dynamically vulcanized thermoplastic elastomer (English name: Thermoplastic Vulcanizate), also known as thermoplastic vulcanized rubber, referred to as TPV. It is a thermoplastic elastomer in which the rubber is sheared into "tiny" particles and dispersed in the polypropylene matrix during the vulcanization and cross-linking process. It has both the high elasticity of traditional rubber and the thermoplastic processing performance of polypropylene resin. It is a new type of environmentally friendly material that is developing rapidly. At present, conventional TPV on the market is made of polypropylene and EPDM dynamically vulcanized. Conventional TPV is not resistant to high temperatures and its dimensional stability needs to be improved by adjusting the content of fillers. The existing technology uses rare earth to strengthen the effect of activated bentonite on carboxylic acid esterification and catalytic activity, and generates a rare earth complex with dicarboxylic acid ester or monocarboxylic acid ester. It uses its good compatibility with rubber and intercrystalline activity to replace traditional carbon black, especially white carbon black, as a filling and reinforcing material, and can improve the heat resistance stability and processability of rubber-plastic alloys. The prior art utilizes the principle that antioxidants have more active hydrogen atoms than EPDM and PP molecules. During the thermal oxidative aging process of EPDM / PP blends, antioxidant hydrogen atoms are more likely to react with peroxy radicals formed by the blend molecular chains under the action of heat and oxygen, inhibiting the chain reaction of free radicals and preventing the molecular chains from breaking or oxidatively breaking. Combined with calcium sulfate whiskers modified with silane coupling agent KH-550, a "hard core-soft shell" coating structure is formed with EPDM during the EPDM / PP blending process, thereby enhancing the heat resistance of EPDM / PP TPV. Limited by the melting point of the components, the high-temperature thermal aging retention rate of this material at 150°C / 168h is below 60%.

[0003] The prior art uses a two-step method to prepare EPDM / PP-TPV, and investigates the regulatory effect of EPDM / PP-TPV dynamic vulcanization with low double bond content (LEPDM). The elongation at break of the product at 100°C / 48h is less than 85%. The prior art uses a phenolic resin vulcanization system to dynamically vulcanize EPDM / PP TPVs, and adds nano-SiO2 during the preparation process. The best performance group of EPDM / PP TPVs obtained by dynamic vulcanization has an elongation at break of less than 90% at 100°C / 48h. Summary of the invention

[0004] In some special application conditions, such as automobile radiator pipes, engine compartments and other environments that require high temperature resistance, current thermoplastic elastomers are difficult to meet the use requirements. The present invention starts with material formulation and combines preparation technology to disclose a heat-resistant EPDM dynamic vulcanized TPV and its preparation method and application. The prepared product has good heat-resistant aging performance.

[0005] A preparation method of a heat-resistant EPDM dynamically vulcanized TPV comprises the following steps: feeding a masterbatch into a twin-screw extruder for vulcanization; then feeding a COC resin into the twin-screw extruder from a middle section for mixing; then homogenizing; and finally granulating to obtain the heat-resistant EPDM dynamically vulcanized TPV; the masterbatch comprises polypropylene, EPDM, white oil, filler, auxiliary agent, and vulcanizer, or the masterbatch comprises EPDM, white oil, filler, auxiliary agent, and vulcanizer.

[0006] In the present invention, the mass ratio of polypropylene, COC resin, EPDM, white oil, filler, additive and vulcanizer is (0-10): (15-30): (20-40): (20-30): (10-20): (1-3): (0.5-1.5).

[0007] Preferably, the mass ratio of polypropylene, COC resin, EPDM, white oil, filler, additive and vulcanizer is (1-8): (20-28): (25-35): (22-28): (12-17): (2-3): (0.8-1.2).

[0008] In the present invention, the filler is an inorganic material, including calcium carbonate.

[0009] In the present invention, the auxiliary agents include antioxidants, weathering agents, lubricants, colorants and the like.

[0010] In the present invention, the vulcanizing agent is a peroxide.

[0011] In the present invention, the diameter of the twin-screw extruder is 20-120 mm, and the rotation speed is 600-1200 rpm.

[0012] In the present invention, the temperature of the mixing section is 160±5°C, the temperature of the vulcanization section is 220±5°C, and the temperature of the homogenization section is 210±10°C.

[0013] In the present invention, the twin-screw extruder itself is a conventional granulation device, and the middle section feeding refers to adding the COC resin to the twin-screw extruder from the middle feeding port of the twin-screw extruder. The middle section is the vulcanization section of the twin-screw extruder, and the specific operation is a conventional method. The present invention creatively adds COC resin to TPV masterbatch, and through innovative middle section feeding, gives full play to the synergistic effect of polypropylene, rubber, COC resin and vulcanizing agent. The prepared product has good mechanical properties, especially heat aging resistance, which can reach 150°C level, solving the technical defect that most of the existing TPVs are at 135°C level.

[0014] The invention discloses TPV prepared by the preparation method of the heat-aging-resistant EPDM dynamically vulcanized TPV.

[0015] The invention discloses the application of the TPV in preparing TPV materials.

[0016] The invention discloses the application of the TPV in preparing automobile TPV materials.

[0017] The invention discloses the application of the above TPV in preparing heat-aging-resistant TPV materials.

[0018] An automotive material is prepared from the above TPV.

[0019] Preferably, the above-mentioned automobile material is a heat-resistant and aging-resistant automobile material, such as automobile radiator pipes, engine compartments and other materials that require high temperature resistance.

[0020] The present invention uses COC cyclic olefin copolymer as resin for the first time to carry out dynamic vulcanization with EPDM, and combines it with polypropylene, filler and vulcanization system. The obtained product has excellent heat resistance and stability. It can be widely used in products with high temperature resistance and good dimensional stability (such as parts under the engine hood and cooling water pipes, etc.), expanding the application field of TPV materials. DETAILED DESCRIPTION

[0021] TPV is a mixture of rubber and thermoplastic resin. The rubber is vulcanized under high temperature, high shear, initiator and cross-linking agent conditions. The vulcanized rubber phase is sheared into small rubber particles and dispersed in the molten plastic phase to complete dynamic vulcanization. It is generally prepared in a twin-screw extruder. The vulcanization cross-linking reaction causes a sharp increase in the viscosity of the rubber phase. Under the action of high shear force during the dynamic vulcanization process, the rubber phase is sheared into micron-sized vulcanized elastic particles and dispersed in the resin phase, forming a TPV with a "sea-island" structure in which the resin phase is the continuous phase and the rubber particles are the dispersed phase. This makes TPV have both the high elasticity of rubber and the thermoplasticity of resin. The mainstream material of TPV on the market is EPDM / PP. The EPDM main chain is composed of chemically stable saturated hydrocarbons and only contains unsaturated double bonds in the side chains. The system has good physical properties, but for some demanding applications, the heat aging resistance needs to be improved. Filler modification is one direction of improving heat aging performance in the prior art. There are hydroxyl groups on the surface of the filler, which can chemically combine with the double bonds in the rubber molecular chain to play a reinforcing role. However, at higher heat aging temperatures, the hydroxyl groups are greatly reduced, which significantly reduces the reinforcing effect and makes the mechanical property retention rate extremely unsatisfactory. The prior art studies the effect of adding calcium sulfate whiskers on the phase structure and mechanical properties of dynamically vulcanized thermoplastic elastomers (TPVs) based on ethylene propylene diene monomer (EPDM) and polypropylene (PP). Although inorganic whiskers have a fine diameter, a short length, and extremely high stiffness, the heat aging resistance of the modified product is at the 100°C level, which does not meet the requirement of 150°C.

[0022] The present invention solves the difficulty of combining COC resin with TPV vulcanization system and improves the heat resistance stability of TPV materials. The present invention feeds the masterbatch into a twin-screw extruder for vulcanization; then feeds the COC resin into the twin-screw extruder from the middle section for mixing; then homogenizes; and finally granulates to obtain heat-resistant aging EPDM dynamic vulcanized TPV; the masterbatch includes polypropylene, EPDM, white oil, filler, additive, and vulcanizer.

[0023] In the present invention, the mass sum of polypropylene, EPDM, white oil, filler and COC resin is 100%: According to mass percentage, the raw material formula is as follows: Polypropylene Remainder COC resin 15-30% EPDM 25-35% White oil 20-30% Filler 10-20% Other processing additives 1-3% Vulcanizing agent 0.5-1.5% Preferably, the raw material formula is as follows by mass percentage: Polypropylene Remainder COC resin 20-28% EPDM 27-33% White oil 22-27% Filler 13-16% Other additives 2% Vulcanizing agent 1% in: Polypropylene: PP, Shore D hardness 60-70, copolymer or homopolymer; K8003 for experiment; EPDM: ENB content 3.5-5, ethylene content 30-60%, Mooney viscosity (1+4) 100℃: 40-130; 3092PM for experiment; Filler: calcium carbonate, PX-3203 for experimental use; Filling oil: Kinematic viscosity at 40℃ is about 100 or 300, flash point is above 265; KP-100B is used for experiment; Curing agent: Aksu Trigonox101; Other additives: including antioxidants, weathering agents, lubricants and colorants, etc.; in the experiment: antioxidant double bond 1010: 0.2, 168: 0.2, lubricant erucamide: 0.2, weathering agents double bond 5411 and 5590 0.2 each, masterbatch MBB206: 1; COC resin: flexural modulus above 3000MPa, Tg above 140℃; TAMT1410 was used for the experiment.

[0024] COC resin is an existing product, which is a cyclic resin based on metallocene catalyst technology. It is widely used in medical fields such as medical equipment and inspection and diagnostic instruments. The present invention uses COC resin for the first time to participate in the vulcanization of TPV, and the prepared product has high heat aging resistance and dimensional stability.

[0025] In the prior art, TPV is a dynamically vulcanized material with PP as the continuous phase and EPDM as the dispersed phase. It has the elasticity of partially vulcanized EPDM and the thermoplasticity of PP. The TPV material of the PP+EPDM system usually has a maximum use temperature of no more than 120°C, and the performance retention rate after long-term heat aging at 135°C & 1000h is low (less than 65%). The present invention mixes COC material into the PP+EPDM system and combines it with the preparation process to bring better high temperature resistance to the TPV material, significantly improve the heat aging performance retention rate under the conditions of 135°C & 1000h, and at the same time, it can increase the long-term use temperature of the TPV material of the PP+EPDM system (estimated to increase by 10°C), broadening the application of the TPV material of the PP+EPDM system (especially in scenarios requiring high temperature).

[0026] The technical progress of the present invention is described below through specific experiments. The raw materials are all existing products, and the specific preparation operations and performance tests are all conventional techniques, which are briefly described as follows: Density: According to ISO 1183, method A, requirement is 0.95±0.05; Tensile strength: According to ISO 37, 500mm / min, required to be above 7MPa; Elongation: According to ISO 37, 500mm / min, more than 300% is required; Shore hardness: According to ISO 868, 15s reading, Shore A, requirement 80A-90A; Tear strength: According to ISO 34, 500mm / min, required to be above 18KN / m; Short-term heat aging resistance: According to ISO 188, 150℃ / 168h, the tensile strength retention rate is required to be more than 65%; Long-term heat aging resistance: According to ISO 188, 135℃ / 1000h, the tensile strength retention rate is required to be above 75%.

[0027] The preparation methods of the embodiments and comparative examples are as follows: EPDM rubber, PP resin, filler calcium carbonate, filler white oil and additives are conventionally mixed into a premix, and then the premix and the vulcanizer are added from the main feed to a twin-screw extruder for mixing and vulcanization reaction. COC resin is fed into the eighth zone of the twin-screw extruder through a forced feeding screw for mixed extrusion and granulation to obtain a COC resin-modified PP+EPDM system TPV dynamically vulcanized elastomer material.

[0028] The diameter of the twin-screw extruder used is 75 mm, the rotation speed is 600 rpm, and the temperatures of each section of the extruder are 155, 160, 165, 165, 195, 205, 215, 225, 225, 220, 210, 210, 205, and 200°C, respectively.

[0029] The amounts of raw materials used in the examples and comparative examples are shown in Table 1, and the conventional test results are shown in Table 2.

[0030] Table 1 Examples and Comparative Examples Formula, Kg

[0031] Table 2 Material properties

[0032] Comparative Example 4 On the basis of Example 5, COC resin, premix and vulcanizing agent were added into the twin-screw extruder from the main feed, and the rest was the same. The appearance was not good, it was not easy to granulate, and it could not be used for production.

[0033] Comparison example The TPV particles used for extruding automobile pipes on the market are well applied in the production end. The short-term heat aging tensile strength retention rate of the phenolic resin system TPV material is 55%, and the long-term heat aging tensile strength retention rate is 61%.

[0034] Thermal aging is a common phenomenon. In a continuous hot air environment, the original unstable structure of the material will be destroyed. When the elastomer is subjected to high temperature, the chemical reaction caused by oxidation causes a series of structural changes such as degradation, cross-linking and group attachment, which are manifested as discoloration, cracking, mildew, stickiness, etc., and the physical and mechanical properties such as heat resistance, cold resistance, oil resistance, air permeability and light transmittance change. When the performance drops to a certain extent, it loses its use value. Therefore, the thermal aging performance of TPV is directly related to its performance and life. The present invention mixes COC material into the PP+EPDM system, combined with the preparation process, can bring better high temperature resistance to TPV materials, significantly improve the thermal aging performance retention rate under 135℃&1000h conditions, and at the same time can improve the long-term use temperature of PP+EPDM system TPV materials (estimated to increase by 10℃), broaden the application of PP+EPDM system TPV materials (especially in scenarios requiring high temperature), the product of the conventional extrusion of particles in Example 5 of the present invention at the production end, after testing, meets the manufacturer's application requirements.

Claims

1. A method for preparing a heat-resistant EPDM dynamically vulcanized TPV, comprising the following steps: feeding a masterbatch into a twin-screw extruder for vulcanization; then feeding a COC resin from a middle section into the twin-screw extruder for mixing; then homogenizing; and finally granulating to obtain a heat-resistant EPDM dynamically vulcanized TPV; the masterbatch comprises polypropylene, EPDM, white oil, filler, additive, and vulcanizer, or the masterbatch comprises EPDM, white oil, filler, additive, and vulcanizer.

2. The method for preparing the heat-aging-resistant EPDM dynamically vulcanized TPV according to claim 1, characterized in that: The mass ratio of polypropylene, COC resin, EPDM, white oil, filler, additive and vulcanizer is (0-10): (15-30): (20-40): (20-30): (10-20): (1-3): (0.5-1.5).

3. The method for preparing the heat-aging-resistant EPDM dynamically vulcanized TPV according to claim 1, characterized in that: The mass ratio of polypropylene, COC resin, EPDM, white oil, filler, additive and vulcanizer is (1-8): (20-28): (25-35): (22-28): (12-17): (2-3): (0.8-1.2).

4. The method for preparing the heat-aging-resistant EPDM dynamically vulcanized TPV according to claim 1, characterized in that: The middle section is the vulcanization section of the twin-screw extruder.

5. The method for preparing heat-aging-resistant EPDM dynamically vulcanized TPV according to claim 1, characterized in that: In the twin-screw extruder, the temperature of the mixing section is 160±5°C, the temperature of the vulcanization section is 220±5°C, and the temperature of the homogenization section is 210±10°C.

6. TPV prepared by the method for preparing heat-aging-resistant EPDM dynamically vulcanized TPV according to claim 1.

7. Use of the TPV according to claim 6 in the preparation of TPV materials.

8. Use of the TPV according to claim 6 in the preparation of automotive TPV materials.

9. Use of the TPV according to claim 6 in preparing heat-aging-resistant TPV materials.

10. An automotive material prepared from the TPV according to claim 6.

Images