A TPE composition for encapsulating nylon and preparation method thereof

Abstract

The present invention belongs to the technical field of TPE elastomer materials, and in particular to a TPE composition for encapsulating nylon and a preparation method thereof. The TPE composition for encapsulating nylon provided by the present invention includes modified SEBS, polypropylene, modified EPDM rubber, ethylene-acrylate copolymer, mineral oil, a coupling agent, an additive, and a filler. The present invention adopts modified SEBS and modified EPDM rubber as the main elastomers of the TPE composition, cooperates with ethylene-acrylate copolymer and a coupling agent, improves the tensile properties of the TPE composition, adopts allyl glycidyl ether to modify SEBS, introduces the ether bond and epoxy group in allyl glycidyl ether into SEBS, adopts itaconic anhydride to modify EPDM rubber, introduces a polar segment containing a carboxyl group into the EPDM rubber, and effectively improves the bonding performance between the TPE composition and nylon.

Description

Technical Field

[0001] The invention belongs to the technical field of TPE elastomer materials, and particularly relates to a TPE composition for encapsulating nylon and a preparation method thereof. Background Art

[0002] Nylon, with its excellent wear resistance, plays a vital role in the textile and machinery manufacturing sectors. Due to its high heat resistance, high rigidity, high strength, and excellent insulation properties, nylon and its modified materials are often used in the production of power tool casings, handles, and accessories. To enhance the performance of nylon power tools, the nylon material is coated with an adhesive overmolding material for secondary injection molding. Thermoplastic elastomers (TPEs) offer excellent properties such as high elasticity, aging resistance, and oil resistance, along with ease and a wide range of processing options. They have become the latest material to replace traditional rubber and are a globally standardized, environmentally friendly material.

[0003] Existing TPE nylon encapsulation materials are primarily made by blending styrene elastomers and polyurethane elastomers. This type of TPE requires high temperatures for manufacturing, and the composite material has poor tensile properties and high energy consumption, resulting in high processing costs for power tools and not meeting environmental requirements for energy conservation and emission reduction. Furthermore, the bonding properties of existing TPE nylon encapsulation materials are significantly affected by the base material. Nylon is a highly polar polymer, while the main components of TPE, such as hydrogenated styrene-butadiene block copolymer, white oil, polypropylene, and polyolefin elastomer, are non-polar materials. This results in weak bonding between the nylon and the TPE encapsulation material, affecting the product's pass rate and performance.

[0004] The Chinese patent application document with publication number CN111073311A discloses a new TPE nylon encapsulating material and a preparation method thereof. The disclosed new TPE nylon encapsulating material includes components such as styrene elastomer, white oil, maleic acid grafted polystyrene elastomer, maleic acid grafted polyethylene and calcium carbonate. By improving the formula of the TPE nylon encapsulating material, the polyurethane elastomer is replaced with maleic acid grafted polystyrene elastomer. The maleic acid grafted polystyrene elastomer particles are dispersed in the nylon matrix to form stress concentration points, thereby improving the bonding strength between the TPE encapsulating material and the nylon matrix. However, the amount of maleic acid grafted polystyrene elastomer added is limited. The main components of the TPE encapsulating nylon material are still styrene elastomer, white oil and other components. It has strong non-polarity and poor bonding performance with nylon materials with strong polarity. Although the addition of maleic acid grafted polystyrene elastomer can improve the bonding performance between the TPE encapsulating material and the nylon material, there is still a risk of poor bonding between the TPE encapsulating material and the nylon material as time increases or the temperature changes. Summary of the Invention

[0005] In order to solve the technical problems existing in the above-mentioned related technologies such as poor tensile properties and bonding properties between TPE encapsulated materials and nylon, the purpose of the present invention is to provide a TPE composition for encapsulating nylon and a preparation method thereof.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A TPE composition for encapsulating nylon, comprising the following components in parts by weight:

[0008] Modified SEBS 20-30 parts, polypropylene 10-15 parts, modified EPDM rubber 10-20 parts, ethylene-acrylate copolymer 5-10 parts, mineral oil 25-40 parts, coupling agent 5-10 parts, additive 3-5 parts, filler 5-15 parts;

[0009] The preparation method of the modified SEBS comprises the following steps: dissolving SEBS in toluene, dropwise adding an aqueous solution of allyl glycidyl ether and azobisisobutyronitrile under the protection of an inert gas, heating the mixture to 90-110° C., and reacting the mixture for 6-9 hours. After the reaction is completed, the reaction solution is poured into acetone, stirred for precipitation, filtered, and dried to obtain the modified SEBS.

[0010] The above-mentioned technical solution utilizes modified SEBS and modified EPDM as the primary elastomers in the TPE composition, effectively improving the tensile properties of the TPE composition. SEBS is grafted with allyl glycidyl ether via a solution grafting method under the action of an initiator. The polar ether and epoxy groups in the allyl glycidyl ether are introduced into the SEBS. During the encapsulation process, the polar groups form hydrogen bonds with the amide groups in the nylon, enhancing not only the tensile properties and processing performance of the SEBS but also the adhesion between the TPE composition and the nylon matrix. Polypropylene exhibits excellent compatibility with the EB segments in SEBS, effectively reducing the melt viscosity of SEBS and improving processing performance. Furthermore, polypropylene has a high melting point, and when formed into a co-continuous phase structure with SEBS, it effectively enhances the temperature resistance of the TPE composition. Ethylene-acrylate copolymers exhibit good polarity, and based on the principle of like dissolves like, they significantly improve the compatibility of the TPE composition with nylon, enhancing its tensile and adhesive properties.

[0011] Furthermore, in the preparation method of the modified SEBS, the mass ratio of SEBS, allyl glycidyl ether and azobisisobutyronitrile is 1:(0.075-0.125):(0.033-0.037).

[0012] In the above technical solution, the grafting rate of allyl glycidyl ether is controlled by controlling the mass ratio of SEBS, allyl glycidyl ether and azobisisobutyronitrile. Studies have found that when the amount of allyl glycidyl ether and azobisisobutyronitrile exceeds the above range, allyl glycidyl ether will undergo self-polymerization during the modification process, reducing its grafting rate on SEBS. The reduction in the grafting rate of SEBS will lead to a decrease in the tensile properties and bonding properties of the TPE composition.

[0013] Furthermore, in the preparation method of the modified SEBS, the mass ratio of SEBS, allyl glycidyl ether and azobisisobutyronitrile is 1:(0.095-0.115):(0.035-0.037).

[0014] Furthermore, in the preparation method of the modified SEBS, the mass percentage of the aqueous solution of azobisisobutyronitrile is 7%-10%.

[0015] Furthermore, the preparation method of the modified EPDM rubber is as follows: dried itaconic anhydride, EPDM rubber and dicumyl peroxide are put into a high-speed mixer and mixed evenly, put into a twin-screw extruder for melt blending, cooled and then placed in a pelletizer for granulation, the obtained pellets are dried and immersed in xylene, heated until the pellets are dissolved, and then poured into acetone, stirred and precipitated, filtered and dried to obtain the modified EPDM rubber.

[0016] Through the above-mentioned technical solution, itaconic anhydride is used to melt-graft modify EPDM rubber, and polar chain segments containing carboxyl groups are introduced into the EPDM rubber. Under the action of temperature during the encapsulation process, the carboxyl groups can chemically react with the amide groups on the nylon surface to form a "rubber-itaconic acid-nylon" molecular bridge, thereby reducing phase separation and improving the bonding performance between the TPE composition and nylon. At the same time, the carboxyl groups can also react with the hydroxyl groups on the filler surface to form a "filler-rubber" chemical bridge, thereby reducing filler agglomeration.

[0017] Furthermore, in the preparation method of the modified EPDM rubber, the mass ratio of itaconic anhydride, EPDM rubber, and dicumyl peroxide is (0.065-0.104):1:(0.015-0.030).

[0018] In the above technical solution, the grafting rate of itaconic anhydride in EPDM rubber is controlled by controlling the mass ratio of itaconic acid, EPDM rubber and dicumyl peroxide. Studies have found that when the amount of itaconic anhydride used is small, the grafting rate is low, which has little effect on improving the bonding performance of the TPE composition with nylon. When the amount of itaconic anhydride used exceeds the above range, although the grafting rate increases, the itaconic acid undergoes homopolymerization, resulting in a decrease in the elasticity of the EPDM rubber and affecting the tensile properties of the TPE composition.

[0019] Furthermore, in the preparation method of the modified EPDM rubber, the mass ratio of itaconic acid, EPDM rubber, and dicumyl peroxide is (0.080-0.095):1:(0.020-0.030).

[0020] Furthermore, the temperatures of the twin-screw extruder in the preparation method of the modified EPDM rubber are set in sequence as follows: zone 1 160-170°C, zone 2 180-190°C, zone 3 220-230°C, zone 4 220-230°C, zone 5 210-220°C, and the screw speed is set to 400-500rpm.

[0021] Furthermore, the melt index of the ethylene-acrylate copolymer is 5-10 g / 10 min (190° C. / 2.16).

[0022] Furthermore, the mineral oil is one of paraffin oil, silicone oil and white oil.

[0023] Furthermore, the coupling agent includes a titanate coupling agent and a peroxide.

[0024] In the above technical solution, the long-chain alkane of the titanate coupling agent can be entangled with the TPE matrix, and the polar group at the other end is bonded to the nylon through hydrogen bonding, effectively improving the bonding performance between the TPE composition and nylon, while the peroxide can form a cross-linked network in SEBS, effectively improving the tensile properties of the TPE composition.

[0025] Furthermore, the coupling agent is composed of triisostearyl isopropyl titanate and di-tert-butyl peroxy isopropyl benzene in a mass ratio of 5-9:1-4.

[0026] Furthermore, the auxiliary agent is one of antioxidant 1010, antioxidant 1076, antioxidant 168 and antioxidant 626.

[0027] Furthermore, the filler is one of calcium carbonate, talc, kaolin, mica and wollastonite.

[0028] The present invention also provides a method for preparing the TPE composition for encapsulating nylon, specifically:

[0029] S1: uniformly mix modified SEBS, modified EPDM rubber and mineral oil to form a premix;

[0030] S2: uniformly mixing the above premix with polypropylene and ethylene-acrylate copolymer, and adding a coupling agent, an additive and a filler to obtain a mixture;

[0031] S3: feeding the mixed material obtained in step S2 into the feeding barrel of a twin-screw extruder, adding the melt, extruding and granulating, and obtaining a TPE composition for encapsulating nylon.

[0032] Through the above technical solution, the TPE composition is melt-blended using a twin-screw extruder, and the coupling agent, additives and filler can be fully and evenly dispersed. No solvent or complex initiation system is required, the operation is simple, the equipment cost is low, and it is suitable for industrial mass production.

[0033] Furthermore, the temperatures of the twin-screw extruder in step S3 are set sequentially as follows: zone 1 120-140°C, zone 2 140-160°C, zone 3 170-180°C, zone 4 170-180°C, zone 5 160-180°C, and the screw speed is set to 300-400 rpm.

[0034] Compared with the prior art, the TPE composition for encapsulating nylon and the preparation method thereof provided by the present invention have the following technical advantages:

[0035] (1) The present invention uses modified SEBS and modified EPDM rubber as the main elastomers of the TPE composition, and adds ethylene-acrylate copolymer and coupling agent to the formula to effectively improve the tensile properties of the TPE composition;

[0036] (2) The present invention adopts allyl glycidyl ether to graft-modify SEBS by solution grafting method under the action of initiator, introduces polar group ether bond and epoxy group in allyl glycidyl ether into SEBS, adopts itaconic anhydride to melt-graft-modify EPDM rubber, introduces polar chain segment containing carboxyl group into EPDM rubber, and effectively improves the bonding performance between TPE composition and nylon;

[0037] (3) The TPE composition provided by the present invention can be well coated on nylon, has strong adhesion, good appearance, no abnormal lines, good tensile properties and temperature resistance, and is suitable for use in the coating of nylon power tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the infrared spectrum of the modified SEBS prepared in Example 4;

[0039] Figure 2 This is the infrared spectrum of the modified EPDM rubber prepared in Example 5. DETAILED DESCRIPTION

[0040] The following will be further described in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Those skilled in the art may make various modifications based on the basic concept of the present invention, but as long as they do not depart from the basic concept of the present invention, they are all within the scope of the present invention.

[0041] In this specific embodiment, the raw materials are all commercially available unless otherwise specified.

[0042] Example 1

[0043] A TPE composition for encapsulating nylon, comprising the following components in parts by weight:

[0044] 20g modified SEBS, 10g polypropylene, 20g modified EPDM rubber, 5g ethylene-acrylate copolymer, 25g paraffin oil, 5g coupling agent, 3g antioxidant 1010, and 5g calcium carbonate; the melt index of the ethylene-acrylate copolymer is 5g / 10min (190℃ / 2.16); the coupling agent is composed of triisostearyl isopropyl titanate and di-tert-butyl peroxyisopropylbenzene in a mass ratio of 5:1.

[0045] The preparation method of modified SEBS is as follows: add 100g SEBS to 200mL toluene, heat to 60°C, stir until completely dissolved, and under the protection of inert gas, dropwise add 7.5g allyl glycidyl ether and 7% by mass aqueous solution of azobisisobutyronitrile (the mass of azobisisobutyronitrile is 3.3g), heat to 90°C, and keep warm for 9h. After the reaction is completed, pour the reaction solution into 400mL acetone, stir and precipitate, filter and then place the precipitate in a vacuum drying oven at 40°C for 14h to obtain modified SEBS.

[0046] The preparation method of modified EPDM rubber is as follows: 6.5g of itaconic anhydride is dried at 120℃ for 12h, then put into a high-speed mixer with 100g of EPDM rubber and 1.5g of dicumyl peroxide to be fully mixed, and then put into a twin-screw extruder for melt blending (the temperature of the twin-screw extruder is set as follows: zone 1 160℃, zone 2 180℃, zone 3 220℃, zone 4 220℃, zone 5 210℃, and the screw speed is set to 400rpm), and then cooled and placed in a refrigerator. The pellets were granulated in a pelletizer and dried in a vacuum drying oven at 70°C for 14 hours. They were then immersed in xylene (the mass ratio of pellets to xylene was 1:20), heated in an oil range, and heated for 30 minutes after reflux (at which time the pellets were completely dissolved). The heating was stopped and the solution was poured into acetone (the mass ratio of solution to acetone was 1:2) while hot. The solution was stirred until no precipitation occurred. After filtering, the precipitate was dried in a vacuum drying oven at 90°C for 15 hours to obtain modified EPDM rubber.

[0047] The preparation method of the TPE composition for encapsulating nylon is specifically as follows:

[0048] S1: uniformly mix modified SEBS, modified EPDM rubber and mineral oil to form a premix;

[0049] S2: uniformly mixing the above premix with polypropylene and ethylene-acrylate copolymer, and adding a coupling agent, an additive and a filler to obtain a mixture;

[0050] S3: The mixed material obtained in step S2 is fed into the feeding barrel of a twin-screw extruder (the temperatures of the twin-screw extruder are set as follows: zone 1 120°C, zone 2 140°C, zone 3 170°C, zone 4 170°C, zone 5 160°C, and the screw speed is set to 300 rpm), melted, and extruded into granules to obtain a TPE composition for encapsulating nylon.

[0051] Example 2

[0052] A TPE composition for encapsulating nylon, comprising the following components in parts by weight:

[0053] 30g modified SEBS, 15g polypropylene, 10g modified EPDM rubber, 10g ethylene-acrylate copolymer, 40g white oil, 10g coupling agent, 5g antioxidant 1076, and 15g talc; the melt index of the ethylene-acrylate copolymer is 10g / 10min (190℃ / 2.16); the coupling agent is composed of triisostearyl isopropyl titanate and di-tert-butyl peroxyisopropylbenzene in a mass ratio of 9:4.

[0054] The preparation method of modified SEBS is as follows: add 100g SEBS to 200mL toluene, heat to 80°C, stir until completely dissolved, and under the protection of inert gas, dropwise add 12.5g allyl glycidyl ether and a 10% by mass aqueous solution of azobisisobutyronitrile (the mass of azobisisobutyronitrile is 3.7g), heat to 110°C, and keep warm for 6h. After the reaction is completed, pour the reaction solution into 400mL acetone, stir and precipitate, filter and then place the precipitate in a vacuum drying oven at 60°C for 12h to obtain modified SEBS.

[0055] The preparation method of modified EPDM rubber is as follows: 10.4g of itaconic anhydride is dried at 140℃ for 10h, then put into a high-speed mixer with 100g of EPDM rubber and 3.0g of dicumyl peroxide to be fully mixed, and then put into a twin-screw extruder for melt blending (the temperature of the twin-screw extruder is set as follows: zone 1 170℃, zone 2 190℃, zone 3 230℃, zone 4 230℃, zone 5 220℃, and the screw speed is set to 500rpm), cooled and placed The pellets were granulated in a pelletizer and dried in a vacuum drying oven at 80°C for 12 hours. The pellets were then immersed in xylene (the mass ratio of pellets to xylene was 1:20), heated in an oil region, and heated for 50 minutes after reflux (at which time the pellets were completely dissolved). The heating was stopped and the solution was poured into acetone (the mass ratio of solution to acetone was 1:2) while hot. The solution was stirred until no precipitation occurred. After filtering, the precipitate was dried in a vacuum drying oven at 95°C for 10 hours to obtain modified EPDM rubber.

[0056] The preparation method of the TPE composition for encapsulating nylon is specifically as follows:

[0057] S1: uniformly mix modified SEBS, modified EPDM rubber and mineral oil to form a premix;

[0058] S2: uniformly mixing the above premix with polypropylene and ethylene-acrylate copolymer, and adding a coupling agent, an additive and a filler to obtain a mixture;

[0059] S3: The mixed material obtained in step S2 is fed into the feeding barrel of a twin-screw extruder (the temperatures of the twin-screw extruder are set as follows: zone 1 140°C, zone 2 160°C, zone 3 180°C, zone 4 180°C, zone 5 180°C, and the screw speed is set to 400 rpm), melted, and extruded into granules to obtain a TPE composition for encapsulating nylon.

[0060] Example 3

[0061] A TPE composition for encapsulating nylon, comprising the following components in parts by weight:

[0062] Modified SEBS 27g, polypropylene 13g, modified EPDM rubber 16g, ethylene-acrylate copolymer 8g, silicone oil 30g, coupling agent 7g, antioxidant 168 4g, kaolin 12g; the melt index of ethylene-acrylate copolymer is 8g / 10min (190℃ / 2.16); the coupling agent is composed of triisostearyl isopropyl titanate and di-tert-butyl peroxy isopropyl benzene in a mass ratio of 7:3.

[0063] The preparation method of modified SEBS is as follows: 100g SEBS is added to toluene, heated to 70°C, and stirred until completely dissolved. Under the protection of inert gas, 10.5g allyl glycidyl ether and a 9% by mass aqueous solution of azobisisobutyronitrile (the mass of azobisisobutyronitrile is 3.6g) are added dropwise. The temperature is raised to 105°C and kept warm for 8h. After the reaction is completed, the reaction solution is poured into 400mL acetone, stirred and precipitated, and after filtering, the precipitate is placed in a vacuum drying oven and dried at 50°C for 13h to obtain modified SEBS.

[0064] The preparation method of modified EPDM rubber is as follows: 8.7g of itaconic anhydride is dried at 130℃ for 11h, then put into a high-speed mixer with 100g of EPDM rubber and 2.5g of dicumyl peroxide to mix thoroughly, and then put into a twin-screw extruder for melt blending (the temperature of the twin-screw extruder is set as follows: zone 1 165℃, zone 2 185℃, zone 3 225℃, zone 4 225℃, zone 5 215℃, and the screw speed is set to 450rpm), cooled and placed The pellets were granulated in a pelletizer and dried in a vacuum drying oven at 75°C for 13 h. They were then immersed in xylene (the mass ratio of pellets to xylene was 1:20), heated in an oil region, and heated for 40 min after reflux (at which point the pellets were completely dissolved). The heating was stopped and the solution was poured into acetone (the mass ratio of solution to acetone was 1:2) while hot. The solution was stirred until no precipitation occurred. After filtering, the precipitate was dried in a vacuum drying oven at 93°C for 12 h to obtain modified EPDM rubber.

[0065] The preparation method of the TPE composition for encapsulating nylon is specifically as follows:

[0066] S1: uniformly mix modified SEBS, modified EPDM rubber and mineral oil to form a premix;

[0067] S2: uniformly mixing the above premix with polypropylene and ethylene-acrylate copolymer, and adding a coupling agent, an additive and a filler to obtain a mixture;

[0068] S3: The mixed material obtained in step S2 is fed into the feeding barrel of a twin-screw extruder (the temperatures of the twin-screw extruder are set as follows: zone 1 130°C, zone 2 150°C, zone 3 175°C, zone 4 175°C, zone 5 170°C, and the screw speed is set to 350 rpm), melted, and extruded into granules to obtain a TPE composition for encapsulating nylon.

[0069] Example 4

[0070] The difference between the TPE composition for encapsulating nylon in this embodiment and that in Example 3 is that the preparation method of the modified SEBS in this embodiment is as follows: 100 g of SEBS is added to toluene, the temperature is raised to 70° C., and the mixture is stirred until completely dissolved. Under the protection of inert gas, 11 g of allyl glycidyl ether and a 9% by mass aqueous solution of azobisisobutyronitrile (the mass of azobisisobutyronitrile is 3.5 g) are added dropwise, the temperature is raised to 105° C., and the reaction is kept warm for 8 hours. After the reaction is completed, the reaction solution is poured into 400 mL of acetone, stirred and precipitated, and after filtering, the precipitate is placed in a vacuum drying oven and dried at 50° C. for 13 hours to obtain the modified SEBS.

[0071] The rest of this embodiment is the same as that of embodiment 3.

[0072] Example 5

[0073] The difference between the TPE composition for encapsulating nylon in this embodiment and that in Example 3 is as follows: the preparation method of the modified EPDM rubber in this embodiment is as follows: 9.2g of itaconic anhydride is dried at 130°C for 11h, then mixed with 100g of EPDM rubber and 2.9g of dicumyl peroxide in a high-speed mixer and then melt-blended in a twin-screw extruder (the temperatures of the twin-screw extruder are set as follows: zone 1 165°C, zone 2 185°C, zone 3 225°C, zone 4 225°C, zone 5 215°C, and the screw speed is 200-3000rpm). The speed was set to 450 rpm), and after cooling, the mixture was placed in a pelletizer for granulation. The obtained pellets were placed in a vacuum drying oven and dried at 75°C for 13 h. The pellets were then immersed in xylene (the mass ratio of pellets to xylene was 1:20) and heated in an oil range. After reflux, the heating was continued for 40 min (at which time the pellets were completely dissolved). The heating was stopped and the solution was poured into acetone (the mass ratio of solution to acetone was 1:2) while hot. The mixture was stirred until no precipitate was precipitated. After filtering, the precipitate was placed in a vacuum drying oven and dried at 93°C for 12 h to obtain modified EPDM rubber.

[0074] Comparative Example 1

[0075] The TPE composition in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is that the SEBS is not modified in this comparative example.

[0076] Comparative Example 2

[0077] The TPE composition in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is that the modified SEBS in this comparative example is prepared by adding 100 g of SEBS, 11 g of dried maleic anhydride, and 3.5 g of dicumyl peroxide to a high-speed mixer and mixing thoroughly. The mixture is then put into a twin-screw extruder for melt blending, followed by cooling and pelletizing to obtain the modified SEBS.

[0078] Comparative Example 3

[0079] The TPE composition in this comparative example is similar to that in Example 4. The difference between this comparative example and Example 4 is that the preparation method of the modified SEBS in this comparative example is as follows: 100 g of SEBS is added to toluene, the temperature is raised to 70° C., and stirred until completely dissolved. Under the protection of inert gas, 20 g of allyl glycidyl ether and a 9% by mass aqueous solution of azobisisobutyronitrile (the mass of azobisisobutyronitrile is 5 g) are added dropwise, the temperature is raised to 105° C., and the reaction is kept warm for 8 hours. After the reaction is completed, the reaction solution is poured into 400 mL of acetone, stirred and precipitated, and after filtering, the precipitate is placed in a vacuum drying oven at 50° C. and dried for 13 hours to obtain the modified SEBS.

[0080] Comparative Example 4

[0081] The TPE composition in this comparative example is similar to that in Example 5. The difference between this comparative example and Example 5 is that the EPDM rubber is not modified in this comparative example.

[0082] Comparative Example 5

[0083] The TPE composition in this comparative example is similar to that in Example 5. The difference between this comparative example and Example 5 is that the preparation method of the modified EPDM rubber in this comparative example is as follows: 17g of itaconic anhydride is dried at 130°C for 11h, then mixed with 100g of EPDM rubber and 5.0g of dicumyl peroxide in a high-speed mixer and then melt-blended in a twin-screw extruder (the temperatures of the twin-screw extruder are set as follows: zone 1 165°C, zone 2 185°C, zone 3 225°C, zone 4 225°C, zone 5 215°C, and the screw The rod speed is set to 450rpm), and after cooling, it is placed in a pelletizer for granulation. The obtained pellets are placed in a vacuum drying oven and dried at 75℃ for 13h, then immersed in xylene (the mass ratio of pellets to xylene is 1:20), heated in an oil range, and heated for 40min after reflux (at which time the pellets are completely dissolved). The heating is stopped, and the solution is poured into acetone (the mass ratio of solution to acetone is 1:2) while hot, stirred until no precipitate is precipitated, filtered, and dried in a vacuum drying oven at 93℃ for 12h to obtain modified EPDM rubber.

[0084] Test example

[0085] Preparation of test samples: The TPE composition pellets obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were fed into a BP-8180-A injection molding machine, and the pellets were processed and injection-molded into standard samples. The process parameter settings of the horizontal injection molding machine are shown in Table 1. The prepared standard specimens were placed at room temperature for more than 24 hours for performance testing. Glass fiber reinforced PA6 was selected as the matrix material. Before sample preparation, the nylon PA6 was dried. First, the dried reinforced PA6 was injection-molded into a standard sample using a BP-8180-A horizontal injection molding machine. The reinforced PA6 after injection molding was embedded in another mold, and the dried TPE composition was subjected to secondary injection molding using an injection molding machine so that the TPE composition was evenly covered on the surface of the reinforced PA6 as a coating layer to make a rubber-coated nylon specimen. It was placed at room temperature for more than 24 hours in preparation for subsequent performance testing. The process parameters of the secondary injection molding are shown in Table 2.

[0086] Table 1 Horizontal injection molding machine process parameter settings

[0087]

[0088] Table 2 Secondary injection molding process parameter settings

[0089]

[0090] Tensile Properties: Tensile properties were tested on the test specimens using a WDW-100H universal testing machine in accordance with GB / T 1040-2018. The test method was as follows: The ends of the dumbbell-shaped specimens, which were injection-molded into standard specimens, were firmly fixed to the instrument's fixtures. The tensile rate was set at 100 mm / min. The tensile strength and elongation at break were measured. Each sample group was tested five times, and the average value was calculated to minimize error. The test results are shown in Table 3.

[0091] Peel strength test: A 180° peel test was conducted using a WDW-100H electronic universal testing machine in accordance with GB / T15254-2014. The test sample was secured to one end of the testing machine's fixture, while the other fixture held the coating material. After both ends of the specimen were firmly secured to the fixtures, the test was initiated. The peel strength test was performed at a 180° angle until the coating layer was completely separated from the substrate. The peel strength of the sample was recorded. Each sample group was tested five times, and the average value was calculated. The test results are shown in Table 3.

[0092] Infrared spectrum analysis test: The modified SEBS prepared in Example 4 and the modified EPDM rubber prepared in Example 5 were subjected to infrared spectrum analysis test. Specifically, the test samples were hot-pressed into thin films with a thickness of no more than 1 mm using a tablet press. The samples were tested using a Fourier transform infrared spectrometer with a scanning wave number of 500-4000 cm -1 , resolution 2cm -1 The test results are shown in Figure 1 and Figure 2 .

[0093] Table 3 Performance test results

[0094]

[0095] As can be seen from Table 3, the tensile strength of the TPE composition for encapsulating nylon provided by the present invention after encapsulating nylon is 9.9-12.6 MPa, the elongation at break is 721.0%-785.6%, and the peel strength is 6.4-8.4 kN / m, which fully demonstrates that the TPE composition for encapsulating nylon provided by the present invention has good tensile properties and bonding properties, and can be well encapsulated on nylon.

[0096] Compared with Example 4, in Comparative Example 1, SEBS was not modified, but the peel strength of the obtained sample was significantly reduced, which indicates that the modification of SEBS in the present invention can effectively improve the bonding performance of the TPE composition to nylon; in Comparative Example 2, SEBS was modified with maleic anhydride, but the tensile properties and peel strength of the obtained sample were reduced to varying degrees, which indicates that the effect of modifying SEBS with maleic anhydride is not as good as the effect of modifying SEBS with allyl glycidyl ether; in Comparative Example 3, the mass ratio of SEBS, allyl glycidyl ether and azobisisobutyronitrile was changed, but the tensile properties and peel strength of the obtained sample were reduced to varying degrees, which indicates that in the modification process of SEBS, the amount of modifier and initiator is the key to controlling the grafting rate of the modifier.

[0097] Compared with Example 5, in Comparative Example 4, the EPDM rubber was not modified, but the peel strength of the obtained sample was reduced, which indicates that the modification of the EPDM rubber in the present invention can improve the bonding performance between the TPE composition and nylon; in Comparative Example 5, the mass ratio of itaconic anhydride, EPDM rubber, and dicumyl peroxide was changed, but the tensile properties and peel strength of the obtained sample were reduced to varying degrees, which indicates that in the modification process of EPDM rubber, the amount of modifier and initiator is the key factor in controlling the grafting rate of the modifier.

[0098] Depend on Figure 1 It can be seen that the infrared spectrum of modified SEBS is at 1212 cm -1 The asymmetric stretching vibration absorption peak of the ether bond in allyl glycidyl ether appears at 900 cm -1 The characteristic absorption peak of the epoxy group in allyl glycidyl ether appeared at , which shows that allyl glycidyl ether has been grafted into the molecular structure of SEBS.

[0099] Depend on Figure 2 It can be seen that the infrared spectrum of modified EPDM rubber is at 1717cm -1 The stretching vibration peak of the carbonyl group in itaconic acid appears at 1629 cm -1 The bending vibration peak of the carboxyl group in itaconic acid appears at , which indicates that itaconic acid has been grafted into the molecular structure of EPDM rubber.

[0100] The above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Persons skilled in the art should not modify the above embodiments without departing from the spirit and scope of the present invention. Any equivalent modifications or alterations made by persons skilled in the art without departing from the technical spirit of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A TPE composition for encapsulating nylon, characterized in that: The composition comprises the following components in parts by weight: 20-30 parts of modified SEBS, 10-15 parts of polypropylene, 10-20 parts of modified EPDM rubber, 5-10 parts of ethylene-acrylate copolymer, 25-40 parts of mineral oil, 5-10 parts of coupling agent, 3-5 parts of additive, and 5-15 parts of filler; coupling agents include titanate coupling agents and peroxides; The modified SEBS preparation method comprises: dissolving SEBS in toluene, adding dropwise an aqueous solution of allyl glycidyl ether and azobisisobutyronitrile under inert gas protection, heating to 90-110° C., and reacting at this temperature for 6-9 hours. After the reaction is completed, pouring the reaction solution into acetone, stirring and precipitating, filtering, and drying to obtain the modified SEBS; wherein the mass ratio of SEBS, allyl glycidyl ether, and azobisisobutyronitrile is 1:(0.075-0.125):(0.033-0.037); The preparation method of the modified EPDM rubber comprises the following steps: adding dried itaconic anhydride, EPDM rubber and dicumyl peroxide into a high-speed mixer and mixing them uniformly, adding the mixture into a twin-screw extruder for melt blending, cooling the mixture and pelletizing the mixture in a pelletizer, drying the obtained pellets and immersing them in xylene, heating the pellets until the pellets are dissolved, pouring the mixture into acetone, stirring and precipitating the mixture, filtering and drying the mixture to obtain the modified EPDM rubber; wherein the mass ratio of itaconic anhydride, EPDM rubber and dicumyl peroxide is (0.065-0.104):1:(0.015-0.030).

2. The TPE composition for encapsulating nylon according to claim 1, characterized in that: The mass percentage of the aqueous solution of azobisisobutyronitrile in the preparation method of the modified SEBS is 7%-10%.

3. The TPE composition for encapsulating nylon according to claim 1, characterized in that: The temperatures of the twin-screw extruder in the preparation method of modified EPDM rubber are set as follows: zone 1 160-170°C, zone 2 180-190°C, zone 3 220-230°C, zone 4 220-230°C, zone 5 210-220°C, and the screw speed is set to 400-500rpm.

4. The TPE composition for encapsulating nylon according to claim 1, characterized in that The coupling agent is composed of triisostearyl isopropyl titanate and di-tert-butyl peroxy isopropyl benzene in a mass ratio of 5-9:1-4.

5. The method for preparing a TPE composition for encapsulating nylon according to any one of claims 1 to 4, characterized in that: Specifically: S1: uniformly mix modified SEBS, modified EPDM rubber and mineral oil to form a premix; S2: uniformly mixing the above premix with polypropylene and ethylene-acrylate copolymer, and adding a coupling agent, an additive and a filler to obtain a mixture; S3: feeding the mixed material obtained in step S2 into the feeding barrel of a twin-screw extruder, adding the melt, extruding and granulating, and obtaining a TPE composition for encapsulating nylon.

6. The method for preparing a TPE composition for encapsulating nylon according to claim 5, characterized in that: The temperatures of the twin-screw extruder in step S3 are set sequentially as follows: zone 1 120-140° C., zone 2 140-160° C., zone 3 170-180° C., zone 4 170-180° C., zone 5 160-180° C., and the screw speed is set to 300-400 rpm.

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