Thermoplastic elastomer, process for its preparation and use thereof

Abstract

The present application relates to a kind of thermoplastic elastomer and its preparation method and application, the thermoplastic elastomer includes the following components by weight parts: styrene-based copolymer 5-50 parts, polyolefin resin 1-30 parts, polyacrylic hydrophilic resin 20-80 parts, paraffin oil 10-60 parts, compatible agent 1-20 parts.The present application is obtained by multi-component complex, has excellent strength and high temperature resilience performance, and expansion occurs when meeting water, original size can be restored when losing water, the sealing effect of material is improved, is suitable for the field in the municipal waterproof, automobile, building, household appliance etc. with waterproof demand.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a thermoplastic elastomer, its preparation method, and its application. Background Technology

[0002] Styrene copolymers are the lowest-priced thermoplastic elastomers and the most widely used. They are block copolymers, made of rigid polystyrene segments linked to flexible segments (such as polybutadiene, polyisoprene, ethylene propylene rubber, or styrene). These materials possess excellent mechanical properties, thermal stability, a soft touch, low odor and emission, and are safe and non-toxic, making them widely used in the automotive, construction, toy, medical, consumer goods, and home appliance industries.

[0003] Rubber seals are widely used in automotive, construction, and home appliance applications, such as automotive window seals, glass sunroof seals, and washing machine seals. For example, CN109456544A discloses a method for preparing an environmentally friendly valve seal, comprising the following steps: mixing polystyrene, EPDM rubber, titanate coupling agent, and antioxidant to obtain a rubber compound; mixing expanded graphite, vermiculite powder, nano-mica powder, polyacrylonitrile-based carbon fiber, calcium sulfate whiskers, aluminum borate whiskers, carrageenan, sodium carboxymethyl cellulose, and water, ultrasonically dispersing, and spray drying to obtain a dispersion; and feeding the rubber compound, dispersion, and microcrystalline wax into a twin-screw extruder for extrusion and granulation to obtain an environmentally friendly valve seal. The resulting seal is halogen-free and flame-retardant, resistant to heat aging, has high tensile strength, and high elongation at break.

[0004] CN108707276A discloses a method for preparing a flame-retardant and sound-insulating sealing strip for automobiles. The method includes the following steps: placing nickel ferrite fiber, a chain extender, and a foaming agent in a polymer emulsion and heating to react, obtaining modified nickel ferrite fiber; ultrasonically washing and drying the composite fiber, followed by high-temperature treatment at 200-250℃ for 10-20 minutes to obtain composite fiber; feeding EVA resin, phenolic resin, composite fiber, mesoporous silica, acrylonitrile-butadiene-styrene copolymer, α-methylstyrene-acrylonitrile copolymer, and an antioxidant into a twin-screw extruder, followed by melt extrusion and granulation to obtain a composite masterbatch; and then performing secondary injection molding on the composite masterbatch to obtain the flame-retardant and sound-insulating sealing strip for automobiles. The resulting sealing strip is lightweight, has good sound absorption and flame-retardant properties, meeting modern requirements for lightweighting, environmental protection, and comfort.

[0005] However, these sealing products often suffer from poor high-temperature resistance and water resistance. Under prolonged high-temperature environments, their resilience decreases, leading to a deterioration in sealing performance and making them prone to liquid leakage in rainy weather or water-contact applications. Therefore, how to provide a sealing material that is both high-temperature resistant and leak-proof has become an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a thermoplastic elastomer, its preparation method, and its application. Through multi-component compounding, the thermoplastic elastomer expands upon contact with water and recovers upon water loss, while also exhibiting excellent high-temperature resilience, thus improving the sealing effect of the material and meeting the temperature-resistant and waterproof requirements of rubber sealing parts in municipal waterproofing, automobiles, buildings, and home appliances.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a thermoplastic elastomer, which, by weight, comprises the following components: 5-50 parts of styrene-based copolymer, 1-30 parts of polyolefin resin, 20-80 parts of polyacrylic acid hydrophilic resin, 10-60 parts of paraffin oil, and 1-20 parts of compatibilizer.

[0009] This invention utilizes a styrene-based copolymer and a polyolefin resin to create a thermoplastic elastomer with excellent mechanical strength and high-temperature resilience. Further, it combines this elastomer with a hydrophilic polyacrylic resin to regulate its water absorption and loss capabilities, allowing it to expand in volume after absorbing water and return to its original size after losing water. This prevents leakage of the sealing material under high-temperature conditions or upon contact with water. Furthermore, the addition of a compatibilizer and paraffin oil improves the system's compatibility, resulting in a thermoplastic elastomer with significantly improved sealing performance, meeting the application needs of a wider range of fields.

[0010] The styrene-based copolymer is 5-50 parts, for example, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts or 45 parts, etc.

[0011] The polyolefin resin is 1-30 parts, for example, 2 parts, 5 parts, 8 parts, 10 parts, 15 parts, 20 parts or 25 parts, etc.

[0012] The polyacrylic hydrophilic resin is 20-80 parts, for example, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 60 parts or 70 parts, etc.

[0013] The paraffin oil is 10-60 parts, for example, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts or 55 parts, etc.

[0014] The compatibilizer is 1-20 parts, for example, 2 parts, 5 parts, 8 parts, 10 parts, 12 parts, 15 parts or 18 parts, etc.

[0015] Preferably, the thermoplastic elastomer comprises, by weight, the following components: 10-23 parts of styrene-based copolymer (e.g., 12, 15, 18, 20, or 22 parts), 5-17 parts of polyolefin resin (e.g., 6, 8, 10, 12, 14, or 16 parts), 40-65 parts of polyacrylic acid hydrophilic resin (e.g., 42, 45, 48, 50, 52, 55, 58, or 60 parts), 20-35 parts of paraffin oil (e.g., 22, 25, 28, 30, or 32 parts), and 5-13 parts of compatibilizer (e.g., 6, 7, 8, 9, 10, 11, or 12 parts).

[0016] As a preferred embodiment of the present invention, the styrene-based copolymer in the thermoplastic elastomer has a mass percentage content of 10-23%, for example, it can be 11%, 13%, 15%, 17%, 19% or 21%, etc.

[0017] As a preferred embodiment of the present invention, the mass percentage of polyolefin resin in the thermoplastic elastomer is 5-17%, for example, it can be 6%, 8%, 10%, 12%, 14% or 16%, etc.

[0018] As a preferred embodiment of the present invention, the mass percentage of polyacrylic acid hydrophilic resin in the thermoplastic elastomer is 40-65%, for example, it can be 41%, 43%, 45%, 47%, 49%, 51%, 53%, 55%, 57%, 59%, 61% or 63%, etc., and more preferably 42-58%.

[0019] As a preferred embodiment of the present invention, the paraffin oil content in the thermoplastic elastomer is 15-35% by mass, for example, it can be 18%, 20%, 21%, 23%, 25%, 27%, 29%, 31% or 33%, etc.

[0020] As a preferred embodiment of the present invention, the compatibilizer in the thermoplastic elastomer has a mass percentage content of 5-13%, for example, it can be 6%, 7%, 8%, 9%, 10%, 11% or 12%, etc.

[0021] In this invention, the styrene-based copolymer includes copolymers of styrene and olefin monomers and / or hydrogenated products of copolymers of styrene and olefin monomers; the olefin monomers include, but are not limited to, any one or a combination of at least two of ethylene, propylene, butene, butadiene, and isoprene.

[0022] It should be noted that the styrene-based copolymers include styrene-based random copolymers and / or styrene-based block copolymers, with styrene-based block copolymers being preferred.

[0023] Preferably, the styrene-based copolymer includes any one or a combination of at least two of styrene-butadiene copolymer (SBS), styrene-ethylene-butene-styrene copolymer (SEBS), or styrene-poly(ethylene / ethylene / propylene)-styrene copolymer (SEEPS).

[0024] Preferably, the styrene-based copolymer includes linear styrene-based copolymers and / or network styrene-based copolymers, with linear styrene-based copolymers being more preferred. As a preferred embodiment of the present invention, the use of linear styrene-based copolymers facilitates the absorption and loss of water in thermoplastic elastomers. When other network crosslinking structures (e.g., a two-star structure) are used, the styrene-based copolymer has a stronger encapsulation of the polyolefin resin, leading to difficulties in water absorption and loss, and thus failing to achieve the "elastic waterproof" effect.

[0025] Preferably, the weight-average molecular weight (Mw) of the styrene-based copolymer is 60,000-300,000 g / mol, for example, it can be 70,000 g / mol, 80,000 g / mol, 100,000 g / mol, 120,000 g / mol, 150,000 g / mol, 160,000 g / mol, 170,000 g / mol, 180,000 g / mol, 190,000 g / mol, 200,000 g / mol, 2 The values ​​are 0.5000 g / mol, 210000 g / mol, 215000 g / mol, 220000 g / mol, 225000 g / mol, 230000 g / mol, 240000 g / mol, 250000 g / mol, 260000 g / mol, or 280000 g / mol, etc., with 150000-250000 g / mol being more preferred, and 200000-230000 g / mol being even more preferred.

[0026] As a preferred technical solution of the present invention, a styrene-based copolymer with a specific weight-average molecular weight is compounded with other components, which improves the tensile strength of the resulting thermoplastic elastomer and reduces compression set.

[0027] For example, the styrene-based copolymers described in this invention can be commercially available products, such as Gobalprene 7551, Taipol 6151, Kraton G1651, etc.

[0028] Preferably, the polyolefin resin includes polypropylene (PP) and / or polyethylene (PE), and more preferably polypropylene.

[0029] Preferably, the polypropylene includes copolymer polypropylene and / or homopolymer polypropylene, and more preferably homopolymer polypropylene.

[0030] Preferably, the polyethylene includes low-density polyethylene and / or high-density polyethylene.

[0031] As a preferred technical method of the present invention, homopolymer polypropylene has better compatibility with other components in thermoplastic elastomers, which is conducive to forming a uniform and stable system and improving the mechanical strength and high-temperature resilience of the material.

[0032] Preferably, the melt index of the polypropylene at 230°C and 2.16 kg is 1-10 g / 10 min, for example, it can be 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min or 9 g / 10 min, etc.

[0033] Preferably, the melt index of the polyethylene at 190°C and 2.16 kg is 1-10 g / 10 min, for example, it can be 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min or 9 g / 10 min, etc.

[0034] As a preferred embodiment of the present invention, a polyolefin resin with a specific melt index is compounded with a styrene-based copolymer, a hydrophilic polyacrylic resin, paraffin oil, and a compatibilizer. This approach is more conducive to giving the thermoplastic elastomer high strength, excellent high-temperature resilience, and water absorption properties. If the melt index of the polyolefin resin is too high, it will lead to a decrease in the resilience of the elastomer material and a reduction in its water absorption properties.

[0035] Preferably, the polyacrylic hydrophilic resin includes polyacrylic acid and / or polyacrylate.

[0036] Preferably, the polyacrylate comprises any one or a combination of at least two of sodium polyacrylate, potassium polyacrylate, and ammonium polyacrylate, with sodium polyacrylate being more preferred.

[0037] Preferably, the particle size (raw material) of the polyacrylic acid hydrophilic resin is 20-100 mesh, for example, it can be 30 mesh, 40 mesh, 50 mesh, 60 mesh, 70 mesh, 80 mesh or 90 mesh, etc.

[0038] This invention does not specifically limit the paraffin oil; commercially available Group II hydrogenated paraffin oil can be used, such as Formosa Plastics 500N, CNOOC 150N, or Hansheng Pionier 2071P.

[0039] Preferably, the paraffin oil has a kinematic viscosity of 60-150 cst at 40°C, for example, 70 cst, 80 cst, 90 cst, 110 cst, 120 cst, 130 cst or 140 cst.

[0040] Preferably, the compatibilizer comprises any one or a combination of at least two of ethylene-acrylic acid copolymer (EAA), ethylene-vinyl acetate copolymer (EVA), maleic anhydride-grafted polyolefin, or maleic anhydride-grafted ethylene propylene diene monomer (EPDM), more preferably ethylene-acrylic acid copolymer and / or maleic anhydride-grafted polyolefin, and more preferably ethylene-acrylic acid copolymer.

[0041] As a preferred technical solution of the present invention, using ethylene-acrylic acid copolymer as a compatibilizer can further improve the compatibility of the system, thereby ensuring that the material has excellent tensile strength and water absorption swelling rate.

[0042] Preferably, the melt index of the ethylene-acrylic acid copolymer at 190°C and 2.16 kg is 8-15 g / 10 min, for example, it can be 9 g / 10 min, 10 g / 10 min, 11 g / 10 min, 12 g / 10 min, 13 g / 10 min or 14 g / 10 min, etc.

[0043] Preferably, the mass percentage of acrylic acid-based structural units in the ethylene-acrylic acid copolymer is 5-20%, for example, it can be 6%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, etc., and more preferably 6.5-15%.

[0044] Preferably, the maleic anhydride-grafted polyolefin includes any one or a combination of at least two of maleic anhydride-grafted polypropylene (PP), maleic anhydride-grafted ethylene / α-olefin copolymer (POE), or maleic anhydride-grafted polyethylene.

[0045] Preferably, the melt index of the maleic anhydride-grafted polypropylene at 230°C and 2.16 kg is 50-200 g / 10 min, for example, it can be 60 g / 10 min, 80 g / 10 min, 100 g / 10 min, 120 g / 10 min, 140 g / 10 min, 150 g / 10 min, 160 g / 10 min or 180 g / 10 min, etc.

[0046] Preferably, the maleic anhydride-grafted polyethylene comprises maleic anhydride-grafted linear low-density polyethylene (LLDPE).

[0047] Preferably, the melt index of the maleic anhydride-grafted polyethylene at 190°C and 2.16 kg is 0.5-10 g / 10 min, for example, it can be 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min or 9 g / 10 min, etc.

[0048] It should be noted that the thermoplastic elastomer of the present invention may also include any other additives that are motivated to be added in the art.

[0049] Preferably, the thermoplastic elastomer further includes 0.2-0.8 parts by weight of antioxidant, such as 0.25 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, or 0.7 parts by weight.

[0050] Preferably, the antioxidant includes any one or a combination of at least two of the following: hindered phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, and thioester antioxidants.

[0051] Preferably, the antioxidant comprises any one or a combination of at least two of the following: 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetra(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) (antioxidant 1010), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076), 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione (antioxidant 1790), tris(2,4-di-tert-butyl)phenyl phosphite (antioxidant 168), or pentaerythritol tetra(3-lauryl thiopropionate) (antioxidant 412S).

[0052] In a second aspect, the present invention provides a method for preparing the thermoplastic elastomer as described in the first aspect, the method comprising the following steps:

[0053] The thermoplastic elastomer is obtained by mixing styrene-based copolymer, polyolefin resin, polyacrylic hydrophilic resin, paraffin oil, compatibilizer and optional antioxidant, followed by extrusion and granulation.

[0054] Preferably, the mixing is carried out in a high-speed mixer.

[0055] Preferably, the extrusion is carried out in a twin-screw extruder.

[0056] Preferably, the length-to-diameter ratio of the twin-screw extruder is ≥52, for example, it can be 53, 55, 60, 65, 70, 75 or 80, etc.

[0057] Preferably, the rotational speed of the twin-screw extruder is 180-450 rpm, for example, it can be 200 rpm, 220 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm, etc.

[0058] Preferably, the temperature of the twin-screw extruder is 140-180℃, for example, it can be 145℃, 150℃, 155℃, 160℃, 165℃, 170℃ or 175℃, etc.

[0059] Preferably, the extrusion feed rate is 150-450 kg / h, for example, it can be 180 kg / h, 200 kg / h, 250 kg / h, 300 kg / h, 350 kg / h or 400 kg / h.

[0060] Preferably, the granulation is carried out in a pelletizer.

[0061] Preferably, the extrusion and granulation operation includes plasticizing the material using a twin-screw extruder, feeding it into a cold water tank, and then drawing it into a pelletizer for pelletizing to obtain the thermoplastic elastomer.

[0062] Thirdly, the present invention provides a sealing element, the raw material for which the sealing element is prepared includes the thermoplastic elastomer as described in the first aspect.

[0063] The sealing component provided by this invention can be used as a rubber sealing part in applications requiring waterproofing, such as municipal waterproofing, automobiles, buildings, and home appliances, achieving excellent waterproof and temperature-resistant effects.

[0064] Compared with the prior art, the present invention has at least the following beneficial effects:

[0065] The thermoplastic elastomer provided by this invention comprises styrene-based copolymer, polyolefin resin, polyacrylic hydrophilic resin, paraffin oil, and compatibilizer. The components work synergistically to achieve "elastic water absorption," improving the material's temperature resistance and waterproof performance while maintaining excellent mechanical strength, thus expanding the application field of the obtained thermoplastic elastomer as a sealing material. Detailed Implementation

[0066] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0067] In the following specific embodiments of the present invention, the materials involved are as follows:

[0068] (1) Styrene-based copolymers

[0069] SEBS1, SEBS 7550U, Li Changrong, linear structure;

[0070] SEBS2, SEBS 7551, Li Changrong, linear structure;

[0071] SEBS3, SEBS YH-688, Yuehua, two-star structure;

[0072] SBS, SBS 3566, Huizhou Li Changrong, linear structure.

[0073] (2) Polyolefin resin

[0074] PP1, homopolymer polypropylene, PPH-T03, Sinopec, melt index of 3.0 g / 10 min at 230℃ and 2.16 kg;

[0075] PP2, copolymer polypropylene, Globalene ST611M, Li Changrong, melt index of 1.8 g / 10 min at 230℃ and 2.16 kg;

[0076] PP3, homopolymer polypropylene, Daqing Petrochemical, melt index of 5.4 g / 10 min at 230℃ and 2.16 kg;

[0077] PP4, homopolymer polypropylene, Zhenhai Refining & Chemical, melt index of 26g / 10min at 230℃ and 2.16kg;

[0078] Linear low-density polyethylene (LLDPE), DFDA-7042, Guangzhou Petrochemical, melt index of 2.0 g / 10 min at 190℃ and 2.16 kg.

[0079] (3) Hydrophilic resin

[0080] Sodium polyacrylate, GS-3100H, LG Chem;

[0081] Polyacrylamide, 18 million anionic PAM, Zibo Lanerqing.

[0082] (4) Paraffin oil

[0083] Paraffin oil, 500N, Formosa Plastics, kinematic viscosity 90cst at 40℃.

[0084] (5) Compatibilizer

[0085] EAA, EAA Nucrel 3990, Dow Chemical;

[0086] Maleic anhydride-grafted polypropylene (MAH-PP), FH118, Ganzhou Nengzhiguang;

[0087] Maleic anhydride-grafted linear low-density polyethylene (MAH-LLDPE), PC-31-4, Foshan Baichen.

[0088] (6) Antioxidants

[0089] Antioxidant 1010, Irganox 1010, BASF.

[0090] (7) Ethylene propylene diene monomer (EPDM) rubber

[0091] EPDM 3072EPM, Sinopec Mitsui, Mooney viscosity at 125℃ is 51MU.

[0092] Example 1

[0093] A thermoplastic elastomer, by weight, comprises 15 parts SEBS (SEBS 7550U), 8 parts homopolymer polypropylene (Z30-S), 50 parts sodium polyacrylate (GS-3100H), 20 parts paraffin oil (500N), 7 parts compatibilizer EAA, and 0.2 parts antioxidant 1010 (Irganox 1010).

[0094] The thermoplastic elastomer is prepared by the following method:

[0095] The components are mixed evenly in a high-speed mixer and added at a rate of 300 kg / h to a twin-screw extruder with a length-to-diameter ratio of 52. The twin-screw extruder rotates at 300 rpm and is heated at 170°C. After plasticizing by the twin-screw extruder, the material is fed into a cold water tank and then drawn into a pelletizer for pelletizing to obtain the thermoplastic elastomer.

[0096] The thermoplastic elastomer provided in Example 1 was subjected to the following performance tests:

[0097] (1) Shore hardness

[0098] Thermoplastic elastomer was added to an injection molding machine and injection molded at 190°C into a square plate with a length, width, and height of 100mm × 100mm × 2mm. After standing for 24 hours at 23°C and 50% relative humidity, the three square plates were stacked to form a sample with a thickness of 6mm. The hardness of the sample was measured and recorded using a Shore A hardness tester.

[0099] (2) Tensile strength

[0100] The thermoplastic elastomer was added to the injection molding machine and injection molded at 190°C into a square plate with a length, width, and height of 100mm × 100mm × 2mm. The plate was then cut into strips of the Type 1A size in the ISO 37-2024 standard using a cutter. The strips were then tested using a universal tensile testing machine in accordance with the ISO 37-2024 standard, with a tensile rate of 500mm / min.

[0101] (3) Water absorption swelling rate

[0102] Thermoplastic elastomer was added to an injection molding machine and processed into a sample with dimensions of 100mm × 10mm × 2mm at 190℃. The volume of the sample before immersion was measured and recorded using a vernier caliper. The sample was then completely immersed in 5 liters of distilled water at 23℃ and allowed to stand for 24 hours. Afterward, the sample was removed and its dimensions were immediately measured to obtain the volume of the sample after immersion. The water absorption swelling rate was calculated using the following formula:

[0103] Water absorption swelling rate = 100% × (volume of the sample after soaking - volume of the sample before soaking) / volume of the sample before soaking.

[0104] (4) Rate of change in water volume

[0105] Thermoplastic elastomer was added to an injection molding machine and processed into strips with dimensions of 100mm × 10mm × 2mm at 190℃. The weight of the strips was recorded. The strips were then soaked in distilled water according to the water absorption swelling rate measurement method, and placed in a 100℃ oven for 24 hours. The weight of the strips was measured. When the weight difference before and after soaking was less than 0.1g, the dimensions of the strip after water loss were tested to obtain the volume of the dried strip. The water loss volume change rate was calculated using the following formula:

[0106] Water loss volume change rate = 100% × (volume of dried sample - volume of sample before soaking) / volume of sample before soaking.

[0107] (5) Permanent compression deformation

[0108] Thermoplastic elastomer was added to an injection molding machine, and circular blocks conforming to the dimensions of GB / T 7759.1-2015A type specimen were obtained at 190℃, with dimensions of 29±0.5mm and a height of 12.5±0.5mm. The permanent compression set was tested at 70℃ for 22 hours according to GB / T7759.1-2015A type, method A. A smaller value indicates better high-temperature resilience of the material.

[0109] The test results are summarized in Table 1.

[0110] Examples 2-13, Comparative Examples 1-5

[0111] A thermoplastic elastomer differs from Example 1 in that its formulation is different, as shown in Tables 1 and 2; the amount of each component is expressed in "parts by weight" of solid content; the preparation method and performance testing method of the thermoplastic elastomer are the same as those of Example 1.

[0112] Table 1

[0113]

[0114]

[0115] Table 2

[0116]

[0117]

[0118] The test results show that this invention, by compounding styrene-based copolymers, polyolefin resins, polyacrylic hydrophilic resins, paraffin oil, and compatibilizers, obtains a thermoplastic elastomer material that swells upon contact with water and reverts upon loss of water. Its Shore hardness is 44-62A, its volume expansion rate after water absorption is ≥248%, its volume change rate after water loss is ≤15%, its tensile strength is ≥1.2MPa, and its permanent compression set at 70℃ / 22 hours is ≤82%. In a further preferred embodiment, the thermoplastic elastomer material has a volume expansion rate of 301-372% after water absorption, a volume change rate after water loss is ≤8%, a tensile strength of ≥2.8MPa, and a permanent compression set at 70℃ / 22 hours is ≤68%, meeting the application requirements of sealing materials for temperature resistance, waterproofing, and high strength.

[0119] By comparing Examples 2 and 3, it can be seen that the present invention can obtain the best water absorption swelling rate and volume change rate after water loss by selecting a linear SEBS structure. In contrast, the star-shaped SEBS network structure is prone to encapsulating the resin matrix, which prevents the hydrophilic resin from expanding freely and reduces the volume swelling rate after water absorption.

[0120] By comparing Examples 2 with Examples 4 and 8, it can be seen that the present invention, by selecting EAA as a compatibilizer, has better compatibility with the matrix resin, thereby improving the permanent compression set, water absorption swelling rate and tensile strength of the obtained thermoplastic elastomer.

[0121] By comparing Example 2 with Examples 6 and 7, it can be seen that under the condition of a specific ratio of hydrophilic resin, the volume expansion rate after water absorption reaches the optimal level. Further increasing the hydrophilic resin does not increase the volume expansion rate, while reducing the ratio of hydrophilic resin reduces the volume expansion rate after water absorption.

[0122] A comparison of Examples 2 with Examples 9 and 10 shows that the present invention preferably uses homopolymer polypropylene as the polyolefin resin component, which is superior to copolymer polypropylene and linear low-density polyethylene in terms of permanent compression set. This is mainly because the melting temperature of the crystalline region of homopolymer polypropylene (T) is... m The viscosity is higher than that of copolymer polypropylene and linear low-density polyethylene, which makes the blended resin have low molecular activity at high temperatures, resulting in less permanent deformation.

[0123] Furthermore, as can be seen from Examples 2, 11 and 12, the preferred melt index of polypropylene in this invention is 1-10 g / 10 min. When combined with other components, it can achieve better resilience and water absorption properties. If the melt index of polypropylene is too high, it will lead to an increase in the permanent compression deformation of the material, a decrease in water absorption, and an increase in the volume change rate after water loss.

[0124] As can be seen from Examples 2 and 13, in this invention, the thermoplastic elastomer using SEBS exhibits superior performance in terms of strength, water absorption, and high-temperature resilience compared to SBS.

[0125] Comparing Example 2 with Comparative Example 1, it can be seen that the thermoplastic elastomer of the present invention uses sodium polyacrylate as a hydrophilic resin. Under the same addition ratio, the volume expansion rate after water absorption is significantly better than that of polyacrylamide. This is mainly because the ionic bonds in the structure of sodium polyacrylate are more likely to undergo ion exchange with water than the amino covalent bonds in polyacrylamide, thus resulting in stronger water absorption. At the same time, the compounding of sodium polyacrylate with other components also helps to improve the high-temperature resilience and strength of the thermoplastic elastomer.

[0126] By comparing Example 2 with Comparative Examples 2-5, it can be seen that the present invention improves the tensile strength of the material and obtains a lower permanent compression set by compounding styrene-based copolymers, polyolefin resins, polyacrylic hydrophilic resins, paraffin oil, and compatibilizers, thereby increasing the water absorption volume expansion rate of the material and giving the resulting thermoplastic elastomer an "elastic water absorption" effect that expands when exposed to water and recovers its original size when water is lost.

[0127] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A thermoplastic elastomer, characterized in that, The thermoplastic elastomer comprises, by weight, the following components: 5-50 parts of styrene-based copolymer, 1-30 parts of polyolefin resin, 35-70 parts of polyacrylic acid hydrophilic resin, 10-60 parts of paraffin oil, and 1-20 parts of compatibilizer. The compatibilizer includes any one or a combination of at least two of ethylene-acrylic acid copolymer and ethylene-vinyl acetate copolymer; The polyolefin resin is polypropylene; the polypropylene is homopolymer polypropylene.

2. The thermoplastic elastomer according to claim 1, characterized in that, The thermoplastic elastomer comprises, by weight, the following components: 10-23 parts of styrene-based copolymer, 5-17 parts of polyolefin resin, 40-65 parts of polyacrylic acid hydrophilic resin, 20-35 parts of paraffin oil, and 5-13 parts of compatibilizer.

3. The thermoplastic elastomer according to claim 1, characterized in that, The styrene-based copolymer includes any one or a combination of at least two of the following: styrene-butadiene copolymer, styrene-ethylene-butene-styrene copolymer, or styrene-poly(ethylene / ethylene / propylene)-styrene copolymer.

4. The thermoplastic elastomer according to claim 1, characterized in that, The styrene-based copolymers include linear styrene-based copolymers.

5. The thermoplastic elastomer according to claim 1, characterized in that, The weight-average molecular weight of the styrene-based copolymer is 60,000-300,000 g / mol.

6. The thermoplastic elastomer according to claim 5, characterized in that, The weight-average molecular weight of the styrene-based copolymer is 150,000-250,000 g / mol.

7. The thermoplastic elastomer according to claim 1, characterized in that, The polypropylene has a melt index of 1-10 g / 10 min at 230°C and 2.16 kg.

8. The thermoplastic elastomer according to claim 1, characterized in that, The polyacrylic hydrophilic resin includes polyacrylic acid and / or polyacrylate.

9. The thermoplastic elastomer according to claim 1, characterized in that, The thermoplastic elastomer contains 40-65% by mass of polyacrylic acid hydrophilic resin.

10. The thermoplastic elastomer according to claim 1, characterized in that, The compatibilizer is an ethylene-acrylic acid copolymer.

11. The thermoplastic elastomer according to claim 1, characterized in that, The thermoplastic elastomer also includes 0.2-0.8 parts by weight of antioxidant.

12. The thermoplastic elastomer according to claim 11, characterized in that, The antioxidants include any one or a combination of at least two of the following: 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetratetra(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, tris(2,4-di-tert-butyl)phosphite, or pentaerythritol tetratetra(3-lauryl thiopropionate).

13. A method for preparing the thermoplastic elastomer according to any one of claims 1-12, characterized in that, The preparation method includes the following steps: The thermoplastic elastomer is obtained by mixing styrene-based copolymer, polyolefin resin, polyacrylic hydrophilic resin, paraffin oil, compatibilizer and optional antioxidant, followed by extrusion and granulation.

14. The preparation method according to claim 13, characterized in that, The mixing is carried out in a high-speed mixer.

15. The preparation method according to claim 13, characterized in that, The extrusion is carried out in a twin-screw extruder.

16. The preparation method according to claim 15, characterized in that, The length-to-diameter ratio of the twin-screw extruder is ≥52.

17. The preparation method according to claim 15, characterized in that, The twin-screw extruder operates at a speed of 180-450 rpm.

18. The preparation method according to claim 15, characterized in that, The temperature of the twin-screw extruder is 140-180℃.

19. The preparation method according to claim 13, characterized in that, The extrusion feed rate is 150-450 kg / h.

20. The preparation method according to claim 13, characterized in that, The granulation is carried out in a pelletizer.

21. A sealing element, characterized in that, The raw materials for preparing the seal include the thermoplastic elastomer as described in any one of claims 1-12.

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