Thermoplastic hot melt adhesive for bonding cover plates of household appliances and preparation method of thermoplastic hot melt adhesive

Abstract

The invention provides a thermoplastic hot melt adhesive for bonding cover plates of household appliances and a preparation method of the thermoplastic hot melt adhesive. The thermoplastic hot melt adhesive for bonding cover plates of household appliances comprises the following components in parts by mass: 40-70 parts of a high-polarity thermoplastic elastomer; 5 to 10 parts of a copolymer containing amorphous alpha-olefin; 10 to 50 parts of tackifying resin with a high softening point; 0.5 to 2 parts of an antioxidant; 0.5 to 2 parts of a light stabilizer; 0.2 to 0.5 part of a silane coupling agent; wherein the high-polarity thermoplastic elastomer is at least one of TPU, EAA, TPEE, ACM and PA. The bonding performance is improved through the high-polarity thermoplastic elastomer; the copolymer containing the amorphous alpha-olefin promotes wetting and permeation on the surface of an adhered object, so that the adhesion is improved, and the toughness of the high-temperature-resistant hot melt adhesive is improved; physical cross-linking curing is carried out through temperature reduction, the curing process is not directly influenced by humidity, and the sealing requirement of sizing equipment for water vapor is reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of hot melt adhesives, and particularly to a thermoplastic hot melt adhesive for bonding household appliance covers and a preparation method thereof. Background Art

[0002] The rice cooker cover adhesive is an adhesive used for bonding the rice cooker cover and the plastic frame base, and is a glue with high requirements for properties such as high temperature resistance and high humidity resistance; currently, basically all adhesives on the market are reactive adhesives, such as one-component silicone adhesives, one-component polyurethane adhesives, etc.

[0003] Among them, silicone adhesives and polyurethane adhesives can crosslink and cure with water vapor. Silicone adhesives and polyurethane adhesives need to be moisture-proof and waterproof. During the use of the hot melt adhesive, strict sealing of the gluing equipment is required to prevent water vapor from affecting the colloid; at the same time, when using these two adhesives, the curing time is relatively long, significantly affecting the processing efficiency.

[0004] For example, a one-component moisture-curing polyolefin hot melt adhesive and a preparation method disclosed in the comparative document CN201610915592.9. The one-component moisture-curing polyolefin hot melt adhesive is composed of the following raw materials by mass fraction: styrene-isoprene-styrene block copolymer 25%, α-amorphous olefin copolymer 25%-40%, hydrogenated petroleum resin 32%-41%, plasticizer 0-5.8%, initiator 0.8%, coupling agent 1.6%, antioxidant 0.8%. The hot melt adhesive of this solution has good high temperature resistance, but the one-component moisture-curing polyolefin hot melt adhesive needs to react with water vapor to crosslink and cure to form chemical bonds, thereby improving the bonding strength. The one-component moisture-curing polyolefin hot melt adhesive needs to be applied with sealing, and the curing process is greatly affected by environmental humidity, and the use environment is limited.

[0005] Another example is a reactive polyurethane hot melt adhesive for bonding household appliance covers and a preparation method disclosed in the comparative document CN202411603265.0. The polyurethane hot melt adhesive is made of the following raw materials in parts by weight: thermoplastic acrylic resin 5-25 parts, aliphatic polyester polyol 10-60 parts, polyether diol 8-20 parts, isocyanate 10-30 parts, filler 15-40 parts, stabilizer 0.01-0.1 part, and catalyst 0.05-0.5 part; the NCO% content in the reactive polyurethane hot melt adhesive for bonding household appliance covers is 1.0%-3.5%. The hot melt adhesive of this solution has the characteristics of short open time and strong adhesion. The curing process of the polyurethane hot melt adhesive needs to crosslink and cure with water vapor. The polyurethane hot melt adhesive needs to be applied with sealing, and the curing process is greatly affected by environmental humidity, and the use environment is limited. Summary of the Invention

[0006] The object of the present disclosure is to overcome the deficiencies in the prior art, and to provide a thermoplastic hot melt adhesive for bonding household appliance covers with good adhesion and toughness, and good high temperature and humidity resistance, and a preparation method thereof.

[0007] The object of the present disclosure is achieved through the following technical solutions:

[0008] A thermoplastic hot melt adhesive for bonding household appliance covers, comprising the following mass components:

[0009]

[0010] Among them, the high-polarity thermoplastic elastomer is at least one of TPU thermoplastic polyurethane elastomer, EAA ethylene acrylic acid copolymer, TPEE thermoplastic polyester elastomer, ACM acrylate rubber and PA polyamide resin.

[0011] In one embodiment, the softening point of the thermoplastic hot melt adhesive for bonding household appliance covers is 140°C - 150°C.

[0012] In one embodiment, the copolymer containing amorphous α-olefin is POE polyolefin elastomer.

[0013] In one embodiment, the softening point of the high softening point tackifying resin is 120°C - 160°C; and / or,

[0014] The high softening point tackifying resin is at least one of monomer resin, rosin resin, terpene resin, hydrogenated petroleum resin, phenolic resin.

[0015] In one embodiment, the antioxidant is at least one of sterically hindered phenolic antioxidants and phosphite antioxidants.

[0016] In one embodiment, the light stabilizer is at least one of benzotriazole ultraviolet absorbers and piperidine light stabilizers.

[0017] In one embodiment, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide.

[0018] A preparation method of a thermoplastic hot melt adhesive for bonding household appliance covers, used to prepare the thermoplastic hot melt adhesive for bonding household appliance covers in any of the above embodiments, comprising the following steps:

[0019] Put the high-polarity thermoplastic elastomer, copolymer containing amorphous α-olefin, high softening point tackifying resin, antioxidant and light stabilizer into the planetary stirring kettle in sequence and heat and stir. The heating temperature is 180°C - 200°C. Vacuumize the planetary stirring kettle, and the vacuum degree is -0.08 Mpa to -0.1 Mpa to obtain a premixed colloid.

[0020] Put the silane coupling agent into the premixed colloid for mixing and stirring. Keep the heating temperature and vacuumize the planetary stirring kettle. The vacuum degree is -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time is 10 min - 20 min to obtain a molten colloid.

[0021] After the molten colloid is stirred evenly, discharge and cool and shape it to obtain a thermoplastic hot melt adhesive for bonding household appliance covers.

[0022] In one embodiment, the curing time after melting of the thermoplastic hot melt adhesive for bonding household appliance covers is 10 min - 20 min.

[0023] In one embodiment, the viscosity of the thermoplastic hot melt adhesive for bonding household appliance covers at 190°C is 15000 mPa·S - 25000 mPa·S.

[0024] Compared with the prior art, the present disclosure has at least the following advantages:

[0025] The above-mentioned thermoplastic hot melt adhesive for bonding household appliance covers is mixed with high-polarity thermoplastic elastomer, copolymer containing amorphous α-olefin, high softening point tackifying resin and antioxidant, so that the thermoplastic hot melt adhesive for bonding household appliance covers has a higher softening point temperature and better thermal stability, thus making the thermoplastic hot melt adhesive for bonding household appliance covers have better heat resistance; a strong interfacial bond is formed between the polar groups of the high-polarity thermoplastic elastomer and the adhered material, improving the bonding performance of the high-temperature resistant hot melt adhesive for bonding; the copolymer containing amorphous α-olefin promotes the wetting and penetration of the thermoplastic hot melt adhesive for bonding household appliance covers on the surface of the adherend, improving the adhesiveness of the thermoplastic hot melt adhesive for bonding household appliance covers. The amorphous phase structure of the α-olefin copolymer with amorphous phase structure provides flexible chain segments, reducing the brittleness of the thermoplastic hot melt adhesive for bonding household appliance covers and increasing the toughness of the high-temperature resistant hot melt adhesive; the thermoplastic hot melt adhesive for bonding household appliance covers forms physical cross-linking and curing by temperature reduction, and environmental water vapor does not participate in the curing. The curing process is not directly affected by humidity, reducing the sealing requirement of the sizing equipment for water vapor, making the construction of the hot melt adhesive more convenient, thus reducing the sizing cost. By quickly forming physical cross-linking and curing by temperature reduction, the processing time can be greatly shortened, and then the production efficiency of cover bonding can be improved. Brief Description of the Drawings

[0026] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present disclosure and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a flowchart of the steps of a preparation method of a thermoplastic hot melt adhesive for bonding household appliance covers in an embodiment. Detailed implementation manners

[0028] To facilitate the understanding of the present disclosure, the following will describe the present disclosure more comprehensively with reference to the relevant drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure content of the present disclosure more thoroughly and comprehensively understood.

[0029] It should be noted that when an element is referred to as "fixed to" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation manner.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present disclosure belongs. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific implementation manners and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] To better understand the technical solutions and beneficial effects of the present disclosure, the following will further describe the present disclosure in detail with specific embodiments:

[0032] Please refer to the thermoplastic hot melt adhesive for bonding household appliance covers in an embodiment of the present invention, which includes the following mass components:

[0033]

[0034] Among them, the high-polarity thermoplastic elastomer is at least one of TPU thermoplastic polyurethane elastomer, EAA ethylene acrylic acid copolymer, TPEE thermoplastic polyester elastomer, ACM acrylate rubber and PA polyamide resin.

[0035] In this embodiment, the high-polarity thermoplastic elastomer is at least one of TPU thermoplastic polyurethane elastomer, EAA ethylene acrylic acid copolymer, TPEE thermoplastic polyester elastomer, ACM acrylate rubber and PA polyamide resin. The TPU thermoplastic polyurethane elastomer contains polar urethane groups, the EAA ethylene acrylic acid copolymer contains carboxylic acid groups, the TPEE thermoplastic polyester elastomer, a block linear copolymer containing PBT polyester hard segments and polyether soft segments, contains ester groups, the ACM acrylate rubber contains ester groups, and the PA polyamide resin contains polar amide groups. The polar groups, such as urethane, carboxylic acid, and amide groups, form strong interfacial bonds of dipole-dipole interaction, hydrogen bonding, or chemical bonding with the surfaces of adherends such as metals, ceramics, and polar plastics, thereby enhancing the interfacial adhesion between the thermoplastic hot melt adhesive for bonding household appliance covers and the adherends. The interaction of the polar groups of the high-polarity thermoplastic elastomer forms good compatibility. By compounding the TPU thermoplastic polyurethane elastomer, EAA ethylene acrylic acid copolymer, TPEE thermoplastic polyester elastomer, ACM acrylate rubber, and PA polyamide resin, the balance of the strength and toughness of the high-polarity thermoplastic elastomer can be regulated, so as to obtain a thermoplastic hot melt adhesive for bonding household appliance covers with better heat resistance, strength, and flexibility. The high softening point tackifying resin can increase the viscosity and cohesion of the adhesive layer, improve the strength and durability of the adhesive layer. The high softening point tackifying resin forms close contact with the surface of the adherend, enhancing the adhesion of the adhesive layer. The high softening point tackifying resin also increases the curing speed of the thermoplastic hot melt adhesive for bonding household appliance covers.

[0036] It can be understood that the amorphous structure of the copolymer containing amorphous α-olefin provides flexible chain segments. The flexible chain segments of the copolymer containing amorphous α-olefin have a low glass transition temperature and high chain segment mobility. The flexible chain segments penetrate into the pores of the metal oxide layer or the microcracks on the plastic surface, forming close contact with the surface of the adherend, thereby improving the wettability and adhesion of the thermoplastic hot melt adhesive for bonding household appliance covers. When the material is subjected to external forces, the flexible chain segments can absorb energy through chain segment slippage or orientation, avoiding stress concentration. The flexible chain segments can also wrap the crack tip, inhibiting the crack propagation, thereby improving the toughness of the thermoplastic hot melt adhesive for bonding household appliance covers.

[0037] It is understandable that during the use of the thermoplastic hot melt adhesive for bonding the home appliance cover plate, it needs to be heated and melted and extruded for use while maintaining a molten state. The antioxidant prevents the oxidation and thermal decomposition of the hot melt adhesive at high temperatures. The antioxidant prevents the oxidation and thermal decomposition of the thermoplastic hot melt adhesive for bonding the home appliance cover plate at high temperatures. The light stabilizer can absorb, disperse, and transfer harmful ultraviolet radiation, thereby protecting the hot melt adhesive from ultraviolet damage, and thus extending the service life of the thermoplastic hot melt adhesive for bonding the home appliance cover plate. The silane coupling agent can chemically react or physically adsorb with the polymer molecules in the hot melt adhesive. The silane coupling agent can improve the interfacial bonding effect between the thermoplastic hot melt adhesive for bonding the home appliance cover plate and the material to be bonded, and further improve the bonding strength of the thermoplastic hot melt adhesive.

[0038] It is understandable that when the high-polarity thermoplastic elastomer, the copolymer containing amorphous α-olefin, the high softening point tackifying resin, and the antioxidant are mixed, the softening point temperature of the high-polarity thermoplastic elastomer is relatively high, and the softening point temperature of the high softening point tackifying resin is relatively high, which is beneficial to increasing the softening point temperature of the thermoplastic hot melt adhesive for bonding the home appliance cover plate. The amorphous state of the copolymer containing amorphous α-olefin shows a disordered arrangement state, and a higher temperature is required to enable the chain segments to move, thereby increasing the softening point temperature of the thermoplastic hot melt adhesive for bonding the home appliance cover plate. The antioxidant can also enhance the heat resistance of the thermoplastic hot melt adhesive for bonding the home appliance cover plate, enabling it to maintain more stable performance in a high-temperature environment, thus making the softening point temperature of the thermoplastic hot melt adhesive for bonding the home appliance cover plate relatively high, and further improving the heat resistance and thermal stability of the thermoplastic hot melt adhesive for bonding the home appliance cover plate.

[0039] It is understandable that during the curing process of the thermoplastic hot melt adhesive for bonding the home appliance cover plate, as the temperature drops below the glass transition temperature, the formed material of the polymer of the thermoplastic hot melt adhesive for bonding the home appliance cover plate crosslinks to generate bonding force. There is no chemical crosslinking curing, and environmental water vapor does not participate in the curing reaction, so that the curing process of the thermoplastic hot melt adhesive for bonding the home appliance cover plate is not directly affected by humidity.

[0040] The above-mentioned thermoplastic hot melt adhesive for bonding household appliance covers is prepared by mixing a highly polar thermoplastic elastomer, a copolymer containing amorphous α-olefin, a high softening point tackifying resin, and an antioxidant. As a result, the thermoplastic hot melt adhesive for bonding household appliance covers has a relatively high softening point temperature and good thermal stability, thus exhibiting good heat resistance. The polar groups of the highly polar thermoplastic elastomer form strong interfacial bonds with the materials to be bonded, enhancing the bonding performance of the high-temperature resistant hot melt adhesive for bonding. The copolymer containing amorphous α-olefin promotes the wetting and penetration of the thermoplastic hot melt adhesive for bonding household appliance covers on the surface of the adherend, improving the adhesiveness of the thermoplastic hot melt adhesive for bonding household appliance covers. The amorphous phase structure of the α-olefin copolymer with an amorphous phase structure provides flexible segments, reducing the brittleness of the thermoplastic hot melt adhesive for bonding household appliance covers and increasing the toughness of the high-temperature resistant hot melt adhesive. The thermoplastic hot melt adhesive for bonding household appliance covers undergoes physical crosslinking and curing as the temperature decreases, and environmental water vapor does not participate in the curing process. The curing process is not directly affected by humidity, enhancing the moisture-proof and moisture-resistant performance of the thermoplastic hot melt adhesive for bonding household appliance covers.

[0041] Further, in one embodiment, the highly polar thermoplastic elastomer includes TPEE thermoplastic polyester elastomer, TPU thermoplastic polyurethane elastomer, and PA polyamide resin, and the ratio of the TPEE thermoplastic polyester elastomer, TPU thermoplastic polyurethane elastomer, and PA polyamide resin is 50%-70%: 20%-30%: 10%-20%. In this embodiment, the TPEE thermoplastic polyester elastomer can increase the heat resistance of the thermoplastic hot melt adhesive for bonding household appliance covers, the TPU thermoplastic polyurethane elastomer has good elasticity to provide flexible compensation, and the PA polyamide resin provides rigidity for the thermoplastic hot melt adhesive for bonding household appliance covers, thereby obtaining a thermoplastic hot melt adhesive for bonding household appliance covers with good heat resistance, high strength, and good flexibility.

[0042] In one embodiment, the softening point of the thermoplastic hot melt adhesive for bonding household appliance covers is 140°C - 150°C. In this embodiment, the softening point of the thermoplastic hot melt adhesive for bonding household appliance covers is relatively high and it is not easily softened under the high temperature of water vapor. The high-temperature resistant hot melt adhesive maintains good bonding performance, enabling the high-temperature resistant hot melt adhesive to remain stable in a high-temperature and high-humidity environment, thereby extending the service life of the thermoplastic hot melt adhesive for bonding household appliance covers.

[0043] In one of the embodiments, the copolymer containing amorphous α-olefin is a POE polyolefin elastomer. In this embodiment, the copolymer containing amorphous α-olefin includes an APAO amorphous α-olefin copolymer with a completely amorphous structure and a POE polyolefin elastomer with a semi-crystalline structure. Since the molecular chain of the APAO amorphous α-olefin copolymer has a relatively low polarity, its compatibility with high-polarity thermoplastic elastomers is poor, which may lead to insufficient interfacial bonding force. In the molecular structure of the POE polyolefin elastomer, there are both crystalline region structures and amorphous region structures. The amorphous region of the POE polyolefin elastomer can be graft-modified by introducing a small amount of polar monomers such as maleic anhydride, thereby improving the compatibility of the POE polyolefin elastomer with high-polarity thermoplastic elastomers. The amorphous region structure of the POE polyolefin elastomer provides flexible chain segments, reducing the brittleness of the thermoplastic hot melt adhesive used for bonding home appliance covers and increasing the toughness of the high-temperature resistant hot melt adhesive. The amorphous region of the POE polyolefin elastomer penetrates to the interface of high-polarity materials through chain segment movement, improving the wettability of the thermoplastic hot melt adhesive used for bonding home appliance covers and its conformability to the bonding substrate.

[0044] It can be understood that the relatively low molecular weight and random arrangement of the molecular chain of the APAO amorphous α-olefin copolymer result in relatively weak thermal stability of the APAO amorphous α-olefin copolymer; the POE polyolefin elastomer has a relatively high molecular weight, and its structure is formed by the copolymerization of ethylene and α-olefin through metallocene catalysis. The molecular chain contains long-chain branching and short-chain branching structures, and the POE polyolefin elastomer has good thermal stability, making the thermoplastic hot melt adhesive used for bonding home appliance covers have good thermal stability. When preparing the thermoplastic hot melt adhesive used for bonding home appliance covers, it needs to be heated to 180°C - 200°C. When the APAO amorphous α-olefin copolymer is close to 200°C, it is prone to thermal degradation. The thermoplastic hot melt adhesive prepared by heating the APAO amorphous α-olefin copolymer has poor stability. The POE polyolefin elastomer has better short-term high-temperature resistance at 200°C than the APAO amorphous α-olefin copolymer, making the thermoplastic hot melt adhesive prepared by heating the POE polyolefin elastomer have good stability.

[0045] In one embodiment, the softening point of the high softening point tackifying resin is 120°C - 160°C; and / or, the high softening point tackifying resin is at least one of monomer resin, rosin resin, terpene resin, hydrogenated petroleum resin, and phenolic resin. In this embodiment, the softening point of the high softening point tackifying resin directly affects the melt viscosity and cooling and curing rate of the hot melt adhesive. The softening point of the high softening point tackifying resin is 120°C - 160°C, resulting in a relatively fast curing speed for the thermoplastic hot melt adhesive used for bonding home appliance covers; when the purity of the monomer resin is relatively high, its softening point is relatively high, and the softening point of the monomer resin can be controlled by adjusting the chemical composition and degree of polymerization of the monomer resin; the softening point of rosin resin is relatively low, and a modified and stabilized rosin resin is formed by the esterification reaction of rosin acid and polyol; terpene resin can be directionally obtained a high softening point product of 120°C - 140°C by controlling the degree of polymerization and hydrogenation modification; hydrogenated petroleum resin; the benzene ring and cross-linked network in the molecular structure of phenolic resin endow phenolic resin with excellent high-temperature stability, good hardness and good wear resistance.

[0046] Furthermore, in one embodiment, the high softening point tackifying resin is a mixture of hydrogenated petroleum resin and phenolic resin, and the proportion of the hydrogenated petroleum resin to the phenolic resin is 20% - 80%. By compounding hydrogenated petroleum resins with different softening points and the phenolic resin, the high softening point hydrogenated petroleum resin improves the heat resistance of the system and expands the high-temperature usage range, and the phenolic resin increases the high-temperature stability, hardness and wear resistance. By adjusting the ratio of the hydrogenated petroleum resin to the phenolic resin, the softening point, adhesion performance and heat resistance of the thermoplastic hot melt adhesive used for bonding home appliance covers can be effectively controlled.

[0047] In one embodiment, the antioxidant is at least one of sterically hindered phenol antioxidants and phosphite antioxidants. In this embodiment, sterically hindered phenol antioxidants contain phenolic hydroxyl groups (-OH), and this group can accept an electron from a free radical to form a relatively stable free radical, thereby preventing the continuation of the oxidation reaction. The molecular structure of sterically hindered phenol antioxidants contains one or more groups with relatively large steric hindrance, and these groups can prevent the interaction between antioxidant molecules and other molecules, thereby enhancing their antioxidant effect; phosphite antioxidants delay the oxidation process of the polymer materials in the thermoplastic hot melt adhesive used for bonding home appliance covers and extend the service life of the thermoplastic hot melt adhesive used for bonding home appliance covers by decomposing the peroxides generated during the oxidation process to form stable non-active products; specifically, the sterically hindered phenol antioxidant is at least one of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 2,6-di-tert-butyl-4-methylphenol; the phosphite antioxidant is tris(2,4-di-tert-butylphenyl)phosphite.

[0048] It is understandable that the antioxidant includes the sterically hindered phenolic antioxidant and the phosphite antioxidant. The ratio of the sterically hindered phenolic antioxidant to the phosphite antioxidant is 1:1 to 1:3. The combined use of the sterically hindered phenolic antioxidant and the phosphite antioxidant can produce a synergistic effect. The highly active sterically hindered phenolic antioxidant can effectively capture oxidation free radicals or peroxide free radicals, while the phosphite antioxidant can decompose hydroperoxides. The sterically hindered phenolic antioxidant and the phosphite antioxidant cooperate with each other to jointly protect the thermoplastic hot melt adhesive used for bonding household appliance covers from oxidative degradation, thereby improving the antioxidant property and stability of the thermoplastic hot melt adhesive used for bonding household appliance covers.

[0049] In one embodiment, the light stabilizer is at least one of benzotriazole ultraviolet absorbers and piperidine light stabilizers. In this embodiment, the benzotriazole ultraviolet absorber protects the polymer from photo-degradation by absorbing ultraviolet light. Specifically, the benzotriazole ultraviolet absorber is at least one of 2'-tert-butyl-6'-(5-tert-butyl-2-hydroxy-3-tolyl) benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, and 2-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole; the piperidine light stabilizer includes bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate.

[0050] Further, in one embodiment, the light stabilizer includes 2'-tert-butyl-6'-(5-tert-butyl-2-hydroxy-3-tolyl) benzotriazole and bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, and the ratio of 2'-tert-butyl-6'-(5-tert-butyl-2-hydroxy-3-tolyl) benzotriazole to bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate is 1:0.5 - 1:2. In this embodiment, 2'-tert-butyl-6'-(5-tert-butyl-2-hydroxy-3-tolyl) benzotriazole and bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate are ultraviolet absorbers, and bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate is a hindered amine light stabilizer. The ultraviolet absorber absorbs ultraviolet light to reduce excited state molecules, and the hindered amine light stabilizer captures free radicals, providing double protection, thereby improving the light stability of the thermoplastic hot melt adhesive used for bonding household appliance covers; when the amount of the hindered amine light stabilizer is small, the effect of the hindered amine light stabilizer in capturing free radicals is poor, and ultraviolet light initiates a chain reaction of un-captured free radicals. When the amount of the hindered amine light stabilizer is large, its alkalinity may catalyze the hydrolysis of some polymers. Therefore, the ratio of 2'-tert-butyl-6'-(5-tert-butyl-2-hydroxy-3-tolyl) benzotriazole to bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate is 1:0.5 - 1:2.

[0051] In one embodiment, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and bis-(γ-triethoxysilylpropyl)tetrasulfide. In this embodiment, the silane coupling agent can improve the cross-section adhesion performance and the weather resistance of the material, thereby enhancing the adhesion performance of the thermoplastic hot melt adhesive used for bonding the home appliance cover plate.

[0052] This application also provides a preparation method of a thermoplastic hot melt adhesive for bonding a home appliance cover plate, which is used to prepare the thermoplastic hot melt adhesive for bonding a home appliance cover plate described in any of the above embodiments, and includes the following steps:

[0053] Put a high-polarity thermoplastic elastomer, a copolymer containing amorphous α-olefin, a high softening point tackifying resin, an antioxidant, and a light stabilizer into a planetary stirring kettle in sequence for heating and stirring. The heating temperature is 180°C - 200°C, and vacuum is drawn in the planetary stirring kettle. The vacuum degree is -0.08 Mpa to -0.1 Mpa to obtain a premixed colloid;

[0054] Put the silane coupling agent into the premixed colloid for mixing and stirring, maintain the heating temperature, draw vacuum in the planetary stirring kettle, the vacuum degree is -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time is 10 min - 20 min to obtain a molten colloid;

[0055] After the molten colloid is stirred evenly, it is discharged and cooled and shaped to obtain a thermoplastic hot melt adhesive for bonding a home appliance cover plate.

[0056] It is understandable that antioxidants such as pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol and tris(2,4-di-tert-butylphenyl) phosphite all have good thermal stability and are not easily degraded in the temperature range of 180°C - 200°C. The benzotriazole ultraviolet absorbers as light stabilizers such as 2'-tert-butyl-6'-(5-tert-butyl-2-hydroxy-3-tolyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole and bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate all have good thermal stability and are not easily degraded in the temperature range of 180°C - 200°C. γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide all have good thermal stability and are not easily degraded in the temperature range of 180°C - 200°C, making the thermoplastic hot melt adhesive for bonding home appliance covers prepared from high-polarity thermoplastic elastomers, copolymers containing non-crystalline α-olefins, high softening point tackifying resins, antioxidants, light stabilizers and silane coupling agents have good heat resistance and thermal stability.

[0057] It is understandable that under a vacuum degree of -0.08 Mpa to -0.1 Mpa, vacuum pumping is carried out and mixing and stirring are carried out. During the vacuum pumping process, the molten colloid is in a negative pressure state, enabling gas to escape from the molten colloid. At the same time, mixing and stirring are carried out. The mixing and stirring break the bubbles in the colloid and accelerate the discharge of the gas in the molten colloid, thereby reducing the bubbles in the obtained molten colloid and further improving the quality of the thermoplastic hot melt adhesive for bonding home appliance covers.

[0058] For the above preparation method of the thermoplastic hot melt adhesive for bonding home appliance covers, the high-polarity thermoplastic elastomers, copolymers containing non-crystalline α-olefins, high softening point tackifying resins, antioxidants, light stabilizers and silane coupling agents have good thermal stability, making the thermoplastic hot melt adhesive for bonding home appliance covers prepared have good thermal stability; by adding high-polarity thermoplastic elastomers and copolymers containing non-crystalline α-olefins, the copolymers containing non-crystalline α-olefins improve the toughness and adhesiveness of the thermoplastic hot melt adhesive for bonding home appliance covers, making the thermoplastic hot melt adhesive for bonding home appliance covers prepared have good adhesive strength and toughness; by carrying out vacuum pumping and mixing and stirring, the bubbles in the molten colloid are reduced, thereby improving the quality of the thermoplastic hot melt adhesive for bonding home appliance covers.

[0059] In one embodiment, the curing time of the thermoplastic hot melt adhesive for bonding the household appliance cover plate after melting is 10 min - 20 min. In this embodiment, when the thermoplastic hot melt adhesive for bonding the household appliance cover plate is used to bond the rice cooker cover plate, the high softening point tackifying resin affects the curing speed of the thermoplastic hot melt adhesive for bonding the household appliance cover plate. When the curing time of the thermoplastic hot melt adhesive for bonding the household appliance cover plate after melting is greater than 20 min, due to the long curing time, the time taken to bond the rice cooker cover plate with the thermoplastic hot melt adhesive for bonding the household appliance cover plate is longer, thus affecting the production efficiency of the bonded rice cooker cover plate. By selecting a tackifying resin with a higher softening point for adjustment and increasing the addition amount of the high softening point tackifying resin; when the curing time of the thermoplastic hot melt adhesive for bonding the household appliance cover plate after melting is less than 10 min, the curing time is too fast, and the surface of the thermoplastic hot melt adhesive for bonding the household appliance cover plate forms a skin, thus affecting the bonding effect. By selecting a tackifying resin with a lower softening point for adjustment and reducing the addition amount of the high softening point tackifying resin; when the curing time of the thermoplastic hot melt adhesive for bonding the household appliance cover plate after melting is 10 min - 20 min, the effect of bonding the rice cooker cover plate with the thermoplastic hot melt adhesive for bonding the household appliance cover plate is better and the speed is faster.

[0060] In one embodiment, the viscosity of the thermoplastic hot melt adhesive for bonding the household appliance cover plate at 190 °C is 15000 mPa·S - 25000 mPa·S. In this embodiment, when the viscosity of the thermoplastic hot melt adhesive for bonding the household appliance cover plate is 15000 mPa·S - 25000 mPa·S after being heated to 190 °C, it is an ideal range for spraying, roll coating or knife coating of the thermoplastic hot melt adhesive for bonding the household appliance cover plate; when the viscosity of the thermoplastic hot melt adhesive for bonding the household appliance cover plate is less than 15000 mPa·S after being heated to 190 °C, the viscosity of the thermoplastic hot melt adhesive for bonding the household appliance cover plate during coating is low and the permeability is strong, which easily causes bleeding or insufficient cohesive strength of the thermoplastic hot melt adhesive for bonding the household appliance cover plate; when the viscosity of the thermoplastic hot melt adhesive for bonding the household appliance cover plate is greater than 15000 mPa·S after being heated to 190 °C, the fluidity of the thermoplastic hot melt adhesive for bonding the household appliance cover plate is poor, increasing the pumping resistance and reducing the coating efficiency.

[0061] Compared with the prior art, the present disclosure has at least the following advantages:

[0062] The above-mentioned thermoplastic hot melt adhesive for bonding household appliance covers is prepared by mixing a highly polar thermoplastic elastomer, a copolymer containing amorphous α-olefin, a high softening point tackifying resin and an antioxidant, so that the thermoplastic hot melt adhesive for bonding household appliance covers has a relatively high softening point temperature and good thermal stability, and thus has good heat resistance; a strong interfacial bond is formed between the polar groups of the highly polar thermoplastic elastomer and the material to be bonded, improving the bonding performance of the high-temperature resistant hot melt adhesive for bonding; the copolymer containing amorphous α-olefin promotes the wetting and penetration of the thermoplastic hot melt adhesive for bonding household appliance covers on the surface of the adherend, improving the adhesiveness of the thermoplastic hot melt adhesive for bonding household appliance covers. The amorphous phase structure of the α-olefin copolymer with an amorphous phase structure provides flexible chain segments, reducing the brittleness of the thermoplastic hot melt adhesive for bonding household appliance covers and increasing the toughness of the high-temperature resistant hot melt adhesive; the thermoplastic hot melt adhesive for bonding household appliance covers undergoes physical cross-linking and curing by reducing the temperature, and environmental water vapor does not participate in the curing. The curing process is not directly affected by humidity, reducing the sealing requirement of the sizing equipment for water vapor, making the construction of the hot melt adhesive more convenient, thus reducing the sizing cost. By quickly forming physical cross-linking and curing by reducing the temperature, the processing time can be greatly shortened, thereby improving the production efficiency of cover bonding.

[0063] The following are some specific examples. If % is mentioned, it means by weight percentage. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial channels without special instructions.

[0064] Example 1

[0065] 60 kg of TPU thermoplastic polyurethane elastomer, 7 kg of POE polyolefin elastomer, 30 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1 kg of light stabilizer UV-326 were successively put into a planetary stirring kettle and heated and stirred at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum was drawn and mixed and stirred at a vacuum degree of -0.08 Mpa to -0.1 Mpa for 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, it was discharged and cooled and shaped to obtain a thermoplastic hot melt adhesive for bonding household appliance covers.

[0066] Example 2

[0067] 65 kg of thermoplastic polyurethane elastomer (TPU), 7 kg of polyolefin elastomer (POE), 25 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1 kg of light stabilizer UV-326 are sequentially put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 is put into the premixed colloid, and vacuum is pumped and mixed and stirred at a vacuum degree of -0.08 Mpa to -0.1 Mpa for 10 min - 20 min to obtain a molten colloid; after the molten colloid is stirred evenly, it is discharged and cooled and shaped to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0068] Example 3

[0069] 70 kg of thermoplastic polyurethane elastomer (TPU), 10 kg of polyolefin elastomer (POE), 15.5 kg of phenolic resin, 2 kg of antioxidant 1010 and 2 kg of light stabilizer UV-326 are sequentially put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 is put into the premixed colloid, and vacuum is pumped and mixed and stirred at a vacuum degree of -0.08 Mpa to -0.1 Mpa for 10 min - 20 min to obtain a molten colloid; after the molten colloid is stirred evenly, it is discharged and cooled and shaped to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0070] Example 4

[0071] 65 kg of ethylene acrylic acid copolymer (EAA), 7 kg of polyolefin elastomer (POE), 25 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1 kg of light stabilizer UV-326 are sequentially put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 is put into the premixed colloid, and vacuum is pumped and mixed and stirred at a vacuum degree of -0.08 Mpa to -0.1 Mpa for 10 min - 20 min to obtain a molten colloid; after the molten colloid is stirred evenly, it is discharged and cooled and shaped to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0072] Example 5

[0073] 65 kg of TPEE (thermoplastic polyester elastomer), 7 kg of POE (polyolefin elastomer), 25 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1 kg of light stabilizer UV-326 were successively put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing and stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding household appliance covers.

[0074] Example 6

[0075] 65 kg of ACM (acrylate rubber), 7 kg of POE (polyolefin elastomer), 25 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1 kg of light stabilizer UV-326 were successively put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing and stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding household appliance covers.

[0076] Example 7

[0077] 65 kg of PA (polyamide resin), 7 kg of POE (polyolefin elastomer), 25 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1 kg of light stabilizer UV-326 were successively put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing and stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding household appliance covers.

[0078] Example 8

[0079] Put 65 kg of TPU (thermoplastic polyurethane elastomer), 7 kg of POE (polyolefin elastomer), 25 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1.4 kg of light stabilizer UV-326 into a planetary stirring kettle in sequence and heat and stir them. The heating temperature is 180°C - 200°C to obtain a premixed colloid; put 0.1 kg of silane coupling agent KH550 into the premixed colloid, evacuate and mix and stir it under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time is 10 min - 20 min to obtain a molten colloid; after the molten colloid is stirred evenly, discharge and cool and shape it to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0080] Example 9

[0081] Put 18 kg of TPU (thermoplastic polyurethane elastomer), 30 kg of TPEE (thermoplastic polyester elastomer), 10 kg of ACM (acrylate rubber), 7 kg of POE (polyolefin elastomer), 30 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1.5 kg of light stabilizer UV-326 into a planetary stirring kettle in sequence and heat and stir them. The heating temperature is 180°C - 200°C to obtain a premixed colloid; put 0.5 kg of silane coupling agent KH550 into the premixed colloid, evacuate and mix and stir it under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time is 10 min - 20 min to obtain a molten colloid; after the molten colloid is stirred evenly, discharge and cool and shape it to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0082] Example 10

[0083] Put 15 kg of TPU (thermoplastic polyurethane elastomer), 10 kg of EAA (ethylene acrylic acid copolymer), 10 kg of TPEE (thermoplastic polyester elastomer), 10 kg of ACM (acrylate rubber), 15 kg of PA (polyamide resin), 7 kg of POE (polyolefin elastomer), 30 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1.5 kg of light stabilizer UV-326 into a planetary stirring kettle in sequence and heat and stir them. The heating temperature is 180°C - 200°C to obtain a premixed colloid; put 0.5 kg of silane coupling agent KH550 into the premixed colloid, evacuate and mix and stir it under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time is 10 min - 20 min to obtain a molten colloid; after the molten colloid is stirred evenly, discharge and cool and shape it to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0084] Example 11

[0085] 65 kg of thermoplastic polyurethane elastomer (TPU), 7 kg of polyolefin elastomer (POE), 25 kg of phenolic resin, 1 kg of antioxidant 1010, 0.5 kg of antioxidant BHT, and 1 kg of light stabilizer UV-326 were sequentially put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0086] Example 12

[0087] 65 kg of thermoplastic polyurethane elastomer (TPU), 7 kg of polyolefin elastomer (POE), 25 kg of phenolic resin, 1.5 kg of antioxidant 1010, 0.5 kg of light stabilizer UV-326, and 0.5 kg of light stabilizer UV-770 were sequentially put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0088] Comparative Example 1

[0089] 65 kg of thermoplastic polyurethane elastomer (TPU), 7 kg of amorphous α-olefin copolymer (APAO), 30 kg of phenolic resin, 1.5 kg of antioxidant 1010, and 1.5 kg of light stabilizer UV-326 were sequentially put into a planetary stirring kettle for heating and stirring at a heating temperature of 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0090] Comparative Example 2

[0091] 65 kg of SBC styrenic thermoplastic elastomer, 7 kg of POE polyolefin elastomer, 30 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1.5 kg of light stabilizer UV-326 were successively put into a planetary stirring kettle for heating and stirring, and the heating temperature was 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing and stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0092] Comparative Example 3

[0093] 57 kg of TPU thermoplastic polyurethane elastomer, 10 kg of POE polyolefin elastomer, 30 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1.5 kg of light stabilizer UV-326 were successively put into a planetary stirring kettle for heating and stirring, and the heating temperature was 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing and stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0094] Comparative Example 4

[0095] 65 kg of SBC styrenic thermoplastic elastomer, 7 kg of POE polyolefin elastomer, 30 kg of phenolic resin, 1.5 kg of antioxidant 1010 and 1.5 kg of light stabilizer UV-326 were successively put into a planetary stirring kettle for heating and stirring, and the heating temperature was 180°C - 200°C to obtain a premixed colloid; 0.5 kg of silane coupling agent KH550 was put into the premixed colloid, and vacuum pumping and mixing and stirring were carried out under a vacuum degree of -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time was 10 min - 20 min to obtain a molten colloid; after the molten colloid was stirred evenly, discharging and cooling and shaping were carried out to obtain a thermoplastic hot melt adhesive for bonding home appliance covers.

[0096] It should be noted that tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester is antioxidant 1010, octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is antioxidant 168, 2,6-di-tert-butyl-4-methylphenol is antioxidant 1076, tris(2,4-di-tert-butylphenyl) phosphite is antioxidant BHT, and antioxidant 1010 in Examples 1-10 and Comparative Examples 1-4 can be replaced by at least one of antioxidant 168, antioxidant 1076 and antioxidant BHT;

[0097] It should be noted that 2'-tert-butyl-6'-(5-tert-butyl-2-hydroxy-3-tolyl) benzotriazole is light stabilizer UV-326, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole is light stabilizer UV-327, 2-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole is light stabilizer UV-770, and light stabilizer UV-326 in Examples 1-10 and Comparative Examples 1-4 can be replaced by at least one of UV-327, UV-5411 and UV-770;

[0098] It should be noted that γ-aminopropyltriethoxysilane is silane coupling agent KH550, γ-(2,3-epoxypropoxy)propyltrimethoxysilane is silane coupling agent KH560, γ-methacryloxypropyltrimethoxysilane is silane coupling agent KH570, bis-(γ-triethoxysilylpropyl)tetrasulfide is silane coupling agent A-792, and silane coupling agent KH550 in Examples 1-10 and Comparative Examples 1-4 can be replaced by at least one of KH560, KH570 and A-792.

[0099] It should be noted that the phenolic resin in Examples 1-10 and Comparative Examples 1-4 can be replaced by at least one of monomer resin, rosin resin, terpene resin and hydrogenated petroleum resin with a softening point within 120°C - 160°C.

[0100] It should be noted that POE is maleic anhydride grafted polyolefin elastomer.

[0101] Table 1 Mass Components of Hot Melt Adhesive Formulation

[0102]

[0103]

[0104] It should be noted that in Table 1, compared with Comparative Example 1, the content of TPU is different among Examples 1-3, the content of TPU in Comparative Example 1 is the same as that in Example 2, and the copolymer containing amorphous α-olefin in Comparative Example 1 is APAO, which is different from the POE in Examples 1-3;

[0105] When comparing Example 1 with Comparative Example 2, the content of TPU in Comparative Example 3 is less than 40%, and when comparing Example 1 with Comparative Example 4, the content of TPU in Comparative Example 4 is greater than 70%.

[0106] When comparing Example 2 with Examples 4 - 7, the types of high - polarity thermoplastic elastomers are different.

[0107] When comparing Example 2, Examples 4 - 7 with Comparative Example 2, Comparative Example 2 uses non - polar SBC styrene - based thermoplastic elastomer, while Example 2, Examples 4 - 7 use thermoplastic elastomers with polar groups

[0108] When comparing Example 2 with Example 8, the content of KH550 silane coupling agent in Example 8 is 0.5%, and the content of KH550 silane coupling agent in Example 2 is 0.1%.

[0109] When comparing Example 2 with Example 9 and Example 10, the thermoplastic elastomer in Example 2 is TPU, the thermoplastic elastomer in Example 9 is a mixture of TPEE, TPU and PA, and Example 10 is a mixture of thermoplastic elastomers TPU, EAA, TPEE, ACM and PA;

[0110] When comparing Example 2 with Example 11, the antioxidant in Example 2 is antioxidant 1010, and the antioxidant in Example 11 is a synergistic combination of antioxidant 1010 and antioxidant BHT;

[0111] When comparing Example 2 with Example 12, the light stabilizer in Example 2 is UV - 326, and the light stabilizer in Example 12 is a synergistic combination of UV - 326 and UV - 770.

[0112] Table 2 Physical property test table of hot - melt adhesives of Examples 1 - 12 and Comparative Examples 1 - 4

[0113]

[0114] Table 3 Other property test table of hot - melt adhesives of Examples 1 - 12 and Comparative Examples 1 - 4

[0115]

[0116] It should be noted that:

[0117] For the bonding strength test, the hot - melt adhesive is coated on the test block. After curing for 20 min, it is tested by a strength testing machine;

[0118] For the low - temperature fracture experiment test, the hot - melt adhesive is coated on the test plate. After curing at room temperature, it is placed in an environment of 0℃ for 2 h and then dropped freely from a height of 60 cm to observe whether the hot - melt adhesive breaks;

[0119] Boiling water test: The hot melt adhesive is bonded to the test board. After the glue is completely cured, the hot melt adhesive is completely immersed and placed in boiling water for 5 hours to observe whether it debonds.

[0120] Load-bearing test: The cover and base of the rice cooker are bonded with hot melt adhesive. After the glue is completely cured, it is horizontally suspended at room temperature. An 8 kg load-bearing weight is evenly distributed and placed on the panel to observe whether it can withstand without falling off for 24 hours.

[0121] It can be seen from Table 1 and Table 2 that:

[0122] Compared with Comparative Example 1, Examples 1-3 have better bonding strength, while Comparative Example 1 has lower bonding strength, indicating that the compatibility of the APAO amorphous α-olefin copolymer and the high-polarity thermoplastic elastomer in Comparative Example 1 is poor, which may lead to insufficient interfacial bonding force. The maleic anhydride grafted polyolefin elastomer POE in Examples 1-3 has better compatibility with the high-polarity thermoplastic elastomer, and the bonding strength of the whole system is higher.

[0123] Compared with Example 1, Comparative Example 3 and Comparative Example 4, the TPU content in Comparative Example 3 is less than 40%, and the adhesive layer is brittle in the low-temperature fracture test, indicating that the content of the high-polarity thermoplastic elastomer is less, and the prepared thermoplastic hot melt adhesive has the risk of low-temperature brittleness; the TPU content in Comparative Example 4 is greater than 70%. When the content of the high-polarity thermoplastic elastomer is relatively high, the curing time of the prepared thermoplastic hot melt adhesive is longer, thus affecting the bonding efficiency of the thermoplastic hot melt adhesive used for bonding the home appliance cover.

[0124] Compared with Example 2, Examples 4-7 and Comparative Example 2, the non-polar thermoplastic elastomer SBS used in Example 2 has lower bonding strength, and it falls off after boiling water for 5 hours and falls off after 2 hours of load-bearing test; the bonding strengths of Examples 2, 4-7 are higher, indicating that the thermoplastic hot melt adhesives prepared from high-polarity thermoplastic elastomers such as TPU, EAA, TPEE, ACM and PA for bonding home appliance covers all have good bonding performance; Examples 2, 4-7 do not fall off after boiling water for 5 hours, indicating that the thermoplastic hot melt adhesives prepared from high-polarity thermoplastic elastomers such as TPU, EAA, TPEE, ACM and PA for bonding home appliance covers all have good high-temperature resistance and moisture resistance stability; Examples 2, 4-7 do not fall off after 24 hours of load-bearing test and have a fast curing time, indicating that the thermoplastic hot melt adhesives prepared from high-polarity thermoplastic elastomers such as TPU, EAA, TPEE, ACM and PA for bonding home appliance covers are not directly affected by humidity during the curing process and have good bonding performance after curing.

[0125] Compared with Example 2, Example 9 and Example 10, the bonding strength of Example 9 and Example 10 is higher than that of Example 2. In Example 9, a thermoplastic hot melt adhesive for bonding home appliance covers is prepared by mixing TPEE, TPU and PA. In Example 10, a thermoplastic hot melt adhesive for bonding home appliance covers is prepared by mixing TPEE, EAA, TPU and PA. By adjusting the mixing of different high-polarity thermoplastic elastomers, the bonding performance of the thermoplastic hot melt adhesive for bonding home appliance covers can be improved.

[0126] Compared with Example 2, Example 11, the antioxidant in Example 2 is antioxidant 1010, and the antioxidant in Example 11 is the synergistic combination of antioxidant 1010 and antioxidant BHT. The properties of the thermoplastic hot melt adhesives prepared in Example 2 and Example 11 are similar, indicating that antioxidant 1010 can be replaced with a mixture of antioxidant 1010 and antioxidant BHT to prepare a thermoplastic hot melt adhesive for bonding home appliance covers;

[0127] Compared with Example 2, Example 12, the light stabilizer in Example 2 is UV-326, and the light stabilizer in Example 12 is the synergistic combination of UV-326 and UV-770. The properties of the thermoplastic hot melt adhesives prepared in Example 2 and Example 12 are similar, indicating that the light stabilizer UV-326 can be replaced with a mixture of UV-326 and UV-770 to prepare a thermoplastic hot melt adhesive for bonding home appliance covers.

[0128] The above-described embodiments merely represent several implementation manners of the present disclosure, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation on the scope of the disclosed patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present disclosure, several modifications and improvements can be made, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure patent shall be subject to the appended claims.

Claims

1. A thermoplastic hot melt adhesive for bonding the cover plate of household appliances, characterized in that, It includes the following quality components: High-polarity thermoplastic elastomer: 40 parts - 70 parts; Copolymer containing amorphous α-olefin: 5 parts - 10 parts; High softening point tackifying resin: 10 parts - 50 parts; Antioxidant: 0.5 parts - 2 parts; Light stabilizer: 0.5 parts - 2 parts; Silane coupling agent: 0.2 parts - 0.5 parts; Among them, the high-polarity thermoplastic elastomer is at least one of TPU thermoplastic polyurethane elastomer, EAA ethylene acrylic acid copolymer, TPEE thermoplastic polyester elastomer, ACM acrylate rubber and PA polyamide resin.

2. The thermoplastic hot melt adhesive for bonding the cover plate of household appliances according to claim 1, wherein The softening point of the thermoplastic hot melt adhesive for bonding household appliance covers is 140°C - 150°C.

3. The thermoplastic hot melt adhesive for bonding the cover plate of household appliances according to claim 1, wherein The copolymer containing amorphous α-olefin is POE polyolefin elastomer.

4. The thermoplastic hot melt adhesive for bonding the cover plate of household appliances according to claim 1, wherein, The softening point of the high softening point tackifying resin is 120°C - 160°C; and / or, The high softening point tackifying resin is at least one of monomer resin, rosin resin, terpene resin, hydrogenated petroleum resin, phenolic resin.

5. The thermoplastic hot melt adhesive for bonding the cover plate of household appliances according to claim 1, characterized in that, The antioxidant is at least one of sterically hindered phenol antioxidants and phosphite antioxidants.

6. The thermoplastic hot melt adhesive for bonding the cover plate of household appliances according to claim 1, characterized in that The light stabilizer is at least one of benzotriazole ultraviolet absorbers and piperidine light stabilizers.

7. The thermoplastic hot melt adhesive for bonding the cover plate of household appliances according to claim 1, characterized in that, The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane and bis-(γ-triethoxysilylpropyl)tetrasulfide.

8. A preparation method of a thermoplastic hot melt adhesive for bonding the cover plate of household appliances, characterized in that, To prepare the thermoplastic hot melt adhesive for bonding household appliance covers according to any one of claims 1 - 7, it includes the following steps: Sequentially put the high-polarity thermoplastic elastomer, copolymer containing amorphous α-olefin, high softening point tackifying resin, antioxidant and light stabilizer into a planetary stirring kettle for heating and stirring. The heating temperature is 180°C - 200°C, and evacuate the planetary stirring kettle. The vacuum degree is -0.08 Mpa to -0.1 Mpa to obtain a premixed colloid; Put the silane coupling agent into the premixed colloid for mixing and stirring, keep the heating temperature, evacuate the planetary stirring kettle. The vacuum degree is -0.08 Mpa to -0.1 Mpa, and the mixing and stirring time is 10 min - 20 min to obtain a molten colloid; After the molten colloid is stirred evenly, discharge and cool and shape it to obtain the thermoplastic hot melt adhesive for bonding household appliance covers.

9. The preparation method of the thermoplastic hot melt adhesive for bonding the household appliance cover plate according to claim 8, characterized in that, The curing time after the thermoplastic hot melt adhesive for bonding household appliance covers is melted is 10 min - 20 min.

10. The preparation method of the thermoplastic hot melt adhesive for bonding the home appliance cover plate according to claim 8, wherein, The viscosity of the thermoplastic hot melt adhesive for bonding household appliance covers at 190°C is 15000 mPa·S - 25000 mPa·S.

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