Hot melt adhesive for induction cooker panel and preparation method thereof

Abstract

The application discloses a hot melt adhesive for an induction cooker panel and a preparation method thereof, and belongs to the field of adhesives. The preparation steps comprise the following steps: ethylene-vinyl acetate copolymer is put into a reaction kettle, heated and stirred until completely melted, polybutadiene and styrene-isoprene-styrene block copolymer are added, and stirring is continued until completely melted, modified rosin resin is added, stirring is continued until completely dissolved, silane coupling agent and antioxidant are added, and the mixture is cooled and discharged after stirring. By introducing PBD and SIS, the flexibility and impact resistance of the hot melt adhesive are significantly improved, so that the hot melt adhesive can better adapt to the stress changes of the induction cooker panel during cold and hot cycles and when subjected to external force impact, and cracking or delamination is not prone to occur. Meanwhile, the use of the silane coupling agent improves the bonding strength and durability of the hot melt adhesive and the panel material, and prolongs the service life of the induction cooker.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of hot melt adhesive for induction cooker panel and preparation method thereof, belong to adhesive field. BACKGROUND

[0002] As a kind of efficient, convenient kitchen appliance, induction cooker has been widely used in modern family. Induction cooker panel usually adopts glass or ceramic material, and is bonded and fixed with base or other components by hot melt adhesive. However, the hot melt adhesive for induction cooker panel in the prior art has the following problems in practical application:

[0003] Firstly, the flexibility and impact resistance are insufficient. During the use of induction cooker, it is often operated to place a pot filled with soup on the panel, and it is also operated to stir-fry or even to shake the pot, which is actually an impact on the panel. However, the traditional hot melt adhesive has high hardness and poor flexibility, and is prone to brittle fracture, which causes the panel and the base to separate, affects the normal use of the induction cooker, and even causes safety hazards. In addition, for example, when the pot is ignited, the previous soup base is poured out and the next pot of cold soup base is replaced. When the induction cooker works in a cold and hot cycle, the panel and the base will generate thermal stress due to the difference in thermal expansion coefficient. If the flexibility of the hot melt adhesive is insufficient to buffer these stresses, long-term use will cause cracking or delamination.

[0004] Secondly, the bonding strength and durability need to be improved. The induction cooker panel needs to withstand a certain weight and vibration, especially during the process of stir-frying or cleaning. The hot melt adhesive needs to provide sufficient bonding strength to prevent the panel from falling off. However, the bonding strength of the traditional hot melt adhesive will gradually decrease under high temperature, humidity or long-term load conditions, and delamination is prone to occur. At the same time, the aging of the hot melt adhesive itself will also reduce its bonding performance and shorten the service life of the induction cooker.

[0005] Currently, there are some methods in the market that add toughening agents or coupling agents to improve the performance of hot melt adhesive. However, these methods often have the problems of insignificant toughening effect, limited improvement of bonding strength, insufficient durability, etc. Therefore, it is a technical problem to be solved in the field to develop a hot melt adhesive for induction cooker panel with excellent flexibility, impact resistance, high bonding strength and durability. SUMMARY

[0006] In order to overcome the deficiencies of the prior art, the present application provides a kind of hot melt adhesive for induction cooker panel and preparation method thereof, improve the flexibility and impact resistance of hot melt adhesive for induction cooker panel, improve bonding strength and durability.

[0007] The technical scheme adopted by the present application to solve its technical problems is:

[0008] In a first aspect, the present application provides a preparation method of hot melt adhesive for induction cooker panel, comprising the following steps:

[0009] Put the ethylene-vinyl acetate copolymer into the reaction kettle, heat and stir until completely melted;

[0010] Put the polybutadiene and styrene-isoprene-styrene block copolymer into the reaction kettle, continue to stir until completely melted;

[0011] Put the modified rosin resin into the reaction kettle, stir until completely dissolved;

[0012] Put the silane coupling agent and antioxidant into the reaction kettle, stir and mix;

[0013] Cool and discharge to obtain the hot melt adhesive for induction cooker panel.

[0014] The preparation method of the hot melt adhesive for induction cooker panel provided in the present application uses EVA to provide basic hot melt performance and adhesion, adds PBD (polybutadiene) to significantly improve the flexibility and impact resistance of the hot melt adhesive, reduces the glass transition temperature, so that the hot melt adhesive can also maintain good elasticity at low temperature, SIS (styrene-isoprene-styrene block copolymer) as a thermoplastic elastomer can further enhance the flexibility and resilience of the hot melt adhesive, improve its fatigue resistance, modified rosin resin can improve the adhesion strength of the hot melt adhesive to glass or ceramic panel, silane coupling agent can improve the interfacial bonding between the hot melt adhesive and the panel material, improve the adhesion durability, and antioxidant can prevent the hot melt adhesive from being oxidized and degraded at high temperature, improve its aging resistance.

[0015] Further, the vinyl acetate content of the ethylene-vinyl acetate copolymer is 20wt%-35wt%, the cis-content of the polybutadiene is above 95%, and the weight average molecular weight is 400,000-600,000; the styrene-isoprene-styrene block copolymer is a linear polymer, the styrene content is 10%-20%, and the weight average molecular weight is 80,000-200,000; the softening point of the modified rosin resin is 90℃-110℃; and the silane coupling agent is a silane coupling agent with amino group.

[0016] The required EVA not only retains hot melt fluidity, but also can fully react with the silane coupling agent; the high cis-structure PBD molecular chain has high regularity, so that the flexibility of the hot melt adhesive is significantly improved; the required PBD ensures the strength of the elastomer and avoids excessive melt viscosity; the linear SIS is more likely to form a uniform blending system with PBD and EVA, and the appropriate proportion of styrene in SIS balances the hardness and resilience of the thermoplastic elastomer; the modified rosin resin has good compatibility with EVA, which is conducive to inhibiting cracking or delamination of the cured adhesive.

[0017] Further, the mass of each raw material added is as follows: 40-60 parts of the ethylene-vinyl acetate copolymer, 10-20 parts of the polybutadiene, 10-20 parts of the styrene-isoprene-styrene block copolymer, 10-25 parts of the modified rosin resin, 0.5-1 part of the silane coupling agent, and 0.1-0.3 parts of the antioxidant.

[0018] The amount of EVA dominates the adhesion base. If the amount of EVA is less than 40 parts, the adhesion will be insufficient. If the amount of EVA is more than 60 parts, the proportion of elastomer will decrease, and the flexibility will be poor. The amount of modified rosin resin is balanced to the adhesion. The appropriate amount of PBD and SIS cooperates to toughen. The amount of 0.5-1 part of the coupling agent is sufficient to form a chemical bonding network at the interface. If the amount of the coupling agent is too much, the system may become brittle. The antioxidant can effectively inhibit the oxidative degradation during high-temperature processing and long-term use. If the amount of the antioxidant is insufficient, the aging resistance will be poor. If the amount of the antioxidant is excessive, the melt flowability will be affected.

[0019] Further, the amount of the modified rosin resin is 15-25 parts. The α-methyl styrene resin in an amount of 1-3 parts is also added simultaneously with the modified rosin resin.

[0020] The α-methyl styrene resin is a thermoplastic resin with the characteristics of fast curing. In the molten state of the hot melt adhesive, the α-methyl styrene resin can form a uniform mixture with EVA, PBD, and SIS. When the hot melt adhesive cools down, the α-methyl styrene resin can quickly solidify to form a hard skeleton structure, thereby quickly improving the adhesion strength of the hot melt adhesive. At the same time, increasing the amount of the modified rosin resin can further improve the adhesion strength of the hot melt adhesive to the glass or ceramic panel, thereby significantly improving the initial adhesion strength of the hot melt adhesive. The benzene ring structure in the α-methyl styrene resin and the rosin acid structure in the modified rosin resin can interact through van der Waals force to enhance the compatibility between the resins, thereby improving the adhesion strength.

[0021] Further, the weight average molecular weight of the α-methyl styrene resin is 1000-3000, and the softening point is 95-110°C.

[0022] The molecular weight ensures that the α-methyl styrene resin quickly disperses in the EVA, PBD, and SIS system, avoiding the increase in melt viscosity and uneven dispersion caused by too high molecular weight.

[0023] Further, the heating temperature is maintained at 140-160°C from the addition of the first raw material to the addition of the last raw material, which is beneficial to ensure that each component is fully melted and mixed, and also avoids overheating and oxidative degradation. At this temperature, the silane coupling agent can also fully react with the vinyl acetate group of EVA to form a chemical bond.

[0024] Further, the temperature of the outfeed is 115-125 DEG C.

[0025] At this temperature, the hot melt adhesive still maintains good melt flowability, avoiding the extension of cooling time caused by too high outfeed temperature or the increase of melt viscosity caused by too low outfeed temperature.

[0026] Further, in the step of adding the silane coupling agent and the antioxidant into the reactor and stirring and mixing, the stirring time is 15-30 min, which is favorable for the full reaction of the silane coupling agent with the EVA and the uniform distribution of the antioxidant in the system, thereby inhibiting the oxidation reaction of the whole system.

[0027] Further, in the step of adding the ethylene-vinyl acetate copolymer into the reactor and heating and stirring until completely melted, the air in the reactor is replaced by a protective gas; and in the step of adding the polybutadiene and the styrene-isoprene-styrene block copolymer into the reactor and continuing to stir until completely melted, the pressure in the reactor is reduced to negative pressure.

[0028] The exclusion of air in the reactor can avoid the oxidative degradation of the EVA, PBD and SIS at high temperature; and the negative pressure stirring can make the air bubbles in the material break and discharge, reduce the air holes in the hot melt adhesive and improve the interface adhesion of the hot melt adhesive to the panel.

[0029] In the second aspect, the application provides a hot melt adhesive for an induction cooker panel, which is prepared by the method of the first aspect.

[0030] The hot melt adhesive has better flexibility and impact resistance, so that it is not easy to break or delaminate when subjected to external impact or thermal stress, and has higher bonding strength and durability, so that it can withstand greater weight and vibration, and the silane coupling agent can improve the interface bonding and cohesive strength between the hot melt adhesive and the panel material.

[0031] The application has the advantages that the introduction of PBD and SIS significantly improves the flexibility and impact resistance of the hot melt adhesive, so that it can better adapt to the stress changes of the induction cooker panel during cold and hot cycles and when subjected to external impact, and is not easy to crack or delaminate, and the use of the silane coupling agent improves the bonding strength and durability of the hot melt adhesive to the panel material, thereby prolonging the service life of the induction cooker. DETAILED DESCRIPTION

[0032] In order to make the purposes, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by a person of ordinary skill in the art without any inventive effort belong to the scope of protection of the present disclosure.

[0033] It should be understood that any and all embodiments of the present application can be combined with the technical features in any other embodiment or multiple other embodiments to obtain additional embodiments, without conflict. The present application includes such combinations to obtain additional embodiments.

[0034] In the present specification, the groups and substituents thereof can be selected by those skilled in the art to provide stable moieties and compounds. When a substituent is described by a conventional chemical formula written from left to right, the substituent equally includes a chemically equivalent substituent resulting from writing the structure from right to left.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which the claimed subject matter belongs. In case of conflict between the definitions of terms in different documents including the priority documents, the definition provided herein will control.

[0036] The present application provides a preparation method of hot melt adhesive for induction cooker panel, raw material composition and dosage range:

[0037] Ethylene-vinyl acetate copolymer (EVA): 40-60 parts by weight;

[0038] Polybutadiene (PBD): 10-20 parts by weight, more preferably 10-15 parts;

[0039] Styrene-isoprene-styrene block copolymer (SIS): 10-20 parts by weight;

[0040] Modified rosin resin: 10-20 parts by weight;

[0041] Silane coupling agent (KH-550): 0.5-1 parts by weight;

[0042] Antioxidant: 0.1-0.3 parts by weight.

[0043] The preparation steps include:

[0044] EVA is put into a reaction kettle with stirring and heating functions, heated to 140-160℃, and stirred until EVA is completely melted.

[0045] PBD and SIS are added in sequence, and continue to stir until completely melted and uniformly mixed.

[0046] Add modified rosin resin, stir until completely dissolved.

[0047] Add silane coupling agent and antioxidant, continue stirring for 30 minutes to ensure uniform mixing.

[0048] Cool the mixture to about 120°C, discharge, and prepare the hot melt adhesive for induction cooker panel.

[0049] The vinyl acetate groups in EVA react with the amino groups in the silane coupling agent to form a chemical bond at the interface, thereby improving adhesion strength. The butadiene units in PBD and the isoprene units in SIS can slide and entangle their molecular chains when under stress, thereby absorbing impact energy and improving impact resistance.

[0050] Specifically, the raw material selection range and optimal objects are as follows:

[0051] Ethylene-vinyl acetate copolymer (EVA): vinyl acetate content is 20wt%-35wt%, preferably 25wt%-35wt%, and the optimal object is Elvax 260 from DuPont, with a vinyl acetate content of 28wt%.

[0052] Polybutadiene (PBD): the optimal object is UBEPOL-BR150B from Ube Industries, Japan.

[0053] Styrene-isoprene-styrene block copolymer (SIS): the optimal object is Kraton D1161 from Kraton Polymers LLC.

[0054] Modified rosin resin: the optimal object is A-100 from Shenzhen Xingchengda, with a softening point of 95°C-105°C.

[0055] Silane coupling agent (KH-550): γ-aminopropyl triethoxysilane, purity ≥98%, and the optimal object is a product from Nanjing Shuguang Chemical Group Co., Ltd.

[0056] Antioxidant (1010): pentaerythritol tetra(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and the optimal object is Irganox 1010 from BASF.

[0057] In some embodiments, the specific preparation steps are as follows:

[0058] Put EVA into a reaction kettle with stirring and heating function, protect with nitrogen to exclude air in the kettle and prevent material oxidation. Heat to 150°C, control the stirring speed at 60rpm, stir until EVA is completely melted, and the melting time is about 30 minutes.

[0059] PBD and SIS were added in sequence, and stirring was continued until complete melting and uniform mixing, with the stirring speed controlled at 80 rpm, and the mixing time being about 45 minutes.

[0060] The modified rosin resin was added, and stirring was continued until complete dissolution, with the stirring speed controlled at 70 rpm, and the time taken being about 20 minutes.

[0061] The silane coupling agent and the antioxidant were added, and stirring was continued for 30 minutes to ensure uniform mixing, with the stirring speed controlled at 60 rpm.

[0062] Heating was stopped, and natural cooling was performed to about 120°C, and the product was discharged, thereby obtaining the hot melt adhesive for the induction cooker panel.

[0063] After PBD and SIS were added, vacuum degassing treatment was performed, with the pressure in the reactor being reduced to -0.08 MPa while stirring was continued, and the pressure was maintained for 15 minutes to remove bubbles in the material. The vacuum degassing treatment can reduce pores in the hot melt adhesive, and improve the density and bonding strength. The presence of bubbles can reduce the effective bonding area of the hot melt adhesive, and affect the bonding effect. Through vacuum degassing, the bubbles can be significantly reduced, and the bonding strength and durability can be improved.

[0064] In actual applications, the hot melt adhesive also has the problem of insufficient initial bonding strength, which can cause the induction cooker panel to be easily displaced during assembly, and affect the production efficiency.

[0065] The optimized raw material composition and amount range are as follows:

[0066] Ethylene-vinyl acetate copolymer (EVA): 45-55 parts by weight;

[0067] Polybutadiene (PBD): 10-15 parts by weight;

[0068] Styrene-isoprene-styrene block copolymer (SIS): 10-20 parts by weight;

[0069] Modified rosin resin: 15-25 parts by weight;

[0070] α-methylstyrene resin: 1-3 parts by weight;

[0071] Silane coupling agent (KH-550): 0.5-1 parts by weight;

[0072] Antioxidant (1010): 0.1-0.3 parts by weight.

[0073] Among them, the most preferred object of α-methylstyrene resin is Kristalex F100 of Eastman, and the softening point is 96-104°C.

[0074] Compared with the basic formula scheme, the optimized formula scheme significantly improves the initial bonding strength of the hot melt adhesive by introducing α-methylstyrene resin and increasing the amount of modified rosin resin, so that it can better meet the bonding requirements of the induction cooker panel during the assembly process and improve the production efficiency.

[0075] The optimized preparation steps are as follows:

[0076] Put EVA into the reaction kettle with stirring and heating functions, protect with nitrogen to exclude air in the kettle and prevent material oxidation. Heat to 160°C, control the stirring speed at 60 rpm, and stir until EVA is completely melted, with a melting time of about 30 minutes.

[0077] Add PBD and SIS in sequence, continue to stir, control the stirring speed at 80 rpm, and stir until completely melted and uniformly mixed, with a mixing time of 45 minutes (the last 15 minutes of the 45 minutes reduce the pressure in the reaction kettle to-0.08 MPa).

[0078] Add modified rosin resin and α-methylstyrene resin, control the stirring speed at 90 rpm, and stir until completely dissolved, which takes about 20 minutes.

[0079] Reduce the temperature to 140°C, add silane coupling agent and antioxidant, continue to stir for 15 minutes to ensure uniform mixing, and control the stirring speed at 60 rpm.

[0080] Stop heating and naturally cool to about 120°C, discharge, and obtain the hot melt adhesive for induction cooker panel.

[0081] In this optimized example, the amount of PBD is reduced, the temperature of the molten high molecular material is increased, the temperature of adding silane coupling agent is adjusted, and the stirring time after adding silane coupling agent is shortened, which is beneficial to optimizing the flowability of the melt and reducing the self-condensation of silane coupling agent. After adding modified rosin resin and α-methylstyrene resin, the stirring speed is increased to 90 rpm, and high-speed shearing stirring is maintained for 10 minutes. High-speed shearing stirring can promote the dispersion of α-methylstyrene resin in the hot melt adhesive system, making it better mixed with EVA, PBD, SIS and other components to form a more uniform system. The uniform dispersion of α-methylstyrene resin is crucial to improving the initial bonding strength of the hot melt adhesive.

[0082] Example 1

[0083] The formula of the product is as follows:

[0084] Ethylene-vinyl acetate copolymer (EVA): 50 parts by weight (Elvax 260, DuPont, USA);

[0085] Polybutadiene (PBD): 15 parts by weight (UBEPOL-BR150B, Ube Industries, Japan);

[0086] Styrene-isoprene-styrene block copolymer (SIS): 15 parts by weight (Kraton D1161, Kraton Polymers LLC);

[0087] Modified rosin resin: 18 parts by weight (A-100, Shenzhen Xingchengda);

[0088] Silane coupling agent (KH-550): 0.8 parts by weight (Nanjing Shuguang Chemical Group Co., Ltd.);

[0089] Antioxidant (1010): 0.2 parts by weight (Irganox 1010, BASF).

[0090] The product preparation method is as follows:

[0091] EVA, PBD, SIS, modified rosin resin, silane coupling agent and antioxidant were weighed according to the formula proportion for standby.

[0092] EVA was put into a reaction kettle with stirring and heating function, protected by nitrogen to exclude air in the kettle and prevent material oxidation. Heated to 150°C, the stirring speed was controlled at 60 rpm, and the EVA was completely melted after stirring for about 30 minutes.

[0093] PBD and SIS were added in turn, and the stirring speed was controlled at 80 rpm. After complete melting and uniform mixing, the mixing time was about 45 minutes. Among them, the last 15 minutes were treated by vacuum degassing: while stirring, the pressure in the reaction kettle was reduced to-0.08 MPa to remove bubbles in the material.

[0094] Modified rosin resin was added, and the stirring speed was controlled at 70 rpm. After complete dissolution, it took about 20 minutes.

[0095] Silane coupling agent and antioxidant were added, and the stirring was continued for 30 minutes to ensure uniform mixing, with the stirring speed controlled at 60 rpm.

[0096] Stop heating and naturally cool to about 120°C, discharge, and prepare the hot melt adhesive for electromagnetic oven panel.

[0097] The product performance was tested according to the standard of ASTM D3654. The sample was prepared by coating the hot melt adhesive on a glass substrate, bonding with another ABS plastic substrate, applying a pressure of 2 kg for 5 minutes, and then curing at 25℃ for 24 hours to obtain a test sample.

[0098] (1) Initial bonding strength test:

[0099] Test method: The test sample was subjected to 180° peeling test at a speed of 50 mm / min, and the maximum peeling force was recorded.

[0100] Test result: The initial bonding strength was 8.5 N / mm.

[0101] (2) Moisture and heat aging resistance test:

[0102] Test method: The test sample was placed in a constant temperature and humidity chamber at 85℃ and 85% relative humidity for aging treatment for 168 hours. Then, the 180° peeling strength test was performed, and the peeling force was recorded.

[0103] Test result: The bonding strength after aging was 6.2 N / mm.

[0104] (3) Impact strength test:

[0105] Test method: The test was performed using a falling weight impact tester. The falling weight was dropped freely from a height of 50 cm to impact the bonding part of the test sample, and whether delamination occurred was recorded.

[0106] Test result: No delamination occurred.

[0107] Example 2

[0108] The formulation of the product is as follows:

[0109] Ethylene-vinyl acetate copolymer (EVA): 45 parts by weight (Elvax 260, DuPont, USA);

[0110] Polybutadiene (PBD): 18 parts by weight (UBEPOL-BR150B, Ube Industries, Japan);

[0111] Styrene-isoprene-styrene block copolymer (SIS): 17 parts by weight (Kraton D1161, Kraton Polymers LLC);

[0112] Modified rosin resin: 19 parts by weight (A-100, Shenzhen Xingchengda);

[0113] Silane coupling agent (KH-550): 0.7 parts by weight (Nanjing Shuguang Chemical Group Co., Ltd.);

[0114] Antioxidant (1010): 0.3 parts by weight (Irganox 1010, BASF).

[0115] The product is prepared as follows:

[0116] The EVA, PBD, SIS, modified rosin resin, silane coupling agent and antioxidant are weighed according to the formula proportion for standby.

[0117] The EVA is put into a reaction kettle with stirring and heating function, protected by nitrogen to exclude air in the kettle and prevent material oxidation. Heat to 150°C, control the stirring speed at 60 rpm, stir until the EVA is completely melted, the melting time is about 30 minutes.

[0118] PBD and SIS are added in turn, continue to stir, control the stirring speed at 80 rpm, stir until completely melted and mixed uniformly, the mixing time is about 45 minutes. Among them, the last 15 minutes adopts vacuum degassing treatment: while stirring, the pressure in the reaction kettle is reduced to-0.08 MPa to remove bubbles in the material.

[0119] Modified rosin resin is added, the stirring speed is controlled at 70 rpm, and stirring is continued until complete dissolution, which takes about 20 minutes.

[0120] Silane coupling agent and antioxidant are added, continue to stir for 30 minutes to ensure uniform mixing, and the stirring speed is controlled at 60 rpm.

[0121] Stop heating, naturally cool to about 120°C, discharge, and prepare the hot melt adhesive for electromagnetic oven panel.

[0122] The product is tested for performance: the hot melt adhesive is coated on a glass substrate and bonded to another ABS plastic substrate, 2kg of pressure is applied, maintained for 5 minutes, and then cured at 25°C for 24 hours to obtain a test sample.

[0123] (1) Initial bonding strength test:

[0124] Test method: 180° peeling test is performed on the test sample at a speed of 50mm / min, and the maximum peeling force is recorded.

[0125] Test result: the initial bonding strength is 8.8 N / mm.

[0126] (2) Moisture and heat aging resistance test:

[0127] Test method: The sample was placed in a constant temperature and humidity chamber at 85°C and 85% relative humidity for aging treatment for 168 hours. Then, 180° peeling strength test was performed, and the peeling force was recorded.

[0128] Test result: The bonding strength after aging was 6.5 N / mm.

[0129] (3) Impact strength test:

[0130] Test method: A falling weight impact tester was used for testing. The falling weight was dropped freely from a height of 50 cm to impact the bonding part of the sample, and whether delamination occurred was recorded.

[0131] Test result: No delamination occurred.

[0132] Example 3

[0133] The formulation of the product is as follows:

[0134] Ethylene-vinyl acetate copolymer (EVA): 50 parts by weight (Elvax 260, DuPont, USA);

[0135] Polybutadiene (PBD): 15 parts by weight (UBEPOL-BR150B, Ube Industries, Japan);

[0136] Styrene-isoprene-styrene block copolymer (SIS): 15 parts by weight (Kraton D1161, Kraton Polymers LLC);

[0137] Modified rosin resin: 20 parts by weight (A-100, Shenzhen Xingchengda);

[0138] Alpha-methylstyrene resin: 2 parts by weight (Kristalex F100, Eastman);

[0139] Silane coupling agent (KH-550): 0.8 parts by weight (Nanjing Shuguang Chemical Group Co., Ltd.);

[0140] Antioxidant (1010): 0.2 parts by weight (Irganox 1010, BASF).

[0141] The preparation method of the product is as follows:

[0142] EVA, PBD, SIS, modified rosin resin, alpha-methylstyrene resin, silane coupling agent and antioxidant were weighed according to the optimized formulation ratio for standby.

[0143] Put EVA into the reactor with stirring and heating function, and protect it with nitrogen to remove the air in the reactor and prevent the material from oxidizing. Heat to 150°C, control the stirring speed at 60rpm, and stir until the EVA is completely melted, which takes about 30 minutes.

[0144] Add PBD and SIS in turn, continue to stir, control the stirring speed at 80rpm, and stir until completely melted and mixed evenly, which takes about 45 minutes. During the last 15 minutes, use vacuum degassing treatment: while stirring, reduce the pressure in the reactor to-0.08MPa to remove bubbles in the material.

[0145] Add modified rosin resin and α-methyl styrene resin, control the stirring speed at 90rpm, and maintain high-speed shearing stirring for 10 minutes, then adjust the stirring speed to 70rpm, and stir until completely dissolved, which takes about 20 minutes.

[0146] Add silane coupling agent and antioxidant, continue to stir for 15 minutes to ensure uniform mixing, and control the stirring speed at 60rpm.

[0147] Stop heating and naturally cool to about 120°C, discharge, and prepare the hot melt adhesive for electromagnetic oven panel.

[0148] Test the performance of the product: apply the hot melt adhesive to a glass substrate, bond it with another ABS plastic substrate, apply 2kg of pressure, maintain for 5 minutes, and then cure for 24 hours in an environment of 25°C to obtain a test sample.

[0149] (1) Initial bonding strength test:

[0150] Test method: test the test sample at 180° peeling with a speed of 50mm / min, and record the maximum peeling force.

[0151] Test result: the initial bonding strength is 10.2 N / mm.

[0152] (2) Moisture and heat aging resistance test:

[0153] Test method: place the test sample in a constant temperature and humidity chamber at 85°C and 85% relative humidity for aging treatment for 168 hours. Then test the 180° peeling strength, and record the peeling force.

[0154] Test result: the bonding strength after aging is 7.0 N / mm.

[0155] (3) Impact strength test:

[0156] Test method: A falling weight impact tester was used for the test. The falling weight was dropped freely from a height of 50 cm to impact the adhesive portion of the sample, and whether delamination occurred was recorded.

[0157] Test result: No delamination occurred.

[0158] Example 4

[0159] The formulation of the product is as follows:

[0160] Ethylene-vinyl acetate copolymer (EVA): 45 parts by weight (Elvax 260, DuPont USA);

[0161] Polybutadiene (PBD): 15 parts by weight (UBEPOL-BR150B, Ube Industries, Japan);

[0162] Styrene-isoprene-styrene block copolymer (SIS): 17 parts by weight (Kraton D1161, Kraton Polymers LLC);

[0163] Modified rosin resin: 21 parts by weight (A-100, Shenzhen Xingchengda);

[0164] Alpha-methylstyrene resin: 2 parts by weight (Kristalex F100, Eastman);

[0165] Silane coupling agent (KH-550): 0.7 parts by weight (Nanjing Shuguang Chemical Group Co., Ltd.);

[0166] Antioxidant (1010): 0.3 parts by weight (Irganox 1010, BASF).

[0167] The preparation method of the product is as follows:

[0168] The EVA, PBD, SIS, modified rosin resin, alpha-methylstyrene resin, silane coupling agent, and antioxidant were weighed according to the optimized formulation ratio for standby use.

[0169] The EVA was placed in a reaction kettle with stirring and heating function, protected by nitrogen gas to exclude air in the kettle and prevent material oxidation. It was heated to 160°C, the stirring speed was controlled at 60 rpm, and stirring was continued until the EVA was completely melted, with a melting time of about 30 minutes.

[0170] PBD and SIS were added in sequence, and stirring was continued with a stirring speed of 80 rpm until complete melting and uniform mixing, with a mixing time of about 45 minutes. During the last 15 minutes, vacuum degassing treatment was performed: while stirring, the pressure in the reaction kettle was reduced to -0.08 MPa to remove air bubbles in the material.

[0171] Add modified rosin resin and α-methyl styrene resin, control the stirring speed to 90 rpm, and maintain high-speed shearing stirring for 10 minutes, then adjust the stirring speed to 70 rpm, and stir until completely dissolved, which takes about 20 minutes.

[0172] Cool down to 140℃, add silane coupling agent and antioxidant, continue stirring for 15 minutes, ensure uniform mixing, control the stirring speed to 60 rpm.

[0173] Stop heating, naturally cool to about 120℃, discharge, and prepare the hot melt adhesive for induction cooker panel.

[0174] Test the performance of the product: coat the hot melt adhesive on a glass substrate, bond with another ABS plastic substrate, apply 2kg of pressure, maintain for 5 minutes, and then cure for 24 hours in an environment of 25℃ to obtain a test sample.

[0175] (1) Initial bonding strength test:

[0176] Test method: test the test sample at 180° peeling with a speed of 50mm / min, and record the maximum peeling force.

[0177] Test result: the initial bonding strength is 10.5 N / mm.

[0178] (2) Moisture and heat aging resistance test:

[0179] Test method: place the test sample in a constant temperature and humidity chamber at 85℃ and 85% relative humidity for aging treatment for 168 hours. Then test the 180° peeling strength, and record the peeling force.

[0180] Test result: the bonding strength after aging is 7.2 N / mm.

[0181] (3) Impact strength test:

[0182] Test method: use a falling weight impact tester to test. Drop the falling weight from a height of 50cm, impact the bonding part of the test sample, and record whether delamination occurs.

[0183] Test result: no delamination occurs.

[0184] Select a certain brand of hot melt adhesive for induction cooker panel on the market (hereinafter referred to as "market hot melt adhesive") as the control group, prepare the sample in the same way, and test the same performance.

[0185] (1) Initial adhesive strength test: 180° peeling strength test was performed according to ASTM D3654 standard, and the test result was 7.0 N / mm.

[0186] (2) Moisture and heat aging resistance test: the sample was placed in a constant temperature and humidity chamber at 85°C and 85% relative humidity for aging treatment for 168 hours, and then 180° peeling strength test was performed according to ASTM D3654 standard, and the test result was 5.0 N / mm.

[0187] (3) Impact strength test: a falling weight impact tester was used for testing, and the falling weight was freely dropped from a height of 50 cm to impact the adhesive part of the sample, and delamination occurred.

[0188] From the test results of the above implementation cases and the control cases, it can be seen that the hot melt adhesive for the panel of the electromagnetic oven provided by the present application significantly improves the flexibility and impact resistance of the hot melt adhesive by introducing PBD and SIS. Compared with commercially available hot melt adhesives, the hot melt adhesive for the panel of the electromagnetic oven provided by the present application has higher initial adhesive strength and better moisture and heat aging resistance. The optimized embodiment further improves the adhesive strength by introducing alpha-methylstyrene resin and increasing the amount of modified rosin resin.

[0189] In the description of the present specification, the description referring to the terms "one embodiment", "certain embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, materials or characteristics described in connection with the described embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0190] The above is the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements are also considered within the protection scope of the present application.

Claims

1. A method for preparing hot melt adhesive for induction cooker panels, characterized in that, The steps include: The ethylene-vinyl acetate copolymer was added to the reactor and heated and stirred until completely melted; Polybutadiene and styrene-isoprene-styrene block copolymer were added to the reactor and stirred until completely melted. Add modified rosin resin to the reactor and stir until completely dissolved; Add silane coupling agent and antioxidant to the reaction vessel and stir to mix; Cool and discharge the material to obtain the hot melt adhesive for the induction cooker panel; The vinyl acetate content of the ethylene-vinyl acetate copolymer is 20wt%-35wt%; the cis content of the polybutadiene is above 95%, and the weight-average molecular weight is 400,000-600,000; the styrene-isoprene-styrene block copolymer is a linear polymer, the styrene content is 10%-20%, and the weight-average molecular weight is 80,000-200,000; the softening point of the modified rosin resin is 90℃~110℃; the silane coupling agent is an amino-containing silane coupling agent. The mass and dosage of the various raw materials added are as follows: 40-60 parts of the ethylene-vinyl acetate copolymer, 10-20 parts of the polybutadiene, 10-20 parts of the styrene-isoprene-styrene block copolymer, 15-25 parts of the modified rosin resin, 0.5-1 part of the silane coupling agent, and 0.1-0.3 parts of the antioxidant; 1 to 3 parts of α-methylstyrene resin were also added along with the modified rosin resin; The weight-average molecular weight of the α-methylstyrene resin is 1000-3000, and the softening point is 95℃~110℃.

2. The method for preparing hot melt adhesive for induction cooker panels according to claim 1, characterized in that, From the addition of the first raw material to the addition of the last raw material, the heating temperature is maintained at 140℃-160℃.

3. The method for preparing hot melt adhesive for induction cooker panels according to claim 2, characterized in that, The discharge temperature is 115℃-125℃.

4. The method for preparing hot melt adhesive for induction cooker panels according to claim 2, characterized in that, In the step of adding silane coupling agent and antioxidant to the reaction vessel and stirring and mixing, the stirring time is 15 min-30 min.

5. The method for preparing hot melt adhesive for induction cooker panels according to claim 1, characterized in that, In the step of adding the ethylene-vinyl acetate copolymer into the reactor and heating and stirring until it is completely melted, the air in the reactor is replaced by a protective gas; in the step of adding polybutadiene and styrene-isoprene-styrene block copolymer into the reactor and continuing to stir until it is completely melted, the pressure inside the reactor is reduced to a negative pressure.

6. A hot melt adhesive for an induction cooker panel, characterized in that, It is made by the hot melt adhesive preparation method for induction cooker panels as described in any one of claims 1 to 5.