Modified hot melt adhesive for electronics and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a modified hot melt adhesive for electronics and a preparation method of the modified hot melt adhesive. The component A is prepared from the following raw materials: thermoplastic polyurethane, an ultraviolet light absorber, nanofibers, filler, an adhesion promoter, a light curing agent and an antioxidant; the component B comprises the following raw materials: isocyanate, polyester polyol, polyether polyol, acrylic resin, a catalyst and a chain extender. The modified hot melt adhesive product is stable in quality, good in mechanical property and water resistance, high in curing speed, good in bonding strength, excellent in weather resistance, convenient to process better, capable of meeting the bonding requirements of lighter, thinner and narrow edges of electronic products such as mobile phones and tablet personal computers, and good in practicability.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a modified hot melt adhesive for electronics and a preparation method thereof. Background Art

[0002] Hot melt adhesive is a thermoplastic polymer adhesive that changes its physical state with temperature within a certain temperature range. It is molten and fluid when heated, and can easily penetrate the surface of the substrate to achieve a good wetting state. After the temperature drops, it cools to a solid state. At this time, the adhesive film has strong tensile strength and elongation, forming a good adhesive joint, thereby providing good bonding strength. Hot melt adhesive has the advantages of excellent bonding performance, good weather resistance, green environmental protection, and suitability for mechanized and automated production. It is currently widely used in the automotive, home appliance, electronics and other industries.

[0003] Especially with the rapid development of electronic products, people have higher and higher requirements on the appearance of electronic products such as mobile phones and tablets. For example, they require mobile phones and tablets to be thinner and lighter. In addition, a large number of mobile phones, tablets and other electronic products with narrow bezels have appeared. Therefore, higher performance requirements are also put forward for hot melt adhesives used for bonding to meet higher bonding needs.

[0004] However, current adhesives still have problems such as bubble generation, easy bulging, slow curing and high temperature resistance, which limit their application. It is necessary to improve these properties, break through the limitations, and develop PUR hot melt adhesive products with higher performance levels. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies in the prior art, the purpose of the present invention is to provide a modified hot melt adhesive for electronic use. The modified hot melt adhesive product has stable quality, good mechanical properties and water resistance, and has a fast curing speed, good bonding strength, and excellent weather resistance. It is easy to process better and can meet the bonding requirements of mobile phones, tablet computers and other electronic products that are thinner and have narrow edges, and has good practicality.

[0006] Another object of the present invention is to provide a method for preparing a modified hot melt adhesive for electronic use, which method has simple operation, convenient control, high production efficiency, low production cost, and is suitable for large-scale production.

[0007] The object of the present invention is achieved by the following technical solution: A modified hot melt adhesive for electronics, comprising component A and component B, wherein the mass ratio of component A to component B is 0.3-0.6:1.2-1.5;

[0008] The component A comprises the following raw materials in parts by weight: 20-40 parts of thermoplastic polyurethane, 1-5 parts of ultraviolet absorber, 4-8 parts of nanofiber, 1-3 parts of filler, 1-3 parts of adhesion promoter, 1-5 parts of photocuring agent and 0.5-2.5 parts of antioxidant;

[0009] The component B comprises the following raw materials in parts by weight: 15-30 parts of isocyanate, 20-40 parts of polyester polyol, 10-20 parts of polyether polyol, 5-10 parts of acrylic resin, 0.5-1.5 parts of catalyst, and 1-5 parts of chain extender.

[0010] The modified hot melt adhesive product of the present invention has stable quality, good mechanical properties, water resistance, fast curing speed, good bonding strength, excellent weather resistance, and is easy to process better. It can meet the requirements of thinner and narrower bonding of electronic products such as mobile phones and tablets, and has good practicality. Among them, the thermoplastic polyurethane itself has certain viscoelasticity and adhesion, and synergizes with other components (such as adhesion promoters, etc.) to further enhance the overall adhesion performance; and the addition of ultraviolet absorbers can effectively absorb ultraviolet rays, reduce the damage of ultraviolet rays to the hot melt adhesive, and prevent aging, discoloration, performance degradation and other problems caused by long-term illumination; the components such as isocyanate, polyester polyol, polyether polyol in component B interact with the relevant components in component A (such as thermoplastic polyurethane, light curing agent, etc.), and by adjusting the ratio of each raw material, the curing speed and degree of curing of the hot melt adhesive can be controlled to meet the requirements of different electronic assembly processes. At the same time, the various raw materials in the light curing agent (toluene diisocyanate, linear polyester diol, etc.) also help to achieve rapid curing under specific conditions and improve production efficiency. The isocyanate in component B will react with polyester polyols and polyether polyols, and the -NCO in the isocyanate will react with the -OH in the polyol to form a carbamate bond (-NHCOO-). Through this reaction, a polymer with a certain molecular weight and performance is gradually formed, thereby giving the hot melt adhesive basic bonding and curing properties; the silaneoxy group (-Si(OMe)3) in the adhesion promoter γ-mercaptopropyltrimethoxysilane will react with the hydroxyl group on the surface of the filler (such as silica) to form a chemical bond, thereby playing a coupling role between the filler and the hot melt adhesive matrix, improving the dispersion of the filler in the system and the bonding force with the matrix, thereby enhancing the overall performance of the hot melt adhesive.

[0011] Preferably, the ultraviolet absorber is at least one of zinc oxide, aluminum oxide, 2-hydroxy-4-methoxybenzophenone, and 2-hydroxy-4-methoxy-5-sulfonic acid benzophenone.

[0012] The ultraviolet absorber used in the present invention is composed of an inorganic ultraviolet absorber and an organic ultraviolet absorber, which can effectively absorb ultraviolet rays, reduce the damage of ultraviolet rays to the hot melt adhesive, and prevent aging, discoloration, performance degradation and other problems caused by long-term light exposure, thereby extending its service life in electronic equipment and enabling it to adapt to different usage environments.

[0013] Preferably, the adhesion promoter is at least one of bis-(γ-trimethoxysilylpropyl)amine, γ-mercaptopropyltrimethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-isocyanatepropyltrimethoxysilane and N-phenyl-γ-aminopropyltrimethoxysilane.

[0014] The adhesion promoter used in the present invention, such as γ-mercaptopropyltrimethoxysilane, can improve the adhesion effect of the hot melt adhesive to different substrates, so that it can be better used in the bonding of electronic devices, ensuring that electronic components will not fall off easily during use.

[0015] Preferably, the filler is at least one of silicon dioxide, montmorillonite, talc, graphene nanosheets, hydrotalcite and hydronaphthene.

[0016] The silicon dioxide, graphene nanosheets and the like used in the filler of the present invention can effectively improve the mechanical properties of the hot melt adhesive, such as hardness and strength, so that it can still maintain good structural integrity under certain external forces, and is more suitable for bonding parts of electronic equipment that require certain mechanical support or protection.

[0017] More preferably, the filler is composed of silicon dioxide and graphene nanosheets in a mass ratio of 0.4-0.8:1.0-1.4.

[0018] The graphene nanosheets need to be pretreated before use:

[0019] Step ① Take graphene nanosheets and add deionized water, heat in a water bath to 70-75° C. and stir until uniform to obtain solution A, which is set aside; the ratio of the graphene nanosheets to the deionized water is 0.1-0.5:2-5;

[0020] Step ②: γ-aminopropyltriethoxysilane, ethanol and deionized water are stirred and mixed, and then ultrasonically dispersed to obtain a dispersion liquid for standby use; the ratio of the γ-aminopropyltriethoxysilane, ethanol and deionized water is 0.1-0.3:0.8-1.2:2-6.

[0021] Step ③: adding dicyclohexylcarbodiimide and the dispersion into solution A, heating in a water bath at 30-70° C. and stirring for reaction, and then filtering and drying to obtain pretreated graphene nanosheets; the ratio of the dicyclohexylcarbodiimide, the dispersion and the solution A is 0.05-0.1:0.8-1.2:1-3.

[0022] The graphene nanosheets pretreated by the above method in the present invention have good dispersion performance and constant wettability. That is, through a series of pretreatment steps, especially ultrasonic dispersion and other operations, the graphene nanosheets can be better dispersed in the system in subsequent applications to avoid agglomeration, so as to more evenly exert their performance. In the hot melt adhesive, the uniformly dispersed graphene can interact with other materials more effectively and improve the performance of the overall material; the use of γ-aminopropyltriethoxysilane coupling agent and the reaction treatment with dicyclohexylcarbodiimide as a catalyst can introduce functional groups on the surface of graphene nanosheets or change its surface properties, so that it has better reaction activity when further reacting or combining with other substances in the future, which is conducive to forming a more stable and better performance product structure; and dicyclohexylcarbodiimide (DCC) mainly plays a role in promoting condensation reactions in the reaction. When it is mixed with the dispersion and solution A containing the above-mentioned γ-aminopropyltriethoxysilane treatment, it can activate functional groups such as carboxyl and amino groups in the reactants, promote dehydration condensation reactions between them, make the connection between γ-aminopropyltriethoxysilane and graphene nanosheets more stable, and may also promote other potential reactions in the system to achieve a better pretreatment effect on graphene nanosheets.

[0023] Preferably, the isocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate.

[0024] Preferably, the polyester polyol is at least one of aliphatic polyester polyol, aromatic polyester polyol and mixed acid polyester polyol.

[0025] Preferably, the polyether polyol is at least one of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyoxyethylene polyol.

[0026] Preferably, the catalyst is at least one of tetrabutyl titanate, dimorpholinyl diethyl ether and N,N,N'-trimethyl-N'-hydroxyethyl-diaminoethyl ether, triethylenediamine, dibutyltin dilaurate, and dimorpholinyl diethyl ether.

[0027] Preferably, the chain extender is at least one of ethylene glycol, glycerol, trimethylolpropane, diethylene glycol, 1,4-butanediol, trimethylolpropane, and diethylene glycol.

[0028] Preferably, the antioxidant is at least one of antioxidant 245, antioxidant 264, antioxidant 1076, and antioxidant 1010.

[0029] The above specific types of antioxidants added to the hot melt adhesive of the present invention can inhibit the oxidation reaction of the hot melt adhesive during storage and use, avoid molecular chain breakage and performance degradation caused by oxidation, and maintain the stability and performance of the hot melt adhesive.

[0030] Preferably, the photocuring agent comprises the following raw materials in parts by weight: 10-20 parts of toluene diisocyanate, 5-10 parts of linear polyester diol, 1-5 parts of trimethylolpropane, 10-20 parts of alkyd resin, and 0.5-2.5 parts of 1-hydroxycyclohexyl phenyl ketone.

[0031] Preferably, the photocuring agent is prepared by the following method:

[0032] A1. Add toluene diisocyanate, linear polyester diol and trimethylolpropane into a reaction kettle according to parts by weight, heat to 70-90° C. and stir for 1-3 hours to obtain a mixture, which is set aside;

[0033] A2. Add alkyd resin and 1-hydroxycyclohexyl phenyl ketone to the mixture obtained in step A1 according to parts by weight, heat to 60-90° C. and stir at a rate of 300-600 r / min for 30-60 min to obtain a photocuring agent.

[0034] The photocuring agent in the present invention is prepared by using the above raw materials and methods, wherein the raw materials such as toluene diisocyanate, linear polyester diol, trimethylolpropane, alkyd resin, 1-hydroxycyclohexyl phenyl ketone, etc. will undergo a series of photochemical reactions under light conditions. Specifically, the photoinitiator (1-hydroxycyclohexyl phenyl ketone, etc.) will produce free radicals or ion active species after absorbing light of a specific wavelength, and these active species will trigger polymerization reactions between other raw materials, such as toluene diisocyanate, linear polyester diol, trimethylolpropane, etc., reacting with each other, further cross-linking and curing the hot melt adhesive, so that it can reach a higher degree of curing in a short time, and improving the curing speed and efficiency.

[0035] The present invention also provides a method for preparing a modified hot melt adhesive for electronics, comprising the following steps:

[0036] S1. Add thermoplastic polyurethane, ultraviolet absorber, nanofiber, filler, adhesion promoter, photocuring agent and antioxidant into a reaction kettle according to weight parts, heat to 90-100° C., mix and stir to obtain mixture A, and set aside;

[0037] S2, according to parts by weight, adding isocyanate accounting for two-thirds of the total amount of isocyanate to the polyester polyol and heating and stirring in a reaction kettle to obtain a mixture B, which is set aside;

[0038] S3, adding the remaining isocyanate to the polyether polyol according to parts by weight, heating and stirring in a reaction kettle to obtain a mixture C for later use;

[0039] S4, according to weight parts, add acrylic resin, catalyst, chain extender, and mixture C to mixture B, heat to 100-130° C. and stir for 1-3 hours, and obtain mixture D after reaction, which is set aside;

[0040] S5. Add mixture A to mixture D and heat to 110-120° C. to completely melt the mixture, mix the mixture under uniform stirring, evacuate the mixture, and heat to 100-120° C. to react for 1-3 hours to obtain a modified hot melt adhesive.

[0041] The modified hot melt adhesive of the present invention is prepared by the above method. The prepared modified hot melt adhesive product has stable quality, good mechanical properties, water resistance, fast curing speed, good bonding strength, excellent weather resistance, and is easy to process better. It can meet the requirements of thinner and narrower bonding of electronic products such as mobile phones and tablet computers, and has good practicality. When used, the reaction between isocyanate and polyol begins to occur. Under the action of a catalyst (such as tetrabutyl titanate), the reaction is accelerated to gradually form a hot melt adhesive polymer with certain properties. If light curing is required, a light curing reaction can be carried out using a light curing agent under appropriate lighting conditions to allow the hot melt adhesive to quickly reach the desired degree of curing.

[0042] The beneficial effects of the present invention are as follows: the modified hot melt adhesive product of the present invention has stable quality, good mechanical properties and water resistance, and has a fast curing speed, good bonding strength, and excellent weather resistance, which is convenient for better processing and can meet the requirements of lighter and thinner and narrow-edged bonding of electronic products such as mobile phones and tablet computers, and has good practicality.

[0043] The modified hot melt adhesive for electronics of the present invention has simple preparation operation, convenient control, high production efficiency, low production cost and is suitable for large-scale production. DETAILED DESCRIPTION

[0044] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0045] Example 1

[0046] A modified hot melt adhesive for electronics, comprising component A and component B, wherein the mass ratio of component A to component B is 0.3:1.2;

[0047] The component A comprises the following raw materials in parts by weight: 20 parts of thermoplastic polyurethane, 1 part of ultraviolet absorber, 4 parts of nanofiber, 1 part of filler, 1 part of adhesion promoter, 1 part of photocuring agent and 0.5 part of antioxidant;

[0048] The component B comprises the following raw materials in parts by weight: 15 parts of isocyanate, 20 parts of polyester polyol, 10 parts of polyether polyol, 5 parts of acrylic resin, 0.5 parts of catalyst, and 1 part of chain extender.

[0049] The ultraviolet absorber is zinc oxide.

[0050] The adhesion promoter is bis-(γ-trimethoxysilylpropyl)amine.

[0051] The filler is composed of silicon dioxide and graphene nanosheets in a mass ratio of 0.4:1.0.

[0052] The graphene nanosheets need to be pretreated before use:

[0053] Step ① Take graphene nanosheets and add deionized water, heat to 70° C. in a water bath and stir until uniform to obtain solution A, which is set aside; the ratio of the graphene nanosheets to the deionized water is 0.1:2;

[0054] Step ②: γ-aminopropyltriethoxysilane, ethanol and deionized water are stirred and mixed, and then ultrasonically dispersed to obtain a dispersion for later use; the ratio of the γ-aminopropyltriethoxysilane, ethanol and deionized water is 0.1:0.8:2.

[0055] Step ③: adding dicyclohexylcarbodiimide and the dispersion into solution A, heating in a water bath at 30° C. and stirring for reaction, and then filtering and drying to obtain pretreated graphene nanosheets; the ratio of the dicyclohexylcarbodiimide, the dispersion and the solution A is 0.05:0.8:1.

[0056] The isocyanate is toluene diisocyanate.

[0057] The polyester polyol is an aliphatic polyester polyol.

[0058] The polyether polyol is polyethylene glycol.

[0059] The catalyst is triethylenediamine.

[0060] The chain extender is ethylene glycol.

[0061] The antioxidant is antioxidant 245.

[0062] The photocuring agent comprises the following raw materials in parts by weight: 10 parts of toluene diisocyanate, 5 parts of linear polyester diol, 1 part of trimethylolpropane, 10 parts of alkyd resin, and 0.5 parts of 1-hydroxycyclohexyl phenyl ketone.

[0063] The photocuring agent is prepared by the following method:

[0064] A1. Add toluene diisocyanate, linear polyester diol and trimethylolpropane into a reaction kettle according to parts by weight, heat to 70° C. and stir for 3 hours to obtain a mixture, which is set aside;

[0065] A2. Add alkyd resin and 1-hydroxycyclohexyl phenyl ketone to the mixture obtained in step A1 according to parts by weight, heat to 60° C. and stir at a rate of 600 r / min for 60 min to obtain a photocuring agent.

[0066] A method for preparing a modified hot melt adhesive for electronics comprises the following steps:

[0067] S1. Add thermoplastic polyurethane, ultraviolet absorber, nanofiber, filler, adhesion promoter, photocuring agent and antioxidant into a reaction kettle according to weight parts, heat to 90° C., mix and stir to obtain mixture A, and set aside;

[0068] S2, according to parts by weight, adding isocyanate accounting for two-thirds of the total amount of isocyanate to the polyester polyol and heating and stirring in a reaction kettle to obtain a mixture B, which is set aside;

[0069] S3, adding the remaining isocyanate to the polyether polyol according to parts by weight, heating and stirring in a reaction kettle to obtain a mixture C for later use;

[0070] S4, according to weight parts, add acrylic resin, catalyst, chain extender, and mixture C to mixture B, heat to 100° C. and stir for 3 hours, and obtain mixture D after reaction, which is set aside;

[0071] S5. Add mixture A to mixture D and heat to 110° C. to completely melt the mixture. Mix the mixture under uniform stirring, evacuate the mixture, and heat to 100° C. to react for 3 h to obtain a modified hot melt adhesive.

[0072] Example 2

[0073] A modified hot melt adhesive for electronics, comprising component A and component B, wherein the mass ratio of component A to component B is 0.5:1.4;

[0074] The component A comprises the following raw materials in parts by weight: 30 parts of thermoplastic polyurethane, 3 parts of ultraviolet absorber, 6 parts of nanofiber, 2 parts of filler, 2 parts of adhesion promoter, 3 parts of photocuring agent and 1.5 parts of antioxidant;

[0075] The component B comprises the following raw materials in parts by weight: 25 parts of isocyanate, 30 parts of polyester polyol, 15 parts of polyether polyol, 8 parts of acrylic resin, 1.0 part of catalyst, and 3 parts of chain extender.

[0076] The ultraviolet absorber is composed of zinc oxide and 2-hydroxy-4-methoxybenzophenone in a mass ratio of 1:1.

[0077] The adhesion promoter is γ-mercaptopropyltrimethoxysilane.

[0078] The filler is composed of silicon dioxide and graphene nanosheets in a mass ratio of 0.6:1.2.

[0079] The graphene nanosheets need to be pretreated before use:

[0080] Step ① Take graphene nanosheets and add deionized water, heat to 73° C. in a water bath and stir until uniform to obtain solution A, which is set aside; the ratio of the graphene nanosheets to the deionized water is 0.3:4;

[0081] Step ②: γ-aminopropyltriethoxysilane, ethanol and deionized water are stirred and mixed, and then ultrasonically dispersed to obtain a dispersion for later use; the ratio of the γ-aminopropyltriethoxysilane, ethanol and deionized water is 0.2:1.0:4.

[0082] Step ③: adding dicyclohexylcarbodiimide and the dispersion into solution A, heating in a water bath at 45° C. and stirring for reaction, and then filtering and drying to obtain pretreated graphene nanosheets; the ratio of the dicyclohexylcarbodiimide, the dispersion and the solution A is 0.08:1.0:2.

[0083] The isocyanate is isophorone diisocyanate.

[0084] The polyester polyol is an aromatic polyester polyol.

[0085] The polyether polyol is polytetrahydrofuran diol.

[0086] The catalyst is tetrabutyl titanate.

[0087] The chain extender is composed of trimethylolpropane and trimethylolpropane in a mass ratio of 1:1.

[0088] The antioxidant is composed of antioxidant 1076 and antioxidant 1010 in a mass ratio of 1:1.

[0089] The photocuring agent comprises the following raw materials in parts by weight: 15 parts of toluene diisocyanate, 8 parts of linear polyester diol, 3 parts of trimethylolpropane, 15 parts of alkyd resin, and 2.0 parts of 1-hydroxycyclohexyl phenyl ketone.

[0090] The photocuring agent is prepared by the following method:

[0091] A1. Add toluene diisocyanate, linear polyester diol and trimethylolpropane into a reaction kettle according to parts by weight, heat to 80° C. and stir for 2 hours to obtain a mixture, which is set aside;

[0092] A2. Add alkyd resin and 1-hydroxycyclohexyl phenyl ketone to the mixture obtained in step A1 according to parts by weight, heat to 80° C. and stir at a rate of 450 r / min for 45 min to obtain a photocuring agent.

[0093] A method for preparing a modified hot melt adhesive for electronics comprises the following steps:

[0094] S1. Add thermoplastic polyurethane, ultraviolet absorber, nanofiber, filler, adhesion promoter, photocuring agent and antioxidant into a reaction kettle according to weight parts, heat to 95° C., mix and stir to obtain mixture A, and set aside;

[0095] S2, according to parts by weight, adding isocyanate accounting for two-thirds of the total amount of isocyanate to the polyester polyol and heating and stirring in a reaction kettle to obtain a mixture B, which is set aside;

[0096] S3, adding the remaining isocyanate to the polyether polyol according to parts by weight, heating and stirring in a reaction kettle to obtain a mixture C for later use;

[0097] S4, according to weight parts, add acrylic resin, catalyst, chain extender, and mixture C to mixture B, heat to 120° C. and stir for 2 hours, and obtain mixture D after reaction, which is set aside;

[0098] S5. Add mixture A to mixture D and heat to 115° C. to completely melt the mixture. Mix the mixture under uniform stirring, evacuate the mixture, and heat to 110° C. to react for 2 h to obtain a modified hot melt adhesive.

[0099] Example 3

[0100] A modified hot melt adhesive for electronics, comprising component A and component B, wherein the mass ratio of component A to component B is 0.6:1.5;

[0101] The component A comprises the following raw materials in parts by weight: 40 parts of thermoplastic polyurethane, 5 parts of ultraviolet absorber, 8 parts of nanofiber, 3 parts of filler, 3 parts of adhesion promoter, 5 parts of photocuring agent and 2.5 parts of antioxidant;

[0102] The component B comprises the following raw materials in parts by weight: 30 parts of isocyanate, 40 parts of polyester polyol, 20 parts of polyether polyol, 10 parts of acrylic resin, 1.5 parts of catalyst, and 5 parts of chain extender.

[0103] The ultraviolet absorber is 2-hydroxy-4-methoxybenzophenone.

[0104] The adhesion promoter is γ-isocyanate propyltrimethoxysilane.

[0105] The filler is composed of silicon dioxide and graphene nanosheets in a mass ratio of 0.8:1.4.

[0106] The graphene nanosheets need to be pretreated before use:

[0107] Step ① Take graphene nanosheets and add deionized water, heat to 75° C. in a water bath and stir until uniform to obtain solution A, which is set aside; the ratio of the graphene nanosheets to the deionized water is 0.5:5;

[0108] Step ②: γ-aminopropyltriethoxysilane, ethanol and deionized water are stirred and mixed, and then ultrasonically dispersed to obtain a dispersion for later use; the ratio of the γ-aminopropyltriethoxysilane, ethanol and deionized water is 0.3:1.2:6.

[0109] Step ③: adding dicyclohexylcarbodiimide and the dispersion into solution A, heating in a water bath at 70° C. and stirring for reaction, and then filtering and drying to obtain pretreated graphene nanosheets; the ratio of the dicyclohexylcarbodiimide, the dispersion and the solution A is 0.1:1.2:3.

[0110] The isocyanate is hexamethylene diisocyanate. The polyester polyol is aliphatic polyester polyol.

[0111] The polyether polyol is polyoxyethylene polyol, the catalyst is tetrabutyl titanate, the chain extender is 1,4-butanediol, and the antioxidant is antioxidant 1010.

[0112] The photocuring agent comprises the following raw materials in parts by weight: 20 parts of toluene diisocyanate, 10 parts of linear polyester diol, 5 parts of trimethylolpropane, 20 parts of alkyd resin, and 2.5 parts of 1-hydroxycyclohexyl phenyl ketone.

[0113] The photocuring agent is prepared by the following method:

[0114] A1. Add toluene diisocyanate, linear polyester diol and trimethylolpropane into a reaction kettle according to parts by weight, heat to 90° C. and stir for 3 hours to obtain a mixture, which is set aside;

[0115] A2. Add alkyd resin and 1-hydroxycyclohexyl phenyl ketone to the mixture obtained in step A1 according to parts by weight, heat to 90° C. and stir at a rate of 300 r / min for 30 min to obtain a photocuring agent.

[0116] A method for preparing a modified hot melt adhesive for electronics comprises the following steps:

[0117] S1. Add thermoplastic polyurethane, ultraviolet absorber, nanofiber, filler, adhesion promoter, photocuring agent and antioxidant into a reaction kettle according to weight parts, heat to 100° C., mix and stir to obtain mixture A, and set aside;

[0118] S2, according to parts by weight, adding isocyanate accounting for two-thirds of the total amount of isocyanate to the polyester polyol and heating and stirring in a reaction kettle to obtain a mixture B, which is set aside;

[0119] S3, adding the remaining isocyanate to the polyether polyol according to parts by weight, heating and stirring in a reaction kettle to obtain a mixture C for later use;

[0120] S4, according to weight parts, add acrylic resin, catalyst, chain extender, and mixture C to mixture B, heat to 130° C. and stir for 1 hour, and obtain mixture D after reaction, which is set aside;

[0121] S5. Add mixture A to mixture D and heat to 120° C. to completely melt the mixture. Mix the mixture under uniform stirring, evacuate the mixture, and heat to 120° C. to react for 1 hour to obtain a modified hot melt adhesive.

[0122] Example 4

[0123] A modified hot melt adhesive for electronics, comprising component A and component B, wherein the mass ratio of component A to component B is 0.5:1.4;

[0124] The component A comprises the following raw materials in parts by weight: 30 parts of thermoplastic polyurethane, 3 parts of ultraviolet absorber, 6 parts of nanofiber, 2 parts of filler, 2 parts of adhesion promoter, 3 parts of photocuring agent and 1.5 parts of antioxidant;

[0125] The component B comprises the following raw materials in parts by weight: 25 parts of isocyanate, 30 parts of polyester polyol, 15 parts of polyether polyol, 8 parts of acrylic resin, 1.0 part of catalyst, and 3 parts of chain extender.

[0126] The ultraviolet absorber is composed of zinc oxide and 2-hydroxy-4-methoxybenzophenone in a mass ratio of 1:1.

[0127] The adhesion promoter is γ-mercaptopropyltrimethoxysilane.

[0128] The filler is composed of silicon dioxide and graphene nanosheets in a mass ratio of 0.6:1.2.

[0129] The graphene nanosheets need to be pretreated before use:

[0130] Step ① Take graphene nanosheets and add deionized water, heat to 73° C. in a water bath and stir until uniform to obtain solution A, which is set aside; the ratio of the graphene nanosheets to the deionized water is 0.3:4;

[0131] Step ②: γ-aminopropyltriethoxysilane, ethanol and deionized water are stirred and mixed, and then ultrasonically dispersed to obtain a dispersion for later use; the ratio of the γ-aminopropyltriethoxysilane, ethanol and deionized water is 0.2:1.0:4.

[0132] Step ③: adding dicyclohexylcarbodiimide and the dispersion into solution A, heating in a water bath at 30-70° C. with stirring for reaction, and then filtering and drying to obtain pretreated graphene nanosheets; the ratio of the dicyclohexylcarbodiimide, the dispersion and the solution A is 0.08:1.0:2.

[0133] The isocyanate is hexamethylene diisocyanate.

[0134] The polyester polyol is an aliphatic polyester polyol.

[0135] The polyether polyol is polyoxyethylene polyol.

[0136] The catalyst is at least one of tetrabutyl titanate, dimorpholinyl diethyl ether, N,N,N'-trimethyl-N'-hydroxyethyl-diaminoethyl ether, triethylenediamine, dibutyltin dilaurate, and dimorpholinyl diethyl ether.

[0137] The chain extender is 1,4-butanediol.

[0138] The antioxidant is antioxidant 1010.

[0139] The photocuring agent comprises the following raw materials in parts by weight: 20 parts of toluene diisocyanate, 10 parts of linear polyester diol, 5 parts of trimethylolpropane, 20 parts of alkyd resin, and 2.5 parts of 1-hydroxycyclohexyl phenyl ketone.

[0140] The photocuring agent is prepared by the following method:

[0141] A1. Add toluene diisocyanate, linear polyester diol and trimethylolpropane into a reaction kettle according to parts by weight, heat to 90° C. and stir for 3 hours to obtain a mixture, which is set aside;

[0142] A2. Add alkyd resin and 1-hydroxycyclohexyl phenyl ketone to the mixture obtained in step A1 according to parts by weight, heat to 90° C. and stir at a rate of 300 r / min for 30 min to obtain a photocuring agent.

[0143] A method for preparing a modified hot melt adhesive for electronics comprises the following steps:

[0144] S1. Add thermoplastic polyurethane, ultraviolet absorber, nanofiber, filler, adhesion promoter, photocuring agent and antioxidant into a reaction kettle according to weight parts, heat to 100° C., mix and stir to obtain mixture A, and set aside;

[0145] S2, according to parts by weight, adding isocyanate accounting for two-thirds of the total amount of isocyanate to the polyester polyol and heating and stirring in a reaction kettle to obtain a mixture B, which is set aside;

[0146] S3, adding the remaining isocyanate to the polyether polyol according to parts by weight, heating and stirring in a reaction kettle to obtain a mixture C for later use;

[0147] S4, according to weight parts, add acrylic resin, catalyst, chain extender, and mixture C to mixture B, heat to 130° C. and stir for 1 hour, and obtain mixture D after reaction, which is set aside;

[0148] S5. Add mixture A to mixture D and heat to 120° C. to completely melt the mixture. Mix the mixture under uniform stirring, evacuate the mixture, and heat to 120° C. to react for 1 hour to obtain a modified hot melt adhesive.

[0149] Comparative Example 1

[0150] The difference between this comparative example and the above-mentioned embodiment 2 is that no light curing agent is added to the raw materials of the modified hot melt adhesive in this comparative example. The rest of the contents of this comparative example are the same as those of embodiment 2 and will not be repeated here.

[0151] Comparative Example 2

[0152] The difference between this comparative example and the above-mentioned Example 2 is that no thermoplastic polyurethane and ultraviolet absorber are added to the raw materials of the modified hot melt adhesive in this comparative example. The rest of the contents of this comparative example are the same as those of Example 2 and will not be repeated here.

[0153] Comparative Example 3

[0154] The difference between this comparative example and the above-mentioned Example 2 is that the filler in the raw material of the modified hot melt adhesive in this comparative example is only silicon dioxide. The rest of the contents of this comparative example are the same as those in Example 2, and will not be repeated here.

[0155] The performance of the modified hot melt adhesive prepared in Example 2 was tested, and the results are shown in Table 1:

[0156] 1. Carry out melt viscosity test according to GB / T 2794 standard;

[0157] 2. Bonding strength test:

[0158] (1) Sample preparation method: Each embodiment and comparative example was glued at 100° C. when used. The test piece was a PA sheet. After bonding, it was left to stand for 24 hours to cure. After the curing was completed, a tensile shear test was performed in accordance with GB / T 7124. Five groups of samples were prepared for each condition and the average value was taken.

[0159] (2) Curing conditions: temperature 25±1°C, humidity 60±5%RH, stand for 24h.

[0160] 3. Peel strength test is carried out in accordance with GBT2791-1995

[0161] 4. The tensile strength is tested in accordance with GB / T 528-2009.

[0162] Table 1

[0163]

[0164] The modified hot melt adhesives prepared in Example 2 and Comparative Example 1 were tested for bonding strength, tensile strength and peel strength. The results are shown in Table 2:

[0165] Table 2

[0166] project 24h tensile shear strength (MPa) Tensile strength(MPa) Peel strength (kN / m) Example 2 13.5 24.1 9.5 Comparative Example 1 7.6 13.5 7.1

[0167] The modified hot melt adhesives prepared in Example 2 and Comparative Example 2 were tested for bonding strength, tensile strength and peel strength. The results are shown in Table 3:

[0168] Table 3

[0169] project 24h tensile shear strength (MPa) Tensile strength(MPa) Peel strength (kN / m) Example 2 13.5 24.1 9.5 Comparative Example 2 5.7 11.8 6.4

[0170] The modified hot melt adhesives prepared in Example 2 and Comparative Example 3 were tested for hardness, bonding strength, tensile strength and peel strength. The results are shown in Table 4:

[0171] Table 4

[0172] project Hardness HD 24h tensile shear strength (MPa) Tensile strength(MPa) Peel strength (kN / m) Example 2 52 13.5 24.1 9.5 Comparative Example 3 37 10.4 19.5 7.8

[0173] It can be seen from Example 2 that the modified hot melt adhesive prepared in the present invention has good mechanical properties such as melt viscosity, bonding strength, tensile strength and peel strength.

[0174] From the comparison between Example 2 and Comparative Examples 1-3, it can be seen that under the same conditions, the modified hot melt adhesive prepared by adding a photocuring agent, a thermoplastic polyurethane, an ultraviolet absorber, and using a composite filler in the formula has better mechanical properties such as melt viscosity, bonding strength, tensile strength and peel strength, and has broad market prospects and application value.

[0175] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A modified hot melt adhesive for electronic use, characterized in that: It comprises component A and component B, wherein the mass ratio of component A to component B is 0.3-0.6:1.2-1.5; The component A comprises the following raw materials in parts by weight: 20-40 parts of thermoplastic polyurethane, 1-5 parts of ultraviolet absorber, 4-8 parts of nanofiber, 1-3 parts of filler, 1-3 parts of adhesion promoter, 1-5 parts of photocuring agent and 0.5-2.5 parts of antioxidant; The component B comprises the following raw materials in parts by weight: 15-30 parts of isocyanate, 20-40 parts of polyester polyol, 10-20 parts of polyether polyol, 5-10 parts of acrylic resin, 0.5-1.5 parts of catalyst, and 1-5 parts of chain extender.

2. The modified hot melt adhesive for electronics according to claim 1, characterized in that: The ultraviolet absorber is at least one of zinc oxide, aluminum oxide, 2-hydroxy-4-methoxybenzophenone and 2-hydroxy-4-methoxy-5-sulfonic acid benzophenone.

3. The modified hot melt adhesive for electronics according to claim 1, characterized in that: The adhesion promoter is at least one of bis-(γ-trimethoxysilylpropyl)amine, γ-mercaptopropyltrimethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-isocyanatepropyltrimethoxysilane and N-phenyl-γ-aminopropyltrimethoxysilane.

4. The modified hot melt adhesive for electronics according to claim 1, characterized in that: The filler is at least one of silicon dioxide, montmorillonite, talc, graphene nanosheets, hydrotalcite and hydronaphthene.

5. The modified hot melt adhesive for electronics according to claim 1, characterized in that: The isocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate.

6. The modified hot melt adhesive for electronics according to claim 1, characterized in that: The polyester polyol is at least one of aliphatic polyester polyol, aromatic polyester polyol and mixed acid polyester polyol.

7. The modified hot melt adhesive for electronics according to claim 1, characterized in that: The polyether polyol is at least one of polyethylene glycol, polypropylene glycol, polytetramethylene glycol and polyoxyethylene polyol.

8. The modified hot melt adhesive for electronics according to claim 1, characterized in that: The catalyst is at least one of tetrabutyl titanate, dimorpholinyl diethyl ether, N,N,N'-trimethyl-N'-hydroxyethyl-diaminoethyl ether, triethylenediamine, dibutyltin dilaurate, and dimorpholinyl diethyl ether.

9. The modified hot melt adhesive for electronics according to claim 1, characterized in that: The chain extender is at least one of ethylene glycol, glycerol, trimethylolpropane, diethylene glycol, 1,4-butanediol, trimethylolpropane and diethylene glycol.

10. A method for preparing the modified hot melt adhesive for electronics according to any one of claims 1 to 9, characterized in that: The steps include: S1. Add thermoplastic polyurethane, ultraviolet absorber, nanofiber, filler, adhesion promoter, photocuring agent and antioxidant into a reaction kettle according to weight parts, heat to 90-100° C., mix and stir to obtain mixture A, and set aside; S2, according to parts by weight, adding isocyanate accounting for two-thirds of the total amount of isocyanate to the polyester polyol and heating and stirring in a reaction kettle to obtain a mixture B, which is set aside; S3, adding the remaining isocyanate to the polyether polyol according to parts by weight, heating and stirring in a reaction kettle to obtain a mixture C for standby use; S4, according to weight parts, add acrylic resin, catalyst, chain extender, and mixture C to mixture B, heat to 100-130° C. and stir for 1-3 hours, and obtain mixture D after reaction, which is set aside; S5. Add mixture A to mixture D and heat to 110-120° C. to completely melt the mixture, mix the mixture under uniform stirring, evacuate the mixture, and heat to 100-120° C. to react for 1-3 hours to obtain a modified hot melt adhesive.

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