Flame-retardant high-stripping thermocuring structural adhesive and adhesive film and adhesive tape containing flame-retardant high-stripping thermocuring structural adhesive

Abstract

The invention belongs to the field of structural adhesives and structural adhesive tapes. The flame-retardant high-stripping thermosetting structural adhesive comprises the following raw materials in percentage by mass: 20-60 wt% of an acrylic polymer; 20 to 60 wt% of an epoxy resin composition; 0.5 to 5 wt% of a curing agent; 0.15 to 2.5 wt% of an accelerator; 0.05 to 3 wt% of a photoinitiator; 0-5 wt% of a multifunctional acrylic monomer; and 10 to 20 weight percent of flame retardant. The structural adhesive disclosed by the invention has initial viscosity at normal temperature; the coating thickness range is wide; rapid positioning can be realized; the operable time is long; the flame-retardant requirement of UL94V0 is met, and the high shear strength is achieved; structural firm connection can be achieved, the requirement for high stripping torque can be met, and the adhesive is suitable for bonding of structural components in the automobile industry.

Description

Technical Field

[0001] The invention belongs to the field of structural adhesives and structural adhesive tapes, and in particular relates to a flame-retardant high-peeling heat-curing structural adhesive and an adhesive film and an adhesive tape containing the same. Background Art

[0002] CN106062020A discloses a thermosetting pressure-sensitive adhesive, which comprises a tacky polymer, a polyvinyl acetal, an epoxy resin, and an epoxy resin curing agent. CN107709497A discloses a UV-curable epoxy / acrylate adhesive composition, which comprises a (meth)acrylate tetrahydrofurfuryl copolymer; an epoxy resin; a polyether polyol; and an adhesive composition of a hydroxyl-functional film-forming polymer. The adhesive can be used for structural and semi-structural bonding applications. The adhesives described above use a UV free radical curing / thermal curing system and a UV cationic curing / thermal curing system; although good shearing can be achieved between metals and between metals and glass, the resulting adhesive film needs to be stored at low temperatures, which is not conducive to storage and transportation.

[0003] CN108300389A discloses an epoxy adhesive composition, comprising: at least two epoxy resins; at least one bifunctional epoxy diluent; at least three toughening agents; at least one inorganic filler; at least one dehydrating agent; at least one thixotropic agent; at least one heat-activated latent curing agent; at least one curing accelerator. After curing, the epoxy adhesive composition has high impact strength at room temperature and high temperature, and can achieve high peeling requirements, but requires a certain amount of hot pressing for positioning, which reduces work efficiency.

[0004] CN112646536A discloses a two-component acrylic structural adhesive for bonding metal oily surfaces, which can not only achieve direct bonding to metal oily surfaces, but also achieve bonding to metal oily surfaces with high bonding strength (higher than 5N / mm), and does not cause significant loss of solid content and environmental pollution during the curing process. However, it has a short open time and is corrosive to metals to a certain extent, affecting the electrochemical insulation stability.

[0005] In summary, the main problems with existing thermosetting structural adhesives are: they cannot be stored for a long time at room temperature, and their mechanical properties decrease significantly after a long time; they have a short open time and low applicability, and are not suitable for bonding large areas or complex structures; they require hot pressing for positioning, which can easily damage the structure and reduce work efficiency, but if the strength of the structural adhesive is too high, the operation will be inconvenient.

[0006] Therefore, a tape is needed that has a certain degree of pressure sensitivity before bonding, a longer open window before bonding, and after a period of curing, it can reach the strength of structural adhesive. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a flame retardant high-peeling heat-curing structural adhesive and an adhesive film and an adhesive tape containing the same. The structural adhesive of the present invention has initial adhesion at room temperature; a wide coating thickness range; can achieve rapid positioning; has a long operating time; meets the flame retardant requirements of UL94 V0, has high shear strength; can achieve structural firm connection, and can also meet high peeling torque requirements, and is suitable for bonding structural parts in the automotive industry.

[0008] The technical solution adopted by the present invention to solve the above problems is as follows:

[0009] A flame retardant high-peeling heat-curing structural adhesive, comprising the following raw materials in percentage by mass:

[0010] (I) 20 to 60 wt % of an acrylic acid polymer;

[0011] (II) 20 to 60 wt % of an epoxy resin composition;

[0012] (III) 0.5 to 5 wt% of a curing agent;

[0013] (IV) 0.15 to 2.5 wt% of an accelerator;

[0014] (V) 0.05 to 3 wt % of a photoinitiator;

[0015] (VI) 0 to 5 wt% of a multifunctional acrylic monomer;

[0016] (VII) 10 to 20 wt% of a flame retardant.

[0017] Furthermore, the mass ratio of the acrylic ester polymer to the epoxy resin composition is (3:7) to (7:3).

[0018] (I) 20-60 wt% of acrylic acid polymer:

[0019] Furthermore, based on 100% of the acrylic polymer, the acrylic polymer includes the following components in percentage by mass: 60-90% of C1-C8 (meth) alkyl acrylate monomers; 10-30% of alkaline polymerizable vinyl monomers; 0-10% of cationically curable acrylate monomers; and 0.01-1% of a photoinitiator.

[0020] Furthermore, the mass ratio of the C1-C8 (meth)acrylic acid alkyl ester monomer to the alkaline polymerizable vinyl monomer is 1-9:1.

[0021] Furthermore, the C1-C8 (meth)acrylic acid alkyl ester monomer is at least one of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and isooctyl (meth)acrylate.

[0022] Preferably, the C1-C8 (meth)acrylic acid alkyl ester monomer is at least one of methyl (meth)acrylate and butyl (meth)acrylate.

[0023] Furthermore, the alkaline polymerizable vinyl monomer is at least one of N-vinyl pyrrolidone and N-vinyl caprolactam.

[0024] Furthermore, the cationic curable acrylic monomer is at least one of glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

[0025] Preferably, the cation-curable acrylic ester monomer is glycidyl acrylate.

[0026] Furthermore, the photoinitiator is a free radical photoinitiator; the free radical photoinitiator is at least one of benzoin alkyl ether, acetophenone, benzophenone, benzyl dimethyl acetal, and hydroxycyclohexyl phenyl ketone.

[0027] (II) 20-60 wt% epoxy resin composition:

[0028] Furthermore, based on 100% of the epoxy resin composition, the epoxy resin composition includes the following components in percentage by mass: 0 to 60% of bisphenol A liquid epoxy resin or bisphenol F liquid epoxy resin, 10 to 60% of bisphenol A solid epoxy resin, 0 to 10% of dicyclopentadiene epoxy resin and 5 to 40% of epoxy toughening agent.

[0029] Furthermore, the epoxy equivalent of the bisphenol A type liquid epoxy resin is 170-200; the epoxy equivalent of the bisphenol F type liquid epoxy resin is 160-180; the epoxy equivalent of the bisphenol A type solid epoxy resin is 500-1200; and the epoxy equivalent of the dicyclopentadiene type epoxy resin is 240-290.

[0030] Furthermore, the epoxy toughening agent is at least one of core-shell toughened epoxy resin, CTBN toughened epoxy resin, polyurethane toughened epoxy resin, and blocked high temperature deblocking polyurethane resin.

[0031] Preferably, the epoxy toughening agent is CTBN toughened epoxy resin and blocked high temperature deblocking polyurethane resin.

[0032] (III) 0.5-5 wt% of a curing agent:

[0033] Furthermore, the curing agent is at least one of diaminodiphenyl sulfone and dicyandiamide.

[0034] (IV) 0.15-2.5 wt% of accelerator:

[0035] Furthermore, the accelerator is at least one of a modified imidazole accelerator, a modified amine accelerator, and a modified urea accelerator.

[0036] Preferably, the accelerator is a modified urea accelerator.

[0037] (V) 0.05-3 wt% of photoinitiator:

[0038] Furthermore, the photoinitiator is a free radical photoinitiator; the free radical photoinitiator is at least one of benzoin alkyl ether, acetophenone, benzophenone, benzyl dimethyl acetal, and hydroxycyclohexyl phenyl ketone.

[0039] (VI) 0 to 5 wt% of a multifunctional acrylic monomer:

[0040] Furthermore, the multifunctional acrylic monomer is at least one of a difunctional acrylic monomer and a trifunctional acrylic monomer.

[0041] Preferably, the multifunctional acrylic monomer is one or two of 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate.

[0042] (VII) 10 to 20 wt% of a flame retardant:

[0043] Furthermore, the flame retardant includes a liquid phosphate ester flame retardant and a solid phosphate ester flame retardant; the liquid phosphate ester flame retardant accounts for 3 to 10 wt % of the mass of the flame retardant.

[0044] Furthermore, the flame-retardant high-peeling heat-curing structural adhesive also includes the following constituent raw materials: a silane coupling agent, a thixotropic agent, and a reaction inhibitor.

[0045] Furthermore, the silane coupling agent is selected from at least one of KH-560, KH-570, KH-550 and A-187.

[0046] Furthermore, the reaction inhibitor is selected from at least one of methyl p-toluenesulfonate, phosphoric acid, and boric acid ester. When low-temperature curing is adopted, adding a reaction inhibitor is selected to help preserve stability and accelerate curing, thereby ensuring curing activity.

[0047] Furthermore, the thixotropic agent is at least one of fumed silica and hydrogenated castor oil. The thixotropic agent selected in the present invention can ensure the stability of the material in the coating process and guarantee the coating shape.

[0048] Preferably, the thixotropic agent is hydrophilic fumed silica, which can improve the stability of the material in a hot and humid environment and ensure the performance consistency of the material under various environmental conditions.

[0049] Furthermore, the flame-retardant high-peeling heat-curing structural adhesive further comprises the following raw materials in percentage by mass: 0.5-2 wt % of a silane coupling agent, 0.05-1 wt % of a reaction inhibitor, and 0.05-5 wt % of a thixotropic agent.

[0050] An adhesive film comprises the flame-retardant high-peeling heat-curing structural adhesive as described above.

[0051] Furthermore, the thickness of the adhesive film is 0.03-1 mm.

[0052] The present invention also provides an adhesive tape, comprising the adhesive film as described above.

[0053] The present invention has the following beneficial effects:

[0054] The heat-curing structural adhesive of the present invention can be stably stored at room temperature; it has initial adhesion at room temperature; it has a wide range of coating thicknesses and can meet the needs of different coating thicknesses; it can achieve rapid positioning; and it has a long operating time. The heat-curing structural adhesive of the present invention meets the flame retardant requirements of UL94 V0, has high shear strength, and can maintain stable bonding performance under various stress conditions; for the bonding between metal and metal, metal and plastic, it can not only achieve a structurally firm connection, but also meet high peeling torque requirements, and is suitable for bonding structural components in the automotive industry, and can meet the industry's high requirements for material strength, flame retardancy and stability. The structural adhesive has an obvious color change reaction before and after heat curing, and this feature provides customers with an intuitive basis for judging the product curing effect; through the color change indication, it can effectively reduce product abnormalities caused by poor curing, and improve production efficiency and product quality. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further described below by specific implementations. It should be understood that those skilled in the art can conceive of other various implementations and can modify them according to the teachings of this specification without departing from the scope or spirit of the present disclosure. Therefore, the following specific implementations are not restrictive.

[0056] Unless otherwise specified, the test materials, reagents, methods and equipment used in the present invention are conventional test materials, reagents, methods and equipment in the technical field; unless otherwise specified, the test materials and reagents used in the present invention can be obtained from commercial channels.

[0057] The present invention provides a flame retardant high-peeling heat-curing structural adhesive, comprising the following constituent raw materials in percentage by mass:

[0058] (I) 20 to 60 wt % of an acrylic acid polymer;

[0059] (II) 20 to 60 wt % of an epoxy resin composition;

[0060] (III) 0.5 to 5 wt% of a curing agent;

[0061] (IV) 0.15 to 2.5 wt% of an accelerator;

[0062] (V) 0.05 to 3 wt % of a photoinitiator;

[0063] (VI) 0 to 5 wt% of a multifunctional acrylic monomer;

[0064] (VII) 10 to 20 wt% of a flame retardant.

[0065] In some specific embodiments of the present invention, the mass ratio of the acrylate polymer to the epoxy resin composition is (3:7) to (7:3).

[0066] (I) 20-60 wt% of acrylic acid polymer:

[0067] In some specific embodiments of the present invention, based on 100% of the acrylic polymer, the acrylic polymer includes the following components in percentage by mass: 60-90% of C1-C8 (meth) alkyl acrylate monomers; 10-30% of alkaline polymerizable vinyl monomers; 0-10% of cationically curable acrylate monomers; and 0.01-1% of a photoinitiator.

[0068] In some specific embodiments of the present invention, the mass ratio of the C1-C8 (meth)acrylic acid alkyl ester monomer to the alkaline polymerizable vinyl monomer is 1-9:1.

[0069] In the above technical solution, the acrylic polymer is a polymer obtained by polymerizing C1-C8 (meth) alkyl acrylate monomers with alkaline polymerizable vinyl monomers and cationically curable acrylic ester monomers. During the polymerization process, a photoinitiator needs to be added simultaneously.

[0070] Specifically, optional examples of the C1-C8 (meth) alkyl acrylate monomer include, but are not limited to, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isooctyl (meth) acrylate, and the like.

[0071] In certain preferred embodiments of the present invention, the C1-C8 (meth)acrylic acid alkyl ester monomer is at least one of methyl (meth)acrylate and butyl (meth)acrylate.

[0072] In the above technical scheme, the alkaline polymerizable vinyl monomer specifically refers to a polymerizable vinyl monomer containing a basic group in its molecular structure; specifically, optional examples of the alkaline polymerizable vinyl monomer include but are not limited to N-vinyl caprolactam, N-vinyl pyrrolidone, (meth)acryloylmorpholine, (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, (meth)acrylonitrile, etc.

[0073] In certain preferred embodiments of the present invention, the alkaline polymerizable vinyl monomer is at least one of N-vinyl pyrrolidone and N-vinyl caprolactam. Specifically, optional examples of the cationic curable acrylic monomer include, but are not limited to, glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and the like.

[0074] In certain preferred embodiments of the present invention, the cation-curable acrylic ester monomer is glycidyl acrylate.

[0075] In some specific embodiments of the present invention, the photoinitiator is a free radical photoinitiator; the free radical photoinitiator is at least one of benzoin alkyl ether, acetophenone, benzophenone, benzyl dimethyl acetal, and hydroxycyclohexyl phenyl ketone.

[0076] Specifically, optional examples of the free radical photoinitiator include, but are not limited to, Irgacure 819, Irgacure 651, Darocur 1173, TPO, and the like.

[0077] (II) 20-60 wt% epoxy resin composition:

[0078] In some specific embodiments of the present invention, taking the epoxy resin composition as 100%, the epoxy resin composition includes the following components by mass percentage: 0-60% of bisphenol A liquid epoxy resin or bisphenol F liquid epoxy resin, 10-60% of bisphenol A solid epoxy resin, 0-10% of dicyclopentadiene epoxy resin and 5-40% of epoxy toughening agent.

[0079] In the above technical solution, if the content of liquid epoxy resin is higher than 60wt%, the adhesive surface of the obtained structural adhesive will be sticky and the cohesive strength will be poor; if the content of solid epoxy resin is lower than 10wt%, the surface of the obtained structural adhesive will be sticky after curing, and if the content of solid epoxy resin is higher than 60wt%, the strength of the obtained structural adhesive will decrease; if the content of dicyclopentadiene epoxy resin is higher than 10wt%, the obtained structural adhesive will be hard and the peel strength will not increase significantly. If the content of epoxy toughening agent is lower than 5wt%, the peel strength of the obtained structural adhesive is insufficient, and if the content of epoxy toughening agent is higher than 40wt%, there is a risk of glue overflow.

[0080] In some specific embodiments of the present invention, the epoxy equivalent of the bisphenol A type liquid epoxy resin is 170-200; the epoxy equivalent of the bisphenol F type liquid epoxy resin is 160-180; the epoxy equivalent of the bisphenol A type solid epoxy resin is 500-1200; the epoxy equivalent of the dicyclopentadiene type epoxy resin is 240-290.

[0081] Specifically, optional examples of the bisphenol A type liquid epoxy resin include but are not limited to DER331, EPON945, EPON1001F, etc.

[0082] Specifically, optional examples of the bisphenol A type solid epoxy resin include but are not limited to NPES901.

[0083] Specifically, optional examples of the dicyclopentadiene epoxy resin include but are not limited to Nippon Kayaku's XD1000, DIC's HP7200, and the like.

[0084] Specifically, optional examples of the bisphenol F type liquid epoxy resin include but are not limited to EPON862 and the like.

[0085] In some specific embodiments of the present invention, the epoxy toughening agent is at least one of a core-shell toughened epoxy resin, a CTBN toughened epoxy resin, a polyurethane toughened epoxy resin, and a blocked high temperature deblocking polyurethane resin.

[0086] In certain preferred embodiments of the present invention, the epoxy toughening agent is a CTBN toughened epoxy resin and a blocked high temperature deblocking polyurethane resin.

[0087] Specifically, optional examples of the core-shell toughened epoxy resin include but are not limited to Zhongyuan's MX125, MX154, MX257, etc.

[0088] Specifically, optional examples of the CTBN toughened epoxy resin include, but are not limited to, Huntsman's CTBN 1300X13 and the like.

[0089] Specifically, optional examples of the polyurethane toughened epoxy resin include but are not limited to ERS-133 and ERS-DC11 from Shanghai Zhongsi.

[0090] Specifically, optional examples of the blocked high temperature deblocking polyurethane resin include but are not limited to ADEKA's QR9466 and the like.

[0091] (III) 0.5-5 wt% of a curing agent:

[0092] In some specific embodiments of the present invention, the curing agent is at least one of diaminodiphenyl sulfone and dicyandiamide.

[0093] Specifically, optional examples of the dicyandiamide include but are not limited to Evonik's Dyhard 100S, etc.; optional examples of the diaminodiphenyl sulfone include but are not limited to 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, etc.

[0094] In the above technical solution, if the content of the curing agent is lower than 0.5wt%, the obtained structural adhesive is insufficiently cured; if the content of the curing agent is higher than 5wt%, the obtained structural adhesive is relatively hard after curing and has poor peelability.

[0095] (IV) 0.15-2.5 wt% of accelerator:

[0096] In some specific embodiments of the present invention, the accelerator is at least one of a modified imidazole accelerator, a modified amine accelerator, and a modified urea accelerator.

[0097] In certain preferred embodiments of the present invention, the accelerator is preferably a modified urea accelerator.

[0098] Specifically, optional examples of the modified imidazole accelerator include, but are not limited to, Shikoku Chemical 2E4MZ, Shikoku Chemical 2MZ-A, PN-23, PN-H, PN-40, and the like.

[0099] Specifically, optional examples of the modified amine accelerator include but are not limited to FXR-1020, FXR-1081, and the like.

[0100] Specifically, optional examples of the modified urea accelerator include, but are not limited to, Dyhard UR300 and Dyhard UR500 of Evonik.

[0101] In the above technical solution, if the content of the accelerator is lower than 0.15 wt %, the obtained structural adhesive cures slowly; if the content of the accelerator is higher than 2.5 wt %, the storage stability of the structural adhesive is affected.

[0102] (V) 0.05-3 wt% of photoinitiator:

[0103] In some specific embodiments of the present invention, the photoinitiator is a free radical photoinitiator; the free radical photoinitiator is at least one of benzoin alkyl ether, acetophenone, benzophenone, benzyl dimethyl acetal, and hydroxycyclohexyl phenyl ketone.

[0104] Specifically, optional examples of the free radical photoinitiator include, but are not limited to, Irgacure 819, Irgacure 651, Darocur 1173, TPO, and the like.

[0105] (VI) 0 to 5 wt% of a multifunctional acrylic monomer:

[0106] In some specific embodiments of the present invention, the multifunctional acrylic monomer is at least one of a difunctional acrylic monomer and a trifunctional acrylic monomer.

[0107] Specifically, optional examples of the multifunctional acrylic monomer include, but are not limited to, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, and the like.

[0108] In certain preferred embodiments of the present invention, the multifunctional acrylic monomer is one or two of 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate.

[0109] (VII) 10 to 20 wt% of a flame retardant:

[0110] In some specific embodiments of the present invention, the flame retardant includes a liquid phosphate ester flame retardant and a solid phosphate ester flame retardant; the liquid phosphate ester flame retardant accounts for 3 to 10 wt % of the mass of the flame retardant.

[0111] In the above technical solution, the flame retardants selected are all halogen-free flame retardants. If the content of the liquid phosphate flame retardant is less than 3wt% of the flame retardant, the effect of reducing the viscosity of the system is not obvious, and the processing performance of the material cannot be effectively improved; if it is higher than 10wt% of the flame retardant, it will act as a plasticizer, resulting in a decrease in the shear strength and peel strength of the material.

[0112] Specifically, optional examples of the liquid phosphate flame retardant include but are not limited to Japan Daihachi CR-733S.

[0113] Specifically, optional examples of the solid phosphate flame retardant include but are not limited to Clariant OP930 and Clariant OP935.

[0114] In some specific embodiments of the present invention, the flame retardant high release thermal curing structural adhesive further comprises the following constituent materials: a silane coupling agent, a thixotropic agent, and a reaction inhibitor.

[0115] Specifically, the optional examples of the silane coupling agent include but are not limited to at least one of KH-560, KH-570, KH-550, and A-187. The coupling agent selected in the present invention helps to form a good bonding interface between different materials, enhance or improve the bonding effect between different materials, and thus improve the bonding reliability.

[0116] Specifically, as an example, the reaction inhibitor is selected from at least one of methyl p-toluenesulfonate, phosphoric acid, and boric acid ester. When low-temperature curing is adopted, adding a reaction inhibitor is selected to help preserve stability and accelerate curing, and ensure curing activity.

[0117] In certain preferred embodiments of the present invention, the borate ester is selected from tributyl borate.

[0118] In some specific embodiments of the present invention, the thixotropic agent is at least one of fumed silica and hydrogenated castor oil. The thixotropic agent selected in the present invention can ensure the stability of the material in the coating process and ensure the coating shape.

[0119] In certain preferred embodiments of the present invention, the thixotropic agent is hydrophilic fumed silica. Hydrophilic fumed silica can improve the stability of the material in a hot and humid environment and ensure the performance consistency of the material under various environmental conditions.

[0120] Specifically, optional examples of the hydrophilic fumed silica include, but are not limited to, Evonik AEROSIL A200.

[0121] In some specific embodiments of the present invention, the flame retardant high release thermal curing structural adhesive further comprises the following raw materials in percentage by mass: 0.5-2 wt % of a silane coupling agent, 0.05-1 wt % of a reaction inhibitor, and 0.05-5 wt % of a thixotropic agent.

[0122] The present invention provides an adhesive film, comprising the flame-retardant high-peeling heat-curing structural adhesive as described above.

[0123] Furthermore, the thickness of the adhesive film is 0.03-1 mm.

[0124] The present invention also provides an adhesive tape, comprising the adhesive film as described above.

[0125] In the present invention, the adhesive film / tape is formed by the structural adhesive of the present invention, and illustratively, the adhesive film / tape can be formed by hot extrusion or melt extrusion. More specifically, the structural adhesive of the present invention can be firstly hot extruded or melt extruded onto a flexible or non-flexible substrate (including a release film), and then UV cured to form an adhesive film; the adhesive tape structure provided by the present invention can be compounded with a release film on the front and back sides of the adhesive film, or can be compounded with a release film only on one surface of the adhesive film.

[0126] The present invention is described in more detail below in conjunction with the embodiments. It should be noted that these descriptions and embodiments are intended to facilitate the understanding of the present invention, rather than to limit the present invention.

[0127] The raw materials used in this application are shown in Table 1.

[0128] Table 1 Raw material information:

[0129]

[0130]

[0131] Table 2 Amount of raw materials used in Examples 1 to 4 and Comparative Examples 1 to 2 (unit: wt%):

[0132]

[0133]

[0134] The present invention does not limit the preparation method of the structural adhesive. The structural adhesive of the present invention can be prepared by conventional methods for preparing structural adhesives in the art, such as conventional mixing and stirring.

[0135] Specifically, the preparation method of the structural adhesive of the embodiment and the comparative example includes: firstly mixing the raw materials 2EHA, BA, NVC, GMA and Irgacure 651 (1) in the amounts shown in Table 2 to obtain a mixture; then using 0.5 mW / cm 2 The obtained mixture is irradiated with an ultraviolet lamp, and when the viscosity of the mixture is between 1000 and 3000 mPa.s, the irradiation is stopped; and then other remaining raw materials are added in the amounts shown in Table 2 to obtain a structural adhesive.

[0136] The structural adhesives obtained in the examples and comparative examples were applied to transparent PET release films respectively, and then coated with another transparent PET release film. Determine the appropriate thickness and use 0.5 mW / cm 2 The sheet-like adhesive was irradiated with ultraviolet rays to obtain adhesive films of Examples and Comparative Examples.

[0137] The adhesive films prepared in Examples 1 to 4 and Comparative Examples 1 to 2, domestic adhesive film products (selected as the structural adhesive film of Siland, model MF1009) and international adhesive film products (selected as the structural adhesive film of 3M, model 9214) were respectively subjected to the following performance tests:

[0138] (1) Storage stability:

[0139] At room temperature, remove the PET release film on one side of the film and attach a 25μm PET backing (placed at 25℃ for at least 1 day); then take out the sample, cut it into 12.7mm wide and at least 120mm long, press it back and forth on the mirror steel plate with a 5kg roller, place it at room temperature for 20mins, and then perform a 90° peel force test at a speed of 300mm / min;

[0140] After the structural adhesive composition is prepared, it is stored in a container and the peeling force after being stored offline and in an environment of 25°C for 180 days is tested. The storage stability of the structural adhesive is evaluated according to the following evaluation criteria:

[0141] "PASS" means the peeling force at 90 degrees at room temperature is reduced by less than 5%; "NG" means the peeling force at 90 degrees at room temperature is reduced by more than 5%. The evaluation results are shown in Table 3.

[0142] (2) Thickness change rate before and after curing and product appearance color:

[0143] Thickness change rate = (thickness after curing - thickness before curing) / thickness before curing * 100%; a positive value of thickness change rate indicates that the film expands after curing; a negative value of thickness change rate indicates that the film shrinks after curing. The results are shown in Table 4. The color change of the structural adhesive film after thermal curing is observed, and the results are shown in Table 5.

[0144] (3) Elongation at break (%) and breaking strength (MPa):

[0145] The film was treated according to two conditions: before curing and after curing. The film was cut into pieces of 5 mm wide and 60 mm long and tested using a universal material testing machine at a speed of 500 mm / min. The results are shown in Table 6.

[0146] (4) Shear strength:

[0147] Preparation before testing: 5052 anodized aluminum sheet (without sandblasting), size 30*75mm, thickness 3mm. Clean the surface of the sheet with IPA or ethanol, and after sample preparation, press with a 5kg press for 10s.

[0148] 4.1.Initial 20mins

[0149] At room temperature, prepare a 10*25mm film sample, and then immediately laminate it on an aluminum plate. Use a 5kg roller to move back and forth once. Place it in a room temperature environment for 20 minutes. Set the tensile testing machine speed to 50mm / min to test its shear strength.

[0150] 4.2.Normal temperature 24hrs

[0151] A 10*25mm film sample was prepared and placed in an environment of 140℃ / 30mins. After being taken out, it was placed in an environment of room temperature for 24hrs. The speed of the tensile testing machine was set to 50mm / min, and its shear strength was tested and the failure mode was recorded by taking photos.

[0152] Thermal aging

[0153] Prepare a 10*25mm film sample (after curing), place it in an environment of 80℃ / 672hrs, take it out and place it in a room temperature environment for 24hrs, set the tensile machine speed to 50mm / min, test its shear strength and take photos to record the failure mode.

[0154] 4.4. Hot water immersion

[0155] Prepare a 10*25mm film sample (after curing), place it in a hot water bath at 50°C / 672hrs, take it out and place it at room temperature for 24hrs, and test its shear strength at a speed of 50mm / min.

[0156] 4.5.High temperature and high humidity

[0157] Prepare a 10*25mm film sample (after curing), place it in a high temperature and high humidity environment of 50℃ / 95%RH / 672hrs, take it out and place it in a room temperature environment for 24hrs, set the tensile machine speed to 50mm / min, test its shear strength and take photos to record the failure mode.

[0158] 4.6. High temperature 80℃

[0159] A 10*25mm film sample (after curing) was prepared and placed in a high temperature environment of 80°C for 30 minutes. Then, at the temperature of 80°C, the tensile machine speed was set to 50mm / min, the shear strength was tested and the failure mode was recorded by taking photos.

[0160] 4.7. Low temperature -40℃

[0161] A 10*25mm film sample (after curing) was prepared and placed in a high temperature environment of -40°C for 30 minutes. Then, at a temperature of -40°C, the tensile testing machine speed was set to 50mm / min, the shear strength was tested and the failure mode was recorded by taking photos.

[0162] The above results are shown in Table 7.

[0163] (5) Static creep test:

[0164] Preparation before testing: zinc alloy round rearview mirror seat, structural film die-cut parts (5cm 2 ).

[0165] Clean the adhesive surface of the metal mirror base with alcohol, and then immediately stick the die-cut adhesive film component on the metal mirror base (2kg pressure, 5s). 2 The pressure of (27.5kg) was applied to the glass surface, and the pressure was maintained for 10 seconds. Then the temperature of the component was raised to about 140℃ and maintained for 30 minutes for curing. After being placed at room temperature for one day, it was used for testing. The prepared cured adhesive component was placed in the anti-creep fixture for testing. The loading conditions were as follows:

[0166] 5.1. High temperature load 1.0kg

[0167] Test fixture, adjust the angle to 45°, then load 1kg, set dry heat oven condition to 80℃, test time 30 days, record the drop time, photos before and after the test (adhesive surface visible), and calculate the drop ratio %.

[0168] 5.2. High humidity load 2.7kg

[0169] The test fixture was adjusted to a 45° angle, then loaded with a 2.7kg load, and the environmental chamber conditions were set to 50°C / 95%RH. The test time was 125 days, and the drop time, photos before and after the test (the bonding surface was visible) were recorded, and the drop ratio was calculated.

[0170] 5.3 High humidity load 4.0kg

[0171] Test fixture, adjust the angle to 45°, then load 4.0kg, set the environmental box conditions to 50℃ / 95%RH, test time 80 days, record the drop time, photos before and after the test (the bonding surface is visible), and calculate the fall-off percentage.

[0172] The above results are shown in Table 8.

[0173] (6) Component peeling torque test:

[0174] Preparation before testing: zinc alloy shield-shaped rearview mirror seat, structural film die-cut parts (5cm 2 , adapted to shield-type rearview mirror holder).

[0175] Clean the adhesive surface of the shield-type rearview mirror seat with alcohol, and then immediately stick the die-cut adhesive film part on the metal mirror seat evenly (2kg pressure, 5s), and press the prepared adhesive part at room temperature at 5kg / cm 2The pressure of (27.5kg) was applied to the glass surface, and the pressure was maintained for 10s. After being placed at room temperature for 20mins, it was kept at 140℃ for 30mins to cure (the timing started when the overall temperature of the component was raised to 140℃). It was taken out and placed at room temperature for one day. The prepared cured adhesive component was placed in the peeling torque tooling and tested at a tensile speed of 50mm / min. The loading conditions were as follows:

[0176] 6.1 24hrs at normal temperature

[0177] The prepared adhesive parts were heated at room temperature at 5 kg / cm 2 The pressure of (27.5kg) is applied to the glass surface, and the pressure is maintained for 10s. After being placed at room temperature for 20mins, the temperature is raised to 140℃ and maintained for 30mins. The sample is cured under the condition of a 1kg weight (the oven + weight are heated to 140℃ first, and the total number of samples is preferably kept at 16pcs or less). The sample is taken out and placed at room temperature for one day, and then put into the peeling torque tooling for testing.

[0178] 6.2. Hot and cold cycles

[0179] The prepared samples were placed in a hot and cold cycle condition of 90°C (2 hrs), 23°C (0.5 hr), -40°C (2 hrs), and 23°C (0.5 hr). After running 10 cycles, they were taken out and placed at room temperature for 1 hr and placed in a peel torque tool for testing.

[0180] 6.3. Hot water immersion

[0181] The prepared sample was placed in warm water at 50°C for 336 hours, taken out and dried, left at room temperature for 1 hour, and then placed in a peeling torque tester for testing.

[0182] 6.4.High temperature and high humidity

[0183] The prepared samples were placed in an environment of 50° C., 95% RH, and 336 hrs, taken out and placed at room temperature for 1 hr, and then placed in a peeling torque tool for testing.

[0184] 6.5. WOM Xenon Lamp Aging

[0185] Place the prepared sample with the non-component-bonded glass surface facing the xenon lamp, and the aging conditions are 550W / ㎡, 120mins sun exposure, 10mins water shower cycle, totaling 1000hrs. Take it out and place it at room temperature for 1hr, and put it into the peel torque tooling for testing.

[0186] 6.6 Low temperature -40℃

[0187] The prepared film sample was placed in an environment of -40°C for 8 hours, taken out and placed at room temperature for 1 hour, and then placed in a peeling torque tool for testing.

[0188] The above results are shown in Table 9.

[0189] (7) 1600N torque impact:

[0190] The high torque impact test uses the car's windshield mirror base components and windshield as test objects.

[0191] The prepared adhesive parts were heated at room temperature at 5 kg / cm 2 (27.5kg) pressure is applied to the glass surface, the pressure is maintained for 10s, and after 20mins, the temperature is raised to 140℃ and maintained for 30mins, and a 1kg weight is pressed to cure (the oven + weight are heated to 140℃ first, and the total number of samples is preferably kept at 16pcs or less), taken out and placed at room temperature for one day, loaded into the torque test fixture, and a torque of 68N.m (about 1600N.cm) is applied at 130mm of the lever, maintained for 1 minute, tested, and the sample damage was recorded.

[0192] The above results are shown in Table 10.

[0193] (8) Flame retardant test

[0194] The films prepared in Examples 1 to 3 and Comparative Examples 1 to 2, domestic products and international products were made into 12.5 mm*80 mm strips, and the samples were tested before curing and at 140°C, cured for 30 minutes, at a pressure of 0.3 MPa, and placed at room temperature for 30 minutes, and then flame retardant tests were performed. The results are shown in Table 11.

[0195] Table 3 Storage stability

[0196]

[0197] Table 4 Thickness change rate of thermal curing structural adhesive film

[0198] sample Thickness before start Thickness of heat cured Thickness change rate Example 1 0.51 0.555 8.80％ Example 2 0.505 0.555 9.90％ Example 3 0.5 0.545 9％ Comparative Example 1 0.512 0.535 4.45％ Comparative Example 2 0.523 0.543 3.80％ Domestic products 0.519 0.583 12.40％ International Products 0.48 0.522 8.90％

[0199] Table 5 Color change of heat-cured structural adhesive film after heat curing

[0200]

[0201]

[0202] Table 6 Curing fracture strength and elongation at break of thermally cured structural adhesive films

[0203]

[0204] Table 7 Curing shear strength of thermally cured structural adhesive film (MPa)

[0205]

[0206]

[0207] Table 8 Static creep test of thermally cured structural adhesive film (MPa)

[0208]

[0209] Table 9 Peeling torque test of thermally cured structural adhesive film components (N*M)

[0210]

[0211] Table 10 1600N torque impact of thermal curing structural adhesive film

[0212] Test environment normal temperature Example 1 100% bonding parts without falling off or damage (glass is not broken) Example 2 100% bonded parts without falling off or damage Example 3 100% bonded parts without falling off or damage Comparative Example 1 100% bonded parts fall off Comparative Example 2 100% bonded parts fall off Domestic products 100% of the bonded parts fell off (glass was not broken) International Products 100% bonding parts without falling off or damage (glass is not broken)

[0213] Table 11 Flame retardant test of thermal curing structural adhesive film

[0214]

[0215] From the test results in the above table, it can be seen that: the heat-curing structural adhesive of the present invention has a significant thickness change rate, which is more conducive to the assembly tolerance control of parts; the color of the heat-curing structural adhesive of the present invention changes significantly before and after curing, indicating that the adhesive film undergoes a chemical reaction when heated, and the bonding condition and curing degree can be preliminarily judged in real time; the performance of the heat-curing structural adhesive of the present invention before and after curing is relatively excellent, with good elongation at break and fracture strength. The heat-curing structural adhesive film of the present invention achieves high shear strength of the adhesive film after heat curing by introducing dicyclopentadiene phenol epoxy resin and end-capped high-temperature deblocking polyurethane resin, while achieving a peeling force torque of more than 45N*m between metal and glass, which significantly exceeds similar international and domestic products; by adding liquid flame retardants and solid flame retardants in combination, the purpose of halogen-free flame retardancy is achieved; while meeting strong bonding, the safety performance of automotive products is significantly improved, and it is suitable for the growing application needs of the automotive industry.

[0216] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0217] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0218] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A flame retardant high peeling heat curing structural adhesive, characterized in that: The invention comprises the following raw materials in percentage by mass: (I) 20 to 60 wt % of an acrylic acid polymer; (II) 20 to 60 wt % of an epoxy resin composition; (III) 0.5 to 5 wt% of a curing agent; (IV) 0.15 to 2.5 wt% of an accelerator; (V) 0.05 to 3 wt % of a photoinitiator; (VI) 0 to 5 wt% of a multifunctional acrylic monomer; (VII) 10 to 20 wt% of a flame retardant.

2. The flame retardant high peeling heat curing structural adhesive according to claim 1, characterized in that: Taking the acrylic polymer as 100%, the acrylic polymer includes the following components by mass percentage: 60-90% of C1-C8 (meth) alkyl acrylate monomers; 10-30% of alkaline polymerizable vinyl monomers; 0-10% of cationically curable acrylic ester monomers; and 0.01-1% of photoinitiator.

3. The flame retardant high peeling heat curing structural adhesive according to claim 2, characterized in that: The alkaline polymerizable vinyl monomer is at least one of N-vinyl pyrrolidone and N-vinyl caprolactam.

4. The flame retardant high peeling heat curing structural adhesive according to claim 1, characterized in that: Taking the epoxy resin composition as 100%, the epoxy resin composition comprises the following components in percentage by mass: 0-60% of bisphenol A liquid epoxy resin or bisphenol F liquid epoxy resin, 10-60% of bisphenol A solid epoxy resin, 0-10% of dicyclopentadiene epoxy resin and 5-40% of epoxy toughening agent.

5. The flame retardant high peeling heat curing structural adhesive according to claim 4, characterized in that: The epoxy toughening agent is at least one of a core-shell toughened epoxy resin, a CTBN toughened epoxy resin, a polyurethane toughened epoxy resin, and a blocked high temperature deblocking polyurethane resin.

6. The flame retardant high peeling heat curing structural adhesive according to claim 1, characterized in that: The accelerator is at least one of a modified imidazole accelerator, a modified amine accelerator, and a modified urea accelerator.

7. The flame retardant high release heat curing structural adhesive according to claim 1, characterized in that: The multifunctional acrylic monomer is at least one of a difunctional acrylic monomer and a trifunctional acrylic monomer.

8. The flame retardant high peeling heat curing structural adhesive according to claim 1, characterized in that: The invention also comprises the following raw materials: a silane coupling agent, a thixotropic agent and a reaction inhibitor.

9. An adhesive film, characterized in that: The invention comprises the flame retardant high peeling heat curing structural adhesive as described in any one of claims 1 to 8.

10. An adhesive tape, characterized in that: The adhesive film comprises the adhesive film as claimed in claim 9.

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