Anhydride-cured epoxy resin bonding sheet and preparation method thereof

Abstract

The invention discloses an anhydride-cured epoxy resin bonding sheet, which comprises a base material, the thermal expansion adhesive layers are arranged on two sides of the base material, and the thermal expansion adhesive layer is characterized by consisting of multifunctional epoxy resin, an anhydride curing agent, a temperature-sensitive foaming agent, thermoplastic resin and an accelerant. According to the invention, acid anhydride is used as a curing agent, and the thermal expansion adhesive layer is solid at room temperature, so that the product can maintain low viscosity and good expansibility at high temperature while maintaining surface non-viscosity at room temperature, can improve the fluidity of the thermal expansion adhesive layer when heated, and has a favorable effect on thermal expansion of the thermal expansion adhesive layer; in addition, the anhydride curing agent is also beneficial to increasing the glass transition temperature (Tg) of the adhesive sheet and improving the heat resistance; and the price of the anhydride curing agent is relatively low.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical industry, and in particular relates to an anhydride-cured epoxy resin adhesive sheet and a preparation method thereof. Background Art

[0002] Epoxy resin adhesives have excellent heat resistance and strong adhesion, so they are widely used in component bonding, structural bonding, etc. In related fields such as electrical and electronic, automobiles, and civil engineering, adhesive sheets are often used to fix components. Sometimes it is necessary to achieve bonding in a small area of ​​an industrial component. For example, in the motors of electric and hybrid vehicles that have developed rapidly in recent years, the coils wound with enameled wire need to be fixed to the stator core with adhesives. Since the gap between the coil and the stator core is very narrow, it is necessary to use an adhesive sheet with heat expansion properties, which will expand to fill the gap and solidify when heated.

[0003] The adhesive sheet in the prior art is sticky at room temperature and usually requires a permeable layer or surface coating of a non-woven fabric. The use of a permeable layer or surface coating may affect the performance of the adhesive sheet, increase the complexity of the process, and may also hinder the foaming effect of the foaming agent when heated and expanded. For example, patent CN112189041B proposes a heat-expandable adhesive sheet, the epoxy resin used in the adhesive sheet is sticky at room temperature, and the adhesive sheet prepared by the adhesive sheet needs to be provided with a permeable layer of non-woven fabric at room temperature to make its surface non-sticky; patent CN105940071B discloses an adhesive sheet that maintains sufficient foaming performance and has excellent operability, the resin system used by the adhesive sheet is sticky at room temperature, and an amide curing agent (such as dicyandiamide) is used, the adhesive layer prepared by the adhesive sheet is sticky at room temperature, and the surface needs to be coated to prevent the product from sticking at room temperature; the above two patents will increase the process complexity due to the use of a permeable layer or surface coating of non-woven fabric, resulting in a decrease in the performance of the adhesive sheet; patent CN105745236A prepares an adhesive, and its hardener component uses dicyandiamide and its derivatives, and the glass transition temperature (Tg) of the adhesive prepared by the adhesive sheet is relatively low. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these purposes and other advantages according to the present invention, an anhydride-cured epoxy resin adhesive sheet is provided, comprising a substrate; a thermal expansion adhesive layer arranged on both sides of the substrate, characterized in that the thermal expansion adhesive layer is composed of a multifunctional epoxy resin, an anhydride curing agent, a temperature-sensitive foaming agent, a thermoplastic resin, and an accelerator.

[0006] Preferably, the acid anhydride curing agent is solid at room temperature and has a melting point above 30°C.

[0007] Preferably, the anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and chlorohydric anhydride, and the added amount of the anhydride curing agent is 20-90 parts by mass relative to 100 parts by mass of the epoxy resin.

[0008] Preferably, the substrate is one or more of a polyester film, a polyimide film, an aramid film, and polyethylene naphthalate, and the thickness of the substrate is in the range of 5-200 μm.

[0009] Preferably, the multifunctional epoxy resin is one or more of o-cresol epoxy resin, cresol novolac epoxy resin, phenol novolac epoxy resin, and 1,1,1-tris(4-hydroxyphenyl)ethyl triglycidyl ether.

[0010] Preferably, the temperature-sensitive foaming agent is a heat-expandable microsphere having a diameter of 5-50 μm, and the amount of the temperature-sensitive foaming agent added is 1-20 parts by mass relative to 100 parts by mass of the epoxy resin.

[0011] Preferably, the thermoplastic resin is one or more of polyester, polyurethane, polyolefin, phenoxy resin, acrylic resin, polyvinyl butyral (PVB), and the amount of the thermoplastic resin added is 1-50 parts by mass relative to 100 parts by mass of the epoxy resin.

[0012] Preferably, the accelerator is one or more of 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) and N,N-dimethylbenzylamine (BDMA), and the amount of the accelerator added is 0.1-2.0 parts by mass relative to 100 parts by mass of the epoxy resin.

[0013] The present invention also provides a method for preparing anhydride-cured epoxy resin adhesive sheet, which is characterized by comprising the following steps:

[0014] S1, dissolving a multifunctional epoxy resin, an acid anhydride as a curing agent, a temperature-sensitive foaming agent, a thermoplastic resin, and an amine compound as a accelerator in a ketone solvent to form a glue solution;

[0015] S2. Apply the glue liquid directly or successively to both sides of the substrate, and dry it to obtain an epoxy resin adhesive sheet; or apply the glue liquid to release paper, and dry it to obtain a heat-expandable adhesive layer, and transfer the two heat-expandable adhesive layers successively or simultaneously to both sides of the substrate at a temperature higher than the softening point of the expansion adhesive layer by a transfer method, and then tear off the release papers on both sides to obtain an epoxy resin adhesive sheet.

[0016] Preferably, the ketone solvent is acetone, butanone or a combination of both, and the content of the ketone solvent is 100-300 parts by mass relative to 100 parts by mass of the epoxy resin.

[0017] The present invention includes at least the following beneficial effects: the present invention adopts anhydride as a curing agent, which is solid at room temperature, but its melt viscosity will be significantly reduced when it is higher than its melting point, so that the product can maintain no surface stickiness at room temperature while maintaining low viscosity and good expansion properties at high temperatures, which can improve the fluidity of the adhesive layer when heated and has a favorable effect on the thermal expansion of the adhesive layer; in addition, since the acid anhydride curing agent is a non-adhesive solid at room temperature, the surface of the adhesive layer of the adhesive sheet can be made non-sticky at room temperature; the use of the acid anhydride curing agent is also beneficial to increasing the glass transition temperature (Tg) of the adhesive sheet and improving heat resistance; the price of the acid anhydride curing agent is also relatively low.

[0018] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in further detail below so that those skilled in the art can implement it according to the description.

[0020] Example 1

[0021] A method for preparing an anhydride-cured epoxy resin adhesive sheet comprises the following steps:

[0022] S1, 100g of phenol novolac epoxy resin F44, 75g of methyltetrahydrophthalic anhydride as a curing agent, 10g of heat-expandable microspheres (SEKISUI CHEMICAL, EMH302, particle size 20um) as a temperature-sensitive foaming agent, 25g of PVB (Kuraray, Mowital B20H) as a thermoplastic resin, and 1g of DMP-30 as a accelerator were dissolved in 125g of butanone to form a glue solution;

[0023] S2. directly coating the adhesive solution or coating it successively on both sides of a polyimide film with a thickness of 100 um, and drying it to obtain an epoxy resin adhesive sheet.

[0024] Example 2

[0025] A method for preparing an anhydride-cured epoxy resin adhesive sheet comprises the following steps:

[0026] S1, dissolving 100g of phenol novolac epoxy resin F44, 75g of methyltetrahydrophthalic anhydride as a curing agent, 10g of heat-expandable microspheres (SEKISUI CHEMICAL, EMH302, particle size 20um) as a temperature-sensitive foaming agent, 25g of PVB (Kuraray, Mowital B20H) as a thermoplastic resin, and 1g of DMP-30 as a accelerator in 125g of butanone to prepare a glue solution; applying the glue solution on a release paper, and drying to form a heat-expandable adhesive layer attached to the release paper;

[0027] S2. Then, the two heat expansion adhesive layers are transferred successively or simultaneously to both sides of a polyimide film with a thickness of 100 um at a temperature higher than the softening point of the heat expansion adhesive layer (80° C.) by transfer printing, and then the release films on both sides are torn off to obtain an epoxy resin adhesive sheet.

[0028] Comparative Example 1

[0029] The method of preparing the adhesive sheet without using anhydride curing agent in the prior art includes the following steps:

[0030] S1, 100g of phenol novolac epoxy resin F44, 4.5g of dicyandiamide as a curing agent, 10g of heat-expandable microspheres (SEKISUI CHEMICAL, EMH302, particle size 20um) as a temperature-sensitive foaming agent, 25g of PVB (Kuraray, Mowital B20H) as a thermoplastic resin, and 1g of DMP-30 as a accelerator were dissolved in 125g of butanone to form a glue solution;

[0031] S2. directly coating the adhesive solution or coating it successively on both sides of a polyimide film with a thickness of 100 um, and drying it to obtain an epoxy resin adhesive sheet.

[0032] Comparative Example 2

[0033] The method of preparing the adhesive sheet without using anhydride curing agent in the prior art includes the following steps:

[0034] S1, dissolving 100g of phenol novolac epoxy resin F44, 4.5g of dicyandiamide as a curing agent, 10g of heat-expandable microspheres (SEKISUI CHEMICAL, EMH302, particle size 20um) as a temperature-sensitive foaming agent, 25g of PVB (Kuraray, Mowital B20H) as a thermoplastic resin, and 1g of DMP-30 as a accelerator in 125g of butanone to prepare a glue solution; applying the glue solution to a release paper, and drying to form an expansion adhesive layer attached to the release paper;

[0035] S2. Then, the two heat-expandable adhesive layers are transferred successively or simultaneously to both sides of the 100 um polyimide film at a temperature (80° C.) higher than the softening point of the expandable adhesive layer, and then the release films on both sides are torn off to obtain an epoxy resin adhesive sheet.

[0036] The epoxy resin bonding sheets prepared in Examples 1-2 and Comparative Examples 1-2 were cut into 50 mm × 50 mm samples, and two samples of the same epoxy resin bonding sheet were stacked and sandwiched between two 304 stainless steel sheets, and a 500 g weight was placed on them. After the samples were pressed at room temperature for 5 days, the 304 stainless steel sheets were removed and the two samples were peeled off to observe the bonding state. The results were: the bonding sheets prepared in Examples 1 and 2 had no bonding at room temperature, while the samples in Comparative Examples 1 and 2 had bonding.

[0037] The glass transition temperature (Tg) of the epoxy adhesive sheets prepared in Example 1-2 and Comparative Example 1-2 was tested. The Tg of the epoxy resin adhesive sheet prepared in Example 1-2 was 150°C, while the Tg of Comparative Example 1-2 was 135°C. It can be seen that the present invention can increase the glass transition temperature by adding anhydride curing agent, thereby improving the heat resistance of the epoxy resin adhesive sheet.

[0038] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. An anhydride-cured epoxy resin adhesive sheet, characterized in that: The invention comprises a substrate and a heat expansion adhesive layer arranged on both sides of the substrate, wherein the heat expansion adhesive layer is composed of a multifunctional epoxy resin, anhydride curing agent, a temperature-sensitive foaming agent, a thermoplastic resin and an accelerator.

2. The anhydride-cured epoxy resin adhesive sheet according to claim 1, characterized in that: The acid anhydride curing agent is solid at room temperature and has a melting point above 30°C.

3. The anhydride-cured epoxy resin adhesive sheet according to claim 1, characterized in that: The acid anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride and chlorohydric anhydride. The added amount of the acid anhydride curing agent is 20-90 parts by weight relative to 100 parts by weight of epoxy resin.

4. The anhydride-cured epoxy resin adhesive sheet according to claim 1, characterized in that: The substrate is one or more of a polyester film, a polyimide film, an aramid film, and polyethylene naphthalate, and the thickness of the substrate is in the range of 5-200 μm.

5. The anhydride-cured epoxy resin adhesive sheet according to claim 1, characterized in that: The multifunctional epoxy resin is one or more of o-cresol epoxy resin, cresol novolac epoxy resin, phenol novolac epoxy resin, and 1,1,1-tris(4-hydroxyphenyl)ethyl triglycidyl ether.

6. The anhydride-cured epoxy resin adhesive sheet according to claim 1, characterized in that: The temperature-sensitive foaming agent is a heat-expandable microsphere with a diameter of 5-50 μm. The amount of the temperature-sensitive foaming agent added is 1-20 parts by mass relative to 100 parts by mass of the epoxy resin.

7. The anhydride-cured epoxy resin adhesive sheet according to claim 1, characterized in that: The thermoplastic resin is one or more of polyester, polyurethane, polyolefin, phenoxy resin, acrylic resin, and polyvinyl butyral. The amount of the thermoplastic resin added is 1-50 parts by mass relative to 100 parts by mass of the epoxy resin.

8. The anhydride-cured epoxy resin adhesive sheet according to claim 1, characterized in that: The accelerator is one or more of 2,4,6-tris(dimethylaminomethyl)phenol and N,N-dimethylbenzylamine, and the added amount of the accelerator is 0.1-2.0 parts by mass relative to 100 parts by mass of the epoxy resin.

9. A method for preparing an anhydride-cured epoxy resin adhesive sheet according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, dissolving a multifunctional epoxy resin, an acid anhydride as a curing agent, a temperature-sensitive foaming agent, a thermoplastic resin, and an amine compound as a accelerator in a ketone solvent to form a glue solution; S2. Apply the glue liquid directly or successively to both sides of the substrate, and dry it to obtain an epoxy resin adhesive sheet; or apply the glue liquid to release paper, and dry it to obtain a heat-expandable adhesive layer, and transfer the two heat-expandable adhesive layers successively or simultaneously to both sides of the substrate at a temperature higher than the softening point of the expansion adhesive layer by a transfer method, and then tear off the release papers on both sides to obtain an epoxy resin adhesive sheet.

10. The method for preparing anhydride-cured epoxy resin adhesive sheet according to claim 9, characterized in that: The ketone solvent is one or a combination of acetone and butanone, and the content of the ketone solvent is 100-300 parts by mass relative to 100 parts by mass of the epoxy resin.