adhesive

Abstract

Provided is an adhesive obtained by combining a base agent and a curing agent, wherein the degree of biomass is not less than 50%, the base agent includes a sorbitol-type epoxy resin, and the shear adhesive strength of a cured product obtained by curing the adhesive at a temperature of 20-50°C is not less than 5 MPa, said shear adhesive strength being measured at a temperature of 25°C and at a tensile speed of 5mm / min using JIS K 6850 as a related test method.

Description

glue CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2023-161487, filed on September 25, 2023, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to adhesives.

[0003] Patent Document 1 proposes a curing agent consisting of a reaction product of a naturally occurring polyfunctional carboxylic acid, a hydroxyl group-containing solvent, and an epoxidized triglyceride, the curing agent being characterized by including an ester bond formed between the hydroxyl group-containing solvent and the naturally occurring polyfunctional carboxylic acid.

[0004] Special Publication No. 2021-532199

[0005] An object of the present invention is to provide an adhesive that has a high biomass content and an excellent balance of physical properties.

[0006] One aspect of the present disclosure relates to an adhesive comprising a combination of a base agent and a curing agent, the adhesive having a biomass content of 50% or more, the base agent including a sorbitol-type epoxy resin, and the adhesive cured at 20°C or more and 50°C or less, the cured product having a shear bond strength of 5 MPa or more, the shear bond strength being measured at 25°C and a tensile speed of 5 mm / min according to JIS K 6850 as the relevant test method.

[0007] It is possible to provide an adhesive having a high biomass content and an excellent balance of physical properties. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description.

[0008] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit.

[0009] The present disclosure relates to the following. [Technology 1] An adhesive comprising a combination of a base agent and a curing agent, the adhesive having a biomass degree of 50% or more, the base agent including a sorbitol-type epoxy resin, and the adhesive cured at 20°C or more and 50°C or less, and the shear bond strength of the cured product is 5 MPa or more, the shear bond strength being measured at 25°C and a tensile speed of 5 mm / min according to JIS K 6850 as the relevant test method. [Technology 2] The adhesive according to Technology 1, in which the biomass degree is 60% or more. [Technology 3] The adhesive according to Technology 1 or 2, in which the epoxy equivalent of the sorbitol-type epoxy resin is 162 g / eq or more and 200 g / eq or less. [Technology 4] The adhesive according to any one of Technology 1 to 3, in which the epoxy equivalent of the sorbitol-type epoxy resin is 162 g / eq or more and 182 g / eq or less. [Technology 5] The adhesive according to any one of Technology 1 to 4, in which the curing agent includes an amine compound. [Technology 6] The adhesive according to Technology 5, wherein the amine compound is an aliphatic polyamine having two or more primary amino groups. [Technology 7] The adhesive according to Technology 6, wherein the aliphatic polyamine compound has an ether bond. [Technology 8] The adhesive according to Technology 7, wherein the aliphatic polyamine compound has a polyoxyalkylene chain. [Technology 9] The adhesive according to any one of Technology 1 to 8, wherein the breaking elongation of the cured product is 5% or more, measured at 25°C and a tensile speed of 5 mm / min according to JIS K 7161 as the related test method.

[0010] (Adhesive) The adhesive according to the present disclosure (hereinafter also referred to as "adhesive (HB)") is an adhesive having a biomass content of 50% or more, which is a combination of a base agent and a curing agent. The adhesive may be a one-component type or a two-component type. At least a portion of the base agent is a sorbitol-type epoxy resin. The biomass content of the sorbitol-type epoxy resin is, for example, 70% or more and 100% or less, or 90% or more and 100% or less, and can also be 99% or more and 100% or less.

[0011] By using a sorbitol-type epoxy resin as the main component of the base resin, the biomass content of the adhesive (HB) as a whole is significantly increased. The biomass content of the adhesive (HB) is, for example, 50% to 90%, or 60% to 90%, or may be 70% to 90% (e.g., 80% or less). For example, by making the content of components other than the sorbitol-type epoxy resin 45% by mass or less, or even 35% or less, or 30% or less, the biomass content of the adhesive (HB) can easily be 50% or more. The components other than the sorbitol-type epoxy resin are mainly curing agents and may contain small amounts of additives.

[0012] The "main component" of the base agent refers to a component that accounts for 60% by mass or more, preferably 70% by mass or more or 90% by mass or more of the base agent (or epoxy resin). In other words, 60% by mass or more, preferably 70% by mass or more or 90% by mass or more (or 100%) of the base agent contained in the adhesive (HB) according to one embodiment of the present disclosure is a sorbitol-type epoxy resin.

[0013] The degree of biomass can be measured by testing the biobased carbon content of biobased products using radiocarbon measurements, based on ASTM D6866-22 Method B.

[0014] The sorbitol-type epoxy resin is an epoxy resin having a sorbitol skeleton represented by the following structural formula (1).

[0015] Structural formula (1):

[0016]

[0017] Sorbitol-type epoxy resins can be obtained, for example, by reacting sorbitol with epichlorohydrin to epoxidize the hydroxyl groups. The following structural formula (2) shows an example of a sorbitol-type epoxy resin in which four hydroxyl groups have been epoxidized.

[0018] Structural formula (2):

[0019]

[0020] An example of a commercially available sorbitol-type epoxy resin is the GEX-600 series of "Green Denacol (registered trademark)" manufactured by Nagase ChemteX Corp. The sorbitol-type epoxy resin preferably has an average of 3.8 to 4.2 (preferably an average of 4.0) epoxy groups (glycidyl ether groups) per molecule, from the viewpoint of realizing a cured product having a good balance of high adhesive strength, tensile strength, tensile modulus, and elongation at break.

[0021] From another perspective, the epoxy equivalent of the sorbitol-type epoxy resin may be, for example, 162 g / eq or more and 200 g / eq or less. If the epoxy equivalent is within this range, a cured product having high adhesive strength, tensile strength, tensile modulus, and elongation at break in a well-balanced manner can be obtained.

[0022] The epoxy equivalent of the sorbitol-type epoxy resin is preferably 162 g / eq or more and 182 g / eq or less. A sorbitol-type epoxy resin having an epoxy equivalent in this range can produce a cured product with a better balance of adhesive strength, tensile strength, tensile modulus, and elongation at break.

[0023] Unlike petroleum-derived epoxy resins with a low biomass content, it is generally considered difficult to obtain a cured product with a high elastic modulus from sorbitol-based epoxy resins, which have a high biomass content. However, in reality, sorbitol-based epoxy resins are promising alternatives to petroleum-derived epoxy resins. In particular, sorbitol-based epoxy resins with approximately four epoxy groups per molecule can form cured products with an excellent balance of physical properties, such as adhesive strength and elastic modulus. Furthermore, by appropriately selecting the type of curing agent, it is possible to design physical properties according to the desired application.

[0024] In the present disclosure, the curing agent is selected so that the cured adhesive (HB) has a shear bond strength of 5 MPa or more. The shear bond strength is measured at 25°C and a tensile speed of 5 mm / min according to JIS K 6850. The shear bond strength is measured using an aluminum (Al) plate adherend that has been polished and degreased with acetone. Depending on the type of curing agent, the shear bond strength can be 10 MPa or more, or even 20 MPa or more.

[0025] The adhesive (HB) may be cured, for example, at room temperature for 24 hours. The curing temperature of the adhesive (HB) is typically, but not limited to, 25°C. The adhesive (HB) may be cured by being left at a temperature in the range of 20°C to 50°C for 24 hours.

[0026] In the present disclosure, the curing agent is preferably selected so that the glass transition temperature (Tg) of the cured product of the adhesive (HB) is, for example, room temperature or higher (e.g., 25°C or higher). By setting the Tg of the cured product of the adhesive (HB) to room temperature or higher, it becomes easier to ensure high adhesive strength. The Tg of the cured product is, for example, preferably 30°C or higher and 85°C or lower, and may be 40°C or higher and 60°C or lower. The Tg of the cured product may be measured using a differential scanning calorimeter (DSC).

[0027] The tensile strength of the cured product of the adhesive (HB) is preferably 40 MPa or more, and more preferably 50 MPa or more.

[0028] The tensile modulus of elasticity of the cured product of the adhesive (HB) is preferably 2000 MPa or more, and more preferably 3000 MPa or more.

[0029] The breaking elongation of the cured product of the adhesive (HB) is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more.

[0030] When the cured product of adhesive (HB) has the above-mentioned Tg, tensile strength, tensile modulus, and elongation at break, it can be said that adhesive (HB) satisfies not only adhesive strength but also other physical properties generally required of an adhesive.

[0031] The tensile strength, tensile modulus and breaking elongation of the cured adhesive (HB) are measured in accordance with JIS K 7161 at 25° C. and at a pulling rate of 5 mm / min.

[0032] The type of curing agent is not particularly limited, but the main component of the curing agent is preferably an amine compound. By using an amine compound, an adhesive (HB) can be obtained that has low viscosity, sufficient usable life (life), and curing speed, as well as excellent adhesive properties.

[0033] The "main component" of the curing agent refers to a component that accounts for 60% by mass or more, preferably 70% by mass or more or 90% by mass or more of the curing agent. In other words, it is preferred that 60% by mass or more, preferably 70% by mass or more or 90% by mass or more (or 100%) of the curing agent contained in the adhesive (HB) according to one embodiment of the present disclosure is an amine compound.

[0034] Among the amine compounds, aliphatic polyamines having two or more primary amino groups are preferred. From the viewpoint of increasing adhesive strength, the aliphatic polyamine compound may have an ether bond. The aliphatic polyamine compound preferably has a plurality of ether bonds.

[0035] Among aliphatic polyamine compounds having an ether bond, aliphatic polyamine compounds having a polyoxyalkylene chain are preferred. The polyoxyalkylene chain may be a polyoxyethylene chain, a polyoxypropylene chain, or a copolymer chain of oxyethylene and oxypropylene.

[0036] Specific examples of the amine compound include polyether diamines having a molecular weight of 200 to 400, polyether diamines having a molecular weight of 400 to 450, and polyether triamines having a molecular weight of 400 to 450.

[0037] The equivalent of hydrogen bonded to a nitrogen atom of the amine compound (hereinafter also referred to as "active hydrogen") (amine equivalent) is, for example, preferably from 50 g / eq to 100 g / eq, more preferably from 55 g / eq to 85 g / eq.

[0038] The amount of the amine compound used is, for example, 0.7 to 1.5 amine equivalents, alternatively 0.8 to 1.3 amine equivalents, or alternatively 0.9 to 1.1 amine equivalents per 1 epoxy equivalent of the sorbitol-type epoxy resin. From the viewpoint of increasing the biomass content of the adhesive (HB), it is preferable that the amine equivalent per 1 epoxy equivalent be 1.1 or less.

[0039] It is desirable that the curing reaction of the adhesive (HB) cures quickly at room temperature and does not proceed too rapidly. For example, the time required for the adhesive (HB) to double in viscosity (the time required for the viscosity to double) at 25°C is preferably 10 minutes to 40 minutes.

[0040] The adhesive (HB) may contain various optional components in addition to the base agent and curing agent. Examples of optional components include, but are not limited to, an adhesion promoter, an antifoaming agent, a curing catalyst, etc. Among these, the adhesion promoter is effective in improving adhesion.

[0041] As the adhesion promoter, for example, a silane coupling agent is preferably used. Examples of silane coupling agents that can be used include 3-glycidoxypropyltrimethoxysilane (γ-glycidoxypropyltrimethoxysilane), 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane. These may be used alone or in combination of two or more. When a silane coupling agent is used, the amount used is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the base agent.

[0042] [Examples] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples. Table A shows the components, roles and structural formulas of the raw materials used.

[0043]

[0044] Examples 1 to 3 A sorbitol-type epoxy resin (GEX-600 series manufactured by Nagase ChemteX Corporation) represented by the structural formula (2) was used as the base resin. The amine compounds shown in Table 2 were used as the curing agents. Two-component liquid adhesives A1 to A3 of Examples 1 to 3 were prepared by blending 100 parts by mass of the sorbitol-type epoxy resin (GEX-600 series) with the parts by mass of the curing agent and adhesion promoter shown in Table 2. For example, in the case of adhesive A1, 35 parts by mass of polyoxypropylenediamine as a curing agent and 1 part by mass of 3-glycidoxypropyltrimethoxysilane as an adhesion promoter were blended with 100 parts by mass of the sorbitol-type epoxy resin as the base resin. The amine equivalent per 1 epoxy equivalent (eq / eq ratio) is shown in Table 2.

[0045] Reference Example 1 A two-component liquid adhesive R1 was prepared by using a petroleum-derived bisphenol A epoxy resin as the main agent instead of a sorbitol epoxy resin, and blending 100 parts by mass of the main agent with the parts by mass of a curing agent shown in Table 2. The amine equivalent per 1 epoxy equivalent (eq / eq ratio) is shown in Table 2.

[0046] [Evaluation] (Adhesive Strength) For adhesives A1-A3 and R1, the shear adhesive strength was measured at 25°C and a tensile speed of 5 mm / min using JIS K 6850 as the relevant test method. Specifically, adhesives A1-A3 and R1 were applied to adherend 1, and adherend 2 was then attached to the applied adhesive. The adherends were aluminum plates measuring 1.5 mm thick, 25 mm wide, and 150 mm long, with the surface of the adhesive portion polished and degreased with acetone. The plates were then left at 25°C for 24 hours to allow the adhesive to cure. The shear adhesive strength was measured at a tensile speed of 5 mm / min using a tensile tester (manufactured by Instron). An adhesive strength of 5 MPa or more is preferable, and 20 MPa or more is ideal. Here, five or more measurements were performed for each example, and the average adhesive strength was calculated. The results are shown in Table 2.

[0047] (Tg) Adhesives A1 to A3 and R1 were left to stand at 25°C for 24 hours to obtain cured products. The Tg of the cured products was measured by DSC. The results are shown in Table 2.

[0048] (Tensile Test) For adhesives A1 to A3 and R1, a tensile test was performed at 25°C using JIS K 7161 as the relevant test method to measure the tensile strength, tensile modulus, and elongation at break. Specifically, adhesives A1 to A3 and R1 were injected into a mold to prepare dumbbell-shaped test specimens for tensile testing, measuring 2 mm thick x 4 mm wide (12.5 mm for the test specimen grip) x 90 mm long. Tests were performed using a tensile tester (manufactured by Instron) under conditions of a chuck distance of 25 mm and a tensile speed of 5 mm / min. The tensile strength is the maximum stress measured until the test specimen breaks, the tensile modulus is the ratio of stress to strain during tension, and the elongation at break is the ratio of the permanent elongation (stretched length) after the test specimen breaks to the original rating distance D. Here, measurements were performed five or more times for each example, and the average values ​​of each physical property were calculated.

[0049]

[0050] From Table 2, it can be seen that adhesive (HB), which has a high biomass content and uses a sorbitol-type epoxy resin as the main agent, has sufficient adhesive strength. Furthermore, it can be seen that among adhesives (HB), adhesives A1 and A3 in particular can achieve adhesive strength comparable to that of adhesives using a bisphenol A-type epoxy resin as the main agent by selecting the curing agent. It can also be seen that adhesive (HB) has a significantly greater breaking elongation than adhesive R1, which uses a bisphenol A-type epoxy resin as the main agent.

[0051] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

Claims

1. An adhesive that combines a base agent and a curing agent, the base agent having a biomass ratio of 50% or more, the base agent containing a sorbitol-type epoxy resin, the adhesive cured at 20°C or more and 50°C or less having a shear bond strength of 5 MPa or more, the shear bond strength being measured at 25°C and a tensile speed of 5 mm / min according to the relevant test method of JIS K 6850.

2. The adhesive according to claim 1, wherein the biomass content is 60% or more.

3. The adhesive according to claim 1, wherein the epoxy equivalent of the sorbitol-type epoxy resin is 162 g / eq or more and 200 g / eq or less.

4. The adhesive according to claim 1, wherein the epoxy equivalent of the sorbitol-type epoxy resin is 162 g / eq or more and 182 g / eq or less.

5. The adhesive of claim 1, wherein the curing agent comprises an amine compound.

6. The adhesive according to claim 5, wherein the amine compound is an aliphatic polyamine having two or more primary amino groups.

7. The adhesive according to claim 6, wherein the aliphatic polyamine compound has an ether bond.

8. The adhesive according to claim 7, wherein the aliphatic polyamine compound has a polyoxyalkylene chain.

9. The adhesive according to claim 1, wherein the breaking elongation of the cured product is 5% or more, measured at 25°C and a tensile speed of 5 mm / min according to the relevant test method of JIS K 7161.

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