Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J163/00—Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins

Definitions

• the present invention relates to an adhesive.
• 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.
• One of the objectives of the present invention is to provide an adhesive that has a high biomass content and an excellent balance of physical properties.
• One aspect of the present disclosure relates to 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 including a sorbitol-type epoxy resin, the adhesive cured at 20°C or more and 50°C or less having a shear adhesive strength of 5 MPa or more, the shear adhesive strength being measured at 25°C and a tensile speed of 5 mm/min according to the relevant test method of JIS K 6850.
• the present disclosure relates to the following: [Technology 1] An adhesive that combines a base agent and a curing agent, The biomass ratio is 50% or more,
• the base resin contains a sorbitol-type epoxy resin,
• the adhesive is cured at a temperature of 20° C. or higher and 50° C. or lower, and the cured product has a shear adhesive strength of 5 MPa or higher;
• the shear adhesive strength is measured according to JIS K 6850 at 25°C and a tensile speed of 5 mm/min.
• the adhesive according to the present disclosure (hereinafter also referred to as "adhesive (HB)" is an adhesive having a biomass degree of 50% or more in 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 part of the base agent is a sorbitol-type epoxy resin.
• the biomass degree 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.
• the biomass degree of the adhesive (HB) as a whole is significantly increased.
• the biomass degree of the adhesive (HB) is, for example, 50% to 90%, or 60% to 90%, and may be 70% to 90% (e.g., 80% or less).
• the biomass degree of the adhesive (HB) can easily be 50% or more.
• the components other than the sorbitol-type epoxy resin are mainly hardeners and may contain small amounts of additives.
• the "main component" of the base agent refers to a component that occupies 60% by mass or more, preferably 70% by mass or more or 90% by mass or more of the base agent (or epoxy resin).
• 60% by mass or more, preferably 70% by mass or more or 90% by mass or more (it may be 100%) of the base agent contained in the adhesive (HB) according to one embodiment of the present disclosure is a sorbitol-type epoxy resin.
• the biomass content can be measured by testing the biobased carbon content of biobased products using radiocarbon measurements, based on ASTM D6866-22 Method B.
• Sorbitol-type epoxy resins are epoxy resins whose main structure is sorbitol, as shown in the following structural formula (1).
• 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.
• a commercially available sorbitol-type epoxy resin is, for example, the GEX-600 series of "Green Denacol (registered trademark)" manufactured by Nagase ChemteX Corporation.
• Sorbitol-type epoxy resins preferably have an average of 3.8 to 4.2 (preferably an average of 4.0) epoxy groups (glycidyl ether groups) in the molecule, from the viewpoint of realizing a cured product with a good balance of high adhesive strength, tensile strength, tensile modulus, and breaking elongation.
• 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 with a good balance of high adhesive strength, tensile strength, tensile modulus, and breaking elongation can be achieved.
• the epoxy equivalent of the sorbitol-type epoxy resin is preferably 162 g/eq or more and 182 g/eq or less. Sorbitol-type epoxy resins with an epoxy equivalent in this range can produce cured products with a better balance of adhesive strength, tensile strength, tensile modulus, and elongation at break.
• 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, using JIS K 6850 as the relevant test method.
• the shear bond strength is measured using an aluminum (Al) plate adherend that has been polished and degreased with acetone.
• the shear bond strength can be 10 MPa or more, and can even be 20 MPa or more.
• the adhesive (HB) may be cured, for example, at room temperature for 24 hours to form a cured product.
• the curing temperature of the adhesive (HB) is typically 25°C, but is not limited to this.
• the adhesive (HB) may be cured, for example, by leaving it at a temperature within the range of 20°C to 50°C for 24 hours.
• the curing agent is preferably selected so that the glass transition temperature (Tg) of the cured product of the adhesive (HB) is, for example, at or above room temperature (e.g., at or above 25°C).
• Tg glass transition temperature
• the Tg of the cured product is preferably, for example, at or above 30°C and at or below 85°C, and may be at or above 40°C and at or below 60°C.
• the Tg of the cured product may be measured using a differential scanning calorimeter (DSC).
• the tensile strength of the cured adhesive (HB) is preferably 40 MPa or more, and more preferably 50 MPa or more.
• the tensile modulus of the cured adhesive (HB) is preferably 2000 MPa or more, and more preferably 3000 MPa or more.
• the breaking elongation of the cured adhesive (HB) is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more.
• 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 the adhesive strength but also other physical properties generally required of an adhesive.
• the tensile strength, tensile modulus and breaking elongation of the cured adhesive (HB) are measured at 25°C and a tensile speed of 5 mm/min according to JIS K 7161, the relevant test method.
• the type of curing agent is not particularly limited, but it is preferable that the main component of the curing agent is an amine compound.
• an amine compound By using an amine compound, it is possible to obtain an adhesive (HB) that has low viscosity, sufficient pot life and curing speed, and excellent adhesive properties.
• the "main component" of the curing agent refers to a component that occupies 60% by mass or more, preferably 70% by mass or more or 90% by mass or more of the curing agent.
• 60% by mass or more, preferably 70% by mass or more or 90% by mass or more (it may be 100%) of the curing agent contained in the adhesive (HB) according to one embodiment of the present disclosure is an amine compound.
• the aliphatic polyamine 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. It is preferred that the aliphatic polyamine compound has multiple ether bonds.
• 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, a copolymer chain of oxyethylene and oxypropylene, etc.
• amine compounds include polyether diamines with a molecular weight of 200 to 400, polyether diamines with a molecular weight of 400 to 450, and polyether triamines with a molecular weight of 400 to 450.
• the equivalent weight (amine equivalent) of hydrogen bonded to nitrogen atoms of the amine compound (hereinafter also referred to as "active hydrogen”) is, for example, preferably from 50 g/eq to 100 g/eq, more preferably from 55 g/eq to 85 g/eq.
• the amount of the amine compound used is, for example, 0.7 to 1.5 amine equivalents, or 0.8 to 1.3 amine equivalents, or 0.9 to 1.1 amine equivalents per epoxy equivalent of the sorbitol-type epoxy resin. From the viewpoint of increasing the biomass content of the adhesive (HB), it is preferable to set the amine equivalent per epoxy equivalent to 1.1 or less.
• the adhesive (HB) may contain various optional components in addition to the base agent and curing agent.
• Optional components include, but are not limited to, adhesion promoters, defoamers, curing catalysts, etc. Among these, adhesion promoters are effective in improving adhesion.
• a silane coupling agent is preferably used as an adhesion promoter.
• silane coupling agents that can be used include 3-glycidoxypropyltrimethoxysilane ( ⁇ -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.
• 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.
• Examples 1 to 3 As the base resin, a sorbitol-type epoxy resin (GEX-600 series manufactured by Nagase Chemtex Corporation) represented by the structural formula (2) described above was used. As the curing agent, an amine compound shown in Table 2 was used. 100 parts by mass of the sorbitol-type epoxy resin (GEX-600 series) was mixed with the curing agent and adhesion promoter shown in Table 2 to prepare two-part liquid adhesives A1 to A3 of Examples 1 to 3.
• GEX-600 series a sorbitol-type epoxy resin represented by the structural formula (2) described above
• the curing agent an amine compound shown in Table 2 was used. 100 parts by mass of the sorbitol-type epoxy resin (GEX-600 series) was mixed with the curing agent and adhesion promoter shown in Table 2 to prepare two-part liquid adhesives A1 to A3 of Examples 1 to 3.
• a two-part liquid adhesive R1 was prepared by using a petroleum-derived bisphenol A epoxy resin as the base agent instead of a sorbitol-type epoxy resin, and mixing 100 parts by mass of the base agent with the parts by mass of the curing agent shown in Table 2.
• the amine equivalent per 1 epoxy equivalent (eq/eq ratio) is shown in Table 2.
• Adhesive strength For adhesives A1 to 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 to A3 and R1 were applied to adherend 1, and adherend 2 was attached to the applied adhesive.
• the adherend was an aluminum plate with a thickness of 1.5 mm, a width of 25 mm and a length of 150 mm, the surface of the adhesive portion was polished, and the plate was degreased with acetone. The plate was then left at 25°C for 24 hours to harden the adhesive.
• the shear adhesive strength was measured at a tensile speed of 5 mm/min using a tensile tester (manufactured by Instron).
• the adhesive strength is preferably 5 MPa or more, and ideally 20 MPa or more.
• five or more measurements were performed for each example, and the average adhesive strength was calculated. The results are shown in Table 2.
• Tg Adhesives A1 to A3 and R1 were left to stand at 25° C. for 24 hours to obtain cured products.
• tensile test For adhesives A1 to A3 and R1, tensile tests were performed at 25°C using JIS K 7161 as the relevant test method, and the tensile strength, tensile modulus and breaking elongation were measured. Specifically, adhesives A1 to A3 and R1 were injected into a mold to prepare dumbbell-shaped test pieces for tensile tests with a thickness of 2 mm, a width of 4 mm (the test piece gripping portion is 12.5 mm) and a length of 90 mm, and tests were performed using a tensile tester (manufactured by Instron) under conditions of a chuck distance of 25 mm and a pulling speed of 5 mm/min.
• a tensile tester manufactured by Instron
• the tensile strength is the maximum stress measured until the test piece breaks
• the tensile modulus is the ratio of the stress and strain during pulling
• the breaking elongation is the ratio of the permanent elongation (length extended) after the test piece breaks to the original rating distance D.
• five or more measurements were performed for each example, and the average value of each physical property was calculated.
• adhesive (HB) which has a high biomass content and uses sorbitol-type epoxy resin as the base agent, has sufficient adhesive strength. Furthermore, it can be seen that among adhesives (HB), particularly A1 and A3, by selecting the curing agent, adhesive strength comparable to that of adhesives using bisphenol A-type epoxy resin as the base agent can be achieved. It can also be seen that adhesive (HB) has a significantly greater breaking elongation than adhesive R1, which uses bisphenol A-type epoxy resin as the base agent.

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