JP7779066B2 - glue - Google Patents

Description

This disclosure relates to adhesives.

Various components that make up a vehicle are sometimes joined using adhesives containing epoxy resins (see, for example, Patent Documents 1 to 3).

Japanese Patent Application Publication No. 4-185686 Japanese Patent Application Laid-Open No. 2006-257228 JP 2009-108278 A

While conventional adhesives containing epoxy resins exhibit good adhesion to a variety of adherends, the cured products of epoxy resin-based adhesives tend to have low tan δ near room temperature. A low tan δ affects damping characteristics, so it is desirable for adhesives used to bond adherends used in vehicle components to have a high tan δ near room temperature. On the other hand, if the tan δ of the cured adhesive becomes high, the elastic modulus may decrease and rigidity may decrease. For this reason, adhesives for vehicles are required to form cured products that can achieve both a high tan δ and elastic modulus near room temperature.

The objective of this disclosure is to provide an adhesive that can form a cured product that exhibits both a high tan δ and a high modulus of elasticity at around room temperature.

The present disclosure relates to an adhesive containing an aromatic epoxy compound, an aliphatic epoxy compound, and a curing agent.

This disclosure provides an adhesive that can form a cured product that exhibits both a high tan δ and a high modulus of elasticity at around room temperature.

Embodiments of the present disclosure are described below. However, the present disclosure is not limited to the following embodiments.

The same applies to the numerical values and ranges in this disclosure, and do not limit this disclosure. In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with the value shown in the examples.

Unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When the adhesive contains multiple substances corresponding to each component, the content of each component refers to the total amount of those multiple substances present in the adhesive, unless otherwise specified.

The adhesive according to this embodiment contains an aromatic epoxy compound, an aliphatic epoxy compound, and a curing agent. By using both an aromatic epoxy compound and an aliphatic epoxy compound, the glass transition temperature of the cured product can be adjusted, achieving both a high tan δ and a high modulus of elasticity at around room temperature.

In this embodiment, the aliphatic epoxy compound is an epoxy compound that does not have an aromatic ring. The aliphatic epoxy compound may be an aliphatic diglycidyl ether having at least one aliphatic group selected from the group consisting of an alkylene group, an oxyalkylene group, and a cycloalkylene group.

Examples of aliphatic diglycidyl ethers include diglycidyl ethers with alkylene groups such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether; diglycidyl ethers with oxyalkylene groups such as diethylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether; diglycidyl ethers with hydroxyl groups such as glycerin diglycidyl ether; and diglycidyl ethers with cycloalkylene groups such as hydrogenated bisphenol A diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, and diglycidyl-1,2-cyclohexanedicarboxylate.

From the viewpoint of increasing tan δ around room temperature, the content of the aliphatic epoxy compound is preferably 25 parts by mass or more, and may be 30 parts by mass or more, or 35 parts by mass or more, per 100 parts by mass of the total amount of epoxy compounds. From the viewpoint of increasing the elastic modulus around room temperature, the content of the aliphatic epoxy compound may be 80 parts by mass or less, 75 parts by mass or less, or 70 parts by mass or less, per 100 parts by mass of the total amount of epoxy compounds.

Examples of aromatic epoxy compounds include phthalic acid diglycidyl ester, bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AD epoxy resin, bisphenol S epoxy resin, phenol novolac epoxy resin, cresol novolac epoxy resin, biphenyl epoxy resin, and biphenyl aralkyl epoxy resin.

The curing agent is a curing agent that cures the epoxy compound. Examples of curing agents include amine-based curing agents, imidazole-based curing agents, phenol-based curing agents, and acid anhydride-based curing agents. These curing agents may be used alone or in combination of two or more.

In order to shorten the curing time, the curing agent may contain at least one selected from the group consisting of amine-based curing agents and imidazole-based curing agents.

The amine-based curing agent may be an aliphatic amine compound or an aromatic amine compound. Examples of aromatic amine compounds include diethyltoluenediamine, 1-methyl-3,5-diethyl-2,4-diaminobenzene, 1-methyl-3,5-diethyl-2,6-diaminobenzene, 1,3,5-triethyl-2,6-diaminobenzene, 3,3'-diethyl-4,4'-diaminodiphenylmethane, 3,5,3',5'-tetramethyl-4,4'-diaminodiphenylmethane, and dimethylthiotoluenediamine.

Examples of imidazole curing agents include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 2,3-dihydro-1H-pyrrolo-[1,2-a]benzimidazole, and 2,4-diamino-6(2'-methylimidazole(1'))ethyl-s-triazine. , 2,4-diamino-6(2'-undecylimidazole(1'))ethyl-s-triazine, 2,4-diamino-6(2'-ethyl-4-methylimidazole(1'))ethyl-s-triazine, 2,4-diamino-6(2'-methylimidazole(1'))ethyl-s-triazine isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-3,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 1-cyanoethyl-2-phenyl-3,5-dicyanoethoxymethylimidazole. The curing agent may also include a latent curing agent in which an imidazole-based curing agent is microencapsulated.

From the perspective of shortening the curing time and lowering the curing temperature, the content of the curing agent may be 1 to 50 parts by mass, 2 to 45 parts by mass, 3 to 40 parts by mass, or 4 to 35 parts by mass per 100 parts by mass of the total amount of epoxy compounds.

The adhesive according to this embodiment may further contain a filler to improve its applicability to the adherend. The filler may be either an inorganic filler or an organic filler. The adhesive may contain both an inorganic filler and an organic filler to increase the rigidity of the cured product.

Examples of inorganic fillers include inorganic fine particles such as silica, alumina, silica-alumina, titania, zirconia, magnesia, kaolin, talc, calcium carbonate, bentonite, mica, sericite, glass flakes, glass fiber, graphite, magnesium hydroxide, aluminum hydroxide, antimony trioxide, barium sulfate, zinc borate, wollastonite, xonotlite, and whiskers.

The content of the inorganic filler may be 60 parts by mass or more, 80 parts by mass or more, or 100 parts by mass or more, and may be 200 parts by mass or less, 150 parts by mass or less, or 130 parts by mass or less, per 100 parts by mass of the total amount of epoxy compounds.

Examples of organic fillers include organic fine particles such as silicone, acrylic silicone, MBS (methacrylate butadiene styrene), polyamide, and polyimide. The organic filler may have a uniform structure or a core-shell structure.

The content of the organic filler may be 1 part by mass or more, 5 parts by mass or more, or 8 parts by mass or more, and may be 30 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less, per 100 parts by mass of the total amount of epoxy compounds.

The adhesive according to this embodiment may further contain a silane coupling agent. The silane coupling agent may be, for example, a compound having a hydrolyzable silyl group and a functional group that reacts with at least one of an epoxy compound or a curing agent. The hydrolyzable silyl group is, for example, a group having a silicon atom and 1 to 3 alkoxy groups bonded to the silicon atom. The alkoxy group bonded to the silicon atom may have, for example, 1 to 4 carbon atoms. Examples of functional groups include an amino group, an epoxy group, a mercapto group, and a (meth)acryloyl group.

Examples of silane coupling agents include 3-glycidyloxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane.

Commercially available silane coupling agents include, for example, KBM-303, KBM-402, KBM-403, KBE-402, KBE-403, KBM-4803, KBM-502, KBM-503, KBE-502, KBE-503, KBM-5103, KBM-5803, KBM-602, KBM-603, KBM-903, KBE-903, KBE-9103P, KBM-573, KBM-575, KBM-802, and KBM-803, all manufactured by Shin-Etsu Chemical Co., Ltd.

The content of the silane coupling agent in the adhesive may be 0.1 to 10 parts by mass, 0.2 to 8 parts by mass, or 0.5 to 5 parts by mass per 100 parts by mass of the total epoxy compound.

The adhesive according to this embodiment may further contain other components as needed. Examples of other components include pigments such as carbon black and titanium oxide particles, and elastomers.

The adhesive according to this embodiment can form an adhesive layer that exhibits excellent adhesion to a variety of adherends. The adhesive curing temperature may be, for example, 120 to 200°C, 140 to 180°C, or 150 to 170°C. The adhesive curing time may be, for example, 60 minutes or less, 30 minutes or less, or 20 minutes or less.

The glass transition temperature (Tg) of the cured adhesive may be 10 to 50°C, 15 to 40°C, or 20 to 35°C. From the viewpoint of improving damping characteristics, the tan δ of the cured adhesive at 20°C is preferably 0.40 or higher, more preferably 0.42 or higher, and even more preferably 0.45 or higher. From the viewpoint of improving rigidity, the storage modulus (E') of the cured adhesive at 20°C is preferably 400 MPa or higher, more preferably 500 MPa or higher, and even more preferably 600 MPa or higher.

The adhesive according to this embodiment has excellent adhesion to adherends and can form a cured product that exhibits both a high tan δ and a high modulus of elasticity at around room temperature, making it particularly suitable for use as an adhesive for connecting vehicle components.

The present disclosure will be explained in more detail below using examples. However, the present disclosure is not limited to these examples.

[Preparation of adhesive]
The epoxy compound, curing agent, silane coupling agent, inorganic filler, and organic filler in the amounts (parts by mass) shown in Table 1 were mixed together to prepare an adhesive.

Details of each raw material shown in the table are as follows:
(aromatic epoxy compounds)
EPICLON 850 (bisphenol A epoxy resin, DIC Corporation)
(Aliphatic epoxy compounds)
Denacol EX-212 (1,6-hexanediol diglycidyl ether, Nagase ChemteX Corporation)
Denacol EX-211 (Neopentyl glycol diglycidyl ether, Nagase ChemteX Corporation)
(hardening agent)
Novacure HX-3613 (capsule-type latent hardener, Asahi Kasei Corporation)
(Silane coupling agent)
KBM-403 (3-glycidyloxypropyltrimethoxysilane, Shin-Etsu Chemical Co., Ltd.)
(inorganic filler)
Hakuenka CCR-S (synthetic calcium carbonate, Shiraishi Kogyo Co., Ltd.)
(organic filler)
Kane Ace MZ-120 (core-shell rubber particles, Kaneka Corporation)

[evaluation]
The adhesive was used to carry out the following evaluations.

(Glass Transition Temperature, Tan δ, and Storage Modulus)
The adhesive was placed in a mold (size: 10 mm x 50 mm, thickness: 0.5 mm) placed on a release PET film, and after laminating the release PET film, the adhesive was heated at 160°C for 20 minutes to obtain a cured film of the adhesive. A dynamic viscoelasticity measurement test was conducted on the cured film to measure tan δ and storage modulus (E'). The peak temperature of tan δ was taken as the glass transition temperature (Tg). The dynamic viscoelasticity measurement test was conducted using a dynamic viscoelasticity measurement device (DMA+300, manufactured by Metravib) under conditions of a chuck distance of 10 mm, a frequency of 1 Hz, and a measurement temperature range of -20°C to 150°C.

(Adhesive strength)
Two steel plates (size: 25 mm x 100 mm, thickness: 1.6 mm) were prepared as adherends, and two silicone rubber sheets (size: 10 mm x 30 mm, thickness: 0.2 mm) were prepared as spacers. Silicone rubber was placed on one of the steel plates, and an adhesive was applied so that the adhesive area was 12.5 mm x 25 mm. The other steel plate was then placed on top of the other steel plate and fixed in place, and the resulting mixture was heated at 160°C for 20 minutes. The silicone rubber sheet was then removed, and an evaluation sample was obtained.

A tensile shear test was conducted using the above evaluation samples. An autograph (AGS-X, manufactured by Shimadzu Corporation) was used for the tensile shear test, and the shear adhesive strength was measured at a tensile speed of 50 mm/min at room temperature. The maximum stress on the resulting strain-stress curve was taken as the shear adhesive strength. The stress was calculated from the measured load and the adhesive area (12.5 mm x 25 mm).

Claims (5)

The epoxy resin composition contains an aromatic epoxy compound, an aliphatic epoxy compound, a curing agent, and a filler ,
the content of the aliphatic epoxy compound is 35 parts by mass or more per 100 parts by mass of the total amount of the epoxy compounds,
The adhesive , wherein the filler comprises an inorganic filler and an organic filler . 2. The adhesive according to claim 1 , wherein the aliphatic epoxy compound is an aliphatic diglycidyl ether having at least one aliphatic group selected from the group consisting of an alkylene group, an oxyalkylene group, and a cycloalkylene group. The adhesive according to claim 1 or 2, wherein the content of the inorganic filler is 60 parts by mass or more and 200 parts by mass or less relative to 100 parts by mass of the total amount of the epoxy compounds. The adhesive according to any one of claims 1 to 3, wherein the content of the organic filler is 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the total amount of the epoxy compounds. The adhesive according to any one of claims 1 to 4, further comprising a silane coupling agent.