JPH04335081A - Epoxy resin adhesive composition - Google Patents

Abstract

PURPOSE:To provide the title composition which enables accurate positioning of joining members when they are temporarily fixed, becomes non-tacky and reveals excellent bonding characteristics when cured, and is excellent in storage stability. CONSTITUTION:The title composition contains an epoxy resin that is liquid at ordinary temperature, an adduct of an epoxy compound with an imidazole compound, and a thermoplastic resin having a weight-average molecular weight of 2,000 to 30,000 and has a tensile shear strength of 0.3kg/cm<2> or higher before curing and that of 60kg/cm<2> or higher after curing.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention relates to an epoxy resin adhesive composition, and more specifically, when uncured, it can be temporarily bonded and accurately positioned, and after curing, it is non-stick. An object of the present invention is to provide an epoxy resin adhesive composition that becomes sticky and exhibits strong adhesive strength. [0002] Epoxy resins have excellent electrical insulation, heat resistance, and adhesive properties, and are used as adhesive compositions in liquid, paste, and sheet forms, such as in the automobile and electronic industries. It is widely used in a wide range of fields. [0003] Heat-curable epoxy resin adhesive compositions that have been commonly used include two-component adhesive compositions in which a main ingredient and a curing agent are mixed before use, boron trifluoride amine complexes, dicyandiamide, organic There are one-component types that use latent curing agents such as hydrazide and imidazole compounds, and hot-melt types that do not require a heat curing process. [0004] Problems to be Solved by the Invention However, the above 2
With the liquid type, it is possible to vary the reaction rate, but there are issues with the amount of mixture of the base agent and curing agent and the pot life, and production efficiency may decrease if large quantities are used. be. In addition, in the case of one-component types, there is a problem that those with excellent storage stability generally take a long curing time, and those that can be cured at relatively low temperatures have poor storage stability. [0005] On the other hand, when using an epoxy resin adhesive composition, a method is often adopted in which the adhesion site is positioned and then adhered, that is, the so-called temporary adhesion is followed by curing and final adhesion. Appropriate adhesive strength is required. As a method to solve this problem, it is preferable to use an adhesive composition that has a high viscosity at room temperature or is semi-solid. However, dispenser application using a nozzle is suitable for applying the adhesive to a desired position, and the above-mentioned high viscosity or semi-solid compositions have the drawback of being difficult to apply. In addition, in the case of dispenser application, the liquid reservoir is usually heated to perform the work, but conventional adhesive compositions have problems with stability during heating, and are not sufficiently satisfactory for practical use. It wasn't. [Means for Solving the Problems] Therefore, the present inventors solved the above-mentioned problems of conventional epoxy resin adhesives, and
The present invention was completed as a result of extensive research aimed at obtaining an adhesive composition that can be easily positioned accurately during temporary bonding, becomes non-stick upon curing, and exhibits excellent adhesive properties. reached. That is, the epoxy resin adhesive composition of the present invention comprises (A) an epoxy resin that is liquid at room temperature, (B) an adduct of an epoxy compound and an imidazole compound, and (C) a weight average molecular weight of 2,000 to 30,000. It is characterized by containing a thermoplastic resin and having an uncured tensile shear strength (according to JIS-K6850) of 0.3 kg/cm2 or more. The epoxy resin as component (A) used in the present invention is not particularly limited as long as it is liquid at room temperature, but usually has an epoxy equivalent of 100 to 700, preferably 100 to 700.
About 300 are used. Moreover, the amount of epoxy groups in one molecule is preferably two or more on average. Examples of such epoxy resins include bisphenol type epoxy resins such as bisphenol A type and bisphenol F type, cycloaliphatic epoxy resins, hydantoin type epoxy resins, novolak type epoxy resins, glycidyl type epoxy resins, and polyalkylene glycol type epoxy resins. Examples include resins, and these can be used alone or in combination of two or more. Among these, bisphenol A type epoxy resin is preferably used from the viewpoint of workability, reactivity, and adhesiveness. Note that an epoxy resin that is solid at room temperature may be optionally mixed as long as it does not impede the properties of the epoxy resin adhesive composition of the present invention and does not cause an extreme increase in solution viscosity. can. [0009] The adduct of an epoxy compound and an imidazole compound as component (B) in the composition of the present invention is
This is a curing agent for curing the epoxy resin as the component (A), and is blended in an amount of 1 to 12 parts by weight per 100 parts by weight of the epoxy resin as the component (A). If the amount is less than 1 part by weight, the storage stability will be excellent, but the curing speed during heating will be slow, and if the amount exceeds 12 parts by weight, the storage stability will be poor. Epoxy compounds for forming such adducts include:
It may be a monoepoxy compound or a polyepoxy compound,
Examples of the monoepoxy compound include butyl glycidyl ether, hexyl glycidyl ether, phenyl glycidyl ether, p-xyl glycidyl ether, glycidyl acetate, glycidyl butyrate, glycidyl hexoate, glycidyl benzoate, and the like. Further, examples of the polyepoxy compound include a glycidyl ether type epoxy resin of bisphenol A, a glycidyl ether type epoxy resin of phenol novolak, and the like. The above epoxy compounds can be used alone or in combination of two or more. In the present invention, among the above-mentioned epoxy compounds, polyepoxy compounds having a large amount of functional groups are preferably used from the viewpoint of curing reactivity. On the other hand, examples of imidazole compounds for forming adducts include imidazole and 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-dodecylimidazole, 2-
Examples include 2-substituted imidazoles such as ethyl-4-methylimidazole and 2-phenylimidazole. In addition, the imidazole compound in the present invention includes a salt of the above imidazole compound and a carboxylic acid such as lactic acid, acetic acid, salicylic acid, benzoic acid, adipic acid, phthalic acid, citric acid, succinic acid, tartaric acid, maleic acid, trimellitic acid, etc. can also be used for adduct formation. The reaction ratio of the above epoxy compound and imidazole compound to form the adduct as component (B) is usually 0.8 to 1.5 epoxy groups per active hydrogen of the imidazole compound, Preferably 1:1.2~
Adjust so that the ratio is 1:1.5. The addition reaction may be carried out without a solvent, but the imidazole compound is used in an organic solvent that is inert to the epoxy resin, such as an aromatic organic solvent such as toluene or xylene, or a ketone organic solvent such as methyl ethyl ketone or methyl isobutyl ketone. When the epoxy compound is dropped into a solution in which the epoxy compound is dissolved, the reaction occurs gradually, the heat of reaction is removed, and the viscosity is reduced, which is preferable. In this case, it is preferable to remove the organic solvent after the reaction is completed, cool it, and then grind it to an appropriate particle size before use. The adhesive composition of the present invention contains a specific curing agent as the component (B), and for the purpose of improving storage stability, a compound having an isocyanate group is added to 100 parts by weight of the epoxy compound. It is preferable to mix it in a range of about 0.1 to 10 parts by weight. Examples of such compounds include monoisocyanate compounds such as phenyl isocyanate and tolyl isocyanate, tetramethylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isopropylidenecyclohexyl isocyanate, lysine isocyanate, tolylene diisocyanate and trimethylolpropane. Examples thereof include polyethylene glycol, an adduct with polypropylene glycol, a prepolymer of hexamethylene diisocyanate and polyethylene adipate, and among these, polyisocyanates are preferably used from the viewpoint of reactivity. In addition, in order to shorten the curing time during heating, aromatic amines such as dicyandiamide, m-phenylenediamine, p,p'-bis-(aminophenyl)methane, and phenol, which are known as curing agents for epoxy resins, are used. A curing agent such as a resin, melamine resin, or urea resin can also be blended within a range that does not impair the storage stability of the adhesive composition of the present invention. Furthermore, if the above-mentioned component (B) alone is not sufficient for curing and requires a higher heating temperature or a longer curing time, a commonly used curing accelerator may be used as long as the storage stability is not impaired. It is preferable to add an agent. Preferred curing accelerators include, for example, alkyl-substituted guanidine-based, 3-substituted phenyl-1,1-dimethylurea-based,
Examples of curing accelerators include imidazole-based, imidazoline-based, tertiary amine-based, monoaminopyridine-based, and amineimide-based curing accelerators. The preferred amount is 10 parts by weight or less, preferably 2 to 6 parts by weight, based on 100 parts by weight of the epoxy resin as component (A). [0015] The thermoplastic resin blended as component (C) in the adhesive composition of the present invention imparts tackiness to the epoxy resin adhesive composition of the present invention and allows accurate temporary bonding. It is a component that enables accurate positioning, and has a weight average molecular weight of 2,000 to 2,000 to maintain adhesiveness during temporary fixing.
30,000 will be adopted. [0016] As such thermoplastic resins, for example, polyester resins, polyurethane resins, phenoxy resins, acrylic resins, etc. can be used singly or in combination of two or more kinds, and preferably saturated polyester resins,
In particular, it is desirable to use a saturated polyester resin having a weight average molecular weight of 10,000 to 20,000. From the viewpoint of adhesiveness, these thermoplastic resins are contained in an amount of 5 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the epoxy resin as the component (A). The epoxy resin adhesive composition of the present invention has the above-mentioned structure, but may also contain silica, clay, gypsum, calcium carbonate, barium sulfate, quartz powder, glass fiber, kaolin, mica, alumina, etc. , various fillers such as hydrated alumina, aluminum hydroxide, talc, dolomite, zircon, titanium compounds, molybdenum compounds, and antimony compounds.The surface of these fillers is coated with a silane cup to prevent stringing during application. A filler surface-treated with a coupling agent such as a ring agent, a titanate coupling agent, or an aluminum chelate coupling agent, especially surface-treated bentonite, is preferable, and other additives such as pigments, anti-aging agents, and other optional additives are also preferred. It can be blended as appropriate depending on the purpose and use. Usually, the blending amount is 3 to 30 parts by weight, preferably 10 to 20 parts by weight, per 100 parts by weight of the epoxy resin as component (A). If the amount is less than 3 parts by weight, the adhesive strength in the uncured state may not be sufficient and accurate positioning may not be possible during temporary bonding. Furthermore, if the amount exceeds 30 parts by weight, the viscosity becomes too high and there is a risk that the workability of coating onto joining members, particularly the discharging properties during nozzle-type dispenser coating, may deteriorate. The epoxy resin adhesive composition of the present invention contains the above-mentioned components, and is applied to joining members in an uncured state and temporarily bonded for accurate positioning. Considering the coating workability at this time, it is preferable to adjust the viscosity at 40 to 70°C to about 500 to 2500 poise, and the composition of the present invention has an uncured tensile shear strength (
JIS-K6850, adherend: Fe/Fe) is 0.3k
g/cm2 or more, preferably 0.5 to 1 kg/cm2
has been adjusted to the range of After temporary fixing in this manner, the composition of the present invention is heated and cured to make it non-adhesive, thereby completing the adhesion. The tensile shear strength (JIS-K6850, adherend: Fe/Fe) when adhesion is completed (hardening is completed) is 6
0 kg/cm2 or more, strong adhesion is achieved. EXAMPLES The epoxy resin adhesive composition of the present invention will be specifically explained below, but various modifications can be made without departing from the technical idea of the present invention. In addition, hereinafter, parts in the text mean parts by weight. Examples and Comparative Examples According to the formulations shown in Tables 1 to 3, an epoxy resin as component (A) and a saturated polyester resin as component (C) were heated and melted at 120 to 150°C, and then (B)
A curing agent, a curing accelerator, and a filler as components were mixed at room temperature using a three-roll roll to obtain epoxy resin adhesive compositions of each example and comparative example. The components used in the Examples and Comparative Examples are as follows. <Examples 1 to 4 and Comparative Examples 1 to 7> (A) Component: Bisphenol A epoxy resin (weight average molecular weight approximately 380, epoxy equivalent approximately 190, viscosity 125
Poise/25℃) (B) Component: Latent curing agent, trade name "Novacure HX-"
3613'' (manufactured by Asahi Kasei Industries, Ltd.) (C) Component: Saturated polyester resin consisting of (sebacic acid + terephthalic acid)/ethylene glycol (sebacic acid: terephthalic acid = 45:55 mol) Curing accelerator: dicyandiamide (however, comparative example 4 only 2
-Ethyl-4-methylimidazole was blended. ) Filler: Organic coupling agent treated bentonite (however,
Only Comparative Example 5 contained untreated bentonite. )00
23] <Examples 5-6> (A) Component: Bisphenol A type epoxy resin (weight average molecular weight approximately 380, epoxy equivalent approximately 190, viscosity 125
Poise/25℃) (B) Component: Latent curing agent, trade name "Novacure HX-"
3742'' (manufactured by Asahi Kasei Industries, Ltd.) (C) Component: Saturated polyester resin consisting of (sebacic acid + terephthalic acid)/adipic acid = 100/70-80 neopentyl glycol/ethylene glycol = 81/100 [0024] As above The properties of each of the epoxy resin adhesive compositions obtained were measured and evaluated using the methods described below, and the results are also listed in each table. Note that the curing conditions were 150° C. for 30 minutes. <Gelification time> Each adhesive composition was placed on a hot plate heated to 150° C., and the time until stringiness disappeared was measured. <Tensile shear strength> According to JIS-K6850, a steel plate (SPCC; 100×25×1
．． 6 tmm), the adhesive area was 25 x 12.5 mm (thickness 150 μm), and the tensile shear strength after curing was measured at a tensile rate of 5 mm/min. <Adhesive strength before curing> In the same manner as the measurement of the tensile shear strength described above, the tensile shear strength of the composition before curing (uncured) on the same steel plate was measured. The measurement conditions were as follows: bonding with an adhesive area of 25 x 12.5 mm (thickness: 100 μm), and measuring the tensile shear strength at a tensile rate of 50 mm/min. <Storage stability> 60°C using a B-type viscometer
The change in viscosity over time was measured. The storage stability was determined by reading the viscosity at 5 rotations and measuring the time it took for the viscosity to become at least twice the initial viscosity. <Stringability> Judgment was made based on the following criteria using a thixotropy ratio determined from the ratio of viscosity at 50 and 5 rotations using a B-type viscometer at a temperature similar to the coating temperature. ○...Thixotropy ratio is 3 or more. ×...Thixotropy ratio is 3 or less. <Dischargeability> When each adhesive composition was discharged under the following conditions, it was determined whether or not it was dischargeable. Heating temperature: 60℃, discharge pressure: 3kg/cm2 (or 4kg/cm2), needle inner diameter: 0.5mm,
Needle length: 12mm [Table 1] [Table 2]
*: Unit kg
/cm2 [Table 3] [Effects of the Invention] Since the epoxy resin adhesive composition of the present invention has the above-mentioned structure, it has excellent temporary adhesion when uncured and can be used as a bonding member. This enables precise positioning of
Moreover, it has high adhesive strength after heat curing, has particularly appropriate viscosity, and has excellent storage stability.

Claims (2)

[Claims] Claim 1: (A) an epoxy resin that is liquid at room temperature, (
B) adduct of an epoxy compound and an imidazole compound,
(C) contains a thermoplastic resin with a weight average molecular weight of 2000 to 30000, and has tensile shear strength (JIS-K6
850) is 0.3 kg/cm2 or more. Claim 2: Tensile shear strength (according to JIS-K6850) when cured and non-adhesive is 60 kg/cm
The epoxy resin adhesive composition according to claim 1, wherein the epoxy resin adhesive composition is 2 or more.