JPH0248192B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is a liquid epoxy resin adhesive with excellent adhesive properties that exhibits pseudo-curing properties by short-term heating and allows the pseudo-cured film to be easily peeled off from the base material. The present invention relates to a sexual composition. (Prior Art) Conventionally, heat-curing adhesive compositions based on liquid epoxy resins have been used for bonding metals. However, after applying the adhesive, the base material is bent and
When performing processing such as cutting, degreasing, cleaning, and acid treatment,
Adhesives tend to fall off, scatter, and contaminate the environment, work area, and processing fluids. In order to improve this drawback, West German Patent Publication No. 2002880 proposes an adhesive in which polyvinyl chloride (PVC) plastisol is added to a liquid epoxy resin composition. According to this method, a non-adhesive sheet can be obtained by heating for a short time at a temperature above the melting point of PVC. This material can develop adhesive properties by heating it to 160-180°C and melting and hardening it. Therefore, by applying the adhesive to the base material and then heating it for a short time, it becomes a non-adhesive state, i.e. It is said that the above-mentioned problems can be solved by forming a pseudo-cured product, then bending, cutting, degreasing, cleaning, acid treatment, etc. the base material. The disadvantage of this adhesive is that the hydrochloric acid gas generated during high heat treatment accelerates metal corrosion.
In the automobile industry, etc., metal parts are generally bent and joints are spot welded, and if spot welding is performed with an adhesive composition containing PVC interposed, the high heat may cause damage. It is impossible to prevent PVC from decomposing and generating hydrochloric acid gas. A liquid or paste thermosetting resin that can be pre-gelled by mixing a halogen-free powdered thermoplastic resin with an epoxy resin has been proposed (Japanese Patent Application Laid-Open No.
56-82865). Thermoplastic resins include polyamide, ethyl cellulose, polyvinyl formal, and polyvinyl butyral, which can be applied in liquid form, become dry to the touch after being heated for a short time, and do not generate corrosive gases even when treated at high temperatures. , it is said that there are no problems mentioned above. The disadvantage of this composition and method is that the pseudo-cured coating
The problem is that it is difficult to peel off from the base material, and the adhesiveness after main curing is reduced due to the presence of the thermoplastic resin. That is, in the automobile industry, there is a process of applying adhesive, performing processing such as bending and joining, and then heating for a short time to pseudo-cure, and then removing protruding and excess parts. This is done in order to prevent rust due to moisture intrusion into the cavity after the product is manufactured by filling the inner surface of the bent part such as the hemming part with adhesive and eliminating the cavity. It is processing. The protruding portion is usually removed mechanically or manually, so it must be easily peelable into a film. The composition described in JP-A No. 56-82865 does not have such characteristics and therefore poses a practical problem. Further, the adhesiveness after main curing must be sufficient for the structure, but since the thermoplastic resin does not react with the epoxy resin, there is a drawback that adding a large amount will impair the original adhesiveness. (Problems to be Solved by the Invention) In order to solve the above-mentioned drawbacks, the present inventors have conducted extensive research on various polymer compositions that can be mixed with liquid epoxy resin adhesive compositions, and have found that they do not have the above-mentioned problems. The present inventors have discovered that a composition can be obtained, and have achieved the present invention. In other words, the object of the present invention is that after coating on a base material, the base material can be subjected to processing such as bending and joining, and then can be pseudo-cured by heating for a short time, and furthermore, this cured product can be cured by heating for a short time. An object of the present invention is to provide an epoxy resin composition that is flexible, has excellent adhesive properties, and allows unnecessary parts to be easily peeled off in the form of a film. (Means for Solving the Problems) The object of the present invention is to include a liquid epoxy resin and a heat-activated curing agent for epoxy resin, and optionally add a curing accelerator, viscosity modifier, filler, pigment, etc. An epoxy resin-based thermosetting adhesive made of a liquid epoxy resin and an acrylate or methacrylate (hereinafter referred to as (meth)acrylate) powdered polymer containing 0.2% by weight or more of epoxy groups are added to the liquid epoxy resin in an amount of 10 to 100%. This is achieved by weight percent mixing. The epoxy resin used in the present invention may be any liquid resin having one or more epoxy groups in one molecule, and even a solid epoxy resin can be used after being dissolved in a liquid epoxy resin. Examples include condensates of ordinary bisphenol A and epichlorohydrin, diglycidyl ethers such as condensates of bisphenol F and epichlorohydrin, aliphatic diglycidyl ethers, alicyclic epoxides, condensates of phthalic acid derivatives and epichlorohydrin. Diglycidyl esters, hydantoin epoxy resins, novolac type epoxy resins, glycidylamine type epoxy resins and the like can be used alone or in combination of two or more types. Note that an epoxy-modified liquid acrylonitrile-butadiene copolymer can also be used in combination. The heat-activated curing agent may be a conventional curing agent that exhibits curing action when heated, such as dicyandiamide, 4,4'-diaminodiphenylsulfone, imidazole derivatives such as 2-n-pentadecyl imidazole, isophthalic acid, etc. Dihydrazide, N,N'-dialkyl urea derivative, N,N'-
Examples include dialkylthiourea derivatives, melamine, and guanamine. These are appropriately blended into the composition depending on the equivalent weight of the epoxy resin used and the curing conditions, but it is usually desirable to use 1 to 15 parts by weight per 100 parts by weight of the epoxy resin. Imidazole derivatives, N,N'-dialkyl urea derivatives, alkylaminophenol derivatives, etc. can also be used as accelerators. The amount of the curing agent and accelerator necessary and sufficient for curing can be easily determined by conducting a preliminary test. As the viscosity modifier, thickeners such as anhydrous silicic acid, hydrated silicic acid, asbestos, finely divided calcium carbonate, and bentonite, and reactive diluents such as monoepoxide can be used in the same way as in normal applications, if necessary. As the filler, calcium carbonate, talc, clay, etc. can be added according to the usual method. Colorants such as carbon can be used as pigments in the same way as in normal applications. Plasticizers such as phthalate esters and phosphate esters can also be added to give the adhesive flexibility after pseudo-curing and main curing. If a large amount of plasticizer is used, it may cause a decrease in adhesive strength or cause bleeding, so it is preferable to use one that is compatible with the epoxy resin.
A range of 0 to 80 parts by weight is suitable. The powdered reactive polymer that is the gist of the present invention is a finely powdered (meth)acrylate polymer containing at least 0.2% by weight of epoxy groups based on the polymer (hereinafter referred to as an epoxy group-containing copolymer). It is. To introduce an epoxy group into a polymer, an epoxy group-containing monomer or polymer is mixed with a (meth)acrylate monomer or polymer by any known method such as copolymerization, graft polymerization, post-treatment, or mixing. It can also be done. Examples of epoxy group-containing monomers or polymers for introducing epoxy groups include allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, glycidyl-p-vinyl benzoate, methylglycidyl itaconate, glycidyl ethyl maleate, glycidyl Monomers such as glycidyl esters of unsaturated acids such as vinyl sulfonate and glycidyl (meth)allylsulfonate, epoxy olefins such as butadiene monooxide, vinylcyclohexene monooxide, and 2-methyl-5,6-epoxyhexene, or the like; Examples include polymers obtained by polymerizing. Particularly preferred are allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate.
Monomers constituting the (meth)acrylate polymer include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, and stearyl methacrylate; alkyl acrylates such as methyl acrylate and butyl acrylate; and alkoxyalkyl (such as butoxyethyl (meth)acrylate). Examples include meth)acrylate and alkylene glycol mono(meth)acrylate. A preferred (meth)acrylate is methyl methacrylate. A method for obtaining an epoxy group-containing polymer by copolymerization will be explained. Copolymerizing at least one selected from the epoxy group-containing monomer group and at least one monomer selected from the (meth)acrylate monomer group together with other monomers as necessary in a medium, It is then separated from the medium and dried. As an example of a method for obtaining it by graft polymerization, it can be obtained by polymerizing one monomer in advance and then adding and polymerizing the other monomer.
It is also possible to sequentially polymerize two or more monomer mixtures having different ratios in advance. As an example of a method for obtaining it by post-treatment, it can be obtained by bringing an epoxy group-containing monomer into contact with a (meth)acrylate polymer and adding it. As an example of a method for obtaining by mixing, a polymer obtained by polymerizing an epoxy group-containing monomer and a (meth)acrylate polymer are mixed in a dispersion medium. The method for incorporating epoxy groups is not limited, and it is sufficient to contain 0.2% by weight or more of epoxy groups per epoxy group-containing polymer. If the epoxy group content is less than 0.2% by weight, adhesiveness will be poor. The polymer needs to have a fine particle size, with an average particle size of 50μ or less, preferably 0.1 to
A value of 5μ is desirable. If the average particle size is too large, the pseudo-curing properties of the adhesive composition will be poor, and the coating strength will be brittle. If the average particle size is too small, the powder properties will be poor, causing problems during production and mixing. Come. Emulsion polymerization, milk suspension polymerization, and suspension polymerization are preferably used to obtain an epoxy group-containing polymer having a preferred basic particle size. After the polymerization reaction, spray drying, fluidized bed drying, coagulation dehydration drying, etc. are preferably used for separation from water. Basic average particle size is 50μ
If it is below, the particles may exhibit a weak agglomeration state and have a coarser apparent particle size in order to improve powder properties. The higher the molecular weight of the epoxy group-containing polymer is, the more desirable it is, and the average molecular weight is preferably 300,000 or more. If the molecular weight is lower than this, when formed into an adhesive composition, the physical properties of the pseudo-cured film will be poor, and it will be difficult to peel off into a film when removing unnecessary parts. The epoxy group-containing polymer can be used in an amount of 10 to 100% by weight based on the liquid epoxy resin. More preferably, it can be used at 30 to 70% by weight. If the amount of the epoxy group-containing polymer used is less than 10% by weight, the pseudo-curing properties will be insufficient and, of course, it will be impossible to peel off and remove unnecessary parts.
If it is more than 100% by weight, the original epoxy properties such as heat curing performance and adhesion performance as an adhesive will be insufficient, and the viscosity of the adhesive will increase, making it difficult to apply. The epoxy group-containing polymer used in the present invention is insoluble in epoxy resin at room temperature, but easily dissolves in epoxy resin when heated to high temperature.
It is thought that it swells and absorbs liquid epoxy resin to form a film. As for the film forming temperature, a temperature of around 1 minute at 100°C and around 30 seconds at 120°C is sufficient. The main curing conditions can be appropriately set depending on the combination of the epoxy resin, curing agent, and curing accelerator used. Normally, it is preferable that the temperature is 20°C or more higher than the preheating temperature. For example, in the automobile production process,
The temperature is between 140℃ and 200℃. The epoxy group-containing polymer can be mixed with the epoxy resin using a conventional mixer. For example, a kneader, Henschel mixer, disper, planetarium mixer, etc. can be used. It may also be pulverized into fine particles using an ink roll to form a smoother paste. The mixed epoxy resin adhesive composition is applied onto the substrate to be bonded by a conventional method such as spraying, sealer gun, brushing, etc. The substrate is generally a metal, and even if antirust oil is attached to the substrate, the adhesiveness of the composition will not be impaired after the composition is fully cured. After the adhesive composition of the present invention is applied, it is subjected to processing such as bending and bonding, and
Preheating is performed at a temperature of 180°C to 180°C to achieve pseudo-curing, but heating at low temperatures and for short periods of time is desirable for production cost and efficiency reasons. If the composition of the present invention is
It has the advantage that it can be cured even with extremely short heat treatment. The pre-cured film has appropriate flexibility and strength, and after bending and joining the base materials, the excess portion can be easily peeled off into a film. This property is extremely useful in rust prevention treatment of joints in automobile outer panels. In other words, after the exterior panels of automobiles are coated with adhesive, bent, joined, etc., they are degreased and cleaned to remove the rust-preventive oil that has adhered to the metal surface, and then subjected to surface activation treatment and electrodeposition coating. However, if the adhesive is not pseudo-cured, the adhesive may leak or scatter during processes such as degreasing and cleaning, surface activation treatment, and electrocoating, which not only contaminates the work environment and the processing solution. ,
Even the original adhesiveness is lost. Furthermore, when bending and joining, excess adhesive will seep out from the bends and joints, but if this is left untreated,
It may seriously damage the appearance or interfere with the next process. In particular, since the paint sealer will be applied unevenly, it is necessary to peel off the excess portion in advance. Therefore, it is an extremely important characteristic that it can be easily removed in the form of a film during the peeling and removal process. It can be said that In addition, the epoxy group-containing polymer used in the present invention is cured by a curing agent for epoxy resin during main curing.
It reacts with the epoxy resin to form a network structure, and also exhibits adhesion to metals, so it has the advantage of not impairing its adhesion even when used in large amounts. (Effects of the Invention) As explained above, according to the present invention, after coating on a base material, the base material is subjected to processing such as bending and joining, and then pseudo-cured by heating for a short time. Moreover, this cured product is flexible and the unnecessary parts can be easily peeled off and removed in the form of a film.
An epoxy resin adhesive composition with excellent adhesive properties can be provided. (Example) The present invention will be described in more detail with reference to Examples below. In addition, parts and % in Examples and Comparative Examples
are based on weight unless otherwise specified. Examples 1 to 3, Comparative Examples 1 to 2 A liquid epoxy resin that is a condensate of bisphenol A and epichlorohydrin and has a molecular weight of about 380 (Epicoat 828 manufactured by Yuka Ciel Epoxy Co., Ltd.) 100
5 parts of dicyacydiamide, 3 parts of p-chlorophenyl-dimethylurea (Monyuron, manufactured by Chemical Service Co., Ltd.), 50 parts of heavy calcium carbonate (Whiten SB, manufactured by Shiroishi Kogyo Co., Ltd.), 20 parts of light calcium carbonate.
(Shiraishi Kogyo Co., Ltd. Shiroenka CCR),
A homogenized liquid adhesive epoxy resin composition was obtained. This is used as a standard composition. On the other hand, 5 parts of glycidyl methacrylate (epoxy compound) and 95 parts of methyl methacrylate were emulsion polymerized, and then spray-dried to produce a basic particle size of 0.2μ.
A fine powder of an epoxy group-containing polymer was obtained. The average molecular weight of this product was 1.5 million. Let's take this. After adding it to the standard composition and homogenizing it, the compositions of Examples 1 to 3 and Comparative Example 2 shown in Table 1 were prepared, and for comparison, a composition containing only the standard composition was prepared as Comparative Example 1.
The composition was applied to the surface of an iron plate to a thickness of about 2 mm, and after the iron plate surface temperature reached 120°C in a hot air oven, it was held for 1 minute to perform pseudo-curing, and then cooled to room temperature. Thereafter, the surface condition of the adhesive was observed, and the degree of pseudo-curing was determined based on the degree of stickiness using the following criteria. 5: Completely dry 4: Almost dry 3: Slightly sticky 2: Severely sticky 1: Not cured Next, by peeling from the iron plate, the peelability was evaluated according to the following criteria. 5: It has elasticity and can be easily peeled off into a film. 4: Slight stickiness remains, but can be peeled off into a film. 3: There is no elasticity and a portion remains when peeled off. 2: Although it is cured, it has strong adhesiveness and can be easily cut. 1: It cannot be peeled off because it has not become a solid. Furthermore, the adhesion performance after main curing was examined by tensile shear adhesive strength (JIS K 6850) when two iron plates were bonded together by heating at 180° C. for 20 minutes via an adhesive. The measurement results are shown in Table 1. When the epoxy group-containing polymer of the present invention is added in an amount of 10 parts or more to the epoxy resin, it exhibits good pseudo-curing properties and good peelability. Furthermore, the adhesion after main curing is also good.

[Table] Examples 4 to 9, Comparative Examples 4 to 6 According to Example 1, various polymers shown in Table 2 were synthesized and added to the standard formulation in the amounts shown in the table. A composition No. 6 was obtained, and the same test as in Example 1 was conducted. The results are also listed in Table 2. The composition of the present invention had pseudo-curing properties and peelability of the pseudo-cured product, and also had good adhesive strength after main curing.

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Claims (1)

[Claims] 1 Add an acrylate or methacrylate powder polymer containing 0.2% by weight or more of epoxy groups to an epoxy resin thermosetting adhesive containing a liquid epoxy resin and a heat-activated curing agent for epoxy resin.
An epoxy resin adhesive composition having excellent pseudo-curing properties, peeling and removability, and adhesion properties, which is characterized by being mixed with a liquid epoxy resin in an amount of 10 to 100% by weight.