JPH0341181A - Reactive hot-melt composition - Google Patents

Abstract

PURPOSE:To improve the stability of viscosity during coating and the adhesive properties to an oily surface of a steel plate by compounding an epoxy resin encapsulated in specific capsules, a latent curative, and a thermoplastic elastomer. CONSTITUTION:A reactive hot-melt compsn. which is applied at the coating temp. at which is softens, cures when heated to a temp. higher than the coating temp., and has a viscosity (40 deg.C) of 5000P or higher is obtd. by compounding 100 pts.wt. epoxy resin (e.g. a bisphenol-epichlorohydrin type epoxy resin) encapsulated in capsules which do not break at the coating temp. but melt to release the contents at a temp. higher than the coating temp. (e.g. capsules made of an acrylic resin); 5-50 pts.wt. latent curative comprising e.g. a nitrogen compd.., acid anhydride, or metal salt which is stable at room temp. and decomposes to become active at a higher temp. (e.g. dicyandiamide); 50-100 pts.wt. thermoplastic elastomer which does not degrade the adhesive properties of the epoxy resin; and a reactive diluent, a filler, etc., as required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a reactive hot melt composition that can be used as an adhesive having sealing properties in sheet metal processing processes such as automobile production lines.

[Prior Art] Conventionally, adhesives used on automobile production lines, particularly in the hemming parts of car bodies, are applied to steel plates coated with anti-corrosion oil, and then subjected to a washing process and an electrodeposition coating process. Baking is a heat hardening process. The adhesive used here is often in the form of a paste, which tends to cause problems such as it spilling out of the bonded area or scattering due to drought during the degreasing and cleaning process of anti-corrosive oil or showering with cleaning fluid. Therefore, we use a reactive hot-melt adhesive that is applied hot, thickens after being left to cool, and withstands showers, does not scatter in the shower, and hardens during post-process baking to form a strong bond. is being considered.

As a reactive type, JP-A-61-18187
No. 0 discloses a one-component reactive hot melt comprising an epoxy resin, a reactive diluent, nitrile rubber, and a latent curing agent. Furthermore, JP-A-62-1774@ discloses a hot-melt adhesive containing a copolymer having a polyisoprene block or a polybutadiene block having styrene blocks at both ends, an epoxy resin, and a room-temperature curing agent. be. Furthermore, JP-A-64-1428
Publication No. 7 discloses a reactive hot-melt adhesive containing a crystalline urethane prepolymer having a structure in which a polyester skeleton and a polybutadiene skeleton are bonded by a urethane bond, and in which an isocyanate group remains at the end of the molecule. be.

In addition, when it is not possible to immediately cure the adherend to which the adhesive has been applied, heating it for a short time above the melting point of the thermoplastic resin contained in the adhesive will gel it and form a non-adhesive film after cooling. There are known thermosetting adhesives that form pre-gels and improve workability. For example, JP-A-62-
Publication No. 252491 discloses an adhesive using a microencapsulated thermoplastic resin in which the surface of the thermoplastic resin is coated with paraffin wax, stearic acid, stearic acid amide, stearyl alcohol, etc. that are insoluble in epoxy resin at room temperature. An epoxy resin thermosetting adhesive containing 3 to 50% by weight of the epoxy resin is disclosed.

[Problems to be Solved by the Invention] The above-mentioned epoxy resin-based hot melt adhesive is heated to lower the viscosity and applied with an applicator in order to make it easier to apply to the adherend. It has problems with viscosity stability, and gels in the applicator, making long-term continuous application difficult. Further, urethane-based hot melt adhesives are not preferred because they do not adhere well to oil-surface steel plates after being heated and hardened. Therefore, these adhesives have not yet been applied in this field. Furthermore, in the case of a pregelling adhesive, the heating temperature for pregelling is as high as 150°C, which is the melting point of the resin, and is close to the curing temperature of the adhesive, 180°C, making it difficult to control the gelling state.

The present invention was developed in view of the above circumstances, and it has excellent viscosity stability during coating, does not ooze out or scatter during the degreasing and cleaning process before curing, and has excellent adhesion to oil-surfaced steel plates. The objective is to create a hot melt composition.

[Means for Solving the Problems] The reactive hot melt composition of the present invention has a reactive property that is heated to a coating temperature, softened, applied to an adherend, and cured by being heated to a temperature higher than the coating temperature. 5 to 50 parts by weight of a latent curing agent per 100 parts by weight of an encapsulated epoxy resin, which is a hot melt composition and is made of an epoxy resin encapsulated in capsules that does not melt at the application temperature but melts at a temperature higher than the application temperature. It is characterized by containing 50 to 100 parts by weight of thermoplastic elastomer.

This reactive hot-melt composition is heated to the application temperature, softened, and applied to the adherend, and cured at a temperature higher than the application temperature, making it easier to mix the ingredients and apply it to the adherend. In order to improve viscosity stability and shower resistance at high temperatures, it is formulated in the above ratio.

The viscosity of this reactive hot melt composition is 50°C at 40°C.
00 poise or more, preferably 10,000 poise or more, and 6,000 poise or less, preferably 3,000 poise or less at 80°C
It is desirable that it is less than Boise. That is, since the temperature of the shower liquid is around 40'C, in order to exhibit hot shower properties, if it has a viscosity of 5000 poise or more at 40'C, the reactive hot melt composition before curing will not ooze out. , can prevent it from scattering. On the other hand, since the application of this reactive hot melt composition is carried out at around 80'C, if the viscosity at this time is 6000 poise or less, it can be applied from the discharge port of the applicator without any trouble.

The loss of thermoplastic elastomer in this reactive hot null composition is 50 to 100 parts by weight per 100 parts by weight of encapsulated epoxy resin. If it is less than 50 parts by weight, the dischargeability of the composition will decrease and the reactive hot melt composition will not be able to be mixed uniformly, which is not preferable. 10
If it exceeds 0 parts by weight, the melt viscosity increases and the dischargeability decreases, which is not preferable. The amount of latent curing agent is 5 to 50 parts by weight. If the amount is less than 5 weight, the epoxy resin cannot be sufficiently cured, which is not preferable. Moreover, if it exceeds 50 parts by weight, storage stability decreases, which is not preferable.

As mentioned above, this reactive hot melt composition is composed mainly of a one-component epoxy resin. However, the epoxy resin is coated with a capsule to prevent it from reacting and gelling at the temperature during application. The curing agent is also stable at room temperature, but contains a latent type that decomposes and becomes active at high temperatures. As a result, the baked electrodeposition coating is hardened during the process and exhibits adhesive strength. In addition, a reactive diluent may be added for the purpose of improving the mixability of the reactive hot melt composition and adjusting the adhesiveness, viscosity, and coating properties. The amount of this reactive diluent is 30 to 120.
A range of parts by weight is preferred to achieve clearing objectives.

During the process, the reactive hot melt composition may be retained in the applicator due to work interruptions, holidays, etc. Therefore, in order to prevent abnormal viscosity and gelation, the reactive hot melt composition of the present invention has storage stability that does not increase viscosity at the temperature at which it is applied.

As the encapsulated epoxy resin, encapsulated products such as epibis type epoxy resin obtained by condensation of bisphenol and epichlorohydrin, novolac type epoxy resin, and elastomer-modified epoxy resin are used. As the material for forming the capsule, acrylic resin, methacrylic resin, or the like is used, which does not destroy the capsule at the coating temperature and can melt at a temperature higher than the coating temperature to release the contents of the capsule.

Examples of latent curing agents include nitrogen compounds, acid anhydrides, and metal salts that are stable at room temperature and become active by decomposing at high temperatures. Nitrogen compounds include urea, thiourea, carbamide,
Hydrazide compounds are used, specifically dicyandiamide, 3-(p-chlorophenyl>-1,1-dimethylurea, 2,4-bis(N,N-dimethylcarbamide)toluene, and acid anhydrides. , phthalic anhydride, maleic anhydride, dodecylsuccinic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, dichlorosuccinic anhydride, benzophenonetetracarboxylic anhydride, chloredicic anhydride, imidazole compound: 2 -methylimidazole, 2-ethyl-4
-Methylimidacil, 2-phenylimidazole, 2-
Undecylimidazole, 2-heptadecyl imidazole, 2-ethylimidazole, 2-isopropylimidazole, 2.4 dimethylimidazole, 3.4 dimethylimidazole, 2-phenyl-4-methylimidazole, 2-methylimidacillin, 2- Ethyl-4-ethylimidacilline, 2-phenylimidacilline, 2-undecylimidacilline, 2-heptadecylimidacillin, 2-
Ethylimidacillin, 2-isopropylimidacillin,
2.4-dimethylimidacyline, 2-phenyl-4-methylimidacyline, and metal salts include lead octylate, zinc octylate, and the like.

Any thermoplastic elastomer may be used as long as it does not reduce the adhesive performance of the epoxy resin. For example, polyolefin elastomastyrene, which is a block polymer obtained from ethylene, propylene, isoprene, butadiene, isobutyne, etc., polystyrene elastomer made of butadiene, isoprene, hydrogenated butadiene, syndiotactic-1,2-polybutadiene, and amorphous Polybutadiene elastomer, which is a block polymer of polybutadiene, polyester elastomer made of aromatic dibasic acid, linear aliphatic diol, and polyalkylene ether glycol, polyurethane elastomer obtained from diisocyanate, polyester diol or polyether diol, and glycols. ], a polyisoprene elastomer which is a block copolymer of 4-polyisoprene and amorphous polyisoprene, and a polyamide elastomer which consists of a polyether or polyester block and a polyamide block. Particularly preferred are polyester elastomers.

Reactive diluents include compounds having at least one glycidyl ether group at the end, such as diglycidyl ether of 1.6 hexanediol, diglycidyl ether of resorcinol, p-tert-butylphenylglycidyl ether, cresyl glycidyl ether, and neopentyl. diglycidyl ether of glycol, triglycidyl ether of triglycidyl ether of trimethylolethane, triglycidyl-p-aminophenol, N,N--diglycidyl 72-one, N,
Examples include N,N-,N-tetraglycidyl m-xylylenediamine.

Additionally, commonly used fillers can also be added to this composition. Examples of fillers include various fillers such as rhusium carbonate, quartz powder, gypsum, kaolin, clay, mica, tar, dolomite, alumina, hydrated alumina, zircon, titanium compounds, molybdenum compounds, and antimony compounds. Can be used. In order to particularly improve spot weldability, iron powder, aluminum powder, silver powder stainless steel powder, copper powder, carbon powder, alumina fiber, stainless steel fiber, and carbon fiber may be used.

This reactive hot-melt composition is applied to an adherend at about 80° C. and is thermally cured at about 140° C. or higher to exhibit adhesive strength.

[Example] Hereinafter, this will be explained in detail using examples.

Encapsulated epoxy resin, latent curing agent, thermoplastic elastomer, and reactive diluent are blended in the proportions shown in the table, heated and mixed at 120°C using a kneader, and this mixture is extruded using an extruder to produce a hot melt VJ material. Formed.

Matsumoto Microsphere-EP (manufactured by Matsumoto Yushi Seiyaku Aji) was used as the encapsulating epoxy resin, and DICY (dicyandiamide) and DCMU (3- (
p-chlorophenyl〉-1,1-dimethylurea), S
D port (sepatic acid dihydrazide), polyester elastomer Vylon 50 as thermoplastic elastomer
0 (manufactured by Toyobo ■), ED503 as a reactive diluent
(manufactured by Asahi Denka@) was used.

(Evaluation) Storage stability was determined by maintaining the temperature at 80°C and examining the period until gel formation.

The discharge property was determined by examining the discharge amount of the hot melt material at 80° C. using a bulk meter. Furthermore, the viscosity at 80℃ is SO
Measured with a D viscometer. The results are shown in the table.

Shower resistance is determined by applying hot melt material to a designated signboard and applying 40'C hot water at 3K from a distance of 30cm.
It was sprayed at a pressure of g/crA, and the presence or absence of bulging of the applied material was examined. Furthermore, the viscosity at 40°C was measured using an SOD viscometer.

The shear strength, which indicates adhesive strength, was measured by autography after applying a hot melt material to a steel plate and curing it (180°C x 30 minutes).The results are shown in the table.

NO within the composition range of the present invention as shown in the table.

1 to 5 all show good results. Nao N0.

No. 5 has slightly poor shower resistance, but this is because the viscosity at 40° C. is 4,300 poise, which is slightly lower than the preferred viscosity of 5,000 poise, due to too much reactive diluent. No. 1 with few stars for thermoplastic elastomer. No. 6 could not be kneaded uniformly during blending, and the dischargeability was poor, making it impossible to measure the viscosity.

When NBR rubber, which has good compatibility with Epivis-type solid epoxy, is used instead of thermoplastic elastomer and a filler is added to the coating, No. 7.8 has storage stability at 80°C (viscosity stability at the time of application). properties) It gels within one day and cannot be used stably for a long period of time. Especially solid rubber NB
If R is not added, the shower resistance will be significantly reduced.

[Operations and Effects of the Invention] The reactive hot melt composition of the present invention is composed of a one-component epoxy adhesive blended with a thermoplastic elastomer, and the epoxy resin is encapsulated so that it does not come in contact with a curing agent. Since the coating is completely free of viscosity, it maintains viscosity stability at high temperatures and has excellent storage stability, with no curing reaction occurring during heating when applied to adherends. Therefore, during storage and application, the powdered encapsulated epoxy resin and latent curing agent are in a fractional state in the thermoplastic elastomer and can be easily maintained within a predetermined viscosity range. In addition, since the solid powder encapsulated epoxy resin and latent curing agent are held in the highly viscous thermoplastic elastomer, problems such as seepage and scattering do not occur at shower temperatures. By heating the capsule to a temperature higher than the coating temperature, the capsule melts, and the epoxy resin inside reacts with the curing agent to form a strong cured product that adhesively seals the adherend.

Claims (1)

[Claims] (1) A reactive hot melt composition that is applied to an adherend in a softened state by being heated to a coating temperature and cured by being heated to a temperature higher than the coating temperature, which does not melt at the coating temperature and is applied to the adherend. 5 parts by weight of a latent curing agent for 100 parts by weight of an encapsulated epoxy resin made of an epoxy resin encapsulated in a capsule that melts at a temperature higher than
50 parts by weight of a thermoplastic elastomer and 50 to 100 parts by weight of a thermoplastic elastomer.