JP6348317B2 - Decomposable adhesive composition - Google Patents

Description

  The present invention relates to a dismantling adhesive that allows a structure or article assembled with an adhesive to be easily disassembled at its adhesive joint.

  Adhesives, including structural adhesives, are required to have stronger adhesive strength, longer durability, and more resistant to heat resistance and temperature fluctuations, and have been developed. However, in terms of recycling in order to effectively use limited resources, it is essential to develop an adhesive that can be disassembled in order to reuse the assembled parts. A decomposable adhesive can be peeled off by some treatment after a period of use. As such an adhesive, the thermoplastic adhesive can be disassembled by heating, but once cooled, the adhesive strength is restored again. When disassembling, since it is difficult to heat only the adhesive, it is necessary to disassemble at a high atmospheric temperature. However, disassembling a bonded product that has reached a high temperature is highly dangerous.

  In order to solve this problem, as a decomposable adhesive that can be applied to thermosetting adhesives that require higher strength than thermoplasticity, the adhesive component can be made of heat such as vermiculite or thermally expandable graphite. Development of a dismantling adhesive to which an expansive inorganic substance is added is in progress. However, these decomposable adhesives have a problem that the strength does not completely become zero although the adhesive strength decreases after heating (see Patent Document 1). In addition, since the disassembly temperature is assumed to be 400 ° C. or higher, a large amount of heat energy is required. In addition, when the adherend is a resin material, the adherend itself is thermally deteriorated during heating. There was a problem that utilization was difficult (refer patent document 2).

  Development of a decomposable adhesive in which a heat-expandable resin balloon or a chemical foaming agent is added to the adhesive component is also underway. However, these dismantling adhesives cannot dismantle high-strength adhesives, and have only been dismantling adhesives having an adhesive strength of 10 MPa or less (see Patent Documents 3 and 4).

  In order to dismantle adhesives with high adhesive strength, the development of decomposable adhesives in which an organic polymer is added to the adhesive component is underway, but the adhesive strength becomes zero only under high temperature conditions of 200 ° C or higher. As with the thermoplastic adhesive, there is a problem that the disassembly of the bonded product that has reached a high temperature has a high risk (see Patent Document 5).

  Although development of oxidant-mixed adhesives that can be applied to thermosetting adhesives has also been promoted, there is a problem that in some cases, foaming is caused by the reaction between the oxidant and the curing agent, and the initial strength is lowered. (See Patent Document 6). In order to avoid this problem, a method of reacting an onium salt containing an oxidizing anion with an amine compound before mixing with the adhesive has been studied. However, it is necessary to increase the number of steps for manufacturing the adhesive. (See Patent Document 7).

  In addition, demolition adhesives with added organic cation halides are being developed, but due to high deliquescence in some areas, large-scale humidity control equipment is required during adhesive production, adhesive application, and pasting And work in a nitrogen atmosphere was necessary (see Patent Document 8).

JP 2000-204332 A Japanese Patent Application No. 2004-189856 JP 2002-187773 A JP 2003-171648 A Japanese Patent Laid-Open No. 2004-231808 International Publication No. 2007/083566 International Publication No. 2009/011421 JP 2011-42705 A

  The problem to be solved by the present invention is that a structure or article bonded using a high-strength adhesive by a simple manufacturing method can be used to form an adhesive bonded part at a relatively low temperature by external stimulation when necessary. It is to provide a decomposable adhesive composition.

As a result of intensive studies and experiments to solve the above-mentioned problems, the present inventor is able to solve the above-mentioned problems by a heat- disintegratable adhesive composition containing a halogenated inorganic onium compound in an organic adhesive component. As a result, the present invention has been completed.
That is, the present invention is as follows.
[1] A heat decomposable adhesive composition comprising (A) an organic adhesive component, and (B) a compound of an inorganic onium ion and a halogen ion.

[2] The heat decomposable adhesive composition according to [1], wherein the inorganic onium ion is a hydride of nitrogen.

[3] The heat decomposable adhesive composition according to [2], wherein the nitrogen hydride is an ammonium ion.

[4] The heat decomposable adhesive composition according to any one of [1] to [3], wherein the halogen ion is iodide ion.

[5] The heat decomposable adhesive composition according to any one of [1] to [4], wherein the (A) organic adhesive component is an epoxy resin adhesive.

  According to the present invention, the compound of inorganic onium ions and halogen ions is not reactive with organic adhesives and does not have deliquescence. Therefore, a structure or article bonded using a high-strength adhesive is used. When necessary, it is possible to easily provide an adhesive capable of disassembling the adhesive joint at a relatively low temperature by external stimulation.

Hereinafter, preferred embodiments of the present invention will be described in detail.
The organic adhesive component that can be used in the present invention is not limited in any way. However, since the gist of the present invention is to dismantle one that is difficult to disassemble, it is preferable to use a structural adhesive. A structural adhesive is "a reliable adhesive that can apply a stress that is relatively close to its maximum breaking load without breaking for a long period of time" (adhesive application technology, Nikkei Technical Library Co., Ltd., 1991) According to the classification by chemical composition (see book P99), thermosetting and alloy are good.

  Examples of adhesive components that can be used in the dismantling adhesive of the present invention include vinyl acetate resin, polyamide resin, polyurethane resin, polyester resin, urea resin, melamine resin, resorcinol resin, phenol resin, epoxy resin, polyimide resin. And an adhesive mainly composed of polybenzimidazole, acrylic (SGA), acrylic acid diester, silicone rubber, and the like. As the alloy, epoxy phenolic, epoxy polysulfide, epoxy nylon, nitrile phenolic, chloroprene phenolic vinyl phenolic, or the like, a resin obtained by modifying the above substances, or a resin in which two or more kinds of the above substances are mixed can be used. In particular, the epoxy resin adhesive is preferable because it cures without liberating by-products and has high shear strength.

  When an epoxy resin is used as the adhesive component of the present invention, examples of the main agent include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, brominated epoxy resin and the like. Glycidyl ether type epoxy resins, glycidyl esters such as hexahydrophthalic acid glycidyl ester, dimer acid glycidyl ester, triglycidyl isocyanurate, glycidyl amines such as tetraglycidyl diaminodiphenylmethane, epoxidized polybutadiene, epoxidized soybean oil, etc. Aliphatic epoxides, alicyclic epoxides such as 3,4 epoxy-6 methylcyclohexylmethyl carboxylate, or a mixture of two or more of these You can use.

Curing agents include polyaddition curing agents such as amine curing agents such as diethylenetriamine, metaxylenediamine, and dicyandiamide, acid anhydride curing agents such as phthalic anhydride and tetrahydromethylphthalic anhydride, and other phenol novolak curing agents. Agents and polymercaptan curing agents can be used. Moreover, as a catalyst type hardening | curing agent, a tertiary amine and a Lewis acid complex can be used, for example, and what mixed these 2 or more types can be used.
In the case of structural adhesives, those showing a value of 10 MPa or more when adhesive strength measurement as shown in the examples is carried out at room temperature are preferred.

  In the present specification, the inorganic onium ion is an ion generated by protonation of an inorganic hydride, such as ammonium ion, hydroxylammonium ion, hydrazinium ion, phosphonium ion, oxonium ion, sulfonium ion, dia Examples thereof include zenium ions and diazonium ions, and a mixture of two or more of these can also be used. In particular, the inorganic onium ion is preferably a hydride of nitrogen, and more preferably an ammonium ion, because it is relatively low in harmfulness to the human body and has excellent adhesive disassembly.

  Halogen is fluorine, chlorine, bromine or iodine described in Group 17 of the periodic table, and a mixture of two or more of these can also be used. As the halogen ion, iodine is particularly preferable because it is excellent in the disassembly of the adhesive.

  The content of the compound of inorganic onium ions and halogen ions is preferably 1 part by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the organic adhesive component. If it is this range, there will be no degradation of the dismantling property by too little content of the compound of an inorganic onium ion and a halogen ion, and conversely, there will be no remarkable increase in the viscosity of the adhesive due to too much content. The content of the compound of inorganic onium ions and halogen ions is more preferably 2 parts by weight or more and 50 parts by weight or less, and further preferably 3 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the adhesive component. .

  The particle size of the compound of inorganic onium ions and halogen ions is preferably 1 mm or less since the thickness of the adhesive is generally about 1 mm at the maximum. 400 μm or less is preferable, 100 μm or less is more preferable, and 10 μm or less is particularly preferable because the coating workability of the adhesive is improved and the dispersibility in the adhesive component is also improved. In the present invention, the particle diameter means a median diameter measured using a laser diffraction particle size distribution meter.

In the present invention, a non-reactive diluent, a reactive diluent, or a filler such as calcium carbonate, talc, or alumina can be added to adjust the fluidity of the adhesive.
In order to impart flexibility, a plasticizer such as monoepoxide, diepoxide, polythiol, or liquid rubber may be added.
In order to improve dismantling properties, chemical foaming agents such as thermally expandable graphite, thermally expandable resin balloons, and azodicarbonamide can also be added.

The mixing order of the compound of the adhesive component, inorganic onium ion and halogen ion, other fluidity adjusting component, flexibility imparting component, etc. is the order of mixing as long as the adhesive strength and dismantling properties of the adhesive are not impaired. May be. Moreover, you may mix immediately before application | coating, and may mix one part component previously.
The adhesive of the present invention may be used in liquid form, or may be applied to a film substrate for use in a tape form.

Since adhesiveness of the adhesive of the present invention decreases or disappears due to external stimuli, it is possible to easily disassemble an adhesive structure bonded using the adhesive.
In the present specification, “external stimulus” refers to physical stimulus such as heat and fire, and more specifically, hot air heating, infrared irradiation, high frequency heating, microwave heating, heat of chemical reaction, heat of friction. Etc., heating with a fire such as a gas burner. When the external stimulus is applied to the bonded structure bonded by the adhesive of the present invention, the temperature of the adhesive increases, and the cohesive force of the adhesive component itself and the adhesive force with the adherend decrease. In addition, when subjected to an external stimulus, the compound of inorganic onium ions and halogen ions promotes thermal decomposition of the organic adhesive and can greatly reduce or eliminate the adhesive force.

  In terms of uniformly heating a large bonded structure, there is a method of heating the structure in the internal space of the internal structure of an electric furnace, gas furnace, etc., where the outside is composed of a heat insulating material. More preferred. As for the temperature at the time of disassembly, it is an extremely important issue that a metal / FRP joined body, an FRP / FRP joined body, etc. can be disassembled in a short time below the melting point of the matrix resin of FRP. For example, when disassembling adhesive structures such as resins PPS (polyphenylene sulfide, melting point: 280 ° C.) and PEEK (polyether ether ketone, melting point: 335 ° C.) used for composite materials, On the other hand, it is important not to perform heating at a temperature equal to or higher than the melting point for a long period of time so as not to cause deterioration of the resin, and the heating temperature is preferably 350 ° C. or lower, more preferably 300 ° C. or lower.

Regarding the heating rate at the time of heating demolition, it is preferable to heat the adhesive at a high heating rate because it suppresses thermal degradation of the adherend and may give high dismantling properties. Specifically, it is preferable to raise the temperature at a rate of temperature increase of 5 ° C./min or more, more preferably 10 ° C./min or more.
In consideration of recycling of the adherend, etc., it is desirable to peel at the interface of the adherend to be recycled. For this reason, a disassembly surface can be selected by heating from the adherend side to be recycled.
The location of use of the adhesive of the present invention is not particularly limited, but can be used for recycling, reuse, and rework applications. For bonding of different materials such as metal-FRP and metal-glass. It can be used suitably. It can also be used for bonding different metals-metals, FRP-FRP.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
A widely used epoxy resin adhesive was used as the structural adhesive. The epoxy resin-based adhesive is a bisphenol F type epoxy (manufactured by ADEKA Corporation, trade name Adeka Resin EP-4901) as a main agent, and a modified aliphatic polyamine (manufactured by ADEKA Corporation, trade name Adeka Hardener EH-463) as a curing agent. )It was used.
As a compound of inorganic onium ions and halogen ions, ammonium iodide (Wako Pure Chemical Industries, Ltd.) and ammonium chloride (Wako Pure Chemical Industries, Ltd.) were used.
About each Example and each comparative example, creation of an adhesive joined body, a tensile shear test, and a heating dismantling test were performed by the following methods with the compositions shown in Table 1 below.

<Preparation of bonded assembly>
According to each adhesive composition shown in Table 1 below, the main agent, a compound of inorganic onium ions and halogen ions, and a curing agent were sufficiently mixed in this order to prepare an adhesive. As the adherend, a metal plate (made of SUS304) having a width of 25 mm, a length of 100 mm, and a thickness of 1.6 mm was used, and the wrap length was 12.5 mm. The adhesion surface was subjected to surface treatment by ultraviolet ozone treatment. The prepared adhesive was applied to the adhesive surface and pasted together, and the adhesive joint was stopped with a clip and held in a thermostatic bath at 25 ° C. for 24 hours (precure). Thereafter, it was held in an electric furnace at 120 ° C. for 1 hour and cured (post cure).

<Tensile shear test>
After the bonded assembly obtained by the above method is cooled to 25 ° C., a test piece is obtained at a tensile mode and a displacement speed of 5 mm / min using an autograph (model AGS-J, for 1 ton load cell) manufactured by Shimadzu Corporation. The maximum load until failure was measured. The tensile shear bond strength was calculated by dividing the maximum load by the area of the adhesive joint. Measurements were made on five specimens, and the average value was calculated. The measurement results are shown in Table 1 below.

<Heating disassembly test>
After the bonded assembly obtained by the above method was cooled to 25 ° C., the heating during the peeling test was carried out using an electric furnace. The test piece was put in a heating furnace at 270 ° C., heated for 30 minutes, and it was confirmed whether the bonded joint was disassembled by heating. When not dismantled, tensile shear strength was obtained under the same test conditions as above. The results are shown in Table 1 below.

  Since the decomposable adhesives of Example 1 and Example 2 do not have the deliquescent properties of the compound of inorganic onium ions and halogen ions, the adhesives can be mixed and pasted without problems in normal atmospheric conditions. did it. In addition, there was no reactivity between the compound of inorganic onium ions and halogen ions and the curing agent, and no event that would lead to a decrease in strength such as foaming was observed.

  Under the conditions of Example 1, it has a tensile shear strength of 10 MPa or more, but it was found that the adhesive strength was reduced to about 1 MPa by heating at 270 ° C. for 30 minutes. Under the conditions of Example 2, it had a tensile shear strength of 10 MPa or more, but the adhesive strength disappeared during heating at 270 ° C., and the adhesive joint was disassembled. However, although the adhesive of Comparative Example 1 containing no compound of inorganic onium ions and halogen ions has an adhesive strength of 10 MPa or more, no decrease in tensile shear strength was observed after heating at 270 ° C. for 30 minutes.

  By using the disassembling adhesive of the present invention, a high-strength adhesive can be easily disassembled. Therefore, the adhesive of the present invention is useful for recycling, reuse, and rework applications, and can be suitably used for bonding different materials such as metal-FRP and metal-glass.

Claims (5)

A heat decomposable adhesive composition comprising (A) an organic adhesive component, and (B) a compound of an inorganic onium ion and a halogen ion. The heat decomposable adhesive composition according to claim 1, wherein the inorganic onium ion is a hydride of nitrogen. The heat decomposable adhesive composition according to claim 2, wherein the nitrogen hydride is an ammonium ion. The heat decomposable adhesive composition according to any one of claims 1 to 3, wherein the halogen ion is an iodide ion. The heat decomposable adhesive composition according to any one of claims 1 to 4, wherein the (A) organic adhesive component is an epoxy resin adhesive.