JP2009114276A - Decomposable adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily separating an adhesive with high strength by external stimulation. <P>SOLUTION: The decomposable adhesive composition comprises an adhesive component and a liquefacient, wherein a melting point of the liquefacient is not lower than a curing temperature of the decomposable adhesive and not higher than 350&deg;C. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

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, a 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, but have been limited to 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).

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

  An object of the present invention is to provide an adhesive capable of disassembling an adhesive bonded portion at a relatively low temperature by an external stimulus when necessary, for a structure or article bonded using a high-strength adhesive. To do.

As a result of diligent research in order to overcome the problems of the prior art, the inventor of the present invention melted the melting agent by external stimulation by including a melting agent having a melting point in a specific temperature range in the adhesive. It has been found that the residual strength of the adhesive can be minimized or completely lost.
That is, the present invention provides an adhesive that can be disassembled, an adhesion method, and a disassembly method as described below.
(1) A dismantling adhesive composition comprising an adhesive component and a melting agent, wherein the melting point of the melting agent is not less than the curing temperature of the disassembling adhesive and not more than 350 ° C. Composition.
(2) The decomposable adhesive composition as described in (1) above, wherein the melting agent has a weight reduction rate at 350 ° C. of 10% or more.
(3) The dismantling adhesive composition according to (1) or (2), wherein the adhesive component is an epoxy resin.
(4) An adhesion method in which the adherend and the adherend are bonded with the disassembling adhesive composition according to any one of (1) to (3).
(5) The bonding method according to (4), wherein one adherend and the other adherend are made of different materials.
(6) A dismantling method in which the adhesion strength of the adhesion structure bonded by the method according to (4) or (5) is lost by external stimulation.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive agent which can be easily disassembled by the external stimulus defined later can provide the structure or article | item of high adhesive strength.

Hereinafter, the present invention will be described in detail with a focus on preferred embodiments thereof.
The 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-based 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, the main agent is, for example, glycidyl such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, brominated epoxy resin, etc. Linear types such as ether type epoxy resins, glycidyl esters such as glycidyl hexahydrophthalate and glycidyl dimer, glycidyl amines such as triglycidyl isocyanurate, tetraglycidyl diaminodiphenylmethane, epoxidized polybutadiene, epoxidized soybean oil Use aliphatic epoxides, alicyclic epoxides such as 3,4 epoxy-6 methylcyclohexylmethyl carboxylate, or a mixture of two or more of these. It can be.
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 novolac curing 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 the adhesive strength measurement as shown in the examples is carried out at room temperature are preferred.

  The melting agent contained in the adhesive of the present invention has a melting point not lower than the curing temperature of the adhesive and not higher than 350 ° C. If the melting point is lower than the curing temperature of the adhesive, the melting agent melts when the adhesive is cured, and thus the adhesive strength and disassembly of the adhesive may be reduced due to bleeding out or decomposition of the melting agent. Also, when the melting point is 350 ° C. or higher, it is necessary to heat the bonded structure to 350 ° C. or higher for dismantling the bonded joint, which requires a lot of energy and the adherend is thermally degraded. There is. More preferably, the melting point of the melting agent is 100 ° C. or higher and 300 ° C. or lower, more preferably 150 ° C. or higher and 250 ° C. or lower, and further preferably 200 ° C. or higher and 240 ° C. or lower. Specific examples of the melting agent include urea, biuret, guanidine nitrate, 2-biphenylcarboxylic acid, o-acetamidophenol, and the like, and two or more of these may be combined. The melting point in the present invention refers to the melting point measured using a differential scanning calorimeter (DSC).

The content of the melting agent is preferably 5 parts by weight or more and 200 parts by weight or less, and more preferably 10 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the adhesive component. If the content of the melting agent is less than 5 parts by weight, disassembly may not be imparted sufficiently, and the adhesive strength may not be reduced after heating. If the content exceeds 200 parts by weight, the viscosity of the adhesive is significantly increased, and the coating workability is improved. It may get worse.
Regarding the particle diameter of the melting agent, since the thickness of the adhesive is generally about 1 mm at the maximum, the particle diameter of the melting agent is preferably 1 mm or less. Since the coating workability of the adhesive is improved and the dispersibility of the melting agent in the adhesive component is also improved, the particle size of the melting agent is preferably 0.1 to 400 μm, more preferably 0.5 to 100 μm, 1-50 micrometers is especially preferable. In the present invention, the particle diameter means a median diameter measured using a laser diffraction particle size distribution meter.

If the melting agent reacts with the adhesive component during curing, the adhesive component may change and the adhesive strength after curing may decrease, or the melting agent may deteriorate and dismantling may decrease. Those that do not chemically react with the agent components are preferred.
The melting agent permeates the interface between the adhesive and adherend after heating and melting, and lowers or disappears the adhesive strength. Therefore, the lower viscosity after melting and the higher compatibility with the adherend penetrates the interface. Easy to dismantle.
It is preferable that the weight loss rate at 350 ° C. is 1 to 100%, particularly 10 to 100% when the melting agent is vaporized. After melting, the melting agent that has permeated the interface between the adhesive and the adherend is vaporized, so that the dismantling property at the adhesive interface can be remarkably improved. The weight reduction rate in the present invention is a value obtained using a differential thermothermal gravimetric simultaneous measurement apparatus (TG-DTA). About 5 mg of a melting agent is put in an open aluminum cell, and 15 ° C./min in an air atmosphere. Calculated from the weight loss when the temperature was raised from room temperature to 350 ° C.

In the present invention, a non-reactive diluent, a reactive diluent, a filler such as calcium carbonate, talc, alumina, etc. is added in an amount of 0 to 200 parts by weight with respect to 100 parts by weight of the adhesive component in order to adjust the fluidity of the adhesive. Preferably, 0 to 100 parts by weight can be added.
In order to impart flexibility, 0 to 200 parts by weight, preferably 0 to 100 parts by weight, of plasticizers such as monoepoxide, diepoxide and polythiol, and liquid rubber are added to 100 parts by weight of the adhesive component. May be.
The mixing order of the adhesive component and the melting agent, other fluidity adjusting component, flexibility imparting component and the like may be mixed in any order as long as the adhesive strength, dismantling property and the like of the adhesive are not impaired. Further, they may be mixed immediately before application, or some components may be mixed in advance.
The adhesive of the present invention may be used in a liquid state, 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.
The external stimulus referred to in the present invention refers to a physical stimulus such as heat and fire, and more specifically, hot air heating, infrared irradiation, high frequency heating, microwave heating, heat of chemical reaction, frictional heat, gas, etc. Heating with a fire such as a burner can be mentioned. 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 to the external stimulus, the melting agent contained in the adhesive component melts and penetrates into the interface between the adhesive and the adherend, thereby greatly reducing or eliminating the adhesive force. Can be made.

  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. Further, as a 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 FRP matrix resin. 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 time so as not to cause the quality 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. It is preferable to increase the temperature at a temperature increase rate 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 use location of the adhesive of the present invention is not particularly limited, but can be used for recycling, reuse, and rework applications. For example, metal-FRP and metal-glass can be used. It can be suitably used for bonding different materials. It can also be used for bonding different metals-metals, FRP-FRP.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.
The abbreviations of the samples used in the examples are as follows.
EP-4901: Bisphenol F type epoxy, manufactured by ADEKA Corporation, Adeka Resin EP-4901
EH-463: Modified aliphatic polyamine curing agent, manufactured by ADEKA Corporation, Adeka Hardener EH-463
o-AAP: o-acetamidophenol, melting point 210 ° C., Wako Pure Chemical Industries, Ltd. reagent 2-BPCA: 2-biphenylcarboxylic acid, melting point 114 ° C., Wako Pure Chemical Industries, Ltd. reagent GN: guanidine nitrate , Melting point 210 ° C., Wako Pure Chemical Industries, Ltd. reagent BU: Biuret, melting point 190 ° C., Wako Pure Chemical Industries, Ltd. reagent ADCA: azodicarbonamide, 225 ° C. decomposition (no melting point), Wako Pure Chemical Industries ( Co., Ltd. Reagents For each example and each comparative example, the composition shown in Table 1 was used to prepare an adhesive joined body, a tensile shear test, and a heating disassembly test by the following methods.

<Creation of bonded assembly>
According to each adhesive composition shown in Table 1, the main agent, the melting agent and the 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 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). Then, it hold | maintained in the oven of the postcure temperature of Table 1 for 1 hour, and it was made to harden | cure (postcure).

<Tensile shear test>
After the bonded assembly obtained by the above method is cooled to 25 ° C., a test piece with 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 breakage 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.

<Heating disassembly test>
The adhesive joined body obtained by the above method was cooled to 25 ° C. and then placed on a 300 ° C. hot plate, and it was visually confirmed whether or not the adhesive joined portion was disassembled. In addition, in the bonded assembly, the opposite surface of the adherend surface of one adherend (lower adherend) is in contact with the hot plate, and the other adherend (upper adherend) is not in contact with the hot plate. Place on a hot plate. By arranging in this way, a gap corresponding to the sum of the thickness (1.6 mm) of the lower adherend and the adhesive thickness is secured between the upper adherend and the hot plate. Dismantling refers to a state in which when the adhesive strength is reduced by heating, the adhesive joint is naturally removed by the weight of the upper adherend and the upper adherend is in contact with the hot plate. Even if the temperature of the lower adherend reached 290 ° C., it was determined that it was not disassembled (denoted by “x” in Table 1). The temperature of the lower adherend was measured with a surface temperature measuring thermometer, and the temperature at the time of dismantling was recorded. The results are shown in Table 1.
In the conditions of Examples 1 to 4, the adhesive strength of 10 MPa or more and the disassembling property at 200 to 230 ° C. were combined. However, Comparative Example 1 to which no melting agent was added had good adhesive strength, but did not disassemble even after the adherend reached 290 ° C. In Comparative Example 2, since the resin was cured at a temperature equal to or higher than the melting point (114 ° C.) of the melting agent, the adhesive strength was lowered, and further, it was not disassembled even after reaching 290 ° C. Further, Comparative Example 3 to which a substance that decomposes without melting (azodicarbonamide) was added and Comparative Example 4 (3 parts by weight) with a small amount of melting agent showed good adhesive strength, but reached 290 ° C. It was not demolished later.

  If the disassembling adhesive of the present invention is used, 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 (6)

A dismantling adhesive composition comprising an adhesive component and a melting agent, wherein the melting point of the melting agent is not less than the curing temperature of the disassembling adhesive and not more than 350 ° C. The disintegrating adhesive composition according to claim 1, wherein a weight reduction rate of the melting agent at 350 ° C is 10% or more. The dismountable adhesive composition according to claim 1 or 2, wherein the adhesive component is an epoxy resin. The adhesion | attachment method which adhere | attaches a to-be-adhered body and a to-be-adhered body with the dismantleable adhesive composition of any one of Claims 1-3. 5. The bonding method according to claim 4, wherein one adherend and the other adherend are made of different materials. A disassembling method in which the adhesive strength of the bonded structure bonded by the method according to claim 4 or 5 is lost by an external stimulus.