JP4826729B2 - Heat-expandable sheet adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sheetlike adhesive composition which is used when an adherend has unevenness, warpage, distortion, low dimensional accuracy or processing precision of adherend or a gap is formed between mutual adherends and in which a sheetlike adhesive is expanded by heating and is cured while filling in a gap to develop excellent adhesiveness. <P>SOLUTION: The thermally expandable adhesive composition is obtained by forming a component composed of (a) a film-forming resin solid at a normal temperature, (b) an epoxy resin liquid or semisolid at a normal temperature, (c) a latent curing agent, (d) a thermally expandable capsule and (e) lubricant fine particle powder into a film. The preferable mixing amount is 50-180 parts wt. of the component (a), 1-50 parts wt. of the component (c) based on the 100 parts wt. of the component (b) and 0.3-20 wt.% of the component (d) based on the total of the composition and 3-30 wt.% of the component (e) based on the total of the composition. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a gap filling adhesive sheet composition, which foams and expands when heated and fills an interlayer (gap) of the adherend to adhere the adherend.

  Conventionally, adhesives are used in various places. The adhesive can be bonded by being cured or solidified between the layers of the adherend. Usually, adherends are often close to each other such as flat surfaces, but the adherend surface has relatively deep irregularities, is porous, and the adherend itself is warped or distorted. There are cases where the adherend is not uniform. Also, when connecting pipes, inserting dowels into dowel holes, fitting shafts with bearings, etc., if the dimensional accuracy and processing accuracy of the members are low, ) May increase. In such a case, if the adhesive is completely filled in the gap between the adherends, sufficient adhesive strength can be exhibited, but if the filling is insufficient, the adhesive area may be reduced and the adhesive strength may be reduced. There is.

  In such a place, thickly apply the adhesive on the surface of the adherend in advance, pour the liquid adhesive into the gap after adhering the adherend, infiltrate, or use a fine nozzle such as an injection needle to form a liquid adhesive Generally, a method of filling the gap in the gap is taken.

  However, since the liquid adhesive is in a liquid state before it is cured and solidified, it flows before curing, and there are also problems such as flowing out and sticking out of the bonded part. Accurate control was difficult. In particular, when a heat-curable adhesive such as an acrylic resin or an epoxy resin is used, the viscosity is lowered by heating, and it tends to sag. When the liquid adhesive drips, not only the adherend and the work periphery are contaminated, but also the adhesive strength decreases as a result of the decrease in the bonding area, and in the worst case, the liquid does not adhere. For this reason, the adhesive must be held by using a jig such as an enclosure or a wall that prevents the liquid adhesive from flowing down in addition to the bonded portion, and the work is complicated. Therefore, it is difficult to adhere an adherend having a gap formed in advance using a normal liquid adhesive.

  In addition, when the diameter of the hole is larger than the diameter of the shaft in a place where the shaft is fixedly bonded to the hole, it is possible to bond by filling the gap generated from these members with an adhesive, but the center of the shaft If the center of the hole is not aligned, it will be eccentric and cause a problem. Especially in the case of rotating motors, small eccentricity can cause serious problems. For this reason, it has been necessary to use a jig until the adhesive is solidified.

  For the reasons described above, it is easier to attach or wrap a sheet-like adhesive that is solid at room temperature on an adherend than to use a liquid adhesive. However, it is good when the adherends are divided into two parts and assembled or bonded together, but when fitting pipes, dowels, etc., the sheet-like adhesive does not create gaps between adherends. It cannot be completely filled. This is because if the sheet-like adhesive is thicker than the gap, it cannot be inserted due to cramping. If it is forcibly inserted, the sheet-like adhesive may be peeled off, torn, or wrinkled, resulting in non-uniform adhesion area, resulting in decreased adhesion strength and variations in adhesion strength. Conversely, if the sheet-like adhesive is made thinner than the gap to facilitate fitting, the gap cannot be filled and cannot be bonded, or the adhesive strength is extremely weak.

  Therefore, it is effective to use a sheet-like adhesive that expands by heating. Patent Document 1 discloses thermally expandable fine particles, and Patent Document 2 discloses an expandable adhesive using a foaming agent. These are those in which the adhesive expands in volume when heated, and is applied to the adherend surface where a gap is formed with an appropriate coating thickness. It is to be filled. However, the heat-expandable adhesive has lower adhesive strength than the non-expandable. In particular, the heat-expandable sheet-like adhesive had a remarkable decrease in adhesive strength as compared with the heat-expandable liquid adhesive.

The cause of this is thought to be a decrease in the amount of adhesive components due to the addition of non-adhesive thermally expandable particles, and bubbles due to the foaming agent reduce the strength of the cured adhesive. Was caused by the timing balance between curing (crosslinking) and foaming, and Patent Document 3 was invented. In this document, by using a common amine carbonate as a curing agent for crosslinking an adhesive component and a foaming agent, the timing of crosslinking and foaming is measured to improve the adhesive strength. However, this has the disadvantage that it is difficult to change the expansion ratio and a free design is not possible.
JP-A-5-179213 Japanese Patent Publication No. 60-37837 JP-A-5-186625

  The present invention has been intensively studied to solve the above-mentioned problems, and is a heat-expandable sheet-like adhesive composition that can fill gaps and irregularities caused by the adherend and exhibits excellent adhesive strength. To provide things.

That is, the present invention includes (a) a film-forming resin that is solid at room temperature, (b) a liquid or semi-solid epoxy resin at room temperature, (c) a latent curing agent, (d) a thermally expandable capsule, (e) silicone Ri Do and a lubricating fine particles selected from rubber powder, fluorocarbon resin powder, polyamide powder, said component (b) 100 parts by weight, the component (a) is 50 to 180 parts by weight, the component (c)) 1 to 50 parts by weight, the component (d) is 0.3 to 20% by weight of the total composition, and the component (e) is 3 to 30% by weight of the total composition. The present invention provides a heat-expandable sheet-like adhesive composition.

Since the sheet-like adhesive obtained by the sheet-like adhesive composition of the present invention is not liquid, it is easy to form a thick film and has surface lubricity, so that the adherend is applied when applied to the fitting portion. Easy to insert. Therefore, an optimal amount of adhesive can be applied without causing curling, tearing, wrinkling, etc. during insertion.
In addition, even when the adherend has irregularities, warpage, distortion, or when the gap between the adherends is generated when the dimensional accuracy or processing accuracy of the adherend is low, by using this sheet adhesive The gap can be filled and excellent adhesion can be expressed. In particular, the sheet-like adhesive composition of the present invention has higher adhesive strength than conventional ones, and even when the expansion ratio is changed, there is little variation in adhesive strength, and highly reliable bonding is possible.

  In addition, when the shaft is fixed to the hole, the sheet-like adhesive is wound around the shaft to swell evenly with respect to the clearance generated between the shaft and the hole, and the shaft is cured substantially at the center of the hole. be able to. This eliminates the need for a holding jig for centering, which was necessary for the liquid adhesive.

  Hereinafter, the present invention will be described in detail. The component (a) of the present invention is a shape-retaining component for retaining the composition in a sheet form, and is a resin component that is solid at room temperature. Here, room temperature means 25 ° C. Preferred examples of component (a) are thermoplastic resins, thermosetting resins, and elastomers. Examples of thermoplastic resins include polyester, polyether, polyamide, polyurethane polyvinyl alcohol, polystyrene, polycarbonate, acrylic, EVA, phenoxy, alkyd, and terpene. , Coumarone indene, petroleum resin, etc. Examples of thermosetting resins include bisphenol A type epoxy, bisphenol F type epoxy, cresol novolak or phenol novolac type epoxy, brominated epoxy, phosphorus-containing epoxy and thiirane compounds. Can be mentioned. Examples of elastomers include ionomers, nitrile rubbers and hydrogenated products thereof, styrene elastomers, natural rubbers, chlorine rubbers, EPDM, isoprene, butyl rubber, and fluorine elastomers. These components may be used alone or in combination of several types. Among these, a thermoplastic resin is preferable in terms of high heat-curing adhesive strength. These components (a) may have either a reactive functional group or not. Examples of reactive functional groups include amine-based curing agents, acid anhydride-based curing agents, and functional groups that react with cationic catalysts.

  The component (b) of the present invention is a liquid or semi-solid epoxy resin at room temperature. The epoxy resin is a compound having at least one glycidyl group in the molecule, and is crosslinked by the glycidyl group to cure the entire composition. The semi-solid form is a liquid that is not liquid but apparently has fluidity and easily changes its shape by gravity. However, since semi-solid epoxy has low reactivity, it is preferable to use an epoxy resin that is liquid at room temperature.

  Preferred examples of the component (b) include bisphenol A type epoxy, bisphenol F type epoxy, novolac type epoxy, brominated epoxy, heterocyclic epoxy, glycidyl ester type epoxy, glycidyl amine type epoxy, linear aliphatic epoxy, alicyclic. Epoxy, reactive diluent, multi-sensitivity epoxy, fatty acid-modified epoxy, rubber-modified epoxy, rubber-dispersed epoxy, thiirane compound, etc. You may do it.

  The blending ratio of the component (a) and the component (b) varies depending on the curing conditions, and the blending amount varies depending on the curing conditions. However, the component (a) is 50 to 250 parts per 100 parts by weight of the component (b). Parts by weight.

  The component (c) of the present invention is a latent curing agent for crosslinking the component (b), has no activity of crosslinking the component (b) during storage, and may be crosslinked by heating. It can be done. Examples of such components include cationic curing agents such as imidazole, dicyandiamide, hydrazide compounds, phenol novolac, cresol novolac, protonic acid, and Lewis acid. The latent curing agents as described above can be used alone or in combination of two or more.

  Here, the epoxy curing agent capable of crosslinking the component (b) is present in addition to the component (c), but the component (c) is selected from the balance between the expansion start temperature of the thermally expandable capsule and the reaction rate. Curing agents other than can not be used. That is, if it is other than the component (c), the sheet-like adhesive is cured in an unexpanded state or the adhesive strength becomes extremely low.

  The amount of component (c) added varies depending on the component used. For example, the amount added relative to the total amount of components (a) and (b) is 1 to 10 parts by weight in the case of imidazole, and 15 to 50 in the case of acid anhydride. 20 to 60 parts by weight is the optimum range for parts by weight and phenol novolac, and when combined, the amount of component (c) is 1 to 60 parts by weight per 100 parts by weight of components (a) and (b).

  The component (d) of the present invention is a thermally expanded capsule. The component (d) is a microcapsule in which a thermoplastic resin having a gas barrier property is used as a shell, and a low boiling point substance (thermal expansion agent) is included in the shell. When the thermally expanded capsule is heated, the thermoplastic resin in the shell is softened, and the capsule expands as the volume increases due to the vaporization of the low-boiling substance, resulting in hollow spherical particles.

  Examples of the thermoplastic resin constituting the shell of the thermally expanded capsule include vinylidene chloride, acrylonitrile, polystyrene, polymethacrylate, and polyvinyl alcohol. Since the thermoplastic resin has a gas barrier property, the low boiling point substance is retained in the particles even when heated and expanded. Examples of the low-boiling substance contained in the shell include low-boiling liquid hydrocarbons, among which isopentane and n-pentane that are easily gasified.

  The expansion start temperature of the thermally expandable capsule needs to be lower than the decomposition temperature of the above-mentioned latent hardener. Ideally, it is desirable that the thermal expansion capsule is expanded in a low temperature range, and the latent curing agent is activated by further increasing the heating temperature in a sufficiently swollen state to start crosslinking of the component (b). It is difficult to control the temperature of the sheet-like adhesive existing between body layers. Therefore, by gradually heating from a low temperature state, the thermal expansion capsule first expands in the process of increasing the temperature, and the latent curing agent starts to be activated in the middle of the expansion, and the crosslinking reaction of (b) Begins to begin gradually. Next, the crosslinking reaction of component (b) proceeds so that most of the thermally expandable capsules end expansion and alternate with it. In this way, a finally expanded three-dimensional cross-linked cured product is obtained.

  The volume expansion coefficient of component (d) is preferably 8 to 60 times. Examples of commercially available thermal expansion capsules include EXPANSEL (manufactured by Nippon Philite), Matsumoto Microsphere (manufactured by Matsumoto Yushi Seiyaku), and Microsphere (manufactured by Kureha Chemical). Component (d) is added in an amount of 0.3 to 20% by weight based on the entire sheet-like adhesive composition of the present invention (excluding the organic solvent). If it is less than 0.3% by weight, a sufficient expansion ratio cannot be obtained, and if it is more than 20% by weight, the adhesive strength is lowered.

  Component (e) of the present invention is a lubricating fine particle powder and is a characteristic component of the present invention. Addition of this component produces three effects. The first is to relax the strictness of the balance between expansion and crosslinking. As described above, the expansion of the component (c) must be started before the component (b) is crosslinked, and the quantitative and speed balance has a great influence on the adhesive strength of the cured product. It was very difficult to achieve that balance. However, by adding the component (e), the strictness of the balance can be relaxed, and the conditions can be relaxed. In the first place, the sheet-like adhesive of the present invention is in a solid state and does not easily have fluidity. In this state, the component (c) is expanded inside the composition to deform the solid state. The distortion in the composition at that time is expected to cause a decrease in the adhesive strength, and by adding this component, the deformation in the composition becomes smooth, and as a result, the adhesive strength does not decrease. Therefore, it is expected to exhibit excellent adhesive strength.

  The second is that by adding the component (e), the cured product forms a sea-island structure with the thermosetting resin, and the adhesive strength is improved. In particular, the epoxy resin has a disadvantage that the shear adhesive strength is excellent but the peel adhesive strength is weak. However, the addition of the component (e) can increase the peel adhesive strength.

  Thirdly, the lubricity of the surface of the sheet-like adhesive is improved by adding the component (e). Therefore, when it is applied to pipe connection or shaft fitting, damage such as peeling or turning up due to friction between adherends during fitting is eliminated.

  Examples of the lubricating fine particle powder of the component (e) include silicone rubber, fluororesin powder, polyamide, polyimide, polyamideimide, phthalocyanine, and a core-shell structured acrylic rubber, or these lubricating fine particles in advance. Examples of the resin component that are uniformly dispersed in a liquid or semi-liquid resin include 1 to 50% by weight of the total composition (excluding the organic solvent) as the addition amount of the resin component, but preferably 3 to 30% by weight. %. These lubricating fine particle powders may be used alone or in combination. Among these, silicone rubber, fluororesin powder, and polyamide having excellent lubricity are preferable.

  With the sheet-like adhesive composition of the present invention, the sheet-like adhesive can be obtained by forming a thin film on a substrate such as a release film or by forming a thin film directly on one side of the adherend. The thin film can be formed by dispersing the adhesive composition in a known organic solvent such as toluene or xylene, applying it with a bar coater or roll coater, and drying. Moreover, you may form in a thin film by extrusion molding. The film thickness is usually about 20 to 200 μm, but can be appropriately changed as desired. However, it cannot be formed below the average particle size of the thermally expandable capsules used.

  Moreover, the sheet-like adhesive obtained by the sheet-like adhesive composition of the present invention, when a release film is used, peels the release film and presses or wraps around the adherend. At this time, if preheating is performed at a temperature lower than the swelling start temperature, the adhesion to the adherend is improved. And it joins with the adherend which opposes, and heats. The heating temperature is appropriately determined depending on the selected components, but is generally 80 ° C to 160 ° C. By heating, the sheet-like adhesive expands and fills the gap generated by the adherend, and the cured component cures in that shape, thereby adhering the adherend.

Hereinafter, the present invention is demonstrated by examples.
The compounds listed in Table 1 were prepared in the amounts shown in Table 1. However, the abbreviations in the table are as described later. The preparation example is described as follows in the composition of Example 1.

  In a container with a stirring function, 50 parts by weight of PKHH, 10 parts by weight of EP1001, 40 parts by weight of EXA835, and 100 parts by weight of methyl ethyl ketone were weighed and mixed and stirred at room temperature for 3 hours. Next, 5 parts by weight of DICY7 and 2 parts by weight of 2P4MHZ were added, and 1 part by weight of 92DU80 was added and mixed for 1 hour.

  Furthermore, 10 parts by weight of FS700 was added, and the mixture was stirred again with a stirrer for 30 minutes to obtain a uniform composition as a whole. The composition was formed on a 50 μm PET film that had been subjected to a release treatment so that the layer thickness would be 50 μm using a roll coater. Similarly, the compositions shown in Table 1 were prepared, and various sheet-like adhesive compositions were prepared.

・ PKHH (phenoxy resin: manufactured by Union Carbide)
・ TP236 (Polyester resin: manufactured by Nippon Synthetic Chemical)
EP1001 (Epicoat 1001, bisphenol A type epoxy resin: manufactured by Japan Epoxy Resin Co., Ltd.)
・ EXA835 (bisphenol F type epoxy resin: manufactured by Dainippon Ink & Chemicals, Inc.)
・ EP152 (Epicoat 152, novolac type epoxy resin: manufactured by Japan Epoxy Resin Co., Ltd.)
・ DICY7 (Dicyandiamide: manufactured by Japan Epoxy Resin Co., Ltd.)
2P4MHZ (imidazole derivative: manufactured by Shikoku Kasei Kogyo Co., Ltd.)
C11Z-A (imidazole derivative: manufactured by Shikoku Kasei Kogyo Co., Ltd.)
・ HF-1M (phenol novolak: manufactured by Meiwa Kasei Co., Ltd.)
・ 92DU80 (Expansel 92DU80, thermal expansion capsule: Nippon Philite) Capsule dissolution start temperature 121 ° C
・ H750 (Microsphere H750 thermal expansion capsule: manufactured by Kureha Chemical Industry Co., Ltd.) Capsule dissolution start temperature 126 ° C
・ FS700 (silicone powder: manufactured by NOF Corporation)
・ Lublon L5 (fluorine powder: manufactured by Daikin Industries)
・ 2002UDNATCUS (Nylon powder: Atofina Japan)
AS-40 (alumina powder: Showa Denko)
・ PF40E (PF40E-401, glass powder: Nitto Boseki Co., Ltd.)
・ MEK (methyl ethyl ketone)

  A fitting test was performed using the aluminum pin shown in FIG. 1 and the aluminum collar shown in FIGS. The pin has a diameter of 6 mm, the collar a has a hole diameter of 6.1 mm, and the collar b has 7.0 mm.

[Insertion]
Various sheet-like adhesives were wound around the pins and heated to 100 ° C. to fix the adhesive layer on the pins. It returned to normal temperature, the said pin was inserted in the color a, and it pulled out after completion of insertion, and looked at the surface state of the sheet-like adhesive. At this time, a sample that could be smoothly inserted and that had no damage on the surface after being pulled out was rated as “Good”. The ones that could not be inserted smoothly were indicated by Δ, and the ones that were damaged such as peeling or turning on the surface were indicated by ×.

[Punching strength]
Various sheet-like adhesives were wound around the pins and heated to 100 ° C. to fix the adhesive layer on the pins. This pin was inserted into the collar b and placed in a curing furnace preheated to 150 ° C. for 1 hour to expand and cure the adhesive sheet. Then, the pin was pushed in the direction shown by the arrow in FIG. 3, the adhesive strength when the pin moved was measured, and the punching strength of the pin and collar was measured. The moving speed was 50 mm / min.

[Shear bonding]
The shear bond strength was measured according to the shear bond strength measurement method of JIS K 6249. As the adherend, an SPCC steel plate was used. Various sheet adhesives were affixed to the end of the test piece, and the adhesive layer was fixed by pressing for 30 seconds with a thermocompression bonding machine at 120 ° C. and 0.1 MPa. Then, the end part of the test piece was bonded and put into a curing furnace preheated to 150 ° C. for 1 hour to expand and cure the adhesive sheet. The moving speed was 50 mm / min.

[Expansion rate]
Various sheet adhesives were transferred to a glass plate t = 2.0 × 100 × 100 mm with a rubber roll at 80 ° C. and placed in a curing furnace preheated to 150 ° C. for 1 hour to expand and cure the adhesive sheet. . Moreover, the expansion coefficient was calculated from the film thickness of the expanded sheet before curing and the film thickness change after curing. These results are shown in Table 1.

  For example, it can be used in a body joint portion which is a constituent member of an automobile, a fitting portion such as various shafts, pipes, rings and pins, a flange portion, or a portion where a plurality of members are required to be assembled.

The figure which shows the pin used in the Example of this invention The figure which shows the color used in the Example of this invention The figure which shows the mode of the Example of this invention

Explanation of symbols

1 ... Pin 2 ... Color

Claims (2)

(A) Film forming resin that is solid at room temperature, (b) Liquid or semi-solid epoxy resin at room temperature, (c) Latent curing agent, (d) Thermal expansion capsule, (e) Silicone rubber powder, Fluorine resin powder, Ri Do and a lubricating fine particles selected from polyamide powder, said component (b) 100 parts by weight, the component (a) is 50 to 180 parts by weight, the component (c)) is 1 to 50 wt Wherein the component (d) is 0.3 to 20% by weight of the whole composition and the component (e) is 3 to 30% by weight of the whole composition. A heat-expandable sheet-like adhesive composition.   The heat-expandable sheet-like adhesive composition according to claim 1, wherein the component (a) is selected from a thermoplastic resin, a thermosetting resin, and an elastomer.