JP3725894B2 - Steel sheet reinforcement sheet - Google Patents

Description

  The present invention relates to a steel plate reinforcing sheet, and more particularly, to a steel plate reinforcing sheet used by being attached to a steel plate of various industrial machines such as transportation machines.

Conventionally, in order to reduce the weight of a vehicle body, an automobile body steel plate is generally processed into a thin plate of 0.6 to 0.8 mm. Therefore, it is known to reinforce by sticking a steel plate reinforcing sheet inside the steel plate.
As such a steel sheet reinforcing sheet, an uncured adhesive layer made of an epoxy resin composition having an adhesive property at room temperature and containing a heat-decomposable foaming agent on the surface of the uncured epoxy resin composition substrate layer. A heat-curing thin steel sheet reinforcing adhesive sheet arranged in a stacked manner has been proposed (see, for example, Patent Document 1).
JP 2002-283526 A

However, reinforcing layers based on epoxy resins, such as the above-mentioned heat-curable thin steel sheet reinforcing adhesive sheet, have poor adhesion to oil-surfaced steel, especially in winter, and various types such as degreasing, pretreatment, and electrodeposition coating. There is a problem of dropping off in the process.
On the other hand, if the base resin is softened to improve the adhesiveness, there is a problem that the strength after curing is insufficient and sufficient reinforcement cannot be achieved.

  This invention is made | formed in view of such a malfunction, The place made into the objective is to provide the steel plate reinforcement sheet which can improve both adhesiveness and reinforcement.

In order to achieve the above object, a steel sheet reinforcing sheet according to the present invention is a steel sheet reinforcing sheet comprising a constraining layer and a reinforcing layer, wherein the reinforcing layer includes foaming containing styrene-butadiene rubber, epoxy resin and epoxy-modified rubber. The constraining layer and the reinforcing layer have a thickness of 3.5 mm or less, and the adhesive force at 5 ° C. to the oil cold-rolled steel sheet is 2.0 N / 25 mm or more, at 160 ° C. The bending strength after heating for 20 minutes is characterized by 18N or more.

  According to the steel sheet reinforcing sheet of the present invention, it is possible to achieve both an adhesive force and a reinforcing property that have been contradictory so far, and to ensure both a sufficient adhesive force and reinforcing property for the steel plate. Therefore, the steel plate can be effectively reinforced by sticking and foaming to the steel plate of various industrial machines.

The steel plate reinforcing sheet of the present invention includes a constraining layer and a reinforcing layer.
The constraining layer imparts toughness to the reinforcing layer after foaming (hereinafter referred to as a foam layer), is formed into a sheet shape, and is made of a material that is light and thin and can be closely integrated with the foam layer. Preferably formed, such materials include glass cloth, resin-impregnated glass cloth, synthetic resin nonwoven fabric, metal foil, carbon fiber, and the like.

  The glass cloth is made of glass fiber and a known glass cloth is used. The resin-impregnated glass cloth is obtained by impregnating the above glass cloth with a synthetic resin such as a thermosetting resin or a thermoplastic resin, and a known one is used. In addition, as a thermosetting resin, an epoxy resin, a urethane resin, a melamine resin, a phenol resin etc. are used, for example. As the thermoplastic resin, for example, vinyl acetate resin, ethylene-vinyl acetate copolymer (EVA), vinyl chloride resin, EVA-vinyl chloride resin copolymer, and the like are used. As the thermoplastic resin, for example, vinyl acetate resin, ethylene-vinyl acetate copolymer (EVA), vinyl chloride resin, EVA-vinyl chloride resin copolymer, and the like are used. In addition, the above-described thermosetting resin and the above-described thermoplastic resin (for example, melamine resin and vinyl acetate resin) can be mixed and used.

As metal foil, well-known metal foil, such as aluminum foil and steel foil, is used, for example.
Of these, glass cloth and resin-impregnated glass cloth are preferably used in consideration of weight, adhesion, strength and cost.
The thickness of such a constraining layer is, for example, 0.05 to 0.40 mm, preferably 0.10 to 0.30 mm.

Moreover, the foaming composition which foams by a heating layer is formed in the reinforcing layer in the sheet form. The foamable composition contains at least a styrene-butadiene rubber, an epoxy resin, and a foaming agent.
Styrene-butadiene rubber, if example embodiment, the scan styrene-butadiene random copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butadiene copolymer, etc. styrene-ethylene-butadiene-styrene block copolymer Is mentioned. These styrene / butadiene rubbers may be used alone or in combination. Such styrene-butadiene rubber has a styrene content of, for example, 50% by weight or less, and preferably 35% by weight or less.

Such styrene-butadiene rubber has a number average molecular weight of 30,000 or more, preferably 50,000 to 1,000,000. If the number average molecular weight is less than 30,000, the adhesive strength, particularly the adhesiveness to the oil-surfaced steel plate, may be lowered.
In addition, such a styrene-butadiene rubber has a Mooney viscosity of, for example, 20 to 60 (ML1 + 4, at 100 ° C.), preferably 30 to 50 (ML 1 + 4, at 100 ° C.).

The mixing ratio of the styrene-butadiene rubber, per 100 parts by weight of styrene-butadiene and epoxy resins, for example, 30 to 70 parts by weight, preferably, 40 to 60 parts by weight. If the blending ratio of styrene / butadiene rubber is less than this, the adhesiveness to the oil-surfaced steel sheet may be lowered. On the other hand, if more than this, the reinforcing property may be lowered.
The epoxy resin is not particularly limited. For example, bisphenol type epoxy resin (for example, bisphenol A type epoxy resin, dimer acid-modified bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, etc.), novolac Type epoxy resin (for example, phenol novolak type epoxy resin, cresol novolak type epoxy resin, etc.), aromatic epoxy resin such as naphthalene type epoxy resin, for example, alicyclic epoxy resin, triglycidyl isocyanurate, hydantoin epoxy resin, etc. Nitrogen-containing ring epoxy resin, water-added bisphenol A type epoxy resin, aliphatic epoxy resin, glycidyl ether type epoxy resin, biphenyl type epoxy resin that is the mainstream of low water absorption rate cured body type, di Such as black ring type epoxy resins. These may be used alone or in combination. Of these epoxy resins, aromatic reinforcing resins and further bisphenol type epoxy resins are preferably used in view of reinforcement.

Moreover, such an epoxy resin has an epoxy equivalent of, for example, 150 to 1000 g / eqiv. , Preferably, 200 to 800 g / eqiv. It is. The epoxy equivalent can be calculated from the oxirane oxygen concentration measured by titration with hydrogen bromide.
Moreover, the compounding ratio of an epoxy resin is 30-70 weight part with respect to a total of 100 weight part of a styrene butadiene rubber and an epoxy resin, Preferably it is 40-60 weight part. When the blending ratio of the epoxy resin is less than this, the reinforcing property may be lowered. On the other hand, when it is more than this, the adhesion to the oil surface steel plate may be lowered.

Examples of the foaming agent include inorganic foaming agents and organic foaming agents.
Examples of the inorganic foaming agent include ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, azides and the like.
Examples of organic foaming agents include N-nitroso compounds (N, N′-dinitrosopentamethylenetetramine, N, N′-dimethyl-N, N′-dinitrosotephthalamide, etc.), azo compounds, and the like. (Eg, azobisisobutyronitrile, azodicarboxylic amide, barium azodicarboxylate, etc.), fluorinated alkanes (eg, trichloromonofluoromethane, dichloromonofluoromethane, etc.), hydrazine compounds (eg, p-toluenesulfonyl) Hydrazide, diphenylsulfone-3,3′-disulfonylhydrazide, 4,4′-oxybis (benzenesulfonylhydrazide), allylbis (sulfonylhydrazide) and the like, semicarbazide compounds (for example, p-toluylenesulfonyl semicarbazide, 4,4 '-Oxybis ( Emissions Zen semicarbazide), etc.), triazole compound (e.g., 5-morpholyl-1,2,3,4-thiatriazole, etc.) and the like.

  As the foaming agent, a heat-expandable substance (for example, isobutane, pentane, etc.) is contained in a microcapsule (for example, a microcapsule made of a thermoplastic resin such as vinylidene chloride, acrylonitrile, acrylic acid ester, methacrylic acid ester). Encapsulated thermally expandable fine particles may be used, and as such thermally expandable fine particles, for example, commercially available products such as microspheres (trade name, manufactured by Matsumoto Yushi Co., Ltd.) may be used.

These may be used alone or in combination. Among these foaming agents, 4,4′-oxybis (benzenesulfonylhydrazide) is preferably used in consideration of stable foaming without being influenced by external factors.
The blending ratio of the foaming agent is, for example, 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of the total of styrene / butadiene rubber and epoxy resin. If the blending ratio of the foaming agent is less than this, foaming does not occur sufficiently and the reinforcing property may be reduced due to insufficient thickness. On the other hand, if it is more than this, the density may be reduced and the reinforcing property may be reduced.

Moreover, such foamable compositions, in addition to the above components, that contain epoxy-modified rubber as a compatibilizer. The compatibilizing agent is intended to compatibilize the styrene-butadiene rubber and the epoxy resin, and by adding such a compatibilizing agent, it is possible to further improve the adhesiveness and the reinforcing property .
The epoxy-modified rubber is, for example, a rubber having an epoxy group modified at the molecular chain end or molecular chain, such as the above-described styrene / butadiene rubber , and the epoxy equivalent thereof is, for example, 100 to 10,000 g / eqiv. And 400 to 3000 g / eqiv. Are preferably used. In order to modify the rubber with an epoxy group, a known method is used. For example, a double bond in the rubber is reacted with an epoxidizing agent such as peracids or hydroperoxides in an inert solvent. Just do it.

Examples of such epoxy-modified rubber include an AB block copolymer and an ABA block copolymer (A represents a styrene polymer block, and B represents a butadiene polymer block or isoprene polymer). A conjugated diene polymer block such as a block is used.) A polymer block into which an epoxy group is introduced is used.
More specifically, for example, an epoxy-modified styrene / butadiene / styrene block copolymer, an epoxy-modified styrene / ethylene / butadiene / styrene block copolymer, and an epoxy-modified styrene / isoprene / styrene block copolymer are used. These may be used alone or in combination. Among these epoxy-modified rubbers, an epoxy-modified styrene / butadiene / styrene block copolymer is preferably used in consideration of the balance between reinforcement and adhesiveness.

  In addition, in the above-mentioned AB type block copolymer and ABA type block copolymer, the A block copolymer which is a styrene polymer block has a weight average molecular weight of about 1000 to 10,000. The glass transition temperature is preferably 7 ° C. or higher, and the B block copolymer which is a conjugated diene polymer block has a weight average molecular weight of about 10,000 to 500,000 and a glass transition temperature of − It is preferable that it is 20 degrees C or less. The weight ratio of the A block copolymer to the B block copolymer is 2/98 to 50/50, more preferably 15/85 to 30/70 as the A block copolymer / B block copolymer. It is preferable that

The blending ratio of the epoxy-modified rubber is, for example, 1 to 20 parts by weight, preferably 5 to 15 parts by weight with respect to 100 parts by weight of the total of styrene / butadiene rubber and epoxy resin. When the blending ratio of the epoxy-modified rubber is less than this, the reinforcing property and the adhesiveness may not be improved. On the other hand, when it is more than this, the adhesiveness at a low temperature may be lowered.
Further, such a foamable composition preferably contains a rubber cross-linking agent and / or an epoxy resin curing agent in addition to the above components. By including a rubber cross-linking agent and / or an epoxy resin curing agent, it is possible to improve the reinforcement.

As the rubber cross-linking agent, a known rubber cross-linking agent (vulcanizing agent) capable of cross-linking styrene-butadiene rubber or epoxy-modified rubber by heating is used. Examples of such rubber cross-linking agents include sulfur, sulfur compounds, selenium, magnesium oxide, lead monoxide, organic peroxides (for example, dicumyl peroxide, 1,1-ditertiarybutylperoxy-3, 3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-ditertiarybutylperoxyhexane, 2,5-dimethyl-2,5-ditertiarybutylperoxyhexine, 1,3-bis (ter (Sali-butyl peroxyisopropyl) benzene, tertiary butyl peroxyketone, tertiary butyl peroxybenzoate), polyamines, oximes (for example, p-quinone dioxime, p, p'-dibenzoylquinone dioxime, etc.) Nitroso compounds (eg, p-dinitrosobenzidine), resins (eg, alkyl Nord - formaldehyde resin, melamine - formaldehyde condensate, etc.), ammonium salts (e.g., ammonium benzoate), and the like.

These may be used alone or in combination. Of these rubber cross-linking agents, sulfur is preferably used in consideration of curability and reinforcement.
The blending ratio of the rubber crosslinking agent is, for example, 1 to 20 parts by weight, preferably 2 to 15 parts by weight with respect to 100 parts by weight of the total of styrene / butadiene rubber and epoxy resin. If the blending ratio of the rubber cross-linking agent is less than this, the reinforcing property may be lowered. On the other hand, if it is more than this, the adhesive property may be lowered, which may be disadvantageous in cost.

As the epoxy resin curing agent, a known epoxy resin curing agent is used. For example, amine compounds, acid anhydride compounds, amide compounds, hydrazide compounds, imidazole compounds, imidazoline compounds. Examples thereof include compounds. Other examples include phenolic compounds, urea compounds, polysulfide compounds, and the like.
Examples of the amine compounds include ethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, amine adducts thereof, metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone.

Examples of the acid anhydride compounds include phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl nadic acid anhydride, pyromellitic anhydride, dodecenyl succinic anhydride, dichloromethane. Succinic acid anhydride, benzophenone tetracarboxylic acid anhydride, chlorendic acid anhydride, etc. are mentioned.
Examples of amide compounds include dicyandiamide and polyamide.

Examples of hydrazide compounds include dihydrazide.
Examples of imidazole compounds include methylimidazole, 2-ethyl-4-methylimidazole, ethylimidazole, isopropylimidazole, 2,4-dimethylimidazole, phenylimidazole, undecylimidazole, heptadecylimidazole, and 2-phenyl-4. -Methylimidazole etc. are mentioned.

Examples of the imidazoline compounds include methyl imidazoline, 2-ethyl-4-methyl imidazoline, ethyl imidazoline, isopropyl imidazoline, 2,4-dimethyl imidazoline, phenyl imidazoline, undecyl imidazoline, heptadecyl imidazoline, 2-phenyl-4. -Methyl imidazoline etc. are mentioned.
These may be used alone or in combination. Of these epoxy resin curing agents, dicyandiamide is preferably used in consideration of adhesiveness.

Moreover, the mixture ratio of an epoxy resin hardening | curing agent is 0.5-15 weight part with respect to a total of 100 weight part of styrene butadiene rubber and an epoxy resin, Preferably, it is 1-10 weight part. When the blending ratio of the epoxy resin curing agent is less than this, the reinforcing property may be lowered, whereas when it is more than this, the storage stability may be deteriorated.
In addition to the above components, such a foamable composition may be, for example, a foaming aid, a crosslinking accelerator, a curing accelerator, a filler, a tackifier, and, if necessary, a pigment (for example, Carbon black etc.), thixotropic agents (eg montmorillonite etc.), lubricants (eg stearic acid etc.), scorch inhibitors, stabilizers, softeners, plasticizers, anti-aging agents, antioxidants, UV absorbers, coloring Known additives such as agents, fungicides, and flame retardants may be appropriately added.

Examples of foaming aids include zinc stearate, urea compounds, salicylic acid compounds, benzoic acid compounds, and the like. These foaming auxiliaries may be used alone or in combination. The blending ratio is, for example, 0.5 to 10 parts by weight, preferably 1 to 100 parts by weight of the total of styrene / butadiene rubber and epoxy resin. ~ 5 parts by weight.
Examples of the crosslinking accelerator include zinc oxide, dithiocarbamic acids, thiazoles, guanidines, sulfenamides, thiurams, xanthogenic acids, aldehyde ammonias, aldehyde amines, and thioureas. These crosslinking accelerators may be used alone or in combination, and the blending ratio thereof is, for example, 1 to 20 parts by weight, preferably 3 to 15 parts per 100 parts by weight of the total of styrene / butadiene rubber and epoxy resin. Parts by weight.

Examples of the curing accelerator include imidazoles, tertiary amines, phosphorus compounds, quaternary ammonium salts, and organometallic salts. These curing accelerators may be used alone or in combination. The blending ratio is, for example, 0.5 to 20 parts by weight, preferably 1 to 100 parts by weight in total of the styrene / butadiene rubber and the epoxy resin. -10 parts by weight.
Examples of the filler include calcium carbonate (for example, heavy calcium carbonate, light calcium carbonate, white luster), talc, mica, clay, mica powder, bentonite, silica, alumina, aluminum silicate, titanium oxide, acetylene black, aluminum Examples include powder. These fillers may be used alone or in combination, and the blending ratio thereof is, for example, 50 to 150 parts by weight, preferably 75 to 125 parts by weight with respect to 100 parts by weight of the total of styrene / butadiene rubber and epoxy resin. Part.

Examples of the tackifier include rosin resins, terpene resins (for example, terpene-aromatic liquid resins), coumarone indene resins, petroleum resins (for example, C5 / C9 petroleum resins), and the like. Can be mentioned. These tackifiers may be used alone or in combination, and the blending ratio thereof is, for example, 10 to 200 parts by weight, preferably 20 to 150 parts, based on 100 parts by weight of the total of styrene / butadiene rubber and epoxy resin. Parts by weight.

The foamable composition is prepared as a kneaded product by blending the above-described components in the above-described blending ratio, and is not particularly limited. For example, the foamable composition is kneaded by a mixing roll, a pressure kneader, an extruder, or the like. Can do.
In addition, it is preferable to prepare so that the flow tester viscosity (60 degreeC, 24 kg load) of the kneaded material obtained in this way may be 1000-5000 Pa.s, for example, Furthermore, 1500-4000 Pa.s.

Thereafter, the kneaded product obtained is not particularly limited, and a reinforcing layer is formed by rolling, for example, by calender molding, extrusion molding or press molding under a temperature condition where the foaming agent is not substantially decomposed. A steel plate reinforcing sheet is obtained by bonding the reinforcing layer to the constraining layer.
The thickness of the reinforcing layer thus formed is, for example, 0.2 to 3.0 mm, preferably 0.5 to 1.3 mm.

In addition, you may stick a release paper on the surface of a reinforcement layer as needed to the obtained steel plate reinforcement sheet.
Moreover, in the steel plate reinforcement sheet obtained in this way, the volume expansion ratio at the time of foaming of the foamable composition used as the reinforcing layer is 1.5 to 4.0 times, and further 2.0 to 3. It is preferably 5 times. The density of the foam in the foam layer (foam weight (g) / foam volume (g / cm ³ )) is, for example, 0.2 to 0.8 g / cm ³ , and It is preferable that it is 3-0.7 g / cm < ³ >.

  In the steel sheet reinforcing sheet of the present invention, the total thickness of the constraining layer and the reinforcing layer bonded together in this way is 3.5 mm or less (generally 0.3 mm or more), preferably 0.3 to 3.4 mm. More preferably, it is set to 0.6 to 1.6 mm. If it is thicker than 3.5 mm, it becomes thick and heavy, which is disadvantageous in terms of cost. On the other hand, if it is thinner than 0.3 mm, sufficient reinforcement may not be obtained.

Further, the steel sheet reinforcing sheet of the present invention has an adhesive strength at 5 ° C. of 2.0 N / 25 mm or more, preferably 3.0 to 10 N / 25 mm, and is heated at 160 ° C. for 20 minutes. The later bending strength is 18N or more, preferably 18 to 50N.
When the adhesive strength is less than 2.0 N / 25 mm, the steel sheet is easily peeled off, and when the bending strength after heating at 160 ° C. for 20 minutes is less than 18 N, the reinforcing property is insufficient.

  Therefore, the total thickness of the constraining layer and the reinforcing layer described above is 3.5 mm or less, the adhesive strength at 5 ° C. to the oil-surface cold-rolled steel sheet is 2.0 N / 25 mm or more, and after heating at 160 ° C. for 20 minutes. If the bending strength of the steel is 18N or more, the adhesiveness to the oil-surfaced steel plate is particularly good in winter, it is difficult to drop off in various processes such as degreasing, pretreatment, and electrodeposition coating, and sufficient reinforcement can be achieved. A steel plate reinforcing sheet can be provided.

In order to obtain the adhesive strength and bending strength within the above ranges, for example, the formulation of the foamable composition may be appropriately selected from the above, and in particular, 30 to 70 parts by weight of styrene-butadiene rubber, 70 to 70 epoxy resin 30 parts by weight, 0.5 to 10 parts by weight of foaming agent, 1 to 20 parts by weight of epoxy-modified rubber (compatibilizer), 1 to 20 parts by weight of rubber cross-linking agent, 0 to 10 parts by weight of epoxy resin curing agent (optional component) It is preferable to blend in a formulation containing 1 to 20 parts by weight of a crosslinking accelerator, 50 to 150 parts by weight of a filler, 1 to 40 parts by weight of a terpene resin, and 20 to 80 parts by weight of a C5 / C9 petroleum resin.

  And the steel plate reinforcement sheet | seat of this invention obtained by doing in this way is used in order to stick on the steel plate of various industrial machines, such as a transport machine, and to reinforce the steel plate. More specifically, in the steel sheet reinforcing sheet of the present invention, as shown in FIG. 1A, a reinforcing layer 2 is laminated on the constraining layer 1, and a release paper 3 is attached to the surface of the reinforcing layer 2 as necessary. In use, the release paper 3 is peeled off from the surface of the reinforcing layer 2 as shown by phantom lines, and the surface of the reinforcing layer 2 is adhered to the steel plate 4 as shown in FIG. Then, as shown in FIG. 1C, the foam layer 5 is formed by heating, foaming, crosslinking and curing by heating at a predetermined temperature (for example, 160 to 210 ° C.). It is done.

Such a steel plate reinforcing sheet of the present invention can be suitably used for reinforcing a car body steel plate of an automobile that is required to be reduced in weight. In that case, the steel plate reinforcing sheet is, for example, an assembly of a car body steel plate first. After being stuck in the process, it is then used in such a manner that the foam layer is formed by heating, foaming, crosslinking and curing by utilizing the heat during electrodeposition coating.
And the steel plate reinforcement sheet of this invention can express sufficient adhesive force with respect to an oil surface steel plate also in winter. And the steel plate reinforcement sheet of this invention can express sufficient reinforcement after heating foaming.

  Therefore, the steel plate reinforcing sheet of the present invention can achieve both the adhesive force and the reinforcing property which have been contradictory so far, and can ensure both the sufficient adhesive force and reinforcing property for the steel plate.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these.
Examples and Comparative Examples In the formulation shown in Table 1, each component was blended and kneaded with a 10-inch mixing roll to prepare a kneaded product. In this kneading, first, a resin component (at least one of SBR, epoxy resins A to C and epoxy-modified SBS), a filler component (at least one of heavy calcium carbonate and talc), adhesive An imparting agent component (terpene-aromatic liquid resin, at least one of C5 / C9 petroleum resin) is kneaded at 130 ° C., and then added to a foaming agent, sulfur, an epoxy resin curing agent, and zinc oxide. A crosslinking accelerator was blended and kneaded at 20 ° C.

The obtained kneaded material is used as a reinforcing layer, and a glass cloth as a constraining layer having a thickness of 0.2 mm is bonded by a heat press, and the total thickness of the reinforcing layer and the constraining layer is 0.8 mm. A steel sheet reinforcing sheet was prepared by sticking a release paper on the opposite surface to which the layers were bonded.
Evaluation About the obtained steel plate reinforcement sheet of each Example and each comparative example, reinforcement (bending strength, impact resistance) and low temperature oil surface adhesiveness were evaluated as follows. The results are shown in Table 1.
-Reinforcing property test The release paper of the steel sheet reinforcing sheet of each example and each comparative example was peeled off, and each steel sheet reinforcing sheet was oil cold-rolled steel sheet (SPCC-SD) having a width of 25 mm x 150 mm length x 0.8 mm. ) (Manufactured by Nippon Test Panel Co., Ltd.) in an atmosphere of 20 ° C. and heated at 160 ° C. for 20 minutes to foam the reinforcing layer, thereby obtaining a test piece.

Then, with the steel plate facing upward, each test piece was supported with a span of 100 mm, and at the center in the longitudinal direction, the test bar was lowered from the upper vertical direction at a compression speed of 1 mm / min, and then contacted with the steel plate. The strength (N) when the foam layer was displaced by 1 mm was evaluated as the bending strength.
・ Impact resistance test (slamming test)
The steel sheet reinforcing sheet of each example and each comparative example was cut into a 50 mm width × 100 mm length and the release paper was peeled off, and was stuck to the center of a test steel plate having a thickness of 200 mm × 300 mm length × 0.8 mm, Each sample was prepared by crimping for 5 seconds so that a pressure of 5.9 KPa was applied to the whole.

After that, each sample obtained was set in a slamming tester, and impact was applied from an angle of 10 ° in accordance with the method described in JIS K 6830, and the steel sheet reinforcing sheet was observed for peeling, slipping, floating, etc. did. If there was no peeling, slipping or floating, the impact was repeated up to 10 times at the same angle. During this time, if there was no peeling, deviation, or float, the angle was further increased by 10 °, the same test was repeated with the same sample, and this test was repeated up to a maximum of 90 °. The angle and number of occurrences of peeling, slipping, floating, etc. (90 °, 10 times indicate no peeling, slipping, floating, etc.) were evaluated as impact resistance.
3) Low temperature oil surface adhesion Oil surface cold rolled steel plate (SPCC-SD) (manufactured by Nippon Test Panel Co., Ltd.) is prepared corresponding to each Example and each Comparative Example, and a rust inhibitor (Idemitsu Kosan Co., Ltd.) Daphne Oil Z-5) was applied and stood vertically at 20 ° C. overnight.

  Thereafter, the steel sheet reinforcing sheets of each example and each comparative example were cut out with a width of 25 mm, the release paper was peeled off, and the coated surface of each steel sheet coated with a rust preventive was pressure-bonded with a 2 kg roller in a 5 ° C. atmosphere. Then, 30 minutes later, the adhesive strength (N / 25 mm) was measured by a 90 ° peel test (tensile speed 300 mm / min), and this was evaluated as low temperature oil surface adhesion.

Details in Table 1 are shown below.
SBR: Styrene-butadiene random copolymer, number average molecular weight 240000, styrene content 25% by weight, Mooney viscosity 35 (ML1 + 4, at100 ° C.)
Epoxy resin A: Semi-solid bisphenol A type epoxy resin, epoxy equivalent 250 g / eqiv.
Epoxy resin B: Semi-solid dimer acid-modified bisphenol A type epoxy resin, epoxy equivalent of 600 to 700 g / eqiv.
Epoxy resin C: solid bisphenol A type epoxy resin, epoxy equivalent 450-500 g / eqiv.
Epoxy-modified SBS: Epoxy-modified styrene / butadiene / styrene block copolymer, styrene content 40% by weight, epoxy equivalent 1067 g / eqiv. (Daicel Chemical Industries, Epofriend AT501)
Foaming agent: 4,4′-oxybis (benzenesulfonylhydrazide)
Epoxy resin curing agent: dicyandiamide crosslinking accelerator: dibenzothiazyl disulfide From Table 1, it can be seen that Comparative Example 1 containing only epoxy resin A has good bending strength but poor impact resistance and low-temperature adhesion. . Further, it can be seen that Comparative Example 2 containing only SBR has good low-temperature adhesiveness but poor bending strength and impact resistance.

  On the other hand, in Examples 1 to 3, it can be seen that all of the reinforcing property, impact resistance and low-temperature adhesiveness are good.

BRIEF DESCRIPTION OF THE DRAWINGS It is process drawing which shows one Embodiment of the method of reinforcing a steel plate using the steel plate reinforcement sheet of this invention, Comprising: (a) prepares a steel plate reinforcement sheet and peels a release paper, (b) The step of attaching the steel plate reinforcing sheet to the steel plate, (c) shows the step of heating and foaming the steel plate reinforcing sheet.

Explanation of symbols

1 Constraining layer 2 Reinforcing layer 4 Steel plate

Claims (1)

A steel sheet reinforcing sheet comprising a constraining layer and a reinforcing layer,
The reinforcing layer is made of a foamable composition containing styrene-butadiene rubber, epoxy resin and epoxy-modified rubber,
The constraining layer and the reinforcing layer have a thickness of 3.5 mm or less,
A steel sheet reinforcing sheet having an adhesive strength at 5 ° C to an oil surface cold-rolled steel plate of 2.0 N / 25 mm or more and a bending strength after heating at 160 ° C for 20 minutes of 18 N or more.

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