JPH10139981A - Epoxy resin composition for reinforcing car body, car body reinforcement structure, and method for reinforcing car body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin compsn. for reinforcing car bodies which can be foamed easily and uniformly in a box-shaped member to fill it and can surely increase the stiffness of a car body, and to provide a car body reinforcement structure, and a method for reinforcing car bodies using the same. SOLUTION: This compsn. comprises 100 pts.wt. epoxy resin derived from bisphenol A and/or bisphenol F, 1-40 pts.wt. arom. polyether, 3-30 pts.wt. thermally activated curative for epoxy resins, 0.5-20 pts.wt. thermally decomposable org. blowing agent, and 3-200 pts.wt. inorg. filler. This method for reinforcing a car body comprises arranging a sheet comprising the compsn. in the inside of a box-shaped member and foaming the sheet at the step of baking in the electrodeposition coating of a car body. This car body reinforcement structure is a box-shaped member filled with a foam of the compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel epoxy resin composition for reinforcing a vehicle body, and more particularly, to a method in which an aromatic polyether is blended as a modifier for imparting toughness and heat resistance. After mounting on a preformed steel plate, assembling a box-shaped member using the steel plate, baking and filling in the body electrodeposition coating, foaming and filling to improve body rigidity The present invention relates to an epoxy resin composition, a vehicle body reinforcing structure, and a vehicle body reinforcing method.

[0002]

2. Description of the Related Art In general, in a vehicle body structure, a skeleton of each part of the vehicle body is firmly formed in terms of running stability, riding comfort, noise and vibration performance. Conventional body structures often employ a box-shaped closed cross-section structure, and have various cross-sectional shapes.However, due to social demands to improve fuel efficiency from the viewpoint of preventing fossil fuel depletion and air pollution. In order to reduce the weight of the vehicle body, each of them has a thin plate structure, and a metal reinforcing agent is generally used to compensate for a decrease in rigidity.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 48-2631 proposes a vehicle body structure in which a rigid urethane foam is filled in the closed section structure to reinforce the vehicle body skeleton. Filling the foam has a high effect of suppressing wall buckling and significantly improves the rigidity of the box-shaped member. And the rigidity can be improved.

[0004] As the resin foam type filler,
In addition to the urethane-based resin, an olefin-based resin foam filler (Seakalastomer 240, manufactured by Nippon Sika Co., Ltd.) and an epoxy resin-based foam filler (ORIDEX81, manufactured by Iida Sangyo)
5) and the like, which are foamed and filled in vehicle body painting.

[0005]

However, according to the above-mentioned reinforcing method using urethane resin, when the urethane stock solution is injected and foamed into the box-shaped closed-section member during construction, the small holes of the box-shaped member and the closed-section box-shaped member are removed. Since the leakage of the urethane material from the joints occurs to a considerable extent, it is necessary to take measures to prevent this, and it is considered that application to a production line of an automobile is difficult. In recent years, from the viewpoint of improving the working environment, in recent years, the foaming method using CFCs has been replaced with a foaming method using water.However, the water foaming method achieves more uniform foaming than the CFC foaming method. There is a problem that it is difficult.

On the other hand, in the case of an olefin-based resin foam material, since low-molecular-weight polyethylene wax or the like is used as an olefin resin serving as a base, the rigidity of the material is not sufficient. There is a problem that the effect of improving the rigidity is not sufficient.

[0007] In the case of epoxy resin foam,
The disadvantage of the poor impact resistance of epoxy resins must be compensated for. Further, the load input to the vehicle body is not always static, and an impact load may be applied to the vehicle body due to uneven road surface during traveling. Impact resistance and toughness are required.

The method of improving the impact resistance is roughly classified into a method of improving the chemical structure itself of the epoxy resin and a method of adding a separately prepared impact modifier to the epoxy resin. An epoxy resin capable of sufficiently satisfying impact resistance cannot be obtained by the method alone. On the other hand, in the latter method, (1) a method of adding a soluble elastomer monomer to an uncured epoxy resin and simultaneously polymerizing the two, (2) a method of adding a compatible elastomer polymer, and (3)
A method of dispersing a fine particle-like polymer for improving impact resistance and the like are known.

[0009] The method of the above (1) is characterized in that the interpenetrating network structure:
IPN (Inter-Penorating Ne)
However, this method generally has disadvantages such as a decrease in softening point of the product and a variation in mechanical strength.

Regarding the method (2), various examples have been proposed in which rubber is modified by adding an elastomer component such as butadiene-acrylonitrile (CTBN or ATBN) having a carboxyl group or an amino group at the terminal. Has been put into practical use, but the result obtained by this method is
It cannot be said that it is sufficiently satisfactory in terms of impact resistance and toughness for use in reinforcing vehicle body rigidity.

Furthermore, in the method (3), many impact modifiers such as polyamide resins have been proposed, but all of them are mechanically kneaded, so that not only a small amount of particles are dispersed in the particles. There is a disadvantage that non-uniformity remains and mechanical performance is hardly stabilized.

In general, when a rubber component having a glass transition temperature of -30 ° C. or less is added as an impact resistance improving agent for plastics, the effect of relieving external stress is exerted and the impact resistance is greatly improved. Although it is known, many of such rubber components, when a liquid epoxy is used as a base material, the dispersibility thereof is easily affected by mixing conditions, and the obtained composition has an unstable storage property, It is not practical for automotive production applications where long-term stability is required.

Further, when the viscosity of the resin sharply decreases in the foaming temperature range, it becomes difficult to retain the gas generated from the foaming agent in the resin, and it becomes difficult to foam to form a foam. In order for foam cells to be stably present in the foam, the temperature dependence of the resin viscosity in the foaming temperature range must be controlled. To this end, it is necessary to control the temperature dependence of the viscosity by adding an elastomer or the like having high compatibility with the epoxy resin, or to control the temperature dependence of the viscosity by physical crosslinking.

However, the method of controlling the viscosity by adding the elastomer has the disadvantage that the rigidity inherent in the epoxy composition is reduced, and when the viscosity is controlled by crosslinking involving a chemical reaction, the crosslinking density is reduced. Since it cannot be strictly controlled depending on the reaction conditions, the viscosity is too high and the foaming becomes insufficient, so that the above-mentioned box-shaped member may not be sufficiently filled.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to easily and uniformly foam and fill a box-shaped member. It is an object of the present invention to provide an epoxy resin composition for reinforcing a vehicle body, a vehicle body reinforcing structure, and a vehicle body reinforcing method capable of reliably improving the rigidity of the vehicle body.

[0016]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, by mixing a certain aromatic polyether with an epoxy resin, an epoxy resin having impact resistance has been obtained. A resin-based composition is obtained, and after forming this into a sheet, it is mounted on a pre-formed steel sheet, and after assembling a box-shaped member using the steel sheet, foaming and filling in a baking step at the time of body electrodeposition coating. As a result, the inventors have found that the vehicle body skeleton can be reinforced while reducing the weight, and the present invention has been completed.

That is, the epoxy resin composition for reinforcing a vehicle body according to the present invention comprises: (A) 100 parts by weight of an epoxy resin derived from bisphenol A and / or bisphenol F; 40 parts by weight,
(C) 3 to 30 parts by weight of a thermally activated curing agent for epoxy resin,
(D) 0.5 to 20 parts by weight of a thermal decomposition type organic foaming agent and (E) 3 to 200 parts by weight of an inorganic filler.

The vehicle body reinforcing structure of the present invention is characterized in that a box-shaped member is filled with a foam obtained from the epoxy resin composition.

Further, according to the method for reinforcing a vehicle body of the present invention, when reinforcing a vehicle body provided with a box-shaped member made of a steel plate, a portion of the steel plate corresponding to the inside of the box-shaped member is
A sheet made of the epoxy resin composition for reinforcing the vehicle body is arranged, and then the steel plate is assembled to assemble the box-shaped member. Thereafter, the assembled box-shaped member is subjected to an electrodeposition coating process, and baking of this process is performed. The method is characterized in that the sheet is foamed in the step.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As described above, the epoxy resin composition of the present invention comprises (A)
An epoxy resin derived from bisphenol A and / or bisphenol F, (B) an aromatic polyether,
It contains (C) a thermally activated curing agent for epoxy resin, (D) a thermally decomposable organic foaming agent, and (E) an inorganic filler.

Here, as an example of the epoxy resin derived from bisphenol A used as the component (A), the following general formula [1]

[0022]

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(Wherein n is a number equal to or greater than 0). Examples of the epoxy resin derived from bisphenol F include the following general formula [2]

[0024]

Embedded image

(In the formula, n represents a number of 0 or more.) The epoxy resin represented by the general formulas [1] and [2] in which n is less than 1 as an average value is liquid at room temperature and can be suitably used.

In the present invention, the epoxy resins represented by the above general formulas [1] and [2] can be used as a mixture. In addition, the bisphenol chain represented by the general formula [1] or [2] can be used. As a part, a chain in which a bisphenol A unit and a bisphenol F unit are mixed can also be suitably used.

Next, as the aromatic polyether used as the component (B), polyether sulfone and polyetherimide are particularly desirable. These have good compatibility with the bisphenol A and F type epoxy resins described in the above-mentioned component (A), and can obtain a uniform composition with a polar solvent such as methylene chloride. Further, such a polyether has a benzene ring in its main chain skeleton, and thus has extremely high heat resistance, whereby the heat resistance of the obtained composition can be significantly improved.

The amount of the aromatic polyether used as the component (B) is not particularly limited, but is usually 1 to 40 parts by weight based on 100 parts by weight of the epoxy resin (A). . If it is less than 1 part by weight, sufficient impact resistance and heat resistance cannot be obtained, and if it exceeds 40 parts by weight,
The viscosity of the uncured product increases remarkably, making it difficult to adhere to the steel plate member and making it difficult to increase the expansion ratio.

Examples of the heat-active curing agent for epoxy resin used as the component (C) include dicyandiamide, 4,4'-diaminodiphenylsulfone,
Imidazole derivatives such as 2-n-heptadecyl imidazole, isophthalic dihydrazide, N, N′-dialkyl urea derivatives, N, N′-dialkyl thiourea derivatives, acid anhydrides such as tetrahydrophthalic anhydride, isophorone diamine; m-phenylenediamine, N-aminoethylpiperazine, melamine, guanamine, boron trifluoride complex compound, trisdimethylaminomethylphenol, etc., and these may be used alone or in any combination of two or more. it can.

Among these curing materials, dicyandiamide can be particularly preferably used. In this case, in order to perform sufficient foaming, the baking temperature of the electrodeposition coating is set to 140.
The baking time is preferably in the range of 10 to 30 minutes.

The amount of the heat-active type curing agent (C) is not particularly limited, but is usually 3 to 30 parts by weight based on 100 parts by weight of the epoxy resin (A). If the amount is less than 3 parts by weight, the composition is not sufficiently cured and the rigidity is remarkably reduced. If the amount is more than 30 parts by weight, an excessive exothermic reaction occurs during the curing, causing partial decomposition and thermal deterioration. It may cause significant deterioration of the target strength.

Next, examples of the organic blowing agent used as the component (D) include azo compounds such as azodicarbonamide and azobisisobutyronitrile; nitroso compounds such as dinitrosopentamethylenetetramine; -Sulfohydrazide compounds such as -toluenesulfonylhydrazide and 4,4'-oxybenzenesulfonylhydrazide, and these can be used alone or in any combination of two or more. Also,
Among them, azodicarbonamide can be particularly preferably used.

When an organic pyrolysis type foaming agent is used, zinc white, zinc nitrate, lead phthalate, lead carbonate, and tribasic phosphorus are usually used as foaming aids in order to control an appropriate foaming temperature. Inorganic salts such as lead acid, tribasic lead sulfate, etc., metal soaps such as zinc fatty acid soap, lead fatty acid soap, cadmium fatty acid soap, acids such as boric acid, oxalic acid, succinic acid, adipic acid, urea, biurea, ethanolamine , Glycol,
One or more of glycerin and the like can be mixed and used.

The amount of the organic foaming agent (D) is not particularly limited, but is usually in the range of 0.5 to 20 parts by weight per 100 parts by weight of the epoxy resin (A). Is preferred. If this amount is less than 0.5 parts by weight,
If the foaming becomes insufficient, and if it exceeds 20 parts by weight, the control of the foaming becomes insufficient, and stable mechanical properties cannot be obtained.

The inorganic filler used as the component (E) includes, for example, calcium carbonate, talc,
Clay, mica, aluminum hydroxide, glass beads,
Shirasu balloons and the like can be mentioned, and these can be used alone or in any combination of two or more.
Among them, calcium carbonate can be particularly preferably used.

The amount of the inorganic filler used as the component (E) is not particularly limited, but is usually 3 to 3 based on 100 parts by weight of the epoxy resin (A).
00 parts by weight. If the amount is less than 3 parts by weight, a sufficient reinforcing effect cannot be obtained. If the amount exceeds 200 parts by weight, the viscosity is remarkably increased to make application and adhesion difficult, and the composition becomes brittle and the mechanical strength is significantly impaired. Become.

Next, a method for producing the epoxy resin composition of the present invention will be described. This epoxy resin composition,
Component (A) is an epoxy resin, component (B) is an aromatic polyether, component (C) is a thermally activated curing agent, component (D) is an organic foaming agent, component (E) is an inorganic filler, It can be prepared by blending the additive components used as required and mixing them uniformly.

The above-mentioned additional components include, for example, plasticizers, diluents, stabilizers, emulsifiers, reinforcing agents, coloring agents, antioxidants,
UV absorbers, lubricants, thixotropic agents, and curing accelerators.

Next, a method of reinforcing a vehicle body according to the present invention will be described. This reinforcing method is based on the fact that the above-described epoxy resin composition of the present invention is foamed and filled inside a box-shaped member, and typically includes the following steps.

That is, the above-mentioned epoxy resin composition is formed into a sheet, and the obtained composition sheet is adhered to a pre-formed steel sheet constituting a box-shaped member. In this case, the composition sheet needs to be adhered to a portion corresponding to the inside of the box-shaped member in the portion of the steel plate. Next, a box-shaped member is assembled using the steel sheet to which the composition sheet is adhered to form an automobile body. Then, an automobile body provided with such a box-shaped member is subjected to an electrodeposition coating process, and the adhered composition sheet is heated and foamed in the baking step in this process, and the formed foam is a box-shaped body. The inside of the member is uniformly filled, and the reinforcement of the vehicle body is completed.

As described above, in the reinforcing method of the present invention, since the composition sheet is solid, unlike the urethane resin foaming, the stock solution does not leak and the handling property is extremely good. In addition, in the above-described steps, it is a matter of course that, after assembling the box-shaped member, the composition sheet may be adhered inside the box-shaped member. The above-mentioned baking step is preferably performed by heating at 140 to 210 ° C. for 10 to 30 minutes in order to sufficiently foam the composition sheet.

[0042]

EXAMPLES 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. The physical properties of the epoxy resin compositions obtained in each example were evaluated by the following methods.

(1) Static test A foam obtained by foaming the epoxy resin composition of each example with respect to a central portion 100 mm of a box-shaped section member 20 having a cross section of 50 × 60 × 400 mm as shown in FIG. The material 10 was filled and subjected to a bending test. The epoxy resin composition was compared with a box-shaped cross-section member when not filled, and the bending rigidity was evaluated according to the following criteria. The filling condition of the foam material is 17
Baking was performed at 0 ° C. for 20 minutes.

○: Rigidity higher than unfilled member of the same weight Δ: Rigidity equivalent to unfilled member of the same weight ×: Rigidity lower than unfilled member of the same weight

(2) Impact Test Using the box-shaped section member 20 shown in FIG. 1, a 7 kg weight was dropped at a speed of 25 km / h to conduct a bending impact test, and the epoxy resin composition of each example was used. The comparison was made between the filled and unfilled cases, and the energy absorption was evaluated according to the following criteria. The filling condition of the foam material is the same as the static test.

：: Rigidity higher than unfilled member of the same weight △: Rigidity equivalent to unfilled member of the same weight ×: Rigidity lower than unfilled member of the same weight

Example 1 100 parts by weight of a liquid bisphenol A type epoxy resin and 2 parts by weight of polyethersulfone were dissolved in 200 ml of methylene chloride and vacuum-dried with stirring to obtain a paste. Next, 6 parts by weight of a curing agent dicyandiamide, 5 parts by weight of an organic blowing agent azodicarbonamide, and 100 parts by weight of an inorganic filler calcium carbonate were mixed with the paste at room temperature using a planetary mixer. An epoxy resin composition was prepared. Table 1 shows the evaluation results.

Example 2 An epoxy resin composition was obtained by repeating the same operation as in Example 1 except that the blending amount of polyethersulfone was changed to 30 parts by weight. Table 1 shows the evaluation results.

Comparative Example 1 An epoxy resin composition was obtained by repeating the same operation as in Example 1 except that the amount of the polyether sulfone was changed to 0.5 part by weight. Table 1 shows the evaluation results.

Comparative Example 2 An epoxy resin composition was prepared by repeating the same operation as in Example 1 except that the blending amount of polyethersulfone was changed to 50 parts by weight. But,
The viscosity of the obtained composition was too high to foam sufficiently.

Example 3 The same operation as in Example 1 was repeated except that the blending amount of the polyether sulfone was changed to 10 parts by weight and the blending amount of the curing agent dicyandiamide was changed to 3 parts by weight. Obtained. Table 1 shows the evaluation results.

Example 4 The same operation as in Example 1 was repeated except that the blending amount of polyether sulfone was changed to 10 parts by weight and the blending amount of the curing agent dicyandiamide was changed to 30 parts by weight. Obtained. Table 1 shows the evaluation results.
Shown in

Comparative Example 3 The same procedure as in Example 1 was repeated except that the blending amount of polyethersulfone was changed to 10 parts by weight and the blending amount of the curing agent dicyandiamide was changed to 1 part by weight. Obtained. Table 1 shows the evaluation results.

Comparative Example 4 The same operation as in Example 1 was repeated except that the blending amount of polyether sulfone was changed to 10 parts by weight, and the blending amount of the curing agent dicyandiamide was changed to 40 parts by weight. Obtained. Table 1 shows the evaluation results.
Shown in

Example 5 An epoxy resin composition was obtained by repeating the same operation as in Example 1 except that the amount of the organic blowing agent azodicarbonamide was changed to 1 part by weight. Table 1 shows the evaluation results.

Comparative Example 5 The same operation as in Example 1 was repeated except that the blending amount of the polyether sulfone was changed to 10 parts by weight and the blending amount of the organic blowing agent azodicarbonamide was changed to 0.1 parts by weight. Thus, an epoxy resin composition was obtained. Table 1 shows the evaluation results.

Comparative Example 6 The same operation as in Example 1 was repeated except that the blending amount of the polyether sulfone was changed to 10 parts by weight and the blending amount of the organic blowing agent azodicarbonamide was changed to 25 parts by weight. A resin composition was obtained. Table 1 shows the evaluation results.

Example 7 The same operation as in Example 1 was repeated except that the amount of the polyether sulfone was changed to 10 parts by weight and the amount of the inorganic filler calcium carbonate was changed to 5 parts by weight. A composition was obtained. Table 1 shows the evaluation results.

Example 8 The same operation as in Example 1 was repeated except that the blending amount of the polyether sulfone was changed to 10 parts by weight and the blending amount of the inorganic filler calcium carbonate was changed to 200 parts by weight. A composition was obtained. Table 1 shows the evaluation results.

Comparative Example 7 The same operation as in Example 1 was repeated except that the amount of the polyether sulfone was changed to 10 parts by weight and the amount of the inorganic filler calcium carbonate was changed to 1 part by weight. A composition was obtained. Table 1 shows the evaluation results.

Comparative Example 8 The same operation as in Example 1 was repeated except that the blending amount of the polyether sulfone was changed to 10 parts by weight and the blending amount of the inorganic filler calcium carbonate was changed to 250 parts by weight. A composition was obtained. Table 1 shows the evaluation results.

Example 9 The same procedure as in Example 1 was carried out except that 100 parts by weight of a liquid bisphenol F type epoxy resin was used instead of the liquid bisphenol A type epoxy resin, and the blending amount of polyether sulfone was changed to 10 parts by weight. The operation was repeated to obtain an epoxy resin composition. Table 1 shows the evaluation results.
Shown in

Example 10 An epoxy resin composition was obtained by repeating the same operation as in Example 1 except that 10 parts by weight of polyetherimide was used instead of polyethersulfone. Table 1 shows the evaluation results.

[0064]

[Table 1]

(Embodiment 11) As shown in FIG. 2, a steel plate 2 formed in advance so as to constitute a center pillar waist portion and a roof rail / center pillar joint portion of a vehicle body is formed as shown in FIG.
The epoxy resin composition sheet 1 of the present invention was adhered. Next, after welding the steel plate 2 and further assembling the vehicle body 3,
The body 3 was washed with a caustic treatment solution in order to improve the adhesion of the coating film. Further, after the vehicle body 3 is immersed in the electrodeposition liquid tank 4 and subjected to rust prevention treatment, the vehicle body 3 is placed in a baking furnace 5 and heated at 170 ° C.
When the electrodeposition coating film was baked under the conditions of 20 minutes, the composition sheet 1 was sufficiently foamed and cured to form a uniform foamed material 1 '. As described above, the epoxy resin composition of the present invention can be favorably used in an actual automobile production line, and the rigidity of the box-shaped structural member of the vehicle body can be reliably improved.

[0066]

As described above, according to the present invention,
By mixing a certain kind of aromatic polyether with an epoxy resin, an epoxy resin composition having impact resistance is obtained, and after forming this into a sheet, it is mounted on a preformed steel sheet, and the steel sheet is attached. After assembling the box-shaped member, it is foamed and filled in the baking process at the time of electrodeposition coating of the car body, so it can be easily and uniformly foamed and filled in the box-shaped member, ensuring the rigidity of the car body The present invention can provide an epoxy resin composition for reinforcing a vehicle body, a vehicle body reinforcing structure, and a method of reinforcing a vehicle body, which can be improved.

That is, according to the present invention, it is possible to reliably reinforce the body frame while reducing the weight. In addition, this is expected to improve the riding comfort of the vehicle and reduce noise and vibration, and furthermore, since the highly rigid foam is filled in the box-shaped closed section member, the energy absorbing effect at the time of vehicle collision is also improved. You can expect.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a test device for evaluating the rigidity of a vehicle body reinforcement structure according to the present invention.

FIG. 2 is a process chart showing an application example of the vehicle body reinforcing method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Epoxy resin composition sheet 1 'Foaming material 2 Steel plate 3 Car body 4 Electrodeposition bath 5 Baking furnace 10 Foaming material 20 Box-shaped section member

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 81/06 C08L 81/06 // C08G 59/24 C08G 59/24 59/40 59/40

Claims (7)

[Claims] 1. An epoxy resin derived from bisphenol A and / or bisphenol F (A) (100 parts by weight), (B) 1 to 40 parts by weight of an aromatic polyether,
(C) 3 to 30 parts by weight of a thermally activated curing agent for epoxy resin,
An epoxy resin composition for reinforcing a vehicle body, comprising (D) 0.5 to 20 parts by weight of a thermally decomposable organic foaming agent and (E) 3 to 200 parts by weight of an inorganic filler. 2. The epoxy resin composition for reinforcing a vehicle body according to claim 1, wherein the aromatic polyether (B) is a polyether sulfone. 3. The epoxy resin composition for reinforcing a vehicle body according to claim 1, wherein the aromatic polyether (B) is a polyetherimide. 4. A foamed body formed in a solid state at normal temperature and foamed by a heat treatment.
The epoxy resin composition for reinforcing a vehicle body according to any one of the above items. 5. A vehicle body reinforcing structure characterized by filling the inside of a box-shaped member with the foam according to claim 4. 6. The reinforcing member according to claim 1, wherein a portion of the steel plate corresponding to the inside of the box-shaped member is provided for reinforcing a vehicle body having a box-shaped member formed of a steel plate. A sheet made of an epoxy resin composition for reinforcing the vehicle body is arranged, and then the steel plate is assembled to assemble the box-shaped member. Thereafter, the assembled box-shaped member is subjected to an electrodeposition coating process.
A reinforcing method for a vehicle body, wherein the sheet is foamed in a baking step of this processing. 7. The baking step is performed at 140 to 210 ° C.
7. The method according to claim 6, wherein the heating is performed for 10 to 30 minutes.