JPH10166503A - Thin steel plate reinforcing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize well-balanced reinforcing effects in rigidity and in toughness by a method wherein a reinforcing resin coating film layer formed on the rear surface of a thin steel plate is made of epoxy resin-based paint (excluding non-rigid type paint). SOLUTION: A thin steel plate reinforcing structure is a reinforcing resin coating film layer 10 formed on the rear surface of a thin steel plate 12a. By adopting a liquid rigid type epoxy resin and a liquid non-rigid type epoxy resin as the essential components of the base resin of an epoxy resin-based paint forming the reinforcing resin coating film layer, well-balanced reinforcing effect in rigidity and in toughness. Further, the rubbery skeleton epoxy resin in the non-rigid type epoxy resin gives a toughness reinforcing effect to coating film, resulting in following up with the deformation of the steel plate and taking a roll for absorbing the difference between the thermal expansion coefficient of the steel plate and that of the coating film so as to secure the adhesion to the steel plate. The epoxy resin-based paint and a hardener are mixed together in a mixing tank and coated in spray with an air spray or the like after being fed from the mixing tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin steel sheet reinforcing structure in which a thin resin sheet has a reinforcing resin coating layer formed on the back surface thereof. In particular, the present invention is suitable for a steel plate for a vehicle (body sheet metal) for which weight reduction and automation are required.

[0002]

2. Description of the Related Art In recent years, there has been a tendency to use thin steel plates (usually 1 mm or less) more than ever in order to reduce the weight of automobile bodies.

However, when a thin steel plate is used for a large area such as a door panel, there is a problem that rigidity is insufficient and dent resistance is reduced.

For this reason, there is a door panel (thin steel plate) reinforcement structure in which an adhesive prepreg sheet is set on the back surface of a door panel (thin steel plate), and the prepreg sheet is thermoset integrally in an electrodeposition furnace or the like. (JP-A-6-171
001 and the like). Here, the prepreg means a glass fiber mat impregnated with a thermosetting resin such as an epoxy resin in a semi-cured state (stage B) and self-adhered to a steel plate or the like.

[0005]

However, the above-mentioned thin steel plate reinforcing structure has the following problems.

[0006] The construction of the reinforcing structure is difficult to automate,
The number of construction steps increases.

Since the glass fiber mat is rigid, if it has a curved surface such as a door outer panel in recent years, it is difficult to sufficiently follow a prepreg corresponding to the curved surface, increasing the number of construction steps and increasing the reinforcing effect in toughness. Problems are easy to occur.

[0008] It is necessary to trim the prepreg sheet according to the shape of the construction site, which increases construction man-hours and causes material loss due to the trimming.

In view of the above, it is an object of the present invention to provide a thin steel plate reinforcing structure capable of reducing the number of construction steps and material loss.

Another object of the present invention is to provide a thin steel plate reinforcing structure having a sufficient reinforcing effect balanced with rigidity and toughness.

[0011]

SUMMARY OF THE INVENTION A thin steel plate reinforcing structure according to the present invention is solved by the following constitution.

[0012] A thin steel plate reinforcing structure in which a reinforcing resin coating layer is formed on the back surface of a thin steel plate, wherein the reinforcing resin coating layer is an epoxy resin-based paint (excluding only the soft type). Is formed.

[0013] Here, the base resin of the epoxy resin-based paint is composed of a liquid hard type epoxy resin and a liquid soft type epoxy resin as essential components, so that both the rigidity and the toughness are balanced. It is desirable because effects can be obtained.

Further, it is desirable from the viewpoint of coating workability that silica is added to the epoxy resin paint as a reinforcing agent and a thixotropic agent.

[0015]

[Detailed Description of Means] Next, each component of the above means will be described in detail. In the following description, the blending unit is a weight unit unless otherwise specified.

A. A thin steel plate reinforcing structure in which a reinforcing resin coating layer is formed on the back surface of a thin steel plate, wherein the reinforcing resin coating layer is formed of an epoxy resin-based coating (excluding only a soft type). This is the basic configuration.

Here, the thin steel plate is not particularly limited.
Usually 0.1 to 1.5 mm, desirably 0.2 to 0.8
Applies to those within mm. Naturally, the thin steel plate may be one subjected to a surface treatment such as plating.

B. The base resin of the epoxy resin-based paint may be either a two-pack type or a one-pack type, and is not particularly limited. Usually, a liquid hard type epoxy resin and a liquid soft type epoxy resin are essential components, and react as necessary. What is appropriately diluted to a viscosity with an acidic diluent is used.

(1) Here, the liquid hard type epoxy resin is not particularly limited, but has a viscosity (25 ° C.) (JI
SK 7117 rotational viscometer method;
0-25000 cPs, desirably 10,000-16
000 cPs is used. If the viscosity is too low, that is, if the molecular weight is low, it is difficult to obtain toughness, and if the viscosity is too high, it is difficult to adjust the coating material to an appropriate viscosity, which tends to cause problems in coating workability.

(2) As the liquid soft type epoxy resin, a rubber skeleton epoxy resin is preferable because it has a high reinforcing effect on toughness with respect to the coating film (hereinafter referred to as “toughness reinforcing effect”). And to some extent
It is desirable to adjust the viscosity using a polyether skeleton epoxy resin having a toughness reinforcing effect. When the viscosity is adjusted only with the reactive diluent, the reinforcing effect of the rubber skeleton epoxy resin is reduced, and the strength of the coating film is reduced.

The ratio of the former and the latter is 8/2 to 3 /
7 (preferably 7/3 to 4/6).

The mixing ratio of the soft type epoxy resin to the hard epoxy resin is set to hard type / soft type = 9/1 to 5/5 (preferably 8/2 to 6/4).

If the hard type is too small, it is difficult to obtain a reinforcing effect in rigidity (hereinafter, referred to as "rigidity reinforcing effect"). If the soft type is too small, it is difficult to obtain toughness, and it is difficult to obtain a balanced reinforcing effect in rigidity and toughness.

(I) The above-mentioned rubber skeleton epoxy resin is a so-called reactive elastomer or rubber-modified epoxy resin. A low-molecular-weight epoxy resin is added to a liquid rubber having an acid or amine introduced into a terminal. It refers to a product in which an epoxy group is introduced by reacting.

The rubber skeleton epoxy resin generally has a viscosity of 2000 to 90000 cPs, preferably 2 to 90000 cPs.
Those with 500 to 6000 cPs are used.

The rubber skeleton epoxy resin gives the coating film a toughness reinforcing effect, follows the deformation of the steel sheet, and also acts to absorb the difference in the coefficient of thermal expansion between the steel sheet and the coating film, thereby ensuring the adhesion to the steel sheet.

Examples of the liquid rubber include liquid NBR (nitrile rubber), liquid CR (chloroprene rubber), liquid BR (butadiene rubber) and the like.

More specifically, those prepared by reacting a low-viscosity epoxy resin (bisphenol A) with an acid-terminated liquid NBR or an amine-terminated liquid NBR, such as “Hiker CTBN precondensed epoxy resin” and “Hiker ATBN”
A product marketed by Zeon Corporation under a trade name such as "precondensed epoxy resin" can be suitably used.

(Ii) The polyether skeleton epoxy resin is
It refers to a product obtained by reacting epichlorohydrin or the like with an end of a polyether (polyglycol) to introduce an epoxy group. Usually, those having a viscosity (25 ° C.) of 30 to 200 cPs and an epoxy equivalent of 150 to 400 cPs can be used. Viscosity (25 ° C.): 55 to 100 cPs, epoxy equivalent: 305 to 335, and under the trade name “DER732”
Those marketed by Dow Chemical Co., Ltd. can be suitably used.

The polyether skeleton epoxy resin has a function of adjusting the viscosity of the paint (base agent) to a low level without reducing the toughness reinforcing effect of the rubber skeleton epoxy resin.

(3) The reactive diluent is added to adjust the viscosity of the paint (base material) to a low level, but is not inevitable if the viscosity can be adjusted with a polyether skeleton epoxy resin.

Usually, the viscosity of the base material (2
When considering the sagging property after coating at 5 ° C.) of 1000 to 80,000 cPs, the addition is desirably performed in the range of 50,000 to 80,000 cPs. At this time, the addition amount differs depending on the viscosity of the hard type and the soft type.
0 to 35 parts for 0 parts.

As the reactive diluent, the following monofunctional and polyfunctional materials can be used.

Butyl glycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether,
p-tert-butyl glycidyl phenyl ether, tertiary carboxylic acid monoglycidyl ether, 2-ethylhexyl glycidyl ether and the like.

1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, trimethylolpropane triglycidyl ether and the like.

(4) The curing agent is not particularly limited as long as it is used for an epoxy resin, and the following amine-based curing agents (polyamines), acid anhydride-based curing agents, and latent curing agents can be used.

Aliphatic amine: diethylene triamine,
Ethylenediamine, aromatic amine: diaminodiphenylmethane, diaminodiphenylsulfone, tertiary amine: benzyldimethylamine, 2-methylimidazole cyclic anhydride: methyltetrahydrophthalic anhydride,
MTE hexahydrophthalic anhydride, linear anhydride: adipic anhydride Thermosetting type: dicyandiamide, BF ₃ amine complex, acid hydrazide, water setting type: ketimine, UV setting type: diazonium salt, sulfonium salt It is desirable to use a combination of a fast curing agent and a slow curing agent as the curing agent from the viewpoints of paint handling properties and application workability.

The fast-curing and slow-curing compounds may be used in combination with the above-mentioned curing agents. However, usually, the above-mentioned amine-based curing agents are modified, that is, steam obtained by polycondensing polyamine and dicarboxylic acid. It is desirable to use a combination of a fast-setting low-molecular-weight polyamidoamine and a low-hardness-reactive high-molecular-weight polyamine among the polyamidoamines having a reduced pressure because a flexible coating film can be easily obtained.

As the high molecular weight polyamidoamine, those having a viscosity (25 ° C.) of 30 or more and an amine value of 100 to 400 can be used. Specifically, “Tomide 215X · 2
25X · 235S ”(trade name of Fuji Kasei),“ Persamide 125 ”(trade name of Henkel Hakusui Co., Ltd.) and the like can be suitably used.

The low molecular weight polyamidoamines include
Those having a viscosity (25 ° C.) of less than 30 and an amine value of more than 400 can be used.
500 "(trade name of Henkel Hakusui) can be preferably used.

The amount of the curing agent is usually 20 to 80 parts, preferably 40 to 6 parts, per 100 parts of the epoxy resin.
0 copies.

C. Next, a method for producing the thin steel sheet reinforcing structure of the present invention using the above epoxy resin paint will be described.

(I) A main agent and a curing agent satisfying the above requirements are mixed in a mixing tank, and the outer panel (substrate to be coated) 12a of the suspended back door 12 needs to be reinforced by air spray or the like from the mixing tank. Spray coating is applied to the portion (hatched portion) A (see FIGS. 1 and 2). The coating thickness of the reinforcing resin coating layer 10 at this time depends on the required reinforcing strength, but is usually 1 to 10 mm, more usually 2 to 5 mm. The object to be coated is subjected to a pretreatment such as a degreasing treatment as necessary.

The reinforcing portions to which the present invention can be applied can be applied to each of the front door 14, the rear door 16, and the quarter panel 18 requiring reinforcing (hatched portion) A shown in FIG.

(Ii) Subsequently, the epoxy resin is cured.
Curing conditions are unnecessary in the case of a room temperature curing type, but in the case of a heat curing type, for example, 150 to 200 ° C. ×
30 to 10 minutes. In this way, the epoxy resin coating film, which is the reinforcing resin coating layer 10 formed on the back surface of the outer panel 12a, has a balanced reinforcing effect in rigidity and toughness, as supported by the later-described examples. The tensile strength and dent resistance are improved.

When the reinforcing coating film is formed by spraying, since the thickness of the peripheral coating film can be gradually changed, sink and distortion due to resin shrinkage of the thin steel plate hardly occur.

[0047]

The function and effect of the present invention are as follows.
As described above, since the reinforcing resin coating layer made of the epoxy resin-based paint is formed on the back surface of the thin steel plate, the following operations and effects are achieved.

By selecting the molecular weight of the base resin, the skeletal structure, and the type of the curing agent, the epoxy resin adheres the reinforcing resin coating layer having the necessary strength (balance of rigidity and toughness) to the adhesive resin. Since it can be formed at a desired portion of a thin steel plate with good performance, the following problems in the case of reinforcement with a conventional glass mat prepreg can be solved.

The construction of the reinforcing structure is difficult to automate,
The number of construction steps increases.

Since the glass fiber mat is rigid, if it has a curved surface such as a door outer panel of recent times, it is difficult to sufficiently follow the prepreg to the curved surface, which increases the number of construction steps and increases the reinforcing effect in toughness. Problems are easy to occur.

It is necessary to trim the prepreg sheet according to the shape of the construction site, which increases the construction man-hour cost and causes a material loss due to the trimming.

Therefore, the thin steel plate reinforcing structure of the present invention can reduce the number of construction steps and material loss, and also has a reinforcing effect.

In particular, when the reinforcing resin coating layer is formed by spray coating, the peripheral coating thickness can be gradually changed.
Sinking and distortion due to resin shrinkage are unlikely to occur in thin steel plates.

When the base resin of the epoxy resin-based paint contains a liquid hard type epoxy resin and a liquid soft type epoxy resin as essential components, a rubber skeleton epoxy resin is further used as the soft type epoxy resin. When a resin-containing material is used, a reinforcing effect that balances rigidity and toughness can be obtained.

Further, when a reinforcing filler is added to the epoxy resin-based paint, the degree of reinforcement is further improved. In this case, when the reinforcing filler can impart thixotropic properties such as silica, the coating workability (sagging resistance immediately after coating) can be improved.

[0056]

EXAMPLES Examples and comparative examples performed to confirm the effects of the present invention will be described below.

(I) Preparation of test piece: SPC of a thin plate placed horizontally using each epoxy resin paint having the formulation shown in Table 1
A weir was provided around a C steel plate (150 mm length × 25 mm width × 0.8 mm thickness) 20 and spray-coated at a thickness of 2 mm.
Then, one hour after the application, the composition was heated and cured under the indicated conditions to form the reinforcing resin coating layer 10.

A suspended steel plate having a similar size was spray-coated so as to have a thickness of about 2 mm, and the dripping property of the coating film was also observed.

(Ii) Compression test: As shown in FIG. 4, each test piece obtained above was placed between fulcrums F with a span of 100 mm.
Set with steel plate 20 on top, compression speed 500mm / min
I went in. Then, the upper yield load of each test piece and the deformation amount at that time were measured.

Further, a product reinforced with a commercially available glass fiber epoxy resin prepreg (3 mmt) (conventional example), or
The same test was performed for the above-mentioned SPCC steel plate (blank) without reinforcement.

(Iii) Test results and evaluation: Table 1 shows the test results.
Shown in In the conventional example, the upper yield load was 11 kg, the deformation amount was 4 mm, and the blank was the upper yield load: 3.5 kg and the deformation amount was 4 mm. From Table 1, it can be seen that each of the examples has at least the same reinforcing effect as the conventional prepreg.

Further, it can be seen that the comparative example using only the soft epoxy resin has almost no reinforcing effect.

Further, compared with the case of using only the hard epoxy resin, the combined use of the soft epoxy resin can provide a reinforcing effect balanced in rigidity and toughness. It can be seen that the reinforcing effect (breaking strength) is increased.

Further, with respect to the sagging resistance of the coating film,
It can be seen that there was no coating sagging except for.

[0065]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a front view of an outer panel of a back door to which the present invention is applied.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is an isolated front view of a vehicle body sheet metal showing a portion to which the present invention is applied;

FIG. 4 is an explanatory view showing a method of a compression load test in Examples.

[Explanation of symbols]

 10 Reinforcement resin coating layer 12 Back door 12a Outer panel (substrate to be coated)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Landlord 1 Ochiai Ogata, Kasuga-cho, Nishikasugai-gun, Aichi Prefecture Inside Toyota Gosei Co., Ltd. (72) Inventor Yasunori Tsuji 100 Kanayama, Ichiriyama-cho, Kariya City, Aichi Prefecture Inside the Auto Body Co., Ltd. (72) Inventor Kenji Sugiura 100, Kanayama, Ichiriyama-machi, Kariya City, Aichi Prefecture Inside Toyota Auto Body Co., Ltd.

Claims (5)

[Claims] 1. A thin steel plate reinforcing structure in which a reinforcing resin coating layer is formed on the back surface of a thin steel plate, wherein the reinforcing resin coating layer is made of an epoxy resin-based paint (excluding only a soft type). ). A thin-walled steel plate reinforcing structure characterized by being formed by: 2. The thin-walled steel sheet reinforcing structure according to claim 1, wherein the base resin of the epoxy resin-based paint contains a liquid hard type epoxy resin and a liquid soft type epoxy resin as essential components. . 3. The thin steel plate reinforcing structure according to claim 2, wherein a rubber skeleton epoxy resin is contained as the soft type epoxy resin. 4. The thin steel sheet reinforcing structure according to claim 2, wherein silica is further added to the epoxy resin-based paint as a reinforcing agent and a thixotropic agent. 5. The thin steel plate reinforcing structure according to claim 1, wherein the reinforcing resin coating layer is formed by spray coating.