JPH0670151B2 - Method for manufacturing vehicle outer panel structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a vehicle outer panel, and more particularly to a method for manufacturing a vehicle outer panel structure having excellent heat insulation and reinforcement.

(Problems to be Solved by Conventional Techniques and Inventions) In recent years, it has been desired to improve the quality of vehicle exterior panel panels from the following viewpoints.

(1) Improving livability in the passenger compartment by increasing heat insulation, and (2) Improving a solid feel by increasing rigidity.

First, the significance of high heat insulation of the outer panel will be explained.

Generally, the heat inflow into the vehicle interior and the heat outflow to the outside of the vehicle compartment are highly likely to occur through the outer panel such as the door, fender, floor, roof and dash.

Therefore, in order to alleviate the inflow and outflow of heat, various heat insulating materials such as felt and glass mat are used on the back surface of the outer panel. For example, a roof panel is a part that is easily exposed to the heat of sunlight and is exposed to a high temperature of 80 to 100 ° C. in summer, and thus has a large amount of heat inflow. As a countermeasure against this, a heat insulating structure as shown in FIGS. 2 and 3 is generally adopted. 2 and 3 show an example of a suspended ceiling structure. The structure of the back surface of the roof panel 1 is a heat insulating material 6 and a double-sided tape interposed between the heat insulating material 6 for attaching the heat insulating material 6 to the back surface of the roof panel 1. And a head lining 4 suspended from a listing wire 3 stretched on the lower surface thereof. As the heat insulating material 6, felt or glass fiber mat made of natural or synthetic fiber is used. The same kind of heat insulating material is used for the outer panels of other floors and dashes to insulate the passenger compartment.

Next, the necessity of increasing the rigidity of the outer panel will be described.
In automobiles, weight saving is being promoted to save resources and energy. In this regard, if the material thickness is reduced or the structural members are reduced to reduce the weight, the strength decreases, and in the case of automobile doors, the decrease in the strength of the part causes insufficient surface tension and rigidity as a part. Problems such as lack of feeling appear. In order to solve this problem, Japanese Utility Model Laid-Open No. 55-101659 proposes a method of using a reinforcing material for a door panel. FIG. 4 shows the reinforcing structure. In FIG. 4, 7 is a door panel and 8 is a thermosetting reinforcing material. Of these outer panel members,
The heat insulating material is a molded product that is molded in advance and is manually attached, but there is a problem in that it takes time to work because it is large. Moreover, since the heat insulating material is, for example, a molded product obtained by simply laminating synthetic fibers or glass fibers in the vertical and horizontal directions, the heat insulating property is not always sufficient and the performance is not satisfied. Further, conventionally, since the heat insulating material and the reinforcing material are separately attached, workability is poor. Under such circumstances, it has been desired to develop a highly heat-insulating material with good workability.

An object of the present invention is to provide a method for manufacturing a vehicle outer panel structure that is easy to construct and has excellent heat insulation and reinforcement.

(Means for Solving Problems) As a result of studying a method of hardening vinyl chloride without lowering the foamability of vinyl chloride, the present inventors have found that vinyl chloride resin for paste, plasticizer, high-temperature foamable foaming agent. ,Epoxy resin,
A foaming agent does not foam in advance a composition comprising a heat-activatable curing agent for an epoxy resin as an essential component, and if necessary, a heat stabilizer, a foaming accelerator, a filler, a colorant, an adhesive, etc. After being molded at a temperature and made into a sheet, it is attached to the back surface of the vehicle outer panel and then heated to foam and cure, making it easy to construct, high-magnification, and hard foam. Therefore, it was found that the heat insulating property and the reinforcing property can be improved, and the object of the present invention was achieved.

The present invention will be described in detail below.

The foamable resin composition used in the present invention contains at least a vinyl chloride resin for paste, a plasticizer, a high-temperature foaming foaming agent, an epoxy resin and a heat-activatable curing agent for epoxy, and optionally, a cell regulator. , A filler, a pigment agent, a heat stabilizer, a composition comprising a viscosity modifier, etc., which has been previously formed into a sheet at a temperature not higher than the foaming temperature of the foaming agent, and further 120 ° C to 200 ° C. When heated, the foaming agent foams and can be cured by crosslinking the epoxy resin.
Vinyl chloride resin is produced by emulsion polymerization or emulsion suspension polymerization for processing paste, and homopolymer alone or vinyl chloride and vinyl acetate, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, maleic acid. ,
Known copolymers such as maleic acid ester can be used alone or in a blend with a vinyl chloride homopolymer. Further, vinyl chloride or a vinyl chloride copolymer produced by suspension polymerization can be used as a blend.

Examples of the plasticizer include dioctyl phthalate, dibutyl phthalate and other phthalates, tricresyl phosphite and other phosphates, dioctyl adipate,
Fatty acid ester such as dioctyl sebacate, for example, a polyester such as a condensate of adipic acid and ethylene glycol, trimellitic acid ester such as trioctyl trimellitate, chlorinated paraffin, alkylbenzene, known chlorination such as high molecular weight aromatic The plasticizers for vinyl can be used alone or in combination. The blending amount of the plasticizer is not particularly limited, but vinyl chloride 100
It is preferable to blend in the range of more than 10 parts by weight and 150 parts by weight or less with respect to parts by weight. If the compounding amount is 10 parts by weight or less, the foaming ratio does not improve, and if it exceeds 150 parts by weight, the hardness does not increase and the reinforcing effect decreases.

As the foaming agent, a high temperature decomposition type organic or inorganic foaming agent, a high temperature expansion type microcapsule and the like are used. As the organic foaming agent, azodicarbonamide, p-toluene sulfonyl hydrazide, dinitrosopentamethylene tetramine, 4,
4'-oxybisbenzenesulfonyl hydrazide and the like are used. The decomposition temperature of the organic foaming agent may be arbitrarily adjusted with urea, a zinc compound, a lead compound or the like. The inorganic foaming agent is
Examples include sodium bicarbonate and sodium borohydride. As the high temperature expansion type microcapsules, those obtained by encapsulating a low boiling point hydrocarbon with vinylidene can be used. In the present invention, any foaming agent can be applied, but an organic foaming agent having a decomposition temperature of 100 ° C. or higher is particularly preferable in view of easiness of forming into a sheet, appearance of the foam, uniform foaming and compactness. If the decomposition temperature is 100 ° C or less, foaming will start when it is formed into a sheet, and when foaming in a heating furnace, the resin will not melt sufficiently and gas will not escape and the expansion ratio will not rise, and it will be difficult to obtain a uniform foam . It is also possible to use inorganic foaming agents and microcapsules, but the expansion ratio and
There are difficulties in terms of economy. The blending amount of the foaming agent is preferably 0.5 to 15 parts by weight with respect to 100 parts by weight of the vinyl chloride resin. If the blending amount is less than 0.5 parts by weight, foaming is insufficient, and if the blending amount exceeds 15 parts by weight, the foaming ratio does not change, and excessive addition is economically wasteful.

Examples of the epoxy resin applicable to the present invention include usual glycidyl ether type, glycidyl ester type, glycidyl amine type, linear aliphatic epoxide type, and aliphatic epoxide type epoxy resins, and desired foams. They can be used alone or in combination depending on the physical properties of. The epoxy resin is added in an amount of 20 to 500 parts by weight based on 100 parts by weight of the vinyl chloride resin. Compounding amount is 20
If it is less than parts by weight, it is difficult to obtain a rigid foam, and if it exceeds 500 parts by weight, the heat generated during the curing reaction is large, so that decomposition of vinyl chloride occurs or expansion of the foaming agent due to decomposed gas is suppressed, resulting in high magnification. There is a problem that it is difficult to obtain the foam.

As the heat-activatable curing agent for the epoxy resin, a usual curing agent exhibiting a curing action by heating can be used. A preferable curing agent is a curing agent having an exothermic peak temperature in the range of 100 ° C to 200 ° C in combination with an epoxy resin.
Examples of the curing agent include dicyandiamide, 4,4′-diaminodiphenylsulfone, imidazole derivative such as 2-n-heptadecylimidazole, isophthalic acid dihydrazide, N, N-dialkylurea derivative, N, N-dialkylthiourea derivative. Acid anhydrides such as tetrahydrophthalic anhydride, isophoronediamine, metaphenylenediamine, N-aminoethylpiperazine, boron trifluoride complex compounds, trisdimethylaminomethylphenol and the like. The curing agents can be used alone or in combination as desired. Epoxy resin 10
It is preferably 1 to 20 parts by weight with respect to 0 parts by weight. If the blending amount is less than 1 part by weight, the rigidity of the foam is insufficient due to insufficient curing. On the other hand, if the blending amount is more than 20 parts by weight, the rigidity of the foam does not change, and excessive addition is economically wasteful.

The curing temperature referred to here is the temperature of the medium at which the heat generated by curing reaches a peak when a mixture of an epoxy resin and a curing agent at room temperature is heated by an oil bath, a heater, or the like.

The preferred combination and amount of the epoxy resin and the curing agent depending on the heating conditions can be easily determined by conducting a test in advance.

In the present invention, in addition to these compounding agents, for example, fillers such as calcium carbonate, talc and clay, heat stabilizers, foaming agents, foam adjusting agents, and colorants can be blended. The amount of each additive to be added is in the range of 0 to 200 parts by weight for the filler, 0 to 10 parts by weight for the heat stabilizer, and 0 to 10 parts by weight for the cell regulator, relative to 100 parts by weight of the vinyl chloride resin. . When adding each additive, if the filler is more than 200 parts by weight, the fineness of foaming is lost, the expansion ratio does not rise, and the heat stabilizer and the cell regulator are effective even if they are more than 10 parts by weight. It doesn't go up.

The expandable resin composition applied to the method of the present invention includes a vinyl chloride resin for paste, a plasticizer, a foaming agent, an epoxy resin,
In addition to the epoxy resin curing agent, if necessary, a bubble regulator, a filler, a heat stabilizer, a coloring agent, etc. are added, and the mixture is mixed and stirred in a commonly known mixer to prepare.

Next, a method for producing an unfoamed sheet from the above composition will be described. When the composition is in a liquid state, it can be formed into a sheet by, for example, applying it to a release paper or a steel belt in a film shape to a uniform thickness and then heating. The vinyl chloride resin for paste is advantageous because it easily absorbs the plasticizer or epoxy resin by heating and gels. As the heating condition, it is necessary to select a temperature condition that does not cause decomposition and foaming of the foaming agent or reaction of the epoxy resin. If foaming or reaction of epoxy resin occurs in this sheet forming process, there is a problem that in the heat foaming process after being attached to the vehicle outer panel, an abnormal foaming state is shown or the magnification does not improve,
Be careful. The sheeting condition is that the internal temperature of the sheet due to heating should not exceed the foaming temperature of the foaming agent.
However, if the sheeting conditions are too weak, the strength of the sheet after molding is too weak and there is a possibility that it will break or fall off when it is attached to the panel. It is necessary to raise the height above 1 kg / cm ² (according to JIS K-6301). For example, the decomposition temperature of the blowing agent is 150
In the case of ℃, the manufacturing conditions of a sheet having a thickness of 1 mm are preferably 140 ℃ × 2 minutes. Even at 170 ° C, foaming does not occur for about 1 minute, which is good. The optimum sheet preparation conditions can be easily selected by preliminary testing of the composition. As another sheet forming method, a calendar or a mixture of the mixed composition, a method of using a general sheet forming machine, or a vinyl chloride resin, an epoxy resin or other compounding ingredients are dissolved and mixed in a solvent, A method of forming into a film and volatilizing the solvent to form a sheet can also be used. These are advantageous, for example, when the mixed composition before being formed into a sheet is a solid. However, the most preferable method is to form a liquid composition and apply and mold it on a substrate such as release paper. The sheeted composition is a flexible sheet that is thin and highly elastic, and is easy to wind, cut and carry.

Next, a method of applying the composition to the inner surface of the vehicle outer panel by being formed into a sheet will be described. The sheeted composition exhibits self-adhesiveness, and can be easily adhered simply by pressing it against the outer plate without any adhesive treatment or using an adhesive.

It is considered that this is because the epoxy resin is absorbed by the vinyl chloride resin in the step of forming a molded sheet, but the epoxy resin that is not completely absorbed remains in the sheet and exhibits tackiness. Although such a phenomenon was not expected at all at first, it was discovered by chance in the process of searching for sheeting conditions, and the present invention is practically excellent and epoch-making. You can Of course, in order to further increase the tackiness, it is possible to additionally add a tackifier other than the epoxy resin in the composition, and to apply the adhesive to the surface of the molded sheet or the outer panel. Is also possible.

In any case, compared to the conventional method of pasting a heat-insulating agent such as a foamed molded article or felt using an adhesive, a thin and flexible sheet is just crimped, so it can be installed very easily. Moreover, it is possible to apply the entire surface uniformly according to the shape of the outer panel.

Next, a method for foaming and curing the above sheet composition will be described. The composition formed into a sheet attached to the outer panel is passed through a heating furnace, foamed and cured,
An outer panel structure having improved heat insulation and strength is obtained. It is most rational to use an existing paint baking oven as the heating oven used when heating after being attached to the inner surface of the vehicle outer panel. The coating baking furnace is roughly classified into an undercoat baking furnace, an intermediate coating baking furnace, and an overcoat baking furnace, but the intermediate coating baking furnace or the overcoat baking furnace is preferably used in the present invention.

FIG. 1 shows an example of an automobile suspended ceiling structure similar to that shown in FIG. 3 produced by the above-described molding method.
The structure of the back surface of the roof panel 1 is different from that shown in FIG.
A vinyl chloride foam is directly adhered to the panel 1, and further comprises a head lining 4 suspended and held by a listing wire 3 stretched on the lower surface thereof.

The mechanism of foaming and hardening by compounding an epoxy resin is considered as follows, taking organic foaming as an example. First, by heating, vinyl chloride is melted, and then the foaming agent is decomposed to generate gas. The evolved gas causes the system to foam and form cells. Subsequently, the epoxy resin contained and dispersed in the composition causes a curing reaction due to activation of the curing agent, and the foam is hardened. Therefore, the characteristics of the formed foam are affected by the gelation rate of vinyl chloride resin, the decomposition rate of the foaming agent, and the curing rate of the epoxy resin, and it is necessary to select the material based on the target foaming density, curing degree, etc. There is.

(Effects of the Invention) As described above, according to the method of the present invention, it is possible to easily obtain the desired vehicle outer panel structure having excellent heat insulation and reinforcement. The sheet-like composition used in the method of the present invention is a thin and flexible elastic sheet having self-adhesiveness, and can be easily attached in the manufacturing process of automobiles and the like. In the conventional method, the reinforcing material for the outer plate and the heat insulating material, individually using an adhesive or the like, must be manually attached, which is a heavy burden on the operator, according to the method of the present invention, Not only can it be installed very easily and labor can be reduced, but a structure that has the characteristics of both conventional heat insulating materials and reinforcing materials can be obtained with a single material, saving resources and energy. Can be achieved.

The heat insulating property of the foam has a close relationship with the foaming ratio, and the higher the foaming ratio, the more the gas such as air is contained and the smaller the thermal conductivity, so the heat insulating property is improved. Table 1 shows the expansion ratio of the vinyl chloride foam obtained according to the present invention and the thermal conductivity of the foam, which were measured as an index of heat insulation and compared with the conventional heat insulating material. Then the construction method,
Although it was difficult to increase the expansion ratio to 4 times or more due to physical properties such as heat resistance, setting the expansion ratio to 4 times or more can exceed the level of heat insulation of conventional heat insulating materials. Recognize. According to the method of the present invention, a high-magnification foam can be easily obtained.

There is a close relationship between the hardness of the foam and the reinforcing property of the outer panel.The higher the hardness, the higher the elastic modulus of the foam, and the more the reinforcing property of the outer panel structure increases. The effect of being complemented is great. The present inventors measured the hardness of the foam according to the method of the present invention and the bending rigidity of the panel structure as an index of the reinforcing property, and the results are as shown in Table 2, and if the hardness is 40 or more, , The bending rigidity ratio is
Since it is 1.2 or more, I found that there is a reinforcing effect.

According to the method of the present invention, the heat insulating and reinforcing effects of the vehicle outer panel are significantly improved.

(Examples) Hereinafter, the present invention will be described with reference to Examples and Comparative Examples. Parts and% in Examples and Comparative Examples are based on weight unless otherwise specified. The physical properties of the composition of each example were evaluated according to the following test methods.

Test method (b) Adhesiveness The surface composition of the sheet composition, which was applied on release paper to a thickness of 1 mm and formed at a specified temperature, was adhered in an area of 2 cm x 2 cm, and the tensile shear peel strength was measured to determine the adhesiveness. It was used as an index.

(B) Foaming ratio 1mm thick, a sheet of foamable composition is pasted on the panel, and foamed and cured in a hot air heating oven at 150 to 160 ° C for 30 minutes,
The thickness a (mm) of the foam was measured and used as the foaming ratio a.

(C) Thermal insulation The thermal conductivity of the foam was measured with a thermal conductivity meter (HC-071 H manufactured by Eiko Seiki Co., Ltd.) and used as an index of thermal insulation.

(D) Hardness The hardness of the foam was measured with a rubber stator C (manufactured by Kobunshi Keiki Co., Ltd.).

(E) Reinforcing property A 0.8 mm thick steel plate is pasted with a 1 mm thick foamable composition, which is then foamed and hardened in a hot air heating oven at 150-160 ° C for 30 minutes and then bent according to JIS K-6911. Using a strength measuring device, measure the bending strength at a fulcrum distance of 100 mm and a load speed of 5 mm / min to obtain the load (y ₁ ) at a displacement of 2 mm. 2 mm of steel plate alone
The bending rigidity ratio y ₁ / y ₀ is calculated from the load (y ₀ ) at the time of displacement and y ₁ .
It was used as an index of reinforcement.

Examples 1 to 5 and Comparative Examples 1 to 3 The foamable resin compositions having the compounding ratios shown in Table 3 were mixed by a Hobart type mixer for 20 minutes, and then produced on release paper.
Apply to a thickness of 1mm and heat in a hot air oven for 2 minutes at 150 ℃,
It was an unfoamed sheet. After sticking this unfoamed sheet on a 0.8 mm thick steel plate, remove the release paper and put it in a hot air oven for 150
By heating for 30 minutes at ℃, to obtain a foam, in the above method, the expansion ratio,
The heat insulating property, hardness and reinforcing property were measured. Moreover, the tackiness was measured from the unfoamed sheet. The results obtained are shown in Table 3.

The tensile strength of each unfoamed sheet was 5 to 10 kg / cm ² .

If the amount of the epoxy resin is less than 20 parts by weight, the tackiness of the sheet will be insufficient and the reinforcing effect after curing will be small. Again 50
If it exceeds 0 parts by weight, the epoxy resin bleeds and the tackiness is insufficient. Further, the epoxy resin generated a large amount of heat during curing, and the foam was thermally decomposed.

Examples 6 to 11 and Comparative Examples 4 to 5 The foamable resin composition of Example 3 in Table 3 was prepared by mixing for 20 minutes with a Hobart type mixer, and then about 1 mm on the release paper.
It was applied thickly and heated in a hot air heating furnace under the respective temperature conditions shown in Table 4 to give an unfoamed sheet. This unfoamed sheet was foamed by the method described above, and the characteristics were measured. The results are shown in Table 4.

If the sheet is formed into a sheet, the heating is sufficient, and if it is formed into a sheet, the construction is very good, while if the heating is excessive and the decomposition temperature condition of the foaming agent is exceeded,
Foaming occurs at the stage of making into a sheet, and when such a sheet is pasted on a metal and foamed, it is not sticky and difficult to attach, and the foaming state is non-uniform and heat insulating and curable. Has become inferior to.

Example 12 The unfoamed sheet of Example 9 was cut into a piece having a width of 400 mm and a length of 1,000 mm, and the sheet was attached to four places on the inner surface of the roof panel of the vehicle.
This was passed through a coating baking oven with setting conditions of 160 ° C. for 30 minutes to obtain the heat insulation reinforcing structure shown in FIG. The thickness after curing was about 6 mm. When the relationship between the load and the displacement was evaluated with the roof panel, the relationship shown in Fig. 5 was obtained, and the reinforcing effect was confirmed. In FIG. 5, the curve A shows the relationship between the load and the displacement of the roof panel according to the present invention, and the curve B shows the same relationship as the conventional roof panel. Further, in the figure, above the judgment reference line is a pass, and below is a fail. The thermal conductivity is 0.038 (k
cal / m.Hr. ° C).

As shown in Examples 1 to 11, according to the method of the present invention, it is possible to improve the commercial property due to high heat insulation and high reinforcement. In addition, since it has the characteristic that it can be easily installed, it has an effect of greatly contributing to labor saving of outfitting work for vehicle products.

[Brief description of drawings]

FIG. 1 is a perspective view of an example of roof insulation and reinforcement structure which is heat-insulated and reinforced by the method of the present invention, FIG. 2 is a cross-sectional view of a conventional roof structure, and FIG. 3 is a conventional roof insulation structure of an automobile. Explanatory drawing, FIG. 4 is explanatory drawing of the conventional door panel reinforcement structure of a motor vehicle, and FIG. 5 is a curve figure which shows the reinforcement performance of the roof structure of this invention, and the conventional roof structure. 1 ... Roof panel 2 ... Vinyl chloride foam 3 ... Listing wire 4 ... Headlining 5 ... Double-sided tape 6 ... Insulation material, 7 ... Door panel 8 ... Thermosetting reinforcing material

Claims (1)

[Claims] 1. A vinyl chloride resin for paste, a plasticizer, a high-temperature foaming foaming agent, an epoxy resin, a heat-activatable curing agent for an epoxy resin as essential components, and the vinyl chloride resin 100 as described above.
With respect to parts by weight, the foaming resin composition containing 20 to 500 parts by weight of the epoxy resin is heat-molded in advance at a temperature at which the foaming agent does not foam, so that the tensile strength of the molded product is 1 kg / cm ² or more. After making it into a sheet, attach it to the back of the vehicle outer panel,
Then, a method for manufacturing a vehicle outer panel structure, which is heated to foam and cure.