JP2663320B2 - Manufacturing method of rubber coated stainless steel sheet for gasket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing acrylonitrile butadiene rubber (NBR) coated stainless steel sheet for metal gaskets.

[0002]

2. Description of the Related Art Conventionally, engine gaskets using asbestos as a raw material have predominantly been used, but as attention has been paid to asbestos pollution, the trend toward non-asbestos has increased. Recently, demands for improving engine performance have been further increased, and attempts have been made to apply steel plates and stainless steel plates as gasket materials to replace asbestos.

In these metal gaskets, a single metal plate is used as it is or a plurality of such plates are laminated. In this case, a heat-resistant paint or carbon is applied to the surface in order to maintain sufficient sealing properties. It was necessary to form a strong elastic film by applying graphite or rubber to prevent leakage of the seal. And this micro seal had a great influence on the performance of the gasket.

For this reason, the characteristics (mechanical properties, workability, adhesion, etc.) of the elastic film as a micro-seal attract attention, but these are not only affected by the material of the elastic film, but also It was greatly affected by the material of the metal plate to be applied and the application conditions. For example, stainless steel, which has excellent spring characteristics and heat resistance, is a particularly promising material among metal gasket materials, but because of its poor adhesion to coated materials, it has the necessary characteristics as a micro seal. It is said that it is very difficult to form a flexible elastic film. Therefore, the formation of the elastic film on the stainless steel plate is usually performed by "post-coating", which is performed with great care after being formed into a required shape. However, in this case, since a large number of processing steps are required, mass production is difficult, and as a result, the cost is greatly increased.

In view of such circumstances, the present applicant has previously developed means for stably coating a rubber layer having excellent characteristics on a stainless steel plate or the like.
Japanese Patent Application Nos. 23990/1990 and 291473/1990.
No. proposed. It was expected that this would make it possible to pre-coat rubber on a stainless steel plate using the roll coating method.

Here, the "roll coat method" uses a roll coater having a pickup roll 1 and an applicator roll 2 as schematically shown in FIG. 1, for example. Needless to say, this means a coating method in which the paint in the paint pan 3 is applied to the workpiece 5 passing along the backup roll 4.

However, when a rubber-based paint is to be pre-coated on a stainless steel plate by a roll coating method, a desired coating cannot be performed because the viscosity of the paint is remarkably increased during work. It became clear.

That is, in the continuous coating by the roll coating method, first, the film thickness of the paint adhering to the applicator roll surface of the roll coater is adjusted to a constant value. After that, this is continuously transferred to a material to be coated (a steel plate or the like), and a product is produced by baking for a short time. Of course, prior to this, it is needless to say that a trial coating must be performed on the actual machine line to evaluate the coating state. Therefore, depending on the length of the steel plate or the like as the material to be coated, it usually takes several hours to finish the coating. However, in the case of coating rubber-based paints, it is generally said that ketone-based solvents are the best for rubber coating. As the coating operation is performed for a long time as described above, the paint thickens during the operation and becomes rubbery in the paint pan, which adheres to the roll of the roll coater. This caused a situation in which the film thickness control and leveling (smoothing of the coating material) were adversely affected.

In view of the above, an object of the present invention is to suppress the increase in viscosity of a coating material when a rubber coating material is continuously coated by a roll coating method, and to sufficiently use the coating material for a gasket. The objective is to establish a means for stably producing satisfactory rubber-coated stainless steel sheets.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above object, and have found that the thickening of the paint in the paint pan can be suppressed by adding a diluent. In particular, using a rubber-based paint (acrylonitrile-butadiene rubber, carboxylated nitrile rubber, a mixture of nitrile rubber and vinyl chloride resin) based on a ketone-based solvent, and continuously coating stainless steel plates on a roll coat line of an actual machine During the coating, various diluents (acetone, methyl ethyl ketone, chloroform, chromium benzene, cyclohexanone, xylene, toluene, hexane, diethyl ether, cellosolve acetate) are added to the paint in the paint pan.
Was added, and the effect was examined. The degree of increase in the viscosity of the paint when the pick-up roll of the roll coater is kept rotating while taking the above measures, and the coating film obtained by coating the paint with the measures on a stainless steel plate From the results of the survey on the properties of, the following became clear.

That is, among rubbers used as a coating material, "acrylonitrile butadiene rubber (NBR)" has excellent properties as a gasket micro-sealing film. However, in a coating material obtained by coating this NBR with a ketone solvent, In particular, when xylene, cyclohexane, cellosolve acetate or toluene is used as a viscosity modifier (diluent), the volatilization of the solvent is effectively suppressed, and the coating workability is improved. In addition to maintaining a constant viscosity, it is possible to manufacture a rubber-coated stainless steel sheet by the roll coating method, and the viscosity modifier has good compatibility with the ketone-based solvent used for forming the coating, so that NBR can be obtained. In addition to not impairing the original performance of the coating film, the tackiness (adhesion between rubber coated surfaces) has also been improved, and adhesion by winding the coating material Also eliminates the harmful occurs, thus the use of said viscosity modifier has revealed that paves the way that can be produced with good productivity economically suitable rubber-coated stainless steel plate for the gasket.

The present invention has been made on the basis of the above findings and the like. "The present invention relates to a method of converting NBR into a paint with a ketone-based solvent and using xylene, cyclohexanone,
Using one or more of cellosolve acetate and toluene, this is continuously coated on the surface of a stainless steel plate by a roll coating method, and then calcined at 240 to 330 ° C. for a short time to obtain a micro seal. In that a rubber-coated stainless steel sheet for gaskets with excellent properties can be produced with high productivity ", and further," as the NBR, acrylonitrile: 15 to 40% by weight, vulcanizing agent: 0.5 ~
3% by weight, carbon: 40 PHR or more, thereby further stabilizing the characteristics of the rubber coating as a microseal. "

As the NBR to be used, those to which various additives are added as necessary can be used.
15 to 40% by weight of solid content of acrylonitrile
(Preferably 25 to 35% by weight) makes it possible to obtain a balanced NBR. That is, if the amount of acrylonitrile is less than 15% by weight, there is a concern that the amount of the solvent may be excessive and cause an explosion at the time of sintering.
If it exceeds 0% by weight, there are signs that the leveling property and adhesion of the coating film are deteriorated.

Further, in order to secure excellent coating film properties by a rubber-coated stainless steel sheet, 0.5 to 3% by weight of NBR is required.
It is preferred to add a vulcanizing agent in the ratio of That is, in the roll coating method, the material to be coated after the coating is completed (for example, steel strip).
Is wound by a tension reel, and in the case of a rubber-coated stainless steel plate, the rubber surfaces of the coating film may adhere to each other due to the tightening pressure. In order to prevent the adhesion (tackiness) between the rubber surfaces, it is effective to completely bake (cure) and vulcanize the applied coating film,
For this vulcanization, the addition of a vulcanizing agent is recommended.
A peroxide vulcanizing agent is desirable as a vulcanizing source for vulcanizing a rubber coating film quickly, and a combination of a thiuram-based and a thiazole-based vulcanizing accelerator is effective. In this case, if the amount of the vulcanizing agent is less than 0.5% by weight, a sufficient vulcanizing effect cannot be expected, while if it exceeds 3% by weight, the properties of the coating film are deteriorated. In order to enhance the vulcanizing effect, it is preferable to increase the firing temperature to such an extent that the performance of the coating film is not deteriorated. With these measures, it is possible to omit steps such as applying a release agent to the rubber coating surface to prevent the rubber surface from sticking.

Further, it is desirable to secure a carbon content of 40 PHR or more as a reinforcing agent for NBR. By setting the carbon content to 40 PHR or more, sufficient strength, rebound resilience and compression set can be obtained as a micro-sealing film of a gasket.

As a solvent for converting NBR into a paint,
Ketone solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetone and cyclohexanone can be used.
K and MEK are preferred. Of course, these can be used alone, but it is also possible to use a mixture of several types.

In the present invention, xylene, as a viscosity modifier, is added to NBR coated with a ketone solvent.
Cyclohexanone, cellosolve acetate or toluene is used, and the NBR paint whose viscosity has been adjusted by this is continuously coated on the surface of a stainless steel sheet by a roll coating method.
It will be By using the above-mentioned viscosity modifier, the volatilization of the solvent is suppressed, the coating workability is improved, and the tackiness of the formed rubber coating film is also improved. In addition, the coating test of the NBR thus adjusted in viscosity by the roll coating method (line speed 15 m
/ min), the coating operation could be continued for 6 hours without adding a diluent. This viscosity modifier may be used alone or in a mixed form, but xylene is the most preferable.

NB whose viscosity is adjusted by the viscosity modifier
The viscosity of the R paint at the time of application is 70 as a measured value of a forecup
~ 230 seconds is most preferred. That is, if the above value is less than 70 seconds, it is difficult to control the film thickness to 10 μm or more, while if the value is more than 230 seconds, it is necessary to secure the film thickness control and leveling property when performing roll coating. Is difficult.

The rubber coating is applied to the gasket microsheet.
When used as a film, it is necessary to control the film thickness to an arbitrary value according to the application.
(E.g., remarkable in the case of rubber), and there is a risk that a solvent exceeding a limit amount for preventing danger may be introduced into the firing furnace. However, when the NBR coating material whose viscosity is adjusted by the viscosity modifier is used, two-coat two-bake becomes possible, and the control of the film thickness can be arbitrarily performed by the two-coat two-bake. The above concerns will be eliminated because they will be able to do so.

In the case where the film thickness is to be increased by two coats and two bake, the first coat is set to at least 1/2 of the predetermined film thickness,
By using a paint whose viscosity is less than that of the paint in the second coat and a viscosity about 20% lower than that of the paint in the first coat, the leveling property is the same as in the case of the first coat material. Good coating film can be obtained.

Now, a stainless steel sheet obtained by continuously coating the NBR paint by a roll coating method is subsequently treated with a 24
It is fired for a short time at 0 to 330 ° C. (final reaching plate temperature) to enhance the vulcanization effect, and to improve the rubber coating strength, rebound resilience, compression set, tackiness and the like. In this case, even if the firing temperature is lower than 240 ° C. or higher than 330 ° C., desired coating film characteristics cannot be secured.

The temperature of the firing furnace at the time of actual production is set as follows.
It is necessary to lower the heating temperature of about 1/2 of the inlet side by about 10 to 15 ° C. below the temperature at which the boiling point of the used viscosity modifier (diluent) is reached. This is to prevent the occurrence of pinholes in the coating film due to rapid evaporation of the diluting solvent and to prevent the coating film from forming during thick film coating. Then, by controlling the temperature so as to reach the target plate temperature in the remaining 1/2 heating zone, continuous coating by a roll coater becomes possible.

Next, the effects of the present invention will be specifically described with reference to examples.

First, NBR containing 30% by weight of acrylonitrile, 1% by weight of thiazole-based vulcanizing agent, and 50 PHR of carbon was converted into a paint with the solvent shown in Table 1 and further shown in Table 1 above. The viscosity was adjusted using the prepared viscosity adjuster (diluent).

[0023]

[Table 1]

Next, the NBR paint adjusted as described above was continuously applied to the surface of a stainless steel plate (SUS301) on a continuous coating line (line speed 15 m / min) to which a roll coater was applied, Further, firing was performed at various temperatures (sintering time: 1.5 minutes) to produce a rubber-coated stainless steel sheet. The coating results at this time are also shown in Table 1 above, and the results of measurement of viscosity increase for some of the coatings are shown in FIG.

As is clear from the results shown in Table 1 and FIG. 1, when xylene or cyclohexanone specified in the present invention is used as a viscosity modifier (diluent), the viscosity can be set even after several hours of operation. It stayed within the target range, and good work results were obtained. Note that NBR is
In the case of coating with BK and then adjusting the viscosity with xylene, it was also confirmed that the ratio of MIBK to xylene was appropriate at "30 to 50:70 to 50". Good results were also obtained when toluene or cellosolve acetate was used as the viscosity modifier (diluent).

Further, Table 2 shows that NBR was made into a coating material with MIBK, and the viscosity was adjusted with xylene (MIB coating material).
K: xylene = 50: 50) and the mechanical properties of the coating film for each baking temperature of the rubber-coated stainless steel sheet (JI
SK6301) and LLC resistance. Note that the LLC resistance was measured by using an autoclave in which a test piece was filled with a mixture (50/50 vol%) of an LLC liquid and distilled water.
After performing the treatment at 130 ° C. for 72 hours, take out, cool to room temperature, and observe the coating for blistering and peeling,
Further, a cellophane tape peeling test was performed to evaluate the adhesion.

[0027]

[Table 2]

As is apparent from Table 2, the elongation tends to decrease as the temperature is increased.
Within the temperature range of 330 ° C., adhesion between the rubber surfaces after coil development does not occur at all, and it can be seen that the temperature range is suitable for preventing the occurrence of blocking (tack). Therefore, it can be understood that sintering in the above temperature range eliminates the steps of applying a release agent and the like. In addition, from the result of the examination of LLC resistance, which is the most important as a microseal material, no blistering or peeling of the coating film was observed, and it was confirmed that excellent coating film performance was maintained.

[0029]

As described above, according to the present invention, it is possible to stably produce a rubber-coated stainless steel sheet having excellent performance for a gasket with good workability. Is brought.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a roll coating method.

FIG. 2 is a graph showing a relationship between an elapsed time of a rubber paint in a paint pan and an increase in viscosity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pickup roll 2 Applicator roll 3 Paint pan 4 Backup roll 5 Material to be coated

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location C09D 109/02 PGQ C09D 109/02 PGQ (72) Inventor Akira Kakiuchi Minamidera Higashi-dori, Moriguchi-shi, Osaka 6-52, Daito Polymer Industry Co., Ltd. (72) Inventor Mikio Nishida 6-52, Minamijikata Higashi Dori, Moriguchi-shi, Osaka Prefecture Daito Polymer Industry Co., Ltd. (56) References JP-A-3-149465 (JP) , A) Japanese Patent Laid-Open No. 1-254782 (JP, A)

Claims (2)

(57) [Claims] An acrylonitrile-butadiene rubber is formed into a paint with a ketone-based solvent, and at least one of xylene, cyclohexanone, cellosolve acetate and toluene is used as a viscosity modifier, and the paint is made of stainless steel by a roll coating method. After continuous coating on steel sheet surface, 2
A method for producing a rubber-coated stainless steel plate for a gasket, comprising baking at 40 to 330 ° C. for a short time. 2. As acrylonitrile butadiene rubber, acrylonitrile amount: 15 to 40% by weight, vulcanizing agent amount:
The method for producing a rubber-coated stainless steel sheet for a gasket according to claim 1, wherein the rubber-coated stainless steel sheet having a carbon content of 0.5 to 3% by weight and a carbon amount of 40 PHR or more is used.