JP2927699B2 - Joint sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a petrochemical plant,
The present invention relates to a joint sheet which is a base material of a gasket used in a wide range of fields such as various industrial machinery, automobiles and home appliances, and is particularly suitable as a joint sheet for a refrigerator.

[0002]

2. Description of the Related Art A general method of manufacturing a joint sheet is as follows. First, a rubber swollen with a solvent (or a mixture of powdered rubber or latex and a solvent) is mixed with a fibrous material, a filler, and a rubber chemical using a Henschel mixer. Kneaded well, composition for forming a joint sheet (hereinafter abbreviated as kneading material)
Is prepared and then the kneaded material is heated on a hot roll (about 150 ° C).
And a cold roll (approximately 20 ° C) between the pair of rolls (calender rolls), the solvent is evaporated and vulcanized while laminating on the hot roll side, and finally the laminated sheet is peeled off and manufactured. It has been. Depending on the product, secondary vulcanization may be further performed on the sheet in an autoclave or the like in order to advance vulcanization. In addition, as a constituent material, in addition to the above materials, a softener, a plasticizer,
A small amount of a water swelling agent or an oil swelling agent is added, and a pigment may be blended for storage and identification.

[0003] Conventionally, asbestos joint sheets have been widely used as joint sheets. Utilizing the unique shape of asbestos fibers and excellent heat resistance, they are used as gaskets for piping such as water, oil, air, steam, etc. and equipment. It has been stamped and used. However, asbestos fiber is a natural mineral, and there is a concern that resources may be depleted.Also, health disorders that are presumed to be caused by asbestos fiber have become a social problem and the use of asbestos has been restricted worldwide. Have been. For these reasons, recently, asbestos-free joint sheets or non-asbestos joint sheets using asbestos-free inorganic sheets and / or non-asbestos fibers and / or non-asbestos fibers are used. NA joint sheet) has been used.

The fiber materials used for the NA joint sheet include organic fibers and inorganic fibers (other than asbestos fibers).
There are, in thicker fiber diameter than the asbestos fibers rigid ones are many, since much difference in terms of heat resistance is observed, but use a combination of various fibers depending on the application, the tensile strength Ya In terms of heat resistance, it has not reached the point where it is completely comparable to the asbestos joint sheet.

[0005]

In particular, a joint sheet for a refrigerator used for a compressor of a refrigerator or an air conditioner is an ordinary joint sheet for sealing a mixed system of Freon (refrigerant) and refrigerator oil (lubricating oil). Higher sealing properties are required, and even if used while receiving vibration, it does not cause blowout, so it is necessary to have a high tensile strength during use as well as the initial stage. At present, there are few things that can guarantee the safety against long-term use. Furthermore, the use of chlorine-based chlorofluorocarbons has been subject to restrictions worldwide due to the recent problem of depletion of the ozone layer. Because of its easiness, problems such as a decrease in tensile strength and deterioration of refrigerating machine oil have been added, which has become a more difficult problem.

For example, in order to maintain a high sealing property, it is effective to increase the amount of rubber which is a binder contained in the joint sheet. The tensile strength is reduced, and the rubber swells or dissolves out, so that the tensile strength after long-term use is significantly reduced, and there is a possibility that the refrigerating machine oil may be deteriorated. In addition, when the kneaded material is made with a calender roll, the kneaded material becomes too soft and the sheet is broken.

In view of the above situation, an object of the present invention is to provide not only an initial strength but also a large tensile strength after immersion in a mixed system of chlorofluorocarbon and refrigerating machine oil, less deterioration of the refrigerating machine oil, and sealability. An object of the present invention is to provide an NA joint sheet having excellent properties such as compression ratio and stress relaxation ratio.

[0008]

According to the present invention, a composition comprising a base fiber composed of inorganic fibers and / or organic fibers, a rubber material, a filler and a rubber chemical such as a vulcanizing agent or a vulcanization accelerator is used as a solvent. And the kneaded material is heated and rolled by a hot roll and a cold roll, and the amount of rubber material used is 15 to 30% by weight in the joint sheet, and at least fibrillated as a base fiber. The amount of the fibrillated fiber is 30 to 200 parts by weight with respect to 100 parts by weight of rubber, and carbon black having a particle size of 10 to 80 μm, which is at least active fine particles, is added as a filler. A joint sheet wherein the amount of the carbon black is 30 to 300 parts by weight based on 100 parts by weight of rubber.

The fibrillated fibers used in the joint sheet of the present invention include fibrillated aromatic polyamide fibers, fibrillated polyethylene fibers, fibrillated cellulose pulp such as bamboo pulp and softwood pulp, and may be used alone or in combination. Can be used. In some cases, organic fibers such as phenol fibers, acrylic fibers, aromatic polyamide fibers (chopped fibers), and nylon fibers, and inorganic fibers such as rock wool, carbon fibers, glass fibers, and sepiolite may be used in combination. As the rubber material, acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, acrylic rubber, ethylene propylene rubber, styrene butadiene rubber, chloroprene rubber, natural rubber, isoprene rubber, and the like can be used.In particular, acrylonitrile butadiene rubber, hydrogenated acrylonitrile Oil-resistant rubber such as butadiene rubber and acrylic rubber is desirable.

[0010] The active fine particles used as the filler are carbon black, a fine silicic acid / silicate compound (generally called white carbon) whose particle surface is activated with respect to rubber, Is 10 to 80 .mu.m, and particularly, carbon black having a high affinity for rubber of about 10 to 60 .mu.m is most suitable. The addition amount is 30 to 300 parts by weight, preferably about 30 to 150 parts by weight based on 100 parts by weight of rubber. As the filler other than the active fine particles, clay, talc, barium sulfate, sodium bicarbonate, graphite, kaolinite, sericite, calcined clay, wollastonite or the like is used alone or in combination of two or more.

As the vulcanizing agent / vulcanization accelerator to be used next, vulcanizing agents such as sulfur, zinc oxide, magnesium oxide, peroxide, dinitrobenzene, aldehyde ammonia type,
Vulcanization accelerators such as thiuram, dithiocarbamate, sulfenamide, thiazole, guanidine, thiourea, xanthate and aldehydeamine can be used.

As the rubber chemicals other than the vulcanizing agent and the vulcanization accelerator, an appropriate amount of an antioxidant, an anti-scorch agent, a plasticizer, a coloring agent and the like can be used.

[0013]

The present inventors have been conducting research on the mixing ratio of fibers and rubber of the NA joint sheet.
Among them, it was found that the sealing property was rapidly improved as the amount of rubber increased, and that the ratio of fibrillated fiber to rubber greatly affected the tensile strength. Here, FIG. 1 shows the relationship between the amount of rubber in the joint sheet and the sealing property, and FIG. 2 shows the relationship between the ratio of the fibrillated fiber / rubber amount and the tensile strength. Based on the relationship between the maximum tensile strength values shown in FIG. 2, the present inventor tried a trial production of a sheet having a composition of 25% fibrillated fiber and 20% rubber. The plate was made with the conditions changed, but the tensile strength was particularly low after immersion in a mixed system of Freon and refrigerating machine oil. Did not. Therefore, paying attention to the filler, 30 to 300 parts by weight of active fine particles having a particle size of 10 to 80 μm such as carbon black are added to the rubber while the rubber is added in the joint sheet at 15% or more. Preferably 30
By adding about 150 parts by weight, the tensile strength after immersion in a mixed system of chlorofluorocarbon and refrigerating machine oil is greatly improved,
Refrigerator oil was found not to be contaminated.

To explain this from another aspect, the NA joint sheet invented this time is different from a normal one.
It is characterized by the fact that fibrillated fibers, rubber and carbon black are blended in a considerably large amount. As mentioned earlier, joint sheets are generally rubber swollen in solvent,
Fibers and fillers are kneaded with a Henschel mixer or the like, but if a large amount of carbon black is added to the fibrillated fiber or rubber-rich composition, the kneaded material initially becomes extremely viscous and a large shear force is applied. Therefore, a crosslinking point is generated by the carbon gel in which the rubber and the carbon black are combined.

[0015] normal joint sheet, but the entangled fibers are out strength than <br/> the entanglement of the fibers is a state in which the rubber as a binder is fixed, pressurized crosslinking points of the rubber is such as sulfur In the case of using only a sulfuric acid, the rubber is easily swelled and eluted, and the fibers which are tightly entangled by the swelling of the rubber are melted and the tensile strength is reduced. Particularly for refrigerators, the amount of vulcanizing agents such as sulfur must be reduced in order to reduce the corrosiveness of the copper plate, and this tendency is further observed. However, when the cross-linking of the rubber is caused by the cross-linking point of the vulcanizing agent and the carbon gel as in the present invention, the swelling is reduced, so that the entanglement of the fiber is difficult to unwind and the initial tensile strength can be maintained. It has been found that deterioration of the refrigerating machine oil can be suppressed because elution is reduced. Further, it was found that the adhesiveness of the kneaded material gradually decreased and became harder as the number of cross-linking points of the rubber carbon gel increased, so that the sheet was less likely to be torn and the plate making property was greatly improved.

[0016] It is generally said that carbon black has a reinforcing effect on rubber, but this is considerably achieved by using a kneading machine such as a Banbury mixer, a pressure kneader, a twin-screw roll or the like as it is or after mastication. When kneading while giving shear force is the center, when using rubber swelled in a solvent (or a mixture of powdered rubber or latex with a solvent) like a joint sheet,
The viscosity of the rubber is low and it is difficult for shear to be applied during kneading. For example, the viscosity of the kneaded material does not occur in a 10% blend with a small amount of rubber, and the blend is too soft with a low fiber blend or 3% carbon black. No sufficient amount of carbon gel is produced due to no shear. In general, when kneading a rubber material such as a rubber mold product, a shear is likely to be applied during kneading, contrary to a joint sheet, and carbon black at this time can be blended in a large amount if the particle size is 90 μm or more, If it is less than 80 μm, the heat generation during kneading becomes large and it is difficult to add carbon black in an amount of 40 parts by weight or more to 100 parts by weight of rubber, which is a great difference from the present invention.

From the above, the present inventors have found that the optimum ratio of rubber, fibrillated fiber and carbon black,
That is, 15 to 30% by weight of the rubber in the joint sheet, and 30 to 200% by weight of the fibrillated fiber with respect to 100 parts by weight of the rubber.
Parts by weight and at least 30 to 300 parts by weight of carbon black having a particle size of 10 to 80 μm with respect to 100 parts by weight of rubber.
A joint sheet could be provided.

[0018]

The present invention will be described below in detail with reference to examples.

Example 1 A predetermined amount of an acrylonitrile-butadiene rubber material which had been thinned to 0.2 mm by a rubber kneading roll was weighed,
Swelled in 300 parts by weight of toluene and kneaded with a fiber material, carbon black, fillers other than carbon black, vulcanizing agents, vulcanization accelerators and other rubber chemicals in the composition shown in Table 1 for 80 minutes using a Henschel mixer. did. The kneaded material obtained in this way is pressed and vulcanized by a calender roll of a hot roll at 150 ° C. and a cold roll at 20 ° C.
A 1.5 mm joint sheet was obtained.

Examples 2 to 4 The joint sheets of Examples 2 to 4 were prepared in the same manner as in Example 1 except for the compositions shown in Table 1.

Comparative Examples 1 to 4 The joint sheets of Comparative Examples 1 to 4 were prepared in the same manner as in Example 1 except for the compositions shown in Table 1.

Table 2 shows the kneading materials, plate making properties and physical properties of the joint sheets of Examples 1 to 4 and Comparative Examples 1 to 4. In addition,
The tensile strength, compression ratio, restoration ratio, and stress relaxation ratio of the joint sheet were measured according to JIS R3453. Also,
The sealing performance was determined by submerging the gasket punched in a ring shape between flanges under an N ₂ gas pressure of 15 kgf / cm ² for 1 hour by submersion. In addition, Freon resistance +
For the refrigerating machine oiliness, the tensile strength reduction rate and extraction rate after immersion at 150 ° C. for 22 hours were measured.

[0023]

[Table 1]

[0024]

[Table 2]

Examples 1 to 4 had good plate making properties.
In Comparative Example 1, the amount of rubber was small and the kneading material was difficult to be laminated on the hot roll. In Comparative Examples 2, 3, and 4, the amount of rubber was large, the kneading material was soft, and the sheet was partially broken, resulting in poor plate making. There was a problem.

In terms of physical properties, all of Examples 1 to 4 have a large initial tensile strength, and sufficiently maintain the tensile strength even after immersion in Freon and refrigerator oil. In addition, it can be seen that the extraction amount and the sealing property are very excellent. In contrast, Comparative Example 1
Since the amount of rubber is small, the sealing property is extremely poor, and the initial tensile strength is also small. Comparative Examples 2, 3, 4
Although the rubber content was relatively large and the sealability was relatively good, large shear force was not applied during kneading, and carbon gel was not easily formed, so that the tensile strength after immersion and the extraction amount were poor.

[0027]

As described above, the joint sheet obtained according to the present invention not only has a large initial tensile strength but also has a large tensile strength after immersion in a mixed system of Freon and refrigerating machine oil, and has a good sealing property. It can be seen that the product has excellent performance with little deterioration of the refrigerating machine oil due to elution. In addition,
Since the joint sheet obtained this time is excellent in tensile strength, sealability, and stress relaxation rate, it is needless to say that it is not limited to use in the field of refrigerators but can be used for general equipment and piping.

[Brief description of the drawings]

FIG. 1 is a graph illustrating the effect of the present invention and showing the relationship between the amount of rubber in a joint sheet and the sealing property.

FIG. 2 is a graph for explaining the function of the present invention and showing the relationship between the fibrillated fiber / rubber amount ratio and the tensile strength.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takuya Hirokawa 4-1000-3L, Matsumi-cho, Kanagawa-ku, Yokohama-shi, Kanagawa-ken (56) References JP-A-4-13792 (JP, A) JP-A-4-50282 ( JP, A) JP-A-2-20587 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09K 3/10 F16J 15/10

Claims (1)

(57) [Claims] A composition comprising a base fiber composed of inorganic fibers and / or organic fibers, a rubber material, a filler and a rubber chemical such as a vulcanizing agent and a vulcanization accelerator is kneaded together with a solvent, and the kneaded material is In a joint sheet that is heated and rolled by a hot roll and a cold roll, the amount of rubber material used is 15 to 30% by weight in the joint sheet, and at least fibrillated fibers are added as base fibers, and the fibrils are added. The amount of the modified fiber is 30 to 200 parts by weight based on 100 parts by weight of rubber, and carbon black having a particle size of 10 to 80 μm, which is at least active fine particles, is added as a filler, and the amount of this carbon black is 100 parts by weight of rubber. 30 to 300 parts by weight of the joint sheet.