JP2775679B2 - Sheet gasket and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is intended to prevent a fluid from leaking from a joint surface of a machine such as a sewing machine, agriculture, construction, a ship or an automobile. The present invention relates to a novel sheet gasket to be used and a method for producing the same.

[Conventional technology]

Conventionally, asbestos has been used as a solid sheet-like gasket that is sandwiched and sealed between these joints. Asbestos is a mineral fiber which has heat resistance and is inexpensive. Therefore, asbestos is produced in combination with various binders and is widely used.

[Problems to be solved by the invention]

However, recently, it has been pointed out that asbestos is a carcinogen, and therefore, asbestos-based sheet-like asbestos gaskets have been shunned and their use has been regulated.

In view of such circumstances, sepiolite has attracted attention and has been tried as an alternative to the sheet-like asbestos gasket, but none of them has been able to achieve a satisfactory sheet-like gasket, and has not been realized yet.

[Specific description of the present invention]

The present inventors have found that fibers of sepiolite are continuously formed using rubber as a binder, and vulcanization molding is performed to form a sheet, which has led to the present invention.

That is, the present invention provides: a. Sepiolite having an aspect ratio of 50 or more, and a defibration degree of 200 seconds / 1.5 g or more by a Blaine air permeability device; b. 10 to 67 weight based on the weight of the sepiolite. % Of natural rubber or synthetic rubber or a mixture thereof, and the total amount of component a and component b is 85% by weight or more of the entire gasket.

Also, the present invention provides a. Sepiolite having an aspect ratio of 50 or more, and a defibration degree of 200 seconds / 1.5 g or more by a Blaine air permeability device, b. 10 to 67 weight based on the weight of the sepiolite % Of natural rubber or synthetic rubber or a mixture thereof, using a roll or a mixer or the like without using a solvent such as an organic solvent, and preforming the kneaded dough; A second step of vulcanizing and molding the preformed cloth in a mold to form a sheet, and a sheet-like gasket manufacturing method.

Sepiolite used in the present invention is a fibrous magnesium silicate clay, characterized by a crystalline structure having pores,
It has no swelling and is not affected by electrolytes.It has a long and narrow tunnel structure along the fiber.In addition, the OH group is innumerable both inside and outside the fiber, and ions floating in the tunnel It has a peculiar structure such as absence of a compound, and its composition is often produced in two types represented by the following general formula.

_{(I) (H 2 O)} 4 (OH) 4 Mg 8 Si 12 O 30 (H 2 O) 6~8 (II) Mg 8 H 2 (Si 4 O 11) 3 3H 2 O The sepiolite, Blaine air A fiber having a transmittance of 200 seconds / 1.5 g or more and a fibrillation degree of 50 or more in aspect ratio (ratio of fiber diameter to length) is used. When the Blaine air permeability is less than 200 seconds / 1.5 g, it is difficult to use rubber as a binder and it is impossible to form a sheet.

The synthetic rubber used in the present invention is isoprene rubber,
Nitrile rubber, styrene rubber, butadiene rubber, chloroprene rubber, butyl rubber, acrylic rubber, silicone rubber, fluorine rubber, chlorosulfonated polyethylene rubber, and copolymers of these, etc., consisting of one or a combination of two or more of these Can be used as a mixture. When the content of these synthetic rubbers in sepiolite is 67% by weight or more, heat resistance and oil resistance are poor, and the stress relaxation rate is low. On the other hand, when the amount of rubber is 10% by weight or less, the function as a binder for sepiolite cannot be obtained.

Vulcanizing agents used for vulcanization include sulfur for vulcanization, zinc oxide, magnesium oxide, aromatic nitro compounds, paraquinone dioxime, etc. Vulcanization accelerators include guanidines, aldehyde ammoniums, aldehyde amines Organic accelerators such as carboxylic acids, alkylamines, nitrones, thiazoles, thiazolines, imidazolines, thioureas, thioates, carpithioates, and isothioureas. In particular, cyclohexylbenzothiazylsulfinamide (abbreviated as CZ), tetramethylthiuram monosulfide (abbreviated as TT), and tetraethylthiuram disulfide (abbreviated as TET) are remarkable in the present invention as organic accelerators.

In order to carry out the present invention, first, the fibers of sepiolite are loosened so as to have a fibrillation degree of an aspect ratio of 50 or more.
10-67% by weight of natural rubber or synthetic rubber with respect to 0 parts by weight is kneaded well with a kneading roll or an intermixer.
At this time, a vulcanizing agent and a vulcanization accelerator are added. At the time of this kneading, first, the kneaded dough is kneaded for a short time at a high temperature, and the kneaded dough is preformed and then vulcanized in a mold to form a sheet-like gasket. The mold may be either a steam or an electric heat press mold, and can be formed into a specific shape with these molds.

When kneading sepiolite with rubber, a vulcanizing agent and a vulcanization accelerator, fillers such as calcium carbonate and other additives such as a plasticizer, a rubber antioxidant and a coloring agent may be added as necessary. it can.

〔Example〕

 Next, specific examples will be described.

Example 1 Sepiolite (Brain air permeability: 340 seconds / 1.5 g) 300 parts by weight Acrylonitrile butadiene copolymer 120 parts by weight Knead with 50 parts by weight of calcium carbonate by an upside-down method using an intermixer, and further 7 parts by weight of sulfur for vulcanization And 4 parts by weight of CZ were added and kneaded. This is preformed by calender rolls, cut to a fixed size, and first heated to 160 ° C using an electric heat press.
For 10 minutes and then at 150 ° C. or higher to complete a sepiolite sheet having a thickness of 1.00 mm.

Example 2 Sepiolite (Brain air permeability 340 sec / 1.5 g) 350 parts by weight Styrene-butadiene rubber 120 parts by weight Vulcanizing sulfur 7 parts by weight TT 4 parts by weight in the same manner as in Example 1 having a thickness of 1.50 mm Completed sepiolite sheet.

Example 3 Sepiolite (Brain air permeability 480 sec / 1.5 g) 300 parts by weight Chlorosulfonated polyethylene 120 parts by weight Calcium carbonate 50 parts by weight Sulfur for vulcanization 7 parts by weight TET 2 parts by weight CZ 2 parts by weight In the same manner, a sepiolite sheet having a thickness of 0.80 mm was completed.

Reference Example 1 The following is a comparison of the physical properties of the embodiment of the present invention and the conventional asbestos sheet.

Reference Example 2 The sheets of Examples 1 to 3 of the present invention were cut so as to conform to the flange defined by JISK 6820, and the sheet was clamped to the flange with a contact pressure of 160 kg / cm ² to perform a pressure test. Temperature (° C) Withstand pressure (kg / cm ² ) Room temperature 120 80 ° C 100 150 ° C 100 200 ° C 80 were obtained. From this fact, it has been found that the present invention can be sufficiently used as a gasket in place of an asbestos sheet gasket, and has various characteristics that cannot be obtained by a conventional sheet gasket of this type.

Examples 4, 5, and 6 The following blends were treated in the same manner as in Example 1 to complete a sepiolite sheet.

The performance test results of the above Examples 4, 5, and 6 are as follows.

[Effects of the Invention] The present invention uses sepiolite having a degree of fibrillation of 200 seconds / 1.5 g or more by a Blaine air permeability device because the fibers have good entanglement because the aspect ratio is 50 or more as described above. Therefore, good fusion between the fiber and various rubbers, without adding a volatile solvent such as an organic solvent, only by mixing natural rubber or synthetic rubber or a mixture thereof with sepiolite, in the voids of the sepiolite fiber. Since the rubber component is well mixed, even in an amount of 10 to 67% by weight with respect to sepiolite, it sufficiently fulfills the function of the binder and has strength.

The sheet obtained in this way is as flexible as a rubber sheet despite its small amount of rubber, that is, organic matter, and has high heat resistance, oil resistance, and water resistance. Thus, a gasket having an excellent stress relaxation rate without a flow phenomenon can be obtained.

Further, by setting the total amount of the sepiolite and the natural rubber or the synthetic rubber or a mixture thereof to 85% by weight or more of the entire gasket, addition of an extra component such as an inorganic filler can be minimized. It can maintain the basic performance and strength as a sheet-like gasket.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09K 3/10 F16J 15/10 C08J 5/04 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. Sepiolite having an aspect ratio of 50 or more and a degree of defibration of at least 200 seconds / 1.5 g by a Blaine air permeability device; b. 10 to 67% by weight based on the weight of the sepiolite. A sheet-like gasket comprising the natural rubber or the synthetic rubber or a mixture thereof, and wherein the total amount of the component a and the component b is 85% by weight or more of the entire gasket. 2. Sepiolite having an aspect ratio of not less than 50 and a defibration degree of not less than 200 seconds / 1.5 g by a Blaine air permeability device; and b. 10 to 67% by weight based on the weight of the sepiolite. A first step of kneading a compound containing natural rubber or synthetic rubber or a mixture thereof with a roll or a mixer or the like without using a solvent such as an organic solvent, and preforming the kneaded dough; A second step of vulcanizing and molding the preformed dough in a mold to form a sheet, and a sheet-like gasket manufacturing method.