JPH02212581A - Production of joint sheet - Google Patents

Abstract

PURPOSE:To obtain a joint sheet with a low void content and excellent sealing and strength properties by preforming a mixture of a specific aggregate with a rubber soln. contg. a vulcanizing agent into a sheet, heating the sheet to remove an org. solvent, then thermally molding and vulcanizing the sheet. CONSTITUTION:At least one aggregate selected from the group consisting of an inorg. fiber, an org. fiber, a graphite powder and an expandable graphite powder is mixed with a rubber soln. contg. a rubber, a vulcanizing agent and a vulcanization accelerator (e.g. a trichloroethylene soln. of a mixture of acrylonitrile-butadiene rubber, sulfur, tetramethylthiuram disulfide and zinc oxide, each in a specified amt.). The resulting mixture is preformed at 120 deg.C or lower into a sheet, from which the org. solvent is removed by heating during or after the preforming, then the sheet is thermally molded at the vulcanizing temp. of the rubber, thus producing a joint sheet. The resulting joint sheet has a low residual void content and high sealing and strength properties.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a joint sheet used as a sealing material and a gasketing material.

(Prior art) According to Japanese Industrial Standards JIS 3453, 9 asbestos joint sheets are made by mixing asbestos fibers of 65 inches or more by weight with 10 inches or more of rubber as a binder, other rubber chemicals, and fillers. , which is heated and compressed into a dense and uniform cardboard shape. The specific manufacturing method is to add a rubber solvent to the above-mentioned materials and mix them, then heat and roll them on a calendar roll to evaporate the solvent and vulcanize the rubber. be.

Recently, de-stone M (
Due to the demand for asbestos-free materials, studies are underway to incorporate organic fibers such as aramid fibers, inorganic fibers such as glass fibers, or graphite or expanded graphite instead of asbestos. However, when organic fibers are used, heat resistance deteriorates, and inorganic fibers other than asbestos have poor compatibility with rubber, resulting in low strength. Furthermore, when graphite or expanded graphite is used, the graphite particles become a sheet with planar orientation, which improves the sealing performance, but the sealing strength becomes low because there is no entanglement between the first fibers.

Therefore, we are currently at the stage of searching for materials to replace asbestos.

(Problems to be Solved by the Invention) Asbestos joint sheets have the advantages of high strength and low cost, but one disadvantage is that asbestos fibers are harmful to the human body, and there is also a problem in sealing performance. In other words, asbestos has many microscopic voids between its fibers, and when used as a gasket, the fluid that should be sealed by sewing these microscopic voids leaks to the outside. .

This defect is common to non-asbestos jointed sheets containing fibers other than asbestos, and cannot be improved simply by increasing the heating rolling time of the hot rolls.

For example, in the case of a 1 m thick sheet made of pressure-formed expanded graphite particles, no leakage will occur even if 0.7 kgf 7 cm" of LLC lower glaia coolant is added to one side, but if the sheet is made from commercially available sheets with a thickness of 1 m, no leakage will occur. Both the asbestos joint sheet and the aramid fiber joint sheet leak at a rate of 0.2 kg f/an''. Expanded graphite sheets are oriented in one plane, and the graphite particles provide good sealing properties, but their strength is low; Since they are connected, the sealing performance deteriorates.

When graphite or expanded graphite is used, voids occur between graphite particles, but since graphite particles are planar, the sealing performance does not deteriorate; in this case, the presence of voids may reduce the strength. and K.

Ultimately, in order to improve the sealing performance and strength of the joint sheet, the voids remaining inside the joint sheet must be removed. However, in the conventional method of hot rolling using hot rolls, voids are left inside the product.

Another problem is that new voids are created due to evaporation of the solvent.

An object of the present invention is to provide a method for manufacturing a joint sheet that eliminates the above-mentioned drawbacks.

(Means for Solving the Problems) The present invention provides one or more aggregates selected from the group consisting of inorganic fibers, organic fibers, graphite powder, and expanded graphite powder.
A mixture of rubber, a rubber solution containing a vulcanizing agent, and a vulcanization accelerator is preformed into a sheet at a temperature of 120°C or less, and heated during or after the preforming to remove the organic solvent. The present invention relates to a method for producing a joint sheet that is heat-formed at a vulcanization temperature.

In the present invention, aggregates include inorganic fibers such as glass fibers and ceramic fibers, organic fibers such as aramid fibers and kynol fibers, and graphite powder (preferably scaly graphite powder with a particle size of 11 or more).
and one or more members of the group consisting of expanded graphite powder,
More must! Depending on the requirements, inorganic fillers such as calcium carbonate, talc, bentonite, etc. are added thereto, and there is no particular restriction on the composition in the case of more than one. Expanded graphite is obtained by a known method using the above-mentioned scaly graphite as a raw material.

Rubber is added as a flexible binding material, and NB
R, Fluorine Rubber A* 8 BR, CR and other artificial rubbers are preferred; NBR is most preferred from the viewpoints of strength, oil resistance and cost. The rubber is used after being dissolved in a solvent, and the solvent is preferably a chlorine-containing hydrocarbon such as trichlorethylene or an organic solvent with a high dissolving power such as acetone. The above rubber is vulcanized to improve heat resistance and strength, so ICF! , vulcanizing agents such as sulfur.

Organic vulcanization accelerators such as guanidines, aldehyde ammonias, aldehyde amines, alkyl amines, and more! Depending on the requirements, an inorganic vulcanization accelerator such as zinc white is added to the rubber solution.

The above rubber solution is added to the aggregate and mixed, and the mixture is preformed into a sheet at a temperature of 120° C. or lower, at which the rubber can be plastically deformed without being vulcanized.

The solvent is sufficiently removed by volatilizing the solvent at the temperature during preforming, or by drying after performing the preforming at room temperature.

If the solvent remains, the temperature is further raised to vulcanize the rubber in the ninth and final step, and the resulting joint sheet contains bubbles due to volatilization of the residual solvent. The heating temperature for vulcanization is preferably 140 to 170°C.

There are no particular restrictions on the method of preforming and final forming (main forming); pressing in a mold may be acceptable, but from the standpoint of production efficiency and solvent removal (degassing), it is preferable to use rolls. A method of rolling is preferred, and there are no restrictions on the method of heating the mouth or mold during preforming and main forming.
The rolls and residual dust may be directly heated, or, for example, a busy roll portion may be placed inside the heating chamber.

Further, it is preferable to set the sheet density at the time of preforming to 50 inches or more, which is the density of the joint sheet to be obtained, since this will ensure sufficient deaeration.

(Example) Next, the present invention will be explained in detail.

Example I 100 parts by weight of NBR (acrylonitrile butadiene rubber manufactured by Nippon Gosei Rubber), 3 parts by weight of sulfur, and 3 parts by weight of tetramethylthiuram disulfide and 5 parts by weight of zinc white as vulcanization accelerators were mixed with 100 parts by weight of trichlorethylene. Further, 100 parts by weight of pulp-like aramid fibers and 600 parts by weight of calcium carbonate powder were added and mixed again. The mixture was preformed into a sheet shape on a roll at room temperature, and then heated and dried to volatilize and remove trichlorethylene.

The density of the sheet after drying was 1.3 g/am''.The sheet was then heated and rolled at 155°C with a calendar roll to give a density of 1.8 g/am'' and a thickness of 0.5 mm. I got a joint sheet.

Comparative Example 1 A joint sheet was obtained in the same manner as in Example 1 except that the preforming of the mixture was omitted. The density was as low as 1.6 g/an''.

Comparative Example 2 In Comparative Example IJC, the gap between the rolls during hot rolling with calender rolls was made smaller than in Comparative Example 1, and the load on the shear rolls was increased to produce a roll with a density of 1.8 g/an'' and a thickness of 0.5 m. When I created the Into sheet, wrinkles and cracks appeared on the surface of the sheet.

Example 2 100 parts by weight of NBR, 3 parts by weight of sulfur and 8 parts by weight of tetramethylthiuram disulfide were mixed with 3000 parts by weight of acetone, and expanded graphite powder (bulk density 0.005
g/cm") and mixed again, the mixture was preformed through rolls at 60°C and the acetone was removed. The density of this preformed sheet was 1.45
g 7cm".

This sheet was heated and rolled at 155° C. using a calendar roll to obtain a stained sheet having a density of 1.5 g/an” and a thickness of 0.5111 mm.

Comparative Example 3 A joint sheet was obtained in the same manner as in Example 1 except that the preforming of the mixture was omitted, but! ! ! Many blisters containing air appeared on the surface.

Table 1 shows the results of measuring the tensile strength and LLC liquid leakage pressure of the joint sheets obtained in the above Examples and Comparative Examples.

As is clear from Table 1, the joint sheets of Examples are superior to those of Comparative Examples in both tensile strength and sealing properties.

(Effect of the invention) According to the present invention, the joint sheet obtained is:

Excellent roundness, sealability, and strength with little residual air, that is, fewer voids.

Agent: Patent Attorney Kunihiko Wakabayashi) Table 1

Claims (1)

[Claims] 1. A mixture of one or more aggregates selected from the group consisting of inorganic fibers, organic fibers, graphite powder, and expanded graphite powder, and a rubber solution containing rubber, a vulcanizing agent, and a vulcanization accelerator. 1
A method for producing a joint sheet, which comprises preforming into a sheet at a temperature of 20°C or less, heating during or after the preforming to remove the organic solvent, and then heat forming at a temperature at which rubber is vulcanized. .