JPH0623381B2 - Manufacturing method of joint sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a joint sheet used as a material for a gasket, and this gasket is used in the chemical industry, automobiles, ships, various equipment devices, etc.
Used in a wide range of industrial fields.

(Prior Art) Conventionally, an asbestos joint sheet has been used as a material for a gasket. This asbestos joint sheet uses asbestos fiber as a base fiber, and a rubber material and a rubber chemical as a binder, and a filler are kneaded to prepare a joint sheet-forming composition. It has been manufactured by heating, rolling and vulcanizing between a pair of rolls consisting of a roll and a cold roll to laminate them on the hot roll side, and then peeling the laminated sheet-like material to form a plate.

In the above-mentioned conventional asbestos joint sheet, the addition of the rubber material has been used as a rubber paste in which the rubber is dissolved in a solvent or a rubber latex in which the rubber is dispersed in water.

By the way, the above-mentioned conventional joint sheet is made of asbestos fiber.
Although it is contained in a proportion of 60 to 80% by weight, its use has been reconsidered due to the depletion of resources and its adverse effects on the human body. Therefore, as an alternative to asbestos fibers, attempts have been made to use inorganic fibers such as glass fibers, carbon fibers, ceramic fibers, sepiolite fibers, or organic fibers such as aromatic polyamide fibers and polyethylene fibers.

However, there is a problem that inorganic fibers such as glass fibers and ceramic fibers are crushed at the time of kneading with rubber paste or rubber latex and the aspect ratio is lowered, so that the tensile strength of the obtained joint sheet is lowered. On the other hand, organic fibers such as aromatic polyamide fibers, in particular, fibrillated aromatic polyamide fibers, a joint sheet with high tensile strength can be obtained, but it is difficult to uniformly disperse and knead with rubber paste or rubber latex, for this reason. There is a problem that the sealing characteristics of the joint sheet are not uniform.

For this reason, joint sheets have been proposed in which flexible sepiolite fibers are used in combination with other inorganic fibers, and sepiolite fibers are used in combination with organic fibers (JP-A-62-1273).
80, JP-A-63-105087, etc.). However, compared with the joint sheet based on asbestos, the joint sheet based on sepiolite has a considerable difference in properties, and the reduction of the aspect ratio of the inorganic fibers used together or the non-uniform dispersion of the organic fibers are eliminated. However, there was a problem especially in the compression recovery characteristic and the stress relaxation resistance characteristic.

What can be pointed out about the conventional joint sheet is
It was found to be the following manufacturing problem.

That is, the composition containing fibers other than asbestos fibers as the main component has a larger fiber diameter (because of the smaller surface area) than asbestos fibers, so that the state of water absorption of the rubber paste solvent and rubber latex is different, The softness and tackiness of the mixture called is significantly different from that of asbestos fiber. Therefore, in the mixing of raw materials, agglomeration / entanglement of fibers occurs, and if it is attempted to disperse it by force, not only the fibers are divided, but also scorch easily occurs due to the heat being received by the binder, Unfavorable cold roll adhesion occurs during hot rolling with hot rolls and cold rolls, making it difficult to make the thickness of the kneading sheet uniform, etc. It has been found that the fluctuation of decrease in the thickness of the joint sheet or variation in the thickness and dispersion of the joint sheet is likely to occur.

(Problems to be Solved by the Invention) An object of the present invention is to provide a stable method for producing a joint sheet containing a base fiber, regardless of whether it is an inorganic fiber or an organic fiber, as a base material. Another object of the present invention is to provide a method for producing a joint sheet which does not have a decrease in aspect ratio when inorganic fibers are used, and in particular, does not cause nonuniform aggregation when organic fibers are used.

(Means and Actions for Solving the Problems) The present inventors have conducted diligent research in order to solve the problems associated with the above-mentioned conventional techniques, and have found the following findings regarding dry mixing of powder rubber. Got

That is, when the fibers and the rubber paste swollen with a solvent are mixed as in the conventional technique, the viscosity of the rubber paste is very high, and thus the fibers are agglomerated and entangled to form the rubber paste in the initial stage of mixing. It will be wrapped. It is difficult to completely loosen the agglomerate of fibers once made, and if you try to forcibly loosen this agglomerate, shear stress must be applied at a fairly high speed, the temperature of the mixing material rises, and the rubber material Not preferred for materials that are prone to scorch.

On the other hand, when dry mixing is performed with a mixer that rotates at a high speed, the agglomerates of fibers do not occur as described above, but rather the powder rubber collides with the fibers and the fiber disintegration progresses. Will be evenly dispersed. Then, when a solvent is added and kneaded, the powdered rubber dispersed in the fibers swells and a uniform raw material (seed) for manufacturing a joint sheet can be obtained.

When the rigid inorganic fiber and the high-viscosity rubber glue are directly mixed as in the prior art, the fiber is likely to break due to the shearing force at the initial stage of mixing. Furthermore, since many glass fibers and carbon fibers are bundled with hundreds of sizing agents,
It takes a considerable amount of time to disperse the fibers evenly in the rubber, and the fiber breaks further and the aspect ratio becomes smaller.

On the other hand, when the rigid inorganic fiber and the powdered rubber are dry-mixed, the rubber serves as a cushioning material to mitigate the collision between the fibers, the fibers do not break easily and they mix well, and after the solvent is added. The mixing time is also short because the fiber and powdered rubber are already well mixed, and the aspect ratio does not decrease much.

Based on the above-mentioned findings, the present invention by dry mixing powder rubber uniformly mixes a fiber material, a powdery elastic polymer material having a particle size of 0.1 to 5.0 mm, a filler, and an additive such as a rubber chemical. It is a manufacturing method including a step of dry mixing, a step of adding a solvent to the mixture and kneading while swelling, and a step of plate-making the kneaded material.

The elastic polymer material for dry mixing has a particle size of 0.1
~ 5.0 mm, preferably 0.1 ~ 2.0 mm is suitable for uniform mixing. The powdered rubber may be surface-treated (filled) with a filler or the like in order to prevent the particles from sticking to each other during storage. In the preparation, first, the fiber material, the filler, the powdered rubber, the rubber chemical, etc. are put into a high-speed mixer and dry-mixed, so that the inorganic fibers are uniformly mixed without lowering the aspect ratio. Next, when a rubber-dissolving solvent is added and mixing is continued at a medium speed, the powder rubber uniformly dispersed in the fiber material, the filler, the rubber chemical, etc. is swollen and kneaded in that state, and a more uniform mixture is obtained. It will become. At that stage, a liquid additive in the additives, rubber latex, or the like is added, and mixing is advanced to obtain a final mixture (seed) without aggregation.

The types of elastic polymer materials used in the present invention include natural rubber,
Isoprene rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, butyl rubber,
Acrylic rubber, urethane rubber, silicone rubber, fluorine rubber, polysulfide rubber, ethylene propylene rubber, chlorosulfonated polyethylene rubber, ethylene vinyl acetate rubber, chlorinated polyethylene rubber, alfin rubber, polyester rubber, epichlorohydrin rubber, chlorinated butyl rubber, Examples thereof include nitrile isoprene rubber, other thermoplastic elastomers, and elastic resins such as elastic epoxy.

As the form of the powdered rubber, fine powder obtained by dehydrating latex by a freeze-drying method, okara, etc., such as a cube obtained by crushing solid rubber, an anisotropic body, or a sphere can be used. Although it is not particular about the form, one with a large surface area is preferable.

Among the fiber materials, as the organic fibers, polyamide-based, polyester-based, polyacrylonitrile-based, polyvinyl alcohol-based, polyolefin-based, polyvinyl chloride-based, polyurethane-based, polyurea-based, polyfluorocarbon-based,
In addition to synthetic fibers such as phenol-based, polybenzimidazole, polyphenylene sulfide, polyoxysadiazole, polyimide, ladder polymer and cellulose pulp, natural polymer fibers can be mentioned.

The inorganic fiber improves the compression recovery property and stress relaxation resistance property especially at high temperature. In particular, glass fibers and rock wool are preferable, and among the glass fibers, chopped strands that are converged with a sizing agent that dissolves in a solvent are particularly preferable. In addition, inorganic fibers that can be used include ceramic fibers, mineral wool, boron fibers, fused silica fibers, chemically treated high silica fibers, fused silica silicate fibers, alumina continuous fibers, stabilized zirconia fibers, boron nitride fibers, nitrided fibers. Examples include silicon fibers, alkali titanate fibers, whiskers, asbestos fibers, sepiolite, wollastonite, attapulgite, and the like.

The usual rubber chemicals are used. Fillers are also compounded for the desired properties, such as clay, talc, barium sulfate, sodium bicarbonate, graphite, lead sulfate,
Tripoli stone, attapulgite, halloysite, kaolinite, pyrophyllite, sericite, vermiculite, montmorillonite, chlorite, zeolite, calcined kaolinite, etc., calcined clay, Kanuma soil (allophane), charcoal, calcium sulfate, microfiber, titanate fiber , Silicon carbide fiber, glass clay, hollow glass microspheres, glass beads, antigorite and the like.

(Examples) Hereinafter, the present invention will be specifically described based on Examples.

Examples 1 to 4 As glass fibers, chopped strands having a length of 3 mm converged by a sizing agent dissolved in a solvent, and as aromatic polyamide fibers, fibrillated fibers were treated with a coupling agent on the surface of Enka Co. Twaron ”, sepiolite fiber has a fiber length of 1000 μm, powder rubber is NBR rubber with an average particle size of 1.0 mm, rubber latex is NBR rubber with a solid content of 40% by weight, and clay is used as the filler, and compounded as shown in Table 1. .

First, put a certain amount of powdered rubber, rubber chemicals, and filler in the Henschel mixer, perform high-speed dry mixing at a rotation speed of 700 rpm for 10 minutes, then lower the rotation speed to 300 rpm and remove the solvent for rubber. Added. At the same time, rubber latex and a liquid processing aid are sequentially added and mixed at medium speed for 30 minutes. The composition taken out from the Henschel mixer is put in a curing can and left in a thermostatic chamber at a temperature of 25 ° C. for 24 hours. The obtained composition for joint sheets (seeds) was laminated, heated, rolled and vulcanized on a joint sheet molding machine (heat roll 130 ° C, cold roll 30 ° C) to obtain a sheet-like product from a heat roll with a doctor blade. And peeled off to obtain a joint sheet having a thickness of 1.5 mm.

The test results of the state of the seeds and the characteristics of the joint sheet are first
It is also shown in the table. JIS for tensile strength, recovery rate and stress relaxation rate
The R3453, also the sealing property, the outer diameter 69Mmfai, a sample punched out in the inner diameter 55Mmfai, clamping clamped between the flanges at pressure 300 kgf / cm ^2, leakage of 10 minutes when loaded with N ₂ gas pressure 7 kgf / cm ² The amount was determined by the water displacement method. As shown in Table 1, the sealability and fiber dispersion of the examples are remarkably improved as compared with the following comparative examples.

Comparative Examples 1-3 The formulations are shown in Table 1. First, solid NBR rubber is thoroughly kneaded with a masticating roll, then thinly threaded to a thickness of 0.2 mm, immersed in 45 parts by weight of 70 parts by weight of solvent (toluene), and left to swell for 24 hours. Let The swollen rubber liquid is stirred for 48 hours in a low-speed stirring tank to form a uniform rubber paste.

Next, the rubber glue is subjected to high-speed shear mixing in a homogenizer for 5 minutes, then rubber chemicals and processing aids are added, and the mixture is further mixed for 5 minutes at high speed. This is transferred to a Henschel mixer, glass fibers, asbestos fibers, aromatic polyamide fibers, and sepiolite fibers are added, and the mixture is mixed uniformly for 20 minutes at medium speed. The composition taken out from the Henschel mixer is put into a curing can and left in a thermostatic chamber at a temperature of 25 ° C for 24 hours. The obtained composition for joint sheet was laminated, heated, rolled and vulcanized by a joint sheet molding machine (heat roll 130 ° C, cold roll 30 ° C), and the sheet-like material was peeled off from the heat roll with a doctor blade to obtain a thickness. A 1.5 mm thick joint sheet was obtained.

(Effects of the Invention) As described above, according to the present invention, (1) powder rubber is uniformly mixed with organic fibers, inorganic fibers, rubber chemicals, etc., and then a rubber dissolving solvent is added to the joint sheet. Since it is a mixture, it is possible to prevent the inorganic fibers from breaking and crushing, and not to reduce the aspect ratio, and as a result, the properties that the inorganic fibers originally have can be extracted, which is related to the sealing properties. The compression recovery and stress relaxation resistance are improved.

(2) Since the powdered rubber is dry-mixed, the organic fiber is appropriately defibrated so that the powdered rubber is uniformly contained between the fibers, and in that state, the powdered rubber swells with the solvent to give seeds without agglomerates. . In the joint sheet using such seeds, the dispersed state of the fibers becomes good, and the sealing property and the surface smoothness are improved.

(3) For the rubber material, the conventional solid rubber was cut out from a block in the required amount, kneaded with a masticating roll, thinned, then left for natural swelling with a solvent, and a complicated long-term pre-process of rubber lapping However, the previous step can be omitted and the manufacturability can be significantly improved. In addition, there is no danger of solvent fire in the previous process.

In addition, even when inorganic fibers such as glass fibers and organic fibers such as aromatic polyamide fibers are combined, or when base fibers containing only organic fibers and fillers such as clay are combined, (1) and (2) The effects of the joint are compatible, and the problems of the joint sheet can be broadly solved.

After all, it is possible to solve practical problems and problems in joint sheets using asbestos substitute fibers, especially compression and restoration characteristics that affect sealability, stress relaxation resistance characteristics, fiber dispersion uniformity, and asbestos-based joint sheet Instead, it can open up bright prospects.

Claims (2)

[Claims] 1. A step of uniformly dry-mixing a fiber material, a powdery elastic polymer material having a particle diameter of 0.1 to 5.0 mm, a filler, and additives such as rubber chemicals, and adding a solvent to the mixture. A method for producing a joint sheet, which comprises a step of kneading while swelling and a step of plate-making the kneaded product. 2. A fiber material containing an inorganic fiber, having a particle size of 0.1-.
5.0 mm of a powdery elastic polymer material, a filler, and a step of uniformly dry mixing with additives such as rubber chemicals; a step of adding a solvent to this mixture and kneading while swelling;
A method for manufacturing a joint sheet, which comprises a step of plate-making the kneaded product.