JPH03199777A - Joint sheet - Google Patents

Abstract

PURPOSE:To improve the qualities of reinforcement, heat resistance, steam resistance, oil resistance and chemicals resistance, by realizing a fibrous condition by containing fluorine resin powder at the rate of a specific weight percent against a joint sheet solid portion. CONSTITUTION:About 18weight% aromatic polyamid fibre material, about 12weight% NBR latex solid portion rubber material, and filler of about 9weight% baryte and about 9weight% clay and about 50weight% fluorine resin powder, and a rubber chemical, are used as compound agents. Loosening treatment is administered to the aromatic polyamid fibre the process of mixing. Compound agents and toluene are thrown into a mixer and mixing is done. A joint sheet is obtained by conducting vulcanization formation on a compoundlike mixing material by means of a calender roll. Hereupon, fluorine resin powder is made to be fibrous by shearing at the times of material mixing and sheeting, and a network is formed within the sheet, and because of this tructure, the qualities of heat resistance, steam resistance and chemicals resistance are remarkably improved.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention is a joint sheet for improving the reinforcing properties, heat resistance, water vapor resistance, oil resistance, and chemical resistance of a gas get base material. Regarding.

(Prior art) Conventional joint sheets are composed of fiber materials, rubber materials, fillers, and rubber chemicals, and if necessary for purposes of use, storage, and identification, coupling agents, softeners, Contains small amounts of additives such as plasticizers, water swelling agents, oil swelling agents, and pigments. Among these, the fiber materials used can be classified as (1) asbestos fibers (2) inorganic fibers other than asbestos (3)
) divided into organic fibers.

(1) Joint sheets that use asbestos fibers are called asbestos joint sheets, and joint sheets that do not use asbestos fibers at all, that is, (2) inorganic fibers other than asbestos, and (3) both or both of organic fibers. A joint sheet using either one of these is called an asbestos-free joint sheet or a non-asbestos (NA) joint sheet.

Until recently, only asbestos joint sheets were used, but as the occurrence of pneumoconiosis, which is thought to be caused by asbestos fibers, has become a social problem, asbestos-free joint sheets are now required.

Differences between asbestos joint sheets and asbestos-free joint sheets include the presence or absence of asbestos fibers, as well as the difference in the blending ratio of the fiber cod material to the solid content of the joint sheets. Generally, asbestos joint sheets contain 50-90% by weight of asbestos fibers, while asbestos-free joint sheets contain 10-60% by weight of fibrous material. The main reason why the blending ratio of fiber materials in asbestos-free joint sheets is lower than that in asbestos-free joint sheets is that problems occur in manufacturing.

That is, in the case of asbestos free joint sheets, sheeting with calender rolls tends to become more difficult as the blending ratio of fiber materials increases. In addition, asbestos-free joint sheets use filler to compensate for the decrease in the blending ratio of fiber materials, and the filler blending ratio of asbestos-free joint sheets is 3.
-50% by weight, while that of asbestos free joint sheets is used in the range of 10-80% by weight.

Next, we will discuss the characteristics of each fiber material when used in asbestos free joint sheets.

In the case of organic fibers, the fibers themselves are relatively flexible, and their SP values (solubility parameters) are similar to those of rubber materials, so they can become entangled, bonded, and bonded with rubber materials and fillers, resulting in a reinforcing effect. There is.

In particular, pulp made by fibrillating aramid fibers, which is the most commonly used pulp, has significant fiber branching and a large surface area, so the entanglement with rubber materials and fillers is much more developed than in chopped pulp. Therefore, the reinforcing effect is large, and characteristic values such as tensile strength and flow resistance are improved.

In the case of inorganic fibers other than asbestos, they are generally more rigid than organic fibers and have a different SP value, so they have poor entanglement, bonding, and bonding properties with rubber materials and fillers, and cannot be expected to have much of a reinforcing effect.

In addition, in terms of manufacturability, they tend to be inferior to organic fibers in conforming to the roll surface. However, it is recognized that inorganic fibers have good stress relaxation properties and have improved heat resistance and water vapor resistance compared to organic fibers.

The fiber materials, rubber materials, fillers, and rubber chemicals for asbestos-free joint sheets have been studied depending on the intended use, and now the performance of asbestos-free joint sheets is at the same level as asbestos joint sheets, with the exception of some properties, especially heat resistance. It is gradually approaching.

(Problem to be solved by the invention) However, in such a conventional asbestos-free joint sheet, the constituent fiber material is (3
) In the case of organic fibers, they have a reinforcing effect, but due to manufacturing reasons, it is not possible to increase the amount of fiber blended with asbestos fibers.
Therefore, it is difficult for a joint sheet using an organic fiber material to reach the same level of strength as an asbestos joint sheet. Furthermore, when used under high heat conditions and a steam atmosphere, the fiber material as well as the rubber material deteriorates significantly, resulting in a significantly shorter product life compared to asbestos join sheets.

(2) In the case of inorganic fibers, the fibers themselves have high heat resistance and water vapor resistance, but their reinforcing effect is significantly lower than that of organic fibers. In addition, since the reinforcing performance is largely dependent on the adhesive strength between the fiber and the rubber material, the fiber itself will not deteriorate much if used under high heat conditions or a steam atmosphere.
As the rubber material deteriorates, the reinforcing effect of the fibers is lost, resulting in a shorter product life compared to asbestos joint sheets.

In addition, when fluororesin fibers are used as the fiber material, the adhesive strength between the fibers themselves and the rubber material is very small, so the heat resistance as a joint sheet is
There was a problem in that water vapor resistance was hardly improved.

<Means and effects for solving the problems> The present invention has been made by focusing on such conventional problems, and it provides a fiber material, a rubber material, a filler, a rubber chemical, and a fluororesin that can be made into a fiber. The fluororesin powder is contained in a proportion of 0.1 to 70% by weight based on the solid content of the joint sheet, and after the material is formed into a sheet, the fluororesin powder is This joint sheet is characterized by being in a fibrous state.

In this invention, a fluororesin powder that can be made into fibers is added to the joint sheet formulation, and the fluororesin powder is highly and fibrillated into fibers by shearing force during the material mixing process and during sheeting on a calendar roll. This forms a three-dimensional, spider web-like network of fibrous fluororesin powder inside the sheet, which improves the resistance to flow due to misalignment of the composition materials of the joint sheet, and also improves the thermoplastic properties of the fluororesin. The above problems can be solved by supplementing the hardening caused by thermal deterioration of the rubber binder so that the compressive elasticity of the joint sheet itself does not decrease.

The three-dimensional network of fibrous fluororesin powder is
This is different from a network obtained by simply mixing fluororesin fibers whose surface is branched (fibrillated). In a network of branched (fibrillated) fluororesin fibers, planar connections of the fluororesin fibers are dominant, and fibrils form. While the three-dimensional network of fibers is not sufficient, in the network of fibrous fluororesin powder, the fluororesin powder is subjected to mechanical shearing force while mixed with other compositions, and the molecules are stretched in one direction. This is because fine differentiation and fine differentiation occur at the same time, and as a result, fine, high-strength fiber forms appear, as if a three-dimensional mesh structure network containing other compositions becomes dominant.

Next, the constituent materials of the present invention will be explained.

As the fiber material, both inorganic fibers and organic fibers are used. Examples of inorganic fibers include asbestos fibers, natural inorganic fibers such as sepiolite, and wollastonite, metal fibers such as steel fibers, glass fibers, rock wool,
Examples include oxide fibers such as slag wool, silica fibers, ceramic fibers, alumina fibers, and zirconia fibers, carbide fibers, nitride fibers, carbon fibers, boron fibers, tyranno fibers, and potassium titanate fibers. Examples of organic fibers include synthetic fibers such as aromatic polyamide fibers, nylon fibers, acrylic fibers, polyester fibers, polyurethane fibers, polyethylene fibers, polyvinyl chloride fibers, phenolic fibers, and fluororesin fibers, recycled fibers such as rayon, and acetate fibers. Examples include semi-synthetic fibers such as wood pulp, hemp pulp, and natural organic fibers such as cotton. Note that the fluororesin fibers mentioned here as examples of synthetic organic fibers are not fluororesin powders but fluororesin fibers.

The blending amount of the fiber material is suitably in the range of 50 to 90% by weight for asbestos joint sheets and 10 to 60% by weight for asbestos-free joint sheets, similar to the blending amount in conventional joint sheets.

Rubber materials include NR (natural rubber), IR (synthetic imprene rubber), 5BR (styrene butadiene rubber), N
BR (acrylonitrile butadiene rubber), BR (butadiene rubber), CR (chlorobrene rubber), IIR (butyl rubber), EPR (ethylene propylene rubber), BP
DM (ethylene propylene rubber containing unsaturated bonds), EV
A (ethylene acetate rubber), PIB (polyisobutylene rubber), Eco (epichlorohydrin rubber), NIR (acrylonitrile isoprene rubber), water-added NBR, acrylic rubber, urethane rubber, silicone rubber, fluororubber, chlorinated butyl rubber, chlorosulfonated polyethylene rubber, chlorinated polyethylene rubber, polyisobutylene rubber,
Polyester rubber etc. are used. The rubber material is preferably used in an amount of 5 to 50% by weight.

Filling materials include clay, pottery stone, talc, mica, sericite, silica, diatomaceous earth, perlite, vermiculite,
pallite, calcium carbonate, bentonite, kaolinite, calcined kaolinite, carbon, white carbon,
Graphite, elastic graphite, etc. are used.

The amount of filler mixed is generally 3 for asbestos joint sheets.
~50% by weight, asbestos free joint sheet 1
It is used in a range of 0 to 80% by weight, and it is preferable to use this range in the present invention as well.

Examples of the fibrous resin powder to be blended in the present invention include polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-ethylene copolymer. polymer,
Examples include polychlorotrifluoroethylene and low molecular weight polytetrafluoroethylene, among which polytetrafluoroethylene, which is obtained by emulsion polymerization and has a small intermolecular cohesive force, is desirable.

The blending amount of the fluororesin powder is in the range of 0.1 to 70% by weight based on the solid content of the joint sheet.

If the amount of the fluororesin powder exceeds 70% by weight, the rubber after kneading the fluororesin powder becomes difficult to swell in the solvent, which is not preferable.

Next, we will discuss the processing process.

It is preferable that the above-mentioned compounded materials are kneaded into a compound, or that the fiber material is opened before kneading to improve dispersion, and if necessary, a surface treatment agent such as a coupling agent may be added to the fiber material. may be sprayed.

When using dry rubber, the rubber material needs to be immersed in a solvent such as toluene and kneaded in a swollen state. However, in the case of powdered rubber or latex, swelling by solvent is extremely fast, so swelling can be caused by adding a solvent during the kneading process. For dry rubber, appropriate amounts of fiber material, filler, rubber chemicals, and fluororesin powder may be kneaded in advance using a rubber wire drawing roll, a pressure kneader, or the like.

As for the filler, if necessary, a surface treatment agent such as a coupling agent may be sprayed on the filler before entering the crosstalk process. Further, if the filler and the fluororesin powder are dry mixed before the kneading step, the dispersion in the mixed wire material is further improved.

The kneading machine used may be a Henschel mixer, a kneader-paddle type mixer, etc., but it is necessary to be able to apply a shearing force sufficient to fiberize the fluororesin powder. The fibrosis of the fluororesin powder in the kneading step does not necessarily require 100% fibrosis, and it is fine if some fluororesin powder remains that has not been fibrousized. The compound that has undergone the cross-wire process is then molded into a joint sheet in a molding process.

Calendar rolls are used to form joint sheets, and the cross-wire material is passed through two rolls, a heating roll and a cooling roll, so as to be thinly stretched, then wound onto the heating rolls, and then vulcanized and formed. be done. A strong shearing force is applied between these two rolls, and even the fluororesin powder that has not been turned into fibers during the kneading process is almost completely turned into fibers, and the fiber material, binder (vulcanized rubber)
And the filler is a network of fibrous fluororesin powder.
The structure is closely intertwined with the workpiece.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 As a compounding material, 18% by weight of aromatic polyamide fiber (Kevlar pulp IF502 manufactured by DuPont) was added to the fiber material.
12% by weight solid content of NBR latex as rubber material.
Fillers include 9% by weight of pallite, 9% by weight of clay, and 50% by weight of fluororesin powder (CD-1 manufactured by Asahi Glass Co., Ltd.).
, and even used rubber chemicals. Note that the aromatic polyamide fibers were subjected to an opening treatment using a hammer mill before the kneading step. A Henschel mixer was used as a kneader, and I! was used as the compounding material and solvent. One amount of toluene was added and kneaded. The compound-like mixed wire material thus obtained was vulcanized and molded using calender rolls (temperature of heating rolls was approximately 140°C) to obtain a joint sheet with a thickness of 1°51.

Example 2 As a compounding material, 18% by weight of aromatic polyamide fiber (Kevlar pulp IF502 manufactured by DuPont) was added to the fiber material.
12% by weight solid content of NBR latex as rubber material.
29% by weight of pallite and 29% by weight of clay as fillers.
and 10f of fluororesin powder (CD-1 manufactured by Asahi Glass Co., Ltd.)
! % and further rubber chemicals were used. In addition, the kneading method,
The joint sheet of Example 2 was obtained using the same sheeting method as in Example 1.

Comparative Example 1 In the formulation of Example 2, Palite and clay were added instead of 10% by weight of fluororesin powder to create Palite 34.
The clay content was 34% by weight. Other formulations, kneading methods, and sheeting methods were the same as in Example 2 to obtain a joint sheet of Comparative Example 1.

Table 1 shows the characteristic values of Example 1.2 and Comparative Example 1.

Note that the oil resistance properties are for No. 3 oil.
The rate of decrease in tensile strength of water vapor resistance is determined by the vapor pressure of 18kof/
It is the reduction rate of the tensile strength in the vertical direction of the fiber after 100 hours of exposure under an', and the leakage property is the vapor pressure of 18 kgf/an2,
Steam line with steam temperature of 280℃, ventilation for 10 hours a day,
This is the number of days in which a leak occurs when a 14-hour stop cycle is performed. The acid immersion tensile strength reduction rate for chemical resistance is 0.1N.
These are the results in the vertical direction of the fiber after immersion in HCI for 24 hours, and the alkali immersion tensile strength reduction rate is 0.1N Na
This is the result in the vertical direction of the fiber after being immersed in the OH solution for 24 hours.

From the comparison results between Examples 1 and 2 and Comparative Example 1, the present invention
It can be seen that this has the effect of significantly improving the tensile strength, oil resistance, and water vapor resistance of conventional joint sheets.

Example 3 As a compounding material, 18% by weight of aromatic polyamide fiber (Gebler Valp 1 F2O3 manufactured by DuPont) was added to the fiber material.
The rubber material used was 12% by weight of NBR latex in terms of rubber solid content, 68% by weight of clay as the filler, 0.5% by weight of fluororesin powder (CD-1 manufactured by Asahi Glass Co., Ltd.), and rubber chemicals. The aromatic polyamide fibers were subjected to opening treatment using a hammer mill before kneading.
A Henschel mixer was used as a kneader, and the above compounded materials and an appropriate amount of toluene as a solvent were charged and kneaded. The compound-like mixed wire material thus obtained was vulcanized and molded using a calendar roll (temperature of the heated roll was around 140°C) to obtain a joint sheet.

Comparative Example 2 Of the compounded materials in Example 3, instead of 0.5% by weight of fluororesin powder, the same amount of clay was added to make 68.5% by weight.
shall be. The kneading method and sheeting method were performed in the same manner as in Example 3 to obtain a joint sheet. The characteristic values of Example 3 and Comparative Example 2 are also listed in Table 1.

The results of Example 3 show that adding 0.5% by weight of fluororesin powder improves tensile strength (fiber direction) and chemical resistance (acid resistance, alkali resistance).

(Effects of the Invention) As explained above, according to the present invention, fluororesin powder is added as a compounding agent, the fluororesin powder is made into fibers by shearing force during material kneading and sheeting, and a network is formed inside the sheet. Because of its structure, it has the advantage of significantly improving tensile strength, sharpness, water vapor resistance, and chemical resistance compared to conventional joint sheets. Furthermore, the effect of lowering the coefficient of friction and reducing the tendency to seize on the flange is also seen.

Claims (1)

[Claims] 1 Compounded with materials containing fiber materials, rubber materials, fillers, rubber chemicals, and fluororesin powder that can be made into fibers,
The fluororesin powder is contained in a proportion of 0.1 to 70% by weight based on the solid content of the joint sheet, and the fluororesin powder is in a fiberized state after the material is formed into a sheet. Features a joint seat.