JPH0557471B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a joint sheet intended to improve the reinforcing properties, heat resistance, water vapor resistance, oil resistance, and chemical resistance of gasket base materials. (Prior art) Conventional joint sheets are composed of fiber materials, rubber materials, fillers, and rubber chemicals, and if necessary for use, storage, and identification, coupling agents, softeners, plasticizers, etc. A small amount of additives such as a hydrogen lubricant, an oil swelling agent, and a pigment are blended. Among these, the classification of the fiber materials used is (1)
It can be divided into asbestos fibers (2), inorganic fibers other than asbestos, and (3) 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, joint sheets that use (2) inorganic fibers other than asbestos, and (3) organic fibers or both. Joint sheets using either one of these are called asbestos-free joint sheets or non-asbestos (NA) joint sheets. 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 material to the solid content of the joint sheets. in general,
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 fillers to compensate for the decrease in the blending ratio of fiber materials, and while the filler blending ratio of asbestos-free joint sheets is 3 to 50% by weight, the asbestos-free joint sheets have a lower blending ratio of fiber materials. It has been 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, which is made by fibrillating aramid fibers, which is the most commonly used fiber, has significant branching and a large surface area, so the entanglement with rubber materials and fillers is much more developed than with chopped fibers. 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 has been recognized that inorganic fibers have good stress relaxation properties and 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 the case of such a conventional asbestos-free joint sheet, if the constituent fiber material is (3) organic fiber, it has a reinforcing effect, but it is difficult to manufacture. On the other hand, the amount of fiber added cannot be increased as much as asbestos fiber. Therefore, (3) it is difficult for joint sheets using organic fiber materials to reach the level of asbestos joint sheets in terms of strength. Further, 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 joint 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, reinforcing performance is also largely dependent on the adhesive strength between the fiber and the rubber material, so when used under high heat conditions or a steam atmosphere, the fiber itself will not deteriorate much, but the rubber material will deteriorate. As a result, 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 and water vapor resistance of the joint sheet is almost non-existent. The problem was that it did not improve. (Means and effects for solving the problem) The present invention was made by focusing on such conventional problems, and it is directed to a fiber material, a rubber material, a filler, a rubber chemical, and a fluororesin that can be made into a fiber. It is made by blending a material containing powder, the fluororesin powder is contained in a proportion of 0.1 to 70% by weight based on the joint solid content, and the fluororesin powder is made into a fiber after the material is made into a sheet. It is a joint sheet characterized by being in a 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 made into a highly fibrillar state by shearing force during the material kneading process and during sheeting on a calendar roll. By forming a three-dimensional, spider web-like network of fluororesin powder inside the sheet, it improves the resistance to flow due to misalignment of the composition materials of the joint sheet, and also improves the flow resistance of the fluororesin powder. Thermoplasticity complements the hardening caused by thermal deterioration of the rubber binder and prevents the compressive elasticity of the joint sheet itself from decreasing.
The above problems could be solved. The three-dimensional network of the fibrous fluororesin powder is different from the network obtained by simply mixing fluororesin fibers whose surfaces are branched (fibrillated). In the network of branched (fibrillated) fluororesin fibers, the planar connections of the fluororesin fibers are dominant and the three-dimensional network of the fibril fibers is insufficient, whereas the network of fibrillated fluororesin powder is In the network,
When the fluororesin powder is mixed with other compositions and subjected to mechanical shearing force, the molecules are stretched in one direction and fine differentiation occurs at the same time, resulting in
This is because a fine, high-strength fibrous form appears, and a three-dimensional network containing other components 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. Inorganic fibers include natural inorganic fibers such as asbestos fiber, sepiolite, and wollastonite, metal fibers such as steel fiber, oxide fibers such as glass fiber, rock wool, slag wool, silica fiber, ceramic fiber, alumina fiber, and zirconia fiber. , carbide fibers, nitride fibers, carbon fibers, boron fibers, tyrannofibers, titanate caulifibers, and the like. 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, phenol fibers, and fluororesin fibers, recycled fibers such as rayon, and acetate fibers. semi-synthetic fibers such as
Examples include natural organic fibers such as wood pulp, hemp pulp, and cotton. Note that the fluororesin fibers mentioned here as examples of synthetic organic fibers are not fluororesin powders but fluororesin fibers. The amount of fiber material blended in asbestos joint sheets is the same as that in conventional joint sheets.
A suitable range is 50 to 90% by weight, and 10 to 60% by weight for asbestos free joint sheets. Rubber materials include NR (natural rubber), IR (synthetic isoprene rubber), SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber),
BR (butadiene rubber), CR (chloroprene rubber),
IIR (butyl rubber), EPR (ethylene propylene rubber), EPDM (ethylene propylene rubber containing unsaturated bonds), EVA (ethylene acetate rubber), PIB (polyisobutylene rubber), ECO (epichlorohydrin rubber), NIR (acrylonitrile isoprene rubber), Water-added NBR, acrylic rubber, urethane rubber, silicone rubber, fluorine rubber, 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, pearlite, vermiculite, barite, calcium carbonate, bentonite, kaolinite, calcined kaolinite, carbon, white carbon, graphite, elastic graphite, etc. are used. The amount of filler is generally used in the range of 3 to 50% by weight for asbestos joint sheets and 10 to 80% by weight for asbestos-free joint sheets, and in the present invention, it is also used in this range. is preferred. 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. Examples include polytetrafluoroethylene, polychlorotrifluoroethylene, and low molecular weight polytetrafluoroethylene, among which polytetrafluoroethylene with low intermolecular cohesive force obtained by emulsion polymerization is preferred. The amount of fluororesin powder blended is in the range of 0.1 to 70% by weight based on the solid content of the joint sheet.
If the amount of 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. The above compounded materials are kneaded into a compound, but it is preferable to open the fiber material before kneading to improve dispersion.If necessary, a surface treatment agent such as a coupling agent may be sprayed on the fiber material. You may do so. 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 and latex, they swell extremely quickly with solvents, so
Swelling can be achieved by adding a solvent during the kneading process. Further, in dry rubber, appropriate amounts of fiber materials, fillers, rubber chemicals, and fluororesin powders may be kneaded in advance using a rubber masticating roll or a pressure kneader. As for the filler, a surface treatment agent such as a coupling agent may be sprayed on the filler before the kneading step, if necessary. Furthermore, if the filler and the fluororesin powder are dry mixed before the kneading step, the dispersion in the kneaded material will be further improved. The kneading machine used may be a Henschel mixer, a kneader, a paddle type mixer, etc., but it is necessary to be able to apply a shearing force sufficient to fiberize the fluororesin powder. The fibrous resin powder in the kneading process does not necessarily have to be 100% fiberized, and there is no problem even if some fluororesin powder remains that has not been fiberized. The compound that has undergone the kneading process is then molded into a joint sheet in a molding process. A calender roll is used to form the joint sheet, and the kneaded material is passed between two rolls, a heating roll and a cooling roll, so as to be thinly stretched, then wound onto the heating roll, and then vulcanized and formed. be done. There is a strong shearing force 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, resulting in fiber material, binder (vulcanized rubber), and filler. The material has a structure that is tightly intertwined with a network of fibrous fluororesin powder. (Example) Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 As a compounding material, aromatic polyamide fiber (Kevlar pulp IF302 manufactured by DuPont) was added to the fiber material.
12% by weight of NBR latex in solid content as a rubber material, 9% by weight of barite as a filler, 9% by weight of clay, and 50% by weight of fluororesin powder (CD-1 manufactured by Asahi Glass Co., Ltd.). Using rubber chemicals. The aromatic polyamide fibers were opened using a hammer mill before the kneading process. A Henschel mixer was used as a kneader, and the above compounded materials and an appropriate amount of toluene as a solvent were added and kneaded. The resulting compound-like kneaded material is vulcanized and molded using a calendar roll (temperature of the heating roll is around 140°C), and the thickness is
A 1.5 mm joint sheet was obtained. Example 2 As a compounding material, aromatic polyamide fiber (Kevlar pulp IF302 manufactured by DuPont) was added to the fiber material.
12% by weight of NBR latex as a rubber material, 29% by weight of barite as a filler, 29% by weight of clay, and 10% by weight of fluororesin powder (CD-1 manufactured by Asahi Glass Co., Ltd.). Using rubber chemicals. The joint sheet of Example 2 was obtained using the same kneading method and sheeting method as in Example 1. Comparative Example 1 In the formulation of Example 2, barite and clay were added instead of 10% by weight of fluororesin powder,
Palite was 34% by weight and clay 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 Examples 1 and 2 and Comparative Example 1. Note that oil resistance properties are for No. 3 oil, and the rate of decrease in tensile strength for water vapor resistance properties is based on steam pressure.
It is the reduction rate of tensile strength in the vertical direction of the fiber after 100 hours of exposure under 18Kgf/ ^cm2 , and leakage is the rate of decrease in tensile strength at a vapor pressure of 18Kg.
f/cm ² and a steam line with a steam temperature of 280°C, 10 times a day.
This is the number of days in which a leak occurs when a cycle of 14-hour ventilation and 14-hour shutdown is performed. The acid immersion tensile strength reduction rate of chemical resistance properties is the result in the fiber vertical direction after 24 hours immersion in 0.1N NCl, and the alkali immersion tensile strength reduction rate is the result after 24 hours immersion in 0.1N NaOH solution. This is the result in the fiber perpendicular direction. From the comparison results between Examples 1 and 2 and Comparative Example 1, it can be seen that the present invention has the effect of significantly improving the tensile strength, oil resistance, and water vapor resistance of conventional joint sheets.

【table】

[Table] Example 3 As a blending material, aromatic polyamide fiber (Keplar pulp IF302 manufactured by DuPont) was added to the fiber material.
NBR latex was used as the rubber material at a rubber solid content of 12% by weight, clay was used as the filler at 68% by weight, fluororesin powder (CD-1 manufactured by Asahi Glass Co., Ltd.) was used at 0.5% by weight, and rubber chemicals were used. Note that the aromatic polyamide fibers were subjected to an 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 kneaded material thus obtained was vulcanized and molded using calender rolls (temperature of heating rolls was around 140°C) to obtain a joint sheet. Comparative Example 2 Among the compounded materials of Example 3, fluororesin powder
Add the same amount of clay instead of 0.5% by weight
68.5% by weight. 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. From the results of Example 3, by adding 0.5% by weight of fluororesin powder, the tensile strength (fiber direction),
It can be seen that chemical resistance (acid resistance, alkali resistance) is improved. (Effect of the invention) As explained above, according to this invention,
It is added as a fluororesin powder compounding agent, and the fluororesin powder is fiberized by shearing force during material kneading and sheeting, forming a network inside the sheet, so it has a higher tensile strength than conventional jointed sheets. The effect is that strength, heat resistance, water vapor resistance, and chemical resistance can be significantly improved. 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 A material containing a fiber material, a rubber material, a filler, a rubber chemical, and a fluororesin powder that can be made into fibers is blended, and the fluororesin powder is in a proportion of 0.1 to 70% by weight based on the solid content of the joint sheet. 1. A joint sheet characterized in that the fluororesin powder is contained in a fluororesin powder, and the fluororesin powder is in a fibrous state after the material is formed into a sheet.