JP2002194331A - Gasket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a gasket having excellent strength and sealing properties at high temperatures. SOLUTION: This gasket is characterized by containing a poly(p-phenylene benzobisoxazole) fiber as a fibrous substrate in the case of the gasket comprising the fibrous substrate, a filler and a binder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various industrial machines for petrochemical plants, valves and pumps,
Pipe connection parts such as automobiles, home appliances, and pipe joints,
The present invention relates to a gasket used in a wide range of fields such as a fire prevention seal.

[0002]

2. Description of the Related Art Conventionally, asbestos fiber has a unique shape and excellent heat resistance, so that it is used as a gasket for piping, equipment such as water, oil, air, and steam. It has been stamped and used. Because asbestos is an inorganic substance, it is very flexible and highly fibrillated.
Even when high shear strength or compressive strength is required, there is no problem in use, heat resistance even at high temperatures, very flexible and highly fibrillated asbestos are entangled, maintaining the shape of the gasket and improving sealing performance. Can be secured. However, asbestos is known to be harmful to the human body and cause health problems, especially by inhalation. In addition, because of the problem of environmental pollution, its use is restricted, and gaskets that do not use asbestos have been developed and used. Conventionally, as a gasket that does not use such asbestos, a fiber base material such as aramid fiber, rock and slag fiber, a filler such as talc, kaolin, and graphite, and a binder made of rubber and rubber chemicals are uniformly dispersed. After that, those formed in a sheet shape are known.

[0003]

Among the organic fiber substrates used as an alternative to asbestos in gaskets that do not use asbestos, aramid fibers, particularly fibrillated aramid fibers, have excellent mechanical strength. It has a very high strength, a high modulus and a high temperature resistance and is used as a preferable material. Although fibrillated aramid fibers are effective in increasing the strength of gaskets, they have poor heat resistance compared to asbestos, and therefore have the problem of reduced tensile strength when used in environments exposed to heat and steam. . Other inorganic fibers are used as an alternative to asbestos to improve heat resistance.However, compared to asbestos, many fibers have a thicker and more rigid fiber, insufficient fiber entanglement, and gasket shearing. The effect of improving strength and compressive strength is small. Aramid fiber is required as the heat-resistant organic fiber in order to supplement the effect, and is currently in practical use. However, aramid fiber has better heat resistance among organic fibers, but it is still not enough

An object of the present invention is to solve the above problems by using polyparaphenylene benzobisoxazole fiber, which is an organic fiber having better strength, heat resistance and flame retardancy than aramid fiber, at a high temperature. An object of the present invention is to provide a gasket that can exhibit excellent shear strength, compressive strength, and sealing properties.

[0005]

In order to achieve the above object, the present invention provides a gasket comprising a fiber base, a filler and a binder, wherein polyparaphenylene benzobisoxazole fiber is used as the fiber base. It is intended to provide a gasket containing the same. As the polyparaphenylene benzobisoxazole fiber constituting the gasket of the present invention, a fiber fibrillated by beating treatment is suitably used.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The function and composition of each material constituting the gasket of the present invention will be described in detail below. The fibrous base material forms a uniform stitch structure inside the sheet, is bonded by rubber as a binder, and has a mechanical strength such as supporting the tensile strength and the compressive load on the sheet and preventing spread during compression. Is to be granted. As the fiber base material, it is preferable to use polyparaphenylene benzobisoxazole pulp having a pulp form by fibrillation using polyparaphenylene benzobisoxazole fibers.

The polyparaphenylene benzobisoxazole (hereinafter referred to as PBO) pulp used in the present invention is obtained by fibrillating PBO fibers. PB
O-fiber has excellent properties such as strength and elasticity higher than aramid fiber and higher heat resistance than aramid fiber. Therefore, PBO fibrillated PBO fiber
A gasket made of BO pulp is a gasket having excellent strength and sealing properties under a high temperature environment. P
As the BO fiber, specifically, for example, a trade name “ZYLON” of Toyobo Co., Ltd. is used.

[0008] These PBO pulp can be produced by beating using long fibers of PBO fibers or short fibers of about several mm. Here, as a means for producing PBO pulp, a ball mill, a beater, a lampen mill, a PFI mill, a joclomill, and a general beater such as a ball mill are used.
PBO using DR, DDR and other refiners
PBO pulp is obtained by beating the fibers.

The fiber substrate of the present invention may optionally contain other organic fibers and inorganic fibers described below. As the other organic fibers, aramid fibers, polyamide fibers, polyolefin fibers, phenol resin fibers, aromatic polyester fibers, aromatic polyimide fibers, aromatic polybenzimidazole fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, Examples thereof include polyvinyl chloride fibers, polyurea fibers, polyurethane fibers, polyfluorocarbon fibers, and cellulose fibers.

On the other hand, the inorganic fibers function to improve the heating strength, particularly to prevent thermal deformation (heat creep) during initial heating, and to prevent shrinkage during drying after wet papermaking. As the inorganic fibers,
Rock wool, carbon fiber, glass fiber, sepiolite, ceramic fiber, fused quartz fiber, fused alumina silicate fiber, continuous alumina fiber, stabilized zirconia fiber, boron nitride fiber, alkali titanate fiber, wollastonite, whisker, boron fiber and Metal fibers and the like can be applied to the present invention.

The PBO fiber according to the present invention is an organic fiber, but has a great feature that it has heat resistance and strength comparable to those of an inorganic fiber, and is a material most suitable for a specific application such as a gasket.

The filler functions as a plugging material, improves the sealing performance to a certain level, and contributes to the improvement of the tightening load resistance and the heat resistance. Fillers include kaolin, sepiolite, clay, talc, heavy calcium carbonate, light calcium carbonate, silica, mica,
One or more kinds of barium sulfate, alumina, vermiculite, etc., and powders of hydrated silicate minerals containing silicon, aluminum, magnesium, iron, alkaline earth metals, alkali metals, wollastonite, etc. Inorganic powders such as natural mineral powders may be used. Further, graphite-based fillers such as flaky graphite, earthy graphite, and carbon black may be used.

As the binder constituting the gasket of the present invention, a rubber-based material is preferably used. The rubber-based material serves as a binder for the fibrous base material and contributes to the improvement of the sealing property. Specific examples of the rubber-based material include natural rubber, styrene-butadiene copolymer, and ethylene-vinyl acetate. -One or more of acrylic acid ester copolymer, methacrylic acid ester copolymer, acrylonitrile-butadiene copolymer, acrylic rubber, silicone rubber, fluorine rubber or other synthetic or natural rubber latex or solid rubber May be used.

The rubber-based material is used in combination with the following rubber chemicals. That is, the rubber chemicals include sulfur, zinc oxide, magnesium oxide, peroxides, vulcanizing agents such as dinitrosobenzene, polyamine compounds, aldehyde amine compounds, thiuram compounds, dithiocarbamate compounds, sulfenamides. -Based compounds, thiazole-based compounds, guanidine-based compounds, thiourea-based compounds, xanthate-based compounds and other vulcanization accelerators, and anti-aging agents, anti-scorch agents, dispersants, plasticizers, pigments, colorants, etc. are heat-resistant It is selected and used depending on the purpose such as oil resistance, acid resistance, and color tone.

A fiber base material constituting the gasket of the present invention;
The mixing ratio of the filler and the binder is preferably 5 to 20% by weight of the fiber base material, 40 to 70% by weight of the filler, and 5 to 20% by weight of the binder. The setting is not limited, and can be appropriately changed according to the purpose of use.

In the above mixing ratio, if the fiber base exceeds 20% by weight, the voids become too large due to the increase in the fiber quality, and the sealing property deteriorates. The strength is weakened, and a problem that the gasket is easily damaged by the tightening force is likely to occur.

On the other hand, if the filler content exceeds 70% by weight, the mechanical strength of the gasket decreases because the mixing ratio of the fiber base material and the binder is relatively small, while if it is less than 40% by weight. In the extreme case, the tightening load at the time of mounting the gasket tends to decrease. In an extreme case, the gasket is cut to deteriorate the sealing property, and also tends to cause a large stress relaxation at the time of heating.

Furthermore, if the binder exceeds 20% by weight,
Heat resistance decreases, thermal creep and stress relaxation increase,
On the other hand, if it is less than 5% by weight, a gap is left, the sealing property is reduced, and the original reinforcing effect of the binder tends to be insufficient.

Further, the bulk density of the gasket composed of the above materials is 0.8 to 1.9 g.
/ Cm ³ is preferably set. 0.8 g bulk density
If it is smaller than / g / cm ³ , the porosity is large and there is a risk of permeation leakage. If it is larger than 1.9 g / cm ³ ,
Flexibility is lost and familiarity is poor.

[0020]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to only these examples. Compounding materials and amounts shown in Table 1 (% by weight)
Is made into a sheet by a wet papermaking method using a fourdrinier machine, and the bulk density of each of Examples and Comparative Examples is 1.7 g / m.
^3. A gasket having a thickness of 1.5 mm was produced. here,
As the aramid fiber and the PBO fiber, fibrillated fibers are used. The fiber diameter is 0.1 to 20 μm, the fiber length is 0.1 to 10 mm.
５０50 μm, fiber length 1-20 μm, kaolin particle size 0.1-10 μm, graphite particle size 0.1
〜5 mm was used.

[0021]

[Table 1]

The sealing properties at high temperatures and the tensile strength before and after steam deterioration were measured for the gaskets of Examples and Comparative Examples produced from the above-mentioned compounding materials and amounts, and the results are shown in Tables 2 and 3. . As for the sealing property, a gasket punched in a ring shape was fitted into a union joint having a nominal diameter of 1/2 B, and after heat treatment at 850 ° C. for 30 minutes, N
The amount of leakage for 1 minute when 420 mmAq of 2 gas was loaded was measured. Regarding the tensile strength after steam deterioration, the test piece was placed in a saturated steam atmosphere of 2 MPaG for 5 minutes.
After holding for 0 hour and then performing standard state treatment, the tensile strength was measured according to JISR3453.

[0023]

[Table 2]

[0024]

[Table 3]

From Tables 2 and 3, it was found that the use of PBO fibers as a material constituting the gasket was effective in improving the sealing properties and tensile strength at high temperatures.

[0026]

As described above, according to the present invention, the strength,
By using polyparaphenylene benzobisoxazole fiber, which is an organic fiber excellent in heat resistance and flame retardancy, especially fibrillated polyparaphenylene benzobisoxazole pulp, strength and sealability at high temperatures can be maintained. An excellent gasket can be provided.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 3J040 EA16 EA19 FA06 FA20 HA06 HA15 4H017 AA17 AA18 AA27 AA29 AD01 AD04 AE02 4L055 AF01 AF14 AF44 AG02 AG27 AG74 AG76 AG89 AH01 AH37 FA11 FA13 FA19 FA30 GA50

Claims (2)

[Claims] 1. A gasket comprising a fiber base material, a filler and a binder, wherein the gasket contains polyparaphenylene benzobisoxazole fibers as the fiber base material. 2. The gasket according to claim 1, wherein the polyparaphenylene benzobisoxazole fiber is fibrillated.