JP4734271B2 - Joint sheet and gasket using the same - Google Patents

Description

  The present invention relates to a joint sheet suitable as a gasket material for industrial pipes, and more particularly to a joint sheet formed from a material having expanded graphite, aramid fiber, and a rubber binder.

  As this type of joint sheet, one disclosed in Patent Document 1 is known. In other words, it was developed as a material to replace asbestos joint sheets, and is a material that combines aramid fibers, mineral fibers, inorganic fillers (kaolin, sepiolite, calcium carbonate, graphite, etc.), and rubber-like binders. It is a joint sheet consisting of so-called non-asbestos joint sheets.

  The joint sheet has been developed as a replacement for an asbestos joint sheet. That is, in the old days, asbestos beater sheets composed mainly of white asbestos and a rubber latex binder and a vulcanizing agent, and asbestos, the rubber and additive asbestos binder. Asbestos joint sheets made by blending rubber chemicals such as vulcanizing agents swept the market. However, asbestos-based joint sheets (gaskets) are harmful to the human body, and there are also problems of environmental pollution, so their use has been restricted, and the development of gaskets that do not use asbestos has become an urgent issue. Yes.

However, the non-asbestos-based joint sheet disclosed in Patent Document 1 and the like has a room for improvement in that the use state in a high-temperature region is unstable and the high-temperature characteristics as much as the asbestos-joint sheet cannot be easily obtained. .
Patent Publication No. 2538509

  The object of the present invention is to provide heat resistance (heat-resistant sealability) so that a joint sheet formed from a material having expanded graphite, aramid fiber, and a rubber binder can be used stably even at high temperatures by further material innovation. It is in providing as what it has.

The invention according to claim 1 is a joint sheet formed of a material having expanded graphite, aramid fiber, and a rubber binder,
The mass ratio of the expanded graphite, the aramid fiber, and the rubber binder to the material is set to 40 to 50% ,
The mass ratio of the expanded graphite to the material is set to 15 to 35%,
The mass ratio of the aramid fiber to the material is set to 4 to 15%,
The mass ratio of the rubber binder to the material is set to 10-18%,
NBR is employed as the rubber binder, and the material contains inorganic fibers.
The mass ratio of the inorganic fibers to the material is set to 20 to 40% .

The invention according to claim 2 is characterized in that the gasket is formed using the joint sheet according to claim 1 .

  According to the invention of claim 1, in a joint sheet formed of a material having expanded graphite, aramid fiber, and a rubber binder, various experimental data and test data predicting the sum of these three components As a result of earnest research and development such as obtaining non-asbestos joint sheets, it is possible to improve the properties of the non-asbestos joint sheets at high temperatures to the same performance as the asbestos joint sheets. As a result, a joint sheet formed of a material having expanded graphite, aramid fiber, and a rubber binder can be provided as having heat resistance (heat resistant sealability) so that it can be used stably even in a high temperature range.

If the mass ratio of the expanded graphite to the entire material is set to 15 to 35% as in the invention of claim 1 , the sealing performance, strength (tensile strength), and thermal creep properties are prevented from deteriorating, It is possible to provide a joint sheet that is excellent in resilience during heating.

If the mass ratio of the aramid fiber to the entire material is set to 4 to 15% as in the invention of claim 1 , strength (tensile strength) or A joint sheet effective for the thermal creep test can be provided.

If the mass ratio of the rubber binder to the entire material is set to 10 to 18% as in the first aspect of the invention, the sealing performance and strength (tensile strength) are maintained without adversely affecting the simple steam test and the thermal creep test. It is possible to provide a joint sheet having an effect of favorably affecting (strength).

If the rubber binder is NBR as in the first aspect of the invention, the oil resistance, the compression recovery property, and the mechanical strength are excellent in a good balance.

As in the first aspect of the invention, a material containing inorganic fibers contributes to improvement of heating strength, particularly prevention of thermal deformation (thermal creep) during initial heating, improvement of resilience, and the like. In addition, it functions as a plugging material and improves the sealing performance to a certain level, and contributes to the improvement of the tightening load resistance and heat resistance. If the blending amount of the inorganic fiber exceeds 40%, the strength tends to decrease, and if it is less than 20%, the clamping load at the time of mounting the gasket tends to decrease, so the blending ratio is preferably set to 20 to 40%. .

According to invention of Claim 2, the joint sheet gasket which has the said effect by invention of Claim 1 can be provided.

  Embodiments of a joint sheet according to the present invention and a gasket using the joint sheet will be described below with reference to the drawings. FIGS. 1 and 2 are diagrams showing component tables of joint sheets of Examples 1 to 7 and Comparative Examples 1 to 6, respectively, and FIGS. 3 to 5 are blends of aramid fiber, rubber binder, and expanded graphite, respectively. The figure which shows the characteristic graph related to a ratio, FIG. 6, FIG. 7 are the operation | movement diagrams which show a simple steam test and a thermal creep test, respectively.

  The joint sheet according to the present invention is formed from a material composed of expanded graphite, aramid fiber, rubber binder, inorganic fiber, and rubber chemical, and is a sum of the three of expanded graphite, aramid fiber, and rubber binder. It is created using a material whose mass ratio to the entire material is set in the range of 40 to 50%. Individually, the mass ratio of expanded graphite is set in the range of 15-35%, the mass ratio of aramid fibers is set in the range of 4-15%, and the mass ratio of the rubber binder is 10-18. It is desirable to set in the range of%. A gasket (joint sheet gasket) G shown in FIG. 6 is formed in a ring shape by piercing the joint sheet.

  Sample preparation as a joint sheet is performed by a method according to a method for producing an asbestos joint sheet. That is, first, base fiber, filler, rubber chemicals, and rubber dissolved in a solvent are added and mixed with a Henschel mixer. Then, the mixture (mixed material composition) is put between a pair of calender rolls consisting of a hot roll heated to 150 ° C. and a cold roll kept at 20 ° C., and laminated on the hot roll side. In this manufacturing method, the solvent is evaporated and vulcanized while the sheet having a thickness of 1.5 mm is peeled off from the hot roll.

  As can be seen from the characteristic graph for expanded graphite of the joint sheet (gasket) shown in FIG. 5 (relationship graph with various performances with respect to the amount of expanded graphite (blending ratio)), the expanded graphite increases the blending amount (blending ratio). It is a material that has an effect on resilience during heating, and contributes particularly to the simple steam test. However, if the amount of expanded graphite is excessively increased, the sealing property and strength (tensile strength) are gradually deteriorated, and the thermal creep property tends to be abruptly deteriorated. Therefore, in order to enjoy the advantages while avoiding those adverse effects, the blending ratio of the expanded graphite is set to 15 to 35% by mass.

  As can be seen from the characteristic graph for the amount of aramid fibers (mixing ratio) of the joint sheet (gasket) shown in FIG. 3, the aramid fibers that are organic fibers are excellent in the tensile test and the thermal creep test, that is, excellent in the reinforcing effect. Material. However, it has been found that if the blending amount (blending ratio) is increased too much, the simple steam test and the sealing performance are adversely affected, as shown in FIG. Therefore, the desirable blending ratio of the aramid fiber is set to 4 to 15% by mass.

  As can be seen from the characteristic graph for the amount of rubber binder (mixing ratio) of the joint sheet (gasket) shown in FIG. 4, the sealing performance of the rubber binder is improved by increasing the blending ratio (mixing ratio). It is an effective material. And, if the blending amount is set to an appropriate range, it has a characteristic that has a positive effect on the tensile strength and the like. However, if the blending amount (blending ratio) is increased too much, the simple steam test and the thermal creep test are adversely affected in addition to the tensile strength, so the blending ratio of the rubber binder is set to 10 to 18% by mass. In addition, as a kind of rubber binder, NBR which is excellent in oil resistance, compression recovery property and mechanical strength is adopted.

  In order to achieve good sealing performance at the same high temperature as that of asbestos joint sheet, that is, heat-resistant sealing, clear all four tests of simple steam test, thermal creep test, seal test, and tensile test (strength test). It is necessary to get good results. Therefore, the outline of each test will be briefly described below.

  A simple steam test is a test which shows the capability to ensure the sealing performance of the joint sheet (gasket) in the heated state (200-400 degreeC level). This is because the gasket is required to have a performance of having a resilience in a heated state and less stress relaxation. For example, as shown in FIG. 6, a pressure vessel 1 capable of containing water, a heating means (not shown) such as an electric furnace, etc. are prepared, and a ring-shaped gasket G is exposed to high-pressure and high-temperature steam in use. Is implemented. The pressure vessel 1 is formed by fastening an upper flange 2 and a lower flange 3 with a plurality of bolts and nuts 4 via an annular gasket G. The plug (plug) 6 is equipped. Then, the pressure vessel 1 is heated by a heating means (not shown), steam S is generated in the upper portion of the vessel using the water W contained therein as pressurized water, and the steam S is added for a predetermined time, whereby the gasket G The sealability and durability of this product are tested.

The thermal creep test is a test for examining deformation of the joint sheet (gasket) when compressed in a heated state (200 to 400 ° C. level) (a test for creeping at a high temperature). This is because the gasket is required to have high strength and resistance to compression because it is not easily deformed. For example, as shown in FIG. 7A, a circular joint sheet J for a gasket as a sample is placed on a stainless steel cradle 11 adjusted to a predetermined high temperature (eg, 200 ° C.), and a hydraulic press B Thus, a test is applied between the receiving table 11 and the pressing table 12 to apply a load for a set time (for example, 1 minute) at a high surface pressure (for example, 98 N / mm ² ). In this case, as shown in FIG.7 (b), the average value of the diameter of two places of a joint sheet is measured in both the state Jb before hot press, and the state Ja after, and a thermal creep rate is calculated | required. That is, assuming that the diameter before the test is d1 and the diameter after the test is d2, the thermal creep rate (%) R is calculated as R = d22−d12 / d12 × 100.

  The seal test is a test showing the ability to prevent fluid leakage. This is because it is required to have moderate flexibility and resilience, to be in close contact with the seating surface, and to have little (or no) continuous voids in the gasket itself to prevent leakage from the gasket body. It is. For example, it is standardized by JIS that pressurizes to a predetermined surface pressure and holds it for 3 minutes, and then measures the amount of leakage by the soap film transfer method after loading with nitrogen gas and holding for 10 minutes. A room temperature gas seal test is performed according to the seal test method.

  The tensile test (strength test) is a test conducted in accordance with JIS, and is capable of holding the shape by cutting it into a free shape, or holding the shape even if it is mounted on a flange and tightened with a bolt and compressed. Can be shown. By this test, it is possible to observe the handleability of the joint sheet gasket according to the present invention and the comparative gasket.

  1 and 2 show component tables of a plurality of examples of joint sheets and a plurality of comparative examples. Examples 1 to 7 are joint sheets in which the blending ratio (mass ratio) of the three components of expanded graphite, aramid fiber, and rubber binder is set in the range of 40 to 50%. 6 is a joint sheet in which the mixing ratio (mass ratio) of the three components is set to be less than 40% or more than 50%. Each Example and each Comparative Example use the same materials themselves. Rubber chemicals also contain sulfur, vulcanization accelerators, anti-aging agents, colorants and the like. In FIGS. 1 and 2, “x” indicates failure, and other circles indicate “pass”. The higher the number of passing circles, the higher the level of passing. In FIG. 1, the numbers shown to the right of the circles represent the rank of data excellence in Examples 1-7.

  Inorganic fibers are not particularly limited, but include rock / slag fibers, alumina-silicate fibers, alumina fibers, zirconia fibers, ceramic fibers such as rock wool, glass fibers such as quartz glass fibers and high silicate glass fibers, carbon fibers, and phosphate fibers. Metal fibers or the like may be used.

  The inorganic fiber contributes to improvement of heating strength, particularly prevention of thermal deformation (thermal creep) during initial heating, improvement of resilience, and the like. This inorganic filler also functions as a plugging material, improves the sealing performance to a certain level, and contributes to the improvement of the clamping load and heat resistance. Accordingly, the blending amount (blending ratio) is preferably 20 to 40% (wt%). If the blending amount exceeds 40%, the strength is likely to decrease, and the blending amount is less than 20%. Tightening load when mounting a gasket tends to decrease. As inorganic fillers, one or more of kaolin, sepiolite, clay, talc, heavy carbonate, light carbonate, silica, mica, barium sulfate, carbon black, alumina, vermiculite, etc., silicon In addition, inorganic powders such as powders of hydrous silicate minerals mainly composed of aluminum, magnesium, iron, alkaline earth metals and alkali metals, and natural mineral powders such as wollastonite may be used.

The figure which shows the component table | surface of the joint sheet | seat of Examples 1-7. The figure which shows the component table | surface of the joint sheet of Comparative Examples 1-6 The figure which shows the relationship graph of the compounding ratio of an aramid fiber, and a reinforcement effect The figure which shows the relationship graph of the compounding ratio of NBR and various characteristics The figure which shows the relational graph between the compounding ratio of the expanded graphite and various characteristics Principle diagram showing the outline of the simple steam test The thermal creep test is shown, (a) is the principle diagram of the hot press, (b) is the diagram showing the creep state of the gasket by the hot press.

G Gasket J Joint sheet

Claims (2)

A joint sheet formed from a material having expanded graphite, aramid fiber, and a rubber binder,
The mass ratio of the expanded graphite, the aramid fiber, and the rubber binder to the material is set to 40 to 50% ,
The mass ratio of the expanded graphite to the material is set to 15 to 35%,
The mass ratio of the aramid fiber to the material is set to 4 to 15%,
The mass ratio of the rubber binder to the material is set to 10-18%,
NBR is employed as the rubber binder, and the material contains inorganic fibers.
A joint sheet in which the mass ratio of the inorganic fibers to the material is set to 20 to 40% . A gasket formed using the joint sheet according to claim 1.

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