JP2005187718A - Dimethyl ether-resistant sealing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing material having resistance to DME and also to LPG. <P>SOLUTION: The dimethyl ether-resistant sealing material is a sealing material which is used in a member brought into contact with a gas or liquid of dimethyl ether and has a core formed of a rubber material the outer peripheral surface of which is covered with a resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sealing material used in an apparatus or device that comes into contact with gaseous or liquid DME at the stage of manufacturing, storing, transporting, supplying, or using dimethyl ether (hereinafter abbreviated as “DME”), and further, DME. The present invention relates to a seal material that can be used for both DME and LPG used in devices and equipment used as an alternative fuel for LPG.

  Like rubber O-rings, rubber-based seals made of synthetic rubber as the main material, blended with rubber chemicals such as cross-linking agents, cross-linking aids, fillers, etc., and pressed with heat using a mold, etc. are softly bonded. Because it is familiar with the surface and has excellent sealing properties, it is widely used in various industrial devices and equipment.

  Among these, in the LPG industry, rubber-based sealing materials are used for connecting parts of piping and valves, etc. in supply facilities such as primary bases, secondary bases, filling stations, and transportation facilities such as ocean-going vessels, coastal ships, and tank trucks. In particular, NBR and fluorine rubber, which have good chemical resistance against LPG, are often used. (For example, refer nonpatent literature 1).

  Here, LPG is liquefied petroleum gas mainly composed of propane and butane, and since it is easy to transport, it is used by about 55% of all households in the country and 25 million households for transportation. It is used as fuel for almost all taxis. In addition, it is widely used for industrial purposes such as steel, industrial use, electric power, petrochemical raw materials, etc., and it has become an indispensable energy in national life and industrial economy.

  However, this LPG relies on imports for about 80% of its supply and about 80% of its imports for the Middle East. In recent years, Asian countries such as China and India have diversified as income levels rise. The demand for LPG as a type fuel is increasing rapidly, and there is a problem that high price stability is becoming constant due to tight supply and demand.

In response to this situation, there is an active movement to find new energy sources, and LNG, GTL, DME, etc. are attracting attention as alternative fuels for LPG, but LNG and GTL are compared to DME. DME is particularly attracting attention because of the high construction costs of the plant. This DME has a chemical structure of CH ₃ OCH _{3 and} is usually obtained by DME synthesis using synthetic gas (CO ₂ , H ₂ ) obtained by gasifying natural gas, associated gas, coal, etc., and burned. Since it has a clean characteristic that dust and SOx are not generated sometimes and NOx is small, the use as fuel for power generation, boiler, home use, automobile use, etc. has been studied. In addition, since the physical properties such as boiling point of DME are similar to those of LPG, the DME has an advantage that it is possible to utilize the infrastructure of LPG and is economical.

"DME Review Committee" report, issued on August 8, 1996, Agency for Natural Resources and Energy, Petroleum Distribution Division, Resources and Fuel Department, LP Gas Promotion Center Japan LP Gas Association, p. 5-p. 6

  However, DME is chemically classified as ether, and its chemical properties are completely different from LPG consisting of propane and butane, which are paraffinic hydrocarbons, and has high gas permeability to organic compounds such as plastic and rubber. It has a feature that it is easy to swell and dissolve. As described above, NBR and fluorine rubber are used as a sealing material for LPG storage tanks and piping, and when this is used for DME, there is a possibility that the function as a sealing material may not be performed sufficiently. found.

  Thus, in order to be able to use the infrastructure of LPG as it is while DME is attracting attention as a promising candidate as an alternative fuel for LPG, the development of a material having high resistance to DME (DME resistance) has been developed. It is an urgent need. Then, an object of this invention is to provide the sealing material which has the tolerance with respect to DME and also LPG.

  The inventors of the present invention have made extensive studies to solve the above-described problems. As a result, the rubber material is used as a core, and a sealing material coated with a resin, particularly a specific rubber material and a coating resin, It has been found that both DME property and LPG resistance are good and that the sealing performance is also excellent, and the present invention has been completed.

  That is, in order to achieve the above object, the DME-resistant sealing material according to claim 1 of the present invention is characterized in that the rubber material is the core and the outer peripheral surface is coated with the resin.

  The DME-resistant sealing material according to claim 2 has a volume change rate of 40% or less when the rubber material forming the core is measured within 5 minutes after being immersed in DME liquid for 2 weeks. It is characterized by being.

  The DME-resistant sealing material according to claim 3 is characterized in that the resin is a fluororesin or a polyamide.

  The DME-resistant sealing material according to claim 4 is characterized in that the base rubber is EPDM or silicone rubber.

  ADVANTAGE OF THE INVENTION According to this invention, the sealing member which can fully be used for the apparatus and apparatus which contacts DME, and can be similarly used for the apparatus and apparatus for LPG similarly to the former can be provided.

  Hereinafter, the present invention will be described in detail.

  The DME-resistant sealing material of the present invention has a rubber material as a core and its outer peripheral surface is coated with a resin. Specifically, FIG. 1 illustrates a cross section when an O-ring is used, but the core A is covered with a coating resin B. Details of the rubber material and the coating resin will be described below.

(Rubber material)
In the present invention, a rubber having a volume change rate of 40% or less when immersed in a DME solution for 2 weeks and measured within 5 minutes after being taken out is suitably used as the base rubber forming the core.

  In general, swelling of rubber is explained by a solubility parameter (SP value), and it is said that the closer the SP value of rubber and solvent is, the better they are melted. Therefore, there is currently no method other than confirming by experiment. And, in order to evaluate the DME resistance of rubber, it is common to actually immerse a sample in a DME solution for a predetermined time and obtain a volume change rate before and after immersion, but DME is a gas at room temperature, Even after the sample is taken out from the DME solution, DME volatilizes, and the volume changes during that time. Therefore, in the present invention, the evaluation criteria are set to be stricter by setting the immersion time to 2 weeks, and the more accurate volume change rate is obtained by setting the time from taking out to measurement within 5 minutes, and the volume change rate is 40% or less. It has been found that suitable DME resistance is exhibited. As a matter of course, the smaller the volume change rate, the better the DME resistance. In the present invention, it is preferable to use a rubber having a smaller volume change rate.

  As rubbers satisfying the above volume change rate, fluoro rubber (volume change rate 35% when measured within 5 minutes after immersion in EPDM), NBR (20%), silicone rubber (25%) and EPDM ( However, silicone rubber and EPDM are more preferable from the viewpoints of excellent heat resistance and being difficult to deteriorate when forming a sealing material.

  The base rubber is preferably blended with a crosslinking additive. As the crosslinking additive, a peroxide-based or sulfur-based crosslinking agent, a crosslinking accelerator, a crosslinking acceleration assistant, a co-crosslinking agent, and the like are selected according to the type of the base rubber. In addition, any of them may be known, and the blending amount thereof is appropriately selected.

  Moreover, you may mix | blend another additive and filler as needed. For example, an appropriate amount of an antiaging agent, a known rubber additive such as a plasticizer, or a filler such as carbon black or white carbon can be blended.

  In order to produce a core, a crosslinking compound, and further additives and fillers are added to the above base rubber and kneaded with an open roll, a pressure kneader, a Banbury mixer, etc. to form a rubber compound. This rubber compound May be formed into a desired shape by a method such as hot press molding using a mold, extrusion molding, blow molding, transfer molding, or injection molding. The molding conditions are appropriately selected depending on the composition of the rubber compound. Further, secondary cross-linking may be performed if necessary.

(Coating resin)
Since the coating resin is in direct contact with DME, it preferably has DME resistance and has appropriate flexibility. In the present invention, a fluororesin and a polyamide can be suitably used. In addition, there is no restriction | limiting in the kind of fluororesin and polyamide, It can select suitably.

  There is no limitation on the method for producing the DME-resistant sealing material. For example, a sheet made of a coating resin is produced, the core produced as described above is sandwiched between the resin sheets, and the whole is put into a mold and integrated. What is necessary is just to shape | mold. In order to obtain an O-ring, a tube made of a coating resin is produced by extrusion molding, and after inserting a core formed in a string shape into the tube, both end surfaces may be heated and fused. The resin coating thickness is preferably 0.1 to 0.7 mm, particularly preferably 0.25 to 0.50 mm, in order to ensure DME resistance.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to the following Example. In addition, the volume change rate shown below is a change rate calculated from the thickness measured after taking out after being immersed in DME liquid for 2 weeks and within 5 minutes.

(Example 1)
To 100 parts by weight of silicone rubber, 2 parts by weight of PO (C-8) as a crosslinking additive is added and kneaded with an open roll to form a rubber compound, which is extruded to form a rod shape having a diameter of 2.9 mm. Molded into. The volume change rate of the silicone rubber was 25%. PFA was extruded to produce a tube having an inner diameter of 3.5 mm and a wall thickness of 0.3 mm. Then, each of the rubber rod and the tube was cut into a predetermined length, and after inserting the rubber rod into the tube, both end surfaces were fused to obtain an O-ring.

(Example 2)
To 100 parts by weight of EPDM, 6 parts by weight of PO-dicup40, 2 parts by weight of TAIC and 60 parts by weight of FEF carbon are added as cross-linking additives and kneaded with an open roll to form a rubber compound, which is extruded. To form a rod having a diameter of 2.9 mm. The volume change rate of this EPDM was 20%. PFA was extruded to produce a tube having an inner diameter of 3.5 mm and a wall thickness of 0.3 mm. Then, each of the rubber rod and the tube was cut into a predetermined length, and after inserting the rubber rod into the tube, both end surfaces were fused to obtain an O-ring.

(Comparative Example 1)
100 parts by weight of fluoro rubber, 3 parts by weight of MgO as a crosslinking additive, 3 parts by weight of bisphenol AF, 3 parts by weight of curative 30 and 20 parts by weight of MT carbon are added and kneaded with an open roll. A compound was formed and extruded to form a rod having a diameter of 3.5 mm, and both end surfaces were fused to obtain an O-ring. The volume change rate of the fluoro rubber was 35%.

(Comparative Example 2)
For 100 parts by weight of NBR rubber, 0.5 parts by weight of sulfur as a crosslinking additive, 2 parts by weight of Noxeller TS and 50 parts by weight of FEF carbon are added and kneaded with an open roll to obtain a rubber compound. Extrusion molding was performed to form a rod having a diameter of 3.5 mm, and both end surfaces were fused to obtain an O-ring. The volume change rate of this NBR rubber was 20%.

  Each O-ring obtained above was set as a sealing material for a DME immersion test container, and the container was filled with the DME liquid and held at 70 ± 2 ° C. for 4 weeks, and the amount of leakage of DME was measured during that period. Moreover, the external appearance was evaluated visually. The results are shown in Table 1, and it can be seen that by applying the resin coating according to the present invention, the sealing property against DME is enhanced and the appearance is also kept good.

It is sectional drawing which shows an example (O-ring) of the DME-resistant sealing material of this invention.

Explanation of symbols

A Core (Rubber material)
B Coating resin

Claims (4)

A dimethyl ether-resistant sealing material, which is a sealing material used for a member that comes into contact with a gas or liquid of dimethyl ether, wherein a rubber material is a core and an outer peripheral surface is coated with a resin. 2. The dimethyl ether resistance according to claim 1, wherein the rubber material forming the core has a volume change rate of 40% or less when measured within 5 minutes after being immersed in a dimethyl ether solution for 2 weeks. Sealing material. The dimethyl ether-resistant sealing material according to claim 1 or 2, wherein the resin is a fluororesin or a polyamide. The dimethyl ether-resistant sealing material according to any one of claims 1 to 3, wherein the base rubber is EPDM or silicone rubber.

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