JPH01138A - Rubber composition for wiper seals - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a wiper seal rubber composition that is used in large oil storage tanks and has excellent flexibility and aromatic liquid resistance to prevent volatilization of stored liquid. relating to things.

[Prior art] A wiper seal is placed around the periphery of a float deck in a large oil storage tank, and deforms flexibly in response to the vertical movement of the deck due to fluctuations in the liquid level in the tank, and slides on the tank's inner wall surface. to prevent the stored liquid from volatilizing into the upper space of the tank.

Figure 1 is a vertical sectional view showing a wiper seal 1 installed on a float deck of a large oil storage tank, Figures 2 (a) and (b)
) are a sectional view and a plan view of the wiper seal 1, respectively, and FIG. 3 is a partially cutaway view of the tank.

In the oil storage tank 10, a roof column 13 installed in the center of the floor 11 connects the floor 11 and a conical roof 12.
It is bridged between. This column 13 is inserted through a float deck 15 in the tank via a column seal 14. The float deck 15 moves up and down as the liquid level changes due to changes in the amount of liquid stored in the tank 10.

A peripheral segment 16 is disposed around the float deck 15 so as to extend in the circumferential direction of the float deck 15. Wiper seal 1 is attached to this peripheral segment 16.
is installed.

As shown in FIG. 2(a), the wiper seal 1 has a slightly thin plate shape at its tip, and has a plurality of mounting holes 2 at its base end, as shown in FIG. 2(b). . As shown in FIG. 1, this wiper seal 1 is fixed to the peripheral segment 16 with a seal rubber 4 interposed therebetween. That is, the wiper seal 1 is tightened between the peripheral segment 16 and the wiper clamp 5 by the bolt 3 through the mounting hole 2 of the wiper seal 1.

When the deck 15 is lowered, the wiper seal 1 is curved as shown by the solid line in FIG.
0 shell 17.

This prevents volatile gas on the liquid surface from leaking above the deck 15, and suppresses volatilization of the stored liquid.

Conventionally, as such a wiper seal, a seal made of nitrile butadiene rubber (hereinafter abbreviated as NBR), a seal made of a combination of Teflon laminate and a stainless steel plate spring, etc. have been used.

[Problems to be solved by the invention] However, the above-mentioned NBR seals (a) cannot be used to store aromatic liquids such as benzene and toluene, (b) have poor ozone resistance, and (c) have poor long-term resistance. There are problems such as hardening during use.

In addition, in the case of sealing using a combination of Teflon laminate and stainless steel plate springs, (a) the sealing performance is poor;
It has problems such as b) lack of flexibility and (c) poor workability.

The present invention has been made in view of such problems, and includes:
The object of the present invention is to provide a rubber composition for wiper seals that has improved various properties such as aromatic liquid resistance, ozone resistance, sealability, workability, and flexibility.

[Means for Solving the Problems] As a result of various studies, the inventors of the present application have added a predetermined amount of liquid fluororubber, precipitated barium sulfate, and diamine vulcanizing agent to oil- and chemical-resistant synthetic rubber. The present invention was completed based on the knowledge that the above object can be achieved by blending the above-mentioned components.

The wiper seal rubber composition according to the present invention includes 90 to 97 parts by weight of oil- and chemical-resistant synthetic rubber, 3 to 10 parts by weight of liquid fluororubber, 10 to 30 parts by weight of precipitated barium sulfate, and 1 to 5 parts by weight of precipitated barium sulfate. It is characterized by containing part by weight of a diamine vulcanizing agent. With such a configuration, a wiper seal rubber composition having excellent flexibility, resistance to aromatic liquids, etc. is provided.

The present invention will be specifically explained below.

Oil- and chemical-resistant synthetic rubber is used as the base polymer in the present invention. Such oil- and chemical-resistant synthetic rubbers include fluororubber and polysulfide rubber, among which ternary fluororubber has the best resistance to aromatic liquids and extremely high wear resistance. Therefore, it is suitable for wiper seals for tanks that store aromatic hydrocarbons.

Note that binary fluororubber is slightly inferior to ternary fluororubber in aromatic liquid resistance, and polysulfide rubber is slightly inferior to ternary fluororubber in various physical properties such as abrasion resistance.

The precipitated barium sulfate blended into the rubber composition according to the present invention is highly miscible with oil- and chemical-resistant synthetic rubber (for example, ternary fluororubber), and It is added at a ratio of 10 to 30 parts by weight to 90 to 97 parts by weight.

The reason why the lower limit was set at 10 parts by weight is because if it is less than that, no remarkable blending effect as a filler can be obtained, and the reason why the upper limit was set at 30 parts by weight is that if it exceeds that, the mechanical strength decreases. This is because you end up doing it.

Preferably, the particle size of the precipitated barium sulfate is in the range of 0.2 to 5 μm. If the particle size is smaller than this, the workability during mixing will be impaired, while if it is larger than this, the dispersibility will be poor and the mechanical strength will be reduced.

Under such addition conditions, increase in hardness is suppressed and flexibility and mechanical strength are effectively maintained.

Examples of the liquid fluororubber blended in the present invention include Paiton LM and the like. Since this liquid fluororubber is difficult to volatilize and extract, it is effective in maintaining the flexibility of the seal, and is added at a ratio of 3 to 10 parts by weight to 90 to 97 parts by weight of the oil- and chemical-resistant synthetic rubber. Ru.

The reason why the lower limit was set to 3 parts by weight is because good flexibility cannot be maintained below this, and the reason why the upper limit was set to 10 parts by weight is that if it exceeds this, mixing and molding will be difficult. Furthermore, the decrease in mechanical strength is significant. Furthermore, this liquid fluororubber is effective in improving extrusion moldability and bending properties.

As the diamine-based vulcanizing agent in the present invention, DiakN
Examples include a3. This Diakk3 has superior tear strength and bending properties compared to other vulcanizing agents (eg, organic peroxides), and is also effective against solvent cracks. The diamine vulcanizing agent is added in an amount of 1 to 5 parts by weight based on 90 to 97 parts by weight of the oil- and chemical-resistant synthetic rubber.

The rubber composition according to the present invention has the predetermined proportion of Viton B.
A suitable amount of ternary fluororubber such as Paiton LM, liquid fluororubber such as Paiton LM, precipitated barium sulfate, diamine vulcanizing agent, and wax such as carbon black, magnesium oxide, and low molecular weight polyethylene is blended as necessary. It can be obtained by dispersing and mixing using a conventional method. Examples of mixing methods include methods using open rolls, kneaders, and the like.

[Example] Next, the results of an evaluation test for an example of the present invention will be described together with the results for a conventional NBR seal (conventional example). “Table 1 below shows the compositions of the compositions according to Examples and Conventional Examples.

Rubber compositions were obtained by dispersing and mixing the components in accordance with a conventional method so as to obtain the respective compositions shown in Table 1.

The performance of the compositions of each Example and Conventional Example was evaluated by the following method.

(1) Tensile test According to JIS K6301 vulcanized rubber physical test method 3°,
The tensile strength and elongation of the rubber at break were measured.

(2) Abrasion test The volume of rubber abrasion loss per 1000 rotations of the abrasive disk was measured using the Williams test method.

(3) Ozone deterioration test The presence or absence of cracks was examined using the JTSK6301 vulcanized rubber physical test method at 16°.

However, the test conditions were: ozone concentration of 50±5 pphm;
The test time was 120 hours, the test temperature was 40±2°C, and the elongation rate was 30%.

(a) Immersion test The rate of change in tensile strength and elongation, as well as the rate of change in volume and mass after immersion was measured at 12° according to the JIS K6301 vulcanized rubber physical test method.

However, the test conditions were that the test liquid was benzene and the test time was 72
The time and test temperature are 60±1°C.

The properties obtained from each of these tests are shown in Tables 2 to 5 below.

Table 2 Table 3 Table 4 Table 5 In addition, B-3 written on the comparison side fence in Table 4 represents the number, size and depth of cracks, B is a large number of cracks, 3 is Indicates that the crack is deep and relatively large (less than 1 mm).

As is clear from Tables 2 to 5, the example shows excellent performance in all the evaluation test items, while the comparative example shows excellent performance in all the evaluation test items. The performance is also worse than that of the example.

[Effects of the Invention] As explained above, the wiper seal rubber composition according to the present invention has excellent flexibility, ozone resistance, solvent resistance, and crack growth resistance, and is also resistant to aromatic liquids and the like. It has suitable properties as a sealing material that is constantly exposed to steam.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing a wiper seal installed on a float deck of a large oil storage tank, Fig. 2(a) is a sectional view of the wiper seal, Fig. 2(b) is a plan view of the wiper seal, and Fig. 2(b) is a plan view of the wiper seal. Figure 3 is a partially cutaway view of the tank. 1; wiper seal, 10. Oil storage tank, 15; Float deck, 16; Peripheral segment, 17; Tank shell

Claims (3)

[Claims] (1) 90 to 97 parts by weight of oil- and chemical-resistant synthetic rubber;
A rubber composition for wiper seals, comprising 3 to 10 parts by weight of liquid fluororubber, 10 to 30 parts by weight of precipitated barium sulfate, and 1 to 5 parts by weight of a diamine vulcanizing agent. (2) The oil- and chemical-resistant synthetic rubber is a terpolymer of vinylidene fluoride, propylene hexafluoride, and ethylene tetrafluoride, as set forth in claim 1. Rubber composition for wiper seals. (3) The precipitated barium sulfate has a particle size of 0.2 to 5μ.
Claim 1, characterized in that it is a granular material of m.
The rubber composition for wiper seals as described in .