JPH0643110B2 - Molding method for seat rings for butterfly valves - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for molding a butterfly valve seat ring.

(Prior Art) As a butterfly valve, flange-shaped flanges are provided at both ends of a short cylindrical body part inside a short cylindrical valve case body to form a U-shaped cross section, and the diameter of the body part It is known that a rubber seat ring having a valve rod insertion hole formed along the same is fixed (see Japanese Utility Model Publication No. 51-36744). Then, the surface of the rubber seat ring, that is, the inner surface of the body portion, the end surface of the flange-shaped collar continuing to the inner surface and the inner surface of the valve rod insertion hole are covered with a fluorine resin liner, and the chemical resistance of the seat ring. It is known to improve the friction resistance and reduce the frictional resistance (Japanese Patent Publication No. 48-19124).
(See the official gazette).

(Problems to be Solved by the Invention) However, the fluororesin used for the liner of the rubber seat ring cannot be injection-molded,
In addition, since the material cost is high in cutting,
As described in Japanese Unexamined Patent Publication No. 8-19124, it is necessary to prepare a fluororesin cylinder in advance and plastically deform it using a jig separately prepared while heating the cylinder to mold it into a desired shape. It is difficult and cannot be bonded at the same time as vulcanization of the rubber ring, so it is necessary to bond it with an adhesive. Furthermore, the sheet ring backed with the above fluororesin is used to transport slurry or powder. When used for roads, the wear resistance was poor and the durability was insufficient.

This invention has excellent chemical resistance and abrasion resistance by using ultrahigh molecular weight polyethylene having an average molecular weight of 700,000 or more instead of fluororesin, and is capable of being vulcanized and adhered to a rubber ring. Is provided.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, flange-shaped flanges are provided at both ends of a short cylindrical body, and a valve rod is provided along the diameter direction of the body. A seat ring for a butterfly valve, which comprises a rubber ring having an insertion hole, an inner surface of the body, a synthetic resin liner covering the inner surface of the flange-like collar and the inner surface of the insertion hole following the inner surface. In doing so, the above-mentioned liner was pre-molded with ultra-high molecular weight polyethylene having an average molecular weight of 700,000 or more, and then the above-mentioned liner was formed in the molding space of the vulcanization molding die for the seat ring, except for its valve rod insertion hole. It is fixed to the outer mold by a support fitted into the valve rod insertion hole so that a gap is formed between the outer surface of the mold and the outer surface of the rubber ring. Organic from the side A rubber composition containing a peroxide as a crosslinking agent is injected and vulcanized.
After the vulcanization, it can be reheated to 180 ° C. or higher in any gas such as nitrogen, argon, helium, and air. This reheating may be performed under reduced pressure of air, and the reheating time is preferably 8 to 15 minutes at 200 ° C., although it depends on the diameter and shape.

Molding of a liner made of ultra-high molecular weight polyethylene having an average molecular weight of 700,000 or more can be performed by injection molding or any other method. And the liner above
Molded in a thickness of 0.5 to 5.0 mm depending on the seat ring diameter. For example, when the diameter is 100 mm, the preferable thickness is 0.5 to 1.5 mm.

When installing the above liner in the molding space of the mold, the liner is supported by fitting the tip of the support fixed to the outer diameter into the valve rod insertion hole of the liner, and at this time, the liner valve rod insertion hole. A gap of preferably 0.3 to 5.0 mm is formed between the mold surface and the liner so that the surface of the other part, that is, the surface opposite to the surface bonded to the rubber ring, does not contact the mold surface. .

The rubber injected into the molding space of the mold is ethylene propylene rubber (EPDM, EPM), nitrile rubber (NB
R), brominated butyl rubber (Br-IIR), chlorinated polyethylene (CPE), and other rubbers having excellent heat resistance are preferable. Then, an organic peroxide is blended in the above rubber as a crosslinking agent. Examples of the organic peroxide include dicumyl peroxide, 2,5-dimethyl-2,5-di (tertiary butyl peroxy) hexane and 1,3-bis (tertiary butyl peroxy isopropyl) benzene. It is exemplified, and its compounding amount is preferably 2.0 to 10.0 PHR.

(Operation) By supporting the liner away from the mold surface, the liner is prevented from being directly heated by the heat transfer from the mold and deformed. And the above liner has an average molecular weight of 7
Since it is a molded product of ultra-high molecular weight polyethylene of more than 0,000, and the injected rubber is blended with organic peroxide, the conventional fluororesin is chemically stable and rubber such as organic peroxide is Unlike the above-mentioned cross-linking agent that could not be bonded by causing a chemical bond, the above rubber is vulcanized and molded into the shape of its molding space as the mold is heated, and The sheet ring is chemically bonded to the liner at the contact surface thereof, and as a result, a sheet ring in which the rubber ring and the liner made of ultrahigh molecular weight polyethylene covering the rubber ring are integrated by chemical bonding is obtained.

The ultra-high molecular weight polyethylene used in this invention is pre-molded, but when this molding is carried out by injection molding, an easily peelable layer (delamination layer) is produced on the surface. Releasing the delamination layer again by reheating it in the above-mentioned inert gas or air or in depressurized air improves the easy peeling property. However, if the reheating temperature is less than 180 ° C, there is no effect. On the contrary, if the temperature exceeds 300 ° C or the reheating time in air exceeds 30 minutes, decomposition of polyethylene occurs, The desired seat ring cannot be obtained due to discoloration or reduced wear resistance.

(Example) FIG. 1 and FIG. 2 show an example of a seat ring for a butterfly valve. 1 and 2, the rubber ring 1 is composed of a short cylindrical body 1a and flange-shaped flanges 1b and 1b at both ends thereof. The body 1a and the flange-shaped flanges 1b and 1b form the rubber ring 1. A circumferential groove 1c having a U-shaped cross section is formed on the outer circumference of the rubber ring 1, and the circumferential groove 1c is fitted to the inner circumference of a short cylindrical valve case body (not shown). And the body portion 1 of the rubber ring 1
A diametrical valve rod insertion hole 1d is opened in a, and the upper and lower shaft portions of the disc-shaped valve A are inserted in the upper and lower valve rod insertion holes 1d. On the other hand, the ultra-high molecular weight polyethylene liner 2 covering the rubber ring 1 is the body portion 1 of the rubber ring 1.
Inner surface of a, end surface of flange-like collar 1b and valve rod insertion hole 1
Short cylindrical body 2 that is in contact with the inner surface of d.
a, flanged flanges 2b, 2b at both ends, and a small cylindrical portion 2c for inserting the valve rod, which are integrally formed.

FIG. 3 shows an example of a mold 10 suitable for molding the seat rings of FIGS. 1 and 2 above. This mold 10
Lower mold 11 having a protrusion 11a in the center, the above protrusion 11a
A middle die 12 placed on the upper die, a separable outer die 12 overlaid on the outer periphery of the lower die 11, a back die 14 fitted inside the upper surface recess of the outer die 13, and an outer periphery of the back die 14. Back ring 15 fitted to the above, the above-mentioned middle die 12, outer die 1
3, the upper die 16 that is laid over the back die 14 and the back ring 15 and the plunger 17 that fits into the ring-shaped rubber reservoir 16a formed on the upper surface of the upper die 16, and the central protrusion of the lower die 11 is formed. 11a and medium size 1
2, the outer surface of the outer mold 13, the inner surface of the rear mold 14, the upper mold 16
The molding space 18 into which the rubber composition B is injected between the lower surface and the lower surface of the
Is formed. Then, a plurality of liners 19 and an injection gate 20 that communicate the molding space 18 and the rubber reservoir 16a are provided.

The molding space 18 is the body portion 1a of the rubber ring 1.
And a body portion 18a corresponding to the flange-shaped collar 1b, respectively.
Also, a portion having the flange portion 18b and corresponding to the valve rod insertion hole 1d of the rubber ring 1 is closed by a plug-like protrusion 13a protruding from the inner periphery of the outer die 13 toward the center. Then, the body portion 18 excluding the plug-like protrusion 13a
An injection gate 20 is formed along the mating surface of the outer mold 13 and the rear mold 14 so as to be positioned in the middle of a, and an L-shaped liner 19 following the injection gate 20 is formed horizontally between the outer mold 13 and the rear mold 14. The upper mold 16 along the vertical mating surface of the back mold 14 and the back ring 14
Is formed so as to extend vertically through and communicate with each other.

Using the above device, the caliber 10 shown in FIG. 1 and FIG.
A 0 mm seat ring was produced. However, the above-described molding space 18 is formed to be slightly larger than the outer shape of the seat ring of FIGS.
Are mounted so as to float in the molding space 18. That is, the two valve rod insertion holes 2 facing each other in the diametrical direction of the liner 2 made of pre-molded ultra high molecular weight polyethylene.
c and 2c, the plug-like projections 13a and 13 of the outer mold 13 are provided.
By fitting a, the liner 2 is supported horizontally, and a gap of about 0.3 to 5.0 mm is formed between the outer surface of the liner 2 and the central projection 11a of the lower mold 11 and the peripheral surfaces of the middle mold 12. To do.

Then, the rubber reservoir 16a on the upper mold 16 is filled with ethylene propylene rubber (EPDM) which has been prepared in advance, and the plunger 17 is pushed down to allow the rubber B to pass through the liner 19 and the injection gate 20 to form the molding space 18 Injected. An example of compounding the rubber B is shown in the table below.

Table EPDM 100 parts by weight Zinc white (vulcanization aid) 5 parts by weight Stearic acid 1 part by weight Wax 1 part by weight Carbon black 55 parts by weight Process oil 7 parts by weight Organic peroxide 5 parts by weight The above mold 10 is heated. After vulcanization molding at 150 ° C. for 30 minutes, the plunger 17, the upper mold 16, the middle mold 1
2, the back ring 15, and the back mold 14 were sequentially removed, and then the seat ring consisting of the rubber ring 1 and the ultrahigh molecular weight polyethylene liner 2 was taken out.

After removing the burr generated around the liner 2 of the obtained seat ring, the seat ring was reheated in air at 200 ° C. for 15 minutes.

In the obtained seat ring, the rubber ring 1 and the liner 2 were firmly adhered, and the delamination layer on the surface of the liner 2 was hardly recognized. Then, when the above-mentioned seat ring was arranged in a pipeline for transporting a liquid containing a slurry and tested, no abnormality occurred after 10,000 hours of operation. On the other hand, molding the liner with fluororesin,
The urethane adhesive adhered to and integrated with the rubber ring requires an adhesive, and the adhesive surface is peeled off after 1500 hours of use, and the liner surface is worn out, making it unusable. .

(Effect of the Invention) In the present invention, a liner made of ultra-high molecular weight polyethylene having an average molecular weight of 700,000 or more is used for the liner, and an organic peroxide is compounded as a cross-linking agent in the rubber. Therefore, a conventional fluororesin liner is used. Molding of the liner is easier than in the case, and no adhesive is required for bonding the rubber ring and the liner, and bonding by chemical bonding is performed simultaneously with vulcanization molding,
Moreover, the wear resistance is improved, and the life of the powder or slurry is extended when it is used in a transportation route.

[Brief description of drawings]

Fig. 1 is a front view of a partially crushed seat ring, and Fig. 2 is a first view.
FIG. 3 is a sectional view taken along line II-II of FIG. 3, and FIG. 3 is a sectional view corresponding to FIG. 2 of the mold for molding the seat ring of FIG. 1 and FIG. 1: rubber ring, 1a: body part, 1b: flange-shaped brim,
1d: valve rod insertion hole, 2: ultra high molecular weight polyethylene liner, 2a: body, 2b: flange, 2c: valve rod insertion hole, 10: mold, 18: molding space, 19: runner, 2
0: injection gate, B: injection rubber composition.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location B29K 23:00 B29L 31:26 4F (72) Inventor Yoshinori Mangi 2 in Honjo, Higashi-Osaka City, Osaka Prefecture 1 at 91-chome Tomoe Technical Research Institute Co., Ltd. (72) Inventor Toshio Sato 4 at 3-22-22 Shiga-ri, Otsu City, Shiga Prefecture

Claims (2)

[Claims] 1. A rubber ring having flanged flanges projecting from both ends of a short cylindrical body and having a valve rod insertion hole along the diameter of the body, and an inner surface of the body. In molding a seat ring for a butterfly valve, which is composed of a synthetic resin liner covering the end surface of the flange-shaped collar and the inner surface of the insertion hole following the inner surface, the above-mentioned ultra high molecular weight polyethylene having an average molecular weight of 700,000 or more is used. The liner is pre-molded, and then the liner is formed in the molding space of the vulcanization molding die for the seat ring so that a gap is formed between a portion other than the valve rod insertion hole and the die surface. The rubber composition is fixed to the outer mold by a support fitted in the insertion hole, and then a rubber composition in which an organic peroxide is mixed as a crosslinking agent from the outer mold side into a molding space corresponding to the body of the rubber ring. Inject and vulcanize Molding method of seat ring for the butterfly valve according to claim. 2. 180 to 300 ° C. in an arbitrary gas after vulcanization
The method for molding a seat ring for a butterfly valve according to claim 1, wherein the seat ring is reheated.