JP2008157383A - Seal and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seal having a totally good flexibility while shortening a molding time, and at the same time, securing well a joining strength between a heel part and a seal part, and its manufacturing method. <P>SOLUTION: The seal 10 comprises a seal part 11 made of synthetic rubber, a dynamic crosslinking thermoplastic elastomer and at the same time, a heel part 12 jointed to the seal part 11. The seal part 11 is formed by heating and crosslinking the synthetic rubber injected to the seal forming part 23 of a molding die 20 in the molding die 20. The heel part 12 is formed by cooling and hardening the dynamic crosslinking thermoplastic elastomer injected in the heel forming part 26 of the molding die 20 in the molding die 20, and at the same time, is joined to the seal part 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a seal attached to a joint portion of a water pipe such as a ductile cast iron pipe, and a manufacturing method thereof.

  Conventionally, as shown in FIGS. 11 and 12, for example, a seal 51 made of synthetic rubber is attached to a joint portion of a ductile cast iron pipe 50. The seal 51 is attached to a circumferential groove 52 a formed on the inner periphery of the female end 52 in one ductile cast iron pipe 50, and is inserted into the inner duct 52 of the other ductile cast iron pipe 50. It is pressed against the outer peripheral surface 53 a of the male end 53. The seal 51 includes a heel portion 51a that is fitted into the circumferential groove 52a of the ductile cast iron pipe 50, and a seal portion 51b that is joined to the heel portion 51a. The heel portion 51a is formed of a synthetic rubber having a hardness higher than that of the seal portion 51b. The heel portion 51a is flexible to easily bend when attached to and detached from the circumferential groove 52a, and holds the seal portion 51b when attached to the circumferential groove 52a. With rigidity.

  The seal is manufactured by the following method, for example. That is, first, a member obtained by extruding synthetic rubber is cut into a predetermined length, and this is bent into an annular shape and placed in a cavity of a sealing mold. This member becomes the seal portion 51b. Next, synthetic rubber is injected into the mold, and the heel portion 51a is molded in the cavity. Next, the mold is heated to maintain the temperature at about 150 to 160 ° C., and this state is maintained for about 15 to 20 minutes. Then, the heat at this time causes the seal portion 51b and the heel portion 51a in the cavity to be heat-crosslinked and integrated. Through the above steps, a seal made of synthetic rubber having different hardness is manufactured. However, the time required for crosslinking of the rubber product increases as the volume increases. Since the time required for the heat crosslinking of the seal requires 15 to 20 minutes, its production cost is high.

In Patent Document 1, as shown in FIG. 13, a seal 62 for a pipe joint in which a seal portion 60 made of a rubber material and a retainer portion (corresponding to the heel portion 51a) 61 made of a synthetic resin are integrated. Is disclosed. The seal 62 is manufactured as follows. That is, first, the seal portion 60 is formed by injection molding or the like. Next, in a state where the seal portion 60 is disposed in the cavity of the sealing mold, the synthetic resin material is injected into the cavity to mold the retainer portion 61. At this time, the synthetic resin material is bonded to the joint surface with the seal portion 60. Since only the seal portion 60 needs to be heated and crosslinked at the time of molding, the molding time of the seal 62 is shorter than that of the seal 51.
JP-A-6-2790

  However, it is known that the bonding strength between the rubber material and the synthetic resin is lower than the bonding strength between the rubber materials. On the other hand, the seal 51 attached to the circumferential groove 52a of the female end 52 of the ductile cast iron pipe 50 has a male end 53 as shown by an arrow a in FIG. Therefore, a force in the direction of separating from the heel portion 51a is applied to the seal portion 51b. For this reason, when the seal 62 of Patent Document 1 is used as a seal of the joint portion of the ductile cast iron pipe 50, the joint strength between the retainer portion 61 and the seal portion 60 is insufficient, and the retainer portion is joined when the ductile cast iron tube 50 is joined. There is a possibility that the seal part 60 falls off from 61.

  Further, when the seal 51 shown in FIGS. 11 and 12 is attached to the circumferential groove 52 a of the female end 52, the female end 52 is bent in a part of the seal 51 in the circumferential direction. Must be put in the inner circumference of However, when the retainer portion 61 is formed of a synthetic resin as in the seal 62 of Patent Document 1, the overall flexibility thereof is insufficient, and it becomes difficult to attach the ductile cast iron pipe 50.

  An object of the present invention is to provide a seal that can shorten the molding time, can secure a good bonding strength between the heel portion and the seal portion, and has good flexibility as a whole, and a method for manufacturing the same. .

  In order to achieve the above object, the invention described in claim 1 is a heel formed of a seal portion made of synthetic rubber and a flexible material having a higher hardness than the seal portion and joined to the seal portion. The heel portion is formed of a dynamically cross-linked thermoplastic elastomer.

  According to a second aspect of the present invention, in the first aspect of the present invention, a concave portion is formed in at least one of the seal portion and the heel portion, and a convex portion disposed in the concave portion is provided on the other side. The sealing portion and the heel portion are mechanically coupled to each other by an anchor action of the convex portion with respect to the concave portion.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the Shore A hardness of the seal portion is in the range of 50 to 60, and the Shore A hardness of the heel portion is 70. It is characterized by being in the range of ~ 90. In addition, this Shore A hardness is based on what is prescribed | regulated to JISK6353.

  According to a fourth aspect of the present invention, there is provided a seal composed of a seal portion made of synthetic rubber and a heel portion formed of a flexible material having a higher hardness than the seal portion and joined to the seal portion. A synthetic rubber is applied to the seal forming portion in a state in which a first mold having a seal forming portion for forming the seal portion and a second die for closing the seal forming portion are combined. After the injection, the first mold and the second mold are heated and the synthetic rubber in the seal forming portion is heated and crosslinked for a predetermined time to form the seal portion, and then the heel forming portion for forming the heel portion is provided. The third mold is combined with the first mold instead of the second mold, and in this state, the thermoplastic elastomer is injected into the heel forming portion, and the dynamically crosslinked thermoplastic elastomer in the heel forming portion is cooled and cured. thing Characterized in that for joining the same sealing portion and the heel portion with shaping more heel.

(Function)
According to the present invention, since the seal portion is formed of synthetic rubber and the heel portion is formed of the dynamic cross-linking thermoplastic elastomer, only the seal portion needs to be heated and cross-linked in the mold at the time of molding by the mold. . For this reason, both the seal part and the heel part are made of synthetic rubber, and the capacity of the molded part that requires heat crosslinking is smaller than when both are heat-crosslinked in the mold. The time required for heat crosslinking is shortened. As a result, the molding time of the seal in the mold is shortened. Further, the bonding strength between the seal portion made of synthetic rubber and the heel portion made of dynamic cross-linking thermoplastic elastomer is improved more than the bonding strength between the seal portion made of synthetic rubber and the heel portion made of synthetic resin. Therefore, the bonding strength between the heel portion and the seal portion can be ensured satisfactorily. Further, the dynamically crosslinked thermoplastic elastomer is more flexible than the synthetic resin. Therefore, good flexibility can be secured as a whole seal.

  According to the present invention, the molding time can be shortened, the bonding strength between the heel portion and the seal portion can be ensured satisfactorily, and excellent flexibility can be ensured as a whole.

(First embodiment)
Next, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1A, 1B, and 2, the seal 10 is formed of an annular seal portion 11 formed of synthetic rubber and a dynamically cross-linked thermoplastic elastomer having a hardness higher than that of the synthetic rubber. And an annular heel portion 12 joined to the seal portion 11. The Shore A hardness of the seal portion 11 defined in JIS K 6353 is in the range of 50 to 60, and the Shore A hardness of the heel portion 12 is also in the range of 70 to 90.

  The synthetic rubber used for the seal part 11 and the dynamically crosslinked thermoplastic elastomer used for the heel part 12 may be combined with ones having good compatibility in order to improve the adhesive strength between the seal part 11 and the heel part 12. preferable. For example, when ethylene / propylene rubber (EP), which is an olefin rubber, is used as the synthetic rubber, an olefin dynamic cross-linked thermoplastic elastomer (olefin resin (PP, PE)) is used as the dynamic cross-linkable thermoplastic elastomer. It is preferable to use a olefin rubber (EPR, EPDM) dynamically crosslinked and finely dispersed (trade name: “Santoprene” (manufactured by AES Japan Co., Ltd.)) in a matrix. -Rubber (SBR) is preferably combined with a styrenic dynamically crosslinked thermoplastic elastomer (styrene / butadiene / styrene block copolymer (SBS), styrene / isoprene / styrene block copolymer (SIS)), or polystyrene-poly ( Ethylene / propylene block (SE ), Polystyrene-poly (ethylene / propylene) block-polystyrene (SEPS), polystyrene-poly (ethylene / butylene) block-polystyrene (SEBS), polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene (SEEPS), etc. Hydrogenated styrenic dynamically crosslinked thermoplastic elastomers have relatively good compatibility with both olefinic synthetic rubbers and styrene synthetic rubbers. The heel portion 12 can be combined with a seal portion 11 made of a plurality of types of synthetic rubber.

  The seal part 11 and the heel part 12 are joined by a conical surface. As shown in FIG. 11, the seal portion 11 formed of synthetic rubber has flexibility to be in close contact with the outer peripheral surface 53 a of the male end portion 53 at the joint portion of the ductile cast iron pipe 50. On the other hand, the heel portion 12 formed of a dynamically crosslinked thermoplastic elastomer having a hardness higher than that of the synthetic rubber is flexible to allow the female end portion 52 of the ductile cast iron tube 50 to be attached to and detached from the circumferential groove 52a. In addition, it has rigidity to hold the seal portion 11 in a predetermined position when the male side end portion 53 is inserted into the female side end portion 52.

Next, a method for manufacturing the seal 10 will be described.
The seal 10 is injection-molded using a molding die 20 as shown in FIGS. The molding die 20 includes a first die 22 including a lower die 21a and a middle die 21b combined with the lower die 21a. The seal portion 11 of the seal 10 is provided on the first die 22. A seal forming portion 23 for forming is formed. The mold 20 includes a second mold 24 and a third mold 25 that are selectively combined with the first mold 22. The second mold 24 closes the seal forming portion 23 in a state where it is combined with the first mold 22. The third mold 25 includes a heel forming part 26 for forming the heel part 12 in a state where it is combined with the first mold 22.

  In order to mold the seal 10, first, as shown in FIG. 3A, the first mold 22 and the second mold 24 are combined with the first mold 22 and a heating device (not shown). 24 is heated, and a synthetic rubber material is injected into the seal forming portion 23 through the gate 24 a of the second mold 24. And the seal | sticker part 11 is shape | molded by heat-crosslinking the synthetic rubber material in the seal | sticker formation part 23 for a predetermined time.

  Next, the second mold 24 is removed from the first mold 22, and the third mold 25 is combined with the first mold 22 instead. In this state, the dynamically crosslinked thermoplastic elastomer is injected into the heel forming portion 26 through the gate 25a of the third mold 25. At this time, the higher the injection speed and injection pressure, the greater the amount of heat generated, and the temperature of the air in the heel forming portion 26 and the temperature of the third mold 25 are likely to rise. In order to suppress this temperature rise and accelerate the curing of the dynamically crosslinked thermoplastic elastomer in the heel forming portion 26, the dynamically crosslinked thermoplastic elastomer is injected to the heel forming portion 26 at a lower pressure. That is, since the heel portion 12 is formed of a dynamically crosslinked thermoplastic elastomer that does not require heat crosslinking, unlike the seal portion 11, there is no need to heat the third mold 25 during molding. At this time, by injecting the dynamically crosslinked thermoplastic elastomer at a low pressure, the heel portion 12 is less prone to molding distortion. Then, the dynamically crosslinked thermoplastic elastomer in the heel forming portion 26 is cooled and cured to form the heel portion 12 and to join the seal portion 11 and the heel portion 12 together. At this time, since the seal part 11 and the heel part 12 are a combination of a synthetic rubber and a dynamically crosslinked thermoplastic elastomer having a higher compatibility than a combination of a synthetic rubber and a synthetic resin, they are joined well.

  Through the above-described steps, the seal 10 constituted by the seal portion 11 made of synthetic rubber and the heel portion 12 made of a dynamically crosslinked thermoplastic elastomer and joined to the seal portion 11 is manufactured. The joint strength between the heel portion 12 and the seal portion 11 in the seal 10 thus molded was 5 MPa or more. On the other hand, the joint strength between the heel portion formed of the synthetic resin and the seal portion 11 was close to 0 MPa. That is, when the seal having the heel portion formed of the synthetic resin is removed from the molding die 20, the seal portion 11 and the heel portion are separated by itself.

  The seal 10 configured as described above has the same outer diameter as the inner diameter of the circumferential groove 52a of the female end 52 in the ductile cast iron pipe 50 shown in FIGS. Used in the department. And the seal | sticker 10 is mounted | worn with the circumferential groove 52a in the state which bent a part in the circumferential direction inside the seal | sticker 10. As shown in FIG. At this time, since the heel portion 12 is formed of a dynamically crosslinked thermoplastic elastomer that is more flexible than synthetic resin, the seal 10 is easily bent as a whole, and the heel portion 12 is in contact with the circumferential groove 52a. Easy to insert.

  When the two ductile cast iron pipes 50 are connected, if the male end 53 of the other ductile cast iron pipe 50 is inserted into the female end 52 of one ductile cast iron pipe 50, The seal portion 11 of the seal 10 is in pressure contact with the outer peripheral surface 53a. And the joint part of the two ductile cast iron pipes 50 is sealed by this seal part 11. When the male end 53 is inserted into the female end 52 in this way, the seal portion 11 of the seal 10 is pushed toward the back of the male end 53 by the male end 53. At this time, since the bonding strength between the heel portion 12 made of the dynamically crosslinked thermoplastic elastomer and the seal portion 11 made of the synthetic rubber is higher than the bonding strength between the synthetic rubber and the synthetic resin, the heel portion of the seal portion 11 Drop-out from 12 is effectively prevented.

This embodiment exhibits the following effects.
(1) Since the seal 10 is composed of the seal portion 11 made of synthetic rubber and the heel portion 12 made of a dynamically crosslinked thermoplastic elastomer, only the seal portion 11 is placed inside the mold 20 when molding with the molding die 20. In this case, heat crosslinking may be performed. For this reason, since the seal part 11 and the heel part 12 are both made of synthetic rubber and both are heated and crosslinked in the molding die 20, the capacity of the molded part that requires heat crosslinking is reduced. The time required for heat crosslinking in the molding die 20 is shortened. As a result, the molding time of the seal 10 is shortened.

  (2) The bonding strength between the seal portion 11 made of synthetic rubber and the heel portion 12 made of dynamic crosslinkable thermoplastic elastomer is improved more than the bonding strength between the seal portion 11 and the heel portion made of synthetic resin. . Therefore, the bonding strength between the seal part 11 and the heel part 12 can be ensured satisfactorily. Therefore, it is possible to prevent the seal portion 11 and the heel portion 12 from being separated when being mounted on the ductile cast iron pipe.

  (3) The dynamically crosslinked thermoplastic elastomer is more flexible than the synthetic resin. Therefore, since favorable flexibility can be ensured as the seal 10 as a whole, it can be easily attached to the ductile cast iron pipe.

(Second Embodiment)
Next, a second embodiment embodying the present invention will be described with reference to FIGS.
As shown in FIG. 5, a plurality of annular groove portions 30 (two in FIGS. 4 and 5) are formed in the seal portion 11 of the seal 10 shown in FIG. Each groove portion 30 has a shape whose cross-sectional area expands on the bottom side. The heel portion 12 is formed with a plurality of ridge portions 31 disposed in the groove portion 30. The seal portion 11 and the heel portion 12 are mechanically coupled by the anchor action of the ridge portion 31 with respect to each groove portion 30 in addition to joining at the boundary surface.

  The seal 10 of this embodiment is injection-molded using a molding die 20 as shown in FIGS. 6A and 6B having substantially the same configuration as the molding die 20 used in the first embodiment. A plurality (two in FIG. 6 (a)) of annular protrusions 24b for forming the groove portions 30 are formed in the second die 24 of the molding die 20. And in the state which combined the 2nd metal mold | die 24 with the 1st metal mold | die 22, the seal | sticker part 11 which has the groove part 30 is shape | molded by inject | pouring a synthetic rubber material to the seal | sticker formation part 23. FIG.

  Next, by projecting the dynamically crosslinked thermoplastic elastomer to the heel forming portion 26 in a state where the third die 25 is combined with the first die 22, the protrusions disposed in the groove portion 30 of the seal portion 11. A heel portion 12 having a portion 31 is formed.

This embodiment configured as described above is easily attached to the circumferential groove 52a of the female side end portion 52 of the ductile cast iron pipe 50, as in the first embodiment.
This embodiment exhibits the following effects in addition to the effects described in (1) to (3) of the first embodiment.

  (4) A plurality of groove portions 30 were formed in the seal portion 11, and the ridge portions 31 arranged in each groove portion 30 were formed in the heel portion 12. And the seal part 11 and the heel part 12 were mechanically combined by the anchor effect | action of the protrusion part 31 with respect to each groove part 30. FIG. For this reason, the joint strength between the seal portion 11 and the heel portion 12 is further improved, and the drop-off of the seal portion 11 from the heel portion 12 is effectively prevented.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS.
A seal 40 shown in FIG. 7 is formed of an annular seal portion 41 formed of a synthetic rubber similar to the seal portion 11 and a dynamic cross-linking thermoplastic elastomer similar to the heel portion 12 and the seal portion 41. And an annular heel portion 42 joined to each other. The seal 40 is formed in the same manner as the seal 10.

  As shown in FIG. 8, the seal 40 includes an inclined surface 52 b formed on the inner peripheral side of the female end 52 in one ductile cast iron pipe 50 and an outer periphery of the male end 53 in the other ductile cast iron 50. It is mounted between the surface 53a. The seal 40 is in a state where the seal portion 11 is pressed against the inclined surface 52b and the outer peripheral surface 53a by pressing the heel portion 42 toward the female end portion 52 side by the push ring 54 attached to the female end portion 52. Retained. The joint portion of the ductile cast iron pipe 50 is sealed by the seal portion 11.

The seal 40 of this embodiment has the effects described in (1) to (3) of the first embodiment.
(Other embodiments)
In addition, this embodiment can also be changed and embodied as follows.

  -In 2nd Embodiment, as shown in FIG. 9, while forming the groove part 30 in the heel part 12, the protrusion part 31 corresponding to the same groove part 30 is formed in the seal part 11. As shown in FIG. Then, the seal portion 11 and the heel portion 12 are mechanically coupled by the anchor action of the protrusion 31 of the seal portion 11 with respect to the groove portion 30 of the heel portion 12.

  As shown in FIG. 10, the boundary surface between the seal part 11 and the heel part 12 is formed into a plurality of pleats extending in the circumferential direction. In this case, the joint area between the seal part 11 and the heel part 12 increases, and the joint strength between the two improves.

  -While forming the hole part in multiple places along the circumferential direction of the seal part 11, the convex part corresponding to each hole part is formed in multiple places along the circumferential direction of the heel part 12. FIG. And the seal | sticker part 11 and the heel part 12 are mechanically combined by the anchor effect | action of the convex part with respect to each hole part.

  -As shown with a dashed-two dotted line in FIG.3 (b) or FIG.6 (b), the heat insulation part 43 is provided in the side which contact | abuts the 1st metal mold | die 22 in the 3rd metal mold | die 25 of the molding die 20. FIG. In this case, since the heat transfer from the first mold 22 to the third mold 25 is restricted by the heat insulating part 43 when the heel part 12 is molded, the third mold by the heat of the first mold 22 is limited. The temperature rise of 25 is suppressed. Accordingly, the dynamically cross-linked thermoplastic elastomer injected to the heel forming portion 26 of the third mold 25 is effectively cooled and its curing time is shortened, so that the time required for molding the seal 10 is further shortened. .

  The seal of the present invention may be formed of a seal portion 11 made of synthetic rubber and a dynamically cross-linked thermoplastic elastomer having a hardness higher than that of the seal portion 11, and includes the seal portions 11 and 41 and the heel. The cross-sectional shapes of the portions 12 and 42 are not limited to the above embodiments.

Hereinafter, the technical idea grasped from each of the above embodiments will be described.
(1) Molding of a seal for a water pipe joint composed of a seal portion made of synthetic rubber and a heel portion formed of a flexible material having a higher hardness than the seal portion and joined to the seal portion A first mold having a seal forming portion for forming the seal portion; a second mold which is combined with the first mold and closes the seal forming portion; A mold for sealing a water pipe joint, comprising: a third mold which is combined with a first mold instead of a mold and has a heel forming part for molding the heel part.

(A) is a front view which shows the seal | sticker of 1st Embodiment, (b) is a side view of a partially broken state similarly. The longitudinal cross-sectional view of a seal | sticker. (A), (b) is a longitudinal cross-sectional view which shows a molding die. The side view of the partially broken state which shows the seal | sticker of 2nd Embodiment. The longitudinal cross-sectional view of a seal | sticker. (A), (b) is a longitudinal cross-sectional view which shows a molding die. The longitudinal cross-sectional view which shows a part of seal | sticker of 3rd Embodiment. The longitudinal cross-sectional view which shows the ductile cast iron pipe with which the seal | sticker was mounted | worn. The longitudinal cross-sectional view which shows the seal | sticker of other embodiment. The longitudinal cross-sectional view which shows the seal | sticker of other embodiment. The longitudinal cross-sectional view which shows the ductile cast iron pipe with which the conventional seal | sticker was mounted | worn. The longitudinal cross-sectional view which shows the junction part of the ductile cast iron pipe | tube with which the seal | sticker was mounted | worn. The longitudinal cross-sectional view which shows another seal | sticker.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Seal for water pipe joints, 11 ... Seal part, 12 ... Heel part, 20 ... Molding die, 22 ... First mold, 23 ... Seal formation part, 24 ... Second mold, 25 ... Third mold , 26 ... heel forming part, 30 ... groove part as a concave part, 31 ... ridge part as a convex part, 40 ... seal, 41 ... seal part, 42 ... heel part.

Claims (4)

A water pipe joint seal composed of a seal portion made of synthetic rubber and a heel portion formed of a flexible material having a hardness higher than that of the seal portion and joined to the seal portion,
A seal characterized in that the heel portion is formed of a dynamically cross-linked thermoplastic elastomer.   A concave portion is formed in at least one of the seal portion and the heel portion, and a convex portion disposed in the concave portion is formed in the other portion, and the seal portion and the heel portion are formed by an anchor action of the convex portion with respect to the concave portion. The seal according to claim 1, which is mechanically coupled.   The Shore A hardness of the seal portion is in the range of 50-60, and the Shore A hardness of the heel portion is in the range of 70-90. The seal described. A seal manufacturing method comprising a seal portion made of synthetic rubber and a heel portion formed of a flexible material having a higher hardness than the seal portion and joined to the seal portion,
Synthetic rubber is injected into the seal forming portion in a state where a first mold having a seal forming portion for forming the seal portion and a second die for closing the seal forming portion are combined, and the first mold is injected. And the second mold is heated to cross-link the synthetic rubber in the seal forming part for a predetermined time to form the seal part, and then the second mold is provided with the heel forming part for forming the heel part. It is combined with the first mold instead of the mold, and in this state, the dynamically crosslinked thermoplastic elastomer is injected into the heel forming portion, and the dynamically crosslinked thermoplastic elastomer in the heel forming portion is cooled and cured to cure the heel. A method for manufacturing a seal, comprising molding a part and joining the seal part and a heel part.

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