JP2000074289A - Polyethylene coated gasket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gasket improved in physical characteristics such as chemical resistance and abrasion resistance without deteriorating flexibility and sealing performance. SOLUTION: In a polyethylene coated gasket 1, a coating layer 4 is provided on the outer surface of a rubber base material 2 through an adhesive layer 3, and the adhesive layer 3 is made of polyethylene hot-melt adhesives having a polyethylene group block polymer having a rubber segment in a molecule or a graft polymer as main component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasket used for sealing pipes and the like, and more particularly, to a gasket excellent in chemical resistance and abrasion resistance.

[0002]

2. Description of the Related Art A gasket used as a sealing member for a joint surface in a pipe joint or the like requires flexibility in order to obtain sufficient sealing and sealing properties. For this reason, conventionally, a gasket made of rubber or rubber having a reinforcing base cloth inside is used. However, in a pipe sealed using such a rubber gasket, there is a portion 93 where the gasket 90 is exposed on the inner peripheral surface 92 of the pipe 91 as shown in FIGS. 5 (a) and 5 (b). Since physical properties such as chemical resistance, abrasion resistance, and trauma resistance are lower than the inner peripheral surface 92 of the pipe, the exposed portion 93 is deteriorated depending on the properties of the fluid in the pipe 91 and the sealing property is insufficient. Or physical damage due to friction with the fluid.

[0003]

In order to solve the above problems, for example, a gasket made of a hard synthetic resin material having excellent chemical resistance and abrasion resistance has been proposed. There is a problem that the flexibility is insufficient and good sealing properties cannot be obtained. In addition, a gasket in which a Teflon resin is coated on an inner core cushion material (rubber base material) is also disclosed (JP-A-7-167303), but the adhesiveness between rubber used as a rubber base material and Teflon resin is disclosed. Therefore, there is a problem that a complicated treatment such as a pre-adhesion treatment is required when coating the Teflon resin, and that the Teflon resin and the rubber substrate are easily peeled off during use.
Furthermore, since the material such as Teflon resin is expensive, there is a problem that the cost of the gasket increases.

An object of the present invention is to provide a gasket having improved physical properties such as chemical resistance and abrasion resistance without impairing flexibility and sealing properties.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have provided a polyethylene coating layer on the surface of a rubber substrate, Is bonded using a predetermined hot-melt adhesive, the rubber substrate and the coating layer can be firmly bonded to each other by a simple method, without impairing flexibility and sealability, chemical resistance, The present inventors have found a new fact that a gasket having improved physical properties such as abrasion resistance can be obtained, and have completed the present invention.

That is, the polyethylene-coated gasket of the present invention is provided with a polyethylene coating layer on the front and / or back surface of a rubber substrate via an adhesive layer, and the adhesive layer is made of a hot melt adhesive for polyethylene. It is characterized by becoming. According to the polyethylene-coated gasket of the present invention, since the body of the gasket is a rubber base material having sufficient elasticity, the gasket has sufficient flexibility and excellent sealing properties. In addition, since the gasket is provided with the polyethylene coating layer on the surface, the gasket has excellent chemical resistance and abrasion resistance.

Further, according to the polyethylene-coated gasket of the present invention, since the rubber substrate and the polyethylene coating layer are bonded with the hot-melt adhesive for polyethylene, the gasket does not go through complicated steps such as pre-bonding treatment. In a simple way,
Both can be firmly bonded. Therefore, the manufacturing cost of the gasket can be reduced, and the peeling of the coating layer and the rubber substrate during use can be sufficiently suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a gasket of the present invention will be described in detail with reference to FIGS. As an embodiment of the gasket 1 of the present invention, as shown in FIG. 1 (b), a rubber substrate 2, a coating layer 4 made of polyethylene provided on the surface thereof, a rubber substrate 2 and a coating layer 4 And an adhesive layer 3 for adhering the above.

In another embodiment, as shown in FIG. 1 (c), a rubber substrate 2 and coating layers 41, 42 made of polyethylene provided on both the front and back surfaces thereof.
And adhesive layers 31 and 32 for bonding the rubber base material 2 and the coating layers 41 and 42. The gasket of the present invention is not limited to the elongated one shown in FIG. 1, but may be an O-ring shaped gasket 11, as shown in FIG. 2, for example.

<< Rubber Base >> As shown in FIG. 3, the rubber base in the gasket of the present invention has a substantially U-shaped main body 21.
And a pair of flat mounting portions (flanges) 22 protruding outward from the tip of the main body 21. The mounting portion 22 is provided with a through hole 23 in which a fixing means such as a bolt for fixing the gasket 1 to the outer peripheral surface of the pipe or the like is arranged.

The height h of the main body 21, the width w inside the main body 21, the width L of the entire rubber base 2 including the mounting portion 22, and the like are determined by the conditions of use of the gasket, the size of the pipe to which the gasket is applied, and the like. It is set appropriately according to the degree of flexibility and elasticity of the rubber base material. The gasket of the present invention is generally used for pipes in water and sewage systems, plants and the like, and has a height h of 50 to 200 mm and a width w of 50 to 500 m.
m, and the overall width L is about 150 to 2000 mm.

The material constituting the rubber substrate is not particularly limited as long as it has sufficient elasticity. For example, natural rubber (NR), isoprene rubber (I
R), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), ethylene propylene rubber (EPM, EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NB)
R), hydrogenated NBR, acrylic rubber (ACM, AE)
M), polysulfide rubber and the like can be used. In addition to the rubbers described above, thermoplastic elastomers such as styrene-isoprene-styrene block copolymer (SIS) and styrene-butadiene-styrene block copolymer (SBS) can also be used.

Various additives such as a reinforcing agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerating aid and oil are added to the rubber constituting the rubber substrate as necessary. . Examples of the reinforcing agent include inorganic reinforcing agents such as carbon black, white carbon, zinc white, surface-treated precipitated calcium carbonate, magnesium carbonate, talc, and clay; coumarone indene resin, phenol resin, and high styrene resin (styrene). Organic reinforcing agent such as a styrene-butadiene copolymer having a large content. Among them, carbon black is preferably used.

As the carbon black, any of various carbon blacks conventionally known for reinforcing rubber can be used.
Carbon black such as EF, HAF, ISAF, and SAF is preferably used. The compounding amount of carbon black is preferably 50 to 80 parts by weight based on 100 parts by weight of the base rubber.

As the vulcanizing agent, for example, sulfur; N, N'-
Organic sulfur-containing compounds such as dithiobismorpholine; organic peroxides such as benzoyl peroxide and dicumyl peroxide; Among them, sulfur is preferably used. Examples of the vulcanization accelerator include thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide, tetrabutylthiuram disulfide and tetramethylthiuram monosulfide; zinc dibutyldithiocarbamate, zinc diethyldithiocarbamate, sodium dimethyldithiocarbamate, and diethyldithiocarbamate. Dithiocarbamic acids such as tellurium; 2-mercaptobenzothiazole,
Thiazoles such as N-cyclohexyl-2-benzothiazolesulfenamide, dibenzothiazyl disulfide, Nt-butyl-2-benzothiazolylsulfenamide; thioureas such as trimethylthiourea and N, N'-diethylthiourea And organic accelerators such as slaked lime, magnesium oxide, titanium oxide and litharge (PbO).

The total compounding amount of sulfur and the vulcanization accelerator is preferably 2.5 to 6.5 parts by weight based on 100 parts by weight of the base rubber. Examples of the vulcanization accelerator include metal oxides such as zinc white and fatty acids such as stearic acid, oleic acid and cottonseed fatty acids. The amount of the vulcanization accelerator is preferably about 1 to 10 parts by weight based on 100 parts by weight of the base rubber.

Examples of the oil include vegetable oils, mineral oils and synthetic oils such as fatty acids (stearic acid, lauric acid, etc.), cottonseed oil, tall oil, asphalt substances, paraffin wax and the like. The compounding amount of the oil is preferably about 1 to 30 parts by weight based on 100 parts by weight of the base rubber.

In addition to the above additives, for example, a vulcanization retarder, an antioxidant, a plasticizer, a tackifier, a lubricant dispersant, a solvent and the like may be appropriately blended. The hardness of the rubber substrate 2 is adjusted so that the hardness after vulcanization is 40 to 70, preferably 55 to 66 in JIS A hardness. When the hardness of the rubber is in the above range, the flexibility of the gasket is sufficient, and good sealing properties can be exhibited. On the other hand, if the hardness of the rubber is less than the above range, the gasket becomes too soft, so that the reaction force at the time of compression becomes insufficient and the sealing property may be insufficient. Conversely, if the hardness of the rubber exceeds the above range, the gasket becomes too hard, so that the amount of deformation at the time of compression is reduced and the sealing property may be insufficient.

The hardness (JIS A) of the rubber substrate 2 is particularly preferably 55 to 66 in the above range in consideration of the balance between the reaction force during compression and the amount of deformation.
It is more preferably from 8 to 62. Various methods can be considered to set the hardness of the rubber after vulcanization to the above range, but in a general rubber composition using carbon black as a reinforcing agent, and using sulfur as a vulcanizing agent. In this case, the content of carbon black in the unvulcanized base rubber and the total content of sulfur and the vulcanization accelerator may be adjusted. Generally, carbon black, sulfur,
In any of the vulcanization accelerators, the hardness of the vulcanized rubber can be increased by increasing the amount thereof.

The rubber substrate 2 is kneaded by adding various additives such as a vulcanizing agent, a vulcanization accelerator, and a reinforcing oil to unvulcanized base rubber in the same manner as in a conventional rubber gasket. The obtained rubber composition is obtained by charging the rubber composition in a mold corresponding to the desired shape of the gasket, and heating and vulcanizing under pressure. When a thermoplastic elastomer is used as the rubber base material, the rubber base material 2 is formed by extrusion using a mouth member corresponding to a desired side (cross-sectional) shape of the gasket as shown in FIG. You can also.

The rubber substrate may contain one or a plurality of conventionally known base fabrics such as canvas. The type and number of base cloths to be used can be appropriately set according to the degree of reinforcement of the rubber base material. Further, as a method for incorporating the base cloth into the rubber substrate, a method similar to the conventional method may be used. << Adhesive layer >> The hot melt adhesive for polyethylene used for the adhesive layer in the gasket of the present invention is not particularly limited as long as it is capable of firmly adhering the rubber base material of the gasket and the polyethylene constituting the coating layer. Although not particularly, a hot-melt adhesive mainly composed of a polyethylene-based block polymer or a graft polymer having a rubber segment in the molecule is used in combination with the polyethylene-based resin constituting the coating layer. It is suitably used in the present invention because it not only has good adhesiveness but also exhibits excellent adhesiveness to a rubber substrate due to the action of the rubber segment in the molecule.

As will be described later, the adhesive layer is formed by applying a hot melt adhesive for polyethylene to a polyethylene sheet constituting the coating layer and volatilizing the solvent. Specific examples of the hot melt adhesive for polyethylene include “SKIP-55” (trade name, manufactured by Sotec Corporation)
"SKIP-66" and the like.

The thickness of the adhesive layer 3 is not particularly limited, but an adhesive is applied from the viewpoint of firmly bonding the rubber substrate 2 and the coating layer 4 and not adversely affecting the flexibility of the gasket. Thickness when the solvent is completely evaporated
It may be adjusted so as to be about 5 to 0.1 mm. << Coating Layer >> The coating layer in the gasket of the present invention is formed by laminating to the surface of a rubber substrate via an adhesive layer, as described later. At this time, the polyethylene constituting the coating layer is preferably formed into a sheet according to the thickness of the coating layer.

The coating layer does not need to be formed on the entire surface of the rubber base 2, and at least the main body 2
It is only necessary that it be formed on the surface portion of No. 1. The polyethylene for forming the coating layer 4 is not particularly limited, and various conventionally known polyethylenes can be used. Among them, a so-called high-density polyethylene having a density of 0.94 to 0.97 g / cm ³ can be used. It is preferable to use the gasket from the viewpoint of enhancing the chemical resistance, abrasion resistance, trauma resistance and the like of the gasket.

High-density polyethylene has a long-term resistance to alcohols, acids, alkalis, salts, and the like, in addition to aliphatic and aromatic hydrocarbons such as benzene, toluene, and mineral oil. Although the thickness of the coating layer 4 is not particularly limited, when the thickness t of the rubber base 2 is about 10 to 20 mm,
To improve the chemical resistance, abrasion resistance, etc. of the gasket, it is sufficient if the thickness of the coating layer is about 1.0 to 3.0 mm.

If the thickness of the coating layer is less than the above range, the gasket may have insufficient chemical resistance, abrasion resistance and the like, and the effect of the present invention may not be obtained. Conversely, if the thickness of the coating layer exceeds the above range, the flexibility of the gasket decreases, and thus the sealing performance may be insufficient,
When the chemical resistance, abrasion resistance, and trauma resistance of the gasket are more strongly required, the thickness of the coating layer can be set to a thickness of about 3 mm. << Production Method of Polyethylene-Coated Gasket >> The polyethylene-coated gasket of the present invention is, for example, a rubber substrate and a polyethylene sheet constituting a coating layer, each set in a mold, and the two are bonded together under pressure. Manufactured by heating.

At this time, the above-mentioned hot melt adhesive is applied to the surface of the polyethylene sheet to completely volatilize the solvent, and in this state, it may be bonded to a rubber substrate which has been vulcanized and molded in advance. Conversely, the adhesive may be applied to a rubber substrate previously vulcanized and formed, or the adhesive may be applied to both the rubber substrate and a polyethylene sheet.

Hereinafter, the method for producing a polyethylene-coated gasket of the present invention will be described with reference to a gasket 1 in which a coating layer 4 is provided only on one surface of a rubber substrate 2 as shown in FIG. 1 (b). The production of the polyethylene-coated gasket 1 is performed, for example, as shown in FIG. That is,
First, the coating layer 4 is placed on a mold 51 (lower mold) having a concave portion corresponding to a substantially U-shaped shape in the main body 21 of the rubber base material 2.
Is set, and a hot-melt adhesive for polyethylene constituting the adhesive layer 3 is applied to the surface thereof to form a layer 53 of the adhesive. Next, in a state where the rubber base material 2 that has been vulcanized and formed in advance is set in a mold (upper mold) 54, the rubber base material 2 and the surface of the polyethylene sheet 52 to which the adhesive has been applied are bonded. Then, it is usually heated to 130 to 180 ° C.,
0 kgf / cm ² , preferably 30 to 80 kgf / cm
By pressing at a pressure of about ² for about 20 minutes, the polyethylene-coated gasket of the present invention is obtained.

The configuration of the polyethylene-coated gasket of the present invention is not limited to the embodiment shown in the above-described drawings, and various design changes may be made without changing the gist of the present invention. be able to.

[0030]

EXAMPLES (Production of rubber substrate) 100 parts by weight of natural rubber,
30 parts by weight of carbon black, 3 parts by weight of an antioxidant, 4 parts by weight of zinc white, 1 part by weight of stearic acid, 3 parts by weight of oil, 1 part by weight of sulfur and 1 part by weight of a vulcanization accelerator are mixed,
Two pieces of canvas were put inside to prepare a rubber substrate having a cross-sectional shape as shown in FIG. The width w of the rubber base body 21 is 1
00 mm, height h is 100 mm, thickness t of the rubber base is 1
5 mm.

Next, the rubber base material is placed in a mold, and
Vulcanized at 50 ° C. for 30 minutes. (Attaching of Coating Layer) As shown in FIG. 4, the rubber substrate 2 was set in a mold (upper mold) 54 having a convex portion corresponding to the substantially U-shaped shape of the main body 21. Next, the aforementioned U
Mold (lower mold) 51 having a concave portion corresponding to the shape of the character
Next, a polyethylene sheet 52 constituting the coating layer 4 (HPDE sheet made by Polyflex, thickness 1.5 mm)
And a polyethylene-based hot melt adhesive (trade name “SKIP-55” manufactured by Sotec Co., Ltd.) on the surface.
Was applied, and the solvent of the adhesive was volatilized and dried.

Further, by joining the upper mold 54 and the lower mold 51, a polyethylene sheet 52 is bonded to the rubber substrate 2 via an adhesive layer 53, heated to 150 ° C., and heated to 10 kgf / cm ² . By pressing under pressure for 10 minutes, a polyethylene-coated gasket 1 having a layer structure shown in FIG. 1 (b) was obtained. In the gasket thus obtained, the rubber substrate and the coating layer were firmly bonded.

[0033]

As described above in detail, according to the polyethylene-coated gasket of the present invention, physical properties such as chemical resistance and abrasion resistance can be improved without impairing flexibility and sealability. Can be. Therefore, the polyethylene-coated gasket of the present invention can be suitably used as a sealing member for pipes or the like that require high chemical resistance and abrasion resistance.

[Brief description of the drawings]

FIG. 1 (a) is a perspective view showing one embodiment of a polyethylene-coated gasket of the present invention, wherein FIG.
(c) is a partially enlarged sectional view thereof.

FIG. 2 is a partially broken perspective view showing another embodiment of the polyethylene-coated gasket of the present invention.

FIG. 3 is an explanatory view showing a cross-sectional shape of the polyethylene-coated gasket of the present invention.

FIG. 4 is a schematic sectional view showing a method for producing a polyethylene-coated gasket of the present invention.

FIG. 5 is a schematic sectional view showing a use state of the gasket.

[Explanation of symbols]

 1,11 Gasket 2 Rubber substrate 3,31,32 Adhesive layer 4,41,42 Coating layer

Claims (1)

[Claims] 1. A polyethylene coating, wherein a polyethylene coating layer is provided on an upper surface and / or a rear surface of a rubber substrate via an adhesive layer, and the adhesive layer comprises a hot melt adhesive for polyethylene. gasket.