GB2084602A

GB2084602A - Water-swelling Sealant

Info

Publication number: GB2084602A
Application number: GB8112791A
Authority: GB
Original assignee: Hayakawa Rubber Co Ltd; Bridgestone Corp
Current assignee: Hayakawa Rubber Co Ltd; Bridgestone Corp
Priority date: 1980-09-26
Filing date: 1981-04-24
Publication date: 1982-04-15
Also published as: GB2084602B; AU6986481A; DE3117560A1; AU526561B2

Abstract

A water-swelling sealant having excellent water-tightness and durability, and which may be moulded e.g. into strip form, is obtained by compounding (A) uncrosslinked rubber and/or partially crosslinked rubber with (B) white carbon (e.g. silicic acid anhydride, hydrated silicic acid or calcium silicate) and (C) a plasticizer, the amount of (B) being 18-45% and that of (C) 13-40% by weight based on the total sealant composition. The sealant may also include an elastomer having a high restoring property after compression, and an adhesive layer may be applied to at least a part of the surface of the moulded sealant.

Description

SPECIFICATION Water-swelling Sealant The present invention relates to a sealant which swells by water and hás excellent watertightness and durability.

Sealant is widely usedin the civil engineering and in the construction industry, and is demanded to have watertightness, durability and weather resistance.

When a sealant is used in a panel water tank and the like where the gap to be filled with the sealant deforms sometimes depending upon the use condition and working environment, water cannot be stopped by conventional sealants.

Recently, a sealant capable of developing excellent watertightness following to the deformation of the gap has been demanded.

Moreover, the easiness in handling, the sticking workability, the price and the bonding ability are important factors in the selection of sealant.

There has most generally been used a sealant formed of an adhesive unvulcanized rubber consisting mainly of butyl rubber. Such sealant seals a gap by an adhesive force to stop water, and has such an excellent workability that the sealant can deform corresponding to the unevenness of a portion to be sealed, and the superposed portion of the sealant can be made into an integral structure. However, the sealant has such drawbacks that the sealant is apt to be easily deformed by the compression force between the flanges, and that the sealant itself often creeps to deteriorate noticeably its waterproofing function when the sealant is extremely deformed. In order to prevent the drawbacks, there has been proposed a sealant which is made of a crosslinked rubber or a foamed body and develops a waterproofing function by the restoring force of the rubber or foamed body.

However, the sealant itself is poor in the adhesion or plasticity. Therefore, the superposed portion of the sealant cannot be formed into an integral structure, and is difficult to be applied to the sealing of a portion having a particularly complicated shape. Furthermore, when the vulcanized rubber and foamed body are once deformed permanently, they cannot restore the original state, and cannot stop water.

The present invention relates to a novel sealant having a plasticity and elasticity inherent to uncross-linked rubber and further having waterswelling property, and capable of developing waterproofing faculty by the swelling force.

Recently, there have been proposed several methods, wherein a water-swelling resin (hydrogel or the like) is incorporated into a matrix rubber to produce a sealant having water-swelling property. However, water-swelling resin is generally poor in the dispersion in matrix rubber, and when a small amount of the resin is incorporated into a matrix rubber, the swelling of the resulting sealant is very poor, while when more than a certain amount of the resin is incorporated into a matrix rubber, the resulting sealant has a satisfactorily high swelling degree, but in this case, the sealant causes phase separation or often causes breakage of the matrix rubber, and is very low in the strength as a sealant.

Further, there has been proposed a technic in Japanese Patent Laid Open Application No.

20,066/79, wherein a hydrophilic polyurethane component is incorporated into natural rubber or the like, and the rubber and the polyurethane component are curred at the same time to produce a water-swelling rubber, and the waterswelling rubber is used as a sealant. However, the polyurethane component is easily hydrolysed, and the sealant is noticeably deteriorated in its performance in the presence of alkali or under the stimulus of repeating swellings and dryings.

The present invention relates to a novel sealant having water-swelling property and excellent watertightness and durability, and not having the above described drawbacks of conventional sealants.

That is, the feature of the present invention is the provision of a water-swelling sealant obtained by compounding (A) uncrosslinked rubber and/or partially crosslinked rubber with (B) white carbon and (C) a plasticizer to form a sealant composition, provided that the amount of component (B) is 18 4-5% by weight and that of component (C) is 1340% by weight based on the total amount of the composition, and moulding the composition.

Another feature of the present invention is the provision of a water-swelling sealant, wherein the above described sealant consisting essentially of components (A), (B) and (C) is combined with an elastomer having a high restoring property after compression.

A further feature of the present invention is the provision of a water-swelling sealant, wherein an adhesive layer is formed on at least a part of the surface of the above described sealant consisting essentially of components (A), (B) and (C).

The water-swelling sealant of present invention contains a stable inorganic component of white carbon as a water-swelling component.

Therefore, the sealant is stable against the deterioration due to oxidation, hydrolysis or putrefaction, which occurs in the use of organic compounds, such as hydrogel and water-swelling polyurethane. Further, the sealant is stable against stimulus of repeating cycles of swelling and drying, and does not substantially deteriorate its performance. Moreover, the sealant does not substantially contain a water-soluble substance.

This fact proves that the water-swelling sealant of the present invention passes the standard of sealant for city water. While, sealants using hydrogel or water-swelling polyurethane have an unstable structure, and form a water-soluble substance due to the hydrolysis or oxidation.

Therefore, the sealants deteriorate their faculty as a sealant and cannot be used for city water.

The water-swelling sealant of the present invention may be used as such or in combination with an elastomer having a high restoring property after compression. That is, sealant is sometimes used under an extremely high compression force. In this case, if the sealant is combined with an elastomer having a high restoring property after compression, the resulting composite sealant exhibit a high waterproofing effect by the combination of the restoring force of the elastomer having a high restoring property after compression and the swelling pressure of the water-swelling sealant itself under a state which is exposed to a compression force.

Furthermore, when an adhesive layer is formed on at least one surface of the water-swelling sealant of the present invention, the wettability of the sealant with a substance to be adhered with the sealant and the sticking workability between them can be remarkably improved.

The water-swelling sealant of the present invention consists essentially of three components of component (A) of uncrosslinked rubber and/or partially crosslinked rubber, component (B) of white carbon and component (C) of a plasticizer.

As the uncrosslinked rubber of component (A), there are used, for example, natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene copolymer rubber, acrylic rubber, ethylene propylene-diene terpolymer rubber, ethylene propylene rubber, chloroprene rubber, butyl rubber, halogenated butyl rubber, polyisobutylene and the like. As the partially crosslinked rubber of component (A), for example partially crosslinked butyl rubber is used. Among these uncrosslinked rubbers, butyl rubber, hologenated butyl rubber, polyisobutylene, ethylene-propylene-diene terpolymer rubber; ethylene-propylene rubber and partially crosslinked butyl rubber are advantageously used. These rubbers can be used alone or in admixture in an optional mixing ratio.

As the white carbon of component (B), there can be used silicic acid anhydride (dry process white carbon), hydrated silicic acid (wet process white carbon), silicate type white carbon and the like. Among them, silicic acid anhydride and hydrated silicic acid are advantageously used.

These white carbons are used alone or in admixture in an optional mixing ratio.

The definition and production method of white carbon are specifically explained, for example, on pages 522-541 of Handbook of Additives for Plastics and Rubbers, edited by Shu Kanbara and Minoru Imoto, published by Chemical Industry Co.

(1970).

Component (B) must be contained in the sealant in an amount of 18 45% by weight, preferably 3040% by weight. When the amount of component (B) is less than 18% by weight, the sealant has a low swelling degree and cannot exhibit a satisfactorily high waterproofing effect. Reversely, when the amount exceeds 45% by weight, the workability in the production of the sealant is poor, and further the resulting sealant is rigid and brittle and has not a necessary property as a sealant.

As the plasticizer of component (C), there can be used so-called synthetic plasticizers, such as esters, sulfonamides, phosphates, paraffin derivatives, epoxy derivatives, polyesters, polyethers, polyamides and the like; and softeners for rubber, such as mineral oil series softener, vegetable oil series softener and the like.

The synthetic plasticizers include dioctyl phthalate, dioctyl adipate, dibutyl sebacate, cresyl diphenyl phosphate, chlorinated paraffin, octyl epoxy stearate, diisodecyl epoxy hexahydrophthalate and the like.

The softeners for rubber include paraffinic oil, naphthenic oil, aromatic oil, paraffin, liquid polychloroprene, liquid isobutylene-isoprene copolymer, liquid polyisoprene, liquid polybutadiene, low molecular weight olefin polymers, such as low molecular weight atactic polypropylene and the like; liquid polybutene, liquid polymers of other unsaturated hydrocarbons, depolymerized rubber, castor oil, tall oil and the like. Among them, liquid polybutene, liquid isobutylene-isoprene copolymer can give concurrently plasticity and adhesivity to the resulting sealant, and are particularly preferably used.

The above described component (C) is used so as to be contained in the sealant in an amount of 13-40% by weight, preferably 1435% by weight. When the amount of component (C) is less than 13% by weight, the workability in the production of the sealant is poor, and moreover the resulting sealant has not an adhesive property and has a low swelling degree. Furthermore, the superposed portion of the sealant is difficult to be formed into an integral structure, and the waterproofing property at the superposed portion is poor. While, when the amount of component (C) exceeds 40% by weight, the sealant is large in the permanent compression set, is low in the cohesive force and cause cold flow. As the result, the sealant itself flows out and does not exhibit a swelling effect and is poor in the waterproofing property.

The sealant according to the present invention may contain commonly used additives, such as filler, reinforcing agent, coloring agent, lubricant, antioxidant, tackifier and the like.

The sealant of the present invention can be produced by kneading the given raw materials and molding the resulting homogeneous mixture of raw materials. The kneading can be carried out by any one of the following processes, that is, a process wherein component (A) is kneaded while adding successively components (B) and (C) and other additives to component (a); a process wherein a mixture of the three components is firstly produced, and the mixture is kneaded; and a process wherein a kneading is carried out by adding a mixture of the three components to the kneading system in several times. As the kneader, there can be used commonly used kneaders for rubber, such as roll mill, kneader, Banbury mixer and the like.As the molding machine for the sealant, there can be used commonly used molding machine for rubber, such as extruder, pressing machine, calender molding machine and the like. The sealant produced through the above described kneading process and molding process can be used as such.

In the present invention, it is preferable that the sealant obtained in the above described method has a swelling degree of at least 25%.

The swelling degree is calculated by the following formula.

W24-W0 Swelling degree (%)= x 100 WO In the formula WO: weight of sealant in dry state, W24: weight of sealant after dipped in city water for 24 hours.

As described above, the sealant according to the present invention consists essentially of component (A), component (B) and component (C), and the water absorbing component (B) is homogeneously dispersed in the rubber matrix, and the strength of the sealant does not deteriorate during the use. Moreover, even when the sealant is subjected to repeated cycles of swelling and drying, the swelling degree is not deteriorated. Further, the sealant is free from the deterioration of swelling degree due to hard water, is excellent in the durability due to the absence of deterioration and putrefaction and has no toxicity due to the absence of water-soluble component.

The above described water-swelling sealant of the present invention is used as such or in combination with an elastomer having a high restoring property after compression. The term "elastomers having a high restoring property after compression" means elastomers, such as vulcanized rubber, thermoplastic rubber, partially crosslinked rubber, rubber-containing foamed body, plastics-containing foamed body and the like, which have a high restoring property when they are compressed and then released from the compression. The restoring property varies depending upon the degree of the compression and the compression time. Therefore, it is difficult to define the restoring property of a sealant under various conditions by a simple formula.However, when a sealant is compressed for 30 minutes under a high load of about 250 kg/cm2, it is preferable that the sealant has a restoring property of at least 60%, particularly at least 70%, expressed by the formula thickness after 24 hours after released x100(%) thickness before compression Among the above described rubbers and foamed bodies, vulcanized rubber, thermoplastic rubber and partially crosslinked rubber are small in the deformation amount and are particularly preferably used.

The elastomer having a high restoring property after compression can be combined with the water-swelling sealant in various methods. For example, the elastomer is applied to one surface or both surfaces of the water-swelling sealant, or is combined with the sealant so as to wrap it, or is embedded in the sealant as a core material. These combination methods can be freely selected depending upon the use purpose.

Further, the water-swelling sealant of the present invention can be advantageously used by forming an adhesive layer on at least a part of the surface of the sealant. In the formation of the adhesive layer, commonly used known adhesives can be used. The adhesives are polymers, such as natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, styrene-butadiene block copolymer, styrene-isoprene block copolymer, butyl rubber, polyisobutylene, silicone rubber, polyvinyl isobutyl ether, chloroprene rubber, acrylonitrile-butadiene rubber, graft rubber, reclaimed rubber, partially crosslinked rubber, atactic polypropylene, ethylene-vinyl acetate copolymer, ethyiene-(meth)acrylate copolymer, ethylene(meth)acrylic acid copolymer, (meth)acrylic acid ester copolymer, polyester, polyurethane, polyamide and the like, which are occasionally mixed with plasticizer, tackifier, antioxidant, crosslinking agent, various stabilizers, coloring agent, filler, reinforcing agent and other additives.

The method for producing the sealant having an adhesive layer formed on at least a part of the sealant surface is not particularly limited. For example, a water-swelling sealant composition is molded by means of an extruder, calender, roll or press into a sealant molded article, and then an adhesive layer is applied to a part or whole of the surface of the sealant molded article by a hotmelt method, solution method, emulsion method, solution curing method or the like, or is pressed and adhered to a part or whole of the surface of.

the sealant molded article by a roll calender or press. Further, the adhesive layer can be formed on a part or whole of the sealant surface by extruding the adhesive and sealant composition at the same time.

The sealant of the present invention is particularly effectively used in the sealing for the watertight portion of a gap between flanges of a panel water tank and for the watertight portion of a gap between flanges of pipes, which gap deforms with the lapse of time.

The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof. In the examples, "parts" means parts by weight.

The waterproof performance of a sealant was ascertained by the following hydraulic test. A water tank was assembled by using two FRP panels of 1 ,000x 1,000 (mm), which were used for panel water tank, and four panels of 1 ,000x 500 (mm), and a sealant was arranged at the joint of the flanges. A hydraulic pressure was raised stepwise 0.1 kg/cm2 by 0.1 kg/cm2, and a hydraulic pressure when water began to leak was recorded. further, the hydraulic pressure, which caused the water leakage, was maintained, and the time, until the leakage of water was stopped by the swelling of the sealant by water, was measured.

Example 1 A mixture of 85 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 15 parts of butyl rubber having a viscosity average molecular weight of 450,000, 10 parts of hydrated silicic acid (trademark: Nipsil VN3, made by Japan Silica Co.), 90 parts of synthetic calcium silicate (trademark; Solex CM, made by Tokuyama Soda Co.), 50 parts of polybutene having an average molecular weight of 1,260 and 2 parts of stearic acid was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded through an extruder to produce a stripshaped sealant.

This sealant had a swelling degree of 39.4%. In a sealing test, water began to leak under a hydraulic pressure of 0.3 kg/cm2, but water was able to be stopped after 14 hours. When a hydraulic pressure was raised to 0.4 kg/cm2, water began to leak again at the same portion as described above, but water was able to be again stopped after 9 hours.

Comparative Example 1 A mixture of 75 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 25 parts of butyl rubber having a viscosity average molecular weight. of 450,000, 14 parts of hydrated silicic acid (nipsil VN3), 20 parts of polybutene having an average molecular weight of 1,260 and 2 parts of stearic acid was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 4.2%. In a sealing test, water began to leak under a hydraulic pressure of 0.2 kg/cm2, and still leaked even after 48 hours, and was not able to be stopped.

Comparative Example 2 A mixture of 75 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 25 parts of butyl rubber having a viscosity average molecular weight of 450,000, 1 50 parts of synthetic calcium silicate (Solex CM), 50 parts of polybutene having an average molecular weight of 1,260 and 2 parts of stearic acid was homogeneously kneaded in a roll mill.

The resulting sealant composition had a swelling degree of 37.0%. However, the composition adhered to the roll mill during the kneading, and was poor in the workability in the roll mill. Further the resulting composition was waxy, had not a sufficient elasticity as a sealant and was easily broken. Therefore, the composition was not suitable as a sealant.

Example 2 A mixture of 100 parts of ethylene-propylenediene terpolymer having a Mooney viscosity ML1+4 of 38 at 1000C, 70 parts of hydrated silicic acid (Nipsil VN3), 40 parts of polybutene having an average molecular weight of 1,260 and 2 parts of stearic acid was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 34.5%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 1 6 hours.

Example 3 A mixture of 100 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 70 parts of silicic acid anhydride (trademark: Aerosil 130, made by Japan Aerosil Co.), 40 parts of polybutene having an average molecular weight of 1,260 and 2 parts of stearic acid was homogeneously kneaded in a roll mill.

The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 43.6%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 1 6 hours.

Example 4 A mixture of 75 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 25 parts of butyl rubber having a viscosity average molecular weight of 450,000, 60 parts of hydrated silicic acid (Nipsil VN3), 40 parts of polybutene having an average molecular weight of 1 ,260, 2 parts of stearic acid and 98 parts of heavy calcium carbonate was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 27.1%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 1 6 hours.

Example 5 A mixture of 75 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 25 parts of butyl rubber having a viscosity average molecular weight of 450,000, 100 parts of synthetic calcium silicate (Solex CM), 50 parts of polybutene having an average molecular weight of 1 ,260, 2 parts of stearic acid and 40 parts of heavy calcium carbonate was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 30.0%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 1 6 hours.

Example 6 A mixture of 75 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 25 parts of butyl rubber having a viscosity average molecular weight of 450,000, 30 parts of hydrated silicic acid (Nipsil VN3), 70 parts of synthetic calcium silicate (Solex CM), 40 parts of polybutene having an average molecular weight of 1,260 and 2 parts of stearic acid was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 37.9%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 14 hours.

Example 7 A mixture of 75 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 25 parts of butyl rubber having a viscosity average molecular weight of 450,000, 90 parts of hydrated silicic acid (Nipsil VN3), 40 parts of polybutene having an average molecular weight of 1,260, 2 parts of stearic acid and 68 parts of heavy calcium carbonate was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 38.2%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 1 6 hours.

Example 8 A mixture of 100 parts of poiyisobutylene having a viscosity average molecular weight of 2,100,000, 100 parts of hydrated silicic acid (Nipsil VN3), 65 parts of polybutene having an average molecular weight of 1,260 and 2 parts of stearic acid was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 55.2%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 1 6 hours.

Example 9 A mixture of 60 parts of polyisobutylene having a viscosity average molecular weight of 1 ,200,000, 40 parts of partially crosslinked butyl rubber (trademark: Polysar Butyl XL-20, made by Polysar Co), 40 parts of hydrated silicic acid (Nipsil VN3), 30 parts of synthetic calcium silicate (Solex CM), 40 parts of polybutene having an average molecular weight of 1,260 and 2 parts of stearic acid was homogeneously kneaded in a Brabender mixer. The resulting homogeneous mixture was continuously molded into a stripshaped sealant through an extruder.

Example 10 A mixture of 100 parts of acrylic rubber (trademark: Hycar 4021, made by Japanese Zeon Co.), 70 parts of hydrated silicic acid (Nipsil VN3), 40 parts of a polyester series plasticizer (trademark: Adekacizer PN400, made by Adeka Chemical Co.) and 2 parts of stearic acid was homogeneously kneaded by means of a Brabender mixer. The resulting homogeneous mixture was continuously molded into a stripshaped sealant through an extruder.

The resulting sealant had a swelling degree of 46%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 16 hours.

Example 11 A mixture of 100 parts of acrylonitrilebutadiene copolymer (trademark: Nipol 1042, made by Japanese Zeon CO.), 60 parts of hydrated silicic acid (Nipsil VN3), 30 parts of synthetic calcium silicate (Solex CM), 40 parts of polybutene having an average molecular weight of 1,260, 20 parts of dioctyl phthalate and 2 parts of stearic acid was homogeneously kneaded in a roll mill. The resulting homogeneous mixture was continuously molded into a strip-shaped sealant through an extruder.

The resulting sealant had a swelling degree of 35%. In a sealing test, water began to leak under a hydraulic pressure of 0.4 kg/cm2, but water was able to be stopped after 16 hours.

Comparative Example 3 A mixture of 75 parts of polyisobutylene having a viscosity average molecular weight of 1,200,000, 25 parts of butyl rubber having a viscosity average molecular weight of 450,000, 113 parts of hydrated silicic acid (Nipsil VN3), 30 parts of polybutene having an average molecular weight of 1 ,260, 2 parts of stearic acid and 98 parts of heavy calcium carbonate was homogeneously kneaded in a roll mill.

The resulting sealant composition had a swelling degree of 49.3%. However, the sealant composition adhered to the roll mill during the kneading, and was poor in the workability in the roll mill. Further, the resulting composition was waxy, had not a sufficient elasticity as a sealant, and was easily broken. Therefore, the composition was not suitable as a sealant.

Example 12 A mixture of 100 parts of polyisobutylene having a viscosity average molecular weight of 1 ,200,000, 70 parts of synthetic calcium silicate (trademark: Florite R, made by Tokuyama Soda Co.), 40 parts of polybutene having an average molecular weight of 1,450 and 2 parts of stearic acid was homogeneously kneaded in a roll mill.

The resulting homogeneous mixture was continuously molded into a stripshaped sealant through an extruder.

Example 13 A composite sealant was produced by using, as a sealant component, a water-swelling sealant produced from the same raw material mixture for sealant as formulated in Example 1 and having a swelling degree of 39.4%. That is, the same raw material mixture for sealant as formulated in Example 1, after homogeneously kneaded in a roll mill, was continuously molded into a strip-shaped sealant molded article having a cross-sectional shape having a thickness of 5 mm and a width of 30 mm.An adhesive was produced by kneading homogeneously 100 parts of partially crosslinked butyl rubber (Polysar Butyl XL-20), 300 parts of polybutene (trademark: 300R, made by Idemitsu Petroleum Chemical Co.), 40 parts of white carbon (Nipsil VN3) and 4 parts of carbon black master batch (trademark: CH52, made by Japan Synthetic Rubber Co.) in a kneader, and was pressed and adhered to all over the upper and lower surfaces of the above obtained strip-shaped sealant molded article to produce a composite sealant.

The composite sealant was applied to a flange made of iron, and another flange made of iron was placed on the former flange through the composite sealanf and pressed and adhered to the former flange. The composite sealant was remarkably superior to the sealant molded article itself, which had no adhesive layer adhered thereto, in the application workability and in the affinity of sealant to flange surface. In a sealing test by applying a pressure between the flanges, a sealing pressure for water of the composite sealant was 5 kg/cm2 which was superior to 4 kg/cm2 of a sealing pressure for water of the sealant molded article itself having no adhesive layer adhered thereto.

Claims

1. A water-swelling sealant obtained by compounding (A) uncrosslinked rubber and/or partially crosslinked rubber with (B) white carbon and (C) a plasticizer to form a sealant composition, provided that the amount of compound (B) is 1845% by weight and that of component (C) is 13 40% by weight based on the total amount of the composition, and molding the composition.

2. A water-swelling sealant, wherein the sealant according to claim 1 is combined with an elastomer having a high restoring property after compression.

3. A water-swelling sealant, wherein an adhesive layer is formed on at least a part of the surface of the sealant according to claim 1.

4. A sealant according to claim 1, wherein the amount of component (B) is 30 40% by weight based on the total amount of the composition.

5. A sealant according to claim 1, wherein component (A) is at least one member selected from the group consisting of butyl rubber, halogenated butyl rubber, polyisobutylene, ethylene-propylene-diene terpolymer rubber and ethylene-propylene rubber.

6. A sealant according to claim 1, wherein component (A) is partially crosslinked butyl rubber.

7. A sealant according to claim 1, wherein component (B) is at least one member selected from the group consisting of silicic acid anhydride and hydrated silicic acid.

8. A sealant according to claim 1, wherein said sealant contains component (B) in an amount of 1435% by weight based on the total amount of the sealing composition.

9. A water-swelling sealant substantially as described in any one of the foregoing Examples 1 to 13.