HK1053490A - Sealing material which swells when treated with water - Google Patents

Description

Water-swellable sealing material

The present invention relates to a water-swellable sealing composition for the manufacture of preformed seals for ground construction, underground engineering and engineering construction, in particular for joint sealing and for compensating for changes in the shape of building components. The sealing composition comprises a combination of an elastomer with a superabsorbent material, such as a polysaccharide, and a hydrophilic polymer, so-called superabsorbents, embedded in a matrix.

Water-swellable sealing compositions are well known.

DE-A-4226198 describes a water-swellable sealing material, in particular for joint sealing and for compensating shape changes in the ground construction, underground works and engineering construction or other technical sectors. The sealant may be made by polymerization of a reactive mixture of monomeric water-soluble or water-miscible acrylic and/or methacrylic acid and/or derivatives thereof. The described sealing material has the disadvantage of using toxic raw materials which, even after curing of the sealing tape, can partially remain in the sealing material and contaminate the environment.

DE-A-3610645 discloses a water-swellable sealing material which comprises a polymeric base material which is not a hydrophobic polymer such as rubber but which is a hydrophilic addition product of a low molecular weight polyolefin polyol and ethylene oxide and contains reactive hydroxyl groups. The composition comprises a saponified PVA-sodium acrylate copolymer, CMC, hydrolyzed polyacrylic acid, a mixture of starch and hydrolyzed polyacrylonitrile, or a mixture of starch and sodium polyacrylate as the water-absorbent polymer. The crosslinking is effected with cyanate esters.

DE-A-3532961 describes a sealing material which comprises water-absorbing substancesThe water-absorbent material is a mixture of a water-absorbent polymer and rubber or a synthetic resin. The water-absorbing polymer is CMC, starch-polyacrylonitrile hydrolysate, starch-polyacrylate and sodium polyacrylate hydrolysate. Foaming the water swelling material to obtain a specific gravity of 0.1-0.9 g/cm³。

EP-A-160438 describes ｃA water-swellable caulking material, the body of which comprises ｃA water-swellable polymeric material and ｃA non-water-swellable material and is surrounded by ｃA layer which is impermeable to water of neutral pH and permeable to alkaline water. The body comprises a water-insoluble rubbery polymer and a super absorbent resin such as a crosslinked polyacrylate, a reaction product of starch and polyacrylic acid, or the like.

US-A-5,011,875 relates to water-swellable caulking compositions of rubber, thermoplastic polymer and water-absorbing material such as acrylic-based polymers, starch-polyacrylic acid graft copolymers, starch-polyacrylonitrile graft copolymers, CMC.

US-A-5,075,373 discloses A water-swellable sealing material comprising particles of A water-absorbent resin, such as A cross-linked polyacrylate, A starch-acrylic acid graft copolymer, A starch-ethyl acrylate copolymer, CMC, embedded in A rubber or synthetic elastomer matrix.

EP-A-118998 relates to ｃA water-swellable sealant material comprising chloroprene rubber mixed with ｃA hydrophilic water-absorbing polymer such as starch-polyacrylate graft copolymer, polyacrylate, poly (meth) acrylate, maleic anhydride copolymer.

EP-A-055848 discloses ｃA water-absorbent rubber mixture consisting of ｃA1, 3-diene rubber and dispersed therein ｃA superabsorbent resin such as ｃA maleic anhydride copolymer, ｃA crosslinked alkali metal polyacrylate.

EP-A-410669 describes ｃA water-swellable sealing composition comprising ｃA vulcanized rubber material, ｃA super absorbent resin such as ｃA poly (acrylic acid) -based resin, ｃA maleic anhydride copolymer, ｃA basic water-absorbent inorganic material, ｃA plasticizer, ｃA vulcanizing agent and usual auxiliaries.

DE-A-19619709 discloses a sealing material comprising a metal sheet with a coating of a superabsorbent polymer, fibres and rubber.

From JP-A-6-157839, there is known ｃA water-swelling type sealing composition containing an unvulcanized resin component composed of ｃA certain uncrosslinked thermoplastic olefinic elastomer and ｃA hydrogenated diene copolymer, and in which ｃA water-absorbent resin and fibers with or without cellulose are present.

However, known sealing materials have disadvantages, particularly when employed in composite seals. Inorganic aggregates can cause severe wear of equipment during the manufacture and processing of seals. The desired extensibility and elasticity is often lost during the drying process. Most sealing materials have too high a specific gravity (> 1 g/cm)³) And has limited flexibility. Further sometimes toxic components.

It is an object of the present invention to provide a water swellable seal material for preformed seals, which is substantially manufactured from non-toxic raw materials and which is amenable to processing into preformed seals, including composite seals. Furthermore, mechanical problems such as wear can be avoided during the manufacture of the seal. The swelling properties meet the specific requirements of surface construction, underground engineering and engineering construction.

This object is achieved by means of a water-swellable sealing composition for preformed seals, comprising a matrix of an elastomer component and an embedded particulate water-absorbing material, characterized in that the water-absorbing material is a combination of (a) a polysaccharide selected from the group consisting of microcrystalline or amorphous cellulose, starch derivatives of non-grafted starch, amylose, amylopectin, dextran, pectin, inulin, chitin, xanthan gum, alginic acid, alginate, carrageenan, umbilicin, guaiazuoglucan, laminarin, gulonic acid, pullulan, lichenin or mixtures thereof, and (B) a superabsorbent synthetic polymer; (B) the superabsorbent synthetic polymer is selected from (meth) acrylic acid based polymers, poly (meth) acrylic acid and its salts, polyacrylamides, polyols or copolymers of the above synthetic polymers. The sealing composition is foamed by means of a foaming agent and heating to a temperature of 100 ℃ or more, and the elastomer component is crosslinked.

Mixtures of superabsorbent synthetic polymers may also be employed.

The water swelling type sealing composition comprises 6.67 to 600 parts by weight of a polysaccharide and 2.67 to 100 parts by weight of a super absorbent synthetic polymer per 100 parts by weight of an elastomer component.

The sealing composition of the present invention includes a foaming agent, which is foamed by heating to 100 ℃ or more.

After the rubber is vulcanized or crosslinked into an elastomer to form an elastomer component, the sealing composition of the present invention expands in volume by 5 to 600 vol.% after 3 to 7 days of immersion in water.

It is particularly preferred to adjust the swelling properties by a suitable choice of the type and percentage of polysaccharide to superabsorbent synthetic polymer, the porosity of the rubber and elastomer, the crosslinking reaction, the hardness, more particularly to create a preformed seal with a relatively poor swelling capacity with a volume expansion of 5-30 vol.%, particularly preferred with a volume expansion of 10-20 vol.%, and/or a preformed seal with a relatively strong swelling capacity with a volume expansion of more than 50-500 vol.%.

The preformed sealing member/composite sealing member can be made into an endless shaped material in the form of a band, a round strand and a cross section having various shapes.

The composite or non-composite sealing element can be used for sealing building structures in ground buildings, underground engineering or ditch engineering, industrial engineering and other applications requiring water swelling type sealing materials.

The invention also provides a process for the production of a water-swellable preformed seal from a sealing composition comprising a matrix of an elastomer component and an embedded particulate water-absorbing material, which comprises mixing the components in a mixing mill, internal mixer or extruder, and then shaping, foaming and crosslinking the elastomer component so that the volume expansion after 3-7 days of immersion in water is from 5 to 600 vol.%.

The sealing composition of the present invention typically further comprises one or more conventional additives such as lubricants, anti-aging agents, dyes, fillers, foaming agents, plasticizers, rubber crosslinking agents, crosslinking accelerators, activators, retarders, elastomer crosslinking agents.

Useful fillers include, in particular, precipitated and/or pyrogenic silicas, silicates, sand, mineral powders such as quartz, talc, mica, chalk, kaolin, gypsum, lime, dolomite, basalt, diatomaceous earth, barite, feldspar, carbon black, polymeric hollow pigments, wood flour, rubber powders.

Useful plasticizers include mineral oils of the alkane, cyclic or aromatic type, ester plasticizers such as dioctyl phthalate, ester plasticizers based on adipates and sebacates, phosphate esters, stearic acid, palmitic acid, castor oil, cottonseed oil, rapeseed oil, but also polymeric plasticizers such as low molecular weight rubbers.

Useful rubber crosslinking or vulcanizing agents and elastomer crosslinking agents are those commonly used for this purpose, such as sulfur, sulfur-containing compounds, peroxides, and the like.

Basically, the crosslinking reaction can also be carried out by electron beam irradiation.

The crosslinking or vulcanization reaction is carried out using the procedures customary in industrial applications.

The elastomer component present in vulcanized or crosslinked form in the final sealing composition is selected from Natural Rubber (NR), trans-1, 4-polyisoprene rubber (IR), polybutadiene (BR), randomly copolymerized styrene-butadiene rubber (SBR or SIR), acrylic rubber, acrylonitrile-diene rubber (NBR or NIR), polychloroprene (CR), ethylene-propylene rubber (EPR), isobutylene-isoprene rubber (IIR), ethylene-propylene-diene rubber (EPDM), epichlorohydrin rubber, silicone rubber, polysulfide rubber, polyurethane, thermoplastic elastomers.

Mixtures of elastomers may also be used.

The elastomeric component imparts particularly good mechanical properties to the seal material, such as higher elasticity and ductility.

The selected polysaccharide, which is highly hydrophilic, absorbs water during contact and serves to transfer water into the sealing composition and also has a swelling function.

The water-insoluble but water-swellable microcrystalline or amorphous cellulose used in the sealing composition of the present invention has an average particle size of usually 30 μm to 200 μm; if the particles are of the type, the average particle size is from 350 to 800. mu.m.

The bulk density of the cellulose with the smaller particle size is preferably from 40g/l to 300g/l, very particularly preferably from 65g/l to 170 g/l. If the pellet type is used, the bulk density is higher and may be 350g/l to 550 g/l.

The starch/starch derivatives may be derived from various routes, such as starch from rice, corn, wheat, potato and legumes. Corresponding powders containing cellulosic plant components may also be used. Cold swelling starches are preferred.

Polygalactomannans in their natural form, such as guar or carob flour, fulfill this property and can be used directly or after slight modifications.

Starches which are not themselves cold water swellable are preferably employed in the form of their derivatives. The chemically derivatized starch preferably contains substituents bonded to the polysaccharide molecular chain with a sufficient number of ester or ether groups to ensure its cold water swelling properties.

Starches modified with ionic substituents such as phosphate groups are particularly suitable and are therefore preferred. It is further possible to use cold water-swellable starches of degraded starch varieties, such as acid-, enzyme-or oxidatively degraded starches or dextrinized starches. The swelling property of the starch derivative is generally preferably modified by degradation and chemical substitution.

To improve the swelling properties, lightly crosslinked starches may also be used. Even alkali-treated starches may be used because of their cold water-soluble properties.

A further option for cold water swellable starches useful for the purposes of the present invention is native starches which have been physically treated to provide the desired cold swelling properties. Including, for example, extruder starch and drum dryer starch.

To increase the water absorption and in particular the associated volume expansion, the sealing composition comprises a synthetic polymer in the form of highly swellable particles or powder. Particularly useful are linear polymers of (meth) acrylic acid having a weight average molecular weight of 5,000-70,000, copolymers of (meth) acrylic acid or salts thereof and crosslinked polymers of (meth) acrylic acid having a weight average molecular weight of 1,000,000-5,000,000, copolymers of (meth) acrylic acid or salts thereof. The copolymers are preferably copolymers of (meth) acrylic acid with maleic acid or maleic anhydride, for example 40 to 90% by weight of (meth) acrylic acid with 60 to 10% by weight of maleic acid or maleic anhydride, with a relative molar mass of 3000 to 100,000, preferably 3000 to 70,000, and particularly preferably 5000 to 50,000, based on the free acid.

Also useful have been tri-and tetrapolycarboxylic acids prepared from (meth) acrylic acid, maleic acid and vinyl alcohol or vinyl alcohol derivatives or from (meth) acrylic acid, ethylenically unsaturated sulfonic acids and sugar derivatives or from (meth) acrylic acid, maleic acid and vinyl alcohol derivatives and sulfo-containing monomers.

Particular preference is given to tri-and tetrapolycarboxylic acids prepared from (meth) acrylic acid, maleic acid and vinyl alcohol or vinyl alcohol derivatives (cf. DE-A-4300772) or from (meth) acrylic acid, 2-alkylallylsulfonic acid and sugar derivatives (cf. DE-A-4221381) or from (meth) acrylic acid, maleic acid and vinyl alcohol derivatives and monomers having sulfonic acid groups (cf. DE-A-19516957).

Synthetic polymers or superabsorbents are crosslinked polymers which have the ability to absorb and bind many times their own weight of water to form hydrogels and thus also swell with water, even if present in small amounts, resulting in a large increase in the volume of the sealing material.

Superabsorbers used according to the invention can, for example, bind up to 600g of water/g of superabsorbent, in some cases even up to 900g of water/g of superabsorbent.

Superabsorbers are particularly preferably capable of absorbing 75g to 200g of water per g of superabsorbent in 50 s.

The average particle size of the superabsorbent polymer is preferably in the range from 5 μm to 800. mu.m. However, products having an average particle size of less than 400 μm are preferred. However, products having an average particle size of 400-800 μm may also be used, if desired.

Very fine superabsorbent particles are preferably used. Superabsorbent particles having an average particle size of 70 to 150 μm do not fall out or swell out of the elastomer matrix, but larger particles of 100 to 800 μm may partly fall out on first swelling and reduce the swelling ratio on re-swelling. In the case of coarse-particle superabsorbers (100 to 800 μm), the accumulation of constituents which can be eluted by water amounts to about 3.5 wt.%, whereas the elution percentage for superabsorbers with finer particles amounts to only 2 to 3 wt.%.

Superabsorbents having the following average particle size distribution are particularly useful:

particle size μm	Average%	Average%	Average%
					Particle size distribution%, sample 1	Particle size distribution%, sample 2	Particle size distribution%, sample 3
				＞800	1.3	0	0
800-560	30.9	0	0
				560-400	30.8	0	0
400-250	19.7	0	0
				250-200	8.0	2.2	0
200-160	3.1	9.6	0
				160-100	4.0	44.6	59.1
100-50	0.2	29.3	37.7
				＜50	0	10.5	2.3

Sample 1: favor SAB 954, sample 2: favor CA100Feinstkorn, sample 3: cabloc C96

The particle size distribution was determined as follows:

10.00g of each swellable medium was weighed on an analytical balance and placed at 800; 560; 400, respectively; 250 of (a); 200 of a carrier; 160; on top sieves of 100 and 50 μm size sieve groups. Followed by a medium intensity shaker set for about 5 min. The product was then weighed back on an analytical balance after each sieve was fully tapped. Each product was assayed in triplicate.

The amounts of the polysaccharide (A) and the synthetic polymer (B) are 6.67 to 600 parts by weight of the polysaccharide (A) and 2.67 to 100 parts by weight of the synthetic polymer (B) per 100 parts by weight of the elastomer component. The polysaccharide (A) is preferably present in an amount of from 12.5 to 553.33 parts by weight, very particularly preferably from 33.3 to 100 parts by weight, per 100 parts by weight of elastomer component in the sealing composition according to the invention.

The amount of the super water-based agent polymer is preferably 12.5 to 37.5 parts by weight per 100 parts by weight of the elastomer component.

The elastomer component is selected from the group consisting of vulcanized Natural Rubber (NR), vulcanized trans-1, 4-polyisoprene rubber (IR), vulcanized polybutadiene (BR), vulcanized random copolymer styrene-butadiene rubber (SBR or SIR), vulcanized acrylic rubber, vulcanized acrylonitrile-diene rubber (NBR or NIR), vulcanized polychloroprene (CR), vulcanized ethylene-propylene rubber (EPR), vulcanized isobutylene-isoprene rubber (IIR), vulcanized ethylene-propylene-diene rubber (EPDM), vulcanized epichlorohydrin rubber, vulcanized silicone rubber, vulcanized polysulfide rubber, crosslinked polyurethane, crosslinked thermoplastic elastomer.

The sealing compositions of the invention may contain the following amounts of customary auxiliaries, based on 100 parts by weight of elastomer component:

filler material	533-.0	Parts by weight
			Lubricant agent	114.3-0	Parts by weight
Anti-aging agent	15.4-0	Parts by weight
			Dye material	15.4-0	Parts by weight
Activating/accelerating agent	15.4-0	Parts by weight
			Crosslinking agent	15.4-0	Parts by weight
Foaming agent	66.7-0	Parts by weight
			Plasticizer	114.3-0	Parts by weight

In the case of the water-swellable sealing materials of the invention used in conventional sealing systems, the sealing elements can be quickly adapted to the desired basic shape, in particular the shape of the joint, because of their high swelling capacity. This effectively prevents the water seepage phenomenon that generally occurs at an earlier stage of the destruction. If the sealing material is used as a profile for the joint, the profile can swell in contact with water and can adapt to changes in the volume of, for example, the structural body. The adjustment slit during the forming of the profile at the joint will achieve self-sealing due to the fast, size-adjustable and controllable swelling behaviour.

Because there is no problem of friction, the sealing material of the present invention has greatly improved processability as compared to known sealing materials comprising bentonite and rubber. Furthermore, the sealing material according to the invention is very resistant to elution with water, the percentage of eluting components not exceeding 2%, based on the initial mass of the tape. Furthermore, the sealing material of the present invention is manufactured from non-toxic main components, compared to sealing materials comprising acrylates/methacrylates or isocyanates. The foamed sealing material of the present invention has a low density, greatly reduces the demand for raw materials and facilitates a suitable reduction in the cost of the sealing material.

The sealing material of the present invention does not significantly harden during drying, as compared to the water-swellable acrylate sealing material that hardens during drying due to loss of the plasticizer effect.

It is particularly desirable to foam the composition of the present invention to reduce the specific gravity. This can be achieved by the processes known per se for foaming elastomers. Useful blowing agents include water, ammonium bicarbonate, sodium bicarbonate or organic blowing agents such as sulfonyl hydrazide (1, 3-disulfonyl benzenedihydrazide) or azodicarboxamide (azobiscarboxamide), 5-morphinyl-1, 2, 3, 4-thiatriazole.

Not only open-celled foams but also closed-celled foams can be produced.

Foaming further improves the water swelling properties.

The specific gravity of the composition of the invention in the foamed state is in the range of 0.01g/cm³～1.5g/cm³. When fillers are used in combination, the specific gravity is generally higher, particularly at higher levels, than at lower levels.

The volume expansion of the preformed seal test piece by the action of water was determined as follows:

a sample, for example 5cm long, is placed in 500ml of water having a pH of 7 and a German hardness of 10 ℃ in a 600ml glass beaker, and is required to be completely immersed in water and swollen at 230 ℃. Then, samples are taken out of the swollen water at regular intervals, the adhering water is sucked off with filter paper and the swelling tape is measured within 1min after immersion in a water-filled portion (e.g. 10cm in volume)³(5 cm. times.1 cm. times.2 cm) in a100 ml measuring cylinder containing 50ml of water). The sample was then placed in water with a German hardness of 10 ℃ for further swelling.

The volume expansion is then the relative percentage of the volume increase, i.e. the

The volume before swelling can be calculated in the case of regular geometry, but is also determined by the volume expansion during immersion in water, the immersion and reading being carried out within 20 s.

Preformed seals made from the sealing composition of the present invention swell 5-60 vol.% after 3-7 days of submersion.

The seal required for the present invention, which has relatively poor swelling properties, swells 5 to 30 vol.%, preferably 10 to 20 vol.% after 3 to 7 days of immersion in water.

The sealing member with relatively strong swelling performance has swelling more than 50-500 vol% after being soaked in water for 3-7 days.

To delay the time for the preformed seal to begin swelling under the action of water, a relatively stable and/or impermeable film of water having a near neutral pH is applied over at least a portion of the surface of the preformed seal to effect a seal.

For the purpose of the present invention, the near neutral pH at which the topcoat film is water/water impermeable is in the range of 5 to 9, and not only pH 7. The topcoat film is permeable to water upon contact with water in the alkaline range, i.e., a pH greater than 9.

The relative water resistance or water impermeability can be adjusted by the thickness of the coating. The layer thickness is generally from 5 μm to 500. mu.m, preferably from 20 μm to 300. mu.m.

The topcoat film comprises a matrix of a film-forming polymer of virtually water insoluble material embedded with a particulate alkali soluble material. The matrix is particularly preferably composed of the same elastomer component as the sealing composition of the invention. Useful alkali-soluble materials include weakly acidic polymers such as lower olefins or copolymers of styrene and maleic anhydride, polyacrylic or polymethacrylic acids, polyacrylates or polymethacrylates, or alkali-soluble inorganic materials such as aluminum phosphate, basic zinc carbonate, metal powders of amphoteric metals such as aluminum.

The topcoat film may be applied in various ways. Such as coating the surface of the preformed seal with a solution or dispersion of the components.

In one embodiment of the invention, the structure of the preformed seal is a composite seal, compounded with at least two or more portions differing in water-swelling properties.

Depending on the shape of the preformed sealing member, as a band, a round strand, an endless profile, the structure of the parts may be parallel layers or a layer which more or less participates in forming a part. The swelling behavior of the portion or portions embedded in the profile surface can be different for each profile than for the main portion of the profile.

Generally, in the embodiment of the composite type seal, a portion having a relatively poor swelling property is composited with a portion having a relatively strong swelling property.

In order to retard swelling during immersion in water, it is also possible, for example, to form the inner core of a composite seal with a sealing composition having relatively high swelling properties and to at least partially or completely encapsulate this inner core with a layer of a sealing composition having relatively low swelling properties.

When a less strongly swelling layer is applied to the outer layer of the preformed seal, then the swelling rate at the beginning is small and can only be increased gradually. This is required in market applications so that preformed seals do not swell violently, i.e. lose some of their swelling properties, at the job site, for example by contact with rain, and then the pre-swollen seal material has a greatly reduced swelling property when contacted with water or dries and then shrinks at the job site, then the initial sealing effect is lost.

However, it is also possible to form a composite type sealant having an inner core line which has a lower swelling property than an outer layer tape which at least partially surrounds it and is made of a sealant composition having a high swelling property.

The swelling properties of the sealing composition can be adjusted by varying the above parameters affecting the swelling properties: the percentage of polysaccharide selected, the percentage of synthetic polymer, the degree of foaming or density and porosity of the material, the degree of crosslinking and hardening.

Examples of changes in swelling properties are given in the following table:

material	Rubber mixtures of example 1	Super absorbent Cabloc C96	Starch	Preformed seal density g/cm3	Swelling degree (volume)%
						Slightly strong swelling type	50	10	35	> 1, not foamed	＜10(5)*
Slightly strong swelling type	35	2.5	62.5	0.66	＜25(20)*
						Slightly strong swelling type	50	5	45	0.54	＜30(25)*
High strength swelling type	50	15	35	0.52	＞100(120)*
						High strength swelling type	35	15	50	0.57	＞300(400)*

Swelling degree: the value reached after 3-7 days; swelling in water with pH 7 and German hardness 10 deg.C at 23 deg.C to obtain sample 5cm × 2cm × 2 cm; swelling after 5 days).

Particularly preferred sealing compositions comprise a mixture of natural rubber, starch and superabsorbent; foaming is carried out by heating with the aid of water contained in the material or an added foaming agent and subsequent vulcanization. Foamed elastomer, a rubber sponge material, is advantageous in use because of its lower density, since it is then more numerous and easier to handle and install in building structures. It is particularly preferred that the swelling capacity of the foamed material is many times higher and faster than that of an unfoamed material of the same composition.

The sealing composition of the invention can be manufactured in any possible form, in particular in the form of a tape, a sheet, a bale or a profile of any desired geometry. Depending on the desired application, for example, tapes can be made for joint sealing and sheets for building exterior seals.

For preformed seals, shaping can be carried out using subsequent roll calenders with size correction devices, injection or compression molding, or extruders equipped with slot dies, circular section dies, or forming dies.

When the sealing composition includes a foaming agent, the rubber and/or elastomer may be vulcanized or crosslinked by heating to 100 ℃ or higher for foaming during molding so that the specific gravity thereof is in the range of 0.01g/cm³～1.5g/cm³。

For preformed composite seals formed of at least two or more portions of differing water-swellable properties, the sealing compositions of differing water-swellable properties are formed together or sequentially, such as by coextrusion for integration. Other molding processes suitable for co-molding may be used.

In one embodiment of the preformed composite sealing member, the sealing composition has a different water swelling property due to the sealing composition having a volume swelling of 5 to 30 vol.% after being immersed in water for 3 to 7 days and the sealing composition having a volume swelling of 50 to 500 vol.%.

Examples Example 1c) Preparation of the mixture

The rubber compound of the sealing material was manufactured using a laboratory scale mixing roll supplied by Schwabenthan of Berlin. The speed ratio of the rear roller to the front roller (friction) is about 1.2. The front roller speed was about 12 rpm; roll temperature: 60 ℃; the mastication time is as follows: 5-30 min.

100 parts of natural rubber (SMR, Uniroyal Aachen) were placed on a roll having a roll width of about 3 mm. The roll gap is reduced until a continuous sheet is carried around the front roll. In order to accelerate mastication, the rubber was repeatedly cut with a knife edge. Mastication degrades the rubber and thus forms the desired consistency.

After mastication, 1.5 parts zinc oxide (active), 2.5 parts sulfur (90% crystalline), 0.1 part dibenzothiazyl disulfide (Vulkazit DM, Bayer AG, Leverkusen), 1.2 parts diethyl zinc dithiocarbamate (Vulkazit LDA, Bayer AG, Leverkusen), 0.4 parts tetramethyl Thiuram disulfide (Vulkazit Thiuram, Bayer AG, Leverkusen), 1 part stearic acid and 5 parts Porofor TSH (foaming agent, Bayer AG, Leverkusen) were mixed in.

50 parts of the rubber mixture are then mixed with 35 parts of potato starch (from MullersMuhle) and 15 parts of superabsorber (from Cabloc C96, from Stockhausen Krefeld) mixed in advance, and added in portions until the starch-superabsorber of the previous time has been absorbed by the rubber. The sheet was taken out and 3mm thick. d) Foaming, shaping, crosslinking

The resulting pieces of about 120g were cut into strips of about 1-1.5cm in width. The strips were pressed together one above the other and placed on a strip of about 50cm in length and 2cm x 2cm in internal cross-section. The mold was closed and placed in a100 ℃ oven for 30 min. The oven was then heated to 160 ℃ (for about 20 min). And taking the mold out of the oven box after reaching the temperature, rapidly cooling and demolding the belt body. The density of the sealing tape obtained by the method is 0.5-0.7 g/cm³。Example 2

The tablets from example 1a were introduced into an extruder (Brabender, manufactured by Duisburg) and all the heating zones and the die were adjusted to 80 ℃. The die diameter was 3mm and the barrel diameter 2.1 cm. The screw was operated at 50 rpm. The sausage-shaped extrudate is introduced into a furnace and foamed at 100 ℃ for 30min and then vulcanized at 160 ℃.Example 3

Example 1 was repeated, partially replacing or increasing the starch content to produce sealing compositions with different percentages of superabsorber (5 to 20 parts).

Swelling performance tests have shown that sealing materials comprising 15 to 20% superabsorbent have a swelling capacity of 50 vol.% after 3 days, whereas sealing compositions comprising 10 parts superabsorbent swollen only 20 vol.% and sealing compositions comprising 5 parts superabsorbent only 10 vol.%.

It is therefore noted that the amount of superabsorbent has a great influence on the swelling properties of the sealing composition.Comparative example 1

Example 1 was repeated to produce a sealing composition comprising 15 parts of superabsorbent but no starch.

Swelling performance tests showed that the swelling capacity of the sealing material without starch was 1 vol.% after 3 days, whereas the swelling capacity of the sealing composition of example 1, which contained 15 parts of superabsorbent and 35 parts of potato starch, was 50 vol.% after 3 days.

Thus, combinations of polysaccharides with superabsorbent synthetic polymers are notedIs essential for the swelling properties of the sealing material.Example 4

Example 1 was repeated and the tablets were kneaded from 100 parts of natural rubber, 5 parts of zinc oxide (active), 1 part of antioxidant WSL, 1 part of stearic acid, 3 parts of sulfur (90% crystalline), 1.5 parts of Vulkazit D (Bayer AG, Leverkusen) at 40 ℃ via mixing rolls. 50 parts of the rubber mixture are then mixed via mixing rolls with 40 parts of potato starch, 5 parts of Favor SAB superabsorbent and 5 parts of sodium bicarbonate.

The mass swell given by the tablets in the unfoamed and uncured state is only 20%, even after 11 days. The density is about 1.04g/cm³. On the contrary, the density is about 0.5 to 0.6g/cm³Gives a mass swelling of 500% at the end of 7 days.

It is therefore noted that the foaming treatment or the density of the sealing material has a decisive influence on the swelling properties of the composition.Example 5

The foam of example 4 was vulcanized at 160 ℃ and had a mass swell of 300% after 7 days.

It is therefore noted that vulcanization or crosslinking of the rubber/elastomer component has a significant effect on the swelling properties of the material.Example 6

Example 4 was repeated, using superabsorbers of finer particle size: favor CA100Feinstkorn, Stockhausen, manufactured by Krefeld, to make a sealing composition.

Swelling performance tests have shown that the use of superabsorbents with a finer particle size greatly reduces the visible detachment or swelling of the superabsorbents, so that no superabsorbents are found on the surface of the swollen belt anymore. The amount of eluting component was 3.5 wt.% when using a coarse superabsorbent and 2.9 wt.% when using a finer superabsorbent.

It is therefore noted that the particle size of the superabsorber has an important influence on whether it remains in the material during the swelling process or is still eluted to a certain extent.Example 7

Example 2 was repeated to produce a sealing composition without superabsorbent, but instead with swellable alginate. 50 parts of the rubber mixture of example 1 were mixed with 10 parts of alginate and 40 parts of potato starch, 15 parts of alginate and 35 parts of potato starch, and also 20 parts of alginate and 30 parts of potato starch.

The swelling performance test shows that 20 parts of alginate gives a 50% volume expansion. However, in this process, 10% by weight of the sealing material was eluted and reached only 50 vol.% during the re-swelling.

It is therefore clearly noted that a certain particle size is required for a firm adhesion in the elastomer matrix, which according to example 6 should not be too large at first, and which is also insoluble in water, since water-soluble alginates can be eluted.

Claims (19)

1. A water-swellable sealing composition for a preformed seal comprising a matrix of an elastomeric component and, embedded therein, a particulate water-absorbing material which is a combination of (a) a polysaccharide selected from the group consisting of microcrystalline or amorphous cellulose, starch derivatives other than grafted starch, amylose, amylopectin, dextran, pectin, inulin, chitin, xanthan, alginic acid, alginates, carrageenans, umbilicin, guaiaglucan, laminarin, gulonic acid, pullulan, lichenin or mixtures thereof, and (B) a superabsorbent synthetic polymer; (B) the superabsorbent synthetic polymer is selected from (meth) acrylate based polymers, poly (meth) acrylic acid and its salts, polyacrylamides, polyols or copolymers of the above synthetic polymers, the sealing composition is foamed by means of a foaming agent and heating to a temperature of 100 ℃ or more, the elastomeric component being crosslinked.

2. The water-swellable composition of claim 1, characterized in that it comprises 6.67 to 600 parts by weight of the polysaccharide (A) and 2.67 to 100 parts by weight of the synthetic polymer (B) per 100 parts by weight of the elastomer component.

3. A sealing composition according to any preceding claim, characterised in that the rubber/elastomer component is selected from the group consisting of vulcanised Natural Rubber (NR), vulcanised trans-1, 4-polyisoprene rubber (IR), vulcanised polybutadiene (BR), vulcanised randomly copolymerised styrene-diene rubber (SBR or SIR), vulcanised acrylate rubber, vulcanised acrylonitrile-diene rubber (NBR or NIR), vulcanised polychloroprene (CR), vulcanised Ethylene Propylene Rubber (EPR), vulcanised isobutylene-isoprene rubber (IIR), vulcanised ethylene-propylene-diene rubber (EPDM), vulcanised epichlorohydrin rubber, vulcanised silicone rubber, vulcanised polysulphide rubber, cross-linked polyurethane, cross-linked thermoplastic elastomers.

4. A sealing composition according to any one of the preceding claims 1 to 3, characterised in that the superabsorbent synthetic polymer has an average particle size in the range of from 5 μm to 800 μm.

5. Sealing composition according to any one of claims 1 to 4, characterized in that it comprises one or more usual additives selected from the group consisting of lubricants, anti-ageing agents, dyes, fillers, blowing agents, plasticizers, crosslinking agents, crosslinking accelerators, activators, retarders.

6. A sealing composition according to any one of claims 1 to 5, characterised in that it has a specific gravity in the range of 0.01g/cm³～1.5g/cm³。

7. A sealing composition according to claim 6, characterised in that the volume expansion after 3 to 7 days immersion in water is 5 to 600 vol.%.

8. A sealing composition according to claim 7, characterised in that the volume expansion after 3-7 days of immersion in water is 5-30 vol.%, preferably 10-20 vol.%.

9. The sealing composition of claim 7, characterized in that it expands in volume by more than 50 vol.% to 500 vol.% after 3-7 days of immersion in water.

10. A sealing composition according to any one of claims 1 to 9, characterised in that it is preformed into a tape, round strand, endless profile.

11. A sealing composition according to claim 10, characterised in that the structure of the preformed sealing member is a composite sealing member formed of at least two or more portions differing in water-swelling properties.

12. A sealing composition according to claim 11, characterised in that the composite seal comprises one or more portions which expand in volume to 5-30 vol.% after 3-7 days of immersion in water and one or more portions which expand in volume in excess of 50 vol.% to 500 vol.%.

13. Sealing composition according to any of claims 10 to 12, characterized in that the swelling of the preformed seal or composite seal under the action of water is substantially delayed at least over a part of the surface of the preformed seal or composite seal by means of a layer of a water-labile and water-permeable top coat film which is substantially stable and/or impermeable with respect to water having a near neutral pH value but is unstable and water-permeable with respect to water having an alkaline pH value.

14. A process for the manufacture of a preformed sealing member capable of swelling under the action of water from a sealing composition comprising a matrix of elastomer components and an embedded particulate water-absorbing material according to any one of claims 1 to 9, which comprises mixing the components in a mixer, internal mixer or extruder and then shaping, wherein the sealing composition is foamed and the crosslinked elastomer component is formed by means of a foaming agent and heating to a temperature of 100 ℃ or more, so that the volume expansion after 3 to 7 days of immersion in water is from 5 to 600 vol.%.

15. The process according to claim 14, characterized in that the shaping is carried out subsequently with a sizing device, a roller calender for injection molding or compression molding or an extruder equipped with a slot die, a circular section die or a die.

16. A process according to claim 14 or 15, characterised in that the foamed sealing composition has a specific gravity in the range of 0.01g/cm³～1.5g/cm³。

17. A process according to any one of claims 14 to 16, characterised in that a preformed composite sealing member having at least two or more portions differing in water-swelling properties is formed by co-moulding a sealing composition which expands by 5 to 30 vol.% and 50 to 500 vol.% after 3 to 7 days of immersion in water.

18. A process according to any one of claims 14 to 17 for the manufacture of a preformed seal capable of swelling upon exposure to water, characterised in that a substantially pH neutral water-labile and water-permeable top coat film is applied over at least part of the surface of the preformed seal or composite seal, which top coat film is substantially pH stable and/or impermeable but at a basic pH, so that swelling upon exposure to water is substantially delayed.

19. Use of a sealing composition according to any one of claims 1 to 13 and/or obtained by the process of claims 14 to 18 for sealing building structures in ground construction, underground works or trench works.