Water-sealing sheet

Abstract: A water-sealing sheet comprises a water-swelling resin (C) obtained by kneading a non-water-swelling thermoplastic resin (A) and a water-swelling material (B).

Description: The present invention relates to a water-sealing sheet used in the various civil engineering and construction works. In the various civil engineering and construction works, water-sealing sheets for preventing water leakage have been conventionally used 1 between the segment of sealed tunnel and the second covering, 2 between water-sealing boards such as steel sheet pile and concrete, 3 between underground continuous wall and concrete, and 4 between the junction portion of box culvert and its outer peripheral portion. Examples used as the above-mentioned water-sealing sheet include polyvinyl chloride sheets such as plasticized PVC sheet and ultra plasticized PVC sheet which are excellent in the elasticity and has the ductility to follow the crustal movement. However, in spite of the fact that these polyvinyl chloride sheets have a tensile strength of 14 MPa (140 kgf/cm 2 ) or more, they are easy to suffer from tears or pinholes by scratching during the processing work and water leakage cannot be prevented reliably. On the other hand, water-sealing sheets comprising water-swelling urethane resin have been also used in the various civil engineering and construction works. However, although these sheets have durability, there are such problems as that they have not the sufficient elasticity, so that the following the crustal movement is insufficient. JP-A-60-044575 discloses waterproof sheets formed from a composition comprising a hard thermoplastic resin, a water-swellable urethane resin and optionally a plasticizer. EP-A-0055848 discloses a water-absorbing rubber composition comprising a 1,3-diene rubber (e.g. a chloroprene rubber) and a highly water-absorbing resin dispersed in said rubber. The object of the present invention is to provide an improved water-sealing sheet which can solve the problems of the conventional water-sealing sheet, that is, a water-sealing sheet capable of preventing the water leakage resulted in tears or pinholes by scratching and capable of following the crustal movement efficiently. The present invention has been achieved the above object by providing a water-sealing sheet comprising a water-swelling resin (C) obtained by kneading together: 10 to 97% by weight of a non-water-swelling thermoplastic resin (A) being a polyvinyl chloride, 3 to 90% by weight of a water-swelling material (B) being a water-swelling urethane resin including prepolymer(s) having isocyanate groups, in which the content of terminal NCO groups amounts to 1 to 12%, preferably 2 to 7%, obtained by the reaction of one or more polyether polyols represented by the following general formula and polyisocyanate; R[(OR l )n OH]p wherein R represents a polyhydric alcohol residue; (OR l )n represents a polyoxyalkylene chain comprising oxyalkylene groups each having an oxyethylene group and an alkylene group carrying three or four carbon atoms, provided that the content of the oxyethylene groups amounts to 20 to 100% of the total molecular weight; n is a number corresponding to the degree of polymerization of the oxyalkylene groups and giving a hydroxyl group equivalent of 200 to 2500; and p is a number of 2 to 8, preferably 2 to 4, and additionally 80 to 200 parts by weight of a plasticizer based on 100 parts by weight of said polyvinyl chloride. The water-sealing sheet of the present invention is capable of preventing the water leakage resulted in tears or pinholes by scratching, which are disadvantages of the conventional water-sealing sheets made of polyvinyl chloride, and capable of following the crustal movement reliably. Therefore, the water-sealing sheet of the present invention can be effectively used 1 between the segment of sealed tunnel and the second covering, 2 between water-sealing boards such as steel sheet pile and concrete, 3 between underground continuous wall and concrete, and 4 between the junction portion of box culvert and its outer peripheral portion, for prevention water leakage. Fig. 1 is a side view of a test apparatus for carrying out the water-sealing test of the water-sealing sheet. Fig. 2 is a plane view of the test apparatus shown in Fig. 1. The present invention will be described in detail. Examples of the polyhydric alcohol represented as R (polyhydric alcohol residue) in the above-described general formula include aliphatic dihydric alcohols such as ethylene glycol, propylene glycol, 1,4-butylene glycol and neopentyl glycol; trihydric alcohols such as glycerol, trioxyisobutane, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-1,2,3-propanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-pentanetriol, 2,3,4-hexanetriol, 4-propyl-3,4,5-heptanetriol, 2,4-dimethyl-2,3,4-pentanetriol, pentamethyl glycerol, pentaglycerol, 1,2,4-butanetriol, 1,2,4-pentanetriol and trimethylolpropane; tetrahydric alcohols such as erythritol, pentaerythritol, 1,2,3,4-pentanetetrol, 2,3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol and 1,3,4,5-hexanetetrol; pentahydric alcohols such as adnite, arabitol and xylitol; and hexahydric alcohols such as sorbitol, mannitol and iditol. The polyether polyols represented by the above-described general formula may be obtained by adding alkylene oxide having 3 to 4 carbon atoms and ethylene oxide to these polyhydric alcohol in such a conventional manner as to give the desired molecular weight and to give the desired content of the ethylene oxide group. Either random or block addition of the alkylene oxide having 3 to 4 carbon atoms and the ethylene oxide may be employed therefor. The content of the oxyethylene group based on the molecular weight of polyether polyols ranges from 20 to 100% by weight. When the content of the oxyethylene group is less than 20%, the swelling ratio of the prepolymer having isocyanate groups obtained by reacting isocyanate becomes small, so that sufficient water-proof cannot be obtained. Example of the polyisocyanate include any polyisocyanates such as 1,4-butane diisocyanate, 1,6-hexane diisocyanate, dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, 1,5-bis-isocyanato-1,3,5-trimethyl-cyclohexane, 1,3-bis-(isocyanatomethyl)-benzene and methylcyclohexane diisocyanate. Fatty acid triisocyanate may be employed together partially. Preferable Examples of aromatic polyisocyanate include any aromatic diisocyanates such as 2,4- or 2,6-tolylene diisocyanate or their isomer mixtures; 4,4'-diphenylmethane diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, m- or p-phenylene diisocyanate, 1,5-naphthylene diisocyanate and their isomers. Further, aromatic polyisocyanate having carbodiimide-, urethodione-, urethane-, urethoimine- or biuret group or isocyanurate circles may be employed alone or together. The prepolymer having isocyanate groups thus obtained can be used independently or simultaneously with an active hydrogen compound by kneading. The active hydrogen compound is polyol, polyamine or a mixture thereof each having 2 to 6 active hydrogen atoms per one molecule and having an average molecular weight per active hydrogen atom of 30 to 15,000, for example, low-molecular weight di or triols such as ethylene glycol, 1,4-butanediol, glycerol and trimethylol propane; polyalkylene glycols such as polypropylene glycol, ethylene oxide-propylene oxide copolymers; polymers of alkylene oxide such as ethylene oxide-propylene oxide and low-molecular weight triols such as glycerol, trymethylolpropane, 1,2-6-hexanetriol; low-molecular weight tetraols such as pentaerythritol or low-molecular weight hexaols such as solbitol; or polyamines such as ethylenediamine, 4,4'-methylenebis-l-chloroaniline or polymers of these polyamines and the above-described alkylene oxide. In the reaction of the prepolymer having isocyanate groups and the active hydrogen compound, any well-known catalyst for promoting the reaction of isocyanate group and an active hydrogen compound can be added. Examples of the catalyst to be added include triethylamine, triehtylenediamine, N-morpholine, stannous octate and dibutyl dilaurate. In connection with the ratio of the polyisocyanate and the active hydrogen compound in the above-described prepolymer having isocyanate groups, [NCO] / [H + ] is preferably 0.8 to 2.0, more preferably 1.1 to 1.7. Further, the above-described water-swelling urethane resin may further contain high molecular materials such as other urethane resins, epoxy resin and acryl resin, optionally, and additives of these resins such as calcium carbonate, clay, aluminium silicate, talc or titanium dioxide. Appropriate amount of color former and antioxidant can be also added thereto. The polyvinyl chloride preferably has an average polymerization degree of 400 to 4000. An average polymerization degree is preferably 500 to 3000, more preferably 700 to 2000. When the average polymerization degree is less than 400, the strength of the water-swelling resin (C) lowers, and when it is more than 4000, the workability deteriorates. The polyvinyl chloride is used in an amount of from 10 to 97% by weight based on the mixture of the polyvinyl chloride and the water-swelling urethane resin, and it is preferably from 20 to 95% by weight, still preferably 30 to 90% by weight. When the amount of the polyvinyl chloride is less than 10% by weight, its workability etc. is lost, and the adjustment of hardness according to the plasticizer becomes difficult. Contrarily, when it exceeds 97% by weight, the water swellability deteriorates. The plasticizer is not particularly limited. Examples of such a plasticizer are those usually employed when preparing polyvinyl chloride, for example, phthalates such as dioctyl phthalate and ditridecyl phthalate; trimellitates such as trioctyl trimellitate; pyromellitates such as tetra 2-ethylhexyl pyromellitate; and adipate which is a condensate of adipic acid and diol such as 1,2-propylene glycol, triethylene glycol, neopentyl glycol or the like. The plasticizer is added in an amount of from 80 to 200 parts by weight, based on 100 parts by weight of the polyvinyl chloride. When it exceeds 200 parts by weight, bleeding occurs and waterstop lowers. The above-mentioned water-swelling resin (C) may further contain additives generally added to polyvinyl chloride. Examples of such additives include an organotin thermostabilizer such as dialkyltin mercaptide, dialkyltin malate and dialkyltin laurate; a metal soap such as calcium stearate, zinc stearate, cadmium stearate, barium stearate and lead stearate; an inorganic stabilizer such as lead tribasic sulfate, lead dibasic stearate, calcium hydroxide and calcium silicate; a chelating agent such as trisnonylphenylphosphite and alkylmonoallylphosphite; waxes such as ester wax and hydrocarbon wax; an epoxide compound such as soybean oil epoxide, linseed oil epoxide and bisphenolepoxide; and a filler such as calcium carbonate, talc, clay and mica. Pigment, antistatic agent, antioxidant, ultraviolet ray absorbing agent and the like may be also contained therein optionally. The water-sealing sheet of the present invention is produced by molding the above-mentioned water-swelling resin (C) into the sheet form according to the conventional manner. There is no limitation to the form of the sheet, but the one having 0.5 to 2 mm in thickness, 60 to 120 cm in width and several meters to tens meters in length may be suitable for the ordinary sheet. Further, it is preferable that the water-sealing sheet of the present invention has the tensile strength of 7.5 to 12 MPa (75 to 120 kgf/cm 2 ), as the elasticity suffices therein. The present invention will be described in further detail with reference to the Example and Test Example. Example 1 100 parts by weight of polyvinyl chloride having an average polymerization degree of 1450, 80 parts by weight of plasticizer di-(2-ethylhexyl)phthalate, 2.6 parts by weight of stabilizer for vinyl chloride and 40 parts by weight of water-swelling urethane resin were kneaded to thereby prepare a water-swelling resin (water-swelling polyvinyl chloride resin composition). Sequentially, the composition thus obtained was extruded and molded by a T-die extruder to thereby give a water-sealing sheet having the thickness of 1.3 mm. The water-sealing sheet thus obtained has a tensile strength of 8.8 MPa (88 kgf/cm 2 ). Test Example 1 The water-stop of the water-sealing sheet of the present invention produced in the above Example 1 and a sheet made of plasticized polyvinyl chloride (average polymerization degree : 2250) was compared with the use of the test apparatus shown in Fig. 1 as follows. Between two transparent polyvinyl chloride boards 1, 1' (250 x 250 x 20 mm), a test sheet 3 (thickness : 1.3 mm) provided with stainless spacer 2 (thickness : 1.5 mm) in its surroundings was held as shown in Fig. 1, and the upper and lower transparent polyvinyl chloride boards were fastened with a bolt (now shown in Figs). The center of the test sheet 3 and the center of the upper transparent polyvinyl chloride board were provided with a water-passing hole 4 to thereby pass pressurized water through a pipe 5. In Fig. 1, 6 is a pressure gauge. Following three kinds of sheets were used as test sheets; 1. the water-sealing sheet produced in Example 1, 2. the water-sealing sheet produced in Example 1 in which four cuts 7 having a length of 20 mm were provided in four directions as shown in Fig. 2, and 3. a sheet made of plasticized polyvinyl chloride as a blank. When water was passed through the test apparatus, water leakage was recognized between two transparent polyvinyl chloride boards in all of the sheets mentioned above 1, 2 and 3 under the water pressure 0 MPa (0 kgf/cm 2 ). Next, whole of the test apparatus was dipped in a water tank, and it was taken out after a certain period of time. Then, water was passed through the test apparatus again to thereby measure the pressure (water-proof pressure) when water leakage occurred. The results are as follows. Sheet after 15 hours after 7 days 1 0.35 MPa (3.5 kgf/cm 2 ) 0.90 MPa (9.0 kgf/cm 2 ) 2 0.35 MPa (3.5 kgf/cm 2 ) 0.90 MPa (9.0 kgf/cm 2 ) 3 0 MPa (0 kgf/cm 2 ) 0 MPa (0 kgf/cm 2 )

Claims: A water-sealing sheet comprising a water-swelling resin (C) obtained by kneading together: 10 to 97% by weight of a non-water-swelling thermoplastic resin (A) being a polyvinyl chloride, 3 to 90% by weight of a water-swelling material (B) being a water-swelling urethane resin including prepolymer(s) having isocyanate groups, in which the content of terminal NCO groups amounts to 1 to 12%, obtained by the reaction of one or more polyether polyols represented by the following general formula and polyisocyanate; R[(OR l )n OH]p wherein R represents a polyhydric alcohol residue; (OR l )n represents a polyoxyalkylene chain comprising oxyalkylene groups each having an oxyethylene group and an alkylene group carrying three or four carbon atoms, provided that the content of the oxyethylene groups amounts to 20 to 100% of the total molecular weight; n is a number corresponding to the degree of polymerization of the oxyalkylene groups and giving a hydroxyl group equivalent of 200 to 2500; and p is a number of 2 to 8, and additionally 80 to 200 parts by weight of a plasticizer based on 100 parts by weight of said polyvinyl chloride.

Inventors: HARA KOUZI, ICHIZUKA ISAMU, KOBE SHINJI, OHKUBO KEN, OKOUCHI YOSHITAKA, SAKURADA TADAYUKI, SHIMIZU HIROSHI, TAKAHASHI SHUITSU, WAKI HIROSHI, HARA, KOUZI, ICHIZUKA, ISAMU, KOBE, SHINJI, OHKUBO, KEN, OKOUCHI,YOSHITAKA, SAKURADA, TADAYUKI, SHIMIZU, HIROSHI, TAKAHASHI, SHUITSU, WAKI, HIROSHI, HARA, KOUZI, ASAHI DENKA KOGYO K.K., ICHIZUKA, ISAMU, ASAHI DENKA KOGYO K.K., KOBE, SHINJI, ASAHI DENKA KOGYO K.K., Ohkubo, Ken, c/o Riken Vinyl Ind. Co., Ltd., Okouchi,Yoshitaka, c/o Riken Vinyl Ind. Co., Ltd., Sakurada, Tadayuki, c/o Riken Vinyl Ind. Co., Ltd., Shimizu, Hiroshi, c/o Riken Vinyl Ind. Co., Ltd., TAKAHASHI, SHUITSU, ASAHI DENKA KOGYO K.K., WAKI, HIROSHI, ASAHI DENKA KOGYO K.K.
Applicants: ASAHI DENKA KOGYO KK, RIKEN VINYL IND, ASAHI DENKA KOGYO KABUSHIKI KAISHA, RIKEN VINYL INDUSTRY CO., LTD.
Application year: 1993
Main classification: C09K3
IPC codes: C08L75, C08J5, C08L101, E02B3, C08L27, C09K3