# US 5,346,626 A · Method of removing scale > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,346,626 A - Document ID: US5346626A - Status: Granted - Kind: A - Application number: 08/083,236 - Filed: 1993-06-29 - Granted: 1994-09-13 - Earliest claimed: 1992-06-29 - Assignees: Kurita Water Industries Ltd.; Japan Synthetic Rubber Co., Ltd. - Inventors: Katsuhiko Momozaki; Masako Kusunoki; Fumio Kawamura; Hisao Ono; Katsumi Itoh; Yoshihiro Shimizu; Yuuichi Ono - Web page: https://patentgrep.com/patent/US5346626A ## CPC - C02F 5/10: using organic substances - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) ## Abstract A method of removing scale in a cooling water system in which scale is formed comprises adding 0.01 weight % or more based on the total amount of water contained in the cooling water system of a copolymer containing vinyl monomer units having a carboxyl group or salt thereof and vinyl monomer units having a sulfo group or salt thereof in amounts to make the mol ratio of the carboxyl group to the sulfo group in the range of 30:70 to 95:5 and having weight average molecular weight calibrated with polystyrene in the range of 1,000 to 100,000 to the cooling water system while operating the cooling water system and the cleaved or dissolved scale is discharged out of the cooling water system by blowing. The scale removing agent for a cooling water system has excellent ability to remove scale, does not require much man power nor causes loss of productivity because the scale can be cleaned and removed without stopping the circulation of the cooling water while the ordinary operation of the system is maintained and has no possibility of such danger to operator as found in conventional acid cleaning processes because the agent is used in less acidic condition. Furthermore, the polymer itself has the characteristic that is not easily formed. The finishing point of the scale removal can be found easily by measuring the pH value on the spot of the operation without stopping the operation of the cooling water system. ## Claims ### Claim 1 A method of removing calcium compound-containing scale including calcium carbonate in a cooling water system in which said scale is formed which comprises adding to the cooling water in the cooling water system, while the system is operating, 0.01 weight % or more based on the total amount of water contained in the cooling water system of a scale dissolving agent which comprises a copolymer containing vinyl monomer units having a carboxy group or salt thereof and vinyl monomer units having an isoprene sulfonic acid group or salt thereof in amounts such that the mol ratio of the carboxyl group to the sulfonic acid group is in the range of 30:70 to 95:5, said copolymer having a weight average molecular weight calibrated with polystyrene sulfonic acid sodium salt of 1,000 to 100,000, thereby producing a cleaved or dissolved scale solution, and, thereafter discharging said cleaved or dissolved scale solution from the cooling water system. ### Claim 2 (depends on 1) The method of removing scale claim 1, wherein the scale dissolving agent comprises as the effective component thereof an isoprene sulfonic acid copolymer containing: (A) repeating units of the formula (1), ##STR7## wherein R is a hydrogen atom or methyl group and M.sup.1 is a hydrogen atom or a monovalent cation, and (B) repeating units of the formula (2) , ##STR8## or (C) repeating units of the formula (3), ##STR9## wherein M.sup.2 and M.sup.3 are independently a hydrogen atom or monovalent cation, ### Claim 3 (depends on 2) The method of removing scale of claim 2, further comprising, after addition of the scale removing agent containing the copolymer to the cooling water system, measuring the pH of the cooling water and discharging the cleaved or dissolved scale solution when the pH of the cooling water reaches a value of 5 or more. ### Claim 4 (depends on 3) A method of removing scale as claimed in claim 3, wherein the cleaved or dissolved scale solution is discharged when the pH of the cooling water is from 7.0 to 8.0. ### Claim 5 (depends on 1) The method of removing scale of claim 1, further comprising, after addition of the scale removing agent containing the copolymer to the cooling water system, measuring the pH of the cooling water and discharging the cleaved or dissolved scale solution when the pH of the cooling water reaches a value of 5 or more. ### Claim 6 (depends on 5) A method of removing scale as claimed in claim 5, wherein the cleaved or dissolved scale solution is discharged when the pH of the cooling water is from 7.0 to 8.0. ### Claim 7 (depends on 1) The method of claim 1, wherein said cleaved or dissolved scale solution is discharged by discharging cooling water from the cooling water system. ### Claim 8 (depends on 1) The method of claim 1, wherein the cooling water containing the cleaved or dissolved scale solution is diluted by the addition of water before discharging it from the cooling water system. ### Claim 9 (depends on 1) The method of claim 1, wherein the scale dissolving agent is used in an amount of 0.1 to 10% by weight based on the total amount of water in the cooling water system.