	US 11,926,968 B2
	Method for producing paper
Takashi Saigusa, Tokyo (JP)
Assigned to KURITA WATER INDUSTRIES LTD., Tokyo (JP)
Appl. No. 17/252,732
Filed by KURITA WATER INDUSTRIES LTD., Tokyo (JP)
PCT Filed Apr. 11, 2019, PCT No. PCT/JP2019/015787 § 371(c)(1), (2) Date Dec. 16, 2020, PCT Pub. No. WO2019/244454, PCT Pub. Date Dec. 26, 2019.
Claims priority of application No. 2018-115278 (JP), filed on Jun. 18, 2018.
Prior Publication US 2021/0214895 A1, Jul. 15, 2021
Int. Cl. D21H 21/04 (2006.01); B01D 21/01 (2006.01); C02F 1/50 (2023.01); C02F 1/56 (2023.01); D21H 17/28 (2006.01); D21H 17/53 (2006.01); D21H 23/04 (2006.01); C02F 101/34 (2006.01); C02F 103/28 (2006.01)

CPC D21H 21/04 (2013.01) [B01D 21/01 (2013.01); C02F 1/50 (2013.01); C02F 1/56 (2013.01); D21H 17/28 (2013.01); D21H 17/53 (2013.01); D21H 23/04 (2013.01); C02F 2101/34 (2013.01); C02F 2103/28 (2013.01); C02F 2303/04 (2013.01)]

2 Claims

1. A method for producing paper comprising a step of adding a polymer having a polyalkylene oxide moiety to papermaking process water containing a suspended solid containing a papermaking raw material and unfixed starch,

wherein a proportion of the polyalkylene oxide moiety contained in the polymer is 50% by weight or more relative to the total polymer,

a concentration of the suspended solid contained in the papermaking process water is 100 mg/L or more,

a concentration of the unfixed starch contained in the papermaking process water is 10 mg/L or more, and

a salt viscosity of the polymer measured by the following method is 3 mPa·s or more,

the viscosity of an aqueous solution containing 4% by weight of common salt and 0.5% by weight of the polymer is measured under the conditions of 25° C. and a rotor rotating speed of 60 rpm; the viscosity measurement method is based on JIS K 7117-2.