Process for preparing high molecular weight acrylic polymers
AssigneeDai-Ichi Kogyo Seiyaku Co., Ltd.
InventorsAkira Yada, Shusaku Matsumoto, Yoshihiro Kawamori, Yoshitugu Adachi, Yoshio Hatakawa
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Abstract
A process for preparing particulate water-soluble cationic acrylic polymers having a high molecular weight, an excellent water solubility and a uniform particle size with a good productivity by adding a combined photoinitiator system of an azoguanyl compound and other usual photoinitiator to an aqueous monomer solution containing a cationic vinyl monomer, irradiating the aqueous monomer solution in the form of a thin layer on a moving support with ultraviolet rays in at least two stages, and finely dividing the produced aqueous polymer gel in a wet state by a roller cutter and then by a vertical cutter.
Claims10
A process for preparing a particulate water-soluble acrylic polymer having a high molecular weight and an intrinsic viscosity of from 12 to 17 dl/g which comprises:
- (a) adjusting an aqueous monomer solution containing a cationic vinyl monomer or a mixture of the cationic vinyl monomer and at least one other water-soluble vinyl monomer to a monomer concentration of 50 to 80% by weight and a pH of 4 to 7,
- (b) adding one or more of non-ionic surfactants to the aqueous monomer solution in an amount of 0.001 to 1% by weight based on the total weight of the monomer,
- (c) admixing the aqueous monomer solution with at most solution to at most 1 mg/liter,
- (d) admixing the aqueous monomer solution with at most 0.6% by weight of an azoguanyl photopolymerization initiator and at most 0.03% by weight of at least one other photopolymerization initiator based on the total weight of the monomer, said azoguanyl photopolymerization initiator being at least one member selected from a group consisting of a compound of the formula:
- ##STR3## a compound of the formula:
- ##STR4## wherein R.sup.5 is an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms, and R.sup.6 is hydrogen, and alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms, and their salts with a mineral acid, and said other photopolymerization initiator being a member selected from the group consisting of benzophenone, benzoin, a benzoin alkyl ether, anthraquinone, an acetophenone initiator, benzil and a thioxanthone initiator, and the ratio of said other photopolymerization initiator to said azoguanyl photopolymerization initiator being from 1/5 to 1/20 by weight,
- (e) continuously feeding the aqueous monomer solution in the form of a layer having a thickness of 3 to 18 mm onto a moving support located in an atmosphere containing at most 1% by volume of oxygen,
- (f) irradiating the layer of the aqueous monomer solution of the moving support with ultraviolet rays in at least two stages, the conditions of the first stage being a wavelength of 300 to 450 millimicrons, an irradiation time of 30 to 60 minutes and an intensity of 10 to 15 W/m.sup.2, and the conditions of the second stage being a wavelength of 300 to 450 millimicrons, an irradiation time of 30 to 60 minutes and an intensity of 20 to 30 W/m.sup.2,
- (g) continuously taking out the produced polymer in the form of a rubber-like sheet having a thickness of 3 to 18 mm from the moving support,
- (h) irradiating the polymer sheet with ultraviolet rays having a wavelength of 200 to 600 millimicrons for 1 to 6 minutes at an intensity of 1,000 to 2,000 W/m.sup.2,
- (i) breaking the polymer sheet to cubic pieces of 3 to 18 mm in length of a side by a roller cutter, while maintaining the polymer concentration at 50 to 85% by weight,
- (j) pulverizing the cubic pieces to particles having a diameter of 0.3 to 3 mm by a vertical cutter, while maintaining the polymer concentration at 50 to 85% by weight, and
- (k) drying the particles with hot air.
Dependencies are inferred from the claim text.