Use of polymer powder compositions that can be redispersed in water and have cationic functionality, as flocculation aid

Abstract

The invention relates to the use of polymer powder compositions that can be redispersed in water and have cationic functionality, as flocculation aid, for example for dewatering waters or waste waters that are laden with solids.

Claims

1. A method of treating water or wastewater laden with solids, comprising adding to said water or wastewater a flocculation aid comprising a water-redispersible polymer powder composition having cationic functionality, the water-redispersible polymer powder composition comprising a base polymer comprising one or more monomers selected from the group consisting of vinyl esters of unbranched or branched alkylcarboxylic acids having 1 to 15 carbon atoms, methacrylic esters and acrylic esters of alcohols having 1 to 15 carbon atoms, vinylaromatics, olefins, dienes, and vinyl halides, and a cationic polymer comprising a homo- or copolymer comprising one or more cationic monomers having a quaternary ammonium group selected from the group consisting of diallyldimethylammonium chloride (DADMAC), diallyldiethylammonium chloride (DADEAC), (3-methacryloyloxy)propyltrimethylammonium chloride (MPTAC), (2-methacryloyloxy)ethyltrimethylammonium chloride (METAC), and (3-methacrylamido)propyltrimethylammonium chloride (MAPTAC), wherein the cationic polymer contains 50% to 100% by weight of cationic monomer units having a quaternary ammonium group, based on the total weight of the cationic polymer, and wherein the base polymer is selected from the group consisting of a vinyl acetate homopolymer, copolymers of vinyl acetate with ethylene, copolymers of vinyl acetate with ethylene and one or more further vinyl esters, copolymers of vinyl acetate with ethylene and acrylic esters, copolymers of vinyl acetate with ethylene and vinyl chloride, styrene-acrylic ester copolymers, and styrene-1,3-butadiene copolymers.

2. The method as claimed in claim 1, wherein the water-redispersible polymer powder composition having cationic functionality comprises 1% to 10% by weight of the cationic polymer, based on the total weight of the base and cationic polymers comprising the water-redispersible polymer powder composition.

3. The method as claimed in claim 1, wherein the base polymer is selected from the group consisting of a vinyl acetate homopolymer and copolymers of vinyl acetate with 1% to 40% by weight of ethylene.

4. The method as claimed in claim 3, wherein the vinyl acetate copolymer comprises a comonomer selected from the group consisting of vinyl chloride and vinyl esters comprising a carboxylic acid radical having 3 to 12 carbon atoms.

5. The method as claimed in claim 1, wherein the base polymer is a vinyl acetate homopolymer or a copolymer of vinyl acetate and 1% to 40% by weight of ethylene, and the cationic polymer is a diallyldimethylammonium chloride polymer (poly-DADMAC).

6. The method as claimed in claim 1, wherein the water-redispersible polymer powder composition having cationic functionality is added to the water or wastewater laden with solids in an amount of 1 to 1000 ppm by weight, based on the weight of the water or wastewater laden with solids to be treated.

Description

(1) Specific examples of the use are the dewatering of waters or wastewaters laden with solids. These may be any communal or industrial wastewaters, for example wastewaters from water treatment plants, or the dewatering of sludges, for example harbor sludges that have been pumped out or excavated, or from paint shops in the automobile industry, or process waters, suspensions and sludges in mines for obtaining coal or ore, or in oil and gas production, or wastewaters from a wide variety of different industrial operations (for example from agroindustrial, biological, biochemical, chemical, foods industry, petrochemical, pharmaceutical industry, paper and wood industry, metal industry and mechanical engineering operations), or else untreated water which is used as industrial process water for cooling or raising steam in, for example, the abovementioned industrial operations.

(2) With the flocculation aid of the invention, surprisingly, the advantages which follow have been obtained. The flocculation aid contains, as well as the cationic polymer component, a predominant component of thermoplastic polymer with an adhesive effect at ambient temperature. This obviously leads, after the coagulation of solid particles with the positive charges of the cationic protective colloid component, to rapid agglomeration of the coagulated primary particles. This results in formation of large and rapidly sedimenting flocs which can easily be separated from the water phase.

(3) This rapid flocculation to form large particles of sediment is not only obtained in the case of use of the flocculation aid in aqueous dispersion, but alsobecause of the excellent dispersibilityin the case of addition thereof in solid form. The flocculation aid of the invention can consequently be used directly in solid form and not just exclusively in solution, as is the case for polyacrylamide or for poly-DADMAC. This achieves a significant facilitation of logistics (transport) and use.

(4) The examples which follow serve to further elucidate the invention:

(5) Flocculation Aids Used:

(6) Poly-DADMAC: Drewfloc 462 (polydiallyldimethylammonium chloride (Poly-DADMAC) from Ashland)

(7) Flocculation Aid 1 (FA1):

(8) An aqueous dispersion of a vinyl acetate-ethylene copolymer having a glass transition temperature Tg of 6 C. and having a solids content of the aqueous dispersion of about 50% by weight, which has been prepared with 6% by weight of polyvinyl alcohol, having a hydrolysis level of 88 mol % and a Hppler viscosity (in 4% by weight solution at 20 C. according to DIN 53015) of 4 mPas, was mixed with 3% by weight of Drewfloc 462, based on the total weight of the polymeric constituents. This mixture was spray-dried with addition of 12% by weight of calcium carbonate (Omyacarb 5GU) as antiblocking agent, based on the total weight of the polymeric constituents. The powder thus obtained was referred to as flocculation aid 1.

(9) Flocculation Aid 1 Liquid (FA 1 li):

(10) Flocculation aid 1 (FA1) was dispersed in water, by stirring FA1 into water in such an amount that an aqueous dispersion of FA1 with a solids content of 50% by weight has been obtained.

(11) Testing Procedure:

(12) In a 2 liter beaker, 200 ml of a sewage sludge from a biological water treatment plant (solids content about 2% by weight) was diluted to 1000 ml with water. In each case, 100 mg of (solid) flocculation aid were added to the diluted sewage sludge, and the mixture was stirred for 5 seconds and then transferred to a measurement vessel provided with a milliliter scale. After 20 min, the mixtures were filtered through a fluted paper filter into a beaker and, after filtration for 10 min, the volume of the filtrate was determined in each case.

(13) The results of the testing are compiled in table 1.

(14) In comparative example C1, no flocculation aid was used.

(15) In comparative example C2, 100 ppm of poly-DADMAC was used as flocculation aid.

(16) In example 3, 100 ppm of flocculation aid 1 (FA 1) was used as flocculation aid.

(17) In example 4, 100 ppm of (solid) flocculation aid 1 in liquid form (FA 1 li) was used as flocculation aid.

(18) TABLE-US-00001 TABLE 1 (Comparative) example C1 C2 3 4 Filter aid (FA) Poly-DADMAC FA 1 FA 1 li Amount of FA 100 ppm 100 ppm* 100 ppm (ppm in solid form) (solid)** Filtrate after 38 178 71 50 10 min (mL) *The redispersible polymer powder FA 1 contains about 3% by weight of poly-DADMAC. Therefore, only about 3 ppm of cationic polymer is used. **The redispersible polymer powder FA 1 contains about 3% by weight of poly-DADMAC and was used in the form of an aqueous dispersion with solids content 50% by weight, i.e. 200 ppm of polymer dispersion was used.

(19) The test results show that, with inventive examples 3 and 4, in spite of the significantly lower proportion (1/33) of cationic polymer, a distinct improvement in flocculation is obtained compared to the blank value of comparative example 1.