Use of a polymer dispersion as dust control agent

Abstract

The present invention relates to the use of polymer dispersions for dust control, wherein these polymer dispersions can be obtained by radically initiated emulsion polymerisation of the components a to e: a. 2-75% by weight styrene and/or substituted styrene and b. 0 to 75% by weight acrylic acid C1-C2 ester and/or methacrylic acid C1 to C12 ester and c. 0 to 50% by weight acrylonitrile and/or methacrylonitrile and d. 0 to 50% by weight of at least one further copolymerisable ethylenically unsaturated monomers with one or more C—C double bonds in the presence of e. 10 to 7% by weight starch and/or modified starch and/or degraded starch and/or degrated modified starch wherein the polymerisation is carried out in water.

Claims

1. A method of controlling dust comprising: applying to a substrate, which is to be treated, a polymer dispersion as a dust control agent, wherein the polymer dispersion is prepared by free radical initiated emulsion polymerization of: a. 2 to 75% by weight of styrene and/or substituted styrene, b. 0 to 75% by weight of C1 to C12 esters of acrylic acid and/or C1 to C12 esters of methacrylic acid, c. 0 to 50% by weight of acrylonitrile and/or methacrylonitrile; d. 0 to 50% by weight of at least one further copolymerizable, ethylenically un-saturated monomer with one or more carbon-carbon double bonds, and e. 10 to 75% by weight of starch and/or modified starch and/or degraded starch and/or degraded modified starch; wherein components a to e are polymerized in water, the sum of a+b+c+d+e being 100% by weight and the ratio of water to the sum of components a to e being 99:1 to 40:60 by weight; and wherein, when the monomer in group d has more than one carbon-carbon double bond, the monomer is selected from the group consisting of methylene bisacrylamide, polyalkylene glycol di(meth)acrylates, and triallylamine.

2. The method of claim 1, wherein the substrate, which is to be treated, is any type of dusting solid.

3. The method of claim 1, wherein the concentration of the aqueous dispersion is 0.5 to 3% when applied.

4. The method of claim 1, wherein the polymer dispersion dust control agent is applied in an amount of 0.2 to 3 L per m.sup.2 of the surface to be treated.

5. The method of claim 1, wherein the polymer dispersion has a solids content of at least 10% by weight, a viscosity of not more than 1000 mPas and a pH of 1 to 11, and the average size of the polymer particles is less than 1 μm.

6. The method of claim 1, wherein component a is styrene, and this is optionally used in combination with n-butyl acrylate and/or t-butyl acrylate and/or acrylonitrile and/or acrylic acid as monomers b to d.

7. The method of claim 1, wherein a degraded native and/or a degraded modified starch with a molecular weight of 1000 to 50,000 D is used as starch.

8. The method of claim 1, wherein the proportion of starch to the monomers a to d is 20% to 500% by weight.

9. The method of claim 5, wherein the polymer dispersion has a pH of 2 to 9.

10. The method of claim 1, wherein the polymer dispersion is in the form of an aqueous dispersion and applying comprises homogenously spraying the aqueous dispersion onto the surface of or into a substrate which is to be treated.

Description

EXAMPLE 1

(1) Perglutin A 288 (a copolymer of styrene and acrylate, grafted with starch, from BK-Giulini GmbH).

EXAMPLE 2

(2) In a 1 L Quickfit flask with stirrer, reflux condenser and jacket heating, 87 g of cationized potato starch (DS approximately 0.07; Emcat C60 from Emsland Stärke) are dispersed in 578.5 g of decarbonated water.

(3) While stirring, 6 g of an 8.3% solution of calcium acetate, 6.0 mg of copper sulfate pentahydrate, dissolved in 7.5 g of decarbonated water and then 20 g of 15% sodium per sulfate solution are added.

(4) After the addition, the mixture is heated to 80° C. and stirred for 30 minutes at this temperature, a clear to slightly cloudy starch solution being obtained.

(5) After the addition of 200 mg of silicone defoamer with 1 g of decarbonated water, the monomer and the initiator are added at an internal temperature of approximately 83° C.

(6) The monomer consists of a mixture of 189 g of styrene and 47.4 g of n-butyl acrylate and it is added uniformly over a period of 240 minutes.

(7) As initiator, 49.725 g of a 10.6% hydrogen peroxide solution is added over a period of 255 minutes.

(8) After the monomer has been added, the feed line is flushed with 9.055 g of decarbonated water.

(9) When the initiator has been added, 60 mg of ferrous sulfate, dissolved in 3 g of decarbonated water, are added.

(10) After stirring for 10 minutes, 0.5 g of t-butyl hydroperoxide solution (70% in water) are added and stirring is continued for 1 hour at 83° C., after which the reaction mixture is cooled.

(11) Glutardialdehyde solution (1 g of a 24% solution) is added as a preservative.

(12) After filtration through a 100 μm screen, a dispersion is obtained with a solids content of 31.4%.

(13) The dispersion obtained has a viscosity of 10 mPa*s (Brookfield LV spindle 1, 60 RPM) and a pH of 2.

EXAMPLE 3

(14) Oxidatively degraded potato starch (285 g, Amylex 15 from the Südstärke company) is dispersed in 404.72 g of decarbonated water in a 1 L Quickfit flask with stirrer, reflux condenser and jacket heater.

(15) While stirring, 0.07 g of an amylase (Multifect AA18L from the Genencor company), diluted with 5.21 g of decarbonated water, is added.

(16) At the end of the addition, the mixture is heated over a period of 1 hour to 55° C. and then, over a period of 20 minutes, to 75° C. Stirring at this temperature is continued for 2 hours, a clear to slightly cloudy starch solution being obtained.

(17) After the addition of 500 mg of formaldehyde solution (35%), the internal temperature is raised over a period of 30 minutes to about 90° C.

(18) After the addition of 2.75 g of sodium sulfate, dissolved in 6.2 g of decarbonated water, the addition of the monomers, consisting of a mixture of 40.5 g of styrene and 0.9 g of acrylic acid, is commenced.

(19) These are added uniformly over a period of 40 minutes.

(20) At the end of the addition, stirring is continued for a further hour before 0.85 g of sodium formaldehyde sulfoxylate (Rongalit C) in 5 g of decarbonated water is added.

(21) At the same time, 135 g of styrene and 5 g of trimethyl ammonium methyl methacrylate chloride (75%), dissolved in 20 g of decarbonated water, are added over a period of 120 minutes. At the same time, the addition of 42 g of a 12% hydrogen peroxide solution over a period of 240 minutes as initiator is commenced.

(22) After the monomer has been added, the feed line is flushed with 5 g of decarbonated water. After the initiator has been added, the reaction solution is stripped for 30 minutes at about 90° C., then supplemented with 8.5 g of decarbonated water and cooled to 30° C. The pH is adjusted with sodium hydroxide solution to approximately 4, and excess hydrogen peroxide is decomposed by the addition of sodium bisulfite solution. Subsequently, 1 g of Synperonic T701, 1g formaldehyde solution (35%) and 0.5 g of glutardialdehyde solution (24%) are added. After filtration through a 100 μm screen, a dispersion is obtained with a solids content of 44.2%.

(23) The dispersion obtained has a viscosity of 210 mPa*s (Brookfield LV spindle 2, 60 RPM) and a pH of 4.

EXAMPLE 4

(24) In a 1 L Quickfit flask with stirrer, reflux condenser and jacket heating, 60 g of native potato starch from the Südstärke company are dispersed in 595 g of decarbonated water.

(25) While stirring, 12 g of a 4.2% calcium acetate solution, 60 mg of copper sulfate pentahydrate, dissolved in 7.5 g of decarbonated water and then 3 g of hydrogen peroxide (30%) are added.

(26) After the addition, the mixture is heated to 80° C. and stirred for 30 minutes at this temperature, a clear to slightly cloudy starch solution being obtained.

(27) After the addition of 200 mg of silicone defoamer with 1 g of decarbonated water, the addition of the monomer and the initiator is commenced at an internal temperature of approximately 83° C.

(28) The monomer additions consist of: a) a mixture of 118.2 g of styrene, 59.1 g of n-butyl acrylate, 59.1 g of t-butyl acrylate and 1 g of acrylic acid, b) a mixture of 7.5 g of trimethylammonium methyl methacrylate chloride (75%) with 12.5 g of decarbonated water.

(29) As initiator, 49.725 g of a 10.6% hydrogen peroxide solution are added over a period of 255 minutes.

(30) After the monomer has been added, the feed lines are flushed with 10.075 g of decarbonated water.

(31) When the initiator has been added, 60 mg of ferrous sulfate, dissolved in 3 g of decarbonated water, are added and stirred for a further hour at approximately 83° C.

(32) After cooling to 30° C., glutardialdehyde (1 g of a 24% solution) is added as a preservative.

(33) After filtration through a 100 μm screen, a dispersion is obtained with a solids content of 29.9%.

(34) The dispersion obtained has a viscosity of 27 mPa*s (Brookfield LV spindle 1, 60 RPM) and a pH of 2.8.

(35) There are several possibilities for applying the inventive dust control agent. Before use, the polymer dispersion can be diluted with water, a solution/dispersion of defined concentration being obtained, which can then be sprayed in batches. However, with the help of a Venturi valve or a static mixer or a different suitable component, the polymer may also be mixed continuously into the flowing water, which is to be sprayed.

(36) For controlling the dust while transporting dusty solids or substrates on conveyor belts, the aqueous dispersion is applied continuously onto the transported material by spray nozzles. In this connection, the spray nozzles may be above a longer section of the conveyor belt, or at a transfer point, at which the substrate falls from one conveyor belt to a lower one or onto the ground or the storage endpoint.

(37) For controlling dust on unsealed roads, for example in open-cut mines, quarries, industrial storage areas, areas used for agriculture and forestry, sports facilities, helicopter landing areas or aerodromes, etc., the dispersion is sprayed onto the surfaces with the help of a traveling tanker, which is provided with spraying equipment. This listing is not limiting and any type of surface of dusty solids can be treated with the inventive dust control agent.

(38) The following examples describe the most important types of use:

EXAMPLE 5

Use of the Dust Control Agent Prepared According to Example 1

(39) A dry pile of coal with a high proportion of dust was sprayed with 2 L/m.sup.2 of a 5% by volume aqueous dispersion of Example 1 and allowed to dry overnight. A further pile is treated only with water. After about 12 hours, the wind resistance of the pile was tested by means of a conventional commercial hairdryer in that the latter was set at the highest setting and held for 30 seconds approximately 1 cm from the pile, different orientations (wind directions) being covered. The pile, treated with the agent of Example 1, remained stable and there were no significant emissions of dust. On the other hand, the pile, which was treated only with water, was blown away completely. The efficiency of the treatment (dust reduction) was better than 99%.

(40) The mechanical stability of the covering layer was determined by pressing the pile manually from different orientations. In contrast to the pile, which had been treated only with water, the pile, treated with the agent from Example 1, had a significant mechanical stability, a crust, several millimeters thick, having been formed. The water-repelling action of the covering layer was then tested at a still undamaged site of the crust by allowing small water droplets to fall on it. In comparison to the pile treated only with water, the one treated with the agent from Example 1 had an increased water-repelling action.

EXAMPLE 6

(41) As in example 5, sea sand was now used as substrate.

(42) Efficiency of the treatment: >99%

EXAMPLE 7

(43) As in example 5, crude phosphate was now used as substrate.

(44) Efficiency of the treatment: >75%

EXAMPLE 8

Large-Scale Field Trial

(45) A crude phosphate storage area, approximately 30 m long, 5 m wide and 4 m high, was treated. Mobile spraying equipment, model “Dust Boss DB 30” of the DeDusting Technology company (Waldkirch, Germany) was used as application equipment. The agent from Example 1 was mixed continuously in an amount of approximately 5% with the sprayed stream of water with the help of a mechanical proportional pump. The Dustboss was set to swivelling mode and, taking into consideration the direction of the wind, adjusted so that an area of approximately 30 to 40 m.sup.2 was sprayed with a dosage of approximately 2 L/m.sup.2 at one location. After a drying time of approximately 3 hours, the surface was examined. It was noted that the surface had consolidated to a depth of several millimetres. Under the given weather conditions (moderate wind), no dust emissions were observed.

(46) As in Example 5, the following experiments were conducted with the dust control agents from Examples 2 to 4:

(47) TABLE-US-00001 TABLE 1 Example Dust Control Agent Substrate Effiziency Example 9 From Example 2 Sea sand   90% Example 10 From Example 3 Sea sand   90% Example 11 From Example 4 Sea sand   75% Examplel 12 From Example 2 Coal >99% Example 13 From Example 3 Coal >99% Example 14 From Example 4 Coal >99%