DE2243155A1 - ACRYLAMIDE POLYMERISATES, PROCESS FOR THEIR PRODUCTION AND THEIR USE AS FLOCKING AGENTS - Google Patents

Description

SUMITOMO CHEMICAL COMPANY, LIMITED
Osaka, Japan

"Acrylamide polymers, processes for their production and their use as flocculants ".

The invention relates to acrylamide polymers, .Verfahren their Manufacture and their use as flocculants.

Acrylamide polymers are used as sizing agents, fillers, binders, paints and dispersants. Acrylamide polymers with high intrinsic viscosity and high molecular weight are particularly suitable as flocculants =

09813/0990

There are numerous processes for producing such polymers known, among which radical polymerization with radical initiators or redox catalysts in aqueous or organic Phase is most widespread in technology. Suitable organic phases are solvents in which the monomers are soluble, the polymers obtained, however, are insoluble. With this so-called "precipitation polymerization" one achieves because of the Chain transfer reactions are difficult to achieve higher degrees of polymerization. This method is thus for the production of Acrylamide polymers with high intrinsic viscosity and high molecular weight are unsuitable.

In contrast, the so-called "solution polymerization" in the aqueous phase leads to acrylamide polymers with a high degree of polymerization. However, this method has the disadvantage that a considerable heat of reaction is released and the The reaction is difficult to control if the concentration of the starting monomers is high. In addition, the high degree of polymerization, so that the reaction system is extremely viscous and so difficult to stir and work up. Directs if the heat of polymerization is not removed to the required extent, the polymer reacts on the amide group to form water-insoluble ones Products that cannot be used as flocculants.

To avoid these disadvantages of solution polymerization, the reaction is carried out at low monomer concentrations, e.g. 1Ö percent or less, through. Concentration is also important here

40981.3 / 0990

of the polymer in the solution obtained is relatively low, the polymer is precipitated with an organic, water-miscible Solvent such as methanol and separates it from the slurry. Here, however, 'large amounts of the organic water-miscible solvent is required, so that the process is not expedient from an industrial point of view is.

In addition, polymerization processes in suspension and emulsion are known in which the conversion into 0 / W or W / O dispersion under Use of a suitable organic solvent such as n-heptane, carbon tetrachloride, toluene or xylene, as well as one surfactant compound is carried out. However, the dispersions are not sufficiently stable; also is the flammability the solvent disadvantageous. Furthermore, because large amounts of an organic solvent are used to precipitate the polymer are required, these polymerization processes in suspension and in emulsion are not very suitable for industrial use.

From BE-PS 717 128 a process for precipitation polymerization is known in which acetone is used. Acrylamid.oder monovinyl monomers mainly containing acrylamide are polymerized in an acetone / water mixture, .-> £ _s relative contains 30 to 70 percent on the total weight of the mixture, acetone, wherein the polymer is obtained as a slurry. However, the process has the disadvantage that the polymer particles are roughly

40981 3/0990

Bake together grain-sized aggregates. In addition, they accumulate in the course of the polymerization because of the stickiness of the resulting material Polymerizates wall attachments on the inner walls of the reaction vessels. On the one hand, this lowers the product yield, on the other hand the sticky polymer makes filtration difficult and sinters on drying, so that the preparation of the slurry to the commercial product is cumbersome. Although it is known from BE-PS: 717 128, due to the stickiness of the polymer particles to solve the problems caused by adding inorganic salts, such as potassium chloride, Sodium chloride or ammonium sulfate, and / or buffers such as ammonium chloride / ammonia, clogs, however, no satisfactory results can be achieved. Even when using such additives some 10 percent of the polymer formed remains on the inner wall of the reaction vessel.

The object of the invention is therefore to provide water-soluble, pulverulent acrylamide polymers with a high limit number and a high number To create molecular weight and a process for its production, which avoids the disadvantages described.

The invention thus relates to acrylamide polymers obtainable by polymerizing acrylamide or methacrylamide or mainly monovinyl monomers containing these compounds in the presence of free radical or redox catalysts and, if appropriate a dispersion stabilizer in an acetone / water mixture, which contains about 23 to 30 weight percent acetone, based on the total weight of the mixture, and polyvinyl alcohol.

The invention also relates to a process for producing the acrylamide copolymers by polymerizing acrylamide or Methacrylamide or mainly monovinyl monomers containing these compounds in an acetone / water mixture in the presence of radical or redox catalysts as well as given

409813/0990

- CC _

if a dispersion stabilizer, which is characterized is that the polymerization is carried out in an acetone / water mixture carries out, based on about 23 to 30 percent by weight acetone is the total weight of the mixture, and contains polyvinyl alcohol.

The presence of polyvinyl alcohol in an acetone / water mixture, which contains about 23 to 30 percent by weight acetone, allows the production of a barely tacky polymer, so that the above the difficulties described can be avoided. If the acetone concentration is below 23 percent by weight, this will be The reaction mixture is highly viscous and gels immediately ("Weissenberg effect"). If the acetone concentration is above 30 percent by weight, the tackiness of the polymer particles increases and rubber-like agglomerates are deposited on the inner wall of the reaction vessels, from the flocculated polymer particles originate. Only at acetone concentrations within the specified range does the polymer fall as a slurry finer Particles that do not cause any of the difficulties mentioned.

In the process of the invention, acrylamide is polymerized or Methacrylamide or monoviny monomers mainly containing these compounds, i.e. monomers which are not less than 50 percent by weight Contain acrylamide or methacrylamide. In the following, acrylamide and / or methacrylamide are used as "main monomers" and the other monomer units of the Monoviny! monomers as Referred to as "minor monomers".

409813/0990

Compounds that can be used as secondary monomers are those which are present in acetone / Water soluble and their copolymer with the main monomer is insoluble or hardly soluble in this mixture. Suitable examples are acrylonitrile, anionic monomers such as acrylic acid, Methacrylic acid, or its metal or ammonium salts, sodium vinyl sulfonate or sulfonated styrene, or basic monomers, which become cationic during quaternization, such as vinyl pyridine or di-alkylaminoalkyl methacrylate. Such minor monomers are in particular suitable to give the polymer obtained anionic or cationic properties and / or better water solubility to rent. The monovinyl monomer can have such secondary contain monomers, but this is not absolutely necessary.

The monomer concentration in the reaction system is usually about 10 to 30 percent by weight, preferably about 15 to 25 percent by weight.

Compounds which form free radicals and which are soluble in acetone / water can be used as catalysts. Are preferred water-soluble peroxides such as hydrogen peroxide, potassium persulfate or ammonium persulfate, and azobisisobutyronitrile. Also redox catalysts, such as potassium persulfate or sodium hydrogen sulfite, amines or sodium formaldehyde sulfoxylate are suitable, usually about 0.01 to 0.2 percent by weight of the catalyst, based on the weight of the monomers, is used.

Polyvinyl alcohol is usually used in an amount of about 0.5

409813/0990

to H percent by weight, preferably about 1 to 2 percent by weight, based on the weight of the monomers.

If necessary, the reaction system contains a dispersion stabilizer, e.g. water-soluble high polymers such as carboxymethyl cellulose, inorganic salts such as potassium chloride, sodium chloride, Ammonium chloride, sodium sulfate or sodium carbonate, or buffers such as sodium acetate / acetic acid or ammonium chloride / Ammonia.

The polymerization is carried out in a manner known per se, the reaction temperature preferably being about 20 to 60.degree .

In the process of the invention, an acrylamide or methacrylamide polymer is obtained, the particles of which are hardly sticky and therefore avoid the undesired wall deposits in the reaction vessels. The slurry obtained is worked up by customary filtration, where appropriate it is washed with acetone in the reaction vessel . On drying, the polymer particles obtained give fine granules of uniform particle size, which dissolve immediately and completely when stirred in cold water. The granules can optionally be ground to the desired particle size. The intrinsic viscosity [η] at 30 ⁰ C in In sodium nitrate solution is usually 10 or more. A roughly

rice grain-sized polymer, which under similar polymerization conditions, but from an acetone / water mixture with more than

409813/0990

30 weight percent acetone has been obtained shows a lower one Limiting viscosity number.

The slurry obtained in the process of the invention is composed of fine particles and, because of their excellent properties, can Stability can be applied directly, e.g. in the reaction of a monoaldehyde with an amine, without the separation of the polymer from the reaction mixture would be required.

The advantage of the process according to the invention is therefore essentially that the starting monomers are used in high concentrations can polymerize, with a polymer with a molecular weight of more than 3 million as a powder or granules arises. Another advantage is that the acetone / water mixture used as the reaction medium is low in production costs conditional. The acrylamide polymers obtained in the process of the invention are particularly suitable as flocculants.

The examples illustrate the invention.

example 1

A solution of 190 g of acrylamide and 10 g of acrylic acid in a mixture of 505 g of water and 236 g of acetone is about 22 ml 30 percent sodium hydroxide solution and then neutralized with 20 g of a 10 percent aqueous solution of polyvinyl alcohol (Trade name "Gosenol GH-20"). After exchange

409813/0990

the air against nitrogen is added to the reaction mixture with 10 ml of a 1 percent aqueous solution of potassium persulfate and 5 ml of a 1 percent aqueous solution of sodium hydrogen sulfite, a clear solution being formed. After several minutes, the reaction starts and the _# Reäktionsgemisch clouds gradually. During the four-hour polymerization in a stream of nitrogen with stirring at 40 ° C., no deposits were observed on the inner wall of the reaction vessel. The resulting slurry is then filtered off, the pulverulent polymer is washed with acetone and dried under reduced pressure. In this case, one obtains a white polymer powder I98 g with an intrinsic viscosity of 12.1 (determined at 30 ⁰ C in 1 η sodium nitrate solution), The Acetonkonzentrati-on in the reaction medium is 29.5 #.

Example 2

29 g of acrylic acid are dissolved in 200 g of water with stirring and then with about 40 ml of 10 η sodium hydroxide solution at a temperature below 35 ° C neutralized. The resulting solution is 162 g. Acrylamide, 313 g of water and 220 g of acetone mixed and then with 20 g of a 10 percent aqueous solution of polyvinyl alcohol (Trade name "Gosenol GH-17"). After displacing the air the reaction mixture with 5 ml of an Iprozentigen is by nitrogen aqueous solution of potassium persulfate and 2 ml of a 1 percent aqueous solution of sodium formaldehyde sulfoxylate (Trade name "Redole CP") added, whereby a clear solution

409813/0990

After a few minutes the reaction starts and the reaction mixture gradually becomes cloudy. The polymerization is carried out for 4 hours at 25 ° C., a stable slurry being obtained without any deposition of the polymer being observed. The product is filtered off and dried according to Example 1, white particles of excellent water solubility being obtained . The yield is about 90% of theory and the intrinsic viscosity is 17.2. The acetone concentration in the reaction medium is 27.5%

Example 3

According to Example 2, acrylamide is polymerized with a water mixture content of 35 mole percent sodium acrylate in an acetone / acetone with a concentration of 23 weight percent 4 hours at Ί0 to 45 ^0C. This creates a homogeneous, stable slurry without any sticky deposits being observed. The reaction mixture is mixed with water and filtered. After the product obtained has been dried under reduced pressure at 60 ° C. for six hours, a white powder is obtained in 99% yield.

1.0 g of the polymer obtained in this way are added to 99 g of water at room temperature with stirring, a clear solution being formed in 11 minutes without the formation of a residue. The viscosity of the resulting aqueous solution is lprozentigen 1760 cP at 25 ⁰ C.

409813/0990

Example 4

g acrylamide and 60 g acrylic acid are dissolved in ^ 50 g water and neutralized with 110 g of a 10 η sodium hydroxide solution *
Then 40 g of a 5 percent aqueous solution of polyvinyl alcohol and 200 g of acetone are added to the solution, so that the acetone concentration is 25 »2 #. After displacing the air
0.1 g of potassium persulfate and 0.2 g of tetramethylethylenediamine are added through nitrogen. After six hours of polymerization at 20 ^° C., a stable slurry is formed. The product obtained is filtered off according to Example 1 and dried, with
210 g of a white polymer powder with an intrinsic viscosity of 16.5 are obtained.

409813/0990

Claims (1)

22A3155 Paten ta η s ρ r ü c h e t \ Acrylamide polymers, obtainable by polymerizing acrylamide or methacrylamide or mainly monovinyl monomers containing these compounds in the presence of radical or redox catalysts and optionally a dispersion stabilizer in an acetone / water mixture containing about 23 to 30 percent by weight of acetone, based on the total weight of the mixture, and contains polyvinyl alcohol. 2, a process for the preparation of the acrylamide polymers according to claim 1 by polymerization of acrylamide or methacrylamide or monovinyl monomers mainly containing these compounds in an acetone / water mixture in the presence of radical or redox catalysts and optionally a dispersion stabilizer, characterized in that the polymerization carried out in an acetone / water mixture that contains about 23 to 30 percent by weight of acetone, based on the total weight of the mixture, and contains polyvinyl alcohol, 3. The method according to claim 2, characterized in that j about 0.5 to 4 percent by weight of polyvinyl alcohol, based on the weight of the polymerizable monomers, is used. H. The method according to claim 2, characterized in that about 1 to 2 percent by weight of polyvinyl alcohol, based on the weight of the polymerizable monomers, is used. 409613/0090 BATH ORIGINAL 5. The method according to claim 2, characterized in that one a catalyst soluble in acetone / water is used. 6. The method according to claim 2, characterized in that one the polymerization is carried out at a temperature of about 20 to 60 ° C. 7. Use of the acrylamide polymers according to claim 1 as flocculants. 409813/0990