GB2060659A

GB2060659A - Method of Producing Polyacrylamide

Info

Publication number: GB2060659A
Application number: GB7935105A
Authority: GB
Original assignee: NII PERERABOT ISKUSSTVENNYKH I
Current assignee: NII PERERABOT ISKUSSTVENNYKH I
Priority date: 1979-10-10
Filing date: 1979-10-10
Publication date: 1981-05-07
Also published as: GB2060659B

Abstract

A method of producing polyacrylamide comprises polymerizing acrylamide in an aqueous solution under the action of an oxidation-reduction system in the presence of highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having diethylene glycol, dimethyl silyl, aminoethoxy, phenylaminomethylenemethyldiethoxy or butoxy groups grafted on the surface thereof in an amount of 0.4 to 0.9 mmol/g. The method can be used for producing polyacrylamide employed for treatment of textile materials to improve their anti-stain properties, and to make them rigid, soft and elastic.

Description

SPECIFICATION Method of Producing Polyacrylamide This invention relates to a method of producing polyacrylamide. Most advantageously the invention can be used for producing polyacrylamide intended to be employed for treating fabrics with the aim of improving their body, rigidity, draping, and anti-stain properties.

Although polymers of acrylamide have been widely used in the textile industry for a comparatively long period of time, the problem of improving the quality of the polymers and the textile materials treated therewith still remains.

The present invention provides a method of producing polyacrylamide, comprising polymerizing acrylamide in an aqueous solution under the action of an oxidation-reduction system in the presence of highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having diethylene glycol, dimethyl silyl, aminoethoxy, phenylaminomethylenemethyldiethoxy or butoxy groups grafted on the surface thereof in an amount of 0.4 to 0.9 mmol/g.

The method according to the invention makes it possible to produce polyacrylamide in the form of a paste which is readily soluble in water. In addition, the storage life of the polyacrylamide produced is increased from 6 months to 1 to 1.5 years.

Textile material treated with polyacrylamide produced by the method of the invention has the required rigidity and body as well as higher wear resistance and anti-stain properties.

The polymerization is preferably carried out in the presence of highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having a specific surface area of 100 to 400 m2/g. Such a specific surface area provides for a high uniformity of both the polymer and aqueous solutions thereof.

Acrylamide may be suitably used in an amount of 8 to 12% by weight and the polymerization carried out in the presence of 0.5 to 10% by weight of highly dispersed silicon dioxide or modified highly dispersed silicon dioxide.

With such a ratio of the reagents the polymerization of acrylamide takes place in the shell of the silicon dioxide, which defines the mechanism of the polymerization, governs its rate and the growth of a polyacrylamide chain, and finally reduces polymerization of acrylamide, thereby allowing the production of a pasty polymer which is readily soluble in water.

It is further preferable that highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having dimethyl silyl or butoxy groups grafted on the surface thereof is preliminarily mixed with ethyl alcohol in a ratio of from 1:3 to 1:4 and the polymerization carried out in the presence of a film-forming substance selected from polyacrylamide, water-soluble ether of cellulose, and polyvinyl alcohol. Such a modification of the method of the invention permits the production of homogeneous polyacrylamide which retains its properties during storage.

The polymerization may be carried out in the presence of 4% polyacrylamide having a concentration of 10 to 50 g/l, which permits the production of polyacrylamide which renders fabric treated therewith smooth and elastic.

Alternatively the polymerization may be carried out in the presence of water-soluble ester of cellulose having a concentration of 2.5 to 5.0 g/l, which permits the production of polyacrylamide which improves the body of fabric treated therewith. The water-soluble ether of cellulose is preferably ca rboxymethyl cellulose, methyl cellulose, oxymethyl cellulose, or a mixture thereof, which permits the production of polyacrylamide which gives fabric treated therewith the required rigidity and adequate body.

As a further alternative, the polymerization may be carried out in the presence of polyvinyl alcohol having a concentration of 1.0 to 5.0 g/l, which permits the production of polyacrylamide which makes it possible to improve the body of the fabric treated therewith and which is stable during storage.

If there is utilized highly dispersed silicon dioxide with a specific surface area thereof of from 175 to 300 m2/g the polymerization may be suitably carried out in the presence of sodium alumomethylsiliconate at a pH value of 9.5 to 10.0. This permits the production of polyacrylamide which improves the anti-stain properties and wear resistance of fabric treated therewith.

The method according to the invention of producing polyacrylamide may be suitably carried out as foliows.

A required amount of water is poured into a reactor provided with a stirring device, such as a paddle stirrer, acrylamide is added to the water, and the stirrer is energized for operation at a speed of 30 to 50 rpm. In the course of stirring the solution there is added thereto highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having diethylene glycol, dimethyl silyl, aminoethoxy, phenylaminomethylenemethyldiethoxy or butoxy groups grafted on the surface thereof in an amount of 0.4 to 0.9 mmol/g, which modified silicon dioxide is obtained by modifying highly dispersed silicon dioxide with diethylene glycol, dimethyldichiorosilane, monoethanolamine, phenylaminomethylenemethyldiethoxylene or butyl alcohol respectively in the reactor under vacuum and at elevated temperature.There is used highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having a specific surface area of 100 to 400 m2/g. With the aid of an alkaline reagent, such as ammonia, soda or sodium alumomethylsiliconate, there is created an alkaline pH value in the reaction mixture, whereupon an oxidizer and reducer, such as ammonium persulphate and sodium hydrosulphite, are added thereto. After stirring the mixture for a short time, the stirrer is de energized, and acrylamide is polymerized at a temperature of 25 to 500C.

Highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having dimethyl silyl or butoxy groups grafted on the surface thereof can be preliminarily mixed with ethyl alcohol in a ratio of 1 to (3.4) and the polymerization can be carried out in the presence of a film-forming substance such as polyacrylamide, water-soluble ether of cellulose or polyvinyl alcohol. The water-soluble ether of cellulose is suitably carboxymethyl cellulose, methyl cellulose, oxymethyl cellulose, or a mixture thereof.

The obtained polyacrylamide is a pasty mass soluble in water at a temperature of 20 to 250C at any ratio when stirred with a stirrer operating at a speed of 30 to 50 rpm. When stored in a closed polyethylene vessel, the polyacrylamide retains its properties for a long period of time.

The invention will be further described with reference to the following illustrative Examples.

Example 1 Acrylamide in an amount of 80 kg was dissolved in 850 1 of water. The obtained solution was stirred, and there were successively added thereto highly dispersed silicon dioxide taken in an amount of 50 kg and having a specific surface area of 200 mm2/g and a 10% ammonia solution until the pH value was 9. There were also successively added to the reaction mixture being stirred 1.6 kg of ammonium persulphate and 0.5 kg of sodium hydrosulphite. After stirring the mixture for a short period of time (10 min.), acrylamide was polymerized at a temperature of 250C for 15 min, whereupon the temperature was increased to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The obtained polymer was homogeneous and pasty.

An aqueous solution of polyacrylamide was easily formed by stirring the polymer mixture and water with the aid of a frame stirrer operating at a speed of 40 rpm for 20 min. at a temperature of 200C.

Polyacrylamide produced as described above was stored in a polyethylene bag for 18 months at a temperature of 18 to 250C, and its properties were found not to have changed in this period (polyacrylamide produced by a conventional method can be stored for 6 months only).

To treat a cotton fabric, use was made of an aqueous solution of polyacrylamide having a concentration of 40 g/l. The fabric was impregnated with this solution using a padding machine. Then the fabric was wrung out to a degree of 90%, and dried at a temperature of 1000C. The thus treated fabric was characterized by its full body and had the required rigidity.

The anti-stain properties of the fabric were determined in the following way. A specialpurpose vessel was charged with a mixture of carbon black and talc (1 to 39) in an amount of 0.2 g and a piece of fabric having a size of 6x24 cm. The fabric was stained by shaking the vessel for 10 min. under the action of 50 steel balls 3 mm in diameter After cleaning the piece of fabric from excessive impurities with the aid of Zeiss leucometer, the coefficient of reflection was determined using a blue light filter.

The anti-stain properties (AP) are determined by the following formula: R3 AP= .100% R4 where R4 is the coefficient of reflection of the fabric prior to staining; and R3 is the coefficient of reflection of the fabric after staining.

The anti-stain properties of the fabric, determined in the manner described above, were found to be 62%, whereas those of non-treated fabric are known to be 50.1%.

Example 2 Acrylamide in an amount of 10 g was dissolved in 85 ml of water. The obtained solution was stirred, and there were successively added thereto highly dispersed silicon dioxide taken in an amount of 5 g and having a specific surface area of 175 m2/g and a 10% ammonia solution until the pH value was 9. The silicon dioxide had diethylene glycol groups grafted on the surface thereof. There were also successively added to the reaction mixture being stirred 1.6 kg of ammonium persulphate and 0.5 g of sodium hydrosulphite. After stirring the mixture for a short period of time (15 min.), acrylamide was polymerized at a temperature of 250C for 15 min., whereupon the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 100 min. The obtained polyacrylamide was a pasty mass readily soluble in cold water.

The solubility of thus obtained polyacrylamide did not change after 1.5 years of storage.

To prepare an aqueous solution of polyacrylamide having a concentration of 250 girl, 100 parts by weight of polyacrylamide were dissolved in 300 parts by weight of water being stirred in a frame stirrer operating at a speed of 40 rpm for 20 min. at a temperature of 200C.

To treat a lining fabric of viscose rayon, use was made of an aqueous solution of polyacrylamide having a concentration of 50 g/l.

The fabric was impregnated with this solution using a padding machine. Then the fabric was wrung out to a degree of 100%, and dried at a temperature of 1000C. The thus treated fabric was tested to determine its resistance to rubbing.

The testing procedure was as follows.

If cotton, silk and mixed fabrics as well as manmade fabrics and yarn are tested, 10 samples in the form of small discs having a diameter of 27+1 mm are cut out of each selected piece of fabric. If flaxen and semiflaxen (mixed) fabrics are tested, 2 samples in the form of small discs having a diameter of 85+2 mm are cut out of each piece of fabric. The samples are cut out so that the warp and weft threads of each disc do not continue the warp and weft threads of another disc.

In testing the samples there is used an abrasion tester comprising a frame, an abrasive head, runners, a means adapted to stretch a fabric to be tested of an abrasive fabric, a support for supporting the frame, and a system of levers and weights for creating a predetermined pressure.

Prior to carrying out the testing procedure the samples of fabric and the abrasive material are held for not less than 25 hours at a relative humidity of 65+2% and at a temperature of 22 to 250C.

The samples to be tested are tucked in holders of the runners so that the right side of the fabric faces outside. Then spherical members are placed on the samples, whereupon the holders are screwed on the runners. A 95 mm wide strip of rough wool fabric is tucked in the frame, and a ring secured with swing screws is placed thereon.

A contact nickel-chromium wire 0.2 mm in diameter is secured with clamps disposed on the ring. The wire being secured should be straightened, but not tightly stretched, and lie freely on the surface of the abrasive fabric.

Samples of flaxen and semiflaxen fabrics are placed onto a resilient base of the frame, such as current-conducting rubber, so that the right side of the fabric faces outside. A metal ring is placed upon the fabric, and the sample is secured to the frame with the aid of a holder. Discs of rough wool fabric 25 mm in diameter are placed in the holders of the runners and the holders are screwed on the runners. After the samples of cotton, silk and mixed fabrics as well as of manmade fabric and yarn and abrasive fabrics have been secured, the frame, with the aid of the system of levers and weights, is carefully brought in contact with the runners, whereupon the abrasive tester is energized. In the course of testing, all the fabrics are subjected to a specific pressure from the abrasive fabric amounting to 1 kg/cm2.Cotton, silk and mixed fabrics as well as man-made fabrics and yarn are tested at a speed of the abrasive head of 100 rpm and flaxen and semiflaxen (mixed) fabrics are tested at a speed of the abrasive head of 200 rpm.

When a sample is broken, the abrasion tester is automatically de-energized as a result of contact between the nickel-chromium wire and the spherical member if cotton and silk fabrics are being tested, or between the current-conducting rubber and feelers if flaxen fabrics are being tested. The number of cycles of rotation of the head of the abrasion tester at which the fabric being tested broke is recorded. The samples of the fabric and the abrasive fabric are replaced by other ones and the testing process continued.

When testing cotton and silk fabrics, both sides of the abrasive are used; if flaxen fabrics are tested, one side only of the abrasive is used.

In testing flaxen and semiflaxen fabrics the abrasive is changed after each 5,000 cycles of rubbing the fabric.

The arithmetic mean of the results obtained from testing all the selected samples is assumed to be an index of resistance to rubbing. The calculation is carried out so as to be correct to within 0.1 of a cycle and is expressed as a whole number.

Resistance to rubbing of fabrics treated as described above was 2279 cycles, whereas resistance to rubbing of non-treated fabrics was 1 840 cycles.

Example 3 4% polyacrylamide (10 g/l) in an amount of 1 g was dissolved in 65 ml of water. The obtained solution was stirred, and there were successively added thereto acrylamide in an amount of 10 g and a mixture consisting of 5 g of highly dispersed silicon dioxide having a specific surface area of 150 m2/g and 17 ml of ethyl alcohol. The silicon dioxide had diethylene groups grafted on the surface thereof. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also added ammonium persulphate in an amount of 0.16 g and sodium hydrosulphite in an amount of 0.05 g. The reaction mixture was stirred for 10 min, whereupon acrylamide was polyermized at a temperature of 300C for 15 min.Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The polyacrylamide obtained as described above was a pasty mass.

The anti-stain properties of a fabric treated with the polyacrylamide were determined as described in Example 1 and found to be 61.6%.

The fabric treated with the polyacrylamide was subjected to a visual and organoleptic analysis which showed that the fabric was elastic and smooth.

Example 4 4% polyacrylamide (25 g/l) in an amount of 2.5 g was dissolved in 80 g of water. The obtained solution was stirred, and there were successively added thereto acrylamide in an amount of 10 g and a mixture consisting of ethyl alcohol in an amount of 17 g and highly dispersed silicon dioxide taken in an amount of 5 g and having a specific surface area of 1 50 m2/g. The silicon dioxide had butoxy groups grafted on the surface thereof in an amount of 0.45 mmol/g. Then a 10% ammonia solution was added until the pH value was 8.5. To the reaction mixture being stirred there were also added ammonium persulphate in an amount of 0.17 g and sodium hydrosulphite in an amount of 0.05. The reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 300C for 15 min.Then the temperature was raised to 500 within a time period of 30 min., and the reaction mixture was held at this temperature for 1 200C. The polymer thus produced was a pasty mass.

Cotton fabric treated with the polyacrylamide having a concentration of 50 gIl possessed higher resistance to rubbing (520 cycles) as compared with non-treated fabric (443) (the technique of determination of resistance of fabric to rubbing being as described in Example 2).

The polymer was homogeneous and retained its properties after being stored in a polyethylene vessel for 14 months at a temperature of 1 8 to 250C.

The anti-stain properties of fabric made of triacetate threads and treated with the polymer having a concentration of 45 g/l were 60.7%.

Example 5 Acrylamide in an amount of 100 kg was dissolved in 850 1 of water. The obtained solution was stirred, and there were added thereto highly.

dispersed silicon dioxide taken in an amount of 50 kg and having a specific surface area of 180 m2/g.

The silicon dioxide had aminoethoxy groups grafted on the surface thereof in an amount of 0.7 mmol/g. Then a 10% ammonia solution was added until the pld value was 9. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 1.8 kg and sodium hydrosulphite in an amount of 0.5 kg. The reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 250C for 1 5 min. Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 250 gIl, 100 parts by weight of the polyacrylamide were dissolved in 300 parts by weight of water and stirred for 20 min in a frame stirrer operating at a speed of 40 rpm and at a temperature of 20 C.

Example 6 Acrylamide in an amount of 10 g was dissolved in 84 ml of water. The obtained solution was stirred, and there were successively added thereto highly dispersed silicon dioxide taken in an amount of 5 g and having a specific surface area of 380 m2/g and a 10% ammonia solution until the pH value was 9. The silicon dioxide had phenylaminomethylenemethyldiethoxy groups grafted on the surface thereof in an amount of 0.75 mmol/g. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.16 g and sodium hydrosulphite in an amount of 0.05 g.

Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 300C within a time period of 15 min. Then the temperature was raised to 500C for 30 min. and the reaction mixture was held at this temperature for 100 min. The polymer thus produced was a pasty mass.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 400 g/l, 100 parts by weight of the polyacrylamide were dissolved in 150 parts by weight of water and stirred for 20 min. in a frame stirrer operating at a speed of 40 rpm.

Example 7 4% polyacrylamide (10 girl) in an amount of 1 part by weight was dissolved in 84 parts by weight of water. The obtained solution was intensively stirred, and there was added thereto, highly dispersed silicon dioxide taken in an amount of 5 parts by weight and having a specific surface area of 200 m2/g. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also added ammonium persulphate in an amount of 0.16 parts by weight and sodium hydrosulphite in an amount of 0.05 parts by weight. The reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 250C for 15 min.Then the temperature was raised to 50 C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The polymer produced as described above was a homogeneous pasty mass readily soluble in water.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 500 g/l, 100 parts by weight of the polyacrylamide were dissolved in 100 parts by weight of water and stirred for 20 min. at a temperature of 200C in a frame stirrer operating at a speed of 40 rpm.

In treating fabrics of acetate threads of 1 6.7 tex., there was used a solution of the polyacrylamide having a concentration of 50 g/l.

The fabric was padded and wrung out, and dried at a temperature of 1000C.

From the results of a visual and organoleptic analysis it was concluded that the fabric treated with the polyacrylamide had the required rigidity and an improved body.

Example 8 Carboxymethyl cellulose (2.5 g/l) in an amount of 0.25 parts by weight and acrylamide in an amount of 1.2 parts by weight were successively dissolved in 77 parts by weight of water. The obtained solution was intensively stirred, and there was added thereto highly dispersed silicon dioxide taken in an amount of 10 parts by weight and having a specific surface area of 300 m2/g.

The silicon dioxide had diethylene glycol groups grafted on the surface thereof in an amount of 0.9 mmol/g. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.16 parts by weight and sodium hydrosulphite in an amount of 0.05 parts by weight. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 250C within a time period of 15 min. Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min.

The polymer thus produced was a homogeneous and pasty mass.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 250 g/l, 100 parts by weight of the polyacrylamide were dissolved in 300 parts by weight of water and stirred for 20 min. at a temperature of 200C in a frame stirrer operating at a speed of 40 rpm.

After 1.8 years of storage, the polyacrylamide was readily soluble in water and suitable for finishing of fabrics.

Example 9 Oxyethyl cellulose in an amount of 0.3 g and in the form of a 10% solution (3 g/l) and acrylamide in an amount of 12 g were successively dissolved in 60 parts by weight of water. The obtained solution was stirred, and there were added thereto a mixture consisting of highly dispersed silicon dioxide taken in an amount of 10 g and having a specific surface area of 400 m2/g and ethyl alcohol in an amount of 17 g. The silicon dioxide had dimethyl silyl groups grafted on the surface thereof. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were successively added ammonium persulphate in an amount of 0.24 g and sodium hydrosulphite in an amount of 0.08 g. The reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 300C for 15 min.Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 100 min. The polymer thus produced was a pasty mass.

The anti-stain properties of cotton fabric treated with the polyacrylamide having a concentration of 55 g/l were found to be 62.3%.

Example 10 Carboxymethyl cellulose in an amount of 10 kg and in the form of 10% solution (5 g/l) and acrylamide in an amount of 200 kg were successively dissolved in 1 600 1 of water. The obtained solution was intensively stirred, and there was added thereto highly dispersed silicon dioxide taken in an amount of 10 kg and having a specific surface area of 400 m2/g. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also added ammonium persulphate in an amount of 3.6 kg and sodium hydrosulphite in an amount of 1.2 kg. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 250C within a time period of 1 5 min.Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min.

The polymer thus produced was a pasty mass.

To finish cotton fabric, use was made of a finishing agent comprising the polyacrylamide having a concentration of 100 g/l. The anti-stain properties of the finished fabric were found to be 68%.

Example 11 A mixture of solutions of ethers of cellulose (5%) in an amount of 0.8 parts by weight was dissolved in 150 parts by weight of water. The mixture consisted of carboxyl cellulose in an amount of 0.8 parts by weight, oxyethylene cellulose in an amount of 0.1 part by weight, and acrylamide in an amount of 20 parts by weight.

The obtained solution was intensively stirred, and there was added thereto highly dispersed silicon dioxide having a specific surface area of 300 m2/g. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also added ammonium persulphate in an amount of 0.32 parts by weight and sodium hydrosulphite in an amount of 0.1 parts by weight. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polyermized at a temperature of 250C for 15 min. Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The thus produced polyacrylamide was a homogeneous pasty mass readily soluble in water.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 400 g/l, 100 parts by weight of the polyacrylamide were dissolved in 1 50 parts by weight of water and stirred for 20 min. at a temperature of 200C in a frame stirrer operating at a speed of 40 rpm.

After 18 months of storage in a polyethylene bag at a temperature of 18 to 250C, the polyacrylamide was found to have retained its properties.

Viscose rayon fabric having a density of 11.1 tex. was treated with the polyacrylamide having a concentration of 65 g/l.

From the results of a visual and organoleptic analysis it was concluded that the fabric treated with the polyacrylamide produced had the required rigidity.

Example 12 4% polyacryalmide (25 g/l) in an amount of 2.5 g and acrylamide in an amount of 10 g were successively dissolved in 80 ml of water. The obtained solution was stirred, and there were added thereto highly dispersed silicon dioxide taken in an amount of 1 7 g and having a specific surface area of 400 m2/g and ethyl alcohol in an amount of 1 7 g. The silicon dioxide had butoxy groups grafted on the surface thereof in an amount of 0.45 mmol/g. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.1 6 g and sodium hydrosulphite in an amount of 0.05 g.Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 25 OC for 15 min. Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The polymer thus produced was a pasty mass readily soluble in water.

Example 13 4% polyacrylamide (50 g/l) in an amount of 5.0 parts by weight and acrylamide in an amount of 9 parts by weight weresuccessively dissolved in 81 parts by weight of water. The obtained solution was stirred, and there was added thereto highly dispersed silicon dioxide taken in an amount of 5 parts by weight and having a specific surface area of 300 m2/g. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.16 parts by weight and sodium hydrosulphite in an amount of 0.05 parts by weight. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 25 aC for 15 min.

Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The polyacrylamide thus produced was a pasty mass readily soluble in water.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 250 g/l, 100 parts by weight of polyacrylamide were dissolved in 300 parts by weight of water and stirred for 20 min. at a temperature of 200C in a frame stirrer operating at a speed of 40 rpm.

Cotton fabric was treated with a solution of the following composition (g/l): polyacrylamide 60 polyethylene emulsion 0.3 From the results of a visual and organoleptic analysis it was concluded that the fabric treated with the polyacrylamide had the required rigidity and an improved body.

Example 14 Acrylamide in an amount of 12 g and an aqueous solution of polyvinyl alcohol having a concentration of 50 g/l and taken in an amount of 2 g were successively dissolved in 75 ml of water.

The obtained solution was stirred, and there was added thereto highly dispersed silicon dioxide taken in an amount of 10 g and having a specific surface area of 400 m2/g. The silicon dioxide had aminoethoxy groups grafted on the surface thereof in an amount of 0.7 mmol/g. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.18 g and sodium hydrosulphite in an amount of 0.06 g. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 250C for 15 min.

Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The thus obtained polyacrylamide was a homogeneous pasty mass which readily dissolved in water.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 400 g/l,.

100 parts by weight of polyacrylamide were dissolved in 150 parts by weight of water and stirred for 20 min. at a temperature of 20 OC in a frame stirrer operating at a speed of 40 rpm.

Cotton fabric was treated with the polyacrylamide having a concentration of 60 g/l under the same treatment conditions as described in Example 1. The anti-stain properties of the fabric were found to be 61.7%.

A visual and organoleptic analysis showed that the fabric treated with the polyacrylamide had an improved body.

Example 15 Acrylamide in an amount of 10 g and polyvinyl alcohol in the form of a solution (50 g/l) were successively dissolved in 75 ml of water. The obtained solution was stirred, and there was added thereto highly dispersed silicon dioxide taken in an amount of 5 g and having a specific surface area of 300 m2/g. The silicon dioxide had aminoethoxy groups grafted on the surface thereof in an amount of 0.7 mmol/g. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.16 g and sodium hydrosulphite in an amount of 0.05 g. Thereafter the reaction mixture was mixed for a short period of time (10 min.), whereupon polyacrylamide was polymerized at a temperature of 250C for 1 5 min.

Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The polymer thus produced was a pasty mass readily soluble in water.

After 1.6 years of storage in a polyethylene bag at a temperature of 18 to 250C, the polyacrylamide was found to have retained its properties.

Viscose rayon fabric having a linear density of 11.7 tex. and treated with an aqueous solution of polyacrylamide having a concentration of 60 g/l possessed resistance to rubbing amounting to 2305 cycles (the technique of determining resistance to rubbing being as described in Example 2).

A visual and organoleptic analysis of the fabric treated with the polyacrylamide showed that the fabric had an improved body.

Example 16 Acrylamide in an amount of 10 g and polyvinyl alcohol taken in an amount of 10 g and in the form of a solution having a concentration of 50 g/l were successively dissolved in 70 ml of water.

The obtained solution was stirred, and there was added thereto highly dispersed silicon dioxide taken in an amount of 5 g and having a specific surface area of 200 m2/g. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.16 g and sodium hydrosulphite in an amount of 0.05. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 250C for 15 min. The the temperature was raised to 500C within a time period of 30 min, and the reaction mixture was held at this temperature for 120 min. The thus produced polymer was a homogeneous pasty mass readily soluble in water.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 400 g/l, 100 parts by weight of polyacrylamide were dissolved in 150 parts by weight of water and stirred for 20 min. at a temperature of 200C in a frame stirrer operating at a speed of 40 rpm.

After 1.4 years of storage at a temperature of 18 to 250C the polyacrylamide was found to have retained its properties.

Cotton fabric was treated with an aqueous solution of the polyacrylamide having a concentration of 75 g/l. The anti-stain properties of the fabric were determined according to the technique described in Example 1 and were found to be 64%.

Example 17 Acrylamide in an amount of 9 g and a mixture of highly dispersed silicon dioxide taken in an amount of 5 g and having a specific surface of 400 m2/g and ethyl alcohol in an amount of 17 ml were dissolved in 68 ml of water. Then a 10% ammonia solution was added until the pH value was 9. To the reaction mixture being stirred there were successively added thereto ammonium persulphate in an amount of 0.16 g and sodium hydrosulphite in an amount of 0.5. Thereafter the reaction mixture was stirred for a short period of time (10 min). whereupon acrylamide was polymerized at a temperature of 25 or for 15 min.

then the temperature was raised to 500C within a time period of 30 min, and the reaction mixture was held at this temperature for 120 min. The thus produced polymer was a homogeneous pasty mass readily soluble in cold water.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 250 g/l, 100 parts by weight of polyacrylamide were dissolved in 300 parts by weight of water and stirred for 20 min. at a temperature of 200C in a frame stirrer operating at a velocity of 40 rpm.

After 1 6 months of storage the properties of the polyacrylamide were found not to have changed.

To finish a cotton fabric, used was made of an aqueous solution of polyacrylamide having a concentration of 55 g/l. The conditions of the finishing process were as given in Example 1.

The finished fabric had an improved body and the required rigidity.

Example 18 Sodium alumomethylsiliconate having pH value of 9.5 and taken in an amount of 100 kg was dissolved in 750 1 of water. The reaction mixture was stirred, and there were added thereto acrylamide in an amount of 80 kg and highly dispersed silicon dioxide taken in an amount of 50 kg and having a specific surface area of 1 75 m2/g. To the reaction mixture being stirred there were successively added ammonium persulphate in an amount of 1.8 kg and sodium hydrosulphite in an amount of 0.6 kg. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 300C for 15 min. Then the temperature is raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min.The thus produced polymer was a homogeneous pasty mass.

An aqueous solution of polyacrylamide having a concentration of 200 gIl was easily prepared by stirring a mixture of water and polymer for 20 min. at a temperature of 200C in a frame stirrer operating at a speed of 40 rpm.

After storage of the polyacrylamide in a polyethylene bag at a temperature of 18 to 250C, its properties were found not to have changed.

Cotton fabric was treated with an aqueous solution of the polyacrylamide having a concentration of 100 g/l. The treatment conditions were as given in Example 1. The antistain properties of the finished fabric were determined according to the technique described in Example 1 and were found to be 76.3%.

Example 19 Sodium alumomethylsiliconate having pH value of 9.5 and taken in an amount of 300 kg was dissolved in 1400 i of water. The mixture was stirred, and there were added thereto acrylamide in an amount of 160 kg and highly dispersed silicon dioxide taken in an amount of 100 kg and having a specific surface area of 200 m2/g. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.36 kg and sodium hydrosulphite in an amount of 0.6 kg. Thereafter the reaction mixture was again stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 300C for 15 min. Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min.

The thus produced polymer was a homogeneous pasty mass readily soluble in hot water.

In order to prepare an aqueous solution of polyacrylamide having a concentration of 250 girl, 100 parts by weight of polyacrylamide were dissolved in 300 parts by weight of water and stirred for 20 min. at a temperature of 200C in a frame stirrer operating at a speed of 40 rpm.

Textile materials treated with the polyacrylamide were characterized by improved resistance against pigment dirt. The anti-stain properties of cotton fabric treated with an aqueous solution of the polyacrylamide were found to be 78%.

Example 20 Acrylamide in an amount of 8 g was dissolved in 90 ml of water. The mixture was stirred, and there were successively added thereto highly dispersed silicon dioxide taken in an amount of 0.5 g and having a specific surface area of 100 m2/g and a 10% ammonia solution until the pH value was 9. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.16 g and sodium hydrosulphite in an amount of 0.05 g. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 300C for 15 min.

Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 90 min. The thus produced polyacrylamide was a homogeneous mass readily soluble in hot water.

To treat bleached cotton fabric, polyacrylamide in an amount of 10 g was dissolved in 190 g of water. The fabric was impregnated with the obtained solution by using a padding machine and then wrung out at a temperature of 1000C. The bleached fabric was characterized by a full body.

Example 21 Sodium alumomethylsiliconate having a pH value of 10 and taken in an amount of 10 parts by weight was dissolved in 75 parts by weight of water. The mixture was stirred, and there were added thereto acrylamide in an amount of 9 parts by weight and highly dispersed silicon dioxide having a specific surface area of 175 m2/g and taken in an amount of 5 parts by weight. The silicon dioxide had diethylene glycol groups grafted on the surface thereof in an amount of 0.5 mmol/g. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.16 parts by weight and sodium hydrosulphite in an amount of 0.05 parts by weight. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 300C for 15 min.Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 120 min. The thus produced polymer was a homogeneous pasty mass readily soluble in water.

After 1 8 months storage in a polyethylene bag at a temperature of 18 to 250C, the properties Qf the polyacrylamide were found not to have changed.

The anti-stain properties of cotton fabric treated with an aqueous solution of the polyacrylamide having a concentration of 85 g/l were found to be 71%.

Example 22 Sodium alumomethylsiliconate having a pH value of 10 and taken in an amount of 400 kg was dissolved in 3000 1 of water. The reaction mixture was stirred, and there were added thereto acrylamide in an amount of 400 kg and highly dispersed silicon dioxide taken in an amount of 200 kg and having a specific surface area of 1 75 m2/g. To the reaction mixture being stirred there were also successively added ammonium persulphate in an amount of 0.72 kg and sodium hydrosulphite in an amount of 0.24 kg. Thereafter the reaction mixture was stirred for a short period of time (10 min.), whereupon acrylamide was polymerized at a temperature of 300C for 1 5 min.

Then the temperature was raised to 500C within a time period of 30 min., and the reaction mixture was held at this temperature for 90 min. The thus produced polyacrylamide was a pasty mass readily soluble in water.

After 18 months of storage in a polyethylene bag at a temperature of 18 to 250C, the properties of the polyacrylamide were found not to have changed.

A finished fabric treated under the conditions given in Example 1 was characterized by improved body, improved anti-stain properties, and reduced anti-static properties.

Claims

1. A method of producing polyacrylamide, comprising polymerizing acrylamide in an aqueous solution under the action of an oxidationreduction system in the presence of highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having diethylene glycol, dimethyl silyl, aminoethoxy, phenylaminomethylenemethyldiethoxy or butoxy groups grafted on the surface thereof in an amount of 0.4 to 0.9 mmol/g.

2. A method as claimed in Claim 1, wherein the polymerization is carried out in the presence of highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having a specific surface area of 100 to 400 m2/g;

3. A method as claimed in Claim 1 to 2, wherein acrylamide is used in an amount of 8 to 1 2% by weight and wherein the polymerization is carried out in the presence of 0.5 to 10.0% by weight of highly dispersed silicon dioxide or modified highly dispersed silicon dioxide.

4. A method as claimed in any of Claims 1 to 3, wherein highly dispersed silicon dioxide or modified highly dispersed silicon dioxide having dimethyl silyl or butoxy groups grafted on the surface thereof is preliminarily mixed with ethyl alcohol in a ratio of from 1:3 to 1:4, and wherein the polymerization is carried out in the presence of a film-forming substance selected from polyacrylamide, water-soluble ether of cellulose, and polyvinyl alcohol.

5. A method as claimed in Claim 4, wherein the polymerization is carried out in the presence of 4% polyacrylamide having a concentration of 10 to 50 g/l.

6. A method as claimed in Claim 4, wherein the polymerization is carried out in the presence of water-soluble ester of cellulose having a concentration of 10 to 50 g/l.

7. A method as claimed in Claim 4 or 6, wherein the water-soluble ether of cellulose is carboxymethyl cellulose, oxymethyl cellulose, methyl cellulose, or a mixture thereof.

8. A method as claimed in Claim 4, wherein the polymerization is carried out in the presence of polyvinyl alcohol having a concentration of 1.0 to 5.0 g/l.

9. A method as claimed in any of Claims 1 to 3, utilizing highly dispersed silicon dioxide having a specific surface area thereof of from 1 75 to 300 m2/g, and wherein the polymerization is carried out in the presence of sodium alumomethylsiliconate at a pH value of 9.5 to 10.

10. A method according to Claim 1 of producing polyacrylamide, substantially as herein described in any of the foregoing Examples.