Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF ACRYLIC EMULSION COPOLYMERS"

Abstract

An improved process for the preparation of acrylic emulsion copolymers by dissolving anionic and non ionic emulsifiers in deionised water adding a buffer solution and redox initiator heating under stirring at 50-70°C in presence of nitrogen, adding acrylic monomer mixtures containing methyl acrylate, styrene, ethylacrylate butylacrylate and acrylic acid were added very slowly over a period of three hours to obtain acrylic emulsion copolymer.

Full Text

This invention relates to an improved process for the preparation of acrylic emulsion copolymers. This invention particularly relates to a process for the preparation of acrylic copolymers by emulsion polymerization technique which is requested for various applications in the textile industry. Until a few years ago, the modification of textiles was done by the application of natural materials such as starches, natural gums and gelatins. Now the textile industry employs a large variety of synthetic polymers that impart properties difficulty to obtain with natural products. The acrylic family constitutes one of the rapidly advancing groups of these synthetics. Flimsy fabrics can be given a firm, hand full and a heavy body by their use. The tensile strength of week fibres can be increased. Fraying can be lessened for long periods of use and repeated washings. Permanent stiffening of the fabric can be accomplished by acrylic resin treatment. The acrylics can impart these desirable modifications and will not change the appearance of the fabric because of their transperancy. These are resistant to bacterial action, grease and oil. The flexibility of the resin is permanent feature and is not subject to the less permanent affect of a plasticiser. It is also interesting to note that moisture taken up by textiles treated with acrylic emulsion is the same as that of untreated fabric. The popular grease resistant and wash and wear finishes are made by treating the fabric with thermosetting resins. The incorporation of a compatible acrylic emulsion will improve the grease resistance and strengthen the tensile properties of the fabric. (Henry C. Speel and E.W.K. Sehwarz in "Textile Chemicals and Auxiliaries" pub. Reinhold Publishing Company, Newyork (1957) P.127, 138), (Milton B. Hover "Acrylic Resins" Reinhold Publishing Corp., Newyork (1960) pp 133- The continuous flexing and abrasion of fabrics during regular use lead to eventual failure. The use of acrylic resin treatment greatly extends useful life of the fabric There are two major variations in the polymerisation procedure namely; reflux or; redo initiated polymerisation for acrylic monomers. In any given monomer system in the water, the monomer will boil with in a specific temperature range. The polymerisations run in these temperatures range are being run at reflux. If the temperature of the reaction is below the reflux range and slight difference in the rate of polymerisation is usually evident, due to the inhibiting effect of the oxygen in the polymerisation kettle. This oxygen greatly lengthen the induction period before the polymerisation starts and slow down the rate of polymerisation. Therefore, it is necessary to replace the air by flushing or blanketing with a inert gas such as nitrogen or carbondioxide. It was found that higher temperatures of polymerisation lead to lower molecular weight polymers. Attempts were, therefore, made successfully to use a catalyst -activator system that would operate well in the lower temperature range. This catalyst - activator system is also called Redox. The oxidant used is the persulphate catalyst and the reducing agent which serves as an activator is usually a sulfoxy compound or a small amount of ferrous salt. Sulfoxy compounds used generally are sodium meta bisulphite, thiosulphite and hydrosulphite. In such systems there is no need for a condenser and the induction period is small. Under these conditions, it is desirable to flush the reaction kettle with an innert gas such as pure nitrogen. [K.Eisentrager and W.Druschke in "Hand book of Adhesives" Ed.I.Skeist Van Nostrand Reinhold Co. Newyork (1977) pp 528-559], [Milton B.Horn "Acrylic Resins" Reinhold Publishing Corporation, Newyork (1960) -113], [M.S.E1- Aasser and "Emulsion Polymerisation of Vinyl Acetate" ed. M.S.El- / Aasser and J.W.Vandershoff, Applied Science Publishers, London (1981) 215-253], [H. Warson, "Applications of Synthetic Resin Emulsions" (1972)]. The main object of the present invention is to provide an improved process for the preparation of acrylic copolymers by emulsion polymerisation which obviates the draw backs of the previous invention. Another object is to provide a process of the present invention is to prepare acrylic copolymers in the form of emulsions suitable for textile finishing such as to improve flexing, abrasion, grease resistance and to improve the tensile properties of the fabric. Yet another object of the present invention is to prepare acrylic copolymers having excellent clarity. Yet another object of the present invention is to prepare the acrylic copolymers by emulsion polymerization at as low temperatures as 50°C in presence of redox catalyst -activator system. Accordingly, the present invention provides an improved process for the preparation of acrylic emulsion copolymers which comprises dissolving anionic 2 to 6% and non ionic emulsifiers 1 to 4% in deionised water 45 to 65% adding a buffer solution 0 to 0.4% and redox initiator or oxidizing initiator in the range of 0.1 to 0.6% heating under stirring at 50-70°C in presence of nitrogen, adding acrylic monomer mixtures containing methyl acrylate, styrene, ethylacrylate butylacrylate and acrylic acid 35 to 55% were added very slowly over a period of three hours oiptionally adding plasticizer 0 to 5% to obtain acrylic emulsion copolymer. In an embodiment in the present invention the monomers used is methylacrylate, ethylacrylate, butylacrylate, styrene and acrylic acid. In another embodiment of the invention, the initiators used is potassium persulphate, ammonium persulphate, sodium metasulphite and potassium metabisulphite. In another embodiment of the invention, the emulsifiers used may be anionic surface active agents such as sodium lauryl sulphate, sodium lauryl ether sulfate, fatty alcohol sulphates and non anionic surface active agents such as ethylene oxide condensates and alkyl phenol polyethenoxy ethers. In yet another embodiment, .the buffers used are such as sodium acetate and sodium bicarbonate. In a feature of the invention plasticiser used may be such as polyvinylalcohol, polyvinylpyrolidone may be in the range of 0 - 5 % on the total weight of the emulsion polymer solution. In still another embodiment of the invention, the medium of polymerisation used may be such as distilled water or deionised water. To illustrate the efficacy of present invention, various acrylic copolymers made from the combination of monomers like styrene, methyl acrylate, ethyl acrylate, butyl acrylate and acrylic acid were prepared by emulsion polymerisation technique at even as low temperatures as 50 - 60°C. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. EXAMPLE -1 In a stainless steel reactor, distilled water (160g) was taken and in which anionic surfactant sodium lauryl sulphate and nonanionic surfactant ethylene oxide condensates (20g each) were added. To this a buffer sodium acetate (1.6g) seperately dissolved in distilled water (10g) was added to the kettle. The contents were heated to 60°C under stirring at 90 rpm. The kettle was then flushed with very pure nitrogen gas to displace the air present in the kettle. Through the separate inlets, the initiators (as 2% aqueous solutions), potassium persulphate (40ml) and sodium metabisulphite (40ml) were added gradually in 3 equal installments one at the beginning of the polymerisation, 2nd after the 50% addition of the monomers and the last 3rd installment at the end of the polymerisation reaction. Monomers methylacrylate (160ml), styrene (80ml) were mixed and added into the kettle very slowly over a period of 3 hours. At the end of 3 hours, a milky white emulsion polymer was obtained. 500g yield was obtained. The viscosity of the emulsion was 250 CPS and it had solid content of 48%. This emulsion has given moderately flexible film on the textiles which has imparted grease resistant properties to the fabric. EXAMPLE - II In a stainless steel reactor, deionised water (160g) was taken and in which anionic surfactant sodium lauryl sulphate (8g) was added. To this a buffer, sodium bicarbonate (1.6g) seperately dissolved in deionised water (lOg) was added to the kettle. The contents of the kettle were heated to 50°C under stirring at 120rpm. The kettle was then flushed with lolar grade nitrogen to displace the air present in the kettle. Through two separate inlets, the initiators (2% aqueous solution) ammonium persulphate (40ml) and potassium metabisulphite (40ml) were added gradually throughout the process of polymerisation. Monomers, butyl acrylate (120ml), styrene (120ml) were mixed and added into the kettle through a separate inlet very slowly over a period of 3 hours. At the end of 3 hours, a milky white emulsion polymer was obtained having viscosity of 300 CPS and had solid content 50%. A yield of 490g emulsion was obtained. This emulsion gave a very flexible film on the textiles which has given crush resistant properties to the fabric. EXAMPLE - III In a stainless steel polymerisation reactor, deionised water (400g) was taken and in which anionic surfactant sodium lauryl ether sulphate (24g) was added. The contents were heated to 75°C under stirring at 120rpm. The kettle was once flushed with nitrogen gas to displace the air present in the kettle. Through a separate inlet, an oxidizing initiator (2% aqueous solution) potassium persulphate (40ml) was added in 3 equal installments, one at the beginning of the polymerisation, second after the addition of 50% of the monomers and last at the end of the polymerisation reaction. The monomer mixture containing styrene (160ml) and ethyl acrylate (80ml) and acrylic acid (4ml) were added into the kettle continuously over a period of 3 hours. This addition is called delayed addition. At the end of the 3 hours, the contents of the kettle were heated to 90°C to ensure the completion of polymerisation process. The milky white emulsion in the viscosity of 300 CPS and having 35% solids was obtained. A yield of 700g emulsion was obtained. This emulsion has given moderately flexible film on the textiles and has imparted soft and elastic properties to the fabric. EXAMPLE - IV In a stainless steel polymerisation kettle, deionised water (500g) was taken in which an anionic surfactant sodium oleyl sulphate (35g) was added. The mixture was heated to 85°C under stirring at 120rpm. Through a separate inlet, potassium persulphate as 2% acqeous solution (60ml) was added in 3 equal installments, one at the beginning of the polymerisation, second after 50% addition of the monomer and the last at the end of the polymerisation reaction. Monomer mixture containing styrene (250ml), methyl acrylate (125ml) and acrylic acid (6ml) was added by a delayed addition process over a period of 4 hours. The polymerisation was continued for further period of one hour to ensure the complete polymerisation of the monomers. The milky white polymer emulsion was obtained and to which the water soluble plasticiser polyvinyl alcohol (50g) was added. The emulsion had a viscosity of 400CPS and has given a very flexible film on the textiles which has imparted transparent and resistance to light and ageing property to the fabric. This emulsion had 41% solids. The yield of emulsion 1000g was obtained. EXAMPLE V In a stainless polymerisation kettle, deionised water (500g) was taken and in which an anionic surfactant sodium lauryl sulphate (45g) was added. The mixture was heated to 90°C under stirring at 120 rpm. Through a separate inlet potassium persulphate as 7% aqueous solution (50ml) was added in three equal installments, one at the beginning of the polymerisation reaction, second after the 50% of addition of monomer and the last at the end of the polymerisation reaction. Monomer mixture containing styrene (200ml), methyl acrylate (100ml) and acrylic acid (5ml) were added by a delayed addition process over a period of 3 hours. The polymerisation was continued at the same temperature for further period of one hour to ensure the complete polymerisation of the monomers. In this experiment, nitrogen gas was not used as temperature of the polymerisation was maintained well above the boiling point of methyl acrylate. The milky white polymer emulsion thus obtained has 35% solids and has viscosity of 300 CPS. A water soluble plasticizer poly vinyl pyrrolidone (45 g) was added. A yield of 940g emulsion was obtained. This emulsion gave a very flexible and transparent film on the textiles which has imparted rub resistance and added strength to the fabric. EXAMPLE - VI In a stainless steel polymerisation kettle, distilled water (200ml) and anionic surfactant sodium decyl sulphate (25g) was added and the contents were stirred at 120rpm at 90°C. Through a separate inlet potassium persulphate as 10% aqueous solution (50ml) was added in 3 equal installments, one at the beginning of the polymerisation reaction, second after 50% addition of the monomer and the last at the end of the polymerisation reaction. In a separate container, distilled water (300ml) was taken and in which anionic surfactant sodium decyl sulphate solution (25g) was stirred into it at 30°C. To this a monomer mixture of styrene 200ml, methyl acrylate 100ml and acrylic acid (5ml) was added in 10 minutes and stirred. This gave a milky white monomer emulsion. This monomer emulsion was then added to the stainless steel polymerisation kettle slowly over a period of 3 hours. At the end of the 3 hours, white polymer emulsion was obtained and it was neutralised to pH 6.5 to 7 using ammonical solution. To this 5% of the total charge (i.e., 40g) water soluble plastiser poly vinyl pyrrolidone was added. The product was then cooled and discharged. This acrylic copolymer emulsion had the viscosity 350 CPS and had solid content 35%. A yield of 930g emulsion was obtained. It gave a very flexible film on the textiles which has imparted grease resistance property to the fabric. It has also imparted light and age resistant property to the fabrics. The main advantages of this process are: 1) The acrylic copolymers of varied types and proportions can be made by this method of emulsion polymerisation, to suit to various requirements for the processing of textiles. 2) The emulsion polymerisation process may be conducted by redox initiators or only oxidizing initiator. 3) The emulsion polymerisation may be carried out in presence or absence of nitrogen atmosphere by varying the temperature of the polymerisation process between 50°C to 85°C. 4) The copolymers composition may be adjusted in such a manner that the films of the copolymers thus obtained are soft and flexible. These soft acrylic copolymers are important in making crush resistant textile finishes. 5) The copolymers of styrene and butyl acrylate are useful in producing soft elastic to stiff finishes to the textile fibres. 6) These acrylic copolymers form films of excellent clarity which are resistant to light, aging and chemical action to the textile fibres. WE CLAIM: 1) An improved process for the preparation of acrylic emulsion copolymers which comprises dissolving anionic 2 to 6% and non ionic emulsifiers 1 to 4% in deionised water 45 to 65% adding a buffer solution 0 to 0.4% and redox initiator or oxidizing initiator in the range of 0.1 to 0.6% heating under stirring at 50-70°C in presence of nitrogen, adding acrylic monomer mixtures containing methyl acrylate, styrene, ethylacrylate butylacrylate and acrylic acid 35 to 55% were added very slowly over a period of three hours Optionally adding plasticizer 0 to 5% to obtain acrylic emulsion copolymer. 2) An improved process as claimed in claim (1), wherein the monomers used are methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid and styrene. 3) An improved process as claimed in claims (1) to (2), wherein the buffers used are sodium acetate and sodium bicarbonate. 4) An improved process as claimed in claims (1) to (3), wherein the oxidative initiators used are potassium persulphate and ammonium persulphate. 5) An improved process as claimed in claims (1) to (4), wherein the redox initiators used are in combination of sodium metabisulphite and potassium metabisulphite. 6) An improved process as claimed in claims (1) to (5), wherein the anionic and non ionic surfactants used are sodium lauryl sulphate sodium lauyl ether sulphate sodium oleyl sulphate, sodium decyl sulphate. 7) An improved process as claimed in claims (1) to (6), wherein the plasticizers used are polyvinylalcohol and polyvinylpyrrolidone is in the range of 0-5% on the total weight of emulsion polymer solution. 8) An improved process for the preparation of acrylic emulsion copolymers substantially as herein described with reference to the examples.

Documents:

322-del-2000-abstract.pdf

322-del-2000-claims.pdf

322-del-2000-correspondence-others.pdf

322-del-2000-correspondence-po.pdf

322-del-2000-description (complete).pdf

322-del-2000-form-1.pdf

322-del-2000-form-19.pdf

322-del-2000-form-2.pdf