Four component amide copolymer

#This invention relates to new compositions of matter comprising polymeric material. More particularly, the invention relates to compositions of matter comprising polymeric material which is soluble in aqueous media and which is capable of acting as a thickening or gelling agent in such media. Such compositions are useful in a variety of industrial applications, thus for example they have been found to be extremely valuable in explosives technology, in the metal, mining, textile, cosmetic, pharmaceutical, horticultural and agricultural industries, and to a lesser extent in other industries, where there is a need for thickened or gelled water-based products.

#The use of naturally occurring gums as thickening agents for water bearing systems has long been known and typical examples of such gums include gums arabic, gum tragacanth, gum dammar, galactomannan gums such as guar gum, hydroxypropyl guar gum, locust bean gum, and xanthan gums such as the biopolymeric gums. More recently synthetic polymeric substances, for example polyacrylamide, have been used for the same purpose and in the specification of U.S. Pat. No. 4,077,820 it has been disclosed that suitably thickened or suspended aqueous compositions may be derived from the use of copolymers having pol(acrylamide) as a major component and poly(methacryloyl acetone) as a minor component. Such copolymers contain in major proportions acrylamide mer units represented by the formula ##STR1## and in minor proportions methacryloyl acetone mer units, represented by the formula ##STR2## U.S. Pat. No. 4,077,820 also discloses the use of copolymers comprising poly(acrylamide) with a poly(methacryloyl acetone) and either poly(acrylonitrile) or poly(methylmethacrylate) as the minor constituents.

#Such polymeric materials are known to form gels in aqueous systems. Gel formation is particularly desirable when undissolved solids are present in a system and must be maintained in a relatively uniform state of dispersion therein. As used herein, a gel is a mixture, one component of which is water, homogeneous down to substantially colloidal dimensions and capable of resisting a finite shearing force. This resistance to shearing is evidence of some sort of continuous mechanical network or structure which, however, can constitute a relatively small fraction of the total mass of the composition of which the gel is a component. Thus the gel forms a matrix in which both dissolved and undissolved components can be distributed. It is commonly desirable that such gels, although they are aqueous in nature, should have a high degree of waterproofness. They are often applied in situations where extraneous water is present and if they are not waterproof they will readily take up water with the consequent destruction of the gel.

#The invention is now illustrated by, but is not limited to, the following examples in which all parts and percentages are on a weight basis unless otherwise specified. Examples 26 to 31, 33, 34 and 36 do not lie within the invention and are included for the purposes of comparison.

#140 parts of a mixture of monomers of commercially available acrylamide (which contained about 0.5% of acrylic acid), acrylonitrile and hydroxyethyl methacrylate in a molar ratio of 955:35:10 respectively were placed in a reaction vessel fitted with stirring means, heating means, gas inlet and outlet ports and condensing means. The mixture was stirred, 1858 parts of water were added thereto and sufficient sodium hydroxide was added to adjust the pH value of the contents of the reaction vessel to 6.7. A stream of nitrogen gas was bubbled through the contents of the vessel and the temperature of the said contents was adjusted to 50.degree. C. 5 parts of a water soluble azo type initiator, available commercially under the designation V-50, were added to the hot contents, and about 20 minutes after the addition of the initiator the temperature of the contents of the vessel was observed to rise to 60.degree. C. and remained at approximately that value for a further 3 hours. The contents were stirred for a total time of 6 hours after the addition of the initiator. There was thus obtained a solution of precursor polymeric material comprising a copolymer constituted by poly(acrylamide), poly(acrylonitrile) and poly(hydroxyethyl methacrylate) and which had a molecular weight of about 600,000 and which in the form of an aqueous solution containing 7% of the copolymer had a viscosity of 9000 poise. The copolymer so obtained which was a precursor of the polymeric material of the invention contained about 0.5% of poly(acrylic acid). The solution of the precursor polymeric material referred to above was diluted with sufficient water to provide a copolymeric solution containing 4% of solids. 50000 parts of the above copolymeric solution was heated to a temperature of 50.degree. C. in a reaction vessel and to this hot solution there was added aqueous 20% w/v solution of sodium hydroxide sufficient to adjust the pH of the copolymeric solution to a value of 11.2, and secondly 143 parts of an aqueous 40% w/v solution of formaldehyde. The contents of the reaction vessel were stirred for 30 minutes, at which time the pH value of the contents of the vessel was 9.6. The contents of the reaction vessel were cooled to ambient temperature and the pH value thereof adjusted by the addition of a dilute hydrochloric acid solution to 6.7. There was thus obtained a solution containing polymeric material according to the invention and being a modified copolymer of poly(acrylamide), poly(acrylonitrile) and poly(hydroxyethyl methacrylate) in a molar ratio which approximated to 191:7:2 and which contained, as expressed as a percentage of the acrylamide mer units, 4.8 % w/w of methylol groups and 1.5% w/w of carboxy groups (see table 3). The copolymeric material was recoverable from the solution by conventional means.

#Copolymeric materials according to the present invention, having the compositions given in table 3, were made by the method described in example 1 except that different proportions of monomers were used to produce the solution of precursor polymeric material. The viscosities of aqueous solutions (7.0% w/w) of the copolymeric materials made in examples 1 to 8 inclusive are recorded in table 3.