Hydrophilic Modified Acrylic Polymers Particularly Hydrodispersible or Hydrosoluble Modified Acrylic Polymers and Method of Preparing the Same

The present invention relates to hydrophilic modified acrylic polymers, particularly hydrodispersible or hydrosoluble modified acrylic polymers, and to a method of preparing said polymers.

Many hydrodispersible or hydrosoluble polymers are already known, such as certain vinyl polymers, the most usual being polyvinyl alcohols and polyacrylamides.

The invention provides novel hydrophilic polymers, particularly hydrodispersible or hydrosoluble polymers which are derived from polyacrylic acids or esters.

The novel modified acrylic polymers of the invention contain, expressed in molar percentages, p % units A of the formula ##STR1## q % units B of the formula: ##STR2## r % units C of the formula: ##STR3## and s % units D of the formula: ##STR4## wherein R represents one or more radicals selected from the groups comprising hydrogen and the ethyl and methyl radicals, R.sub.1 stands for hydrogen or an alkyl radical containing 1 to 4 carbon atoms, the symbols R and R.sub.1 never representing at the same time an hydrogen atom or a methyl radical, i, j, and k stand for integers which may vary from 1 to 6 and .alpha. and .beta., which may be identical or different, are equal to 0 or 1, R.sub.2 represents an hydrogen atom or a methyl radical and R.sub.3 stands for a monovalent radical selected from the group comprising the amido, amino, pyridyl and pyrrolidonyl radicals, p, q, r and s represent integers so selected that 1.ltoreq.p.ltoreq.95, 0.ltoreq.q.ltoreq.99, 0.ltoreq.r.ltoreq.99 and 0.ltoreq.s.ltoreq.40, the sum p+q+r+s being equal to 100 and q and r never being nil simultaneously, while more particularly 1.ltoreq.p.ltoreq.85, 0.ltoreq.q.ltoreq.90, 5.ltoreq.r.ltoreq.95 and 0.ltoreq.s.ltoreq.30.

The units A of the modified acrylic polymers are derived from one or more acrylic monomers selected from the group comprising the ethylacrylic or methacrylic acids, the alkyl acrylates and ethylacrylates the alkyl radical of which contains 1 to 4 carbon atoms and the alkyl methacrylates the alkyl radical of which contains 2 to 4 carbon atoms.

The units B of said polymers are obtained from the units A by substituting the carboxylic acid or the ester group with an alkanolamide, particularly an ethanolamide or diethanolamide group, while the units C are derived from the units A substituting the carboxylic acid or ester group by an alkanolammonium carboxylate group, particularly an ethanolammonium, diethanolammonium or tri-ethanolammonium carboxylate group.

As to the units D, which may be present in a minor proportion with respect to the entire amounts of units A, B and C, they are derived from one or more monomers selected from the group comprising acrylamide, methacrylamide, vinylamine, vinylpyridine and vinylpyrrolidone.

The molecular weight of the modified acrylic polymers of the invention may vary within rather wide limits, advantageously between 0.2.times. 10.sup.6 and 100.times. 10.sup.6, more particularly between 0.4.times. 10.sup.6 and 50.times. 10.sup.6, and preferably between 1.times. 10.sup.6 and 20.times. 10.sup.6.

The modified acrylic polymers according to the invention may include the polymers formed exclusively of units A and B and/or C in molar percentages p, q and r which are so selected that 1.ltoreq.p.ltoreq.95, 0.ltoreq.q.ltoreq.99 and 0.ltoreq.r.ltoreq.99, the sum (p+q+r) being equal to 100, q and r not being nil simultaneously, said percentages being preferably so selected that 1.ltoreq.p.ltoreq.85, 0.ltoreq.q.ltoreq.90 and 5.ltoreq.r.ltoreq.95. The polymers for which 5.ltoreq.p.ltoreq.80, 2.ltoreq.q.ltoreq.80 and 7.ltoreq.r.ltoreq.80 are particularly suitable.

Some of the modified polymers of this class may be particularly mentioned, to wit those wherein the units A constituted by at least one of the radicals ##STR5## i.e., radicals which are derived respectively from methyl acrylate and/or from methacrylic acid, while the units B are constituted by the following radicals: ##STR6## and/or ##STR7## (i= j= 2 and .alpha. = 0 or 1), and the units C are formed of the following groups: ##STR8## (i= j= k= 2, and .alpha. and .beta. = 0 or 1).

The method of preparing the modified acrylic polymers according to the invention comprises reacting an acrylic polymer, which has been prepared by polymerizing one or more of the monomers leading to units A, possibly mixed with one or more of the monomers leading to units D, with at least an alkanolamine of formula: ##STR9## wherein i, j, k represent numbers which may vary from 1 to 6, and wherein .alpha. and .beta., which may be identical or different, are equal to 0 or 1, and then separating the modified acrylic polymer from the reaction medium.

The acrylic polymer reacted with the alkanolamine or alkanolamines may be prepared by any method known in the art enabling production of an acrylic polymer of adequate molecular weight, and particularly by emulsion or solution polymerization in the presence of a catalytic system of the Redox type, or by bulk polymerization with active radiations, particularly gamma rays.

The reaction between the acrylic polymer and the alkanolamine or alkanolamines, particularly mono-, di- or triethanolamine, may be carried out in the absence of any solvent or diluent. The reaction may also be performed in a solvent or diluent of the non polar type, particularly in an aromatic, aliphatic or cycloaliphatic hydrocarbon, especially xylene or toluene, or also in a solvent or diluent of the polar type, and more particularly in an aqueous phase.

Depending on whether the solvent is non-polar (hydrocarbon of the xylene type) or polar (aqueous phase), the resulting modified polymer will have a major content of units B having an amide function, or units C having a quaternary ammonium function.

The amount of alkanolamine reacted with the acrylic polymer may vary widely. For example, the molar ratio of the amount of alkanolamine used to the amount of acrylic polymer to be modified may vary between 0.1 and 15, said ratio being more particularly comprised between 0.3 and 5.

The reaction between acrylic polymer and alkanolamine may be carried out at temperatures comprised between 25.degree. and 200.degree. C., the preferred temperatures being comprised between 50.degree. and 150.degree. C. When the reaction is carried out in the presence of a solvent or a diluent, it can be advantageously performed at the boiling temperature of said solvent or diluent, or close to this temperature.

When the reaction between acrylic polymer and alkanolamine is carried out by contacting said alkanolamine with a solution or a dispersion of the acrylic polymer in a solvent or a diluent, the polymer concentration of said solution or dispersion may be advantageously comprised between 1 and 60% by weight, and more particularly between 3 and 40% by weight.

The duration of the reaction between the acrylic polymer and the alkanolamine(s) may vary widely. It may be comprised more particularly between 30 minutes and 120 hours, and advantageously between 1 hour and 80 hours.

The modified acrylic polymer may be separated from the reaction medium by any method known in the art allowing a polymer to be isolate from its solution or its suspension medium. For example, when the modified acrylic polymer is suspended in the reaction medium, it may be separated by mere filtration. When the modified acrylic polymer is dissolved, it may be separated by precipitation in a medium in which the polymer is not soluble, or by evaporation of the volatile components of said solution.

The following examples are given by way of illustration, but not of limitation, of the invention.

Monoethanolamine (MEA) was reacted with methyl polyacrylates (MPA) of various molecular weights in dissolved in xylene, said methyl polyacrylates being prepared by polymerization of methyl acrylate dissolved in benzene in the presence of a free radical initiator, which was in the present instance azobisisobutyronitrile.

The reaction of modification of the methyl polyacrylate by ethanolamine was carried out at a temperature of 135.degree. C. for 16 hours, except in example 4 where the time was only 8 hours.

The reaction mixture was then cooled to room temperature in order to precipitate the modified acrylic polymer, said polymer was separated by filtration, washed alternately with acetone and methanol and dried in a vacuum oven at 50.degree. C.

The specific operating conditions and the results obtained are listed in Table I hereinabove.

Methyl polyacrylates (MPA) having different molecular weights, prepared either as indicated in example 1 (examples 6 to 8, 11, 12 and 15) or by emulsion polymerization (examples 9, 10, 13 and 14), were reacted with monoethanolamine (MEA), the reaction being carried out at a temperature of 100.degree. C., using water as a diluent.

The reaction mixture was maintained at this temperature for various durations, then was cooled and the modified acrylic polymer was separated by precipitation in a non solvent medium, namely aceton, followed by filtration. The filtered polymer was then washed with aceton and dried in a vacuum oven at a temperature of 50.degree. C.

The specific operating conditions and the results obtained are recorded in Table II hereinabove.

Operating conditions similar to those of example 6 were used, however the methyl polyacrylate was replaced by a polymethacrylic acid having a molecular weight of 1.5.times. 10.sup.6, and the reaction was performed with monoethanolamine at a temperature of about 105.degree. C.

The resulting modified polymer contained, by moles, 47% units A of the formula: ##STR12## 3% units B of the formula: ##STR13## and 50% units B of the formula: ##STR14##

Operating conditions similar to those of example 1 were used, however the methyl polyacrylate was replaced by an ethyl polyacrylate having a molecular weight of 1.2.times. 10.sup.6 (test I) or by an ethyl polymethacrylate having a molecular weight of 0.8.times. 10.sup.6 (test II), the reaction being carried out at a temperature of 130.degree. C. in test I and 145.degree. C. in test II.

The modified polymer obtained in test I contained, by moles, 20% units A of the formula: ##STR15## 58% units B of the formula: ##STR16## and 22% units C of the formula: ##STR17##

As to the modified polymer obtained in test II, it contained, by moles, 28% units A of the formula: ##STR18## 62% units B of the formula: ##STR19## and 10% units of the formula: ##STR20##

The hydrophilic modified acrylic polymers according to the invention may be advantageously used where it is endeavoured to improve the flow conditions of an aqueous liquid in a conduit. Indeed, adding a small amount of one of said modified polymers to an aqueous liquid flowing in a conduit results in considerably reducing the turbulence which is produced by the displacement of said liquid in said conduit. When performing flow tests in the presence and in the absence of the modified polymer, respectively, flow rates improved by about 15 to 20% where obtained, with a reduction of about 50 to 60% of the friction, when the flowing aqueous liquid contained 5 to 300 ppm of one of the modified polymers according to the invention.