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

The present invention relates to modified hydrophilic acrylic polymers, especially to hydrodispersible or hydrosoluble modified acrylic polymers. The invention also relates to a method for preparing such polymers.

A great number of hydrophilic polymers are known, especially polymers which are hydrodispersible or hydrosoluble, such as certain vinyl polymers, the most universally known of which are polyvinyl alcohols and polyacrylamides.

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

The hydrophilic modified acrylic polymers according to the invention contain, expressed in mole %:

p % units A having the formula: ##STR1## q % units B having the formula: ##STR2## r % units C having the formula: ##STR3## and s % units D having the formula: ##STR4## in which the formula R designates one or more radicals selected from the group comprising hydrogen and methyl and ethyl radicals, R.sub.1 designates hydrogen or an alkyl radical containing 1 to 4 carbon atoms, Z designates one or more members of the group comprising the alkali metals, the alkaline earth metals, ammonium and the quaternary ammonium radicals having the formula: ##STR5## the proportion of Z representing the quaternary ammonium radicals being comprised between 0% and 10% of the entire amount of Z, while i, j and k, which may be identical or different, are comprised between 1 and 6, and while .alpha. and .beta. are equal to 0 or 1, whereas R.sub.2 represents one atom of hydrogen or/and a methyl radical, R.sub.3 represents one or more monovalent radicals selected from the group comprising amido, amino, pyridyl and pyrrolidonyl radicals, and p, q, r and s represent integers and are so selected that 1.ltoreq.p.ltoreq.99, 0.ltoreq.q.ltoreq.96, 1.ltoreq.r.ltoreq.99, and 0.ltoreq.s.ltoreq.40, the sum (p+q+r+s) being equal to 100, and more particularly 2.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 acrylic, methacrylic and ethylacrylic acids, and the alkyl acrylates, methacrylates and ethylacrylates the alkyl groups of which contains 1 to 4 carbon atoms.

The units B of said polymers are obtained from the units A by substituting the carboxylic acid group or the ester group by an alkanolamide radical, especially by an ethanolamide or diethanolamide radical, while the units C are derived from the units A by substituting the carboxylic acid group or ester group by an ammonium carboxylate group, an alkali metal or alkaline-earth metal carboxylate group, and possibly by an alkanolammonium carboxylate group.

As regards the units D, which are possibly present in minor amounts as compared to the combined amounts of units A, B and C, they are derived from one or more monomers preferably selected from the group comprising acrylamide, methacrylamide, vinylamide, vinylpyridine and vinylpyrrolidone.

The molecular weight of the hydrophilic modified acrylic polymers according to the invention may vary within rather broad limits. Advantageously, it may vary between 0.2 .times. 10.sup.6 and 100 .times. 10.sup.6, and more particularly between 0.4 .times. 10.sup.6 and 50 .times. 10.sup.6. The preferred molecular weight is comprised between 1 .times. 10.sup.6 and 20 .times. 10.sup.6.

An advantageous class of hydrophilic modified acrylic polymers according to the invention comprises the polymers composed only of units A, B and/or C in mole % proportions such that, with reference to the above defined symbols, p, q and r, 1.ltoreq.p.ltoreq.99, 0.ltoreq.q.ltoreq.96, 1.ltoreq.r.ltoreq.99, the sum (p+q+r) being equal to 100. Said proportions are selected preferably in such a way that 2.ltoreq.p.ltoreq.85, 0.ltoreq.q.ltoreq.90, and 5.ltoreq.r.ltoreq.95, and more particularly 5.ltoreq.p.ltoreq.80, 2.ltoreq.q.ltoreq.80 and 5.ltoreq.r.ltoreq.80.

Amongst the modified polymers of this class, those polymers may be particularly mentioned which contain units A in the form of one or more of the following radicals: ##STR6## i.e. units which are derived respectively from acrylic acid, methyl acrylate, methacrylic acid and methyl methacrylate, while the units B are constituted by at least one of the following radicals: ##STR7## and units C being of the kind ##STR8## wherein Z.sub.1 is at least one of the members constituting the group comprising sodium, potassium, ammonium and the quaternary ammonium radicals having the formula: ##STR9## and wherein the proportion of Z.sub.1 representing quaternary ammonium radicals is comprised between 0 and 10% of the entire amount of Z.sub.1, while .alpha. and .beta. have the signification indicated hereinabove.

The method of preparing the hydrophilic modified acrylic polymers according to the present invention comprises the steps of reacting an acrylic polymer obtained by polymerization of one or more monomers leading to the units A possibly mixed with one or more monomers leading to the units D, with at least one alkanolamine having the formula: ##STR10## wherein i, j and k represent numbers comprised between 1 and 6, and wherein .alpha. and .beta., which may be identical or different, are equal to 0 or 1, then submitting the product obtained of said reaction to alkaline hydrolysis by treating it with an aqueous alkaline solution of a compound of an alkali metal, of an alkaline earth metal, or of ammonium, and finally separating the thus modified acrylic polymer from the hydrolysis medium.

The acrylic polymer reacted with the alkanolamine or alkanolamines may be prepared by any known method which leads to obtaining an acrylic polymer having a molecular weight close to the molecular weight of the hydrophilic modified acrylic polymer to be obtained. The acrylic polymer may be obtained, in particular, by emulsion or solution polymerization in the presence of a catalytic system of the so-called REDOX type, or by bulk polymerization under the effect of active radiation, especially of gamma rays.

The reaction of the acrylic polymer with the alkanolamine or alkanolamines such as monoethanolamine, diethanolamine and triethanolamine may be performed without any solvent or diluent. This reaction may also be performed in a solvent or diluent of the non-polar type, especially in an aromatic hydrocarbon, such as xylene or toluene, in an aliphatic or cycloaliphatic hydrocarbon, or in a solvent or diluent of the polar type, especially in an aqueous phase.

Depending on whether the solvent or diluent is non-polar (hydrocarbon) or polar (aqueous phase), the product resulting from the reaction of the acrylic polymer with alkanolamine or alkanolamines will contain a major amount of units B having an amide function, or of units C having a quaternary ammonium function.

The amount of alkanolamine which is reacted with the acrylic polymer may vary within wide limits. Thus the molar ratio between the amount of alkanolamine used and the amount of acrylic polymer may be comprised between 0.1 and 15, this ratio being preferably comprised between 0.3 and 5.

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

When the reaction of the acrylic polymer with the alkanolamine is performed by contacting said alkanolamine with a solution or dispersion of the acrylic polymer in a solvent or diluent, the polymer concentration of said solution or dispersion is advantageously comprised between 1 and 40% by weight, preferably between 3 and 40% by weight.

The duration of the reaction of the acrylic polymer and the alkanolamine or alkanolamines may vary within wide limits, depending on the desired alkanolamide and/or quaternary ammonium content of the product resulting from the reaction. This duration may be comprised more particularly between 30 minutes and 120 hours, preferably between 1 hour and 80 hours.

Advantageously, the hydrolysis of the product resulting from the reaction of the acrylic polymer and the alkanolamine or alkanolamines may be obtained by contacting said product, after separating the same from the reaction medium, with the aqueous solution of the alkali metal, alkaline earth metal or ammonium compound. When the reaction of the acrylic polymer and the alkanolamine or alkanolamines has been performed in an aqueous phase, it is possible to carry out the hydrolysis by adding the alkali metal, alkaline earth metal or ammonium compound or compounds to said aqueous phase.

The alkali metal, alkaline earth metal or ammonium compounds used for the hydrolysis may advantageously be selected from the group comprising oxides, hydroxides and carbonates of said alkali metals, alkaline earth metals or ammonium. It is particularly recommended to use to this end sodium hydroxide and potassium hydroxide.

The molar ratio of the amount of alkali metal, alkaline earth metal or ammonium compound or compounds to the amount of product resulting from the reaction of the acrylic polymer with the alkanolamine or alkanolamines, which ratio is equal to the molar ratio of the amount of alkali metal, alkaline earth metal or ammonium compound to the amount of initial acrylic polymer, may vary advantageously between 0.02 and 1.2 and is preferably comprised between 0.05 and 0.9.

The temperature at which the hydrolysis is performed may vary within wide limits, and may be comprised more particularly between 50.degree. C. and 150.degree. C. However for convenience it is preferable to perform the hydrolysis at a temperature equal to the boiling temperature of the aqueous phase in which the hydrolysis is carried out, or at a temperature close to this boiling temperature.

The concentration of the polymer treated with the alkanolamines in the aqueous phase may be comprised advantageously between 0.5 and 60% by weight, said concentration being preferably comprised between 1 and 40% by weight.

The duration of the hydrolysis reaction may vary within wide limits, depending on the amount of alkali metal carboxylates, alkaline earth metal carboxylates or ammonium carboxylates which are to be obtained in the resulting hydrophylic modified acrylic polymer. In most cases the said duration will be comprised between 1 hour and 80 hours, and more particularly between 5 and 60 hours.

The product resulting from the reaction of the acrylic polymer and the alkanolamine or alkanolamines, as well as the modified acrylic polymer resulting from the hydrolysis of the aforementioned reaction product, may be separated from their respective reaction media by any convenient known method adapted to achieve the separation of a polymer from its solution (precipitation in a medium in which the polymer is not soluble, evaporation of the volatile constituents of the solution) or from its suspension medium (filtration, centrifugation).

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

Monoethanolamine (abbreviation : MEA) was reacted with methyl polyacrylates (abbreviation : MPA) having different molecular weights, dissolved in xylene (Examples 1 to 16) or in dimethylformamide (Examples 17 and 18), 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 azo-bis-isobutyronitrile.

The reaction of modification of the methyl polyacrylate by ethanolamine was performed at a temperature of 135.degree. C. during 16 hours (Examples 1 to 11), 40 hours (Examples 12 to 14), 27 hours (Example 15), 24 hours (Examples 16 and 17) and 7 hours (Example 18), respectively.

The reactive mixture was then cooled to ambient temperature so as to precipitate the acrylic polymer treated with ethanolamine, said polymer then being separated by filtration, and washed alternatively with acetone and methanol.

The product resulting from the reaction of methyl polyacrylate and ethanolamine was then introduced into an aqueous sodium hydroxide solution, and the mixture thus obtained was heated to a temperature of 100.degree. C. and maintained at this temperature during various periods of time.

The hydrolysis medium was then cooled to ambient temperature, and the modified acrylic polymer was separated from the hydrolysis medium and dried under vacuum in an oven at 50.degree. C.

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

The formulas of units A, B, C of the acrylic polymers according to Examples 1 to 18 are the following: ##STR11##

Monoethanolamine was reacted with a polyacrylic acid having a molecular weight of 0.8 .times. 10.sup.6 (test I) and with a polymethacrylic acid having a molecular weight of 0.9 .times. 10.sup.6 (test II), in an aqueous solution at a temperature of about 110.degree. C., with a molar ratio monoethanolamine: polymer equal to 1.05 (test I) and equal to 0.7 (test II).

After separating the reaction medium the product resulting from the reaction of the polyacrylic acid or the polymethylacrylic acid with monoethanolamine was introduced into an aqueous solution of sodium hydroxide, and the resulting mixture was heated to a temperature of 100.degree. C.

The hydrolysis medium was then cooled to ambient temperature, and the modified polymer was separated from the hydrolysis medium and dried under vacuum in an oven at 50.degree. C.

The modified polymer obtained in test I contained, by moles, 20% units A having the formula: ##STR12## 9% units B having the formula: ##STR13## and 71% units having the formula: ##STR14##

As regards the modified polymer obtained in test II, the same contained

40% units A having the formula: ##STR15## 12% units B having the formula: ##STR16## and 48% units C having the formula: ##STR17##

The same operating procedure as the one described in Example 1 was used, while however replacing the methyl polyacrylate by an ethyl polyacrylate having a molecular weight of 0.9 .times. 10.sup.6 (test III) or by a methyl polymethacrylate (test IV), and using diethanolamine instead of monoethanolamine.

The modified polymer obtained in test III contained, by moles, 48% units A having the formula: ##STR18## 20% units B having the formula: ##STR19## and 32% units C having the formula: ##STR20## As regards the modified polymer obtained in test IV, the same contained, by moles,

45% units A having the formula: ##STR21## 22% units B having the formula: ##STR22## and 33% units C having the formula: ##STR23##

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.