GB2269178A - Water-soluble amphiphilic polymers, their preparation process and their use as thickeners - Google Patents

Description

2269178 WATER-SOLUBLE AMPHIPHILIC POLYMERS, THEIR PREPARATION PROCESS AND

THEIR USE AS THICKENERS The present invention relates to water-soluble amphiphilic polymers, their preparation process and their use as thickeners.

Alkali metal polyacrylates, with a very high molecular weight, crosslinked or not, are widely used for their thickening properties in various industrial compositions or formulations intended in particular for the textile, oil or cosmetic industry.

It is known that the thickening properties of these polymers are significantly reduced in the presence of mineral salts.

Therefore water-soluble polymers are sought which can suitably thicken aqueous fluids containing mineral salts in solution such as drilling muds, and compositions intended for pigment printing.

Water-soluble amphiphilic polymers based on polyacrylic acid were therefore proposed, a few carboxyl groups of which were chemically converted, in an organic solvent medium, into N-alkyl carbamoyl groups distributed in a statistical fashion along the polymer chains (T.K. WANG et al, ACS Symp. Ser., 1991, 467, Water-soluble Polymers, 218-231, and Polym. Bull., 1988, 20, 577-582). Although these polymers have thickening properties in aqueous medium and even in the presence of mineral salts, they are very expensive to manufacture on an industrial level.

Now, the Applicant has discovered new water-soluble amphiphilic polymers having very useful thickening properties in saline aqueous medium.

Therefore a subject of the present invention is the water-soluble amphiphilic polymers of formula (I):

CH2-CH ( CH2-CH ---- 1 1 COOMI m CONHR n in which R represents a c,_C16 alkyl group, M represents a sodium or potassium- atom, m and n satisfy the following 2 relationships: m + n is comprised between about 500 and about 20.000 and the m/n molar ratio is comprised between 99.5/0.5 and 80/20, and in which the N-alkyl acrylamide units are distributed along the polymer chains in a non-statistical fashion.

The term C,-CM alkyl can refer to, for example, an octyl, nonyl, decyl, undecyl, dodecyl, tetradecyl or hexadecyl group.

The expression "distributed along the chains in a non-statistical fashion" means that the distribution of the monomer units along the polymer chains does not satisfy a statistical distribution according to Bernoullils law but that the monomer units are grouped in S1 and S2 sequences respectively, sequence S1 containing very few N-alkyl acrylamide units and sequence S2 being rich in these units. In other words, the distribution of the N-alkyl acrylamide units along the polymer chains is rather of block type.

A more particular subject of the invention is polymers as defined above characterized in that in formula (I), the number of m + n units is about 2000 and the m/n molar ratio is comprised between 99.5/0.5 and 88/12. Among the last-named polymers, a particular subject of the invention is the polymers of formula (I) in which R represents an octyl, decyl, dodecyl and tetradecyl radical.

Also a subject of the present invention is a preparation process for water-soluble amphiphilic polymers of formula (I) above characterized in that a polyacrylic acid of formula (II):

CH2-CH (II) 1 - COO+H m+n in which m- and n have the meaning already indicated, is reacted, in aqueous solution, at a pH of about 8 + 1, with an amine of formula (III):

3 R-NH2 (Ill) in which R has the meaning already indicated, in the presence of a water- soluble carbodiimide, then an excess of alkali metal hydroxide: MOH where M has the meaning already indicated is introduced into the reaction medium in order to completely salify the carboxyl groups of the polymer obtained, and in that finally the reaction medium is poured into methanol in order to obtain the corresponding polymer of formula (I).

The polyacrylic acids of formula (II) as well as the amines of formula (Ill) are commercial products. There can be used as water-soluble carbodiimides in particular those described by J.C. Sheehaw et al, J. Org. Chem., 26, 2525 (1961), such as 1-ethyl 3 - (3 -dimethyl amino propyl) carbodiimide hydrochloride designated EDC, which is a commercial product.

In the preferred conditions for implementing the invention, the process described above is carried out in the following manner:

- condensation of the polyacrylic acid of formula (II) with the amine of formula (Ill) is carried out at a temperature below WC, under vigorous agitation, - the water-soluble carbodiimide is added in the solid state to the reaction solution, - the molar quantity of the amine of formula (Ill) used is comprised between 1 and 3 n, where n has the meaning already indicated, - the molar ratio of water-soluble carbodiimide to amine of formula (III) is comprised between 1 and 5, - the polyacrylic acid of formula (I1) is dissolved before-hand in an aqueous solution of alkali metal hydroxide of formula MOH where M has the meaning already indicated, so as to obtain a solution having a pH of about 8 + 1, - the amine of formula (Ill) is dissolved beforehand in hydrochloric acid so as to obtain an aqueous solution having 4 a PH of about 8 + 1.

The distribution of the N-alkyl acrylamide units along the polymer chains was determined by NMR 13C at 62.5 MHz, with a Bruker WP 250 apparatus, in solution at 8-12% by weight in a D20/CD3 OD mixture, 80-20 by volume. Study of the resonance peak of the carbon of the carboxylate group enables the nature of the units situated in adjacent positions to be known. If by A is meant the alkali metal acrylate unit and by B is meant the N-alkyl acrylamide unit, the presence of three triplets is detected: AAA, AAB or BAA, and BAB, the chemical displacements of which relative to the TMS are 185.5, 184.8 and 183.9 ppm respectively. After deconvolution of these peaks using a program generating Lorentz-shaped curves, the molar percentages of these different triplets are obtained. The experimental results thus found show that the distribution of A and B monomer units along the polymer chains does not satisfy Bernoullils law and that the B units are preferably grouped in sequences rich in this type of monomer unit.

The polymers according to the invention are therefore different from those described previously by K.T. Wang et al (reference already cited) and B. Magny et al, Polymer., ready for publication, which have a statistical distribution of their A and B monomer units.

The polymers according to the invention of formula (I) have useful thickening properties. Their solubility in water, their high viscosifying effect and their anti-polyelectrolytic property make them particularly suitable for thickening aqueous solutions loaded with mineral salts.

It is known that the viscosity of aqueous solutions of polyelectrolytes, cross-linked or not, reduces significantly in the presence of dissolved mineral salts. Now, the polymers of the present have an inverse effect, the viscosity of their aqueous solution increases in the presence of dissolved mineral salts. This effect is referred to as an anti-polyelectrolytic property. This property is very advantageous on an industrial level because the vast majority of aqueous solutions that it is desired to thicken contain in quite considerable amounts of dissolved mineral salts.

The polymers previously described by K. T. Wang et al (reference already cited) also have ant i-polyel ectrolyt ic properties but these are significantly weaker than those shown by the polymers according to the invention.

The following examples illustrate the invention.

The NMR 'H spectra were recorded with a Fourier transform spectrometer operating at 250 MHz. The samples were dissolved in heavy water. The integration ratio of the peak corresponding to the terminal methyl group of the alkyl chain (about 0.07 ppm) to that of the peak corresponding to the methine group of the polymer chain (about 1.6-2.4 ppm) enables the m/n ratio to be calculated.

The NMR 13C spectra were recorded with a Bruker WP 250 spectrometer, operating at 62.5 MHz with proton decoupling. The spectral width is 12, 500 Hz, the "pulse" angle is 30, the acquisition time is 0.65 seconds, the waiting time is 0.5 seconds and the accumulation number is 50,000. The internal reference is methanol d4 (49 ppm relative to the TMS). The deconvolution of the spectra is carried out with an HP 9836 computer. The temperature of the samples is comprised between 45 and 60'C. The distribution of the triplets AAA, BAB and AAB or BAA found experimentally is given in the column of the tables marked exp., compared with that calculated (calc.) using Bernoullils law.

The viscosities, expressed in mPa.s, were determined on a Contraves "LowShear 3011 apparatus with a low speed gradient (from 0. 06 to 1 s-1), at a temperature of 25 + 1 C.

The in/n ratio was also calculated from the percentages by weight of carbon and nitrogen found by elementary analysis.

For the designation of the polymers, the following 6 rule was used: the first three figures indicate the average molecular weight divided by 1000 of the starting polyacrylic acid. The next number indicates the substitution rate expressed as a molar percentage. The letter C followed by a number indicates the number of carbon atoms of the amine used. Finally, the letter P indicates that the polymer was obtained according to the process described in the comparative examples Cl-CS.

EXAMPLE 1

An aqueous solution with 25% by weight of polyacrylic acid, of a molecular weight of about 150,000, marketed by Polysciences Inc. is lyophilized. In this way a dry and solid polyacrylic acid is obtained, designated hereafter 150-OC.

7 g (97.14 mmoles) of 150-OC is dissolved under agitation, at ambient temperature, in 39.2 ml of 2M soda, then 12.2 inl of an aqueous solution, neutralized at pH = 7 with 1M hydrochloric acid and containing 0.788 g (6. 1 mmoles) of octylamine, is introduced slowly under agitation, at ambient temperature, into the solution thus obtained which has a pH of about 7, and the reaction medium is then left under agitation until a homogeneous solution is obtained. 2.331 g (12.2 mmoles) of 3-ethyl 1-(3-dimethylamino propyl) carbodiimide hydrochloride is then introduced in the solid state, under vigorous agitation and at ambient temperature, into this solution. The condensation reaction is almost instantaneous and the reaction solution thickens within a few minutes. Excess soda at 40% by weight is then introduced into the reaction medium so as to completely salify the carboxylic functions of the polymer obtained, then the reaction medium is poured into a large volume of methanol. The sought polymer precipitates, it is isolated by filtration, then it is washed with methanol and finally it is dried to a constant weight under reduced pressure at 50C. In this way a water-soluble amphiphilic polymer is obtained 7 with a degree of polymerization equivalent to that of the precursor, based on sodium acrylate and N-octyl acrylamide, 95/5 in molar proportions, and the N-octyl acrylamide units of which are distributed in a non-statistical manner along the polymer chains. This polymer is designated 150-5 C8 and its physical characteristics are given in tables I-III. The 95/5 molar ratio of the polymer obtained was determined on the one hand by elementary analysis and on the other hand by NMR 1H and 13C analysis.

EXAMPLES 2-9

Example 1 is reproduced but the octylamine is replaced by x mmoles of an amine of formula (III) dissolved in water, in the presence of 1M hydrochloric acid so as to obtain a concentration of 0. 5M and a pH of 7, and in the presence of 2 x moles of the same carbodiimide, EDC. In this way corresponding different polymers of formula (I) are obtained whose characteristics are given in-tables I-III.

COMPARITIVE EXAMPLES Cl-CS (according to K.T. Wang et al, reference already cited) g (69.4 mmoles) of 150-OC is dissolved under agitation, at 60C, in 150 ml of N-methyl 2-pyrrolidinone (MPD), then y mmoles of an amine of formula (III) and 1.1 y mmoles of dicyclohexylcarbodiimide dissolved in 20 ml of MPD are introduced successively into this agitated solution, maintained at 60C. Once the introductions are completed, the reaction medium is left under agitation at 60C for 24 hours, then after cooling down to ambient temperature, the dicyclohexylurea formed is eliminated by filtration and the filtrate is then diluted with soda at 40% by weight. The sought polymer precipitates, it is isolated by filtration then washed successively with MPD previously heated to 60C and with methanol; the precipitate thus washed is then dissolved in water, then reprecipitated by the addition of methanol. After filtration and drying to a constant weight

8 at 50C under reduced pressure, a water-soluble amphiphilic polymer is obtained with a degree of polymerization similar to the precursor, based on sodium acrylate and N-alkyl acrylamide, the N-alkyl acrylamide units of which are distributed according to Bernoullils law along the polymer chains, as mentioned by K.T. Wang et al, reference already cited, page 578 and B. Magny et al, Polymer, ready for publication.

The comparitive polymers mentioned in table IV were prepared in this way, the characteristics of which are given in tables II-M Examination of tables I-III shows that the polymers according to the invention differ from the polymers of the prior art with the same monomer composition by a different micro-structure which gives them a very dif f erent rheological behaviour in pure water and in salt water. In particular, in salt water, the polymers according to the invention have a viscosity which increases as a function of the increase in the salt concentration. Thus, for example, polymer 150-5 C8 at 2.5% has a viscosity of 34 mPa.s in pure water at a temperature of 25C, and a viscosity of 162 mPa.s in water with 2-% sodium chloride. This effect is surprising and extremely useful on an industrial level.

1 TABLE I

Ex. Designation R X m:n -h Distribution of the triplets (mmole) (mPa.s) AAA AM=BAA BAB exp. calc.: exp. calc. exp. calc.

1 150-5 C8 octyl 6.1 95:5 25 91.6 90.25 8.1 9.5 0.25 0.25 2 150-3 C8 octyl 3.66 97:3 20 3 150-4 C8 octyl 4.9 96:4 21 4 150-10 C8 Octyl 12.2 90:10 1620 86 81 12 18 2 1 150-15 C8 Octyl 18.3 85:15 330 83.5 72.25 13.9 25.5 2.6 2.25 6 150-20 C8 Octyl 24.4 80:20 45 77 64 18 32 5 4 7 150-0.7 C12 dodecyl 3.66 99.3:0.7 151 8 150-1 C12 dodecyl 3.66 99:1 164 9 150-0.5 C14 tetradecyl 0.6 99.5:0.5 1170 determined at 2% by weight in pure water at 250C 14 TABLE II

Rheology of aqueous solutions with C% of polymer, at 250C.

VISCOSITY (mPa.s) C% 150-OC 150-3C8 150-5C8 150-15C8 150-20C8 150-3C8P 150-10C8P 150-20C8P 0.1 3.3 2.9 3.9 3 3.8 2.9 3.6 4 0.2 4.4 5.6 5.8 4 5.4 4.1 0.3 6.4 6.8 7.0 4.8 6.5 4.9 0.5 7.9 8.8 9.4 6.2 8.4 10.2 7.7 8 1 11.9 12.5 13 10.9 14.2 10 11.7 12.5 2 17.3 20.3 25 330 45 14.8 18.7 60 3 25.2 34 71 120000 440 21 39 85 538 34.6 7 53 192 4400 49.1 9 71.1 446 70.3 11 105 1024 100 13 133 3214 127 177 5446 168 CD determined with a CARRIMED CS 100 type apparatus.

TABLE III

Rheology of aqueous solutions containing C% of C1Na and M of polymer, at 250C VISCOSITY (mPa.s) C% K = 1.3% K = 2.5% K = 3% 150-OC 150-10C8 150-10C8P 150-OC 150-5C8 150-5C8P 150-OC 150-IC12 150- 1C12P 0 13.4 24.4 15.8 21.5 34 24.7 25.2 164 25.3 0.1 9.6 41.8 10 17.9 32.7 19.9 0.3 6.8 106 7.3 13.8 38.1 14.5 157 18.7 0.5 5.7 126 6.3 11.4 51 13 181 15.3 1 4.4 40.6 6.0 8.6 96.7 10.2 81 12.1 1.5 3.7 17.5 5.6 7.1 143 2 3.3 9.9 5.3 6.1 162 9 46 10.6 2.5 3.0 6.2 4.8 5.6 155 8.5 3 2.8 4.4 5.2 141 8.5 TABLE IV

Ex. Designation R y m:n TI Distribution of the triplets (mmole) (mPa.s) AAA AM=BAA BAB exp. calc. exp. calc. exp. calc.

cl 150-3 C8P octyl 2.3 97:3 14.8 94.5 94.1 5.4 5.8 0.1 0.09 C2 150-5 C8P octyl 3.83 95:5 21 C3 150-10 C8P octyl 7.66 90:10 18.7 81.5 81 17.5 18 1 1 C4 150-20 C8P octyl 15.33 80:20 63.5 64 32.5 32 4 4 C5 150-1 C12P dodecyl 0.76 99:1 18.7 determined at 2% by weight in pure water at 250C -a K.) --1

Claims (9)

13 CLAIMS

1. Water-soluble amphiphilic polymers of formula M:

CH2-CH /'H2-CH COOM m CO n in which R represents a CCC16 alkyl group, M represents a sodium or potassium atom, m and n satisfy the following relationships: m + n is comprised between about 500 and about 20000 and the m/n molar ratio is comprised between 99.5/0.5 and 80/20, and in which the N-alkyl acrylamide units are distributed along the polymer chains in a non-statistical fashion.

2. Polymers according to claim 1, characterized in that in formula (I), the m/n molar ratio is comprised between 99.5/0.5 and 88/12.

3. Polymers according to claim 2, characterized in that in formula (1) of claim 1, R is chosen from the group constituted by octyl, decyl, dodecyl and tetradecyl radicals.

4. Preparation process for polymers of formula (I) as defined in claim 1, characterized in that a polyacrylic acid of formula (II):

- CH2-CH - 1 COOH m+n in which m and n have the meaning already indicated, is reacted, in aqueous solution, at a pH of about 8 + 1, with an amine of formula (III):

R-NH7 in which R has the meaning already indicated, in the presence of a water- soluble carbodiimide, then an excess of alkali 14 metal hydroxide: MOH where M has the meaning already indicated is introduced into the reaction medium in order to completely salify the carboxyl groups of the polymer obtained, and in that finally the reaction medium is poured into methanol in order to obtain the corresponding polymer of formula (1).

5. Process according to claim 4, characterized in that the condensation of the polyacrylic acid of formula (II) with the amine of formula (III) is carried out at a temperature below WC.

6. Process according to claim 4, characterized in that the water-soluble carbodiimide is 1-ethyl 3-(3-dimethylamino propyl) carbodiiinide hydrochloride.

7. Water-soluble amphiphilic polymers of formula (I) as defined in claim 1, substantially as described in any one-of the foregoing Examples 1 to 9.

8. A process according to claim 4, substantially as described in any one of the foregoing Examples 1 to 9.

9. Water-soluble polymers according to any one of claims 1 to 3 and 7, whenever prepared by a process as claimed in any one of claims 4 to 6 and 8.

- Use of polymers according to claim 1, as thickening agents for saline aqueous solutions.