CROSSLINKED COPOLYMER, PREPARATION METHOD AND PRINTING PASTE COMPRISING SAID COPOLYMER

Abstract

The present invention relates to a crosslinked copolymer obtained by precipitation polymerization of at least one monomer comprising at least one carboxylic acid function, at least one hydrophobic monomer, and at least one crosslinking agent. The copolymer is mainly characterized in that 30 mol % to 90 mol % of the carboxylic acid functions are in salified form prior to the precipitation polymerization, the solvent used for the precipitation polymerization comprises at least one alcohol comprising 1 to 4 carbon atoms, and the copolymer is obtained in the absence of water-soluble non-ionic monomers.

Claims

1. A crosslinked copolymer obtained by precipitation polymerization of at least: 60 mol % to 99.8 mol % of at least one anionic monomer comprising at least one carboxylic acid function, 0.1 mol % to 20 mol % of at least one hydrophobic monomer of formula (I), ##STR00003## wherein: R.sub.1, R.sub.2 and R.sub.3 are, independently of each other, a hydrogen atom or a methyl group, X is a group C(═O)—O—Y or CH.sub.2—C(═O)—O—Y, wherein Y is a hydrocarbon group, saturated or unsaturated, wherein Y is linear, branched, cyclic, or aromatic, wherein Y comprises 3 to 30 carbon atoms, and from 0 to 4 heteroatoms selected from the group consisting of O, N, and S, 1*10.sup.−9 mol % to 2 mol % of at least one crosslinking agent, the crosslinked copolymer being having 30 mol % to 90 mol % of the carboxylic acid functions of the anionic monomer in salified form prior to the precipitation polymerization, the solvent used for the precipitation polymerization comprising at least one alcohol comprising 1 to 4 carbon atoms, and the copolymer being obtained in the absence of water-soluble non-ionic monomers.

2. The crosslinked copolymer according to claim 1, wherein the copolymer is obtained in the absence of water-soluble non-ionic monomers selected from acrylamide, methacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N diethylacrylamide, N-methylolacrylamide, N-vinylformamide, N-vinyl acetamide, N-vinylpyridine, N-vinylpyrrolidone, acryloyl morpholine or diacetone acrylamide.

3. The crosslinked copolymer according to claim 1, wherein the monomer comprising at least one carboxylic acid function is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid and fumaric acid.

4. The crosslinked copolymer according to claim 1, wherein the monomer comprising at least one carboxylic acid function is acrylic acid.

5. The crosslinked copolymer according to claim 1, wherein the carboxylic acid functions are salified with a salifying agent selected from the group consisting of ammonia, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, and mixtures thereof.

6. The crosslinked copolymer according to claim 5, wherein the salifying agent is ammonia.

7. The crosslinked copolymer according to claim 1 wherein the copolymer is obtained by precipitation polymerization of 0.1 mol % to 10 mol % of the hydrophobic monomer of formula (I).

8. The crosslinked copolymer according to claim 1 wherein the hydrophobic monomer is of formula (I) wherein: R.sub.1 is a methyl group, R.sub.2 and R.sub.3 are hydrogen atoms, and X is a group C(═O)—O—Y, wherein Y is a linear alkyl chain of 18 carbon atoms.

9. A method for preparing a crosslinked copolymer according to claim 1 by precipitation polymerization, comprising: preparing a reaction medium comprising at least one solvent and from 5% to 35% by weight of at least one monomer comprising at least one carboxylic acid function, salifying 30 mol % to 90 mol % of the carboxylic acid functions of the monomer comprising at least one carboxylic acid function by the addition of a salifying agent, introducing 0.01% to 20% by weight of at least one hydrophobic monomer of formula (I) and 1×10.sup.−6% to 2% by weight of at least one crosslinking agent into the reaction medium, polymerizing monomers comprising at least one carboxylic acid function and hydrophobic monomers of formula (I) to obtain the crosslinked copolymer.

10. A printing paste comprising at least one crosslinked copolymer according to claim 1.

11. The printing paste according to claim 10, wherein the amount of crosslinked copolymer in the printing paste is comprised between 0.1% and 5% by weight.

12. A method for printing a textile material using a printing paste according to claim 10.

13. The method for printing a textile material according to claim 12, comprising the following steps: preparing a printing paste by mixing at least one crosslinked copolymer according to claim 1 with at least one dye or at least one pigment, and applying the printing paste over a textile material.

14. The method for printing a textile material according to claim 12 wherein the textile material is selected from natural polyamides, synthetic polyamides, polyamine, polypropylene, polyester, silk, wool, viscose, rayon, cotton, or a wool/polyamide mixture.

Description

EXAMPLES OF EMBODIMENTS OF THE INVENTION

[0087] Protocol for the Preparation of a Copolymer (A-O) by Precipitation Polymerization

[0088] 654 g of pure tert-butanol are mixed in a reactor with 16.77 g of water in order to obtain a mixture comprising 97.5% by weight of tert-butanol. Afterwards, acrylic acid is added into the reactor. Afterwards, the acrylic acid is neutralized by addition of gaseous ammonia until obtaining a pH comprised between 6 and 6.5. Once this pH has been obtained, stearyl methylacrylate and MBA (N,N-methylene-bis-acrylamide) are added. The preparation is degassed in the reactor by injecting nitrogen. Afterwards, 18.75 ppm of HTPO (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) are added and the temperature of the reactor is maintained at 70° C. using a thermostated bath. The polymerization reaction is initiated by adding 0.32 g of V50 (2,2′-azobis[2-methylpropionamidine],dichlorhydrate) and 0.64 g of VA044 (2,2′-[azobis(1-methylethylidene)]bis[4,5-dihydro-1H-imidazole dihydrochloride]). In general, the initiation of the polymerization is observed after 1 to 8 minutes. The thermostated bath is adjusted at 90° C. for 2 hours.

[0089] The presence of a white precipitate in the solvent is observed. This white precipitate corresponds to the copolymer of the invention. The latter is separated from the solvent by distillation using a rotary evaporator with oil heated to 90° C. and under a reduced pressure of 700 mbar. Afterwards, the copolymer obtained in powder form is placed in an oven for 12 hours at 70° C.

[0090] The copolymers A to O are prepared according to the protocol hereinbefore. The amounts of the different monomers are adjusted in order to obtain the proportions indicated in Table 1 hereinbelow for each example.

[0091] Preparation of the Polymer P

[0092] The polymer P is prepared according to the protocol hereinbefore, i.e. by precipitation polymerization, but without using stearyl methacrylate (MAS).

[0093] Preparation of the Polymer Q

[0094] The polymer Q is prepared according to the following protocol, by inverse emulsion polymerization.

[0095] The ingredients of the aqueous phase are loaded into a 1 L beaker under magnetic stirring: [0096] 310 g of deionized water [0097] 217 g of acrylic acid [0098] 168 g of ammonia in 30% solution [0099] 13.33 g of stearyl methylacrylate [0100] 0.696 g of methylenebisacrylamide (2400 ppm)

[0101] Afterwards, in a 1 L glass reactor, under mechanical stirring, the organic phase is prepared with: [0102] 133.5 g of paraffinic mineral oil (celtis 903) [0103] 133.5 g of aliphatic hydrocarbon (Isopar L) [0104] 22.5 g of sorbitan monooleate.

[0105] The aqueous phase is progressively transferred into the organic phase. Thus, the formed pre-emulsion is then subjected to high shear for 45 seconds (Ultra Turrax, IKA).

[0106] The inverse emulsion is then degassed for 30 minutes by simple nitrogen bubbling.

[0107] An aqueous solution containing 0.5% by weight of sodium metabisulphite and another solution containing 0.35% by weight of TBHP are added at a flow rate of 10 mL/h for a period of 60 minutes. Once the maximum temperature has been reached, the temperature of the reaction mixture is maintained for 60 minutes before cooling.

[0108] Afterwards, the polymer is isolated by precipitation in acetone.

[0109] Preparation of the Polymer R

[0110] The polymer R is prepared according to the protocol for the polymer Q, but without using stearyl methacrylate (MAS).

[0111] The results are indicated in Table 1 hereinbelow.

TABLE-US-00001 TABLE 1 Summary of tests and characteristics Monomer (mol %) MBA Neutralization Characteristics AA ACM MAS *10.sup.−4 (%) Precipitation.sup.(c) Viscosity.sup.(a) Dispersion.sup.(d) pH.sup.(b) Counter- A 29.68 69.67 0.65 2,400 — good 2,700 difficult 3.6 examples B 49.68 49.67 0.65 2,400 — good 2,860 difficult 3.6 C 30.00 70.00 — 2,400 — good 2,300 difficult 3.6 D 50.00 50.00 — 2,400 — good 2,500 difficult 3.6 E 100.00 — — 2,400 — no impossible impossible na F 99.35 — 0.65 2,400 — no impossible impossible na G 99.35 — 0.65 2,400 15 no impossible impossible na H 99.35 — 0.65 2,400 20 no impossible impossible na I 99.35 — 0.65 2,400 100* no impossible impossible — J 99.35 — 0.65 2,400  100** good 17,000 easy 7.3 Invention K 99.35 — 0.65 2,400 35 good 4,600 easy 5.3 L 99.35 — 0.65 2,400 40 good 14,860 easy 5.5 M 99.35 — 0.65 2,400 50 good 19,750 easy 5.8 N 99.35 — 0.65 2,400 75 good 22,500 easy 6.2 O 99.35 — 0.65 2,400 90 good 29,500 easy 6.7 Counter- P 100 — — 2,400 75 good 18,500 — 6.2 examples Q 99.35 — 0.65 2,400 75 — 2,600 — 6.2 R 100 — — 2,400 75 — 2,500 — 6.2 AA: acrylic acid ACM: acrylamide MAS: stearyl methacrylate MBA: in ppm relative to the weight of the monomers *post-neutralized = acrylic acid neutralized after polymerization **pre-neutralized = acrylic acid neutralized before polymerization .sup.(a)Viscosity (mPa/s) is measured at 0.5% by weight of copolymer in deionized water at 25° C., with a Brookfield RV module viscometer at a speed of 20 revolutions per minute. .sup.(b)The pH is measured at 1% by weight of copolymer in deionized water at 25° C. .sup.(c)The precipitation is evaluated visually according to the apparition or not of a precipitate. .sup.(d)The dispersion is considered easy when dispersion is complete in less than 10 minutes under (three blade) stirring at 500 rpm in a beaker of 300 ml of water at 25° C. for a polymer concentration of 0.5% by weight.

[0112] As described before, all molar percentages are expressed relative to the total number of moles of monomers including the crosslinking agent. This is also the case for all of the polymers in Table 1. However, in order to simplify reading of the results, the concentration values (mol %) have been rounded to the hundredth for the monomers and to the ten thousandth for the crosslinking agent.

[0113] In case of 100% pre-neutralization of acrylic acid, the final pH (pH=7.3) is too high for a carpet printing application requiring a pH preferably in the range of 5.6 to 6.5 to enable setting of the dyes. Hence, a 100% neutralization requires a subsequent pH adjustment for use as a printing paste thickener.

[0114] For all examples, the total amount of monomers and crosslinking agent is equal to 15.5% by weight, relative to the total mass of the (final) reaction medium.

[0115] Printing Paste Preparation Protocol

[0116] 498 g of deionized water and 2 g of acid black dye MR 125% (from Evron dyestuff) are added to a beaker. The whole is mixed then the copolymer, as a thickener, is added under stirring to thicken the mixture forming a printing paste. The amount of copolymer is determined in order to obtain a final viscosity of the printing paste of 2,500 mPa/s, measured with a Brookfield RV module viscometer at a speed of 20 revolutions per minute at 25° C.

[0117] On a Chromojet HSV 400 type laboratory digital printing system, the printing pastes obtained from the copolymers J to O are tested on their ability to pass through the printing nozzles in a given time.

[0118] This capacity to be able to transfer a sufficient amount of printing paste conditions the level of color obtained when printing a pattern on a textile, and the level of productivity of the printing step.

[0119] To carry out this test for each printing paste, the print head is ordered to continuously open for 15 seconds and the transferred printing paste is collected in a collector. The amount of printing paste transferred during this elapsed time is then weighed. The obtained results are indicated in Table 2 hereinbelow.

TABLE-US-00002 TABLE 2 application examples using different copolymers Amount of Amount of Neutraliza- thickener in transferred Polymer tion % g/kg of paste paste (in g) J 100%  4.12 70 K 35% 4.63 102 L 40% 4.67 105 M 50% 4.51 99 N 75% 4.28 97 O 90% 4.2 92 P 75% 4.6 94 Q 75% 11.2 61 R 75% 11.1 62

[0120] As one could notice, the amount of transferred printing paste drops sharply when the neutralization rate is between 90% and 100% neutralization before polymerization.

[0121] Yet, as described before, the amount of deposited printing paste is essential in this textile printing application because it directly impacts the obtained level of color.

[0122] Consequently, based on the results of Table 2, one could notice that a neutralization of the acrylic acid comprised between 30 and 90% allows maximizing the amount of printing paste transferred onto the textile substrate and therefore improving the quality and productivity of the printing method compared to those of the prior art.

[0123] Through these results, one could deduce that the neutralization rate directly impacts the rheological profile of the copolymer.

[0124] As regards the polymer P (counterexample), an amount of transferred paste close to the polymers K to O of the invention is obtained. Nevertheless, on application, a white veil is observed at the surface of the printed textile. This reflects the icing or “frosting” phenomenon, frequently observed in the methods known to a person skilled in the art when printing a textile material with a printing paste based on acrylic acid. As described before, this phenomenon is mainly due to insufficient holding of the printing paste at the surface of the textile during printing.

[0125] Moreover, one could clearly notice that the synthesis by inverse emulsion polymerization (Q and R polymers) leads to a product consuming much more polymer to obtain the target viscosity, and leads to polymers that considerably limit the transfer of paste through a printing nozzle. In particular, the polymer R corresponds to Example 2A of the document EP0161038 described at the beginning of the text, which relates to a polymer obtained by inverse emulsion polymerization of acrylic acid/ammonium acrylate in the presence of MBA as a crosslinking agent, with the exception of the 40/60 ratio of acrylic acid/ammonium acrylate.

[0126] Thus, the preceding examples demonstrate the synergy of the characteristics of the copolymer of the invention, namely (1)-(2) the presence of the anionic monomer and the hydrophobic monomer of formula (I) in the described concentration ranges, (3) the precipitation polymerization, (4) the neutralization of 30% to 90% of the carboxylic acid functions of the anionic monomer prior to the polymerization, and (5) the use of an alcohol comprising 1 to 4 carbon atoms, in obtaining a crosslinked copolymer having thickening properties at least equivalent to those of copolymers of the prior art, while dispensing with acrylamide, and that being so, without any glazing phenomenon.