WO1996002582A1

WO1996002582A1 - Procedure for manufacturing and application of novel polycarboxylate types

Info

Publication number: WO1996002582A1
Application number: PCT/US1995/008865
Authority: WO
Inventors: Dusan Miljkovic; Radoslav Kobilarov
Original assignee: Dusan Miljkovic; Radoslav Kobilarov
Priority date: 1994-07-18
Filing date: 1995-07-15
Publication date: 1996-02-01
Also published as: YU48814B; YU45794A

Abstract

This invention is related to the synthesis of novel types of maleic-acrylic copolymers containing 60 to 100 % of maleate units (by weight), respectively, 40 to 0 % of acrylate units (by weight) based on the sum of both monomeric units composing the copolymer. These copolymers show significant techno-economical and ecological advantages over previously synthesized and described acrylic-maleic copolymers. According to the optimal synthetic procedure for this class of copolymers, one uses very concentrated starting alkaline maleate solutions (at best over 60 %), hydrogen peroxide and alkaline peroxy salts as initiators-catalysts for the copolymerization process, as well as reaction temperatures between 105 and 115 °C. The obtained copolymers have average molecular masses around 20000, while CCDC values are approximately 17-18 ml 0,25M calcium acetate per 1 g of copolymer. The obtained copolymers are well suited for their use as incrustation inhibitors, dispersants or ionic exchangers.

Description

HUE

PROCEDURE FOR MANUFACTURING AND APPLICAΗON OF NOVEL

POLYCARBOXILATE TYPES

TECHNICAL FIELD OF THE DISCOVERY The discovery belongs to the field of chemical technology of organic compounds, more speci ically to the field of synthesis and application of polycarboxylates.

Technical Problem to Be Solved

Technical problem to be solved by this discovery involves copolymerization of maleic and acrylic acids or their alkaline salts in aqueous medium, whereupon maleic acid (or its alkaline salt) is used in greater molar and/or weight ratio in regard to acrylic acid and/or its alkaline salt. This fact has a positive technical and economical impact.

BACKGROUND OF THE INVENTION Porycarboxylate type of polymers are widely used in industry and in households. In recent years, they are particularly used in so called phosphate-free detergents, where polycarboxylates, together with zeolites, efficiently substitute sodium tripolyphosphate and other phosphate species used for the same purpose. There are numerous data in the Uterature regarding this fact (see, e.g., J.Peraer and H.W.Neumann, Tensides Surfactants and Detergents, 24,1987,6, 334-340).

Many patents can be found in this field covering the synthesis and/or application of numerous types of polycarboxylates. For example. German patent, DE-OS 22 12 623. describes a procedure for the synthesis of maleic- acrylic acid copolymer by copolymerization of maleic anhydride in benzene with acrylic acid in the presence of benzoyl peroxide as a free-radical initiator. An improved method of the synthesis of this type of copolymer is described in U.S. Patent No. 2 887 480, whereupon the copolymerization was carried out in an aqueous medium with a free radical initiator, such as potassium peroxy bisulfate.

Further synthetic development for this type of polycarboxylates was described in German patent, DE 31 38 574, where a research group from BASF AG company worked out contemporary technical basis of the acrylic-maleic copolymer synthesis. The process is carried out in an aqueous medium, in the presence of water soluble initiator (0,5-5% related to the sum of monomers), in such a way that an aqueous solution of a dicarboxyhc acid (like maleic acid) or its salt are simultaneously added a monocarboxylic monoun saturated acid (one like acrylic acid) and an initiator during 4 to 10 hours at 60 - 150° C. It is interesting to note that the patent claims in this patent are formulated as follows: "a procedure of producing copolymers containing 10-60% (based on the sum of monomers) of a monoethylene unsaturated dicarboxyhc acid with 4-6 C atoms, its salt with alkaline metals, or its anhydride, and 90-40% of a monoethylenic unsaturated monocarboxylic acid with 3-10 C atoms or its alkaline salts". BASF AG company and its researchers, independently from this patent for the synthesis of polycarboxylates of the acrylic-maleic copolymer types, in a new patent. EP 0 025 551, protects separately the usage of these copolymers as incrustation inhibitors, i.e., as agents for binding Ca++ and Mg++ ions from hard waters, in laundry detergent formulations. In a short patent claim from this patent one says: "the use of copolymers containing, by weight.40-90% of (Met) Acrylic acid and 60-10% of maleic acid, their alkaline or ammonium salts, respectively, as incrustation inhibitors in laundry detergents."

Among many copolymer modifications, whereupon a third monomer is often introduced to a copolymer. we mention, as examples, the following patents: EP 0 106 1 10. EP 0 344 591. USP 4 559 159, USP 4 647 396 and USP 4 659 793 (this, by no means, covers the whole relevant and/or related Uterature devoted to this broad field).

BRIEF DESCRIPTION OF THE INVENTION This invention relates to the synthesis and apphcation of maleic-acryUc acid copolymer with prevailing maleic monomeric units. More specificaUy, this invention enables the synthesis and appUcation of the copolymers of maleic and acryUc acid, wherein the weight ratio of maleic residues in the copolymer is 60-100%, while the content of acryUc acid residues is 40 - 0%. The above mentioned ratio of maleic to acryUc residues in the new type of copolymer has neither been described nor claimed in any patent Uterature so far (see, in particular, patents: DE 31 38 574 and EP 0 025 551). This is most probably due to the fact that the reaction conditions described in the mentioned patents for the synthesis of the described copolymers. can not provide the copolymers described by our invention. Namel . taking into account a decreased reactivity of maleic acid and its alkaline salts in polymerization or copolymerization processes, in respect to acryUc acid and/or its alkaline salts, it was necessary to find out the reaction conditions that enable sufficient reactivity of the maleic acid constituent thus providing its final higher content in the synthesized copolymer(s). This invention describes reaction conditions which enable the production of maleic-acrylic copolymers having the content of maleic monomer unit that is 60% or higher. These newly found reaction conditions involve high starting concentrations of maleates (60 - 80%), high starting pH- value of the reaction medium (9- 11 ), as weU as an elevated reaction temperature ( 105- 1 15° C ). The last parameter can be achieved at atmospheric pressure due to a high sohd content of the aqueous reaction medium. In order to sufficiently increase the reactivity of the maleic acid, one needs to increase the quantity of the used initiator (hydrogen peroxide and peroxy salt) thus enabling the satisfactory kinetics of the copolymerization process.

This invention covers the intermediary range between acryUc-maleic copolymers of the BASF - type and pure homopolymers - polymaleates (the production of the last mentioned homopolymers is described in USP 4 668 735). An additional value of our invention is the fact that the use of KOH instead of NaOH during the copolymer synthesis process pro\ides copolymers of a superior quahty. Namely, the obtained copolymers show a significant increase in CCDC-values (CCDC stands for Calcium Carbonate Dispersion Capacity).

Another additional value of the invention represents the fact that Disodium Peroxy Bisulfate can be efficiently replaced (with better final results) with other commerciaUy readily available peroxy salts, such as sodium percarbonate or sodium perborate (which are, otherwise, widely used in laundry detergent formulations worldwide. The result of this fact has been a decreased investment in starting materials, as weU as a decreased time needed for a synthetic batch to be finished (from 3 to 6 hours per batch). Therefore, our invention has profound techno-economical advantages in regard to other disclosed procedures in scientific and/or patent Uterature.

Finally, the copolymers obtained by our method have better ecological properties in comparison to other commercial types of acrylic-maleic copolymers. (Namely, since maleates are significantly less toxic than acrylates. the permitted residues of the former are much higher than the ones of the latter).

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

The reaction vessel for polycarboxylate synthesis has four necks (for a mechanical stirrer. for a condenser and for parallel and simultaneous adding of acryUc acid and an initiator). The vessel must be of an appropriate volume such that 2/3 of the vessel volume corresponds to the total volume of reaction mixture after neutralization. In the reaction vessel one prepares a concentrated alkaline solution of Na-maleate (Solution A). Solution A is refluxed and while stirring slowly, a simultaneous addition of solution B (a mixture of water, hydrogen peroxide and Na-peroxy salt of the selected concentration) and solution C (mixture of water and acryUc acid of the selected composition) is carried out. This simultaneous addition of solutions B and C lasts 3-6 hours depending on the nature of the catalyst (e.g., in the presence of Na perborate the reaction time is 3 hours, while in the case of Na-persulphate, 6 hours. During this time, reaction mixture is constantly kept at reflux temperature. Since the copolymerization reaction is exothermic, usually one does not need external heating during the process. especiaUy when one works with larger quantities. The excess of the heat is taken out by an efficient reflux condenser. However, if one works on a smaUer scale, external heating may be necessary due to certain heat losses from the reaction system- In pilot plants and industrial plants these parameters can and must be exactly determined. After all of the acryUc acid and initiator are added, one adds an excess of hydrogen peroxide for discoloration or for decreasing the intensive yeUow to dark color of the concentrated alkaline solution of the freshly synthesized polycarboxylate and for transformation of possibly left unreacted maleic acid into nontoxic tartaric acid.

At the end of the reaction one usuaUy adds water or diluted NaOH in order to adjust the final pH of the aqueous solution of polycarboxylate (7,5 - 8,5), as weU as its final concentration at approximately 40%.

During the process, every hour, one withdraws a smaU aUquot of the reaction mixture (0,5 g) and after dUution with water (100 ml) and adding cone. sulphuric acid (20 ml) one titrates with 0,5 N K permanganate. If the copolymerization reaction went in a satisfactory way. the final permanganate consumption should not exceed 0,5 ml. In the following examples we only give the material balance and the concentrations (quantities) of aU reactants in solutions A. B, C and D. The cited wp (weight pans) and vp (volume parts) coπespond propoπionaUy to each other (g - ml kg-Ut, etc.).

EXAMPLE 1

SOLUTION A: 60 wp 485 NaOH. 20 vp water and 40 wp maleic anhydride SOLUTION B: 10 vp water, 2,5 wp Na persulphate and 5 wp 35% hydrogen peroxide (subsequently, after finishing the addition of B and C. one adds another 5 vp 35% hydrogen peroxide for bleaching polycarboxylate solution and for ending the reaction process). SOLUTION C: 22 vp 100% acryUc acid and 5 vp water SOLUTION D: 12 wp 48% NaOH and 30 vp water

Consumption of K permanganate (after) 1. hour 12,7 ml 3. hours 1.63 ml

5 hours 0.30 ml

Final concentration of copolymer (determined gravimetricaUy): 43,2% pH of the polycarboxylate solution: 8 Average Molecular Mass (AMM): 14300

(determined by HPLC using reference samples) CCDC: 14 ml

(given in ml of standard (0,25 M) Ca(OAc)2 - solution consumed for a titration (ti l permanent turbidity visualized against background)of 100 ml of a solution containing 2M Na2 COS ( 10 ml), at pH 10, in the presence of 1 g of copolymer (or approximately 2,5 ml of 40% aqueous copolymer solution).

EXAMPLE 2: SOLUTION A: 42 wp 48% KOH; 3,8 vp water; 20 wp maleic anhydride

SOLUTION B: 5 vp water; 1,25 wp Na persulphate; 2,5 vp 35% hydrogen peroxide

(subsequently was added additional 2,5 vp of 35% hydrogen peroxide for discoloration and ending the copolymerization process).

SOLUTION C: 11 vp 100% acryUc acid; 2,5 vp water; SOLUTION D: 4,03 wp KOH in 30 vp water.

Consumption of 0.5 N KMnO4 : after 1 hour 12,0 ml after 3 hours 1,13 ml after 5 hours 0,40 ml

Final concentration of the copolymer solution. 37,8 pH of the copolymer solution: 8,5

Average Molecular Mass (AMM): 18125 CCDC: 17 ml

EXAMPLE S

SOLUTION A: 100 wp 50% KOH; 40 wp maleic anhydride SOLUTION B: 10 vp water; 2,5 wp Na - persulphate; 5 vp 35% hydrogen peroxide ( subsequently was added another portion of 5 vp 35% hydrogen peroxide for discoloration and ending the copolymerization process). SOLUTION C: 14,7 vp acryUc acid ( 100%); 3 vp water; SOLUTION D: 60 vp water

Final copolymer solution concentration: 44,3% pH of the copolymer solution: 8,7 AMM: 23000

CCDC: 21 ml

EXAMPLE 4

SOLUTION A: 57,6 WP NAOH; 62,4 VP WATER; 80 WP MALEIC ANHYDRIDE; SOLUTION B: 13,25 vp 35% hydrogen peroxide; 10 vp water; 4 wp Na - perborate (in six portions of 0.75 wp. during the synthesis in equal time intervals; total reaction time : 3 hours);

13.25 hydrogen peroxide subsequently added for discoloration and ending the process.

SOLUTION C: 46,2 vp 100% acryUc acid; 28 vp water;

SOLUTION D: 10 wp NaOH; 30 vp water.

KMnO4 Consumption:

11,9 ml after the first hour

6.5 ml after the second hour

0.4 ml after the third hour 0.2 ml after neutralization.

pH at the end of the synthesis: 6 pH after neutralization: 8,5

Dry matter: 56% CCDC: 17-18 ml

Viscositv: 5,146 x 10-3 Pa sec The Optimal Mode for Polycarboxylate Use

Depending on the final use of polycarboxylates, the reaction conditions for their synthesis have to be precisely chosen so that the synthesized copolymers have the selected and wanted properties (AMM, CCDC etc.).

Depending on the purpose of use concentrations of the appUed copolymer range from several ppm to 40%.

Described polycarboxylates are mostly compatible with various aqueous solutions of other ingredients, but are, as a rule, incompatible with various organic solvents of low polarity.

Claims

CJLΔJMSI claim:

1. A synthetic procedure for obtaining copolymers of maleic and acryUc acids by a copolymerization of acryUc acid with maleic acid, its anhydride or its alkaline salts, in an aqueous medium, in the presence of water soluble initiators of free radical polymerization, with the following copolymer chemical composition.

- the content (the weight part ) of maleic acid in the copolymer, calculated on the basis of the monomer sum, Ues between 60 and 100%;

- the content ( the weight part) of acryUc acid in the copolymer, calculated on the basis of the monomer sum. Ues between 40 and 0%.

2. The procedure of claim 1 wherein said synthesis is carried out in an aqueous medium in the presence of alkaline monovalent hydroxides, hydrogen peroxide and commerciaDy readily available peroxy salts.

3. The procedure of claim 1 and claim 2 wherein said commerciaUy available salts involve Sodium Persulphate. Sodium Perborate and Sodium Percarbonate.

4. The procedure of claim 1, 2, and 3 wherein the copolymerization process is carried out with high starting concentrations of alkaline maleate (30 to 90%), at the pH value between 3 and 14. at reaction temperatures of 50 to 150° C.

5. The copolymers synthesized according to claims 1,2,3 and 4 can be efficiently used as incrustation inhibitors, ionic exchangers and/or dispersants in various washing and cleaning formulations, in various closed cooling and heating systems for inhibiting scale formation, in sea water desalination, in sugar and other organic compounds refining, in drink and waste water treatments, in water- and/or oil- based pigment dispersions, in printing dyes, as weU as in different pharmaceutical, cosmeticaL and/or esticidal formulations.

6. A method for obtaining copolymers of maleic and acryUc acids comprising the steps of: preparing a first solution comprising a highly concentrated alkaline solution of Na- maleate; placing the first solution into a reaction vessel; elevating the temperature of the first solution; adding a second solution and a third solution to the first solution to form a reaction mixture wherein the second solution includes water, hydrogen peroxide and peroxy salt and wherein the third solution includes water and acryUc acid; n-aintaining the reaction mixture at an elevated temperature for 3-6 hours: and adding an excess amount of hydrogen peroxide to the reaction mixture.

7. A method for obtaining copolymers of maleic and acryUc acids comprising the steps of: preparing a first solution comprising a highly concentrated alkaline solution of Na- maleate; placing the first solution into a reaction vessel; refluxing and stirring the first solution; adding a second solution and a third solution to the first solution to form a reaction mixture wherein the second solution includes water, hydrogen peroxide and peroxy salt and wherein the third solution includes water and acryUc acid; refluxing and stirring the reaction mixture; mamtaining the reaction mixture at a reflux temperature for 3-6 hours; and adding an excess amount of hydrogen peroxide to the reaction mixture.