CA2495360A1 - Copolymers of polyaspartic acid and polycarboxylic acids and polyamines - Google Patents

Abstract

Copolymers of polyaspartic acid which are suitable for the inhibition of scale deposition were obtained by reacting maleic acid, an additional polycarboxylic acid and ammonia in a stoichiometric excess, at 120-350°C, preferably 180-300°C, to provide copolymers of polysuccinimide. In a second embodiment, a polyamine was added to the reaction mix. These intermediate polysuccinimide copolymers could then be converted to the salts of copolymers of polyaspartic acid by hydrolysis with a hydroxide. Such copolymers are useful in preventing deposition of scale from water and find applications in treating water. Other applications include scale prevention additives for detergents. In addition, such copolymers inhibit dental tartar and plaque formation.

Description

COPOLYMERS OF POLYASPARTIC ACID AND POLYCARBOXYLIC ACIDS AND POLYAMINES
This is a divisional application of copending application 2,183,068, filed February 14, 1994.

This invention relates to a process for the production of copolymers of pdysuccinimide, their conversion to salts of copolymers of pdyaspartic acid and the use d these materials.
BACKGROUND OF THE INVENTION
Polyaspartic acid is a peptide chain in which amide linkages extend the chain.
In the thermal polymerization of aspartic acid, the stereochemistry of the aspartic acid is racemized and the formation of both a and (3 carboxylic acid groups have the ability to react to form such amide bonds. Such materials have bean used for fertilizers and scale inhibition agents. They are particularly useful for the prevention of scale deposition in borer water, reverse osmosis membranes, detergents and as inhib'ttors of dental tartar and plaque formation (tartar barrier agents). These materials are readily biodegradable.
Methods for the. preparation of pdyaspartk: ~~Cid have been developed (See U.S. Patent Nos, 5,057,592 and 4,839,461 ) .
Biodegradabl0ty, calcium ion exchange ability and the disruption of calcium salt crystal structure are important properties of materialsused in the prevention of scale deposition in boier water, on reverse osmosis membranes, in detergent use and as inhibitors of dental tartar and plaque formation (tartar barrier agents). We searched for economically useful materials, having a greater retention on the object wherein inhibition of scale deposition is desired. Other desirable properties were greater stability to biodegradation in addition to intrinsic value for the prevention of scale deposition in boiler water, on reverse osmosis membranes, during detergent use and as inhibitors of dental tartar arui plaque formation (tartar barrier agents). We have found that the addition of polycarboxylic acids in the thermal polymerization of malefic acid or aspartic acid produced novel and highly effective copolymers which possessed these properties.
DESCRIPTION OF RELATED ART
A number of methods of preparaYron of polyaspartic acid are disclosed in the I'tterature and other patents, however, no mention is made of methods of preparation of copdymers of polysuccinimide and polycarboxyfic acids which may then be converted to copolymers of pdyaspartic acid and polycarboxylic acids.
SUMMARY OF THE INVENTION
Copolymers of polysuccinimide were prepared by reacting malefic acid, ammonia, and a polycarboxylic acid at temperatures greater than 120° C. These copolymers could be converted to copolymers of polyaspartic acid by addition of a hydroxide.
In a second embodiment of the invention, copolymers of polysuccinimide were prepared by reacting malefic acid, ammonia, a polycarboxylic acid and a polyamine at temperatures greater than l2fl C. These copolymers could be converted to copolymers of poiyaspartic acid by addition of a hydroxide.
This invention provides a means of preparing copolymers of polysuccinimide.

Further, this invention provides a means of preparing copolymers of polyaspartic acid. This invention also provides novel compositions which are useful for the inhibition of salt deposition, especially bivalent metal salts, whether in water treatment, detergent addition, oral health care or cosmetic formulation. This invention also provides novel compositions which may be further reacted to provide useful compounds for water treatment, cosmetics, oral health care and detergents.
In specific aspects, the invention provides:
A process for the preparation of a copolymer of polyaspartic acid, comprising reacting malefic acid, a polycarboxylic acid and ammonia, at a temperature of from 120 to 350°C, and converting the resultant polymer into a salt by adding a hydroxide.
A process for the preparation of a copolymer of polyaspartic acid, comprising reacting malefic acid, a polycarboxylic acid, ammonia and a polyamine, at a temperature of from 120 to 350°C, and converting the resultant polymer into a salt by adding a hydroxide, wherein the polyamine has at least two or more primary or secondary amines available for reaction.
A copolymer of polyaspartic acid with a polycarboxylic acid.
A polymer produced by polymerizing malefic acid, ammonia, a polycarboxylic acid and a polyamine, wherein the polyamine has at least two or more primary or secondary amines available for reaction.

A process for the preparation of a copolymer of polysuccinimide, comprising reacting malefic acid, a polycarboxylic acid and ammonia at a temperature of from 120 to 350°C .
A process for the preparation of a copolymer of polysuccinimide, comprising reacting malefic acid, a polycarboxylic acid, ammonia and a polyamine at a temperature of from 120 to 350°C, wherein the polyamine has at least two or more primary or secondary amines available for reaction.
A copolymer of polysuccinimide and a polycarboxylic acid.
A copolymer of polysuccinimide, a polycarboxylic acid and a polyamine, wherein the polyamine has at least two or more primary or secondary amines available for reaction.
Use of a copolymer of polyaspartic acid and a polycarboxylic acid for preventing deposition of tartar on teeth.
Use, for preventing deposition of tartar on teeth, of a copolymer of polyaspartic acid, a polycarboxylic acid, and a polyamine, wherein the polyamine has at least two or more primary or secondary amines available for reaction.
A method of preventing deposition of scale from mineral containing water, comprising the addition of an effective amount of a copolymer of polyaspartic acid with a polycarboxylic acid to the water.
A method of preventing deposition of scale from mineral containing water, comprising the addition of an effective amount of a copolymer of polyaspartic acid, a 2a polycarboxylic acid, and a polyamine, wherein the polyamine has at least two or more primary or secondary amines available for reaction.
DETAI7~ED DESCRIPTION OF THE E1~ODIMENTS
Copolymers of polyaspartic acid which are suitable for the inhibition of scale deposition may be obtained by reacting malefic acid, an additional polycarboxylic acid and ammonia in a stoichiometric excess, at 120°-350°C., preferably 180°-300°C., and then converting the copolymer of polysuccinimide formed to a salt of a copolymer of polyaspartic acid by hydrolysis with a hydroxide.
In a second embodiment, copolymers of polyaspartic acid which are suitable for the inhibition of scale deposition may be obtained by reacting malefic acid, an additional polycarboxylic acid, ammonia in a stoichiometric excess, and a compound having 2 or more primary or secondary amine groups per molecule, at 120°-350°C., preferably 180°-300°C., and then converting the copolymer of polysuccinimide formed to a salt of a copolymer of polyaspartic acid by hydrolysis with a hydroxide.
The reaction is carried out first by the addition of water to malefic anhydride, thus forming malefic acid, or to malefic acid itself, and the polycarboxylic acid, followed by addition of the appropriate amount of ammonia in the form of gaseous ammonia or as its aqueous solution. At this point, the polyamine may be added to either of these alternative embodiments. This solution is then heated to remove water. As water is removed, the mixture becomes a solid and then a melt of the mixture is formed. Water removal continues as the reaction proceeds and the 2b temperature is brought to 120°-300°C. When the theoretical quantity of water formed in the production of the copolymer of polysuccinimide has been removed, which, depending on the temperature, may occur in even less than 5 minutes, the reaction mixture is allowed to cool. Typically, it may take over 4 hours at 120°C, whereas it may take less than 5 minutes at 300°C. The copolymer of polysuccinimide formed can be used to make other novel and useful products by reactions such as those described in U.S. Patent 4,363,797 or U.S. Patent 3,486,380, wherein useful derivatives for cosmetic use are described. The copolymers of polysuccinimide can also undergo alkaline hydrolysis to provide the appropriate salt of a copolymer of polyaspartic acid. Further manipulation to remove the water or the salts can be carried out to provide water free powders of the salts or the free acid.
The polyamines which may be used to produce these copolymers of this invention are amines which have at least two or more primary or secondary amines available for reaction. Preferred polyamines have at least two primary amine groups. The concentration may range from greater than 0 to 500, however, the preferred range is greater than 0 to 30a.
Any aliphatic or aromatic polycarboxylic acid may be used in this invention, but the preferred 2c acids are adipic acid, citric acid, fumaric acid, malic acid, malonic acid, succinic acid, glutaric acid, oxalic acid, pimelic acid, itaconic acid, nonanedioic acid, dodecanedioic acid, octanedioic acid, isophthalic, terpMhalic and phthalic acid. The concentration may range from greater than 0 to 5096, however, the preferred range is grater than 0 to 3096.
The hydroxides useful in converting the copolymers of polysuccinimide formed above to copolymers of polyaspartic acid indude, but are not limited to, the alkali and alkaline earth metals and ammonia, examples of which as their rations are, Na+, K", Mg+, l.i*, and Ca++, 2n++, ~++, Co++, Fe++, Fe'+, and NI~+.
Polysuccinimide is the amide form of pdyaspartic acid and is also known as anhydropolyaspartic acid.
The term'succinimide' is understood in the art to indude many of the p~ !e, amide and amidine species which are also°formed by this reaction. The predominant product ho; . . . 3r is sucdnimide and this term is used to refer to the thermally polymerized reaction pr~-~~!ct of malefic acid and ammonia or a polyamine. The polyaspartic moieties formed by hydrolysis of the polysuccinimides formed would be principally a and Q aspartates.
The copolymers of pdyaspartic acid provided by the present invention are advar>tageous for inhibition of scale depos'ttion in water treatment, as detergent additives, in oral health care or in cosmetic formulation. Solutions of the salts of copolymers of polyaspartic acid formed in this manner have excellent scale inhibition performance. Salts which may be inhibited are the salts a. Mg, Ca, Sr, Ba, and Ra. The carbonate, sulfate and phosphate salts are those in which greatest inhibition is shown.
The following examples are by way of ~iustration and not by way of limitation.

Preparation of a polyaspartic acid/citric acid copolymer.
A slurry of 19.6 g (0.2 mole) malefic anhydride was dissolved in 40 ml water at 8CP-9,~ C. and 4.2 g (0.02 moles) of citric acid monohydrate (Formula weight 210) was added and the mixture was stirred until all solids were in solution, after which the mixture was allowed to cool to 25° C. To this solution at 2S C. was added 60 g of 3096 aqueous solution of ammonium hydroxide (0.44 mol NFi3).
This solution was evaporated to dryness over a period of 8 minutes. The solid was then heated at 235°-24~ C. for 5 minutes, removed from the heat, allowed to cool and broken up w'tth a spatula. The solid was then heated at 23~ -24~ C. for a second 10 minute period, removed from the heat, allowed to cool and broken up w'tth a spatula. Finally, the solid was heated at 23S -24~ C.
for a third 10 minute period, removed from the heat and allowed to cool to room temperature. The resulting water insoluble copolymer of polysuccinimide and citric acid (21.7 g) was slurried in 29.1 ml of water and a solution of 8.0 g of sodium hydroxide in 12 ml of water was added over 5 minutes. The solution was stirred for 10-20 minutes to give a clear red-brown solution of a copolymer of polyaspartic acid and citric acid.

Preparation of a polyaspartic acid/succinic acid copolymer.
A slurry of 19.6 g (0.2 mole) malefic anhydride was dissolved in 40 ml water at 8CP -95° C. and 2 g (0.02 moles) of succinic anhydride (Formt~a weight 100) was added and the mixture was stirred until all solids were in solution, after which the mixture was allowed to cool to 2S
C. To this solution at 25°
C. was added 60 g of 30% aqueous solution of ammonium hydroxide (0.44 and N1-h). This solution was evaporated to dryness over a period of 8 minutes. The soUd was then heated at 235' -245° C. for 5 minutes, removed from the heat, allowed to cool and broken up with a spatula.
The solid was then heated at 235° -245° C. for a second 10 minute period, removed from the heat, allowed to cod and broken up with a spatula. Finally, the solid was heated at 235°-245° C. for a third 10 minute period, removed from the heat and allowed to cool to room temperature. The resulting water insoluble copolymer of polysuccinimide and succinic acid (21.9 g) was scurried in 29.1 ml of water and a solution of 8.0 g of sodium hydroxide in 12 ml of water was added over 5 minutes. The solution was stirred for 10-20 minutes to give a dear red-brown solution of a copolymer of polyaspartic acid and succinic acid.

~recipital~n assay for calcium sulfate.
The material to be tested as an inhibitor of scale fom~ation was added in appropriate quantities to a solution of 5 ml of calcium chloride sdutions (21.6 g/L of CaCh dihydrate and 41.4 g/L of NaG) and 5 ml of sulfate solution (20.9 g/L of NalS04 and 41.4 g NaG). The mixttue was then placed in an oven at 16ff F for 3 hours. Finally the mbdure was f~tered through Whatman ~2 paper and dried at 16~ F for 8 hours, after which the weight of predp'rtate was determined.
The polycarboxylic add/polyaspartic acid copolymers were tested in the above assay. The results are given below in Table t.
Table 1 compound polycarboxylic weight of precipitate (mg) acid blank polyacrylate, 5000 molecular weight 46 copolymer polyaspartate/citrate citric acid 16 copolymer polyaspartate/succinate succinic acid 13 The copolymers of pdyaspartic acid and polycarboxylic acids were very effective agents for the inhibition of mineral scale.

Calcium oxalate titration.
A 0.25 g sample of the sodium salt of the polyaspartic/c'ttric acid copolymer prepared in Example 1 was placed in a beaker with 100 ml of deionized water and 1 ml of 396 sodium oxalate was added. The solution was titrated w'tth 0.1 mol of calcium chloride till the slurry turned white.

and 8.1 mi while a poiyaspartic acid prepared from diammonium maleate required 8.3 and 8.5 ml. This shows that pdycarboxylic acid copdymers of pdyaspartic acid are effective calcium chelators.

Preparation of a polyaspartic/citric acid copolymer with a polyamine A solution of 2.1 g (0.01 mdes) of citric add monohydrate (Formula weight 210) and 0.32 g (.0028 moles) hexanediamine was added to 19.6 g (0.2 mote) maleic anhydride which had been dissolved in 40 ml water at 8a° -95° C., and finally 30 g of 3096 aqueous solution of ammonium hydroxide (0.22 and NH,~ ) was added. This sdution was evaporated to dryness over a period of 30 minutes. The slid was then heated at 19~ -220° C. for 10 minutes, removed from the heat, allowed to cool and broken up w'tth a spatula. The slid was then heated at 230° -24~ C. for 10 minutes, removed from the heat, allowed to cool and broken up with a spatula. Finally, the sdid was heated at 230' -24~ C. for 10-15 minutes, removed from the heat and allowed to cool to room temperature. The ~i~.g ~Tiat3r irsdu4fe pdymer was slurried in 40.0 ml of water and a sdution of 8.0 g of sodium hydroxide in 12 ml of water was added over 5 minutes. The sdution was stirred for 10-20 minutes to give a dear red-brown solution, pH 10-11.0 of a copolymer of pdyaspartic acid, dtric add and hexanediamine. The tests for CaSO, , Example 3, and CaC03 (below) were run and the rest~t are recorded in Table 2.
Inhibition of calcium carbonate precipitation by the calcium drat assay.
J
this assay a supersaturated solution of calcium carbonate is formed by adding 29.1 ml of 0.55 M NaCI and 0.01 M KG to 0.15 mi of 1.0 M CaCh and 0.3 ml of 0.5 M NaHCOj. The reaction is in'ttiated by adjusting the pH to 7.5,8.0 by titration with 1 N NaOH and addition of the material to be tested for inhibition of CaC03 precip'ttation at a level of 1.7 ppm. At three minutes, 10 mg of CaC03 is added and the pH is recorded. The decrease in pH is directly correlated to the amount of CaC03 that precipitates.

Sample CaS04 CaC03 ppt Drift . (mg) (pH units) none 84 ,72 copdymer 74 .26 These assays indicate that the copdymer of Example 5 is effective in prevention of CaS04 and CaC03 scale.
The following examples will serve to illustrate the tartar barrier compositions of this inventi~~
Copolymers of Examples 1, 2 and 5 are suitable tartar barrier agents.
Humectants are materials s~.,:~

as glycerol, Foaming agents are suitable surfactants. Sweetening agents may be normal or artificial sweeteners. Common abrasives are materials like fumed silica. Gelling agents are polymers which are used to prepare thickened solutions.
EXAMPLE A - Mouthwash%w/w Tartar barrier agent 0.5-2 humectant 6.0 foaming agent 1.0 sweetener 0.3 deionized water q.s. to 100 flavors i .0 EXAMPLE B -Abrasive Dentrrfic~s Ge1 Tartar barrier agent 2-10 detergent 1.5 i5 humectant 10.0 sweetener 0.2 deionized water q.s. to 100 flavors 1.0 abrasive 55.0 gelling agent 2.0 EXAMPLE C - Chewing gum Tartar barrier agent 1.0-11 Gum base 21.3 sugar 48.5-58.5 corn syrup 18.2 flavors 1 It will be apparent to those skilled in the art that the examples and embodiments described herein are by way of illustration and not of limitation, and that other examples may be utilized without departing from the spirit and scope of the present invention, as set forth in the appended claims.

Claims (14)

1. A process for the preparation of a copolymer of polysuccinimide, comprising reacting maleic acid, a polycarboxylic acid and ammonia at a temperature of from 120 to 350°C.

2. The process of claim 1, wherein the temperature is from 200 to 300°C.

3. The process of claim 1 or 2, wherein the polycarboxylic acid is selected from the group consisting of adipic acid, citric acid, fumaric acid, malic acid, malonic acid, succinic acid, glutaric acid, oxalic acid, pimelic acid, itaconic acid, nonanedioic acid, dodecanedioic acid, octanedioic acid, isophthalic, terphthalic and phthalic acid.

4. A process for the preparation of a copolymer of polysuccinimide, comprising reacting maleic acid, a polycarboxylic acid, ammonia and a polyamine at a temperature of from 120 to 350°C, wherein the polyamine has at least two or more primary or secondary amines available for reaction.

5. The process of claim 4, wherein the temperature is from 200 to 300°C.

6. The process of claim 4 or 5, wherein the polyamine has at least one primary amine and wherein the additional amine group or groups consist of at least one primary or secondary amine.

7. The process of claim 6, wherein the polyamine is selected from the group consisting of diethylene triamine, a polyoxyalkyleneamine diamine or triamine, melamine, an alkyl diamine or triamine, ethylene diamine and hexanediamine.

8. The process of any one of claims 4 to 7, wherein the polycarboxylic acid is selected from the group consisting of adipic acid, citric; acid, fumaric acid, malic acid, malonic acid, succinic acid, glutaric acid, oxalic acid, pimelic acid, itaconic acid, nonanedioic acid, dodecanedioic acid, octanedioic acid, isophthalic, terphthalic and phthalic acid.

9. A copolymer of polysuccinimide and a polycarboxylic acid.

10. The copolymer of claim 9, wherein the polycarboxylic acid is selected from the group consisting of adipic acid, citric acid, fumaric. acid, malic acid, malonic acid, succinic acid, glutaric acid, oxalic acid, pimelic acid, itaconic acid, nonanedioic acid, dodecanedioic acid, octanedioic acid, isophthalic, terphthalic and phthalic acid.

11. A copolymer of polysuccinimide, a polycarboxylic acid and a polyamine, wherein the polyamine has at least two or more primary or secondary amines available for reaction.

12. The copolymer of claim 11, wherein the polyamine has at least one primary amine and wherein the additional amine group or groups consists of at least one primary or secondary amine.

13. The copolymer of claim 12, wherein the polyamine is selected from the group consisting of diethylene triamine, a polyoxyalkyleneamine triamine, melamine, an alkyl diamine or triamine, ethylene diamine and hexanediamine.

14. The copolymer of claim 11, 12 or 13, wherein the polycarboxylic acid is selected from the group consisting of adipic acid, citric acid, fumaric: acid, malic acid, malonic acid, succinic acid, glutaric acid, oxalic acid, pimelic acid, itaconic acid, nonanedioic acid, dodecanedioic acid, octanedioic acid, isophthalic, terphthalic and phthalic acid.