Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-01-07
2001-02-06
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S328000
Reexamination Certificate
active
06184336
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a new family of biodegradable, environmentally friendly poly(amino acid) polymers and copolymers, as well as, to new and improved methods for making them. More particularly, it relates to high molecular weight poly(amino acid) polymers and copolymer derivatives thereof useful in water treatment applications as coolants and the like. The copolymers are derivatized to incorporate pendant hydroxyl, ether, hydroxyalkoxyalkyl, hydroxyalkylaminoalkyl, carboxylate and phosphonate functionality.
Poly(amino acids) are generally known in this art. Polyaspartic acid is known to be biodegradable. However, some modified poly(amino acids) are not biodegradable. For example, a homopolymer of hyroxyethylaspartamide synthesized by reacting a polysuccinimide of aspartic acid with more than 100 mol % of 2-hydroxyethylamine is reported to not be enzymatically degradable. A crosslinked polyhydroxyethylglutamide prepared by reacting poly(L-2-hydroxyethylglutamide) with various amounts of a diaminododecane crosslinking agent is enzymatically degradable, with the rate of degradation increasing with increasing crosslinking density. However, the same linear non-crosslinked polymer is not enzymatically degradable in vivo or in vitro.
The biodegradability and chelating properties of partially derivatized polyaspartic acid have heretofore been unknown and no known method for predicting them have existed prior to this invention. The partially derivatized polyaspartic acid, i.e., aspartic acid containing copolymers, in accordance with this invention were unexpectedly discovered to be more biodegradable and much between scale inhibitors and corrosion inhibitors than both unmodified polyaspartic acid and 100% derivatized polyaspartic acid.
Methods for making poly(amino acid) polymers and copolymers are generally known. Polyaspartic acid is prepared by reacting maleic anhydride with ammonia. Alternatively, maleic anhydride may be reacted with alcohols to form a half ester, and thereafter, reacted with ammonia alone or in combination with amines. These methods are generally effective to prepare rather low molecular weight polymers of less than about 1000. Solid phase polymerization of aspartic acid alone or in the presence of acid catalysts has also been performed. Lower molecular weight materials having molecular weights of less than 50,000 are generally provided by these methods.
Previous efforts to provide sulfonic acid (e.g., taurine or sulfonomethylamine) functionality to aspartic acid polymers having included reacting the starting materials in a toxic, dimethylformamide solvent. The molecular weights of polymers produced in dimethylformamide solvents are generally very low, i.e., less than about 1000. These processes require the steps of removing toxic DMF and recovering product polymer using complicated and expensive procedures. Moreover, the prior art methods result in degradation of the polymer backbone so that the molecular weights of the resulting products are significantly less than the already low molecular weight starting materials.
SUMMARY OF THE INVENTION
Unexpectedly, in view of the foregoing, it has now been discovered that high molecular weight poly(amino acid) polymers and copolymers may be prepared which are non-toxic and biodegradable.
In an embodiment, the present invention provides new and improved polyaspartic acid and polyglutamic polymers having a weight average molecular weight of greater than or equal to 70,000. These polyaspartic acid and polyglutamic acid homopolymers are biodegradable and have molecular weights which are considerably higher than those obtained from prior art methods.
In an embodiment, the present invention provides a new and improved method for making higher molecular weight polyaspartic acid and polyglutamic acid polymers which comprises: admixing aspartic acid or glutamic acid with super polyphosphoric acid to form a reaction mixture;
heating the reaction mixture at elevated temperatures of from about 100° to about 200° C. and at reduced pressures to form a soft, semi-fluid reaction mixture;
stirring the semi-fluid reaction mixture;
heating the stirred semi-fluid reaction mixture at elevated temperatures of from about 130° to about 240° C. and at reduced pressures for a time sufficient to provide a polysuccinimide;
separating the polysuccinimide from the remaining portions of the reaction mixture; and
thereafter, hydrolyzing the polysuccinimide to provide a polyaspartic acid or a polyglutamic acid polymer having a weight average molecular weight of greater than or equal to 70,000.
In an embodiment, the present invention provides new and improved high molecular weight lightly crosslinked polyaspartic acid and polyglutamic acid polymers having weight average molecular weights in excess of 100,000, in both water soluble and water insoluble forms. The lightly crosslinked polyaspartic acid and polyglutamic acid polymers may be prepared by reacting a corresponding polysuccinimide with a diamine or triamine crosslinking agent. Thereafter, the crosslinked polysuccinimides are hydrolyzed to convert any remaining succinimide groups to aspartic acid or glutamic acid groups to provide the crosslinked polyaspartic acid and polyglutamic acid polymers. The crosslinked poly(amino acid) homopolymers in accordance with this embodiment are represented at least by the following general isomeric structural formulas:
wherein M is a cation selected from the hydrogen, alkali metal, alkaline earth metal, ammonium or alkyl-substituted ammonium cations; R
3
is a divalent alkylene of 1 to 2 carbon atoms; R
4
is divalent alkylene of 1 to 12 carbon atoms, cycloalkyene, arylene, alkarylene, W is CO
2
M; and Y=R
3
CO
2
M, said crosslinked polymer having a weight average molecular weight of greater than or equal to 100,000.
Preparation of these crosslinked poly(amine acids) in accordance with an embodiment comprises forming a solution of a high molecular weight polysuccinimide in an aqueous medium or in a polar organic solvent and adding a selected amount of a solution of crosslinker in water or in a polar organic solvent to form a reaction mixture. The reaction mixture is stirred at room temperatures for a time sufficient to form a crosslinked polysuccinimide. A less polar organic solvent is added to the reacted solution to precipitate crosslinked polysuccinimide product. The precipitated crosslinked product is separated, suspended in water and hydrolyzed to form the crosslinked poly(amino acid) final product.
In an embodiment, the present invention provides new and improved storage stable, substantially linear, biodegradable poly(amino acid) copolymers having a broad range of molecular weights. The new and improved copolymers comprise amino acid units of at least one amino acid or a salt thereof and derivatized units of at least one derivatized amino acid. The derivatized amino acid units include a substituent group selected from hydroxyamide, alkylolamide, arylolamide, hydroxyalkoxyalkylamide, alkoxyalkylamide, hydroxyalkylaminoalkylamide, N-(O-sulf)oxyalkylamide, N-(O-phospho)alkylamide, sulfonoalkylamide and phosphonoalkylamide groups. The copolymers may contain derivatized units which are all the same. The copolymers may also include a plurality of different derivatized units, so that copolymers, terpolymers and polypolymers may be provided. The amino acid units preferably comprise aspartic acid units, glutamic acid units or salt forms of these units.
In an embodiment, the new and improved derivatized poly(amino acid) copolymers, terpolymers and polypolymers in accordance with the invention generally comprise polymers of the formula:
wherein R
1
is H or C
1
-C
4
alkyl; R
2
is OH, ZOH, ZOPO
3
M
2
, ZOSO
3
M, ZOR
4
, or GPO
3
M
2
; R
3
is divalent alkylene having 1 to 2 carbon atoms; R
4
is C
1
-C
4
alkyl or benzyl; Z is selected from C
1
-C
12
alkyl, cycloalkyl and aryl, CH
2
CH
2
(OCH
2
CHR
5
)
p
(OCH
2
CH
2
)
q
, CH
2
CH
2
(NR
5
CH
2
CHR
6
)
r
wherein p is 0 to 50, q is 0 to 50, p+=1 t
Breininger Thomas M.
Martin Michael B.
Nalco Chemical Company
Nutter Nathan M.
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