Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1999-01-15
2000-08-29
Acquah, Samuel A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
528272, 528274, 528296, 528302, 528308, 528361, 525437, 525438, 525444, C08F 2000, C08G 6306
Patent
active
061110337
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to biodegradable polyesters and to methods for their preparation.
BACKGROUND ART
Biodegradable polymers have been used, for example, as excipients in sustained release compositions for drugs. See, e.g., U.S. Pat. Nos. 3,773,919 and 4,767,628. Examples of such polymers are copolymers of lactic acid and glycolic acid, which are made by either the polycondensation of lactic acid and glycolic acid, or by ring opening polymerization with lactide and glycolide. See, e.g., Drug Carriers in Biology and Medicine, ed. Gregoriadis, G., pages 241-245 (Academic Press, London 1979).
International Publication No. WO 94/15587 describes sustained release ionic conjugates of polymers and drugs. As the basic drug is ionically conjugated to the acidic polymer, increasing the acidity of the polymer is important to facilitate the formation of the conjugate.
DISCLOSURE OF INVENTION
An aspect of this invention features a biodegradable polyester comprising lactic acid units, wherein the polyester contains 4-100 (e.g., 4-40) carboxyl groups and has an average molecular weight of 1,000 to 200,000 g/mol. In one example, the polyester also includes glycolic acid units, or further includes a hydroxy-polycarboxylic acid unit (i.e., one or more units, such as tartaric acid, pamoic acid, or an ester acid thereof). The polyester can be made of 45 to 99.9 mole percent lactic acid units, 0 to 50 mole percent glycolic acid units, and 0.1 to 10 mole percent hydroxy-polycarboxylic acid units, in which the hydroxy-polycarboxylic acid contains 1 to 20 (e.g., 2-20) hydroxyl groups and 2 to 40 carboxyl groups (e.g., 2-20).
In another aspect, this invention features a method for preparing a biodegradable polyester or its derivative. The method includes reacting a polyhydroxy-polycarboxylic acid, such as tartaric acid, pamoic acid, or an ester acid, with lactic acid or lactide to produce a polyester, e.g., heating the reactant between 100.degree. C. and 250.degree. C. If desire, the polyhydroxy-polycarboxylic acid can also be concomitantly reacted with glycolic acid or glycolide. The method can further include esterifying hydroxyl groups in the polyester thus formed with a second polycarboxylic acid or a second anhydride or alkylated with a polyepoxy.
A third aspect of this invention features a method for preparing a biodegradable polyester derivative. The method includes reacting a polyol (e.g., glucose, sorbitol, lactose, mannitol, or gluconic acid) with lactic acid or lactide to produce a polyester (e.g., heating the reactant between 80.degree. C. and 250.degree. C.); and esterifying free hydroxyl groups of the polyester thus formed with a polycarboxylic acid (e.g., succinic acid) or an anhydride (e.g., succinic anhydride or 1,2,4,5-benzene tetracarboxylic dianhydride or glutaric anhydride optionally catalyzed with an acid, e.g., p-toluene sulfonic acid). If desired, polyol can be concomitantly reacted with glycolic acid or glycolide.
In a still another aspect, this invention features a method for preparing a biodegradable polyester. The method includes reacting a polyol with a polycarboxylic acid or an anhydride to produce a hydroxy-polycarboxylic acid, wherein the polyol has at least three hydroxy groups; and reacting the hydroxy-polycarboxylic acid thus formed with lactic acid or lactide to produce a polyester (e.g., heating the reactant between 80.degree. C. and 250.degree. C.). If desired, the method the hydroxy-polycarboxylic acid can be concomitantly reacted with glycolio acid or glycolide, and, optionally, the remaining hydroxyl groups in the polyester can be esterified with a second polycarboxylic acid (e.g., succinic acid) or a second anhydride (e.g., succinic anhydride or 1,2,4,5-benzene tetracarboxylic dianhydride) or alkylated with a polyepoxy (e.g., 1,2,7,8-diepoxyoctane). The second polycarboxylic acid or second anhydride may be incorporated at the end of the polyester chain (e.g., acid tipping) or the second polycarboxylic acid, second anhydride, or polyepoxy may be incorporated within
REFERENCES:
patent: 3773919 (1973-11-01), Boswell et al.
patent: 4767628 (1988-08-01), Hutchinson
patent: 5084553 (1992-01-01), Hess et al.
patent: 5672659 (1997-09-01), Shalaby et al.
"Drug Carriers in Biology and Medicine", G. Gregoriadis, Ed., 1979 Academic Press Inc. (London) Ltd., pp. 241-245.
Loughman Thomas Ciaran
Russell Ruth Mary
Touraud Franck Jean-Claude
Acquah Samuel A.
Conway John D.
Kinerton Limited
Morrill Brian R.
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