Chemical compounds

Details Chemical compounds Chemical compounds

1995-01-10

1996-11-12

Lipman, Bernard

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

526304, 526321, 5263231, 5263232, 528 59, 528271, 528296, 536 551, C08F 800

Patent

active

055740979

DESCRIPTION:

BRIEF SUMMARY
This invention concerns biodegradable polymers, more particularly lipophilic polymers which are biodegradable to form water-soluble polymers.
Biodegradable polymers have long been used in the medical field, for example to provide biodegradable implant materials and delayed release drug delivery systems. They are now of wider interest in overcoming the problem of pollution by long-lived insert packaging materials, household articles, detergents and the like.
There is also a need for polymers which, when they wholly or partially break down by chemical or biological means, give reliably non-toxic and readily eliminable products.
In general, biodegradation commonly involves enzymic hydrolysis of particular chemical bonds in the polymer, notably ester, urethane or amide groups which are otherwise stable in the absence of enzymes; such hydrolysis may additionaly or alternatively be effected by the presence of acids or bases. Thus, for packaging materials, aliphatic polyesters such as polycaprolactone, polyethylene adipate and polyglycolic acid are candidate materials although polyethylene terephthalate, which is very widely used in textiles and fibres, is resistant to biodegradation.
In the medical field, resorbable polymers are of interest for sutures and in wound closure, resorbable implants in the treatment of osteomyelitis and other bone lesions, tissue stapling and mesh tamponades, anastomosis as well as drug delivery systems and diagnostics. In these fields, polylactic acid, polyglycolic acid, poly (L-lactide-co-glycolide), polydioxanone, poly (glycolide-cotrimethylene carbonate), poly (ethylene carbonate), poly (iminocarbonates), polyhydroxybutyrate, poly (amino acids), poly (ester-amides), poly (orthoesters) and poly (anhydrides) have all been proposed (T. H. Barrows, Clinical Materials 1 (1986), pp. 233-257) as well as natural products such as polysaccharides. U.S. Pat. No. 4,180,646, in particular, describes novel poly (orthoesters) for use in a very wide range of products.
In our co-pending International Patent Application No. WO92/04392 the contents of which are incorporated herein by reference, we describe a broad range of polymers characterised in that they contain optionally substituted methylene diester units of the formula (I) carbon-attached monovalent organic group or R.sup.1 and R.sup.2 together form a carbon-attached divalent organic group). Such units are particularly rapidly degraded by common esterase enzymes but are stable in the absence of enzymes. They may be attached not only to carbon-attached organic groups as in simple carboxylate esters but also to --O-- atoms as in carbonate esters.
The aforementioned units of formula (I) are normally present in the polymer backbone, either as repeating units or as linking units between polymer sections, or are present in crosslinking groups between polymer chains. In this latter context one may, for example, convert a water-soluble long chain natural or synthetic non-biodegradable or slowly biodegradable substance, e.g. a protein such as gelatin or albumin, a polysaccharide or oligosaccharide, or a short chain polyacrylamide, into a water-insoluble but biodegradable form by crosslinking using crosslinking groups containing units of formula (I); this may reduce the cost of the product in comparison with polymers which contain units of formula (I) in the polymer backbone by reducing the relative content of the comparatively expensive units of formula (I).
While such crosslinked polymers have a wide variety of uses as described in the above-mentioned Application No. WO92/04392, their structure inevitably places some limitations on the processability of the polymers, since by virtue of their crosslinked nature they will generally be insoluble in organic as well as aqueous solvents and will not exhibit thermoplastic properties. Accordingly they cannot be subjected to conventional techniques such as solvent casting or melt processing.
The present invention is based on our finding that it is possible to prepare substantially uncrosslinked (e.g. linear)

REFERENCES:
patent: 4356166 (1982-10-01), Peterson
patent: 4741956 (1988-05-01), Thaler
CA: 118:125529, "Studies on Beaded Crosslinked Functionalized Phenyl Acrylate Copolymers," Narasimhaswamy et al., 1991.
CA:77:62754, "Adhesives Containing Benzoyloxalkyl Groups", Sakuraki et al, 1972.

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