Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1999-12-06
2001-05-08
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S059000, C528S073000, C528S074000, C528S075000, C528S076000, C428S423100, C428S425100, C525S457000, C525S458000, C525S054310
Reexamination Certificate
active
06228969
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Prior Art
Although plastics are produced in large quantities only since about 1930, they have become indispensable now for modern life. However, the rapidly expanding production and increasing consumption of plastic materials are increasingly posing problems. In the foreground is in particular the pollution of the environment with plastic refuse. Known statistical data show that the component of plastic refuse is alarmingly high: about 18% of the volume of municipal refuse is caused by plastic materials, with about half of that volume being attributed to packaging refuse. The disposal of plastic materials continues to be extremely problematic in this connection, for example because highly toxic dioxins may be formed in the incineration of such materials. In the USA, approximately 96% of the total amount of plastic refuse ends up in garbage dumps, 3% is incinerated, and only about 1% is recycled.
The search for an equivalent substitute material becomes more and more urgent because the demand for plastic materials is constantly growing. There is consequently an extraordinarily high demand for biodegradable materials that offer the advantages of plastics, but are nonetheless biodegradable at the same time.
Attempts have been increasingly made in the last few years to meet these requirements. However, it has been found that the realization is connected with huge problems due to the fact that the required properties are mutually exclusive in most cases.
A possible solution is described in EP 0 696 605 A1, which relates to a biodegradable multi-block polymer, which is prepared by linear polycondensation of two &agr;, &ohgr;-dihydroxy polyesters/ethers with diisocyanate, di-acid halide, or phosgene. The &agr;, &ohgr;-dihydroxy polyesters are obtained through trans-esterification of poly-(R)-(3)-hydroxy-butyric acid in the form of Biopol®, and are thus degraded by means of an ester interchange catalyst, or catalysts, with degradation of the ester bonds. Biopol ® is commercially available and is obtained in the form of a bacterial product. Other &agr;, &ohgr;-dihydroxy polyesters are produced through ring-opening polymerization of cyclic esters or lactones, for example &egr;-caprolactone with aliphatic diols.
The microstructure of the produced macrodiols results here depending on the monomer distribution, whereby stereospecific structures are produced exclusively.
The macrodiol is produced without or also with a catalyst, whereby SnO(Bu)
2
or dibutyl tin laurate is employed at temperatures of from 100° to 160° C.
Also polyurethanes are produced in this connection by reacting the macrodiols with diisocyanate such as, for example 1,6-hexamethylene diisocyanate, whereby the block polymers consisting of macrodiol and diisocyanate, other than with the present invention, always have valerate segments in the final product.
According to EP 0 696 605 A1, the bio-compatible or biodegradable polymers are used as medical implants, for which reason the material has to satisfy high technical requirements.
It is particularly disadvantageous in this connection that both the starting and the final products are stereo-specific, i.e. that only certain configurations are present (e.g., the bacterial product only has the R-configuration). Furthermore, bacterial polymers are, as a rule, very brittle because of their very regular crystal structure, and consequently very fragile. The polymeric products of EP 0 696 605 A1 are slightly softer, however, they still exhibit a brittle property to some extent. Furthermore, the bacterial starting products are relatively expensive. Moreover, said block polymers exhibit different discolorations, i.e. like their bacterial starting products, they are milk-colored, as a rule, which may give them a visually unattractive appearance. Said drawbacks limit the fields of application of the products of EP 0 696 605 A1 at least to some extent.
An attempt is made according to DE 195 08 627 A1 to avoid said drawbacks of the bacterially obtained PHA-material through the synthesis of polyester urethanes built up from diisocyanate and macrodiols, which in turn are produced from alkylene oxides and carbon monoxide. This method particularly has the drawback that the process has to be carried out with toxic and combustible gases under high pressure.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to avoid the drawbacks of the prior art and to make available enhanced polymer products, which, like poly-3-hydroxy-butyric acid, are biodegradable. The polymers should have a visually attractive appearance, and their properties should permit them to be usable in many different ways. Furthermore, the goal is to provide a process that is enhanced versus the methods of the prior art, and which, in a simple way, permits the production of said polymers on a large industrial scale at favorable cost, using starting products which are not produced bacterially.
The object is achieved according to the invention by making available biodegradable, linear polyester urethanes, whereby the linear polyester urethanes are structured by units of the general formula (I); i.e. consist of such units.
whereby R is an unsubstituted or substituted, saturated or unsaturated (C
1
-C
10
) hydrocarbon group, preferably methyl, ethyl or propyl,
and the substituents are selected from the group consisting of
halogen, pseudo-halogen, (C
1
-C
10
)-alkyl, (C
1
-C
10
)-alkoxy, allyl, vinyl, benzyl, unsubstituted or substituted aryl such as phenyl or naphthyl, alkenyl, alkinyl, amide, (C
1
-C
6
)-dialkylamino, unsubstituted or substituted (C
3
-C
8
)-cycloalkyl; and the aryl or cycloalkyl substituents are halogen, pseudo-halogen, (C
1
-C
10
)-alkyl, (C
1
-C
10
)-alkoxy, amide, (C
1
-C
6
)-dialkylamino, alkenyl, alkinyl, allyl and/or vinyl;
R
I
is selected from the group consisting of:
with a=2 to 12, and b=1 to 3000;
R
II
is a ring opening product of a compound selected from the group consisting of &bgr;-propio-lactone, &ggr;-butyro-lactone, &dgr;-valero-lactone, &egr;-capro-lactone, or N-protected D, L-serine-lactone, which, if need be, may be substituted with a substituent from group A;
R
III
and R
IV
are independently of each other the same or different and selected from the group consisting of H, —OR, whereby R is as defined above, halogen, pseudo-halogen, benzyl, allyl, vinyl, unsubstituted or substituted aryl, such as phenyl or naphthyl or the like, (C
1
-C
10
)-alkyl, alkenyl, alkinyl, amide, (C
1
-C
6
)-dialkylamino, unsubstituted or substituted (C
3
-C
8
)-cycloalkyl, with at least one hetero-atom, if need be, unsubstituted or substituted five-, six- or seven-link aromatics or hetero-aromatics with at least one hetero-atom, whereby the hetero-atom is O, S or N, and the substituents are taken from group A;
whereby O≦x+y≦60, and 2≦1+m≦60, and z=1 to 25.
Furthermore, the object of the invention are biodegradable cross-linked polyester urethanes ensuing from the linear polyester urethanes with units of formula (I) because they are cross-linked by diisocyanate bridges and contain fragments of the general formula (II):
whereby R, R
I
, R
II
, R
III
, R
IV
and x, y, z, l and m are defined as above.
By varying the degree of cross-linking it is possible to adjust the physical, chemical and biological properties of the polyester urethanes in a targeted manner. In particular, it is possible to vary their biodegrad-ability rate, because the biodegradation takes place at a lower rate as the degree of crosslinking increases.
The total number n of the recurring units, i.e. the number of units according to the general formula (I) present per molecule, generally amounts to at least about 2, and may be in the range of up to about 60.
In a preferred embodiment of the invention, the parameters of the general formulas (I) and (II) are in the following ranges: 0≦x+y≦30, 2≦1+m≦30, and z=6 to 10. A particularly good rate of biodegradability is available in said ranges, and the polymeric products can be
Happ Erwin
Lee Yoon Jick
Seliger Hartmut
Bagwell Melanie D.
Collard & Roe P.C.
Elbe Technologies Ltd.
Seidleck James J.
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