Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-07-21
2001-01-09
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S335000, C528S337000, C528S339000, C528S354000, C528S361000, C525S424000, C525S425000, C525S450000, C525S452000, C525S454000, C525S462000, C525S540000
Reexamination Certificate
active
06172167
ABSTRACT:
The present invention relates to new biologically degradable aliphatic copolymers of the polyesteramide or polyesterurethane type. The invention further relates to monomers from which the copolymers are built up, a method for preparing the copolymers and products which can be manufactured from the new copolymers.
There is a very wide variety of (co)polymers. Depending on their application, they have a great diversity of properties. Especially the mechanical properties are of particular importance for the use of (co)polymers in end products. At the moment however, one other property is also becoming increasingly important from an environmental viewpoint. Because plastics are used on very large scale, they cause an enormous waste problem. There is therefore increasingly a preference for (biologically) degradable plastics.
Aliphatic polyesters are known. Most of these are low melting (Tm=50-70° C.) with insufficient mechanical properties for the manufacture of end products. The good biological degradability of this class of materials is known.
Aliphatic polyamides (nylon) are known as high-melting materials with good mechanical properties. Their biological degradability is however not described, except for a few copolyamides such as the alternating copoly(amide) of glycine and &egr;-caprolactam and copolymers of nylon-6,6 and glycine.
Aliphatic polyester amides and polyester urethanes are in principle also known. They can be manufactured via diverse routes from polyesters and polyamides or from their monomers, for instance by ester-amide exchange reactions, by polycondensation of oligoamide prepolymers with oligo-ester prepolymers, by combined ring opening and polycondensation, by successive ring opening of lactones and lactams or by polyaddition of a polyester-diacid and a diisocyanate, or by ring opening of morpholinediones.
The materials from this class exhibit a wide diversity of properties. However, many of the above mentioned polyester-amides do not possess, either the suitable, particularly mechanical, properties for the manufacture of end products.
Literature is available on the biological degradability of aliphatic oligo-polyesteramides. Arvanitoyannis, Nakayama, Kawasaki & Yamamoto (Polymer 36(4), 857-866 (1995)) describe that polyesteramides with a maximum of 50 mol % amide bonds are degradable. Polyesteramides with a high mol weight (Mn>10,000) were not synthesized.
There are however a number of patent publications concerning biologically degradable polyester-amides with a high mol weight. U.S. Pat. No. 4,343,931 and U.S. Pat. No. 4,529,792 relates to polyester-amides prepared from lactic acid, diamines and dicarboxylic acid dichlorides. JP-79/119593 and JP-79/119594 relate to polyester-amides manufactured from caprolactone and caprolactam. Both types of polyesteramides are however difficult to synthesize. Moreover, the obtained amide block length is not uniform and the average block length is known only by approximation or not at all. From DE-4.327.024 and DE-4.234.305 are known aliphatic polyester-amides which can be obtained via polycondensation of aliphatic diols, dicarboxylic acids and cyclic lactams, such as caprolactam. Of such polyester-amides, those with 30 to 70% by weight of amide structures and 70 to 30% by weight of ester structures are biologically degradable. The publication does not mention anything concerning the (average) amide block length in the polymer or the morphology of these polymers.
Aliphatic polyester-urethanes can in principle be manufactured by polyaddition of an aliphatic polyester-diol prepolymer and an aliphatic diisocyanate. A chain extender is often added, such as a diamine- or diol-, in order to obtain the required mol weight. It is known that the degree of elasticity and the degree of stiffness of the polyester-urethanes can be varied. On the morphology of the aliphatic polyester-urethanes little has been written however, particularly concerning the role of phase separation in relation to uniform urethane block length. It is however known that some polyester-urethanes are biologically degradable. In the manufacture of these polyester-urethanes an environmentally unfriendly diisocyanate is usually used.
It can be seen from the foregoing that for the known (co)polymers good mechanical properties (comparable to polyethylene and polypropylene), (biological) degradability and an environmentally friendly method of preparation do not go together. It is therefore the object of the invention to provide new aliphatic copolymers which do combine these properties.
According to the present invention it has now been found that from symmetrical, crystalline diamide-diols or diamide-diacids as well as from symmetrical, crystalline diurethane-diols respectively copolyesteramides and copolyesterurethanes can be manufactured in simple and efficient manner. The diamide-diols, diamide-diacids and diurethane-diols are herein the primary monomers which are copolymerized with a secondary monomer. “Secondary monomer” here designates one or more monomers or prepolymers. The primary monomers herein form blocks with a constant chain length, which are to a great extent responsible for the final properties of the copolymer.
According to the invention new copolymers are therefore provided with the general formula:
&Brketopenst;CB—VB&Brketclosest; I
Wherein CB is a symmetrical constant block and VB is a variable block, which are mutually linked by an ester or anhydride bond. The definitions for the variable and constant blocks are given in claim
1
.
The copolymers are therefore built up from a chain of building blocks, which each in turn consist per copolymer of a block with a fixed chemical structure and therefore a constant block length (designated hereinafter “constant block”) and a block with a variable chemical structure and block length (designated hereinafter “variable block”).
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Ioannis Arvanitoyannis et al., “Synthesis and study of novel biodegradable oligo (ester amide)s based on sebacic acid, octadecanedioic acid, 1,6-hexanediamine and ∈-caprolactone:2”, Polymer, vol. 36, No. 4, (1995) pp. 857-866.
Antoinette van Bennekom, “Fast Crystallizing Polyesteramides”, (1995), CIP-Data Koninklijke Bibliotheek, Den Haag.
Peter Serrano, “Alternating Polyesteramides Based on 1,4-Butylene Terephthalamide”, (1996), CIP-Data Koninklijke Bibliotheek, Den Haag.
Dijkstra Pieter Jan
Feijen Jan
Stapert Hendrik Roelof
Acquah Samuel A.
Universiteit Twente
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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