Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
2001-08-10
2004-06-08
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyester
C528S295000, C528S296000, C528S298000, C528S300000, C528S302000, C528S307000, C528S308000, C528S308600, C524S081000, C524S082000, C524S113000, C524S233000
Reexamination Certificate
active
06746779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to solvent soluble, biodegradable polyesters, method of production, and use thereof. These products are useful as biodegradable shaped articles and as biodegradable coatings.
2. Description of the Related Art
The inadequate treatment of municipal solid waste which is being put in landfills and the increasing addition of nondegradable materials, including plastics, to municipal solid waste streams are combining to drastically reduce the number of landfills available and to increase the costs of municipal solid waste disposal. While recycling of reusable components of the waste stream is desirable in many instances, the costs of recycling and the infrastructure required to recycle materials is sometimes prohibitive. In addition, there are some products which do not easily fit into the framework of recycling. The composting of non-recyclable solid waste is a recognized and growing method to reduce solid waste volume for landfilling and/or making a useful product from the waste to improve the fertility of fields and gardens. One of the limitations to marketing such compost is the visible contamination by undegraded plastic, such as film or fiber fragments.
It is desired to provide components which are useful in disposable products and which are degraded into less contaminating forms under the conditions typically existing in waste composting processes.
Polyesters have been considered for biodegradable articles and enduses in the past. Biodegradable polyesters can be described as belonging to three general classes; aliphatic polyesters, aliphatic-aromatic polyesters, and sulfonated aliphatic-aromatic polyesters. Aliphatic polyesters are polyesters derived solely from aliphatic dicarboxylic acids. Aliphatic-aromatic polyesters are polyesters derived from a mixture of aliphatic dicarboxylic acids and aromatic dicarboxylic acids. Sulfonated aliphatic-aromatic polyesters are polyesters derived from a mixture of aliphatic dicarboxylic acids and aromatic dicarboxylic acids and, in addition, incorporate a sulfonated monomer, such as the salts of 5-sulfoisophthalic acid. Many of these prior materials do not provide desired biodegradability and/or solubility in common solvents.
U.S. Pat. No. 4,104,262, teaches water-dispersible polyester resins. The water-dispersibility of the polyester resins is due, at least in part, to the incorporation of moieties of an alkali metal-sulfo group and to the very low molecular weights of the polymers, e.g., between 300 and 3,000. The low molecular weight polyester resins would tend to give brittle, low toughness films and coatings.
U.S. Pat. No. 4,340,519, teach aqueous dispersions of polyester resins which contain 0.5 to 10 mole percent of an aromatic dicarboxylic acid having a metal sulfonate group. Many of the polyesters of this patent incorporate neopentyl glycol. Example A-1, contained within Table 2 of the patent, incorporates 16.7 mole percent of isophthalic acid within the aromatic dicarboxylic acid component. This example was found to be crystalline, based on the reported melting point of 116° C., and is not expected to be soluble in polar solvent. Such solubility is often desired, e.g., to allow solvent casting of coatings and films.
Miller, in U.S. Pat. No. 4,394,442, teaches a subbing layer composed of an aqueous dispersion of certain copolyester resins which incorporate 0.1 to 10 mole percent aromatic sulfonated compounds. The patent exemplifies copolyester resins which incorporate 10 mole percent, (based on the total of dicarboxylic acids), of the sodium salt of 5-sulfoisophthalic acid in combination with 56.7 mole percent, (based on the total of diols), di(ethylene glycol). Such polyesters that are soluble in water are often undesired because they do not have the desired dimensional stability in the presence of water.
The above-mentioned polyesters of the art often suffer from poor solubility in polar solvent systems, low molecular weights, which could lead to brittle films, or high moisture sensitivity, which could lead to dimensional instability under varying moisture conditions. The present invention overcomes these shortcoming and provides solvent soluble, film forming copolyesters which have improved moisture insensitivity.
SUMMARY OF THE INVENTION
The present invention provides a copolyester having an inherent viscosity of equal to or greater than about 0.3 dL/g comprising:
(a) about 20 to about 60 mole percent based on the moles of aromatic dicarboxylic acid or ester, of one or more of isophthalic dicarboxylic acid or an alkyl diester thereof,
(b) about 40 to about 80 mole percent based on the moles of aromatic dicarboxylic acid or ester, of one or more of terephthalic acid, an alkyl diester thereof, 2,6-naphthalene dicarboxylic acid, or an alkyl diester thereof,
(c) about 10 to about 60 mole percent based on the moles of dicarboxylic acid or ester, of one or more aliphatic dicarboxylic acids or an alkyl diester thereof,
(d) about 0.1 to about 5 mole percent based on the moles of total dicarboxylic acid or ester, of one or more alkali or alkaline earth metal salts of 5-sulfoisophthalic dicarboxylic acid or an alkyl diester thereof,
(e) about 90 to 100 mole percent based on the moles of glycols, of one or more aliphatic glycols, and
(f) 0 to about 10 mole percent based on the total amount of glycols of one or more of di(ethylene glycol) and tri(ethylene glycol).
Further objects, features and advantages of the present invention will become apparent form the detailed description that follows.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
One aspect of the present invention provides solvent soluble, biodegradable sulfonated aliphatic-aromatic copolyesters with IV equal to or greater than about 0.30 dL/g, such as above about 0.4 or above about 0.5 dL/g. The IV should preferably be sufficient to give non-brittle films, but not so high as to give undesired high solution viscosities.
The sulfonated aliphatic-aromatic copolyesters are preferably comprised of (A), (B) (C), (D), and (E):
(A) about 89.9 to about 35, preferably about 88 to about 46, more preferably about 84.5 to about 47, mole percent (based on the total moles of dicarboxylic acid) of an aromatic dicarboxylic acid component comprised of (i) and (ii):
(i) about 20 to about 60, preferably about 25 to about 50, more preferably about 30 to about 40, mole percent, (based on the total moles of aromatic dicarboxylic acid), of isophthalic dicarboxylic acid or a lower alkyl (C
1
-C
6
) diester derived therefrom, such as dimethylisophthalate, diethylisophthalate, and the like and
(ii) about 80 to about 40, preferably about 78 to about 50, more preferably about 75 to about 60 mole percent, (based on the total moles of aromatic dicarboxylic acid), of an aromatic dicarboxylic acid selected from terephthalic acid and 2,6-naphthalene dicarboxylic acid, and lower dialkyl (C
1
-C
6
) esters derived therefrom, such as dimethylterephthalate, diethylterephthalate, dimethyl-2,6-naphthalene dicarboxylate, diethyl-2,6-naphthalene dicarboxylate, and the like;
(B) about 10 to about 60, preferably about 12 to about 50, more preferably about 15 to about 50 mole percent (based on the total moles of dicarboxylic acid) of a linear aliphatic dicarboxylic acid component comprised of one or more aliphatic dicarboxylic acids, which generally has from 2 to 36 carbon atoms, such as oxalic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, dimer acid, or mixtures therefrom, and lower dialkyl diesters derived therefrom, such as dimethyl oxalate, dimethyl succinate, diethyl succinate, dimethyl glutarate, diethyl glutaratate, dimethyl azealate, and the like;
(C) about 0.1 to about 5, preferably about 0.1 to about 4, more preferably about 0.5 to about 3 mole percent (based on the total amount of dicarboxylic acid) of a sulfonate component comprised of one or more alkali or alkaline earth metal salts of 5-sulfoisophthalic acid and lower (C
1
-C
6
) alkyl diesters derived therefrom, such as alkali or alkaline metal salts of dimethyl-5
Hayes Richard Allen
Kosinski Leonard Edward
Acquah Samuel A.
E. I. du Pont de Nemours and Company
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