Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Layered – stratified traversely of length – or multiphase...
Reexamination Certificate
2000-02-17
2001-12-18
Short, Patricia A. (Department: 1712)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Layered, stratified traversely of length, or multiphase...
C264S165000, C264S172180, C525S425000, C525S437000
Reexamination Certificate
active
06331264
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns polymer compositions that exhibit reduced levels of degradation product emissions during processing. This invention further concerns processes for the fabrication of polymer articles with low emissions of polymer degradation products.
TECHNICAL BACKGROUND
3-Hydroxypropanoxy terminated polymers have the problem of being prone to thermal degradation processes that result in acrolein emissions. Acrolein is an irritant chemical, for which workplace levels are strictly regulated, i.e. to limit its content in the air to be less than 0.1 ppm [AEL].
SUMMARY OF THE INVENTION
The present invention solves this problem by providing compositions comprising 3-hydroxypropanoxy terminated polymers of improved stability with regard to acrolein emission. The present invention comprises compositions prepared by contacting molten 3-hydroxypropanoxy terminated polymer with an effective amount of a melt stable, organic nitrogen-containing stabilizing compound to reduce the emission of acrolein from said molten polymer.
This invention also comprises a process for the fabrication of polymer articles from 3-hydroxypropanoxy terminated polymers exhibiting low levels of acrolein emissions, which process comprises:
a) contacting in the molten state said 3-hydroxypropanoxy terminated polymer with an effective amount of a melt stable, organic nitrogen-containing stabilizing compound to reduce the emission of acrolein from said polymer in the molten state, and
b) fabricating said polymer into said article.
DETAILED DESCRIPTION OF THE INVENTION
3-Hydroxypropanoxy terminated polymers, i.e., those polymers bearing an end group of the structure —O—CH
2
CH
2
CH
2
OH, are prone to degradative processes when molten that result in the generation and emission of acrolein, CH
2
═CHCHO.
3-Hydroxypropanoxy terminated polymers comprise those polymers prepared from 1,3-propanediol or its chemical equivalents. The 1,3-propanediol can be prepared chemically or biologically. For purpose of this specification the term 3-hydroxypropanoxy terminated polymers includes, but is not limited to 1,3-propanediol dicarboxylate polymer, examples of which include poly(trimethylene terephthalate, poly(trimethylene naphthalenedicarboxylate), poly(trimethylene isophthalate) and blends and copolymers thereof. Other dicarboxylic acids useable in the 3-hydroxypropanoxy terminated polymers include 1,4-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, succinic acid, glutaric acid, adipic acid, sebacic acid and 1,1 2-dodecane dioic acid. Depending on the route of synthesis employed in the preparation of the polymers of the present invention, the dicarboxylic acids may be introduced to the polymerization process as the dicarboxylic acids or as the lower dialkyl esters of the dicarboxylic acids, for example, the dimethyl, diethyl, or dipropyl esters of these dicarboxylic acids.
Copolymers useable with the polymers of the present invention typically comprise any of the dicarboxylic acids mentioned above and diols other than 1,3-propanediol, for example, up to 30 mol% of such other diol, based on the total moles of diol present. These diols include ethylene glycol, 1,4-butane diol, 1,2-propanediol, diethylene glycol, triethylene glycol, 1,3-butane diol, 1,5-pentane diol, 1,6-hexane diol, 1,2-, 1,3- and 1,4-cyclohexane dimethanol, and the longer chain diols and polyols made by the reaction product of diols or polyols with alkylene oxides.
When the polymers of the present invention are used in blends, the blend polymer can be prepared from any of the diacids or the diols listed above. A specifically preferred blend comprises poly(ethylene terephthalate) and poly(trimethylene terephthalate).
These polymers have a high molecular weight so as to be commercially useful. Such molecular weight can be characterized by the polymer having an intrinsic viscosity (IV) of at least 0.1 dl/g, determined by measuring the flow time of a solution of known polymer concentration and the flow time of the polymer solvent in a capillary viscometer, as set forth in ASTM D2857.95
The polymer can be a homopolymer or blends and copolymers containing at least 10% of one or more 3-hydroxypropanoxy terminated polymer. For example a blend comprising 90% poly(ethylene terephthalate) and 10% poly(trimethylene terephthalate)—(containing up to 1 weight % of a polyamide polymer as the stabilizing compound), is within the envisioned scope of the present invention.
The melt stable, organic nitrogen-containing stabilizing compound with which the 3-hydroxypropanoxy terminated polymer is intimately blended is selected from melt stable primary, secondary and tertiary amines, either aliphatic or aromatic, and aliphatic or aromatic amides. Also included are polymers containing such functional groups either as a polymer side chain or in the polymer backbone, e.g., polyamides, and copolymers and blends of polyamides.
When polyamides are employed, they can be linear or branched in chain structure. Examples of linear polyamides include, monomeric polyamides, such as poly(caprolactam), nylon 6, and bis monomeric polyamides, such as poly(hexamethylenediamine adipate), nylon 4,6, nylon 6,6, nylon 6,10, nylon 6,12, nylon 12,12, or their copolymers and blends. Certain aromatic polyamides, for example poly(p-phenylene terephthalamide) and poly(m-phenylene isophthalamide), can also be employed. Polyamides prepared from the use of tri-,tetra- or multifunctional amines, e.g., bis(hexamthylenetriamine) or BHMT can also be used.
To reduce the emission of acrolein from the 3-hydroxypropanoxy terminated polymer, it is only necessary that the stabilizing compound contain nitrogen and be stable in the polymer melt. Preferably, the stabilizing compound will also be in the liquid state in the melt of 3-hydroxypropanoxy terminated polymer so as to be intimately mixed with the polymer. Typically, the compound is of sufficient molecular weight so as to achieve stability in molten 3-hydroxypropanoxy terminated polymer, in which case, the liquid state of the compound will be the molten state. The stabilizing should also not introduce or cause color in the polymer. Polyamides such as described above fulfill all of these characteristics and thus are a preferred class of stabilizing compounds.
While not meaning to be bound by any theory, it is believed that the nitrogen functionality in the melt stable, organic nitrogen-containing stabilizing compound either interacts with the 3-hydroxypropanoxy terminus of the polymer chain, or a degradation product thereof, to hinder or stop degradative pathways that generate acrolein or interacts with generated acrolein on the molecular level to hinder or prevent emission. The reactions between amines (primary, secondary, and tertiary) and aldehydes giving different adducts is well documented in literature. For a review of the reactions between amines and aldehydes, See Rec. Chem. Prog., 29, 85-101 (1968).
The amount of melt stable, organic nitrogen-containing stabilizing compound present in the composition of the present invention is defined as an amount to be effective in the reduction of acrolein emission. This is generally less than 10% by weight based on the amount of the 3-hydroxypropanoxy terminated polymer present. One percent by weight has been demonstrated to be effective. The range of effective amounts can be from about 0.01% to about 10% by weight.
Articles of manufacture prepared from 3-hydroxypropanoxy terminated polymers, copolymers and blends can include fibers (monocomponent, bicomponent, for example bicomponent with poly(ethylene terephthalate, or multicomponent), filaments, films, castings and moldings. The manufacture of these articles generally require the starting polymer to be in molten form at some stage of the manufacturing process. It is during this molten stage that acrolein emission is most prevalent.
The composition comprising the 3-hydroxypropanoxy terminated polymer and the melt stable, organic nitrogen-containing stabilizing compound can be formed from the 3-hydroxypropanoxy te
Chang Jing Chung
Kurian Joseph Varapadavil
E. I. Du Pont de Nemours and Company
Kuller Mark D.
Mayer Nancy S.
Short Patricia A.
Siegell Barbara C.
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