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...
Patent
1994-12-29
1997-11-18
Thibodeau, Paul J.
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...
528 56, 528 58, 528 83, 525440, 525453, C08G 1808, C08G 1822, C08G 1824
Patent
active
056888902
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to thermoplastic polyurethane compositions having excellent moldability and being capable of minimizing the decrease of the molecular weight of molded articles therefrom, which decrease would otherwise deteriorate their properties, whereby the molded articles have excellent properties such as tensile strength and elongation, compression set, heat resistance and resistance to hydrolysis, and to a process for producing the same. The present invention further relates to a polymer diol composition to be used for the above thermoplastic polyurethane compositions and to a process for producing the same. The present invention still further relates to molded articles and elastic fibers obtained from the above thermoplastic polyurethane compositions and processes for producing the same.
2. Description of the Prior Art
Upon manufacture of thermoplastic polyurethanes, various polymer diols are used as the raw material for constituting their soft segments and these diols include polyester diols, polyesterpolycarbonate diols, polycarbonate diols and polyether diols. Among these diols, polyester diols are most widely used, since they give thermoplastic polyurethanes having excellent mechanical properties.
Ester-based polymer diols, such as polyester diols, polycarbonate diols and polyesterpolycarbonate diols are generally produced by polycondensing an dicarboxylic acid or its ester-forming derivatives such as esters or anhydrides thereof and a short-chain diol by direct esterification or transesterification, or by subjecting a lactone to ring-opening polymerization. Titanium-based compounds, having high catalytic activity, are widely used as catalysts (esterification catalyst) for these esterifications, including direct esterification, transesterification and ring-opening polymerization, to produce these ester-based polymer diols.
Thermoplastic polyurethanes are obtained by subjecting to urethanization one of the above polymer diols, together with an organic diisocyanate such as 4,4'-diphenylmethane diisocyanate or naphthalene diisocyanate and a chain extender of a short-chain diol such as 1,4-butanediol.
However, thermoplastic polyurethanes obtained by conducting melt polymerization using an ester-based polymer diol having been obtained with a titanium compound catalyst, while the activity of the catalyst was not permitted to decrease after the polymer preparation, have insufficient uniformity in their properties, such as heat resistance and resistance to hydrolysis. Molded articles obtained by melt molding, such as injection molding or extrusion molding, of these polyurethanes are therefore inferior in such properties. There are also available thermoplastic polyurethanes obtained by melt polymerization of an ester-based polymer diol having been obtained with a titanium compound catalyst, which is then subjected to an activity-decreasing treatment. These polyurethanes will, upon melt molding thereof, tend to give molded articles sticking together. In this case also, the obtained molded articles tend to become inferior in tensile strength, elongation, compression set, heat resistance and like properties.
The mechanisms involved in the above cases were studied by the present inventors and found to be as follows.
With the above former type of thermoplastic polyurethanes, during melt polymerization and melt molding thereof, the ends of short-chain diols formed by scission of the inside of the hard segments and the ends of other short-chain diols formed by scission of the inside of the soft segments originating from the polymer diol used undergo transesterification, whereby the blocks become no longer distinct from each other (that is, local randomization occurs) and, as a result, the properties of the thermoplastic polyurethanes and molded articles therefrom become non-uniform and inferior.
With the above latter type of thermoplastic polyurethanes, the urethanization reactivity decreases between the isocyanate groups and hydroxyl groups di
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Die Angewandte Makromolekulare Chemie, vol. 160, pp. 1-15, May 1988, Werner Mormann, et al., "Solvolytic Degradation of Aliphatic Polyesteroligomers: Poly(Tetramethylene Adipate) Diol".
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Hirai Koji
Ishiguro Michihiro
Nakayama Kimio
Ono Hiroyuki
Oshita Tatuya
Critharis Mary
Kuraray Co. Ltd.
Thibodeau Paul J.
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