Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1998-11-30
2001-08-07
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S401000, C428S483000, C428S492000
Reexamination Certificate
active
06270896
ABSTRACT:
The invention relates to an elastic fibre containing a copolyester ether or a copolyester ester.
Copolyether esters and copolyester esters will hereinafter jointly be referred to as copolyester.
Such a copolyester fibre is known from the report of a paper, ‘Neues aus Forschung und Entwicklung’, read by Vieth during the 34th Internationale Chemiefasertagung Dornbirn, 20-22 Sep. 1995.
A drawback of this known fibre is its low elastic recovery manifesting itself in a high permanent elongation which occurs after stretching of the fibre. The aforementioned publication shows that, after the fibre has been stretched by 100% of its original length, its recovery from this stretch is not more than 90%. Thus the length of the fibre has increased permanently by at least 10% of its original length. This substantially limits the application of the known fibre as a component imparting elastic properties to a yarn or fabric. This limitation is conceded also in said publication. The same publication shows that, while the permanent elongation is indeed reduced by after-stretching, the elongation at break shows a substantial deterioration.
What has now been found is an elastic fibre containing a mixture of a copolyester ether or a copolyester ester and a chemically crosslinked rubber.
Surprisingly, such a fibre has a permanent elongation of at most 9% after the fibre has been stretched 100% and an elongation at break of at least 450%. Indeed, fibres have been found showing a permanent elongation of at most 6% after stretching the fibre 100% and an elongation at break of at least 500% and even 600%.
It has been found that by after-stretching the fibres according to the invention fibres are obtained having an even substantially lower permanent elongation after stretching the fibre 100%. The invention therefore also relates to fibres of the composition described having a permanent elongation of at most 5% after stretching the fibre 100% and even at most 3% and even at most 2%.
Thus the fibre according to the invention has been found to possess a particularly high degree of elastic recovery in combination with a high elongation at break.
Many applications of elastic fibres involve elongations substantially higher than 100% of the original length. Even at these higher elongations the fibre according to the invention has been found to exhibit an excellent elastic recovery. Even on being stretched by 200% of its original length, the fibre according to the invention exhibits a permanent elongation of at most 15% and in many cases of at most 10% and even 5% or 2% of the length of the fibre before stretching.
The permanent elongation after stretching, henceforth referred to as ‘tension set’, is measured at room temperature by gripping a fibre of a given length in the jaws of a tensile testing machine and moving the jaws apart at a speed of 200 mm/min until the desired stretch is reached. To this end, markings are provided on the fibre at a distance of 50 mm, l
0
. The fibre is kept in its stretched state for 10 seconds, whereupon the tensile force acting on the fibre is removed and the fibre is taken from the jaws. After allowing the fibre to relax at room temperature for 1 hour, the tension set in % is determined by dividing the difference in distance between the markings, 1, on the fibre that has been allowed to relax after stretching and the original distance, l
0
, between these markings by that original distance l
0
and multiplying the quotient by 100.
Copolyether esters and copolyester esters are segmented block copolymers built up from hard, crystalline and relatively high-melting polyester segments and soft, flexible and relatively low-melting polyether or polyester segments. Suitable hard polyester segments for the fibres according to the invention are, for instance, polyalkylene terephthalates, for instance poly(butylene-naphthalene dicarboxylic acid), poly(cyclohexanedicarboxylic acid-cyclohexanemethanol) and preferably polybutyleneterephthalate and polytrimethyleneterephthalate-2,6-naphthalate. Other types of hard polyester segments conforming to the requirements set can be used in a block copolymer as well and also a plurality of types can be used simultaneously. Polyester units suited for the hard crystalline segment are built up, for instance, from an acid and a glycol. Suitable acids are, for instance, terephthalic acid and 2,6-naphthalenedicarboxylic acid. In addition to the terephthalic acid and/or 2,6-naphthalenedicarboxylic acid a small amount of a different dicarboxylic acid can be added, for instance isophthalic acid, or an aliphatic dicarboxylic acid, for instance adipic acid, cyclohexane-1,4-dicarboxylic acid or a dimeric acid. The chosen glycol component of the polyester unit may be a glycol having, for instance, two to twelve carbon atoms, for instance ethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexane diol or decane diol.
Suitable soft polyester segments are, for instance, aliphatic polyesters, including polybutylene adipate and preferably polytetramethyladipate and polycaprolactone. Other types of soft polyester segments conforming to the requirements set can be used in a block copolymer as well and also a plurality of types can be used simultaneously. Suitable polyether segments are, for instance, polyalkylene oxides, including polytetramethylene oxide, polypropylene oxide, polyethylene oxide. Other types of polyether segments conforming to the requirements set can be used in a block copolymer as-well and also a plurality of types can be used in a copolyester simultaneously. Highly suited are copolyether esters in which the polyester segments are polyalkyleneterephthalates, preferably polybutyleneterephthalate, and the polyether segments are polyalkyleneoxides, preferably polytetramethyleneoxide.
Suitable copolyether esters in the fibre according to the invention in any case have a processing temperature, particularly a melting temperature, below the temperature at which an appreciable thermal degradation takes place in the polymer.
There are no special limitations regarding the upper limit of the melting point of the low-melting portion of the copolyester. It is usually 130° C. or lower, preferably 100° C. or lower. The weight-average molecular weight of the low-melting polymer segment is between 200 and 10000 g/mol, preferably between 400 and 6000 g/mol.
The % (wt) ratio between the high-melting crystalline segment and the low-melting flexible segment of the copolyester is between 95:5 and 5:95 and preferably between 70:30 and 30:70.
By a chemically crosslinked rubber is meant a rubber which through chemical reactions has been formed into an insoluble and unmeltable polymer, the molecule chains in which are interlinked to form a three-dimensional network structure. Examples of the said reactions are described in the Encyclopedia of Polymer Science and Engineering, Second Edition, John Wiley and Sons, Volume 4, page 350 et seq. and page 666 et seq.
Suitable rubbers for the fibre of the invention are acrylic rubbers, butyl rubbers, halogenated rubbers, for example brominated and chlorinated isobutylene-isoprene, (styrene-)butadiene rubbers, butadiene-styrene-vinylpyridine, nitrile rubbers, natural rubber, urethane rubbers, silicone rubbers, polysulphide rubbers, fluorocarbon rubbers, ethylene-propylene-(diene-)rubbers (generally referred to as EP(D)M rubbers), polyisoprene, epichlorohydrine, chlorinated polyethylene, chloroprene, chlorosulphonated polyethylene. Preferably, the fibre contains the economically attractive and commonly used acrylic rubbers, (styrene-)butadiene rubbers, butyl rubbers, chlorinated polyethylene, chloroprene, chlorosulphonated polyethylene, epichlorohydrine, ethylene-propylene-(diene-)rubbers, nitrile rubbers, natural rubber, polyisoprene or silicone rubbers. EP(D)M rubbers are highly suitable. The fibre may also contain mixtures of different rubbers, at least one of which is chemically crosslinked.
The rubber in the fibres may be crosslinked by any known technique, the most suitable technique being chosen for each ru
Bastiaansen Cornelis W. M.
Gelissen Franciscus W. M.
Versluis Cornelis
Willems Edwin
DSM N.V.
Hess Bruce H.
Pillsbury & Winthrop LLP
Shewareged B.
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