Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2002-02-20
2003-03-25
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S394000, C528S075000, C528S085000
Reexamination Certificate
active
06537661
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to melt processable, bleach resistant durable fibers; and to polyurethane elastomers from which such fibers are formed.
BACKGROUND OF THE INVENTION
Melt processable elastomeric compositions which are easily compression moulded or melt blown into elastic fibers or films having low stress relaxation, low hysteresis, and high recoverable energy and made from hydrogenated polystyrene-polybutadiene-polystyrene block copolymers are described in U.S. Pat. Nos. 4,970,259 and 5,093,422. The elastic fibers and films described in these patents are useful in a variety of applications such as diaper waistbands and non-woven fabrics. Such applications are non-durable fiber applications and are so described because they do not require the retention of properties at relatively high service temperatures, such as 50 to 60° C., and they do not require an exceedingly high elastic recovery. Further, the articles constructed from them are designed for short-term use. While hydrogenated styrenic block copolymers are useful in short-term and disposable applications, their low upper service temperatures limit their long-term use in reusable, washable fabrics. The chemical composition of the rubbery section of styrenic block copolymers does offer out-standing resistance to oxidative and hydrolytic environments. Common durable fibers such as polyurethane, polyurethane-urea and polyester fibers generally have good upper service temperatures such that they are suitable for durable applications. They are, however, susceptible to oxidation and hydrolysis. Further, polyurethane-urea, or spandex, fibers are not melt processable and so must be spun from solutions employing costly solvents.
Currently, the material most often used for a durable elastic fiber for fabrics used in athletic-wear and swimwear applications is spandex. The usual definition of spandex is a fiber made from polyether polyols, diisocyanates, and diamines to form a segmented polyurethane-urea. The polyurethane-urea has “soft segments” and “hard segments,” which refer to specific portions of the polymer chain. The soft segments are the portions of the spandex polymer chain that can be derived from the polyether polyols. The hard segments are the portions of the spandex polymer chain that are derived from the reaction of an isocyanate and a diamine or diol chain extender. Spandex polymers and their method of manufacture are described in U.S. Pat. No. 2,929,804 from DuPont. In another DuPont spandex patent, U.S. Pat. No. 5,666,960, spandex fibers are said to be known to be detrimentally affected by exposure to chlorinated water, as for example in swimming pools.
Commercially available spandex fibers are generally made from poly(tetramethylene ether)glycol, methylene-bis(4-phenylisocyanate), and an amine such as ethylene diamine. Fibers made from spandex are not melt processable because of the chemical composition of the reactant with the amine chain extender. It becomes a thermoset resin which is not melt processable. Therefore, spandex fibers are made by solution spinning. This is a very tedious and expensive process which requires a solvent such as dimethylacetamide which itself is expensive and the cost of its recovery is also expensive. Melt processing techniques for making fibers are much simpler and much easier to carry out and also are much less expensive.
It can be seen that it would be highly advantageous if there was a way to manufacture a durable fiber which had the characteristics of spandex fibers but could be melt processed. It would also be advantageous to be able to produce a durable fiber which was not susceptible to attack by chlorine such as in bleach and was resistant to hydrolysis. The present invention provides such a durable fiber.
SUMMARY OF THE INVENTION
The present invention provides melt processable, bleach resistant durable fibers having an elastic recovery above 50% after an extension to 160% elongation and a stress relaxation below 50% after an extension to 150% for 30 minutes which are formed from a (soft) polyurethane elastomer. This elastomer is comprised of
(a) from 75 to 90% weight of a polydiene diol having up to about two terminal hydroxyl groups per molecule and a number average molecular weight between 500 and 20,000,
(b) from 9 to 25% weight of a diisocyanate,
(c) from 0.8 to 5% weight of a chain extender which is a low molecular weight aliphatic diol, or a mixture of the low molecular weight aliphatic diol and from 0.1 to 4.0 mol % of the total amount of chain extender, i.e. the mixture, of a diamine wherein the hard segment content of the polyurethane elastomer is from about 10 to about 30% weight. Such chain extenders will have not more than two functional groups which will react with the diisocyanate and have a number average molecular weight from 40 to 600 and a hydroxyl equivalent weight of 20 to 300 grams per hydroxyl group. Preferably, the chain extender is a linear aliphatic diol having 2 to 40 carbon atoms and is more preferably selected from the group consisting of ethylene glycol, 1,3-propane diol, 1,4-butane diol, 1,5-pentane diol, and 1,6-hexane diol. The hard segment contents can be calculated according to equation 1.
Hard segment content=100*(isocyanate mass+chain extender mass)/(total mass) (1)
According to a further aspect the present invention relates to a polyurethane elastomer comprised of
(a) from 75 to 90% weight, basis the total of (a), (b) and (c), of a polydiene diol having up to about two terminal hydroxyl groups per molecule and a number average molecular weight between 1000 and 20,000,
(b) from 9 to 25% weight, basis the total of (a), (b) and (c), of a diisocyanate, and
(c) from 0.8 to 5% weight, basis the total of (a), (b) and (c), of a chain extender which is a mixture of a low molecular weight aliphatic diol and from 0.1 to 4.0 mol %, basis the total mixture, of a diamine,
wherein the hard segment content of the polyurethane elastomer is in the range from about 10 to about 30% weight.
DETAILED DESCRIPTION OF THE INVENTION
As discussed above, the hydrogenated styrene-butadiene-styrene block copolymers that are used to make elastic fibers do not allow the retention of properties at high service temperatures and also they do not stretch and recover well enough for durable fiber applications. Spandex is the industry standard for durable elastic fibers but spandex fibers are not melt processable and are expensive to manufacture and they also are not bleach resistant. The polyurethane elastomeric fibers of the present invention are not thermosets so they are melt processable and thus have that advantage over spandex fiber. Furthermore, the polyurethane elastomeric fibers of the present invention are resistant to chlorine bleach which is highly advantageous since it is desirable to wash such fibers in bleach from time to time. The polyurethane elastomeric fibers of the present invention equal spandex fibers in terms of their elastic recovery and stress relaxation properties and the retention of strength properties at higher service temperatures, up to 100° C., is very good.
The film and fiber products designed for durable applications, such as in textile garment, industrial uses need to meet several performance criteria. Among these, the products should exhibit excellent elastic performance (high strength, high hysteresis recovery, low stress relaxation) at use temperature. The products should retain their integrity and elastic performance after passing hot water and hot cleaner dryer cycles. In addition, the products also need to have sufficient retention of properties upon exposure to various chemicals, such as bleach, acid, and cleaning solvents. To have good consumer appeal, the product should be able to colour upon dyeing with dyestuff.
The term “elastic” is used herein to mean any material which, upon application of a tensile force, is stretchable, that is, elongatable at least about 60 percent (i.e., to a stretched, length which is at least about 160 percent of its relaxed length) and which will recover
Djiauw Lie Khong
Masse Michael A.
Edwards N.
Kraton Polymers U.S. LLC
LandOfFree
Melt processable, bleach resistant, durable fibers having... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Melt processable, bleach resistant, durable fibers having..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Melt processable, bleach resistant, durable fibers having... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3084522