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...
Reexamination Certificate
1999-08-27
2001-06-12
Seidleck, James J. (Department: 1711)
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...
C264S177180, C264S180000, C264S181000, C264S184000, C528S068000
Reexamination Certificate
active
06245876
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/JP98/00832 which has an International filing date of Feb. 27, 1999 which designated the United States of America.
1. Technical Field
The present invention relates to a polyurethaneurea (hereinafter referred to as PUU) continuous shaped article having excellent characteristics such as a segmented PUU fiber and a segmented PUU tape, and a process for producing the same. The present invention relates in more detail to a PUU continuous shaped article having a high initial stress, a high elongation and a high strength as compared with conventionally obtained polyurehtaneurea continuous shaped articles. Moreover, the present invention relates to an improved process for producing a PUU continuous shaped material suited to the production of a PUU continuous shaped article having a small thickness (film-like for a tape, etc.) at a high rate.
2. Background Art
Polyurethane has been used for a wide range of applications such as foams, adhesives, paints, elastomers, synthetic leathers and fibers, and many useful products have been produced therefrom.
Of the materials as mentioned above, the elastic PUU fiber required to have a particularly high elasticity has been used for a wide range of applications such as an alternate material for rubber in the stretch portions of pantihose, foundation garments, stockings, paper diapers which have been recently put into practice, etc.
The production processes PUU fibers include a dry spinning process, a wet spinning process and a reaction spinning process. Commercially available spandexes obtained by these processes are classified into the following two types.
(1) A spandex which shows a relatively high stress (initial stress, 0.06 to 0.09 g/d) when elongated by 100% and a high strength at break (at least 1.0 g/d), but which shows no significantly large elongation at break (500 to 700%), and a sharp rise in the stress when elongated by about 400%. When consumers wear such a type of fiber products (elastic PUU fiber obtained by dry or wet spinning), they have an excessively tightening feel.
(2) A spandex which shows a low initial stress (up to 0.05 g/d), a strength at break from about 0.5 to 1.0 g/d and a high elongation at break (at least 700%), but which shows no sharp rise in the stress. When consumers wear such a type of fiber products (elastic PUU fiber obtained by reaction spinning), there is no tightening feeling, and the feel is agreeable.
The low initial stress and the sharp increase in the stress at the time when the fiber is elongated by 400% as mentioned in (1) are not necessarily desirable for the elastic PUU fiber. An elastic PUU fiber having really desirable characteristics has not been developed yet.
Next, problems of the conventional production process of PUU continuous shaped articles will be explained below by taking an elastic PUU fiber as an instance. A polyurethaneurea solution (dope) for spinning which can be used for dry spinning and wet spinning is generally obtained by the two-stage process. That is, a diisocyanate component and a diol component are reacted in a molten state as a first stage to give a molten prepolymer having isocyanate groups at the molecular ends, which is dissolved in a solvent such as N,N-dimethylacetamide or N,N-dimethylformamide to give a solution of the prepolymer (hereinafter abbreviated to PUP) (melting synthesis process). Alternately, both components are directly reacted in such a solvent as mentioned above to give a prepolymer solution (solution synthesis process). In a second step, the prepolymer is polymerized (chain extension) with a aliphatic diamine as disclosed in the specification of U.S. Pat. No. 2,929,804 to give a polyurethaneurea solution. An elastic PUU fiber is shaped by evaporating the solvent from the solution within a heated spinning cylinder in dry spinning, or by coagulating the fiber in a coagulating bath in wet spinning.
However, production of an elastic PUU fiber having a thickness (size) larger than 10 denier at an economical spinning speed is difficult because the rate of removing solvent from the polymer solution is slow in these processes. Accordingly, multifilaments must be produced, the production of which is technologically more difficult, when a PUU fiber having a thickness larger than 10 denier is desired. Conversely, an elastic PUU fiber having a thickness smaller than 10 denier, the demand of which is sharply increasing recently due to the recent tendency toward making the products lightweight, is also difficult because of the air resistance and solution resistance.
On the other hand, the reaction spinning process is a simple one and comprises preparing a PUP by a melting synthesis method containing no solvent or containing a solvent in an extremely slight amount, and directly producing polyurethaneurea in a reaction solution containing a polyamine and simultaneously shaping a filament material. Moreover, the process has an excellent advantage that the composition of the PUU can be widely selected, which advantage is practically difficult to obtain from the other spinning processes. As explained above, in the dry spinning process, the polymer must be soluble in a solvent. As a result, the polymer composition is restricted. On the other hand, in the reaction spinning process, a prepolymer is directly formed into a polymer without dissolving the prepolymer in a solvent; therefore there is no such a restriction. The reaction spinning process potentialy provides weathering resistance, yellowing resistance and chlorine resistance of the elastic PUU fiber, which have been said to be its drawbacks, by greatly changing its chemical structure.
The specifications of U.S. Pat. Nos. 3,115,384 and 3,387,071 disclose examples of the reaction spinning process. U.S. Pat. No. 3,387,071 discloses a process comprising synthesizing a prepolymer by melting synthesis, directly extruding the molten prepolymer into a solution of a diamine which is a chain extender, and winding the filament polyurethaneurea thus obtained.
However, the elastic PUU fiber obtained by the conventional reaction spinning process has problems as explained below:
(1) First, increasing the spinning speed is difficult due to a large reaction bath solution resistance for reasons as explained below. Since the polyamine bath is substantially stationary in the conventional technology, the PUU filament material in the course of shaping suffers a markedly large solution resistance to have poor physical properties and is finally broken when the take-up speed (withdrawal speed) exceeds a certain level. For a yarn having a thickness of about 100 denier, the process can only ensure a spinning speed as low as about 60 to 70 m/min. The dry spinning process can ensure a spinning speed as high as 500 to 1,000 m/min.
(2) Second, production at an economical production rate of an elastic PUU fiber having a thickness as small as up to 50 denier, the demand of which is great, is difficult because of the solution resistance in the reaction bath.
(3) Third, an elastic PUU fiber produced by the conventional reaction spinning process shows a high elongation at break, but it shows an extremely low initial stress (which is approximately half of that of the elastic PUU fiber produced by dry spinning) to lower the product quality. For reasons as mentioned in (3) and for reasons of difficulty in producing the elastic PUU fiber having a small fineness as mentioned in (2), the applications of the elastic PUU fiber produced by the conventional reaction spinning process have been restricted.
When an elastic PUU fiber is to be processed, the fiber is fed without slack while the fiber is being stretched to have a given elongation (from about 100 to 200%) by applying a predetermined stretch tension, and formed into a fabric. However, since the stress corresponding to the elongation imparted to the fiber during the processing is not sufficiently high, a slight variation of the tension during processing results in slackening of the elastic PUU fiber, or i
Hanahata Hiroyuki
Shimaya Yoshihiko
Asahi Kasei Kogyo Kabushiki Kaisha
Bagwell Melanie D.
Birch & Stewart Kolasch & Birch, LLP
Seidleck James J.
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