Polyhexamethyleneadipamide fiber and composition

Details Polyhexamethyleneadipamide fiber and composition Polyhexamethyleneadipamide fiber and composition

1999-01-08

2001-09-11

Short, Patricia A. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S394000, C524S423000, C524S429000, C524S430000

Reexamination Certificate

active

06288153

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to hexamethylene adipamide fibers having significantly excellent thermal yellowing resistance to heat during fiber processing, etc. and a composition thereof, ad a process for advantageously producing such fibers. The present invention relates to polyhexamethylene adipamide fibers for clothing capable of being dyed in bright shades and dyed deeply in addition to having significantly excellent thermal yellowing resistance, and a commercially advantageous process for producing the same.
BACKGROUND OF THE INVENTION
Since polyamides (nylon) are generally excellent in mechanical properties and durability, they are used in large amounts as fibers for industrial materials such as tire cords, fibers for carpet and molded articles. On the other hand, polyamides are also used in large amounts as fibers for clothing, particularly for inner wear due to their excellent flexibility and dyeability.
Polyhexamethylene adipamide (nylon 66) is a typical representative of polyamides, and is also used as fibers for industrial materials, fibers for carpet, fibers for clothing, molded articles, and the like. Polyhexamethylene adipamide, however, has a serious disadvantage as fiber for clothing in that it suffers considerable thermal yellowing compared with poly-&egr;-capramide (nylon 6) which is also a typical representative of polyamides. The disadvantage matters a great deal regardless of whether it is used as fibers or molded articles, in application where the whiteness in external appearance is required. In addition to the fact that fibers for clothing are particularly susceptible to oxidation inherently due to the small single fiber diameter (large specific surface area), they are thermally set (heat treated) without exception in the process for producing fabrics and in fabrication. As a result, the problem of yellowing mentioned above is manifested. The use of polyhexamethylene adipamide in fibers for clothing is, therefore, extremely limited.
For example, inner wear such as lingerie and foundation garments is an appropriate application for polyamide fibers having flexibility and suitable hygroscopicity. Since polyhexamethylene adipamide fibers suffer considerable yellowing during thermal setting as described above, the whiteness of the products is lowered or the color development thereof becomes a dull shade (dull in shade). Accordingly, the polyhexamethylene adipamide fibers are not substantially used at present for inner wear. Poly-&egr;-capramide fibers and polyester fibers have overwhelmingly high shares at present in the application thereof to the inner wear.
Since the poly-&egr;-capramide fibers are significantly excellent in thermal yellowing resistance and suffer thermal setting-caused yellowing very slightly, compared with the polyhexamethylene adipamide fibers, they can be used for the inner wear substantially without a problem. Moreover, the polyester fibers have still more excellent thermal yellowing resistance than the poly-&egr;-capramide fibers, and suffer almost no yellowing caused by thermal setting, that is, the whiteness of the fibers is maintained.
Improving the thermal yellowing resistance of the polyhexamethylene adipamide fibers to a level comparable to that of the poly-&egr;-capramide fibers is, therefore, the first goal for the manufacturers thereof. Improving the resistance to a level comparable to that of the polyester fibers is the final goal for them. The techniques for achieving these goals, however, have not been created.
In melt molding and melt spinning thermoplastic organic polymer, a thermal stabilizer such as a thermal oxidation inhibitor is incorporated in the polymer starting materials to inhibit or decrease the thermal alteration such as thermal degradation and discoloration of the polymer. Although the selection of suitable additives depends on the types of polymers, examples the thermal stabilizer commonly used for polymers which have currently been used at large are phenolic antioxidants including hindered phenols. The level of degradation resistance of a polymer considerably differs depending on the requirement of polymer molded articles to be produced therefrom. As a result, various incorporation formulations such as the use of phenolic antioxidants in combination with other chemical substances, for example, organic antimony compounds, phosphorous compounds and thioether antioxidants have been attempted.
Japanese Patent KOKAI Publication No. 46-7455 discloses that the incorporation of organic antimony compounds and phenolic antioxidants prevents the oxidation deterioration of polymers of all types including polyolefin. Numerous phenolic antioxidants including 2,4-bis(alylthio)-6-(3,5-dialkyl-4-hydroxyanilino)-1,3,5-triazine are exemplified in the specification of the patent publication. Concrete examples in which the triazine derivatives are applied to polypropylene as antioxidants are disclosed therein. The prior technique evaluates the antioxidation effect on the polymer by an oxygen absorption amount, and does not refer to the thermal yellowing prevention effect on the polymer.
Japanese Patent KOKAI Publication No. 6-16929 discloses that the incorporation of the three types of agents: hindered phenolic antioxidants, phosphorus type antioxidants and thioether type antioxidants, in polyamides can suppress the discoloration caused by oxidation deterioration of injection molded polyamide articles. The patent publication, however, discloses no quantitative effect of inhibiting discoloration. As a result of investigation, the present inventors have found that no satisfactory thermal yellowing resistance can be obtained even when the compounds in the patent publication are incorporated in the polyhexamethylene adipamide fibers. For example, when the fibers to be used for lingerie are to be dyed in pale pink or pale blue, the desired color development cannot be obtained due to yellowing caused by thermal setting, and only products giving an impression of a dull shade can be obtained. That is, a thermal yellowing resistance which promotes the utilization of the polyhexamethylene adipamide fibers in the field of inner wear has not been obtained at any by the techniques disclosed in the patent publication. Moreover, among the antioxidants exemplified in the patent publication, there is no 2,4-bis(alkylthio)-6-(3,5-dialkyl-4-hydroxyanilino)-1,3,5-triazine.
The specification of Japanese Patent KOKAI Publication No. 51-1557 discloses that the incorporation of a phenolic antioxidant which completely differs from the compound of the present invention and which has a specific structure and, if necessary, a phosphorus compound can suppress the thermal yellowing of the polyamides. The patent publication, however, gives no description related to the effect of preventing thermal yellowing. As a result of investigation, the present inventors have found that sufficient inhibition of the thermal yellowing cannot be achieved even when the compounds disclosed in the patent publication are incorporated in the polyhexamethylene adipamide fibers. For example, when the fibers to be used for lingerie are to be dyed to pale pink or pale blue, the desired color development cannot be obtained due to yellowing caused by thermal setting, and only products giving an impression of a dull shade can be obtained. That is, a thermal yellowing resistance which promotes the utilization of the polyhexamethylene adipamide fibers in the field of inner wear has not been obtained at all by the technique disclosed in the patent publication.
Furthermore, since the compounds concretely disclosed in the specification of the patent publication have low heat resistances, adverse effects of deteriorating the compounds themselves have been caused when the compounds are melt kneaded with polyhexamethylene adipamide having a melting point as high as more than 260° C.
The specification of U.S. Pat. No. 3,594,448 discloses that many types of hindered phenol compounds are effective in improving the whiteness of fibers obtained from a blend of polyamides

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