Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Reexamination Certificate
2001-05-10
2003-12-23
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
C264S210800, C525S227000, C525S241000, C525S437000, C526S329700, C526S346000, C526S348100
Reexamination Certificate
active
06667003
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for the manufacture of synthetic filaments from a mixture of fiber forming polymers. The filaments can be used as endless filaments or they can be further processed to staple fibers.
2. Summary of the Related Art
Spinning of polymer mixtures to form synthetic filaments is known. The purpose of using an additive polymer to form a mixture is to achieve, at a given spinning speed, a higher elongation at break of the spun filament. This permits a higher stretch ratio for the manufacture of the final yarn, which, in turn, results in a higher productivity of the spinning unit.
Increased production leads to improved profitability for the manufacturing process. Productivity is reduced to a certain extent by production difficulties and more expensive high-speed installations. The additional costs for the additive polymer can be considerable so, depending on the quantity added, zero profitability can result. The market availability of the additive polymer also plays an important role. Many of the additives described in the literature are commercially unfeasible for large-scale industrial conversion.
Producers or process operators must take into account the entire production chain and cannot limit themselves to increasing the production of a single step (for example, the spinning process), only. The subsequent processes must not be negatively impacted. In particular it is a main objective of the present invention not to negatively impact the subsequent processes, preferably to improve said subsequent processes despite of an increased spinning speed.
In the manufacture of POYs (partially oriented yarns), very high elongations at break for polymer mixtures have been achieved (even at high spinning speeds) and is characterized by a strong reduction in the degree of orientation. Such spun filaments are known to be unstable during storage and cannot be applied and processed in stretch texturing at high speeds. Elongations at break of <70% (indicated for high spinning speeds) in turn means a considerable degree of crystallization, which reduces the strength that can be achieved in the texturing process.
The first proposed solutions for these problems were disclosed in the Patents EP 0 047 464 B (Teijin), DE 197 07 447 (Zimmer), DE 199 37 727 (Zimmer), DE 199 37 728 (Zimmer) and WO 99/07 927 (Degussa). EP 0 047 464 B concerns an unstretched polymer yarn, where, as a result of the addition of 0.2-10 wt % of a polymer of the type —(—CH
2
—CR
1
R
2
—)
n
— (e.g., poly(4-methyl-1-pentene) or polymethyl methacrylate), improved productivity and higher stretch ratios are achieved as a result of the increase in the elongation at break of the spun filament at speeds of 2500-8000 m/min. It is necessary to achieve a fine and homogeneous dispersion of the additive polymer by mixing, where a particle diameter ≦1 &mgr;m avoids fibril formation. The effect arises from the combined action of three properties—chemical additive structure, which allows almost no elongation of the additive molecule, low mobility, and the compatibility between polyester and additive. These factors serve to increase productivity. No requirements for the stretch texturing are disclosed. Carrying out the method disclosed in WO 99/07927 leads to a high comsumption of additive polymer and an impairment of the quality and the subsequent processability of the resulting fibers.
DE 197 07 447 (Zimmer) concerns the manufacture of polyester or polyamide filaments with an elongation at break of ≦180%. The addition of 0.05-5 wt % of a copolymer made of 0-90 wt % (meth)acrylic acid alkyl ester, 0-40 wt % maleic acid (anhydride), and 5-85 wt % styrene to the polyester or polyamide allows a clear increase in the spinning draw-off speed.
Patent DE 199 37 727 (Zimmer) discloses the manufacture of polyester staple fibers from a polymer mixture, which mixture contains 0.1-2.0 wt % of an immiscible, amorphous, additive polymer having a glass transition temperature of 90-170° C. The ratio of the additive polymer melt viscosity to the melt viscosity of the polyester component is indicated to be from 1:1 to 10:1.
DE 199 37 728 (Zimmer) relates to a method for the manufacture of HMLS fibers made of polyester, additive polymer, and optionally additives with a spinning draw-off speed of 2500-4000 m/min. The additive polymer is reported to have a glass transition temperature of 90-170° C., and the ratio of the melt viscosity of the additive polymer to the melt viscosity of the polyester component is reported to be from 1:1 to 7:1.
WO 99/07927 relates to the manufacture of POYs by spinning polymer mixtures based on polyester at a draw-off speed &ngr; of at least 2500 m/min, where a second, amorphous, thermoplastically processible copolymer is added to the polyester and has a glass transition temperature of more than 100° C. The ratio of the melt viscosity of the copolymer to the melt viscosity of the polyester is reported to be from 1:1 to 10:1. At least 0.05 wt % of copolymer is added to the polyester, and the quantity M of the copolymer added to the polyester is dependent on the draw-off speed &ngr; and is
M
=
[
1
1600
·
v
(
m
min
)
-
0.8
]
[
wt
%
]
Although the foregoing methods result in very good filament rupture rates that are suitable for practical use, industrial use nevertheless requires methods for spinning polymer mixtures with even lower number of filament ruptures to further increase the efficiency of the spinning method. Furthermore, the behavior of the synthetic filaments during subsequent processing, particularly during stretch texturing, should be improved.
In the foregoing methods, the additive polymer agents for increasing elongation are usually granulated in order to increase their flowability before addition by metering to the polyester. However, due to large particle size, the granulated additive polymer is relatively difficult to add, and the metering is not consistent. This leads to a worsening of the yarn characteristics, e.g., dye uptake behavior and particularly the homogeneity of the synthetic fibers.
SUMMARY OF THE INVENTION
We recognized that granulating the elongation increasing agent is time and cost intensive, and, therefore, methods for the melt spinning of polymer mixtures using non-granulated elongation increasing agents would be desirable. We report here that the elongation increasing agents can be added evenly and continuously by metering without granulating. As described below, this is accomplished according to the present invention by employing amorphous additive polymers obtained by multiple initiation. We have unexpectedly found that use of such amorphous additive polymers significantly lessens the residual monomer content of the synthetic fibers produced, thereby obviating the need to granulate the additive polymers as practiced in the art.
The present invention comprises a simple method for the manufacture of synthetic filaments from a mixture of fiber forming matrix polymers that allows the manufacture of synthetic fibers with a lower fiber rupture rate. In particular, the method of manufacture yields POYs having values of elongation at break of 90-165%, high consistency with regard to the filament characteristics, and a low degree of crystallinity.
The present invention also comprises a method for the manufacture of synthetic fibers from a mixture of fiber forming matrix polymers that allows the use of non-granulated elongation increasing agents and thus is considerably more cost effective than methods known in the state of the art.
The present invention also comprises a method for spinning synthetic filaments that can be carried out on a large industrial scale in a cost effective manner. In particular, the method of the invention allows the manufacture of POYs with very high draw-off speeds, preferably ≧2500 m/min.
The method of the invention does not negatively impact subsequent processing; rather it improves it despite the increased spinning speed.
According to the inv
Janas Wolfgang
Klein Alexander
Kretschmann Bernd
Schwind Helmut
Ude Werner
McDonnell & Boehnen Hulbert & Berghoff
Tentoni Leo B.
Zimmer A.G.
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