Process For Producing Filaments And Yarns Of Blended Incompatible Polymers

Abstract

Conjugate filaments the components of which are comprised of the same constituents in dissimilar relative concentrations are produced by allowing the constituents of the molten stream of blended incompatible polymers partially to segregate in a forced flow conduit so that material removed from the outer periphery of the stream near the wall of the conduit will be of different relative concentration of constituents than material remaining near the center of the conduit and then removing separate streams of partially segregated material which are fed through suitable spinnerets to produce conjugate filaments. In another embodiment yarns the filaments of which are comprised of the same constituents in dissimilar relative concentrations are produced in the same manner.

Description

BACKGROUND OF THE INVENTION

This invention relates to filaments and yarns of blended incompatible polymers. In one of its aspects, it relates to conjugate filaments the components of which differ in concentration of constituents. In another of its aspects, this invention relates to producing streams of different concentrations of blends of incompatible polymers from a single molten stream of blended incompatible polymers. In still another of its aspects, this invention relates to the production of conjugate filaments the components of which differ in concentration of constituents. In still another of its aspects, this invention relates to the production of yarn in which the filaments differ in concentration of constituents.

In one concept of the invention a method is provided for producing streams of blended incompatible polymers of different concentration from a single molten stream of blended incompatible polymers by removing from a conduit a portion of the blended incompatible material that has been allowed partially to segregate within the conduit. In another of its concepts, the invention provides a method for removing portions of the partially segregated blend of incompatible polymers from the conduit to produce a sidestream of different concentration from the molten material remaining in the conduit. In still another concept of the invention, a method is provided for producing a conjugate filament by combining components of blended incompatible polymers, which components differ in concentration of constituents, in a spinning block suitable for producing conjugate fibers from disparate feeds. In still another concept of the invention, a method is provided for producing a yarn by combining components of blended incompatible polymers which components differ in concentration of constituents in a spinning block suitable for producing yarns from disparate feeds.

The production of conjugate filaments from incompatible polymers has been accomplished by melting the individual constituents in separate extruders and conducting the molten material into spinnerets adapted to produce side-by-side or sheath-and-core conjugate filaments. It is possible to produce both conjugate filaments and yarns of disparate concentrations of blended incompatible polymers using multiple extruders and blending the molten polymers, but these processes require a large investment in equipment.

It is therefore an object of this invention to provide an economical and efficient method for producing conjugate fibers of blended incompatible polymers. It is another object of this invention to provide an economical and efficient method for producing yarn of blended incompatible polymers. It is another object of this invention to provide a conjugate filament of components consisting of the same incompatible polymers but blended in different relative concentrations. It is another object to provide a yarn containing filaments comprised of the same incompatible polymers but with some filaments blended in a concentration dissimilar to the remainder of the filaments in the yarn bundle. It is another object to provide a method for producing a yarn containing filaments comprised of the same incompatible polymers but with some filaments blended in a concentration dissimilar to the remainder of the filaments in the yarn bundle.

Other aspects, concepts and objects of the invention are apparent from a study of this disclosure, the drawing and the appended claims.

SUMMARY OF THE INVENTION

According to the present invention there is provided a conjugate filament in which each component is composed of a blend of the same incompatible polymers but in which the relative concentrations of the incompatible polymers constituting each component are different.

In one embodiment of the invention there is provided a method for producing conjugate filaments comprised of components of dissimilar concentration from a molten blend of incompatible polymers which method comprises (a) force flowing the molten blend of incompatible polymers through a conduit of sufficient length to allow partial segregation of the polymers; (b) separating the molten material into two streams by (1) removing from the conduit a portion of the polymer stream nearest the conduit wall or at the center of the conduit and (2) removing the remaining polymer from the conduit; and (c) passing the separated molten streams separately into a spinning block suitable for producing continuous conjugate filaments so that the separated molten polymer streams are joined into conjugate filaments.

In another embodiment of the invention there is provided a method for producing yarn comprised of filaments of dissimilar concentration of blended incompatible polymers which method comprises (a) force flowing the molten blend of incompatible polymers through a conduit of sufficient length to allow partial segregation of the polymers; (b) separating the molten material into two streams by (1) removing from the conduit a portion of the polymer stream nearest the conduit wall or at the center of the conduit and (2) removing the remaining polymer from the conduit; and (c) passing the separated molten streams separately into a spinning block suitable for producing a continuous yarn bundle of dissimilar filaments so that a yarn is produced comprised of filaments of the same incompatible polymers but with some filaments blended in a concentration dissimilar to the polymer blend of the remainder of the filaments in the yarn bundle.

DESCRIPTION OF THE DRAWING

In the drawing,

FIG. 1 shows a complete system for carrying out the method of the invention for producing conjugate fibers or yarn comprised of components of dissimilar concentrations.

FIG. 2 shows the preferred means for removing partially segregated polymer from the conduit line.

FIG. 3 shows a front view of the gear arrangement within the conduit for preferentially removing partially segregated polymer from the periphery of the conduit.

FIG. 4 shows an alternative means for removing segregated material from a forced flow conduit for feeding into a spinning block.

FIGS. 5 and 6 show cross sections of typical conjugate filaments produced by the process of this invention.

Referring now to FIG. 1 of the drawing, which illustrates the process of this invention. A pellet mixture of two incompatible polymers is fed into a hopper 11. This mixture of polymers is picked up by an extruder 12 in which the mixture is melted and mixed into a homogeneous composition which is fed into an outlet line 13. This outlet line 13 is of sufficient length that the molten blend of the incompatible polymers will tend to separate into two phases while flowing through the conduit with the component having the lower melt viscosity tending to concentrate near the wall of the conduit. In this illustration, a gear pump 14 consisting of two stages is placed in the line of flow. In the first stage of the gear pump 15 partially segregated molten polymer is drawn by the pump preferentially from the periphery of the conduit. This material which is richer in the material of lower melt viscosity is fed into an outlet conduit 16. The molten material remaining in the conduit from the extruder is now richer in the higher melt viscosity material. It is removed by the second stage of the gear pump 17 into an outlet conduit 18. The material in conduit 16 which is relatively richer in the lower melt viscosity component and the material in conduit 18 which is relatively richer in the higher melt viscosity component are fed as separate streams into a suitable conjugate spinpack 19 to produce side-by-side or sheath-and-core conjugate filaments. In producing yarn a spinpack suitable for the use of disparate feeds 19 is used wherein some of the spinnerets are fed from stream 16 and some from stream 18 to produce a yarn 20 in which some of the filaments are composed entirely of material of one concentration of incompatible polymers and the remaining filaments in the yarn have another concentration of incompatible polymers.

In the preferred embodiment of this invention a split stream gear pump is used to separate the partially segregated molten incompatible polymers in the conduit from the extruder into streams of dissimilar concentration. This is illustrated in FIGS. 2 and 3 of the drawing, In the cut-away top view of the gear pump illustrated in FIG. 2 the blended incompatible polymer stream which has partially segregated so that the material near the conduit wall is richer in the lower melt viscosity constituent enters the gear pump 14 through conduit line 13. The first stage of the gear pump 15, which can be better visualized in the front view of the gear pump illustrated in FIG. 3, is positioned with respect to conduit 13 so that the gears 21 of the pump preferentially draw the lower melt viscosity rich material from the periphery of conduit 13 into the outlet line 16. The material left in the conduit line which is then relatively richer in the higher melt viscosity material is removed to outlet line 18 by means of the second stage of the pump 17.

FIG. 4 shows an alternative means for separating the partially segregated incompatible polymers in the conduit 13. In a forced flow system an outlet inserted in the conduit in the manner of a pitot tube 23 can serve to conduct material from the larger conduit line 13. The relative concentrations in separated outlet lines 22 and 24 would depend on the placement of the pitot tube 23 within the conduit. A placement near the center of the conduit 13 would draw material relatively richer in higher melt viscosity material into line 24, while a placement near the periphery of the conduit 13 would draw material of relatively lower melt viscosity into the outlet line 24. The separate streams are individually passed into the conjugate spinpack 19 to produce conjugate filaments 20.

The filaments produced are of the types shown in FIGS. 5 and 6 of the drawing. In FIG. 5 is shown a side-by-side conjugate filament half of which is relatively rich in the lower melt viscosity incompatible constituent 25 and the other half is relatively rich in the higher melt viscosity material 26. By varying the amount of material fed into the conjugate spinpack the configuration of the filament cross section can be varied from the half and half configuration illustrated here to a barely discernible quantity of one of the components. In FIG. 6 is shown the sheath 27 and core 28 configuration of a conjugate filament. Variation of the amounts of material in the filament cross section configuration is well within the skill of the art.

As shown in the discussion of the drawing various means can be employed for removing the partially segregated incompatible polymer from the conduit line. Variations of the pitot tube outlet or other means for preferentially withdrawing material from a specific portion of the conduit can be employed. At present, a split stream gear pump as illustrated in FIGS. 2 and 3 of the drawing is the preferred means for producing two streams of material of dissimilar concentration from a single stream of blended incompatible polymers.

The length of the conduit from the outlet of the mixing and melting means to the point of removal of material from the conduit will vary with the relative incompatibility of the materials in the blended mixture. The conduit must be of sufficient length to allow the amount of segregation required to yield streams of conjugate filament components of the degree of similarity desired.

It should be understood that while an extruder is cited as a preferred means for melting and blending the incompatible polymer mixture other means are not precluded. This invention can employ any means of producing a relatively homogeneous blend of incompatible polymers in a molten state which can be force flowed in a conduit to allow segregation of the constituents.

Various mixtures of polymers are appropriate for use in this invention. The polymer mixes must be sufficiently incompatible to allow segregation while flowing in the molten state in a conduit. Particularly appropriate are blends of polypropylene and polyethylene terephthalate, polyethylene terephthalate and nylon 66, polypropylene and polyethylene, nylon 66 and arylene sulfide polymer, and the like.

The following example illustrates the production of component streams of dissimilar concentration of blended incompatible polymers from a single stream of homogeneously blended incompatible polymers which can be used as feed to a conjugate spinpack to produce the conjugate filaments of this invention.

EXAMPLE 1

A pellet blend of 100 parts polypropylene and 35 parts polyethylene terephthalate was passed through a screw extruder where the material was melted and mixed. In the test runs identified by a "C" in the table below, the blended material was passed through a conduit and allowed to segregate before entering a Zenith type-HPD 2-stage gear pump. In the test runs marked "D" in the table below, a Kenics static mixer was introduced in the line upstream of the gear pump to decrease segregation of the material within the conduit. The Zenith pump was connected to a spinneret pack so that discharge from the upstream set of gears was fed into the right side of the spinneret pack. This set of gears contacts the stream within the conduit only at or near the wall of the conduit. The remaining portion of the stream deadends in the pump cavity serving the downstream set of gears so that all material discharging into the left portion of the spinpack contains material deficient in material from near the wall. Data collected are presented in the table below.

TABLE 1

Extruder Screw C or D Position Pump Density Pressure Right or Left Gears Range Average psi 2750 C right 1st 0.9833 0.9929 0.9897 C left 2nd 0.9861 0.9879 0.9867 D right 1st 0.9700 0.9937 0.9829 D left 2nd 0.9700 0.9937 0.9829 4000 C right 1st 0.9980 1.0067 1.0020 C left 2nd 0.9836 0.9950 0.9925 D right 1st 0.9881 0.9960 0.9943 D left 2nd 0.9881 0.9997 0.9948

These data illustrate that streams of dissimilar concentration suitable for the production of conjugate filaments or a yarn were produced from a homogeneous blend of incompatible polymers.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, the drawing and appended claims to the invention the essence of which is that there has been provided a method for producing feedstreams of dissimilar concentrations for the production of conjugate filaments by allowing the segregation of an incompatible polymer blend in a conduit from which a feedstream is taken from the center or the periphery of the conduit leaving the remainder of the material in the conduit as a second feedstream.

Claims

We claim:

1. A method for producing streams of dissimilar concentration of components from a single molten stream of blended incompatible polymers comprising: (a) force flowing said molten blend through a conduit of sufficient length to allow partial segregation of said polymers; (b) removing from the conduit a portion of the polymer nearest the conduit walls or from the center of the conduit; and (c) removing the remaining polymer from the conduit.

2. A method of claim 1 wherein said molten polymer nearest said conduit wall is pumped from said conduit.

3. A method of claim 2 wherein said material nearest said conduit wall is removed from the conduit by the action of a gear pump with gears placed in the flow within the conduit to preferentially remove polymer nearest said conduit wall.

4. A method for producing conjugate filaments comprised of components of dissimilar concentration from a molten blend of incompatible polymers which method comprises: (a) producing streams of molten polymer of dissimilar concentration by the method of claim 1 and (b) passing said molten streams separately into a spinpack suitable for producing continuous conjugate filaments wherein the molten polymer is joined in the conjugate elements by passage through the said spinpack.

5. A method of claim 4 wherein said conjugate filaments are of a type chosen from sheath-and-core and side-by-side.

6. A method for producing yarn comprised of filaments of dissimilar concentration of blended incompatible polymers which method comprises: (a) producing streams of molten polymer of dissimilar concentration by the method of claim 1 and (b) passing said molten streams separately into a spin-pack suitable for producing a yarn from dissimilar feed materials so that the yarn produced has some filaments comprised of an incompatible polymer blend dissimilar in concentration from the concentration of the blend of incompatible polymers in the remaining filaments of the yarn.