Method for producing textile yarn from a mono
US 3112160 A
Description (OCR text may contain errors)
Nov. 26, 1963 R. L. RUSH 3,112,150
METHOD FOR PRODUCING TEXTILE YARN FROM A MONOFILAMENT OF A BLEND OF OLEFIN POLYMERS Filed July 11, 1960 WIND-UP ROLL FIG. 3
F rs J 0 LL! U O O o II 7 J g co E E g INVENTOR. Jr- R. L. RUSH m o 8m wngw A 7' TOR/VEVS United States Patent Ofiiice 3,112,160 Patented Nov. 26, 1963 METHOD FOR PRODUCING TEXTILE YARN FROM A MONOFILAB'IENT OF A BLEND F OLEFIN POLYMERS Robert L. Rush, Wellington, Kans., nssignor to Phiilips Petroleum Company, a corporation of Delaware Filed July 11, 1960, Ser. No. 41,751 5 Claims. (CI. 18-54) This invention relates to the manufacture of a multifibrous yarn from a continuous monofilament of a blend of thermoplastic polymers. In another aspect it relates to causing the fibrillation of a thermoplastic extrudate.
Thermoplastics have been considered, and certain types developed, as a source of textile fibers, but they have also been found to present problems which were long ago solved with the older cellulosic fibers. For example, the prior art teaches a method for fibrillation of continuous, multifilament fibers, by cutting or abrasion, to provide a yarn with properties called for in many textile applications.
Polyolefins, among other thermoplasties, because of their chemical resistivity are a class of textile yarns of highly desirable properties, if the physical processing requirements can be attained. Polyolefins can be readily prepared as a continuous single filament by extrusion through a die. It is then desirable to form a multi-fibrous fiber therefrom in many textile applications. However, when an attempt was made to fibrillate a monofilamcnt comprising a monopolyolefin, with a sharp edged means, as taught in the prior art, for multifilaments only, failure resulted. This failure came about because the monofilament tended to be completely severed or abraidcd in two filaments by the cutting edge, rather than effecting a controlled fibrillation.
l have discovered that in order to fibrillate a monofilament of a polyolefin, it is first necessary to blend two or more semi-compatible olefin polymers by conventional methods, and then prepare an extrudate therefrom. I have further found that a suitable range. for the blend of polyolefins is between 20 and 60 parts by weight of the one polymer, such as polypropylene, and from 80 to 40 parts by weight of another polyolefin, such as linear polyethylene. It is preferred to remain within these limits, as tests have shown that when the blend approaches 100% by weight of any one of the polymers, the fibrillation of the monofilamcnt becomes quite unsatisfactory and tends toward a cutting action, as is desired in preparing staple fibers.
It has been further discovered that a blend of polymers, when extruded through a die having the shape of a trefoil, give the best results in the subsequent fibrillation of the monofilament produced.
Besides monofilaments composed of blends of the aforementioned homopolymers of polypropylene and polyethylene, any combination of two or more polymers comprising, firstly, polypropylene, and secondly, the polymeric forms of l-butcnc, isobutylene. or a eopolymcr of ethyl cne and l-butcne, may also be used for producing monofilaments that may be fibrillated satisfactorily according to this invention. The monofilaments of the blended polyolefins so produced can then be run over a sharp edge in a variety of ways, such as disclosed in the prior art, and an acceptably fibrillated monofilament will result.
-It is, therefore, an object of this invention to provide an essentially continuous yarn of a polyolefin. It is another object to prepare a multifibrous filament trom a monofilament comprising a blend of thermoplastic olefin polymers. It is still another object to provide a method of fibrillating a monofilament of a blend of olefin homopolymers.
Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention and it should be understood that the latter is not necessarily limited to the aforementioned discussion.
FIGURE 1 is a diagrammatic side elevational view of an apparatus suitable for the practice of this invention;
FIGURE 2 is an elevational view of a die suitable for use according to this invention; and
FIGURE 3 is an elevational view of a fibrillated monofilament of this invention.
The polymers which are used for forming the filamentous articles treated according to my invention are blends of polyolefins of high density, that is, having a density in the range of 0.940 to I00 at 25 C. These polymers include, polypropylene, polyethylene and/or, also copolymers of ethylene with monoole-fins having 3 to 4 carbon atoms per molecule, i.e., propylene, l-butene, or isobutylene. In order for the copolymer to fall in the desired density range the monomer system from which the copolymer is polymerized should not contain over 30 weight percent propylene or butene, and preferably not over 15 weight percent based on the total monomer charge. It is preferred to use in this blend, polyethylene having a density at 25 C. of 0.950 to 0.980 gram per cubic centimeter.
It should be noted that the blend of polyolefins should comprise firstly polypropylene and, secondly, a polymer selected from the group consisting of polyethylene, polybutene, polyisobutylene, and a copolymer of ethylene and l-butene.
The prefererd method of making a polymer or eopolymer is that described in the patent to Hogan et al., U.S. 2,825,721. Other methods can be used, for example, low pressure methods employing organometallic catalysts systems are suitable. An example of such a process is the polymerization of ethylene in a hydrocarbon diluent in the presence of a mixture of triethyl-al-uminum and titanium tetrachloride as the catalyst system. The temperature can be from room temperature up to about 300 C. with a pressure suflicient to maintain a liquid phase.
Fibers, especially the monofilaments used in my invention, have a diameter of 0.01 to I00 mils and more usually about 0.1 to 50 mils. The tensile strength of these fibers cold drawn is above 30,000 p.s.i., frequently above 90,000
to l00,000 p.s.i., and can range as high as 150,000 to 250,000 p.s.i. measured at a temperature in the range of 65 to F.
Reference is now made to the drawing in detail, and to FIGURE 1, in particular, wherein a molten blend of polymers contained in extruder 5 passes through a die 6, which optionally may contain a plurality of holes of similar cross section. The extruded monofilament 7, only one being shown for clarity, passes under a roller 8 in cooling bath 9 disposed within the cooling liquid parallel therein. The cooled monofilament pases from bath 1 1 over and around a pair of Godet rolls 12 and 13, from thence it is drawn, preferably at right angles, across a sharp cutting edge 14. A strand 16 composed of many fine fibrils passes from edge :14 to wind-up roll .17.
In FIGURE 2 is shown a typical ie having an eighthole trefoil cross section orifice.
in FIGURE 3 is shown a typical multi-fibrous filament which results from passing the monofilament of a blend of thermoplastic olefin polymers.
Another form of an apparatus which can be conveniently employed in practicing the method of this invention is that described in the patent to Finlayson et al., U.S. 2,197,857. This apparatus is quite suitable for the practice of this invention. However, the cutting edge of the present invention need not be limited to a razor-like type as disclosed in the referenced patent. Almost any style of sharp cutting edge from a razor-like to a right angle edge will be suitable for fibrillating a monofilament of blended polyolefins. A second feature of the referenced apparatus which can be omitted in the practice of the present invention, is the oscillation of the filament to and fro lengthwise of the cutting edge. However, this fpature may be employed to prolong the sharpness of the cutting edge, and to prevent simultaneous accumulation of loose severed fragments on the cutting edge.
in density determinations the specimens should be prepared by compression molding the polymer at 340 F. until completely molten followed by cooling to 200 F. at a rate of about 'F. per minute. Water is then circulated through the mold jacket to continue the cooling to 150 F. at a rate not exceeding F. per minute. The polymer is then removed from the mold and cooled to room temperature.
Density was determined by placing a smooth, void-free, pea-sized specimen cut from a compression molded slab of the polymer in a 50-ml., glass-stoppered graduate. Carbon tetrachloride and methyl cyclohexane were added to the graduate from burettes in proportion such that the specimen is suspended in the solution. During the addition of the liquids the graduate is shaken to secure thorough mixing. When the mixture just suspends the specimen, a portion of the liquid is transferred to a small test tube and placed on the platform of a Westphal balance and the glass bob lowered therein. With the temperature shown by the thermometer in the bob in the range 73-78-F. the balance is adjusted until the pointer is at zero. The value shown on the scale is taken as the specific gravity. With the balance standardized to read 1,000 with a sample of distilled water at 4 C. the specific gravity will be numerically equal to density in grams per cc.
A better understanding of my invention and appreciation of its advantages is provided by the following example.
Thirty parts by weight of a polypropylene resin, in the form of pellets, were admixed with 70 parts by weight of a linear polyethylene, also in the form of pellets. The two polymers were heated and mixed to assure thorough blending. The molten blend of polymers were then passed to a hopper of a conventional extruding machine,
well known to those skilled in the art. -In this run a 1%" Hartig extruder was employed, using a setting of a screw speed of 2.0. The die itself was an 8-hole, trefoil orifice. The back pressure was 2,000 pounds, and the cylinder temperatures in the three zones, adjacent to the hopper, intermediate, and next to the die, were 500 F., 500 F., and 450 F., respectively. The extruded monofilaments were passed to a cooling tank of a conventional type, and then over a pair of Godet rolls. The speed of the first roll was feet per minute, and the second roll 250 feet per minute. There were produced a number of smooth trefoil monofilaments. The resulting monofilaments were individually subjected to mechanical treatment as taught in the apparatus of the Finlayson patent. in these runs a sharp metal edge was employed. The blend polymer monofilament separated into many fine fibrils of a desired texture and quality.
Subsequent runs were undertaken in the same equipment employing as the feed to the extruding equipment either 100% linear polyethylene or 100% polypropylene plastic. Neither of these resulting monofilaments fibrillatcd as well as the blend polyolefin filament and therefore failed to produce as satisfactory a type of yarn.
As will be evident to those skilled in the art, various modifications can be made in my invention without departing from the spirit or scope thereof.
1. A method for fibrillating a monofilament of a blend of at least a first and second thermoplastic polymer, said first polymer consisting of polypropylene, and said second polymer selected from the group consisting of polyethylene, polybutene, polyisobutylcnc, and a copolymer of ethylene and l-butene comprising adding said thermoplastic polymcrs to a mixing zone, heating, melting and mixing said polymers therein, extruding as a monofilament the resulting blend of said polymers, said monofilament comprising from 20 to 60 parts by weight of said first polymer, and to 40 parts by weight of said second polymer, and continuously drawing the said monofilament over a sharp edge so that fibrillation thereof is brought about.
2. In a method for fibrillating a monofilament of a thermoplastic polymer comprising continuously drawing the monofilament over a sharp edge so that at intervals along the monofilament partial shearing occurs, the improvement comprising preparing said monofilament from a blend of at last two thermoplastic polymers, the first of which is polypropylene and the second of which is selected from the group consisting of polyethylene, polybutene, polyisobutylene, and a copolymer of ethylene and l-butene said monofilament comprising from 20 to 60 parts by weight of said first polymer, and 80 to 40 parts by weight of said second polymer.
3. A method for fibrillating a monofilament of a blend of at least a first and second thermoplastic polymer, said I first polymer consisting of polypropylene, and said second polymer selected from the group consisting of polyethylene, polybutene, polyisobutylene, and a copolymer of ethylene and l-butene comprising adding said thermoplastic polymers to a mixing zone, heating, melting and mixing said polymers therein, extruding as a trefoil cross section monofilament the resulting blend of said polymers, said monofilament comprising from 20 to 60 parts by weight of said first polymer, and 80 to 40 parts by weight of said second polymer, and continuously drawing the said monofilament over a sharp edge so that fibrillation thereof is brought about.
4. In a method for fibrillating a monofilament of a thermoplastic polymer comprising extruding said polymer in the form of a trefoil cross section monofilament, continuously drawing the monofilment over a sharp edge so that at intervals along the monofilament partial shearing occurs, the improvement comprising preparing said monofilament from a blend of at least two thermoplastic polymers, sa-id monofilament comprising from 20 to 60 parts by weight of said first polymer, and 80 to 40 parts by weight of said second polymer, the first of which is polypropylene and the second of which is selected from the group consisting of polyethylene, polybut-ene, polyisobutylene, and a copolymer of ethylene and l-butene.
5. As an article of manufacture, a filbrillated monofilament of a blended thermoplastic material comprising: a first polymer consisting of polypropylene and a second polymer selected from the group consisting of polyethylene, polybutene, polyisobutylene, and a copolymer of ethylene and l-butene said monofilament comprising from 20 to 60 parts by weight of said first polymer, and 80 to 40 parts by weight of said second polymer.
References Cited in the file of this patent UNITED STATES PATENTS 2,531,234 Seckel Nov. 21, 1950 2,700,657 Look et al Jan. 25, 1955 2,920,349 White Jan. 12. 1960