US3579618A - High speed fibrillation process - Google Patents

Abstract

PREVENTING SUCH SEVERED RIBBONS FROM BECOMING ENTAGLED IN THE STRETCHING ROLLS.

A PROCESS FOR FORMING A FIBRILLATED PRODUCT COMPRISING FORMIG A FILM FROM A FLATTENED PLASTIC TUBE, MOLECULARLY ORIENTING THE FILM AND FIBRILLATING THE ORIENTED FILM, WHEREIN VACUUM MEANS REMOVE THE SYSTEM ANY LOOSE ENDS OF RIBBONS THAT MAY BECOME SERVED DURING ORIENTATION,

Description

United States Patent 3,579,618 HIGH SPEED FIBRTLLATION PROCESS Dan F. Stewart, Bob C. Blair, Max E. Greene, and Lloyd R. Alexander, Bartlesville, Okla., assignors to Phillips Petroleum Company Filed Aug. 9, 1968, Ser. No. 751,458 Int. Cl. B290 17/14; B29d 7/24; D01d /00 US. Cl. 264-37 4 Claims ABSTRACT OF THE DISCLOSURE A process for forming a fibrillated product comprising forming a film from a fiattened plastic tube, molecularly orienting the film and fibrillating the oriented film, wherein vacuum means remove from the system any loose ends of ribbons that may become severed during orientation, preventing such severed ribbons from becoming entangled in the stretching rolls.

This invention relates to a new and improved method for producing fibrillated products.

The molecular orientation of a plastic film followed by fibrillation thereof and the fibrillated product obtained thereby is known in the art and fully and completely disclosed in US. Patent 3,3 02,501 the disclosure of which is hereby incorporated by reference. However, an operation which will simply fibrillate a molecularly oriented film is not necessarily, and is usually far from, a commerically feasible process wherein large amounts of film are oriented and fibrillated at high speeds to thereby produce commercial quantities of the fibrillated product. 'It is well known to be quite difficult to scale up an experimental process to the extent necessary to make that process commercially feasible and still produce a commercially acceptable grade of fibrillated product.

By this invention, large amounts of commercially acceptable grade fibrillated product can be produced at high speeds by providing a molecularly orientable tube of plastic which is flattened to produce a two-layered film, passing the tube through a heating zone and molecularly orienting the tube while in said heating zone by the use of first and second rolling zones upstream and downstream, respectively, of the heating zone, the molecularly oriented tube thereafter being fibrillated downstream of the second rolling zone. The fibrillated tube is passed through a third rolling zone for tensioning (straightening out) the fibrillated product. This tensioning by use of a third rolling zone can be carried out during the fibrillation operation, subsequent to the fibrillation operation, or both.

The fibrillated product of this invention is useful in making conventional carpeting. For example, the fibrillated product can be used as face yarn, i.e., the wearing surface of a carpet, and/or as carpet backing, i.e., the supporting material for the face yarn. The fibrillated products of this invention can be made into carpets as the face yarn therein by conventional methods known in the art. For example fibrillated product can be used as carpet backing and additional fibrillated product pushed through the carpet backing by conventional needling process to form tufts in the form of closed loops thereby producing a conventional closed loop carpet.

Accordingly, it is an object of this invention to provide a new and improved process for making fibrillated products.

Other aspects, objects, and the several advantages of this invention will be apparent to those skilled in the art from the description, drawings, and appended claims.

FIGS. 1 and 2 show two different systems embodying this invention.

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In FIG. 1 there is shown a conventional mixer 1 wherein polymer pellets, pigment and other materials that are desired to be incorporated into the final fibrillated product are physically mixed. This mixture is then passed by way of line 2 to conventional melt extruder 3, the output end of which is fitted with a die and adapter 4 which carries an air ring 5, from which issues cylindrical blown tubing 6. Blown tubing 6 passes between a pair of nip rolls 7, 7', between which the tubing is flattened to produce a two-layered film, the two layers of the film being integral with one another at both edges of the film.

The flattened tube then passes over rollers 8 and 9 into first rolling zone 10. This rolling zone is composed of three separate rolls 11 through 13 over which the tube passes in a sinusoidal manner. These rolls can be nipped together.

This first rolling zone can also be thought to be composed of restraining nip rolls which produce drag on the tube as it passes through heating zone 15 thereby causing plastic deformation of the tube in the direction of at least substantially parallel to the longitudinal axis of the tube thereby molecularly orienting the tube and rendering same amiable to being subsequently fibrillated.

Heating zone 15 is composed of two separate and distinct heaters 16 and 17, each of which has separate temperature controls so that each can be maintained at a temperature different from the other. For example, heater 17 can be at a temperature 50 more degrees than heater 16 or vice versa or both heaters can be at the same temperature if desired. Two separate heaters are employed for flexibility of operation, for more thorough heating of the tube as it passes air through at a high rate of travel, and to allow the throughput of larger quantities of tube if necessary. Of course, a single heater can be used if desired.

The tube issuing downstream from heater 17 passes through a second rolling zone 20 which is composed of four rolls, the tube again passing in a sinusoidal manner around the four rolls. The four rolls 21 through 24 are operated so that they pull the tube therearound at a rate faster than the first rolling zone 10 allows the tube to pass therethrough so that the net effect is that the tube is passing through the second rolling zone faster than it is passing through the first rolling zone, thereby causing the plastic deformation of the tube between the two rolling zones, and at least partially in the heating zone 15.

One or more of rolls 21 through 24 can be driven and one or more of these rolls can be externally cooled such as by cooling water passing through the interior thereof to cool the heated tube down to a temperature suitable for fibrillation thereof. One or more rolls 21 through 24 can be at least one of vertically movable or laterally movable or any combination thereof so that by moving the roll or rolls against or away from the tube passing thereover, the tension in the tube can be increased or decreased, for ease of threading the tube through the rolls. These rolls can be nipped together. For example, roll 23 can be a rubber roll which is vertically movable while rolls 21, 22 and 24 can be steel rolls which are internally cooled by water passing therethrough, rolls 21, 22 and 24 not being movable as is roll 23. The speed at which the rolls are driven in the second rolling zone 20 can be made to vary relative to the speed of the rolls in the first rolling zone 10 and/or first nip rolls 7, 7 thereby providing the capability of adjusting to varitions in the rate of issuance of blown tubing from air ring 5 to allow for immediate change in the amount of plastic deformation taking place between rolling zones 10 and 20, and the like.

The now molecularly oriented tube is passed through a coating machine 25 wherein a conventional lubricant is applied to the film by spraying or other conventional means.

The tube issuing from coater can then be passed to a storage bin 26 by way of dotted line 27 or passed directly on for subsequent treatment.

Coated tube from coater 25 or storage zone 26 by way of dotted line 28 is passed through a eyelet 30 which has an inside diameter substantially less than the width of the tube, thereby causing the tube to be bunched on itself by folding the outer edges of the tube over towards the center of the tube and at least partially down into contact with a central portion of the tube. The bunched or folded over the tube then passes between a pair of driven nip rolls 31, 31.

Nip rolls 31, 31 push the tube into stutter box 32. Rolls 31, 31 can be run at the same, slower, or faster rate than the rolls in second rolling zone 20 to thereby keep the slack out of the tube upstream of rolls 31, 31 and to allow flexibility in the rate at which the tube is jammed into suffer box 32.

Stuffer box 32 is a piece of conventional apparatus utilized for crimping fibers and has a door 33 is hinged at 34. Door 33 is resiliently biased towards stuffer box 32 by way of spring 35 so that the pressure of the tube jammed into stuifer box 32 must become sufficiently great to overcome the resistence of spring 35 before door 33 will open sulficiently for the material to fall out of the stuffer box into an accumulation zone or J box '38.

In the operation of stuffer box 32, the tube is forced into the box and because the tube in the box is constantly Working against the pressure of spring 35 in order to fall from the stuifer box into the J box, the tube is folded inside the stuffer box, the folds being substantially perpendicular to the longitudinal axis (orientation direction) of the tube. Thus, in the stufier box the molecularly oriented tube is subjected to a force acting in a direction substantially parallel to direction of orientation of the tube under confronting conditions which cause folding of the tube at a plurality of points along the direction of orientation of the tube (longitudinal axis of the tube), this folding being substantially transverse to that direction of orientation. The folding of the tube causes the molecularly oriented tube to at least partially fibrillate. The degree of fibrillation of the tube can be adjusted by varying the speed of rolls 31, 31 and/or the force required to compress spring 35 sufficiently to allow folded tube material to issue from stulfer box 32. Generally the force used for fibrillation will be such that at least five folds per inch of film along the direction of orientation of that film is obtained, preferably from about five to about fifty folds per inch being used.

Because the amount of folded tube material issuing from stuifer box 32 can vary, accumulator 38 is employed as a temporary storage means so that, in effect, oriented material can be withdrawn from the fibrillation process at a constant rate, the fibrillated product actually being withdrawn from the J box at a constant rate and the J box being fed fibrillated material from stutter box 32 at a nonconstant rate.

Fibrillated product from the J box can be passed to another storage bin 40 by way of dotted line 41. Fibrillated material from the J box or storage by way of line 42 then passes into a third rolling zone 43.

In this rolling zone, there is a series of five bars 45 through 49 which can be termed tensioning bars in that they are substantially close enough to one another and in substantially the same line so that when the fibrillated product passes sinusoidally thereover it is straightened to a certain extent. After issuing from the tensioning bars the film can pass by way of line 50 into a conventional piddler which is a hollow frusto-conical tube 51 which oscillates back and forth in the direction of arrow 52, thereby laying contiguous layers of fibrillated material in a storage container 53 for subsequent disposition as desired.

The fibrillated product issuing from the tensioning bars can also pass between a pair of rollers 55, 55 which are run at a speed greater than the speed at which the fibrillated product passes between the tensioning rollers, to thereby put the fibrillated product under a slight tension, further straighten same, and render same more readily cuttable. Rotating cutting knife apparatus 56 is then used to cut the fibrillated product into staple, preferably the length of from about /2 to about 6 inches. The staple falls into a storage bin 57 for subsequent disposition.

If it is desired that the staple be further fibrillated so as to break down the fibrils therein to get smaller fibrils, staple can be removed from collecting zone 57 and passed by way of line 58 to another fibrillation process 59 such as a conventional carding machine. If the staple is to be used to make carpet backing, an additional fibrillation step can be practiced thereon, if desired, such as passing the staple through a conventional card.

It should be pointed out that in rolling zones 10, 20 and 43, varying numbers of individual rolls can be used. For example, four or more can be employed in rolling zone 10, just as three and five or more rolls can be used in rolling zone 20. Such reasoning also applies to rolling zone 43 and particularly to the number of tensioning bars used in that rolling zone. It should also be pointed out that tube can be coated with lubricant at most any place downstream of the point at which the heated tube is cooled in second rolling zone 20. For example, a pool lubricant can be provided inside of stufier box 32 so that the tube material is coated with lubricant while in stuffer box 32 rather than upstream of eylet 30. Similarly, sprays, pools, and the like of lubricant can be provided in I box 38 for the same purpose.

In FIG. 2 mixing and extrusion steps 1 and 3 which are similar to or the same as those disclosed with respect to FIG. 1 are also employed. However, a cutting zone is disposed between roll 9 and first rolling Zone 10. This cutting zone can be composed of a conventional film edge cutter'71 and a conventional ribbon cutter 72 which may be employed as a single unit or separately as shown in FIG. 2. Edge cutter 71 merely severs the integral edges from the flattened tube thereby providing two edge strips, e.g. about /2 inch in Width, disposed on either side of two separate distinct films which are disposed contiguous to one another in a vertical relationship. The edge cutter can merely be composed of two knives disposed so as to cut edge strips from both edges of the flattened tube.

Ribbon cutter 72 can be a plurality of knives disposed across the width of the now two separate films passing therethrough so as to cut each film into a plurality of ribbons, e.g., from about /2 to about 2 inches in width for each ribbon, thereby providing an upper group of ribbons from the upper film and a lower group of ribbons from the lower film, the two groups of ribbons still being contiguous with one another.

The two groups of ribbons then pass through the first rolling zone as described with respect to FIG. 1. Immediately downstream of first rolling zone 10 is a first vacuum zone 73 which is composed of separate vacuum means 74 through 76. These vacuum means can be sepa rated as shown in the figure, or a single vacuum means with compartments therein, or simply a single vacuum means which is not compartmented in any manner.

A vacuum is constantly maintained in the interior of vacuum means 74 and the bottom side of vacuum means 74 is open and exposed to the groups of ribbons passing thereunder. The ends of the edges cut from the flattened tube are initially fed into vacuum means 74 and thereafter vacuum means continuously pull these severed edges from the groups of ribbons through line 77, grinder 78 wherein the severed edges are cut up or comminuted into particles and/or shreds which are then passed by line 79 into line 2 as feed for extruder 3.

Vacuum means 75 and 76 are constructed similar to vacuum means 74 and support a similar function in that any ribbon that might be broken through because of tension from the plastic deformation of the ribbons takes place between first and second rolling zones and 22, respectively, is prevented from becoming entangled in the first rolling zone 10 by these vacuum sources. The loose end of the ribbon or ribbons that is broken through downstream of first rolling zone 10 is pulled into one of the vacuum devices and 76, and thereby removed from the system and disposed of through lines 75 or 76', thereby preventing the loose ended ribbon from becoming entangled in any of the apparatus in the process.

The two separate groups of ribbons are now separated from one another and the contiguous relation which has been maintained since issuing from between first nip rolls 7, 7 by means of divider bar 80. Idler rollers 81 and 81' can be employed just upstream of divider bar if desired.

The two separate groups of ribbons now pass through heating zone 15 and second rolling zone 20. Molecular orientation of these separate groups of ribbons is carried out in the same manner as discussed hereinabove with respect to FIG. 1 so that issuing from second rolling zone 20 are two separate groups of ribbons which have been molecularly oriented and cooled so that they are now immediately available for the fibrillation operation.

In second rolling zone 20, there are provided two separate sets of rolls 83 through 85 for the upper group of ribbons, and 83' through 85' for the lower group of ribbons. Both sets of rolls operate at a speed greater than the speed of the roll restraining nip rolls in first rolling zone 10 thereby causing the plastic deformation of the ribbons between these two rolling zones. Each set of rolls in second rolling zone 20 can be varied as to the operating speed in relation to the restraining nip rolls in rolling zone 10 as discussed hereinabove with respect to FIG. 1. As with FIG. 1, one or more of the rolls in each of the two sets of rolls in rolling zone 20 can be externally cooled and vertically movable for applying greater or lesser amounts of tension to the groups of ribbons as discussed hereinabove with respect to FIG. 1. For ex ample, rolls 84 and 84 can be vertically movable rolls, while rolls 2 and/or 4 can be immovable in the vertical sense, but are internally water cooled to cool the oriented ribbons to suitable fibrillation temperature.

Downstream of second rolling zone 20 is a second vacuum zone 86 composed of upper and lower vacuum means 87 and 87. These vacuum means are constructed in the same manner and operate substantially the same as the vacuum means of first vacuum zone 73. Thus, vacuum means 87, 87 will remove from the system by way of lines 88, 88 and loose ends of ribbons that may become severed downstream of second rolling zone 20, thereby preventing such severed ribbons from becoming entangled in the rolls of rolling zone 20, and, as with the first vacuum zone, preventing the shutdown of the entire system simply because one or more ribbons have become broken through in a transfer stretch. This selective use vacuum devices in the process allows for a high speed continuous operation since the operator need not worry about ribbon breakage because any broken ribbons are automatically disposed of without fouling equipment or causing process stoppage. Thus, the system is run continuously notwithstanding ribbon breakage and can be run at a higher throughput because risks of ribbon breakage can be more readily taken since ribbon breakage no longer causes process stoppage.

The molecularly oriented ribbons then pass through a fibrillation zone 90 which can be any suitable fibrillation process such as that shown in FIG. 1, or an apparatus wherein two rollers are placed in a close but spaced apart relationship along the axis of rotation and at least one of the rollers oscillates parallel to its axis of rotation thereby rubbing the oriented ribbons back and forth as they pass between the opposed rollers. The rollers, 91, 91' can have a smooth or rough surface since the opposing surfaces do not touch one another but rather are spaced apart from one another just suflicient to allow the two groups of ribbons to pass therebetween. The spacing between the opposed surfaces of the two rolls 91, 91' is just sufficient so that these surfaces bear on the adjacent group of ribbons, thereby applying pressure to the ribbons passing therebetween without the surfaces of the rolls in themselves touching one another. One or both of the rolls can oscillate in a direction parallel to the axis of rotation, i.e., in a direction transverse, preferably substantially normal to, the longitudinal axis and therefore direction or orientation of the ribbons passing therebetween. It should be emphasized that even though the one or both rollers 91, 91' are oscillating parallel to their axis of rotation, both rolls are, at the same time, rotating about their axis of rotation in the direction of arrows 92, 92'. The rate of oscillation of the roll or rolls can -vary widely, depending upon the degree of fibrillation desired, but is preferably from about one oscillation per minute to about 5000 oscillations per minute, preferably at least 100 oscillations (i.e., movement from one point to another point and then back to that same point again) per minute. Oscillating rolls are well suited to the process of FIG. 1 because they can obtain the desired amount of fibrillation with a very high throughput and this is necessary for the system of FIG. 2 because, due to the use of the vacuum zones, the ribbons can be run through the system at extremely high throughput. For example, the throughput of ribbons that can be handled by the oscillating rolls in the fibrillation zone can vary from a few feet per minute up to 2000 feet per minute, a very practical range of throughput being from about 100 to about 1000 feet per minute.

More than one set of oscillating rolls can be employed if desired. For example, all the ribbons can pass together through a series of two or more sets of oscillating rolls. A series of oscillating roll sets can be simulated with a single set of rolls by recycling ribbons issuing from said single set of rolls upstream of said single set of rolls and back into said rolls beside ribbons passing into said rolls for the first time. This allows a ribbon to be passed between one set of oscillating rolls two or more times thereby simulating two or more sets of rolls in series. Also, two or more sets of rolls can be used in parallel. For example, one or more ribbons can be run through one set of oscillating rolls while one or more other ribbons are run through another set of oscillating rolls. Referring to FIG. 2, the ribbons issuing from vacuum zone 86 can be divided into four groups and each group passed through a separate set of oscillating rolls so that four separate sets of oscillating rolls are used in parallel because no ribbon passes through a set of oscillating rolls more than once.

Downstream of the fibrillation zone is a third rolling zone 43 which has variable drive speeds and is used primarily to pull the ribbons through the oscillating zone and to keep slack from forming in the ribbons downstream of second rolling zone 20.

The now fibrillated ribbons can then be passed through a coating zone 94 which can contain a bath of lubricant or sprays of lubricant for coating the fibrillated ribbons.

The now fibrillated ribbons can then be passed by way of line 95 for subsequent disposal as desired such as rolling up of the ribbons into individual rolls for storage and the like. If desired, additional fibrillation steps can be carried out on these ribbons depending upon the degree of fineness of fibers in the fibrillated product.

Retrieval systems such as 73 and 86 in FIG. 2 can be used any place in the process of FIGS. 1 and 2. For example, a retrieval system can be employed downstream of third rolling zone 43 of FIG. 1 to catch and remove broken ends of the fibrillated product.

Generally, films of l-olefins having from 2 to 8 carbon atoms per molecule which have been oriented by stretching in at least one direction so that the film after stretching is at least three times longer in the direction of stretching than it was before stretching, i.e. 3 to 1, can be used. When film of polyethylene which has a density of at least about 0.94 gram per cubic centimeter is employed the ratio of length in the stretched direction to original length should be at least 4 to 1 and when polypropylene is employed this ratio should be at least 6 to 1. Polymers of l-olefins can be made in any conventional manner. A particularly suitable method is that disclosed in US. Pat. 2,853,741. The film can be made from the polymers in any conventional manner such as by extrusion, casting, flattening blown tubing, and the like.

Other conventional plastic films that can be employed in this invention include blends and copolymers of 1- olefins as above described with each other and with other polymers such as nylon, polyesters, polyvinyl alcohol, acrylic polymers, polyvinyl chloride, polyvinyl acetate, poyvinylidene chloride, and the like. Of course, homopolymers of the l-olefins and other materials described can also be employed as well as copolymers. A stretch, draw, or orientation ratio of at least 3 to 1 can also be employed with these plastic films.

The plastic material passing through the heating zone 15 should be exposed to temperatures of at least 150 F., preferably temperatures in the range of from about 200 to about 500 F. for suflicient time to heat the material above ambient temperature and to render the material orientable plastic upon stretching thereof, e.g., at least 0.5 second, preferably from about 0.5 to about 3 seconds.

EXAMPLE I Bright, cylindrical pellets of polypropylene of about /3 inch in diameter and about /8 inch in height are physically mixed with pigment for use in the apparatus shown in FIG. 1. The polypropylene pellets are a homopolymer of propylene having a density of .91 gram per cubic centimeter at 25 C., and a melt flow of 3 (ASTM D 123862T, Condition L).

The polypropylene pellet mixture is passed by line 2 to extruder 3 at a rate of about 102 pounds per hour. Extruder 3 is a conventional melt extruder fixed with a blown tubing die, adaptor, air ring, and blower for producing blown tubing at the rate of about 102 pounds per hour, the blown tubing having a 2-mil wall thickness. The tubing, after flattening between first nip rolls 7, 7 have a 30-inch lay flat width, the lay flat thickness being about 4 mils.

The flattened tube passes through first rolling zone 10 at a speed of about 42 feet per minute, and then through heating zone wherein heater 16 is maintained at a temperature of 400 F., the residency time for the film in further flattened tube in this heating zone being 0.8 second.

The flattened tube then passes through second rolling zone 20 at a speed of about 510 feet per minute. In rolling zone 20, the flattened tube is cooled to substantially ambient temperature by cooling roll 21, 22 and 24 internally by passing tap water continuously therethrough.

The cooled, flattened tube then passes through a spray of lubricant which is available commercially, such as emulsion type fiber lubricant, available from the Nopco Chemical Company, the spray coating both the top and bottom sides of the flattened tube.

The tube then passes through eyelet 30 which has an internal diameter of 4 inches, the tube at this point having a lay-fiat width of 8 inches due to the molecular orientation step, then passes between dry rolls 31, 31 at a speed of 510 feet per minute and into stutter box 32. The stuffer box is a stainless steel box having the approximate dimensions of /2 inch by 1 /2 inches by 3 inches.

Fibrillated product is removed from J box 38 at a rate of about 450 feet per minute, passed through rolling zone 43 at this same rate and cut into staple of about 6 inches in length. This staple can then be used for making carpet backing and the like.

8 EXAMPLE II The same polypropylene pellets and mixing extruding apparatus as discussed in Example I are employed in the process of FIG. 2, thereby producing the same type of flattened tube as discussed in Example 1.

However, the flattened tube has its edges severed there from and the thus-formed two separate films cut into two groups of ribbon, each ribbon about 1 inch in width, using conventional fixed knife cutters in cutting zone 70. The flattened tube passes through the cutting zone at 35 feet per minute and then through first rolling zone 10 at 35 feet per minute.

Heating zone 15 is maintained at a temperature of 410 F. and the two groups of ribbons pass through this heating zone in about 1 second.

The two separate groups of ribbons pass through the second rolling zone 20 at about 350 feet per minute and therein are cooled substantially to ambient temperature by way of rolls 83 and 83' being externally cooled by continuous passage of tap water therethrough.

The oriented and cooled, separate groups of ribbons are passed through second vacuum zone 86 wherein the vacuum is maintained in devices 87, 87 as maintained in devices 74 through 76, and then between oscillating rolls 91, 91'. The ribbons pass between the oscillating rolls at about 350 feet per minute and roll 91 is oscillated parallel to its axis of rotation at about 2400 oscillations per minute.

The fibrillated product passes through third rolling zone 43 and is coated at 94 wherein both sides of each fibrillated ribbon are coated with a lubricant such as emulsion type fiber lubricant by passing through a bath of that lubricant.

The thus-fibrillated product is a continuous yarn which can be used as carpet face yarn in making carpets for commercial or home use.

Reasonable variations and modifications are possible within .the scope of this disclosure without departing from the spirit and scope thereof.

We claim:

1. A process comprising providing a molecularly orientable tube of plastic which is flattened to produce a twolayered film, the two layers being integral at the edge of the film, passing said tube through a cutting zone, in said cutting zone severing said integral edges of said tube from the remainder of said tube thereby providing two separate films, in said cutting zone cutting each of said two separate films into ribbons to form two groups of ribbons, each group containing a plurality of ribbons, passing said tube through a heating zone, plastically deforming said tube at least in a direction substantially parallel to a longitudinal axis of said tube by passing said film through a first rolling zone upstream of said heating zone and a second rolling zone downstream of said heating zone, said second rolling zone pulling the film through said heating zone at a rate greater than the rate at which said first rolling zone emits said tube to said heating zone, passing said groups of ribbons through a dividing zone upstream of said heating zone to physically separate said two groups of ribbons, maintaining said two groups of ribbon in said separated condition through said heating zone and said second rolling zone, fibrillating said oriented groups of ribbons by passing said groups of ribbons between at least one pair of rolls in a direction of rotation of said rolls, said rolls being in a spaced engagement along their axis of rotation which is sufficient to cause pressing of said rolls on both sides of said groups of ribbons, at least one of said rolls oscillating parallel to its axis of rotation, and passing said fibrillated tube through a third rolling zone, said third rolling zone being a zone for tensioning said tube during the fibrillation step, subsequent to the fibrillation step or both during and subsequent to the fibrillation step, wherein said two groups of ribbons and said severed edges pass through a first vacuum zone downstream of said first rolling zone and upstream of said heating zone, in said first vacuum zone removing said severed edges from said groups of ribbons, said first vacuum zone also having a sufficient vacuum to separate from said groups of ribbons any ribbon that may be broken through downstream of said first rolling zone thereby removing broken ribbons before entry of same into said heating zone, and passing the oriented groups of ribbons through a second vacuum zone downstream of said second rolling zone and upstream of said fibrillation zone, the vacuum in said second zone being sufficient to separate from said oriented groups of ribbons any ribbon that may be broken through downstream of said second rolling zone and upstream of said fibrillation zone.

2. The method according to claim 1 wherein said third rolling zone is downstream of said fibrillation zone and the fibrillated ribbons are coated with a lubricant.

3. The method according to claim 1 wherein scrap plastic removed by at least one of said vacuum zones is comminuted and used as plastic for making said flattened tube.

4. The method according to claim 1 wherein said plastic is one of a polymer of ethylene, a polymer of propylene and mixtures thereof.

References Cited UNITED STATES PATENTS 2,293,178 8/1942 Stocker 16417 2,955,318 10/1960 Cook 18-1 2,976,567 3/1961 Jones 264-210 3,003,304 10/ 1961 Rasmussen 264-Fibrillating digest 3,336,174 8/ 1967 Dyer 264Fibrillating 3,398,220 8/ 1968 Port 264Fibrillating 3,344,218 9/1967 Chopra 26437X 3,402,548 9/1968 Winninger 264Fibrillating 3,420,004 1/ 1969 OBrien 264161X 3,448,183 6/1969 Chisholm 26437 FOREIGN PATENTS 810,001 3/1959 Great Britain 264-140 1,061,136 3/1967 Great Britain 264-146 1,067,514 5/1967 Great Britain 264147 20 ROBERT F. WHITE, Primary Examiner Disclaimer and Dedication 3,579,618.-Dam F. Stewart, Bob 0. Blair, Mam E. Greene, and Lloyd R. Alema/nder, Bartlesviile, Okla. HIGH SPEED FIBRILLATION PROC- ESS. Patent dated May 18, 1971. Disclaimer and dedication filed Dec. 28, 1971, by the assignee, Phillips Petroleum Company. Hereby disclaims said patent and dedicates to the Public the remaining term of said patent.

[Oficz'al Gazette April 11, 1.972.]

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