US 3369435 A
Description (OCR text may contain errors)
Feb. 20, 1968 H. D. BOULTINGHOUSE 3,
METHOD AND APPARATUS FOR FIBRILLATING Filed Dec. 2, 1965 v 2 Sheets-Sheet 1 INVENTOR H. D. BOULTINGHOUSE A 770 RNE rs 1968 H. D. BOULTINGHOUSE 3,
, METHOD AND APPARATUS FOR FIBRILLATING vllMl boo. III, 1965 2 Sheets-Sheet 2 INVENTOR.
H. D. BOULTINGHOUSE BY V9 ATTORNEYS United States Patent G METHOD AND APPARATUS FOR FIBRILLATING ABSTRACT OF THE DISCLOSURE Fibrillatable film fibrillated by impinging thereon a plurality of freely movable, rotating needle means.
This invention relates to a method and apparatus for fibrillating oriented plastic film.
Heretofore films have been fibrillated by piercing same with a plurality of fixed needle means.
Quite surprisingly, it has now been found that if the needle means are freely rotatably carried around a rotatable support means, film can be fibrillated very economically at an extremely high rate. Thus, the fibrillation method of this invention includes the step of impinging a plurality of freely movable rotating needle means on a film, the needle means being rotated at a speed such that the centrifugal force acting upon the needles is sufficient to cause same to pierce the film.
The fibrillation apparatus of this invention therefore includes a plurality of needle means freely rotatably carried around a rotatable support means and means for rotating the support means at a speed sufficient to generate a centrifugal force which will cause the needle means to pierce the film.
Accordingly, it is an object of this invention to provide a new and improved method and apparatus for fibrillating film.
Other aspects, objects, and the several advantages of this invention will be apparent to those skilled in the art from the description, drawings, and the appended claims.
FIGURE 1 shows a system embodying this invention.
FIGURE 2 shows a single needle means carried on a support bar as employed in FIGURE 1.
FIGURE 3 shows an isometric view of the needle carrying device of FIGURE 1.
In FIGURE 1 there is shown an oriented plastic film 1 passing around idler rollers 25 in the direction of arrow 6. A plurality of needles 7 are carried on a plurality of support bars 8 in a manner such that needles 7 are free to rotate about and slide along the longitudinal axis of bar 8. Bars 8 are supported by a pair of spaced apart plates 9 (one not shown). Shaft 10 is connected to plates 9 and is connected by conventional means (not shown) to a motor means (not shown) so that needles 7 can be rotated with sufiicient speed to make needles 7 sufficiently stable to cause same to pierce film 1 when they come in contact therewith.
The speed at which needles 7 must be rotated is that which will cause fibrillation, i.e., splitting of the film into a network of longitudinally extending stern fibers integrally connected with cross fibers formed from the Stem fibers thereby producing a network of fibers with an appearance of a porous woven fabric, and this speed can vary widely depending upon the needles used, the type of film treated, the thickness of the film, the degree of orientation of the film, and many other factors. However, if the speed is too low fibrillation will not occur because the needles will rotate back on support bar 8 when impinged on the film and therefore not pierce same. Similarly, if the speed is too fast, the needles will tear through, thereby shredding the film and not just pierce hoe and fibrillate same. Needles 7 can generally be any size of length and can be mounted longitudinally across the drum formed by plates 9 and bars 8 or transversely around the drum, or in a spiral around the drum. Needles 7 can be rotated in either clockwise or counter clockwise direction relative to the film movement.
FIGURE 2 shows a bar 8 on which needle 7 is carried and by reason of gap 11 it can be seen that needle 7 is only supported by bar 8 and is free to rotate about or slide along bar 8 at will.
FIGURE 3 shows two spaced apart plates 9 joined by both a shaft 10,and a plurality of bars 8 which bars are spaced around a periphery of plates 9. The plurality of needles 7 are carried on each of bars 8, said needles being freely rotatable and freely laterally slidable on each bar 8 shown in FIGURE 2.
Generally, any orientable plastic film can be employed in this process. The film can be in a uniaxially, biaxially, or other multiaxially oriented condition. The film can be oriented in any conventional manner including supercooling the film and then orienting same by stretching and the like, or heating the film to a temperature below that at which the film is in the molten state and then stretching same. By orientation, what is generally meant to be covered is deforming, e.g., stretching the film below that temperature at which the film is substantially in the molten state, to thereby increase the strength of the film at least in the direction in which it is deformed.
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 3 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 at 25 C. 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 1-olefins can be made in any conventional manner. A particularly suitable method is that disclosed in U.S. Patent 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 l-olefins as above-described with each other and with other polymers such as polyamides, polyesters, polyvinyl alcohol, acrylic polymers, polyvinyl chloride, polyvinyl acetate, polyvinylidene 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 0r orientation ratio of at least 3 to 1 up to the breaking point can also be employed with these plastic films.
The film can be of any length and width and substantially any thickness, the minimum thickness of the film being that which will produce a substantially self-sustaining film and the maximum thickness being dictated by the piercing capability of the piercing means employed. Preferably, the thickness of the film will vary from that which is sufiicient to form a self-sustaining film to 6 mils. Thicker films can be treated by using heavier duty piercing apparatus or by passing the same film through the same piercing apparatus two or more times. By repeated passes through the same piercing apparatus lighter duty piercing means can be employed to effectively fibrillate thicker and/ or tougher plastic films than can be accommodated on a single pass. The film can also be just partially penetrated by the needles to facilitate subsequent fibrillation.
Example needles /8 inch in diameter were carried in each bar 8. a
The drum formed from plates 9 and bars 8 was rotated at about 800 revolutions per minute at which time the needles 7 stood out substantially away from bars 8 as shown in FIGURE 1.
The oriented polyethylene film was then drawn past the rotating drum at 80 feet per minute and at a spacing from the drum such that a substantial length of needles 7 could extend through the film as shown in FIGURE 1.
A uniformly fibrillated product was obtained which was composed of a network of substantially parallel, longi tudinally extending stem fibers each joined integrally to the adjacent stem fiber at a plurality of points along its length by smaller length and diameter cross fibers.
Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope thereof.
1. In a method of fibrillating a fibrillatable plastic film, the steps of providing a means for supporting a plurality of freely rotatable needle means, rotating said support means at a speed sufiicient to generate a centrifugal force of said needle means sufficient to pierce said film, im-
pinging said needle means on said film, and passing said film into contactwith said needle means at a speed relative to said rotating needle means so that said needle means do not shred said film.
2. The method according to claim 1 wherein, said needle means is rotated at a speed sufficient to cause piercing ofv the film by said needle means but insufficient to cause shredding of the film by said needle means.
3. The method according to claim 1 wherein said film is a polymer formed from at least one olefin having from 2 to 8 carbon atoms per molecule, inclusive, and the needles are rotatably and laterally freely movable.
4. An apparatus for fibrillating a fibrillatable plastic film comprising a plurality of needle means freely r0- tatably carried around a rotatable support means, means i for rotating said support means at a speedsufficient to generate a centrifugal force of said needle means sufficient to pierce said film and means for passing said film into contact with said needle means at a speed relative to said rotating support so that said needle means pierce but do not shred said film.
'5. The apparatus according to claim 4 wherein said rotatable support means comprises a plurality of bars spaced around the periphery of and supported by a pair of spaced apart plates, a plurality of needles being freely rotatably and .freely laterally slidably carried on each of said bars.
References Cited UNITED STATES PATENTS ANDREW R. JUHASZ, Primary Examiner.