DE2102902A1 - Apparatus for the production of fiber webs from extruded, monoaxially oriented polymer films - Google Patents

Description

Chevron Research Company San Francisco, CaI., V.St.A.

Device for the production of fiber tracks from extruded, monoaxially oriented polymer films ' _ M

Addendum to patent (patent application P 19 22 419.2)

In the patent (patent application P 19 22 419.2)

a method for producing uniform fiber webs from monoaxially oriented polymer films and the device used for this purpose are described. In general, this device consists of a first and a second roller, the circumferential surfaces of which are arranged parallel and closely adjacent, but at a distance from one another. These rollers are rotated largely synchronously, but in the opposite direction to one another, by appropriate, functional means connected to them. The first roller is equipped with cutting elements W or teeth which project radially from the circumferential surface and which are arranged in helical rows. The second roller has helical grooves in its circumferential surface, so that when the rollers are rotating, the rows of cutting elements come into engagement with corresponding helical recesses in the counter roller.

The device described above is used as follows Fibrillation of monoaxially oriented films used: The film is guided between the two rollers in such a way that the Orientation is in the machine direction and in such

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that they come first with the peripheral surface of the second or pressure roller comes into contact and rests on it. The peripheral speed of the two rollers is about 1.5 to 20 times as high as the running speed of the slide. When these run in between the rollers, the cutting elements pierce and reach

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into the recesses of the second or pressure roller. Since the cutting elements move faster than the film, they cut longer slots in it. Due to the synchronous movement of the cutting elements and the cutouts, the elements remain in the Cutouts as they slit the foil. After the elements have slit the film and stand out from the film, the film is pulled off the roller, whereby it rests on the circumferential surface of the second roller.

The method and apparatus described above have been used to manufacture uniform fiber products for the textile industry used industrially, but there were two major problems in operation. First, the items are in use somewhat dull and press the film more and more into the pressure roller groove instead of cutting it open. These usually A phenomenon occurring at the edges of the fibrillated film is referred to as "edge skipping". With continued r As the elements wear and tear, an increasing irregularity occurs. Second, there is this "edge skipping" the endeavor by moving the cutting elements closer and closer together to improve the denier of the product even without significant wear of the elements. These irregularities have an impact on the quality of the textile end product.

The present invention therefore relates to an improvement of the device of the patent application P 19 22 Ί19, whereby the operating times between the sharpening of the visual cutting elements considerably extended and also cutting elements arranged closer together can be used.

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The latter leads to fiber webs which are extremely uniform and a much finer denier than when using these known ones Own device.

The improvement of the present invention includes a change to the helically grooved pressure roller. In the improved

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Device, the recesses of the second or pressure roller are filled with a solid elastic material. This elastic material must adhere well to the material from which the grooved pressure roller is made, withstand the continuous piercing of the cutting elements (teeth) arranged in rows W of the first or cutting roller without crumbling, and be wear-resistant. Elastic material that works well for this purpose is natural and synthetic rubber, and mixtures of both. Synthetic rubbers suitable for this purpose are rubbers of the butadiene type, such as butadiene / styrene mixed polymers, polyisoprene and polybutadiene, the urethane rubbers, the silicone rubbers and the butyl rubbers. These rubbery materials are well known and are commercially available. Rubber is preferred both because of its wear properties and because of its ease of application.

The grooves in the pressure roller can be filled with the elastic material in various ways. Natural rubber and thermoplastic rubber can be softened by heating and then pressed into the groove under pressure. Urethane and silicone rubbers are generally made in situ . "Two-Gefäfö system ⁿ (two-pot system) stored in separate containers until the moment of application, where they are then mixed well after; In this method, a liquid base resin and a catalyst (curing agent) according to the will. Mixing, the thick material is pressed into the recesses and then allowed to harden into the final gourami-like product. The time for complete hardening depends on the type and quantity of the catalyst and on the temperature ^^ segt? & Feer normally between 12 and HS hours .

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These variables are well known in the resin curing art. Sometimes it is advisable, heating the rubber-filled grooves possessing pressure roll to elevated temperatures, such as 10O ⁰ C, (post your) for "post-curing" of the synthetic rubber. The "one-pot" resins, which are also known and which harden to a rubber-like product after exposure to the atmosphere, can also be used to fill the pressure roller recesses.

The recesses are practically completely filled with the elastic material. The filler is said to be with the outer surface of the Complete roller, protruding 'material must be removed, before beginning slitting or fibrillation of the film.

After filling the recesses, the pressure roller is mounted so that its peripheral surface is parallel and closely adjacent to the peripheral surface the cutting roller is arranged. The rows of teeth on the cutting drum and the recesses filled with rubber are matched in such a way that corresponding rows of teeth and corresponding rubber-filled recesses fit into one another in a complementary manner. Then the two rollers are pressed into the position intended for operation in which they lie against one another, so that the teeth lower themselves approximately in the middle of the rubber-filled recesses. The rollers are then set in rotation and the film to be fibrillated is passed between them.

The general technology for making the in the invention The film used in the device is well known in the art. The polymer is made in a conventional extrusion press extruded into a film of the desired thickness and width. For the sake of simplicity, in the extrusion press a very wide film can be extruded, which can then be divided and cut to the desired width.

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The film can be oriented by stretching at an elevated temperature. It is heated to the desired stretching temperature, which depends on the polymer used, by passing it through a heating zone or over heated rollers or drums. The stretching takes place either in one or in several stages. The individual stretching ratios used to orient the film are ultimately at least 4: 1 and can be increased to below the ratio at which spontaneous fibrillation of the film occurs. The final draw ratio in a given particular case will again depend on the ' M polymer that is used. For normally solid, substantially crystalline polypropylene, for example, draw ratios between 6: 1 to 10: 1, preferably 7: 1 to 9: 1, are desirable.

The film thickness depends on the desired degree of fineness of the fiber product, which according to the method according to the invention oriented film being treated is essentially uniform in thickness. The thicknesses of the oriented foils are between approx 12.7 / u and about 76.2 / u, preferably 17 * 8 to 50.8 / u, with the lower values within this range are used for the production of fine products with good handle and strengths in the Upper Boreich result in coarser materials. ™

Orientable, normally solid-crystalline polymers and mixed polymers can be used to produce these films. Typical polymers of this type are high-density polyethylene »polypropylene, poly-4-methyl-l-pentene, polyester, polyamides, e.g. the Nylons, u'l: * l, mixtures of these polymers can optionally be used. The polymers can also contain additives such as light stabilizers, Contain antioxidants, heat stabilizers, dye, accupors, pigments, dyes, fillers and the like.

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The driven cutting roller used in the invention can be conveniently prepared by reacting, preferably in the Umfangsfj-äche a roll having the desired diameter, which usually is between about 5 and 38 cm in helical parallel lines with angles of about 0.5 and 45 » Provides 5 to 15 ° recesses and inserts a grinding wire provided with saw teeth into these recesses, so that the teeth protrude and protrude radially from the circumferential surface of the roller. The wire rows are expediently attached to the roller at regular intervals from one another. Similar rollers wrapped with garnet wire are used in the textile industry for cutting up natural staple fibers.

According to the invention, the working angle of the teeth of the garnet wire is expediently about 90 °. If the angle is very acute, the fiber web can more easily get caught in the teeth and wind around the toothed roller. The lateral offset due to distances between the tips of adjacent teeth are practically equal and are about 25, ¹ to about 1270 J .u, preferably 127-381 yes. Since each tooth acts as a cutting element, this distance corresponds approximately to the fibril width in a web or tissue. In other words, the individual pibrils are formed by the cutting action of two adjacent teeth in a row, which are laterally offset from one another due to the helical winding of the wire. The teeth normally have a tapering cross-section and flat tips about 2.54 to about 254 / u, preferably 25 to 250 ax wide. Sharper teeth are generally used for fine fibrils, while wider teeth are used to produce larger fibrils. The tooth base is usually about 381 to about 635 ax wide. There are usually about 3 to 15 teeth per inch of wire.

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So that each tooth of the garnet wire cuts slots in the film of the same length as far as possible, the tolerance with regard to the distance from the cutting roller axis to the tips of the teeth must be kept small. Preferably, this distance ^ura should not vary by more than about 51 / u.

According to the invention, rows of teeth in practically any number, greater than 1, can be used. In any particular case, the preferred number of rows will depend on the pattern desired, the cutting roll diameter, the peripheral speed and the penetration. "Penetration" is understood to mean that part of the tooth height that pierces the film. In general, the number of rows is between h and 30.

The circumferential surface of the present pressure roller is provided with helical recesses which are such that certain ο recesses in the pressure roller can come into engagement with certain rows of teeth on the cutting roller. The recesses thus have practically the same inclination as the rows of teeth, and the longitudinal spacing (parallel to the roller axis) between adjacent recesses essentially corresponds to the longitudinal spacing between adjacent rows of teeth. However, the inclination of the recesses is negative in relation to the inclination of the rows of teeth. As already mentioned, the width of the recesses is larger than the face width. The recesses are normally about 508 to 1520 m wide and, as already explained, filled with elastic material.

The surface of the recessed pressure roller is more exposed to friction, since it comes into contact with the film and becomes faster than the slide moves. It is therefore recommended that this roller be made of hard material, e.g. chrome or ceramic-coated To manufacture steel. Other materials, such as hard plastics,

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e.g. nylon or Teflon can be used. Also the cutting roller can be made from the above substances. The pressure roller is usually also of a diameter of about 5 to about 38.1 cm.

The accompanying drawings serve to further explain the invention. It is

Figure 1 shows the schematic representation of the device according to the invention for film production and fibrillation;

Figure 2 is a partial side view of the fibrillation rollers of Figure 1;

FIG. 3 shows a partial illustration of the fibrillation device shown in FIG in cross section, showing a cutting element within a rubber-filled recess of the pressure roller is;

FIG. 4 shows a partial view of the fibrillation device according to FIG. 1 in detail;

FIG. 5 is a photograph of a fibrous web that has been produced with a fibrillation device was made in which the recesses of the pressure roller were not filled with elastic material;

FIG. 6 is a photograph of a fiber web that was produced with the fibrillation device was generated according to Figure 1, wherein the recesses of the pressure roller were filled with rubber.

In Figure 1, an extruder 1 for producing the film 13 is shown, which in the stretching device 3 to form a

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mcnoaxially oriented film 13 is oriented. Furthermore, FIG. 1 shows holding rollers 25 and 26, the cutting roller 11 / the pressure roller 12, a motor for synchronous drive of the cutting and printing roller (the drive belt system between the cutting roller and the driven roller is not shown), pull rollers 27 and 28, a mo-

gate to drive "these Zügwälzen, a take-up roller 7 and a Motor to drive the pick-up roller.

The position of the rollers, cutting elements and rubber-filled recesses in relation to one another is shown in FIGS.

FIG. 2 shows a view of the cutting roller 11 and the pressure roller 12 in the opposite direction to the running direction of the film 13 * Die Schneid roller 11 and pressure roller 12 are arranged to each other that their two peripheral surfaces are parallel and closely adjacent. the Cutting roller 11 rotates clockwise, while the pressure roller 12 rotates counterclockwise, so that the 13 with the film surfaces of each roller which come into contact move in the same direction as the film 13. When the arranged in rows Metal cutting elements 14 pierce the foil 13 they sink into complementary rubber-filled recesses 15 of the Pressure roller. The distance caused by the lateral displacement of adjacent cutting elements in a row is denoted by a. The helix angle θ of the rubber-filled recesses essentially corresponds to that angle of the helix of the rows of cutting elements, however negative about it.

Figure 3 shows in partial cross section a cutting element I ^ inside of the cummy-filled recess 15 · The recess is rectangular shown, but need not have this form. She can beispit. wise also be trapezoidal or it can have a rounded bottom surface. The height of the recess is denoted by b. As already mentioned, the width of the recess c depends on the width ftes ß- ^ hnpiApl ^ mciiCec Ab.

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In general, the element 1H should engage symmetrically in the recess 15.

FIG. 4 is the partial side view of the through the cutting roller 11 and pressure roller 12 running film 13 according to the invention. The film 13 is at an angle £ between the toothed roller 11 and the pressure roller 12 rre guides. The angle aC is defined by a tangent drawn from the point of first contact between film and pressure roller 12, and one the arc of Cutting roller 11 (measured at the tips of the cutting elements) and the pressure roller 12 cutting tendon. So that the slide with first the pressure roller 12 comes into contact, this angle, expressed in units of arc, is greater than

Arch units

where ρ is the depth of the greatest penetration of the cutting element into the rubber-filled recesses of the pressure roller 12, D _{1 is} the diameter of the cutting roller, measured up to the tip of the cutting elements, and D _{2 is} the diameter of the pressure roller. This angle is usually around 3-15 °. The film thus first touches the pressure roller and then comes into engagement with the cutting elements 1H. As soon as the cutting elements have pierced the film, they reach the top into the rubber-filled recess 15. As a result of the different speeds of the cutting roller and the film, braids of practically the same length are cut in the latter. After the cutting elements have already detached themselves from the film emerging between the rollers, the film is still in contact with the pressure roller. The fibrillated film is pulled off the rollers at an angle β.

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The angle β is in turn bounded by the chord that cuts the arches of the printing and cutting rollers and the tangent which is laid through the point on the printing roller at which the film lifts off the printing roller. The minimum value for the angle ß is the same as stated above for the angle. As a rule, it is expedient to choose practically the same size for angles as for angles β.

The following examples explain the process according to the invention and the device as well as the use in production of fiber webs made of monoaxially oriented polymer films, but without restricting the invention.

example 1

Commercially available, practically crystalline polypropylene was extruded into a continuous film at a speed of about 9 meters per minute. The film was cut to a width of ¹ 25j J cm and then oriented by stretching on the heated rolls at 120 to 138 ⁰ C. The final stretch ratio was about -7: 1. This resulted in a film about 19 cm wide and 25.4 cm thick. A thin coating of an aqueous emulsion of an antistatic agent was applied to the underside of the film.

The film was cut into 17 mm wide strips, and these were in the same position as they had in the film to each other by a set of holding rollers and then between a cutting and a pressure roller out. The holding rollers ran at a peripheral speed of 61 m / min. Cutting and platen rotated in the opposite direction at a peripheral speed of 216 m / min each. These two rollers were connected by a timing belt drive system and connected to a common drive shaft. The tendon: ·*- roller was helical with garnett wire

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wrapped around j and the pressure roller became accordingly helical Provided notches so that the teeth of the wire and the notches could engage.

The wire wrapped roll was 38 cm and had lanp, to the tip of Zä'hne measured cm a diameter of 17 ». 5 Around this roller, 16 separate, essentially parallel rows of green wire were prexviekelt helically in the form of a right-hand thread. At 25.4 mm, there were 11 equally spaced: rows of teeth. Each row contained lengths of garnet wire Ί ₃ 5 Z'Jhne on 25.4 mm. The outer edges of the teeth of the teeth extended perpendicular to the surface of the roller, that is, the working angle of the teeth was 90 ° at the tip 0.2286 mm thick.

The recessed platen was 38.1 cm long and had a diameter of 17.5 cm. 16 helical ^. · Recesses 0.51 mm wide and 1.27 mm deep were the same Distance and in a number of 11 per 25 ** 1 mm in the roller surface circumcised. The recesses existed in the form of a Left-hand thread. The area of this roller · had the area of the Cutting roller (at the base of the teeth) a distance of about 1.52 nc, so that the maximum depth of penetration of a tooth into a recess about 0.38 mm.

The oriented film came into contact with the pressure roller at an angle of 7 " above the tanrente and also left this roller at an angle of 7 °. The fibrillated film then ran through a pair of draw rollers, which were ) Speed of 61.27 m / min, rotated.

D-s product had an average of 42 fibrils over a 1 cm width (106 fibrils per inch).

■ i-'Ch liner oper-bsz & it for a few months the teeth were gradually becoming blunt, and os came more and more to "ed ^ e skipping"

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(Edge warping). The operation was interrupted in order to fill the recesses of the pressure roller with a commercially available silicone rubber (General Electric RTV-108). For this purpose, the pressure rollers were cleaned in order to remove all foreign body particles from the recesses, and then degreased and de-oiled by washing with perchlorethylene. The thixotropic, viscous rubber was worked into the recesses of the pressure roller by hand, the material being pressed in firmly with a spatula. All recesses were filled in this way, excess rubber was removed from the surface of the pressure roller, then the roller was left to stand for 2k hours at room temperature. Fibrillation was resumed and could be continued for several months without any "edge skipping".

Example 2

In pale manner, set a different cutting roller forth with αερ except that 25 separate, substantially parallel rows of garnet wire teeth around a steel roll having a surface width of 6'3 ₃ 5 cm and a diameter of 30.48 were wound cm. The rows of teeth were evenly spaced 10 per 25 ^ nim. Each row contained 9 teeth per 25> 4 mm along the wire. The thickness at the tip was 0.0635 mm.

The recessed platen was complementary with • rl_-r C cutting roller. The recesses were 0.635 mm wide and 1.27 «■ .π deep. The rollers were installed so that the tooth surface was up penetrated the recess to a depth of 0.76 mm.

GL> After Borinn of the fibrillation treatment, "edge skipping" occurred frequently. A photographed sample of this product can be seen in Pi'ur 5. This fibrillation device was shut down, and the recesses in the pressure roller were as described in Beißpi'-l 1 with silicone rubber (General Electric RTV-77)

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filled. After resumption of operation, a fibrillated product was obtained which showed no "edge skipping". One A sample of this product is illustrated in FIG. The average number of pibrils per each was 25.4 mm

The invention can be modified in various ways without departing from the scope thereof.

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Claims (2)

Patent claims: (Tl. 'Device for the production of a fiber web from a •? Xtruded monoaxially oriented film by cutting elongated slots in the film, consisting of a>: rsten, with helical rows of cutting elements v-.?rsth: -rien roller, whose Sehneid-learning duck radially from the ^Umf.infsfl; cozy raise the roller, and a second en-rmiß with schraubenlini'.r f '/ recesses on the peripheral surface WnIz- provided, wherein the Umfan-'S surfaces of the two rollers. include, but are spaced apart in parallel and closely adjacent, and v / obei further rows of the first roller with Schneideleiponten W ^ ircsvrt rhenden recesses of the second roller while rotating in engagement koiunen could n, and Γ-'ittcl for substantially synchronous Rotating · 1: .ν first and second rollers in opposite directions to one another, according to claim 9 of the patent specification,. iF't.ntanr-.cldun? F 19 22 * J19.2), in that the screw-crimped linear recesses of the second roller r.it vir: -rr. elistii-cher. Ftststcff are filled. 2. Vcrrichiunir according to claim 1, by means of which the elastic · .. Ft-ststoff Mntürpumni, synthetic rubber or Ocv-.is-r-hc from bci'.ic-n are. ^. Execution according to claim I _1, characterized in that the ■ - ^: l ;; sti3? Ho Fostsrcff is a silicone gun. For: Chevröh Research Company Law 109833/1959 ■ & ■ &? £ -'-> Κ * ϊ. BATH