DE1961815A1 - Method and device for producing webs of polymeric material with molecularly oriented regions distributed in specific patterns - Google Patents

Description

PATENT ADVOCATE « DIPII.-ING. AMTHOB DIPL-IIfG. WOtF

Γ »- β FHANKFUBT AX SKIN

-β FBANXFTTHT A. M., Λ "J 2.69

(Oeil) 55 20 23 ^ q ggg

FMC Corporation, 1617 Pennsylvania Boulevard, Philadelphia, Pa. /UNITED STATES

Method and device for the production of webs from polymer »material with in certain patterns distributed, molecular-oriented areas

The invention relates to a method and an apparatus for the production of polymeric webs or films of high strength, rigidity and wear resistance,

in U.S. Patent 3,386,876 is a method and Apparatus for producing a non-rectified network structure disclosed, according to which an unoriented film of thermoplastic, polymeric material is provided with a certain pattern of perforations, so that the film areas between the Holes are given the shape of webs, each having a narrow section and being widest towards their ends, in front the perforated film is stretched in at least one of its two main axis directions. to widen the hole openings and to stretch at least certain webs in one axial direction.

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Albeit a certain amount of leeway with regard to the shape of the hole and the. Hole spacing in the starting film and with regard to the thickness of the stretching is given, these factors are, however regulated in such a way that orientation is limited to selected areas of the film and the guarantee is even more specific is that the oriented webs run out or are connected to unstretched film areas or connection points.

During the stretching of the perforated film, the webs are increasingly in the direction of the applied stretching or tensile forces oriented. That means, with the pull in one axial direction, which is exerted on each subsequent group of parallel webs which occur at the same time, and with the long distances in the longitudinal direction of the web up to a predetermined degree before the train begins in the neighboring group with this in-line webs. According to the instructions of this patent specification, two basic requirements must be met, to ensure perfect stretching, as follows:

(1) ridges that pull in a parallel direction to each other must be sifted to practically the same level,

(2) Bars that are to be drawn in a row with one another,

must have a comparable cross-section »so that a stretch begins in a group of bridges that are still unstretched,.

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after the stretching process in the neighboring group of webs is completed and before these webs stretched in this way over their tear limit or over a predetermined point have been stretched out, which is still compatible with the other drawing process to be carried out or carried out. In particular should furthermore, according to the aforementioned patent specification, the distance, of the perforations produced in the unoriented film must be such that the ratio between the widest and the narrowest Dividing the webs is at least equal to the ratio between the required force, which is necessary for a long pulling of the webs and the force required to maintain the train once the webs have given way to have. Are such bars up to the maximum permissible dimensions elongated, then represents the line that denotes the end of such an elongated web and in the patent specification "Zuglinie" is called, approximates the maximum achievable length, and that can be achieved without the connecting piece between the ends of adjacent webs having experienced any stretching and without, that the stretch line of a web does not intervene in the tension lines of the other webs at such a connection point or this crosses.

For cases where an openwork product finished If the product is not satisfied, you can also use the above-mentioned patent specification and select the spacing

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paint or dye or otherwise cover areas of an unoriented thermoplastic film that are separate from one another with a black or other heat-absorbing pigment. These coated areas would then correspond to the perforations in the film and by biaxial stretching of such a film under working conditions such as those for hot stretching, e.g. by means of heat irradiation, the coated areas would absorb most of the heat and therefore give way without becoming oriented if the. Film is exposed to stretching forces. On the other hand, only the uncovered web surfaces would react to the stretching forces exerted along their respective longitudinal axes and would thereby be uniaxially stretched, while the connections between these extended webs would remain unstretched.

According to another embodiment, this patent specification also provides, instead of the aforementioned coating or in combination with it, a heat-reflecting material, such as aluminum paint, to be applied to the oriented polymer film in a specific pattern corresponding to the desired arrangement of webs and unstretched connections. Through the biaxial orientation by means of hot stretching, the web areas with their heat-reflecting coating are then heated the least and experience a uniaxial orientation, while the

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coated areas would yield in biaxial directions.

While stretching the film with a coat of heat absorbing material and / or heat reflective material according to the above patent specification softened the covered areas of the film so far that the coatings are gradually thinner and thus in their intended mode of action with continued The stretches of the film increasingly diminish.

U.S. Patent 3,255,065 relates to a method and apparatus for making composite films by laminating or otherwise combining an uninterrupted and unoriented film of thermoplastic polymer with a similar film, but which has a certain perforation pattern, as described in patent specification 3,386,876 ben - and then by stretching this layer structure in the desired directions.

By stretching such a layer structure in longitudinal, vie in transverse directions, the parts of the uninterrupted film that cover the perforations of the perforated film, biaxially oriented. The webs of the perforated film with the overlying parts of the uninterrupted film are oriented in only one axial direction and thus result in the desired rigidity of the finished composition film, while

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the parts of the layer structure that lie between the ends of such webs remain unstretched.

Making composite films by the process the American patent 3,255,065 initially requires for itself the production of unoriented films from thermoplastic polymer! Material, then the punching of one film, furthermore the lamination of non-perforated with perforated film and finally the biaxial stretching of the finished layer structure. These make various stages of work as they must be carried out with great care if proper film punching is to be achieved and layering should be guaranteed, this patented work process is slow and costly.

Accordingly, it is the primary object of the present invention Line to provide a more satisfactory way of working and a device to make webs or sheets of polymeric Obtain material that has good strength and stiffness in desired directions as well as better wear resistance properties exhibit·

Another object is an improved method and apparatus for making a web or film of polymeric material of uniform thickness throughout with a certain patterns. uniaxial and biaxially oriented surfaces.

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Furthermore, according to the invention, a method and a device are to be created in order to achieve a controlled orientation in the event of a problem to facilitate perforated films or tracks along selected areas of the same.

Finally, it is a further object to provide a method and an apparatus for producing openwork polymeric webs or Films with a mainly imperceptible network of uniaxially oriented, longitudinal and transverse directions Produce webs, the ends of which are separated from each other.

For a better understanding of the invention, reference is made to the following Description in detail referred to the drawing in which

Fig. 1 shows a schematic side view of a device according to the invention.

Fig. 2 is a front view of part of a chill roll,

as it is used in the device according to FIG. 1;

FIG. 3 is a perspective view of a portion of a polymeric sheet material produced by the method of FIG Invention is made;

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4 is a perspective view of the web of FIG. 3 after biaxial stretching in accordance with the invention and FIG

5 shows a plan view of a biaxially oriented material, as it is produced by a modified procedure according to the invention.

The foregoing and other objects of the invention are accomplished by a method and apparatus to which selected and spaced apart areas of an extruded flat, uninterrupted stream of flowable film-forming polymeric material, which areas are longitudinally aligned and as well in the transverse direction as well as essentially the same shape, can be stamped out of the surface of the extruded stream as long as the material is still in a flowable state, without interrupting the continuously unbroken stream of material, whereupon the stream is solidified to form a self-supporting path or to obtain a self-supporting film and finally stretching the sheet or film in biaxial directions. The term “surface” is understood throughout the description and claims as a geometric term, ie as a two-dimensional geometric location of points. Thus, the expression "surface ¹ * also includes streams of film-forming material that are both flat and those that are curved or curved.

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13618 IS

During the biaxial stretching of the web or film the areas between the selected sections in a row in an axial direction, namely transversely oriented to the web or film direction, while the areas which are oriented longitudinally adjacent to the selected ones Partial areas can also be oriented in one axial direction, but in one direction along the path or the direction runs. Other regions of the web or film, including the selected areas, can also be biaxial be oriented.

It is important that the selected and spaced areas are forced out of the surface of the extruded stream of film-forming material without breaking the stream and that these areas are free of sharp corners. Such sections can, for example, be round or elliptical in shape or in the shape of rectangles with rounded corners . These selected areas can be forced out of the surface of the extruded stream while the material which forms is in such a state that neither orientation, n:, c'a biaxial orientation of the polymer molecules occurs within their sections. For example, with <? Ίη ~ :? ^ ahn or a film of thermoplastic polymer material push the selected areas out of the surface of the stream, while the thermoplastic material des-

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same is still in a highly molten state, so that no molecular orientation along such areas takes place. On the other hand, the selected areas can also be printed out of the surface, while the thermoplastic polymeric material that forms is at the orientation temperature, i.e. at a temperature above the second degree of transition of the temperature of the polymeric material and below the temperature at which relaxation the orientation effect achieved by stretching occurs so quickly that the stretched structure as soon as the Stretching stops, no noticeable orientation is left behind.

The degree to which the selected areas are removed from the stream of the film-forming material, embossed from the surface Desirably, in the eventual biaxially stretched web or film, those selected Areas generally lie in the same plane as the bars.

During the stretching stage of the process of the invention For example, the webs or films are preferably drawn or stretched in two directions, i.e. biaxially, in order to thereby achieve the resultant oriented webs or films, tensile strength, flexural strength and high tear resistance that are as desirable as possible granted.

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It is desirable to have such a degree of biaxial stretching that the boundary lines the areas drawn in one axial direction are connected to normal, unstretched web or film parts, without interfering with one another.

Oriented webs of the manufacture of the present invention are useful in a variety of applications, e.g. for protective covers or sleeves such as shields for construction, wrapping materials for packaging or bagging, and for inflatable structures such as observation balloons, life rafts and others.

Albeit the method according to the present invention in particular is suitable for use with thermoplastic polymeric materials such as polypropylene, polyethylene and Polyesters, it is also very well suited for an application with orientable polymeric film-forming materials that be converted into solid films by chemical reactions. For example, using the teachings of the present Invention comprises selected, spaced apart portions of an extruded flat endless stream of viscose the material and such a stream before its concuaculation and after the solidification of the viscose to one Film and then stretch the film before the material thereof is regenerated.

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The apparatus of the present invention includes devices for extruding a continuous flat unbroken stream of flowable film-forming material, one endless movable carrier, ζ. B. a conveyor belt, preferably a roller, which is arranged so that they the flat unbroken Record current of the film-forming material on their peripheral surfaces can, as it emerges from the extrusion devices and with the roller at intervals deep embossing its' surface has, which are arranged substantially in the longitudinal direction and circumferential direction in line and wherein a device for Apply a vacuum to these recesses of the roll and means for stretching the web or film are in place as soon as they are in place The film or web solidify on the roll, at least to stretch in one of two biaxial directions. The depressions in the roller are smooth and should have rounded walls throughout or can also have a flat bottom. As Already mentioned above and subsequently described in detail, the present invention is particularly suitable for use with thermoplastic polymeric film-forming materials materials. In the case of such thermoplastic materials, the roll in the used apparatus should be cooled in order to produce the extruded To convert material on the roller into a self-supporting film.

For a detailed description of the method and apparatus of the present invention, reference is made to FIG

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Fig. 1 of the drawing, in which the number 15 denotes a pouring approach or a nozzle, as they are usually used as a working part Extrusion lines are common and from the flatter unbroken Stream 17 molten thermoplastic polymeric Ma-r material, such as polypropylene, is pressed out. The pressed stream 17 is taken up by the cooling roller 19, which is with a central rotatable hollow shaft 21 is provided and deep embossing or has cups 23 which are formed on their peripheral surface. These impressions 23 are practically the same both in their shape as well as in their depth and are in the longitudinal direction and circumferential direction on the roll surface arranged in series. The roller 19 is by a circulating cooling liquid, which one on its inner surface in usual Way circular lets chilled. In order to let the roller rotate continuously, one uses a conventional drive, the is not shown and with the aid of which the roller is given a uniform rotational speed in the direction of arrow 25.

The troughs 23 in the roller are each designed so that they are through special pipes 27, which in the corresponding Hollow troughs of the roller open out, let suction and these lines are led through the hollow shaft 21 and connect to a line 29 which is located in the hollow shaft 21. The administration 29 rotates with the roller 19 and its shaft 21 is hatched to any suitable evacuation device, as indicated by the arrow 31. Special facilities like s, B,

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a fixed plate 33, with respect to which the line 29 can rotate relatively, can be arranged in the line 29, in order to close off the individual lines 27 at points where the depressions 23 of the roller do not need to be sucked dry is, as will be described in more detail later.

As soon as the stream 17 of molten thermoplastic material hits the surface of the roller 19, those parts of the stream that lie over the troughs 23 are sucked into them and against the trough walls, as indicated by 35, by the applied vacuum through the pipes 27 and the lines 29. The thermoplastic material of the stream 17 remains flowable for a certain period of time after its first contact and also over a certain section of its arcuate path around the cooling roller 19 and precisely during this period in which selected sections of such Stream 17 are sucked into the depressions 23 of the roller. Due to the initial contact with the chill roll 19, the parts of the flow which overlap or span the troughs 23 of the chill roll experience a slight cooling until they are drawn into the trough recesses by the applied vacuum. As a result, no noticeable molecular orientation occurs in any areas of the flow when it rotates with the cooling roller 19 and is consolidated into a self-supporting web 37 \ ^y .

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This solidified web 37 is then pulled off the cooling roll 19 with the aid of a stripping roll 19, and as can be seen in FIG. 3 sees, it is continuous and uninterrupted with its slightly upwardly projecting portions 35, which in the longitudinal and transverse directions of the film are aligned in a row.

As soon as the web is pulled off the cooling roll 19, it becomes biaxially directly, either simultaneously or in special work stages, preferably by simultaneously performing a Orientation temperature required height for the respective polymeric material from which the web 37 is made. In a device as shown in FIG the web is stretched biaxially at the same time. More precisely, from the stripping roller 39, the web 37 migrates between a in Spaced pair of take-off rollers 41 and 43, respectively in the orientations illustrated by arrows rotate, but wherein the take-off rollers 43 rotate at a higher rotational speed than the rollers 41, whereby they cause a longitudinal stretching of the web.

During the path between the pairs of pulling rollers 41 and 43, the web is also stretched in the transverse direction by conventional means Facilities, as indicated generally at 45. Such devices 45 include, for example, clips 47 which hold the web in place grab opposite longitudinal edges as well as guides 49, for

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Conducting the brackets that have attacked the opposite edges and led on paths that lie apart should be when they move away from the take-off rollers 4I and run towards the pulling rollers 43. These clamps 47 are moved forward along these diverging paths gradually increasing speed, as determined by the longitudinal stretching forces that be exerted on the web 47 by the take-off rollers 43. Infrared heating sources 51 are provided for heating the web to the desired orientation temperature during stretching and a cooling roller 53 can also be provided for cooling the web after it has been stretched.

Corresponding to the stretching forces running in the longitudinal direction, the dashed areas 55 according to FIG. 3, which run transversely to the web 37, are drawn in the longitudinal direction at intervals so that their molecules are oriented. At the same time , the dashed areas 57, which run in the longitudinal direction of the web 37, specifically in the transverse direction in each case at a distance from one another, so that their molecules are oriented. The selected areas 35, which lie outside the plane of the web 37, experience neither the action of stretching forces in the longitudinal nor in the transverse direction and as a result remain unoriented. The areas of the web as a whole around these selected areas are stretched and so all parts of the web which leave the pulling rollers 43 and are through the roller lie

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- 17 53 is cooled essentially in the same plane.

In the web shown in FIG. 4, after it has been cooled, the selected areas 35 are unstretched, while the webs 37 between the longitudinally aligned areas 35 and the webs 59 between the transversely aligned areas 35 in each case are stretched in an axial direction and oriented in the directions as indicated by the double arrows in the corresponding Bridges are indicated. The remaining areas 61 of the web 37 are exposed to stretching forces in the longitudinal as well as in the transverse direction that one can see through the intersecting arrows and as a result their molecules have been oriented biaxially.

The webs 57 and 59, which are oriented in one axial direction, give the webs of the web 37 special features in the corresponding directions Flexural rigidity and, together with the biaxially oriented areas 61, an increased tensile strength of the web. the unoriented areas 35 are well insulated from one another by the surrounding orienting webs 57 and 59 and bars good services for inhibiting tearing that could start elsewhere on the web.

Even if the size, shape and / or outline of such are selected unoriented areas 35, which are formed in the !! »oriented track section 37» can »vary * in order to end up with them finished direct product certain desired flexural strength "

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To obtain speed and other strength properties, such areas should be of essentially the same size and in the longitudinal and transverse directions of the web in alignment and equidistant from each other in their respective Longitudinal and transverse directions.

The procedure described above can easily be modified by delayed evacuation of the cooling roller troughs 23 to the stream 17 of molten polymeric material after its placement on the cooling roll 19 is on the for such a polymer Material has cooled down to the appropriate orientation temperature. In this way, the selected areas 35 become simultaneously biaxially oriented as soon as they are embossed from the surface of the stream 17. After such a stream solidifies it is subjected to biaxially directed stretching forces in a manner as described above. That web material resulting from such an operation, as seen at 63 in FIG. 5, is similar to that shown in FIG 4, with the exception that the selected areas 65 have been biaxially oriented. While the biaxially oriented areas 65 of the web 63 are not able to inhibit the web from tearing, like that in the unoriented area. 35 of the web 37 is the case »

however, convey such biaxially oriented areas 63 Railway has the property of improved tensile strength.

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Claims (9)

Expectations π J method of making a web polymeric, with a certain patterns of molecularly oriented parts, from a flat flowable extruded uninterrupted Stream of film-forming material, characterized that selected, spaced apart regions of the extruded web, which are in alignment in the longitudinal and transverse directions of the web and have essentially the same shape from the web surface be pushed out without interrupting the context as long as the material of the extruded stream is still in is flowable, the stream is solidified into a self-supporting web and the web is biaxially stretched, so that the portions of the web between adjacent transversely juxtaposed areas in a single Axial direction are oriented in the web transverse direction, the web areas are oriented in the longitudinal direction of the web and biaxially orienting at least some of the remaining areas of the web. 2. The method according to claim 1, characterized in that that the selected areas are free of sharp corners and consistently smooth, e.g. circular Have construction. 009828/1768 So 3. The method according to claims 1 or 2, characterized in that that the web is made of thermoplastic material and the selected areas the surface of the web material, which is still in the molten state, can be pressed out in such a way without that a remarkable orientation is thereby produced in it. 4. The method according to claims 1 or 2, characterized that in the manufacture of the sheet of thermoplastic material the expression of the special Areas out of the plane of the path during the state of the thermoplastic material at the orientation temperature, whereby the molecules are biaxially oriented along such areas. 5. The method according to one or more of claims 1-4, characterized in that the Forms a web of thermoplastic, film-forming material, so that the boundary lines that mark the ends of axially drawn areas that are at common naughty Parts of the track end, do not intermesh. 6. The method according to claim 5, characterized in that said areas from the upper 009828/1768 surface of the extruded stream are so pronounced that they are practically not subject to any orientation during of stretching these areas and generally in the plane of these regional sections once the web is in biaxial Direction is stretched. 7. The method according to claims 1 or 2, characterized in that the flowable, film-forming Material is viscose and where the selected areas of the squeezed stream are out of the plane of the stream before it Coagulation will be squeezed out and the regions will be stretched after a coagulation of the film forming Material has taken place, but before its regeneration. 8. Apparatus for producing a polymeric material according to the method according to any one of claims 1-7, characterized through means for extruding an endless, flat, unbroken stream of fluid, film-forming Material, a consumer with this unbroken stream being deposited on its surface after it has emerged from the extruder, with the drive device, the doffer for removal and in the doffing surface lengthways and across Escape to these recessed points provided and into these opening arrangements for creating a vacuum, Means for solidifying the extrusion stream to a ../4 009828/1768 -y- self-supporting web and means for stretching it in at least one of its biaxial directions. 9. Apparatus according to claim 8, characterized that the taker is a chill roll. 009828/1768