DE2152060A1 - Extruding hollow thermoplastics sheet - by sliding between stationary shaping plates with suction application of sheet - Google Patents

Abstract

A method for making a hollow thermoplastics sheet with smooth outer surfaces consists of extruding thermoplastics sheet through a hollow-sheet nozzle, then passing it through a shaping zone formed by upper and lower plates associated with suction appts. to apply the surface of the sheet to these plates; on entering this zone, the surface condition of the sheet is such that it will not adhere to the plates, though the sheet is still easily deformable; during forming, the sheet is cooled, and opt. further cooled after leaving the former. Pref. the surface is slightly hardened by blown air before the sheet enters the former; materials treated in this way are e.g. polyethylene, polypropylene, an ethylene/propylene copolymer or a mixture of polyethylene and polypropylene.

Description

Method of making a hollow sheet from a thermoplastic Synthetic resin The invention relates to a method for producing a hollow film with a large percentage of voids at low cost and on continuous Way that is suitable for many purposes, taking advantage of the characteristic Properties of thermoplastic synthetic resins.

As a result of an amazing recent development in the field the petrochemical industry are constantly large amounts of thermoplastic synthetic resins, z. B. in particular poly-a-olefins, such as polyethylene and polypropylene, produced and for various purposes as a substitute for common natural substances used. In particular because of their property of thermoplasticity, which is natural If there are no substances present, such synthetic resins can be easily deformed when heated and therefore easily deformed into intricate shapes. Because of this will be the thermoplastic synthetic resins are used in a wide variety of fields.

An object of the present invention is: to provide a method of manufacture a hollow sheet made of a thermoplastic synthetic resin with the aid of a device specify which is structured in such a way that the properties of the thermoplastic synthetic resin, d. H. the deformability of the resin according to the temperatures used, can be fully exploited, so that every part of the device is subject to the changes the physical state of the resin from the softened state at increased Temperatures adjusted to the fully cured state at room temperature is.

The above synthetic resin films have been produced in such a way that a synthetic resin material softened under the influence of heat with the aid of quenching rollers (Chill rolls) calendered or a molten film extruded through a die Quenched on a chilled plate or pressurized by air or water was deterred. However, these conventional methods are for manufacturing of hollow foils with an intricate Structure not suitable, because of the uneven cooling and the external forces that existed at the time of There is a tendency to deformation because of the resin layers are thin compared to the total thickness of the film. To avoid these difficulties, a method for forming a hollow sheet has already been proposed in which a hot, hollow film extruded through a nozzle between two ribbons with a large number of holes is held and both sides of the foil can be sucked onto the belts and put them together with the belts between chill rolls leads through. With this deformation method, however, the hollow film hardens, while she is sucked onto the ligaments and therefore those parts of the hollow Foil, which are in contact with the suction holes, hardened while they are being removed from the protrude from other parts of the film.

Such a disadvantage makes this deformation method unsuitable for the production of a hollow foil with smooth surfaces.

Another object of the present invention is to provide a method specify for the production of a hollow foil with a complicated structure, which does not have the disadvantages mentioned above.

Accordingly, the present invention relates to a method of manufacture a hollow film made of a thermoplastic synthetic resin with smooth surfaces at least in the machine direction, that is characterized by that at least one molten thermoplastic resin from a nozzle extruded into a hollow sheet, the hollow sheet extruded in this way in introduces a shaping zone that has at least a pair of upper and lower smooth Has surfaces with a desired shape, the surfaces being practical at the same distance as the thickness of the hollow foil entering the zone are arranged and with at least one suction device and at least one Cooling device is provided, the hollow film entering the zone in is in such a state that it does not stick to it when it is with the surface comes into contact, but that they are deformed even by a small force can, wherein the hollow film is cooled in this zone by the cooling device and sucked by the suction means so as to both surfaces of the sheet practically # in full contact with the top and bottom surfaces of the zone and in which they are under pressure along the surfaces of the zone is guided, whereby the sucked-in point of the film is continuously shifted and the shape of the film is brought into the desired shape and as required the thus formed hollow sheet is further cooled to fix the shape of the sheet.

The present invention will hereinafter be described with reference to FIG explained in more detail in the accompanying drawings. Therein mean: Fig. 1 a schematic view showing a cross section through a thermoplastic Represents synthetic resin-made hollow sheet; Fig. 2 is a schematic view, which is an embodiment of a device for producing a represents hollow foil; Fig. 3 shows a longitudinal section # through a suction, cooling and Curing unit of a hollow film according to the invention; Fig. 4 is a partially planar Plan view of the unit according to FIG. 3; Fig. 5 is a schematic view of a other Ausfü ehungsform, which corresponds to FIG. 2; Fig. 6 is a longitudinal section through the embodiment according to FIG. 5, which corresponds to FIG. 3, and FIG. 7 is a partial plan view of FIG. 6.

In Fig. 1 of the accompanying drawings are several examples of cross-sections represented by hollow foils. According to the method according to the invention can also hollow foils with different internal structures than those shown in these examples provided that the film surfaces are smooth in the machine direction are.

In Fig. 2 of the accompanying drawings, reference numeral 1 denotes a Nozzle mandrel, the reference pin 2 a nozzle lip and these provide a nozzle for the Extrusion of a hollow film with a cross section as shown in FIGS. La to 1b is shown. When extruding into a hollow sheet can sometimes be inside a partial vacuum is created in the cavities and in this case it is necessary to that air is allowed to flow into the cavities or air under pressure into the cavities introduces. To meet this requirement, the mandrel 1 is provided with an air passage 3 provided.

Since the viscosity of a thermoplastic resin, e.g. B. one Poly - «- olefins, such as polyethylene, polypropylene, ethylene / propylene copolymers a mixture of polyethylene and polypropylene; a styrene resin such as polystyrene, an AS or ABS resin; of polyvinyl chloride, polyvinylidene chloride, methyl methacrylate resin, Methyl acrylate resin; a polyamide, e.g. E.g. nylon-6 or nylon-66; a polycarbonate; of polyethylene terephthalate or the like., Is so low that it is difficult to obtain the Maintain original shape when melted and out of an extruder is extruded through an orifice in the molten state, the extrudate should cooled quickly to maintain its extruded shape, and it should be cured quickly so that it has smooth and fine surfaces. For this Reasons the hollow sheet 4 extruded through the nozzle becomes instantly into the shaping zone, e.g. B. a molding and cooling apparatus 5 of FIG. 2; introduced, which consists of an upper part 6 and anem lower part 7, both in one predetermined distance are attached opposite each other. These parts 6 and 7 have widths which are greater than that of the film to be passed between them.

The upper and lower parts 6 and 7 are provided with at least one suction groove 8 which are perpendicular to the machine direction at a given distance extends as shown in FIG. Periodically are in each Groove suction openings, e.g. B. suction holes 9 are provided.

When entering between the upper part 6 and the lower part 7 of the Forming and cooling device 5, the hollow film 4 against the surfaces 10 of the upper part 6 and the lower part 7 sucked and loosely brought into contact therewith due to the vacuum created between the hollow sheet 4 and the groove 8 as a result the suction of air is generated in the vicinity of the grooves 8 through the suction holes 9 will. At this stage the film still has a low viscosity because of its temperature is close to the extrusion temperature. As a result appear when the relative position of the hollow film 4 to the grooves 8 remains unchanged the surfaces of the film on the part that has the suction grooves 8, in particular the Suction holes 9, opposite, suction marks. To prevent this disadvantage, is allowed according to the invention the hollow sheet 4 between the upper Part 6 and the lower part -7 of the molding and cooling device 5, which is stationary, move. Therefore, the sucked point of the hollow film 4 is continuously displaced, so that the suction is applied to the entire slide. The use of the surface 10 of the top and bottom parts made smooth and flat in the machine direction have been, it allows the hollow film, which along the surface 10 along slides, is smoothed and allows the surface shape of the film to be adjusted to the desired shape while the film is being cooled and cured and wherein Finally the shape is fixed, the cooling devices 11 are parallel to each other and arranged in the vicinity of the suction grooves 8 in the upper part 6 and the lower part 7, so that the suction through the grooves 8 be carried out at suitable temperatures can by circulating a cooling liquid through the cooling devices. the -Suction holes 9 are with the suction opening of a vacuum pump or a blower tied together. The suction pressure is adjusted so that there is a suitable suction force at the grooves 8 receives. For foils with thin surface layers on both sides, such as B. the hollow sheet 4, it is necessary that the suction pressure and size the suction grooves 8 is precisely controlled.

While the hollow extruded from the nozzle in a molten state When the slide passes a series of suction grooves 8, the surface shape of the slide becomes gradually adjusted to the shape of the sliding surface 10 in the machine direction and the surface of the film is smoothed, at the same time the film is cooled, to harden to a certain extent. Due to the low thermal conductivity of thermoplastic resin in general and because of its hollow structure however, with a high percentage of voids, the hollow sheet 4 lies in some Cases still in a softened state by being neither completely cooled down is still fully cured.

In these cases, the hollow film 4 comes after passing a A plurality of suction grooves 8 with the surfaces 13 of a cooling and fixing zone 12, which is provided in the upper part 6 and in the lower part 7, in sliding Contact, causing the film to fix the shape it has in the shaping zone assumed is being cooled. For this purpose, the surfaces 13 are designed so that they correspond to the shape of the shaping zone for complete contact to ensure between the surfaces 13 and the film surfaces. As a cooling and fusing zone 12 is preferably a water cooling jacket with a smooth surface 13 used. In order to achieve closer contact between the hollow film 4 and the surface 13 To ensure the cooling and fixing zone 12, some suction grooves 14 are provided with suction holes 15 preferably as a suction zone in the vicinity of the cooling and fixing zone or on one suitable location of the cooling and fixing zone attached, the hollow Foil 4, which has been deformed and smoothed to the predetermined shape, is carried out at a regular speed with the help of a take-off device, consisting of a pair of conveyor belts 16 or a clamping device then cut to the desired length with the help of a cutter 17 and transported further, by holding them between a pair of rollers 18.

An example of another embodiment is shown in FIGS 7 of the accompanying drawings. In this embodiment, the hollow film 4 between the nozzle and the forming and cooling device 5 in the first Embodiment an air stream 20 from nozzles with a suitable temperature, a exposed to suitable fan pressure and flow rate, so that only the outer skins, i.e. the outermost layers of skin on both sides the hollow foil1 bits must be cooled to solidify. The term used here "Air of a suitable temperature, a suitable fan pressure and a suitable one Flow rate "means that this air is capable of only the to cool the outer skin of the hollow film to a suitable temperature without a Cause distortion of the film. The surfaces of the hollow film that are on the have been brought to a suitable temperature, are neither so soft that the film surfaces scratched or stuck, no matter how hard that the film is not deformed will when it enters the shaping zone or the molding and cooling device 5. Accordingly, the film is easy to handle and the processing conditions can be selected within a wider range so that the permanent and effective production of hollow foils with smooth surfaces becomes possible.

Example 1 (Figures 2 to 4) Using an ordinary extruder and a nozzle for a hollow film with the cross section shown in Fig. 1a became polypropylene with a melt index of 0.4 at a die temperature of 200 0C and between a pair of first upper and lower suction grooves at 1300C and 569 mm Hg and a second pair of upper and lower suction grooves passed through at 800C and 460 mm Hg, each pair in a pair of top and lower parts were arranged facing each other at a distance of 5 mm as shown in FIG. The received Slides were then brought into contact with a water jacket by adding water of 150C and then it was removed with a conveyor belt take-off device withdrawn and obtained continuously at a speed of 1000 mm / minute hollow foils with a thickness of 5 mm and a basis weight of 1000 g / m2.

Example 2 Using an ordinary extruder and a A nozzle for a hollow film with the cross section shown in Fig. 1b was a High density polyethylene with a melt index of 0.04 at nozzle temperature extruded from 2300C and then passed through a molding and cooling device, in which the upper part and the lower part at a distance of 2 mm from each other and in which the temperature and pressure of the suction groove 1000C and 1000C, respectively. 560 mm Hg. The resulting hollow film was then with a The water jacket was brought into contact, then a water of 400C was circulated it was peeled off by means of a conveyor take-off device and obtained continuously at a speed of 2000 mm / minute hollow films with a Thickness of 2 mm and a basis weight of 500 g / m2.

Example 3 (Figures 5 to 73 Using an ordinary extruder and a nozzle for a hollow film with the cross section shown in Fig. 1a became polypropylene with a melt index of 0.4 at a die temperature of 2100C extruded # As shown in Figure 5, the extrudate was a stream of air of 300C, which comes from a nozzle with an inner diameter of 4 mm with a speed of 20 mm / second, which emerged at a distance of 30 mm of the extrudate was placed, then the extrudate immediately through a molding and cooling apparatus having a first pair of suction grooves of FIG 150 ° C and 560 mm; g and a second pair of suction grooves of 100 ° C and 360 mm Hg (the distance between the upper and lower parts was 4 mm} passed through it. The resulting hollow film was brought into contact with a water jacket, by circulating water of 140 c to cool the film, thereby continuously at a speed of 2000 mm / minute hollow foils with a thickness of 4 mm and with a basis weight of 700 g / m2.

The above procedure was repeated with no air flow this time was allowed to act on the extrudate. The surface of the extrudate became rough and the speed of movement of the extrudate fluctuated intermittently, so that a continuous production of hollow foils was not possible.

Example 4 Using an ordinary extruder and a A nozzle for a hollow film with the cross-section shown in FIG. 1b was a High density polyethylene with a melt index of 0.04 at nozzle temperature extruded from 2000C. As shown in Figure 5, the extrudate was subjected to a stream of air exposed to 230C at a speed of 40 m / second from a nozzle emerged with an inner diameter of 4 mm, which in a distance 30 mm from the extrudate, after which the extrudate was immediately through guided a molding and cooling apparatus that had a first pair of suction grooves of 1000 c and 560 mm Hg and a second pair of suction grooves of 1000 C and 360 mm Hg (the Distance between the upper and lower parts was 1.8 mm). The one with it The obtained hollow sheet was provided with a water jacket in which water of 140C was circulated was brought into contact to cool the film, thereby continuously with a speed of 4000 mm / min. hollow foils with a thickness of 1.8 mm and with an Easisgewicllt of 350 g / m2.

Example 5 Using an ordinary extruder and a Nozzle for a hollow film with the cross-section shown in Fig. 1c, vylon-6 extruded at a die temperature of 250 ° C and the extrudate was a stream of air of 25 ° C, which comes out of a nozzle at a speed of 8.3 m / second with an inner diameter of 4 mm that stepped out at a distance of 30 mm from the extrudate was attached, then the extrudate was immediately through a mold and cooling device, in which the upper part and the lower part in one Distance of 3 mm from each other and in which the temperature and the Pressure at the suction grooves was 1500G or 360 mm Hg. The resulting hollow Slide was subsequently with a water duck in the water of 150C was brought into contact to cool the film, whereby continuously at a speed of 2000 mm / min. hollow foils of a thickness of 3 mm and with a basis weight of 630 g / m2.

Example 6 Using an ordinary extruder and a Nozzle for a hollow film with the cross section shown in Fig. 1a was a Methyl methacrylate resin was extruded at a nozzle temperature of 235 ° C., then was exposed the extrudate to a stream of air at 25 ° C. at a rate of of 20 m / second from a nozzle with an internal diameter of 4 mm, the at a distance of 30 mm from the extrudate, after which the extrudate immediately passed through a molding and cooling device in which the upper part and the lower part were fixed at a distance of 4 mm from each other and in the the temperature and the pressure at the suction grooves 1300C resp.

460 mm Hg. The hollow sheet thereby obtained was then brought into contact with a water jacket in which water at 150C was circulated, to cool the foil, thereby continuously at a speed from 20002 mm / minute hollow foils 4 mm thick and with a basis weight of 980 g / m2, Example 7 Using an ordinary Extruder and a nozzle for a hollow film with the cross section shown in Fig. 1a an ABS resin was extruded at a die temperature of 2100 C and the extrudate was then exposed to a stream of air of 30 0C, which at a rate of 20 m / second from a nozzle with an inner diameter of 4 mm, which in a distance of 30 mm from the extrudate, after which the extrudate was immediately passed through a molding and cooling device in which the upper part and the lower part were fixed at a distance of 3 mm from each other and in which the temperature and pressure at the suction grooves were 1200C and 480 mm Hg, respectively. the The resulting hollow film was then # with a water jacket, item water of 150C was brought into contact to cool the film, whereby continuously at a speed of 1900 mm / minute hollow films with a Thickness of 3 mm and a basis weight of 550 g / m2.

Example 8 Using an ordinary extruder and a Nozzle for a hollow film with the cross-section shown in Fig. La was polystyrene at a die temperature of 2150C and the extrudate was then a Air flow of 300C emitted at a speed of 20 m / second a nozzle with an inner diameter of 4 mm, which emerged at a distance 30 mm from the extrudate, after which the extrudate immediately passed through guided a molding and cooling device, in which the upper part and the lower Part fixed at a distance of 4 mm from each other and in which the temperature and the pressure at the suction grooves were 1000C and 470 mmHg, respectively.

The resulting hollow film was then covered with a water jacket, in which water at 15 0C was circulated, brought into contact to cool the film, making hollow foils continuously at a speed of 1900 mm / minute with a thickness of 4 mm and a basis weight of 1020 g / m2.

Example 9 Using an ordinary extruder and a Nozzle for a hollow film with the cross section shown in Fig. La was polypropylene with a melt index of 0.4 at a die temperature of 2100C and then by a Forming and cooling device out in which the upper part and the lower part at a predetermined distance from each other were attached and which had a shape corresponding to that of Fig. le, the temperature and pressure at the suction grooves were 1500C and 350 mmHg, respectively. The resulting hollow film was then covered with a water jacket in which Water of 140C was circulated, brought into contact to cool the film, making hollow films continuously at a speed of 500 mm / minute with the cross section according to Fig. Le with a maximum thickness of 5 mm and a basis weight of 1000 g / m2.

Claims (7)

P a t e n t a n s p r ü c h e Method of making a hollow sheet from a thermoplastic Synthetic resin with smooth surfaces at least in the machine direction, characterized in that that at least one molten thermoplastic resin from a nozzle for a hollow sheet, the hollow sheet thus extruded into introduces a shaping zone that has at least a pair of upper and lower smooth Has surfaces with a desired shape that are practically the same spacing spaced apart as the thickness of the hollow film upon entering this zone are and with at least one suction device and at least one cooling device are provided, the hollow film entering this zone in such a There is a condition that it does not stick to the surfaces when it is in contact therewith comes that it can still be deformed by a weak force, that the hollow film in this zone is cooled by the cooling device and by the suction device is sucked in, so that both surfaces of the film are practically completely with the upper and lower surfaces of the zone come into contact and that they are under pressure is slid along the surfaces of the zone, whereby the sucked Place the slide shifted continuously and the shape of the foil is brought to the desired shape and that the hollow sheet thus formed, if necessary to fix the shape of the film is further cooled. 2. The method according to claim 1, characterized in that as a thermoplastic Synthetic resin, polyethylene, polypropylene, an ethylene / propylene copolymer or a mixture of polyethylene and palypropylene is used. 3. The method according to claim 1, characterized in that the extruded hollow film with a stream of air at a suitable temperature, a suitable one Brought blower pressure and a suitable flow rate in contact before it enters the shaping zone to only the outer layers of the skin to harden the hollow foil. 4. The method according to claim 1, characterized in that in the cavities air is introduced into the hollow film through the nozzle. 5. The method according to claim 1, characterized in that the hollow Foil that has left the shaping zone on the surfaces of a pair of upper and lower water cooling jackets which are the same shape as the surface the shape of the giving zone and which are at the same distance as / between to the Pairs of surfaces are attached in this zone, are slid along, to cool the film and fix the shape of the film. 6. The method according to claim 5, characterized in that the water cooling jackets have a suction device at a suitable point in order to maintain contact between the hollow foil and the surfaces of the jackets. 7. The method according to claim 1, characterized in that at least two pairs of upper and lower suction devices and at least two pairs of upper and lower cooling devices that are perpendicular to the machine direction extend, are provided in the shaping zone. Blank page