DE1629255A1 - Method and device for producing plastic films on the extruder, in particular rigid PVC, with certain technical properties - Google Patents

Description

Process and device for making plastic films on the extruder, esp. Rigid PVC, with certain technical properties The invention relates to a method and a device for the production of high quality films, esp. made of rigid PVC, on the extruder with certain technical properties, such as mechanical (Strength, elongation), thermal (shrinkage) and optical (transparens, gloss) Properties, these properties being within wide limits in the manufacture of Slides are adjustable.

In order to clarify the advantages of the method according to the invention, appears it is necessary to change the changes made when processing thermoplastics to explain the technical properties in more detail. Essential feature of thermoplastics represents the change in its plasticity with temperature. This results in cause the different processing possibilities of thermoplastics. That at Ordinary temperature solid material will ii range of softening temperature more elastic and goes at higher temperature (above the flow temperature) into the plastic state, and finally when the temperature rises still further to decompose. Depending on the material, there are naturally more or less pronounced transitions between dos technological state. Experience has shown are the elastic and plastic areas for rigid PVC somewhat as follows; Room temperature up to 850 s fixed range 85 - 100 ° = softening range 10 # - 175 ° = more thermoplastic Area 175 - 190 ° = flowing area 190 - 200 ° = thermoplastic area over 200 ° - decomposition @ area (see Schenkel "Kunststeff-Extrudert @@ huit, Ha @@ er Verlag, @@@ e @ en, 1963, page 95) Like from Bbb. 1 can be seen Experience has shown that there are two temperature ranges in which the material is stretched to the maximum can be. The first area is slightly above the softening temperature (ET), i.e. in the thermoelastic range. When the material is stretched in this temperature range the technical properties are influenced in the following way: strength, Shrinkage, transparency and gloss increase; the elongation (drawability) decreases against it.

The strength, shrinkage and elongation are related to the extension the slide in direct context. It can therefore films with certain technical Properties are specifically produced.

The second range is above the flow temperature (FT), depending on higher above it - but still below the decomposition temperature - the greater it is the possible stretch. Since the stretching takes place in the thermoplastic area, this is largely without orientation (see "Research reports of the Ministry of Economics and Transport North Rhine-Westphalia ", No. 304," Contribution to the ther @ oelastic hot formability of hard polyvinyl chloride (hard PVC) ", published by Westdeutscher Verlag, Cologne and Opladen, 1956, p. 48.

The film properties are observed, except for one at times Improvement of the impact strength otherwise kaui significantly influenced. the big advantage lies in the fact that the pile strength without any significant change in the properties of the film can be reduced. From this arises the possibility of using diokerus starting foils to produce dtinn.re without changing their technical properties.

The plastic foils produced up to now on the extruder, especially made of hard PVC, do not or only partially have the required properties. In addition, this can only be influenced within very narrow limits, as is the case with the introduction of extruded hard PVC films has significantly inhibited up to now. The one for polyolefino best practices have been adopted in general for rigid PVC films, with which allerdiag @ significant shortcomings in the technical characteristics these foils have been accepted.

In the known blown film process, the film leaves, e.g. with reference on Fig. 2, the blow head 1 in tubular form 2 and in predominantly thermoplastic State (Zone I in Fig. 2).

As a result of the cooling by means of a cooling ring, the film is in the area of the Transition zone II transferred to the thermoelastic state. Located in Zone III the film is already in the hard state. The film is peeled off at the same time and expanded by bubbles. Because the thermoplastic zone I is relatively short, the film is essentially stretched in transition zone II; therefore neither will a purely plastic or purely elastic stretch, but rather a stratification both elongation states are preserved. So in this slide there are at the same time Layers in the elastic and in the plastic state; this can mean that the Strength cannot be adjusted as desired by stretching. This also applies to the shrinkage and elongation increase. That is why the technical properties can also be found mixed before. The film does shrink as a result of the different layers with delay; In addition, the film lacks the elasticity.

A targeted production of foils with desired or specific technical properties for different uses is in this way not possible. The process is used to produce relatively thin films; however, these do not have the necessary strength.

The so-called chill roll process developed for polyolefins is also for the production of rigid PVC foils.

Since in this process with reference to Fig. 3 by the cooling roller 4 is cooled more intensely, zone I of the thermoplastic expansion is greatly shortened, transition zone II is also relatively short. The slide 5 is borrowed at very different Temperature layers stretched across the thickness; therefore, similar to the blown film, polien with mixed technical properties. The flat sheet is although it looks glossier due to the fact that it lies on the smooth roller surface, but it is more cross-spliced because it is peeled off at different temperatures than the blown film.

The inventors have now set themselves the task of making thermoplastic Films, especially rigid PVC films, utilizing the two temperature ranges discussed to produce films with certain technical properties. Solved this task is graded by the following process: a) The film is after their Exit from the nozzle as long as in the temperature range above the flow temperature (FT) of the thermoplastic elongation maximum held until the intended elongation is carried out. b) The film is, without stretching, up to the temperature range cooled above the softening temperature of the thermoelastic elongation maximum and kept at this temperature until the intended stretching is carried out is. c) The film is kept under tension to below the softening temperature (Freezing temperature).

In the method according to the invention, the elongation is both in the thermoplastic as well as in the thermoelastic area, steplessly independent of each other but directly performed one after the other in a heat.

The invention is based on the representations in AusfUhrungsbeispielen explained and illustrated in more detail. They show: Fig. 1 State diagram with expansion curves for thermoplastic materials; Fig. 2 shows a known device for manufacturing of tubular films using an extruder; Fig. 3 shows a known device for manufacturing of flat films by means of an extruder; Fig. 4 an embodiment of the device for Implementation of the method according to the invention for the production of tubular films by means of an extruder; Fig. 5 shows an embodiment of the device for performing the process according to the invention for producing flat films by means of an extruder; Fig. 6 temperature shrinkage @ diagre @@ with thermoplastic Materials.

In Figures 2 and 3, the known measures are Blown film process (Fig. 2) and chill roll process (Fig. 3) shown schematically. In Fig. 4 is an embodiment of a device developed according to the invention for the production of tubular films shown.

The one from the round nozzle 1 in the temperature range of the thermoplastic Extension maximum extruded tubular film 2 occurs in the first conical, at Temperieriantel 6 kept approximately the same temperature and becomes ion more usual Inflated way, i.e. the plastic expansion is mainly in the width direction exploited. The diameter ratio at the entry and exit of the film Coat determines the degree of stretch. In this way, the film then ends up in the second conical tempering jacket 7. This jacket has the temperature of the thermoelastic anticipation maximum.

The slight taper of this jacket runs counter to the running direction the film, so that it is now stretched in its longitudinal direction. The next temperature control jacket 8 has the same temperature as the previous one and is conical similar to the jacket 6 formed so that the expansion of the width of the film according to the diameter ratio is achieved. In the last jacket 9, the film is below the softening temperature cooled down.

With the device according to the invention so films with biaxial modified or improved properties are produced. To a better one To achieve sliding of the film on the inner surface of the jacket, these are more common Apply a thin layer of varnish.

In Fig. 5 is an embodiment of one made in accordance with the invention Device for the production of Flaohfolien by means of an extruder dargeatellt. From the film 5 emerging from the Breitsohlitzdüse 1 'meets heated, non-driven Rolls lo and 11, which have the temperature of the thermoplastic elongation maximum. The film is stretched as long as until the required thermoplastic Elongation is achieved.

The roller 12 has its own drive. It can therefore change the stretch ratio can be adjusted continuously. In order to prevent the film 5 from slipping on the roller To prevent 12, the film can be squeezed off with a rubber roller 13 if necessary will. The rollers 12 and 14 have the temperature of the thermoelastic elongation maximum. The take-off rollers 17, 18 allow the longitudinal expansion of the film 5 at that temperature can be adjusted continuously. The rollers 15 and 16 are cooled; thereby the Foil cooled below the freezing temperature under tension. The surfaces the rollers lo and 11 is mirror-finish chrome-plated to ensure a flawless film surface to obtain; if necessary, they can be coated with known release agents.

Both embodiments of the devices explained above according to the invention enable the implementation of the method. Some practical Examples are intended to highlight the essential differences between the films according to the known Explain the method and the inventive method below.

Exemplary embodiment no. 1: Production of a deep-drawable film with a thickness of 0.2 mm The normal slot die film, peeled off after cooling roller process, results in a relatively high shrinkage of over -40% for logo, The film produced on the device according to the invention, however, has only one Shrinkage of about -5%.

Embodiment Mr. 2s Production of an adhesive tape film with increased Strength at a film thickness of 0.05 mm The normal slot die film, Manufactured using the Kühlwalien method, results in only a slightly raised gani strength namely - instead of 500 kp / cm2 - 600 to 650 kp / ¢ m2 according to the invention The film produced by this method has a tear strength of 1,500 to 2,000 kgf / cm2 on; this means a very substantial saving in film thickness.

Embodiment # @: Manufacture of rigid PVC films with certain Shrinkage Both produced on conventional stretching machines and by extrusion Films can only be obtained with characteristic shrinkage. the end the temperature-shrinkage diagram (Fig. 6) are each a typical curve for the am Films A produced by extruder or normally stretched films B can be seen. the commercially available hard PVC shrink films B have too steep an angle of inclination α, i.e. they shrink too quickly and develop considerable forces through which the Packs can be deformed. As a result, the use of such films is largely restricted. On the other hand, that is normal. extruded film too weak and too slow in the shrinkage (angle α 'too small). With the devices according to the invention Depending on the temperature setting, all shrinkages between the course of the Shrink curves B and C are produced. To understand the possible differences in the technical To be able to compare properties better, these are in the following table compiled.

F-flat film Flat film Property blown film (cooling rollers according to the new process) Process Tear strength (2000) Soo - 600 Soo - 700 500 - 2000 (Kp / cm²) Elongation (%) 2o - So lo - 40 5 - loo (2000) Shrinkage -30-70% -30-70% -4-75% (at 100 ° C) Transparency medium good good Surface medium good good Appearance S streaks little little streaks streaks Drawability medium poor good The films produced by the inventive method on the extruder can be used for a wide variety of applications, aurgrund of @estimmten @ ecnn @ scnen Eigenenscna @ ten will. So z. B excellent deep-drawing films with very slight shrinkage at the deep-drawing temperature and reduced brittleness can be produced. The foils produced in the same way are particularly suitable for records; the transparent sleeves made from the film produced in this way show no stress whitening and have a higher number of alternating flexures.

In addition, films with the highest achievable strength values can be used for the production of adhesive tapes, tapes or the like. to serve. It is also possible, Shrink films with certain shrink forces according to the method according to the invention and thus avoid deformation of the packaged goods, which Disadvantage has so far been accepted with the common hard PVC shrink films is.

Those produced on the system according to the invention, withdrawn and Stretched thin films have an increased transparency and a potentiated surface gloss and significantly increased strength. Given these elevated values, the foils produced by the process according to the invention for use as Packaging and laminating film of particular importance.

Claims (5)

P a t e n t a n s r ü c h e (1.) Process for the production of plastic films on the extruder, especially hard PVO films with certain technical properties, characterized in that the extruded film (2) after leaving the die gap one or more @ ale in a heat immediately, optionally change @, in Temperature ranges above the flow temperature and above the softening temperature is stretched in such a way that a) great elongation above the flow temperature and only slight elongation above the softening temperature to be largely free of kinks Slides leads; b) high elongation above the flow temperature and high elongation above the softening temperature leads to largely shrinking films; c) great elongation above the flow temperature and high elongation far above the softening temperature according to the desired shrinkage angle to foils with prescribed shrinkage behavior leads. 2. Apparatus for performing the method according to claim 1 for the production of tubular films, characterized by several with separate temperature control provided, exchangeable, double-walled healing and cooling gowns in a row (6, 7, 8, 9) whereby the shells are conical depending on the required ratio are designed. 3. Apparatus according to claim 2, characterized in that the jacket inner surfaces are provided with a thin sliding layer. 4. Vorri.htung sur performing the method according to claim 1 for the production of fla @ hf @ lien, characterized by several successive ones provided with separate temperature control rollers (lo, 11, 12, 1 14),), their Circumferential speeds can be set independently of one another. 5. Apparatus according to claim 4, characterized in that between the driven rollers are some non-driven guide or squeegee rollers.