WO1988009716A1

WO1988009716A1 - Process and tool to facilitate processing of thermoplastic polymers

Info

Publication number: WO1988009716A1
Application number: PCT/HU1988/000039
Authority: WO
Inventors: Zoltán Balajthy; István PÓKA; Péter SEIDA; Géza SZÉKELY
Original assignee: Müanyagipari Kutató Intézet
Priority date: 1987-06-03
Filing date: 1988-06-03
Publication date: 1988-12-15
Also published as: EP0316415A1; HUT48518A

Abstract

A process and a tool facilitate processing of thermoplastic polymers, in particular of linear polyethylene. The inner surfaces of the processing machine which come into contact with the plastic polymer material are totally or partially degreased, roughened, and, if necessary, treated chemically and/or provided with a primary coat, and then coated with one or more layers of fluoropolymers or fluoroelastomers containing 35 to 76 % by mass of fluorine and having a molar mass of at least 105.

Description

Processes and tools to facilitate the processing of thermoplastic polymers

The invention relates to a method for facilitating the processing of thermoplastic polymers, in particular linear polyethylene. The invention further relates to tools for performing this method. The essence of the invention is that the surfaces of the structural parts of the processing machine that come into contact with the plastic polymer, or at least some of these surfaces, are completely or partially provided with a coating of fluoroolymer

It is known that the research and development results achieved with the so-called "third generation" superactive catalysts enable certain α-olefins (for example butene-1, hexene-1, 4-methylpentene-1, octene-1, dodecene) -1) with ethylene to linear polyethylene of ultra low density (0.860-0.900; LULDPE), very low density (0.901-9.15; LVLDPE), low density (0.916-0.925; LLDPE) or medium density (0.925-0.940; LMDPE) to polymerize and on this

To produce types of polyethylene whose properties differ significantly from the known low-density (LDPE) or high-density polyethylene (HDPE). The types LULDPE, LVLDPE, LLDPE and LMDPE offer economic advantages in particular in the production of ready-to-use films and finished products because they include: lower specific material expenditure (lower film thickness) have the same strength properties or better strength properties than the known polyethylene products, they are also more weldable and improve some properties of HDPE.

The linear polyethylenes (LPE) mentioned show, compared to the conventional LDPE types, in the Schen speed range of 100-2000 s ^-1 in the plastic state a high viscosity, the plastic mass tends to break, its strength is low, and therefore these types of polyethylene can only be processed economically on special machines or on LDPE machines that have been converted with considerable effort.

Even the special machines designed directly for the processing of linear polyethylene have an average 10% lower output than the conventional processing machines for LDPE - despite greater machine stress and greater energy consumption.

It is known that in order to reduce the large torque requirement, the high dynamic pressure and the high shear rate (up to about 2000 s ^-1 ), furthermore to avoid that the plastic mass breaks or pulsates due to the high shear rate, in the construction of The following mechanical engineering solutions are recommended or applied for the processing of devices intended for LPE:

- The drive motors and gears are designed for higher performance.

- The sole bearing of the extruders is dimensioned for a 50% higher load.

- The compression ratio of the screws is reduced by reducing the flow cross section and by using a smaller number of shear and mixing elements. - The flow cross section of the tools is increased, the gap of the tools is dimensioned wider. When purchasing new (special) machines, considerable costs are incurred for the first two of the above-mentioned measures; machines originally intended for the processing of LDPE incur costs for all four measures.

When blowing foils, for example, increasing the tool gap is the most important means of reducing the dynamic pressure and the shear rate. In order to ensure the film thickness required in practice with the enlarged tool gap, the elongation in the longitudinal direction, i.e. the withdrawal speed can be increased. However, increasing the take-off speed has a detrimental effect on the mechanical properties of the product, since the mechanical strength increases in the longitudinal direction (machine direction) but decreases in the transverse direction, and the product becomes mechanically anisotropic, for example the impact strength of the film deteriorates.

In order to compensate for this, tools with a smaller diameter are used for blowing LPE films, the so-called blowing ratio (ratio between the diameter of the film tube and the diameter of the tool gap) is larger and therefore allow a greater stretch across the machine direction. As a result, however, the effect of the widening of the gap, which reduces the dynamic pressure and the shear rate, is partially lost, and the stability of the film tube also deteriorates, which can lead to the formation of rejects.

It is also known to increase the so-called "solidification line height" of the film tube on a redesigned cooling device in order to reduce the anisotropy of films which have been produced from LPE on machines designed for processing LDPE and have been subjected to the aforementioned longitudinal expansion. The conversion of the cooling device increases the investment also cost.

All the measures listed here, which relate to the mechanical engineering of the construction and are primarily intended to make the processing aids superfluous, have not changed much that even today, when an existing machine line is to be used for processing LPE, a compromise between the output of the machine and the quality of the product must be found. It is also a compromise of this type, as is common in industrial practice, to use the types LULDPE, LVLDPE, LLDPE, LMDPE mixed with LDPE as a so-called "blend". An indication of the problem of LPE processing in itself is the fact that a significant proportion of the quantity produced worldwide today is processed in the form of blend. Blends in general contain 25-50 mass linear Polvätnylen, usually about 25-30 M _a sse%.

These solutions have the advantage that the existing film machine lines can be used unchanged, the output of the machines is only a little lower. A significant disadvantage, however, is that the blends are increasingly subject to segregation due to the differences in density of the components in the course of their storage, transport and metering, and the products made from blends therefore have a poorer quality. The processing of the so-called "hot blends" is generally not economical because of the additional granulation costs; the additional heat load can also lead to degradation, heat decomposition, and in order to avoid this, a larger amount of the expensive heat stabilizers must be added

For the purpose designed for the processing of LDPE and in industry worldwide Made processing machines for the processing of LULDPE, LVDPE, LLDPE, LMDPE or their mixtures formed with LDPE economically suitable (i.e. to be able to operate while avoiding loss of performance, are measures other than those mentioned above which require significant investments) Proposed known or applied in industrial practice.

For example, it is known from US-PS 3 125 547 that the problems mentioned in the processing of

LPE, i.e. The decrease in machine performance, the tear-off of the plastic mass caused by - in the interest of performance improvement - increase in the screw speed, as well as the overloading of the drive motor and transmission depending on the construction of the machine and the tool, can be at least partially avoided if the polyethylene in a small amount of certain fluorinated hydrocarbon polymers can be added. The patent mentioned recommends fluorinated for the stated purpose

Hydrocarbon mono- and copolymers in which fluorine and carbon atoms are present in a mass ratio of 1: 2, which further preferably have a melting point (in the case of crystalline polymers) or a softening point (in the case of amorphous polymers) between 150 and 250 ° C, which is the processing temperature corresponds to linear polyethylene, so that the fluoropolymers in plastic polyethylene are liquid, but are in solid phase in solidified polyethylene, and in the critical temperature and shear rate range of processing their viscosity is similar to that of the LPE to be processed. The effective fluorinated hydrocarbon polymers must have a molecular weight that corresponds to this melting or softening point, because in If the molar mass is too low, the polymer does not exert the desired sliding action, but if the molar mass is too high, the polymer is solid even at processing temperature and does not improve the processing properties of the polyethylene in this state.

Suitable fluorinated hydrocarbon homo- or copolymers are, according to the teaching given in the description, polyvinylidene fluoride, poly (vinyl fluoride-chlorotrifluoroethylene), polytetrafluoroethylene, polychlorotrifluoroethylene telomeres and fluorinated hydrocarbon rubbers, such as, for example, the vinylidene fluoride-hexafluoropropylene copolymer. The concentration of the proposed fluorinated polymers is given as 0.005-2% by mass. A higher concentration does not result in an increase in activity, and since the fluorinated polymers mentioned are immiscible with polyethylene, they form a phase of their own and thereby deteriorate, among other things, the optical properties (for example the light transmission) of the product.

In recent years, as processing of linear polyethylene has increased, numerous processing aids and fluoropolymer-based additives have appeared on the market. They are traded either as pure fabrics or in the form of masterbatches made with linear polyethylene. Such products include VITON A (Du Pont de Nemours Co.), TECHNOFLON NM (Montefluors SpA), KYNAR (Pennwalt Plastics Ltd). Masterbatches which contain the fluoropolymer applied to different supports made of linear polyethylene are available from Ampacet Corporation, under the name FERNAFLON from Ferro (Holland), under the name POLIAID from BP Performance Polymers Inc. and under the name AFK 1000205 from the company Sydplast launched. The processing aids for linear polyethylene which are provided with the trademark BOOSTER and are compatible with fluorinated elastomers and are manufactured by Du Pont Canada Inc. are not chemically defined.

According to U.S. Patent 4,535,113, the economic one

Processing of linear polyethylene with a density of

0.860-0.940 also possible with ethylene oxide groups and vicinal epoxy or amino groups containing silicone processing aids. Amounts of approximately 0.01-5% by mass are recommended for use. These products are manufactured by Union Carbide Corporation and sold under the trademark UCARSIL PA (Modern Plastics International, July 1986, p. 46: "Ucarsil PA Processing Aids for extrusion grade polyolefins", product description by UCC, Danbury, Connecticut, USA 1986).

Recently, many manufacturers of linear polyethylene have launched their products mixed with fluorinated processing aids, such as Esso Chemical Canada, ESCORENE, Novacor, GX-3111 and GX-3510-P, and Saudi Basic Industries the product LADENE. In recent times, the Canadian company

Polysystem Machinery Manufacturing Inc. (Ontaria) Patents pending which relate to precisely regulated heating for tools with a narrow gap and according to which continuous heating loops are installed, which are fitted in rings made of an alloy and arranged on both sides of the tool (Modern Plastics International , March 1987, p. 20). The purpose of this measure is to make the use of processing aids superfluous. The mechanism of action of the fluoropolymer aid Substances have not yet been fully clarified. It appears that the fluorocarbon polymers liquid at the processing temperature of the polyethylene form a thin film on the metal surface of the internal structural elements of the extruder and act as a lubricant for the plastic polyethylene (Plastververarbeitung, Vol. 37, No. 5, p. 90/1986 /; Modern Plastics International, Dan. 1960, p. 60).

When the plastic mass of the polyolefin travels through the machine, it spreads a thin film of the fluoroelastomer liquid; this layer adheres to the metal surface and is only slowly worn out by the plastic polyethylene. Even after the addition of the fluoropolymer has ceased, the effect can still be felt for a long time. As a result of this lubricating effect, the speed difference within the plastic mass, i.e. the difference between the speed of the outer (for example close to the metal layer of the tool sleeve) and the inner (for example close to the core of the tool) layer is lower, the acceleration of the surface layers when leaving the tool is smaller, the feared as a scrap " Sharkskin does not develop. According to H. Landin (Modern Plastics International,

Febr. 1986, p. 16), fluorine is split off from the fluorinated hydrocarbon polymers or fluorinated elastomers during the processing process, which migrates to the surface of the plastic mass and accumulates in the interface between metal and polyethylene. The fluorine, which has a low surface energy, wets the metal surface, forms a sliding layer on it and thereby reduces the apparent viscosity of the polyethylene. According to other views, some fluoroelasto act mere, for example the Kynar, as a theological lubricant. The same is said of the Ucarsil silicone processing aid.

Whatever the mechanism of action, depending on the design of the machine, the use of the processing aids mentioned is associated with minor or major advantages, which can already be seen from the fact that the use of these products is increasing. Their main advantage is that when they are used, the tubular extruder designed worldwide for processing low-density polyethylene and having a narrow (0.6-1.3 mm) die gap does not have to be converted. New, expensive machine parts, for example, would be used for this conversion

Wide gap tool (1.5-3.2 mm), motor and gearbox dimensioned for higher performance, if necessary a new screw or another cooling system used. Another advantage of the processing aids is that, with their help, the existing machines suitable for processing low-density polyethylene with approximately the same output, ie more or less economically, can also be used to process linear polyethylene or its mixtures prepared with LDPE, while the machines specially designed for processing linear polyethylene are unsuitable in most cases for processing LDPE. As a further advantage of the processing aid, it should also be mentioned that - at least according to the literature references available so far in the already mentioned viewing speed range - the use of processing machines with a narrow gap increases by 15-20% and the dynamic pressure increases

can be.

Finally, it is advantageous that the use of processing aids in the critical shear rate range of 100-2000 s ^-1 prevents the breakage of the plastic polyethylene; this break leads to the creation of the "Sharkskin" committee.

As an advantage of the processing aid Ucarsil based on silicone it is mentioned that in an amount of 500-1000 million parts by mass it also enables the processing of mixtures (blends) containing more than 30% linear polyethylene and, compared to the processing aids based on fluoropolymer, the inclination of the film reduced to sticking together, when the machine is started up or changed over to another starting material, the breakage of the plastic polyethylene mass is eliminated more quickly

Finally, the processing aids known from the prior art also reduce the deposits of degraded polyethylene or crosslinked or not completely melted polyethylene granules on the mouth of the tool due to their sliding action. These deposits cause the dispute of the film (pin striping) or "fish eyes (gel striking)", ie they worsen the optical properties of the film, in some cases they can also lead to the film being torn off from the tool, ie to a much larger reject quantity and significant Cause loss of production.

In addition to the numerous advantages, the processing aids also have significant disadvantages.

First of all it should be mentioned that precisely because of their low concentration, the homogeneous distribution is extremely important; either a special mixing device (when using 100% auxiliary substances) or a very precise dosing device

Use of masterbatches). If the processing aids are even overdosed locally, they deteriorate the optical properties of the product because they are immiscible with polyethylene; in addition, the machine performance drops or the machine pulsates (A. Rudin, AT Worn, ZE Blacklock, Plastics Engineering, Vol. 42, No. 3, 63-66 / 1986 /), and the weldability and printability of the film deteriorate. The processing aids must necessarily be replaced, although in small quantities, but continuously, because the plastic polyethylene wears the fluoroelastomer layer from the metal parts. The amount of fluoroelastomer additive required is determined by the balance between application and wear. Since the wear of the sliding film depends on the type of polyethylene, the pigments and fillers used and the tool design. A higher proportion of fluoroelastomer must be used for filled systems. After all, these processing aids are quite expensive, they cost 30-50 times as much as polyethylene, so their use is associated with constant additional production costs, which of course also increases the price of the product and worsens the economy of production. Finally, the fluorinated hydrocarbon polymers or fluoroelastomers deteriorate the effect of the so-called “antiblockers” which are usually used to prevent the film from sticking together. Industrial experience to date shows that the erosive wear of machine parts is much greater when processing LPE than in the case of LDPE or HDPE. This means that spare parts have to be replaced more frequently than usual, which means that maintenance costs increase. If it

proves to be correct that the sliding effect of the flu If carbon-based processing aids are actually due to the adherence of free fluorine atoms to the metal surface (as H. Landon assumes), there is likely to be a corrosive effect.

After all, the processing aids adhere so strongly to the functional elements of the extruder that their "extension" can take hours, even shifts, and therefore, in the event of a raw material changeover, considerable production loss and rejects must be expected.

It has now been found that the technical and economic advantages currently achievable through design changes to the machines and through the use of processing aids can not only be achieved but even surpassed if certain fluorinated hydrocarbon homo- or copolymers or fluo relast omere do not do so to be processed linear polyethylene or blends containing linear polyethylene, but are applied with a suitable method in the form of a permanent, solid coating to the surfaces of the internal functional elements of the processing machine that come into contact with the polymer or to at least some of these surfaces.

The fluorinated homo- or copolymers or fluoroelastomers to be used in the sense of the invention differ from the previously known solutions and, in contrast to current technical practice, have a Swiss or softening point of over 250 ° C, i.e. are solid in the processing temperature range of polyethylene and polypropylene

They contain 35-76% by mass fluorine and have a molecular weight of over 10 ⁵ . Suitable are: tetrafluoropropylene homopolymers (PTFE), tetrafluoroethylene-hexafluoropropylene -Copolymers (FEP), ethylene-chlorotrifluoroethylene copolymers (ECTFE), vimlydenfluoride-chlorotrifluoroethylene copolymers (VDF-EETFE), vinilydenfluoride-hexafluoropropylene copolymers (VDF-HFP) or perfluoroalkoxy resins (PFA). This finding is surprising because, according to the current state of the art, it was not foreseeable, on the contrary: it has been disputed that fluorinated hydrocarbon polymers or fluoroelastomers with a melting or softening point above 250 ° C in the shear rate range of 100-2000 s ^-1 with a tool with narrow gap processing of linear polyethylene or linear polyolefins are able to permanently prevent the appearance of the breaking of the plastic mass and are able to reduce the dynamic pressure. The invention is also advantageous because the problems that occur in the processing of linear polyethylene and described above are not eliminated by expensive machine conversions or processing aids added to the raw material, but by the partial or complete coating of the functional elements of already existing machines.

With the method according to the invention, the performance of the processing machines for thermoplastic polymers, in particular for linear polyethylene, high-density polyethylene, high-density polyethylene and ultra-large molar mass. Polyethylene and its copolymers, in particular the performance of hose blow extruders provided with a narrow tool gap can be increased, the power consumption being lower and. Drive motors and gears are protected against overload. It is characteristic of the method that the surfaces of the inner functional elements of the processing machine that come into contact with the plastic polymer or a part of these surfaces after a possibly in known manner, for example with solvent or detergent or by degreasing and / or a mechanical, preferably by particle blasting roughening of the surface, optionally by phosphating or chromating and / or with a primer which improves the adhesion to the metal surface by pretreatment by application with a brush, or preferably with a spray gun or by means of electrostatic spraying or by immersion in a fluidized bed with the solution, dispersion or powder of fluorine-containing 35-76% by weight fluorine, having a softening or melting point of over 250 ° C. or copolymers or fluoroelastomers with an average molecular weight of more than 10 ⁵ , preferably with tetrafluoroethylene homopolymers

(PTFE), tetrafluoroethylene-hexafluoropropylene copolymers (FEP), ethylene-chlorotrifluoroethylene copolymers

(ECTFE), vinylidene fluoride-hexafluoropropylene copolymers (VDF-HFP), vinylidene fluoride-chlorotrifluoroethylene copolymers (VDF-CTFE) or with perfluoroalkoxy resins (PFA), coated and the machine parts treated in this way are heat-treated at 100-420 ° C, that Cover and repeat the heat treatment if necessary several times on this

A 10-150 μm thick coating, which is solid at temperatures below 250 ° C., is produced on the machine parts and the processing of the thermoplastic polymers takes place on the processing machine containing the machine parts coated with solid fluorinated hydrocarbon polymer or fluoroelastomer.

The coating produced in this way is also stable under the conditions of mechanical and thermal stress during the extrusion process. The invention has the following advantages: a) It enables the processing of LULDPE,

LVLDPE, LLDPE, LMDPE and HDPE - including the latter

Ultra-large molecular weight and high density polyethylene (UHMW-HDPE) - and polypropylene in the form of homo- or copolymers and the processing of their mixtures formed with low-density polyethylene in the temperature range of 150-250 ° C at shear rates around 10,000 s ^-1 , without that the plastic mass breaks. Hose blow tools with a narrow gap can also be used. b) According to the invention, LULDPE, LVDPE, LLDPE, LMDPE, HDPE and their mixtures formed with LDPE can also be processed practically without loss of performance on machines designed for processing low-density polyethylene. c) The strong back pressure, which arises in the case of narrow tool gaps when processing linear polyethylene, as well as the axial force are reduced by the coating by 20-40%. It is therefore not necessary to purchase and install more powerful motors and gearboxes, and the life of the machines is also longer. d) The performance of the machines designed for processing LDPE can be increased with the method. e) The method enables considerable energy savings because the machines containing the coated elements have a 5-25% improved energy ratio. (The energy ratio number denotes the ratio between material output and energy expended; "mass flow / power ratio"), f) In the case of tubular film texting equipped with tools coated according to the invention, no residues of degraded or crosslinked polymer due to excessive heat are deposited on the tool mouth (slip-stick ). these deposits can lead to partial blockage of the tool and thus to waste. g) No processing aids are used in the process according to the invention, so that the disadvantages of the processing aids (tendency of the film to stick together, deterioration in the optical properties, weldability and printability) do not occur. h) In contrast to the known technical solutions, pulsation-free flow conditions are ensured with the method according to the invention. i) The process is much more economical than the known processes because neither expensive additional investments nor expensive processing aids are required.

In contrast to the known processing aids, the fluorinated hydrocarbon homo- and copolymers and fluoroelastomers used in the context of the invention are substances whose melting or softening point is above 250 ° C., ie they exist in the solid state in the temperature range of polyethylene processing. Their average molecular weight is over 10 ⁵ , their fluorine content between 35 and 76% by mass. Suitable are tetrafluoroethylene homopolymers (PTFE), tetrafluoroethylene-hexafluoropropylene copolymers (FEP), ethylene-chlorotrifluoroethylene copolymers (ECTFE), vinylidene fluoride-hexafluoropropylene copolymers (VDH-HFP), vinylidene fluorophorylene-chlorotrifluorophenylene-chloroform PFA) In the case of PTFE, ECTFE and PFA, the machine parts are coated with polymer powder and in the case of PTFE, FEP, VDF-HFP and VDF-CTFE with the aqueous dispersion or the solvent-prepared solution of the polymer. Covering in the manner described nigt, optionally roughened and pretreated metal surface is carried out in a manner known per se by immersion in a fluidized bed, by electrostatic application, by means of spray guns operated with compressed air, by airless high-pressure spray devices ("airless") or by brushing and subsequent heat treatment.

When coating with polymer powder in a fluidized bed (fluid bed), preference is given to using PTFE, ECTFE or PFA powders which have been produced by emulsion polymerization and have a particle size of 0.1-5.0 μm and which, for example, have air at a flow rate of 0.1-5.0 μm. 1.0 m / s are kept in suspension in the fluid bed. The metal object, preheated to 260-290 ° C, is immersed in the powder bath for 5-20 s, then pulled out and exposed to a temperature of 270-300 ° C for a further 2-12 hours. Then it is cooled.

If the fluorinated hydrocarbon polymer or the fluoroelastomer is to be applied in the form of powder, a dispersion or a solution by electrostatic spraying, a voltage of 80,000-90,000 V is expediently used. The coated article is then heat treated. The duration and temperature of the heat treatment depend on the material used for the coating. Depending on how thick the coating should be, it can be applied in one or more layers.

The dispersions or solutions prepared with solvents can also be applied by means of a spray gun operated with compressed air or with a high-pressure spray device which works without air or by brushing on. Here, too, the application can take place in one or more layers, and after each newly applied layer the article is heat-treated. When using compressed air is a press air pressure of 1.5-3.8 kg / cm ² is recommended, when spraying from a pressure container, the container pressure is expediently 0.4-0.6 kg / cm ² .

The invention is illustrated by the following examples, but is not limited to these examples.

example 1

Production of the cover

An extruder with a screw diameter of 30 mm and an L: D ratio of 31 has a tubular film blowing tool with a gap width of 0.60 mm. The inner surface of the sleeve of the tool and the outer surface of the tool core are degreased with trichlorethylene vapor and then dried. The surfaces are roughened to a roughness of 6-8 μ by sandblasting with corundum grains with an average grain size of 0.3-0.5 mm and then blown clean with compressed air. Care must be taken to ensure that the cleaned surface is not touched by hand. Teflon is applied in four layers to the prepared surface.

1st layer: A mixture of 100 g Teflon 850-314 (aqueous PTFE dispersion) and 40 g WM 7799 (chrome and phosphoric acid accelerator; both products are manufactured by Du Pont) is kept in constant motion in a paint spraying system and with the Spray gun on the tool shown in Fig. 1, sprayed onto the areas highlighted in the drawing

The 5-10μ thick layer is dried in a heat chamber of 100 ° C internal temperature for 13 minutes and then in a heat chamber of the internal temperature of 200 ° C

Heat treated for 13 minutes. Then the tool is cooled to room temperature.

2nd layer: The first layer is sprayed with an aqueous dispersion of Teflon FEP 856-204 (tetrafluoroethylene-hexafluoropropylene copolymer, manufacturer: Du Pont) applied in about 10 μ layer thickness. Then the tools are heat treated at 100 ° C for 13 minutes, then at 400 ° C for 13 minutes and finally cooled to room temperature.

3rd layer: The procedure is the same as for the application of the second layer, but with the difference that Teflon 856-200 (tetrafluoroethylene-hexafluoropropylene copolymer as an aqueous dispersion, manufacturer: Du Pont) is applied, the temperature of the second step of the heat treatment being 340 ° C.

4th layer: Finally, a dispersion of Teflon 856-200 is applied to the tool in a layer thickness of approximately 10μ, and the workpiece is heat-treated at 100 ° C. for 13 hours, then at 360 ° C. for 45 minutes and finally cooled to room temperature.

Extruding film tube

On a TIPELIN FS 340-02 brand extruder, which has a screw diameter of 30 mm and an L / D ratio of 31, linear polyethylene of medium density (manufactured in the chemical plant on the Tisza; density: 0.934 g / ml, flow number: 14 g / 10 min and 190 ° C, 21.6 kp) extruded to a film tube. Two foil blowing tools of identical dimensions are used; the inner diameter of the sleeve part is 60.00 mm in the smoothing section, the outer diameter of the tool core is 58.80 mm at the same point, ie the gap width is 0.60 mm. 1 shows a schematic image of the tool. The two tools differ in that in the one the inner sleeve and the outer core surface, that is to say the metal surfaces which come into contact with the plastic polymer, have been provided with the coating described, which is composed of four layers, while the other tool was left untreated. The temperatures in the heating zones, from the funnel towards the tool, were as follows:

While gradually increasing the screw speed, work was first carried out with the untreated, then with the tool provided with the coating according to the invention. In the screw speed range of 50-120 min, axial force and dynamic pressure, engine torque and the machine's output were measured. The measurement results are summarized in Table 1. In the table mean:

A = extruded according to Example 1 with one

Coated tool B = extruded with the untreated tool 1) = strong breaking of the mass, "shark skin", pulsation

2) = ratio of output (g / s) and energy expended: x 10 ²

These measurement results prove the following:

1) Depending on the screw speed, the output of the extruder equipped with the tool coated according to the invention is higher by 7.3-12.3% and increases with the speed.

2) While in the case of the extruder equipped with the conventional tool, when the speed of 90 min ^{-1 is} exceeded, the appearance of the fracture of the plastic, which manifests itself as "shark skin" Mass occurs, the machine pulsates, ie the quantity conveyed over the unit of time is not uniform, such phenomena have not been observed once with the coated tool even at the highest speed.

3) The back pressure occurring in the extruder head is 36-38% lower in the extruder equipped with the tool treated according to the invention, despite the higher output, than the back pressure in the extruder having the conventional tool.

4) The occurring axial force is 25-30% lower in the case of the tool coated according to the invention.

5) The engine torque also shows a clear decrease.

6) The energy utilization factor of the processing machine, i.e. the output quantity per unit of energy ("mass flow / power") increases by 7-22% in the case of the machine equipped according to the invention. Example 2

The procedure is as described in Example 1, ie the extruder, the tool and the surface treatment of the latter are as described in Example 1. However, a linear low-density polyethylene is extruded (GRSN 7047; manufacturer: Union Carbide Corporation, USA; density: 0.918 g / ml, flow number: 1.0 g / 10 min / 190 ° C., 2.16 kp /). The two tools according to Example 1 are used to produce the film tubes. The temperature of the heating zones of the extruder is also set to the same value as in Example 1. The screw speed is gradually increased in the range between 50 and 90 min ^-1 , and the characteristic processing parameters are measured. The results are summarized in Table 2. In the table, the meaning of A, B and 1) is the same as in Example 1, 2) means strong breakage of the plastic mass, and 3) stands for the ratio between the output (g / s) and the energy used

(kW):

These values show the following:

1) The output of the machine equipped with the tool according to the invention is over

4.5-7% higher.

2) While in the case of the extruder equipped with the conventional tool, when the speed of 50 min ^-1 is exceeded, the phenomenon of the breakage of the plastic mass manifesting itself as "shark skin" occurs and increases to very strong breaks at a speed of 90 min ^-1 , such was not recorded in the tool coated according to the invention. 3) The dynamic pressure occurring in the extruder head is 43-45% lower in the extruder equipped with the tool treated according to the invention, despite the higher output, than the dynamic pressure in the extruder having the conventional tool. 4) The occurring axial force is around 36-39% lower in the case of the tool coated according to the invention.

5) A decrease in the engine torque can also be seen in this case. 6) The energy recovery factor of the processing machine is better by around 10-15% when using the method according to the invention. Example 3 Preparation of the coating An extruder with a screw diameter of

30 mm and an L: D ratio of 31 has a tubular film blowing tool of 70.0 mm diameter and 0.50 mm gap width. The inner surface of the sleeve of the tool and the outer surface of the tool core are degreased by washing with the 1% by mass solution of MAVEBIT TP 35 (manufacturer: Egyesül Vegyimüvek, Budapest) and dried after rinsing with water. From the inner surface of the tool sleeve, the smooth section shown in solid lines in FIG. 2, but from the core, the entire surface to that in Example 1 described roughened and then treated for 10 minutes with a 75 ° C warm, previously run in with iron filings phosphating solution of the following composition: phosphoric acid (spec. wt. 1.64) 65 g Na ₃ PO ₄ 35 g

Thiourea 5 g.

Then the surface of the tool is rinsed thoroughly and finally dried. In order to improve the adhesion of the fluorinated polymer to the metal surface, the tool surfaces mentioned are brushed with a 50% solution of CHEMOSIL X 5122 (a silane polymer marketed by Henkel, Germany) prepared with methyl ethyl ketone primed. The treated tool parts are rocked at 90 ° C for 3 hours.

A two-layer coating of fluorinated hydrocarbon polymers is then applied to the tool surfaces. 1st layer

Using a paint spray gun, a layer thickness of 1520 μ is applied to the surfaces of the tool TEFLON S 959-205 (modified PTFE dispersed in an organic solvent, manufacturer: Du Pont, USA). The coated tool parts are heat-treated in a heat chamber of 100 ° C internal temperature for 15 minutes, then in a heat chamber of internal temperature 200 ° C also for 15 minutes and then cooled to room temperature. 2 layer

The spray gun is coated onto the first layer in a layer thickness of approximately 10-15 μ with TEFLON 856-200 (aqueous dispersion of tetrafluoroethylene-hexafluoropropylene copolymer, manufacturer: Du Pont, USA). The coating is kept at 100 ° C for 13 minutes, 42 minutes treated for long at 360 ° C and then cooled to room temperature.

Extrusion of film tube through a tool with a narrow gap. Linear polyethylene is reduced on the extruder

Density (SCLAIR 11 D1, manufacturer: Du Pont Canada Inc .; density: 0.920 g / ml, flow number: 0.62 g / 10 min / 190 ° C, 2.16 kp /) extruded to a film tube. Two identical injection molding tools are used (inner diameter of the sleeve: 70.00 mm, outer diameter of the core in the smoothing section: 69.0 mm, ie the gap width is 0.5 mm), of which one in the manner described with double polymer layer is provided, but the other is not. The temperature values in the heating zones were the same as in Example 1.

The screw speed is gradually increased, and both the untreated tool and the treated tool are measured at different speeds, the axial force, the dynamic pressure, the torque of the motor and the output. The measurement results are summarized in Table 3, in which the following terms are used:

A: The extrusion was carried out with the tool treated according to Example 3

B: The extrusion was carried out with the untreated tool. (Fracture of the plastic mass did not occur even with variant 8.) 1) Ratio of output (kg / h) and energy used (kW):

These measurements show the following.

1) The output of the extruder equipped with the die coated according to the invention increases only slightly in the case of SCLAIR 11 D1 (because this LLDPE also contains processing aids).

2) Even in the case of film production with the untreated tool, there is no breakage of the mass, which is proof of this, since the material contains auxiliary processing material.

3) The im is at

the extruder equipped with the tool treated according to the invention is nevertheless around 19-28 lower than the dynamic pressure in the extruder having the conventional tool. 4) The values of the axial force are 17-20% lower in the case of the coated tool.

5) The engine torque also shows a clear decrease. The phenomena mentioned under points 3, 4 and 5 essentially mean that the fluorinated hydrocarbon polymer coating according to the invention has an important protective effect even if the material contains processing aids. The coating protects the motor and gearbox of the machine working with a narrow tool gap against overload.

6) The energy recovery (kg output per energy unit) is also improved by the method according to the invention if the LLDPE to be processed still contains processing aids. Example 4

Film blowing tests and measurements are carried out using a KIEFEL R-4 extruder (screw diameter 40 mm, L / D ratio 18.5). In Fig. 3 the tool is shown in section. In a first test series, the metal surface of the tool is left, in the second test series, the spiral core with the tool distribution channel (diameter 118.6 mm) and the inner surface of the sleeve with a diameter of 120 mm (tool gap 0.7 mm) are placed on the in the example 1 described manner roughened, degreased and then provided with four layers of Teflon coating. The thickness and heat treatment of the individual layers is as described in Example 1, and the total thickness of the layers is 0.06-0.08 mm both on the core and in the sleeve. Extruding tubular film

LDPE of Soviet origin (SOETEN 15813-020; density: 0.920 g / ml; flow number: 2.0 g / 10 min./190 ° C, 2.16 kp) is processed on the machine to form a tubular film measuring 500x0.040 mm .

The heating zones have the following temperatures:

1st zone in the snail shell 180 ° C

2nd zone in the sieve 180 ° C

3rd zone in the intermediate piece 180 ° C 4th zone in the head 180 ° C

5th zone in the head 180 ° C

The values for the speed of the screw, the current consumption of the drive motor, the emission and the peeling are shown in the T _a ble. 4 Pure SOETEN 15813-020 was processed first.

In a second test series, one with 16.7 mass% LMDPE, in a third test series with 30 mass% LMDPE (in both cases it is TIPELIN 381-10, manufacturer: Chemical Combine on the Tisza: density: 0.938 g / ml , Flow number: 0.28 g / 10 min / 190 ° C, 2.16 kp /) prepared blend processed.

In the case of the blend of 16.7% and 83.3% Tipelin Soeten the heating temperature in all five heating zones to 190 ° C is set in the F _a of 30% Tipelin lle-containing blends to 200 ° C.

The processing parameters and the measured values are shown in Table 4.

LDPE: 100% SOET 15813-020

Blend I: 16.7% LMDPE (TIPELIN FA 3810-10 83.3% LDPE (SOETEN 15813-020)

Blend II: 30.0% LMDPE (TIPELIN FA 3810-10) 70.0% LDPE (SOETEN 15813-020) Then the working up is repeated with a tool which is identical to the extent but, according to the invention, coated with Teflon. The same basic materials are processed, but there is also a Blend III, which consists of 50 mass% SOETEN and 50 mass% TIPELIN of the types mentioned.

The temperatures in the heating zones are set to the values already mentioned for the individual mixtures, Blend III is processed at 210 ° C. The screw speed is 120 or 150 min ^-1 . The processing parameters are given in Table 5.

Bark shows a comparison of the two T _a, that in the case of the tool according to the invention provided with the top pull de both at a speed of 120 min ^-1 as well as a rotational speed of 150 min ^-1 in the investigated concentration range of 0-50% by weight of LMDPE ejection r the machine was larger than in the case of the tool with the usual metal surface. This is also clearly illustrated by diagram 1.

With the Blend II containing 30% LMDPE and 70% LDPE, for example, a back pressure of only 87 bar occurred at a speed of 120 min ^-1 in the case of the coated tool, which - compared to the uncoated tool (152 bar) - resulted in a reduction corresponds to around 43%, and even at a speed of 150 min ^-1 , the dynamic pressure (105 bar) is still about 35% lower than that of the uncoated tool (161 bar). It is therefore clear that in the In the case of the tool provided with the cover, the speed without the risk of a machine break over 150 min ^-1

increase can, which leads to a further increase in output. The dynamic pressure differences are also shown graphically in diagram 2.

The possibility of increasing the speed is also supported by the measured values for the current consumption of the motor: when processing Blend II, the current consumption in the case of the tool not coated was 120 min ^-1 19 A, at 150 min ^-1 21 A, while for the same speeds in the case of the coated tool, the current consumption is only 18 or 19 A.

Example 5

Production of the cover

The tool of a film tube extruder (screw diameter 120 mm, L / D ratio 25, type E 120.

50 D from the manufacturer Windmöller-Hölscher) with a twin head (see FIG. 4) is roughened and degreased in the manner described in Example 1, namely the 120 mm diameter core on the outer surface and the sleeve on the inner surface (Gap dimension 0.7 mm).

A Teflon coating of four layers is applied to the prepared tool surface in the manner described in Example 1. The materials used, the thickness of the layers and the type of heat treatment correspond to the information in Example 1; The thickness of the finished layer is 0.05-0.07 mm both in the sleeve and on the core.

The second tube blowing tool of the extruder, which has the same construction but different dimensions (diameter of the core 160 mm, gap dimension 0.8 mm), was not treated.

Extrude the film tube

First linear medium density polyethylene (TIPELIN FS 340-02 manufacturer. Chemistry combined on the Tisza; Density: 0.934 g / ml, flow number: 14 g / 10 min / 190 ° C, 21.6 kp /) processed to a film tube. The heating zones have the following temperatures: Zone 1 in the cylinder 215 ° C Zone 2 in the cylinder 230 ° C

Zone 3 in the cylinder 210 ° C

Zone 4 in the cylinder 230 ° C

Zone 6 when changing the screen 210 ° C

Zone 7 in the adapter 210 ° C with without

coating

Zone 8 tool guide 210 ° C 210 ° C

Zone 9 head 210 ° C 210 ° C

Zone 10 head 215 ° C 215 ° C

Zone 11 head 210 ° C 210 ° C

The screw speed is 37 min ^-1 , the current consumption of the drive motor 360 A, the dynamic pressure 545 bar, the temperature of the plastic mass 225 ° C, and hose with the dimensions 550x0.20 mm was produced.

With the coated tool (a) an output of 149 kg / h is achieved, with the uncoated tool an output of 97 kg / h. The pull-off speeds are 12.7 m / min (a) and 7.7 m / min. Although the performance is lower in the case of the uncoated tool, the plastic mass breaks. By using the tool coated according to the invention, a performance increase of 53.6% can accordingly be achieved. The total output of the machine is 246 kg / h. Next on the twin-head machine is a blend consisting of 50% by mass linear medium density polyethylene (TIPELIN FS 340-02; manufacturer: Chemiekombinat an der Tisza) and 50% by mass polyethylene low density (TIPELIN FA 2210, manufacturer: Chemiekombinat an der Tisza; density: 0.922 g / ml, flow number: 0.3 g / 10 min / 190 ° C, 2.16 kp /), processed into film tube. The screw speed is 38 min ^-1, the current consumption of the drive motor 270 A, the back pressure 445 bar, the temperature of the plastic M _a sse 230 ° C, and the tubing produced has in the case of both tools mm the dimensions 550x0,20. With the coated tool (a) an output of 118 kg / h is achieved, with the non-coated tool (b) an output of 88 kg / h. The peel rates amounted to 10.0 m / min (a) and 7.0 m / mi n (b), let nt e re not possible to st EIGE rn is t because breakage of the plastic M _a sse enters The example shows that a performance increase of 34.1% can be achieved with the tool coated according to the invention in the processing of _a blend containing 50 mass% LMDPE. The total output of both tools is 205 kg / h.

The following values were calculated for energy utilization (Table 6): Table 6: Energy utilization coefficient

In the case of the coated tool, the film blown from the blend containing 50% LMDPE has a tensile strength in the longitudinal direction of 30.0 N / mm ² , in the upright direction of 26.0 N / mm ² and a tensile strain in longitudinal direction of 885% or in the transverse direction of 1060%, while the corresponding values for the film produced with the uncoated tool were 32.0 N / mm ² , 29.0 N / mm ² , 990% and 1090%.

Claims

1. Process for facilitating the processing of thermoplastic polymers, in particular linear polyethylene, high density polyethylene, polypropylene in the form of homopolymers and copolymers, characterized in that the surfaces of the internal functional elements of the processing machine that come into contact with the plastic polymer (appropriately a Blown film extruder with a narrow die gap) or part of these surfaces degreased and / or mechanically roughened, optionally chemically pretreated and / or provided with a primer coating and then with the powder, the dispersion or the solution from a melting or Softening point, 35-76 mass% fluorine-containing fluorinated hydrocarbon homo- or

copolymers or fluoroelastomers with an average molecular weight of at least 10 ⁵ are coated in one or more layers in a known manner, the coating is heat-treated at 100-420 ° C. and the processing of the thermoplastic polymers takes place on the machine containing the coated surfaces.

2. The method according to claim 1, characterized in that the functional elements of the processing machine degreased with solvent or detergent and then roughened by blasting particles.

3. The method according to claim 1 or 2, characterized in that the surfaces are coated with tetrafluoroethylene homopolymer.

4. The method according to claim 1 or 2, characterized in that the surfaces are coated with tetrafluoroethylene-hexafluoropropylene copolymer.

5. The method according to claim 1 or 2, characterized ge indicates that the surfaces are coated with athylene-chlorotrifluoroethylene copolymer.

6. The method according to claim 1 or 2, characterized in that the surfaces are coated with vinylidene fluoride-hexafluoropropylene copolymer.

7. The method according to claim 1 or 2, characterized in that the surfaces are coated with vinylidene fluoride-fluorethylene copolymer.

8. The method according to claim 1 or 2, characterized in that the surfaces are coated with perfluoroalkoxy resin.

9. extrusion tool for thermoplastic polymers, in particular for the homo- and copolymers of

Ethylene and propylene, characterized in that its surfaces coming into contact with the plastic polymer mass entirely or for. Part are provided with a coating of fluorinated hydrocarbon homo- and / or copolymers and / or fluoroelastomers.