BE1025431B1 - Process for the extrusion blow molding of polymers using a zeolite-containing additive - Google Patents

Abstract

The present invention relates to a process for extrusion blow molding of polymers, wherein a process improvement additive is added to the polymer prior to the extrusion blow molding process and wherein the process improvement additive comprises a carrier polymer, a binding component, one or more fluoropolymers and one or more zeolites.

Description

METHOD FOR EXTRUSION-BLOW FORMING POLYMERS WITH

USE OF A ZEOLITE CONTAINING ADDITIVE

TECHNICAL DOMAIN

The invention relates to a process for the extrusion blow molding of polymers. It is in the technical field of polymer chemistry, in particular polymer formation processes and their optimization.

BACKGROUND ART

Accumulation of polymer material around the extrusion die, or that buildup, during extruding, often results in inconsistent or poor performance of the formed polymer extrudate. This accumulation of polymer material also gives rise to degradation of the polymer due to an extended heating around the extrusion nozzle. These degradation products can come off the extrusion nozzle during the extrusion and give rise to black spots or holes in the formed polymer product, also called black holes or black spots. These defects in the polymer product can cause poor performance and are often unaesthetic.

Accumulation of polymer material around the extrusion nozzle mainly concerns the accumulation of low molecular weight polymers that arise during extrusion due to polymer degradation due to exposure to high temperatures and exposure to friction. The addition of antioxidants can often reduce this accumulation due to heat and friction. For example, US 6,156,421 describes the addition of a sterically hindered phenol to reduce polymer accumulation around the extrusion die.

US 4,740,341 describes the addition of a fluoropolymer, such as polyvinylidene fluoride, to improve the extrusion of linear low density polyethylene (LLDPE). The fluoropolymer behaves like a lubricant and forms a coating around the extrusion die, whereby the polymer to be extruded is exposed to less friction and, consequently, that buildup considerably decreases. Similarly, US 6,642,310 describes the optimization of the polyethylene extrusion process by adding a fluoropolymer with an average particle size greater than 2 µm.

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BE2018 / 5438 Although the addition of antioxidants and fluoropolymers significantly reduces that buildup by reducing the degradation of polyethylene and the formation of low molecular weight polymers, the formation of black spots and black holes is not completely excluded. Especially with multimodal polyethylene extrusion, that buildup is a common problem.

The use of zinc stearate and calcium stearate to reduce that buildup is known from US 2005/011622, as well as commercial compositions available which use fluoropolymers and zinc stearate to improve polymer extrusion. The zinc stearate serves as an acid scavenger and, in combination with the use of fluoropolymers and / or antioxidants, can efficiently prevent buildup. As discussed in Die lip build-up in the filled low density polyethylene wire and cable extrusion, C.D. Lee, Equistar Chemicals, LP, published by LyondellBasell Industries, however, is difficult to determine the dosage of stearates to limit that buildup. The concentration of stearates at which that buildup is minimal is, after all, in a very narrow range. If the stearate dose is too high or too low, that buildup is not reduced, but potentially promoted. This is of course an undesirable effect and a large uncertainty factor.

In conclusion, new methods are needed for the reduction of that build-up in order to solve this problem that the polymer industry still faces today. It is an object of the present invention to find a solution to the above problem by providing a new method which reduces that buildup in the extrusion blow molding of polymers.

SUMMARY OF THE INVENTION

To the above object, the present invention provides a process for the extrusion blow molding of polymers according to claim 1, wherein a process improvement additive is added to the polymer prior to the extrusion blow molding process and wherein the process improvement additive is a carrier polymer, a binding component, one or more fluoropolymers and one or more zeolites includes.

Preferred forms of this method are given in claims 2 to 16.

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BE2018 / 5438 According to an embodiment, the process improvement additive used comprises one or more zeolites in a total concentration comprised between 0.25 and 1.25 m%. The concentration is preferably between 0.25 and 1.25 m%, even more preferably between 0.25 and 1.00 m%. It is determined that a process improvement additive with a maximum of 1.00 m% of zeolites has a maximum acid-catching capacity.

According to a further embodiment, the process improvement additive used comprises one or more fluoropolymers with a total concentration comprised between 1.00 and 4.00 m%, more preferably between 1.00 and 3.50 m%, even more preferably between 1 , 00 and 3.00 m%. In a most preferred form, the maximum concentration of fluoropolymers is 2.95 m%. Use of fluoropolymers in these concentration ranges implies good lubricating properties with regard to the extrusion screw and head, the jacket and the extrusion nozzle.

According to a further embodiment, the process improvement additive used comprises one or more antioxidants with a total concentration comprised between 0.50 and 3.00 m%, preferably between 0.50 and 2.00 m%, even more preferably between 0, 50 and 1.70 m%. The antioxidants present in the process improvement additive counteract the degradation of the polymer to low molecular weight compounds.

An embodiment of the present invention comprises the zeolites in a ratio comprised between 1: 4 and 1: 2 with respect to the fluoropolymers. The synergistic effect between the various additive components was greatest when this specific ratio was used. As a result, less additive was required to achieve the intended beneficial effect.

In one embodiment, the process improvement additive is diluted in the polymer in a ratio comprised between 1:10 and 1: 150, preferably between 1:75 and 1: 150. Diluting the process improvement additive according to this ratio implies an efficient reduction of that build-up.

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DETAILED DESCRIPTION

Unless defined otherwise, all terms used in the description of the invention, including technical and scientific terms, have the meaning as generally understood by those skilled in the art of the invention. For a better assessment of the description of the invention, the following terms are explicitly explained.

A, the and the reference in this document to both the singular and the plural unless the context clearly presupposes otherwise. For example, a segment means one or more than one segment.

When approximately or around in this document is used with a measurable quantity, a parameter, a duration or moment, and the like, variations are meant of +/- 20% or less, preferably +/- 10% or less, more at preferably +/- 5% or less, even more preferably +/- 1% or less, and even more preferably +/- 0.1% or less than and of the quoted value, insofar as such variations apply in the described invention. However, it must be understood that the value of the quantity at which the term is used approximately or around is itself specifically disclosed.

The terms include, comprising, consisting of, provided with, containing, containing, contents, including its synonyms and its inclusive or open terms indicating the presence of what follows, and which do not exclude or prevent the presence of other components, characteristics, elements, members, steps, known from or described in the prior art.

The citation of numerical intervals by the end points includes all integers, fractions and / or real numbers between the end points, including these end points.

A polymer is a chemical compound with a molecular structure that consists of a sequence of linked, identical or specific parts. Polymers can be subdivided according to their properties into the categories of thermoplastic, thermoset and elastomer, which are respectively meltable, non-meltable or difficult to melt and which have elastic properties.

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The physical shape of a polymer is determined during polymer molding and can include processes such as extrusion, extrusion blow molding, injection molding, pressure molding, and thermoforming.

Blow molding is a molding technique for the production of polymers with a hollow shape and may or may not be directly linked to an extrusion process, namely extrusion blow molding. The soft thermoplastic material is inflated with the aid of a gas, for example compressed air, so that it is pressed against a mold. The thermoplastic retains its final shape after cooling.

The Melt Flow Index (MFI) is a measure of the flow behavior of a polymer material. The longer the molecular chain, the higher the viscosity of the polymer and the higher the MFI. The MFI is determined by flowing a certain amount of polymer at a constant temperature and constant pressure through a tube of predetermined length and diameter. The time is hereby measured, whereby the MFI is expressed in mass per time unit of flow.

Masterbatch means a solid or liquid additive that is used in the production of polymers to provide the end product with specific properties. For example, a masterbatch can be used to give the polymer a specific color or, for example, to build in a fire-retardant or antimicrobial effect.

That build-up is the accumulation and deposition of polymeric material and / or degradation products thereof against the extrusion screw and head, the jacket and the extrusion nozzle. Such deposits may arise due to a temperature that is incorrectly selected, a too large difference in MFI between the polymer and the masterbatch, poor miscibility or the presence of harmful components in the polymer mixture, etc. This build-up often gives rise to the visual take black spots and black holes. These defects are not only unaesthetic but can also negatively influence the performance and / or strength of the polymer.

A process improvement additive is a component that is added to a process to improve its overall operation or to minimize or solve related problems. Become a process improvement additive

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BE2018 / 5438 is usually added in very low concentrations in order not to influence the properties of the end product.

The binding component is understood to be a component that is added to a composition in order to be able to better mix the various components thereof. In the context of the process improvement additive, the binding component also ensures a smooth mixing of the process improvement additive and the polymer product.

A fluoropolymer is a polymer whose molecular structure comprises one or more fluorine atoms. These polymers are generally very resistant to solvents, acids and bases and have a very low frictional resistance due to their fluorine content. This makes fluoropolymers extremely suitable as a friction-reducing component.

An antioxidant is a component that is able to neutralize free radicals. They are often used industrially as stabilizers to prevent oxidation. In polymer chemistry, antioxidants are used to prevent the oxidative degradation of polymers, so that strength and flexibility of the end product is guaranteed.

Zeolites are minerals belonging to the tectosilicates and are made up of silicon, aluminum and oxygen atoms. Zeolites generally have a very porous structure and can be used as ao molecular sieves, ion exchangers or as a catalyst. Zeolites are also very suitable as an acid scavenger.

The present invention relates to a process for extrusion blow molding of polymers, wherein a process improvement additive is added to the polymer prior to the extrusion blow molding process and wherein the process improvement additive comprises a carrier polymer, a binding component, one or more fluoropolymers and one or more zeolites. Use of the process improvement additive during blistering significantly reduces the risk of black spots and black holes, which is a direct effect of the specific composition of this additive. The fluoropolymers present in the additive form a dynamic, rheological coating around the extrusion screw and head, the jacket and the extrusion nozzle, which has lubricating properties, whereby

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BE2018 / 5438 accumulation of polymer degradation products due to heat and friction is reduced. Zeolites act as acid scavengers, which helps to reduce the reactivity and degradation of the polymer. Unlike the frequently used zinc stearate, these zeolites have the advantage that they are easy to dose and that they always have the effect of reducing that build-up during shaping. Zinc stearate, however, can increase that build-up with a limited under or overdose, which is an undesirable side effect. Bladder formation in which the combination of one or more zeolites, one or more antioxidants and one or more zeolites were added to the polymer yields a higher quality end product with clearly less visible and invisible defects than when another masterbatch or additive composition is used. An additional advantage of blow molding with the use of this process improvement additive is that the screw speed during extrusion can be increased without additional risk of the development of that build-up, black spots and / or black holes. A higher permitted screw speed also implies an increased production speed. Moreover, blow molding with this process improvement additive leads to a reduced melt pressure, a reduced extrusion temperature and a reduced gel formation, which ultimately gives rise to a higher quality extruded product.

According to an embodiment of the present invention, the process improvement additive used comprises one or more zeolites which serve as acid scavengers and are selected from the group of analgesia, clinoptilotite, chabazite, laumontite, mazzite, heulandite, stilbe, natrolite, mordenite, gottardite and brewsterite. Known process additives for improving polymer design often use calcium or zinc stearate as an acid scavenger. The disadvantage of this compound, however, is that it only has an optimum effect in a very narrow range, so that a small under or overdose just increases the risk of the formation of black spots and black holes. Zeolites also have acid-retaining properties, but remain optimally effective in a broad concentration range. This makes dosing simple and ensures an unambiguous reduction in the risk of black spots and black holes during the blistering process.

Preferably, the process improvement additive comprises one or more zeolites in a total concentration comprised between 0.25 and 1.25 m%. The concentration is preferably between 0.25 and 1.25 m%, even more preferably between 0.25 and 1.00 m%. It is determined that a process improvement additive with maximum

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1.00 m% of zeolites has a maximum acid-catching capacity, without negatively influencing the shaping process.

According to a further embodiment, the process improvement additive used comprises one or more fluoropolymers with a total concentration comprised between 1.00 and 4.00 m%, more preferably between 1.00 and 3.50 m%, even more preferably between 1 , 00 and 3.00 m%. In a most preferred form, the maximum concentration of fluoropolymers is 2.95 m%. Use of fluoropolymers in these concentration ranges implies good lubricating properties with respect to the extrusion screw and head, the sheath and the extrusion nozzle, thereby minimizing the accumulation of any degradation products during the blow molding, without thereby negatively influencing this blow molding process. In addition, the need for maintenance of the extrusion screw and head, the jacket, the extrusion nozzle, and other parts when using the process improvement additive is minimal to absent. As a result, the blistering process can be continued continuously for longer when using the process improvement additive without having to interrupt the process for maintenance or resolution of common problems. Since in the event of a process interruption, and in particular when the production process is restarted, a considerable amount of waste material is created, a smaller number of interruptions also implies a smaller amount of waste. Since the blow molding process takes place at a lower temperature and at a reduced melt pressure, the waste that is produced is of such a quality that this waste can be reused as source material. This drastically reduces the amount of waste in its entirety.

In particular, the fluoropolymers will be selected from the group of polyvinyl fluoride (PVF), polyethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF) and tetrafluoroethylene propylene (FEPM), preferably from the group of PVF and ETFE. These fluoropolymers exhibit strong lubricating properties and, as a direct result, reduce the accumulation of polymer and degradation products thereof around the extrusion screw and head, the jacket and the extrusion nozzle. This makes maintenance when using this process improvement additive superfluous, as a result of which the blow molding process has a longer continuous duration and less waste is produced as a result of the discontinuation and restart of production.

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BE2018 / 5438 According to an embodiment, the process improvement additive comprises one or more antioxidants with a total concentration comprised between 0.50 and 3.00 m%, preferably between 0.50 and 2.00 m%, even more preferably between 0 , 50 and 1.70 m%. The antioxidants present in the process improvement additive counteract the degradation of the polymer to low molecular weight compounds. In the presence of antioxidants with a concentration comprised between 0.50 and 3.00 m%, radicals are neutralized and the reactivity of the process mixture is sufficiently reduced so that the formation of black spots in the final product is minimized. Incidentally, the antioxidants have no negative influence on the blistering process within this concentration range. The antioxidants include 20 m% octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 80 m% tris- (2,4-di-tert-butylphenyl) phosphite, which composition is commercially available is in powder form such as, among others, Irganox B900 (BASF). This specific composition has already proven to be a good antioxidant composition for use in polymer blistering. The advantage of this composition is that it is compatible with a wide spectrum of polymers, namely polyethylene, ethylene vinyl acetate copolymers, polycarbonates, polyesters, styrene homo- and copolymers, polyurethanes and other elastomers. The antioxidant composition provides a solid thermostability and prevents the degradation of the polymer during extrusion blow molding. The various components present in the current process improvement additive have a synergistic effect with this antioxidant composition, which considerably reduces the risk of the formation of black spots and black holes.

An embodiment of the present invention comprises the zeolites in a ratio comprised between 1: 4 and 1: 2 with respect to the fluoropolymers. The synergistic effect between the various additive components was greatest when this specific ratio was used. As a result, less additive was required to achieve the intended beneficial effect. This ratio is preferably included between 3:10 and 4:10.

According to an embodiment, the process improvement additive used comprises a binding component, namely ethylene oxide, and the carrier polymer is selected from the group of polyethylene (PE), polypropylene (PP), polycarbonates, polyesters, polyurethanes (PU), polyvinyl chloride (PVC) and other elastomers. The use of ethylene oxide as a binding component guarantees a good, mutual mixing between the various components of the process improvement additive on the one hand and a good interference of the additive in the

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BE2018 / 5438 polymeric material on the other. A homogeneous distribution of the additive in the polymer material is essential to obtain an end product with homogeneous quality and functionality.

According to one embodiment, the process improvement additive used is diluted in the polymer in a ratio comprised between 1:10 and 1: 150, preferably between 1:75 and 1: 150. Diluting the process improvement additive according to this ratio implies an efficient reduction of that build-up and the associated formation of black spots and black holes. Moreover, a dilution between these ratios has the advantage that the additive is administered sparingly, which simplifies the logistics in this regard. Use of the process improvement additive has the additional advantage that the concentration of a color masterbatch can be reduced to 50%. The process improvement additive ensures that pigments are better dispersed during the plasticizing process. This implies a more efficient and economical coloring. In addition, a faster color transition and protection of the extrudate during extrusion can be achieved when using this process improvement additive if the concentration is increased to a maximum of 5%. This allows a fast and efficient transition between successive color master batches. In the case of blow molding where the process improvement additive is applied, a color transition can be realized in ideal conditions that takes place twice as fast as in a blow molding process without this process improvement additive. A rapid color transition implies that only a little waste material is created when the color changes. In addition, optical properties of the resulting polymer, such as transparency, are also improved as a result of the use of this process improvement additive.

According to a further embodiment, the polymer is selected from the group of polyethylene (PE), polypropylene (PP), polycarbonates, polyesters, polyurethanes (PU), polyvinyl chloride (PVC) and other elastomers. The carrier polymer of the process improvement additive is usually tailored to the polymer to be shaped.

In a preferred form, the present invention comprises a method wherein a process improvement additive is used comprising:

a total concentration between 0.25 and 1.50 m%, more preferably between 0.25 and 1.25 m%, even more preferably between 0.25 and 1.00 m% of one or more zeolites;

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BE2018 / 5438 a total concentration between 1.00 and 4.00 m%, more preferably between 1.00 and 3.50 m%, even more preferably between 1.00 and 3.00 m% of one or more fluoropolymers ;

a total concentration between 0.50 and 3.00 m%, more preferably between 0.50 and 2.00 m%, even more preferably between 0.50 and 1.70 m% of one or more antioxidants;

ethylene oxide as a binding component and a carrier polymer;

and wherein this process improvement additive is metered into the polymer according to a dilution ratio comprised between 1:10 and 1: 150, even more preferably between 1:75 and 1: 150.

The blow molding process is used to shape polymer products such as cans and containers. Containers produced using this process improvement additive showed an increased top load, which means that the end product can withstand greater pressure from the top without dents. The top load could be increased by 15%. Since a specific top load is imposed for each product, these products can be produced lighter without losing strength.

In the following, the invention is described a.d.h.v. non-limiting examples illustrating the invention, and which are not intended or may be interpreted to limit the scope of the invention.

EXAMPLES

The invention will now be further elucidated with reference to the following examples, without, incidentally, being limited thereto.

EXAMPLE 1: Composition of a clinoptilotite-containing process improvement additive used in a blow molding process

Example 1 relates to a clinoptilotite-containing process improvement additive suitable for the addition to a polyethylene blow molding process.

component clinoptilotite polyvinyl fluoride polyethylene tetrafluoroethylene concentration (m%)

0.50

0.80

0.80

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Irganox B900 ethylene oxide polyethylene

0.80

0.10

97.00

Bladder formation when using this process improvement additive for polyethylene has several advantages. By applying this process improvement additive, an increased production speed is realized as a result of an increased screw speed of the extruder. Specifically, the screw speed can be increased by 5 RPM without having an adverse effect on the quality of the polymer formed. Moreover, the shaping can take place at a lower temperature and lower melt pressure. Specifically, the temperature can be lowered by about 20 ° C compared to shaping without applying this process improvement additive. This allows a product to be formed in which black holes and black spots are absent. The overall quality of the polymer is also improved due to a reduced gel production.

The formation of a blister when using this process improvement additive has the additional advantage that the production can be continued continuously for longer, i.e. less maintenance is required and fewer general problems occur, as a result of which the production line must rarely be stopped and restarted. As a result, less waste is produced. Moreover, the waste material created during production can be efficiently reused as new source material.

The above benefits together result in an energy saving of approximately 4% and result in a considerable annual cost reduction.

EXAMPLE 2: Composition of an analgesic and natrolite process improvement additive and dilution of this additive in polypropylene for its blow molding

Example 2 relates to the dilution of an analgesic and natrolite-containing process improvement additive in polypropylene which is formed by a blow molding process. The composition of the relevant process improvement additive is given in the table below.

component anal concentration (m%)

0.30

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natrolite 0.30 polyvinyl fluoride 0.80 polyethylene tetrafluoroethylene 0.50 tetrafluoroethylene propylene 0.30 Irganox B900 0.70 ethylene oxide 0.10 polypropylene 97.00

Dosage of the process improvement additive in the polymer, namely polypropylene, is accomplished by the continuous administration of the additive to the polymer according to a 1: 100 ratio. In this way a final concentration of 0.03 m% of additive components in polypropylene is achieved, which gives rise to an efficient reduction of that build-up and the resulting black spots and black holes in the end product, namely a storage container.

This analgesic and natrolite process improvement additive significantly optimizes the blistering of polypropylene. For example, the melt pressure and operating temperature during extrusion is lowered and a production speed is achieved that is up to 50% higher than when this process improvement additive is not used. Moreover, the quality of the extruded product is higher due to a reduced gel formation. The use of this process improvement additive reduces gel formation to 30%.

Claims (16)

CONCLUSIONS A method for extrusion blow molding of polymers, wherein a process improvement additive is added to the polymer prior to the extrusion blow molding process, characterized in that the process improvement additive comprises a carrier polymer, a binding component, one or more fluoropolymers and one or more zeolites. The method according to claim 1, characterized in that the process improvement additive comprises one or more zeolites selected from the group of analgesic, clinoptilotite, chabazite, laumontite, mazzite, heulandite, stilbite, natrolite, mordenite, gottardite and brewsterite. The method according to claim 1 or 2, characterized in that the zeolites have a concentration in the process improvement additive comprised between 0.25 and 1.50 m%. The method according to any of the preceding claims 1-3, characterized in that the zeolites have a concentration in the process improvement additive comprised between 0.25 and 1.25 m%. The method according to any of the preceding claims 1-4, characterized in that the fluoropolymers have a concentration in the process improvement additive comprised between 1.00 and 4.00 m%. The method according to any of the preceding claims 1-5, characterized in that the fluoropolymers have a concentration in the process improvement additive comprised between 1.00 and 3.50 m%. The method according to any of the preceding claims 1-6, characterized in that the process improvement additive comprises one or more antioxidants which have a total concentration in the process improvement additive comprised between 0.50 and 3.00 m%. The method according to any of the preceding claims 1-7, characterized in that the antioxidants have a concentration in the 2018/5438 BE2018 / 5438 process improvement additive that is included between 0.50 and 2.00 m%. The method according to any of the preceding claims 1-8, characterized in that the zeolites relate to the fluoropolymers according to a mass ratio comprised between 1: 4 and 1: 2. The method according to any of the preceding claims 1-9, characterized in that the process improvement additive comprises one or more fluoropolymers from the group of polyvinyl fluoride (PVF), polyethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF) and tetrafluoroethylene propylene (FEPM) . The method according to any of the preceding claims 1-10, characterized in that the process improvement additive comprises one or more fluoropolymers from the group of PVF and ETFE. The method according to any one of the preceding claims 1-11, characterized in that the process improvement additive comprises the antioxidants octadecyl-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and tris- (2,4-) di-tert-butylphenyl) phosphite according to a mass ratio of 1: 4. The method according to any one of the preceding claims 1-12, characterized in that the binding component comprises ethylene oxide and the carrier polymer is selected from the group of polyethylene (PE), polypropylene (PP), polycarbonates, polyesters, polyurethanes ( PU), polyvinyl chloride (PVC) and other elastomers. The method according to any of the preceding claims 1-13, characterized in that the process improvement additive is diluted in the polymer according to a dilution factor comprised between 1:10 and 1: 150. The method according to any of the preceding claims 1-14, characterized in that the process improvement additive is diluted in the polymer according to a dilution factor comprised between 1:75 and 1: 150. 2018/5438 BE2018 / 5438 The method of any one of the preceding claims 1-15, wherein the polymer is selected from the group of polyethylene (PE), polypropylene (PP), polycarbonates, polyesters, polyurethanes (PU), polyvinyl chloride (PVC) and other elastomers.