DE102023110789A1 - Method for adjusting shrinkage properties of a plastic material, plastic molding system and plastic film - Google Patents

Abstract

The invention relates to a method for producing a multilayer film web, the method comprising at least the following features: b. extruding at least three layers, andc. Combining the layers into a multi-layer film web, andd. Relaxation of the multi-layer film web.Furthermore, the invention relates to a multi-layer, extruded film web, wherein at least one layer of the film web comprises a plastic from the group consisting of polyethylene, polypropylene, EVOH and polyamide and a film laminate, comprising a film web according to the invention, which is a duplex or triplex -Laminate is designed so that it comprises several individual film webs. In addition, the invention relates to a plastic molding system, preferably blown film system, for producing a multi-layer film web from a plastic material

Description

The invention relates to a plastic molding system, in particular for a blown film system, for melting and homogenizing a plastic material. Furthermore, the invention relates to a method for operating an extruder on a plastics molding system, in particular a blown film system, nonwoven system, flat film system and a plastics molding system.

During the manufacturing process of a plastic material, in particular during the manufacturing process of a plastic film, an orientation of the plastic molecules within the plastic film usually occurs due to the process. For example, the manufacturing process using the blown film process known in the prior art may be mentioned here. Depending on the type of loading and further processing, the orientation of the plastic molecules can lead to undesirable effects. An example here is shrinkage of the plastic film under the influence of heat, also referred to as shrinkage. Under the influence of heat, the orientation of the plastic molecules within the plastic film resets, so that the plastic film changes its external dimensions. Depending on the product, this effect can be either desired or undesirable. An example of desired shrinkage is “shrink sleeves” in the consumer goods sector or “shrink hoods” in the industrial packaging sector. For other applications, however, shrinkage that is as small as possible or at least largely non-existent is necessary. Examples include Lidding films or MDO-PE films for the packaging sector.

Molecular orientations in the plastic film are inherent in the system during production in the blown film process, both in the machine direction MD and across the machine direction CD, and are generally unavoidable. This behavior is favored by the main use of semi-crystalline polymers, since, compared to amorphous polymers, they have a greater tendency to orientation and therefore to shrinkage due to the crystalline components.

For example, if an additional, so-called “stretching process” is connected to the blown film process, for example by using an MDO (machine direction orientation) (inline and/or offline), the shrinkage potential is further increased. In the stretching process, the plastic film is mechanically deformed under the influence of temperature, for example via rollers, so that the plastic film after the MDO has a significantly smaller thickness compared to a starting film before the MDO. During this process, further orientations of the plastic molecules are introduced into the plastic film, so that a molecular structure within the plastic film changes, which leads to increased shrinkage potential. This applies to both crystalline and amorphous areas of the plastic film.

Stretched and unstretched films are now often used in composites, so-called laminates.

On the one hand, laminated multilayer films are known from the prior art, which represent excellent packaging materials. Laminates made of at least two or three or several independently produced layers are widespread in the packaging market. Essentially, a distinction is made between the so-called “duplex” laminate films and the so-called “triplex” laminate films. The “duplex” laminate films are films that are usually extruded using the cast or blown process, including barrier films with usually 5, 7 or 9 layers, which are produced in a separate process using a separately produced biaxially stretched film web, usually made of either Polyethylene terephthalate (PET), polyamide (PA) or polypropylene (PP) can be laminated (glued) together. Only with these films, which are produced and laminated in successive, separate process steps, can the sum of the desired and/or required properties be achieved. The required properties of the film web are achieved by combining several layers. For example, two of the required properties (sealability and oxygen or aroma barrier) are achieved by the proportion of an extruded mono- or multi-layer film, and further properties such as printability, heat or heat resistance and mechanical strength are achieved by the proportion of a separately biaxially stretched film web . In addition, it is also common to specifically achieve or increase the oxygen barrier by means of a metallization applied in a further process step. Such films and film composites are, for example, in the WO2020 225 138 described. The situation is similar with the “triplex” laminate film, whereby the sum of the desired and/or required properties is created with three films that are manufactured separately and later laminated (glued) together. For example, a biaxially stretched film web made of PET, PA or PP is laminated with a separate aluminum foil, and this composite is in turn laminated with an extruded cast or blown film. The extruded cast or blown film takes on the task of sealability and the aluminum foil takes on the task the barrier and the biaxially stretched film web have the task of optimal printability, heat resistance and mechanical strength. A side effect of laminating films, however, is that their production is naturally complex, resource-intensive and expensive and that the entire film composite is often very thick, since a number of films must first be produced separately and then in several successive process steps using hot or liquid glue must be glued together to ultimately obtain a laminated multilayer film. Examples of such “triplex” laminate films can be found, for example, in WO2020 225 138 .

On the other hand, multilayer films are known from the prior art, which are produced by means of coextrusion and, if necessary, monoaxial or biaxial stretching. The manufacturing processes used for this allow the production of a multilayer film in just one process step using coextrusion, with the subsequent lamination (gluing) of individual film layers being completely eliminated with the associated disadvantages. At most, the coextruded raw multilayer film is stretched monoaxially or biaxially in order to achieve the desired sum of properties (sealability, heat resistance, barrier, mechanical strength, printability). Apart from sealability, the majority of the required properties such as mechanical strength, heat resistance, printability and barrier (essentially the oxygen or gas barrier) are achieved through the use of raw materials such as PET, PA, ethylene vinyl alcohol copolymer (EVOH ), polyvinyl alcohol (PVOH) or polylactic acid (PLA).

Materials such as EVOH, PVOH, PVDC and PA are preferably used to achieve the oxygen or gas barrier, but materials such as PET or PLA also offer significantly better barrier protection compared to polyolefin-based raw materials such as PE or PP, especially after a monoaxial or biaxial stretching.

In addition, PET and PA in particular are used in the outer layer of films in order to achieve particularly good heat resistance and excellent printability, especially after monoaxial or biaxial stretching. In addition to their outstanding heat resistance, printability and good barrier properties against gas and oxygen, PA and PET in particular also make a decisive contribution to maintaining the desired mechanical strength, especially after monoaxial or biaxial stretching.

Numerous associations that relate to this are known from the prior art, such as: DE 10 227 580 A1 , DE 10 254 172 A1 , DE 10 2006 046 483 A1 , DE 10 2006 036 844 A1 , EP 0 476 836 B2 , EP 1 190 847 B1 , EP 1 084 035 B1 , and EP 1 985 444 A1 .

The embodiments and methods known from the prior art for producing coextruded multilayer barrier films generally have a relatively large shrinkage of usually more than 20%, in any case always more than 5%, in each case in the machine direction (MD) and in the crosswise direction (CD). This is advantageous or even desirable for many applications, such as shrink bags/lid films.

The WO 2020 225 138 lists common examples of co-extruded films on the market. However, to date there is a lack of both monoaxially or biaxially stretched films and multilayer monoaxially or biaxially stretched barrier films, which have a relatively small or no shrinkage (less than 5%, preferably less than 3%), each in the machine direction (MD ) and in the crosswise direction (CD), and have sufficient barrier, sealability, heat resistance, mechanical strength and printability.

Systems previously used in the field of blown film extrusion, so-called annealing stations (see DE10 2012 015 462 A1 ), which are mainly used to improve flatness, consist of tempered and driven steel rollers. Due to the comparatively short contact times of the rollers with the film, especially at high web speeds, this is not sufficient to specifically adjust the shrinkage potential of the film web by influencing the film temperature and thus the relaxation processes that take place.

It is therefore an object of the present invention to provide a method for producing a coextruded and monoaxially stretched composite film, preferably a coextruded and monoaxially stretched multilayer barrier film, and a resulting multilayer film, preferably multilayer barrier film and / or a film composite (laminate) of such films to provide which has at least one of the following properties, preferably all of the following properties: sufficient oxygen and/or water vapor barrier, sealability, heat resistance, printability and mechanical strength even without a further lamination process. The resulting multilayer barrier film - meaning the individual film, not the film composite (laminate) - should also have a relatively small or no shrinkage (less than 5%, preferably less than 3%) in the machine direction (MD).

According to a first aspect, the problem solved is a process for producing a multi-layer film web. The method includes extruding at least three layers, combining the layers into a multilayer film web, and relaxing the multilayer film web.

• Es sei ausdrücklich darauf hingewiesen, dass im Rahmen der hier vorliegenden Patentanmeldung unbestimmte Artikel und unbestimmte Zahlenangaben wie „ein...“, „zwei...“ usw. im Regelfall als mindestens-Angaben zu verstehen sein sollen, also als „mindestens ein...“, „mindestens zwei...“ usw., sofern sich nicht etwa aus dem Kontext oder dem konkreten Text einer bestimmten Stelle ergibt, dass etwa dort nur „genau ein...“, „genau zwei...“ usw. gemeint sein soll. Weiterhin sind alle Zahlenangaben sowie Angaben zu Verfahrensparametern und/oder Vorrichtungsparametern im technischen Sinne zu verstehen, d.h. als mit den üblichen Toleranzen versehen zu verstehen. Auch aus der expliziten Angabe der Einschränkung „wenigstens“ oder „mindestens“ o.ä. darf nicht geschlossen werden, dass bei der einfachen Verwendung von „ein“, also ohne die Angabe von „wenigstens“ o.ä., ein „genau ein“ gemeint ist.

The following is explained conceptually:

• It should be expressly pointed out that in the context of the present patent application, indefinite articles and indefinite numbers such as "one...", "two..." etc. should generally be understood as at least information, i.e. as "at least one ...", "at least two..." etc., unless the context or the specific text of a particular passage shows that there is only "exactly one...", "exactly two..." etc. should be meant. Furthermore, all numerical information as well as information on process parameters and/or device parameters are to be understood in the technical sense, that is to say as provided with the usual tolerances. Even from the explicit specification of the restriction “at least” or “at least” or similar, it should not be concluded that the simple use of “a”, i.e. without specifying “at least” or similar, means “exactly one”. " is meant.

The terms plastic film, foil and film web are preferably to be understood as synonymous in the context of the present invention.

Examples of duplex films that are common on the market are: Foil type Oxygen barrier BOPP/PE none/low BOPA/PE none/low BOPET/PE none/low BOPP/metallization/PE through metallization BOPA/metallization/PE through metallization BOPET/metallization/PE through metallization BOPET/PE-HV-EVOH-HV-PE through barrier layer like EVOH BOPET/PE-HV-PA-EVOH-PA-HV-PE through barrier layer like EVOH Duplex film Heat resistance/ melting temperature of the outer layer Printability Shrink at 90°C BOPP/met/PE 164°C 32 dyn/cm 1-2% BOPET/met/PE 250°C 43 dyn/cm 0-1% BOPET/5-layer barrier film (PE/HV/HVOH/HV/PE) 250°C 43 dyn/cm 0-1% BOPET/7-layer barrier film (PE/HV/PA/HVOH/PA/HV/PE) 250°C 43 dyn/cm 1-2%

Common examples of triplex film on the market include: Foil type Oxygen barrier BOPP/Alu/PE through aluminum foil BOPA/Alu/PE through aluminum foil BOPET/Alu/PE through aluminum foil Triplex film Heat resistance/melting temperature of the outer layer Printability Shrink at 90°C BOPP/Alu/PE 164°C 32 dyn/cm 0% BOPA/Alu/PE 220°C 43 dyn/cm 0-1% BOPET/Alu/PE 250°C 43 dyn/cm 0-1%

The state of the art and use in practice have shown that materials such as PET and PA in the outer layer have proven to be effective in order to achieve the best possible printability and to maintain the highest possible heat resistance. But materials such as PLA or EVOH are also far more suitable from the perspective of printability, heat resistance and further processing than polyolefin-based raw materials such as PE or PP. raw material Heat resistance Melting temperature DSG (ISO 11357) Homo PET 250°C PA6 220°C PLA 210°C EVOH (32 mol%) 183°C HD PE 131°C Homo PP 164°C Raw material f EV A 28% EV A 18% EV A 12% LLDP E mLL PD E Ran do m Co-PP Co-PP EVO H PL A PA6.6 6 PA6 Co-PE T Hom o PET VST (°C) DIN EN ISO 306 40-50 60-70 70-85 100-120 100-120 100 - 120 120 - 140 155-175 160 - 180 180-200 190 - 210 210 - 230 240-260 raw material Printability or polarity surface tension (dyne/cm) P.E 30-32 PP 30-32 PET 43 P.A 43

Raw materials such as PET, PA, EVOH, PVOH and PVDC have been established to achieve a sufficient barrier against oxygen or gas. raw material Oxygen barrier 65% relative humidity 80% relative humidity cm^3 / (m^2 + d + bar) cm^3 / (m^2 + d + bar) EVOH (PE 32 mol%) 0.5 1.2 EVOH (PE 44 mol%) 1 2.3 PVDC (extrusion resin) 4 4 PVDC (dispersion resin) 10 10 PAN 8th 10 PET 50 50 PA6 35 50 PVC 240 240 PE-HG 2500 2500 PP 3000 3000 PE-LD 10000 10000 EVE 18000 18000

Source: Oxygen permeability at 20°C, measured for various barrier plastics (according to Kyoichiro; from: Joachim Nentwig, Kunststoff-Filmen, 3rd edition, 2006, Carl Hanser Verlag; Table 26)

But as experts know, the barrier properties of most of these raw materials are only sufficient if they are adequately protected from moisture.

Therefore, if these raw materials are intended to provide a barrier, they are always used in one of the middle or inner layers of a film.

In order to obtain the best possible sealability, as is known from practice, raw materials based on polyolefin, such as PE or PP, or similar, which have the lowest possible sealing temperature or melting temperature, should always be used. raw material Melting temperature of sealing materials (ASTM D3418) EVA 12% 93°C EVA 18% 84°C POP 95°C mLLDPE 118°C RaCoPP 132°C

What is striking is that the raw materials ideally used to achieve properties such as heat resistance, printability and the oxygen barrier also have a significantly higher strength, especially after biaxial stretching, than polyolefins even approximately despite biaxial stretching are able to.

In an optimal layer structure, the oxygen barrier layer should consist of EVOH, PVOH or PA and be arranged in one of the middle or intermediate layers and the sealing layer, consisting of a heat-sealable polyolefin, in the inner layer.

The outer layer should be made of one of the ideal heat-resistant and printable materials such as PET or PA.

If you take a closer look at the materials that are advantageous for properties such as heat resistance, printability, oxygen barrier and strength, you will notice that all materials have various things in common, for example they all have a density of more than 1.0 g/cm^3 all polar materials, and almost all of them have a melting temperature of over 170 °C.

If you look further at the raw materials that are preferably used as a sealing layer, you will also notice that they all have a density of less than 0.95 g/cm^3 and a melting temperature of <120 °C. raw material Density (g/cm^3) PET 1.33 to 1.4 P.A 1.12 to 1.14 PLA 0.124 to 0.125 EVOH 1.12 to 1.22 P.E 0.89 to 0.96 PP 0.895 to 0.915

Not all of these raw materials with a density of more than 1.0 g/cm3 are equally ideal for printing, like PA or PET, or heat-resistant like PET or PA. Not all of them have the same high oxygen barrier as EVOH, PVOH or PA, nor do they all have the same strength-increasing properties as PA or PET. But all of them have significantly improved properties in each of their individual properties and especially when they work together in a composite film, especially after biaxial stretching, than any raw material based on polyolefin.

It is therefore important to choose a layer structure which, on the one hand, has at least two independent layers with a density of more than 1.0 g/cm3, with one of these layers forming the outer layer and the other forming an intermediate layer. On the other hand, the composite film should contain a heat-sealable layer, which forms the inner layer and consists of a material, preferably a polyolefin, with a density of less than 0.95 g / cm3 and a melting temperature of less than 120 ° C.

The method according to the invention described herein for producing a multilayer composite film can be characterized in that it does not have a step of laminating, i.e. gluing, layers or layer combinations. Accordingly, the multilayer composite film according to the invention described herein may be a non-laminated composite film.

• L0 := Länge eines vorbestimmten Abschnitts der Verbundfolie vor dem Verstrecken;
• LI := Länge desselben Abschnitts der Verbundfolie nach dem Verstrecken und vor dem Relaxieren;
• L2 := Länge desselben Abschnitts der Verbundfolie nach dem Verstrecken und vor dem Relaxieren;
• L3 := Länge desselben Abschnitts der Verbundfolie nach dem Verstrecken und nach dem Relaxieren;

Length definitions (each related to the machine direction or the cross direction):

• L0 := Length of a predetermined section of the composite film before stretching;
• LI := Length of the same section of the composite film after stretching and before relaxing;
• L2 := Length of the same section of the composite film after stretching and before relaxing;
• L3 := Length of the same section of the composite film after stretching and after relaxing;

Definition of the stretching factor: Stretching factor V = length L1 of a predetermined section of the composite film after stretching and before relaxing divided by the length L0 of the same section of the composite film before stretching; (V = L1/L0).

Definition of the relaxation factor: Relaxation factor RL = amount of the difference between (the length L3 of a predetermined section of the composite film after stretching and after relaxation and the length L2 of the same section of the composite film after stretching and before relaxation) divided by the length L2 of the same section the composite film after stretching and before relaxing; (RL = |(L3-L2)|/L2).

Definition of the residual stretch factor; Residual stretching factor RV = length L3 of a predetermined section of the composite film after stretching and after relaxing divided by the length L0 of the same section of the composite film before stretching and before relaxing; (RV = L3/L0)).

Definition of Shrinkage (or Hot Shrinkage): Typically measured in water at 90°C, preferably within 1 second of immersing a sample, but at least within 10 seconds of immersing the sample.

According to the invention, to determine the shrinkage (or hot shrinkage), the sample is immersed in water at 90 ° C for a predetermined period of time, in particular the aforementioned period of time, and, after being removed, is immediately cooled to room temperature with water. The length of a pre-marked section after this treatment is measured and related to the measured length of the same section of the sample before treatment. The resulting aspect ratio (“shrunk” to “unshrunk”), given in percent, defines the shrinkage. Depending on the direction of the length measurement, the shrinkage occurs in the longitudinal (MD) and transverse directions (TD). The total shrinkage is calculated by adding the shrinkage in the longitudinal and transverse directions.

Multiple determinations, such as triplicate or quintuple determinations, of the length measurements, and the formation of the corresponding average values from these, advantageously increase the accuracy of the determination. According to the invention, the shrinkage and the total shrinkage can be determined in particular according to ASTM 2732.

In the context of the invention, the oxygen permeability is measured at 23 ° C and 75% relative humidity (ASTMD 1434).

For the purposes of this application, polyolefin (PO) can be a substance selected from a group consisting of PP, PE, LDPE, LLDPE, polyolefin plastomer (POP), ethylene-vinyl acetate copolymers (EVA), ethylene-methyl methacrylate copolymers (EMMA ), ethylene-methacrylic acid copolymers (EMA), ethylene-acrylic acid copolymers (EAA), copolymers of cycloolefins/cycloalkenes and 1-alkenes or cycloolefin copolymers (COC), ionomers (IO) or a mixture or a mixture thereof be. Furthermore, within the meaning of the present invention, PO also includes a mixture of the above PO with ionomers and/or with adhesion promoters.

In the context of the present invention, polyester can be used as a layer component for layer (a). Polyesters are polymers with ester functions in their main chain and can in particular be aliphatic or aromatic polyesters. Polyesters can be obtained by polycondensation of corresponding dicarboxylic acids with diols. Any dicarboxylic acid suitable for forming a polyester can be used to synthesize the polyester, particularly terephthalic acid and isophthalic acid, as well as dimers of unsaturated aliphatic acids. As the further component for the synthesis of the polyester, diols can be used, such as: polyalkylene glycols, such as ethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, diethylene glycol, polyethylene glycol and polytetramethylene oxide glycol; 1,4-Cyclohexanedimethanol, and 2-alkyl-1,3-propanediol.

PET, which stands for the polyester polyethylene terephthalate, is particularly preferred. PET can be obtained by polycondensation of terephthalic acid (1,4-benzenedicarboxylic acid) and ethylene glycol (1,2-dihydroxyethane).

Another preferred polyester are the polylactides or polylactic acids (PLA), which can be contained as a layer component in the layers for which a polyester is provided as a layer component. These polymers are biocompatible/biodegradable and, in addition to low moisture absorption, have high melting temperatures or high melting points and good tensile strength.

In the context of the present invention, EVOH stands for EVOH as well as a mixture of EVOH with other polymers, ionomers, EMA or EMMA.

In particular, EVOH also includes a mixture of EVOH and PA or of EVOH and ionomer.

Adhesion promoters (HV) can be provided as intermediate layers in the composite film according to the invention and represent adhesive layers that ensure good bonding of the individual layers below worry about others. HV can be based on a base material selected from a group consisting of PE, PP, EVA, EMA, EMMA, EAA and an ionomer, or a mixture thereof. According to the invention, EVA, EMA or EMMA, each with a purity of >99%, preferably >99.9%, are particularly suitable as adhesion promoters (HV).

According to a further preferred embodiment, layers that have HV as a layer component can also be a mixture of PO and HV or a mixture of EVA, EMA, EMMA and / or EAA and HV or a mixture of ionomer and HV or a mixture of a plurality of have HV.

For the purposes of this invention, the melting point of a polymer is determined using differential calorimetry or differential thermal analysis DIN 51007:2019-04 or. DIN EN ISO 11357-1 :2017-02 certainly. Alternatively, the ASTM D3418 method is also known from the prior art.

For the purposes of this invention, the softening point of a polymer is determined using the method for determining the Vicat softening temperature (VST = Vicat softening temperature). DIN EN ISO 306:2014-03 certainly.

For the purposes of this invention, the printability is as follows DIN 16500-2:2018-09 measured.

For the purposes of this invention, the designation of a material as a “layer component” means that a layer of the composite film according to the invention at least partially contains this material. The term “layer component” in the sense of this invention can in particular include that the layer consists entirely or exclusively of this material.

For the purposes of this invention, “middle” or “intermediate” layer means a layer of the composite film which is arranged between layer (a) and layer (c). According to the invention, layer (a) is the layer which forms a surface of the composite film on the outside (outer layer). According to the invention, layer (c) is the layer which forms a surface of the composite film that faces or comes into contact with an item to be packaged (inner layer). By definition, layers (a) and (c) of the composite film according to the invention cannot be a “middle” or “intermediate” layer.

The composite film according to the invention is preferably flat or tubular. Preferably the composite film is a food film or food casing. The composite film is also preferably suitable for use as a non-heat-shrinkable packaging material.

Examples of coextruded and biaxially stretched multilayer films according to the invention with a barrier function with at least three layers (a), (b) and (c) 3-layer structures (a) (b) (c) P.A EVOH P.O

Examples of coextruded and biaxially stretched multilayer films according to the invention with a barrier function with at least four layers (a), (b), (d) and (c) 4-layer structures (a) (b) (c) (d) PET P.O PVDC P.O P.A P.O PVDC P.O (a) (b) (c) (d) PET P.O P.A P.O P.A P.O P.A P.O

Examples of coextruded and biaxially stretched multilayer films according to the invention with a barrier function with at least five layers (a), (b), (d), (c) and (e) 5-layer structures (a) (b) (c) (d) (e) PET P.O EVOH HV P.O P.A P.O EVOH HV P.O PET P.O PVDC HV P.O P.A P.O PVDC HV P.O PET P.O P.A HV P.O P.A P.O P.A HV P.O

Examples of coextruded and biaxially stretched multilayer films according to the invention with a barrier function with at least seven layers (a), (b), (d), (c), (e), (f) and (g) 7-layer structures (a) (b) (c) (d) (e) (f) (G) PET HV P.O HV EVOH HV P.O P.A HV P.O HV EVOH HV P.O PET HV P.O HV PVDC HV P.O P.A HV P.O HV PVDC HV P.O PET HV P.O HV P.A HV P.O P.A HV P.O HV P.A HV P.O

Examples of coextruded and biaxially stretched multilayer films according to the invention with a barrier function with at least seven layers (a), (b), (d), (c), (e), (f), (g), (h) and (i) 9 -layer structures (a) (b) (c) (d) (e) (f) (G) (H) (i) PET HV P.O HV P.A EVOH P.A HV P.O P.A HV P.O HV P.A EVOH P.A HV P.O

In the context of the present invention, extrusion is understood in particular to mean that plastically deformable to viscous masses are continuously pressed out of a shaping opening under pressure. In the context of the invention, relaxation can mean that the orientation of molecules of the plastic material is influenced by heating. The molecules can be brought into a “natural” orientation. Orientations of the molecules that were created during the production process of the film web, for example due to mechanical stress such as stretching, can thus be solved. This is carried out in particular after stretching, since the molecules of the plastic material align themselves in the stretching direction during stretching.

In an embodiment of the first aspect of the invention, the method includes stretching the multilayer film web.

The stretching can be carried out monoaxially or biaxially and preferably before relaxation.

In a further embodiment of the first aspect of the invention, the film web is relaxed in such a way that after relaxation the film web has a shrinkage of less than 0.2, preferably less than 0.05, more preferably less than 0.03, in the machine direction (MD) or has negative shrinkage.

The designations 0.2, 0.05 and 0.03 are to be understood as information that expresses the reduction in the width of the shrinkage in contrast to the entire film width before relaxation. Accordingly, 0.2 can also be understood as 20%, 0.05 as 5% and 0.03 as 3%.

In a further embodiment of the first aspect of the invention, the stretching takes place in the machine direction.

The machine direction is also referred to as “MD” (machine direction) in the context of the present invention.

In a further embodiment of the first aspect of the invention, a stretch factor in the machine direction is at least 2.0.

Accordingly, the original length of the film web is at least doubled. However, lower stretching factors are also conceivable, preferably from 1.25 to 500.

In a further embodiment of the first aspect of the invention, the film web has a temperature of 50 to 160 ° C during stretching.

This temperature range is particularly effective for stretching the plastic material. However, it is also conceivable that temperatures that are +/- 10 °C above or below this range are used.

In a further embodiment of the first aspect of the invention, a relaxation factor in the machine direction is more than 0.00 and preferably more than 0.1.

In a further embodiment of the first aspect of the invention, the film web has a temperature of 50 to 180 °C, preferably 50 to 150 °C, particularly preferably 60 to 120 °C, particularly preferably 80 to 100 °C during relaxation.

In a further embodiment of the first aspect of the invention, a residence time during relaxation is at least 2 seconds, in particular more than 5 seconds, or the duration of relaxation is preferably at least 2 seconds, in particular more than 5 seconds.

A residence time during relaxation can be understood as a period of time during the relaxation process on a respective section of the plastic material. In other words, the residence time describes how long a respective section of the plastic material is exposed to relaxation. The wording or feature “under temperature” refers in particular to the temperature ranges in the previous section, i.e. a temperature of 50 to 180 ° C, preferably 50 to 150 ° C, particularly preferably 50 to 120 ° C, particularly preferably 80 up to 100 °C.

A duration of relaxation can be understood as a total period of time for the relaxation process of the plastic material.

In a further embodiment of the first aspect of the invention, the residence time during relaxation is at most 30 seconds, preferably at most 20 seconds, in particular at most 10 seconds, or the duration of relaxation is at most 30 seconds, preferably at most 20 seconds, in particular at most 10 seconds.

These dwell times and durations can particularly contribute to effective relaxation. However, shorter or longer residence times and durations than those described above are also possible.

The relaxation preferably takes place under the temperatures already listed above of 50 to 180 ° C, preferably 50 to 150 ° C, particularly preferably 50 to 120 ° C, particularly preferably 80 to 100 ° C.

According to a second aspect, the task is solved by a multi-layer, extruded film web. The film web is produced according to the method according to the invention, and at least one layer of the film web comprises a plastic from the group consisting of polyethylene, polypropylene, EVOH and polyamide.

The above list is not intended to be understood as exhaustive, so that other plastics can also be used if they are suitable for the method according to the invention. For example, PA6, PA6.6 or PA 6.12 can be used as polyamide. The film web can have several layers or just a single layer, i.e. only a single material.

In one embodiment of the second aspect of the invention, the film web has an EVOH content of less than or equal to 20%, preferably less than or equal to 10%, particularly preferably less than or equal to 5%.

Alternatively, it is also conceivable that the film web is made entirely of EVOH.

In a further embodiment of the second aspect of the invention, the film web has a polyamide proportion of less than or equal to 20% and preferably less than or equal to 10%, particularly preferably less than or equal to 5%.

Alternatively, it is also conceivable that the film web is made entirely of polyamide.

In a further embodiment of the second aspect of the invention, the film web has a proportion of EVOH and polyamide which together is less than or equal to 30% and preferably less than or equal to 10%, particularly preferably less than or equal to 5%.

It is conceivable that the film web has equal parts of EVOH and polyamide or that EVOH and polyamide are present in different proportions.

In a further embodiment of the second aspect of the invention, the film web has a sealing layer in an outer layer.

The sealing layer forms in particular an inner layer which enables bonding to a counterpart through partial melting.

According to a third aspect, the task is solved by a film laminate, which is designed as a duplex or triplex laminate, so that it comprises several individual film webs.

A duplex laminate can comprise two individual film strips and a triplex laminate can comprise three individual film strips.

In one embodiment of the third aspect of the invention, the film laminate has at least one monoaxially stretched and/or at least one shrink-optimized film web.

In a further embodiment of the third aspect of the invention, the film laminate has at least one monoaxially stretched film web, which is additionally shrink-optimized.

In a further embodiment of the third aspect of the invention, at least one of the film webs in the film laminate is formed by an EVOH film web.

Alternatively, at least one film web can also consist entirely of EVOH.

In a further embodiment of the third aspect of the invention, the EVOH content in the film laminate is less than or equal to 10% and preferably less than or equal to 5%.

The proportions described are particularly suitable for carrying out the process according to the invention, but different proportions are also conceivable.

In a further embodiment of the third aspect of the invention, the layer thickness of the at least one EVOH film web is less than or equal to 10 μm, preferably less than or equal to 5 μm, particularly preferably less than or equal to 2 μm.

The layer thicknesses described are particularly suitable for carrying out the method according to the invention, but different proportions are also conceivable.

In a further embodiment of the third aspect of the invention, a minor proportion of at least one EVOH film web is at most 38%, preferably at most 32%, particularly preferably at most 29%, particularly preferably at most 27%.

The minor proportions described are particularly suitable for carrying out the method according to the invention, but different proportions are also conceivable.

In a further embodiment of the third aspect of the invention, at least one of the film webs, in particular at least one of the monoaxially stretched film webs, is formed in the film laminate by at least one polyamide film web.

In a further embodiment of the third aspect of the invention, the polyamide content in the film laminate is less than or equal to 10% and preferably less than or equal to 5%.

Alternatively, at least one film web can also consist entirely of polyamide.

In a further embodiment of the third aspect of the invention, the layer thickness of the at least one polyamide layer is less than or equal to 10 μm, preferably less than or equal to 5 μm, particularly preferably less than or equal to 2 μm.

The layer thicknesses described are particularly suitable for carrying out the method according to the invention, but different proportions are also conceivable.

In a further embodiment of the third aspect of the invention, at least one film web of the film laminate has been metallized and/or at least one film web of the film laminate has been coated using the CVD process.

This is preferably the same film web, which has therefore been metallized and coated using the CVD process. Alternatively, there can be two different film webs, so that one of the film webs has been metallized and the other has been coated using the CVD process. Furthermore, only metallization or only a CVD process can be used. A CVD process (Chemical Vapor Deposition) is understood to mean, in particular, a chemical vacuum coating process. In particular, metal halides or other highly volatile compounds are introduced into the preheated recipient.

According to a fourth aspect, the problem solved is a plastic molding system, preferably a blown film system, for producing a film web from a plastic material. The system has at least one extruder for melting and homogenizing the plastic material into a melt, and the system has at least one nozzle for extruding the melt. In addition, the system has a means for forming a film web and a tempering module with a temperature control device for setting a defined temperature of the film web in order to influence orientations of plastic molecules within the film web.

The system can be designed as a blown film system and the nozzle is preferably designed for extruding a film tube. The system preferably has a tube formation zone for drawing the film tube longitudinally and transversely and, beyond the tube formation zone, has a flattening area for flattening the film tube into a double-layer film web. In addition, the system has a trigger for removing the film tube.

The embodiments shown here represent only examples of the present invention and should therefore not be construed as limiting. Alternative embodiments contemplated by those skilled in the art are equally included within the scope of the present invention.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2020225138 [0006, 0012]
• DE 10227580 A1 [0010]
• DE 10254172 A1 [0010]
• DE 102006046483 A1 [0010]
• DE 102006036844 A1 [0010]
• EP 0476836 B2 [0010]
• EP 1190847 B1 [0010]
• EP 1084035 B1 [0010]
• EP 1985444 A1 [0010]
• DE 102012015462 A1 [0013]

Non-patent literature cited

• DIN 51007:2019-04 [0050]
• DIN EN ISO 11357-1 :2017-02 [0050]
• DIN EN ISO 306:2014-03 [0051]
• DIN 16500-2:2018-09 [0052]

Claims (29)

A method for producing a multilayer film web, the method comprising at least the following features: a. Extruding at least three layers, and b. Combining the layers into a multi-layer film web, and√ c. Relaxing the multi-layer film web. Procedure according to Claim 1 , with the following additional feature: a. Stretching the multi-layer film web. Procedure according to one of the Claims 1 or 2 , with the following additional feature: a. the film web is relaxed in such a way that after relaxation it has a shrinkage of less than 0.2, preferably less than 0.05, particularly preferably less than 0.03, in the machine direction (MD) or a negative shrinkage. Method according to one of the preceding claims, with the following further feature: a. the stretching takes place in the machine direction. Method according to one of the preceding claims, with the following further feature: a. a stretch factor in the machine direction is at least 2.0. Method according to one of the preceding claims, with the following further feature: a. The film web has a temperature of 50 to 160 °C during stretching. Method according to one of the preceding claims, with the following further feature: a. a relaxation factor is more than 0.00 in the machine direction and preferably more than 0.1. Method according to one of the preceding claims, with the following further feature: a. During relaxation, the film web has a temperature of 50 to 180 °C, preferably 50 to 150 °C, particularly preferably 60 to 120 °C, particularly preferably 80 to 100 °C. Method according to one of the preceding claims, with at least one of the following further features: a. a dwell time during relaxation is at least 2 seconds, in particular more than 5 seconds, or the duration of relaxation is at least 2 seconds, in particular more than 5 seconds, b. the residence time during the relaxation is at most 30 seconds, preferably at most 20 seconds, in particular at most 10 seconds, or the duration of the relaxation is at most 30 seconds, preferably at most 20 seconds, in particular at most 10 seconds. Multilayer, extruded film web, having the following features: a. the film web is according to a method according to one of Claims 1 until 9 manufactured, and b. at least one layer of the film web comprises a plastic from the group consisting of polyethylene, polypropylene, EVOH and polyamide. foil strip Claim 10 , with the following additional feature: a. the film web has an EVOH content of less than or equal to 20%, preferably less than or equal to 10%, particularly preferably less than or equal to 5%. foil strip Claim 10 or 11 , with the following additional feature: a. The film web has a polyamide content of less than or equal to 20% and preferably less than or equal to 10%, particularly preferably less than or equal to 5%. Film strip according to one of the Claims 10 until 12 , with the following additional feature: a. the film web has a proportion of EVOH and polyamide which together is less than or equal to 30% and preferably less than or equal to 10%, particularly preferably less than or equal to 5%. Film strip according to one of the Claims 10 until 13 , with the following additional feature: a. The film web has a sealing layer in an outer layer. Film laminate, comprising a film web according to one of Claims 10 until 14 , with the following feature: a. The film laminate is designed as a duplex or triplex laminate so that it comprises several individual film webs. Foil laminate Claim 15 , with the following additional feature: a. the film laminate has at least one monoaxially stretched and/or at least one shrink-optimized film web. Foil laminate according to one of the Claims 15 and 16 , with the following additional feature: a. the film laminate has at least one monoaxially stretched film web, which is additionally shrink-optimized. Foil laminate according to one of the Claims 15 until 17 , with the following additional feature: a. at least one of the film webs in the film laminate is formed by an EVOH film web. Foil laminate Claim 18 , with the following additional feature: a. the EVOH content in the film laminate is less than or equal to 10% and preferably less than or equal to 5%. Foil laminate according to one of the Claims 18 or 19 , with the following additional feature: a. the layer thickness of the at least one EVOH film web is less than or equal to 10 μm, preferably less than or equal to 5 μm, particularly preferably less than or equal to 2 μm. Foil laminate according to one of the Claims 18 until 20 with the following additional feature: a. a minor proportion of at least one EVOH film web is at most 38%, preferably at most 32%, particularly preferably at most 29%, particularly preferably at most 27%. Foil laminate according to one of the Claims 15 until 21 , with the following additional feature: a. at least one of the film webs, in particular at least one of the monoaxially stretched film web, in the film laminate is formed by at least one polyamide film web. Foil laminate Claim 21 , with the following additional feature: a. the polyamide content in the film laminate is less than or equal to 10% and preferably less than or equal to 5%. Foil laminate according to one of the Claims 21 or 22 , with the following additional feature: a. the layer thickness of the at least one polyamide film web is less than or equal to 10 μm, preferably less than or equal to 5 μm, particularly preferably less than or equal to 2 μm. Foil laminate according to one of the Claims 14 until 23 , with the following additional feature: a. at least one film web of the film laminate is metallized, and/or b. at least one film web of the film laminate has been coated using the CVD process. Plastic molding system, preferably blown film system, for producing a multi-layer film web from a plastic material, in particular designed to carry out a method according to one of Claims 1 until 8th , with the following features: a. the system has at least one extruder for melting and homogenizing the plastic material into a melt, and b. the system has at least one nozzle for extruding the melt, and c. the system has a means for combining several extruded film webs into a multi-layer film web, and a. the system has a means for relaxing the multi-layer film web. Plastic molding system according to Claim 26 with the following characteristics: d. the system is designed as a blown film system, and e. the nozzle is designed to extrude a film tube, and f. the system has a tube formation zone for longitudinal and transverse drawing of the film tube, g. Beyond the tube formation zone, the system has a flattening device for flattening the film tube into a double-layer film web, and h. The system has a trigger for pulling off the film tube. Plastic molding system according to one of the Claims 26 or 27 with the following characteristics: a. the multilayer film web made of a plastic material is according to one of Claims 10 until 14 educated. Plastic molding system according to one of the Claims 26 or 27 with the following characteristics: a. the multilayer film web becomes a film laminate according to one of Claims 15 until 25 added.