Use of a multi-layer film as the inner film of an insert tube and insert tube

Abstract

Use of a multi-layer film as the inner lining of an insertable liner for the rehabilitation of a pipe, preferably a sewer pipe, wherein the inner lining has two outer layers and a layer sequence of at least the following layers: - at least one layer (1) containing at least one homo- and / or copolyamide, preferably as one of the outer layers, - at least one adhesion promoter layer (2), (4), wherein, if ethylene (meth)acrylate copolymer is present in one of the adhesion promoter layers (2), (4), it is functionalized and - at least one further layer (3), (5), preferably as the other of the outer layers, wherein the at least one further layer (3), (5) contains a mixture of at least one thermoplastic olefin homo- or copolymer and at least one ethylene (meth)acrylate copolymer, in functionalized or non-functionalized form.

Description

[0001] The invention relates to the use of a multilayer film as the inner film of an insert hose for the rehabilitation of a pipe, preferably a sewer pipe. Furthermore, the invention relates to such an insert hose.

[0002] The field of application for films with an olefin homo- or copolymer layer (for example a polyethylene (PE) layer) as well as a polyamide (PA) layer is very broad. One area of ​​application is the pipe lining process for trenchless sewer pipe rehabilitation. For example, in the glass fiber pipe liner system with UV or steam curing, a thick-walled film made of high-density PE (HDPE - High Density Polyethylene) is inserted into the pipe to be renovated as a sliding film. This film is usually applied to the inner wall of the pipe in a semicircular cross-section. A flexible insert hose is then pulled into the pipe (pulling process), with the insert hose sliding over the sliding film. This prevents damage to the insert hose from the inner pipe wall or theObjects in the pipe are avoided, on the other hand the friction between the insert hose and the sliding film is very low, which makes it easier to pull in the insert hose.

[0003] Such an insert hose (also called a pipe liner) in the glass fiber pipe liner system with UV or steam curing usually has an outer hose (outer hose film) and an inner hose (inner hose film), between which a carrier material, for example glass fibers, is inserted that is impregnated with reactive plastic resin. Commercially available UP resins (polyester or unsaturated polyester resins), VE resins (vinyl ester resins) or EP resins (epoxy resins) are used as reactive plastic resins. In the case of UP or VE resins, the resins are cured using photoinitiators, for example. Curing can also be carried out thermally. The insert hose is inflated from the inside inside the pipe by compressed air directed against the mechanically stable inner hose film until the outer hose film adheres to the inner pipe wall orThe lubricating film is then applied to cure the resin, for example, using UV light from a UV light source slowly drawn through the interior of the inflated insert tube. Finally, the inner film of the insert tube is peeled off and removed. The layer with the carrier material is then exposed to the substances to be conducted through the tube.

[0004] To prevent unwanted, premature curing of the plastic resin before it is inserted into the pipe to be repaired (especially during storage), the outer film of the insert hose must have a protective layer or consist of a protective layer that prevents premature exposure to UV radiation or shorter-wave visible light radiation on the resin and thus premature resin curing. The inner film of such an insert hose, on the other hand, must have very good permeability to UV radiation and shorter-wave visible light radiation. This enables the curing process, which, when the pipe liner is inflated in the pipe, is carried out by a UV radiation source that is drawn through the inside of the pipe liner, i.e., within the inner film of the hose.

[0005] In trenchless sewer pipe rehabilitation, the synthetic fiber pipe liner system with warm water or steam curing can also use an additional hose as a so-called preliner or as a support or calibration hose. A preliner covers the entire circumference of the pipe to be renovated, fits snugly against it, and is inserted into the pipe either before or at the same time as the insertion hose. The insertion hose is either pulled into the preliner (pull-in method) or inverted within or with the preliner (inversion method).

[0006] One of the disadvantages of the aforementioned PE / PA or PE / HV / PA film (HV: adhesion promoter), which has previously been used as inner tube film, is its low mechanical strength. In the worst case, insufficient mechanical properties of the inner tube film lead to the film bursting when the inner tube film of the insert tube (tube liner), which is designed as a tube, is inflated.

[0007] The inner tube films must therefore meet the highest standards in terms of their mechanical properties, such as tear resistance, tensile strength, stretchability, splicing tendency, impact strength, and puncture resistance. The PE / PA or PE / HV / PA films currently used as inner tube films still require improvement in this regard to offer even greater safety.

[0008] DE 10 2010 023 764 A1 discloses a coextruded tubular multilayer film with the layer sequence a / b / c / d / e, wherein layer e is formed from a polyamide, layer d is an adhesion promoter layer consisting of a zinc salt of an ethylene-methacrylic acid copolymer, layer c is a first further layer and consists of polyamide, layer b is an adhesion promoter layer, layer a forms a second further layer which contains 70% LDPE.

[0009] EP 2 508 338 A1, US 2007 / 0172614 A1 and US 3,697,368 A all relate to packaging films and are therefore not relevant to the present invention, which relates to the use of a multilayer film as the inner film of an insert tube and to such an insert tube.

[0010] US 4,954,393 A discloses a multilayer film with the layer sequence A / B / C, where layer A consists of polyamide, layer B is an adhesion promoter layer, and layer C is a weldable layer. However, this known multilayer film is not a tubular inner film, but rather a tubular outer film, which must meet entirely different requirements.

[0011] US 2004 / 0035485 A1 and the subsequently published DE 10 2013 111 428 A1 also disclose multilayer films.

[0012] The object of the present invention is to propose the use of a multilayer film as the inner film of an insert tube, wherein the inner film meets the high requirements regarding its mechanical stability. Furthermore, the object of the invention is to propose such an insert tube.

[0013] This problem is solved by the use claim 1 and by claim 11 directed to an insert hose.

[0014] In the multilayer film used according to the invention, at least one adhesion promoter layer and / or another layer contains at least one ethylene-(meth)acrylate copolymer, which may be functionalized (also called "modified"). The wt. % content of the at least one ethylene-(meth)acrylate copolymer in the at least one layer may range between 0.1 and 100%. The at least one ethylene-(meth)acrylate copolymer may be an ethylene-methyl acrylate (EMA copolymer), ethylene-ethyl acrylate (EEA copolymer), ethylene-butyl acrylate (EBA copolymer), or ethylene-2-ethylhexyl acrylate (ethylene-2-EHA copolymer).

[0015] The copolymers mentioned have high impact strength, high heat resistance and high flexibility even at low temperatures.

[0016] The term (meth)acrylate applies to monomers or polymers produced by polymerization thereof comprising or based on acrylic acid esters or methacrylic acid esters. In other words, the term "ethylene-(meth)acrylate copolymer" refers to both ethylene-acrylate copolymers and ethylene-methacrylate copolymers.

[0017] Ethylene-(meth)acrylate copolymers within the meaning of this invention are all copolymers formed by (co)polymerization of ethylene (H2C = CH2) with esters of acrylic or methacrylic acid. The esterification of acrylic or methacrylic acid can occur with all common alcohols of the general structural formula R-OH (R = e.g., saturated or unsaturated, branched or unbranched, aliphatic or aromatic hydrocarbon with 1 to 60 carbon atoms). The chemical structural formula of acrylic acid is H2C = CH-COOH, and the chemical structural formula of methacrylic acid is H2C = C(CH3)-COOH. Examples of alcohols are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, hexanol, 2-ethylhexanol, heptanol, octanol, decanol, dodecanol, etc.

[0018] However, the at least one ethylene-(meth)acrylate copolymer is preferably not an ionomer and therefore preferably does not have any chain molecules cross-linked via ionic bonds.

[0019] If one or two additional monomers are polymerized alongside ethylene and (meth)acrylates, the result is terpolymers (made up of three monomers) or quaterpolymers (made up of four monomers). Such additional polymerization of the ethylene-(meth)acrylate copolymer also falls under the term "functionalization" or modification of the ethylene-(meth)acrylate copolymer according to the current terminology. In this case, for example, one or more chemical functions can be introduced into the polymer. For example, ethylene-(meth)acrylate polymers with carboxylic acid groups are obtained when the additional monomer is acrylic or methacrylic acid. Ethylene-(meth)acrylate polymers with hydroxyl groups are formed, for example, with hydroxyethyl acrylate as an additional monomer. Ethylene-(meth)acrylate polymers can also be provided with additional chemical functions by grafting. For example, grafting with maleic anhydride (MA) is common, which introduces acid anhydride groups into the polymer.

[0020] Polymers based on ethylene and (meth)acrylate, which additionally contain three or more other monomers, are also possible, but these are of only minor industrial importance.

[0021] The advantages of the invention are particularly evident in the fact that the films used according to the invention exhibit outstanding mechanical properties such as very high extensibility, low tendency to splice, robustness, durability, puncture resistance, and very high transmission in the wavelength range from 300 to 500 nm. Bursting of the films is thus virtually impossible.

[0022] In particular, it has been found that the multilayer films used according to the invention are characterized by excellent mechanical properties, in particular by very good extensibility (determined by the inflation test method described below), without any layer splitting. The multilayer film used according to the invention preferably has an extensibility up to the "splicing," i.e., a first tear of an inner film layer, of at least 20%, particularly preferably at least 25%, and very particularly preferably at least 30%. The extensibility up to bursting is preferably at least 100%, preferably at least 110%, particularly preferably at least 120%, and most preferably at least 130% and even at least 140%.

[0023] An important parameter related to extensibility is the so-called "yield point," or yield point. Up to this point, the force increases with elongation. Once the yield point is exceeded, the film begins to flow, and the force decreases again with increasing elongation, or at least remains constant.

[0024] A suitable ethylene (meth)acrylate is, for example, Lucofin 1494H from the German company Lucobit AG, which is a chemically modified polyethylene in the form of EBA (ethylene butyl acrylate) grafted with maleic anhydride (MA). In the context of this invention, it is preferably used in an adhesion promoter layer. Another suitable ethylene (meth)acrylate is Lucofin 1400HN Powder, which is a polar copolymer of ethylene and butyl acrylate with low crystallinity. Due to its chemical structure, Lucofin 1400HN Powder is softer and more flexible than ethylene homopolymers of comparable density.

[0025] Resins of the brand name Lotader from the French company Arkema, in particular Lotader MAH (maleic anhydride) and Lotader GMA (glycidyl methacrylate), which are terpolymers, can also be used.

[0026] From DuPont, suitable ethylene (meth)acrylate copolymer resins are marketed under the brand name Elvaloy AC. Examples of ethylene butyl acrylates (EBA copolymers) are Elvaloy AC 3117, Elvaloy AC 3217, Elvaloy AC 3427 and Elvaloy AC 3717. Examples of ethylene ethyl acrylates (EEA copolymers) are Elvaloy AC 2112, Elvaloy AC 2116, Elvaloy AC 2618 and Elvaloy AC 2615. Examples of ethylene methyl acrylates (EMA copolymers) are Elvaloy AC 1125, Elvaloy AC 1209, Elvaloy AC 1218 and Elvaloy AC 1224, Elvaloy AC 1330, Elvaloy AC 1609, Elvaloy AC 1820, Elvaloy AC 1913, Elvaloy AC 12024S and Elvaloy AC 15024S.

[0027] Various suitable ethylene (meth)acrylates are available from BASF under the brand name Lucalen, for example Lucalen A 2710 H, Lucalen A 2910 M, Lucalen A 2910 MQ 47, Lucalen A 2920 M, Lucalen A 2920 MQ 225H, Lucalen A 3110 M, Lucalen A 3110 MQ 244, Lucalen A 3110 MQ 270 and Lucalen A 3120 M.

[0028] As already mentioned for some of the above-mentioned commercially available ethylene-(meth)acrylate copolymers, functionalization or modification of the ethylene-(meth)acrylate copolymers by copolymerization with (meth)acrylic acid, glycidyl methacrylate, or hydroxyethyl acrylate is possible instead of or in addition to grafting with maleic anhydride (MAH). This yields, for example, terpolymers or quaterpolymers.

[0029] Another possible modification of the multilayer film used according to the invention is powdering.

[0030] Particularly preferably, at least one adhesion promoter layer and / or another layer (both of which usually contain at least one thermoplastic olefin homo- or copolymer in the case of inner tube films for trenchless sewer rehabilitation, often even predominantly) contains said at least one ethylene-(meth)acrylate copolymer partially or even predominantly or exclusively. The proportion of the at least one ethylene-(meth)acrylate copolymer in the corresponding layer or layers can preferably be more than 30 wt. %, preferably more than 75 wt. % and up to 100 wt. %. Mixtures in the respective layers with conventional adhesion promoters or thermoplastic olefin homo- or copolymers (or other substances) are readily possible.

[0031] The multilayer film used according to the invention can have a layer structure with three, four, five, or more layers. A three-layer, four-layer, five-layer, or even higher layered tubular inner film can be used, wherein, according to the invention, at least one of the layers—except for the layer(s) based on or containing a homo- and / or copolyamide—contains at least one ethylene-(meth)acrylate copolymer.

[0032] A three-layer film used according to the invention can, for example, have a layer sequence PE / HV / PA, a five-layer film can, for example, have a layer sequence PE / HV / PA / HV / PE, PA / HV / PE / HV / PE or PA / HV / PE / PE / PE or PA / HV / PA / HV / PE, a seven-layer film can, for example, have a layer sequence PE / PE / HV / PA / HV / PE / PE, PA / HV / PE / PE / PE / PE / PE or PA / HV / PA / HV / PE / PE or PA / HV / PA / HV / PA / HV / PE. According to the invention, one or more of the PE and / or HV layers contain at least one ethylene-(meth)acrylate copolymer, in some embodiments even exclusively (wherein the abbreviations PE and HV do not refer to the ingredients in these cases, but are retained for the sake of simplicity).

[0033] The PA layer(s) can be made of the same or different PA materials. PA blends are also preferred. Further details are provided below. If two PA layers are present, a bonding agent can be added. However, bonding can also be done without bonding agents. The use of (conventional) bonding agents between two PA layers is preferred.

[0034] As already mentioned above, it was surprisingly found that the multilayer film used according to the invention, whether in the form of a multilayer tubular film (i.e. a multilayer film produced by (co)extrusion, preferably by blown film (co)extrusion, without a sealed seam) or a multilayer film sealed to form a tube, is characterized by very good mechanical properties, in particular by very good extensibility. During the rehabilitation of underground pipes, it can therefore be used as an inner tube film and withstand the stresses that occur, in particular during inflation in the pipe system. This also applies to the mechanical stresses to which the film is exposed during transport. Furthermore, it was found that the multilayer film used as an inner tube film is sufficiently tear-resistant when removed from the resin / carrier system after the resin has cured.This allows the inner tube film to be removed without leaving any residue, leaving no film fragments in the repaired sewer. Furthermore, the multilayer film used according to the invention provides a good barrier effect when used as an inner tube film against the resin drying out.

[0035] The numbering of the layers in the claimed layer sequences, i.e., layer (1), layer (2), ..., clarifies the order of the various layers. One or more additional layers may be provided between these individual layers, for example, layer (1) and layer (2).

[0036] At least one homo- and / or copolyamide is suitable for producing layer (1) of the multilayer film used according to the invention according to claim 1. Suitable homo- or copolyamides are preferably selected from the group of thermoplastic aliphatic, semi-aromatic, or aromatic homo- or copolyamides. These homo- or copolyamides can be produced from diamines (e.g., aliphatic diamines having 2-10 carbon atoms, in particular hexamethylenediamine, and / or aromatic diamines having 6-10 carbon atoms, in particular p-phenylenediamine) and / or from aliphatic dicarboxylic acids and / or aromatic dicarboxylic acids having 6-14 carbon atoms (e.g., adipic acid, terephthalic acid, or isoterephthalic acid) and / or from lactams having 4-10 carbon atoms (e.g., from ε-caprolactam).

[0037] Preferably, PA 6; PA 11; PA 12; PA 66; PA 6,10; PA 6,12; PA 666, PA 6I, PA 6T or corresponding copolymers or mixtures of at least two of the polyamides mentioned are used.

[0038] The layer (1) of the multilayer film used according to the invention has a layer thickness of 5 µm to 100 µm, particularly preferably of 20 µm to 90 µm.

[0039] To produce the adhesion promoter layers (2) and / or (4) of the multilayer film used according to the invention according to claim 1—with or without the inventive use of at least one ethylene-(meth)acrylate copolymer in these layers (2) and / or (4)—conventional adhesion promoters can be used, unless the layers (2) and / or (4) consist exclusively of at least one ethylene-(meth)acrylate copolymer. If a modified thermoplastic polymer is used for the adhesion promoter layers (2) and / or (4), in particular the same olefin homo- or copolymers as for the further first and second layers (3; 5) (see below) can be used, albeit with suitable modification.Accordingly, at least one modified olefin homo- or copolymer is preferably used, the modification preferably being carried out with at least one organic acid or at least one preferably cyclic organic acid anhydride, preferably with maleic anhydride.

[0040] The layer thickness of the adhesion promoter layers (2) and / or (4) of the multilayer film used according to the invention is preferably between 1 µm and 30 µm, particularly preferably between 2 µm and 20 µm.

[0041] For the production of layers (3) and / or (5) of the multilayer film used according to the invention according to claim 1, at least one thermoplastic olefin homo- or copolymer can be used, for example those of α,β-unsaturated olefins with 2-10 carbon atoms, if the corresponding layer does not consist of 100% ethylene-(meth)acrylate copolymer. Ethylene homopolymers (polyethylene, PE), preferably LDPE (high-density polyethylene in the range of 0.86-0.93 g / cm 3 ), LLDPE (Linear Low Density Polyethylene), HDPE (high density polyethylene in the range of 0.94 and 0.97 g / cm 3 ) and mPE (PE polymerized on the basis of metallocene catalysts), propylene homopolymers (polypropylenes, PP), butylene homopolymers (polybutylenes, PB) and isobutylene homopolymers (polyisobutylenes, PI) or mixtures of at least two of the polymers mentioned.

[0042] The layer thickness of the layers (3) and / or (5) of the multilayer film used according to the invention is preferably 10 µm to 500 µm, particularly preferably from 20 µm to 400 µm, very particularly preferably from 30 µm to 300 µm.

[0043] The layer thickness of the individual layers (3) and / or (5) of the multilayer film used according to the invention amounts to at least 15% of the total layer thickness of the multilayer film, preferably at least 25% and particularly preferably from 30% to 60%.

[0044] Individual or all layers of the multilayer film used according to the invention can, if advantageous or necessary, each independently contain additives. These can be selected from the group comprising antistatic agents, antioxidants, oxygen scavengers, antiblocking agents, antifogging agents, antimicrobial agents, dyes, color pigments, stabilizers, preferably heat stabilizers, process stabilizers, process aids, flame retardants, nucleating agents, crystallization agents, preferably crystal nucleating agents, lubricants, optical brighteners, flexibilizers, sealants, plasticizers, silanes, spacers, fillers, peel additives, waxes, wetting agents, surface-active compounds, preferably surfactants, UV stabilizers, and dispersants. The proportion of additives in the layers can be at least 0.01-20 wt. %, preferably at least 0.1-10 wt.-% (each based on the total weight of a single layer).

[0045] The total layer thickness of the multilayer film used according to the invention is preferably between 20 and 2000 µm, particularly preferably between 50 and 1500 µm, very particularly preferably between 70 and 1000 µm, in particular between 80 and 400 µm.

[0046] In order to use the multilayer film used in the invention as an inner tubular film in pipe rehabilitation (see above), it is advantageously at least partially permeable to UV radiation, i.e., electromagnetic radiation in a wavelength range of 200 to 400 nm, preferably at least 80% and particularly preferably at least 90%. A UV source can then effectively act through the multilayer film used in the invention onto the carrier material, which is preferably impregnated with reactive resin, to cure it.

[0047] In a preferred embodiment, the multilayer film used according to the invention is not only at least partially transparent to UV radiation, but - for the same reason as above - also at least partially transparent to short-wave, visible light (ie electromagnetic radiation in a wavelength range from 400 to 500 nm, preferably from 400 to 450 nm), preferably at least 80%, particularly preferably at least 90%.

[0048] The multilayer film used according to the invention can be produced as a tubular film by (co)extrusion, particularly preferably by blown film (co)extrusion, preferably without a sealed seam. Alternatively, the multilayer film used according to the invention can be obtained in the form of a tubular film, as a cast film by cast (co)extrusion, or as another flat film. Such films can then be sealed to form a tube. Embossing, stretching, conditioning (reversible absorption of moisture, preferably water, by a thermoplastic material such as homo- or copolyamide or the entire multilayer film) and / or printing of the multilayer film used according to the invention can be advantageous. In contrast, the multilayer film used according to the invention is preferably not oriented. The multilayer film used according to the invention is preferably transparent.

[0049] In accordance with the above, the present invention relates to the use of the disclosed multilayer film, preferably in the form of a tubular film, as an inner tube (inner tube film) of an insert tube for the rehabilitation of underground pipes, preferably underground sewer pipes. Due to its at least partial permeability to UV radiation, the multilayer film used according to the invention, preferably in the form of a tubular film, allows the curing of a reactive plastic resin or a carrier material impregnated with reactive plastic resin, which is located between an outer single- or multi-layer tube (outer tube film) and the inner tube (inner tube film) used according to the invention.

[0050] If at least one ethylene-(meth)acrylate copolymer is present in at least one of the adhesion promoter layers of the inner tube film, this is preferably functionalized, for example with maleic anhydride.

[0051] Preferred carrier materials are glass fiber fabrics, synthetic fiber felts (such as needle felts), nonwovens, and / or nonwoven textiles or textiles (such as knitted tubes), each impregnated with at least one reactive plastic resin, preferably with at least one unsaturated polyester resin (UP resin) and α,β-unsaturated monomers, such as styrene. A corresponding example is glass fiber reinforced plastics (GRP). Other resins that can be used, in addition to UP resins, include EP and VE resins.

[0052] The invention also relates to an insert hose for insertion into an underground pipe, in particular a sewer pipe, for its rehabilitation. The insert hose comprises a liquid-tight multilayer film according to use claim 1 as the inner hose (inner hose film, preferably in the form of a tubular film) and a liquid-tight outer tubular film (outer hose film) facing the pipe wall. Between the inner and outer hoses, a UV-curable carrier material, preferably fiberglass material, is provided, which is preferably impregnated with a reactive, unsaturated resin. The rehabilitated sewer pipe is formed from this impregnated carrier material after curing. After curing, the inner multilayer film is preferably removed from the sewer pipe lined with carrier material and pulled out. Alternatively, the inner hose film remains in the rehabilitated pipe.The production of such insert tubes is described in WO 2007 / 054350 A1 or EP 1 155 256 B1. Layer (1) of the multilayer film containing at least one homo- and / or copolyamide is preferably directed toward the resin, while the other layers (2) - (4) - if all present - are directed toward the interior of the tube.

[0053] The outer tubular film can be single-layer or multi-layer. It preferably absorbs and / or reflects UV radiation and / or short-wave visible light. The outer tubular film can be either opaque or at least contact-transparent.

[0054] Preferably, the single- or multi-layer tubular film used as the outer tube of an insert tube (comprising the inner multi-layer film of claim 1, the resin to be cured, and the outer tube) is a tubular film that is at least contact-transparent, absorbs and / or reflects UV radiation and / or short-wave visible light. Such an outer tube is described in WO 2010 / 075946 A1 and DE 10 2010 023 764 A1, wherein this outer tube preferably has the ingredients and properties described therein, preferably including the oxygen barrier layer, water vapor barrier layer, or oil barrier layer (preferably containing a homo- and / or copolyamide) also described therein.

[0055] The disclosed multilayer film can be used not only for sewer rehabilitation by means of the described UV curing or curing with short-wave visible light, but also in pipe rehabilitation systems in which the insert tube (comprising the disclosed multilayer film) is thermally cured or the inversion process is applied. Determination of extensibility

[0056] Inflation tests were conducted to determine the extensibility of a comparative example and various multilayer films used according to the invention in the form of tubular films. In the case of a multilayer film that is not in the form of a tubular film, but rather, for example, a flat film, this is sealed to form a tube in order to subsequently determine its extensibility. The tests within the scope of the invention were carried out on tubular films.

[0057] In preparation, a 5 m long tubular film with a circumference of 1175 mm to 1180 mm is sealed hermetically at both ends using two metal discs (so-called packers) of a suitable diameter. To achieve airtightness, tensioning straps and commercially available fabric adhesive tape were used - as is common practice in such inflation tests. Compressed air is fed into the tubular film through a valve in one of the two packers until it bursts. Before bursting, layer tears of the inner film layers can be seen, these are referred to as "splices". This creates a only locally occurring bubble in the multi-layer film, which then leads to a film tear and bursting of the tubular film upon further inflation.The maximum elongation (expressed in percent) is determined by measuring the outer circumference of the tubular film at its largest point until bursting and comparing it with the initial tubular diameter using the following formula:. Maximum extensibility=[(tube diameter after inflation / initial tube diameter before inflation)−1]⋅100

[0058] The same formula applies to the “film splice”, i.e. the first noticeable tear of a layer of the tubular film (without the entire tube being affected): "Splice"=[(hose diameter after inflation and first detectable layer break / initial hose diameter before inflation)−1]⋅100 Examples of implementation:

[0059] The following examples and comparative examples serve to illustrate the invention and are not to be construed as limiting. I. Chemical characterization of the raw materials used

[0060] Commercially available polyamides (PA) for layer (1) can be used (brand names in parentheses) from BASF (Ultramid), Lanxess (Durethan), DuPont (Zytel), DSM Engineering Plastics (Akulon, Stanyl), EMS-Chemie (Grilamid, Grivory, Grilon), Evonik (Vestamid, Trogamid), Radici (Radilon, Radiflam, Raditer, Heraform, Heraflex), Rhodia (Technyl, Stabamid), UBE, DSM (Novamid), and Atofina (Rilsan). In the examples presented below, a mixture of 12% Durethan B40 FAM (Lanxess) and 88% Durethan C38 F (Lanxess) is always used as the polyamide layer.

[0061] A typical adhesion promoter that can be used is Admer NF 498 E, which is an LDPE modified with maleic anhydride groups from Mitsui.

[0062] Typical polyolefins that can be used include Lupolen 2420 F, which is an LDPE from LyondellBasell Polymers, and Exceed 1327 CA from ExxonMobil Chemical Company, which is an ethylene copolymer produced by metallocene catalysis, in whose polymerization hexene is used as a further comonomer in addition to ethylene.

[0063] Lucofin 1494H from the German company Lucobit AG was used as an ethylene (meth)acrylate. It is a chemically modified polyethylene in the form of EBA (ethylene butyl acrylate) grafted with maleic anhydride (MA). In this case, it was used in adhesion promoter layers of multilayer films used according to the invention. Lucofin 1400HN powder, a polar copolymer of ethylene and butyl acrylate with low crystallinity, was also used. Due to its chemical structure, Lucofin 1400HN powder is softer and more flexible than ethylene homopolymers of comparable density. Lucofin 1400HN powder is supplied as an uncolored, unadditized powder in its natural color. Other suitable ethylene (meth)acrylate copolymers have already been listed above. The two substances, Lucofin 1494H and Lucofin 1400HN powder, are shown in bold in the following tables. II. Production of multilayer films

[0064] The multilayer film of Comparative Example 1 (C1) consists of five layers. The multilayer films used according to the invention in Examples 1-7 (B1-B7) also each consist of five layers. The individual layers of the multilayer films are directly adjacent to one another in the order listed below. The multilayer films of Comparative Example C1 and Examples 1-7 (B1-B7) were each produced as tubular films by blown film co-extrusion. III. Comparative Example V1 and Inventive Examples B1-B7Comparative Example V1:

[0065] The layer structure corresponds to that of a tubular inner film manufactured by BUERGOFOL GmbH and already in use for this application. Shift number composition Share in shift in % Thickness in µm (1) • Durethan C38 F • 88 40 • Durethan B40 FAM • 12 (2) • Adhesion promoter: Admer NF 498 E • 100 10 (3) • Lupolen 2420 F • 70 65 • Exceed 1327 CA • 30 (4) • Adhesion promoter: Admer NF 498 E • 100 10 (5) • Lupolen 2420 F • 70 75 • Exceed 1327 CA • 30 Total thickness: 200 µm Example B1:

[0066] Structure of inner tube film with Lucofin 1494H in layers (2) and (4). Shift number composition Share in shift in % Thickness in µm (1) • Durethan C38 F • 88 40 • Durethan B40 FAM • 12 (2) • Lucofin 1494H • 100 10 (3) • Lupolen 2420 F • 70 65 • Exceed 1327 CA • 30 (4) • Lucofin 1494H • 100 10 (5) • Lupolen 2420 F • 70 75 • Exceed 1327 CA • 30 Total thickness: 200 µm Example B2:

[0067] Structure: Inner film of the tube with Lucofin 1494H in layers (2) and (4) and 100% Lucofin 1400HN powder in layer (3). Shift number composition Share in shift in % Thickness in µm (1) • Durethan C38 F • 88 40 • Durethan B40 FAM • 12 (2) • Lucofin 1494H • 100 10 (3) • Lucofin 1400HN Powder • 100 65 (4) • Lucofin 1494H • 100 10 (5) • Lupolen 2420 F • 70 75 • Exceed 1327 CA • 30 Total thickness: 200 µm Example B3:

[0068] Structure: Inner film of the tube with Lucofin 1494H in layers (2) and (4) and a mixture of 50% Lucofin 1400HN powder with 50% Lupolen 2420 F in layer (3). Shift number composition Share in shift in % Thickness in µm (1) • Durethan C38 F • 88 40 • Durethan B40 FAM • 12 (2) • Lucofin 1494H • 100 10 (3) • Lucofin 1400HN Powder • 50 65 • Lupolen 2420 F • 50 (4) • Lucofin 1494H • 100 10 (5) • Lupolen 2420 F • 70 75 • Exceed 1327 CA • 30 Total thickness: 200 µm Example B4:

[0069] Structure: Inner film of the tube with Lucofin 1494H in layers (2) and (4) and a mixture of 50% Lucofin 1400HN powder with 50% Lupolen 2420 F in layers (3) and (5). Shift number composition Share in shift in % Thickness in µm (1) • Durethan C38 F • 88 40 • Durethan B40 FAM • 12 (2) • Lucofin 1494H • 100 10 (3) • Lucofin 1400HN Powder • 50 65 • Lupolen 2420 F • 50 (4) • Lucofin 1494H • 100 10 (5) • Lucofin 1400HN Powder • 50 75 • Lupolen 2420 F • 50 Total thickness: 200 µm Example B5:

[0070] Structure: Inner film of the tube with usual adhesion promoters in layers (2) and (4) and a mixture of 50% Lucofin 1400HN powder with 50% Lupolen 2420 F in layer (3). Shift number composition Share in shift in % Thickness in µm (1) • Durethan C38 F • 88 40 • Durethan B40 FAM • 12 (2) • Adhesion promoter: Admer NF 498 E • 100 10 (3) • Lucofin 1400HN Powder • 50 65 • Lupolen 2420 F • 50 (4) • Adhesion promoter: Admer NF 498 E • 100 10 (5) • Lupolen 2420 F • 70 75 • Exceed 1327 CA • 30 Total thickness: 200 µm Example B6:

[0071] Structure: Inner film of the tube with usual adhesion promoters in layers (2) and (4) and a mixture of 50% Lucofin 1400HN powder with 50% Lupolen 2420 F in layers (3) and (5). Shift number composition Share in shift in % Thickness in µm (1) • Durethan C38 F • 88 40 • Durethan B40 FAM • 12 (2) • Adhesion promoter: Admer NF 498 E • 100 10 (3) • Lucofin 1400HN Powder • 50 65 • Lupolen 2420 F • 50 (4) • Adhesion promoter: Admer NF 498 E • 100 10 (5) • Lucofin 1400HN Powder • 50 75 • Lupolen 2420 F • 50 Total thickness: 200 µm Example B7:

[0072] Structure of inner tube film with usual adhesion promoters in layers (2) and (4) as well as 100% Lucofin 1400HN powder in layer (3). Shift number composition Share in shift in % Thickness in µm (1) • Durethan C38 F • 88 40 • Durethan B40 FAM • 12 (2) • Adhesion promoter: Admer NF 498 E • 100 10 (3) • Lucofin 1400HN Powder • 100 65 (4) • Adhesion promoter: Admer NF 498 E • 100 10 (5) • Lupolen 2420 F • 70 75 • Exceed 1327 CA • 30 Total thickness: 200 µm Results from the inflation tests: Example / Comparison example Splice [%] Elongation [%] until bursting B1 26,0 115,0 B2 30,0 127,0 B3 34,2 142,3 B4 25,6 133,5 B5 24,9 127,7 B6 29,8 133,1 B7 30,2 130,2 V1 15,9 80,5 Observations and evaluations of the inflation tests:

[0073] The starting point is two values ​​for the extensibility in % of a commercially available tubular film already used as an inner film for pipe liners (comparative example V1, manufacturer BUERGOFOL GmbH). First, until the first "splicing," i.e., tearing of a film layer, is noticeable, and second, until the film bursts. The first tears of a film layer in comparative example 1 were already detected at an elongation of 15.9%, while the film burst at an elongation of 80.5%.

[0074] Although this inner tube film is in principle suitable for use as an inner tube film for pipe liners, there is always a risk that its stretching behavior will fail under real inflation conditions.

[0075] In Example B1, an ethylene-acrylate copolymer, here Lucofin 1494H (an EBA copolymer with maleic anhydride groups), was used 100% in layers (2) and (4) instead of a conventional adhesion promoter as in Comparative Example C1. The film from Example B1 exhibits significantly higher extensibility before film splicing and bursting occur. Splicing only occurs at 26.0% elongation, and bursting only occurs at 115.0% elongation.

[0076] The film from Example B2, which corresponds to the film from Example B1 except that an ethylene-acrylate copolymer (in this case without any additional functional group) was incorporated 100% into the middle layer (3) with Lucofin 1400HN powder, exhibits even better extensibility than the film from Example B1, namely 30.0% elongation until the first tear of an inner layer (i.e., until the film splice occurs) and 127.0% elongation until the film bursts. Compared to the known tubular inner film from Comparative Example V1, the elongation until the splice is thus increased by 14.1%, and the elongation until bursting is even increased by 46.5%.

[0077] Particularly good values ​​for the stretchability until the first tear of a layer or until the film bursts are also found in Example B3. The film corresponds to the film from Example B2, with the difference that in the middle layer (3) a mixture of Lucofin 1400HN powder with a conventional polyolefin, here LDPE Lupolen 2420 F, was used in a 50 / 50 ratio. With an elongation until splice of 34.2% and an elongation until the film bursts of 142.3%, even higher elongation values ​​are found here. This makes this film particularly suitable for use as an inner hose film in insert hoses (hose liners) for trenchless sewer rehabilitation. The mechanical properties with regard to the elongation of the film are outstanding.

[0078] If, as example B4 shows, a mixture of Lucofin 1400HN powder with a common polyolefin, here LDPE Lupolen 2420 F, is used in the layer (5) - starting from the film from example B3 - in a ratio of 50 / 50, the values ​​for the extensibility up to the splice (25.6%) or until the film bursts (133.5%) decrease slightly, but are still at a very high level and also lead to a hose inner film that is ideally suited for the hose lining process.

[0079] Examples B5 to B7 demonstrate that the positive effect of adding ethylene-acrylate copolymers occurs even when these copolymers have no chemical function. In Example B5, compared to Comparative Example C1, a blend consisting of Lucofin 1400HN powder and a conventional polyolefin, here LDPE Lupolen 2420 F, in a 50 / 50 ratio in layer (3) resulted in a very good elongation to splice of 24.9% and an elongation to burst of the film of 127.7%.

[0080] Even better values ​​regarding the elongation until splicing and until the film burst - compared to Example 5 - were found in Example 6, where layers (3) and (5) were made of a mixture consisting of Lucofin 1400HN powder with a conventional polyolefin, here LDPE Lupolen 2420 F, in a 50 / 50 ratio. Splicing occurred at an elongation of 29.8%, and the film burst at an elongation of 133.1%.

[0081] Example B7 corresponds to Example B5, with the difference that a pure layer of an ethylene-acrylate copolymer was used in layer (3) containing 100% Lucofin 1400HN powder. The elongation at splice was 30.1%, and the elongation at bursting of the film was 130.2%.

[0082] Examples B1 to B7 demonstrate the significant improvement in film stretchability when ethylene-acrylate copolymers are used either alone or as blends. This results in highly stretchable and durable films that are suitable for a wide range of applications.

[0083] The invention is not limited to the exemplary embodiments detailed here. Embodiments combining the features of the subclaims are also readily possible.

Claims

[1] Use of a multi-layer film as an inner film of an insert tube for the rehabilitation of a pipe, preferably a sewer pipe, wherein the inner film has two outer layers and a layer sequence of at least the following layers: - at least one layer (1) containing at least one homo- and / or copolyamide, preferably as one of the outer layers, - at least one adhesion promoter layer (2), (4), wherein, if ethylene-(meth)acrylate copolymer is present in one of the adhesion promoter layers (2), (4), this is functionalized and - at least one further layer (3), (5), preferably as the other of the outer layers, wherein the at least one further layer (3), (5) contains a mixture of at least one thermoplastic olefin homo- or copolymer and at least one ethylene (meth)acrylate copolymer, in functionalized or non-functionalized form. [2] Use according to claim 1,characterized by that the percentage by weight of the at least one ethylene-(meth)acrylate copolymer in at least one of the layers (2), (3), (4), (5) is in the range from 0.1 to 100%, preferably at least 30% by weight. [3] Use according to claim 1 or 2, characterized by that the percentage by weight of the at least one thermoplastic olefin homo- or copolymer is between 10% and 100%. [4] Use according to one or more of the preceding claims, characterized by that the at least one adhesion promoter layer (2), (4) consists of more than 50 wt.%, preferably more than 75 wt.%, particularly preferably 100 wt.%, of at least one ethylene-(meth)acrylate copolymer. [5] Use according to one or more of the preceding claims, characterized bythat said at least one ethylene (meth)acrylate copolymer is an ethylene methyl acrylate (EMA copolymer), ethylene ethyl acrylate (EEA copolymer), ethylene butyl acrylate (EBA copolymer) or 2-ethyl hexyl acrylate (2-EHA). [6] Use according to one or more of the preceding claims, characterized by that said at least one ethylene-(meth)acrylate copolymer is functionalized with at least one organic acid or at least one organic acid anhydride, preferably with a cyclic organic acid anhydride, particularly preferably with maleic anhydride (MA). [7] Use according to one or more of the preceding claims, characterized by that said at least one ethylene-(meth)acrylate copolymer is functionalized by copolymerization with (meth)acrylic acid or glycidyl methacrylate or hydroxyethyl acrylate. [8] Use according to one or more of the preceding claims, characterized bythat the inner film of the tubular film, preferably in the form of a tubular film, comprises a layer sequence of at least the following layers: - a layer (1) containing at least one homo- and / or copolyamide, preferably as one of the outer layers - an adhesion promoter layer (2), - another first layer (3), - an adhesion promoter layer (4), - a further second layer (5), preferably as one of the outer layers, wherein at least one adhesion promoter layer (2), (4) and / or at least the further first or second layer (3), (5) contains at least one ethylene-(meth)acrylate copolymer, in functionalized or non-functionalized form. [9] Use according to the previous claim, characterized by that the first and / or the second further layer (3), (5) a) either based on a thermoplastic olefin homo- or copolymer, preferably not containing an ethylene-(meth)acrylate copolymer, or b) is based on at least one ethylene-(meth)acrylate copolymer, preferably not containing any thermoplastic olefin homo- or copolymer, or c) contains a mixture of thermoplastic olefin homo- or copolymer and ethylene (meth)acrylate copolymer. [10] Use according to one or more of the preceding claims, characterized by that it is at least partially permeable to UV radiation and liquid-tight. [11] Insert hose for trenchless sewer rehabilitation, comprising an outer hose film and an inner multi-layer film as the inner hose film, the inner hose film being designed according to one of claims 1 to 10, and a carrier material arranged between these two films, which is impregnated with a reactive plastic resin. [12] Insert hose according to the preceding claim, characterized by that the outer tubular film is liquid-tight and reflects and / or absorbs UV radiation and / or short-wave visible light and is opaque or at least contact-transparent.