KR20040105822A - Hot-sealing lacquer for multilayer films - Google Patents

Abstract

A multilayer film is disclosed, the outer side of which is coated with a first hot sealing adhesive and on the opposite outer side a polyolefin or polyvinyl compound base layer is provided. The first high temperature sealing adhesive may comprise A) cellulose nitrate and an acrylic polymer, and B) a polyvinyl compound base layer. Also disclosed is a method of producing the multilayer film. The multilayer film of the present invention is particularly suitable for the manufacture of flexible packages, for food packaging. Multilayer films of the invention are characterized by small amounts of coatings and adhesives, and thus low total weight.

Description

High Temperature Sealing Lacquer for Multilayer Films {HOT-SEALING LACQUER FOR MULTILAYER FILMS}

The present invention relates to multilayer films, to methods of making such multilayer films, as well as to their use in flexible packaging. Flexible packaging generally consists of paper, aluminum foil and / or plastic films, which are substrate carrier materials. In the form of film composites having a wide variety of properties which, in combination with films which can consist of additional materials, for example various thermoplastic polymers, also exhibit barrier properties against liquids, light and gases as well as fragrance in addition to meeting the basic requirements of mechanical protection. It is possible to produce a multilayer film.

Flexible packaging is widely used in food as well as non-food fields. For example, flexible packaging is used to package sterile medical articles, such as needles, surgical bands or gloves. In the cosmetic field, flexible packaging is used to package soaps, shower gels or shampoos, for example. In the field of preference, multilayer films are used as flexible packaging materials, for example for fragrance hermetic packaging of light bundles. In the food sector, flexible packaging is used for the packaging of sausages, coffee, grain products, soup cubes, bread and bakery items, confectionery (such as chocolate bars) and snack foods (such as potato crisps). Snack foods are referred to herein as examples of foods that are sensitive to oxygen and / or light and / or dry quickly or tend to exhibit undesirable moisture and odor absorption or may lose flavor.

Metallized multilayer films are often used in the packaging of these foods. Metallization is usually a thin film of about 30 to 80 nm on one side of the film, which is carried out by vacuum deposition of a metal or metal oxide, preferably aluminum.

The metal layer or metal oxide layer exhibits barrier properties, in particular against water vapor and light, and therefore protects against the reversal of fat contained in, for example, snack foods sensitive to photooxidation.

Barrier properties are improved by adhesives used for bonding two or more materials, for example plastic films, to produce composite films.

Multilayer films in the form of a composite film are then prepared to laminate an additional film onto a substrate carrier material, called a carrier film, to form the composite film, usually in a dry lamination process. Dry lamination is understood to be a continuous bonding of a large area of the flexible film by bonding, wherein bonding is performed during drying, which is still adhesive active after predrying. Dry lamination in this regard can take place in-line (one step process) or off-line (two step process) after printing.

Two-component (2C) laminated adhesives, in particular 2C polyurethane adhesives and melt adhesives, are used for the bonding. The application amount of the laminating adhesive is in the range of about 1 g / m ² to 5 g / m ² .

Disadvantages of dry lamination with polyurethane based laminating adhesives are about 2 hours of time before the adhesive curing process and possibly additional films can be added to the composite film or before the composite film can be cut into final form. To 48 hours. Before the article, in particular the food, can be packaged, it should be assured that there are no monomers, in particular monomeric diisocyanates, from the laminated adhesive which may still be present in the composite film and are removable. For this purpose, additional time spent on a scale of 5 to 7 days should usually be observed.

Multilayer films can also be produced by extrusion lamination. Extrusion lamination is generally understood to indicate application in the extrusion process of olefinic homopolymers or copolymers in liquid form, in particular polyethylene, from slit dies onto films to be bonded (strips) which are pretreated with a primer. Primers are precoats that are applied in very thin layers (about 1 g / m ² ), for example having a coupling, passivating and / or corrosion inhibiting action. These consist in most cases of dilute solutions of the adhesive component that will also be used for subsequent bonding.

Extrusion lamination is usually performed off-line, i.e. after printing, in a discontinuous process. The applied amount of the olefinic homopolymer or copolymer in liquid form used for the extrusion lamination is about 12 g / m ² to 20 g / m ² , which compares the multilayer film in which the total weight of the multilayer film is produced by dry lamination. Means significantly higher than its weight.

Dry lamination is actually carried out at normal speeds of 500 m / min or less, while for extruded lamination the speed is usually below 200 m / min.

Sealing of the flexible packaging is carried out by sealing. For this purpose, the multilayer film in the form of a single film or composite film should comprise at least one sealing layer arranged on the outside, inside, or outside and inside of the single film or composite film. The term "sealing" is generally understood to refer to the combined curing of a soft sealing medium. The addition of heat and / or the application of minimum sealing pressures is necessary for this purpose. Thus, what type of sealing is used distinguishes, for example, the material used, the object to be packaged (eg its thermal sensitivity), and the hot and cold sealing depending on the type of packaging machine.

In cold sealing, cold sealing agents are used which combine the two polymer layers at approximately room temperature under high pressure. Low temperature sealants are mainly applied as aqueous dispersions in amounts of 1-6 g / m ² to the polymers to be bonded, rubber and rubber-like polymers, PVDC (polyvinylidene chloride), PVAC (polyvinyl acetate) and poly (meth) Acrylate is synthesized based on. The disadvantage of cold sealers is that they can only be sealed to each other and often have insufficient adhesion.

Hot sealant dispersions, hot sealer lacquers, melt adhesives as well as films of extrusion coatings and thermoplastic elastomers are used in hot seals.

Hot sealant dispersions are PVDC-, PVAC-, poly (meth) acrylate- or latex-containing dispersions that form a sealable, dry and usually transparent coating of about 2-15 g / m ^{2 application} , mainly after water evaporation. . A disadvantage of high temperature sealant dispersions is that they often tend to bind to certain printing inks.

In contrast to high temperature sealant dispersions, organic solvents using the same or similar polymers are used for the high temperature sealant lacquers. Hot sealant lacquers are used in amounts of about 1 to 12 g / m ² . In general, hot sealer lacquers cannot be used to seal dissimilar materials.

Molten Adhesive Substrate The high temperature sealant adhesive generally comprises an ethylene / vinyl acetate copolymer as the base component, which is also deposited on the substrate by roller application or extrusion.

Extrusion coatings and thermoplastic polymer films are also used for high temperature sealing, which films are often referred to as "welding films" and the term "welding" is used instead of "sealing". Coextrusions also belong to this group, and the term coextrusion is understood to mean a multi-ply film in which the plies are extruded together in one working step, ie extrusion. All polymers, preferably elastomers, which are thermoplastic in the temperature range of about 50 ° C. to 220 ° C. are sealable and weldable. Especially for PC (polyethylene) extrusion coatings on carrier films such as aluminum, polypropylene, polyesters and polyamides allow for the processing of various packaging materials.

Peelable sealing at low temperature sealing temperatures of films with certain other films or thermoforming sheets is achieved with coextrusion coating of the PE-EVA mixture. Certain polyethylene copolymers comprising carboxylate groups, and in some cases carboxylate groups comprising zinc or sodium ions as counter ions, are also sealed at low sealing temperatures but with high sealing bond strength.

WO 00/39200 discloses a coextruded BOPP film having peelable sealing properties, wherein the film is characterized by at least one polyvinyl butyral (PVB) or at least one ethylene / vinyl acetate copolymer (EVA copolymer) as a characteristic crystalline solid component. And a thermoplastic lacquer that can only be lightly sealed with the coextruded BOPP is printed in a screen-like manner in the unsealed sealing area. Upon heating, the spacing effect of the thermoplastic lacquer becomes weaker due to the gradual softening with elevated temperature, resulting in a more seal-bonding of the coextruded BOPP surface (page 3, lines 1-11). A disadvantage of this invention is that the pigment containing sealing region cannot be clearly coated with a thermoplastic lacquer. It is also not mentioned that the metallized film composite can be sealed in a manner practicable according to the invention.

DE 100 02 167 discloses UV-stable and thermoformable films which are very transparent, high gloss and not easily flammable, provided with at least one surface side hot sealing lacquer or hot sealing layer. The film may be sealed at temperatures below 150 ° C. together with itself or other materials (pages 2, 56-57). The hot sealing layer consists of polyolefins, copolymers thereof, polyvinylidene chloride, certain cover sealing lacquers, preferably polyethylene, in particular LDPE (claim 9). The above description does not contain any suggestion for the selection of hot sealing lacquers.

DE 197 07 786 discloses plastic films for the production of packaging containers in which the outer surface of the film is coated with a sealing lacquer and the opposite outer surface is coated with an acrylate based lacquer. The acrylate based lacquer performs the function of releasing the coat and prevents the overlapped plastic films from adhering to each other during storage (page 6, lines 1-7). Films of this type are not particularly suited to the sealing of the outer surface opposite the outer surface.

US 6,077,602 discloses high temperature sealable polyolefin films comprising a polyolefin substrate having a first side and a second side. The first side has a nitrile monomer based polymer coating, and the acrylic polymer based metal or polymer coating is deposited on the second side. The coating on the first side may be sealed with itself or the coating on the second side (pages 4, lines 37-61).

DE-OS-29 00 291 discloses coating compositions for medium viscosity methyl methacrylate / butyl methacrylate copolymers, polyester resins and nitrocellulose based polyolefin products. The specification does not disclose whether sealing of the outer surface coated with the coating composition is possible and intended with an opposite outer surface not coated with the coating composition.

Notwithstanding the various possibilities described herein for the introduction of commercially sealed films or multilayer films as flexible packaging having a wide variety of properties, inexpensive flexible packaging with improved or at least the same superior properties over currently available multilayer films or flexible packaging need.

It is therefore an object of the present invention to provide an inexpensive multilayer film for flexible packaging. A further object is to provide a multilayer film for flexible packaging that allows for sealing with different materials, preferably with a printed and / or metallized surface.

It is also an object of the present invention to provide a film which can be used directly for packaging, in particular for food packaging, without complex processing steps, ie without very long intermediate storage.

The object is achieved with a multilayer film having a first hot sealing adhesive coated on an outer surface and an opposite outer surface having a polyolefin or polyvinyl compound base layer, wherein the first hot sealing adhesive is:

A) cellulose nitrate and acrylic polymer,

B) can be sealed with a polyvinyl compound base layer.

The multilayer film comprises at least one carrier film (A1).

The carrier film A1 consists of a plastics material, paper or metal. In a preferred embodiment of the invention, the carrier film A1 consists of a plastic film. Depending on the requirements profile and intended use, the carrier film (A1) can be combined with an additional film of plastic material or metal to form a composite film, and can also comprise paper, cardboard, metal or adhesive layers.

The carrier film (A1) has a weight of 15 to 45 g / m ² , preferably 25 to 42 g / m ² , particularly preferably 30 to 38 g / m ² , and is usually stripped according to processes known to those skilled in the art. It is produced continuously in the form of a substance. The carrier film (A1) preferably comprises at least one polymer from the following group: polyamide (PA), polyurethane (PUR), polypropylene (PP), poly (ethylene / co-vinyl alcohol) (EVOH) , Polyvinyl alcohol (PVOH), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polystyrene (PS) or polymethyl methacrylate (PMMA). Preference is given to PET homopolymers and copolymers having a reduced tendency to crystallization. The crystallinity tendency of PET is reduced, for example, by the introduction of comonomers such as isophthalic acid or 1,4-cyclohexanedimethanol by polymerization.

The carrier film (A1) can be present in biaxially orientated modification as well as in non-oriented (unscented) modification or shortening. In a preferred embodiment, the carrier film (A1) consists of oriented polypropylene (OPP), in particular biaxially oriented polypropylene (BOPP).

Preferably the multilayer film is a carrier film (A1) in which one outer surface is coated with a first hot sealing adhesive and the opposite outer surface comprises a polyolefin or polyvinyl compound based sealing layer.

The first high temperature sealing adhesive layer (B) is directly or indirectly, preferably directly and substantially, ie preferably covered over the entire surface, the outer surface of the carrier film (A1), polyolefin or polyvinyl It is located on the opposite outer surface containing the compound base layer. "Indirectly" means that the first hot sealing adhesive layer (B) is applied to a layer, metal layer or surface of a further film of a multilayer film, for example comprising a printing ink which does not form a carrier film A1 but is combined with it. do.

The applied amount of layer (B) is 0.1 to 6 g / m ² , preferably 0.3 to 4 g / m ² , particularly preferably 0.5 to 2 g / m ² .

The first hot sealing adhesive forming layer (B) includes the following components:

I) 5 to 60% by weight, preferably 10 to 45% by weight, particularly preferably 15 to 35% by weight of cellulose nitrate,

II) 0.5 to 20% by weight, preferably 1 to 15% by weight, particularly preferably 2 to 10% by weight of the acrylic polymer,

III) 0.5 to 20% by weight, preferably 1 to 15% by weight, particularly preferably 2 to 10% by weight of polyalkylene glycol,

IV) chelate compounds with titanium in the central reactor of 0.5 to 15% by weight, preferably 1 to 10% by weight, particularly preferably 2 to 8% by weight,

V) 0-10% by weight of one or more plasticizers,

The sum of (components I) to V) is 100% by weight in total).

The first high temperature sealing adhesive preferably includes the following components:

I) 45 to 60% by weight of one or more cellulose nitrates (I),

II) 0.5 to 20% by weight of at least one acrylic polymer (II),

III) 0.5-20% by weight of one or more polyalkylene glycols (III),

IV) at least one chelate compound (IV) having from 0.5 to 15% by weight of the central reactor titanium,

(The sum of components (I) to (IV) is 100% by weight in total).

Acrylic polymer (II) has an average molecular weight of 30,000 to 80,000. Acrylic polymer (II) is preferably a methyl methacrylate copolymer.

Polyalkylene glycol (III) is preferably a water-soluble polypropylene glycol.

Chelating compound (IV) having titanium as the central reactor is preferably ethyl acetonate, acetyl acetonate, lactic acid and salts thereof as well as triethanolamine compounds.

Plasticizers (V) which may be used include monohydric or polyhydric alcohols, preferably glycol monophenyl ethers, hexamethylene glycol, glycerol and polyalkylene glycols with molecular weights 200 to 6000 in particular. Preference is given to polyethylene glycols having a molecular weight of up to about 1000, preferably up to about 600. Polypropylene glycol and polybutylene glycol as well as polymethylene glycol may also be used. Esters such as liquid polyesters and glycerol esters such as glycerol diacetate and glycerol triacetate as well as neopentyl glycol dibenzoate, glyceryl tribenzoate, pentaerythritol tetrabenzoate and 1,4-cyclohexanedimethanol Dibenzoate is conveniently used as a plasticizer. Finally, fatty acids and alkylmonamines preferably having 8 to 36 carbon atoms can also be used. Aromatic dicarboxylic acid ester based plasticizers, ie corresponding esters of phthalic acid, isophthalic acid or terephthalic acid, are preferably used. Alcohol residues in the esters used as plasticizers usually have from 1 to 8 carbon atoms. Medical white oils and naphthenic mineral oils are particularly suitable.

The composition of the first hot sealing adhesive layer (B) is applied to the surface to be coated in the form of a 20-30% by weight solution or dispersion in a volatile organic solvent using conventional methods known to those skilled in the art. As the solvent, for example, ethanol, propanol, iso-propanol, ethyl acetate, n-propyl acetate, acetone, methyl ethyl ketone, low boiling hydrocarbons or mixtures of the above solvents can be used.

After solvent evaporation, the first hot sealing adhesive remains a dry layer (B) on the outer surface of the multilayer film. In a particular embodiment of the multilayer film according to the invention, the carrier film (A1) or the composite film layer comprises aluminum foil which is metallized or bonded to an underlying layer, for example a plastic film, via an adhesive layer. The first hot sealing adhesive layer (B) is applied to the metallized side or the metal film and can be sealed on the opposite outer surface comprising the polyvinyl base layer. When the first hot sealing adhesive is applied to the metal layer, the following components are additionally included:

VI) 1 to 10% by weight of inorganic acid,

VII) 1 to 10% by weight of organosilicon compound,

(The sum of components (I) to (VII) is 100% by weight in total).

As inorganic acid (VI), acids from the group comprising phosphorus- or sulfur-containing acids, such as sulfuric acid or phosphoric acid, are preferably used.

As the organosilicon compound (VII), a compound of the formula (R ₁ O) ₃ Si-R ₂ -X is preferably used.

As the R ₁ O substituent, a methoxyl, ethoxyl or α-methoxylethoxyl group can be used.

As the spacer R ₂ , (CH ₂ ) _y is preferably used (wherein, y = 1 to 10). "X" is a reactive end group, preferably an amino, hydroxy, vinyl, methacrylic or epoxide group.

The first hot sealing adhesive layer (B) protects the metallized surface from contamination and makes the metal coating wear resistant. Thus, for this purpose, the coating process with the removable film or protective lacquer which is usually used is omitted.

In a particularly preferred embodiment of the invention, the first hot sealing adhesive is a high gloss sealing lacquer.

In another particularly preferred embodiment of the invention, the first hot sealing adhesive covers substantially the entire area of the outer surface. Within the scope of the invention, it is particularly preferred that the opposite outer surface comprising the polyolefin or polyvinyl compound base layer (A2) is reliably sealed to the first high temperature sealing adhesive layer (B). A precondition for this is the so-called "inward to outward" sealing. The polyvinyl compound base layer particularly preferably comprises a sealable polyacrylate composition.

In certain embodiments of the present invention, in conjunction with a multilayer film, the coating of the first hot sealing adhesive is applied by the second hot sealing adhesive layer to a total layer thickness such that the two coatings together cover substantially the entire area of the outer surface. Partially replaced.

The first hot sealing adhesive layer (B) is in particular replaced by a second hot sealing adhesive layer (C), in which they are sealed with a layer A2 arranged on the opposite outer surface.

The second hot sealing adhesive layer (C) is applied on the opposite side of the polyolefin or polyvinyl compound base layer (A2). The applied amount of the layer (C) is 0.1 to 5 g / m ² , preferably 0.2 to 3 g / m ² , particularly preferably 0.3 to 1 g / m ² .

Layer (C) is a sealing layer of hot sealing dispersion adhesive, hot sealing lacquer or melt adhesive.

The second high temperature sealing adhesive layer (C) comprises the following components:

i) 25 to 90% by weight, preferably 35 to 80% by weight, particularly preferably 45 to 70% by weight of at least one ethylene / vinyl acetate copolymer,

ii) 1 to 50% by weight, preferably 15 to 40% by weight, particularly preferably 20 to 30% by weight of one or more tackifying resins,

iii) 1 to 40% by weight, preferably 5 to 30% by weight, particularly preferably 10 to 20% by weight of one or more wax based lubricants,

The sum of (components i) to iii) is 100% by weight in total).

The second hot sealing adhesive particularly preferably comprises the following components:

i) 25 to 90% by weight of one or more ethylene / vinyl acetate copolymers,

ii) 1 to 50% by weight of one or more tackifying resins,

iii) 1 to 40% by weight of one or more wax based lubricants,

The sum of (components i) to iii) is 100% by weight in total).

The ethylene-vinyl acetate copolymer i) is characterized by its vinyl acetate content of 30 to 40% by weight as well as a melt index (ASTM D 1238) of 2 to 5 g / 10 min.

Tackifying resin ii) is the following:

a) hydroabiethyl alcohol and esters thereof, especially esters with aromatic carboxylic acids such as terephthalic acid and phthalic acid,

b) preferably alkyl esters of modified natural resins such as gum resins, tall oil resins, or resin acids from wood resins such as fully saponified gum resins or any partially hydrogenated resins having a low melting point, for example methyl, di Ethylene glycol, glycerol and pentaerythritol esters,

c) acrylic acid copolymers, preferably styrene / acrylic acid copolymers, and

d) functional hydrocarbon resin based resins.

As the tackifying resin, an alkyl ester of a partially hydrogenated resin having an alkyl group preferably of 1 to 6 carbon atoms can be used. Preference is given to using partially polymerized tall oil resins, hydrogenated hydrocarbon resins and resin glycerol esters, and mixtures of these resins.

Waxes iii) to be used as lubricants are carnauba wax, paraffin wax, oxazoline wax or a mixture of two or more such waxes.

In particular, in the second hot sealing adhesive,

(i) the ethylene-vinyl acetate copolymer (i) is characterized by its vinyl acetate content of 30 to 40% by weight as well as a melt index of 2 to 5 g / 10 min (ASTM D 1238);

(ii) the tackifying resin (ii) is at least one of a functional hydrocarbon resin and / or a hydrogenated hydrocarbon resin based resin;

(iii) Wax to be used as lubricant (iii) is carnauba wax, paraffin wax, oxazoline wax or a mixture of two or more such waxes.

The second hot sealing adhesive for the formation of layer (C) is directly or indirectly in the form of a dispersion or solution in 20-30% by weight of volatile organic solution to the surface of (A1) to be coated using conventional methods known to those skilled in the art. It is applied on the opposite side to the polyolefin or polyvinyl compound base layer (A2) after application. The second hot sealing adhesive may be sealed on the polyolefin compound base layer located on the opposite outer surface. The polyolefin compound base layer particularly preferably comprises an ethylene-vinyl acetate copolymer and / or a polypropylene copolymer.

The outer surface comprising the polyolefin or polyvinyl compound base layer (A2) is defined as "inside" of the multilayer film. The side on which the sealing layer (C) is provided is defined as "outer". The term indirect application means that the sealing layer (C) in the multilayer film is applied directly to the last layer of the composite, not the carrier film (A1), by counting the polyolefin or polyvinyl compound base layer (A2) as the first layer. .

For application of the second hot sealing adhesive, for example ethyl acetate, n-propyl acetate, acetone, methyl ethyl ketone, low boiling hydrocarbons or mixtures of these solvents can be used as the solvent.

After solvent evaporation, the second hot sealing adhesive remains a dry layer (C) on the surface of the multilayer film. The sealing layer (C) can almost completely cover the outer surface of the multilayer film, but is preferably applied only to the areas where sealing properties are required for economic reasons. The area can be (colored) printed, and thus the sealing layer (C) can be applied to a sealing area containing printing ink as well as a sealing area without printing ink.

Preferably the sealing layer (C) is applied in a specific pattern or form, for example in the form of a strip on each longitudinal side of the multilayer film. In addition, the strips of sealing layer (C) can be arranged between the sealing layers (C) applied longitudinally at specific intervals over the width of the multilayer film. The gap between strip-shaped sealing layers (C) applied over the width of the multilayer film defines the length of the individual packaging. Preferred patterns of the application sealing layer (C) are described in WO 00/39200.

The polyolefin or polyvinyl compound base layer (A2) on the opposite side of the multilayer film is formed by coextrusion or applied by lamination, extrusion lamination or extrusion coating, for example in a flat-film method or a film blowing method. The polyolefin base layer (A2) may be sealed in the second hot sealing adhesive layer (C), and the polyvinyl base layer may be sealed in the first high temperature sealing adhesive layer (B).

Layer (A2) comprises a thermoplastic polymer that can be melted and sealed at a temperature of from 50 ° C to 200 ° C, preferably from 90 ° C to 180 ° C. The term sealing layer is understood to mean a layer that, after application of a predetermined size of pressure and temperature over a predetermined time of operation as is well known and apparent to those skilled in the art, forms a molten hot seal with the outer surface of itself or the opposite side of the multilayer film.

Sealing layer (A2) comprises thermoplastic polymers from the group comprising homopolymers, cross or random copolymers, block copolymers or graft polymers as well as mixtures thereof. In particular, the sealing layer (A2) comprises at least one polymer from the following group: polyethylene terephthalate (PET), polyamide (PA), low density polyethylene (LDPE), low density linear polyethylene (LLDPE), high density polyethylene (HDPE) , Polypropylene (PP), polybutylene (PB), polyhexene, poly (ethylene / vinyl acetate) (EVA), poly (ethylene / butyl acrylate) (EBA), poly (/ ethyl acrylate) (EAA) , Poly (ethylene / acrylic acid) (EMAA) or modified polyolefin copolymers having carboxyl or anhydrous carboxylic acid groups, in particular polypropylene-polyethylene copolymers, propylene-butylene copolymers or ethylene-propylene-butylene terpolymers.

In the modified polyolefin copolymers, they are prepared by graft polymerization with monomers from the group comprising monounsaturated dicarboxylic acids, for example maleic acid and / or monounsaturated carboxylic acids, for example (meth) acrylic acid, Preference is given to polypropylene copolymers or polyethylene copolymers, at least some of which comprise zinc or sodium ions as counterions.

For example, the multilayer film may consist of a homopolymer of oriented polypropylene (OPP) and a heat seal layer (A2) of polypropylene and / or polypropylene copolymer.

Within the scope of the present invention, a multilayer film having only one carrier film (A1) is particularly preferred, and the surface of the carrier film (A1) is the same as the sealable layer (A2). (A1) and (A2) preferably comprise substantially OPP, biaxially oriented polypropylene (BOPP) or biaxially oriented PET. It is also possible to use, for example, a multilayer film in which the carrier film A1 and the sealing surface layer A2 together have a thickness of approximately 0.2 mm to 2 mm, preferably 0.3 mm to 1.8 mm. The sealing layer A2 of the multilayer film is permanently sealable or peelable with itself or with the layer (B) or (C). Within the scope of the present invention, it is preferable that the sealing layer A2 is peelable to itself. This requires a so-called "inward to outward" type of seal.

Depending on the subsequent use, the multilayer film according to the invention may optionally be provided with a functional layer, for example a metal or transparent inorganic or organic barrier layer. Fabrication of the metal barrier layer is carried out by a conventional vacuum coating process. Vacuum coating processes can be used to allow the composite film according to the invention to be coated or metalized with various metals, for example zinc, nickel, silver, copper, gold, indium, tin, stainless steel, chromium, titanium or aluminum. According to the invention, an aluminum coating is preferred, which is applied directly or indirectly to the surface of the carrier film A1, ie to the surface of the further layer of the multilayer film.

According to further processing and processing, for example subsequent printing, lamination or metallization, the surface of the carrier film A1 or the surface of the multilayer film can be directly pretreated. By corona treatment, for example, the surface is activated for cleaning, oxidation and subsequent treatment processes, thereby improving the surface adhesion. Depending on whether the surface of the individual film (carrier film) or multilayer film to be directly metallized has undergone a gloss or matting surface treatment, the multilayer film can be metallized to a glossy high reflective surface or to a non-slightly reflective surface. .

After any pretreatment and metallization, the multilayer film in the form of a composite film-or carrier film (A1)-is preferably printed directly. Printing is generally performed by horizontally in-line feeding a prepared carrier film strip or composite film to a printing machine. Moreover, in manufacture for printing, a carrier film (A1) or a composite film can also be taken out on a roller.

In a printing machine, the multilayer film is directly on the metallized or nonmetallized surface of the composite film or on the surface of the carrier film A1 in an iterative design and / or another angle, for example in an image, decoration or text that is one or more colors. Is printed on Intaglio printing machines, gravure or flexographic machines are typically used. In this connection, printing of the composite film is carried out on the opposite side of the sealable outer layer A2.

Transparent metal containing and / or opaque printing inks are preferably applied by conventional printing methods, such as rotary engraving printing or flexographic printing methods.

Particular preference is given to using transparent printing inks in which the reflectivity of the metal coated surface is shown through the printing ink so that an attractive and distinctive appearance of the packaging material as well as graphics can be obtained. The printing ink consists of 1) a pigment (pigment comprising a filler or dye), 2) a binder and 3) an additive (such as a desiccant, diluent, wax dispersion, catalyst and initiator for spinning drying).

Due to their adhesion and physical resistance properties, polyester resin binder based pigments are preferred, but binder based pigment systems from the group comprising also may be used: cellulose nitrate; Polyvinyl resins such as polyvinyl chloride (PVC), polyvinyl acetate (PVAC) and hydroxyl-modified PVC and PVAC based copolymers; Polymer and copolymer based resins of acrylic acid and methacrylic acid and esters thereof; Polyurethane; Polyamide or polyvinyl butyral (PVB).

If the surface to which the first hot sealing adhesive is applied is printed, for example with an image, decoration or text of one or more colors, the first hot sealing adhesive layer (B) protects the surface from, for example, scratching. The first high temperature sealing adhesive layer (B) and the second high temperature sealing adhesive layer (C) are characterized by excellent compatibility with commercial printing inks. In a preferred embodiment of the present invention, the first and / or second hot sealing adhesive is applied over the sealing area comprising the printing ink and can be sealed with the opposite outer surface. In a particularly preferred embodiment, the layers (B) and (C) are clean and transparent so that the lower printed area remains easily recognizable.

After sealing, high sealing bond strength is also obtained over the area containing the printing ink. Application of an adhesion accelerating material, such as polyethyleneamine (PEI), as a precoat or primer, as is usually done and described, for example, in EP 0544003 B1, is not necessary.

Preferably, in a combination where the first hot sealing adhesive coating is partially replaced over the entire layer thickness of the second hot sealing adhesive layer, the first hot sealing adhesive layer (B) is otherwise inserted into the film composite in other cases, It is replaced with a film having a sealing surface layer sealed as a welding film in the sealing outer layer A2. Apart from the welding film, an adhesive is also no longer needed at the same time, which is usually used for the lamination of the replacement film and crosslinks the film.

This is illustrated by FIGS. 1 and 2, where FIG. 1 represents a state of the art and FIG. 2 represents a particular embodiment of the present invention.

The drawings merely illustrate the invention and do not reproduce the actual size relationship.

The invention also provides a method of making a multilayer film, wherein

a) a first hot sealing adhesive and optionally a second hot sealing adhesive comprising a 20-30 wt. In the form of

b) the solution is evaporated such that substantially the entire area of the outer surface is covered with a first hot sealing adhesive layer and optionally a second hot sealing adhesive layer,

Wherein the first hot seal adhesive coating is partially replaced over the entire layer thickness of the second hot seal adhesive layer.

Hot sealing adhesives are applied by conventional methods known to those skilled in the art.

The first hot sealing adhesive and the second hot sealing adhesive are applied with a suitable application device to the surface to be coated, and substantially directly or indirectly cover the outer surface of the carrier film A1, and the polyolefin compound or polyvinyl compound based sealing layer (A2) is located on the opposite outer surface. This essentially means that the entire surface is preferably coated with (B) and (C), preferably evenly. At the same time, this means that (B) and (C) have the same layer thickness.

The first high temperature sealing adhesive layer (B) is sealed on the opposite outer surface comprising the polyvinyl compound base layer. The second high temperature sealing adhesive layer (C) is sealed on the opposite outer surface comprising the polyolefin compound base layer.

The sealing of the layer (B) and / or the sealing layer (C) to the polyolefin compound or polyvinyl compound base layer (A2) is at a conventional sealing temperature, generally from 100 ° C. to 160 ° C., and a conventional sealing pressure, generally from 0.3 to 6 This is done with "sealing from outside to inside" at bar.

The sealable multilayer film produced under “sealing from inside to outside” is endowed with exfoliation, ie, the flexible packaging produced therefrom can be opened as easily and sufficiently as easily as possible in a way that does not tear without great effort, Despite the changes in pressure conditions, sealing temperatures and applications as well as mechanically unavoidable raw material changes here, it is ensured that the sealing strength remains substantially constant over a wide permissible range.

The multilayer film according to the invention is characterized by the following advantageous properties:

(-) Less coating amount and adhesive amount are required. This reduces the total weight of the composite film as a whole.

(-) Flexible packaging made from the multilayer film according to the invention has properties as good as comparable multilayer films with additional welding films.

In the negative dry lamination process the curing time is significantly shortened due to the absence of the weld film.

Treatment with (-) primer is omitted.

Negative productivity rises:

(P) Printing and dry lamination are performed in-line, allowing higher hourly yields.

(▷) Since less film material is used, the amount of waste is reduced.

In other cases, the storage time required for the absence of monomers is usually shortened or omitted.

The first high temperature sealing adhesive layer (B) imparts a lower coefficient of friction to the surface of the composite film, thereby improving processing. The multilayer film according to the invention is suitable for the manufacture of flexible packaging by sealing. For example, the multilayer film according to the invention is provided for the packaging of sterile medical articles, for example needles or bands.

The multilayer films according to the invention are also suitable for the packaging of articles in the cosmetic field, for example soaps, shower gels or shampoos.

The multilayer films according to the invention are also suitable for the packaging of foods such as sausages, coffee, grain products, individual soups, breads and confections, sugars and snack foods.

The present invention therefore also provides a flexible packaging which can be produced from the multilayer film according to the invention.

The present invention will now be described in more detail.

I. Packaging for Bread and Confectionery

Comparative Example I:

A Liofol UK 3640 comprising a curing agent 6800, for example a Liofol UK 3640 comprising a curing agent 6800, which is a commercial 2C polyurethane adhesive, is printed with an 18 g / m ² weight coextruded OPP film (Mobile Chemical). It was coated with 3 g / m ² and further laminated with a 18 g / m ² weight coextruded OPP film (Mobil Chemical).

Sealing was performed from "inside" to "outside" using a heated sealing tool.

Example I according to the invention:

A 34 g / m ² weight coextruded OPP film (Mobile Chemical) was printed and coated with 1.0 g / m ² of the first hot sealing adhesive and 0.6 g / m ² of the second hot sealing adhesive.

Using a heated sealing tool, sealing was performed from "inside" to "outside" and the lacquered surface was sealed to the sealing surface of the coextruded OPP film.

II. Packaging for Snack Foods

Comparative Example II:

An 18 g / m ² weight coextruded OPP film (Mobile Chemical) was printed and coated with 3 g / m ² , for example of Henkel KGaA, commercially available 2C polyurethane adhesive (Liofol UK 3640 with hardener 6800) It was further laminated with a coextruded OPP film (Mobil Chemical) with one side metalized and 18 g / m ² weight.

Sealing was performed from "inside" to "outside" using a heated sealing tool.

Example II according to the invention:

A 34 g / m ² weight coextruded OPP film (Mobile Chemical) was printed and coated with 1.0 g / m ^{2 of} the first hot sealing adhesive high gloss lacquer and 0.4 g / m ² of the second hot sealing adhesive.

Using a heated sealing tool, sealing was performed from "inside" to "outside" and the lacquered surface was sealed to the sealing surface of the coextruded OPP film.

II. Way

Printing was done with Sun Chemicals' printing ink recommended for the OPP film. For evaluation, a standard printing machine (Schiavi Rotatary Gravure Printer, "Patriot" type) for reel type products was used. The hot sealing adhesive was applied with a segmented lattice roller, the first hot sealing adhesive first followed by the second hot sealing adhesive. The film outer surface area to be sealed (sealing zone) was coated with a second hot sealing adhesive and the remaining area of the film outer surface was coated with the first hot sealing adhesive so that the two hot sealing adhesives covered the outer surface of the film together.

Application was carried out at a printing machine speed of 180 m / min from 80 ° C to 100 ° C.

The outer seal coated with a hot seal adhesive to the opposite outer surface of the coextrusion OPP was performed at 130 ° C.-140 ° C. and 3 bar for a one second sealing time. Brugger-Feinmechanik (Munich) HSG-C1237 type sealing machine (teflonized sealing parts (jaw) 150 x 110 mm) was used for the sealing process.

III. result

I. and II. The multilayer film according to the invention produced in was characterized by low overall weight and equally good composite adhesion and seal bond adhesion properties compared to the corresponding comparative multilayer films of the prior art.

IV. Formulation

The first and second hot seal adhesive formulations used in the illustrated examples are shown in the table below (Table 1).

Example II. For OPP films metallized on one side for the packaging of snack foods, the metal surface is pretreated in a manner known as primer Vitel B 2200 B (about 4% high molecular weight polyester, 96% ethyl acetate, Bostik Company). After that, it was coated with two hot sealing adhesives. Example II. In a further variant of the packaging for snack foods, a mixture of 98% by weight of formulation a), 1% phosphoric acid and 1% epoxysilane (Silquest A 187 (Cromptan (OSI)) or Silane Z 6040 (Dow Corning) in Table 1 Used as the first hot sealing adhesive.

a) first hot sealing adhesive Weight ratio% Chemical name Trade name Supply source 59.8 wt% Ethyl acetate Various suppliers 3 wt% Propylene Glycol Methyl Ether Dowanol PM DOW 3 wt% Methyl Methacrylate / Butyl Methacrylate Copolymer Neocry b725 Neoresins 30.7 wt% Nitrocellulose Solids Content: 50% NC 50 Boainain, Brazil 1.5 wt% Oxydipropyl dibenzoate Benzoflex 9-88 Velsicol 2.0 wt% Tetraalkyl titanate Tyzor GBA Dupont b) second hot sealing adhesive Weight ratio% Chemical name Trade name Supply source 5.0 wt% Ethylene / Vinyl Acetate Polymer Elvax 40 L 08 Dupont 10.0 wt% Ethylene / Vinyl Acetate Polymer Elvax C 11 3226 Dupont 6.0 wt% Hydrocarbon resin Nevex 100 Neville cindu 0.25 wt% N, N'-ethylene bis-oleylamide Advawax 240 Morton international / usa 3.75 wt% Carnauba Wax Kahl & Co. Vertriebs GmbH Wax Refinery 37.5 wt% Light toluene gasoline, boiling range 120-150 ℃ VM & P-Naphtha Americhem, USA 37.5 wt% N-propyl acetate Various suppliers

Reference list:

A1 carrier film

Sealable outer surface with A2 polyolefin substrate or polyvinyl substrate layer

B first hot sealing adhesive

C second hot sealing adhesive

Layer with D Printing Ink

E lamination adhesive

F metal layer (laminated adhesive layer (E) is optionally present between (F) and (A1)).

Claims (19)

A multilayer film having a first hot sealing adhesive coated on its outer surface and having a polyolefin or polyvinyl compound base layer on the opposite outer surface, wherein the first hot sealing adhesive is as follows: A) cellulose nitrate and acrylic polymer, B) can be sealed with a polyvinyl compound base layer. The multilayer film of claim 1 comprising the following components: I) 45 to 60% by weight of one or more cellulose nitrates (I), II) 0.5 to 20% by weight of at least one acrylic polymer (II), III) 0.5-20% by weight of one or more polyalkylene glycols (III), IV) at least one chelate compound having a central reactor titanium of from 0.5 to 15% by weight (IV) (The sum of components (I) to (IV) is 100% by weight in total). The multilayer film of claim 2 wherein: II) acrylic polymer (II) is a methyl methacrylate copolymer having an average molecular weight of 30,000 to 80,000; III) polyalkylene glycol (III) is a water soluble polypropylene glycol; IV) Chelate compound (IV) with titanium as the central reactor is ethyl acetonate, acetyl acetonate, lactic acid and salts thereof as well as triethanolamine compounds. The multilayer film of claim 2 wherein the first hot sealing adhesive applied to the metal layer additionally comprises the following components: VI) 1 to 10% by weight of one or more inorganic acids, VII) 1 to 10% by weight of one or more organosilicon compounds (The sum of components (I) to (VII) is 100% by weight in total). 5. The multilayer film of claim 4, wherein the inorganic acid (VI) is an acid from the group of phosphorus- or sulfur-containing acids. The multilayer film according to the fourth layer, wherein the compound of formula (R ₁ O) ₃ Si-R ₂ -X comprises at least one organosilicon compound (VII): (In the meal, As R ₁ O substituents, methoxyl, ethoxyl or α-methoxylethoxyl groups are used, As spacer R ₂ , (CH ₂ ) _y is used, wherein y = 1 to 10 As "X", reactive end groups such as amino, hydroxy, vinyl, methacrylic or epoxide groups are used). The multilayer film of claim 1 wherein the first high temperature sealing adhesive is a high gloss sealing lacquer. The multilayer film of claim 1 wherein the first hot sealing adhesive covers substantially the entire area of the outer surface. 2. The multilayer film of claim 1, wherein the polyvinyl compound base layer comprises a sealable polyacrylate composition. The multilayer film of claim 1, wherein the first hot seal adhesive coating is partially replaced so that the two coatings together cover substantially the entire area of the outer surface over the entire layer thickness of the second hot seal adhesive layer. The multilayer film of claim 10 wherein the following components are included in the second hot sealing adhesive layer: i) 25 to 90% by weight of one or more ethylene / vinyl acetate copolymers, ii) 1 to 50% by weight of one or more tackifying resins, iii) 1 to 40% by weight of one or more wax based lubricants The sum of (components i) to iii) is 100% by weight in total). 12. The multilayer film of claim 11 wherein the second hot sealing adhesive is as follows: (i) the ethylene-vinyl acetate copolymer i) is characterized by its vinyl acetate content of 30 to 40% by weight as well as a melt index (ASTM D 1238) of 2 to 5 g / 10 min; (ii) tackifying resin ii) is one or more resins based on functional hydrocarbon resins and / or hydrogenated hydrocarbon resins; (iii) Wax to be used as lubricant iii) is carnauba wax, paraffin wax, oxazoline wax or a mixture of two or more such waxes. The multilayer film of claim 10 wherein the second hot sealing adhesive may be sealed to a polyolefin compound base layer located on an opposite outer surface. The multilayer film of claim 13, wherein the polyolefin compound base layer comprises an ethylene-vinyl acetate copolymer and / or a polypropylene copolymer. The multilayer according to claim 1, wherein the first and / or second hot sealing adhesive is applied over the sealing area comprising the printing ink and can be sealed on the opposite outer surface. film. Method for producing a multilayer film according to any one of claims 1 to 15, characterized in that: a) a first hot sealing adhesive and optionally a second hot sealing adhesive is a 20-30% by weight solution of the composition in a volatile organic solvent on the outside of the multilayer film comprising a polyolefin compound or polyvinyl compound base layer on the opposite outer surface, or Applied in the form of a dispersion, b) the solvent is evaporated such that substantially the entire area of the outer surface is covered with a first hot sealing adhesive layer and optionally a second hot sealing adhesive layer, wherein the first hot sealing adhesive coating is the entire layer of the second hot sealing adhesive layer Partially replaced over thickness. Use of a multilayer film made according to any one of claims 1 to 15 and according to claim 16 for producing flexible packaging by sealing. 18. Use according to claim 17, wherein the sealing of the first hot sealing layer and / or the second sealing layer with respect to the polyolefin compound base layer is carried out at 100 ° C to 160 ° C and 0.3 bar to 6 bar. Flexible packaging, which may be prepared from the multilayer film according to any one of claims 1 to 15.