Gelatin film with adhesive properties, use of gelatin film in adhesive applications, window bags and their use

Abstract

Gelatin film which is designed and configured at least in sections to adhere to a joining part surface, wherein adhesion of the gelatin film can be activated by moisture before being applied to the joining part surface.

Description

The present invention relates to a gelatin foil which is designed and configured at least in sections to adhere to a joining part surface, wherein adhesion of the gelatin foil can be activated by moisture before attachment to the joining part surface. The invention further relates to a use of the gelatin film in adhesive applications, in particular as adhesive films or as adhesive strips. The invention further relates to a viewing window bag having at least one window opening, wherein a section of the gelatin film according to the invention forms a viewing window in the window opening of the bag, and to the use of the viewing window bag as a food packaging.Due to the endibility of many raw materials, increasing environmental pollution and also increasing requirements for environmentally friendly packaging, such as is required in the EU packaging regulation PPWR (packaging and packaging waste regulation), the demand for lasting films is constantly increasing. Various concepts are being followed in this context, such as saving material, recycling films and the use of biobased raw materials. Although saving material and recycling provide films suitable for some applications, they often have reduced stability or tear strength and are unsuitable for packaging medicines or foods, for example. In the field of adhesive applications, such as adhesive films, however, the saving of material and recycling often represent the only possibility of a lasting adhesive application, since biobased adhesives often either do not provide sufficient adhesion, decompose rapidly, do not cure sufficiently or are inexpensive and time-consuming to produce.The use of biobased raw materials in film applications and also in adhesive applications is known.For example, DE 10 2005 004 789 A1 discloses a biodegradable film based on a blend of polylactic acids and at least one copolyester, the film further comprising coupling reagents, plasticizers and mineral additives, such as talc or chalk. The biodegradable film can also serve as a carrier film for a self-adhesive adhesive film, the adhesive consisting of natural latex in the form of latex milk or natural resins. When the film is bonded to the adhesive, the film is treated with a coupling agent, which is either physically implemented by corona discharge or chemically by applying a primer, the solvent contained in the coupling agent being evaporated in a further step. The adhesive itself is applied as an aqueous adhesive to the carrier film, which requires evaporation of the water, i.e. heating of the film with the adhesive, it being necessary to ensure that the film does not shrink during heating. The cooling of the film must likewise take place gently, since otherwise the film becomes distorted.As shown in the exemplary method of DE 10 2005 004 789 A1, the production of biodegradable films or sustainable adhesive films is very time-consuming and cost-intensive. In addition, natural latex- or natural resin-based adhesives have not proven to be particularly adhesive.The prior art also discloses concepts which are at least partially applied to biodegradable films or carrier systems in a layer structure.DE 10 2018 005 876 A1 shows the use of a multilayer structure for an element for use as an interior outfitting element, an interior or exterior automotive element or an exterior outfitting element, which comprises a film layer and a metal layer, wherein the film layer can be formed as a carrier layer from a biodegradable material. The biologically degradable materials, including biopolymers, can comprise wood, cellulose, lignin, starch, sugar, vegetable oil, chitin, casein, gelatin, crabshells, animal or vegetable proteins, fungi, insects, bacteria, zein or algae. The film layer is produced by extrusion, casting, calendering and / or blow molding, the film layer being further coated, with corona treatment, flame treatment, plasma treatment and / or fluorination being carried out beforehand.Many layer systems analogous to DE 10 2018 005 876 A1 are known from the prior art. In this case, a layer is optionally produced in a manner that protects the resources, but the entire composite system is therefore not yet lasting or biodegradable. The term "biodegradable" and marketing promising is intended to animate customers and consumers to buy certain products, wherein the production processes of such layer systems do not require less energy than conventional systems and the obtaining of many biodegradable components also costs immense energy.It would therefore be desirable to find a biodegradable raw material whose production or recovery causes no to little CO 2- emission and which is inexpensive.Gelatin is a mixture of substances made from animal proteins, in particular collagen, and is obtained annually as a slaughter waste in several hundred thousand tons, wherein the gelatin is obtained from connective tissues of cattle, pigs, fish or poultry. The production process comprises digestion with acids or bases, but no environmentally hazardous chemicals are used.Gelatin is furthermore harmless to health, since it is supplied as an independent food and accordingly does not have an E number, like other additives.DE 570 228 C discloses retaining corners for attaching cards or photographs to album pages. In this case, the holding corners are made adhesive and foldable by moistening, wherein the holding corners comprise a gelatine film, so that no additional adhesive is required.The field of application of the disclosed gelatin foil is limited, the adhesive surface is small and it is also necessary to pre-punch the shape to be folded.The object of the present invention is therefore to provide a durable, biodegradable film which is easy to produce and store in any size, in particular also as roll goods. Furthermore, the film should have sufficient adhesive strength to avoid the need to combine with commercial adhesives.The object is achieved on the one hand by a gelatin film according to the invention which is designed at least in sections and is configured to adhere to a joining part surface, wherein adhesion of the gelatin film can be activated by moisture before attachment to the joining part surface.According to the invention, a joining part surface is understood to mean the surface of a joining part which is intended to be joined to the gelatin foil via an adhesive effect. It has proven advantageous if the surface of the joining part is planar at least in sections and is degreased, dedusted or similarly prepared before joining, depending on the material of the joining part.In suitable embodiments of the gelatin foil according to the invention, the latter is activated with moisture, then applied to the surface of the joining part and brought into a non-detachable connection by applying pressure, which can be effected with manual pressing or on an industrial scale using pressing or rolling machines, depending on the field of application.The gelatin foil can only be activated with moisture on its upper side or lower side of the foil, which leads to one-sided adhesion, and the opposite side is accordingly configured to be non-adherent due to the lack of activation. In an alternative embodiment of the gelatin film according to the invention, however, it is also possible to activate both the upper side of the film and the lower side of the film with moisture, so that the gelatin film functions as a film adhering to both sides, and accordingly a first joining part can be connected to a second joining part via the gelatin film according to the invention.According to the invention, the gelatin film can be activated with moisture, in particular water, both in the case of one-sided activation and also activation on the film top side and the film bottom side, by applying a liquid, in particular water. For example, the gelatin foil can be spread flat for this purpose and be partly or extensively spun in with the liquid, in particular water. Alternatively, it is also possible to suspend the gelatin foil vertically and spray it in on one side or on both sides, which can be done manually or in a spray chamber. Alternatively, it is also possible to submerge or briefly soak the gelatin foil into a liquid, in particular a water bath, for activation. In a further alternative embodiment, it is possible to steam the gelatin foil according to the invention with water in a chamber for a period of about 20 to 60 seconds. The water used for activation can be simple tap water, in particular in industrial applications, the minerals present do not influence the resultant adhesion effect. In household applications, for example when the gelatin sheet according to the invention is used for applying small labels or the like, saliva of a user can also be used, similar to moistening a stamp.It has furthermore been found that gelatin foils having a layer thickness of from 30 μm to 500 μm, in particular from 100 μm to 300 μm, can be used in a particularly large number of fields of application. With the layer thickness indicated, the gelatin foils are stable enough not to tear, but yet flexible enough to be able to be folded or even rolled up, for example during storage or transport.As already described at the beginning, as raw materials for producing the gelatin foil, slaughter waste in the form of connective tissues, in particular collagen, cattle, pigs, fish or poultry, is used. These are usually subjected to alkaline digestion by means of milk of lime or sodium hydroxide solution, then melted out in a substantially neutral solution and extracted. Alternatively, an acid digestion can be used which has proven particularly suitable as starting product in particular in pig sausage, so that powder gelatin is present at the end independently of the digestion.Tear-resistant, but nevertheless flexible, gelatin foils can be produced from the powder gelatin in particular by means of the following process: a) metering in powder gelatin, optionally collagen hydrolysate, optionally additives and water, into an extruder, b) dissolving the powder gelatin, optionally collagen lysate and optionally additives, in water under the action of shear forces in the extruder, an aqueous gelatin solution having a solids content of 30 to 60% by weight being obtained, c) degassing by applying reduced pressure to the aqueous gelatin solution, an aqueous gelatin solution which is low in air bubbles or free from air bubbles being obtained, d) pouring out the aqueous gelatin solution through a precision slot die onto a carrier, e) allowing the gelatin solution on the carrier to solidify (gel) to form a gelatin layer, f) Drying of the gelatin layer to form the gelatin sheet.In preferred embodiments, the powder gelatin used has less than 25% by weight of fragments of alpha gelatin having a molecular weight of at most 9×10 4 g / mol, the alpha gelatin consisting of intact alpha polypeptide chains, 5 to 15% by weight of microgel, this consisting of polymers of up to 1000 linked alpha chains, 30 to 70% by weight of oligomers of alpha gelatin (n=2 to 15) and 20 to 60% by weight of alpha gelatin.The powder gelatin furthermore preferably has a viscosity above 180 mP, preferably from 200 to 350 mP, and particularly preferably from 200 to 300 mP, these viscosity values referring to a solution of 10 g of gelatin in 100 ml of water at 60° C.In one embodiment of the method for production, collagen hydrolysate can also be added to the powder gelatin, these being non-gelling collagen products which have been obtained by hydrolysis under high pressure and high temperature, by means of acid or alkali or enzymatically from collagen-rich raw material, such as skin or bone, or by degradation of gelatin itself. The collagen hydrolysate is preferably also present in powder form.The gelatin film produced in this way has a tear strength of 50 N / mm 2 to 120 N / mm 2, in particular of 75 N / mm 2 to 100 N / mm 2. The permeation coefficient for oxygen (O 2) of the gelatin film thus produced is, in suitable embodiments, less than or equal to 500 cm 3×μm×m -2×d -1×bar -1, and the permeation coefficient for water vapor is greater than or equal to 50,000 g×μm×m -2×d -1. The gelatin sheet according to the invention thus forms an oxygen-barrier barrier layer, can therefore be used in particular for the packaging of foods which are powdery and should not be stored in moist air, since they tend to draw moisture.It has furthermore proved to be advantageous if the gelatin film retains a residual moisture content of 5 to 25 wt. %, in particular of 10 to 15 wt. %, during drying after step f). The residual water still contained in the gelatin foil can thereby impart greater mobility to the protein chains and act as a natural softener, which makes the gelatin foil more flexible and supple. This has proved to be particularly useful when stored as roll goods, but also when using the gelatin foil which necessitate folding of the gelatin foil.Depending on the field of application, it may be advantageous to subject the gelatin film according to the invention, after drying, at least in sections to a post-treatment with formaldehyde, for example by exposing the gelatin film to a formaldehyde-containing gas atmosphere. The gaseous formaldehyde is adsorbed on the surface of the gelatin film and leads to a cross-linking of the gelatin molecules, which makes them hydrophobic in the areas, which is particularly advantageous for the packaging of moist or adhesive foods.In some embodiments, the gelatin foil can also further comprise additives, which are preferably mixed during the production in step a). The additives may comprise dyes, pigments, plasticizers, crosslinkers, thickeners, emulsifiers, desiccants, preservatives, antioxidants, fillers or mixtures thereof.In principle, the gelatin foil according to the invention is transparent or at least translucent, i.e. it is transparent to light. Depending on the raw materials used, the gelatin foil can also have a milky-turbid to slightly yellowish coloration. The transparent or translucent configuration has proven advantageous in some fields of application, for example in order to be able to examine the content or the fill level of a product in a packaging comprising through the gelatin film according to the invention.However, by adding dyes or pigments it is also possible to color the gelatin film, in particular also to make it opaque, in particular if light-sensitive substances have to be packaged in use as packaging material or a company wishes to form a package in the characteristic company colors.Suitable dyes or pigments have proven to be titanium dioxide, quinoline yellow (E104), azorubin (E122), genuine carmine, tartrazine (E102) and amaranth (E123), an added amount of from 0.1 to 3% by weight, preferably from 0.5 to 2% by weight, based on the solids content, being sufficient to obtain a sufficient coloration of the gelatin film.In a suitable embodiment of the gelatin sheet according to the invention, it has proven advantageous to add glycerol as plasticizer in order to improve the elasticity of the gelatin sheet. Amounts of plasticizer in the range from 3 to 30% by weight, preferably 5 to 10% by weight, based on the solids content, have proven advantageous. Alternative plasticizers may also include mannitol, sorbitol, fat, fatty acid, soap, modified or native starch, ethylene glycol, polyethylene glycol, mono-, di-, triglycerol acetate, sugar fatty acid esters, dimethylene sulfoxide, 2,2,2-trifluoroethanol, and propylene glycol.Potentially added cross-linkers can include synthetic aldehyde, dialdehyde, multiple aldehyde functional molecules, diisocyanate, hexamethylene diisocyanate, dialdehyde starch, acrylic acid, acrylate, hexamethylenediamine, styrene, reactive melamine derivative, glycidyl acrylates, glycidyl methacrylates, succinic anhydride, phenyl isocyanate, mucochloric acid, and / or acrolein. Alternatively or additionally, it is likewise possible to isolate aldehydes from plants, spices, fruits or vegetables and to use these as crosslinkers, wherein in particular vegetable oils or plant extracts have proven particularly suitable, such as peppermint oil. Both the synthetic aldehydes and the naturally obtained aldehydes crosslink the reactive functional groups of the gelatin and, in particular, block their hydrophilic groups, so that the hygroscopicity of the gelatin is reduced. However, the crosslinking does not influence the classification of the gelatin as food, but this remains harmless to health even after the crosslinking and can be processed analogously to uncrosslinked gelatin, for example likewise further processed in the same plants to form leaf gelatin. Amounts of crosslinking agent added of from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight, based on the solids content, have proven to be advantageous.In one embodiment of the gelatin film according to the invention, it is formed as a film adhering on one side or as a tape adhering on one side. According to the invention, only one of the two film sides is activated for adhesion with moisture, while the second film side remains inactivated. In some embodiments, it has proven expedient if the inactivated film side further comprises a carrier film.The carrier film can comprise a paper film, a polylactide film, a homo- and / or copolyester film, a polyhydroxyalkanoate film, a thermoplastic starch film, a cellulose acetate film, a polyethylene film and / or a polyethylene furanoate film. No adhesive or special bonding agent is necessary for bonding the gelatin film according to the invention to the carrier film; furthermore, no energy-intensive, time-consuming process step is required. The gelatin foil is attached to the underside of the carrier foil by the gelatin foil being activated by moisture before being attached to the carrier foil, then being applied to the carrier foil and being connected thereto in a non-detachable manner by pressing it on.The gelatin sheet according to the invention can be stored, shipped and used as roll goods. Alternatively, ready-to-use sheet sheets of any size and cross section can also be cut to size and stored stacked one above the other. It is likewise possible to offer the gelatin film according to the invention on the market, in particular if it is to be used only as a film adhering on one side, as a roll-off tape or adhesive strip.In certain embodiments, the gelatin sheet of the invention may further comprise an embossment. It has proven advantageous here if the embossing is carried out between the method steps e) and f) by the gelatin coating being guided, for example, through two calender rolls. The embossing may include, for example, letters, logos, writings or images.Alternatively or additionally, the gelatin sheet according to the invention can also comprise a print. This can be done, for example, in a 3D printer, by ink jet printing, flexographic printing, or else laser printing.The gelatin sheet of the invention can also be shaped into a shaped body by thermoforming, which means under the action of heat and with the aid of compressed air or vacuum. Possible molded bodies here are in particular packages, for example a viewing window bag described below. However, the production of the viewing window bag does not necessarily have to be carried out according to the invention or exclusively by thermoforming.The object of the present invention is furthermore achieved by a viewing window bag, in particular a block bottom bag (bottom bag) or stand-up bottom bag, in particular completely recyclable, wherein said bag comprises a bag which, in certain configurations, consists of a biodegradable material and has at least one window opening. The pouch can consist, for example, of coated or uncoated paper, polylactide, homo- and / or copolyester, polyhydroxyalkanoate, thermoplastic starch, cellulose acetate, polyethylene, polyethylene furanoate or mixtures thereof. In this case, a section of the gelatin film according to the invention is introduced as a viewing window in the at least one window opening of the pouch. In preferred embodiments, the gelatin film is introduced via the inner side of the pouch, wherein the size of the gelatin film exceeds the size of the window opening, so that the gelatin film adheres to the inner side of the pouch via a further portion, in particular via its edge regions, and the one portion serves as a transparent or translucent viewing window.For fastening, the edge regions of the gelatin film are activated by moisture, i.e. made adhesive, then placed over the window opening of the bag and pressed on, so that the edge regions are non-detachably fastened to the bag. In suitable embodiments, the viewing window bag is designed as a standing bag or as a visual envelope and can serve, for example, for storing and / or transporting foodstuffs, medicaments, documents, bulk material or the like. Conventional standing bags or viewing envelopes use, for example, polypropylene films as viewing windows, these being attached to the inside of the bag by means of an adhesive. This requires a higher material use, adhesives are used which are poorly degradable and the adhesive often becomes smeared when applying the adhesive. In particular in large production plants, this means that the plants must be constantly cleaned of adhesive residues, which is time-consuming and cost-intensive. When using the gelatin film according to the invention, instead adhesive can be dispensed with, so that no complicated cleaning of the installations occurs at regular intervals. Furthermore, the viewing window bags according to the invention can be disposed of and recycled in one piece; no separate disposal of the bag and viewing window is required.The object of the present invention is likewise achieved by using the gelatin film according to the invention in adhesive applications, in particular formed as adhesive films or adhesive strips.The use relates to a gelatin foil which has been produced by the method described and has the properties already described.The object is furthermore achieved by using the viewing window bag according to the invention as a food packaging, in particular for dry products.Example 1According to the above-described method, a biodegradable transparent gelatin sheet for packaging purposes of the present invention was produced. This had the following properties:Appearance:The light yellow is slightly yellowishSolubility:Swelling in cold water, soluble in water above 35° CLayer thickness:100 μmWater content:about 11 wt.%pH:5,5 6 (in 10% strength by weight aqueous solution)Ash residue:1,5 % by weightTemperature stability:up to 85° CDensity:1250 kg / m 3Tear strength:about 75-100 N / mm 2Elongation at break:about 10%Permeation Coefficients:Oxygen (O 2):<500 cm 3×μm×m-2×d-1× bar-1Water vapor:>50,000 g×μm×m-2×d-1The gelatin sheet proved to be durable up to a maximum relative humidity of 65%.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2005 004 789 A1 [0004, 0005]DE 10 2018 005 876 A1 [0007, 0008]DE 570 228 C

[0012]

Claims

Gelatin foil which is designed and configured at least in sections to adhere to a joining part surface, wherein adhesion of the gelatin foil can be activated by moisture before application to the joining part surface.The gelatin sheet of claim 1, wherein the gelatin sheet forms a non-detachable connection upon activation with moisture and attachment to the part surface by pressure.The gelatin foil according to claim 1 or 2, wherein the gelatin foil is activated with moisture on a foil top side and / or a foil bottom side.The gelatin film according to at least one of the preceding claims, wherein the activation with moisture is effected by applying a liquid, in particular by brushing in and / or spraying in, and / or by soaking / dipping in a liquid and / or by vapor deposition with a liquid, in particular wherein the liquid is water.The gelatin foil according to at least one of the preceding claims, wherein the gelatin foil has a layer thickness of 30 μm to 500 μm, in particular of 60 μm to 300 μm.The gelatin sheet according to at least one of the preceding claims, wherein the gelatin sheet has a tear strength of 50 N / mm 2 to 120 N / mm 2, in particular of 75 N / mm 2 to 100 N / mm 2.The gelatin sheet according to at least one of the preceding claims, wherein the gelatin sheet has a permeation coefficient for oxygen (O 2) of less than or equal to 500 cm 3 × μm × m -2 × d -1 × bar 1 and / or a permeation coefficient for water vapor of greater than or equal to 50,000 g × μm × m -2 × d -1.The gelatin foil according to at least one of the preceding claims, wherein the gelatin foil has a residual moisture content of 5 to 25 wt.%, in particular of 10 to 15 wt.%.The gelatin sheet according to at least one of the preceding claims, wherein the gelatin sheet further comprises additives selected from a group consisting of dyes, pigments, plasticizers, cross-linkers, thickeners, emulsifiers, drying agents, preservatives, antioxidants and / or fillers.The gelatin film according to at least one of the preceding claims, further comprising at least one carrier film, wherein the carrier film is selected from a group consisting of paper films, polylactide films, homo- and / or copolyester films, polyhydroxyalkanoate films, thermoplastic starch films, cellulose acetate films, polyethylene films and / or polyethylene furanoate films.The gelatin sheet according to claim 10, wherein the gelatin sheet is attached to the underside of the carrier sheet, in particular wherein the gelatin sheet is activated by moisture before attachment to the carrier sheet and further forms a non-detachable connection by pressing on the carrier sheet.Gelatin foil according to at least one of the preceding claims, wherein the gelatin foil is formed as roll material, foil sheets or adhesive strips.Gelatin foil according to at least one of the preceding claims, wherein the gelatin foil is formed at least in sections transparent and / or translucent, in particular translucent.The gelatin sheet according to at least one of the preceding claims, wherein the gelatin sheet further comprises an embossing and / or a printing.The gelatin sheet according to at least one of the preceding claims, wherein the gelatin sheet is designed and arranged to be shaped into a shaped body by thermoforming.Viewing window pouch comprising a pouch, in particular made of biodegradable material, having at least one window opening, and at least one gelatine film, in particular according to at least one of the preceding claims 1 to 15, wherein a section of the gelatine film forms a viewing window in the window opening of the pouch, and wherein a further section of the gelatine film, in particular the edge regions of the gelatine film, is non-detachably fastened to the pouch.Viewing window bag according to claim 16, wherein the viewing window bag is designed as a standing bag, in particular as a block bottom bag, standing bottom bag or as a visual envelopeUse of a gelatine film, in particular according to at least one of claims 1 to 15, in adhesive applications, in particular as adhesive films or adhesive strips.Use of a gelatin sheet, in particular according to at least one of Claims 1 to 15, wherein the gelatin sheet is obtained by dissolving powder gelatin in an extruder under the action of shear forces to obtain an aqueous gelatin solution having a solids content of from 30 to 60% by weight, then degassing and pouring out the degassed gelatin solution to obtain a gelatin layer, and then solidifying and drying.Use of a viewing window bag according to at least one of claims 16 or 17 as a food packaging, in particular for dry products.