Compostable carrier material for photographic papers

Abstract

The invention relates to a compostable carrier material for photographic papers, comprising a paper layer and a biodegradable polymer layer on at least one side of the paper layer. The invention further relates to photographic paper, comprising a compostable carrier material according to the invention. Furthermore, the invention relates to the use of the compostable carrier material according to the invention in photographic paper according to the invention, and to a method for producing a compostable carrier material according to the invention, comprising the following steps: (a) Providing a paper layer; (b) coating the paper layer on at least one side with a biodegradable polymer layer; (c) optionally coating the biodegradable polymer layer with a bonding layer; (d) coating the biodegradable polymer layer applied in step (b) or the bonding layer applied in optional step (c) with an image receiving layer.

Description

[0001]December 19, 2024 Compostable carrier material for photographic paper The invention relates to a compostable carrier material for photographic paper comprising a paper layer and, on at least one side of the paper layer, a biodegradable polymer layer, a photographic paper comprising the carrier material according to the invention, the use of the carrier material according to the invention in a photographic paper, and a process for producing the carrier material according to the invention. It is known that carrier materials with layers of polymers can achieve high light stability, which is relevant, for example, for the use of such layer supports in photographic paper but also in other products. Due to the high light stability of these carrier materials, the long service life of up to 100 years and more expected by users for products comprising these carrier materials, in particular photographs, can be achieved.The polymers used in these carrier materials are generally synthetic polyolefins, such as polyethylene, which are highly water-resistant and have long-term stability. The carrier materials known in the state of the art for photographic paper are therefore generally durable, and the composite of paper and polymer as well as other components guarantees these properties. However, the high durability of the carrier material also means that recycling of the products manufactured with it and reusing the materials used in the carrier materials is not possible or only possible with very high and uneconomical expenditure. However, a not insignificant proportion of the photographs and other products produced on photographic paper actually have a usage period of only a few years or even months. These products are then generally disposed of with residual waste and are not subjected to a separate recycling process.This is disadvantageous because the valuable materials they contain are no longer available for recycling if they are disposed of with residual waste. State-of-the-art methods for processing and separating corresponding carrier materials are described, but these require a lot of energy and have only limited usability when reused. The pulp obtained using these processes can no longer be used as a raw material for high-quality applications, such as a carrier material for photographic paper. Polymers that are easier to recycle generally have the disadvantage of insufficient light stability and too low a general durability. Aliphatic polyesters, for example, which are known to be biodegradable, are more sensitive to UV radiation and visible light than polyethylene, which is an aliphatic hydrocarbon polymer.Under the influence of UV radiation and visible light, an aliphatic polyester, such as polylactic acid, can rapidly oxidize and lose its color and transparency. This can lead to it becoming brittle and fragile. Furthermore, the processing of such aliphatic polyesters on conventional application equipment presents an additional challenge. Therefore, based on the known prior art, the present invention was based on the object of providing a carrier material for photographic papers that meets the requirements for a long service life and high light stability, while at the same time exhibiting good recyclability. RK / bn 230558WO December 19, 2024 This object was achieved by a compostable carrier material for photographic papers according to claim 1. Further preferred embodiments of the invention can be found in the dependent claims.Compostable within the meaning of the invention means that the carrier material is compostable according to DIN EN 13432 (issue date 2000-12-00) with Corrigendum 2 (issue date 2007-10-00), also referred to as DIN EN 13432 Ber 2:2007-10. A material is considered compostable according to this standard if, after 12 weeks of composting and subsequent fine sieving (sieve fraction < 2 mm), a maximum of 10% of the original dry weight of the material remains and the remainder has been decomposed. The term “compostable” is to be understood in contrast to the term “biodegradable”. Biodegradable within the meaning of the invention means that the carrier material is biodegradable according to DIN EN 13432. A material is considered biodegradable according to this standard if, after 6 months of composting, 90% of the organic material has been decomposed. The compostable carrier material according to the invention is therefore industrially compostable and preferably meets the requirements of the standard DIN EN 13432 Ber 22:2007-10.The compostable carrier material for photographic papers according to the invention comprises a paper layer. .A paper layer within the meaning of the invention is understood to be an unsized or surface-sized paper. In addition to cellulose fibers, a paper may contain sizing agents such as alkyl ketene dimers, fatty acids and / or fatty acid salts, epoxidized fatty acid amides, alkenyl or alkyl succinic anhydride, wet strength agents such as polyamine-polyamide-epichlorohydrin, dry strength agents such as anionic, cationic, or amphoteric polyamides or cationic starches, optical brighteners, fillers, pigments, dyes, defoamers, and other auxiliaries known in the paper industry. The paper can be produced on a Fourdrinier or Yankee paper machine (cylindrical paper machine). The basis weight of the paper can be 50 to 250 g / m², in particular 80 to 180 g / m². The paper can be used in uncompacted or compressed form (smoothed).Papers with a density of 0.8 to 1.2 g / cm³ are particularly suitable, especially with a density of 0.9 to 1.1 g / cm³. Examples of suitable pulp fibers include bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), bleached hardwood sulfite pulp (LBSP), or bleached softwood sulfite pulp (NBSP). Pulp fibers obtained from paper waste can also be used. These pulp fibers can also be mixed, and proportions of other fibers, for example, up to 50% by mass of synthetic resin fibers, can be added. However, pulp fibers made from 100% hardwood pulp are preferred. The average fiber length of the unrefined pulp is preferably 0.5 to 0.85 mm (Kajaani measurement).Examples of fillers used in paper include kaolins, calcium carbonate in its natural forms such as limestone, marble, or dolomite, precipitated calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, silica, aluminum oxide, and mixtures thereof. The paper can be surface-sized. Suitable sizing agents for this purpose include, for example, polyvinyl alcohol or oxidized starch. According to a particular embodiment of the invention, the sizing agent can additionally contain at least one pigment. The pigment is preferably selected from the group consisting of metal oxides, silicates, carbonates, sulfides, or sulfates, as well as mixtures thereof. Pigments such as kaolins, talc, calcium carbonate, and / or barium sulfate have proven particularly useful in practice. The addition of pigment to the sizing agent can improve the surface quality of the paper, particularly its smoothness.The compostable carrier material according to the invention comprises a biodegradable polymer layer on at least one side of the paper layer. The compostable carrier material according to the invention can also have a biodegradable polymer layer on both sides of the paper layer. According to a preferred embodiment of the carrier material according to the invention, the biodegradable polymer layer comprises at least one biodegradable polymer and optionally at least one filler. The type of at least one biodegradable polymer used in the biodegradable polymer layer is fundamentally unlimited. Both biodegradable petroleum-based polymers and biodegradable biopolymers or mixtures thereof can be used.Preferably, the biodegradable polymer is selected from polyhydroxyalkanoates, polylactic acid (PLA), polybutylene adipate-co-butylene terephthalate (PBAT), polybutylene sebacate-co-butylene terephthalate (PBSeT), thermoplastic starch (TPS), cellulose acetate, cellulose ethers, cellulose esters, chitosan and mixtures thereof. Biodegradable petroleum-based polymers that can be used in the biodegradable polymer layer of the carrier material according to the invention are, for example, polycaprolactone, polybutylene adipate-co-butylene terephthalate (PBAT) and polybutylene succinate, polybutylene sebacate-co-butylene terephthalate (PBSeT) as well as analogues of PBAT or PBSeT in which the monomer terephthalic acid has been replaced by 2,5- RK / bn 230558WO December 19, 2024 furandicarboxylic acid, which can be produced from renewable raw materials.Biodegradable petroleum-based polymers within the meaning of the present invention are therefore composed of more than 51 mol% monomers derived from petroleum, but can comprise less than 49 mol% monomers not derived from petroleum. Biopolymers within the meaning of the invention are polymers that are based exclusively on natural or renewable resources and are biodegradable or compostable. They are also referred to as bio-based polymers. In contrast to petroleum-based polymers, which are essentially produced from non-renewable resources such as petroleum, biopolymers are made 100% from renewable raw materials such as corn starch, cellulose, soy protein, and other plant or animal sources. A well-known example of a biopolymer is polylactic acid (PLA), which is produced from fermented corn starch and is used in many applications as an alternative or complement to petroleum-based polymers.Other examples of biopolymers are cellulose acetate, cellulose esters, starch esters, polycaprolactone, and polyhydroxyalkanoates (PHA). There are different types of biopolymers that can be produced from various natural resources. Some well-known examples of biopolymers are listed below: 1. Cellulose: Cellulose is the main component of plant cell walls and can be processed into various biopolymers, such as cellulose acetate, cellulose esters, and cellulose ethers. 2. Starch: Starch is a carbohydrate compound found in many plants and is used to produce biopolymers such as starch acetate, starch esters, and starch ethers. RK / bn 230558WO December 19, 2024 3. Polylactic acid (PLA): PLA is made from fermented corn starch and is biodegradable. It is widely used for packaging and disposable items. 4.Polyhydroxyalkanoates (PHAs): PHAs are a group of biopolymers produced by bacteria and are biodegradable. They can be made from vegetable oils, sugar, or other carbohydrates. 5. Proteins: Proteins such as collagen, gelatin, and soy protein can be processed into biopolymers used for medical applications, food packaging, and textiles. 6. Chitosan: Chitosan is a biopolymer derived from chitin, which is found in the shells of crustaceans and insects. It is used for medical applications and as a coating for packaging. According to a preferred embodiment of the carrier material according to the invention, the biodegradable polymer layer contains or consists of at least one biodegradable biopolymer.Preferably, the at least one biodegradable biopolymer is selected from the group consisting of polyhydroxyalkanoates, polylactic acid (PLA), thermoplastic starch (TPS), cellulose acetate, cellulose ethers, cellulose esters, chitosan, and mixtures thereof. The use of the at least one biodegradable biopolymer in the biodegradable polymer layer makes the carrier material more sustainable compared to the use of only biodegradable petroleum-based polymers in the biodegradable polymer layer. It goes without saying that this effect increases with the increasing proportion of the biodegradable biopolymer in the biodegradable polymer layer. Preferably, the at least one biodegradable biopolymer is polylactic acid. It has surprisingly been found that polylactic acid exhibits good light stability and, in addition, is industrially compostable compared to other polymers. RK / bn 230558WO 19.December 2024 According to a preferred embodiment of the carrier material according to the invention, the biodegradable polymer layer, in addition to the at least one biodegradable polymer, optionally comprises at least one filler. The biodegradable polymer layer can, for example, comprise at least 30 wt. %, preferably 30 to 99 wt. %, in particular 50 to 95 wt. %, particularly preferably 60 to 90 wt. %, of biodegradable polymer, based on the dry weight of the entire biodegradable polymer layer, and at least 1 wt. %, preferably 1 to 30 wt. %, in particular 1 to 20 wt. %, particularly preferably 1 to 10 wt. %, of filler, based on the dry weight of the entire biodegradable polymer layer. Suitable fillers for the biodegradable polymer layer are, in principle, the customary fillers known to the person skilled in the art.The filler is preferably an inorganic mineral-based filler, in particular selected from the group consisting of calcium carbonate, aluminum oxide, aluminum hydroxide, boehmite, clay, calcined clays, kaolins, talc, diatomaceous earth, aluminum trihydrate, silicas, titanium dioxide, zinc sulfide, and mixtures thereof. Calcium carbonate is particularly preferably used as a filler in the biodegradable polymer layer of the carrier material according to the invention. The use of calcium carbonate as a filler in the biodegradable polymer layer of the carrier material according to the invention not only significantly accelerates compostability but also contributes to improving soil quality in the immediate environment in which the carrier material decomposes, by both improving soil structure and additionally ensuring soil deacidification.Furthermore, calcium carbonate can also advantageously help to remedy calcium deficiency in the soil and thereby contribute to healthy soil quality favorable for plant growth. It has surprisingly been found that the addition of a filler to the biodegradable polymer layer of the carrier material according to the invention advantageously leads to accelerated composting and accelerated recycling rates of the carrier material. In addition, the at least one biodegradable polymer layer can contain further adjuvants such as optical brighteners, dyes, and dispersing agents. The compostable carrier material according to the invention preferably exhibits high light fastness in the xenon test at a temperature of 23°C, an air humidity of 60%, an irradiation time of 500 hours, and an irradiation intensity of 1.2 watts / cm. 2, with a filter of 420 nm. With such light resistance, the compostable carrier material according to the invention has a comparable light resistance to the currently known light-stable and long-lasting, but non-compostable, carrier materials for photographic papers. The invention further provides a photographic paper comprising a compostable carrier material according to the invention. The photographic paper according to the invention preferably has, in addition to the compostable carrier material according to the invention, an image-receiving layer on the visible side of the at least one biodegradable polymer layer. In the present case, the visible side is understood to mean the side of the biodegradable polymer layer of the carrier material which faces away from the paper layer of the carrier material and which forms the outermost side of the carrier material before application of the image-receiving layer.The image-receiving layer is preferably selected from an emulsion layer for silver salt photography, a toner-receiving layer for electrophotography, or an ink-receiving layer for inkjet printing. RK / bn 230558WO December 19, 2024 According to a preferred embodiment of the photographic paper according to the invention, the compostable carrier material is coated on both sides with a biodegradable polymer layer and has an image-receiving layer on each visible side, wherein the image-receiving layer is selected from a toner-receiving layer for electrophotography or an ink-receiving layer for inkjet printing. If the image-receiving layer is an emulsion layer for silver salt photography, it can be composed of the usual components known to the person skilled in the art for such an emulsion layer.If the image-receiving layer is a toner-receiving layer for electrophotography, it can be composed of the usual components known to the person skilled in the art for such a toner-receiving layer. The toner-receiving layer preferably contains a water-soluble or water-dispersible binder, a finely divided inorganic pigment, and an antistatic agent. The binder in the toner-receiving layer can be any binder commonly used for paper coatings; starch, polyvinyl alcohol, acrylates, or copolymers of acrylates with other monomers are preferred. Particularly preferred binders are ethylene-acrylic acid copolymers, especially those with a melting range of 70 to 100°C.The finely divided pigment in the toner-receiving layer can be a finely divided inorganic pigment, for example silicon dioxide, aluminum oxide, aluminum oxide hydrate, aluminum silicate, calcium carbonate, zinc oxide, tin oxide, antimony oxide, titanium dioxide, indium oxide, or a mixed oxide of these oxides. In a preferred embodiment, the finely divided pigment is zinc oxide, tin oxide, antimony oxide, titanium dioxide, indium oxide, or a mixed oxide of these oxides. The finely divided pigments can be present individually or as mixtures in the toner-receiving layer. The finely divided pigments in the toner-receiving layer preferably have an average particle size of less than 1000 nm, more preferably less than 200 nm. Particular preference is given to pigments with a BET surface area of ​​30 m² / g to 400 m² / g. Such pigments can be obtained by the flame process or by wet-chemical precipitation processes.The antistatic agent in the toner-receiving layer can be an electrically conductive polymer or an electrically conductive pigment. Mixtures of antistatic agents can also be used. Electrically conductive polymers can be those in which the electrical charge is transported in the form of ions, such as polystyrenesulfonic acid. However, polymers in which the electrical charge is transported in the form of electrons or electron holes are preferred, for example, polyanilines, polythiophenes, or others. Particularly preferred as a conductive polymer is polystyrene acid-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), which is sold, for example, under the name CLEVIOS. ® or ORGACON ®is available. According to the invention, the electrically conductive polymers are present in the toner-receiving layer in an amount of 0.1 to 50% by weight, in particular 1.0 to 4.0% by weight, based on the mass of the dried layer. If a polymer is used as an antistatic agent in the toner-receiving layer, this can completely or partially replace the water-soluble or water-dispersed binder. Conductive pigments can consist, inter alia, of metal powder or carbon. However, preference is given to oxides such as antimony oxide, tin oxide, indium oxide or, more preferably, titanium dioxide or zinc oxide or mixed oxides of the elements antimony, indium, titanium, zinc or tin. The conductive pigments preferably have an average particle size of less than 1000 nm, more preferably less than 200 nm.If a conductive pigment is used as an antistatic agent, this can also simultaneously represent the finely divided pigment of the toner-receiving layer. The toner-receiving layer can additionally contain anionic or non-ionic surfactants in an amount of 0.01 to 4.0 wt. %, in particular 0.05 to 2.5 wt. %, based on the dried layer. The toner-receiving layer can optionally also contain further auxiliaries, for example matting agents, dyes, crosslinking agents, lubricants, anti-blocking agents and other conventional additives. The coating composition for forming the toner-receiving layer can be applied inline or offline using all application units customary in paper production, with the amount selected such that the application weight after drying is at most 3 g / m², in particular 0.1 to 2 g / m², preferably 0.3 to 0.7 g / m².The coating compound can be applied as a coat using a conventional applicator integrated into the extrusion coating system. A three-roller applicator or a doctor blade device is particularly suitable for this purpose. Additional layers, such as protective or gloss-enhancing layers, can be applied to the toner-receiving layer. The application weight of such layers is preferably less than 1 g / m. 2. In the event that the image-receiving layer is an ink-receiving layer for inkjet printing, all known receiving layers for inkjet printing can be used for the ink-receiving layer. These are usually hydrophilic coatings containing water-soluble or water-dispersible polymers. RK / bn 230558WO December 19, 2024 The ink-receiving layer can additionally contain fillers, pigments, dye-fixing substances, such as quaternary polyammonium salts, and other auxiliaries commonly used in such layers. A suitable quaternary polyammonium salt is polydiallyldimethylammonium chloride. The ink-receiving layer preferably contains a pigment and a binder in a ratio of 10:90 to 90:10. The amount of pigment in the ink-receiving layer is preferably 5 to 80% by weight, but in particular 10 to 60% by weight, based on the dry weight of the ink-receiving layer.The pigment is preferably selected from aluminum oxide, aluminum hydroxide, boehmite, and silicas (such as precipitated or fumed silica). The binder can be a water-soluble and / or water-dispersible polymer, for example, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, starch, gelatin, carboxymethylcellulose, ethylene / vinyl acetate, styrene / acrylic acid ester copolymers, or mixtures thereof. A polyvinyl alcohol with a saponification degree of 88 to 99% can be used, for example. The ink-receiving layer can be colored. The coloring can be done with the same color pigments and / or dyes used to color the base paper.The amount (concentration) of the color pigment and / or dye in the ink-receiving layer, based on the dried ink-receiving layer, is preferably about 45 to 75%, in particular 45 to 65%, of the amount of the color pigment and / or dye in the base paper, based on the pulp (dry). The application weight of the ink-receiving layer can be 2 to 25 g / m², in particular 3 to 20 g / m², but preferably 4 to 15 g / m². The ink-receiving layer can be applied using conventional application methods such as roller application, slot die application, gravure or nip application, curtain coating, air brush application, or roller knife application. An adhesive layer can optionally be present between the biodegradable polymer layer and the image-receiving layer to improve the adhesion of the image-receiving layer to the biodegradable polymer layer.No special requirements are placed on the adhesive layer other than providing satisfactory adhesion between the image-receiving layer and the biodegradable polymer layer. Therefore, any of the conventional adhesive layers known to the person skilled in the art to be suitable for this purpose can be used as the adhesive layer. The invention further relates to the use of the compostable carrier material according to the invention in a photographic paper according to the invention.Finally, the invention also provides a process for producing a photographic paper according to the invention, comprising the following steps: (a) providing a paper layer; (b) coating the paper layer on at least one side with a biodegradable polymer layer; (c) optionally coating the biodegradable polymer layer with an adhesive layer; (d) coating the biodegradable polymer layer applied in step (b) or the adhesive layer applied in optional step (c) with an image-receiving layer. The process according to the invention comprises, in step (a), providing a paper layer. The above statements regarding the carrier material according to the invention apply accordingly to the design and composition of the paper layer. RK / bn 230558WO 19.December 2024 According to step (b) of the process according to the invention, the paper layer provided in step (a) is coated on at least one side with a biodegradable polymer layer. The coating can be carried out using the customary methods known to those skilled in the art. Coating in step (b) is preferably carried out by extrusion, coextrusion, curtain coating, doctor blade coating, film press, size press, lamination or laminating. The above statements in connection with the carrier material according to the invention apply accordingly to the design and composition of the biodegradable polymer layer. Step (b) of the process according to the invention can optionally be followed by step (c). According to the optional step (c) of the process according to the invention, the coated paper layer provided in step (b) is coated on at least one side with an adhesive layer.The adhesive layer can be applied using conventional methods known to those skilled in the art. Coating in step (c) is preferably carried out by coextrusion, extrusion, curtain coating, doctor blade application, film press, size press, lamination, or lamination. According to an alternative embodiment of the process according to the invention, the biodegradable polymer layer in step (b) and the adhesive layer in step (c) can be applied simultaneously by coextrusion. Step (b) of the process according to the invention or the optional step (c), if present, can further be followed by step (d). In step (d) of the process according to the invention, the biodegradable polymer layer applied in step (b) or the adhesive layer applied in optional step (c) is coated with an image-receiving layer. The coating can be carried out using conventional methods known to those skilled in the art.Coating in step (d) is preferably carried out by curtain coating, doctor blade application, film press, size press, lamination, or lamination. The above statements regarding the carrier material according to the invention apply accordingly to the design and composition of the image-receiving layer. RK / bn 230558WO December 19, 2024 The following examples serve to further illustrate the invention. Examples Test Methods Surface Resistance The surface resistance is determined using a comb electrode in accordance with DIN 53483. Bonding Test Two sheets of the carrier material in DIN A4 size are placed on top of each other at 23°C and 50% relative humidity and subjected to a 10 kg weight. After 65 h, the sheets are separated manually, and the adhesion / bonding is assessed as follows: +: no bonding, o: slight bonding, strong bonding.Emulsion adhesion The surfaces of the materials are coated with a silver bromide gelatin photographic emulsion and, after drying at 23°C / 50% RH, the adhesion is assessed by applying and removing a TESA 4104 adhesive strip as follows: +: emulsion remains undamaged, o: emulsion slightly torn, -: emulsion completely torn from the carrier. RK / bn 230558WO December 19, 2024 Xenon test The xenon test is a method for testing the lightfastness of materials, particularly paints, varnishes, and plastics. The method simulates the effects of sunlight using xenon light emitting a broad spectrum of wavelengths and intensities. The lightfastness itself is determined using measurements L*-; a*-; b* values ​​of the substrate materials before and after irradiation of the samples and determination of the color difference ΔE according to the standard DIN EN ISO / CIE 11664-4: 2020-03, section 5.3.ΔE is a unit of measurement used in color science to quantify the difference between two colors. This parameter is used to determine how well a material reproduces colors or how stable the color rendering is over time, i.e., how stable the color changes are due to environmental influences, light exposure, and temperature fluctuations. The lower the ΔE value, the smaller the color difference and the more stable the color is against environmental influences, light exposure, and temperature fluctuations. First, the substrates listed in Table 1 were measured before irradiation using the SpectroEye spectrophotometer, and the L*, a*, and b* values ​​were determined. The substrates were then exposed to irradiation at 23°C and a relative humidity of 60% with an irradiance of 50 watts / m. 2and a 320 nm filter. The samples were exposed in an Atlas Weatherometer 3000ci in 10 runs of 50 hours each (= 500 h). After irradiation, the L*, a*, and b* values ​​for the substrates were determined again using a SpectroEye spectrophotometer. The ΔE value is calculated from the L*, a*, and b* values ​​determined by the measurements before and after irradiation in accordance with DIN EN ISO / CIE 11664-4: 2020-03, Section 5.3. RK / bn 230558WO December 19, 2024 Based on the determined ΔE value, the lightfastness of the carrier materials was assessed as follows (see Table 1): +: ΔE < 5 ΔE > 5 Industrial compostability The industrial compostability is determined according to DIN EN 13432 Ber 2:2007-10.The results are assessed as follows: +: The requirements for industrial compostability according to DIN EN 13432 Ber 2:2007-10 are met. -: The requirements for industrial compostability according to DIN EN 13432 Ber 2:2007-10 are not met. Production of the base paper The base paper was made from eucalyptus pulp. For refining, the pulp was refined as an approximately 5% aqueous suspension (thick stock) using a refiner to a freeness of 36 °SR. The average fiber length was 0.64 mm. The concentration of pulp fibers in the thin stock was 1 wt.%, based on the mass of the pulp suspension. Additives such as cationic starch in an amount of 0.4 wt.%, alkyl ketene dimer (AKD) as a neutral sizing agent in an amount of 0.48 wt.%, and polyamine-polyamide-epichlorohydrin resin (Kymene®) as a wet strength agent in an amount of 0.36 wt.-% and a natural CaCO3 in an amount of 10 wt.%. The quantities refer to the dry pulp mass. The thin stock, whose pH value was adjusted to approximately 7.5, was transferred from the headbox to the wire of the paper machine, whereupon sheet formation took place with dewatering of the web in the wire section of the paper machine. In the press section, the paper web was further dewatered to a water content of 60 wt.%, based on the web weight. Further drying took place in the dryer section of the paper machine with heated RK / bn 230558WO December 19, 2024 drying cylinders. The resulting base paper had a basis weight of 160 g / m² and a moisture content of approximately 7%. The base paper is coated on both sides with a coating compound consisting of a styrene acrylate binder, starch and a pigment mixture of calcium carbonate and kaolin with an application weight of 15 g / m² each, dried and then smoothed with a calender.The material obtained in this way is referred to below as base paper. Production of comparison carrier materials A and B Both sides of the base paper were coated with a polyethylene-titanium dioxide mixture consisting of 20 wt.% low-density polyethylene (LDPE, 0.923 g / cm³), 70 wt.% high-density polyethylene (HDPE, d=0.964 g / cm³), and 10 wt.% titanium dioxide (rutile) with a coating weight of approximately 20 g / m² in a laminator at a speed of approximately 250 m / min. The cooling cylinders were selected so that the resulting surfaces of both sides of the carrier material have a roughness Rz, determined according to DIN 4768, of 0.9 µm. The carrier materials obtained are referred to below as comparison carrier material A; they have a high-gloss surface on both sides.In the same way, the base paper was extrusion-coated on both sides with the same polyethylene-titanium dioxide mixture, the cooling cylinders being selected such that the resulting surface of the side to which the image-receiving layer is applied during the later use of the base material in the photographic paper has a roughness Rz, determined according to DIN 4768, of 11.2 µm, and the other side has a roughness Rz, determined according to DIN 4768, of 14.1 µm. The base materials obtained are referred to below as comparative base material B; they display a matt structured surface on the side to which the image-receiving layer is applied during the later use of the base material in the photographic paper. RK / bn 230558WO December 19, 2024 Production of the inventive base materials C and D Both sides of the base paper were coated with a polylactic acid copolymer mixture.The front side is specially coated with a titanium dioxide mixture of 14 wt.%, a blue pigment mixture of 5 wt.%, a violet pigment mixture of 5.81 wt.%, and a polylactic acid copolymer (density 1.25 g / cm³) of 75.6 wt.%, with a coating weight of approximately 20 g / m² in a laminator at a speed of approximately 250 m / min. The cooling cylinders were selected so that the resulting surfaces on both sides have a roughness of 0.9 µm, measured as the Rz value according to DIN 4768. The resulting materials are referred to below as inventive carrier material C; they exhibit a high-gloss surface on both sides.In the same way, the base paper was extrusion-coated with the same polylactic acid copolymer mixture, with the cooling cylinders selected such that the resulting surface of the side to which the image-receiving layer is applied during the later use of the carrier material in the photographic paper has a roughness Rz, determined according to DIN 4768, of 11.2 µm, and the other side has a roughness Rz of 14.1 µm. The materials obtained are referred to below as inventive carrier material D; they display a matt textured surface on the side to which the image-receiving layer is applied during the later use of the carrier material in the photographic paper. Both surfaces of carrier materials A to D were coated with one of the following coating slips 1 or 2 after irradiation with a corona discharge and dried. The coating slip applied was selected to result in a dry application of 0.5 g / m².The composition of the coating slips is given below. Coating slip 1 (conventional adhesive layer): 6.0 g gelatin, 1.0 g chrome alum, 10.0 g isopropanol, 7.0 g butanol, 76.0 g water. RK / bn 230558WO December 19, 2024 Coating slip 2 (adhesion layer with improved adhesion): 5.2 g gelatin, 10.0 g isopropanol, 6.6 g butanol, 1.0 g glycerin, 1.5 g sodium nitrate, 0.1 g chrome alum, 2.6 g PE wax dispersion (Lubaprint® VP 760 / D (manufacturer: LP Bader, Rottweil, Germany)), 73.0 g water. The carrier materials obtained in this way were tested using the test methods described above. The results of these tests can be found in Table 1 below. As can be seen from Table 1, the support materials C and D according to the invention have comparable lightfastness to the comparison support materials A and B.While the carrier materials according to the invention meet the requirements for industrial compostability according to DIN EN 13432 Ber 2:2007-10, this is not the case for the comparison materials A and B. Furthermore, Table 1 shows that the carrier materials coated with an adhesive layer according to coating slip 2 achieved better results in the bonding test. RK / bn 230558WO December 19, 2024 December 19, 2024 Table 1 Test No. Carrier material Surface Surface resistance Bonding test Emulsion Xenon Composting Invention / Coating weight Ohm / cm adhesion testability according to YES / NO 1 A / 1 glossy 13.2 - + + - NO 2 A / 2 glossy 10.1 + - + - NO 3 B / 1 matt 13.3 - + + - NO 4 B / 2 matt 10.2 + - + - NO 5 C / 1 glossy 13.2 - + + + YES 6 C / 2 glossy 9.9 + - + + YES 7 D / 1 matt 13.1 - + + + YES 8 D / 2 matt 10.1 + - + + YES.

Claims

December 19, 2024 P a t e n t a n s p r ü c h e1. A compostable carrier material for photographic paper, comprising a paper layer and a biodegradable polymer layer on at least one side of the paper layer.

2. The compostable carrier material according to claim 1, characterized in that the biodegradable polymer layer comprises at least one biodegradable polymer and optionally at least one filler.

3. The compostable carrier material according to claim 2, characterized in that the biodegradable polymer is a biodegradable biopolymer.

4. The compostable carrier material according to claim 3, characterized in that the at least one biodegradable biopolymer is selected from the group consisting of polyhydroxyalkanoates, polylactic acid, thermoplastic starch (TPS), cellulose acetate, cellulose ethers, cellulose esters, chitosan, and mixtures thereof. 5.Compostable carrier material according to claims 2 to 4, characterized in that the filler is selected from the group consisting of calcium carbonate, aluminum oxide, aluminum hydroxide, boehmite, clay, calcined clays, kaolins, talc, diatomaceous earth, aluminum trihydrate, silicas, titanium dioxide, zinc sulfide and mixtures thereof 6. Compostable carrier material according to one of claims 2 to 5, characterized in that the biodegradable polymer layer contains at least 30% by weight of biodegradable biopolymer and at least 1% by weight of filler, each. - 2 - based on the dry weight of the entire biodegradable polymer layer.

7. Compostable carrier material according to one of the preceding claims, characterized in that it meets the requirements of the standard DIN EN 13432 Ber 22:2007-10.

8. Kompostierbares Trägermaterial nach einem der vorhergehenden Ansprüche, characterized in that it has a lightfastness, measured as ∆E value according to the standard DIN EN ISO / CIE 11664-4: 2020-03, of less than 5.

9. Fotopapier, umfassend ein kompostierbares Trägermaterial nach einem der Claims 1 to 8.

10. Fotopapier nach Anspruch 9, wobei das kompostierbare Trägermaterial auf der The visible side of the biodegradable polymer layer has an image-receiving layer.

11. Fotopapier nach Anspruch 10, wobei die Bildempfangsschicht ausgewählt ist from an emulsion layer for silver salt photography, a toner-receiving layer for electrophotography or an ink-receiving layer for ink-jet printing.

12. Verwendung des kompostierbaren Trägermaterials nach einem der Claims 1 to 8 in a photographic paper according to any one of claims 9 to 11.

13. Verfahren zur Herstellung eines Fotopapiers nach einem der Ansprüche 9 bis 11, comprising the following steps: ( a) Bereitstellen einer Papierschicht; RK / bn 230558WO December 19, 2024 - 3 - ( b) Beschichten der Papierschicht auf mindestens einer Seite mit einer biodegradable polymer layer; ( c) Optionales Beschichten der bioabbaubaren Polymerschicht mit einer adhesive layer; ( d) Beschichten der in Schritt (b) aufgebrachten bioabbaubaren Polymerschicht or the adhesive layer applied in optional step (c) with an image-receiving layer.

14. Verfahren zur Herstellung nach Anspruch 13, dadurch gekennzeichnet, dass das Coating in step (b) is carried out by means of extrusion, curtain coating, doctor blade coating, film press, size press, lamination or laminating.

15. Verfahren zur Herstellung nach Anspruch 13 oder 14, dadurch gekennzeichnet,that the application of the biodegradable polymer layer in step (b) and the application of the adhesive layer in step (c) are carried out simultaneously by coextrusion. RK / bn 230558WO December 19, 2024