Thermal recording materials

Abstract

The present invention relates to a thermosensitive recording material, the color layer of which contains at least one removable dye, more particularly a dye that can be removed in the waste paper cycle; to a method for decolorizing a thermosensitive recording material to obtain a fibrous material mixture, the method comprising the steps of providing a mixture of a thermosensitive recording material and at least one other type of paper, more particularly at least one waste paper type, and then decolorizing the mixture in a deinking process to obtain a fibrous material mixture; to a fibrous material mixture obtained by said method; to a method for producing recycled paper comprising a fibrous material mixture by compressing and dewatering the fibrous material mixture; and to recycled paper obtainable by said method.

Description

[Technical Field]

[0001] The present invention relates to a thermal recording material, a method for decolorizing a thermal recording material to obtain a fibrous material mixture, a fibrous material mixture obtainable by said method, a method for producing recycled paper comprising said fibrous material mixture, and recycled paper obtainable by said method. [Background technology]

[0002] Thermal recording materials are known in principle and a fundamental distinction can be made between two different types of thermal recording materials, more particularly such materials for direct thermal printing:

[0003] Type 1: A thermosensitive recording material in which the printed image is produced in the color layer by a localized, heat-induced chemical reaction between a color former (e.g., a leuco dye) and a color developer (e.g., bisphenol A or a phenol-free alternative). The color layer usually further contains a heat-sensitive solvent (e.g., a long-chain aliphatic alcohol, an amide, an ester, or a carboxylic acid) that melts under the influence of heat to enable the color reaction between the color former and the color developer. Furthermore, the color layer may contain a heat-sensitive sensitizer.

[0004] Type 2: Thermal recording materials in which the printed image is produced by a thermally sensitive top layer that becomes translucent upon exposure to localized heat, e.g., by a direct thermal printer, thereby making the underlying color layer visible. This technology has been described or interpreted differently in the prior art, and such thermal recording materials are obtained by using locally different compositions, porosities and materials of the top layer optimized for direct thermal printing, as explained in more detail below.

[0005] In principle, the following applies:

[0006] 1. The top layer should cover the underlying color layer as well as possible. This is essentially achieved by light scattering (scattering particles) and light absorption.

[0007] 2. The top layer should have as high a contrast as possible (e.g., white / black or blue / yellow) to the underlying color layers to produce a printed image that is readable by the human eye and / or by machines (scanners).

[0008] 3. The top layer should be as heat-sensitive as possible, more particularly so as to become translucent when exposed to localized heat from a conventional direct thermal printer. Where possible, it should be possible to use Type 1 and Type 2 recording materials in conventional direct thermal printers, and the printer settings, more particularly printhead temperature and printer speed, should be comparable.

[0009] The present invention relates to the above-mentioned Type 2 heat-sensitive recording material.

[0010] US2011 / 172094A discloses recording material including: a) a support having a surface impregnated with a colorant or coated with a coating containing a pigment or dye, and disposed thereon; b) A layer comprising polymer particles that comprise a core-shell structure and are hollow to scatter visible light when dry, said particles having an inner first polymer shell with a Tg of 40°C to 130°C and an outer second polymer shell with a Tg of -55°C to 50°C, the outer polymer shell having a lower Tg than the inner polymer shell.

[0011] US2011 / 251060A describes a heat-sensitive recording material comprising a colorant and a flexible carrier substrate, and further comprising a heat-sensitive layer comprising a binder, a plurality of organic hollow sphere pigments and a thermal solvent, the heat-sensitive layer being disposed on the colorant. The heat-sensitive layer may be provided with a barrier layer and a protective layer.

[0012] WO2012 / 145456A1 describes a thermal recording material optimized for conventional direct thermal printing, comprising: a) a support in the form of a sheet-like structure comprising at least one colored surface, and disposed thereon: b) a layer comprising polymer particles having a core-shell structure, the particles comprise an outer first polymer shell having a calculated Tg of 40°C to 130°C, the particles comprising at least one void when dry, and 1 wt% to 90 wt% of an opacity reducer having a melting point of 45°C to 200°C, based on the weight of the polymer particle; The present invention describes a heat-sensitive recording material comprising a layer in which the colored surface has sufficient color density to be clearly more noticeable than the surface of the following layer dispersed thereon, and the opacity reducer is an aromatic oxalic acid ester, aromatic ethylene glycol ether, 1,2-diphenyloxyethane, dibenzyl oxalate, dibenzyl terephthalate, benzyl biphenyl, benzyl-2-naphthyl ether, diphenyl sulfone, m-terphenyl, p-benzyloxybenzyl benzoate, cyclohexanedimethanol benzoate, p-toluenesulfonamide, o-toluenesulfonamide, 2,6-diisopropylnaphthalene, 4,4-diisopropylbiphenyl, erucic acid amide, stearic acid amide, palmitic acid amide, or ethylene bis-stearic acid amide.

[0013] WO2013 / 152287A1 describes a heat-sensitive recording material having a two-layer uniaxially stretched film comprising a first layer comprising a beta-nucleated propylene-based opaque polymer and a second layer comprising a dark pigment.

[0014] US2015 / 049152A describes a thermal recording material comprising a thermal layer disposed on a pigmented solid support substrate, the thermal layer each comprising a center, a surface, single-phase scattering polymer particles having a refractive index at the center different from that at the surface, and a continuous refractive index gradient, the thermal layer further comprising heat-deformable particles and a binder.

[0015] EP2993054A1 describes a web-like thermosensitive recording material having at least a first layer and a second layer at least partially covering the first layer, the first layer having a concentrated coloring at least on the surface facing the second layer, the second layer having hollow body pigments that can be melted by locally limited heat treatment to form a type face, and the second layer also containing one or more fatty acids and one or more heat-sensitive sensitizers in addition to the hollow body pigments.

[0016] US2017 / 337851A states: a release liner base stock layer; an optional adhesive layer; Label base stock layer, an insulating layer disposed on the label base stock layer; an ink layer including at least one color disposed on the thermal insulation layer; a coating layer disposed on the printed ink layer; and A topcoat layer placed on the top layer A recording material comprising: Disclosed is a recording material in which the cover layer comprises an acrylic-based composition containing light-scattering particles that cause the cover layer to be opaque in a first state and transparent in a second state, and at least one of heat and pressure is applied from a printhead to transition the top layer from the first state to the second state, thereby causing at least one color of the ink layer to become visible through the cover layer.

[0017] WO2019 / 183471A1 discloses a recording medium including a substrate, the substrate being associated with first scattering particles having a melting point and including a first solid light-scattering layer, the first light-scattering layer being as close as possible to a plurality of second solid scattering particles, the second solid scattering particles having a melting point lower than the first melting point of the second solid scattering particles, the first light-scattering layer being porous, the second scattering particles being described as solid upon melting, and the first solid scattering particles being arranged to fill spaces between the recording medium.

[0018] WO2019 / 219391A1 describes a thermosensitive recording material comprising a carrier substrate having at least one surface that is black or colored and a thermoresponsive layer on at least one black or colored surface of the carrier substrate, the thermoresponsive layer comprising nanoparticles of at least one cellulose ester.

[0019] WO2021 / 055719A1 describes a heat- or pressure-sensitive recording material including a layer of opaque material, a colorant disposed on a first surface of the layer of opaque material, the layer of opaque material covering the colorant, the opaque material in an opaque state including a plurality of irregularly and / or irregularly shaped opaque polymer particles defining voids therebetween and having different shapes and / or different sizes, and further the opaque material configured to change from an opaque state to a transparent state upon application of sufficient temperature and / or sufficient pressure to expose the colorant underneath the opaque material.

[0020] WO2021 / 062230A1 discloses a recording medium including a substrate, a first light-scattering layer supported by the substrate and containing first scattering particles having a first melting point, and a plurality of second scattering particles adjacent to the first light-scattering layer, the second scattering particles having a second melting point lower than the first melting point, the first light-scattering layer being porous, the second scattering particles being arranged to fill spaces between the first scattering particles when melted, and the first scattering particles including perforated particles. Summary of the Invention [Problem to be solved by the invention]

[0021] All these known thermosensitive recording materials need to be improved, especially if they are also to be used as high-quality raw materials for white paper grades, so-called deinked paper stocks, more particularly with regard to their recyclability in the waste paper cycle.

[0022] Another aspect is that these known thermosensitive recording materials are generally suitable or certified for contact with food only if there is no negative effect on the food. It was therefore a further object of the present invention to provide a thermosensitive recording material which is still suitable or certified for contact with food, more particularly in accordance with the specifications of ISEGA, Forschung-und Untersuchungs-Gesellschaft mbH, Aschaffenburg (as defined herein), and which also meets the strict ruling criteria for the use of, for example, the Blue Angel ecolabel for thermal paper. [Means for solving the problem]

[0023] Surprisingly, these problems have been solved by the thermal recording material according to claim 1.

[0024] The removal of dyes, more particularly the removal of dyes in the waste paper cycle, is also referred to as "deinking". Therefore, suitable removable dyes, more particularly dyes that can be removed in the waste paper cycle, can also be referred to as "deinkable dyes". In principle, the term "deinking" is known to those skilled in the art as the removal of printing ink from paper. In the context of the present invention, the term "dyes" always refers to deinkable dyes.

[0025] Such a thermal recording material is particularly advantageous with regard to its recyclability and therefore its cost-effectiveness. In addition, such a thermal recording material meets the requirements (as defined herein) of the ISEGA, Forschung-und Untersuchungs-Gesellschaft mbH, Aschaffenburg and / or the award criteria for the use of the Blue Angel ecolabel for thermal paper with regard to suitability for use with food.

[0026] Numerous specific details are also discussed below to provide a comprehensive understanding of the present subject matter, however, it will be apparent to one skilled in the art that the present subject matter may be practiced or reproduced without these specific details.

[0027] All features of one embodiment may be combined with features of another embodiment if the features of the different embodiments are not inconsistent.

[0028] The terminology used in the description of this disclosure is intended to describe certain embodiments only and should not be construed as limiting the present subject matter. As used in this specification and claims, the singular forms "a" and "an" should be understood to include the plural unless the context clearly dictates otherwise. This is also true vice versa, i.e., the plural also includes the singular. The term "and / or" as used herein is also understood to mean and include all possible combinations of one or more of the associated listed elements. Furthermore, the terms "include," "including," "comprise," and / or "comprising," as used in this specification and claims, should be understood to specify the presence of stated features, steps, operations, elements, and / or components, but not to exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0029] In this specification and claims, the terms "include," "comprise," and / or "comprising" may also mean "consisting of," i.e., excluding the presence or addition of one or more other features, steps, operations, elements, components and / or groups.

[0030] Thus, in this specification and claims, the term "including" can also mean "exclusively."

[0031] The Bekk smoothness mentioned in this description is determined in accordance with DIN 53107(2016) (unless otherwise specified).

[0032] According to a first aspect, the present invention provides a web-like carrier material; a color layer on one side of a web-like carrier material; and a heat-sensitive layer on the color layer such that the color layer is at least partially covered; Including, 1. A thermal recording material, the thermal layer of which is configured to become translucent when exposed to localized heat, thereby allowing the underlying color layer to become visible, The present invention relates to a heat-sensitive recording material characterized in that the color layer contains at least one removable dye, more particularly at least one dye that can be removed in the waste paper cycle.

[0033] The web-like carrier material is not limited in principle. In a preferred embodiment, the web-like carrier material comprises paper, synthetic paper, and / or plastic film. The carrier material preferably has a density of 30 to 100 g / m 2 , more particularly 40 to 80 g / m 2 The sheet has a basis weight of .

[0034] The web-like carrier material of the thermal recording material according to the present invention comprises at least one color layer, i.e., at least one black or colored side, which is achieved by applying a color layer. The term "colored side" means that the side has a color other than white or black. In other words, the thermal recording material comprises at least one side that is colored so as not to be white. Furthermore, embodiments are possible in which the at least one black or colored side also has several different colors in combination with black.

[0035] Embodiments are also contemplated in which the web-like carrier material itself is colored.

[0036] In a preferred embodiment, the thermal recording material according to the present invention further has the following score according to the Assessment of Printed Product Recyclability, Deinkability Score (January 2, 2017 edition) after reprocessing the thermal recording material according to INGEDE Method 11: a) Luminous intensity Y up to 35 points, b) Color coefficient a in the CIELAB system * Maximum 20 points, c) Small soiling spots in two different size classes A A50 up to 15 points and A250 up to 10 points; d) Dye removal (ink removal) degree IE up to 10 points, and e) filtrate darkening ΔY up to 10 points is achieved; the sum of all points is in the range of 0 to 100, preferably in the range of 51 to 70, more preferably in the range of 71 to 100, and / or preferably the individual point values ​​are non-negative; It is characterized by:

[0037] Preferably, the sum of all points is in the range of 0-50, more preferably in the range of 51-70, and particularly preferably in the range of 71-100.

[0038] Preferably, the value of each point is non-negative.

[0039] Most particularly preferably, the sum of all points is in the range from 0 to 50, preferably in the range from 51 to 70, particularly preferably in the range from 71 to 100, the individual point values ​​being non-negative.

[0040] In a preferred embodiment, the thermal recording material according to the present invention is further characterized in that the at least one dye comprises at least one pigment and / or dye, which may comprise an inorganic or organic dye or an inorganic or organic pigment.

[0041] In a preferred embodiment, the thermal recording material according to the present invention is further characterized in that the at least one dye is selected from the group comprising bleachable dyes, hydrophobic dyes, hydrophobizable dyes and / or magnetic dyes.

[0042] Such dyes are characterized by good deinking properties.

[0043] The at least one dye is preferably contained in the color layer in an amount of 2 to 50% by weight, particularly preferably 10 to 35% by weight, based on the total solid content of the color layer.

[0044] This amount does not apply when at least one dye contains or is carbon black. When at least one dye contains or is carbon black, the carbon black is contained in the color layer in an amount of 24% by weight or less, preferably 19% by weight or less, based on the total solids content of the color layer. Preferably, the carbon black is contained in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0045] In another embodiment, carbon black is contained in the color layer in an amount of less than 2% by weight based on the total weight of the thermal recording material.

[0046] In a preferred embodiment, the thermal recording material according to the present invention further comprises at least one removable (deinkable), more particularly removable in the waste paper cycle, dye carbon black pigments (in small amounts up to a maximum of 24% by weight, preferably up to 19% by weight), - alternative carbon black pigments: e.g. with different particle size, morphology, primary / secondary particle composition and / or surface chemistry, organic dyes, more particularly bleachable organic dyes; - Direct dyes, also known as substantive dyes, - reactive dyes, - Disperse dyes (organic and water-insoluble), pigment dyes, more particularly disperse dyes, - Iron oxide, Fe3O4 (magnetic), - sulfur dyes (e.g., Cassulfon, Diresul Black PFT fl.), - activated carbon as a dispersant, - metal complex dyes, in particular iron-based, such as gall inks (iron(III) gallate), which can be produced, for example, by combining Fe(II)SO4 with gallic acid (or tannin) under the influence of atmospheric oxygen, and Fe(III) gallate is formed in the coating; - graphite, - As a substitute for mica, more particularly inorganic pigments, a combination of carbon black pigments with dark pigments, more particularly dark pigments such as iron oxides, for example Fe3O4; Bio-based or food dyes, such as sepia black, caramel color or hydrothermally treated lignin-based dyes, such as ReForce X4500, XILLIX GmbH, Oberkirch, Germany; - Printing inks for coloring (offset, (UV) flexographic inks), - Charcoal / powdered coal and / or - Activated carbon / activated carbon fine powder The compound is characterized in that it is selected from the group comprising:

[0047] They can be present alone or in any mixture.

[0048] Particularly preferred are direct dyes, water flexographic dyes, graphite, sulphur dyes such as casssulfon, gall inks, inorganic and / or organic pigment dyes and / or iron oxides (Fe3O4), such as Bayferrox 306 or iron oxide black.

[0049] Also preferred is the combination of a carbon black pigment with a dark pigment, more particularly a dark pigment such as iron oxide, e.g., Fe3O4.

[0050] In a preferred embodiment, the thermosensitive recording material according to the present invention is further characterized in that the color layer comprises at least one binder.

[0051] Preferred binders include water-soluble starch, starch derivatives, starch-based Ecosphere biolatex, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, gelatin, casein, partially or completely saponified polyvinyl alcohol, chemically modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, sodium polyacrylate, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, styrene-butadiene copolymer, acrylamide (meth)acrylate copolymer, acrylamide-acrylate-methacrylate terpolymer, polyacrylate, poly(meth)acrylic acid ester, acrylate-butadiene copolymer, polyvinyl acetate, and / or acrylonitrile-butadiene copolymer, which can be used alone or in any mixture.

[0052] The binder is preferably contained in the color layer in an amount of 2 to 40% by weight, particularly preferably 10 to 30% by weight, based on the total solid content of the color layer.

[0053] In another embodiment, the binder is preferably contained in the color layer in an amount of 2 to 60% by weight, particularly preferably 10 to 55% by weight, based on the total solid content of the color layer.

[0054] In a preferred embodiment, the thermal recording material according to the present invention is further characterized in that at least one deinkable dye is crosslinked to the binder.

[0055] In a preferred embodiment, the thermal recording material according to the present invention is further characterized in that at least one deinkable dye is fixed to the binder.

[0056] Particularly preferably, the carbon black is crosslinked or anchored to the binder.

[0057] The color layer is preferably 1 to 10 g / m 2 , more particularly 3 to 8 g / m 2 The sheet has a basis weight of .

[0058] The color layer preferably has a thickness of 1 to 10 μm, more particularly 2 to 8 μm.

[0059] In a preferred embodiment, the thermosensitive recording material according to the present invention is further characterized in that the thermosensitive recording material is suitable for contact with food according to ISEGA, Forschung-und Untersuchungs-Gesellschaft mbH, Aschaffenburg.

[0060] To be suitable for contact with food according to the ISEGA, Forschung-und Untersuchungs-Gesellschaft mbH, Aschaffenburg, preferably at least one, and more particularly all, of the following requirements should be fulfilled:

[0061] 1. "Methoden zur Untersuchung von Papieren, Kartons und Pappen fur Lebensmittelverpackungen", as of 2008, Amtlichen Sammlung von Untersuchungsverfahren (Official Testing Methods) Regulation 80.56, Lebensmittel-und Futtermittelgesetzbuch (LFGB; German Food and Feed Law) Chapter 64. 2. Migration of certain elements, DIN EN 71, Part 3 "Safety of toys, Migration of certain elements", August 2019. 3. Heavy metal content according to Directive 94 / 62 / EC of the European Parliament and of the Council of 20 December 1994 on packaging and packaging waste, last amended by Directive (EU) 2018 / 852 of the European Parliament and of the Council of 30 May 2018, Official Journal of the European Communities L 365 / 10 of 31 December 1994 and Official Journal of the European Union L 150 / 141 of 14 June 2018. 4. Model Toxicology Legislation drawn up by the Conservation Resources Council of the CONEG of December 14, 1989, last amended in December 2008. 5. Directive 2011 / 65 / EU of the European Parliament and of the Council of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment, last amended by Commission Directive (EU) 2019 / 178 of 16 November 2018, Official Journal of the European Union L 174 / 88 of 1 July 2011 and Official Journal of the European Union L 33 / 32 of 5 February 2019. 6. Regulation (EC) No 1935 / 2004 of the European Parliament and of the Council of 27 October 2004 on materials and articles expected to come into contact with food, as amended by Annex No 5.17 to Regulation (EC) No 596 / 2009 of 18 June 2009 and repealing Directives No. 80 / 590 / EEC and 89 / 109 / EEC, Official Journal of the European Union L 338 / 4 of 13 November 2004, Official Journal of the European Union L 188 of 18 July 2009, Article 3. 7. Lebensmittel-, Bedarfsgegenstande-und Futtermittelgesetzbuch (Lebensmittel-und Futtermittelgesetzbuch-LFGB) of the version issued on 3 June 2013 (BGBI.I, p. 1426), as last amended by paragraphs 97, 30 and 31 of the Regulation of 19 June 2020 (BGBI.I, p. 1328). 8. BfR Recommendation XXXVI, last amended by Communication No. 62, as amended by Communication No. 222. Papiere, Kartons und Pappen fur den Lebensmittelkontakt, Bundesgesundheitsblatt 14 (1971) 83, Bundesgesundheitsblatt 62 (2019) 1546, as of 1 June 2019.

[0062] In a preferred embodiment, the thermal recording material according to the present invention is further characterized in that the thermal recording material meets the arbitration criteria for the use of the Blue Angel ecolabel for thermal paper.

[0063] In another preferred embodiment, the thermal recording material according to the present invention is further characterized in that the thermal recording material meets the arbitration criteria regarding recyclability for the use of Blue Angel ecolabel thermal paper.

[0064] The determination of recyclability for the use of Blue Angel eco-label thermal paper for thermal recording materials is carried out as follows.

[0065] To produce the thermal recording material, the coating colors were applied to a base paper as a web-like carrier material to produce respective layers, the thermal layers being configured to become translucent when exposed to localized heat, thereby allowing the underlying color layers to be visible.

[0066] The thermal recording material does not contain additional printing ink on the surface (unprinted thermal recording material).

[0067] Since dye removal (deinking) is a common process in preparing graphic paper or cardboard stock, the thermal recording material should not significantly impair this process.

[0068] Tests were conducted to verify recyclability using the defibration and flotation conditions of INGEDE Method 11 (Deinkability Test, dated January 2018).

[0069] The (unprinted) thermosensitive recording material preferably meets at least one, more particularly both, of the following criteria: a) In an initial mixture consisting of 100% free uncoated copy paper printed on both sides with dry toner at a coverage of 5% (CEN_TEST Master, EN 12281) on one side, the light reflectance value after flotation decreases by a maximum of 6 points and the filtrate darkening by a maximum of 3 points after the addition of 1% thermal recording material compared to the initial mixture without flotated thermal recording material. b) In an initial mixture of newspaper / magazine (offset, uncoated) in a 60% / 40% ratio, the light reflectance value after flotation is only worsened by a maximum of 6 points and the filtrate darkening by a maximum of 3 points after the addition of 5% thermal recording material compared to the initial mixture without flotation thermal recording material.

[0070] In a preferred embodiment, the thermal recording material according to the present invention is further characterized in that it does not contain any azo dyes except in unavoidable amounts, more particularly does not contain any azo dyes at all, particularly preferably does not contain any azo dyes capable of splitting off one of the following aromatic amines (according to Regulation (EC) 1907 / 2007, Annex XVII, No. 43):

[0071] In a preferred embodiment, the thermal recording material according to the present invention is further characterized in that it does not contain any of the following compounds except in unavoidable amounts: 4-aminobiphenyl (92-67-1), Benzidine (92-87-5), 4-chloro-o-toluidine (95-69-2), 2-naphthylamine (91-59-8), o-aminoazotoluene (97-56-3), 2-amino-4-nitrotoluene (99-55-8), p-chloroaniline (106-47-8), 2,4-diaminoanisole (615-05-4), 4,4'-diaminodiphenylmethane (101-77-9), 3,3'-dichlorobenzidine (91-94-1), 3,3'-dimethoxybenzidine (119-90-4), 3,3'-dimethylbenzidine (119-93-7), 3,3'-dimethyl-4,4'-diaminodiphenylmethane (838-88-0), p-Cresidine (120-71-8), 4,4'-methylene-bis-(2-chloroaniline) (101-14-4), 4,4'-oxydianiline (101-80-4), 4,4'-thiodianiline (139-65-1), o-Toluidine (95-53-4), 2,4-diaminotoluene (95-80-7), 2,4,5-triethylaniline (137-17-7), 4-aminoazobenzene (60-09-3), o-Anisidine (90-04-0), 2,4-xylidine (95-68-1), and / or 2,6-Xylidine (87-62-7).

[0072] In accordance with the present invention, the heat-sensitive layer on the color layer is configured to at least partially cover the color layer and become translucent when exposed to localized heat, thereby allowing the underlying color layer to be visible.

[0073] This is preferably achieved by incorporating scattering particles into the heat-sensitive layer.

[0074] In a preferred embodiment, the thermosensitive recording material is characterized in that the thermosensitive layer comprises at least one scattering particle, more particularly a polymer particle, having a glass transition temperature of -55 to 130°C, preferably 40 to 80°C.

[0075] In another preferred embodiment, the thermosensitive recording material is characterized in that the thermosensitive layer comprises at least one scattering particle, more particularly a polymer particle, having a core / shell structure, wherein the scattering particle, more particularly a polymer particle, is selected from the group consisting of (i) scattering particles, more particularly a polymer particle, having an outer shell with a glass transition temperature of 40°C to 80°C and (ii) scattering particles, more particularly a polymer particle, having an inner shell with a glass transition temperature of 40°C to 130°C and an outer shell with a glass transition temperature of -55°C to 50°C, the glass transition temperature of the outer shell being preferably lower than that of the inner shell.

[0076] In another preferred embodiment, the thermosensitive recording material is characterized in that the thermosensitive layer comprises at least one scattering particle, more particularly a polymer particle, having a melting temperature below 250°C, preferably between 0°C and 250°C.

[0077] In another preferred embodiment, the thermosensitive recording material is characterized in that the thermosensitive layer comprises at least one scattering particle, more particularly a polymer particle, with an average particle size in the range of 0.1 to 2.5 μm, preferably 0.2 to 0.8 μm.

[0078] In another preferred embodiment, the thermosensitive recording material is characterized in that the thermosensitive layer has a glass transition temperature of -55 to 130°C, preferably 40 to 80°C, and contains at least one scattering particle, more particularly a polymer particle, having an average particle size in the range of 0.1 to 2.5 μm, preferably 0.2 to 0.8 μm.

[0079] In another preferred embodiment, the thermosensitive recording material is characterized in that the thermosensitive layer comprises at least one scattering particle, more particularly a polymer particle, having a core / shell structure, and the scattering particle, more particularly a polymer particle, is selected from the group consisting of: (i) scattering particles, more particularly polymer particles, having an outer shell with a glass transition temperature of 40°C to 80°C; and (ii) scattering particles, more particularly polymer particles, having an inner shell with a glass transition temperature of 40°C to 130°C and an outer shell with a glass transition temperature of -55°C to 50°C, the glass transition temperature of the outer shell being preferably lower than that of the inner shell, and having an average particle size in the range of 0.1 to 2.5 μm, preferably 0.2 to 0.8 μm.

[0080] In another preferred embodiment, the thermosensitive recording material is characterized in that the thermosensitive layer has a melting temperature of less than 250°C, preferably between 0°C and 250°C, and comprises at least one scattering particle, more particularly a polymer particle, having an average particle size in the range of 0.1 to 2.5 μm, preferably 0.2 to 0.8 μm.

[0081] It has been found advantageous to have a glass transition temperature or melting temperature below 250° C. Above a temperature of 250° C., direct thermal printing is not possible as the temperature-time window is outside the printer specifications.

[0082] An average particle size in the range of 0.1 to 2.5 μm is advantageous, since particles of this size scatter visible light and therefore cover the color layer as much as possible.

[0083] The average particle size can be determined using a Beckman Coulter instrument (laser diffraction, Fraunhofer method).

[0084] The scattering particles, more particularly the polymer particles, are preferably crystalline, semi-crystalline and / or amorphous.

[0085] The glass transition temperatures mentioned above relate to semi-crystalline or amorphous scattering particles, more particularly polymer particles, whereas the melting temperatures relate to crystalline scattering particles, more particularly polymer particles, or the crystalline portion of scattering particles, more particularly polymer particles, respectively.

[0086] The primary property of the scattering particles, preferably polymeric particles, is light scattering in the visible range of light. The secondary property is heat sensitivity.

[0087] The polymer particles preferably comprise a thermoplastic polymer.

[0088] The polymer particles preferably comprise a polymer selected from the polymerization of one or more monomers selected from the group comprising acrylonitrile, styrene, butadiene, benzyl methacrylate, phenyl methacrylate, ethyl methacrylate, divinylbenzene, 2-hydroxyethyl methacrylate, cyclohexyl methacrylate, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, alpha-methylstyrene, beta-methylstyrene, acrylamide, methacrylamide, methacrylonitrile, hydroxypropyl methacrylate, methoxystyrene, N-acrylylglycinamide and / or N-methacrylylglycinamide and / or derivatives thereof.

[0089] In another embodiment, the polymer particles may be polymerized using multiple ethylenically unsaturated monomers. Examples of non-ionic monoethylenically unsaturated monomers include styrene, vinyl toluene, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, (meth)acrylamide, (meth)acrylic acid, various (C1-C 20 ) alkyl or (C3-C 20 ) alkenyl esters, such as methyl acrylate (MA), methyl methacrylate (MMA), ethyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. Typically, acrylic esters, such as MMA, EA, BA, and styrene, are preferred monomers for polymerizing and forming the shell of the polymer particles. As described in U.S. Patent Application Publication No. 2003-0176535A1, difunctional vinyl monomers, such as divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate, can also be copolymerized to form a crosslinked outer shell.

[0090] In another embodiment, the polymer particles preferably also comprise (meth)acrylonitrile copolymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, styrene acrylate, styrene (meth)acrylate copolymer, polyacrylonitrile, polyacrylic ester or a mixture of at least two thereof.

[0091] The strength and durability of polymer particles can be affected by cross-linking of the polymer chains.

[0092] The scattering particles, especially polymeric particles, can be in the form of closed polymeric particles, open polymeric particles and / or solid particles, each of which can be regularly or irregularly shaped.

[0093] Examples of closed hollow body particles include hollow spherical polymer particles or polymer particles with a core / shell structure.

[0094] Examples of hollow spherical polymer particles or core / shell structured polymer particles are Ropaque HP-1055, Ropaque OP-96 and Ropaque TH-1000.

[0095] More specifically, examples of polymer particles may include so-called "cup-shaped" polymer particles. With respect to the shell, these particles have the same material as closed polymer particles, more specifically closed hollow spherical polymer particles. In contrast to classical hollow body pigments, in which an inner core of gas, usually air, is completely enclosed by a shell of an organic, usually thermoplastic, component, "cup-shaped" polymer particles do not have a closed shell, but simply surround the inner core in the form of a bowl or cup that is closed to the greatest extent possible.

[0096] Further examples of open polymer particles may include cage-like polymer particles as described in WO2021 / 062230A1.

[0097] Examples of solid particles may include polyethylene, polystyrene, and cellulose esters.

[0098] The scattering particles, more particularly polymeric particles, mentioned above, can be of regular or irregular shape.

[0099] In an alternative embodiment, the polymer particles are spherical solid particles, preferably irregularly shaped particles, preferably both in the form of droplets, and / or spherical hollow particles. These preferably include polystyrene, such as Plastic Pigment 756A from Trinseo LLC. and Plastic Pigment 772HS from Trinseo LLC., polyethylene, such as Chemipearl 10 W401 from Mitsui Chemicals, Inc., spherical hollow particles (HSP) / spherical hollow pigments, such as Ropaque TH-500EF from The Dow Chemical Co., modified polystyrene particles, such as Joncryl 633 from BASF Corp., 1,2-diphenoxyethane (DPE), ethylene glycol m-tolyl ether (EGTE), and / or diphenyl sulfone (DPS). These can be used alone or in any mixture. These polymer particles preferably have an average particle size of 0.2 μm, 0.3 μm, 0.4 μm, 0.45 μm, 0.75 μm or 1.0 μm.

[0100] The scattering particles, more particularly the polymer particles, are preferably present in the thermosensitive layer in an amount of 20% to 60% by weight, more preferably 30% to 50% by weight, based on the solid content of the thermosensitive layer.

[0101] Preferably, the heat-sensitive layer comprises at least one heat-sensitive material having a melting temperature in the range of 40 to 200°C, preferably 80 to 140°C, and / or a glass transition temperature in the range of 40 to 200°C, preferably 80 to 140°C.

[0102] Preferably, the heat-sensitive layer comprises at least one heat-sensitive material having an average particle size of 0.2 to 4.0 μm, preferably 0.5 to 2.0 μm.

[0103] In another embodiment, the thermosensitive layer is characterized in that it comprises or consists of scattering particles, more particularly a thermosensitive material as scattering particles, more particularly a thermosensitive material selected from the group of biopolymers, modified biopolymers, fats, natural waxes, semi-synthetic waxes and / or synthetic waxes, with semi-synthetic waxes being preferred.

[0104] Such thermal recording materials are more particularly characterized by the fact that sustainable raw materials are used.

[0105] Suitable examples of biopolymers include natural biopolymers such as proteins, peptides, nucleic acids, α-polysaccharides, β-polysaccharides, lipids, polyhydroxyalkanoates, cutin, sulverin and / or lignin.

[0106] The use of so-called technical biopolymers, such as natural polymers, bio-based polymers and degradable petroleum-based polymers, is also possible.

[0107] Examples of natural polymers include regenerated fibers such as viscose and cellophane, celluloid, and thermoplastic starch.

[0108] Examples of bio-based polymers include polylactides, polyhydroxybutyrate, lignin-based thermoplastics and / or oil-based epoxy acrylates, more particularly linseed oil and palm oil-based epoxy acrylates.

[0109] Examples of degradable petroleum-based polymers include polyester, polyvinyl alcohol, polybutylene adipate terephthalate, polybutylene succinate, polycaprolactone, and / or polyglycolide. These may be used alone or as a mixture.

[0110] Suitable examples of modified biopolymers include, for example, esters of cellulose and / or lignin, which may be used alone or in mixtures.

[0111] Suitable examples of fats include fats based on saturated and / or unsaturated fatty acids such as, for example, butyric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, gadoleic acid and / or arachidonic acid.

[0112] Suitable examples of natural waxes include, for example, carnauba wax, candelilla wax and / or montan wax.

[0113] Suitable examples of synthetic waxes include, for example, (hydro)carbon waxes, polyolefin waxes, HD-PE waxes, PE waxes, EVA waxes, polyester waxes, polyethylene glycol waxes, PTFE waxes, fluorine waxes, Fischer-Tropsch waxes, synthetic fatty acid esters and / or reconstituted waxes, which can be used alone or in mixtures.

[0114] Suitable examples of semi-synthetic waxes include, for example, stearamide waxes and / or palmitamide waxes, which may be used alone or in mixtures.

[0115] The use of waxes from the group consisting of animal waxes, vegetable waxes, mineral waxes and / or microwaxes is also conceivable.

[0116] The use of semi-synthetic waxes is preferred as they offer a favorable cost-performance ratio.

[0117] Biopolymers, modified biopolymers, fats, natural waxes, semi-synthetic waxes, and synthetic waxes can be used alone or in mixtures.

[0118] In this embodiment, the heat sensitive material is preferably selected from amide waxes, stearamide waxes, palmitamide waxes, or combinations thereof.

[0119] In this embodiment, the scattering particles, more particularly the heat-sensitive material, are present in the heat-sensitive layer in an amount of 5 to 100% by weight, preferably 40 to 100% by weight, particularly preferably 40 to 95% by weight, relative to the total weight of the heat-sensitive layer.

[0120] In this embodiment, the heat-sensitive recording material is preferably characterized in that the scattering particles, preferably the heat-sensitive material, have a melting temperature in the range of 30-250°C, preferably in the range of 40-200°C.

[0121] In another preferred embodiment, the thermosensitive recording material according to the present invention is characterized in that the thermosensitive layer comprises 20 to 60% by weight, preferably 30 to 50% by weight, of scattering particles, more particularly polymer particles, having an average particle size in the range of 0.1 to 2.5 μm, preferably 0.2 to 0.8 μm; 10 to 80% by weight, preferably 25 to 60% by weight, of a thermosensitive material having a melting temperature in the range of 40 to 200° C. and / or a glass transition temperature in the range of 40 to 200° C.; and 1 to 30% by weight, preferably 5 to 20% by weight, of a binder.

[0122] Such a thermal recording material is more particularly characterized by its functionality, its environmental properties (sustainability) and / or its economical production (simple and cost-effective), and more particularly by an advantageous combination of these three properties.

[0123] Additionally, the heat-sensitive material preferably contributes to the opacity (covering power) of the heat-sensitive layer, for example, by absorbing and / or scattering light. It is hypothesized that the heat-sensitive material rapidly melts locally when exposed to localized heat from the thermal print head of a direct thermal printer, resulting in a localized "softening" of the polymer particles and therefore a localized decrease in opacity (opacity loss), resulting in a translucent top layer and allowing the underlying color layer to become visible.

[0124] The heat-sensitive material may also be called a sensitizer or a thermal solvent.

[0125] Preferably, the heat-sensitive material comprises one or more fatty acids based on vegetable and / or animal oils, such as stearic acid, behenic acid or palmitic acid, one or more fatty acid amides, such as stearamide, behenamide or palmitamide, ethylene-bis-fatty acid amides, such as N,N'-ethylenebis(stearamide) or N,N'-ethylenebis(oleamide), one or more fatty acid alkanolamides, such as N-(hydroxymethyl)stearamide, N-hydroxymethylpalmitamide, hydroxyethylstearamide, more particularly hydroxymethylated fatty acid amides, one or more waxes, such as polyethylene wax, candelilla wax, carnauba wax or montan wax, dimethyl terephthalate, dibenzyl terephthalate, benzyl 4-benzyloxybenzoate, the aromatic hydrocarbons include one or more aromatic ethers such as 1,2-diphenoxyethane, 1,2-di-(3-methylphenoxy)ethane, 2-benzyloxynaphthalene, 1,2-bis(phenoxymethyl)benzene, or 1,4-diethoxynaphthalene; one or more aromatic sulfones such as diphenyl sulfone; and / or one or more aromatic sulfonamides such as 2-, 3-, or 4-toluenesulfonamide, benzenesulfonamide, or N-benzyl-4-toluenesulfonamide; or one or more aromatic hydrocarbons such as 4-benzylbiphenyl; or a combination of the above compounds, which may be used alone or in any mixture.

[0126] Stearamide is preferred as it has a favorable cost-performance ratio.

[0127] The heat-sensitive material is preferably present in the heat-sensitive layer in an amount of about 10 to about 80% by weight, and more preferably about 25 to about 60% by weight, based on the total solid content of the heat-sensitive layer.

[0128] Optionally, a lubricant or release agent may also be present in the thermosensitive layer, more particularly when there is no protective or further layer on the thermosensitive layer.

[0129] These agents are preferably fatty acid metal salts, such as zinc stearate or calcium stearate, or even behenates, synthetic waxes in the form of fatty acid amides, such as stearamide and behenamide, fatty acid alkanolamides, such as stearic acid methylolamide, paraffin waxes of different melting points, ester waxes of different molecular weights, ethylene waxes, propylene waxes of different hardness, and / or natural waxes, such as carnauba wax or montan wax, which can be used alone or in any mixture.

[0130] Zinc stearate is preferred as it has a favorable cost-performance ratio.

[0131] The lubricant or release agent is preferably present in the thermosensitive layer in an amount of about 1 to about 10% by weight, and more preferably about 3 to about 6% by weight, based on the total solids content of the thermosensitive layer.

[0132] In another preferred embodiment, at least one binder (binding agent) is present in the thermosensitive layer. These are preferably water-soluble starch, starch derivatives, starch-based Ecosphere biolatex, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, gelatin, casein, partially or completely saponified polyvinyl alcohol, chemically modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, sodium polyacrylate, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, styrene-butadiene copolymer, acrylamide (meth)acrylate copolymer, acrylamide-acrylate-methacrylate terpolymer, polyacrylate, poly(meth)acrylic acid ester, acrylate-butadiene copolymer, polyvinyl acetate, and / or acrylonitrile-butadiene copolymer. These may be used alone or in any mixture.

[0133] Partially saponified polyvinyl alcohol is preferred as it has an advantageous cost-performance ratio.

[0134] The binder is preferably present in the thermosensitive layer in an amount of 1 to 30% by weight, preferably 5 to 20% by weight, based on the total solids content of the thermosensitive layer.

[0135] In order to achieve performance properties relevant to the specific application of the thermosensitive recording material, the binder is preferably present in the thermosensitive layer in crosslinked form, the optimum degree of crosslinking of the binder being achieved in the drying step of the coating process in the presence of a crosslinking agent (crosslinker).

[0136] The crosslinking agent may be a polyhydric aldehyde such as glyoxal, dialdehyde starch, glutaraldehyde, optionally in a mixture with boron salts (borax), salts or esters of glyoxylic acid, crosslinkers based on ammonium zirconium carbonate, polyamidoamine-epichlorohydrin resins (PAE resins), adipic acid dihydrazide (AHD), boric acid or its salts, polyamines, epoxy resins, formaldehyde oligomers, cyclic ureas, methylol ureas, melamine formaldehyde oligomers, etc. These may be used alone or in any mixture.

[0137] Ammonium zirconium carbonate and polyamidoamine epichlorohydrin resins (PAE resins) are particularly preferred for reasons of food compatibility.

[0138] Self-crosslinking binders such as specially modified polyvinyl alcohols or acrylates can crosslink without any crosslinking agent due to reactive crosslinkable groups already incorporated within the binder polymer.

[0139] The crosslinking agent is preferably present in an amount of from about 0.01 to about 25.0% by weight, and particularly preferably from about 0.05 to about 15.0% by weight, based on the total solids content of the color layer.

[0140] In another preferred embodiment, the thermosensitive layer contains pigments. These pigments are preferably different from the pigments in the color layer. One advantage of using them is that they can fix the molten chemicals produced on their surface during the thermal printing process. Pigments can also be used to adjust the surface whiteness and opacity of the thermosensitive layer and its printability with conventional printing inks.

[0141] Particularly suitable pigments are inorganic pigments of both synthetic and natural origin, preferably clay, precipitated or natural calcium carbonate, aluminum oxide, aluminum hydroxide, silica, precipitated and fumed silica (for example of the Aerodisp type), diatomaceous earth, magnesium carbonate, talc, kaolin, titanium dioxide, bentonite, but also organic pigments such as hollow body pigments with styrene / acrylic copolymer walls or urea / formaldehyde condensation polymers, which can be used alone or in any mixture.

[0142] Calcium carbonate, aluminum hydroxide and fumed silica are preferred, since these allow particularly advantageous applicability of the thermal recording material with regard to its subsequent printability with commercially available printing inks.

[0143] The pigment is preferably present in the thermosensitive layer in an amount of about 2 to about 50% by weight, and more preferably about 5 to about 20% by weight, based on the total solids content of the thermosensitive layer.

[0144] The heat-sensitive layer may also contain carbon black components and / or dyes / color pigments.

[0145] In order to adjust the surface whiteness of the thermal recording material according to the present invention, optical brighteners can be incorporated into the thermal color-forming layer, these preferably being stilbenes.

[0146] The heat-sensitive layer may also contain an inorganic oil-absorbing white pigment.

[0147] Examples of these inorganic oil-absorbing white pigments include natural or calcined kaolin, silica, bentonite, calcium carbonate, aluminum hydroxide, and more particularly boehmite, and mixtures thereof.

[0148] The inorganic oil-absorbable white pigment is preferably present in the heat-sensitive layer in an amount of about 2 to about 50% by weight, and more preferably about 5 to about 20% by weight, based on the total solids content of the heat-sensitive layer.

[0149] In order to improve certain coating properties, it may be advantageous in individual cases to add additional components, such as thickeners and / or surfactants, more particularly rheological additives, to the components of the heat-sensitive recording material according to the invention.

[0150] The additional ingredients are preferably present in conventional amounts known to those skilled in the art.

[0151] The heat-sensitive layer preferably has a thickness of 1 to 8 g / m 2 , more particularly 2 to 6 g / m 2 The sheet has a basis weight of .

[0152] The heat-sensitive layer preferably has a thickness of 1 to 10 μm, more particularly 2 to 8 μm.

[0153] In another preferred embodiment, the thermal recording material is preferably characterized in that an insulating layer is present between the web-like carrier material and the color layer.

[0154] In an alternative embodiment, the thermal recording material is preferably characterized in that the color layer is both a color layer and an insulating layer.

[0155] Such an insulating layer, or color layer, which is both a color layer and an insulating layer, causes a decrease in heat conduction through the thermal recording material, which allows for more efficient localized heat exposure using a direct thermal printer and allows for higher thermal printer speeds. The top layer becomes translucent more quickly due to the amount of heat applied, thus improving sensitivity.

[0156] This means that less dye is required, resulting in improved recyclability (easier deinking, separation of dye and carrier material components) in the material cycle, more particularly in the waste paper cycle.

[0157] The insulating layer or the color layer, both the color layer and the insulating layer, preferably has a Bekk smoothness of more than 50 seconds, particularly preferably more than 100 seconds, most particularly preferably 100 to 250 seconds.

[0158] The insulating layer or the color layer, both the color layer and the insulating layer, preferably comprises a thermal insulating material.

[0159] Preferably, a thermal recording material having an insulating layer or a color layer that is also an insulating layer has a lower thermal conductivity than a thermal recording material that does not include an insulating layer or a color layer that is also an insulating layer.

[0160] The insulating material preferably comprises kaolin, particularly preferably calcined kaolin and mixtures thereof.

[0161] The insulating material may also include hollow sphere pigments, more particularly hollow sphere pigments comprising styrene-acrylate copolymers.

[0162] These hollow sphere pigments preferably have a glass transition temperature of 40 to 80° C. and / or an average particle size of 0.1 to 2.5 μm.

[0163] The heat insulating material is preferably present in the insulating layer in an amount of about 20 to about 80% by weight, and particularly preferably about 30 to about 60% by weight, based on the total solids content of the insulating layer.

[0164] In a color layer that is both a color layer and an insulating layer, the insulating material is preferably present in an amount of about 30 to about 70% by weight, and particularly preferably about 30 to about 60% by weight, based on the total solids content of the color layer that is both a color layer and an insulating layer.

[0165] To achieve performance characteristics relevant to a particular application of the thermal recording material, the binder is preferably present in the insulating layer and / or color layer in a crosslinked form, the optimum degree of crosslinking of the binder being achieved in the drying step of the coating process in the presence of a crosslinking agent (crosslinker).

[0166] The crosslinking agent may be a polyhydric aldehyde such as glyoxal, dialdehyde starch, glutaraldehyde, optionally in a mixture with boron salts (borax), or may be a salt or ester of glyoxylic acid, a crosslinking agent based on ammonium zirconium carbonate, polyamidoamine-epichlorohydrin resin (PAE resin), adipic acid dihydrazide (AHD), boric acid or its salts, polyamine, epoxy resin, formaldehyde oligomer, cyclic urea, methylol urea, melamine formaldehyde oligomer, etc. These may be used alone or in any mixture.

[0167] Ammonium zirconium carbonate and polyamidoamine epichlorohydrin resins (PAE resins) are preferred, especially for reasons of food compatibility.

[0168] Self-crosslinking binders, such as specially modified polyvinyl alcohols or acrylates, can crosslink without any crosslinking agent due to reactive crosslinkable groups already incorporated within the binder polymer.

[0169] The crosslinking agent is each present in an amount of about 0.01 to about 25.0 weight percent, and most preferably about 0.05 to about 15.0 weight percent, based on the total solids content of the insulation or color layer.

[0170] The insulating layer is preferably 1 to 5 g / m 2 , more particularly 2 to 4 g / m 2 The sheet has a basis weight of .

[0171] In another embodiment, the insulating layer preferably has a weight of 1 to 10 g / m 2 , more particularly 2 to 6 g / m 2 The sheet has a basis weight of .

[0172] The insulating layer preferably has a thickness of 1 to 10 μm, more particularly 2 to 8 μm.

[0173] The color layer, which is both a color layer and an insulating layer, is preferably 1 to 10 g / m 2, more particularly 3 to 8 g / m 2 The sheet has a basis weight of .

[0174] The color layer, which is both a color layer and an insulating layer, preferably has a thickness of 1 to 12 μm, more particularly 4 to 8 μm.

[0175] In another preferred embodiment, the thermal recording material is preferably characterized in that a layer comprising starch (starch precoat) and / or modifications thereof (modified starch) is present directly on at least one side of the web-like carrier material, preferably directly on both sides of the web-like carrier material.

[0176] The starch precoat is preferably 0.1 to 3, particularly preferably 0.2 to 1.5 g / m 2 is applied in an amount of

[0177] The starch precoat on the side of the web-like carrier material on which the color layer resides has the advantage of sealing the web-like carrier material, thus improving adhesion of the color layer and reducing or preventing penetration of the color layer into the web-like carrier material.

[0178] A starch precoat on the side of the web-like carrier material where no color layer is present has the advantage that it can reduce or prevent penetration of the color layer through the web-like carrier material.

[0179] The layer containing starch preferably has a Bekk smoothness greater than 20 seconds, more preferably greater than 50 seconds, most preferably between 50 and 200 seconds.

[0180] In another preferred embodiment, the thermosensitive recording material is preferably characterized in that a protective layer is present on the thermosensitive layer.

[0181] The protective layer preferably has a Bekk smoothness greater than 200 seconds, preferably greater than 400 seconds, most preferably between 400 and 1500 seconds, most preferably between 400 and 1300 seconds.

[0182] This layer is on the side of the thermal layer away from the color layer.

[0183] This protective layer preferably comprises at least one binder and at least one pigment, particularly preferably an inorganic pigment.

[0184] Suitable binders include water-soluble starch, starch derivatives, starch-based Ecosphere-type biolatex, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, partially or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohol, such as acetoacetyl-, diacetone-, carboxy-, or silanol-modified polyvinyl alcohol, or styrene-maleic anhydride copolymers, styrene-butadiene copolymers, acrylamide (meth)acrylate copolymers, acrylamide-acrylate-methacrylate terpolymers, polyacrylates, poly(meth)acrylic acid esters, acrylate-butadiene copolymers, polyvinyl acetate and / or acrylonitrile-butadiene copolymers, which can be used alone or in any mixture.

[0185] Suitable inorganic pigments include inorganic pigments of both synthetic and natural origin, preferably clay, precipitated or natural calcium carbonate, aluminum oxide, aluminum hydroxide, silica, precipitated and fumed silica (e.g., Aerodisp type), diatomaceous earth, magnesium carbonate, talc, kaolin, titanium dioxide, bentonite, but also organic pigments, such as hollow body pigments with styrene / acrylate copolymer walls or urea / formaldehyde condensation polymers, which can be used alone or in any mixture.

[0186] Suitable organic pigments include styrene / acrylate copolymer walled hollow body pigments or urea / formaldehyde condensation polymers, which can be used alone or in any mixture.

[0187] The binder is preferably present in the protective layer in an amount of about 40 to about 90% by weight, and more preferably about 50 to about 80% by weight, based on the total solid content of the protective layer.

[0188] The pigment is preferably present in the protective layer in an amount of about 5 to about 40% by weight, and more preferably about 10 to about 30% by weight, based on the total solid content of the protective layer.

[0189] In order to achieve performance properties relevant to the specific application of the thermal recording material, the binder is preferably present in the protective layer in crosslinked form, the optimum degree of crosslinking of the binder being achieved in the drying step of the coating process in the presence of a crosslinking agent (crosslinker).

[0190] The crosslinking agent may be a polyhydric aldehyde such as glyoxal, dialdehyde starch, glutaraldehyde, optionally in a mixture with boron salts (borax), or may be a salt or ester of glyoxylic acid, a crosslinking agent based on ammonium zirconium carbonate, polyamidoamine-epichlorohydrin resin (PAE resin), adipic acid dihydrazide (AHD), boric acid or its salts, polyamine, epoxy resin, formaldehyde oligomer, cyclic urea, methylol urea, melamine formaldehyde oligomer, etc. These may be used alone or in any mixture.

[0191] Ammonium zirconium carbonate and polyamidoamine epichlorohydrin resins (PAE resins) are preferred, especially for reasons of food compatibility.

[0192] Self-crosslinking binders, such as specially modified polyvinyl alcohols or acrylates, can crosslink without any crosslinking agent due to reactive crosslinkable groups already incorporated within the binder polymer.

[0193] The crosslinking agent is preferably present in an amount of from about 0.01 to about 25.0, and most preferably from about 0.05 to about 15.0 weight percent based on the total solids content of the color.

[0194] The crosslinking agent is preferably present in an amount of about 0.01 to about 25.0, and particularly preferably about 0.05 to about 15.0 wt % based on the total solids content of the protective layer.

[0195] The protective layer also preferably includes at least one lubricant or at least one release agent.

[0196] These agents are preferably fatty acid metal salts, such as zinc stearate or calcium stearate, or even behenates, synthetic waxes in the form of fatty acid amides, such as stearamide and behenamide, fatty acid alkanolamides, such as stearic acid methylolamide, paraffin waxes of different melting points, ester waxes of different molecular weights, ethylene waxes, propylene waxes of different hardness and / or natural waxes, such as carnauba wax or montan wax.

[0197] The lubricant or release agent is preferably present in an amount of about 1 to about 30% by weight, and particularly preferably about 2 to about 20% by weight, based on the total solids content of the protective layer.

[0198] In order to adjust the surface whiteness of the heat-sensitive recording material according to the present invention, an optical brightener, preferably a stilbene, can be incorporated into the protective layer.

[0199] The protective layer preferably has a thickness of 0.3 to 5.0 g / m 2 , more particularly 1.0 to 3.0 g / m 2 The sheet has a basis weight of .

[0200] The protective layer preferably has a thickness of 0.3 to 6.0 μm, more particularly 0.5 to 2.0 μm.

[0201] The use of a protective layer has the advantage that the recording material is better protected against external influences.

[0202] In another preferred embodiment, the heat-sensitive recording material is preferably characterized in that an adhesive layer is present on the side of the web-like carrier material on which the color layer is not located.

[0203] When present, the starch precoat is located between the web-like backing material and the adhesive layer.

[0204] The adhesive layer preferably comprises at least one adhesive, preferably a heat-activatable adhesive, more particularly a pressure-sensitive adhesive.

[0205] It is particularly preferred that the adhesive, preferably a heat-activated adhesive, more particularly a pressure-sensitive adhesive, is a rubber-based and / or acrylate-based adhesive.

[0206] The adhesive layer preferably has a thickness of 1 to 40 g / m 2 , more particularly 12 to 25 g / m 2 The sheet has a basis weight of .

[0207] In another preferred embodiment, the thermosensitive recording material is characterized in that a release layer, preferably silicone treated, is present on the thermosensitive layer.

[0208] The terms "siliconized release layer" and "siliconized layer" are to be understood synonymously as meaning "covered with a layer of silicone". Preferably, these layers consist of silicone or contain at least 90% by weight, preferably at least 95% by weight, particularly preferably at least 99% by weight, most preferably exclusively silicone, with the exception of unavoidable traces or additives (e.g. for UV curing of siliconizing liquids).

[0209] The silicone treated release layer preferably has a Bekk smoothness greater than 400 seconds, particularly preferably greater than 800 seconds, and most preferably between 800 and 2000 seconds.

[0210] If a protective layer, more particularly a protective layer as defined above, is present on the thermosensitive layer, the siliconized release layer is preferably located on this protective layer.

[0211] In another preferred embodiment, the thermosensitive recording material is preferably characterized in that a diffusion layer is formed between the siliconized layer and an underlying layer, preferably the thermosensitive layer. This diffusion layer is preferably formed by diffusing at least a portion of the siliconized release layer into the upper region of the underlying layer, preferably 5 to 50% by weight, particularly preferably 6 to 45% by weight, more particularly 7 to 40% by weight of the siliconized release layer into the upper region of the underlying layer. Such diffusion layers are described, for example, in EP 3 221 153 A1.

[0212] A silicone treated release layer is preferably present when the adhesive layer described above is also present.

[0213] The presence of a silicone-treated release layer on the thermosensitive layer and an adhesive layer on the side of the web-like carrier material on which the color layer is not located has the advantage that the thermosensitive recording material can be used as a linerless thermosensitive recording material.

[0214] Linerless means that the (self-adhesive) thermal recording material according to the invention is not applied to a carrier material but is wound up on itself, which has the advantages of further reducing production costs, realizing more running meters per roll, eliminating disposal costs for discarded liners, and allowing more labels to be transported per specific loading space volume.

[0215] If a siliconized release layer is present, it is preferred that at least one platelet-shaped pigment be included in the thermosensitive layer or in a layer immediately beneath the siliconized release layer.

[0216] The at least one platelet-shaped pigment is preferably selected from the group consisting of kaolin, Al(OH)3 and / or talc. The use of kaolin is particularly preferred. The use of coated kaolin is particularly preferred. Such products are available, for example, under the trade name Kaolin ASP 109 (BASF, Germany).

[0217] The use of these platelet-like pigments, and more particularly kaolin, has the major advantage that the layer directly beneath the heat-sensitive layer or the siliconized release layer can be siliconized very easily.

[0218] Platelet pigments are understood to be pigments having a diameter to thickness ratio of about 7 to 40:1, preferably about 15 to 30:1.

[0219] The particle size of the platelet pigment is preferably adjusted so that at least about 70%, preferably at least about 85%, of the particles have a particle size of about <2 μm (Sedigraph). The pH value of the platelet pigment in aqueous solution is preferably 6-8.

[0220] At least one platelet-like pigment is present in the thermal color-forming layer or in the layer immediately beneath the silicone-treated release layer, preferably in an amount of from about 5 to about 60% by weight, and most preferably from about 15 to about 55% by weight, based on the total solids content of the respective layer.

[0221] In another preferred embodiment, the thermal recording material is characterized in that the preferably siliconized release layer comprises at least one siloxane, preferably a poly(organo)siloxane, more particularly an acrylic poly(organo)siloxane.

[0222] In another embodiment, the siliconized release layer comprises a mixture of at least two siloxanes, preferably a mixture of at least two acrylic poly(organo)siloxanes.

[0223] Examples of particularly preferred siloxanes are those available under the trade names TEGO® RC902 and TEGO® RC711 (Evonik, Germany).

[0224] In another embodiment, the thermal recording material is preferably characterized in that the siliconized release layer comprises at least one polysilicone acrylate, preferably formed by condensation of at least one silicone acrylate.

[0225] The siliconized release layer is preferably anhydrous. It is also preferred that the siliconized release layer does not contain any Pt catalyst.

[0226] The silicone-treated release layer preferably contains an initiator, particularly preferably a photoinitiator, which is used for the radical curing of the silicone.

[0227] TEGO® Photoinitiator A18 (Evonik, Germany) is particularly preferred.

[0228] The siliconized release layer may preferably contain further additives such as matting agents and / or adhesion additives.

[0229] The silicone-treated release layer preferably contains 0.1 to 5% by weight or 0.3 to 5.0 g / m 2 , more particularly 1.0 to 3.0 g / m 2 , or preferably has a basis weight of 0.2 to 2.0% by weight.

[0230] The silicone-treated release layer preferably has a thickness of 0.3 to 6.0 μm, more particularly 0.5 to 2.0 μm.

[0231] Due to its hydrophobic characteristics, the application of a silicone-treated release layer generally improves the resistance of the thermosensitive recording material to hydrophilic agents such as alcohol or water, and therefore the silicone-treated release layer is also suitable as a protective layer.

[0232] In another preferred embodiment, the thermal recording material is preferably characterized in that the thermal recording material has a residual moisture content of 2 to 14%, preferably 2 to 12%, most preferably 3 to 10%. A residual moisture content of 3 to 8% is most preferred.

[0233] Residual moisture can be determined as described in connection with the Examples.

[0234] It is hypothesized that the opacity of the thermosensitive layer is caused not only by the scattering particles, more specifically the polymer particles themselves, but also by the air trapped between the scattering particles, more specifically the polymer particles (open porosity). Ingress of moisture into these "pores" displaces the air and reduces the opacity. This can result in an objectionably grayer material.

[0235] In another preferred embodiment, the thermal recording material is preferably characterized in that the thermal recording material has a surface whiteness of 35 to 60%, more particularly 45 to 50%.

[0236] A residual moisture content in the defined range has the advantage that after printing there is a high relative print contrast with advantageous application properties such as better visibility.

[0237] Surface brightness (paper whiteness) can be determined according to ISO 2470-2 (2008) using an Elrepho 3000 spectrophotometer.

[0238] In another preferred embodiment, the thermosensitive recording material is preferably characterized in that the contrast between the locations where the thermosensitive layer has become translucent due to exposure to localized heat and the locations where the thermosensitive layer has not become translucent due to exposure to localized heat is 40 to 80%, more particularly 50 to 70%.

[0239] This contrast can be calculated by taking the difference in optical density between the background and the typeface. Optical density (OD) is measured, for example, using a densitometer.

[0240] All of the above layers can be single layer or multilayer.

[0241] Preferably, the carrier material has a Bekk smoothness at the face on which the color layer is applied of more than 20 seconds, particularly preferably more than 30 seconds, most particularly preferably more than 50 seconds.

[0242] The color layer preferably has a Bekk smoothness at the surface to which the thermosensitive layer is applied of more than 50 seconds, particularly preferably more than 100 seconds, most particularly preferably more than 150 seconds.

[0243] The heat-sensitive layer preferably has a Bekk smoothness of greater than 100 seconds, particularly preferably greater than 150 seconds, on the side not bearing the color layer.

[0244] Preferably, the carrier material has a Bekk smoothness on the side on which the color layer is applied of 20 to 400 seconds, particularly preferably 30 to 300 seconds, most particularly preferably 50 to 200 seconds, most preferably a Bekk smoothness of 50 to 150 seconds.

[0245] The color layer preferably has a Bekk smoothness on the side to which the heat-sensitive layer is applied of 50 to 400 seconds, particularly preferably 100 to 250 seconds, most particularly preferably 150 to 250 seconds.

[0246] Such heat-sensitive recording materials have the advantage of high dynamic sensitivity.

[0247] It is advantageous to provide a smooth web-like carrier material and maintain this smoothness across the individual coatings. The smoother the substrate that can be built up from the bottom up, the better the final smoothness and therefore the sensitivity of the final product.

[0248] Preferably, each layer applied to the web-like carrier material has a Bekk smoothness on its upper surface, i.e. the surface facing away from the web-like carrier material, that is at least as great as or greater than the respective layer below.

[0249] Preferably, each layer applied to the web-like carrier material has, on its upper surface, i.e. the surface facing away from the web-like carrier material, a Bekk smoothness of at least 5% (increase) compared to the respective layer below.

[0250] Preferably, each layer attached to the web-like carrier material has, on its upper surface, i.e., the surface facing away from the web-like carrier material, a Bekk smoothness of at least 5% (absolute increase) compared to the respective layer below.

[0251] The heat-sensitive recording material according to the present invention can be obtained by a known production method.

[0252] The present invention also relates to a manufacturing method for the above-mentioned heat-sensitive recording material.

[0253] The thermosensitive recording material according to the invention is preferably obtained by successively coating a web-like carrier material with (aqueous) suspensions comprising the starting materials for the individual layers, the (aqueous) coating suspensions having a solids content of 8 to 50% by weight, preferably 10 to 40% by weight, by a curtain coating process at an operating speed of the coating system of at least 200 m / min.

[0254] Alternatively, the (aqueous) suspension containing the starting materials for the respective layer can also be applied with a blade.

[0255] This method is particularly advantageous from an economic point of view and for uniform application to the web-like carrier material.

[0256] Below a solids content of approximately 8% by weight, economic efficiency suffers, since large amounts of water must be removed in a short time by gentle drying, which has a detrimental effect on the coating speed, whereas above a value of 60% by weight, the machine must again operate very quickly, which only increases the technical efforts to ensure the stability of the coating color curtain during the coating process and drying of the applied film.

[0257] In the curtain coating process, a free-falling curtain of coating dispersion is formed. The coating dispersion in the form of a thin film (curtain) is "poured" by free fall onto a substrate to apply the coating dispersion to the substrate. DE 10 196 052 T1 discloses the use of the curtain coating process in the production of information recording materials, in which multiple recording layers are realized by applying a curtain of several coating dispersion films to a substrate.

[0258] A "double curtain" embodiment of the method according to the invention is also conceivable. This means that two successive coats are applied in immediate succession. Here, the applications are carried out in immediate succession so that the first applied layer has not yet dried before the next layer is applied. The two layers are therefore preferably applied "wet on wet."

[0259] All definitions relating to the curtain coating process apply equally to the double curtain coating process.

[0260] The advantage of wet-on-wet application using a double curtain coating process is that the two layers have a stronger bond and more particularly there is no need for an intermediate adhesion promoter.

[0261] In a preferred embodiment of the method according to the invention, the aqueous deaerated coating suspension has a viscosity of about 100 to about 1000 mPas (Brookfield, 100 rpm, 20°C). Values ​​below about 100 mPas or above about 1000 mPas lead to poor runnability of the coating mass in the coating unit. Particularly preferably, the viscosity of the aqueous deaerated coating suspension is about 200 to about 500 mPas. The viscosity of successive coating masses in a double curtain should decrease from bottom to top. In the case of an incorrectly adjusted coating, the risk of healing at the point of contact with the curtain increases with the occurrence of "poor wetting".

[0262] In a preferred embodiment, the surface tension of the aqueous coating suspension can be adjusted to about 25 to about 70 mN / m, preferably about 35 to about 60 mN / m (measured according to the standard for bubble pressure tensiometry (ASTM D 3825-90) as described below) to optimize the process. Better control over the coating process can be achieved by determining the dynamic surface tension of the coating color and adjusting it by selecting an appropriate surfactant, determining the required amount of surfactant.

[0263] Dynamic surface tension is measured using a bubble pressure tensiometer. The maximum internal pressure of a bubble formed in a liquid through a capillary tube is measured. The internal pressure p (Laplace pressure) of a spherical bubble depends on the radius of curvature r and the surface tension σ according to the Young-Laplace equation:

[0264]

number

[0265] When a bubble is created in the liquid at the tip of the capillary, the curvature first increases, then decreases again, resulting in a pressure maximum. The maximum curvature, and therefore the maximum pressure, occurs when the radius of curvature corresponds to the capillary radius.

[0266] Pressure characteristics for bag pressure measurement, position of maximum pressure:

[0267] The radius of the capillary is determined using standard measurements made with a liquid of known surface tension, usually water. Once the radius is known, the surface tension can be calculated from the maximum pressure pmax. Because the capillary is immersed in the liquid, the hydrostatic pressure p0 resulting from the immersion depth and the density of the liquid must be subtracted from the measured pressure (this is done automatically in modern instruments). This results in the following equation for the bubble pressure process:

[0268]

number

[0269] The measured value corresponds to the surface tension at a constant surface lifetime, the time from the onset of bubble formation to the occurrence of a pressure maximum. By varying the rate at which the bubbles form, the dependence of surface tension on surface lifetime can be determined, resulting in a curve plotting surface tension against time.

[0270] This dependence plays an important role for the use of surfactants because in many processes the equilibrium value of the interfacial tension is never even reached due to the sometimes low diffusion and adsorption rates of surfactants.

[0271] The individual layers can be applied online or in separate offline coating processes.

[0272] In particular, to ensure that the layer detailed above exhibits the Bekk smoothing described above, the following method steps are preferably performed.

[0273] The web-like carrier material is preferably smoothed in the first cylinder. This high degree of smoothness on one or both sides produced by this process technology already confers advantages on the web-like carrier material. Additional calendering by a downstream calender, preferably before the first coater, can further improve the smoothness and / or ensure a good profile.

[0274] If a starch coating as defined above is applied, this is preferably done using a film press before the color layer is applied using a blade coater.

[0275] Starch on the backside is particularly advantageous to prevent the coating color from penetrating into the blade coater.

[0276] It may also be possible to apply the color layer directly with a film press. However, this would be at a disadvantage in terms of smoothness compared to a blade coater. The use of a blade coater provides a material with good basic smoothness, which is important for the dynamic sensitivity of the final product. There is a correlation between final smoothness and dynamic sensitivity.

[0277] It would also be conceivable to apply the color layer in a film press or even in a curtain coater. In that case the advantage of smoothness would be lost, but this could be compensated for by calendering, more particularly when using a film press. However, this is only suitable if no hollow spheres are used, since they would be destroyed by the film press.

[0278] If present, the insulating layer is deposited in a similar manner.

[0279] The siliconized layer, if present, is also deposited in the same manner.

[0280] The same applies to protective layers, if present. If available, the protective layer can alternatively be printed. Protective coatings that can be cured using actinic radiation are particularly suitable in terms of processing and technical properties. The term "actinic radiation" means UV or ionizing radiation, e.g., electron beam.

[0281] The heat sensitive layer is preferably applied by curtain coating as described above.

[0282] If a web-like carrier material, more particularly paper, is coated on one side, the resulting curl should be flattened.

[0283] This is preferably done with the LAS Moisturizer (LAS Liquid Applicator System). For this purpose, a water film is applied to the less coated surface and then allowed to dry. In this way, the so-called flat position is restored. The application of the water film slightly deteriorates the surface.

[0284] A preferred option for protecting surfaces would be a steam humidifier. Steam is sprayed instead of water. The surface is not damaged. This is highly suitable for applications where the highest surface quality must be achieved.

[0285] Another option would be a spray humidifier, where a mist of water is applied.

[0286] All of the above layers can be single or multilayer.

[0287] The present invention further relates to a heat-sensitive recording material obtainable by the above-described method.

[0288] The present invention also relates to the use of the above-mentioned thermosensitive recording materials as sales receipt rolls, as adhesive label rolls, in refrigerated and deep-freeze applications, and as ticket rolls. These may in particular have a functional side and / or a reverse side (colored, pigmented, black / gray), and may be pre-printed. These rolls are preferably available in typical widths and lengths.

[0289] The present invention also provides a method for producing a fibrous material mixture, the method comprising: a web-like support; a color layer on one side of the web-like support; and a heat-sensitive layer on the color layer such that the color layer is at least partially covered by the heat-sensitive layer; 1. A method for bleaching a thermal recording material, more particularly as defined above, in which the thermal layer is configured to become translucent when exposed to localized heat, so that the underlying color layer becomes visible, comprising: - preparing a mixture of a thermal recording material and at least one other type of paper, more particularly at least one type of recycled paper; - The mixture is decolorized in a deinking process to obtain a fibrous mixture The present invention relates to a method comprising the steps of:

[0290] The thermosensitive recording material decolorized by this method preferably comprises or is the above-mentioned thermosensitive recording material, and therefore all definitions and embodiments of the thermosensitive recording material equally apply to the method for decolorizing a thermosensitive recording material according to the present invention.

[0291] The deinking process is preferably characterized by the following features:

[0292] After removing foreign material such as staples, the paper is preferably mechanically shredded or defibered and mixed with water.

[0293] The resulting waste paper fibrous mixture can be subjected to so-called flotation, to which chemicals, preferably in some processes, such as: complexing agents, caustic soda, flocculants, surfactants, water glass, and / or hydrogen peroxide Add.

[0294] In flotation, other particles present in the stock suspension, such as color particles or fillers, separated from the fibers after the shredding or defibration step, are adsorbed by collector chemicals into air bubbles during the flotation process and transported by these to the surface of the flotation cell. The result is a soiled foam called flotate, which may contain fibers and fillers in addition to the detached colorant particles. This foam can be skimmed, cleaned, and used as ash in paper production.

[0295] The flotation is preferably further characterized in that the flotate is obtained by compressed air supply and addition of a flocculant.

[0296] A mixture of fibers remains.

[0297] This remaining fibrous material mixture is preferably as free as possible from at least one dye.

[0298] This process can be repeated depending on the desired degree of whiteness of the new paper.

[0299] If the new paper is to be light gray or white, the fibrous material mixture can be further bleached with oxygen or hydrogen peroxide after deinking.

[0300] Also, after 5 to 7 recycling processes, the individual fibers are often too short and brittle to ensure the stability of the recycled paper, so preferably virgin fibers (primary or secondary fibers) can be added to the fibrous material mixture.

[0301] As primary fibrous mixtures, wood pulp such as spruce and pine and short fiber fibrous mixtures such as birch, beech, aspen, oak, eucalyptus, or mixtures thereof can be used.

[0302] In principle, all known secondary fibrous mixtures can be used as secondary fiber mixtures.

[0303] The method according to the invention for decolorizing a thermosensitive recording material is further preferably characterized by the following steps: i) preparing a mixture of a thermal recording material and at least one other type of paper, more particularly at least one type of waste paper, wherein a specific amount of at least one other type of paper, more particularly at least one type of waste paper, is selected; ii) processing a sample of the mixture according to INGEDE Method 11 (version of January 2, 2017); iii) Assessment of Printed Product Recyclability, Deinkability Score: a) Luminous intensity Y up to 35 points, b) Color coefficient a in the CIELAB system * Maximum 20 points, c) Small soiling spots in two different size classes A A50 up to 15 points and A250 up to 10 points; d) Dye removal (ink removal) degree IE up to 10 points, and e) Filtrate darkening ΔY up to 10 points, determining the sum of all points is in the range of 0 to 100, preferably in the range of 51 to 70, particularly preferably in the range of 71 to 100, and / or preferably the individual point values ​​are not negative; iv) decolorizing the mixture by the deinking process described above, provided that a sample of the mixture has reached a predetermined number of points to obtain a fibrous material mixture; or If the sample has not achieved the predetermined number of points, starting again from step i) by adding an additional amount of at least one type of paper.

[0304] Preferably, the sum of all points is in the range of 0-50, more preferably in the range of 51-70, and particularly preferably in the range of 71-100.

[0305] Preferably, the individual point values ​​are non-negative.

[0306] Most particularly preferably, the sum of all points is in the range from 0 to 50, preferably in the range from 51 to 70, particularly preferably in the range from 71 to 100, the individual point values ​​being non-negative.

[0307] The present invention also relates to a fibrous material mixture obtainable by the process described above.

[0308] The present invention further relates to a method for producing recycled paper comprising the steps of: - bleaching the thermosensitive recording material according to the method described above to obtain a fibrous material mixture; - producing recycled paper comprising a fibrous material mixture, preferably with the addition of additional primary fibrous material or secondary or recycled fibrous material, optionally by compressing and dewatering the fibrous material mixture containing the additional primary fibrous material or secondary or recycled fibrous material.

[0309] Therefore, all definitions and embodiments of the thermosensitive recording material and the method for decolorizing the thermosensitive recording material apply equally to the method for producing recycled paper.

[0310] As primary fibrous mixtures, wood pulp such as spruce and pine and short fiber fibrous mixtures such as birch, beech, aspen, oak, eucalyptus, or mixtures thereof can be used.

[0311] In principle, all known secondary fibrous mixtures can be used as secondary fibrous mixtures.

[0312] In principle, all types of waste paper can be used.

[0313] The fibrous mixture stream preferably comprises a fibrous mixture that is FSC and PFSC certified.

[0314] The production of recycled paper, which involves the compression and dewatering of a fibrous material mixture, is basically known to those skilled in the art and is preferably characterized by the following features:

[0315] First, a stream of fibrous material is provided.

[0316] This fibrous material mixture stream is preferably supplied, in this order, to at least one headbox, to at least one wire section for forming a fibrous material mixture web, to at least one press section and to at least one dryer section having a group of dryers.

[0317] The headbox is usually of the nozzle type, by means of which the fibrous mixture stream is applied in a uniform amount and consistency across its width to an endless circulating screen, through which the solids are separated from the water content. During the dewatering process, a uniform fibrous mat is formed on the wire, which is the starting base for the subsequent paper.

[0318] In the press section, the fiber mat produced in the wire section is preferably further dewatered. This is usually done with the aid of a felt. This can be done, for example, between two rollers pressed against each other. The felt used here has the function of transporting the web through the press section without breaking it and absorbing the water squeezed out in the press nip.

[0319] The dryer section usually consists primarily of steam-heated cylinders that contact the paper web to heat it sufficiently to evaporate any water still within the web to the desired final moisture content. These successive drying cylinders are preferably grouped together into so-called dryer groups. Steam can be applied to these dryer groups in different ways to allow control of the drying process.

[0320] The fibrous material web can then be smoothed, if necessary, and then fed onto a reel for easier storage and / or transportation.

[0321] The present invention further relates to recycled paper obtainable according to the above-described method.

[0322] Therefore, the definitions and embodiments of the thermal recording material, the method for decolorizing the thermal recording material and the method for producing recycled paper all apply equally to recycled paper obtainable according to the above-mentioned methods.

[0323] Particularly preferred embodiments of the present invention will now be described in more detail.

[0324] A first particularly preferred embodiment comprises a thermal recording material having a web-like carrier material, a color layer attached thereto and a thermally sensitive layer on the color layer.

[0325] In this first embodiment, the web-like carrier material comprises paper.

[0326] In this first embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0327] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0328] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0329] In this first embodiment, the heat sensitive layer includes the embodiments described above.

[0330] A second particularly preferred embodiment comprises a thermal recording material having a web-like carrier material, an insulating layer attached thereto, a color layer attached to the insulating layer, and a thermal layer on the color layer.

[0331] In this second embodiment, the web-like carrier material comprises paper.

[0332] In this second embodiment, the insulating layer comprises a thermally insulating material, preferably kaolin, particularly preferably calcined kaolin, and mixtures thereof, or hollow sphere pigments, more particularly hollow sphere pigments comprising styrene-acrylate copolymers.

[0333] In this second embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0334] Alternatively, the carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0335] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0336] In this second embodiment, the heat sensitive layer includes the embodiments described above.

[0337] A third particularly preferred embodiment comprises a thermal recording material having a web-like carrier material, a color layer which is also an insulating layer applied thereto, and a thermally sensitive layer on the color layer.

[0338] In this third embodiment, the web-like carrier material comprises paper.

[0339] In this third embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0340] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0341] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0342] In this third embodiment, the color layer, which is also an insulating layer, comprises a heat insulating material, preferably kaolin, particularly preferably calcined kaolin, and mixtures thereof, or hollow sphere pigments, more particularly hollow sphere pigments comprising styrene-acrylate copolymers.

[0343] In this third embodiment, the heat sensitive layer includes the embodiments described above.

[0344] A fourth particularly preferred embodiment comprises a thermal recording material having a web-like carrier material with a starch precoat on both sides, a color layer attached thereto, and a thermally sensitive layer on the color layer.

[0345] In this fourth embodiment, the web-like carrier material comprises paper.

[0346] In this fourth embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0347] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0348] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0349] In this fourth embodiment, the heat sensitive layer includes the embodiments described above.

[0350] A fifth particularly preferred embodiment comprises a thermal recording material having a web-like carrier material, a color layer applied thereto and a thermal layer on the color layer, with a protective layer applied to the thermal layer.

[0351] In this fifth embodiment, the web-like carrier material comprises paper.

[0352] In this fifth embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0353] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0354] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0355] In this fifth embodiment, the heat sensitive layer includes the embodiments described above.

[0356] In this fifth embodiment, the protective layer comprises at least one binder and at least one pigment, particularly preferably an inorganic pigment.

[0357] A particularly preferred sixth embodiment comprises a thermal recording material having a web-like carrier material, an insulating layer attached thereto, a color layer attached to the insulating layer, and a thermosensitive layer attached to the color layer, with a protective layer attached to the thermosensitive layer.

[0358] In this sixth embodiment, the web-like carrier material comprises paper.

[0359] In this sixth embodiment, the insulating layer comprises a thermally insulating material, preferably kaolin, particularly preferably calcined kaolin, and mixtures thereof, or hollow sphere pigments, more particularly hollow sphere pigments comprising styrene-acrylate copolymers.

[0360] In this sixth embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0361] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0362] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0363] In this sixth embodiment, the heat sensitive layer includes the embodiments described above.

[0364] In this sixth embodiment, the protective layer preferably comprises at least one binder and at least one pigment, particularly preferably an inorganic pigment.

[0365] A particularly preferred seventh embodiment comprises a thermosensitive recording material having a web-like carrier material, a color layer which is also an insulating layer applied thereto, and a thermosensitive layer on the color layer, with a protective layer applied on the thermosensitive layer.

[0366] In this seventh embodiment, the web-like carrier material comprises paper.

[0367] In this seventh embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0368] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0369] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0370] In this seventh embodiment, the color layer, which is also an insulating layer, comprises a thermal insulating material, preferably kaolin, particularly preferably calcined kaolin, and mixtures thereof, or hollow sphere pigments, more particularly hollow sphere pigments comprising styrene-acrylate copolymers.

[0371] In this seventh embodiment, the heat sensitive layer includes the embodiments described above.

[0372] In this seventh embodiment, the protective layer preferably comprises at least one binder and at least one pigment, particularly preferably an inorganic pigment.

[0373] An eighth particularly preferred embodiment comprises a thermal recording material having a web-like carrier material with a starch precoat on both sides, a color layer deposited thereon, and a thermal layer on the color layer, with a protective layer deposited on the thermal layer.

[0374] In this eighth embodiment, the web-like carrier material comprises paper.

[0375] In this eighth embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0376] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0377] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0378] In this eighth embodiment, the heat sensitive layer includes the embodiments described above.

[0379] In this eighth embodiment, the protective layer preferably comprises at least one binder and at least one pigment, particularly preferably an inorganic pigment.

[0380] A particularly preferred ninth embodiment comprises a thermal recording material having a web-like carrier material, an adhesive layer on the underside of the web-like carrier material and a color layer attached to the other side, and a thermal layer on the color layer, with a siliconized layer attached to the thermal layer.

[0381] In this ninth embodiment, the adhesive layer comprises an adhesive, preferably a thermosetting adhesive, more particularly a pressure sensitive adhesive.

[0382] In this ninth embodiment, the web-like carrier material comprises paper.

[0383] In this ninth embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0384] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0385] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0386] In this ninth embodiment, the heat sensitive layer includes the embodiments described above.

[0387] In this ninth embodiment, the siliconized layer comprises at least one siloxane, preferably a poly(organo)siloxane.

[0388] A particularly preferred tenth embodiment comprises a thermal recording material having a web-like carrier material, an adhesive layer on the underside of the web-like carrier material and an insulating layer attached to the other side thereof, a color layer attached to the insulating layer, and a thermal layer on the color layer, with a siliconized layer attached to the thermal layer.

[0389] In this tenth embodiment, the adhesive layer comprises an adhesive, preferably a thermosetting adhesive, more particularly a pressure sensitive adhesive.

[0390] In this tenth embodiment, the web-like carrier material comprises paper.

[0391] In this tenth embodiment, the insulating layer comprises a thermally insulating material, preferably kaolin, particularly preferably calcined kaolin, and mixtures thereof, or hollow sphere pigments, in particular hollow sphere pigments comprising styrene-acrylate copolymers.

[0392] In this tenth embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0393] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0394] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0395] In this tenth embodiment, the heat sensitive layer includes the embodiments described above.

[0396] In this tenth embodiment, the siliconized layer comprises at least one siloxane, preferably a poly(organo)siloxane.

[0397] An eleventh particularly preferred embodiment comprises a thermal recording material having a web-like carrier material, an adhesive layer on the underside of the web-like carrier material and a color layer which is also an insulating layer attached to the other side, and a thermal layer on the color layer, with a siliconized layer attached to the thermal layer.

[0398] In this eleventh embodiment, the adhesive layer comprises an adhesive, preferably a thermosetting adhesive, more particularly a pressure sensitive adhesive.

[0399] In this eleventh embodiment, the web-like carrier material comprises paper.

[0400] In embodiments, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0401] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0402] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0403] In this eleventh embodiment, the color layer, which is also an insulating layer, comprises a thermal insulating material, preferably kaolin, particularly preferably calcined kaolin, and mixtures thereof, or hollow sphere pigments, more particularly hollow sphere pigments comprising styrene-acrylate copolymers.

[0404] In this eleventh embodiment, the heat-sensitive layer includes the embodiments described above.

[0405] In this eleventh embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0406] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0407] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0408] In this eleventh embodiment, the siliconized layer comprises at least one siloxane, preferably a poly(organo)siloxane.

[0409] A particularly preferred twelfth embodiment comprises a thermal recording material having a web-like carrier material with a starch precoat on both sides, an adhesive layer on the lower surface of the web-like carrier material and a color layer attached to the other surface, and a thermal layer on the color layer, with a siliconized layer attached to the thermal layer.

[0410] In this twelfth embodiment, the adhesive layer comprises an adhesive, preferably a thermosetting adhesive, more particularly a pressure sensitive adhesive.

[0411] In this twelfth embodiment, the web-like carrier material comprises paper.

[0412] In this twelfth embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0413] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0414] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0415] In this twelfth embodiment, the heat sensitive layer includes the embodiments described above.

[0416] In this twelfth embodiment, the siliconized layer comprises at least one siloxane, preferably a poly(organo)siloxane.

[0417] A particularly preferred thirteenth embodiment comprises a thermal recording material having a web-like carrier material with a starch precoat on both sides, an adhesive layer on the lower side of the web-like carrier material and a color layer attached to the other side, and a thermal layer on the color layer, with a protective layer attached to the thermal layer and a siliconized layer attached thereon.

[0418] In this thirteenth embodiment, the adhesive layer comprises an adhesive, preferably a thermosetting adhesive, more particularly a pressure sensitive adhesive.

[0419] In this thirteenth embodiment, the web-like carrier material comprises paper.

[0420] In this thirteenth embodiment, the color layer comprises direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0421] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0422] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0423] In this thirteenth embodiment, the heat-sensitive layer includes the embodiments described above.

[0424] In this thirteenth embodiment, the protective layer preferably comprises at least one binder and at least one pigment, particularly preferably an inorganic pigment.

[0425] In this thirteenth embodiment, the siliconized layer comprises at least one siloxane, preferably a poly(organo)siloxane.

[0426] A particularly preferred fourteenth embodiment comprises a thermal recording material having a web-like carrier material, a color layer attached thereto and a thermal layer on the color layer, the thermal layer comprising only wax.

[0427] In this fourteenth embodiment, the web-like carrier material comprises paper.

[0428] In this fourteenth embodiment, the embodiment includes a color layer comprising direct dyes, water flexographic dyes, graphite, sulfide dyes, gall inks, inorganic and / or organic pigment colors and / or iron oxide (Fe3O4).

[0429] Alternatively, carbon black may be present in the color layer in an amount of 2 to 24% by weight, preferably 2 to 19% by weight, and particularly preferably 10 to 24% by weight or 10 to 19% by weight, based on the total solids content of the color layer.

[0430] In another embodiment, carbon black is present in the color layer in an amount of less than 2% by weight based on the total heat-sensitive recording material.

[0431] The embodiments described above in preferred embodiments 1 to 13 regarding the heat-sensitive layer more specifically include the following embodiments:

[0432] The heat-sensitive layer contains at least one polymer particle having a glass transition temperature of -55°C to 130°C, preferably 40°C to 80°C.

[0433] The thermosensitive layer comprises at least one polymer particle having a core / shell structure, the polymer particle being selected from the group consisting of (i) polymer particles having an outer polymer shell with a glass transition temperature of 40° to 800°C and (ii) polymer particles having an inner polymer shell with a glass transition temperature of 40° to 130°C and an outer polymer shell with a glass transition temperature of -55° to 50°C, the glass transition temperature of the outer polymer shell being preferably lower than that of the inner polymer shell.

[0434] The heat-sensitive layer comprises at least one polymer particle having a melting temperature below 250°C, preferably between 0°C and 250°C.

[0435] The heat-sensitive layer contains at least one polymer particle having an average particle size in the range of 0.1 to 2.5 μm.

[0436] The following figures show schematically the various layer structures for exemplary thermosensitive recording materials according to the present invention, the compositions of the individual layers being understood as defined above for each layer. [Brief explanation of the drawings]

[0437] [Figure 1] 1 is a diagram of a thermosensitive recording material having a web-like carrier material, a color layer attached thereto, and a thermosensitive layer on the color layer.

[0438] [Figure 2] 1 is a diagram of a thermosensitive recording material having a web-like carrier material, an insulating layer attached thereto, a color layer attached to the insulating layer, and a thermosensitive layer on the color layer.

[0439] [Figure 3] 1 is a diagram of a thermosensitive recording material having a web-like carrier material, a color layer which is also an insulating layer applied thereto, and a thermosensitive layer on the color layer.

[0440] [Figure 4] 1 is a diagram of a thermosensitive recording material having a web-like carrier material with a starch precoat on both sides, a color layer attached thereto, and a thermosensitive layer on the color layer.

[0441] [Figure 5] 1 is a diagram of a thermosensitive recording material having a web-like carrier material, a color layer attached thereto, and a thermosensitive layer on the color layer, with a protective layer attached to the thermosensitive layer.

[0442] [Figure 6] 1 is a diagram of a thermal recording material having a web-like carrier material, an insulating layer attached thereto, a color layer attached to the insulating layer, and a thermal layer attached to the color layer, with a protective layer attached to the thermal layer.

[0443] [Figure 7] 1 is a diagram of a thermosensitive recording material having a web-like carrier material, a color layer which is also an insulating layer applied thereto, and a thermosensitive layer on the color layer, with a protective layer applied to the thermosensitive layer.

[0444] [Figure 8] 1 is a diagram of a thermal recording material comprising a web-like carrier material having a starch precoat on both sides, a color layer attached thereto, and a thermal layer on the color layer, with a protective layer attached to the thermal layer.

[0445] [Figure 9] FIG. 1 is a diagram of a thermal recording material having a web-like carrier material, an adhesive layer on the underside of the web-like carrier material, and a color layer attached to the other side, and a thermal layer on the color layer, with a siliconized layer attached to the thermal layer.

[0446] [Figure 10] FIG. 1 is a diagram of a thermal recording material having a web-like carrier material, an adhesive layer on the underside of the web-like carrier material and an insulating layer attached to the other side, a color layer attached to the insulating layer, and a thermal layer on the color layer, with a siliconized layer attached to the thermal layer.

[0447] [Figure 11] 1 is a diagram of a thermal recording material having a web-like carrier material, an adhesive layer on the underside of the web-like carrier material, a color layer which is also an insulating layer attached to the other side, and a thermal layer on the color layer, with a siliconized layer attached to the thermal layer.

[0448] [Figure 12] FIG. 1 is a diagram of a thermal recording material having a web-like carrier material with a starch precoat on both sides, an adhesive layer on the lower surface of the web-like carrier material and a color layer attached to the other surface, and a thermal layer on the color layer, with a siliconized layer attached to the thermal layer.

[0449] [Figure 13]1 is a diagram of a thermal recording material having a web-like carrier material with a starch precoat on both sides, an adhesive layer on the underside of the web-like carrier material and a color layer attached to the other side, and a thermal layer on the color layer, with a protective layer attached to the thermal layer and a siliconized layer attached thereon.

[0450] [Figure 14] 1 is a graph of the measurement of the dynamic sensitivity of thermal recording materials whose carrier material has different Bekk smoothness. The dynamic sensitivity (optical density (ODU)) is shown as a function of the current energy E for three recording materials on different base papers: A: no calendering, smoothness 210 Bekk [sec]; B: calendering, line pressure 0.5 bar, smoothness 490 Bekk [sec]; C: calendering, line pressure 2 × 10 bar, smoothness 1276 Bekk [sec]. DETAILED DESCRIPTION OF THE INVENTION

[0451] The present invention will now be described in more detail with reference to some non-limiting examples: [Example]

[0452] The dyes and / or binders or binder concepts described in Tables 13 to 19 (Comparative Examples and Examples E1 to E39) were used to prepare thermosensitive recording materials according to the present invention. These were produced according to Exemplary Embodiment 2, but with variations in the proportions of the individual formulation components, e.g., the proportion of dyes was balanced using the inorganic pigment calcium carbonate.

[0453] For this purpose, the color layer was applied to the paper substrate in a coating machine using a curtain coater. After application, the drying process of each coated paper carrier was carried out in a conventional manner without negatively affecting the properties of the thermosensitive recording material according to the present invention, such as the surface whiteness of the thermosensitive layer or the paper whiteness.

[0454] Next, the thermal recording materials were finally evaluated according to the INGEDE Method 11, and the scores listed in Tables 13 to 19 were determined according to the Assessment of Printed Product Recyclability, Deinkability Score.

[0455] The thermal recording materials were also tested to determine whether they were recyclable and met at least one of the following recyclability criteria: a) In an initial mixture consisting of 100% fine uncoated copy paper printed on both sides with dry toner at a coverage of 5% (CEN_TEST Master, EN 12281) on one side, the addition of 1% thermosensitive recording material only worsens the light reflectance value after flotation by a maximum of 6 points and the filtrate darkening by a maximum of 3 points compared to the initial mixture without flotated thermosensitive recording material; and / or b) In an initial mixture of newspaper / magazine (offset, uncoated) in a 60% / 40% ratio, the addition of 5% thermal recording material only worsens the light reflectance value after flotation by up to 6 points and the filtrate darkening by up to 3 points compared to the initial mixture without flotated thermal recording material.

[0456] The results of the recyclability tests are shown in the columns, ratings, or notes of Tables 13 to 19, respectively.

[0457] The method for decolorizing the thermal recording material to obtain a fibrous material mixture included the following steps: - preparing a mixture of a thermal recording material and at least one other type of paper, more particularly at least one type of recycled paper; - decolorizing the mixture in a deinking process to obtain a fibrous material mixture.

[0458] Thermal recording materials according to the present invention were prepared with the basic compositions described in Tables 1 to 12. Further examples and modifications of these compositions are listed in Tables 13 to 19.

[0459] All examples are based on 41 or 58 g / m2 made from hardwood and softwood pulp. 2 A paper substrate of a specific basis weight is used as the carrier material.

[0460] All quoted basis weights refer to the respective dry layers.

[0461] The dry content (TG) of each coating formulation is adjusted by adding water as follows: insulating layer (30%), color layer (26%), heat sensitive layer (20%) and protective layer (10%).

[0462] The raw materials were used as dispersions or solutions in the following dry content: Ropaque HP-1055 (21%), styrene butadiene latex (48%), dyes, more specifically as listed in Tables 1-4 (generally 45%; in E1 the amount of dye was approximately halved), Ropaque OP-96 (30%), sodium metaborate tetrahydrate (2%), stearamide wax (22%), silicon oxide (28%), zinc stearate (35%), polyvinyl alcohol (high viscosity) (10%), calcined kaolin (45%), precipitated calcium carbonate (58%), ammonium zirconium carbonate (9%), polyvinyl alcohol (low viscosity) (7%), and kaolin (75%).

[0463] The amounts [% by weight] relate to oven-dry conditions (ods). [Example]

[0464] In exemplary embodiment 1, the color layer and the thermosensitive layer are applied successively to the paper substrate in a coater at a speed of 900 m / min by a single curtain coater and / or simultaneously by a double curtain coater, and each application is followed by a drying process of each coated paper substrate in a conventional manner.

[0465] [Table 1]

[0466] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0467] In exemplary embodiment 2, a starch precoat (0.5 g / m 2 ) are applied to the front and back of the paper substrate on a paper machine using a film press at a speed of 800 m / min. The color layer is applied to the starch-coated paper substrate on a coating machine using a blade coater, and the thermosensitive layer is applied using a curtain coater at a speed of 900 m / min. Each application is followed by a drying process of the respective coated paper substrate in the conventional manner.

[0468] [Table 2]

[0469] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0470] In exemplary embodiment 3, a starch precoat (0.5 g / m 2) is applied to the front and back of the paper substrate in a paper machine using a film press at a speed of 800 m / min. A color layer is applied to the starch-coated paper substrate in a coating machine using a blade coater at a speed of 600 m / min. A heat-sensitive layer and a protective layer are subsequently applied to the starch-coated paper substrate with the color layer in a coating machine using a single and / or simultaneously double curtain coater at a speed of 900 m / min. Each application is followed by a drying process of the respective coated paper substrate in the conventional manner.

[0471] [Table 3]

[0472] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0473] In exemplary embodiment 4, the color layer and the thermosensitive layer are applied successively to the paper substrate in a coater at a speed of 900 m / min by a single and / or double curtain coater, each application being followed by a drying process of each coated paper substrate in a conventional manner.

[0474] [Table 4]

[0475] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0476] In exemplary embodiment 5, the color layer and the thermosensitive layer are applied successively to the paper substrate in a coater at a speed of 900 m / min by a single and / or double curtain coater, each application being followed by a drying process of each coated paper substrate in a conventional manner.

[0477] [Table 5]

[0478] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0479] In exemplary embodiment 6, the insulating layer is applied to the paper substrate in a paper machine using a film press at a speed of 800 m / min. The color layer and the thermal layer are subsequently applied to the insulating layer-equipped paper substrate in a coater using a single and / or simultaneous double curtain coater at a speed of 900 m / min. Each application is followed by a drying process of each coated paper substrate in a conventional manner.

[0480] [Table 6]

[0481] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts.

[0482] The use of any mixture of scattering particles / polymer particles (e.g., styrene-acrylate copolymer) and inorganic pigments (e.g., calcined kaolin) in the insulating / color layer has been shown to offer particular advantages in terms of improved barcode readability of the thermal recording material due to the high degree of fixation of the thermal layer on the color layer.

[0483] The mixing ratio of scattering particles / polymer particles and inorganic pigment is preferably in the range of 8:1 to 1:8, particularly preferably in the range of 4:1 to 1:4, based on the amount [wt %] in the oven-dried state (ods).

[0484] The following examples (Examples 7-12) describe these embodiments in more detail without limiting their scope. [Example]

[0485] In exemplary embodiment 7, the color layer and the thermosensitive layer are successively applied to the paper substrate by a single and / or simultaneous double curtain coater at a speed of 900 m / min. After each application, the drying process of each coated paper carrier is carried out in a conventional manner without negatively affecting the properties of the thermosensitive recording material according to the present invention, such as the surface whiteness of the thermosensitive layer or the paper whiteness.

[0486] [Table 7]

[0487] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0488] In exemplary embodiment 8, the color layer and the thermosensitive layer are successively applied to the paper substrate by a single and / or simultaneous double curtain coater at a speed of 900 m / min. After each application, the drying process of each coated paper carrier is carried out in a conventional manner without negatively affecting the properties of the thermosensitive recording material according to the present invention, such as the surface whiteness of the thermosensitive layer or the paper whiteness.

[0489] [Table 8]

[0490] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0491] In exemplary embodiment 9, the color layer and the thermosensitive layer are successively applied to the paper substrate by a single and / or simultaneous double curtain coater at a speed of 900 m / min. After each application, the drying process of each coated paper carrier is carried out in a conventional manner without negatively affecting the properties of the thermosensitive recording material according to the present invention, such as the surface whiteness of the thermosensitive layer or the paper whiteness.

[0492] [Table 9]

[0493] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0494] In exemplary embodiment 10, the color layer and the thermosensitive layer are successively applied to the paper substrate in a coating machine at a speed of 900 m / min by a single and / or double curtain coater, and after each application, the drying process of each coated paper carrier is carried out in the usual manner without negatively affecting the properties of the thermosensitive recording material according to the present invention, such as the surface whiteness of the thermosensitive layer or the paper whiteness.

[0495] [Table 10]

[0496] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0497] In exemplary embodiment 11, the color layer and the thermosensitive layer are successively applied to the paper substrate by a single and / or simultaneous double curtain coater at a speed of 900 m / min. After each application, the drying process of each coated paper carrier is carried out in a conventional manner without negatively affecting the properties of the thermosensitive recording material according to the present invention, such as the surface whiteness of the thermosensitive layer or the paper whiteness.

[0498] [Table 11]

[0499] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts. [Example]

[0500] In Example 12 of the exemplary embodiment, the insulating layer is applied to the paper substrate in a paper machine using a film press at a speed of 800 m / min. The color layer and the thermosensitive layer are subsequently applied to the paper substrate with the insulating layer in a coater using a single and / or double curtain coater at a speed of 900 m / min. After each application, the drying process of each coated paper carrier is carried out in a conventional manner without negatively affecting the properties of the thermosensitive recording material according to the present invention, such as the surface whiteness of the thermosensitive layer or the paper whiteness.

[0501] [Table 12]

[0502] To improve certain coating properties, additional components, more particularly rheological additives such as thickeners and / or surfactants, are added to the individual layers in amounts such that the weight percent of each layer is up to 100 weight percent. Those skilled in the art are familiar with the corresponding amounts.

[0503] [Table 13]

[0504] [Table 14]

[0505] [Table 15]

[0506] [Table 16]

[0507] [Table 17]

[0508] [Table 18]

[0509] [Table 19]

[0510] 7. Testing the recyclability of the thermal recording materials of Examples E1 to E39 Examples E1-E39 each met at least one of the following recyclability criteria: a) In an initial mixture consisting of 100% fine uncoated copy paper printed on both sides with dry toner at a coverage of 5% (CEN_TEST Master, EN 12281) on one side, the addition of 1% thermal recording material only worsens the light reflectance value after flotation by 6 points and the filtrate darkening by 3 points compared to the initial mixture without flotated thermal recording material; and / or b) In an initial wastepaper mixture of newspaper / magazine (offset, uncoated) in a 60% / 40% ratio, the addition of 5% thermal recording material only worsens the light reflectance value after flotation by 6 points and the filtrate darkening by 3 points compared to the initial mixture without flotated thermal recording material.

Claims

1. Web-like carrier material, The color layer on one surface of the web-like carrier material, and A heat-sensitive layer on the color layer such that the color layer is at least partially covered Includes, A thermal recording material comprising a heat-sensitive layer configured to become translucent when exposed to localized heat, thereby making the underlying color layer visible, wherein the color layer contains at least one removable dye, more specifically, at least one dye that can be removed in the waste paper cycle.

2. After reprocessing the thermal recording material according to the INGEDE method 11, the following score is obtained according to the Assessment of Printed Product Recyclability, Deinkability Score: a) Luminous intensity Y: Maximum 35 points, b) Color coefficient a in the CIELAB system ＊ Up to 20 points, c) Dirt spots in two different size classes: A50 up to 15 points and A250 up to 10 points. d) Dye removal (ink removal) degree IE up to 10 points, and e) A maximum of 10 points of filtrate darkening ΔY was achieved. The sum of all points is in the range of 0 to 100, preferably in the range of 51 to 70, more preferably in the range of 71 to 100, and / or preferably the individual point values ​​are not negative. The thermal recording material according to claim 1, characterized in that

3. The thermal recording material according to claim 1 or 2, characterized in that the at least one removable, more specifically removable in a waste paper cycle, dye is selected from the group including bleachable dyes, hydrophobic dyes, hydrophobizable dyes and / or magnetic dyes.

4. The aforementioned at least one removable, more specifically, dye that can be removed in the recycled paper cycle, - Carbon black pigment, more specifically in an amount of up to 24% by weight, preferably up to 19% by weight. - Alternative carbon black pigments, preferably having different particle sizes, morphologies, primary / secondary particle compositions and / or surface chemistry, - Organic dyes, more specifically bleachable organic dyes, - Direct dye, more specifically, Substantive dye, - Reactive dyes, - Disperse dyes, preferably organic and water-insoluble, - Pigments, more specifically disperse dyes, - Iron oxide, more specifically Fe ３ O ４ , - sulfur dyes, - Activated carbon as a dispersion, - Metal complex dyes such as gall ink (iron(III) gallate), - Graphite, - mica, - Carbon black pigments and dark pigments, more specifically iron oxides, more specifically Fe ３ O ４ A combination of dark pigments like this, - Bio-based / food colorings, e.g., sepia black, caramel coloring, or hot water-treated lignin-based, and / or - Printing inks for coloring (offset, (UV) flexographic inks), - and / or mixtures thereof A thermal recording material according to claim 1, characterized in that it is selected from the group including the group.

5. The thermal recording material according to claim 1, characterized in that the color layer includes at least one binder.

6. The thermal recording material according to claim 1, characterized in that the at least one removable, more specifically, removable in the waste paper cycle, dye is crosslinked and / or fixed to the binder.

7. The thermal recording material according to claim 1, characterized in that the thermal layer comprises at least one scattering particle having a glass transition temperature of -55°C to 130°C, a melting temperature of less than 250°C, and / or an average particle size in the range of 0.1 to 2.5 μm, more specifically polymer particles.

8. The thermal recording material according to claim 1, characterized in that the thermal layer comprises at least one thermally sensitive material having a melting temperature in the range of 40 to 200°C and / or a glass transition temperature in the range of 40 to 200°C, preferably a fatty acid and / or a fatty acid amide.

9. The thermal recording material according to claim 1, characterized in that it has a residual moisture content of 2 to 14%, preferably 3 to 8%.

10. The thermal recording material according to claim 1, characterized by having a surface whiteness of 35 to 60%.

11. The thermal recording material according to claim 1, characterized in that each layer attached to the web-like carrier material has a Beck smoothness on its upper surface that is at least the same as or greater than that of the layer below it, and the upper surface is a surface where the web-like carrier material is absent in each case.

12. The thermal recording material according to claim 1, characterized in that an insulating layer exists between the web-like carrier material and the color layer, and the insulating layer preferably has a Beck smoothness greater than 50 seconds, preferably greater than 100 seconds, or the color layer is both a color layer and an insulating layer, and the color layer, which is also an insulating layer, preferably has a Beck smoothness greater than 50 seconds, preferably greater than 100 seconds.

13. It is recyclable, and the following criteria are used to determine recyclability: a) In an initial mixture consisting of 100% fine uncoated copy paper printed with dry toner on both sides with a coverage of 5% on one side (CEN_TEST Master, EN 12281), the addition of 1% thermal recording material worsens the light reflectance value after flotation by up to 6 points and the filtrate darkening by up to 3 points compared to the initial mixture without flotation thermal recording material; And / or b) In an initial recycled paper mixture of newspaper / magazine (offset, uncoated) in a 60% / 40% ratio, the addition of 5% thermal recording material worsens the light reflectance value after flotation by up to 6 points and the filtrate darkening by up to 3 points compared to the initial mixture without flotation thermal recording material. The thermal recording material according to claim 1, characterized by having at least one of the following.

14. A method for decolorizing a thermal recording material, more specifically according to claim 1, to obtain a fibrous material mixture, comprising a thermal recording material, a web-like carrier material, a color layer on one surface of the web-like carrier material, and a thermal layer on the color layer such that the color layer is at least partially covered, wherein the thermal layer becomes translucent when exposed to localized heat, thereby making the underlying color layer visible. - A step of preparing the thermal recording material and a mixture of at least one other type of paper, more specifically, at least one type of recycled paper; - A method comprising the step of decolorizing the mixture in an ink-decolorizing process in order to obtain a fibrous material mixture.

15. i) A step of preparing a mixture of the thermal recording material and at least one other type of paper, more specifically at least one recycled paper type, wherein a certain amount of the at least one other type of paper, more specifically the at least one recycled paper type is selected. ii) A step of processing a sample of the mixture according to the INGEDE method 11, iii) Assessment of Printed Product Recyclability - Deinkability Score: The following score is obtained according to the Assessment of Printed Product Recyclability, Deinkability Score: a) Luminous intensity Y: Maximum 35 points, b) Color coefficient a in the CIELAB system ＊ Up to 20 points, c) Dirt spots in two different size classes: A50 up to 15 points and A250 up to 10 points. d) Dye removal (ink removal) degree IE up to 10 points, and e) A step of determining the filtrate darkening ΔY, up to a maximum of 10 points, The sum of all points is in the range of 0 to 100, preferably in the range of 51 to 70, more preferably in the range of 71 to 100, and / or preferably the individual point values ​​are not negative, step, iv) A step of decolorizing a fibrous material mixture by a de-inking process, provided that the sample of the mixture reaches a predetermined number of points; or If the sample has not reached a predetermined number of points, add an additional amount of at least one type of paper and start again from step i). The method according to claim 14, characterized by including

16. A fibrous material mixture that can be obtained by the method described in claim 14 or 15.

17. A method for producing recycled paper, - A step of decolorizing a thermal recording material according to the method of claim 14 or 15 in order to obtain a fibrous material mixture, - A method comprising the step of producing recycled paper comprising the fibrous material mixture, preferably the fibrous material mixture with additional primary fibrous material or secondary or recycled paper fibrous material added, the step of compressing and dewatering the fibrous material mixture containing the additional primary fibrous material or secondary or recycled paper fibrous material, wherein the fibrous material mixture comprising the step of compressing and dewatering is the fibrous material mixture containing the additional primary fibrous material or secondary or recycled paper fibrous material.

18. Recycled paper that can be obtained by the method of claim 17.

Images