Polymorphic forms of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate

Abstract

The invention relates to a 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β22.2, characterised by an X-ray powder diffractogram having the Bragg angles (2θ / CuKα) 8.4, 11.0, 12.0, 12.7, 14.7, 16.5, 18.2, 19.4, 20.8, 21.1, 22.2, 25.7, 26.6, 26.9, 33.2, or in the polymorphic form α9.2, characterised by an X-ray powder diffractogram having the Bragg angles (2θ / CuKα) 8.3, 9.2, 15.1, 17.6, 20.0, 22.2, 23.1, 23.4.

Description

[0001] POLYMORPHETIC FORMS OF 2'-(3'-PHENYLUREIDO)PHENYL 3-(3-PHENYLUREIDO)BENZOL SULFONATE TECHNICAL FIELD The present invention relates, according to a first aspect, to 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2 , characterized by an X-ray powder diffractogram with the Bragg angles (2θ / CuKα) 8.4, 11.0, 12.0, 12.7, 14.7, 16.5, 18.2, 19.4, 20.8, 21.1, 22.2, 25.7, 26.6, 26.9, 33.2 or in the polymorphic form ^ 9,2characterized by an X-ray powder diffractogram with Bragg angles (2θ / CuKα) 8.3, 9.2, 15.1, 17.6, 20.0, 22.2, 23.1, 23.4. For the graphical representation of the respective X-ray powder diffractograms, reference is made to the attached Figures 1 and 2. According to a second aspect, the present invention relates to a process for the preparation of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β22.2, wherein phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^ 9,2 or non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is heated in an organic solvent. According to a third aspect, the present invention relates to 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2, obtainable according to the process according to the second aspect. According to a fourth aspect, the present invention relates to a process for the preparation of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^9,2, characterized in that non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is recrystallized from ethyl acetate or that phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^ 9,2 is recrystallized from acetonitrile. According to a fifth aspect, the present invention relates to 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^ 9,2, obtainable according to the method according to the fourth aspect. According to a sixth aspect, the present invention relates to a heat-sensitive recording material comprising a support substrate and a heat-sensitive color-forming layer containing at least one color former and at least one non-phenolic color developer, wherein the at least one non-phenolic color developer is 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2 and / or in the polymorphic form ^ 9,2according to the first, third, or fifth aspect. According to a seventh aspect, the present invention relates to a method for producing a heat-sensitive recording material according to the sixth aspect, wherein an aqueous coating suspension containing the starting materials of the heat-sensitive color-forming layer is applied to a carrier substrate and dried, wherein the aqueous coating suspension preferably has a solids content of 20 wt.% to 75 wt.%, more preferably of 30 wt.% to 50 wt.%, and is applied and dried using the curtain coating method, more preferably at an operating speed of the coating machine of at least 400 m / min. According to an eighth aspect, the present invention relates to a heat-sensitive recording material obtainable according to the method of the sixth aspect.According to a ninth aspect, the present invention relates to the use of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β22,2 and / or in the polymorphic form ^9,2 according to the first, third or fifth aspect as a non-phenolic color developer, in particular in a heat-sensitive recording material, wherein the heat-sensitive recording material comprises a support substrate and a heat-sensitive color-forming layer containing at least one color former and the at least one non-phenolic color developer. TECHNICAL BACKGROUND Heat-sensitive recording materials for thermal direct printing applications, which have a heat-sensitive color-forming layer applied to a support substrate, also referred to as a thermo-reaction layer, have been known for a long time.In the heat-sensitive color-forming layer, a color former and a color developer are usually present, which react with each other under the influence of heat and thus lead to color development. German patent application DE 102020112411 describes a heat-sensitive recording material comprising a support substrate and a heat-sensitive color-forming layer containing at least one color former and at least one non-phenolic color developer, as well as the use of the non-phenolic color developer contained in the heat-sensitive recording material, wherein one of the disclosed color developers is 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, as shown by the following formula (1): Although the compound described in publication DE 102020112411 according to formula (1) has usable properties with regard to its use as a color developer in heat-sensitive recording materials, it is necessary to investigate and eliminate occasional fluctuations in some application-related properties of the heat-sensitive recording materials produced with the compound according to formula (1), which are generally related to changes in the purification conditions during synthesis or in the course of synthesis optimization of the compound according to formula (1) and cannot be explained by fluctuating purity levels of the compound according to formula (1).This is particularly important in light of the use of the compound according to formula (1) as a color developer for the large-scale production of heat-sensitive recording materials, since the adherence to specifications of the raw materials used is an essential requirement that must be ensured by the manufacturing process of the color developer. The heat-sensitive recording materials produced according to German patent DE 102020112411 are characterized by a balance of important application-related properties. Nevertheless, it is desirable to improve individual properties without adversely affecting others.The compound according to formula (1) has, thanks to its diverse functional groups, numerous intra- and intermolecular bonding possibilities in the crystal, which can lead to the occurrence of diverse crystal structures, known as polymorphic modifications, in these crystalline compounds. An important aspect in the characterization of such substances by their physicochemical properties concerns the knowledge of the possible crystal structures. This essentially involves the identification of polymorphic modifications and knowledge of their identity. Polymorphic forms of common non-phenolic color developers and their use in heat-sensitive recording materials are known. Publication WO 03 / 101943 A1 discloses three polymorphic forms of the non-phenolic color developer Pergafast. ^201 (BASF), whose production, conversion and use in heat-sensitive recording materials. Publication EP 3263553 A1 discloses a new polymorphic form of the color developer N-(2-(3-phenylureido)phenyl)benzenesulfonamide and its use in heat-sensitive recording materials. Publication JP 3 991 857 B discloses polymorphic forms of n-butyl 4-(3-(p-toluenesulfonyl)ureido)benzoate and their advantageous use as a color developer in heat-sensitive recording materials. Publication EP 4037909 B1 discloses polymorphic forms of N-(4-((4-(3-phenylureido)phenyl)sulfonyl)phenyl)benzenesulfonamide, their production, conversion and use in heat-sensitive recording materials.DESCRIPTION OF THE INVENTION Objective One object of the present invention is to provide new phase-pure polymorphic forms of the color developer 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, as well as methods for producing phase-pure forms of the color developer 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate. A further object of the present invention is to identify and utilize optimization potential for the application-related properties of heat-sensitive recording materials obtained with different polymorphic forms compared to the prior art.A further object of the present invention is to provide crystalline forms of the color developer 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate and heat-sensitive recording materials containing these crystalline forms, which exhibit a significantly lower static sensitivity, characterized by a higher starting temperature of the color-forming reaction, compared to the corresponding heat-sensitive recording materials of the prior art, without showing other application-related disadvantages, in particular without loss of dynamic sensitivity, which is characterized by the dynamic response sensitivity in the printing process. Within the scope of the present invention, it has been possible to obtain the polymorphic form of the color developer 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate described in German patent DE 10 2020 112 411 according to formula (1) shown above. Formβ. 22.2, characterized by an X-ray powder diffractogram with the Bragg angles (2θ / CuKα): 8.4, 11.0, 12.0, 12.7, 14.7, 16.5, 18.2, 19.4, 20.8, 21.1, 22.2, 25.7, 26.6, 26.9, 33.2 and the polymorphic form ^9.2, characterized by an X-ray powder diffractogram with the Bragg angles (2θ / CuKα): 8.3, 9.2, 15.1, 17.6, 20.0, 22.2, 23.1, 23.4. For the graphical representation of the respective X-ray powder diffractograms, please refer to the attached Figures 1 and 2. The aforementioned problems are solved according to the first aspect by 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2 , characterized by an X-ray powder diffractogram with Bragg angles (2θ / CuKα) 8.4, 11.0, 12.0, 12.7, 14.7, 16.5, 18.2, 19.4, 20.8, 21.1, 22.2, 25.7, 26.6, 26.9, 33.2 or in the polymorphic form ^ 9,2characterized by an X-ray powder diffractogram with Bragg angles (2θ / CuKα) 8.3, 9.2, 15.1, 17.6, 20.0, 22.2, 23.1, 23.4. Here, the superscript 22.2 characterizes the polymorphic form β 22,2 The strongest signal, also called the main peak, of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the X-ray powder diffractogram has a Bragg angle (2θ / CuKα) of 22.2. Here, the superscript 9.2 characterizes the polymorphic form ^ 9,2The strongest signal, also called the main peak, of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the X-ray powder diffractogram with a Bragg angle (2θ / CuKα) of 9.2. In particular, the respective X-ray powder diffractograms of the polymorphic form β22.2 and the polymorphic form ^9.2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylu-reido)benzenesulfonate were obtained by an X-ray diffractometer called "D2 Phaser", provided by the Bruker company. In particular, in the respective X-ray powder diffractogram of the polymorphic form β22,2 and the polymorphic form ^9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylu-reido)benzenesulfonate, only signals with Bragg angles (2θ / CuKα) are considered, whose respective relative intensity (IPeak) to the intensity of the strongest signal (IHauptpeak), also referred to as the main peak, is determined according to the following formula. Peak / I Hauptpeakgreater than or equal to 10%. In particular, the measurement inaccuracy of the Bragg angles in the respective X-ray powder diffractogram of the polymorphic form β22.2 and the polymorphic form^ is greater than or equal to 10%. 9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, each 0.1. According to an advantageous embodiment, the polymorphic form β22,2 exhibits characteristic absorption bands according to Fourier transform infrared spectroscopy at both wavenumbers 1154 cm⁻¹, 1165 cm⁻¹, 1190 cm⁻¹, 1231 cm⁻¹, 1298 cm⁻¹, 1310 cm⁻¹, 1364 cm⁻¹, 1449 cm⁻¹, 1495 cm⁻¹, 1550 cm⁻¹, 1595 cm⁻¹, 1634 cm⁻¹, 3291 cm⁻¹, and exhibits the polymorphic form ^ 9,2Characteristic absorption bands were determined by Fourier transform infrared spectroscopy at wavenumbers 1103 cm⁻¹, 1158 cm⁻¹, 1193 cm⁻¹, 1237 cm⁻¹, 1314 cm⁻¹, 1364 cm⁻¹, 1421 cm⁻¹, 1441 cm⁻¹, 1499 cm⁻¹, 1544 cm⁻¹, 1599 cm⁻¹, 1682 cm⁻¹, 1711 cm⁻¹, and 3392 cm⁻¹. In particular, the respective Fourier transform infrared spectra of the polymorphic form β22,2 and the polymorphic form ^9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate were determined using an IR spectroscope called "Bruker Tensor27" with an ATR unit (ATR = attenuated total reflection), provided by the company Bruker, were obtained. In particular, the respective Fourier transform infrared spectrum of the polymorphic form β22,2 and the polymorphic form ^9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate was obtained using a KBr pellet, taking into account the ATR unit.In particular, the polymorphic form β22,2 exhibits characteristic absorption bands according to Fourier transform infrared spectroscopy with high intensity at the wavenumbers 1190 cm-1, 1231 cm-1, 1364 cm-1, 1449 cm-1, 1550 cm-1, 1595 cm-1, 1634 cm. -1 In particular, the polymorphic form β22,2 exhibits characteristic absorption bands according to Fourier transform infrared spectroscopy with a mean intensity at the wavenumbers 1154 cm⁻¹, 1165 cm⁻¹, 1298 cm⁻¹, 1310 cm⁻¹, 1495 cm⁻¹, 3291 cm⁻¹. In particular, the polymorphic form ^ 9,2 characteristic absorption bands according to Fourier-transform infrared spectroscopy with high intensity at the wavenumbers 1314 cm⁻¹, 1441 cm⁻¹, 1544 cm⁻¹, 1599 cm⁻¹, 1682 cm⁻¹. In particular, the polymorphic form ^ 9,2characteristic absorption bands according to Fourier transform infrared spectroscopy with a mean intensity at the wavenumbers 1103 cm⁻¹, 1158 cm⁻¹, 1193 cm⁻¹, 1237 cm⁻¹, 1364 cm⁻¹, 1421 cm⁻¹, 1499 cm⁻¹, 1711 cm⁻¹, 3392 cm⁻¹. According to one embodiment, the polymorphic form β22,2 has a melting range of 214°C to 217°C and the polymorphic form ^ 9,2 a melting range of 190°C to 192°C. In particular, the respective melting range of the polymorphic form β22,2 and the polymorphic form ^ was determined. 9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate using a heat flow calorimeter designated "DSC 200 F3 Maia®" provided by Netzsch Gerätebau GmbH. In particular, the respective melting range of the polymorphic form β22,2 and the polymorphic form ^ was determined. 9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate by introducing the respective polymorphic form β 22,2, or the respective polymorphic form ^ 9,2of 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in an aluminium crucible with a cold-welded, closed lid within a heat flow calorimeter, by heating the crucible, in particular with a heating rate of 10K / min and / or especially at a temperature of 25°C to 200°C and especially under a nitrogen atmosphere, and by visual and / or automatic evaluation of the phase transition. The polymorphic forms β22,2 and ^9,2 of 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, characterized by X-ray powder diffractometry and especially also by Fourier transform infrared spectroscopy and / or melting range determination, are suitable as an excellent non-phenolic color developer in a heat-sensitive recording material, as described in detail below.Production process of the polymorphic forms of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate. According to a second aspect, the present invention relates to a process for the production of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β22,2, wherein phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^. 9,2 or non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is heated in an organic solvent. In particular, the phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^ 9,2 or the non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is heated in the organic solvent for a period of 1 hour to 20 hours, and / or the phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is obtained in the polymorphic form ^ 9,2or the non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is heated from a temperature of approximately 0°C to the boiling point of the respective organic solvent. The aforementioned problems are solved according to the third aspect by 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2 , obtainable according to the process according to the second aspect. The aforementioned problems are solved according to the fourth aspect by a process for the preparation of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^9,2, wherein non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is recrystallized from ethyl acetate or wherein phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^ 22,2is recrystallized from acetonitrile. The aforementioned problems are solved according to the fifth aspect by 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^ 9,2, obtainable according to the process according to the fourth aspect. Preferably, the organic solvent comprises aromatic hydrocarbons, more preferably chlorinated aromatic hydrocarbons, aliphatic or alicyclic hydrocarbons, chlorinated hydrocarbons, dialkylacylamides, aliphatic esters, aliphatic ketones, alicyclic ketones, aliphatic ethers, cyclic ethers, aliphatic alcohols, alicyclic alcohols, alkylnitriles, or mixtures thereof. Most preferably, the organic solvent comprises toluene, cyclohexane, chloroform, dichloromethane, carbon tetrachloride, chlorobenzene, dimethylformamide, dimethylacetamide, ethyl acetate, acetone, butanone, cyclohexane, diethyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, nitromethane, methanol, ethanol, isopropanol, acetonitrile, and mixtures thereof.The embodiments mentioned for the first aspect are also embodiments for the items according to the second, third, fourth, and fifth aspects, and vice versa. Heat-sensitive recording material. The aforementioned problems are solved according to the sixth aspect by a heat-sensitive recording material comprising a support substrate and a heat-sensitive color-forming layer containing at least one color former and at least one non-phenolic color developer, wherein the at least one non-phenolic color developer is 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β. 22,2and / or in the polymorphic form^9,2 according to one of the claims according to the first, third, or fifth aspect. According to one embodiment, the color developer is present in an amount of 3 wt.% to 35 wt.%, preferably in an amount of 2 wt.% to 25 wt.% based on the total solids content of the heat-sensitive color-forming layer. According to one embodiment, the at least one color former is a triphenylmethane-type, fluorane-type, azaphthalide-type, and / or fluorene-type dye. Preferably, the at least one color former is a fluorane-type dye. A fluorane-type dye, thanks to its availability and balanced application-related properties, enables the provision of a recording material with an attractive price-performance ratio.Particularly preferred fluoran-type dyes are: 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-4-toludinamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-Diethylamino-6-methyl-7-(2,4-dimethylanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-(Cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, 3-Diethylamino-7-(3-trifluoromethylanilino)fluoran, 3-Nn-Dibutylamino-6-methyl-7-anilinofluoran, 3-Diethylamino-6-methyl-7-(3-methylanilino)fluoran, 3-Nn-Dibutylamino-7-(2-chloroanilino)fluorane, 3-(N-Ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-(N-Methyl-N-propylamino)-6-methyl-7-anilinofluorane, 3-(N-Ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluorane, 3-(N-Ethyl-N-isobutylamino)-6-methyl-7-anilinofluorane and / or 3-Dipentylamino-6-methyl-7-anilinofluorane. According to one embodiment, the colorant is present in an amount of 5% to 30% by weight, preferably in an amount of 8% to 20% by weight.-% based on the total solids content of the heat-sensitive color-forming layer. According to one embodiment, in addition to the non-phenolic color developer, at least one color developer of the general formula Ar is present. 1 -NH-CO-NH-C6H4-SO2-O-C6H4- NH-CO-NH-Ar 2 before, whereby Ar 1 and Ar 2 an unsubstituted or substituted phenyl residue. Preferably Ar 1 an unsubstituted phenyl residue. Ar is preferred. 2 an unsubstituted phenyl residue. According to one embodiment, Ar 1 and Ar 2 each independently with at least one C1-C5 alkyl, one alkenyl, one alkynyl, one benzyl, one formyl, one CN, one halogen, one NO2 _, an RO-, an R-CO-, an RO2C-, an R-OCO-, an R-SO2O-, an RO-SO2-, an R-SO2-NH-, an R-NH-SO2-, an R-NH-CO- or an R-CO-NH group, where R is a C1-C5 alkyl, an alkenyl, an alkynyl, a phenyl, a tolyl or a benzyl group, substituted. Ar is preferred. 1 with at least one C1-C5 alkyl group, more preferably with at least one C1-C5 alkyl group, even more preferably with at least one methyl group or butyl group, and most preferably with at least one methyl group, one halogen group, more preferably with at least one chloride group, one RO group, more preferably with one CH3O group, one R-CO group, more preferably with one CH3-CO group or one NO2 group, wherein R is a C1-C5 alkyl group. Ar is preferred. 1 simply substituted. Ar is preferred. 2with at least one C1-C5 alkyl group, more preferably with at least one C1-C5 alkyl group, even more preferably with at least one methyl group or butyl group, and most preferably with at least one methyl group, one halogen group, more preferably with at least one chloride group, one RO group, more preferably with one CH3O group, one R-CO group, more preferably with one CH3-CO group or one NO2 group, wherein R is a C1-C5 alkyl group. Ar is preferred. 2 simply substituted. Ar is most preferred. 1 and Ar 2an unsubstituted phenyl residue. The Ar1-NH-CO-NH group and the Ar2-NH-CO-NH group are preferably arranged in the 2' or 3' position, in the 2' or 4' position, in the 3' or 2' position, in the 3' or 3' position, in the 3' or 4' position, in the 4' or 2' position, in the 4' or 3' position, or in the 4' or 4' position relative to the –C6H4-SO2-O-C6H4 group. The arrangement in the 3' or 2' position or the 4' or 3' position of the Ar1-NH-CO-NH group and the Ar2-NH-CO-NH group relative to the –C6H4-SO2-O-C6H4 group is particularly preferred, since such compounds are relatively easy to prepare and exhibit good properties. According to one embodiment, the heat-sensitive color-forming layer containing at least one (bis)phenolic color developer, such as bisphenol A, bisphenol S, and / or 4-hydroxy-4'-isopropoxydiphenylsulfone, and / or at least one non-phenolic color developer, such as N-((4-methylphenyl)sulfonyl)-N'-(3-((4-methylphenyl)sulfonyloxy)phenyl)urea, N-(2-(3-phenylureido)phenyl)benzenesulfonamide, N1,N3-bis(3-methylphenyl)-5-[(3-methylphenyl)sulfamoyl]benzene-1,3-di-carboxamide, N,N'-bis-{3-[(4-methylphenyl)sulfonyloxy]phenyl}urea, , N-[3-((4-methylphenyl)sulfonyloxy)phenyl]-N'-phenylurea. This achieves the technical advantage that specific application-related properties of the heat-sensitive recording material can be controlled by using different color developers. According to one embodiment, the heat-sensitive color-forming layer comprises at least one sensitizing agent. This achieves the technical advantage that a sensitizing agent, which can also be described as a thermal solvent or melting aid, improves the thermal pressure sensitivity of the heat-sensitive recording material. According to one embodiment, the at least one sensitizing agent comprises at least one crystalline substance with a melting point between 90°C and approximately 150°C.which is designed to dissolve the color-forming components, comprising at least one color former and at least one color developer, in the molten state without disturbing the formation of the color complex, and thus to enable the color-forming reaction. Preferably, the at least one sensitizing agent is selected from the group comprising a fatty acid amide, more preferably stearamide, behenamide or palmitamide, an ethylenebis fatty acid amide, more preferably N,N'-ethylenebisstearic acid amide or N,N'-ethylenebisoleic acid amide, a fatty acid alkanolamide, more preferably N-(hydroxymethyl)stearamide, N-hydroxymethylpalmitamide or hydroxyethylstearamide, a wax, more preferably polyethylene wax or montan wax, a carboxylic acid ester, more preferably dimethyl terephthalate, dibenzyl terephthalate, benzyl 4-benzyloxybenzene, di-(4-methylbenzyl)oxalate, di-(4-chlorobenzyl)oxalate or di-(4-benzyl)oxalate, ketones, more preferably 4-acetylbiphenyl, an aromatic ether,Further preferably 1,2-diphenoxyethane, 1,2-di-(3-methylphenoxy)ethane, 2-benzyloxynaphthalene, 1,2-bis-(phenoxymethyl)benzene or 1,4-diethoxynaphthalene, an aromatic sulfone, further preferably diphenylsulfone, and / or an aromatic sulfonamide, further preferably 4-toluenesulfonamide, benzenesulfonanilide or N-benzyl-4-toluenesulfonamide or aromatic hydrocarbons, further preferably 4-benzylbiphenyl. According to one embodiment, the heat-sensitive color-forming layer comprises at least one stabilizer. This achieves the technical advantage that the at least one stabilizer serves as an anti-aging agent for the heat-sensitive color-forming layer. Preferably, the at least one stabilizer comprises at least one sterically hindered phenol, particularly preferably 1,1,3-Tris-(2-methyl-4-hydroxy-5-cyclohexyl-phenyl)-butane, 1,1,3-Tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)-butane, and / or 1,1-Bis-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane. Preferably, the at least one stabilizer comprises at least one urea-urethane compound, more preferably an oligomeric mixture of 4,4'-diaminodiphenylsulfone, 2,4-toluene diisocyanate, phenol (CAS No.: 321860-75), and / or at least one ether derived from 4,4'-dihydroxydiphenylsulfone, more preferably 4-benzyloxy-4'-(2-methylglycidyloxy)-diphenylsulfone (trade name NTZ-95, ^ , Nippon Soda Co. Ltd.), and / or oligomeric ethers, further preferably a polymer or oligomer of 4,4'-dihydroxy-diphenylsulfone (bisphenol S) with 1,1'-oxybis(2-chloroethane) (CAS No.: 191680-83-8, Trade name D90 ^ , Nippon Soda Co. Ltd.). Preferably, the stabilizer comprises at least one 5-(N-3-methylphenylsulfonylamido)-(N',N"-bis-{3-methylphenyl)isophthalic diamide (trade name PF425). ^, Solenis). Preferably, the at least one stabilizer is present in an amount of 0.2 wt.% to 0.5 wt.%, based on the weight of the at least one non-phenolic color developer, 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2 , and / or in the polymorphic form ^ 9,2According to one embodiment, the heat-sensitive color-forming layer comprises at least one binder, wherein the binder is selected from the group consisting of water-soluble starches, starch derivatives, starch-based biolatices of the EcoSphere type, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, gelatin, casein, partially or fully saponified polyvinyl alcohols, chemically modified polyvinyl alcohols, ethylene-vinyl alcohol copolymers, sodium polyacrylates, styrene-maleic anhydride copolymers, ethylene-maleic anhydride copolymers, styrene-butadiene copolymers, acrylamide-(meth)acrylate copolymers, acrylamide-acrylate-methacrylate terpolymers, polyacrylates, poly(meth)acrylic esters, acrylate-butadiene copolymers, polyvinyl acetates, acrylonitrile-butadiene copolymers, and mixtures thereof. According to one embodiment, the at least one binder is present in an amount of 2 wt.% to 40 wt.%, preferably in an amount of 5 wt.% to 20 wt.%.-%, based on the total dry mass of the heat-sensitive layer, is present in the heat-sensitive layer. According to one embodiment, the heat-sensitive color-forming layer comprises at least one lubricant / release agent. This achieves the technical advantage that at least one release agent acts as a lubricant and provides a non-stick effect. Preferably, the at least one lubricant / release agent comprises fatty acid metal salts, more preferably zinc stearate or calcium stearate, behenate salts, synthetic waxes, more preferably in the form of fatty acid amides, even more preferably stearic acid amide or behenic acid amide, fatty acid alkanolamides, preferably stearic acid methylolamide, paraffin waxes of different melting points, ester waxes of different molecular weights, ethylene waxes, propylene waxes of different hardnesses and / or natural waxes, more preferably carnauba wax or montan wax.According to one embodiment, the heat-sensitive color-forming layer comprises at least one pigment. This achieves the technical advantage that the at least one pigment can fix the chemical melt generated in the thermal printing process on the respective pigment surface, and that the surface whiteness and opacity of the heat-sensitive color-forming layer and its printability with conventional printing inks can be controlled by means of the at least one pigment. In addition, pigments have an "extender function," for example, for the relatively expensive color-forming functional chemicals.Preferably, the at least one pigment comprises at least one inorganic pigment, which may be of synthetic or natural origin, and more preferably clays, precipitated or natural calcium carbonates, aluminum oxides, aluminum hydroxides, silicas, precipitated and pyrogenic silicas, and even more preferably Aerodisp^-types, diatomaceous earths, magnesium carbonates, and / or talc. Preferably, the at least one pigment comprises at least one organic pigment, and more preferably, hollow pigments with a styrene / acrylate copolymer wall and / or urea / formaldehyde condensation polymers. The at least one inorganic pigment and / or the at least one organic pigment may be used alone or in any mixtures. According to one embodiment, the heat-sensitive color-forming layer comprises at least one optical brightener.This achieves the technical advantage that the at least one optical brightener enables control of the surface whiteness of the heat-sensitive recording material. Preferably, the optical brightener comprises at least one stilbene, in particular triazinyl derivatives of 4,4'-diamino-2,2'-stilbenesulfonic acid (flavonic acid), which is marketed under the brand name Blankophor, for example, Blankophor TB 4000 liq. series. According to one embodiment, the heat-sensitive color-forming layer comprises at least one rheology aid, preferably at least one thickener and / or at least one surfactant. This achieves the technical advantage that certain coating properties can be improved by the at least one rheology aid. According to one embodiment, the support substrate comprises paper, synthetic paper, or a plastic film.According to one embodiment, the heat-sensitive recording material comprises at least one intermediate layer arranged between the support substrate and the heat-sensitive color-forming layer. This achieves the technical advantage that the intermediate layer improves the surface smoothness of the support substrate for the heat-sensitive color-forming layer and provides a thermal barrier between the support substrate and the heat-sensitive color-forming layer. In particular, the at least one intermediate layer comprises organic hollow-sphere pigments and / or calcined kaolin. The organic hollow-sphere pigments and / or the calcined kaolin are preferably present in the insulating layer in an amount of 20% to 80% by weight, and particularly preferably in an amount of 40% to 60% by weight, based on the total dry mass of the insulating layer.The at least one intermediate layer comprises, in particular, at least one of the following binders: polyvinyl alcohols, styrene-butadiene copolymers, acrylate-butadiene copolymers, polyacrylates, polyvinyl acetates, acrylonitrile-butadiene copolymers, and mixtures thereof. According to one embodiment, the heat-sensitive color-forming layer of the heat-sensitive recording material has a basis weight of 1 g / m². 2 up to 10 g / m² 2 on, preferably from 3 g / m² 2 up to 6 g / m² 2According to a preferred embodiment, the heat-sensitive color-forming layer comprises a fluorane-type dye as the color former and a sensitizing agent selected from the group consisting of fatty acid amides, aromatic sulfones, benzyl oxalates, and / or aromatic ethers, wherein the non-phenolic color developer is more preferably present in a solids content of 1.5 wt.% to 4 wt.% based on the total weight of the color former. According to one embodiment, the heat-sensitive recording material comprises at least one protective layer arranged outside the heat-sensitive color-forming layer. According to one embodiment, the protective layer comprises at least one pigment, at least one binder, at least one lubricant / release agent, at least one crosslinking agent, and / or at least one rheology aid. In another embodiment, the protective layer contains no pigment(s).The protective layer is further preferably characterized in that it comprises at least one of the following components, selected from a binder, a lubricant / release agent, in particular based on waxes or fats, fatty acids or salts of fatty acids, or silicones, a crosslinking agent, in particular a boron-free crosslinking agent, and / or a rheology aid. According to one embodiment, the heat-sensitive recording material has a release layer, in particular a siliconized release layer, which is arranged on the heat-sensitive recording layer. The siliconized release layer preferably has a Bekk smoothness, measured according to ISO 5267:1995-03, of greater than 400 s, particularly preferably greater than 800 s, and most preferably from 800 to 2000 s.If a protective layer, particularly as defined above, is present on the heat-sensitive layer, the siliconized separating layer is preferably located on this protective layer. In a further preferred embodiment, the heat-sensitive recording material is preferably characterized in that a diffusion layer is formed between the siliconized separating layer and the underlying layer, preferably the heat-sensitive layer. This diffusion layer is preferably formed by the diffuse application of at least a portion of the siliconized separating layer into the upper region of the underlying layer, wherein preferably 5 wt.% to 50 wt.%, more preferably 6 wt.% to 45 wt.%, and particularly 7 wt.% to 40 wt.% of the siliconized separating layer diffuse into the upper region of the underlying layer.Such a diffusion layer is described, for example, in EP 3221153 A1. A siliconized release layer is preferably present when an adhesive layer, as described above, is also present. The presence of a siliconized release layer on the heat-sensitive layer and an adhesive layer on the substrate on the side without the ink layer has the advantage that the heat-sensitive recording material can be used as a linerless heat-sensitive recording material. This has the particular advantage that the heat-sensitive recording material can be wound onto itself without requiring a support ("linerless"), and that after unwinding the self-wound heat-sensitive recording material, it does not exhibit any significant deterioration in its properties.This also has the advantage that manufacturing costs can be further reduced, more linear meters per roll are achievable, no disposal costs are necessary for the liner, and more labels can be transported per specific cargo space volume. If a siliconized release layer is present, it is preferred that the layer directly beneath the siliconized release layer contains at least one platelet-shaped pigment. 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 a spreadable kaolin is especially preferred. Such a product is available, for example, under the trade name Kaolin ASP 109 (BASF, Germany). The use of these platelet-shaped pigments, especially kaolin, has the particular advantage that the heat-sensitive layer or...The layer directly below the siliconized release layer can be siliconized very well. A platelet-shaped pigment is understood to be a pigment in which the diameter-to-thickness ratio is approximately 7 to 40:1, preferably approximately 15 to 30:1. The particle size of the platelet-shaped pigment is preferably adjusted such that at least approximately 70%, preferably at least approximately 85%, of the particles have a particle size of approximately < 2 µm (sedigraph). The pH value of the platelet-shaped pigment in aqueous solution is preferably 6 to 8. The at least one platelet-shaped pigment is present in the heat-sensitive layer or in the layer directly below the siliconized release layer, preferably in an amount of approximately 5 to approximately 60 wt.%, particularly preferably in an amount of approximately 15 to approximately 55 wt.%, based on the total dry mass of the respective layer.If the protective layer is located directly beneath the siliconized release layer, the platelet-shaped pigment is present in the amounts described above for the pigments contained in the protective layer. In a further preferred embodiment, the heat-sensitive recording material is preferably characterized in that the siliconized release layer comprises at least one siloxane, preferably a poly(organo)siloxane, in particular an acrylic poly(organo)siloxane. In a further embodiment, the siliconized release layer comprises a mixture of at least two siloxanes. A mixture of at least two acrylic poly(organo)siloxanes is preferred. Examples of particularly preferred siloxanes are those available under the trade names TEGO® RC902 and TEGO® RC711 (Evonik, Germany).In another embodiment, the heat-sensitive recording material is preferably characterized in that the siliconized separation layer contains at least one polysilicone acrylate, preferably formed by the condensation of at least one silicone acrylate. In a preferred embodiment, the siliconized separation layer is a heat-cured separation layer. This separation layer is formed in the presence of a Pt catalyst. The siliconized separation layer is preferably anhydrous. It is also preferred that the siliconized separation layer does not contain any Pt catalysts. The siliconized separation layer preferably contains an initiator, particularly preferably a photoinitiator. This serves for the radical curing of the silicone. The TEGO® photoinitiator A18 (from Evonik, Germany) is particularly preferred.The siliconized release layer may preferably contain further additives, such as matting agents and / or adhesion promoters. The siliconized release layer preferably has a basis weight of 0.3 to 5.0 g / m². 2 , especially from 1.0 to 3.0 g / m³ 2The siliconized release layer preferably has a thickness of 0.3 to 6.0 µm, in particular 0.5 to 2.0 µm. According to one embodiment, the heat-sensitive recording material comprises at least one back layer, which is arranged on the side of the substrate facing away from the heat-sensitive color-forming layer. In particular, the at least one back layer comprises an adhesive layer, in particular a self-adhesive layer, or a back-coat layer, which consists primarily of polymeric binders and pigments. The back layer designed as an adhesive layer enables effective bonding of the heat-sensitive recording material, while the back-coat layer is used to improve the printability of the back of the heat-sensitive recording material or to minimize the tendency of the heat-sensitive recording material to curl under unfavorable humidity conditions.In particular, the adhesive layer comprises at least one adhesive, preferably a heat-activated adhesive, and more preferably a pressure-sensitive adhesive. If a thickness layer is present, it is located between the substrate and the adhesive layer. The adhesive layer preferably comprises at least one adhesive, preferably a heat-activated adhesive, and in particular a pressure-sensitive adhesive. The adhesive, preferably the heat-activated adhesive, and especially the pressure-sensitive adhesive, is particularly preferably a rubber- and / or acrylate-based adhesive. Preferably, the protective layer exhibits a non-stick effect against the rubber- and / or acrylate-based adhesives. According to one embodiment, the adhesive layer has a basis weight of 1 to 40 g / m². 2 , especially from 12 to 25 g / m² 2, on. In particular, the at least one back side layer comprises at least one magnetic or magnetizable coating. The embodiments mentioned for the first to fifth aspects are also embodiments for the subject matter of the sixth aspect and vice versa. Method for producing a heat-sensitive recording material. The aforementioned problems are solved according to the seventh aspect by a method for producing a heat-sensitive recording material according to the sixth aspect, wherein an aqueous coating suspension containing the starting materials of the heat-sensitive color-forming layer is applied to a carrier substrate and dried. Preferably, the aqueous coating suspension has a solids content of 20 wt.% to 75 wt.%, more preferably of 30 wt.% to 50 wt.%. If the value of the solids content of the aqueous coating suspension is approximately 20 wt.% to 75 wt.%, the process is carried out by means of a method for producing a heat-sensitive recording material according to the sixth aspect, wherein an aqueous coating suspension containing the starting materials of the heat-sensitive color-forming layer is applied to a carrier substrate and dried.If the solids content falls below -%, efficiency deteriorates because a large quantity of water must be removed from the coating quickly through gentle drying, which negatively impacts the coating speed. If the solids content of the aqueous coating suspension exceeds 75 wt.%, this only leads to increased technical effort to ensure the stability of the coating curtain during the coating process. The aqueous coating suspension is preferably applied and dried using a curtain coating process, more preferably at an operating speed of the coating system of at least 400 m / min. In the curtain coating process, also known as the curtain coating process, a free-falling curtain of coating dispersion is formed.The coating dispersion, in the form of a thin film, also known as a curtain, is "poured" onto a substrate by free fall, thus applying the coating dispersion to the substrate. German patent DE 10 196052 T1, for example, discloses the use of the curtain coating process in the production of information recording materials and also heat-sensitive recording materials, wherein multilayer recording layers are realized by applying the curtain, consisting of several coating dispersion films, to substrates, although only a maximum operating speed of 200 m / min is achieved for the coating system. Adjusting the operating speed of the coating system to at least 400 m / min according to the preferred embodiment of the present invention offers both economic and technical advantages.Preferably, the operating speed is at least 750 m / min, particularly preferably at least 1000 m / min, and most preferably at least 1500 m / min. Even at a correspondingly high operating speed of at least 1500 m / min, the resulting heat-sensitive recording material is not impaired in any way, and the operation proceeds optimally even at this high operating speed. This achieves the technical advantage of producing the heat-sensitive recording material in an economically advantageous manner. In an advantageous embodiment, the aqueous coating suspension has a viscosity of 150 mPas to 800 mPas, preferably of 200 mPas to 500 mPas, the viscosity being measured in particular by a Brookfield viscometer at 100 rpm and 20 °C.This achieves the technical advantage that a suitably adjusted viscosity of the aqueous coating suspension enables advantageous application. If the viscosity of the aqueous coating suspension falls below 150 mPas or exceeds 800 mPas, this leads to detrimental runnability of the coating compound on the coating unit. In an advantageous embodiment, the aqueous coating suspension has a surface tension of 25 mN / m to 60 mN / m, preferably 35 mN / m to 50 mN / m, wherein the surface tension was measured in particular according to the static ring method according to Du Noüy in accordance with DIN 53914.In an advantageous embodiment, the aqueous coating suspension for the formation of the heat-sensitive color-forming layer, and in particular also further coating suspensions for the formation of further layers, are applied online or in a separate coating process offline. In an advantageous embodiment, the dried, heat-sensitive color-forming layer is smoothed. Preferably, the Bekk smoothness of the dried, heat-sensitive color-forming layer, measured according to ISO 5627:1995-03, is set to 100 s to 1000 s, more preferably to 250 s to 600 s. Preferably, the surface roughness (PPS), measured according to ISO 8791-4:2008-05, is set to a range of 0.50 µm to 2.50 µm, more preferably to 1.00 µm to 2.00 µm. The aforementioned tasks are solved according to the eighth aspect by a heat-sensitive recording material obtainable according to the procedure according to the seventh aspect.The embodiments mentioned for the first to sixth aspects are also embodiments for the subject matter of the seventh aspect, and vice versa. The embodiments mentioned for the first to seventh aspects are also embodiments for the subject matter of the eighth aspect. Use of the polymorphic form β. 22,2 and / or the polymorphic form ^ 9,2 of 2-(3-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate. The aforementioned problems are solved according to the ninth aspect by the use of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2 and / or in the polymorphic form ^ 9,2According to the first, third, or fifth aspect, as a non-phenolic color developer, particularly in a heat-sensitive recording material, wherein the heat-sensitive recording material comprises a support substrate and a heat-sensitive color-forming layer containing at least one color former and at least one non-phenolic color developer. The embodiments mentioned for the first to eighth aspects are also embodiments for use according to the ninth aspect. FIGURES 1 and 2 Figure 1 shows an X-ray powder diffractogram of the polymorphic form β 22,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, whereas Figure 2 shows an X-ray powder diffractogram of the polymorphic form ^ 9,2of 2'-(3'-Phe-nylureido)phenyl 3-(3-phenylureido)benzenesulfonate. Along the abscissa axis shown in Figures 1 and 2, the Bragg angle (2θ / CuKα) is shown, whereas along the ordinate axis shown in Figures 1 and 2, the intensity of the respective measured signals is shown. From the X-ray powder diffractogram of the polymorphic form β22,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate shown in Figure 1, the corresponding signals at the Bragg angles (2θ / CuKα) of 8.4, 11.0, 12.0, 12.7, 14.7, 16.5, 18.2, 19.4, 20.8, 21.1, 22.2, 25.7, 26.6, 26.9, and 33.2 can be obtained, with the signal at the Bragg angle (2θ / CuKα) of 22.2 having the highest intensity and representing the main peak.From the X-ray powder diffractogram of the polymorphic form ^9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate shown in Figure 2, the corresponding signals at the Bragg angles (2θ / CuKα) of 8.3, 9.2, 15.1, 17.6, 20.0, 22.2, 23.1, 23.4 can be obtained, with the signal at the Bragg angle (2θ / CuKα) of 9.2 having the highest intensity and representing the main peak. EXAMPLE OF PROCESSING Preparation of non-phase-pure 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate The non-phase-pure compound 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate was prepared in three steps A, B and C as follows: According to step A, a solution of 60 mmol 3-nitrobenzenesulfonyl chloride in 15 mL THF is added dropwise at room temperature with stirring to a solution of 60 mmol 2-nitrophenol and 84 mmol triethylamine in 20 mL THF.The reaction solution is stirred for two hours at room temperature and then 65 mL of water are added. The suspension is stirred for three hours at room temperature and then filtered. The residue is washed four times with 10 mL of water. The product obtained according to step A is added to step B without further purification. According to step B, 0.420 mol of SnCl₂ is added to a solution of 0.060 mol of the product from step A in 200 mL of ethyl acetate with stirring. .2H₂O is added portionwise at room temperature. The reaction solution is refluxed. The reaction progress is monitored by thin-layer chromatography using a 1:1 cyclohexane / ethyl acetate mixture as the eluent. After the reaction has stopped for approximately three hours, 200 mL of a 50% aqueous potassium carbonate solution is added, and the mixture is stirred for 30 minutes at room temperature. The phases are separated. The aqueous phase is extracted with 100 mL of ethyl acetate. The combined organic phases are dried over magnesium sulfate. The solvent is removed under vacuum. The product obtained according to step B is used in step C without further purification. According to step C, a solution of 15.2 mmol of phenyl isocyanate in 25 mL of ethyl acetate is added dropwise at room temperature with stirring to a solution of 7.6 mmol of the product from step B in 40 mL of ethyl acetate. The reaction mixture is refluxed.The reaction mixture is refluxed and the reaction progress is monitored by HPLC. After completion of the reaction, the precipitated bis-urea is filtered off, washed 3 times with 10 mL of ethyl acetate, and dried under vacuum to obtain non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate. Preparation of the polymorphic form β22,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate. Option 1: The starting material is the product obtained according to step B in the preparation of non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate. To a mixture of 28.5 mmol of the product according to step B in 62 mL of acetonitrile, 58.5 mmol of phenyl isocyanate is added at room temperature with stirring. The reaction solution is heated under reflux for four hours and the reaction progress is monitored by HPLC. Subsequently, 39.5 mL of acetonitrile is distilled and the mixture is treated with 22.6 mL of acetonitrile.After the reaction is complete, the product is filtered off, washed with cold acetonitrile, and dried under vacuum. The phase-pure polymorphic form β is obtained. 22,2of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, characterized by an X-ray powder diffraction pattern with Bragg angles (2θ / CuKα) 8.4, 11.0, 12.0, 12.7, 14.7, 16.5, 18.2, 19.4, 20.8, 21.1, 22.2, 25.7, 26.6, 26.9, 33.2. Option 2: The starting material can be the non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate prepared according to step C, or the polymorphic form ^9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate described below. 26.8 g of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate obtained according to step C, or 26.8 g of the polymorphic form ^9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate described below, are suspended in 368 mL of ethyl acetate and refluxed for three hours. After cooling, the solvent is removed. The phase-pure polymorphic form β is obtained. 22,2of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, characterized by an X-ray powder diffraction pattern with Bragg angles (2θ / CuKα) 8.4, 11.0, 12.0, 12.7, 14.7, 16.5, 18.2, 19.4, 20.8, 21.1, 22.2, 25.7, 26.6, 26.9, 33.2. Preparation of the polymorphic form of 2'-(3'-phenylureido)phenyl 3-(3-phenylu- Reido)benzenesulfonate Option 1: The starting material is the product obtained according to step C, which yields non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate. The product according to step C is recrystallized from ethyl acetate. The phase-pure polymorphic form ^ is obtained. 9,2 of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, characterized by an X-ray powder diffraction pattern with Bragg angles (2θ / CuKα) 8.3, 9.2, 15.1, 17.6, 20.0, 22.2, 23.1, 23.4. Possibility 2: The previously described polymorphic form ^ is used as the starting material. 22,22'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is used, which was recrystallized from an excess of acetonitrile, for example 66 mL. The phase-pure polymorphic form ^ is obtained. 9,2of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, characterized by an X-ray powder diffraction pattern with Bragg angles (2θ / CuKα) 8.3, 9.2, 15.1, 17.6, 20.0, 22.2, 23.1, 23.4. Preparation of a heat-sensitive recording material. The following dispersions, or starting materials, were provided: Color Former Dispersion A. The aqueous color former dispersion A is prepared by milling 20 parts by weight of 3-Nn-dibutylamine-6-methyl-7-anilinofluorane with 33 parts by weight of a 12% aqueous solution of Ghosenex™ L-3266, which corresponds to a sulfonated polyvinyl alcohol from Nippon Gohsei, in a bead mill. Color Developer Dispersion B. The aqueous color developer dispersion B is prepared by milling 40 parts by weight of the respective color developer 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate, either according to the described polymorphic form ^22,2 or according to the described polymorphic form ^9,2, together with 66 parts by weight ofSensitizing Dispersion C: The aqueous sensitizing dispersion C is prepared by milling 40 parts by weight of the respective sensitizing agent with 33 parts by weight of a 12% aqueous solution of Ghosenex™ L-3266, which is equivalent to a sulfonated polyvinyl alcohol from Nippon Gohsei, in a bead mill. The following sensitizing agents were used: 1,2-Diphenoxyethane (DPE), Stearamide (SA), Diphenylsulfone (DPS), Di-(4-methylbenzyl)oxalate (HS3520), Benzyloxynaphthalene (BON), and / or 1,2-Di(3-methylphenoxy)ethane (EGTE). Lubricant / release agent dispersion D. The lubricant / release agent dispersion D is a 20% zinc stearate dispersion, consisting of 9 parts by weight zinc stearate, 1 part by weight...-Part Ghosenex™ L-3266, which corresponds to a sulfonated polyvinyl alcohol from Nippon Gohsei, and 40 parts by weight water. All dispersions A, B, C, and D produced by milling have a mean particle size D(4,3) of 0.80 to 1.20 μm. The particle size distribution of the dispersions was measured by laser diffraction using a Coulter LS13320 instrument from Beckman Coulter. Pigment P: Pigment P is a 72% spreadable kaolin suspension designated Lustra™ S by BASF. Binder: The binder consists of a 10% aqueous polyvinyl alcohol solution designated Mowiol 28-99 by Kuraray Europe.Heat-Sensitive Coating Suspension The heat-sensitive coating suspension was prepared by mixing and stirring 1 part of the color-forming dispersion A, 1 part of the color-developer dispersion B, 2.5 parts of the sensitizing dispersion C, 1 part of the lubricant / release agent dispersion D, 2.1 parts of the pigment P, and 2.5 parts of the binder solution in the following order of addition: color-developer dispersion B, sensitizing dispersion C, lubricant / release agent dispersion D, pigment P, color-forming dispersion A, and binder solution, whereby the heat-sensitive coating suspension was adjusted with water to a solids content of 25%. Heat-Sensitive Coating Material The substrate used is a paper substrate made from hardwood and softwood pulp with a basis weight of 58 g / m². 2 and 65 g / m² 2A pigmented primer is applied to the first side of the substrate to form an intermediate layer. Specifically, the pigmented primer consists of calcined kaolin and a styrene-butadiene and / or starch-based binder (for example, commercially available styrene-butadiene latex). Alternative pigments, binders, and primers with organic (hollow sphere) pigments, possibly mixed with inorganic pigments, are also possible. The application rate of the pigmented primer is between 2 g / m² and 10 g / m². After the pigmented primer has dried, the intermediate layer is formed.The heat-sensitive coating suspension is applied to the intermediate layer, whereby the application of the aqueous coating suspension to form the heat-sensitive color-forming layer of the heat-sensitive recording material is carried out, particularly on a laboratory scale, by means of a squeegee on the coating side of the carrier substrate pre-coated with the intermediate layer with a basis weight of 65 g / m² and 72 g / m². 2 This process is carried out. After the aqueous application suspension has dried, particularly with a hot air gun (40 cm distance) at a temperature of 90 °C to 110 °C within 1 to 3 minutes, the heat-sensitive, color-forming layer of the heat-sensitive recording material is obtained. The application rate of the heat-sensitive, color-forming layer is between 3.8 g / m². 2 and 4.2 g / m² 2Measurement Methods: Optical Density (o.D.) Measurement: The heat-sensitive recording materials (6 cm wide strips) were thermally printed using a GeBE PrinterLab GPT-10000 test printer from GeBE Elektronik und Feinwerktechnik GmbH, Germany, with a Kyocera printhead of 305 dpi and 1146 ohms at an applied voltage of 24 V. The printhead used a checkerboard pattern with 10 energy levels, a printing speed of approximately 100 mm / s, and a contact pressure of 19 N, where the area of ​​one square of the printed pattern corresponds to 80 x 80 dots. The optical density (o.D.) was measured with an X-Rite SpectroEye densitometer at an energy level of 12.79 mJ / mm². The measurement uncertainty of the o.D. values ​​is estimated at ≤2%. The dispersion of the calculated % values ​​is ≤2% percentage points.Determination of the static starting point: The recording sheet was pressed against five metallic dies heated to different temperatures and thermostatically controlled, with a contact pressure of 4 bar and a contact time of 30 seconds, using the Rycobel GHS-03 device. The optical density of the resulting images was measured with an X-Rite SpectroEye densitometer, where the static starting point is defined as the lowest temperature in °C at which an optical density of 0.2 is achieved. The accuracy of the measurement method is ≤±0.5 °C. Results: The results of the measurements of the aforementioned parameters, optical density (n.d.) and static starting point in °C, for the corresponding heat-sensitive recording materials are presented in Table 1 below for each polymorphic form. 9,2 and β 22,2The sensitization of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate was investigated for various sensitizing agents. These sensitizing agents include 1,2-diphenoxyethane (DPE), stearamide (SA), diphenylsulfone (DPS), di-(4-methylbenzyl)oxalate (HS3520), benzyloxynaphthalene (BON), and / or 1,2-di(3-methylphenoxy)ethane (EGTE). Polymorphic form sensitization oD (12.79) start of color development mJ / mm 2 ) point lers mean (°C) β ^^^^ 1,36 84 ^^^^ EGTE 1,37 84 β ^^^^ 1,36 80 ^^^^ DPE 1 ,37 79 β ^^^^ 1,36 91 ^^^^ SA 1 ,35 90 β ^^^^ 1,33 85 ^^^ BON ^ 1,37 85 β ^^^^ 1,35 85 ^^^^ DPS 1 ,37 85 β ^^^^ 1,40 88 ^^^^ HS 3520 1,34 89 Table 1 As can be seen from Table 1, both the use of the ^ 9,2 -form as well as the use of β 22,2-Form of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate as a color developer to high maximum optical densities of the heat-sensitive recording materials according to the invention, as well as to high temperatures at which a visually noticeable graying of the heat-sensitive recording materials according to the invention occurs (starting point °C). As can be seen from Table 1, the recorded image of the β 22,2The heat-sensitive recording materials obtained with the β22,2-form of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate as a color developer exhibit comparable optical densities at an energization energy of 12.79 mJ / mm² to the corresponding optical densities of the β9,2-form of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate as a color developer. The maximum optical density achieved in the case of HS 3520 as a sensitizer is 1.40 when using the β22,2-form of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate as a color developer. In the case of HS 3520 as a sensitizer, when using the β22,2-form of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate as a color developer, the maximum optical density achieved is 1.40. 9,2 The -form of 2'-(3'-phenylureido)phenyl 3-(3-phenylu-reido)benzenesulfonate as a color developer achieves an optical density of 1.34. In all other cases, the achieved optical densities are almost identical, taking into account the aforementioned measurement inaccuracies.

Claims

Claim E1. 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2 , characterized by an X-ray powder diffractogram with the Bragg angles (2θ / CuKα) 8.4, 11.0, 12.0, 12.7, 14.7, 16.5, 18.2, 19.4, 20.8, 21.1, 22.2, 25.7, 26.6, 26.9, 33.2 or in the polymorphic form ^ 9,2 characterized by an X-ray powder diffractogram with Bragg angles (2θ / CuKα) 8.3, 9.2, 15.1, 17.6, 20.0, 22.2, 23.1, 23.4.

2. 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β22.2 or in the polymorphic form ^9.2 according to claim 1, characterized in that the polymorphic form β 22,2characteristic absorption bands according to Fourier transform infrared spectroscopy at the wavenumbers 1154 cm⁻¹, 1165 cm⁻¹, 1190 cm⁻¹, 1231 cm⁻¹, 1298 cm⁻¹, 1310 cm⁻¹, 1364 cm⁻¹, 1449 cm⁻¹, 1495 cm⁻¹, 1550 cm⁻¹, 1595 cm⁻¹, 1634 cm⁻¹, 3291 cm⁻¹ and exhibits the polymorphic form ^9,2 characteristic absorption bands according to Fourier transform infrared spectroscopy at the wavenumbers 1103 cm⁻¹, 1158 cm⁻¹, 1193 cm⁻¹, 1237 cm⁻¹, 1314 cm⁻¹, 1364 cm⁻¹, 1421 cm⁻¹, 1441 3. 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β22,2 or in the polymorphic form ^9,2 according to claim 1 or 2, characterized in that the polymorphic form β22,2 has a melting range of 214°C to 217°C and the polymorphic form ^ 9,2exhibiting a melting range of 190°C to 192°C.

4. Process for the preparation of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β22,2, characterized in that phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^ 9,2 or non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is heated in an organic solvent.

5. 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2 , obtainable according to the process of claim 4.

6. Process for the preparation of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^9,2, characterized in that non-phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate is recrystallized from ethyl acetate or that phase-pure 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^22,2 is recrystallized from acetonitrile.

7. 2'-(3'-Phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form ^ 9,2 , obtainable according to the method of claim 6.

8. Heat-sensitive recording material comprising a support substrate and a heat-sensitive color-forming layer containing at least one color former and at least one non-phenolic color developer, wherein the at least one non-phenolic color developer is 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β 22,2and / or in the polymorphic form^9,2 according to any one of claims 1 to 3, 5 or 7.

9. Heat-sensitive recording material according to claim 8, wherein the color developer is present in an amount of 3 wt.% to 35 wt.%, preferably in an amount of 2 wt.% to 25 wt.% based on the total solids content of the heat-sensitive color-forming layer.

10. Heat-sensitive recording material according to claim 8 or 9, wherein at least one color-forming agent is a dye of the triphenylmethane type, fluorane type, azaphthalide type and / or fluorene type.

11. Heat-sensitive recording material according to any one of claims 8 to 10, wherein, in addition to the non-phenolic color developer, at least one color developer of the general formula Ar is present. 1 -NH-CO-NH-C6H4-SO2-O-C6H4-NH-CO-NH-Ar 2 is present, whereby Ar 1 and Ar 2 an unsubstituted or substituted phenyl residue.

12. Heat-sensitive recording material according to claim 11, characterized in that Ar 1 and Ar 2 each independently with at least one C1-C5 alkyl, one alkenyl, one alkynyl, one benzyl, one formyl, one CN, one halogen, one NO2 _, is substituted by an RO-, an R-CO-, an RO2C-, an R-OCO-, an R-SO2O-, an RO-SO2-, an R-SO2-NH-, an R-NH-SO2-, an R-NH-CO- or an R-CO-NH group, wherein R is a C1-C5 alkyl, an alkenyl, an alkynyl, a phenyl, a tolyl or a benzyl group.

13. A method for producing a heat-sensitive recording material according to at least one of claims 8 to 12, wherein an aqueous coating suspension containing the starting materials of the heat-sensitive color-forming layer is applied to a carrier substrate and dried, wherein the aqueous coating suspension preferably has a solids content of 20 wt.% to 75 wt.%, further preferably of 30 wt.% to 50 wt.%, and is preferably applied and dried using the curtain coating method, further preferably at an operating speed of the coating system of at least 400 m / min.Heat-sensitive recording material obtainable according to the method of claim 13.

15. Use of 2'-(3'-phenylureido)phenyl 3-(3-phenylureido)benzenesulfonate in the polymorphic form β. 22,2 and / or in the polymorphic form ^ 9,2 according to one of claims 1 to 3, 5 or 7 as a non-phenolic color developer, in particular in a heat-sensitive recording material, wherein the heat-sensitive recording material comprises a support substrate, as well as a heat-sensitive color-forming layer containing at least one color former and at least one non-phenolic color developer.

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