EP4013912A1

EP4013912A1 - Transfer paper for dye sublimation printing processes, and method for producing transfer paper

Info

Publication number: EP4013912A1
Application number: EP20775164.5A
Authority: EP
Inventors: Kari-Pekka INNO; Gerhard Drexler
Original assignee: Mondi AG
Current assignee: Mondi AG
Priority date: 2019-08-16
Filing date: 2020-08-13
Publication date: 2022-06-22
Also published as: AT522767A4; AT522767B1; WO2021030850A1

Abstract

The invention relates to a method for producing transfer paper for dye sublimation printing processes, a transfer paper for dye sublimation printing processes and a method for printing on textiles. The method for producing transfer paper comprises a method step for coating at least one surface of a paper web by applying an aqueous solution of an α-(1,3→glucan) polymer, which α-(1,3→glucan) polymer has a degree of substitution by cationic groups of 0.2-0.8 mol/mol, and a method step for postdrying the coated paper web. The transfer paper has a paper substrate, at least one surface of said paper substrate being provided with a coating which consists at least predominantly of a cationically modified α-(1,3→glucan) polymer having a degree of substitution by cationic groups of 0.2-0.8 mol/mol.

Description

TRANSFER PAPER FOR THERMAL SUBLIMATION PRINTING PROCESSES AND METHODS FOR MANUFACTURING TRANSFER PAPER

The invention relates to a method for producing transfer paper for thermal sublimation printing processes, a transfer paper for thermal sublimation printing processes and a method for printing textiles.

Transfer printing processes are primarily used to apply printed images to objects, which objects cannot be printed, or can only be printed to a very limited extent, or with great effort. In a transfer printing process, a (negative) print image is first printed on a transfer paper, and then transferred to a substrate with heating and, if necessary, pressure. The printing inks used in transfer printing processes include sublimable color components, which can be transferred from the transfer paper onto or into the substrate actually to be printed by the heating and pressure. The transfer paper can in principle be printed on the transfer paper in a contactless manner, for example by means of inkjet printing, or by means of contact printing methods, such as rotary screen printing. Transfer printing is usually used for printing substrates which, for example, have a polyester coating, or textiles suitable for this purpose.

Since in transfer printing, the print image is first printed on a transfer paper and only then transferred to the substrate actually to be printed, the transfer paper has to meet special requirements that cannot be met, or only very poorly, by conventional printing paper intended for printing. In addition to good printability, transfer paper also requires the most complete and qualitatively best possible transfer of the print image to the substrate to be printed. In this case, on the one hand, a high transfer efficiency for the transfer of the printing ink (s) but also a transfer of the printed image applied to the transfer paper that is as true to contrast or as true to the contour as possible is desired. In other words, a transfer paper should be easy to print on the one hand, but on the other hand an applied print image or the sublimation dyes used for this purpose should be released or transferred as completely and true to the image as possible to the substrate to be printed when using heat and pressure. Proposals have already been disclosed in the past which relate in particular to transfer paper with improved transfer efficiency. In US 2005/0186363 A1, for example, a transfer paper with a coating based on carboxymethyl cellulose, polyvinyl alcohol, alginate or gelatin with a certain porosity and kaolin or talc as filler is disclosed. A similar transfer paper is also known from US 2019/0001728 A1, for example. In WO 2018/139925, for example, a transfer paper with a coating based on a cationic polyamine or polyimine is disclosed.

Despite the solutions proposed in the past for designing transfer paper for sublimation transfer printing processes, there is still a need for improvement in terms of transfer efficiency and, above all, the transfer of a printed image from a transfer paper to a substrate to be printed with true-to-contrast or true-to-contour accuracy. Furthermore, the methods known from the prior art for producing the transfer paper are only economically useful to a limited extent, so that the transfer papers produced in this way have correspondingly high costs. In particular, the methods given are only suitable to a limited extent for the production of large quantities of transfer paper.

The object of the present invention was, on the one hand, to provide a method for producing a transfer paper for thermal sublimation printing processes, by means of which transfer paper with good transfer printing properties can be produced in high quality, but nevertheless cost-effectively, in large quantities. Furthermore, the task of the invention was to provide a transfer paper for thermal sublimation printing processes with improved properties, as well as a method for printing textiles using a corresponding transfer paper.

The object of the invention is achieved on the one hand by a method for producing a transfer paper according to the corresponding claims.

The process for the production of transfer paper for dye-sublimation printing processes comprises the process steps a) providing a cellulose or an aqueous cellulose suspension, b) making a suspension of the cellulose in water with a water content of at least 90% by weight, c) optionally adding it from additives, fillers or process chemicals to the aqueous Suspension, d) dewatering the suspension to a water content of 60% by weight to 85% by weight using a wire section, e) drying the dewatered suspension to form a paper web with a water content of 30% by weight to 55% by weight using a press section, f) further drying of the paper web to a water content of 1% by weight to 10% by weight by means of a dryer section, g) coating at least one of the surfaces of the paper web by means of a coating device by applying an aqueous solution of an a- (1.3 g 1 ucan) - Po 1 ymcrs with 90% or more al, 3-glycosidic bonds and a degree of polymerization of 55 to 10,000, which is a- (1, 3 1 ucan) - Po 1 y mcr is cationically modified and one

Has a degree of substitution by cationic groups of 0.2 to 0.8 mol / mol, h) post-drying of the coated paper web by means of a further dryer section or post-dryer section to a water content of 3% by weight to 7% by weight, i) making up the coated and post-dried paper web.

The specified procedural measures or steps enable high-quality transfer paper to be produced in a continuous process in an economically sensible manner and in large quantities. A separate work step for applying a coating, for example by means of doctor blades as indicated in the prior art, can be eliminated here. In particular, the method for producing transfer paper can be provided for thermal sublimation printing processes in which the transfer paper is printed by means of digital inkjet printing.

Because the coating takes place in-line in the process and the backing paper or the paper web with the applied coating is treated together in the process, in particular dried to a desired water content, a composite material with particularly good adhesion properties of the layers can also be achieved which, and are produced with particularly good coating quality. Delamination phenomena or the formation of imperfections in the coating, which in use can, for example, have negative effects on the quality of the print image, can be effectively prevented. As has been found, the specified coating comprising the α- (1,3-glucan) polymer with the specified parameters is particularly advantageous with regard to the requirements placed on a transfer paper. As will be shown in detail below on the basis of exemplary embodiments, a transfer paper produced by means of the specified process measures is characterized by particularly good properties when used in thermal sublimation printing processes. Due to the special coating, the transfer paper has, on the one hand, good printability, i.e. good absorption of the sublimation printing dyes or pigments, but surprisingly, on the other hand, above all good release properties in the course of a thermal sublimation printing process, i.e. when the printing dyes or pigments are transferred to a substrate by sublimation , on. In particular, the coated transfer paper can prevent undesired penetration of the sublimation dyes onto the back of the transfer paper and the associated loss of sublimation dyes for a sublimation printing process, during and after the printing of the transfer paper and also during the transfer printing process. The coating can, for example, consist of more than 90% by weight of the α- (l, 3- ^ glucan) polymer, but can, for example, to a small extent, for example, impurities caused by production or otherwise, as well as additives customary in paper technology Amount included.

As a result of the cationic modification, the a- (1,3-glucan) polymer, which is otherwise insoluble in water, can be dissolved in water. In addition, an improved coating of the paper web can be achieved through the cationic modification of the a- (1.3 g 1 uc a n) - Po 1 y m crs and, above all, good adhesion of the coating to the paper web can be provided. Ultimately, this contributes to particularly good properties of the composite, including good mechanical properties and also high resistance to damage, even during the high load in a dye-sublimation printing process.

Overall, it has been shown that by choosing the a- (1, 3 1 ucan) - Po 1 y mcr for the

Coating as well as an improved transfer paper can be provided through the specific sequence of the process steps. In particular, the targeted influencing of the water content of both the paper substrate or the paper web and the targeted setting of a water content of the coated paper web at the end of the process should be essential. In process step b), a suspension of the pulp in water with a water content of 90% by weight to 99.5% by weight can be produced, which then successively results in a paper web with optimal water content for the coating in process step according to the specified process sequence g) is dried or converted. The coated paper web is then specifically dried to the specified water content of 3% by weight to 7% by weight. In this way, a transfer paper can be produced which is particularly well suited for thermal sublimation printing, as will be explained in more detail below on the basis of exemplary embodiments.

In a further development of the method, it can be provided that in method step g) an aqueous solution of an α- (1,3-glucan) polymer which has been cationically modified with quaternary ammonium groups is used.

A modified a- (1, 3 1 ucan) - Po 1 y mcr has proven to be particularly well suited for the

Production of the coating of the transfer paper has been proven. Furthermore, a transfer paper with such a coating has particularly good properties when used in dye-sublimation printing processes.

In a variant of the method, it can be useful if in method step f) the paper web is dried to a water content of 2.5% by weight to 10% by weight, and in method step g) the aqueous solution of a- (1, 3 g 1 uc an) - Po 1 ym crs is applied to at least one surface of the paper web by means of a size press.

This represents a simple but nevertheless efficient measure for coating at least one of the surfaces of the paper web, with both surfaces of the paper web using a size press with the aqueous solution of the α- (1,3-glucan) polymer in a simple manner can be coated. The coating can be done on a paper web with a high water content.

In this context, it can preferably be provided that the aqueous solution of a- (1.3 g 1 uc an) - Po 1 ym crs is not applied to both surfaces of the paper web, but that in process step g) the aqueous solution of a - (1.3 g 1 ucan) - Po 1 ymers is applied to one surface of the paper web and an aqueous solution containing 5% to 15% by weight of an enzymatically degraded starch is applied to the other surface of the paper web. In this case, the surface of the transfer paper intended for thermal sublimation printing is formed by that surface which is coated with the a- (L 3 g 1 ucan) - Po 1 ymcr. That surface of the transfer paper to which the aqueous solution of the enzymatically degraded starch was applied represents the reverse side of the transfer paper. In other words, the one marked with the a- (L3 1 ucan) - Po 1 y mcr coated surface of the

Transfer paper is printed, and in the course of a thermal sublimation printing process, this surface is also in contact with the substrate to be printed, for example textile. One of the advantages of this procedural measure is that inexpensive production of the transfer paper can be provided without having to accept significant losses when used for dye-sublimation printing processes. Furthermore, a transfer paper produced in this way is distinguished by good durability and good mechanical properties.

In a variant of the method, however, it can also be provided that in method step f) the paper web is dried to a water content of 1.2% by weight to 2.0% by weight, and in method step g) the aqueous solution of the a- (L 3 g 1 uc an) - Po 1 ym crs is applied to at least one surface of the paper web by means of a film press.

In this case, the aqueous solution of the a- (L 3 g 1 uc a n) - Po 1 y m crs is not applied directly to at least one surface of the paper web, but can be applied beforehand in the desired layer thickness to one or two application rollers of the film press. The layer can then be transferred from the applicator roller (s) to the paper web. The application or coating by means of such a film press is particularly suitable for high throughput of the paper web, and is also advantageous with regard to controlling the layer thickness.

Also in the case of using a film press it can preferably be provided that in process step g) the aqueous solution of the a- (L 3 g 1 uc an) -Poly in crs is applied to one surface of the paper web and to the other surface an aqueous solution which contains 5% by weight to 15% by weight of an enzymatically degraded starch is applied to the paper web.

Furthermore, an embodiment of the method can be expedient in which in method step g) an aqueous solution having a concentration of the a- (1,3 ^ glucan) polymer of 5 wt.% To 20 wt.% Is applied to at least one surface of the paper web.

An aqueous solution with a concentration of the a- (1, 3 1 ucan) - Po 1 y mcrs im specified

% By weight range has proven to be particularly well suited for coating at least one surface of the paper web. This is at least largely independent of the type of implementation of the coating. In particular, very homogeneous coatings can be produced by means of aqueous solutions in the specified% by weight range, and the formation of voids or, for example, microcracks in the coating, in particular during the drying in process step h) can be prevented.

It can also be advantageous if an amount of 0.5 g / m ² to 20 g / m ^{2 of} the aqueous solution () of the α- (1.3 g 1 ucan) polymer is applied to at least one surface the paper web is applied.

In this way, the coating, which comprises the a- (1.3 g 1 u c a n) - Po 1 y m c r, can be given a layer thickness that is particularly suitable for dye-sublimation printing processes. On the other hand, an upper limit is given for the layer thickness, which is still expedient in terms of an economically sensible production of the transfer paper.

Finally, the method can also provide that in method step h) a water content of the coated paper web of 4% by weight to 6% by weight is set.

With a water content in this specified range, the best test results could be achieved with regard to the absorption capacity but also the release capacity of sublimation dyes.

The object of the invention is also achieved by a transfer paper for thermal simulation printing processes. The corresponding transfer paper can, in particular, be produced according to a method for producing transfer paper for thermal sublimation processes using the method measures specified above.

The transfer paper comprises a paper substrate with a surface weight of 40 g / m ² to 160 g / m ² . As is known per se, the paper substrate can predominantly comprise cellulose lasers, with other components such as lignin or hemi-celluloses, or else additives and fillers customary in paper technology can also be contained in the paper substrate.

At least one surface of the paper substrate is provided with a coating at least predominantly consisting of an a- (1.3 g 1 ucan) - polymer with 90% or more al, 3-glycosidic bonds and a degree of polymerization of 55 to 10,000 , which a- (1J- ^ glucanj polymer is cationically modified and has a degree of substitution by cationic groups of 0.2 to 0.8 mol / mol. The transfer paper has a water content of 3% by weight to 7% by weight .

As already explained above in connection with the method for producing a transfer paper and shown in detail below with the aid of exemplary embodiments, a transfer paper produced by means of the specified process measures is characterized by particularly good properties when used in dye-sublimation printing processes. In particular, the special coating has, on the one hand, good printability, that is to say good absorption of the sublimation printing dyes or pigments and, in addition, also good release properties in the course of a thermal sublimation printing process. The water content in the specified range also has an advantageous effect. In particular, the transfer paper can be provided for thermal sublimation printing processes in which the transfer paper is printed by means of digital ink jet printing.

In a further development of the transfer paper, it can be advantageous if the coating consists at least predominantly of a 1 ucan) -Poly mcr which has been cationically modified with quaternary ammonium groups.

On the one hand, because such a - (1, 3 g 1 u c a n) - Po 1 y m c has been found to be particularly easy to process. In addition, a transfer paper with a coating comprising an a - (1.3 g 1 u c a n) - Po 1 y m c r modified in this way has particularly good properties when used in dye-sublimation printing processes.

Furthermore, in one embodiment of the transfer paper, it can be provided that the coating has a weight per unit area of 0.2 g / m ² to 4 g / m ² . A basis weight or a layer thickness in the specified range has proven to be particularly well suited for dye-sublimation printing processes. Above all, a layer thickness selected from this range appears to be suitable in order to prevent too large a quantity of sublimation printing dyes or pigments from penetrating into the paper substrate below. On the other hand, the specified range indicates an upper limit for the basis weight, which is still expedient in terms of an economically sensible production of the transfer paper.

In particular, it can be provided that the transfer paper has a water content of 4% by weight to 6% by weight.

In this way, a transfer paper can be provided which has further improved properties with regard to a thermal sublimation printing process.

In addition, an embodiment of the transfer paper can be expedient which has a water absorbency according to Cobb according to ISO 535 of 20 g / m ² to 35 g / m ² .

Such a transfer paper has proven to be particularly well suited primarily with regard to the absorption of sublimation printing dyes or pigments, but also with regard to their re-release in the course of a thermal sublimation process.

Finally, the object of the invention is also achieved by a method for printing textiles. The method comprises the production of a negative print image on a transfer paper using sublimation printing dye (s) and the transfer of the print image to a textile substrate using a thermal transfer press. Here, a transfer paper is used, which is designed as described above and below.

Such a transfer paper can be used to provide textiles with printed images of particularly high quality, in particular high contour accuracy, high contrast and good color density. In the method for printing textiles, provision can preferably be made for the negative print image to be produced on the transfer paper by means of digital inkjet printing.

For a better understanding of the invention, it is explained in more detail with reference to the following figures. They each show in a greatly simplified, schematic representation:

1 shows an exemplary embodiment for a method step d) for the apparatus-related dewatering of a suspension of a cellulose by means of a wire section;

2 shows an exemplary embodiment for a method step e) for further, apparatus-based dewatering of the suspension to form a paper web by means of a press section;

3 shows an exemplary embodiment for a method step f) for the further, apparatus-based drying of the paper web by means of a drying section;

4 shows an exemplary embodiment for a method step g) for coating the dried paper web by means of a coating device;

5 shows a further exemplary embodiment for a method step g) for coating the dried paper web by means of a coating device;

6 shows an exemplary embodiment for a method step i) for making up a coated and dried paper web;

7 shows an exemplary embodiment of a transfer paper for thermal sublimation printing processes;

8 shows an exemplary embodiment of a method for printing textiles.

At the outset, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component designations, and the disclosures contained in the entire description can be transferred accordingly to the same parts with the same reference numerals or the same component names. The position details chosen in the description, such as above, below, side, etc., also relate to the figure immediately described and shown and these position details must be transferred to the new position in the event of a change in position.

In the method for producing transfer paper for thermal sublimation printing processes, provision of a pulp or an aqueous pulp suspension is provided in a first method step a). The pulp can be used as it is known and in the case of printable papers usually consist predominantly of cellulose, although other components, for example lignin or hemicelluloses from the manufacture of the cellulose, or additives and impurities may also be included in small amounts. In principle, cellulose can be dried or made available as an aqueous suspension.

In a further process, step b), a suspension of the cellulose in water with a water content of at least 90% by weight, wherein the water content of this cellulose suspension can be up to 99.5% by weight. This is based on 100% by weight of the suspension of the pulp in water. In an optional process step c), additives, fillers or process chemicals can also be added to the aqueous pulp suspension. In particular, additives customary in paper technology can be added to the aqueous pulp suspension.

As illustrated in FIG. 1, the next method step d) is dewatering of the suspension 1 by means of a wire section 2. In the exemplary embodiment shown in FIG. 1, which is shown in a highly schematic and incomplete manner, such a wire section 2 can have a circulating wire 3, with The aqueous pulp suspension 1 carries onto a surface 4 of the screen 3. The other surface 5 of the screen 3 can be guided over the dewatering means 6 of the screen section 2 with each revolution of the screen 3. Such drainage means can be formed, for example, by drainage and / or suction strips. In principle, dewatering in a wire section can be carried out with the aid of gravity. In addition, however, as shown in FIG. 1, the dewatering of the suspension 1 can be supported by applying a negative pressure to the surface 5 of the screen 3 facing away from the pulp suspension 1 by means of a negative pressure device 7. The aqueous suspension of the pulp in water is adjusted or dehydrated in the process step d) illustrated in FIG. 1 to a water content of 60% by weight to 85% by weight.

In a subsequent process, step e), the dehydrated Sus pension 1 is dried to form a paper web 8 by means of a press section 9, as is also illustrated schematically in FIG. The pulp suspension 1 pre-dewatered in process step d) can for this purpose be passed between at least two rollers 10 of the press section and dried under high pressure between the rollers 10 to form the paper web 8. the. In principle, the press section can also have further pairs of rollers for this purpose. In addition, as shown in FIG. 2, the drying of the suspension 1 to form the paper web 1 can also be supported by means of absorbent support material, such as felt mats 11 illustrated in FIG. 2. By drying using the press section 9 in process step e ) the aqueous suspension 1 from process step d) is dried to form a paper web 8 with a water content of 30% by weight to 55% by weight.

Subsequently, in a further process step f), a further drying of the paper web 8 from process step e) is carried out by means of a drying section 12, as is again illustrated in a highly schematic manner in FIG. 3. Such a drying section 12 can, as shown, comprise numerous rotating drying cylinders 13 over which the paper web 8 can be guided. The drying cylinders can be directly heated. For example, heating channels not shown in detail in FIG. 3 can be formed in the dry cylinder 13, through which a heating medium, for example water vapor, can be passed. As an alternative or in addition, electrical resistance heaters are also basically conceivable. A temperature of the drying cylinder 13 can, for example in the exemplary embodiment shown in FIG. 3, rise gradually from left to right, that is to say in the direction of passage of the paper web 8. In addition, the drying section 12 can also have other aids, such as screen webs 15, 16 guided over deflection rollers 14. With such screen webs 15, 16 direct contact of the paper web 8 with the hot drying cylinders 13 can be avoided. In any case, in process step f) the paper web 8 is dried by means of the drying section 12 to a water content of 1% by weight to 10% by weight.

In the process, in a process step g), at least one of the surfaces 17 of the paper web 8 dried in process step f) is coated by means of a coating device 18. Two alternative solutions for coating at least one of the two surfaces 17 of the paper web 8 are shown in FIGS 4 and 5, and who will be explained in more detail below. Regardless of the way in which the coating is carried out, in process step g) the coating is carried out by applying an aqueous solution (19) of an a- (L 3 g 1 uc an) - Po 1 ym crs. The a- (L 3 g 1 ucan) - Po 1 ymcr has 90% or more al, 3-glycosidic bonds and a degree of polymerization of 55 to 10,000. A corresponding α- (L3 ~ ^ g 1 ucan) -Po 1 y mcr can be produced or obtained, for example, by means of enzymatic methods, as is shown, for example, in FIG US 7,000,000 B1 or US 8,871,474 B2 is described. Furthermore, the α- (1,3-glucan) polymer is cationically modified and has a degree of substitution by cationic groups of 0.2 to 0.8 mol / mol.

In particular, it can be provided that in method step g) an aqueous solution 19 of an a- (L 3 g 1 uc a n) - Po 1 y m crs cationically modified with quaternary ammonium groups is used.

In Fig. 4, a first embodiment for performing the Beschich device of the paper web 8 is shown very schematically. In this embodiment variant, in method step g), the aqueous solution 19 of the a- (L 3 g 1 uc a n) - Po 1 y m crs can be applied to at least one surface 17 of the paper web 8 by means of a size press 20. For this exemplary embodiment of the method, it can then be provided that in method step f) carried out directly beforehand, the paper web 8 is dried to a water content of 2.5% by weight to 10% by weight. In the case of coating, the paper web 8 can be passed between two application rollers 21 by means of a size press 20 as illustrated in FIG. 4, the aqueous solution 19 of the a- (L 3 g 1 uc an) - Po 1 y in crs can be introduced for the purpose of coating between the at least one surface 17 of the paper web 8 and the application roller 21 directly associated with this surface 17.

As can also be seen from FIG. 4, it can be provided in particular that in method step g) the aqueous solution of the a- (L 3 g 1 uc an) - Po 1 y in crs is applied to a surface 17 of the paper web 8 is applied and on the other surface 22 of the paper web 8, an aqueous solution 23 which contains 5% by weight to 15% by weight of an enzymatically degraded starch is applied. For this purpose, the aqueous solution 23 of the enzymatically degraded starch can be introduced between the surface 22 and the application roller 21 directly associated with this surface 22. Corresponding enzymatically degraded starches and the methods for obtaining such starches are known per se, and can be obtained, for example, by boiling wheat or corn starch in an aqueous solution which contains the corresponding degradation enzymes, as described, for example, in BeMiller, JN, & Whistler, RL (2009). Starch: Chemistry and Technology (3rd Edition). Academic Press is described. The enzymatic degradation serves primarily to lower the molecular weight of the starch and the associated lowering of the viscosity to make the starch easier to process. A-amylase is known as an example of a degradation enzyme.

In FIG. 5, an alternative exemplary embodiment for carrying out the coating of the paper web 8 is shown. In this embodiment variant, the aqueous solution 19 of a- (1, 3 1 ucan) - Po 1 y mcrs can be applied to at least one surface 17 of the paper web 8 by means of a film press 24. For this exemplary embodiment of the method, it can then be provided that in method step f) carried out directly beforehand, the paper web 8 is dried to a water content of 1.2% by weight to 2.0% by weight. In the case of coating, the paper web 8 can be passed between two stripping rollers 25 by means of a film press 24. In this case, as can be seen from FIG. 5, the aqueous solution 19 of the a- (1.3 g 1 ucan) -Polyme is applied beforehand in a targeted layer thickness to the stripping roller 25 assigned to the at least one surface 17 of the paper web 8 , and transferred from this stripping roller 25 to the at least one surface 17 of the paper web.

In the embodiment illustrated in FIG. 5, it can also be provided that in method step g) the aqueous solution of the a- (1.3 g 1 uc an) -Poly mcrs is applied to a surface 17 of the paper web 8 and an aqueous solution 23 which contains 5% by weight to 15% by weight of an enzymatically degraded starch is applied to the other surface 22 of the paper web 8. For this purpose, the aqueous solution 23 of the enzymatically degraded starch can, as can be seen from FIG. 5, firstly be applied to the stripping roller 25 directly assigned to this surface 22 of the paper web 8 and then transferred to the surface 22.

Regardless of the type of application of the aqueous solution 19 of the a- (1,3- ^ glucan) polymer or the method used for this purpose, it can be provided that in method step g) an aqueous solution 19 having a concentration of a - (1.3 g 1 ucan) - Po 1 y mcrs of 5 wt.% To 20 wt.% Is applied to at least one surface 17 of the paper web 8.

Furthermore, regardless of the coating method, an amount of 0.5 g / m ² to 20 g / m ^{2 of} the aqueous solution 19 of the a- (1.3 g 1 uc an) -Poly mcrs can be applied to at least one surface 17 the paper web 8 are applied. In principle, it can of course also be provided that an aqueous solution 19 of the α- (1,3-glucan) polymer is applied to both surfaces 17, 22 of the paper web 8. Likewise, however, it can generally also be provided that in process step g) the aqueous solution 19 of the a- (1.3 g 1 ucan) -Polyme crs is applied only to one surface 17 of the paper web, and to the other surface 22 of the paper web 8 only water or no fluid at all is applied.

Subsequent to the coating of the paper web 8 in process step g), in a further process step h), the coated paper web 8 is post-dried by means of a further drying section 12 or post-dryer section 12. Such post-drying of the coated paper web 8 by means of an post-dryer section 12 can be performed in Principle analogous to the drying already illustrated in FIG. 3 by means of the drying section 12 shown, or a corresponding after-drying section 12 can be configured analogously or at least similarly to the drying section 12 used in method step f). A repeated description of a drying process by means of a dryer section 12 or after-dryer section 12 can therefore be dispensed with at this stand, and reference is made to FIG. 3 and the associated description. It is only important that in process step h) the coated paper web 8 is post-dried to a water content of 3% by weight to 7% by weight. In particular, it can be provided that in method step h) a water content of the coated paper web 8 of 4% by weight to 6% by weight is set.

Finally, in the process, i) the coated and post-dried paper web 8 is made up in one process step. One possibility or an exemplary embodiment for assembling the paper web 8 is illustrated in FIG. 6. As shown, the coated and dried paper web 8 can here, for example, first be smoothed by means of a smoothing device 26 and then applied, for example, to a receiving tube 27 for transporting the paper web 8 or for further, external packaging. As an alternative to this packaging, it is of course also conceivable to divide the paper web (not shown) both in the longitudinal direction to form paper strips and to divide it in the transverse direction to form sheets.

The method steps d) to i) illustrated in FIGS. 1-6 can be carried out in a paper machine in direct succession. Are important here the successive dewatering of the suspension 1 of the pulp and the drying of the paper web 8 in the process sequence, including the joint drying of the paper web 8 with the coating or the post-drying of the coated paper web in process step h). This in each case to the specified ranges for water contents for the aqueous pulp suspension 1 and the paper web 8. With water contents in the individual process steps in question, which are outside the respective specified upper and lower limit values, the resulting products or transfer papers can increase poor Have properties, with varying water contents, which are within the limit values specified for the respective process steps, have only minor or hardly any negative effects on the properties desired with regard to a transfer paper for dye-sublimation printing processes.

In Fig. 7, a transfer paper 28 for dye sublimation printing processes is shown in cross section. Such a transfer paper 28 can in particular be produced according to a method as described above with reference to the exemplary embodiments in FIGS. 1 to 6. The transfer paper 28 is shown in FIG. 7 in detail and not true to scale, and can in principle have any dimensions suitable for a thermal transfer printing process provided. For example, a standardized dimensioning for paper can be provided, such as Din A4 or Din A3.

As shown in FIG. 7, the multilayer transfer paper 28 comprises, on the one hand, a paper substrate 29. The paper substrate 29 here has a weight per unit area of 40 g / m ² to 160 g / m ² . At least one surface 30 of the paper substrate 29 is provided with a coating 31. This coating 31 consists at least predominantly of an a- (l, 3- ^ glucan) polymer with 90% or more al, 3-glycosidic bonds and a degree of polymerization of 55 to 10000. In particular, the coating can be over 90 wt. % consist of the a- (1.3 g 1 ucan) - Po 1 ymcr, but may, for example, contain small amounts of impurities caused by production or otherwise, as well as additives customary in paper technology. In particular, the coating 31 contains a water content set in the course of the production of the transfer paper 28, the transfer paper 28 and thus also the coating 31 having a water content of 3% by weight to 7% by weight. The transfer paper 28 and thus also the coating 31 can preferably have a water content of 4% by weight to 6% by weight. In addition, the a- (1, 3 1 ucan) -Po 1 y mcr is cationically modified and has a Degree of substitution by cationic groups of 0.2 to 0.8 mol / mol. In particular, it can be provided that the coating 31 consists at least predominantly of an α- (1,3-glucan) polymer which is cationically modified with quar tary ammonium groups.

The coating 31 can preferably have a weight per unit area of 0.2 g / m ² to 4 g / m ² . Furthermore, it can preferably be provided that the transfer paper 28 has a water absorbency according to Cobb according to ISO 535 of 20 g / m ² to 35 g / m ² .

In principle, only one surface 30 of the paper substrate 29 can be provided with a coating 31 comprising the α- (1,3-glucan) polymer. In principle, however, both surfaces 30, 32 of the paper substrate 29 can also be provided with a coating 31 comprising the α- (1,3-glucan) polymer.

In a preferred embodiment of the transfer paper 28, as illustrated in FIG. 7, a surface 30 of the paper substrate 29 can be provided with the coating 31 comprising the a- (1.3 g 1 ucan) -Polyme and that surface 30 opposite surface 32 of the paper substrate 29 can be provided with a further, different coating 33. In particular, it can be provided that the further coating 33 consists at least predominantly of an enzymatically degraded starch. A description of a corresponding degraded starch has already been made on the basis of the description of the method, and reference is made to this at this point.

In Fig. 8, finally, method for printing textiles is roughly schematically Darge provides. The method here is formed by a dye-sublimation printing process. As can be seen from FIG. 8, in the method for printing textiles, a negative print image is first produced on transfer paper 28 by means of one or more sublimation printing dye (s) 34. This can in principle be carried out by means of conventional printing methods, with contact printing methods such as rotary screen printing or contactless printing methods such as inkjet printing being able to be used. It goes without saying that the printing method can provide for the negative print image to be monochrome or multicolored, with multicolor print images of course being able to use several sublimation dyes or pigments of different colors as is known per se. The transfer paper 28 shown in FIG. 8 is a paper coated at least on one side, as was described above with reference to FIG. Here, the side 35 of the transfer paper 28, which is provided with the coating 31 consisting at least predominantly of the a- (1.3 g 1 ucan) -Po 1 ymc, is intended for printing with the dye (s) 34 for thermal sublimation. As shown in FIG. 8, in the method for printing textiles, the thus printed side 35 of the transfer paper 28, which is provided with the coating 31 as shown in FIG. 7, is then brought into contact with a textile substrate 36 to be printed.

The thermal sublimation dye (s) or the print image formed by the thermal sublimation dye (s) are or are at least partially applied to the transfer paper 28 by means of a thermal transfer printer 37, shown only partially and in a highly schematic manner in FIG the textile sub-start 36 transmitted. In a conventional thermal transfer printer 37, as is known per se, the sublimation dye (s) or the sublimation pigment (s) are / are converted into the gas phase by heating and, if necessary, transferred into the textile substrate with the help of pressure . The transfer paper 28 can then be removed from the textile substrate 36, wherein, as indicated in FIG. 8, a residual amount of sublimation dye (s) can remain in the transfer paper 28.

For a method for printing textiles or for a thermal sublimation printing process, on the one hand, good printability of the transfer paper 28, that is to say the best possible absorption and intermediate storage of the sublimation printing dyes, is important. On the other hand, the best possible transfer efficiency to the textile actually to be printed is important.

The properties of the transfer paper produced by means of the method described above or the transfer paper for thermal sublimation printing processes also described above will now be characterized using exemplary embodiments.

Embodiment 1:

Several transfer papers were used as test papers A, B, C, each with different surface weights of the coating, at least predominantly from a - (1.3 g 1 ucan) - Po 1 ymcr produced. The production took place here according to process steps a) -h) of the process described above. The water content of the aqueous suspension of the pulp and of the paper web formed in the course of the process fluctuated slightly in the course of the manufacture of the individual transfer papers, but were within the ranges specified for the relevant process steps. No significant influences of slightly deviating water contents on the properties of the transfer papers produced could be determined. The aqueous solution of a- (1.3 g 1 ucan) - Po 1 ymcr was applied to one surface of the paper web by means of a film press in all transfer or test papers A, B, C, and a aqueous solution with 10 wt.% of an enzymatically degraded starch applied

The coating of a- (1, 3 g 1 u c a n) - Po 1 y m c r had the following basis weights in the transfer or test papers produced:

A: 0.25 g / m ² ;

B: 0.5 g / m ² ;

C: 1 g / m ² .

These transfer papers A, B, C, and comparative papers D and E were printed with a simple test pattern in the form of filled circular areas of individual sublimation dyes in different colors. The comparison papers used were:

D: conventional printing paper, 50 g / m ² ;

E: commercially available transfer paper with a coating based on carboxymethyl cellulose.

The identical print images applied in each case to the transfer papers A, B, C and to the comparison papers D, E were each transferred to a commercially available polyester textile by means of a thermal transfer press, type Hotronix STX11. The transferred print images were then characterized individually for each printing color by means of densitometry with regard to color density.

Two test series 1 and 2 were carried out, with two different, commercially available sublimation inks for printing the test papers in test series 1 and 2 with four base colors or dyes each were used for inkjet printing. The printing of the test papers before transfer to the polyester textile was carried out by means of inkjet printing.

To measure the color density of the thermal transfer prints of the individual sublimation colors or inks of test series 1 and 2, the relevant prints on the polyester textile were measured in reflection mode using an X-rite eXact advanced densitometer. A respective color density D is calculated as is known per se as D = log io (1 / reflection) or logio (io / i). The respective color density was determined according to ISO 13655: 2017-07.

From the color densities determined in this way, an arithmetic mean D _m for the color density from all color-specific measured values or from the color densities determined for all dyes of an ink from test series 1 and 2 was formed for each test paper of test series 1 and 2.

Table 1 below shows the mean values D _mi and D _m 2 of the color densities for both test rows 1 and 2 for the printed images transferred to the polyester textiles by means of test papers A, B, C, D, E. With regard to the transfer efficiency of the sublimation printing dyes to the test textile, the highest possible values for the color density are desirable in Table 1.

Table 1: Measurement results of polyester textile Embodiment 2:

The test papers B, C, D, E were also used to further characterize the suitability of a transfer paper coated according to the invention with the α- (1, 3 1 ucan) -Po 1 y mcr

Thermal sublimation printing processes carried out, in which each on the back of a In the respective transfer paper or test paper, a conventional printing paper with a surface weight of 50 g / m ^{2 was placed} as the back side test paper. The respective dye-sublimation printing processes were otherwise carried out in a completely analogous manner to that described under embodiment 1.

In embodiment 2, after the thermal sublimation printing had been carried out, the reverse side test papers were tested with regard to a breakthrough of dyes of the inks used in test series 1 and 2 on the reverse side of a respective test paper, i.e. an undesired penetration of the dyes onto the reverse side of the respective test paper and Transfer of the dyes to the test paper on the back is examined visually by a trained test person, and assessed according to the school grade principle, i.e. from 1 to 5. As the corner points, backside test papers that do not include any discernible traces of color are rated 1, whereas backside test papers, which have a print image that is almost completely passed through or transferred to the backside test paper, are rated 5. A reference folder with samples of different quality serves as a basis for the assessment or for the grading of grades for comparison or as a reference point.

In addition, the printed images on the back test papers for the ink of test series 1 were evaluated electronically. For this purpose, the test papers on the back were scanned with a high-resolution scanner and evaluated using the Evaluation Software Print Target from the company Prüfbau. An evaluation was carried out once with the software setting Low sensitivity and once with the software setting High sensitivity.

Both the scores for the visual evaluation of the reverse side test papers with the inks of test series 1 and 2, as well as the values of the electronic evaluation of the reverse side test papers in the modes low sensitivity and high sensitivity are marked accordingly in Table 2. It applies to Table 2 that lower values for the visually evaluated and electronically evaluated print images on the back test papers are desirable, since this represents a lower loss of dye-sublimation dyes due to penetration over the back of a test paper. Table 2: Measurement results on the back test paper

As can be seen from the exemplary embodiments, the paper with the coating produced as described is at least predominantly composed of a- (1, 3 1 ucan) - Po 1 y mcr well suited as transfer paper for dye-sublimation printing processes. Above all, an undesired strike through or a penetration of Th erm o suhl in ati on s dyes on the back of such a transfer paper can be effectively prevented.

The exemplary embodiments show possible design variants, whereby it should be noted at this point that the invention is not restricted to the specifically illustrated design variants, but rather various combinations of the individual design variants are possible with one another and this possible variation is based on the teaching on technical action due to the present invention is within the ability of a person skilled in this technical field.

The scope of protection is determined by the claims. However, the description and the drawings should be used to interpret the claims. Individual features or feature combinations from the different exemplary embodiments shown and described can represent independent inventive solutions for themselves. The task on which the independent inventive solutions are based can be found in the description. All information on value ranges in the present description are to be understood in such a way that they include any and all sub-areas, e.g. the information 1 to 10 should be understood to include all sub-areas, starting from the lower limit 1 and the upper limit 10 are, ie all sections begin with a lower one Limit of 1 or greater and end at an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

For the sake of order, it should finally be pointed out that, for a better understanding of the structure, some elements have been shown not to scale and / or enlarged and / or reduced.

List of reference symbols suspension 31 Coating of the screen section 32 Surface of the screen 33 Coating of the surface 34 Sublimation printing dye surface 35 Side of the dehydrating agent 36 Textile substrate Vacuum device 37 Thermal transfer printer Paper web Press section Roller Felt mat Drying section Drying cylinder Deflecting roller Screen web Screen web surface Coating device solution Size press Application swab alze surface Solution Film press Surface squeegee roll

Claims

P a t e n t a n s p r ü c h e

1. A process for the production of transfer paper for thermal sublimation printing processes, comprising the process steps a) providing a pulp or an aqueous pulp suspension, b) producing a suspension (1) of the pulp in water with a water content of at least 90% by weight, c) optionally adding additives, fillers or process chemicals to the aqueous suspension (1), d) dewatering the suspension (1) to a water content of 60% by weight to 85% by weight by means of a wire section (2), e) drying the dewatered suspension (1) to a paper web (8) with a water content of 30% by weight to 55% by weight by means of a press section (9), f) further drying of the paper web (8) to a water content of 1% by weight to 10% by weight by means of a drying section (12), g) coating at least one of the surfaces (17) of the paper web (8) by means of a coating device (18) by applying an aqueous solution (19) of a- (l, 3 - ^ glucan) polymer with 90% or more al, 3-glycosidic bonds and a degree of polymerization from 55 to 10,000, which a- (1, 3 -> glucan) polymer is cationically modified and a degree of substitution by cationic groups of 0.2 to 0.8 mol / mol, h) post-drying of the coated paper web (8) by means of a further drying section (12) to a water content of 3% by weight to 7% by weight, i) making up the coated and post-dried paper web (8).

2. The method according to claim 1, characterized in that in method step g) an aqueous solution (19) of a cationically modified with quaternary ammonium groups a- (L 3 g 1 u c a n) - Po 1 y m c r s is used.

3. The method according to claim 1 or 2, characterized in that in method step f) the paper web (8) is dried to a water content of 2.5 wt.% To 10 wt.%, And in method step g) the aqueous solution ( 19) des a- (L 3 g 1 ucan) - Po 1 ym crs is applied to at least one surface (17) of the paper web (8) by means of a size press (20).

4. The method according to claim 3, characterized in that in method step g) the aqueous solution (19) of the a- (L3 ~ ^ g 1 ucan) - Po 1 y mcrs on a surface (17) of the paper web (8 ) is applied and an aqueous solution (23) which contains 5% by weight to 15% by weight of an enzymatically degraded starch is applied to the other surface (22) of the paper web (8).

5. The method according to claim 1 or 2, characterized in that in method step f) the paper web (8) is dried to a water content of 1.2 wt.% To 2.0 wt.%, And in method step g) the aqueous one Solution (19) of the a- (L 3 g 1 ucan) - Po 1 y mcrs is applied to at least one surface (17) of the paper web (8) by means of a film press (24).

6. The method according to claim 5, characterized in that in method step g) the aqueous solution (19) of the a- (L3 ~ ^ g 1 ucan) - Po 1 y mcrs on a surface (17) of the paper web (8 ) is applied and an aqueous solution (23) which contains 5% by weight to 15% by weight of an enzymatically degraded starch is applied to the other surface (22) of the paper web.

7. The method according to any one of the preceding claims, characterized in that in method step g) an aqueous solution (19) having a concentration of the a- (l, 3- ^ glucan) polymer of 5 wt.% To 20 wt.% is applied to at least one surface (17) of the paper web (8).

8. The method according to claim 7, characterized in that an amount of 0.5 g / m ² to 20 g / m ^{2 of} the aqueous solution (19) of the a- (l, 3 ~ ^ gl ucan (polymer to at least one Surface (17) of the paper web (8) is applied.

9. The method according to any one of the preceding claims, characterized in that in method step h) a water content of the coated paper web (8) of 4% by weight to 6% by weight is set.

10. Transfer paper (28) for dye sublimation printing processes, in particular Herge provides with a method according to one of claims 1 to 9, comprising a paper substrate

(29) with a basis weight of 40 g / m ² to 160 g / m ² , with at least one surface

(30) of the paper substrate (29) is provided with a coating (31), which coating

(31) at least predominantly from an a- (1, 3 1 ucan) - Po 1 y mcr with 90% or more a-1,3-glycosidic bonds and a degree of polymerization of 55 to 10000, which a- (1.3 g 1 ucan) - Po 1 ymcr is cationically modified and a Has a degree of substitution by cationic groups of 0.2 to 0.8 mol / mol, and the transfer paper (28) has a water content of 3% by weight to 7% by weight.

11. Transfer paper according to claim 12, characterized in that the coating (31) consists at least predominantly of a cationically modified a- (1.3 g 1 u c a n) - Po 1 y m c with quaternary ammonium groups.

12. Transfer paper according to claim 10 or 11, characterized in that the coating (31) has a basis weight of 0.2 g / m ² to 4 g / m ² .

13. Transfer paper according to one of claims 10 to 12, characterized in that it has a water content of 4% by weight to 6% by weight.

14. Transfer paper according to one of claims 10 to 13, characterized in that it has a water absorbency according to Cobb according to ISO 535 of 20 g / m ² to 35 g / m ² .

15. A method for printing textiles, comprising

Production of a negative print image on transfer paper (28) by means of sublimation printing dye (s) (34), Transfer of the print image to a textile substrate (36) by means of a thermal transfer printer (37), characterized in that a transfer paper (28) according to one of Claims 10 to 14 is used.