WO1999036620A1 - Paper having a three-dimensional pattern - Google Patents

Abstract

An impulse-dried paper having a three-dimensional pattern of alternating raised and recessed portions which is conveyed to the paper in connection with the impulse drying. The paper contains at least 0,05 % by weight, calculated on the dry fiber weight, of one one more additives which in connection with impulse drying undergoes a chemical reaction so that they contribute in stabilizing the pattern structure that has been conveyed to the paper at the impulse drying. An example of such an additive is a wet strength agent.

Description

Paper having a three-dimensional pattern

Technical field

The present invention refers to an impulse dried paper having a three-dimensional pattern of alternating raised and recessed portions which is conveyed to the paper in connection with the impulse drying.

Background of the invention

Moist paper webs are usually dried against one or more heated rolls. A method which is commonly used for tissue paper is so called Yankee drying. At Yankee drying the moist paper web is pressed against a steam-heated Yankee cylinder, which can have a very large diameter. Further heat for drying is supplied by blowing of heated air. If the paper to be produced is soft paper the paper web is usually creped against the Yankee cylinder. The drying against the Yankee cylinder is preceded by a vacuum dewatering and a wet pressing, in which the water is mechanically pressed out of the paper web.

Another drying method is so called through-air-drying (TAD). In this method the paper is dried by means of hot air which is blown through the moist paper web, often without a preceding wet pressing. The paper web which enters the through-air-dryer is then only vacuum dewatered and has a dry content of about 25-30% and is dried in the through- air-dryer to a dry content of about 65-95%. The paper web is transferred to a special drying fabric and is passed over a so called TAD cylinder having an open structure. Hot air is blown through the paper web during its passage over the TAD cylinder. Paper produced in this way, mainly soft paper, becomes very soft and bulky. The method however is very energy-consuming since all water that is removed has to be evaporated.

In connection with the TAD drying the patterned structure of the drying fabric is transferred to the paper web. This structure is essentially maintained also in wet condition of the paper, since it has been imparted to the wet paper web. A description of the TAD technique can be found in e g US-A-3,301,746. Impulse drying of a paper web is disclosed in e g SE-B-423 118 and shortly involves that the moist paper web is passed through the press nip between a press roll and a heated roll, which is heated to such a high temperature that a quick and strong steam generation occurs in the interface between the moist paper web and the heated roll. The heating of the roll is e g accomplished by gas burners or other heating devices, e g by means of electromagnetic induction. By the fact that the heat transfer to the paper mainly occurs in a press nip an extraordinarily high heat transfer speed is obtained. All water that is removed from the paper web during the impulse drying is not evaporated, but the steam on its way through the paper web carries along water from the pores between the fibers in the paper web. The drying efficiency becomes by this very high.

In EP-A- 0 490 655 there is disclosed the production of a paper web, especially soft paper, where the paper simultaneously with impulse drying is given an embossed surface. This embossment is made by pressing a pattern into the paper from one or both sides against a hard holder-on. This gives a compression of the paper and by this a higher density in certain portions just opposite the impressions and a lower density in the intermediate portions.

The object and most important features of the invention The object of the present invention is to provide a method of producing an impulse dried paper having a three-dimensional pattern, e g a soft paper intended as toilet paper, kitchen rolls, paper handkerchiefs, table napkins and the like, and where the paper should have a high bulk and a high absorption capacity and the three-dimenisional structure should be maintained in dry as well as in wet condition. This has according to the invention been solved by the fact that the paper contains at least 0,05% by weight, preferably at least 0,25%₀ by weight, of one or more additives which in connection with impulse drying undergoes a chemical reaction so that they contribute in stabilizing the pattern structure that has been conveyed to the paper at the impulse drying.

This contributes in substantially maintaining the pattern structure also in the wet condition of the paper, which strongly improves the absorption properties of the paper. Description of the drawings

The invention will in the following be closer described with reference to some embodiments shown in the accompanying drawings.

Fig. 1-3 are a schematic side views of impulse drying devices according to some different embodiments.

Fig. 4 a-c show in the form of bar charts dry and wet bulk of impulse dried paper produced from different types of pulp with or without wet strength agent.

Fig. 5 shows in the form of bar charts the effect of wet strength agent on the relative absorption of paper that has been dried in a conventional way without simultaneous pressing, impulse dried and impulse dried under simultaneous embossing.

Fig. 6 shows in the form of bar charts the effect of temperature on bulk and absorption of impulse dried paper made from different types of pulp.

Fig. 7 shows in the form of bar charts the effect of temperature on the strength properties of impulse dried paper made of different pulp types.

Description of the invention

Fig. 1 shows schematically a device for performing impulse drying of a paper web.

The wet paper web 10 which is dewatered over suction boxes (not shown) is supported by a compressible press felt 11 and is brought into a press nip 12 between two rotatable rolls 13 and 14, at which the roll 13 which is in contact with the paper web is heated to a temperature which is sufficiently high for providing drying of the paper web. The surface temperature of the heated roll can vary depending on such factors as the moisture content of the paper web, thickness of the paper web, the contact time between the paper web and the roll and the desired moisture content of the completed paper web. The surface temperature should of course not be so high the paper web is damaged. An appropriate temperature should be in the interval 100-400°C, preferably 150-350°C and most preferably 200-350 °C.

The paper web is pressed against the heated roll 13 by means of the roll 14. The press device may of course be designed in many other ways. Two and more press devices may also be arranged after each other. The holder-on 14 may also be a press shoe. It is also possible that the paper web 11 is passed into the press nip unsupported, i e not supported by any wire or felt.

A very rapid, violent and almost explosive steam generation takes place in the interface between the heated roll 13 and the moist paper web, at which the generated steam on its way through the paper web carries away water. For a further description of the impulse drying technique reference is made to the above mentioned SE-B-423 118 sand e g to EP-A- 0 337 973 sand US-A-5,556,511.

The paper is after drying wound on a wmd-up roll 16. If desired the paper can be creped before winding. It is however noted that the need for creping the paper in order to impart softness and bulk which is aimed at for soft paper, is reduced when using the impulse drying method according to the invention, since the paper by the strong steam expansion in the paper web is imparted bulk and softness and besides a three- dimensional structure.

The paper web can before it is brought into the impulse dryer either can be only dewatered over suction boxes or besides slightly pressed according to a conventional process.

Simultaneously with the impulse drying the paper is given a three-dimensional structure. This can be made as shown in Fig. 1 and 2 by the fact that the heated roll 13 is provided with an embossing pattern consisting of alternating raised and recessed areas. This structure is substantially maintained also in a later wetted condition of the paper, since it has been imparted the wet paper web in connection with drying thereof.

Since the term embossing is normally used for a shaping performed on dried paper we have in the following used press moulding for the three-dimensional shaping of the paper that occurs simultaneously with the impulse drying. By this press moulding the bulk and absorption capacity of the paper is increased, which are important characteristics for soft paper. The paper can be pressed against a non-rigid surface, i e a compressible press felt 11. The roll 14 can also have an elastically yielding surface, e g an envelope surface of rubber. The paper is herewith given a three-dimensional structure the total thickness of which is greater than the thickness of the unpressed paper. By this the paper is imparted a high bulk and by that a high absorption capacity and a high softness. Besides the paper will be elastic. At the same time a locally varying density is obtained in the paper.

The paper can also be pressed against a hard surface, e g a wire 11 and/or a roll 14 having a hard surface, at which the pattern of the heated roll 13 is pressed into the paper web under a heavy compression of the paper opposite the impressions, while the portions therebetween are kept uncompressed.

The embodiment shown in Fig. 2 differs from what is shown in Fig. 1 by the fact that under the wire 11 there is arranged a felt 17, which extends around the roll 14. The function of the felt 17 is to improve the dewatering effect and extend the press nip.

According to the embodiment shown in Fig. 3 the paper web 10 is during the drying supported by a wire 11 having a pattern, which is press moulded into the paper web when this passes through the press nip 12 between the rolls 13 and 14. The roll 13 can either be smooth, as is shown in Fig. 3, or have an embossing pattern. In the case the roll 13 is smooth the press moulded paper will have one smooth surface and one surface with impressions. In the case the roll 13 has an embossing pattern this will also be pressed into the paper, which thus on one side will have a pattern corresponding to the structure of the wire 11 and on the opposite side having a pattern corresponding to the embossing pattern of the roll. The pattern may but need not coincide and/or be the same or different.

Paper can be produced by a number of different pulp types. If one disregards recovery pulp, which today is used to a great extent mainly for toilet paper and kitchen rolls, the most commonly used pulp type for soft paper is chemical pulp. This is produced by impregnating wood chips with chemicals and then boil it so that the lignin and the hemicellulose is transferred to the liquid. After finished boiling the pulp is screened and washed before it is bleached. The lignin content in such pulp is practically zero and the fibers, which mainly consist of pure cellulose, are relatively thin and flexible. Chemical pulp can be both of long- and short fiber type depending on the wooden raw material used, and can be of sulphate- or sulphite type depending on the composition of the boiling liquid. Chemical long fiber pulp (softwood), especially of sulphate type, has a favourable effect on the strength properties of the soft paper, both dry- and wet strength.

Chemical pulp is a low yield pulp since it gives a yield of only about 50%> calculated on the wooden raw material used. It is therefore a relatively expensive pulp. It is therefore common to use cheaper so called high yield pulps, e g mechanical or thermomechanical pulp, in soft paper as well as in other types of paper, e g newsprint paper, cardboard etc. Mechanical pulp is produced by grinding or refining and the principle for mechanical pulp production is that the wood is mechanically disintegrated. The entire wood material is utilized and the lignin is thus left in the fibers, which are relatively short and stiff. The production of thermomechanical pulp (TMP) is accomplished by refining in a disc refiner at an increased steam pressure. Also in this case the lignin is left in the fibers.

Chemomechanical pulp (CMP) or chemothermomechanical pulp (CTMP) are terms for a thermomechanical pulp which has been modified by the addition of small amounts of chemicals, usually sulphite, which is added before the refining. One effect of the chemical treatment is that the fibers are freed more easily. A chemomechanical or chemothermomechanical pulp contain more complete fibers and less shives (fiber aggregates and fiber fragments) than a mechanical or thermomechanical pulp. The properties of CMP and CTMP approaches those for the chemical pulps, but there are essential differences depending among other things on that in CMP and CTMP the fibers are coarser and can contain a high amount of lignin, resins and hemicellulose.

The lignin and the resins gives the fibers more hydrophobic properties and a reduced ability ro form hydrogen bonds. The addition of a certain amount of chemothermomechanical pulp in soft paper has due to the reduced fiber- fiber bonding a positive effect on properties like bulk and absorption capacity.

A special variant of chemothermomechanical pulp (CTMP) is so called high temperature chemothermomechanical pulp (HT-CTMP), the production of which differs from the production of CTMP of conventional type mainly by using a higher temperature for impregnation, preheating and refining, preferably no lower than 140°C. For a more detailed description of the production method for HT-CTMP reference is made to WO 95/34711. Characterizing for HT-CTMP is that it is a long fibrous-, easily dewatered- and bulky high yield pulp with a low shives content and low fines content.

It has according to the invention been found that high yield pulp is especially suitable for impulse drying since it is pressure insensitive, easily dewatered and has an open structure which admits the generated steam to pass through. This minimizes the risk for the paper to be overheated and destroyed during the impulse drying, which is performed at considerably higher temperatures than in other drying methods. The pressure insensitivity and the open structure depends on that the fibers in high yield pulp are relatively coarse and stiff as compared to the fibers in chemical pulp.

A further advantage is that the three-dimensional structure that has been given the paper is substantially maintained also in wet condition of the paper, since it has been conveyed to the wet paper web simultaneously with the drying thereof. Impulse drying is further performed at a considerably higher temperature than e g Yankee-drying or through-air-drying, and according to a theory, to which however the invention is not bound, the softening temperature of the lignin in the high yield pulp is reached during the simultaneous impulse drying and press moulding. When the paper then cools down the lignin becomes stiff again and contributes to permanent the three-dimensional structure that has been conveyed to the paper. This structure is therefore substantially maintained also in the wet condition of the paper, which strongly improves the bulk and absorption characteristics of the paper. The amount of high yield pulp should be at least 10 % by weight calculated on the dry fiber weight, preferably at least 30 % by weight and most preferably at least 50 %> by weight. Admixture of a certain amount of other pulp with good strength properties, such as chemical pulp, preferably long-fibrous sulphate pulp, or recovery pulp, is an advantage if a high strength of the finished paper is aimed at.

According to the invention the paper contains at least 0,05% by weight, prefereably 0,25%) by weight, calculated on the dry fiber weight, of one or more additives which in connection with impulse drying has undergone a chemical reaction so that it/they has contributed in stabilizing the pattern structure which has been conveyed to the paper at the impulse drying.

The additives may be of defferent types and undergo different types of hardening reactions in the temperature interval 100-400 °C, which is the temperature the paper web is exerted to at the impulse drying. Examples of such additives are reactive polymers, such as wet strength agents, fixing agents, polysaccharides, polyvinyl alcohol or a polyacid such as polyacrylic acid and copolymers thereof. The additives can either be bonded to the fiber surface or be added as a separate additive either to the fiber furnish or to the moist paper web before the impulse drying. The chemical reaction can either involve a chemical modification of the additive per se such as a crosslinking reaction, a reaction between two or more additives or a reaction between the additive and cellulose or any other component of the pulp fibers, e g lignin. Possible reactions between lignin and additive can comprise ester formation, ether formation, acetal formation and complex formation.

Examples of more or less reactive polysaccharides are starch, oxidized starch, hemicellulose, chitine, chitosane, pectine or alginine. The chemical reactions that the polysaccharides can undergo can be if the type ester formation, ether formation and oxidation. Wet strength agents are water soluble chemicals which either can crosslink internally or with cellulose or any other component of the pulp fibers. They usually comprise cationic oligomeric or polymeric resins. Examples thereof are different types of polyamide-epichlorhydrine resins with reactive functional groups such as amino-, epoxy- or azetidine groups. Wet strength agents of this kind are disclosed in e g the US patents 3,700,623 and 3,772,076. Polyamide-amine-epichlorhydrine resins sold under the trade mark KYMENE® by Hercules Inc. are specially usesful in the present invention.

Other useful water soluble cationic resins are polyacrylic amide resins and acrylic emulsions. Further examples of wet strength agents are urea formaldehyde- and melamine formaldehyde resins and polyethylene imine resins. A description of these kinds of water soluble resins is found in TAPPI Monograph Series, No. 29, Wet Strength In Paper and Paperboard. Technical Association of the Pulp and Paper Industry (New York 1965).

Further examples of crosslinking agents are formaldehyde compounds and N-methylol compounds used in textile industry, and compounds based on polycarboxy acids, such as citric acid and maleinic acid and polymeric carboxy acids.

All these types of wet strenght agents impart a permanent wet strength to the paper. This can in some cases not be desired, especially in those cases where it should be possible to throw the paper in the sewage system where it should be disintegrated in a short time. There are therefore also available temporary wet strength agents, which gives the paper a wet strength that is sufficient for the intended use, but which are decomposed in within a few minutes or less when the paper is placed in water. Examples of such temporary wet strength agents can be found in the US patents 3,556,932 and 3,556,933. Other examples of temporary wet strength agents are modified starch which e g are disclosed in the US patents 4,675,394; 4,981,557; 5,008,344 and 5,085,736 and modified cellulose derivatives. The wet strength agent is added to the fiber furnish or the paper web before impulse drying.

Other examples of additives are hydrophobizing agents, e g resins, fatty acids, alkyl ketenedimers or alkylsuccinic acid preparations. Further examples are inorganic pigments or complex formers which can react with specific groups in lignin and cellulose and form three-dimensional networks, e g oxides or chlorides of zinc or magnesium, phosphates, borates and zirconium.

The additives may be of a kind that can undergo a chemical reaction of the type acetylation, silylation and/or crosslinking with bi- or multifunctional groups, such as diisocyanates and triazine derivatives.

Example Trials have been made in an experimental equipment in which a paper web having a dry content of about 35 % by weight without previous pressing was exerted to impulse drying at temperatures varying between about 200-300 °C and a pressure of about 4 MPA. The pulp types that were tested were 100% chemical sulphate pulp, 100%> HT- CTMP and 50/50 chemical sulphate pulp/HT-CTMP with or without addition of a wet strength agent in the form of KYMENE^®, apolyamide-amine-epichlorhydrine resin

(PAE). The added amounts were 0,5, 1,0 and 1,5% by weight calculated on the dry fiber weight.

In Fig. 5 a-c the results of measurements performed with respect to dry and wet bulk of impulse dried paper containing the above pulps with and without respectively addition of wet strength resin, are shown. The added amounts were 5 mg/g (0,5%> by weight) calculated on the dry fiber weight, 10 mg/g (1% by weight) and 15 mg/g (1,5% by weight). The measurements have been made on unembossed as well as on embossed (press moulded) paper. From the results shown in Fig. 4a-c it can be seen that impulse dried paper that is press moulded (embossed) and contains wet strength agent has a higher wet bulk and by that absoφtion as compred to corresponding papers without wet strength agent. One can see that the difference between the dry and the wet bulk is considerably less in the cases where the paper contains a wet strength agent. This is supposed to depend on that the hardening temperature of the wet strength agent is reached during the simultaneous impulse drying and embossing and thus permanent the three-dimensional structure that has been comveyed to the paper. This is therefore maintained to a higher degree also in the wet condition of the paper, which improves the absorption characteristics of the paper.

It is also worth mentioning that there could not be noticed any corresponding improvement of the wet bulk in those cases where the paper was impulse dried without simultaneous press moulding (embossing). This strengthens the above theory that the hardening of the wet strength agent during the simultaneous impulse drying and press moulding permanents the three-dimensional structure in the paper.

This effect could be noticed in all pulps, in chemical pulp as well as in HT-CTMP and the mixture 50/50 chemical pulp/HT-CTMP. When it comes to paper with lignin containing high yield pulps such as mechanic, thermomechanic (TMP) and chemothermomechanic (CTMP) pulp it is also supposed that the softening temperature of lignin is reached during the simultaneous impulse drying and embossing and when the paper cools down the lignin will stiffen again and contributes in permanenting the three-dimensional structure that has been conveyed to the paper.

It can also be noticed that the wet bulk increases somewhat at the higher concentrations of wet strength agent. This applies especially for the paper containing HT-CTMP.

In Fig. 5 there is shown in the form of bar charts the effect of wet strength agents on the relative absoφtion for paper which had been dried in a conventional way without simultaneous pressing, impulse dried and impulse dried under simultaneous press moulding (embossing). The wet strength agent was also in this case KYMENE^®, a polyamide-amine-epichlorhydrine resin (PAE). The added amount was 1% by weight calculated on the dry fiber weight. The same types of pulp were tested as above, i e 100% chemical sulphate pulp, 100% HT-CTMP and 50/50 chemical sulphate pulp/ HT-CTMP.

From the results shown in Fig. 5 it can be seen that the wet strength agent had little or no effect on the asoφtion of conventionally dried tissue. This applies for all types of pulp.

For impulse dried non press moulded (embossed) tissue the wet strength addition had a negtive effect on the absoφtion for all types of pulp.

On the contrary the addition of wet strength agent had a strongly positive effect on the absoφtion for tissue which had been simultaneously impulse dried and press moulded

(embossed). This applies for all pulp types. The increase was however greatest for the chemical pulp.

In order to investigate the importance of the temperature under the impulse drying, i e the surface temperature of the heated roll, tests were performed on the three different pulp types 100%) unrefined chemical sulphate pulp, 100% HT-CTMP and a 50/50 mixture of unrefined chemical sulphate pulp at two different temperatures 200 and 300°C. All papers contained KYMENE^®, apolyamide-amine-epichlorhydrine resin (PAE). The added amount was 1% by weight calculated on the dry fiber weight. The dry and the wet bulk and the relative absoφtion were measured. The results are shown in Fig. 6.

From these results it can be seen that a raising of temperature from 200 to 300° C did not have any real effect on these characteristics for paper containing 100%) chemical sulphate pulp besides a small increase of the dry bulk. For the papers contaimng 100%)

HT-CTMP and the 50/50 mixture chemical sulphate/HT-CTMP did on one hand the dry bulk decrease somewhat, but on the other hand did the wet bulk and the relative absoφtion increase at a raising of temperature from 200 to 300 °C. The increase was most significant for the paper containing 100% HT-CTMP. These results support the theory that the lignin in the high yield pulp softens during the simultaneous impulse drying and the press moulding (embossing), which contributes in permanenting the three-dimensional structure when the paper is cooled. The higher temperature the more lignin will have time to soften during the impulse drying.

The temperature influence of the strength properties of the paper was also tested. The dry and the wet tensile index (TI) respectively for paper the had been impulse dried at

200 and 300 °C respectively were measured. The results are shown in Fig. 7.

For paper containing 100%> chemical sulphate pulp a lower tensile index was obtained at the higher temperature. The wet tensile index was essentially the same after drying at both temperatures .

For paper containing 100%> HT-CTMP however there was a significant increase of both the dry and the wet tensile index at an increase of the impulse drying temperature from 200 to 300 °C. An explanation could be that a higher degree of softening is achieved at the higher temperature, which contributes in an increased bonding of the fiber stmcture.

For the mixture 50/50 chemical sulphate pulp/HT-CTMP the dry tensile index was essentially unchanged while the wet tensile index increased somewhat at the higher temperature.

The invention is of course not limited to the embodiments described above and shown in the drawings, but may be varied within the scope of the claims. The lignin containing high yield pulp can as previously mentioned be of many different kinds such as mechanical pulp, thermomechanical, chemomechanical and chemothermomechanical pulp and comprise virgin fibers as well as recovery fibers. The admixture of a certain amount of other pulp with good strength properties, such as chemical pulp, preferably long-fibrous sulphate pulp is an advantage if high strength of the finished paper is aimed at. Also other pulps including recovery pulp can be contained in the paper.

The paper web can after the impulse drying be exerted to different types of treatments which per se are known such as addition of different chemicals, further embossing, lamination etc. Such a treatment may be that the paper web after it has been given the three-dimensional pattern is compressed in a subsequent roll nip which has a temperature which is lower than that of the heated roll, by means of which the paper has been given the three-dimensional pattern. Possibly a further pattern may be pressed into the paper web during this compression. The compression involves a decreased bulk of the paper, which saves space during transport and storing. The deformation of the paper web that takes place during this compression is maintained by means of fiber-to-fiber bonds that are not constant in wet condition. The paper will in contact with water or aqueous liquids recover its three-dimensional stmcture that was given to it at the impulse drying, at which by the expansion of the paper an increased water absoφtion capacity is obtained.

Claims

1. An impulse-dried paper having a three-dimensional pattern of alternating raised and recessed portions which is conveyed to the paper in connection with the impulse drying, characterized in that the paper contains at least 0,05%> by weight, preferably at least 0,25% by weight, calculated on the dry fiber weight , of one ore more additives which in connection with impulse drying undergoes a chemical reaction so that they contribute in stabilizing the pattern structure that has been conveyed to the paper at the impulse drying.

2. Paper as claimed in claim 1, characterized in that the additive(-s) is a reactive polymer, such as a wet strength agent, fixing agent, polysaccharide, polyvinyl alcohol or a polyacid, such as polyacrylic acid and copolymers thereof.

3. Paper as claimed in claim 2, characterized in that the wet strength agent is a polyamide-amine-epichlorhydrine resin, polyacryl amide resin, acrylic emulsion, ureaformaldehyde resin, melamine formaldehyde resin, polyethylene imine resin, a modified starch or a modified cellulose derivative.

4. Paper as claimed in claim 2, characterized in that the polysaccharide is starch, oxidized starch, hemicellulose, chitine, chitosane, pectin or alginine.

5. Paper as claimed in claim 1, characterized in that the additive(-s) is a hydrophobizing agent, e g resin, fatty acid, alylketene dimer or a alkyl succinic acid preparation.

6. Paper as claimed in claim 1, characterized in that the additive(-s) is an inorganic pigment or complex former which can react with specific groups in lignin and cellulose and form three-dimensional networks, e g oxides or chlorides of zinc, magnesium, phosphates, borates and zirconium.

7. Paper as claimed in claim 1, characterized in that the additive(-s) is of a kind that can undergo a chemical reaction of the type acetylation, silylation and/or crosslinking with bi- or multifunctional groups, such as diisocyantes and triazine derivatives.

8. Paper as claimed in any of the preceding claims, characterized in that the additive(-s) either may be bonded to the fiber surface or be added as a separate addition either to the fiber furnish or to the moist paper web before the impulse drying.

9. Paper as claimed in any of the preceding claims, characterized in that it contains at least 10% by weight, preferably at least 30%> by weight and most preferably at least 50%) by weight, calculated on the dry fiber weight, of a lignin containing high yield pulp, such as mechanical, thermomechanical (TMP) and chemothermomechanical (CTMP) pulp.

10. Paper as claimed in claim 9, characterized in that the high yield pulp is chemothermomechanical pulp (CTMP).

11. Paper as claimed in any of the preceding claims, characterized in that the paper is absorbent soft paper.