Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F5/00—Dryer section of machines for making continuous webs of paper
  • D21F5/02—Drying on cylinders
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F7/00—Other details of machines for making continuous webs of paper
  • D21F7/008—Steam showers
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F9/00—Complete machines for making continuous webs of paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G1/00—Calenders; Smoothing apparatus
  • D21G1/0073—Accessories for calenders
  • D21G1/0093—Web conditioning devices

Definitions

• the present invention relates to a method for producing a fibrous web, in particular a method for producing a decorative paper, a fibrous web, in particular a decorative paper, in particular obtainable according to this method, and the use of the fibrous web as decorative paper.
• decor papers Special papers for surface finishing, e.g. of wood-based materials, are generally referred to as decor papers.
• Known decorative papers are mainly produced from hardwood pulp. Such decorative papers can either be used directly in one color or printed with different designs. These are used, for example, on furniture surfaces, floors and panels.
• Decor papers are usually printed using the gravure printing process. This process typically involves dispensing ink onto the paper from an engraved roller.
• the interplay of paper color and different printing colors means that there are hardly any limits to the variety in decor design.
• the print designs range from wood, stone to fantasy decors.
• Decor papers can be produced in a variety of colors and basis weights. The surface is either satined or machine-smooth. Other important properties are high porosity, wet strength, lightfastness and color consistency.
• Suitable decor papers are characterized by high wet strength and thus ensure smooth running through the impregnation system.
• suitable decor papers have a very high absorbency.
• decorative papers can also be provided with fillers.
• White and color pigments that have a very high lightfastness and are as chemically resistant as possible are suitable here.
• Decorative papers are usually connected to the surfaces, in particular to wood-based panels, with the aid of pressing and laminating systems.
• the sometimes high temperatures and the corresponding pressures in the presses cause the impregnated resin to harden.
• the decorative paper is connected to the wood material.
• this is usually done using hot-melt adhesives.
• the wood-based materials can be given an almost lifelike surface feel.
• Decorative papers as described above can be produced by known methods. These methods generally include the steps of first generating a stock flow which is then fed in succession to at least one headbox, at least one wire section for forming the fibrous web, at least one press section, at least one dryer section with dryer groups and then to a reel. Fibrous webs, in particular decorative papers, which are obtained using such methods, regularly have the features mentioned below. A high dry content after the press section, especially when using a shoe press, influences the paper in such a way that it has less "sticking" to the drying cylinders of the (first) pre-dryer group in the drying section Paper web understood to the hot cylinder surface.
• the cellulose fibers commonly used in papermaking swell when they absorb moisture/water and shrink when they release water.
• the fibrous web in the dryer section shrinks by around 1 - 5% over the entire dewatering and drying process.
• the shrinking of the paper web is hindered by the "sticking" described.
• the paper When the fibrous web then comes into contact with ink and/or resin during application to a surface and/or printing, the paper may resize and "grow". This occurs at roughly the same rate as drying shrinkage Since the paper web enters the drying section drier when using a shoe press, it adheres less to the drying cylinder and thus shrinks more, which leads to higher paper growth later in the further processing process.
• Such paper growth which can also be described as wet stretching, is only suitable to a limited extent, particularly for dimensionally critical decors.
• the present invention addresses this need.
• a method is to be provided with which high-quality fibrous webs, which are characterized, among other things, by high porosity, wet strength, light fastness and color constancy, can be produced.
• the process should be as simple and economical as possible.
• the shrinkage of the paper during the manufacturing process should be as defined as possible, so that the later "growth" of the paper during printing and/or impregnation is as constant and reproducible as possible.
• Weight per unit area of the fibrous web means the weight per unit area of the fibrous web produced according to the method and not the weight per unit area of the fibrous web at the moistening location.
• the feature "partially or completely moistened by means of a water-containing medium” means that the fibrous web is moistened transversely or lengthwise in the running direction of the fibrous web either only in predetermined areas (partially) or over the entire width, so that in particular through these two measures - targeted strong Drying and targeted remoistening of the fibrous web - a wet elongation behavior of the fibrous web according to Mütek of 2.0% to 4.0% transversely to the machine direction and 0.5% to 1.5% longitudinally in the machine direction can be set and this preferably at very high Pulp web speeds of up to 1100 m/min.
• the dry content is preferably set in the range from 46% by weight to 53% by weight and in the case of shoe presses preferably in the range from 52% by weight to 58% by weight.
• the fibrous web can first be smoothed, if necessary, and then fed to a reel in order to enable easier storage and/or easier transport.
• the fibrous web produced in this way is, in particular, a decorative paper.
• the method according to the invention is characterized in particular by the fact that the amount of water/moisture that is applied after or in the dryer section recreates the "sticking" described above, which prevents later stretching on contact with liquid, e.g. during printing or impregnation. reduced.
• the method is kept simple and allows an economically advantageous implementation due to high web speeds.
• the fibrous webs produced in this way are also characterized by high porosity, wet strength, light fastness and color consistency.
• a fibrous material flow is first provided.
• This flow of fibrous material is preferably characterized in that it comprises or consists of cellulose fibers from hardwood or softwood, or a mixture thereof, the fiber length of which is preferably 0.6 mm to 3 mm, in particular in the range from 0.8 mm to 2 mm.
• the fibrous material flow can contain various fillers such as titanium dioxide, kaolin, etc. and/or color pigments and/or other additives and/or various functional chemicals such as wet strength agents or the like and/or production aids such as retention aids and defoamers.
• the usual consistency in the headbox is usually 0.5% by weight to 2% by weight, in particular 0.8% by weight to 1.5% by weight.
• the fibrous material flow is then fed into at least one headbox and into at least one wire section to form a fibrous material web.
• the headbox is usually a kind of nozzle, which is used to apply the flow of fibrous material evenly across the width in quantity and consistency to an endless circulating screen, through which the solids are separated from the water content.
• the solids content at the end of the wire section is preferably 15% by weight to 25% by weight, in particular in the range from 18% by weight to 22% by weight.
• the fibrous web is then fed into at least one press section.
• the fiber mat produced in the wire section is preferably further dewatered.
• it is usually pressed out with the help of felts. This can happen, for example, between two rollers pressed against each other.
• the felts used have the function of transporting the web non-destructively through the press section and absorbing the water that is pressed out in the press nip.
• the pressed fibrous web is then fed into at least one drying section with drying groups.
• the dryer section usually consists mainly of steam-heated cylinders that are brought into contact with the paper web in order to heat it up enough for the water still in the paper web to evaporate to the desired final moisture content.
• These consecutive drying cylinders are preferably combined into so-called drying groups. Steam can be applied to these drying groups in different ways in order to be able to control the drying process.
• a dry content of the fibrous web in the range from about 45% by weight to 60% by weight is set in the press section. From an energetic point of view, the aim is usually to achieve as high a dry content as possible. From a technical point of view, however, there are limitations. Dry contents of 46% by weight to 53% by weight can be achieved in conventional rollers/presses, depending on the stock input.
• the fibrous web is moistened in the drying section.
• a water application of 0.8 g/m 2 to 45 g/m 2 or 1 ml/m 2 to 30 ml/m 2 is preferred.
• Preferred ranges include in particular: 1 ml/m 2 to 15 ml/m 2 , 2 ml/m 2 to 15 ml/m 2 , 1 ml/m 2 to 10 ml/m 2 or 2 ml/m 2 to 6 ml/m 2 m2 .
• the amount of water to be applied and thus also the water content of the medium, based on the basis weight of the fibrous web can be in the range from 2% to 30%, in particular in the range from 4% to 20%, preferably in the range from 6% to 15% can be set.
• the method according to the invention is further preferably characterized in that the press section comprises a laying press, in particular a shoe press.
• the fibrous web After the formation of a fibrous web in the wire section, the fibrous web must be further dewatered.
• the dry content is usually increased by mechanical pressure perpendicular to the fibrous web surface. This happens in the so-called press section.
• the fibrous web is usually treated between rollers with special pressures. The water pressed out of the fibrous web is regularly absorbed by felts that are applied to the corresponding rollers.
• presses of conventional roll-roll or shoe-roll design are preferably used.
• Shoe presses are well known in the papermaking art and typically include a shoe that presses against a rotating backing roll.
• a flexible plastic jacket can float on the shoe, supported by a film of oil.
• the rotating counter-roller is usually covered with a felt in order to drain off the pressed-out water.
• the moisture remaining in the fibrous web must be further removed. This is usually done by evaporation and/or exposure to a vacuum.
• the most common method is contact drying on steam-heated cylinders. The thermal energy is transferred through direct contact from the outer walls of the drying cylinders to the surface of the fibrous web.
• the drying section consists of a large number of drying cylinders, over which the fibrous web is usually alternately brought once with the upper side and once with the lower side.
• single-tier as well as conventional double-tier dryer groups can be used.
• the method according to the invention is also preferably characterized in that the moistening with the water-containing medium takes place by means of nozzle moistening, in particular by atomizing a water-air mixture, in particular via a two-component nozzle.
• a nozzle moistener with two-component nozzles and/or with pneumatic atomizer nozzles is used as the non-contact application unit.
• the throughput of the water-air mixture can preferably be adjusted and/or regulated in sections in the running direction of the fibrous web and/or in the transverse direction. Each nozzle can preferably be adjusted and/or regulated individually.
• the temperature of the water is suitably 20 to 95° C., preferably 40° C. to 90° C., for good atomization.
• the aqueous medium is preferably free of dyes, so that the color of the fibrous web is not changed.
• the method according to the invention is also preferably characterized in that the moistening can be adjusted transversely to the fiber web.
• the fibrous web is moistened again after or in the drying section.
• the method according to the invention is also preferably characterized in that the moistening takes place at the beginning of the first drying group.
• the moistening takes place at a paper web moisture content of between 30% by weight and 50% by weight, preferably at 42 to 52% by weight. Moistening preferably takes place on a vacuum roller.
• the method according to the invention is further preferably characterized in that the moistening takes place in a dry content range of the paper web from 50% by weight to 70%, preferably at 48 to 68% by weight.
• the method according to the invention is also preferably characterized in that the fibrous web is guided at a speed in the range from 500 m/min to 1100 m/min, in particular at 700 m/min to 900 m/min.
• shoe presses enables a high speed of the fibrous web.
• fiber orientation is preferably longitudinal to transverse to affect growth. This should preferably be set by the V-jet via the headbox.
• the V-jet is the speed difference between the stock jet when it exits the headbox and the wire speed.
• the method according to the invention is further preferably characterized in that the fiber headbox takes place via a V-jet in the range from +50 m/min to -50 m/min, preferably at +40 m/min to -40 m/min.
• the method according to the invention is also preferably characterized in that the paper web has a longitudinal/transverse ratio of the breaking force (ISO 1924-2) of 1.0 to 2.2, preferably 1.2 to 2.0
• the method according to the invention is also preferably characterized in that the pulp flow essentially comprises the following types of pulp.
• Long fiber cellulose such as spruce and pine and short fiber cellulose such as birch, beech, aspen, oak, eucalyptus or mixtures thereof.
• eucalyptus pulp from the species Grandis, Urograndis and Globulus or mixtures thereof is used.
• the method according to the invention is further preferably characterized in that the fibrous material flow is ground to a Schopper degree of beating of 16° to 40°. This can be done together with the filler or exclusively with the pulp.
• the exclusively pure pulp grinding has the advantage that the refiner fillings have a significantly longer service life.
• the method according to the invention is also preferably characterized in that the fibrous material flow comprises cellulose that is certified according to FSC and PFSC in particular.
• the present invention also relates to a fibrous web produced by the method described above.
• the present invention also relates to a decorative paper produced by the method described above.
• the present invention also relates to a fibrous web, in particular a decorative paper, preferably obtainable by the method according to the invention, which has at least one of the following properties.
• a fibrous web in particular a decorative paper, preferably obtainable by the method according to the invention, which has at least one of the following properties.
• a wet elongation behavior according to Mütek from 2.0 to 4.0%, in particular from 2.2% to 3.3% transverse to the machine direction and 0.5 to 1.5%, in particular from 0.7 to 1.3 % lengthways in the machine direction.
• the wet expansion behavior according to Mütek is determined using a Mütek measuring device WSD 02 (Emtec).
• the measurement parameters include a transverse pull of 4N/60mm, a longitudinal pull of 1N/60mm after 25 seconds of one-sided irrigation.
• the measurement result averaged across from the measurement locations 10 cm from the edge, from the middle and from the middle (middle-middle) of the outer and middle measurement.
• FS, TS and center-center stand for driver side, drive side and center-center as the position between the center of the track and the FS.
• a basis weight preferably from 40 g/m 2 to 150 g/m 2 , in particular from 45 to 90 g/m 2 (ISO 536).
• a longitudinal/transverse ratio of the breaking force MD/breaking force CD (ISO 1924-2) of 1.0 to 2.2, in particular of 1.2 to 2.0.
• a width preferably up to 300 cm or up to 227 cm. All of the properties mentioned above are also explicitly disclosed here, as well as all possible combinations of the properties mentioned above.
• the fibrous web according to the invention in particular the decorative paper, is preferably characterized in that it is available in the colors white, cream, beige, brown, gray and/or black.
• the present invention also relates to the use of the fibrous web as decorative paper, in particular for interior design and/or in the furniture industry, preferably for the surface finishing of wood-based materials such as coated boards, tables, floors, kitchen worktops, window sills and/or for outdoor applications such as facades.
• FIG. 1 shows a schematic representation of a possible device which is suitable for carrying out the method according to the invention or for producing the fibrous web according to the invention.
• a slalom guide of the fibrous web over drying cylinders and vacuum rollers is shown here. This is particularly advantageous because the nozzle moistener can be arranged in the lower area of the vacuum rollers, especially between the "3 and 9 o'clock position". This means that excess water can simply drip away without touching the fibrous web.
• the nozzle moistener can also be positioned on vacuum roller 1 or 3.
• a single-row dryer section is particularly suitable for this, as there is free access to the paper web and the water-air mixture can be sucked into the paper web by the nozzle moistener with the help of the vacuum rollers.
• a fibrous web with a basis weight of 72 g/m 2 was produced for use as decorative paper with a finished roll width of 206 cm, which had a Mütek growth of 2.25% across and 0.65% lengthwise (determined as above described) with a Gurley porosity of 14 s (ISO 5636-5).
• the longitudinal/transverse ratio of the breaking strength (ISO 1924-2) was 1.25.
• the fibrous web showed an extremely low real growth of the fibrous web, which was always in the range of 0.8% to 1.8% transverse to the machine direction and in the range of 0.2% to 1.2% lengthways in the machine direction.

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• 2021
  • 2021-02-15 DE DE102021103519.8A patent/DE102021103519A1/de active Pending
• 2022
  • 2022-02-14 WO PCT/EP2022/053545 patent/WO2022171878A1/de active Application Filing
  • 2022-02-14 CN CN202280014926.9A patent/CN116848300A/zh active Pending
  • 2022-02-14 BR BR112023016292A patent/BR112023016292A8/pt unknown
  • 2022-02-14 EP EP22707052.1A patent/EP4291709A1/de active Pending
  • 2022-02-14 CA CA3208542A patent/CA3208542A1/en active Pending

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