Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H5/00—Special paper or cardboard not otherwise provided for
  • D21H5/26—Special paper or cardboard manufactured by dry method; Apparatus or processes for forming webs by dry method from mainly short-fibre or particle material, e.g. paper pulp
  • D21H5/265—Treatment of the formed web
  • D21H5/2657—Consolidation
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/30—Multi-ply

Definitions

• This invention relates to a method of manufacturing a fibrous product comprising the steps of forming a multilayered fi ⁇ brous product consisting of at least two layers on the top surface of a continuously moving gas-permeable forming surface, maintaining a vacuum at the underside of said gas-permeable forming surface and successively supplying streams of a fibre-containing gas to the top surface of said forming surface.
• a wet process is a process in. which the starting material for the manufacture of a fibre layer is a slurry of fibres in water and in which said slurry is dewatered on a wire cloth and is subsequently dried.
• the fibrous product composed of two or more layers may then be crepped or embossed to make the layers adhere to one ano ⁇ ther. It is essential that the adherence between the layers does not become excessive because the product then becomes too rigid . On the other hand, it is also essential that the adherence is suffi ⁇ ciently high to prevent the product from delam ⁇ nating during use.
• the product may be rolled as is the case in the manufacture of toilet paper and rolls of kitchen paper or it may be cut into sheets which may then be suitably folded .
• the fibrous layers which are used in the production of the above mentioned multilayered fibrous products are ordinarily very thin . Thus, their weight may be 10-15 g/m . Due to low thickness and strength of these layers the manufacture of such layers and their removal from the wire cloth on which they are formed present serious problems at the production rates which ordinarily are used in the production of wet paper, viz. production rates of the order of
• the removal of the thin fibrous layers from the wire cloth is difficult to perform and in practice it can only be effected by contacting the wire cloth with the thin moist fibrous layer located thereon with a Yan kee cylinder which is a large intern- ally heated cylinder. As a result of such contact the moist fibrous layer is transferred from the wire cloth to the cylinder surface. However, during this operation the fibrous layer is dried and it may adhere to the cylinder surface.
• the removal of the fibrous layer from the cylinder surface is effected with a scraper, a socalled doctor's knife, or a crepping knife.
• Factories for the production of wet-laid fibrous products are highly energy-consuming which is mainly due to the fact that large amounts of water have to be used to form the fibre slurries used as a starting material and that this water subsequently has to be removed during the dewater ⁇ ng and drying steps. Contrary thereto the energy consumption in. a factory in which fibrous pro ⁇ ducts are manufactured by a dry process is relative small . There- fore, there is a need for utilizing the dry process for the manufac ⁇ ture of a multilayered fibrous product.
• the method of the invention which method is characterized in effecting at least after the formation of the first fibrous layer and before the formation of the second layer a consolidation of the fibrous layer located on the forming surface such that at least the major proportion of the fibres of said layer are oriented in a plane parallel to the forming surface.
• a consolidation of the fibrous layer located on the forming surface such that at least the major proportion of the fibres of said layer are oriented in a plane parallel to the forming surface.
• the integration between the first layer and a further layer formed on top of the first layer can be reduced to a desired level and Is thus adjustable so that the two layers may be displaced relatively to one another.
• the products prepared by the method of the invention have properties which are equal to or better than those of the conventional products consisting of wet formed fibrous layers.
• a multilayered fibrous product can be prepared by the method of the invention without removing the indi-
• the strength and in particular tear strength of the fibrous product is increased.
• Such an increase is generally ob ⁇ tained but is particularly pronounced in cases where moisture and/or binder is added to the fibrous layer prior to the consolidation .
• a low degree of adherence between the thin fibrous layers is normally desired in soft light fibrous products, e. g . products
• the consolidation of the fibrous layer or layers presents significant advantages in cases where It is desired to increase the strength of the layered fibrous product by the addi ⁇ tion of binder.
• the binder is ordinarily a wet strength binder, e. g . a binder of the latex type.
• the fibrous product has to be removed from the wire on which it has been formed and then turned around and transferred to another wire.
• complicated driers are required to effect the drying of the binder-containing fibrous products .
• binders of the latex type are used In fibrous products which are used for polishing purposes, e. g. to polish windows and mirrors, the problem may arise that the surfaces of the articles to be polished may be smeared by binder if the binder Is brought into direct contact with such surfaces .
• This problem can be eliminated by preparing the fibrous product by the method of the invention, viz. by supplying wet strength binder, such as a latex binder, to the fibrous layer only which is located within the product, i. e. which is protected by outer layers . In this case another type of binder may be supplied to these outer layers.
• the wet strength binder may be eliminated from the central layer and the consolidation of the outer layers may be increased by using a binder and/or by heating and moistening these layers. I n the latter case It is possible to form a particularly voluminous and soft product. The softness of such a product Is primarily due to the fact that each outer layer can be displaced relative to the central layer.
• a product of the above mentioned type can also be manu ⁇ factured by preparing the two layers, I . e. a consolidated outer layer and on top of that a fibrous layer which optionally contains a wet strength binder on one forming wire and another consolidated outer layer on a second forming wire and subsequently combining the two layers.
• the fibrous product thus prepared comprises two consolidated outer layers and a non-consolidated central layer.
• the hydrophobic character of the latex can be coun ⁇ teracted by introducing into the fibrous layer a surfactant.
• surfactants sometimes have a harmful effect on the remaining properties of the latex.
• the undesired effect on the liquid absorption rate originating from the latex may be significantly reduced because the outer layers will exhibit the desired high liquid absorption rate.
• a latex binder is to be supplied to an interior layer only, it is possible to use emulsions having significantly higher dry matter contents than the emulsions used in the prior art methods. In such prior art methods the latex .emulsions used ordinarily have a dry matter content of 5-15% by weight and preferably about 10% by weight.
• emul ⁇ sions having a dry matter content of up to about 40% by weight.
• the use of such highly concentrated emulsions significantly reduces the energy consumption during the drying of such products.
• the dry matter content of latex In the final product or in the layer containing latex may be from 5 to 15% in a product prepared by the method of the invention.
• the application of the latex binder e. g . in the form of an emulsion in water, may be followed by a step in which hot air is drawn through the fibrous material on the forming wire in order to evaporate and remove water and to cure the binder.
• a step in which hot air is drawn through the fibrous material on the forming wire in order to evaporate and remove water and to cure the binder.
• the final multilayered product may be heat-treated either while it is still located on the forming wire or after it has been removed from said wire. In both cases a partial transfer of water from the moist latex-containing central layer to the surface layer takes place and the adherence between said layers will be Increased.
• the stream of air used for curing the binder preferably has a temperature of between 150 and 250°C, e.g. about 200°C.
• the curing of the binder can also be effected by means of light having a wave length which has been selected dependent of the properties of a surface layer, if any, containing no latex binder.
• a latex binder can be used to provide a voluminous and highly absorbing product, e.g. a fibrous layer having a weight of
• the latex binder may be used to bond the fibres to one another in an open structure or In other words to keep the fibres spaced from one another.
• binders than latex binders are also suitable. Examp ⁇ les of other binders which are suitable in the method of the Invention are modified starches and polyvinyl alcohols and polyesters. The latter binders are suitable in the form of fibres, In the form of a powder or In liquid form.
• the moisture content of the fibrous layer prior to the heat embossing is preferably between 6 and 15% by weight and the embos ⁇ sing temperature used is preferably above 120°C .
• the embossing rollers used may have a temperature of up to 200 C provided the embossing rate is sufficiently high .
• the fibrous product is embossed in connection with or subsequent to the consolidation, such embossing is preferably effected in a manner so that the strongly embossed zones constitute from 10 to 40% of the total surface area of the product, and so that the remaining zones have pillow shape.
• Soft fibrous products having any given number of layers and the composition and thickness of each layer can be varied by the method of the invention . It is also possible to prepare products in which the thickness of the layers varies from layer to layer. In very light products, i. e. fibrous products having a weight of from 2 30 to 45 g/m , the fibrous layers ordinarily are about the same
• lighter e. g. may have a weight of 40-60 g/m in heavier fibrous products comprising three or more layers.
• composition of the layers can be varied, both as far as the fibre type as well as the properties of a given fibre type Is concerned. Furthermore, the additives contained in said layers including binder and/or filler may also be varied.
• powdered binders e. g . starch, thermoplastic or thermocuring syn- thetic binders and to introduce such binders together with fibres ⁇ which are deposited on the forming surface.
• powdered binders e. g . starch, thermoplastic or thermocuring syn- thetic binders and to introduce such binders together with fibres ⁇ which are deposited on the forming surface.
• the cellulosic fibrous starting material can be mixed with varying amounts of other types of fibres, e.g. synthetic organic fibres . When only one type of fibres is used, it is possible to vary the relative amounts of short and long fibres.
• the number of layers is determined by the number of fibre distributors mounted along the forming surface, for example in the shape of an endless forming wire, and the thickness of the layers deposited from each of these fibre distributors is determined by the construction and operation of these fibre distributors .
• fibre distributors of the type which is disclosed in the specification of British patent No. 1 .207.556.
• This type of fibre distributors consists of a housing having a plane, perforated bottom and comprising two or more stirrers having impellers rotating about axes which are perpendicular to the perforated bottom.
• a particularly suitable embodiment of such a fibre distribu ⁇ tor Is disclosed In British patent specification No. 2.008.038.
• This fibre distributor comprises two or more rows of stirrers provided In the same housing and extending perpendicularly to the direction of movement of a forming wire provided below said housing .
• the consolida ⁇ tion of the fibrous layer Is preferably effected by a set of rollers, of which one roller is provided below and the second roller above the forming wire in such a manner that the fibrous layer deposited thereon is pressed against the forming wire.
• the pattern of the forming wire is embossed Into the underside of the fibrous layer.
• the fibrous layer Is moistened and the consoli ⁇ dation is effected with a heated roller, the provision of such an embossed pattern will Increase the strength of the fibrous product.
• the fibrous layer passing from one fibre distributor to the following one can be slightly raised from said forming wire and thus caused to change position relative to said wire.
• the fibrous product can be raised from said wire, e. g . by directing a stream of air originating from an air slot, against the underside of the fibrous layer.
• the fibrous layer after formation of a further layer on top of it Is passed Into the nip of a pair of rollers mounted after the second fibre distributor, the fibrous layer is in another position relative to the forming wire, and the pattern of said forming wire is consequently embossed into the underside of the fibrous layer in zones which are displaced relative to the corresponding zones of the embossed pattern..already provided in the fibrous layer.
• the above mentioned raising and displacement of the fibrous layer can be repeated when the fibrous layer has passed the second fibre distributor and further fibre distributors .
• the underside of the fibrous product With several overlapping and partially displaced embossed patterns, the number of zones in which the product has been strongly consolidated is increased and consequently, the strength of the fibrous product is also increased . Additionally, the opacity of the product is increas ⁇ ed.
• Such an increased opacity can also be obtained by introdu ⁇ cing into an internal layer, e. g . the central layer of a fibrous pro- duct, a powdered filler, such as kaolin, chalk, talc, titanium di ⁇ oxide and zinc oxide or a pigment.
• a powdered filler such as kaolin, chalk, talc, titanium di ⁇ oxide and zinc oxide or a pigment.
• Fillers e. g . kaolin, in amounts of up to 50% of the weight of the fibrous product can be used but when a filler is used , the amount ordinarily is from 5 to 20% by weight.
• a pigment can be introduced into a central layer. If a three-layered fibrous product comprising a colour ⁇ ed central layer is embossed , a coloured embossed pattern having a high decorative effect can be provided by embossing . By combining a coloured central layer with surface layers
• the provision of the above mentioned surface decorations can be effected while the fibrous product is still present on the forming wire.
• one or more layers of the multilayered product may consist of another type of fibres than the remaining layers.
• one or more internal layers are composed of relatively cheap fibres, such as waste fibres and re-used fibres .
• the fibrous layer is smoothened out by the method of the invention and consequently the final pro ⁇ ducts obtained are more uniform than the products obtained by the wet-forming method and products prepared by the conventional dry -forming methods.
• Fibrous products prepared by the conventional wet process normally have different strengths in the machine and cross-machine directions.
• the fibres of the fibre slurry deposited on the foraminous wire tend to be oriented predominantly in the machine direction instead of being oriented at random. Therefore, It is diffi ⁇ cult to manufacture wet-laid fibrous products having the same strength in all directions.
• Fibrous products having an increased strength in the machine direction (or in another desired direction) can be manufac ⁇ tured by a special embodiment of the process of the Invention.
• a thin fibre layer deposited on the forming surface is subjected to the influence of forces which are acting in the machine direction or any other direction, it is possible to impart to the fibres
• the water is preferably sprayed onto the fibre layer under an acute angle relative to the surface of the fibre layer, e.g. in the machine direction so as to rearrange the fibres and to orient them predominantly in said direction.
• the water is preferably spray ⁇ ed onto the fibre layer when said layer is still located on the forming wire and is under the influence of a vacuum maintained in the suc ⁇ tion box.
• the angle under which the water is sprayed onto the fibre layer is preferably between 10° and 30°. The effect described may be improved by directing flows of water and compressed air against the fibre layer.
• the above mentioned embodiment of the process of the in ⁇ vention also makes it possible to Increase the strength of the fibrous multilayer sheets in the plane of said sheets and to effect a corres ⁇ ponding decrease of the strength in a direction perpendicular there ⁇ to.
• the middle layer(s) is
• the moistening may also be effected when the last layer or layers have been formed, and the heat consolidation is preferably effected at a pressure exceeding 20-50 kg per cm.
• the bottom layer or layers should be treated In a similar manner with water and should be consolidated and optimally subjected to a conventional finishing treatment.
• This balancing consolidation may be effected on a transfer wire which is a wire to which the fibrous layer Is transferred after its formation on the forming wire.
• the transfer wire may have a lower run and a suction box located above said lower run .
• the fibrous layer is introduced into the zone below said lower run, it is sucked against the transfer wire and is maintained in contact with said wire until the vacuum is broken .
• the under- side of the fibrous layer may be moistened and subsequently the product may be consolidated.
• the layers located at the surfaces of the multilayered sheets should preferably be strongly consolidated so as to produce a beam effect and to provide a strong and smooth sur ⁇ face.
• the intermediate layer or layers should be consolidated to a lower degree thus permitting the product to be folded or bent with ⁇ out generating the socalled "biscuit effect" .
• the consolidation and the surface struc- ture may be improved by adding to the surface layer pigments and/or binders either in the form of a powder, a dispersion, or an emulsion .
• the binders may be added to the water for moistening the fibrous layers or in powder form to the' fibres before or during their deposition on the forming surface.

Landscapes

• Paper (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8129424

Family Applications (1)

Country Status (3)

Family Cites Families (4)

• 1981
  • 1981-09-10 DK DK402781A patent/DK402781A/da unknown
• 1982
  • 1982-09-10 WO PCT/DK1982/000081 patent/WO1983000888A1/en unknown
  • 1982-09-10 EP EP19820902719 patent/EP0087453A1/de not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events