IE48088B1 - Methods of preparing dry-laid fibrous products - Google Patents

Abstract

The prepn. of fibrous products by dry deposition, comprises a gaseous medium contg. the suspended fibrous material across a gas-permeable shaping surface so as to form a fibrous sheet thereon. A binder is incorporated in the sheet by contacting the binder with the fibrous material before or during the formation of the fibrous sheet on the shaping surface. Used for the prodn. of fibrous products where the ratio between the fibres and the binder varies between large limits. The fibrous products may comprise two or three fibrous sheets formed separately by separate fibre distributors. The sheet may be compressed to form sanitary towels and other body care products.

Description

This invention relates to a method of preparing drylaid fibrous products comprising the steps of passing a gaseous medium containing a suspended fibrous material through a gas permeable forming surface so as to form a fibrous layer thereon, and incorporating a binder in said fibrous layer. A prior art method of this is disclosed in U.K. Patent No. 1.518.284.

In a prior art method of the above mentioned type the binder is incorporated in the fibrous layer by spraying the fibrous layer with a binder or a binder solution, e.g. an aqueous solution of a binder. Subsequently, the solvent, if any, is removed and the binder is caused to set or cure.

By spraying the binder onto the fibrous layer it is difficult to obtain a predetermined distribution of binder within the fibrous layer. Thus, it may be desirable to provide a relatively high concentration of binder in the middle of the fibrous layer and relatively low binder concentrations at the surfaces thereof. In other cases it may be desirable to provide a relatively high concentration of binder at one surface and a relatively low concentration of binder in the remaining portions of the fibrous layer. - 3 Embodiments of the invention seek to obtain a uniform distribution of binder within the fibrous layer so as to reduce or eliminate the tendency of delamination.

Embodiments of the invention further seek to obtain dense and specially shaped products.

According to the invention there is provided a method of preparing a dry-laid cellulosic fibrous web, wherein a gaseous medium containing a suspended cellulosic fibrous material is supplied to a distributor means, passed through rotating stirring impellers, passed through a perforated distributor means bottom wall, passed through a foraminous forming surface so as to form a fibrous layer thereon and finally into a suction box located below said foraminous forming surface and said perforated distributor means bottom wall, and wherein a binder in powder form is supplied to the gaseous median containing a suspended cellulosic fibrous material before said gaseous median is supplied to said distributor means.

The method of the invention is particularly suitable for use in the manufacture of fibrous products composed of two or more fibrous layers which are formed separately by separate fibre distributors. Thus, by varying the amount and/or, optionally the type of binder used, products can be obtained by such a multideposition technique wherein the binder concentration varies within a given cross section of the product. However, the method of the invention can also be used in the production of products, wherein the binder concentration varies in the machine and/or cross machine direction of the product.

By supplying the binder to the fibrous material before the formation of the fibrous layer, the binder becomes uniformly distributed in said layer and, consequently, the tendency of delamination within such layer is eliminated or reduced.

A fibre distributor which is particularly suitable for use in the method of the invention is described in U.K.

Patent Nos. 1.207.556 and 1.518.284.

The problems caused by heat generation may also be solved by using two defibrators arranged in series and by introducing the binder into the second defibrator and operating said defibrator in such a manner that only a reduced defibration and consequently heat generation take place therein.

In some cases, a separate heat treatment is superfluous because the heat generated in the defibrator may be sufficient to increase the temperature to such an extent that most volatile substances, if any, are removed by evaporation.

The binder may be any substance or mixture of substances capable of binding the fibres together or to a reinforcing net, if any.

Thus, thermoplastic as well as thermocuring organic binders of the polymer type are suitable. Examples of such binders are polyolefines, melamin urea and phenolic resins, and lattices. Another type of organic binders are starch binders and binders based on modified starch, i.e. partially hydrolyzed and/or chemically treated starch. By subjecting starch to such treatments, it is made soluble and in the converted form it is suitable for use in a binder solution.

Also inorganic binders, such as water glass, are suitable for use in the method of the invention.

Various waste materials, e.g. powdered polyethylene, may be used as binders. Such waste materials are available in large amounts in the industry and as a waste product from households.

The cellulosic fibres used may be virgin fibres, i.e. fibres prepared from fresh cellulosic pulp, or waste fibres, i.e. fibres prepared from cellulose-containing waste materials, such as paper. Such materials inpart to the fihrous product a high flexibility without significantly reducing the hydroscopicity of the product. Therefore, such materials are useful in the production of building materials for indoor as well as outdoor use and packaging materials. Apart from natural vegetable fibres, such as cellulosic fibres, synthetic organic fibres having a relatively high melting or softening point may be used in the method of the invention. The synthetic organic fibres used should preferably have a melting or softening point which is higher than that of the binder when using thermoplastic binders.

Inorganic fibres, such as mineral fibres, may be used in admixture with organic fibres. Examples of such mineral fibres are rockwool fibres, glass fibres, fibres of crystallizable glass, fibres of devitrified glass, and slag wool fibres.

The costs of producing the product of the invention may be reduced by introducing therein a mineral powder in an amount of up to about 70 per cent by weight based on the total weight of the fibrous product. For instance devitrified glass powder having particle sizes of up to 500 pm may be used as an additive.

Examples of other mineral additives are kaolin, dolomite, glass, chalk etc.

The addition of a mineral powder to the mixture of 15 fibres and binder is particularly useful if it is desired to produce products having a long life time.In such cases, the product may consist of about 33 per cent by weight of fibres, preferably cellulosic fibres, about 33 per cent by weight of a thermoplastic or thermocuring binder having a particle size of below 100 pm and preferably 10-20 pm, and about 33% of mineral powder having a particle size of below 100 pm and preferably below 50 Pm. However, also relatively smaller amounts of binder, e.g. about 15 per cent by weight, may be used.

When used in the method of the invention, the mineral powder is preferably introduced into the fibre distributor together with the stream of air containing suspended fibres. However, it may also be introduced into the defibrator together with the pulp. Furthermore, the mineral pow30 der may be introduced directly in the zone between the fibre distributor and the forming surface so as to mix with the fibres suspension passing from the fibre distributor towards the forming surface.

The binder and the mineral powder are preferably in35 timately mixed so as to obtain a binder coating on the mineral particles. When the mineral particles are coated with the binder, the subsequent heat treatment will cause the particles to form a solid skeleton. The particle size of the mineral powder is preferably between 50 and 100 um.

When the mixing process is essentially completed, a small amount of solvent may be added in order to improve the coating of the mineral particles.

It may also be desirable to add other auxiliary agents, e.g. water repelling agents, to reduce the water absorption of the fibrous product when said product is to be used as a packaging material or a building material.

Such auxiliary agents are well known, and examples thereof are silicones, water repelling oils, waxes, asphalt, etc. By incorporating into the fibrous layer asphalt in an amount of 1-2% by weight, a product is obtained which is suitable for use as a roof covering element.

The addition of water repelling agents may be effected after the formation of the fibrous layer and as part of the further treatment of the product formed. Ordinarily, it is preferred to add such agents during the last steps of the method of preparing such a product.

The water absorption of a product prepared by the method of the invention can be reduced in a manner which is well known per se by subjecting said product to a finishing treatment so as to close the pores of the material. In this manner a mechanical barrier against water absorption is provided.

However, a porous structure is not necessarily a disadvantageous property of a product for use as a building material. Thus, it is well known that in order to provide a pleasant indoor climate, building materials should preferably present some degree of porosity and should be permeable for- air and/or moisture.

Such a porous product may be prepared by using a mineral powder, e.g. powder of devitrified glass containing no very fine particles. Such a product may consist of particles which preferably have a particle size of 100 um and above.

When preparing a fibrous product from cellulose pulp, the starting material ordinarily contains about 10% of moisture.

During the defibration and the fibre distribution, frictional heat is generated, and the moisture content of the fibrous material is reduced to 2-3% by weight.

Therefore, it may be preferable to add moisture during the defibration or during the formation of the fibrous layer. The addition of moisture may be effected by adjusting the moisture content in the room wherein the defibration and/or fibre distribution takes place at a relatively high value, e.g. at a relative humidity of 5565%.

When using relatively high concentrations of binder, it is particularly easy to add moisture. Thus, in such cases the moisture content of the fibrous material may be increased to 30%. If the method of the invention is to be carried out at such a high moisture content, the adhesion of the powdered binder and/or filler to the surfaces of the fibres is increased, and consequently an increased amount of binder and/or filler may be applied to the surfaces of the individual fibres. By coating the fibres with large amounts of binder in the manner described above, a product containing up to about 75% of binder and containing fibres and optionally filler uniformly distributed therein can be obtained. When heating such a product to an elevated temperature, a strongly coherent product is obtained.

The method of the invention permits the production of fibrous products in which ratio of fibres to binder varies within wide ranges.

Thus, by using two or more fibre distributors to form a fibrous layer composed of two or more individual layers, fibrous products can be obtained having a binder concentration varying within a cross section through the product. Thus, by introducing a relatively large amount of binder in one of the above mentioned layers, a product is formed which at one surface contains a relative high concentration of binder, whereas the binder concentration at the other surface is relatively low. Consequently, the said other surface is more porous than the first surface.

Xt is also possible by using three or more fibre distributors to prepare a sheet material having surface layers of a relatively loose structure and a dense core layer.

Such a product can be obtained either by introducing a relatively large amount of binder into the fibre distributor used for the formation of the intermediate layer of the product or by rolling or compressing the fibrous layer formed by said fibre distributor at a temperature above the melting or softening point of the binder. During said compression the binder is caused to flow and forms a dense layer of fibres.

The method of the invention is particularly suitable for the production of sheet materials and more specifically a fibrous layer formed on an essentially flat forming surface. It should be mentioned, however, that a forming surface, such as a wire having a non-planar surface, e.g. comprising depressions and projections can also be used.

A similar pattern may be provided in the surface of a fibrous product by passing the fibrous product through a set of embossing rollers.

As will appear from the following description, the method of the invention is particularly useful for the production of containers. The term container is to be understood as any kind of articles which are capable of containing solid materials or liquids. Such containers can be produced by using a forming surface having projections or dispersions of a shape corresponding to that of the container to be produced.

The fibrous products prepared by the method of the invention may be composed of fibres which are fixed relative to one another in a relatively loose structure by the binder.

Such products may be converted by compression or embossing into a wide range of products having properties which vary from one part of a cross section to another or vary from one zone to another in the machine or cross machine direction of the product.

Products in which the properties vary from one part of the cross section to another are preferably produced by using different binder concentrations when forming the individual layers forming said fibrous product or by using different compression or embossing conditions.

When using the same compression or embossing conditions, the highest density of the compressed or embossed product is obtained in such zones wherein the binder concentration is highest.

On the other hand, by using the same binder concentration, the highest density is obtained in zones wherein the product has been subjected to the most severe compression or embossing, i.e. the most severe pressure and temperature conditions. As a result of the relatively loose structure of the fibrous product defined above, even a flat product can be converted into a hollow article when suitably compressed or embossed.

A fibrous material of the above mentioned type and consisting of cellulosic fibres and a polyethylene binder may be subjected to compression at a temperature of about 110°C. The material thus obtained can be used as a starting material for a number of products, e.g. diapers, sanitary napkins and other products for the care of the human body.

In order to prevent liquids, such as blood, from penetrating such a material, anticoagulating compositions may be introduced into said material. It is also possible to apply to one of the surfaces of such a layer a polyethylene membrane or another moisture barrier.

The polyethylene membrane may be provided on the surface of such a product by introducing large amounts of binder into the fibrous layer which is to form the surface layer of the fibrous product.

When using such a fibrous product for the care of the body, the fibrous product is arranged so that the membrane does not contact the skin.

In order to prevent the cellulosic fibres from being disengaged from the fibrous product during the use thereof, the surface of the product which is to contact the human body is preferably coated with a layer of non-woven textile material, e.g. a layer which is commercially available under the trade name Cerex. This commercially available product is a spun-bonded material.

A special advantage obtained by using a material of the above mentioned type for the manufacture of diapers and other products for the care of the human body, e.g. sanitary napkins, is that the fibres are fixed relative to one another in an open structure having a large volume which allows considerable amounts of liquid to be absorbed, not only within the fibres, but also in the interstices between the fibres.

When fibres are fixed relative to one another in an open structure, the product does not fluff even when the binder concentration is small. Therefore, such products do not have to be packed or rolled into an envelope, e.g. a separately produced non-woven material, as is the case with prior art products of a similar kind.

However, it is ordinarily preferable to apply to one surface sheet material of the invention, viz. the surface which is to contact the skin, a Cerex layer.

However, even without such a protecting layer, a fibrous product according to the invention may be in direct contact with the skin without causing irritation of the skin.

By using the fibrous product according to the invention, a serious drawback of the prior art diapers and sanitary napkins may be eliminated. Due to the manner in which such prior art products are prepared it is difficult to prepare products having an anatomic correct shape. Since the fibrous products of the invention are capable 8 0 8 8 of being converted into products of different shapes, they are suitable for use in the production of diapers and sanitary napkins having a shape which is adjusted to the portion of the human body with which they are to be in contact.

In a product according to the invention the fibres can be fixed relative to one another throughout the product. Therefore, when used for the care of the human body they remain in the desired position during such use, and they maintain their softness. Therefore, such sanitary napkins and diapers do not require the use of adhesive tapes or other fastening means.

By varying binder content in the machine or cross machine directions of fibrous products of the invention, sanitary napkins and diapers can be prepared in which the binder concentration is high in the edge zones.

A fibrous product containing a latex binder in a relatively high concentration at one surface of the product is particularly suitable for the production of carpets and carpet underlays.

Fibrous products having a shape similar to that of quilted products can be prepared by heating fibrous products of the invention to an elevated temperature within narrow zones forming a linear pattern so as to bond the opposite surfaces of the product together within said zones .

A product of this type affords an excellent heat insulation and is a soft and pleasant product having excellent strength properties.

Since such products can be prepared in a relatively simple manner, they are also suitable as disposable products, e.g. for camping purposes, military purposes, for use in hospitals and for nursing purposes.

If it is desired to make such products more stable, a layer of a spun-bonded material, such as the above mentioned Cerex product, may be incorporated therein.

Fibrous products prepared by the above mentioned method can be converted into valuable semi-manufactured products by subjecting the fibrous layer formed on the forming surface to a compression to increase the density of the product.

Such compression is preferably effected at temperatures close to the softening temperature of the binders used.

A semi-manufactured product of the above mentioned type is suitable for the manufacture of compression moulded packing materials, cups, trays, containers etc.

The fibrous product should preferably be only slight- i ly compressed during the initial compression, because a slightly compressed fibrous product is more suitable for a subsequent strong deformation than a more dense fibrous product. It is preferable to effect the initial compression of the fibrous material and the final shaping thereof immediately following the formation of the fibrous layer on the forming surface, e.g. by using heated rollers and by reducing the thickness from about 2 cm to 2-3 mm or below.

In the production of ordinary plates and soup plates, the fibrous product should preferably be reduced to 0.6-0.7 mm dependent on the binder concentration and the conditions under which the plates are to be used.

The production rate may be increased by preheating the material to a temperature at which the binder is soft.

The tools for compressing semi-manufactured fibrous products are preferably heated to a temperature of 150— 200°C, and the pressure exerted is preferably between 1 2 and 10 kg per cm depending on the desired strength of the final product. When using fibrous products which have been heated to a temperature above the softening point of the binder, e.g. to a temperature of 150°C, it is preferable to use cold tools for the moulding operation.

Plates, cups, trays, etc. which are to be subjected to high temperatures, are preferably manufactured by compressing fibrous products under temperature conditions 8 0 8 8 producing a maximum strength.

The moulded products are preferably introduced into an oven, e.g. a tunnel oven, at a temperature of e.g. 150°C for a period of about 5 minutes.

Products having a high binder concentration may be considered as a fibre reinforced plastics material. Such products have a high ductility and flexibility and a satisfactory tear strength and are particularly suitable for the production of the disposable packing materials, cups, plates, book jackets, and printing materials.

Furthermore, such fibrous products are more susceptible to printing inks than plastics materials, because the fibres make the products opaque and improve the adherence of printing inks.

A fibre reinforced plastics material can be bent many times without breaking and, therefore, such products are suitable for the manufacture of containers with integral lids.

A fibre reinforced product based on cellulosic fib20 res is decomposable when stored in nature. Fibre reinforced products containing about 50 per cent by weight of cellulosic fibres and 50 per cent by weight of binder in the form of an urea binder or a mixture of an urea and melamin binder have sufficiently low water absorption pro25 perties to be suitable for use as packaging materials for e.g. food products. On the other hand, such products are decomposed more rapidly than the prior art plastics materials if they are under the influence of moisture for longer periods of time, e.g. by being stored in nature.

Such products present the further advantage that they are more stable when exposed to sunlight or ultraviolet light than many plastics materials.

It is well known to introduce into a plastics mate35 rial compositions which when exposed to ultraviolet light cause the plastics material to be decomposed.

Articles prepared from such plastics materials are not ’ 0 88 fully satisfactory, because they may undergo such changes that they do no longer perform satisfactorily when they reach the consumers.

Plastics materials reinforced with cellulosic fibres and containing the above mentioned compositions in the binder are decomposed in an ideal manner. Thus, the fibres decompose only after having absorbed moisture and the decomposition of the binder is accelerated only in the presence of moisture in the fibres. If a partial decomposition of the binder is initiated under the influence of ultraviolet light, the fibres will still impart to the material good strength properties, and a final decomposition does not take place until the product is subjected to the influence of both ultraviolet light and moisture. Packaging materials prepared from the fibrous products based on cellulosic fibres preferably contain well known compositions for decomposing plastics materials.

As mentioned above the fibrous products according to the invention are preferably prepared in the form of sheets or webs. However, they may also have a shape corresponding to the shape of a non-planar forming surface. If it is desired to convert a sheet or web material into a product having a three-dimensional structure, it is desirable to effect a pre-moulding by using a forming surface having a configuration such that the shape of the initial fibrous product formed on said forming surface does not differ significantly from the shape of the final product.

Thus, the product according to the invention may comprise projections and/or depressions corresponding to the projections and/or depressions desired in the final product.

The product according to the invention is suitable for the production of packings for frozen products, e.g. food, eggs, chocolate or meat which are to be maintained at a low temperature, or for heated products which are to be maintained in a heated condition during transportation.

In a method of preparing such products it is preferable to combine the dry moulding technique with a vacuum moulding technique.

A vacuum moulding is a method in which a thin layer of a thermoplastic material in heated condition and at a temperature close to the softening point of said material is caused to deform and assume a desired shape.

According to the invention this vacuum moulding technique may be used to provide a packing comprising different compartments for the storage of various products, such as foods and chocolate. The vacuum moulding technique can also be used for the production of products, e.g. bags and trays which combine a desired softness with desired insulation properties and resistance to moisture penetration.

Such a combined dry-laying and vacuum moulding operation may be effected in the following manner. The thickness of fibrous layer leaving the forming surface is reduced to about 50% of its original thickness so as to fix the fibres relative to one another.

The product thus prepared is coated on one surface, e.g. the top surface, with a thin layer of a thermoplastic resin, e.g. polyethylene. Such coating may be effected by a well known extrusion or coating process or by merely placing a layer of polyethylene on the top surface of the product. It is also possible to use a loose separate film of an elastomeric material. In the latter embodiment the film may be used repeatedly.

The composite product is then vacuum moulded in a vacuum mould. By selecting suitable temperatures for the vacuum moulding operation the composite product is deformed and a bond between the polyethylene layer and the fibrous layer is established in one step. The product thus obtained is a laminate which is suitable for many purposes.

A laminated product which comprises a core layer of fibres and wherein one or both surfaces are coated with a layer of a thermoplastic material can be prepared in a similar mannner. Such a product which comprises a moisture impervious layer and a moisture absorbing layer is not only suitable as a packing material but can also be used for the production of diapers, sanitary napkins and bandage materials.

By a similar lamination method products may be prepared wherein the layer of thermoplastic material is located within the material and is covered on both sides by fibrous layers.

In order to use the above mentioned technique for the moulding of laminated materials, the fibrous layer should be pervious to air and the polyethylene film should be impervious to air.

A fibrous product having a relatively high binder concentration at one surface is particularly suitable for the production of containers for hot and cold products, such as coffee and ice-cream, respectively. When preparing such containers, the starting material used is preferably a fibrous product wherein the layer which is to form the interior surface of the container has a high binder concentration, e.g. up to 75 per cent by weight. The binder may be polyethylene or a melamin resin.

By providing a surface layer having a high binder concentration, no special coating at the interior surface of the container is needed and the strength and rigidity of the container is increased.

As mentioned above, a product comprising a surface layer having a relatively high binder concentration may be prepared by using two or more fibre distributors and by introducing different amounts of binder into said fibre distributors.

Containers prepared from the above mentioned product are impervious to both liquid, and gaseous products including oils and fats.

In order to heat insulate such zones of containers, such as cups, for hot or cold products which are to be contacted by the hands, the said zones are preferably composed of a fibrous material having a significantly lower density than that of the remaining zones. Such cups may e.g. be provided with a band shaped zone extending over about 1/3 of the total height of the cup.

Instead of providing such a limited zone on the exterior side of the container, the exterior surface of the whole side wall and, if desired, also the bottom thereof may be composed of a fibrous material of a low density. Such containers are particularly suitable for packing deep-frozen goods. When fibres are fixed relative to one another in such a loose structure, the rigidity of the product formed also becomes satisfactory. Furthermore, such containers can be provided with ornaments which serve decorative purposes and which also increase the friction so that e.g. cups prepared from said product do not slide out of the hand.

Containers of the above mentioned type in the form of trays or boxes are suitable for the storage of eggs and for the storage of deep-frozen products during deriming of refrigerators.

Containers of this type are also suitable for the transportation of deep-frozen articles from shops to the homes of the consumers.

The containers are preferably constructed in a manner so that they can be closed and preferably comprise a lid which is integral with the bottom part and is capable of being folded over the bottom part.

Drinking cups may be prepared from blanks of a flat sheet material of the invention, said blanks being suitably shaped to form cups and overlapping portions being joined by an adhesive.

Instead of preparing cups or similar articles from flat fibrous materials, it is also possible to use forming surfaces having portions of a shape corresponding to that of the articles to be prepared.

By using such forming surfaces and by successively introducing said forming surfaces into gas streams containing suspended fibres, a final fibrous layer which after compression and curing of the binder has the desired properties can be formed thereon.

When compressing a product of the above mentioned type, the mixture of fibres and binder is ordinarily compressed in the direction of compression only.

However, a product may also be obtained wherein the mixture of fibres and binder is compressed both in the direction of compression and in a direction perpendicular thereto.

This effect is obtained by a method wherein a fibrous layer is compressed and simultaneously penetrated by heated needles. By using such a large number of needles that the total cross sectional area thereof constitutes a considerable portion of the area of the product wherein the compression takes place, e.g. of the order of 50%, the said compression will result in a considerable compression not only in the direction of compression but also in a direction perpendicular thereto.

By using heated needles having a diameter of between e.g. 5 and 10 mm and a fibrous product in which the binder is uniformly distributed, a product is obtained in which the fibres and the binder are concentrated in the zones adjacent to the holes. Therefore, the product obtained is resistant to compression in the longitudinal direction of said holes.

When using closely spaced needles, the product obtained becomes rigid and, consequently, a high flexural strength is produced.

A product of the above mentioned type may also be coated on its surfaces with sheets of paper, boxboard or similar materials so as to close the open ends of the holes obtained by said needling. Such a coating may be applied onto one or both surfaces of the material. When applying a coating onto both surfaces of the material, the rigidity of the product is further increased. In many respects such a material possesses properties similar to those of corrugated paper. These materials may advantageously be used for the insulation purposes because they are excellent insulating materials both as far as heat and noise is concerned.

The material described is also suitable for the packing of fragile articles, such as articles of glass, and instruments.

The method of the invention may be used for the production of fibre layers containing binders which may be activated with heat and/or moisture, e.g. binders based on starch and water glass. Such fibre layers are suitable for the production of fibrous products having a structure corresponding to that of corrugated paper.

A product of the invention is also suitable for the production of a buffer material for use in automobiles etc.

Such a material may be prepared from a fibrous layer having a thickness of e.g. 5 cm and consisting of fibres and about 20% of a mixture of urea and melamin resins or other thermosetting binder. This material is compressed so as to form zones of alternating thickness and density. Thus, the thickness within some zones is reduced to 3 cm, whereas it is reduced to 0.6 cm in other zones.

If desired, an artificial leather coating, e.g. made of polyurethane, may be applied to the top surface of the product.

The method of the invention is also suitable for the production of fibrous products which subsequently are to be converted into corrugated fibrous products and in particular a corrugated product consisting of a defibrated fibrous waste material containing binders originating from the production of said fibrous material and additional amounts of binder added during the production of the fibrous product.

Due to the excellent moulding properties of a fibrous product prepared by the method of the invention, such corrugated product can be obtained by passing the fibrous - 21 48088 product through a set of rollers having a surface configuration which results in the obtaining of a corrugated product. The binder used in the production of such corrugated product is preferably a phenolic resin.

Examples of waste materials which may be used in the production of corrugated products are waste clippings of corrugated paper, newsprint materials and sawdust in admixture with mechanical pulp.

A corrugated product prepared from these materials 10 preferably contains about 2% by weight of a phenolic resin, said resin being introduced into the fibrous material in the form of a powder.

The corrugated products prepared in this manner may be products in which the corrugations extend longitudinal15 ly or transversely of the web.

The fibrous products of the Invention may also be used for the production of laminates. A preferred type of laminates may be prepared by preparing a fibrous product of a loose structure, compacting said product and coating the compacted material with a chipboard. A decorative sheet of melamin resin may be applied to the top surface of said chipboard.

These layers may be formed individually in different forming stations and subsequently compressed before being bonded together to form a laminate.

The top surface layer may also be a decorated layer of paper.

The invention will now be described in further detail with reference to the drawings, in which: Figs. 1-9 illustrate various fibrous products obtained by the method of the invention and Fig. 10 schematically illustrates a method of preparing a fibrous product comprising cupshaped portions.

Fig. 1 shows a cross sectional view of a product prepared by the method of the invention. This product compris es a relatively loose fibrous layer 1 having a top layer 2 made from a fibrous material having a high binder concentration.

The composite product has been embossed so as to form depressions 3.

The product illustrated in Fig. 2 comprises three fibrous layers of which the outer layers 4 and 5 have a loose structure and the core layer 6 is dense. The dense core layer 6 may be prepared from a fibrous layer having a relatively high binder concentration or by rolling or ?0 compressing a fibrous layer at a temperature above the melting or softening point of the binder used.

The fibrous product illustrated in Fig. 3 comprises a relatively loose fibrous layer 7 which is coated on one side by a polymer film 8, such as a polyethylene film.

Fig. 4 illustrates a fibrous product in which the binder concentration increases from the upper surface towards the lower surface.

Fig. 5 illustrates a fibrous product prepared by the 30 method of the invention, said product comprising parallel zones 9 of a high binder concentration, said zones being applied to the product in its machine direction.

The fibrous product illustrated in Fig. 6 comprises a loose fibrous layer 10 located between two non-woven nets 11.

The fibrous product shown in Fig. 7 is a fibrous product provided with crossing grooves 12 so as to form a product which is similar to the well known quilted textile products.

Fig. 8 illustrates a box 13 having an integral hinged lid 14, said box and lid being prepared from a rolled fibrous product obtained by the product of the invention.

Fig. 9 shows a cross sectional view of a preferred packing material prepared by embossing a fibrous product of the invention in a pattern comprising alternating rounded projections and depressions.

Fig. 10 shows portion of an endless forming wire 15 mounted on at least two rollers of which only one 16 is shown. The apparatus shown also comprises two cooperating rollers 17 and 18 which are provided with intermeshing projections 19. The forming wire 15 is provided with cupshaped projections 20 on which a fibrous layer 21 containing a binder is deposited in a manner which is well known per se.

The fibrous layer 21 is removed from the forming wire 15 and is introduced into the nip between the two intermeshing rollers 17 and 18. During the passage through said nip the fibrous layer is compressed to form dense cup-shaped elements which are subsequently removed from the roller 18 and separated from one another.

Claims (6)

CLAIMS:

1. A method of preparing a dry-laid cellulosic fibrous web, wherein a gaseous medium containing a suspended cellulosic fibrous material is supplied to a distributor means, passed through rotating stirring impellers, passed through a perforated distributor means bottom wall, passed through a foraminous forming surface so as to form a fibrous layer thereon and finally into a suction box located below said foraminous forming surface and said perforated distributor means bottom wall, and wherein a binder in powder form is supplied to the gaseous medium containing a suspended cellulosic fibrous material before said gaseous medium is supplied to said distributor means.

2. A method as claimed in Claim 1, comprising using a binder selected from polyolefines, melamin urea and phenolic resins, lattices, starch, modified starch and water glass.

3. A method as claimed in Claim 1, or Claim 2 wherein the fibrous layer formed on the forming surface is compressed to increase the density of the product.

4. A method as claimed in Claim 3, wherein the compressed product is embossed to form a corrugated product.

5. A method as claimed in any preceding Claim, comprising forming a fibrous layer comprising two or more plies having different binder concentrations.

6. A method of preparing a uniformly dry-laid cellulosic fibrous web substantially as hereinbefore described with reference to the accompanying drawings.