CA1142394A - Method of preparing dry-laid fibrous products - Google Patents
Method of preparing dry-laid fibrous productsInfo
- Publication number
- CA1142394A CA1142394A CA000322903A CA322903A CA1142394A CA 1142394 A CA1142394 A CA 1142394A CA 000322903 A CA000322903 A CA 000322903A CA 322903 A CA322903 A CA 322903A CA 1142394 A CA1142394 A CA 1142394A
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- binder
- product
- fibrous
- fibres
- products
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Abstract
ABSTRACT
A method of preparing dry-laid fibrous products com-prising the steps of defibrating cellulose pulp to form a stream of gas containing suspended cellulose fibres, dis-tributing said fibres over the surface of a gas permeable forming surface to form a fibrous layer thereon and intro-ducing a binder into said fibrous layer by supplying the binder to the cellulose pulp or to the stream of gas con-taining suspended fibres.
A method of preparing dry-laid fibrous products com-prising the steps of defibrating cellulose pulp to form a stream of gas containing suspended cellulose fibres, dis-tributing said fibres over the surface of a gas permeable forming surface to form a fibrous layer thereon and intro-ducing a binder into said fibrous layer by supplying the binder to the cellulose pulp or to the stream of gas con-taining suspended fibres.
Description
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METHOD OF PREPARING DRY-LAID FIBROUS PRODUCTS
This invention relates to a method of preparing dry-laid 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 ar-t method of this is disclosed in British patent specification 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 concen-tration of binder in the remaining portions of -the fibrous layer.
The main object of the invention is to obtain pre-determined binder concentrations in any portions of the fibrous layer.
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Another object is to obtain a lmiform distribution of binder within the fibrous layer so as to reduce or eliminate the tendency of delamination.
A further object is to allow the introduction of substantial amounts of filler in a fibrous product prepared by a method of the above mentioned type and to retain said filler in the final product.
The present invention provides a method of preparing a dry-laid cellu-losic 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 cellu-losic fibrous material before said gaseous medium is supplied to said distribu-tor 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 or cluring the folmation of the fibrous layer, the binder become uniformly distributed in said layer and, consequently~ the tendency of delamination withirl such layer is eliminated or reduced.
METHOD OF PREPARING DRY-LAID FIBROUS PRODUCTS
This invention relates to a method of preparing dry-laid 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 ar-t method of this is disclosed in British patent specification 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 concen-tration of binder in the remaining portions of -the fibrous layer.
The main object of the invention is to obtain pre-determined binder concentrations in any portions of the fibrous layer.
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Another object is to obtain a lmiform distribution of binder within the fibrous layer so as to reduce or eliminate the tendency of delamination.
A further object is to allow the introduction of substantial amounts of filler in a fibrous product prepared by a method of the above mentioned type and to retain said filler in the final product.
The present invention provides a method of preparing a dry-laid cellu-losic 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 cellu-losic fibrous material before said gaseous medium is supplied to said distribu-tor 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 or cluring the folmation of the fibrous layer, the binder become uniformly distributed in said layer and, consequently~ the tendency of delamination withirl such layer is eliminated or reduced.
- 2 -In a pre:Eerred embodiment of the method of the invention the binder is in the orm of a powder and it is introduced into a defibrator used for the defibration of the fibrous starting material together with said starting mater-ial. The powdered binder may also be introduced into the fibre distributor together with or independently of - 2a -
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the defibrated fibrous material.
A fibre distributor which is particularly suitable for use in the method of the invention is described in British patent specifications ~os. 1.207.556 and 1.518.28~.
The powdered binder may also be supplied to the fibrous material by introducing said binder into the zone between the fibre distributor and the forming surface. When intro-ducing the binder in this manner, the binder concentration may be varied from one zone to another in the machine and/or cross machine direction of the product. Thus, a desired distribution of binder can be obtained by introducing the powdered binder into separate streams of air, each providing a zone of a relatively high binder concentration in the fibrous layer formed during -the deposition of the fibres on the forming surface.
The introduction of the binder in this manner is par-ticularly suitable when using binders having low melting points or low softening points, because such binders or-dinarily cannot be introduced into t~1e defibrator or the fibre distr:ibutor in which substantially frictional heat is generated.
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 cor.sequently heat generation take place therein.
The binder may also be supplied to the fibrous product by treating the starting material, e.g. a fibrous pulp, with a binder solution, slurry, suspension, or a binder foam, and by subsequently drying the pulp thus trea-ted to remove volatile subs-tances, if any, before -the pulp is defibrated.
Thus, the pulp may be hea-ted by using infrared light.
In some cases, a separate hea-t treatment is superfluous because the heat generated i~ the defibrator may be suffi-cient to increase the temperature to such an extent that most volatile substances, if any, are removed by evaporation.
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The ~inder may be any substance or mixture of sub-stances 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. partial-ly hydrolyzed and/or chemically treated starch. By subjec--ting starch to such treatments, it is made soluble and in the converted form it is suitable for use in a binder so-lution.
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 was-te materials are availahle in large amounts in the industry and as a waste product from households.
Cellulosic fibres are particularly suitable for use in the method of the invention. The cellulosic fibres used may be virgin fibres, i.e. fibres prepares from fresh cel-lulosic pulp, or waste fibres, i.e. fibres prepared from cellulose-containing waste ma-terials, such as paper. Also partially defibrated fibrous materials can be used. Such materials impart to the fibrous product a high flexibility without significantly reducing the hydroscopicity of the product. Therefore, such materials are useful in the pro-duction of building materials for indoor as well as outdoor use and pac~aging materials. Apart Erom natural vegetable fibres, such as cellulosic fibres, synthetic organic fibres having a relatively high melting or softening point may be used in the me-thod of the invention. The synthetic organic fibres used should prefera~ly ilave a melting or softening point which is higher than that of the binder when using termoplastic 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, flbres of crystallizable glass, fibres of devitrified glass, and S 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 ~m may be used as an additive.
Examples of other mineral additives are kaolin, dolo-mite, glass, chalk etc.
The addition of a mineral powder to the mixture of 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 ~Im and prefer-ably 10-20 ~m, and about 33% of mineral powder having a particle size of below 100 ~Im and preferably below 50 ~m.
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 fib-; res. ~lowever, it may also be introduced into the defibra-tor together with the pulp. Furthermore, the mineral pow-der may be in-troduced directly in the zone between the fibre dis-tribu-tor and -the forming surface so as to mix with the fibre suspension passing from the fibre distri-butor towards the forming surface.
The binder and the mineral powder are preferably in-timately mixed so as to obtaln a binder CGating on themineral particles. When the mineral particles are coa-ted 9'~
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 ~m.
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, wa-ter repelling oils, waxes, as-phalt, etc. By incorporating into the fibrous layer as-phalt in an amount of 1-2% by weight, a product is obtain-ed which is suitable for use as a roof covering element.
The addition of water repelling agents may be effectedafter 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 produc-t 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 mate-rial. In this manner a mechanical barrier agains-t water absorption is provided.
However, a porous structure is not necessarily a dis-advantageous 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 pre-ferably 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 devi-trified glass con-tain-ing no very fine particles. Such a product may consist ofparticles which preferably have a particle size of 100 ~Im and above.
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When preparing a flbrous product from cellulose pulp, the s-tarting material ordinarily contains about 10%
of moisture.
During the deEibration and the fibre distribution, frictional heat is generated, and the moisture content of the fibrous ma-terial 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 mois-ture 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 55-65%.
When using relatively high concentrations of binder, it is particularly easy to add moisture. Thus, in such cases the moisture con-tent of the fibrous material may be increased to 30%. If the method of the inventian is to be carried ou-t at such a high moisture content, -the adhesion of the powdered binder and/or filler to the surfaces of -the fibres is increased, and consecluently an increased amount of binder and/or filler may be applied to the sur-faces 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 distri-buted therein can be obtained. When hea-ting such a product -to an elevated temperature, a strongly coherent product is obtained.
The method of the invention permits the produc-tion of fibrous products in whicn ratio oE fibres to binder varies within wide ranges.
Thus, by using two or more fibre distributors to form a Eibrous layer composed of two or more indiv:idual layers, fibrous products can be obtained having a binder concentra-tion varying within-a cross section throucJh 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 con-tains a relative high 3~3~
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.
It is also possible by using three or more fibre di-stributors to prepare a sheet ma-terial having surface layers of a relatively loose s-truc-ture and a dense core layer.
Such a product can be obtained either by introducing a relatively large amount of binder into the fibre distri-butor used for the formation of the intermediate layer ofthe product or by rolling or compressing the fibrous layer formed by said fibre distributor at a temperature above the melting or softenlng 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 shee-t materials and more specifical-ly 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 particular]y 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 pro-jections or dispersions of a shape corresponding to -that of the con-tainer to be produced.
The fibrous products prepared by the method of the invention may be composed of fibres which are fixed rela-tive to one another in a rela-tively 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 par-t oE 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 differen-t binder concen-trations when forming the individual layers forming said fibrous product or by using different compression or embossing condi-tions.
When using the same compression or embossing condi-tions, 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 concen-tration, the highest density is obtained in zones wherein the product has been subjected to the most severe compres-sion 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 men-tioned type and consisting of cellulosic fibres and a polyethylene binder may be subjected to compression at a temperature of about 110C. The material thus obtained can be used as a star-t-ing material for a number of products, e.g. diapers, sani-tary napkins and other products for the care of the human body.
In order to prevent liquids, such as blood, from penetrating such a ma-terial, anticoagulating composi-tions may be introduced into said material. It is also possible to apply to one of the surfaces of such a layer a poly-ethylene menbrane or another mois-ture barrier.
The polyethylene membrane may be provided on the sur-face of such a product by in-troducing large amounts of binder into the fibrous layer which is to form the surface layer of the fibrous product.
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When using such a fi.brous 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 there-of, 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". Thi.s 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 absorb-ed, not only within the fibres, but also in the inter-stices 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 rol.led into an envelope, e.g.
a separately produced non-woven material, as is the case with pri.or 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 inventi.on may be in direct contact with the skin without causing irritation of the skin.
By using the fibrous product according to the inven-tion, a serious drawback of the prior art diapers and sanitary nap]cins may be eliminated. Due to the manner in which such prior art products are prepared i-t is diffi-cul-t to prepare products having an anatomic correct shape.
Since the fibrous products of the invention are capable of being converted in-to products of different shapes, they are suitable for use in -the produc-tion of diapers and sa-ni-tary nap]cins 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 inven-tion the fibres can be fixed relative to one another throughout the product.
Therefore, when used for -the care of the human body -thev remain in the desired position during such use, and thev maintain their softness. Therefore, such sanitary napkins and diapers do not require the use of adhesive tapes or other fastening means.
By varying binder contents in the machine or cross machine directions of fibrous produc-ts of the invention, sanitary napkins and diapers can be prepared in wh:ich the binder concentrati.on is high in the edge ~.ones.
A fibrous product containing a latex binder in a relatively high concentration at one surface of the pro-duct is particularly suitable :Eor the production of car-. 20 pets and carpet underlays.
Fibrous products having a shape si.milar to that o:E
quilted products can be prepared by heating fibrous pro-ducts of the invention to an eleva-ted 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 in-sula-tion and is a soft and pleasan-t product having ex-cellent strength properties.
Since such produc-ts can be prepared in a relatively s.imple manner, they are also sui-table as d.isposable pro-ducts, e.g. for camping purposes, military purposes, for use in hospitals and :Eor nursing purposes.
If it is desired to make such products more stable, a layer of a spun-bonded material, such as the above men-tioned "Cerex" produc-t, may be incorporated therein.
Fibrous products prepared by the above mentioned 3~3~
me-thod can be converted in-to valuable semi-manufactured produc-ts by subjecting the flbrous layer formed on the forming surface to a compression to increase the densi-ty o:E the product.
Such compression is preferably effected at tempera-tures close to the softening temperature of the binders used.
A semi-manufactured product of the above mentioned type is sui.table for the manufacture of compression mould-ed packing materials, cups, trays, containers etc.
The fibrous product should preferably be only slight-ly compressed during the i.nitial 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 compres-sion of the fibrous material and the final shaping there-of immeaiately following the -formation of the fibrous layer on the forming su.rface, e.g. by using heated rol-lers and by reducing the thickness from about 2 cm to 2-3 mm or belbw.
In the production of ordinary plates and soup pla-tes, the fibrous product should preferably be reduced to 0.6-0.7 mm dependent on the binder concentra-tion 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 150-200C, and the pressure exerted is preferably between 1 and 10 kg per cm depending on the desired strength of the final procluct. When using fibrous products which have been heated to a temperature above the softening point of the binder, e.g. to a temperature of 150C, it is pre-ferable to use cold tools for the moulding operation.
Plates, cups, trays, etc. which are -to be subjected to high temperatures, are preferably manufactured by com-pressing fibrous products under temperature conditions 3~
producing a maximum strength.
The moulded products are preferably introduced into an oven, e.g. a tunnel oven, at a temperature of e~g.
150C for a period of abou-t 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 sa-tisfactory -tear strength and are par-ticularly suitable for the production of the disposable packing materials, cups, plates, book jackets, and printing materials.
Furthermore, such fibrous products are more suscept-ible to printing inks than plastics materials, because the fibres make the products opaque and improve the ad-herence of printing inks.
A fibre reinforced plastics material can be bended many times wi-thout breaking and, therefore, such produc-ts are suitable for the manufacture of con-tainers wi-th inte-gral lids.
A fibre reinforced product based on cellulosic fib-res is decomposable when stored nature. ~ibre reinforcedproduc~s containing about 50 per cent by weight of cellu-losic fibres and 50 per cent by welght of binder in the form of an urea binder or a mix-ture of an urea and mela-min binder have sufficien-tly low water absorption pro-perties to be suitable for use as packaging materialsfor 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 produc-ts present the further advantage tha-t they are more stable when exposed to sunlight or ultra-violet light than many plastics materials.
It is well known to introduce in-to a plastics mate-rial compositions which when-e~posed to ultraviolet light cause the plastics ma-terial -to be decomposed.
Articles prepared from such plastics materials are not 1 'I
fully satisfactory, because they may undergo such changes that they do not longer perform satisfactori-ly 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 in-fluence of ultraviolet light, the fibres will still im-part to the material good strength properties, and a final decomposition does not take place until the pro-: duct is subjected to the influence of both ultraviolet light and moisture. Packaging materials prepared fromthe fibrous products based on cellulosic fibres prefer-ably contain well known compositions for decomposing plastics materials.
As mentioned above -the fi.brous 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 formi.ng sur-face. If it is desired to convert a sheet or web mate-: rial into a product having a three-dimensional struc-ture, 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 form-ing surface does not differ significantly from the shape of t.he 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 produc-t accordiny to -the invention is suitable for the production of packinys 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 ~, .
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maintained in a heated condition during transporta-tion.
In a method of preparing sueh products it is pre-ferable to combine the dry moulding technique with a va-cuum moulding technique.
A vacuum moulding is a method in whieh a thin layer of a thermoplastie material in heated condition and at a temperature close to the softening point of said mate-rial 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 s-torage of various pro-ducts, such as foods and chocolate. The vaeuum moulding teehnique ean also be used for the produetion of pro-duets, e.g. bags and trays whieh eombine a desired soft-ness with desired insulation properties and resistanee. tomousture penetration.
Such a combined dry-laying and vacuum moulding opera-tion may be effected in the following manner. The thiek-ness of fibrous layer leaving the forming surface is re-dueed to abou-t 50% of its original thiekness so as to fix the fibres relative -to one another.
The product thus prepared is coated on one surface, e.g. the top surfaee, with a thin layer of a thermoplastie resin, e.g. polyethylene. Sueh eoating may be effeeted 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 produet is then vaeuum moulded in a vaeuum mould. By seleeting suitable temperatures for the vaeuum moulding operation the eomposite produet is de-formed and a bond be-tween the polyethylene layer and the fibrous layer is established in one s-tep. The produet thus obtained :is a laminate whieh is suitable ~or many purposes.
A laminated produet whieh eomprises a core layer of ~z'~
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 produet which eomprises a moist-ure 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 produc-ts may be pre-pared 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 im-pervious to air.
A fibrous product having a relatively high binder con-centration at one surface is particularly suitable for the production of containers for hot and cold products, such as coffee and iee-eream, respectively. ~hen preparing such eontainers, the starting material used is preferably a fibrous produet wherein the layer which is to form the in-terior surface oE the eontainer has a high binder concen-tration, 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 eon-eentration, no special eoating at the interior surfaee of the container is needed and the strength and rigidity of the container is inereased.
As mentioned above, a product comprising a surfaee layer having a relatively high binder coneentration may be prepared by using two or more fibre distributors and by introdueing diEferent amounts of binder into said fibre distributors.
Containers prepared from -the above mentioned product are impervious to both liquid and gaseous produets inelu-ding oils and fats.
In order to heat insulate such zones of containers, such dS 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 significan-tly lower density than -that of the remaining zones. Such cups may e.g. be provided with a band shaped zone extend-ing over about 1/3 of -the total height of the cup.
Instead of providing such a limited 7one on the ex-terior 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 con-tainers are particularly suitable for packing deep-froæen goods. When fibres are fixed relative to one another in such a loose structure, -the rigidity of the product formed also becomes satisfactory. Further-more, such containers can be provided with ornamentswhich serve decora-tive purposes and which also increase the friction so that e.g. cups prepared from said pro-duct 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 derim-ing of refrigera-tors.
Contalners of this type are also suitable for the transportation of deep-fro~en articles from shops to the homes of the consumers.
The containers are preferably construc-ted in a man-ner so that they can be closed and preferably comprise a lid which is integral with the bottom par-t and is capable of being folded over the bottom part.
Drinking cups may be prepared from blanks of a flat sheet rnaterial of the invention, said blanks being suit-ably 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 in-to gas s-treams con-taining suspended fibres, a final fibrous layer which af-ter 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 com-pressed 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 e~fect is obtained by a me-thod wherein a fibrous layer is compressed and simultaneously penetrated by heat~
ed needles. By using such a large number of needles that the total cross sectional area thereof consti-tutes a con-siderable portion of -the area of the product wherein -the compression takes place, e.g. of the order of 50~, -the said compression will resul-t in a considerable compression not only ln the direc-tion of compression but also in a direction perpendicular thereto.
By using heated needles having a diameter of between e.g. 5 and lO mm and a fibrous product in which the bind-er is uniformly distributed, a product is obtained in which the fibres and the binder are concen-trated in the zones adjacen-t to the holes. Therefore, the product ob-tained is resistant to compression in the longitudinal direction of said holes.
When using closely spaced needles, the product obtain-ed becomes rigid and, conse~uently, 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 coa-ting may be ap-plied onto one or both surfaces of the material. When ap-plying a coating onto both surfaces of the material, the rigidity of the product is further increased. II} many re~
spects such a material possesses properties similar to those of corrugated paper. These materials may advanta-geously be used for the insulation purposes because they are excellen-t insulating materials both as ~ar as heat and noise is concerned.
The material described is also suitable for the pack-ing of fragile articles, such as articles of ~lass/ and instruments.
The me-thod of the inven-tion may be used for the pro-duction 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 ma-terial for use in automobiles etc.
Such a material may be prepared from a fibrouc; 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 bin~er. 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.
By using mineral fibres, the material is made fire resistant.
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 o~ corrugated fibrous proclucts and in particu-lar a corrugated product consis-ting of a defibrated fibrous waste ma-terial con~aining binders originating from the production of said fibrous material and optionally additional amounts of binder added during the production of the corrugated product.
Due -to the excellen-t moulding pro~erties of a fibrous product prepared by the method of the invention, such cor-rugated product can be obtained by passing the fibrous .., 3~
product through a set of rollers having a surface configu-ra-tion which results in the obtaining of a corrugated pro-duct. The binder used in the production of such corrugated product is preferably a phenolic resin.
Examples of waste ma-terials which may be used in the production of corrugated products are waste clippings of corrugated paper, newsprin-t materials and sawdust in ad mixture with mechanical pulp.
A corrugated product prepared from these ma-terials 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 :longitudinal-ly or transversely of the web.
The fibrous products of -the invention may also be used for -the production of laminates. ~ preferred type of laminates may be prepared by preparing a fibrous product of a loose structure, compacting said product and coating the compac-ted ma-terial 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 subse~uently compressed before being bonded together to form a laminate.
The top surface layer may also be a decorated layer of paper.
In order to obtain final products having a uniform distribution of binder, it may be desirable first to pre-pare an intermediate produc-t and to introduce said inter-mediate product into a defibrator and a distribu-tor so as to prepare the final product.
The intermediate product prepared by -the method of the invention is preferably compacted by being passed through one or more sets of rollers which are moderately heated, e.g. -to a temperature below the setting point of the resin used as birder.
Due to the repeated defibration of the fibrous mate-rial, irregulari-ties in the distribution of binder in the intermediate product can be fully eliminated.
The binder used in the intermediate product is pre-ferably of the thermocuring type.
The invention will now be described in further detail with reference to the drawings, in which:
Figs. 1-9 illustrate various fibrous products obtain-ed by the method of the invention and Fig. lO schematically illustrates a method of pre-paring a fibrous product comprising cup-shaped portions.
Fig. 1 shows a cross sectional view of a product pre-pared by the method of the invention. This product compris-es a relatively loose fibrous layer l having a top layer 2 made from a fibrous material having a high binder concen-tration.
r~he composite product has heen 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 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.
E'ig. 4 illustrates a fibrous product in which the binder concen-tratiorl increases from -the upper surface -to-wards the lower sur~ace.
Fig. 5 illustrates a fibrous product prepared by the method of the invention, sai~ product comprising parallel zones 9 of a high binder concentra-tion, said zones being applied to the product in i-ts machine direction.
The fibrous product illustrated in Fig. 6 comprises a loose fibrous layer lO located between two non-woven nets 11.
The fibrous product shown in Fig. 7 is a fibrous pro-duc-t provided with crossing grooves 12 so as to form a product which is similar -to the well known quilted tex-tile products.
Fig. 8 illustrates a box 13 having an in-tegral hing-ed lid 14, said box and lid being prepared from a rolled fibrous product ob-tained by the produc-t of the invention.
Fig. 9 shows a cross sectional view of a pre~erred packing ma-terial prepared by embossing a fibrous product of the invention in a pa-ttern 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 l9. The forming wire 15 is provided with cup-shaped projections 20 on which a fibrous layer 21 contain-ing a binder is deposi-ted in a manner which is well ]~nown per se.
The fibrous layer 21 is removed from the forming wire 15 and is introduced into the nip between the two in-termeshing rollers 17 and 18. During the passage -through said nip the fibrous layer is compressed to form dense cup-shaped elemen-ts which are subse~uently removed from the roller 18 and separated from one another.
the defibrated fibrous material.
A fibre distributor which is particularly suitable for use in the method of the invention is described in British patent specifications ~os. 1.207.556 and 1.518.28~.
The powdered binder may also be supplied to the fibrous material by introducing said binder into the zone between the fibre distributor and the forming surface. When intro-ducing the binder in this manner, the binder concentration may be varied from one zone to another in the machine and/or cross machine direction of the product. Thus, a desired distribution of binder can be obtained by introducing the powdered binder into separate streams of air, each providing a zone of a relatively high binder concentration in the fibrous layer formed during -the deposition of the fibres on the forming surface.
The introduction of the binder in this manner is par-ticularly suitable when using binders having low melting points or low softening points, because such binders or-dinarily cannot be introduced into t~1e defibrator or the fibre distr:ibutor in which substantially frictional heat is generated.
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 cor.sequently heat generation take place therein.
The binder may also be supplied to the fibrous product by treating the starting material, e.g. a fibrous pulp, with a binder solution, slurry, suspension, or a binder foam, and by subsequently drying the pulp thus trea-ted to remove volatile subs-tances, if any, before -the pulp is defibrated.
Thus, the pulp may be hea-ted by using infrared light.
In some cases, a separate hea-t treatment is superfluous because the heat generated i~ the defibrator may be suffi-cient to increase the temperature to such an extent that most volatile substances, if any, are removed by evaporation.
... ..
,f2~
The ~inder may be any substance or mixture of sub-stances 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. partial-ly hydrolyzed and/or chemically treated starch. By subjec--ting starch to such treatments, it is made soluble and in the converted form it is suitable for use in a binder so-lution.
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 was-te materials are availahle in large amounts in the industry and as a waste product from households.
Cellulosic fibres are particularly suitable for use in the method of the invention. The cellulosic fibres used may be virgin fibres, i.e. fibres prepares from fresh cel-lulosic pulp, or waste fibres, i.e. fibres prepared from cellulose-containing waste ma-terials, such as paper. Also partially defibrated fibrous materials can be used. Such materials impart to the fibrous product a high flexibility without significantly reducing the hydroscopicity of the product. Therefore, such materials are useful in the pro-duction of building materials for indoor as well as outdoor use and pac~aging materials. Apart Erom natural vegetable fibres, such as cellulosic fibres, synthetic organic fibres having a relatively high melting or softening point may be used in the me-thod of the invention. The synthetic organic fibres used should prefera~ly ilave a melting or softening point which is higher than that of the binder when using termoplastic 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, flbres of crystallizable glass, fibres of devitrified glass, and S 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 ~m may be used as an additive.
Examples of other mineral additives are kaolin, dolo-mite, glass, chalk etc.
The addition of a mineral powder to the mixture of 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 ~Im and prefer-ably 10-20 ~m, and about 33% of mineral powder having a particle size of below 100 ~Im and preferably below 50 ~m.
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 fib-; res. ~lowever, it may also be introduced into the defibra-tor together with the pulp. Furthermore, the mineral pow-der may be in-troduced directly in the zone between the fibre dis-tribu-tor and -the forming surface so as to mix with the fibre suspension passing from the fibre distri-butor towards the forming surface.
The binder and the mineral powder are preferably in-timately mixed so as to obtaln a binder CGating on themineral particles. When the mineral particles are coa-ted 9'~
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 ~m.
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, wa-ter repelling oils, waxes, as-phalt, etc. By incorporating into the fibrous layer as-phalt in an amount of 1-2% by weight, a product is obtain-ed which is suitable for use as a roof covering element.
The addition of water repelling agents may be effectedafter 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 produc-t 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 mate-rial. In this manner a mechanical barrier agains-t water absorption is provided.
However, a porous structure is not necessarily a dis-advantageous 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 pre-ferably 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 devi-trified glass con-tain-ing no very fine particles. Such a product may consist ofparticles which preferably have a particle size of 100 ~Im and above.
~ ~23~3~
When preparing a flbrous product from cellulose pulp, the s-tarting material ordinarily contains about 10%
of moisture.
During the deEibration and the fibre distribution, frictional heat is generated, and the moisture content of the fibrous ma-terial 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 mois-ture 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 55-65%.
When using relatively high concentrations of binder, it is particularly easy to add moisture. Thus, in such cases the moisture con-tent of the fibrous material may be increased to 30%. If the method of the inventian is to be carried ou-t at such a high moisture content, -the adhesion of the powdered binder and/or filler to the surfaces of -the fibres is increased, and consecluently an increased amount of binder and/or filler may be applied to the sur-faces 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 distri-buted therein can be obtained. When hea-ting such a product -to an elevated temperature, a strongly coherent product is obtained.
The method of the invention permits the produc-tion of fibrous products in whicn ratio oE fibres to binder varies within wide ranges.
Thus, by using two or more fibre distributors to form a Eibrous layer composed of two or more indiv:idual layers, fibrous products can be obtained having a binder concentra-tion varying within-a cross section throucJh 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 con-tains a relative high 3~3~
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.
It is also possible by using three or more fibre di-stributors to prepare a sheet ma-terial having surface layers of a relatively loose s-truc-ture and a dense core layer.
Such a product can be obtained either by introducing a relatively large amount of binder into the fibre distri-butor used for the formation of the intermediate layer ofthe product or by rolling or compressing the fibrous layer formed by said fibre distributor at a temperature above the melting or softenlng 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 shee-t materials and more specifical-ly 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 particular]y 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 pro-jections or dispersions of a shape corresponding to -that of the con-tainer to be produced.
The fibrous products prepared by the method of the invention may be composed of fibres which are fixed rela-tive to one another in a rela-tively 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 par-t oE 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 differen-t binder concen-trations when forming the individual layers forming said fibrous product or by using different compression or embossing condi-tions.
When using the same compression or embossing condi-tions, 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 concen-tration, the highest density is obtained in zones wherein the product has been subjected to the most severe compres-sion 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 men-tioned type and consisting of cellulosic fibres and a polyethylene binder may be subjected to compression at a temperature of about 110C. The material thus obtained can be used as a star-t-ing material for a number of products, e.g. diapers, sani-tary napkins and other products for the care of the human body.
In order to prevent liquids, such as blood, from penetrating such a ma-terial, anticoagulating composi-tions may be introduced into said material. It is also possible to apply to one of the surfaces of such a layer a poly-ethylene menbrane or another mois-ture barrier.
The polyethylene membrane may be provided on the sur-face of such a product by in-troducing large amounts of binder into the fibrous layer which is to form the surface layer of the fibrous product.
.~ 3~3'~
When using such a fi.brous 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 there-of, 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". Thi.s 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 absorb-ed, not only within the fibres, but also in the inter-stices 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 rol.led into an envelope, e.g.
a separately produced non-woven material, as is the case with pri.or 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 inventi.on may be in direct contact with the skin without causing irritation of the skin.
By using the fibrous product according to the inven-tion, a serious drawback of the prior art diapers and sanitary nap]cins may be eliminated. Due to the manner in which such prior art products are prepared i-t is diffi-cul-t to prepare products having an anatomic correct shape.
Since the fibrous products of the invention are capable of being converted in-to products of different shapes, they are suitable for use in -the produc-tion of diapers and sa-ni-tary nap]cins 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 inven-tion the fibres can be fixed relative to one another throughout the product.
Therefore, when used for -the care of the human body -thev remain in the desired position during such use, and thev maintain their softness. Therefore, such sanitary napkins and diapers do not require the use of adhesive tapes or other fastening means.
By varying binder contents in the machine or cross machine directions of fibrous produc-ts of the invention, sanitary napkins and diapers can be prepared in wh:ich the binder concentrati.on is high in the edge ~.ones.
A fibrous product containing a latex binder in a relatively high concentration at one surface of the pro-duct is particularly suitable :Eor the production of car-. 20 pets and carpet underlays.
Fibrous products having a shape si.milar to that o:E
quilted products can be prepared by heating fibrous pro-ducts of the invention to an eleva-ted 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 in-sula-tion and is a soft and pleasan-t product having ex-cellent strength properties.
Since such produc-ts can be prepared in a relatively s.imple manner, they are also sui-table as d.isposable pro-ducts, e.g. for camping purposes, military purposes, for use in hospitals and :Eor nursing purposes.
If it is desired to make such products more stable, a layer of a spun-bonded material, such as the above men-tioned "Cerex" produc-t, may be incorporated therein.
Fibrous products prepared by the above mentioned 3~3~
me-thod can be converted in-to valuable semi-manufactured produc-ts by subjecting the flbrous layer formed on the forming surface to a compression to increase the densi-ty o:E the product.
Such compression is preferably effected at tempera-tures close to the softening temperature of the binders used.
A semi-manufactured product of the above mentioned type is sui.table for the manufacture of compression mould-ed packing materials, cups, trays, containers etc.
The fibrous product should preferably be only slight-ly compressed during the i.nitial 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 compres-sion of the fibrous material and the final shaping there-of immeaiately following the -formation of the fibrous layer on the forming su.rface, e.g. by using heated rol-lers and by reducing the thickness from about 2 cm to 2-3 mm or belbw.
In the production of ordinary plates and soup pla-tes, the fibrous product should preferably be reduced to 0.6-0.7 mm dependent on the binder concentra-tion 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 150-200C, and the pressure exerted is preferably between 1 and 10 kg per cm depending on the desired strength of the final procluct. When using fibrous products which have been heated to a temperature above the softening point of the binder, e.g. to a temperature of 150C, it is pre-ferable to use cold tools for the moulding operation.
Plates, cups, trays, etc. which are -to be subjected to high temperatures, are preferably manufactured by com-pressing fibrous products under temperature conditions 3~
producing a maximum strength.
The moulded products are preferably introduced into an oven, e.g. a tunnel oven, at a temperature of e~g.
150C for a period of abou-t 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 sa-tisfactory -tear strength and are par-ticularly suitable for the production of the disposable packing materials, cups, plates, book jackets, and printing materials.
Furthermore, such fibrous products are more suscept-ible to printing inks than plastics materials, because the fibres make the products opaque and improve the ad-herence of printing inks.
A fibre reinforced plastics material can be bended many times wi-thout breaking and, therefore, such produc-ts are suitable for the manufacture of con-tainers wi-th inte-gral lids.
A fibre reinforced product based on cellulosic fib-res is decomposable when stored nature. ~ibre reinforcedproduc~s containing about 50 per cent by weight of cellu-losic fibres and 50 per cent by welght of binder in the form of an urea binder or a mix-ture of an urea and mela-min binder have sufficien-tly low water absorption pro-perties to be suitable for use as packaging materialsfor 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 produc-ts present the further advantage tha-t they are more stable when exposed to sunlight or ultra-violet light than many plastics materials.
It is well known to introduce in-to a plastics mate-rial compositions which when-e~posed to ultraviolet light cause the plastics ma-terial -to be decomposed.
Articles prepared from such plastics materials are not 1 'I
fully satisfactory, because they may undergo such changes that they do not longer perform satisfactori-ly 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 in-fluence of ultraviolet light, the fibres will still im-part to the material good strength properties, and a final decomposition does not take place until the pro-: duct is subjected to the influence of both ultraviolet light and moisture. Packaging materials prepared fromthe fibrous products based on cellulosic fibres prefer-ably contain well known compositions for decomposing plastics materials.
As mentioned above -the fi.brous 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 formi.ng sur-face. If it is desired to convert a sheet or web mate-: rial into a product having a three-dimensional struc-ture, 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 form-ing surface does not differ significantly from the shape of t.he 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 produc-t accordiny to -the invention is suitable for the production of packinys 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 ~, .
.~
3~L
maintained in a heated condition during transporta-tion.
In a method of preparing sueh products it is pre-ferable to combine the dry moulding technique with a va-cuum moulding technique.
A vacuum moulding is a method in whieh a thin layer of a thermoplastie material in heated condition and at a temperature close to the softening point of said mate-rial 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 s-torage of various pro-ducts, such as foods and chocolate. The vaeuum moulding teehnique ean also be used for the produetion of pro-duets, e.g. bags and trays whieh eombine a desired soft-ness with desired insulation properties and resistanee. tomousture penetration.
Such a combined dry-laying and vacuum moulding opera-tion may be effected in the following manner. The thiek-ness of fibrous layer leaving the forming surface is re-dueed to abou-t 50% of its original thiekness so as to fix the fibres relative -to one another.
The product thus prepared is coated on one surface, e.g. the top surfaee, with a thin layer of a thermoplastie resin, e.g. polyethylene. Sueh eoating may be effeeted 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 produet is then vaeuum moulded in a vaeuum mould. By seleeting suitable temperatures for the vaeuum moulding operation the eomposite produet is de-formed and a bond be-tween the polyethylene layer and the fibrous layer is established in one s-tep. The produet thus obtained :is a laminate whieh is suitable ~or many purposes.
A laminated produet whieh eomprises a core layer of ~z'~
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 produet which eomprises a moist-ure 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 produc-ts may be pre-pared 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 im-pervious to air.
A fibrous product having a relatively high binder con-centration at one surface is particularly suitable for the production of containers for hot and cold products, such as coffee and iee-eream, respectively. ~hen preparing such eontainers, the starting material used is preferably a fibrous produet wherein the layer which is to form the in-terior surface oE the eontainer has a high binder concen-tration, 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 eon-eentration, no special eoating at the interior surfaee of the container is needed and the strength and rigidity of the container is inereased.
As mentioned above, a product comprising a surfaee layer having a relatively high binder coneentration may be prepared by using two or more fibre distributors and by introdueing diEferent amounts of binder into said fibre distributors.
Containers prepared from -the above mentioned product are impervious to both liquid and gaseous produets inelu-ding oils and fats.
In order to heat insulate such zones of containers, such dS 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 significan-tly lower density than -that of the remaining zones. Such cups may e.g. be provided with a band shaped zone extend-ing over about 1/3 of -the total height of the cup.
Instead of providing such a limited 7one on the ex-terior 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 con-tainers are particularly suitable for packing deep-froæen goods. When fibres are fixed relative to one another in such a loose structure, -the rigidity of the product formed also becomes satisfactory. Further-more, such containers can be provided with ornamentswhich serve decora-tive purposes and which also increase the friction so that e.g. cups prepared from said pro-duct 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 derim-ing of refrigera-tors.
Contalners of this type are also suitable for the transportation of deep-fro~en articles from shops to the homes of the consumers.
The containers are preferably construc-ted in a man-ner so that they can be closed and preferably comprise a lid which is integral with the bottom par-t and is capable of being folded over the bottom part.
Drinking cups may be prepared from blanks of a flat sheet rnaterial of the invention, said blanks being suit-ably 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 in-to gas s-treams con-taining suspended fibres, a final fibrous layer which af-ter 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 com-pressed 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 e~fect is obtained by a me-thod wherein a fibrous layer is compressed and simultaneously penetrated by heat~
ed needles. By using such a large number of needles that the total cross sectional area thereof consti-tutes a con-siderable portion of -the area of the product wherein -the compression takes place, e.g. of the order of 50~, -the said compression will resul-t in a considerable compression not only ln the direc-tion of compression but also in a direction perpendicular thereto.
By using heated needles having a diameter of between e.g. 5 and lO mm and a fibrous product in which the bind-er is uniformly distributed, a product is obtained in which the fibres and the binder are concen-trated in the zones adjacen-t to the holes. Therefore, the product ob-tained is resistant to compression in the longitudinal direction of said holes.
When using closely spaced needles, the product obtain-ed becomes rigid and, conse~uently, 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 coa-ting may be ap-plied onto one or both surfaces of the material. When ap-plying a coating onto both surfaces of the material, the rigidity of the product is further increased. II} many re~
spects such a material possesses properties similar to those of corrugated paper. These materials may advanta-geously be used for the insulation purposes because they are excellen-t insulating materials both as ~ar as heat and noise is concerned.
The material described is also suitable for the pack-ing of fragile articles, such as articles of ~lass/ and instruments.
The me-thod of the inven-tion may be used for the pro-duction 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 ma-terial for use in automobiles etc.
Such a material may be prepared from a fibrouc; 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 bin~er. 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.
By using mineral fibres, the material is made fire resistant.
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 o~ corrugated fibrous proclucts and in particu-lar a corrugated product consis-ting of a defibrated fibrous waste ma-terial con~aining binders originating from the production of said fibrous material and optionally additional amounts of binder added during the production of the corrugated product.
Due -to the excellen-t moulding pro~erties of a fibrous product prepared by the method of the invention, such cor-rugated product can be obtained by passing the fibrous .., 3~
product through a set of rollers having a surface configu-ra-tion which results in the obtaining of a corrugated pro-duct. The binder used in the production of such corrugated product is preferably a phenolic resin.
Examples of waste ma-terials which may be used in the production of corrugated products are waste clippings of corrugated paper, newsprin-t materials and sawdust in ad mixture with mechanical pulp.
A corrugated product prepared from these ma-terials 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 :longitudinal-ly or transversely of the web.
The fibrous products of -the invention may also be used for -the production of laminates. ~ preferred type of laminates may be prepared by preparing a fibrous product of a loose structure, compacting said product and coating the compac-ted ma-terial 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 subse~uently compressed before being bonded together to form a laminate.
The top surface layer may also be a decorated layer of paper.
In order to obtain final products having a uniform distribution of binder, it may be desirable first to pre-pare an intermediate produc-t and to introduce said inter-mediate product into a defibrator and a distribu-tor so as to prepare the final product.
The intermediate product prepared by -the method of the invention is preferably compacted by being passed through one or more sets of rollers which are moderately heated, e.g. -to a temperature below the setting point of the resin used as birder.
Due to the repeated defibration of the fibrous mate-rial, irregulari-ties in the distribution of binder in the intermediate product can be fully eliminated.
The binder used in the intermediate product is pre-ferably of the thermocuring type.
The invention will now be described in further detail with reference to the drawings, in which:
Figs. 1-9 illustrate various fibrous products obtain-ed by the method of the invention and Fig. lO schematically illustrates a method of pre-paring a fibrous product comprising cup-shaped portions.
Fig. 1 shows a cross sectional view of a product pre-pared by the method of the invention. This product compris-es a relatively loose fibrous layer l having a top layer 2 made from a fibrous material having a high binder concen-tration.
r~he composite product has heen 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 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.
E'ig. 4 illustrates a fibrous product in which the binder concen-tratiorl increases from -the upper surface -to-wards the lower sur~ace.
Fig. 5 illustrates a fibrous product prepared by the method of the invention, sai~ product comprising parallel zones 9 of a high binder concentra-tion, said zones being applied to the product in i-ts machine direction.
The fibrous product illustrated in Fig. 6 comprises a loose fibrous layer lO located between two non-woven nets 11.
The fibrous product shown in Fig. 7 is a fibrous pro-duc-t provided with crossing grooves 12 so as to form a product which is similar -to the well known quilted tex-tile products.
Fig. 8 illustrates a box 13 having an in-tegral hing-ed lid 14, said box and lid being prepared from a rolled fibrous product ob-tained by the produc-t of the invention.
Fig. 9 shows a cross sectional view of a pre~erred packing ma-terial prepared by embossing a fibrous product of the invention in a pa-ttern 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 l9. The forming wire 15 is provided with cup-shaped projections 20 on which a fibrous layer 21 contain-ing a binder is deposi-ted in a manner which is well ]~nown per se.
The fibrous layer 21 is removed from the forming wire 15 and is introduced into the nip between the two in-termeshing rollers 17 and 18. During the passage -through said nip the fibrous layer is compressed to form dense cup-shaped elemen-ts which are subse~uently removed from the roller 18 and separated from one another.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
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 gas-eous 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, latices, starch, modified starch and water glass.
3. A method as claimed in claim 1, 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 claim 1, 2 or 3 comprising forming a fibrous layer comprising two or more plies having different binder concentrations.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000322903A CA1142394A (en) | 1979-03-07 | 1979-03-07 | Method of preparing dry-laid fibrous products |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000322903A CA1142394A (en) | 1979-03-07 | 1979-03-07 | Method of preparing dry-laid fibrous products |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142394A true CA1142394A (en) | 1983-03-08 |
Family
ID=4113690
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000322903A Expired CA1142394A (en) | 1979-03-07 | 1979-03-07 | Method of preparing dry-laid fibrous products |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1142394A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2718361B1 (en) | 2011-06-09 | 2023-10-04 | A.P.C.A. (Assemblee permanente des Chambres d'Agriculture) | Protective and/or combustible material made from cellulosic plant material, and corresponding method for manufacturing same |
-
1979
- 1979-03-07 CA CA000322903A patent/CA1142394A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2718361B1 (en) | 2011-06-09 | 2023-10-04 | A.P.C.A. (Assemblee permanente des Chambres d'Agriculture) | Protective and/or combustible material made from cellulosic plant material, and corresponding method for manufacturing same |
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