Technical field The present invention relates to a process for manufacturing a fibre web comprising a thermosetting resin. The invention is further related to a fibre web comprising thermosetting resin which has been obtained by means of the process, and an reinforced thermosetting containing composite which includes the fibre web comprising the thermosetting resin.

The invention will be applied within the field of reinforced thermosetting composites, and their manufacture. The thermosetting composite of the invention can preferably be used for sanitary products, such as washing stands, and toilet chairs, for different surfaces being subject to abrasion, for electricity conducting products, and for many medical technical products, such as devices for lengthening a leg to be implanted, and the similar. Many other applications are considered as well.

Background of the invention At the manufacture of fibre composites thermosetting resins are often used as a binder or matrix material. One reason for this is that thermosetting resins, often before hardening (cross linking) are present in a form of a liquid having a relatively low viscosity at room temperature, something that makes the impregnation of a reinforcing material quite simple.

Certain thermosetting resins, such as urea-formaldehyde (UF) and melamine- formaldehyde (MF) are, however, not in liquid state at room temperature prior to hardening. In order to be able to impregnate a reinforcing material using such a thermosetting resin it has thus previously been proposed that this type of thermosetting resin should be provided in the form of a solution, dispersion, or paste of thermosetting

resin together with a suitable liquid, (e. g, water). The last mentioned is described in e. g., patent description of US-A--4, 101,475, which will be discussed more in detail in the following.

Within the field of reinforced thermosetting resin, here often called thermosetting resin composite it is previously known a number of manufacturing processes, reinforcing materials, and matrix material.

The reinforcing material of a reinforced thermosetting resin is often fibres in the form of roving, web, mats, or non-woven material. Depending on the actual application field the reinforcing fibres may consist of natural or synthetic polymers. Examples of commonly used reinforcing fibres are glass fibres, and carbon fibres, and in some applications also cellulose fibres, such as pulp fibres, rayon or linen.

The binding agent or matrix material in a reinforced thermosetting resin is often an unsaturated ester resin, but also epoxy, pheno-or amino resins are used.

A number of different methods for forming details of reinforced thermosetting resin are known since earlier. A well known forming method is the contact method which comprises that Thermosetting resin and reinforcing material (e. g., ester resin and glass fibre material) are put in layers on a mould at room temperature, whereupon the ready resin detail, after hardening, is brought out off the mould provided with a mould release agent.

A development of the above mentioned process using layering by hand includes that one in stead manually or by means of a robot sprays a two component thermosetting resin and reinforcing material in the form of chopped roving onto the mould.

The hardening of the resin (matrix material) can be carried out under pressure by pressing a film against a contact or spray moulded article using super pressure or vacuo, which provides for an increased strength. By simultaneously applying a pressure and heat in an autoclave the result can be even more improved.

Another common method for manufacturing polymer details of reinforced thermosetting resin is compression moulding. In this method, there is usually first manufactured a preform of reinforcing material, e. g., chopped roving, and a minor amount of thermosetting resin, e. g., polyester as binder. After hardening the preform is brought out off the mould and is placed in a form press together with a sufficient amount of polyester, which then, during heating, is pressed into the material. In stead of preforms, preimpregnated mats of reinforcing material, e. g., glass fibre mats, can be used (Sheet Moulding Compound) or preimpregnated press sheets can be used at compression moulding.

Other previously known methods for manufacturing details of reinforced thermosetting resin is profile drawing, winding, centrifugal and rotational moulding, transfer moulding, and injection moulding Common to several of the above given methods for manufacturing reinforced thermosetting resin composite, are that they utilizes or can utilize different types of reinforcing material being preimpregnated with thermosetting resin, so called "Prepreg".

The manufacture of preimpregnated reinforcing material for the manufacture of Thermosetting resin composite can be done by means of a number of"wet"methods, in which the reinforcing fibres are impregnated with a solution, dispersion or paste containing thermosetting resin.

Thus, e. g., US-A-4,906,505 describes a skin formed product comprising a mixture of amino resin-formaldehyde and fibrous material, whereby the product is characterized in that the resin mixture has a viscosity of 25 Pa. s.-15 x 103 Pa. s. at 120°C in the skin formed product, and that the fibre material in the form of a pile or sheet has a strength of 0.1 MPa-20 MPa at 20°C. According to US-A-4,906,505 the fibre material is impregnated with the resin mixture whereupon the impregnated material is dried until the amino resin mixture obtains a viscosity which exceeds 25 Pa. s. to 15 x 103 Pa. s.

Further, there has been described in the previously mentioned US-A-4,101,475 an abrasion resistant, flame protected material, which is manufactured by producing a compression moulding composition of a precondensate of a melamine aldehyde, silicon dioxide, aluminium trihydrate, a soap having a low solubility, ammonium hydroxide, and an acid salt catalyst. The composition is then applied onto the surface of a sheet of glass fibres comprising a heat hardening binder, and the composite is bound under heat and pressure to harden both binders simultaneously, and to bind the composition to the fibre layer of the sheet.

The previously known"wet"processes for the manufacture of preimpregnated reinforced fibre webs, sheets, boards or smaller sheets can, however, be connected with certain problems.

At the impregnation methods utilizing thermosetting resin solutions or dispersions the reinforcing material has to be added in the form of a continuous fibre sheet or fibre web. A such is considerably more expensive than the fibres present in the reinforcing material per se. As the amount of reinforcing fibre and the liquid absorbing ability are defined by the actual construction of the fibre sheet or fibre web it can be hard to control the amount of reinforcing fibre of the ready material, to a desired level.

In those cases where one wishes to add a filler together with the actual resin mixture, there is in the previously known processes utilizing thermosetting resin solutions or dispersions, depending on the density of the actual filler, a risk that the filler will precipitate or float in the resin mixture so that an uneven application is obtained.

Further, problems with too a high viscosity of the resin mixture can appear at high concentrations of filler, or at the mixing-in of the filler, which functions as a viscosity improver, such as cellulose fibres, micro fibrils, super absorbents, and the similar.

Furthermore, at longer storage periods ageing phenomena may occur in liquid thermosetting resin mixtures.

When using thermosetting resin containing solutions or dispersions for the manufacture of preimpregnated reinforcing fibre webs a particular drying process is needed. Such a drying process may lead to certain problems with uneven drying or prehardening, and thereby result in a fibre web having uneven quality. Further, the drying process requires much energy and is often connected with problem of precipitations of resin in the details present in the drying step.

Previously proposed processes for the manufacture of preimpregnated fibre materials using thermosetting resin, where the thermosetting resin is applied in the form of a paste, some of the above mentioned problems are reduced or eliminated, and makes it possible to use reinforcing fibres in the form of economically advantageous chopped roving. The above mentioned problems using the particular drying step however, will remain fully.

Description of the present invention A first object of the present invention is thus to obtain a method for manufacturing a fibre web containing thermosetting resin, which method eliminates all above mentioned problems.

This first object is achieved, in accordance with claim 1, by that the method comprises shaping a fibre web of at least reinforcing fibres, joining at least one thermosetting resin with said reinforcing fibres, and binding, after joining, the fibre web at least partly by means of the thermosetting resin. The method further comprises adding the thermosetting resin in the form of substantially dry grains of thermosetting resin, joining the grains of thermosetting resin with the Reinforcing fibres at a joining temperature of about room temperature, then binding the fibre web by, prior to and/or under pressure, at least partly heating the grains of thermosetting resin in the fibre web to a binding temperature above the joining temperature, and by then cooling down the fibre web to room temperature.

A second object of the present invention is to obtain a fibre web containing Thermosetting resin obtained by means of the process.

This second object is obtained, in accordance with claim 13, in that the fibre web comprises at least Reinforcing fibres and a Thermosetting resin and is intended to be present in a reinforced Thermosetting resin composite, whereby the Thermosetting resin is present in the fibre web in the form of only partially hardened grains of Thermosetting resin.

A third object of the present invention is to obtain a reinforced Thermosetting resin composite which comprises the fibre web containing the Thermosetting resin.

This third object is achieved, in accordance with claim 24, by means of a reinforced Thermosetting resin composite which has been produced by forming a charge of material comprising at least a part of a fibre web containing a Thennosetting resin according to the invention and by then hardening the Thermosetting resin present in the part at a hardening temperature above room temperature.

Further objects of the present invention will be apparent from the following description while the features that facilitates that these further objects are achieved, are evident from the subclaims Summary of the figures The invention will be described more in detail in the following with reference to the accompanying drawings, whereby Fig. 1 shows a schematic side view of an arrangement suitable for utilizing a process according to a first embodiment of the invention Fig. 2 shows a schematic side view of an arrangement suitable for utilizing a process according to a second embodiment of the invention Fig. 3 shows a schematic side view of an arrangement suitable for utilizing a process according to a third, particularly preferred embodiment of the invention

Detailed description of preferred embodiments With referenced to the accompanying figures 1-3 a process for manufacturing a fibre web containing Thermosetting resin according to the invention will be described more in detail in the following.

On the accompanying figures 1-3 schematic side views of three different arrangements which are suitable for utilizing the different embodiments of the process according to the invention are shown. Thereby it should be noted that other arrangement than those shown in figures 1-3 may be suitable for carrying out the process according to the invention, as well.

The process according to the invention includes forming a fibre web 100; 200; 300 of at least reinforcing fibres 101 ; 201 ; 301 ; to bring together said fibres with a thermosetting resin 102; 202; 202' ; 302 and to join the fibre web 100' ; 200' ; 300'at least partly by means of the thermosetting resin after the bringing together.

According to the invention the process further includes adding the thermosetting resin in the form of a substantially dry grains 103; 203; 303 of thermosetting resin. The thermosetting resin is thus not in liquid state and not in a form of an emulsion or solution either at the confluence with the reinforcing fibres.

The process of the invention further includes bringing the grains of thermosetting resin together with the reinforcing fibres 101,201,301, at a confluence temperature Tl at about room temperature, and to then join the fibre web by prior to and/or under a pressure p at least partly heating the grains of thermosetting resin present in the fibre we 100', 200', 300'to a joining temperature T2 being higher than the temperature T, at the confluence. Then the fibre web 100', 200'300'is cooled to room temperature and the thermosetting resin containing fibre web of the invention is, after an optional treatment and conversion to suitable dimensions, ready for use.

The joining of the fibre web which takes place by means of heating the grains of thermosetting resin under pressure can advantageously be carried out in a pressing device known per se for other purposes of the type which is indicated in figures 1-3 and which is called a dual belt press. In such a pressing device the fibre web is carried between two metal belts and passes together with the belt through a number of press nips whereby both the temperature T2 and the pressure p can be carefully controlled to control the joining. However, one can also consider embodiments of the process of the invention where the joining takes place in another suitable manner e. g., where the fibre web 200 is preheated to a first elevated temperature T2'in a particular preheating step using heated rolls or the similar before being heated to the proper joining temperature T2.

In a first preferred embodiment of the process of the invention, particularly illustrated in fig. 1 the reinforcing fibres 101 are formed in a first step to a fibre pile 100, of textile material or non-woven material. In this embodiment the thermosetting resin 102 is brought together with the reinforcing fibres by with-bringing the grains of thermosetting resin 103 in a gas flow 104 which is led through the fibre pile 100, textile material or non-woven material. Suitable techniques for producing the reinforcing material already formed and optionally bound, before the confluence in this embodiment, are well known to the one skilled in the art. It should, however, be noted that within the scope of the invention it is considered having embodiments where the fibre pile, textile material or non-woven material comprise short cut fibres, continuous fibres or combinations of these.

In a second preferred embodiment of the process according to the invention, particularly illustrated in fig. 2, the reinforcing fibres are added at least partly in the form of short cut fibres 201. In this embodiment the thermosetting resin 202,202'is brought together with the reinforcing fibres by forming the short cut fibres 201 to a reinforcing layer on the top of at least one provided layer of thermosetting resin 205 of the grains of thermosetting resin 203 and/or by having the short cut fibres formed into a reinforcing layer on top of which at least a layer of thermosetting resin 205'of the grains of thermosetting resin 203'is added. Short cut fibres in the dimensions desired

based on different polymers are commercially available from many suppliers of fibres.

In the embodiment shown in fig. 2 the short cut fibres are generated in situ by cutting filaments in the form of so called roving or tow to a desired length in a device arranged therefor.

In a third, particularly preferred embodiment of the invention, in particular illustrated in fig. 3 the reinforcing fibres are added at least partly in the form of short cut fibres 301.

In this embodiment the thermosetting resin 302 is brought together with the reinforcing fibres by having the short cut fibres 301 and the grains of thermosetting resin 303 brought with a gas flow 306 to then together be formed to the fibre web 300. In this embodiment an equipment, per se known for other purposes, for air fluidizing the fibres to form the fibre web 300.

In a particular embodiment of the process according to the invention at least a part of the reinforcing fibres 101, 201,301 in the form of short cut fibres and/or continuous filaments of regenerated cellulose, natural polymers, or synthetic polymers.

In another preferred embodiment at least a part of the reinforcing fibres are added in the form of cotton fibres, linen fibres or other plant fibres.

In an alternative embodiment of the invention the reinforcing fibres are added in the form of short cut fibres and/or continuous filaments of glass, carbon, metal or mineral.

It is, however, also considered possible having embodiments which utilizes other types of inorganic fibres as reinforcing fibres.

The abovementioned grains of thermosetting resin 102,203,203', 303 are particularly preferably added in a form which contains amino resin where the amino groups are present as urea, melamine, or benzoguanamine.

When so desired, or necessary a plasticiser 207 can, most preferably be chosen from the group of sorbitol, caprolactane, ethylene glycol, trioxitol, toluene sulfonamide, benzo

or aceto guanamine and be added to the fibre web 200 prior to joining. It is, however, also possible having other types of plasticisers.

In a particularly preferred embodiment of the process according to the invention a filler 208 is added, which includes a micro crystalline cellulose and/or a superabsorbent to the fibre web 200 prior to the joining. This embodiment is particularly preferred in the case the resulting fibre web containing the thermosetting resin shall be used for reinforced thermosetting resin composite having liquid absorbing properties, e. g., in connection with implantable devices for lengthening of legs and the similar.

In a further alternative embodiment of the process according to the invention a filler is added which most preferably includes calcium oxide, kaolin, carbon, silicon dioxide, or metal particles, to the fibre web prior to the joining. It is, however, also possible to having other types of filling agents.

In a preferred embodiment of the process of the invention a polymer film material is added to the fibre web prior to joining. Thereby it is possible, as well, having embodiments where the polymer film material is added to both sides of the fibre web.

In the following, a number of different embodiments of fibre webs containing thermosetting resin according to the invention, will be described, and when possible, with reference to the different accompanying figures 1-3.

The fibre web containing the thermosetting resin according to the invention includes at least reinforcing fibres and a thermosetting resin and is intended to, after hardening, be present in a reinforced thermosetting resin composite. According to the invention the thermosetting resin is present in the fibre web 100", 200", 300"in the form of only partially hardened grains of thermosetting resin.

In a first preferred embodiment of the fibre web containing the thermosetting resin according to the invention the grains of thermosetting resin are carried by the

reinforcing fibres of a fibre pile 100, textile material or non-woven material present in the fibre web 100".

In a particularly preferred embodiment of the fibre web containing the thermosetting resin according to the invention the reinforcing fibres are at least partly short cut fibres whereby a substantially homogenous mixture of grains of thermosetting resin 203,203', 303 and the short cut fibres 201,301 form or are present in the fibre web 200", 300".

In another preferred embodiment at least a part of the reinforcing fibres is short cut fibres 201,301 and/or continuous filaments of regenerated cellulose, natural polymers or synthetic polymers.

In a further preferred embodiment of the fibre web containing the thermosetting resin according to the invention, at least a part of the reinforcing fibres is cotton fibres, linen fibres or other plant fibres.

In an alternative embodiment of the fibre web containing the thermosetting resin according to the invention at least a part of the reinforcing fibres are short cut fibres and/or continuous filaments of glass, carbon, metal or mineral.

The abovementioned grains of thermosetting resin 103,203,203', 303 of the fibre web containing thermosetting resin according to the invention comprises preferably amino resins, where amino groups are provided by urea, melamine, or benzoguanamine.

In another preferred embodiment of the fibre web of the invention the fibre web comprises sorbitol, caprolaktan, ethylene glycol, trioxytol, toluene sulfonamide, benzo or aceto guanamine.

In a particularly preferred embodiment of the fibre web 200"of the invention this comprises a microcrystalline cellulose 208 and/or a superabsorbent.

In a still further embodiment of the invention the fibre web containing thermosetting resin comprises calcium oxide, silicon dioxide, or metal particles.

In another embodiment the fibre web of the invention comprises a polymer film material which may be chosen of a suitable type for the application in mind.

The fibre web containing thermosetting resin according to the invention is preferably utilized to manufacture a reinforced thermosetting resin composite by forming a material charge (not shown in the figures) which comprises at least a piece of the fibre web 100", 200", 300"containing the thermosetting resin and by then hardening (not shown in the figures) the thermosetting resin present in the piece at a hardening temperature above room temperature. The reinforced thermosetting resin composite is particularly preferably present in or is a sanitary product, an abrasive surface, an electricity conducting material, or a medical technical product as an implantable device for lengthening of a leg.

The present invention will in no way be regarded as restricted to what has been described herein in connection with the different embodiments or to what has been shown in the accompanying figures, but the scope of the invention is defined be the accompanying claims.

The present invention thus facilitates inter alia the manufacture of electricity conducting thermosetting resin composite with a high content of metal, thermosetting resin composite having an aesthetically appealing and abrasive resistant surfaces to be used as abrasive surfaces or sanitary products, and thermosetting resin composite containing superabsorbent to be used as medical technical swelling bodies.