WO2000053667A1

WO2000053667A1 - Sheet prepreg containing carrier sheets

Info

Publication number: WO2000053667A1
Application number: PCT/NL2000/000113
Authority: WO
Inventors: Maurits Frederik Hendrik Van Tol; Karel Franciscus Hubertus Bonekamp
Original assignee: DSM NV
Current assignee: Koninklijke DSM NV
Priority date: 1999-03-05
Filing date: 2000-02-23
Publication date: 2000-09-14
Anticipated expiration: 2001-09-05

Abstract

Sheet prepreg comprising one or more layers of a carrier sheet, which carrier has been impregnated with an as yet uncured resin, the carrier being a porous polymer sheet on the basis of wholly or partly regenerated cellulose and that the elongation at break of the prepreg and of the separate, impregnated carrier sheet is preferably higher than 2 %.

Description

SHEET PREPREG CONTAINING CARRIER SHEETS

The invention relates to a sheet prepreg comprising one or more layers of a carrier sheet, which carrier is impregnated with an as yet uncured resin.

Sheet prepregs comprising a number of stacked carriers of α-cellulose impregnated with the reaction product of formaldehyde and melamme are disclosed, for instance, m US-A-3730828. According to said patent, first paper is impregnated with a melamme- formaldehyde resin. Then a prepreg is made by drying a few layers of this impregnated paper and stacking them on top of one another. The resin is then cured m a press at a pressure of, for instance, 6 MPa and at a temperature of approximately 150°C, yielding a sheet product. The reaction between formaldehyde and melamme m the sheet product thus obtained is virtually complete at the reaction temperature used (completely cured) . The sheet products described said patent appear to have good postform g properties. Postformmg is here understood to mean that the sheet product can be bent at an elevated temperature which is between 160 and 180 °C. It is possible to bend the sheet product to some degree along one axis (the so-called 2D deformation, yielding 2D moulded articles) without the sheet product breaking or cracking. A disadvantage is that, starting from a prepreg according to US-A-3730828, it is not possible to obtain sheet products which can be bent along two (or more) mutually intersecting axes to form complex shapes without breaking or cracking (the so-called 3D deformation, yielding 3D moulded articles) . Complex shapes may be considered to be, for instance, a saddle- type pattern, a small tub, a hemisphere, a sickle pattern or a satchel .

The object of this invention is to provide a prepreg with which complex shapes can be obtained and/or covered.

This object is achieved with a prepreg consisting of one or more layers of a carrier sheet, which carrier has been impregnated with an as yet uncured resm, the carrier being a porous carrier sheet on the basis of wholly or partly regenerated cellulose. Regenerated cellulose is understood to be treated cellulose. This treatment implies that the cellulose is converted into a soluble cellulose derivative (usually the xantagonate) , following which this cellulose derivative can be converted, for instance via a spinning process, into fibres, which can optionally be further reduced size. An acid is subsequently used to convert these fibres into regenerated cellulose. From this regenerated cellulose then a carrier is prepared, which is impregnated with a resin mixture, following which, after drying ( the case of, for instance, F, but depending on the resm) , one or more carriers are stacked to form a prepreg.

Instead of a porous carrier sheet on the basis of wholly or partly regenerated cellulose, the porous carrier sheet can also be prepared on the basis of wholly or partly regenerated cellulose together with wood and/or paper pulp, m particular with kraft paper pulp. The ratio of cellulose to pulp is determined by the final application and may vary within broad limits.

The elongation at break of the separate carrier sheet and of the prepreg obtained is higher than 2%, preferably higher than 5%, and in particular higher than 10%. The elongation at break is measured at a temperature that is close to the temperature at which the carrier is processed.

It has been found that, starting from the prepreg according to the invention, sheet products can be made in the most diverse shapes without any cracks being formed in the sheet product during deformation.

Sheet products are now possible with shapes involving local stretching of the prepregs from 10% to more than 100% during the shaping. Objects in which the required maximum deformation is lower than 10%, too, can be coated better with the sheet product according to the invention than with sheet products on a paper basis. Example are some so-called softline panels, 3D-shaped panels with round edges and/or corners, and/or gradually inclining surfaces or contours.

A further advantage is that the further curing of the resin and the deformation can be performed in one step. This is in contrast to the method described in the above-mentioned US-A-3730828 where, starting from the prepreg, two steps are necessary to obtain a shaped final product .

An additional advantage is that the prepreg can be processed by a multiplicity of techniques, as a result of which the optimum technique can always be used for each final product.

Another advantage is that, starting from the prepregs according to the invention, both 2D and 3D objects can be coated, so that it is possible to obtain identical designs on both objects, for instance the design of a 3D kitchen cabinet and a 2D laminate floor. Starting from the prepreg according to the invention, t is furthermore possible to make sheet products which are bent into an acute angle. Starting from the known prepregs based on a paper carrier, this is impossible.

A porous carrier sheet is understood as meaning any carrier having a high degree of porosity. The porosity of the carrier is essential for obtaining the advantageous properties of the prepreg as described above .

As a result of the high porosity, the carrier sheet can be mixed with the resm. Preferably, the porosity is obtained m the form of microscopically small, mutually communicating cavities and there are preferably few larger cavities and holes present . Larger cavities and holes result m loss of resm during the further processing to give the prepreg its final shape Preferably, the porosity is sufficiently high so that at least 30% by volume of the final moulded article consists of resm.

The porous carrier on the basis of wholly or partly regenerated cellulose will preferably be a woven or non-woven, an open foam sheet or a microporous membrane. Wholly or partly regenerated celluloses are commercially available under, for instance, the generic names viscose and rayon or the brand name Lyocell® (an Acordis product), etc. These rayons and viscoses are prepared by modifying cellulose, which is the mam component of for instance wood or paper pulp, by for instance turning it into an xantagonate. Contrary to cellulose itself, these cellulose xantagonates are capable of being dissolved and spun, so that threads can be obtained. These threads are then wholly or partly regenerated m an acid environment, so that threads of cellulose are obtained. Lyocell® threads are obtained by spinning from a cellulose solution m N-methyl- morphol e-N-oxide (NMNO) . By removing N NO from the resulting threads via extraction with water, regenerated cellulose threads are formed.

All these threads can subsequently be converted into fibres, for instance by reducing the size of the threads, which fibres can be used for the preparation of, for instance, wovens or non-wovens. Preferably, the fibres of the non-woven have a diameter of less than 0.1 mm. Non-wovens with fibres that have a very small diameter are also referred to as open films. This class of non-wovens has, as a result of the small thread diameter, few larger meshes and many microscopically small, mutually communicating cavities.

Polymer foams have mutually communicating cavities, the cavities preferably having a diameter of less than 1 mm. Larger cavities may occasionally be present m the foam provided more than 80% by volume of the cavities have said smaller diameters.

The porous carrier sheet may have both polar and apolar properties. Preferably, the polar properties must predominate. As a result of making use of suitable wetting agents, the desired degree of impregnation of the sheet by the resm can be obtained. As a rule, all the wetting agents known to one skilled m the art can be used. Examples of wetting agents are PAT 523W, PAT^ 959 (PAT^Φ is a Wϋrtz brand name) , Nonidet^* P40 (Nonidet^*5 P40 is a Sigma Chemie brand name) and Amino1 N (Amino1 is a Chem-Y brand name) .

The resm with which the carrier is impregnated may m principle be any known res and may moreover contain a reactive or non-reactive solvent. It is also possible for the resm to consist of polymeπzable monomers. Examples are thermosettmg resms or elastomeπc resms, which resms can be cured via an ionic, radical, oxidation, addition or condensation mechanism or which cure via a combination of these mechanisms, such as for instance m the so- called dual -curing.

Examples of resms that cure via an oxidation mechanism are alkyd resms. Usually, however, cationically and/or radically curing resms are used and/or resms that cure via a condensation or addition reaction.

Cationically or radically curing resms can cure according to a homopolymeπzation or a copolymerization reaction. Radically curing resms can contain unsaturated monomers and/or groups which contain, inter alia, (meth) crylate, itaconate, maleate, fumarate, styrene, fumaramide, maleamide, maleimide, vmylether, allylether and/or vmyl ester groups. Examples are the acrylate resms.

Cationically curing resms can contain monomers which contain polymeπzable groups, such as for instance epoxy, glycidyl, cycloaliphatic epoxide, vmyl ether, vmyl ester, allyl ether, allyl ester, propenyl ether, butenyl ether, vmyl acetate, oxetane, cyclic carbonate and/or dioxalane groups. Examples are epoxy resms .

Examples of res s that cure via an addition or condensation mechanism are ammoplastic resms, phenol -formaldehyde resms (PF resms) and/or two- component resms consisting of hydroxyl-functional polymers or oligomers and isocyanate-functional oligomers or polymers and/or alkylated melamme resms.

Preferably, an ammoplastic resm is used. Compounds of formaldehyde with, for instance, urea, melamme, acetoguanamme or benzoguanamme , or compounds or mixtures of these, can be used as the ammoplastic. Preferably, melamme is used because of the superior mechanical properties of the final product . The ammoplastic resm can be prepared m a process known to one skilled m the art by reaction of, for instance, melamme and/or urea with formaldehyde m water. Optionally, the urea and/or the melamme can be partially replaced by, for instance, phenol, but this may have adverse effects on the colour. Modifiers, such as sorbitol, ε-caprolactam, etnylene glycol, polyethylene glycol, polypropylene glycol, hydroxy- functional polyesters, hydroxy-functional acrylates, tπoxitol, toluene sulphonamide, and benzo- and acetoguanamme can also be added. It is also possible to use resm mixtures or resm combinations that can cure according to different mechanisms, such as for instance a mixture of a melamme- formaldehyde resm and an acrylate- functional res , for impregnation of the carrier. It is possible for these resms to be prepared and/or cured the presence of a catalyst and/or initiator that is specific to each resm system, as known to one skilled m the art .

Mechanical properties that are suitable for practical use are achieved if 10-70% by weight of porous carrier and 90-30% by weight of resm are used. The resm may contain the known fillers, pigments and/or colorants such as for instance as known from the paper industry. Examples are lime, titanium dioxide, iron oxide, glass, carbon, silica and/or metal particles. It has been found, however, that the best results are achieved the absence of fillers or at any rate with less fillers than has been customary so far. The filler to resm weight ratio is preferably between 0 : 1 and 0.5:1. These ratios relate to the cured, final sheet product . The prepreg is made under the conditions which are already known for making prepregs based on a paper carrier, as described, for instance, the above- mentioned US-A-3730828. The viscosity of the resm used for the impregnation can be influenced by, among other things, varying the nature and the amount of the solvent. As yet uncured ammoplastic resm such as melamme formaldehyde resm is for instance dissolved m water and preferably has a viscosity of 1-1000 mPa . s . Preferably, solvents are used m which the carrier does not dissolve or swell. The temperature during the impregnation is typically between 15 and 60 °C and for practical reasons is often room temperature. Higher temperatures are less practical because then the resm might wholly or partially cure during the impregnation. The pressure during the impregnation is not critical and for practical reasons is as a rule atmospheric.

The carriers impregnated m this way can optionally be dried until a certain residual volatility is reached. For melamme-formaldehyde (MF) and phenol- formaldehyde (PF) resms this residual volatility is the prepreg' s mass loss at 160°C for 7 minutes. The residual volatility of the prepreg usually lies between 2 and 20%. The elongation at break of the prepreg as used m the description is defined as the elongation at break at a residual volatility of about 6 to 7% and measured at a temperature that is close to the product's processing temperature. Drying preferably takes place at a temperature of 100-160°C if MF resm is used. Higher temperatures are less practical because the drying times then become too short, resulting m a process that is difficult to control. The temperature will practice also be determined by the type of resm and the type of oven. The optionally dried carriers can be stacked to form a multi-layer prepreg. In principle as many sheets can be stacked as is needed to obtain the desired thickness or strength, for instance for self-supporting 2D and 3D moulded articles such as lamp shades and

(corrugated) sheeting for interior and exterior use. For laminate applications the number of carrier sheets is usually 100 or lower, particular 10 or lower, and preferably 5 or lower. The prepreg may optionally comprise layers of a non-porous carrier besides the porous carriers, provided these carriers also have an elongation at break that is higher than or equal to that of the prepreg.

The prepregs can be processed into a shaped final product by first deforming the prepreg and then curing the intermediate product formed or by combining the deformation and the curing operations one step. Resm curing can for instance be realized by heating the prepreg, optionally at elevated pressure, up to a temperature at which the resm cures. An example is the curing of an MF resm. If the res contains polymerizable groups that can react by means of a radical mechanism, such as for instance a resm containing unsaturations, the res can be cured by treating the prepreg with an electron beam, or irradiating the prepreg with ultraviolet or ionizing radiation. If a prepreg contains a resm that cures via a radical mechanism, it may be advantageous to add a radical initiator. The radical initiator will fully or partly disintegrate into radicals that can start the polymerization reaction. Examples of well-known radical initiators are peroxides from the Trigonox® series

(produced by AKZO-NOBEL) . To accelerate the initiation of the polymerization, an accelerator can be added to the resm. Examples of well-known accelerators are cobalt complexes. The polymerization of resm that cures according to a cationic mechanism and that is impregnated m a carrier can be initiated by the addition of a cationic initiator,

The surface of the final product can be prepared as desired using techniques known to one skilled m the art. A high-gloss surface can for instance be obtained by using for instance a polishing plate m the press, a polishing membrane or a polished mould. An embossed surface can be obtained by using, for instance, an etched or engraved plate m tne moulding operation, or applying an embossed membrane or an embossed mould. Patterns can be provided a similar way. It is also possible, for instance, to use films between the pressing plate or membrane and the moulded article. These films, in turn, can also be smooth, matt or have the desired pattern or relief. Optionally, such films may also be used as membrane. Deforming, optionally in combination with curing, can be performed, for instance, by means of bending, embossing, 3D deformation such as 3D pressing, stamping, pneumatic stretching or mechanical stretching. The deformation temperature will depend on the yield stress of the prepreg. The yield stress is the stress at which the material begins to flow. In principle, said temperature may be between room temperature and 200°C.

The shaped product obtained in this way can be used as a final product or as a protective layer around an object having a core material of, for instance, wood; wood-based materials such as the well- known MDF (Medium Density Fiberboard) and HDF (High Density Fiberboard) materials, metal; glass; plastic, for instance polyethylene, polypropylene, ABS , polyester, polyamide and MF, PF and epoxy resins or composite objects.

The invention also relates to objects provided with a top layer obtained from a sheet prepreg bent along two or more mutually intersecting axes (3D objects) .

Examples of 3D final products of the shaped product are serving trays, washing-up basins, crockery, lamp shades, (corrugated) sheeting, doors, kitchen worktops, furniture and wall panels. Examples of 3D final products where the shaped product is used as a protective layer for a wooden or wood-based core are worktops with a 3D structure and/or, for instance, an acute angle, (kitchen) cupboards, window frames, panels with a 3D structure, for instance on the basis of milled MDF panel, laminated flooring with a 3D structure (for instance with upright edges), skirting boards, etc.. Examples of 3D objects m which the shaped product serves as a protective layer for a plastic core are bumpers, petrol tanks, garden furniture, chairs, helmets, worktops or car bodywork components. The invention relates m particular to sheet prepregs that provide objects with a 3D structure based on milled MDF or HDF board with a top layer. These laminated MDF or HDF boards can be produced m one process step, for instance m an m-mould lamination process.

The sheet products according to the invention can also be used m flat applications (2D deformation) such as laminate flooring, interior door panels, wall panels, table tops, etc., and m post- forming applications.

The top layer may be glued to the core material. Another possibility is for the shaped product to be applied to the core while the resm is still incompletely cured. The resm then serves as a glued joint when it is subsequently cured.

The invention will be elucidated by means of the following, non-limitmg examples. Example 1 (code KB661-1 / KB674-2b)

Preparation of resm

In a reactor, 48 parts of water and 131 parts of formalin (30 wt . % formaldehyde m water treated with 50 wt . % NaOH to adjust its pH to 9.3) were added to 100 parts of melamine . The F/M ratio of the resm was 1.65 (F/M ratio is the molar formaldehyde-melamme ratio) . The condensation reaction was performed at 95°C until the water dilutability of the resm at 20°C was

1.5 g of res per g of water. The water dilutability is the amount (g) of water which can be added to a res solution (g) at 20°C before the solution becomes turbid. Using a 50 wt . % p-toluene sulphonic acid solution the resm pH was adjusted to 7.5 at 20°C to make the solution suitable for further processing.

Preparation of sheet product

A 20 x 20 cm carrier sheet from 100 wt . % rayon, spunlaced, 120 g/m² (from Orlandi S.P.A., fibres from Lenzmg AG) , was impregnated at room temperature with the above-mentioned resm solution, to which 0.5 wt . % PAT^@ TD80 (from Wurtz) had been added for wetting purposes and 0.2 wt . % PAT^® 523/W (from Wurtz) for mould release purposes. After one minute, the resin- impregnated sheet was removed from the impregnation equipment and the excess resm was removed with the aid of a sort of wringer. The sheet was dried m a circulatmg-air oven for 16 minutes at 100°C. See Table 1. Characterization of the prepreg

Resin content : the resin content of the prepreg was determined by weighing the prepreg and the polymer carrier and was 415%. See Table 1. The resin content is defined as:

(g (prepreg) -g (carrier) ) /g (carrier) ,

g (prepreg) and g (carrier) are the weights of the prepreg and of the rayon carrier, respectively.

Residual volatility: the residual volatility was determined by measuring the weight loss after drying and curing the prepreg for 7 minutes in an oven at 160°C and was 6.8%. See Table 1. The residual volatility is defined as:

(g (before) -g (after) ) /g (before) ,

(before) and g (after) are the weights of the prepreg before and after the treatment at 160°C, respectively.

Elongation at break and tensile strength

The elongation at break and tensile strength were measured on test specimens (measuring 4 x 50 x 0.7 mm) using a Standard Zwick tensile tester at 140°C and 160°C according to ISO 527-2, 5A (1993) and amounted to 61 and 73%, respectively. The deformation rate was 100 mm/min. See Table 2. 2D pressing on a flat substrate:

One sheet of a rayon-based prepreg measuring 20 x 20 cm was pressed on a flat Medium Density Fiberboard (MDF) panel into a laminate using the following low-pressure lamination method: The MDF panel with the prepreg on top of it was placed m the press (of the type Fontijne TP400) following which the press is closed and its pressure raised to 20 bar. Only the upper mould half - which is fitted with a polishing plate - was heated and the temperature was 140°C. These conditions are maintained for 3 minutes and then the press is opened and the laminate removed. See Table 1. After cooling the laminate could be characterized.

Characterization of the 2D laminate

- In the first place the laminate was assessed visually, also with the aid of a light microscope.

At microscale the structure was very fine, resembling that of paper. The laminate surface did not contain any air inclusions and looked well-closed.

- In addition, it was subjected to a few standard tests, more specifically the staining test and the Kiton test. These are well-known tests m the world of MF resm laminates, which are used to check whether the laminate surface is closed and whether the resm is adequately cured. Below, a brief description is given together with the results.

- The staining test used here is derived from EN 438-2 and is based on staining of the laminate surface with a neutral solution of an intensive colorant m an organic solvent (ethanol, methanol and a small amount of surfactant) . This solution has a strongly wetting and staining effect. The result of the test is expressed m a rating ranging from 1 up to 5, with 1 standing for: very good (no discoloration) and 5 for: very poor (very strong discoloration) . The score of the above-mentioned laminate was 1.

- The Kiton test is based on staining with an aqueous sulphuric acid solution of an intensive colorant. This test, too, is derived from EN 438-2. The result of this test is expressed using the same numerical values. In this test, too, the laminate was found to be very good: 1. For the results of the staining test and the Kiton test, see Table 3.

3D pressing on a 3D shaped substrate using the membrane pressing technique:

One sheet of the prepreg described above m Example I, based on 100% rayon, 120 g/m² and measuring 20 x 20 cm, was pressed on an MDF panel with 3D shape obtained by milling measuring 12 x 12 cm. The thickness of the MDF was 18 mm. 3D shaping of such panels can take place by providing, for instance, flat MDF boards with internal grooves of random shape by means of milling. These grooves may be round or straight, but they may also be acute-angled. The outer circumference of such panels, too, can such a way be provided with a shape milled out the straight saw-cut.

Pressing took place m a so-called membrane press. In this type of press, the upper (and sometimes also the lower) mould half consists among other things of a rubber membrane which can be pressurized by means of (heated) air or liquid. These presses are used mainly for coating said 3D panels with thermoplastic films or veneer .

The press used in the following examples has one upper 2 mm silicon rubber membrane, which is forced against the edge of a slightly concave metal upper mould. This upper mould has a temperature of 180°C. The required pressure is obtained by means of nitrogen at a temperature of 175 °C. When all material is removed and a vacuum is created in the membrane, the membrane comes into contact with the hot metal upper mould and is then rapidly (preferably within 30 seconds) brought at the required temperature . The temperature at the membrane bottom is then 175-178°C. The lower mould half is flat and is not heated. After the two mould halves have been closed, a vacuum can be created at the bottom of the membrane. This, therefore, is the place where the workpiece is located.

The process then carried out is as follows. In the opened press, with the membrane forced against the hot upper mould, the following are successively placed on the lower mould half: a flat pad, the 3D panel (with the side to be laminated facing upwards) and 1 prepreg. The pad is about 5 mm thick and should be slightly smaller than the panel, so that the bottom edge of the panel can also be properly coated If the panel sides must also be coated, the prepregs should project some distance outside the edges of the panel . After introduction of these materials, the press is closed and a vacuum is drawn in the compartment containing the panel . At the same time the hot nitrogen is used to apply a pressure of 12 bar to the silicon membrane.

These conditions are maintained for 6 minutes, following which the pressures are released and the press is opened. For the pressing conditions see Table 2. The laminate was characterized after cooling.

Characterization of the 3D laminate The laminate was assessed mainly for deformation and bonding, both of the internal milled parts and of the external edges. For good deformation the laminate should fully follow the structure of the panel while being completely forced against it all corners, without any cracking. Furthermore, all parts of the laminate should of course be properly bonded. This was tested by means of a sharp knife that was used to try and remove the laminate. In addition, the appearance was assessed and a staining test was carried out (see Example I) .

The appearance of the 3D laminate is good. Prepreg deformation is complete both the internal deep parts and around the outer edge. The results are presented m Table 5.

Example II (code KB660-3 / KB674-1)

The process of Example 1 was repeated, but as the porous film use was now made of: Matt Lyocell^®, 105 g/m², 1.7 d'tex 38 mm (from Acordis) . Table 1 shows the resm content, the residual volatility content, the 2D pressing conditions of the prepreg on flat MDF. Table 2 presents the resm content, the residual volatility content and the 3D pressing conditions of the prepreg on 3D shaped MDF. Tables 4 and 5 give the characterization of the 2D and the 3D laminate, respectively. Example III (code KB640 / KB674-6a)

The process of Example 1 was repeated, but now TAT^® 2121 (Freudenberg) was used. This is a wet- laid, rayon-based non-woven. See Tables 1, 2, 4 and 5 for further conditions and results.

Example IV (KB658 / KB674-6b)

The process of Example 1 was repeated, but now T1710® (45 g/m²) from Freudenberg was used. This is a wet-laid, rayon-based non-woven. See Tables 1, 2, 4 and 5 for further conditions and results.

Example V (code KB674-2c)

The process of Example 1 was repeated, but now use was made of a spunlaced non-woven on the basis of 100 wt.% rayon, 100 g/m² (from Orlandi S.P.A., fibres from Lenzing AG) . See Tables 1, 2, 4 and 5 for further conditions and results.

Example VI (code KB674-2a)

The process of Example 1 was repeated, but now use was made of a spunlaced non-woven on the basis of 100 wt.% rayon, 80 g/m² (from Orlandi S.P.A. , fibres from Lenzing AG) . In this case only 3D lamination took place. See Tables 2 and 5 for further conditions and results .

Example VII (code KB674-3a)

The process of Example 1 was repeated, but now use was made of Napakon®, 50 g/m² wet -laid non-woven from paper manufacturer Schoeller & Hoesch G.M.B.H., on the basis of 100% Lyocell® fibres (fibres from Acordis) . In this case only 3D lamination took place. See Tables 2 and 5 for further conditions and results.

Example VIII (code KB674-4b) The process of Example 1 was repeated, but now use was made of Dewtech R130 (from O.R.V. S.P.A.), a non-woven on the basis of 100% viscose, 130 g/m² (fibres from Lenzing AG) . In this case only 3D lamination took place. See Tables 2 and 5 for further conditions and results.

Example IX (code KB674-5a)

The process of Example 1 was repeated, but now use was made of Tecnojet A1000 (from Tecnofibra S.P.A.), a non-woven on the basis of 100% viscose, 100 g/m². In this case only 3D lamination took place. See Tables 1, 2, 4 and 5 for further conditions and results.

Comparative Experiment A The same process as in Example 1 was used, but instead of 100% rayon, 120 g/m², use was made of a decorative paper (80 g/m²) . See Tables 1, 2, 3, 4 and 5 for further conditions and results.

Table 1: Laminate preparation conditions (2D on flat MDF)

Table 2 : Conditions of laminate preparation using a membrane press (3D, on 3D-shaped MDF)

Table 3 : Elongation at break and tensile strength of prepregs

Table 4: Laminate characterization (2D, on flat MDF)

Table 5 : Characterization of the 3D laminates (by means of membrane pressing on 3D shaped MDF)

Claims

1. Sheet prepreg comprising one or more layers of a carrier sheet, which carrier has been impregnated with an as yet uncured resin, characterized in that the carrier is a porous carrier sheet on the basis of wholly or partly regenerated cellulose.

2. Sheet prepreg according to claim 1, characterized in that the porous carrier sheet is based on wholly or partly regenerated cellulose together with wood and/or paper pulp.

3. Sheet prepreg according to claim 2, characterized in that kraft paper pulp is used as the wood and/or paper pulp.

4. Sheet prepreg according to any one of claims 1-3, characterized in that the porous carrier is a woven or non-woven sheet, an open foam sheet or a microporous membrane. 5. Sheet prepreg according to any one of claims 1-4, characterized in that the elongation at break of the impregnated carrier sheet and of the prepreg is higher than 2%.

6. Sheet prepreg according to claims 1-5, characterized in that the resin is an aminoplastic resin.

7. Sheet prepreg according to claims 1-6, characterized in that the aminoplastic resin is melamine formaldehyde resin. 8. Sheet prepreg according to claims 1-7, used in self-supporting moulded articles. 9. Sheet prepreg according to claims 1-7, used in sheet products that can be deformed along two or more mutually intersecting axes.

10. Object provided with a top layer obtained from a sheet prepreg according to claims 1-7 which has been deformed along two or more mutually intersecting axes. 11. Sheet prepreg according to claims 1-7 which provides objects with 3D structures based on milled MDF or HDF board with a top layer.

12. Sheet prepreg according to claims 1-7 which provides objects with 2D structures with a laminate top layer.

14. Sheet prepregs and objects as follows from the description and the examples.