CA1243271A

CA1243271A - Decorative panel with improved surface characteristics

Info

Publication number: CA1243271A
Application number: CA000481655A
Authority: CA
Inventors: Johannes C.W. Van Der Hoeven
Original assignee: Hoechst AG
Current assignee: Trespa International BV
Priority date: 1984-05-17
Filing date: 1985-05-16
Publication date: 1988-10-18
Also published as: DE3578388D1; DE3418282A1; NO170267B; US4927572A; EP0166153A1; NO851974L; AU585224B2; NO170267C; ATE54074T1; EP0166153B1; AU4256285A; ES8607826A1; JPH0564104B2; US4801495A; ES543163A0; EP0166153B2; JPS60253542A

Abstract

ABSTRACT OF THE DISCLOSURE

The decorative panel having an underlay or core layer and a decorative layer on one or both sides of the core.
At least one of the two surfaces of at least the outermost layer of the panel comprises a synthetic resin of one or more radiation-polymerized components selected from unsaturated acrylates and methacrylates. This layer, when scratched, has a scratch resistance of at least 1.5 N and preferably 2 to 7 N (DIN 53 799, part 10). In the method for manufacturing the decorative panel, a liquid surface layer which includes the radiation-polymerizable components is applied onto a decorative surface on an underlay and then polymerized by means of radiation. In a further step, the radiation-polymerized surface layer is pressed together with the underlay at an elevated temperature.

Description

43~71 . .

BACKGROUND OF THE INVENTION
The invention relates to a decorative panel comprising a core layer and a decorative layer on one or both sides, as well as to a method for its manufac-ture. Panels of this type are used in the building industry for interior or exterior walls, either as facing panels or as self-supporting elements, depending on their thickness.
The panels used heretofore are, for instance, decorative pressed laminate panels (defined by DIN 16 926), known as "high pressure laminatesl' (H.P.L.
panels). They comprise a core layer consisting of a thermopressed stack of resinated paper webs and a covering layer of resinated decorative paper. These panels have the disadvantage of being attacked by mineral acids, especially at concentrations over 10%
and a reaction time longer than 10 minutes. Further-more, in their standard version, these panels are not sufficiently weather-resistant, because the type of resin used in the covering layer is vulnerable to hydrolysis. Panels of this kind can therefore be used only to a limited extent as work surfaces in chemical laboratories or for the production of wet cells, which must be cleaned with acids. If they are used outdoors, additional, expensive provisions must be made in order to improve their resistance to the effects of weather.

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On the other hand, plastic-based laminates and panels such as polyester or acrylate panels, are particularly vulnerable to scratching and are not sufficiently resistant to o~ganic solvents.
For this reason, they, too, are less well suited to these applica-tions~
It is accordingly an object of the present invention to provide a method and composition for a decorative panel suitable in particular for exterior walls, for interior decoration, and for the manufacture of specialized furniture.
Another object of the invention is to provide a decorati-ve panel, the surface of which is not vulnerable to hydrolysis and is sufficiently resistant to the effects of weathering and to mineral acids and organic solvents.
Yet another object of the invention is to provide a de-corative panel, as above, which is highly scratch-resistant.
According to one aspect of the present invention there is provided a decorative panel comprising an underlay, a decorative layer applied to said underlay and a- transparent outermost layer ap-plied to said decorative layer, said outermost layer consisting es-sentially of the product of radiation-polymerizin~ a mixture consis-ting essentially of (i) a radiation-polymerizable aliphatic urethane acrylate oligomer and (ii) a diacrylate or triacrylate monomer, wherein said outermost layer has a scratch resistance of at least 1.5 Newtons, as measured by DIN 53799, part 10.
According to another aspect of the present invention there is provided a decorative panel as defined above, wherein said panel ~,`

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is a product of a process comprising the steps of (a) providing an underlay;
(b) applying to said underlay a decorative layer;
(c) applying to said decorative layer a liquid coating consisting essentially of said radiation-polymerizable mixture;
(d) polymerizing said mixture by means of radiation to form a layer on said underlay;
(e) thermopressing said underlay, said decorative layer and said radiation~polymerized layer under conditions of elevated tempe-rature and pressure such that a scratch resistance of at least.
about 1.5 Newtons, as measuredby DIN 53799, part lO, is imparted to said layer.

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The panel of the invention is a body of large surface area in proportion to its thickness, the form and structure of the surface being adapted to the intended use; for instance, it may also have an arched shape. A panel as defined by the invention will be understood to include plastic films, in particular of P~C and polystyrene, which may be colored and/or printed as necessary.
It has been found unexpectedly that when at least one of the outer surfaces of this decorative panel utilizes the specialized synthetic resin layer polymerized by radiation, the panel surface not only has excellent weather resistance compared to previously known panels, but unexpectedly has a high scratch resistance as well. It is furthermore substantially less vulnerable to acids and organic solvents.
The core layer performs the load-bearing func-tion of the panel. It is made, for example, of wood.
Other suitable materials for the core layer are plastic panels based, for instance, on polyvinyl chloride or polyethylene; plastic films; or metal plates, for instance of steel, aluminum, copper, brass, or other alloys. The radiation-polymerized synthetic resin layer is located on the immediate surface of these core layers or is bonded to the core layer by means of glue films or glue joints, but preferably with adhesion-promoting synthetic resins such as phenol-formaldehyde precondensate or resorcinol-formaldehyde precondensate.
Glue joints are simply layers of adhesive, while glue films are supporting layers coated or impregnated with adhesive. Adhesion promoters are substances which, while not being adhesive themselves, promote a bond between two different kinds of material.
The core layer may furthermore comprise the usual sheets of thermopressed paper, in particular soda ~raft paper, impregnated with thermosetting synthetic resin, in particular phenol-formaldehyde resin, conventionally used in MPL
panels. Depending on the desired panel thickness, from l to approxi-mately lO0 sheets, one on top of the other, are thermopressed toge-ther.
The core layer may also comprise pressure-stiffened bonded fabric or densified mats of mineral fibers, glass fibers, plastic fibers, or a mixture of fibers, but preferably cellulose. Examples of cellulose-containing fiber layers are those made of randomly de-posited wood fibers or wood chips. The bonded fabric or mat of woodand/or cellulose fibers is manufactured by applying a synthetic resin to the fibers, drying the resinated fibers, shaping a fiber mat, and precompacting this mat by pressure.
There may optionally be an underlay, containing a thermo-setting amino plastic or phenolic resin, on the outer surface or surfaces of this fiber-containing core layer. The underlay may, for instance, comprise a pigmented or unpigmented bonded fabric or paper.
In a preferred embodiment, a decorative radiation-poly-merized synthetic resin, that is~ one which by means of added pig-ments or dyes has a particular visual or decorative effect, is ap-plied directly onto the fiber-containing core layer or onto the underlay. A clear layer, that is, a transparent and pigment-free layer, of radiation-polymerized synthetic resin can be applied to the decorative radiation-polymerized synthetic resin layer, the clear layer forming the outermost layer or layers of the panel.
Instead of the decorative synthetic resin layer, a ....

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..... ~

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decorative layer based on a colored and/or printed plastic film or based on paper can be used. This generally comprises a pigmented, colored, and/or printed paper.
The radiation-polymerized synthetic resin layer, in this case transparent, is then located on the plastic film or decorative paper. For this application, the decorative paper contains conven-tional thermosetting synthetic resin, in particular amino plastic resin, and is located on core layers made up of the soda ~raft paper typical of HPL panels, or of randomly deposited wood or cellulose fibers resinated wiih phenol.
The compounds provided for fabricating the uppermost, radiation-polymerized synthetic resin layer include acrylates or methacrylates which are capable of being radically polymerized by actinic radiation and which are present either individually or together in a polymerizable mixture. The preferred component is a polyfunctional prepolymer, that is, one which is multi-ply unsatu-rated. Also present in the copolymerizable mixture, besides this predominant component, may be a further component having a diluting effect, known as a diluting monomer or a diluting oligomer. In the mixture, the polyfunctional prepolymer is present in a proportion of from 50 to 100% by weight, and in particular from 60 to 90~ by weight, based on the total weight of the copolymerizable components. Pre-polymers of low viscosity (less than lO0 poise at 20C) are used without the diluting monomers or oligomers.
The components used have a pronounced tendency to poly-merize radically under the influence of actinic radiation. Possible ~24327~

sources of actinic radiation are near ultraviolet light or high-energy radiation such as electron beams, particle beams, or X-rays.
The polyfunctional prepolymer is an aliphatic urethane acrylate oligomer. Aromatic urethane acrylate oligomers do produce scratch-resistant surfaces as well, but they yellow after a period of time when they are used outdoors.
The additional suitable monomer or oligomer that may be used in the radically copolymerizable mixture, besides the prepoly-mer, is a di- or triacrylate. These are esters of mono or poly-functional alcohols, i.e., polyols with 1 to 6 OH-groups with acry-lic acid and are therefore also known as polyolacrylates. Suitable diacrylates are esters of acrylic acid with aliphatic divalent al-cohols, especially ethylene glycol, 1,2-propylene glycol, 1,3-pro-pylene glycol, butanediol, 1,6-hexanediol or neopentyl glycol; with aliphatic ether alcohols, in particular diethylene glycol, dipro-pylene glycol, dibutylene glycol, polyethylene glycols or polypro-pylene glycols; with oxyalkylated compounds of the above-named ali-phatic alcohols and ether alcohols; or also with aromatic dihydroxyl compounds, in particular bisphenol A, pyrocatechol, resorcinol, hydroquinone, p-xylylene glycol or p-hydroxybenzyl alcohol. Prefer-red diacrylates are l,6-hexanediol diacrylate, tripropylene glycol diacrylate and 1,4-butanediol diacrylate. Preferred triacrylates are trimethylol propane triacrylate and pentaerythritol triacrylate.
Epoxy acrylate and silicone acrylate oligomers, may be used in addition to the urethane acrylate oligomers mentioned above, 432~
~7- 20731-893 in the radically copolymerizable mixture along with the diacrylates or triacrylates already mentioned.
The prepolymers are compounds known per se and are produ-ced, for example, from hydroxylated copolymers in which the hydroxyl groups are statistically distributed along the copolymer chain.
Statistically unsaturated acrylic copolymers are obtained from this copolymer by esterification of the hydroxyl groups with acrylic acid.
To produce intermediate unsaturated acrylic copolymers, the hydroxyl group is attached to the end of the chain when the hydroxylated co-polymers are produced. Urethane acrylate oligomers are produced bythe reaction of acrylates containing hydroxy groups, such as hy-droxyethyl methacrylate, with multivalent isocyanates, preferably 5~diisocyanates. The di- or polyisocyanates 4~preferably be reaction products of diols, polyether diols, or polyester diols having a stoi-chiometric excess of monomeric di- or polyisocyanate.
~ If the polyfunctional prepolymer predominates in the poly-merizable mixture, then, as the fundamental resin, its chemical nature determines the characteristics of the cured surface layer.
As the diluting monomer or oligomer, the added di- or tri-acrylate makes it possible to adjust the viscosity of the mixture to be cured, which is normally within the range from 20 to 100 poise (at 20C), and participates fully in the radical polymerization. In the process of irradiation, the hardening of the coating is the result of the radical polymerization at the double bonds of the prepolymer and, if present, of the diluting monomers or oligomers. When actinic radia-tion is used for curing, photoinitiators which absorb ultraviolet light and which, by forming radicals, facilitate the initiation of radical polymerization, must be added. On the other hand, when ~Z4327~

electron beams are used for curing, photoinitiators are not needed.
Most photoinitiators include at least one carbonyl group, which is in conjugation with an aromatic ring. A photoinitiator system com-prising several components is usually used.
The synthetic resin polymerized by radiation additionally contains the usual additives, such as plasticizers, fillers, pig-ments, and stabilizers, for attainin~g- the desired decorative, mecha-nical, and physical surface characteristics. Examples of these sub-stances include barium sulfate, silica, aluminum oxide, and pigments that are colorfast when exposed to light.
To produce the decorative laminate panel, the liquid, radiation-polymerizable compounds are applied to the underlay that is to be coated by, for example, spraying or pouring, or by using a scraper system or roller, or by screen printing. The applied layer is transparent and is applied to a decorative layer. Alternatively, it may itself be decorative; in that case it is dyed and/or pigmen-ted and is located on a non-decorative paper layer or directly on the core layer An additional radiation-polymerizable layer, which, however, is transparent instead of decorative, is applied to this decorative, radiation-hardened synthetic resin layer.
The underlay used for applying the radiation-polymerizable compounds is thus a paper layer, a decorative paper layer, or the above-mentioned core layers of wood, plastic, metal, or a stack of further fiber-containing layers, which form the core of the laminate panel that is later obtained. The fiber-containing layers of the stack, which preferably comprise soda craft papers or a bonded fabric made of wood and/or cellulose fibers, contain the preset ther-~243271 mosetting resins typical in HLP panels, in particularphenol-formaldehyde resins, while the papers which may also be present in the stack contain an amino plastic resin, but in particular a phenolic resin. The propor-s tion of thermosetting resins amounts to 20 to 250~ byweight, based on the weight of an individual layer.
The saturation or impregnation of the fiber-containing layers or paper layers is effected by, for example, immersion in a bath having a solution or dispersion containing the thermosetting resin, or by applying or spraying by means of a dispensing system.
The solvent or dispersing agent is of the aqueous alco-hol, aqueous acetone, or aqueous type, depending on the synthetic resin usedO It may also contain up to 20~ by weight of a flame retardant. The desired quantity of resin is then distributed by scraping or squeegeeing it off, for instance using rollers.
Even before the radiation-polymerizable com-pounds are applied to the underlay provided, the ther-mosetting resins of the underlay are pre-cured and dried in the conventional manner.
To initiate the polymerization effected by radiation, a conventional source for forming free radi-cals, such as a photoinitiator, can be used, or else heat is merely applied. If the photopolymerizable layer contains photoinitiators, the polymerization is initiated during a pass beneath mercury vapor lamps.
For curing by means of ultraviolet radiation, the absence of oxygen is not necessary. Electron beams suitable for use in curing the polymerizable compounds have an energy of 150 to 350 keV. The energy of the electron accelerators is determined by the thickness of the synthetic resin layer to be formed, the re~uired radiation dose, and the duration of the reaction or throughput speed.
The devices used for accelerating the electro-nic beams are available on the market. These accelera-3Z7~
tors are known as the scanner type and the linear cathode type.
Free radicals are formed as a result of interaction with the components of the polymerizable layer. This curing process is usually performed at room temperature. Curing by means of elec-tron beams is preferably performed in an inert, that is, largely oxygen-free, atmosphere.
After the radiation-effected polymerization, the under-lays, if they are sufficiently supple, are wound into rolls for storage or else are cut immediately to the desired shape. If the underlay having the radiation-polymerized resin comprises only a paper layer, then it is placed on a stack of fiber-containing layers comprising the core layer. It is also possible to provide the underside of the stack with such an underlay as well.
As in the conventional manufacture of HPL panels, the packet, comprising the fiber-containing core layer and the radiation-polymerized surface layer or layers, and the layers of paper or decorative paper possibly located between them as well, is thermopressed to make a decorative panel; the thermosetting resins are cured in this process. The temperature is preferably in the range from 120 to ~10C, the pressure is in the range from 10 to 100 bar, and the reaction time is from 1 to 30 minutes.
However, if the core layer comprises a wood, plastic, or metal panel, then the temperature and pressure can usually be reduced as far as 80C and 5 bar, respectively.
The pressing is effected in a known stationary, once-through, or continuous press apparatus. The number and thickness of the fiber-containing layers in the core layer, or the thickness of the core layer, is selected depending on the intended use of the panel; for exterior applications, depending on the particular use, panel thicknesses from 3 to 10 mm are required. If a large number of panels having radiation-polymerized synthetic resin layers are stacked on top of one another in the press, which is economically advantageous when the core layer is thin, then each of the individual panels is separated from the others by its own separating means, such as a layer of paper, plastic film, or a 32'71 metal plate, which is capable of imparting some structure to the adjacent outer layer of the particular panel.
The decorative panels manuFactured are unexpectedly highly weather-resistant and scratch-resistant, which may be due to an unforeseeable interaction between the various resins, or perhaps to a subsequent cross-linking of the radically polymer-izable compounds during the thermopressing operation. The scratch resistance and chemical resistance are, unexpectedly, substan-tially greater than if a panel had been given a coating of the same radiation-polymerizable compounds and the coating had merely been radically polymerized by radiation, without the thermopres-slng process.
The invention will be explained in detail by means of the following examples. The percentages given are by weight.
In measuring scratch resistance in accordance with DIN
53799, part 10, the force with which a diamond needle produces a visible scratch on the surface of the panel is ascertained. This measurement is made immediately after the diamond needle has acted on the panel, because the elasticity of -the surface layer means that surface deformation can decrease gradually after being scratched.
Example 1 A pigmented (pigment proportion, 15~) or printed decora-tive paper was impregnated on one side with thermosetting melamine resin (resin application, 80~) and the resin was partially cured.
Using rollers, a transparent liquid (viscosity, 60 poise at 20C) comprising a radiation-polymerizable 6:4 mixture of aliphatic urethane acrylate oligomer as -the prepolymer, and trimethylol propane triacrylate as the diluting monomer, was applied to the opposite side of the decorative paper, whereupon a closed film (layer thickness, approximately 50 /um) formed. Subsequently, the film of radiation-polymerizable compounds was largely homoge-neously cross-linked with electron beams in an inert atmosphere (oxygen content less than 100 ppm), without the application of pressure and at room temperature. The absorbed radiation dose was ~2~32'7~L
60 kGy. One decorative paper at a time was placed, with the poly-merized synthetic resin layer on the outside, upon both surfaces of a stack of 12 papers lying one on top of the other. These papers were previously saturated with -thermosetting phenol-formaldehyde resin, and the resin was partially cured. The packet was pressed in a conventional press for HPL panel manufacturing, between two forming elements, for 10 minutes at 150C and 80 bar.
The resultant packet had the following makeup:
-- a transparent layer (radiation-polymerized synthetic resin);
-- a pigmented or printed decorative paper (with mela-mine resin) as a decorative layer;
-- 12 paper webs (with phenol- formaldehyde resin) as the core layer;
-- pigmented or printed decorative paper (with melamine resin) as a decorative layer; and -- a transparent layer (radiation-polymerized synthetic resin).
The panel taken from the press after cooling, which was decorative on both sides, was 3 mm thick, had a matte surface with a texture similar to orange peel given it by the forming elements in the press and, depending on the decorative paper used, had a scratch resistance of from 3 to 4 N (DIN 53799, part 10). The scratch resistance was measured immediately after the scratching was done. The surface of tne panel exhibits no change after 6 hours of exposure to several drops of concentrated mineral acid, such as sulfuric acid, and rinsing of the acid with water (DIN
53230). The color--fastness of the panel upon exposure to light was assigned the grade of 8 (DIN 54 004). The resistance of the panel to the effects of weather was measured in accordance with ASTM G 53-84, in which a time cycle of 4 h UV/4 h CON (con-densation period) was maintained for 1500 h at a test temperature of 50C. After weathering, the panel exhibited no efflorescence of the fillers, no loss in sheen, and no discoloration.

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Example 2 A first radiation-polymerizable liquid contained:
-- 65 parts by weight of aliphatic urethane acrylate oligomer, as the prepolymer;
-- 28 parts by weight of hexanediol diacrylate, as the diluting monomer; and -- 7 parts by weight of pigment (organic dye).
The various components of this mixture were processed, for instance with a ball mill, into a homogeneous viscous liquid (vis-cosity, 75 poise at 20C) and applied in this form, using a scraper roller, in a layer approximately 80~m thick to a soda craft paper containing a thermosetting, previously hardened phenol-formaldehyde resin (resin application 70~, in terms of the paper). Immediately thereafter and in the same operation, a second radiation-polymeri-zable liquid was applied to this coating layer with a scraper roller in a thickness of 20~m. This layer, in contrast to the first, was transparent and pigment-free and was a mixture of:
-- 70 parts by weight of aliphatic urethane acrylate oligomer as the prepolymer; and -- 30 parts ~y weight of hexanediol diacrylate as the diluting monomer.
The two synthetic resin layers (total thickness, 100~m) were polymerized with electron beams in an inert atmosphere (oxygen content less than 100 ppm) without the application of pressure, at room temperature (radiation dose 60 kGy). One layer of soda craft paper, with the radiation-polymerized synthetic resin layers on the ~2~3~

outside, was applied to each of the two surfaces of a core layer.
The core layer comprised a stack of 50 papers one on top of the other, which had been previously saturated with thermosetting phenol-formaldehyde resin and partially cured. The packet had the fol-lowing makeup:
-- transparent layer (radiation-polymerized synthe-tic resin) as an outermost transparent layer;
-- pigmented, radiation-polymerized synthetic resin, as a decorative layer over a previously impregnated paper layer;
-- 50 paper webs (with phenol-formaldehyde resin), as the core layer;
-- pigmented, radiation-polymerized synthetic resin, as a decorative layer over a previously impregnated paper layer;
and -- a transparent layer (radiation-polymerized syn-thetic resin), as an outermost transparent layer.
The packet was pressed in a press for 20 minutes at 150C
and 80 bar.
The panel obtained, which was 10 mm thick and was decora-tive on both sides, had a scratch resistance greater than 3.0 N (DI53799, part 10). It was not vulnerable to hydrolysis and it exhi-bited no changes after 100 hours of boiling in water. Its surface was not attacked by concentrated mineral acid over a reaction period of 6 hours (DIN 53230). The colorfastness of this panel was measured as grade 8 (DIN 54004). Its resistance to the effects of weathering was measured as in Example 1. After weathering, the panel exhibited ~Z~327~

no efflorescence of the fillers, no loss in sheen, and no discolora-tion.
The panels obtained according to the Examples had a higher scratch resistance after the application of pressure and heat, com-pared with the radiation-polymerized layers which had a scratch resistance of only about 0.6 to:0.9 N, as measured before the appli-cation of pressure and heat.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A decorative panel comprising an underlay, a decorative layer applied to said underlay and a transparent outermost layer applied to said decorative layer, said outermost layer consisting essentially of the product of radiation-polymerizing a mixture con-sisting essentially of (i) a radiation-polymerizable aliphatic ure-thane acrylate oligomer and (ii) a diacrylate or triacrylate monomer, wherein said outermost layer has a scratch resistance of at least 1.5 Newtons, as measured by DIN 53799, part 10.

2. A decorative panel as claimed in Claim 1, wherein said panel is a product of a process comprising the steps of (a) providing an underlay;
(b) applying to said underlay a decorative layer;
(c) applying to said decorative layer a liquid coating consisting essentially of said radiation-polymeri-zable mixture;
(d) polymerizing said mixture by means of radiation to form a layer on said underlay;
(e) thermopressing said underlay, said decorative layer and said radiation-polymerized layer under conditions of elevated temperature and pressure such that a scratch resistance of at least about 1.5 Newtons, as measured by DIN 53799, part 10, is imparted to said layer.

3. A decorative panel as claimed in Claim 1, wherein said underlay is comprised of a thermopressed paper layer, a bonded fabric or a densified fiber mat.

4. A decorative panel as claimed in Claim 3, wherein said underlay is located on a core layer comprising a thermopressed stack of fiber-containing layers.

5. A decorative panel as claimed in Claim 3, wherein said underlay is located on a core layer comprising a thermopressed stack of a plurality of soda kraft paper sheets.

6. A decorative panel as claimed in Claim 3, wherein said bonded fabric is made of wood and/or cellulose fibers.

7. A decorative panel as claimed in Claim 1, wherein said decorative layer essentially consists of a decorative radiation-polymerized synthetic resin.

8. A decorative panel as claimed in Claim 2, wherein said underlay is comprised of wood, plastic or metal, and wherein step (e) is performed, at a temperature ranging between about 80° and about 210°C and at a pressure of between about 5 and about 100 bar, for about 1 to about 30 minutes.

9. A decorative panel as claimed in Claim 8, wherein said process further comprises, prior to step (b), applying to said under-lay a layer comprising an adhesive or adhesion promoting material.

10. A decorative panel as claimed in Claim 2, wherein said thermopressing step is performed at a temperature of from about 120°C to about 210°C, at a pressure of from about 10 to about 100 bar, and for a period of from about 1 to about 30 minutes.

11. A decorative panel as claimed in Claim 1, wherein said monomer (ii) is a diacrylate ester of acrylic acid with an aliphatic divalent alcohol, an aliphatic ether alcohol, an oxyalkylated deri-vative of an aliphatic divalent alcohol or an aliphatic ether alco-hol, or an aromatic dihydroxyl compound.

12. A decorative panel as claimed in Claim 11, wherein said monomer (ii) is a 1,6-hexanediol diacrylate, tripropylene glycol diacrylate or 1,4-butanediol diacrylate.

13. A decorative panel as claimed in Claim 1, wherein said monomer (ii) is trimethylol propane triacrylate or pentaerythritol triacrylate.

14. A decorative panel as claimed in Claim 1, wherein said oligomer (i) is present in a proportion of from 60 by 90% by weight, based on the total weight of the copolymerizable components.