DK154127B - PROCEDURE FOR THE PREPARATION OF A DECORATIVE LAMINATE CONSISTING OF A CORE, IMPROVED DECORATIVE PAPER AND PROTECTIVE, HARD PLASTIC LOW, WHEREAS THE HARDEN PLASTIC LAYER IS APPLIED ON PAPERED PAIR PAPER PAINTED COAT - Google Patents

Description

The method according to the invention is of the kind specified in the preamble of claim 1.

Conventional decorative plastic laminate products of the type to be used as linings on tables, bars, countertops and the like are manufactured by a "high-pressure" process; this method has its name because of the compression of the different layers during manufacture, pressure is used in the range between approx. 55 and approx. 100 kg / cm. These commercial laminates are usually formed from a number of phenolic resin impregnated paper sheets as a base substrate over which decorative resin impregnated sheets of decorative paper are provided. A surface layer of melamine resin impregnated cellulose material is placed on top of the decorative paper and the various layers are pressed together to form a laminate.

The conventional high pressure process requires solid pressing apparatus under the specified pressures and a relatively long cycle time. Therefore, it has been the goal of manufacturers of these laminates to try to find methods and materials that will result in a low pressure laminating process, while at the same time producing a decorative, laminated product that will be as attractive and durable as it is. similar product manufactured at high pressure.

An earlier attempt to produce low-pressure laminates has provided the provision of an impregnated and coated decorative paper sheet that can be bonded to a structural substrate under pressure application and heat adhesion. This method involves the impregnation of the resin solution decorative paper containing polymer, monomer, catalyst and an organic solvent therefor. One of the disadvantages of this process is that it has been difficult to obtain a sufficiently high resin content (i.e., above 65%), which is necessary to provide a superficial coating of such a nature that the resulting laminated product is sufficiently durable for the usual uses for which it is used. Another disadvantage is the migration of surface resin through the paper into the substrate during the bonding operation using heat and pressure, which will result in a too thin surface layer of resin.

A known process which, from a superficial point of view, is similar to the process of the invention, is described in U.S. Patent No. 3,551,241. In this process, however, the solvents are to be stripped, thereby creating a contamination risk which is increased proportionally to the resin content.

According to the invention, there is provided a lamination process and a coating technique which is contaminated with a minimum of pollution problems and which allows the formation of a product having maximum durability and applicability, as well as a method which can be used in both low pressure - and high-pressure operations, which will be economical and flexible in terms of the type of products that can be manufactured.

This is achieved by the features specified in the claim. As can be seen from the characterizing part of the claim, the method comprises the manufacture of a substantially stable, semi-solid resin cap consisting of 100% reactive material on a web of decorative paper. The resin layer is pressed against an embossed separating foil (sometimes referred to as a "texturing foil") to give a laminated intermediate. This can then be laminated to a core material in a single press operation. The first part of the process is carried out as indicated continuously, the texturing film being web-shaped and joined to the resin-coated decorative paper using pressure belts or rollers. The resulting intermediate may be formed into rolls for storage, or it may be cut to the correct size on the production line for subsequent bonding with the core.

It is a great advantage to be able to reduce the flowability of a liquid resin film to semi-solid so that an intermediate product can be obtained which can be handled, transported and stored for a longer period.

One of the most important advantages of the invention is that the thickness of the resin layer on the final laminated products can be easily controlled. For example, if a product intended to withstand only light stresses is desired, a resin layer having a thickness of only 0.08 mm can be applied to the decoration paper. If you want a product that is designed for larger influences, you can apply a resin layer of between 0.1 and 0.3 mm.

The invention will become apparent from the following description with reference to the drawing, in which: FIG. 1 shows a method for making an impregnated decorative paper, while FIG. Figure 2 shows a process for preparing an intermediate product; Figure 3 shows a final decorative laminate made in accordance with the invention; 4 shows another embodiment of the final product according to the invention.

According to FIG. 1, a decorative paper is placed in contact with a primary, liquid, thermosetting resin 2 in a container 3. The excess part of the resin is removed by a scraper 4. If desired, a further coating of resin 2 can be applied by means of a roller 5. using a method commonly referred to as a "kiss-coating". The direction of feed of the paper web can then be reversed by means of a roller 6, and a secondary application by "kiss coating" can be carried out by means of a roller 7, so that liquid resin is also applied to the back of the paper. The impregnated paper is then dried in an oven 8 to form the material 9 used in the invention. It should be noted that the invention encompasses the use of two resin categories: a primary, liquid, thermosetting resin which contains solvents which are generally heat curable, and a secondary, liquid, thermosetting resin which is cured by UV irradiation or by electron irradiation.

As will be appreciated, the terminology used in the claim "hardener by ethylenic crosslinking" denotes that hardening occurs during the opening of ehylenic double bonds. According to the invention, a resin which cures in this way is also used for impregnating the decorative paper. However, when the general term "thermoset" is used in the preamble of claim (a), it is because it belongs to the prior art, cf.

3,551,241, to use a decorative paper impregnated with melamine / formaldehyde resin. Other differences are that the resin according to the patent is introduced into the laminate by means of the separating foil onto which it is applied from a solution containing unpolymerizable solvents which must be stripped off, and that the patent does not teach the use of radiation for the curing of the resin to a semi-solid state, nor about embossed separating film (the disadvantage of volatile solvent evaporation has already been stated above).

Also, according to FR Patent No. 2 013 423 (similar to US Patent No. 3,713,935), an ethylenically unsaturated curing resin present as a solution in styrene, containing no unpolymerizable solvents, is applied to a substrate by means of a separating foil. The plastic is cured here on the substrate by UV radiation through the separating foil.

According to FIG. 2, a liquid resin 45 is applied to one surface of an impregnated decorative paper 44 as it is advanced between rollers 46 and 47. The resin is of the type which cures by irradiation and does not contain any unpolymerizable solvents. The thickness of the resin layer is controlled by the space between the adjustable roller 48 and the roller 46. The resin is then partially cured to a dimensionally stable, semi-solid state by treatment in units 49, which is a curing unit using ultraviolet or electron beams. The decorative substrate with its semi-solid resin layer is further moved between pressure rollers 50 and 51 which also serve to apply the texturing film 52 to the semi-solid resin layer. Generally, a pressure of between 9 and 270 Kp / linear cm between the rollers serves to bond the texturing film to the resin film. The applied pressure depends on the type of texture used, the type of resin and the extent of the resin layer's hardening and / or surface hardness, taking into account that the texturing film must be removed after the final pressing.

The laminated intermediate 53 can be formed into continuous rolls or cut to predetermined lengths for storage and / or transport.

The final laminated product 40 is shown in FIG. 3, and it comprises the chipboard 30 bonded to the pre-impregnated decorative paper 9 and a resin layer 34.

As an alternative to that of FIG. 3, a veneer-like product can be formed by the use of a number of core sheets instead of a chipboard. A product 42 of this type is shown in FIG. 4 with core sheet 41, on top of which is a decorative paper and a resin layer 34.

Although FIG. 3 shows a product having layers of resin 34 on both sides, it is obvious that this is not necessary, since a product can also be made which is only provided with resin on one side.

In a preferred embodiment, the decorative paper 1 (Fig. 1) is contacted with a dissolved, thermosetting unsaturated polyester resin of a type known as isophthalic acid resin. This material, designated 2 in FIG. 1, comprises polymer, monomer, catalyst and a solvent. The monomer may preferably be a vinyl monomer such as diallyl phthalate, styrene or diacetoneacrylamide. Of these, diacetone acrylamide is preferred because it is a solid and thus gives rise to the formation of a decorative paper which is not as sticky as those obtained using a liquid monomer.

In addition, in the case of its presence in the paper, the solid monomer material will not evaporate as readily as a liquid monomer, and thus an impregnated paper 9 is produced which can be stored for a long time without damage.

It is also preferred to use a resin solution containing from 45 to 55% reactive materials (polymer and monomer).

The solvents used may be any suitable solvent for the solids, including methylene ethyl ketone, acetone, water or methylene chloride.

It is advantageous to use such a polymer / monomer ratio such that the resulting melt viscosity of the resin at the time of curing does not become unreasonably low. Extremely low melt viscosities are undesirable because this will result in excessive flow and the resin will tend to flow from the gap between the various layers of intermediates or to migrate through the core material during the pressing operation.

After impregnating the decorative paper, the solvent is expelled at a temperature below the cure temperature of the resin, and an impregnated substrate 9, which can be rolled up, if necessary with an interlayer, is obtained and stored for periods of up to 1 year.

The impregnated decorative substrate material 9 of FIG.

1 can be used as the material 44 of FIG. 2. The flowability of the secondary liquid resin system is reduced by treatment with either UV or electron radiation. A liquid resin with 100% reactive components (no non-reactive solvents) is used to avoid the contamination that occurs when using solvents to be driven into the atmosphere. Thus, as described below, using UV rays or electron beams, a resin consisting essentially of an isophthalic acid type polyester resin and a vinyl monomer, preferably styrene, may be used. Suitable known catalysts may also be used. In the process of the invention, all known radiation curable resins can be used.

Thus, the liquid resin is applied to a continuous web of impregnated decorative paper and then subjected to irradiation in order to reduce the flowability. The resin may be applied, by suitable means, at a substantially constant thickness to the plate, using a curtain coating or the like.

Because of the exact thickness of the resin layer, a reversing roll is preferred.

In the preferred method of the invention, the resilience of the resin layer is reduced by UV radiation.

This method is fast and cheap, and the curing becomes uniform throughout the layer. In addition, the resin after this irradiation has reduced stickiness. It is preferred to expose the resin layer to UV light immediately after the decoration paper has been applied to it. However, the velocity of the web, the location of the light source, the resin thickness and the intensity of the light are all interdependent and adjustable.

It is important that the resin layer is only incompletely cured.

The intermediate produced, which comprises a dimensionally substantially resinous layer, has been found to be capable of being stored for at least 6 months at temperatures below ca. 26 ° C. This means that there is plenty of time for transport to distant destinations, since a laminated final product containing a suitable core, such as chipboard, can only be manufactured economically in the vicinity of the site of application.

The resin layer formed on the decorative paper is pressed against the separating foil. Then this intermediate and the core material are combined using heat and pressure in such a way that the resin will be substantially completely cured. The separating film is then removed leaving a decorative laminate with a textured (embossed) resin coating.

The resin coating on the decorative paper should have an average. thickness of at least 0.13 mm, resulting in a total resin content of at least 65% by weight of the sum of the decorative paper and resin, including the resin impregnating the decorative paper. An excellent product according to the invention, which can withstand heavy loads, has a resin coating having an average thickness of at least 0.38 mm, the resin being present in an amount of at least 80% of the total weight of the decorative paper and resin.

If the final product consists of a core material of the type specified above, the pressure at the final stage must be limited to the pressure that the core can withstand. For example, if using an industrial-grade particleboard with a density of 0.72 g / cm, a pressure of up to 17.6 Kp / cm and a temperature of approx. 150 ° C. These conditions, which are applied for a period of approx. 6 minutes will result in a structurally good product without any damage or crushing of the plate. If you use plates with a higher density, the pressure may be higher. For example, if a plate with a density as high as 1.04 g / cm is used, a drag of up to 2 35 Kp / cm can be used. Thus, while the pressures that can be used will be somewhat limited, it is thus highly advantageous to have a system such as that which can be provided by the invention and which conveniently enables curing at low pressures.

As an alternative to the previously described laminate comprising a relatively bulky core material, the final product may be a decorative laminate consisting of one or two layers of resin impregnated kraft paper, the decorative paper and the resin layer. This product may have a thickness of between 0.38 and 0.64 mm, preferably between 0.46 and 0.56 mm. This can then be applied directly to suitable surfaces, for example as a countertop, using a contact adhesive or other suitable adhesive. Pressure temperatures of between 135 and 182 ° C and pressures of between 5 and 84 Kp / cm can be used, with pressures of between 14 and 2 56 Kp / cm being preferred. If using a core of kraft paper, it should contain 25-50% by weight, preferably 30-35% by weight. of a resin compatible with the resin in the decorative paper. Since high pressures will tend to drive the resin into the other materials, a lower resin content may be used in the intermediate layers on the girund of the resulting increased density. In order to consolidate and obtain an end product of greater density, it has been found advantageous to use pressures of between 14 and 70 Kp / cm 2.

Although the texturing film can be removed from the laminated final product at any time after removal of the press, it may be advantageous to leave it seated on the product as a protective coating until final use.

The texturing film used according to the invention is preferably a relief-coated, textured paper which produces a so-called velvet finish on the surface of the laminate. Embossed types of paper can also be used to produce surfaces having a texture similar to the texture of slate, natural stone, clay or other coarse textured surfaces. The textured sheets can be treated with a release agent which can be applied to the texturing layer either before or after the embossing. Such release agents may preferably comprise stearates such as zinc or calcium stearate.

In the case of curing with UV light, a catalyst or a photopolymerization initiator is used in amounts sufficient for the resin to cure easily. It is often desirable to use a thermoset catalyst such as tert-butyl benzoate. A concentration of 0.2-1.5% by weight of the resin is usually appropriate. The following example serves to further illustrate the invention.

Example·

A liquid resin blend containing an isophthalic acid polyester resin system having 66-68% polyester resin and 32-34% styrene monomer was prepared. Ca. 1% ultraviolet sensitizer was added and the viscosity of the resin was 1100 - 1400 cP. The resin was applied with an etching reversing roll coating apparatus and as a layer whose thickness was approx. 0.13 mm, on a continuous web of impregnated decorative paper with a three-year printing. The coated decorative paper was then passed under an ultraviolet curing oven at a rate of> 16.3 cm / second. The hearth furnace contained two 250-300 watt ultraviolet Hanovia lamps that were 1, 53 m long and fitted with a mutual clearance of 0.6 m, which were powered with 1750 volts and 7.5 Anjp. These bulbs were arranged approx. . 20 cm above the resin film and this resulted in a partially cured, dimensionally stable layer. The decorative paper and film move out of the furnace through a cooling zone which uses air circulation and then between two laminating rollers. A texturing film is brought into contact with the film before insertion between the rollers and pressed into the resin layer during the passage between them.

Rolling pressures, t are kept between 45 and 179 Kp. linear cm. The resulting intermediate was wound into rolls.

Claims (1)

Patent claim: A process for producing a decorative laminate (40, 42) consisting of a core (30, 41), preferably a chipboard, an impregnated decorative paper (9, 44) and a protective hardening layer (34), wherein the decorative paper (1) ( a) is passed through a solution (2) of a heat-curable plastic material, (b) is dried in a dryer (8) to a dry, impregnated decorative paper (9, 44), (d) is placed in a lamination press between a separating foil (52) and the core (30, 41), optionally on either side of the core (30), there being between the decoration paper (44) and the separating foil (52) a layer (34) of a plastic material which cures by ethylenic cross-linking between macromolecules, ) this layer structure is pressed during curing and (f) the separating foil (52) is peeled, characterized in that (a) that the heat-curable plastic material used for impregnating the decorative paper (1) is also of the type hardened by ethylene crosslinking , (c ^) applying the curing plastic layer (34) to d the curing paper (44) by means of a continuous process before being brought together with the separating foil (C2) to apply the curing plastic layer (34) to the decoration paper (44) in the form of a radiation-curing material known per se (45). ), which is free of unpolymerizable solvents, and (C3) the material (4-5) is irradiated until a semi-solid state is obtained by continuous passage through a chamber (49) and then compressed with a single-embossed separating film (52) to form a laminated intermediate (53) which is subdivided for placement in the laminating press.