Process for the production of a decorative thermosetting laminate.

(54) NAME Procedure for the preparation of a wear-resistant, decorative thermosetting laminate (56) QUOTE PUBLICATIONS: EP A2 0 136 577 (B32B 27/10), EP A2 0 122 396 (B32B 29/00)

CH B5 648 979 (B05C 19/00), DE C2 2,543,197 (B05C 19/00) (57) SUMMARY:

Process for producing a wear-resistant decorative thermosetting laminate with durable surface layer, the laminate comprising thermosetting impregnated paper sheets. A paper web is thereby impregnated with a noble thermosetting resin such as melamine-formaldehyde resin. At least one side of the web is coated with small, dry and hard particles with an average particle size of about 1-80 µm evenly distributed throughout the wet resin surface of the web. The resin is then dried, after which the particle-coated, impregnated web, so-called

prepreg, possibly cut to sheets. At least one such sheet or web is placed as a surface layer against a substrate layer and bonded therewith.

ALLF 138 8 122 AA

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The numbers in brackets indicate the international identification code. INID code. Letters in clamps indicate international document code

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The present invention relates to a process for producing a wear resistant decorative thermosetting laminate.

Decorative thermosetting laminates are well known and are used, among other things. as cladding material on walls, cupboards and benches, on tables and other furniture and as flooring material.

Such laminates are often made up of two to seven kraft paper sheets impregnated with phenol-formaldehyde resin, a single-color or decorated pattern sheet impregnated with melamine-formaldehyde resin, and a fine so-called overlay sheet of α-cellulose impregnated with melamine-formaldehyde resin.

The overlay sheet is designed to protect the pattern sheet from abrasion. In some cases, the overlay sheet is demolished.

There are also laminates consisting of a chipboard or wood fiber board carrier provided with such a decor sheet and possibly an overlay sheet. These sheets can be laminated to the support under heat and pressure. If you use only one pattern sheet and no overlay sheet, the pattern sheet can instead be glued to the wearer.

The laminate has many good properties. However, it has been found that there is a great need to improve the abrasion resistance of the laminates subjected to extreme wear. This applies mainly to laminate flooring, but to a certain extent also laminate to countertops and tables.

Attempts have been made in the past to improve the abrasion resistance of these laminates by adding small, hard particles of, for example, alumina already in the manufacture of the overlay paper of α-cellulose.

The particles have thereby sprinkled over a layer of wet 460 274 ​​α-cellulose fibers on the wire of a paper machine. The particles then distribute more or less irregularly throughout the fiber layer. Some of the particles even pass through the wire. Thus, in the resulting overlay paper, the hard particles will disperse in an uncontrolled manner. It is impossible to obtain an even distribution of the hard particles on the surface of the paper with this known method, where they give the greatest effect against abrasion.

In other words, the obtained laminates containing such overlay sheets have an uneven quality in terms of abrasion resistance.

So far, it has not been possible to deal with the above problems satisfactorily. However, by the present invention, it has been unexpectedly possible to solve this problem and to provide a process for producing a wear-resistant decorative thermosetting laminate with a durable surface layer, the laminate comprising thermosetting impregnated paper sheets. The process is characterized in that a paper web is impregnated with a noble thermosetting resin such as melamine-formaldehyde resin, that at least one side of the web is coated with small, dry and hard particles with an average particle size of about 1-80 µπι evenly distributed over the wet resin surface of the web, dried, that the particle-coated impregnated web, so-called prepreg, is optionally cut into sheets, that at least one such sheet or web is placed as a surface layer against a substrate layer and bonded therewith.

The particle-coated paper sheet often consists of a so-called overlay paper, preferably of α-cellulose.

However, it is also possible instead to coat the so-called pattern sheet with the fine particles.

In some cases, it may be conceivable to coat both overlay sheets and pattern sheets with particles or to use two or more such sheets.

460 274 particle-coated overlay sheets. It is also conceivable to lay over the coated sheet or sheets a conventional non-particle coated overlay sheet.

In order to avoid the handling of overlay sheets, it is envisaged that, according to the invention, the pattern sheet should be coated with both hard particles and with finely divided α-cellulose impregnated with thermosetting resin, such as melamine-formaldehyde resin. The coating can then be done in one step or in two separate steps.

The finely divided α-cellulose will form a protective layer on top of the pattern sheet.

The hard particles can be made up of many different materials. Especially suitable is the use of silica, alumina and / or silicon carbide. Mixing of two or more materials is thus possible.

The size of the particles is important for the end result. If the particles are too large, the laminate surface becomes rough and uncomfortable. Too small particles, on the other hand, can cause poor abrasion resistance. Preferably, the particles have an average particle size of about 1 - 80 µm, preferably about 5 - 60 µm.

The substrate layer may be a chipboard or a wood fiber board, whereby the particle-coated paper sheet is bonded to the substrate by means of heat and. pressure or by gluing. The substrate layer may also comprise a number of conventional dry prepreg webs and prepreg sheets which are not particulate coated. The particle-coated web and sheet, respectively, are placed over these conventional webs or sheets, the resin of which is optionally a noble thermosetting resin such as melamine-formaldehyde resin, while the rest of the webs and sheets preferably contain a smaller noble thermosetting resin such as phenol-formaldehyde resin, respectively. respectively a stack of sheets continuously and discontinuously laminated together with the surface layer under high pressure

460 274 and elevated, temperature.

It is obvious that the process of the invention is not bound to laminates made up of sheets of paper containing melamine-formaldehyde resin and phenol-formaldehyde resin. Other thermosets, such as polyester resin, are also conceivable.

In the process of the invention, a special device is preferably used comprising a container containing small, hard particles and an uneven surface rotating metering roller located under the container. The particles are intended to fall from the container to the metering roll and then spread evenly on a paper web continuously fed under the metering roll, impregnated with non-dried thermosetting resin.

Preferably, the device also includes a scraper plate beneath the container, which plate is intended to provide an even discharge of particles along the surface of the roller.

Conveniently, the device also includes an air knife or the like. which ensures that the hard particles release from the roll in a constant amount per unit of time.

The invention is explained in more detail in connection with the following exemplary embodiments and the accompanying drawings. Example 1 shows the preparation of a conventional decorative thermosetting laminate without special abrasion preventive additives. According to Example 2, a specially known overlay paper is used, where small, hard particles have been added to the paper fibers already during the papermaking. Example 3 illustrates a method according to an embodiment of the invention. Example 4 shows the coating of a pattern sheet with only finely divided cellulose. Example 5 shows a method according to another embodiment of the invention, in which both hard particles and finely divided cellulose are applied to a mother ceramic sheet.

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In the drawing, Figure 1 shows a container 1 comprising small, hard particles 2, a rotary metering roller 3 located below the container 1. uneven surface. The particles are intended to fall from the container 1 to the metering roller 3 and then spread evenly on a paper web 4 continuously fed under the metering roller 3 with non-dried melamine-formaldehyde resin.

The paper web 4 is advanced at a constant speed in the direction of the arrow in the figure. However, it is possible that the web is advanced in the other direction instead.

The metering roller 3 can be made of various materials. However, it is advantageous to make it in steel, especially stainless steel. As mentioned above, the surface of the roller 3 should be uneven. This is because it can thereby cause the hard particles 2 to follow. on the surface of the roller 3 in a uniform layer and spread evenly over the paper web 4.

For example, the surface of the roll 3 can be provided with horizontal and / or vertical grooves running along the entire length of the roll. The depth of the grooves may vary. In many cases, however, they preferably have a depth of about 10 - 30 µm.

In order to facilitate that a uniform stream of particles 2 is dispensed onto the surface of the metering roller 3, the device usually includes a scraper plate 5.

Furthermore, it is convenient that the device also comprises an air knife 6 or the like. This is intended to help cause the hard particles 2 to release from the roll 3 in a constant amount per unit of time.

The dosage amount can be varied in different ways. For example, the rotation speed of the roll 3 or the feed rate of the paper web 4 can be varied.

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The device may also comprise a sealing brush 7.

Fig. 2 is an enlarged cross-sectional view of the paper web 4, which is impregnated with thermosetting resin, but not yet coated with particles 2. The web has resin layer 8 on both sides. For clarity purposes, the thickness of the resin layers 8 has been greatly exaggerated in relation to the thickness of the web 4.

Fig. 3 shows a similar cross-section as in Fig. 2. However, the top resin layer 8 is coated there with small, hard particles 2.

Fig. 4 finally shows a similar cross-section as Figs. 2 and 3. However, both the upper and the lower resin layer 8 are coated there with small, hard particles 2. This can be done, for example, by means of two devices according to the invention, first of which one and then the other side of the paper web is coated with particles.

Example 1

A roll of so-called overlay paper of α-cellulose with a surface weight of 40 n

g / m was impregnated with melamine formaldehyde resin solution to a resin content of 70% by weight based on dry impregnated paper. The impregnated paper web was then continuously fed into a heating furnace, where the solvent was evaporated while the resin partially cured to the so-called B-stage. The resulting product is normally called prepreg.

The paper web was cut into sheets of suitable length. The sheets were then automatically stacked on top of each other.

A roll of so-called pattern paper with card printing and a surface weight of 80 g / m was treated in the same way as the overlay paper. The resin content was 48% by weight based on dry impregnated paper.

A roll of kraft paper with a surface weight of 170 g / m was also treated in the same way, except that the resin was made of

460 274 phenol-formaldehyde resin instead of melamine-formaldehyde resin. The resin content was 30% by weight based on dry impregnated paper.

Between two press plates were placed three pieces of the above phenolic resin impregnated prepreg sheets (so-called stump paper), a pattern paper and an overlay paper. These papers were pressed in a conventional multistage press at a pressure of 90 kp / cm and a temperature of 145 ° C for 45 minutes into a homogeneous decorative laminate.

The abrasion resistance of the resulting laminate was tested according to ISO standard 4586 / 2-88 using an apparatus called Taber Abraser model 503. According to that standard, the wear of the pattern layer on the finished laminate is measured in two steps. In step 1, the so-called IP point (initial point) is measured, where initial wear and tear occurs.

In step 2, the so-called EP point (end-point) is measured, where 95% of the pattern is worn.

Furthermore, the above ISO standard stipulates that the number of turns achieved with the test machine in step 1 and step 2 is added, whereby the resultant sum is divided by 2. This gives the 50 percentage point for wear, which is normally reported in norms and specific pressures.

In this and the following examples, however, only the IP point is used.

When testing the above laminate, a value of 200 rpm was obtained for the IP point, which is normal for a decorative laminate without reinforcing the wear layer.

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Example 2

In a paper mill, an α-cellulose overlay paper having a basis weight of 40 g / m was produced by discharging slurry α-cellulose sacrificial material from an outlet box into the wire of a paper machine. On the top of the wet fiber layer, alumina particles were applied in an amount of 3 g / m and with an average particle size of about 50 μιη.

In the continued manufacture of the overlay paper, the hard particles were more or less irregularly distributed throughout the paper. Some particles ended up near the surface, some near the middle and some in the bottom of the paper. Some particles even passed all the way through the fiber layer and out through the wire. Thus, they were not left in the finished paper.

The overlay paper produced was impregnated with the same amount of melamine-formaldehyde resin and then treated otherwise in the same manner as in Example 1.

A laminate was prepared with the same number of sheets and structure as described in Example 1. The pressing was also done under the same conditions.

The abrasion resistance of the resulting laminate was tested in the same way as in Example 1. An IP value of 600 rpm was obtained.

Example 3

The procedure of Example 1 was repeated with the difference that immediately after the impregnation of the overlay paper, but prior to drying, the top aluminum foil particles of the paper were applied in an amount of 3 g / m and with an average particle size of about 50 µm. In the application of the alumina particles, an apparatus according to Fig. 1 is used. The rotational speed of the dosing roller was 1.5 rpm.

Thus, the hard alumina particles were applied in it yet

460 274 non-dried melamine-formaldehyde resin.

In the subsequent drying, the grains were enclosed in the resin layer and consequently concentrated to the surface of the prepreg prepared. The abrasion resistance of the laminate produced was tested in the same way as in Example 1. An IP value of 2000 rpm was measured.

Example 4

Pattern printed decorative paper for decorative laminate having a basis weight of 2 g / m was impregnated with a melamine formaldehyde resin solution to a resin content of 50% by weight based on dry impregnated paper.

The impregnated, dried paper was provided by means of the apparatus described in Figure 1 with a uniform coating of dry grains of an unpigmented cellulose material having an average particle size of about 50 µm. The coating amount was 65 g / m 2.

The cellulose material consisted of high grade, pale cellulose with a high content of α-cellulose, which in a separate process was impregnated with a melamine formaldehyde resin solution, then dried and partially cured to the so-called β-stage of the resin and finally ground to an average particle size of about 50 µm.

This unpigmented cellulose material contained about 70% melamine formaldehyde resin based on dry material.

The impregnated paper coated with cellulose particles was dried in a heating oven in the same manner as in Example 1 to a moisture content of about 6.5%.

The decor sheet was then placed over 3 sheets of phenol formaldehyde resin impregnated kraft paper and pressed into a laminate in the same manner as in Example 1. No overlay paper

460 274 ₁₀ used.

In the pressed laminate, the pattern-printed decor appeared without blur.

Wear resistance was tested in the manner described in Example 1.

An IP value of 300 rpm was measured.

Thus, with the described technique, the overlay paper normally used can be replaced with a fine particulate cellulose material impregnated with melamine formaldehyde resin.

With the above technique, decorative laminates with different levels of abrasion resistance can also be made by varying the amount of applied cellulose particles.

Example 5

The procedure of Example 4 was repeated with the difference that 62 o

g / m melamine formaldehyde resin impregnated cellulose particles and 3 g / m alumina particles with an average particle size of about 50 μιη were applied.

An IP value of 2,000 rpm was measured.

The invention is not limited to the embodiment shown, since it can be varied in various ways within the scope of the invention.

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