DE2718705A1 - WOODEN CHIPBOARD WITH A COATING LAYER OF MELAMINE RESIN ON AT LEAST ONE SIDE AND A METHOD FOR MANUFACTURING SUCH A PANEL - Google Patents

Description

T.EDTKE - BühL.HG - KlNNE - GrUPE

• Dipl.-Chem. G. Buehling

\ '■ .A 2718705 ^Di P '-' n9 · R- chins

L- - ■ --- ·· j. Dipl.-Ing. P. Grupe

Dipl.-Ing. P. Grupe

Bavarlarlng 4, PO Box 202403 8000 Munich 2

Tel .: (0 89) 53 96 Telex: 5-24845 tipat cable: Germaniapatent Munich

4th July 1977

B 8153 / case R 16291 / H

Austrian Hiag works
Corporation

Vienna, Austria

Chipboard, which at least on one side with
is provided with a coating layer made of melamine resin and a process for the production of such a board.

709847/0739

Dresdner Bank (Munich) Account 3β3ββ44 PoctMheck (MOnchen) Account S7O-43- «O4

The present invention relates to a chipboard, which is provided on at least one side with a coating layer made of thermal resin.

Two different ways have found their way into practice for the production of coating layers on chipboard.

The first, less common, approach is to apply a coating of polyester or a combination of alkyd resins with modified aminoplasts. This gives panels that are due to a lack of mechanical resistance are only suitable for applications in which the panels are perpendicular, for example for wall cladding. Furthermore, these plates are sensitive to water.

The second way leads to coated chipboard, whose surface is scratch-proof, waterproof and resistant to household chemicals and which is therefore also suitable for horizontal Suitable for applications, e.g. as a top for work tables. These panels are preferred due to their chemical resistance Use in kitchen furniture construction. These chipboards have layers of paper that are coated with melamine resins impregnated 1st. It is this paper after a drying process with the application of heat and pressure pressed onto the chipboard surface and in this process step the melamine resins harden and result in the desired surface properties. The production of these plates, however, requires a great deal of effort. On the one hand the surface of the plates must be very smooth before the resin-impregnated papers are applied to prevent damage to the To avoid a coating layer when pressing and to obtain adequate adhesion of the paper to the wood chip material and, on the other hand, the impregnation of the papers and their storage require great costs, plus the considerable costs Costs for the paper itself come, taking into account that usually a surface of the chipboard is used to form a Several sheets of paper lying one on top of the other can be used to cover the coating layer.

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It is now an object of the present invention to provide plates of the type mentioned in the opening paragraph, in which the manufacturing expense is significantly reduced, paper no longer needs to be used and nevertheless higher plastic coating layers Quality.

The plate according to the invention of the type mentioned at the outset is characterized in that the coating layer consists of an in the previous state water-soluble, homogeneous melamine resin, this coating layer in the fiber structure of the chipboard surface engages and a smooth synthetic resin film on its outside forms.

This special design of the panels leaves very good performance properties Achieve, with a, compared to other coating techniques, low effort for production Sufficient can be found. Due to the intimate engagement of the melamine resin layer, which consists of a previously water-soluble Resin is made into the fiber structure of the chipboard surface a layered structure in which there is a very intimate interaction between the melamine resin and those in the surface area fibers of the tension plate present, with any anchoring problems the surface layer come to an end. The plates according to the invention can thus be used without difficulty be divided by saw cuts, while previously when sawing coated panels, the coating splintered the cut edges and it has taken a lot of efforts by sawing technology to make this splintering into an optically wearable one Reduce extent. It is preferably provided in the panel according to the invention that the melamine resin with an inorganic Filler is offset.

If desired, the plate according to the invention can be used in this way form that on one side of the board a melamine resin coating layer containing a filler and on the other side of the board an unfilled coating layer of in the previous state water-soluble thermosetting synthetic resin, which is also in the Structure engaging the chipboard surface is provided. Here come as thermosetting synthetic resins, which in the previous state are water-soluble, especially amino resins and phenolic resins. You can also use an amino synthetic resin

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271870b

Use a melamine resin, which may be used to improve the sandability of such layers and in the interest of the lowest possible cost price with a urea resin may be mixed or mixed condensed. If water resistance is not particularly important, it is above all With regard to the cost price, it is advantageous to use a urea resin alone as the amino resin.

In the interests of a good visual appearance, the coating layer is advantageously pigmented on at least one side or filled and / or colored. Furthermore, in the interest of a good appearance of the top layers, the drying or Direct the hardening process in such a way that the filler and pigment accumulate on the inside of the coating layer facing the chip material is, while the outside is low in pigment or filler or practically pigment-free or filler-free, the The outside of the layer is also particularly tight and firm.

The invention also relates to a method for producing a chipboard according to the invention, and this method is characterized by the combination of the measures that a aqueous solution or a water-containing paste of a water-soluble, homogeneous melamine resin is applied that the so applied Layer is then pre-dried, and that on this the smoothing and curing of the pre-dried layer to the cured Coating layer is made with a hot pressing process taking place between press plates. Preferably a Resin solution or resin paste is used, which consists of the resin and an inorganic filler.

The drying of the top layers can advantageously be carried out by means of a stream of hot air and / or by means of thermal radiation, whereby particularly good results can be achieved and with little effort if the drying is carried out in a hot air duct through which the plates are passed. In practice, when drying, the moisture of the applied layer is reduced to a value between 2 and 10%. A reduction to 5%

709847/0739

Residual moisture is particularly favorable for the subsequent hardening of the layers. The drying temperature is advantageously just below 100 ° C held.

The coating layers are hardened by means of hot pressing made between hot press plates.

Let us now consider the structure of plates designed according to the invention explained using an example shown in the drawing.

In the drawing, a panel is shown in which a panel body 1 is present, which is formed by a chipboard which has a top layer 2 or 3 on each side. These coating layers are made in that on the surfaces of the plate body 1 applied aqueous solutions or pastes of a thermosetting synthetic resin, then dried and finally hardened, in the course of which drying and Curing process an intimate anchoring of the synthetic resin material in the fiber structure of the plate body 1 took place, as is symbolized by the hatching of the coating layers 2 and 3 partially in the plate body 1. At least one of the coating layers 2, 3 consists of a homogeneous melamine resin, which is mixed with an inorganic filler. If only such a melamine resin layer is provided, there is the top layer on the opposite side of the board made of a thermosetting synthetic resin without filler.

The invention will now be explained further on the basis of a few examples in which, above all, the composition of the individual layers was discussed.
Examples:

A) Preparation of synthetic resins for the top layers, a) Production of an aqueous melamine resin.

162 g (37% by weight) of formaldehyde, 38 g of water and 20 g of sorbitol are mixed with one another. 126 g of melamine are stirred into this mixture. After dissolution, the pH is adjusted to 9.0 and continuously maintained at 9 by adding sodium hydroxide solution . The mixture is heated and refluxed for as long as

709847/0739

boils until a sample, which has been diluted with water in a ratio of 1: 4, has a turbidity temperature of 50 ° C. when it cools down. 3 g of p-toluenesulfonic acid amide are then added and the reaction mixture is cooled ^{to 20 ° C.}

b) Preparation of an aqueous urea resin solution. 60 g urea, 170 g (37% by weight) formaldehyde and 20 g

Sorbitol is adjusted to a pH of 8.5 with sodium hydroxide solution. The solution is warmed and boiled for 40 minutes calmly; then a pH of 4.5 is adjusted with formic acid and boiled until a sample that is im Ratio 1: 6 was diluted with water, shows a cloud temperature of 3 to 5 ° C on cooling. Then with Sodium hydroxide solution adjusted to pH 8/0 and distilled off until the residue contains 65% solid resin.

c) Manufacture of a mixed amino resin.

1000g of melamine resin from a) are added with 2 ml Hypersal, 2.5 ml of 30% hydrogen peroxide and 0.7 ml of formic acid are adjusted to pH 7.2, and 500g are then added Urea resin from b) was added with the addition of 5g ammonium chloride and intensely stirred.

d) Production of a phenolic resin.

94 g of phenol are mixed with 200 g (37% by weight) of formaldehyde and heated to 90.degree. Be at this temperature 22.5 g of sodium hydroxide solution (33%) were added dropwise over the course of 1 hour and a further 22.5 g of sodium hydroxide solution (33%) were then added. The reaction mixture is kept at 90 ° C until a sample has a viscosity of 200 cP. Now it is cooled down quickly.

e) Production of an amino synthetic resin condensed together with a phenolic synthetic resin.

A mixture of 60 g of urea and 405 g (37% by weight) of formaldehyde is adjusted to a pH of 8.5 with sodium hydroxide solution. The solution is heated and refluxed for 30 minutes. Now is with acetic acid to a pH of 4.8

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- fr -

set and cooked for another 30 minutes. A pH of 9.0 is then set with sodium hydroxide solution and 94 g of phenol are added to the solution. After a further 30 minutes of boiling, the pH is checked and, if necessary, adjusted to 9.0 with sodium hydroxide solution. It is then cooled to 90 ° C. and 63 g of melamine are stirred in. After the melamine has dissolved, the reaction mixture is kept at 90 ° C. after 1 hour and then rapidly cooled.
B) Coating of the plate surfaces.

1) 400 g of a melamine resin obtained according to a) were mixed with 100 g of titanium dioxide, 70 g of kaolin, 200 g of water and formic acid to adjust the pH to 7.2. This resin mixture was injected or poured to form a Coating layer in an amount based on solids of

2
300 g / m 2 applied to the surface of a chipboard.

This coating was then exposed to infrared radiation for 12 minutes, after which the residual moisture of the layer was 5% fraud. The chipboard coated in this way was then placed on top

2 between press plates at a pressure of 20 kp / cm and one Pressed temperature of 150 ° C for 4 5 seconds. The result was a chipboard with a white coating without colored

-In surface homogeneities obtained, wherein the coating layer has no tendency to chip off during mechanical processing showed.

With double-sided coating, there is the possibility of applying the resin substance to the surface of the chipboard one after the other to apply and then to subject both sides to the pre-drying and pressing treatment at the same time.

2) A melamine resin provided with filler according to Example 1 was applied to one side of a chipboard, and a filler-free melamine resin was applied to the other side of the board, which was obtained by adding 2ml Hypersal (wetting agent), 2.5 ml 30% Hydrogen peroxide and 0.7 ml of formic acid (85%) were obtained in 1000 g of melamine resin according to a), a pH of 7.2 being obtained. The application was carried out by spraying or brushing, in one

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2
Amount of 30Og solid resin / m. It was dried with circulating air to a residual moisture content of 5% and then pressed according to Example 1.

The filler-free coating layer was also made in an analogous manner coated by using a synthetic resin according to b), c), d) or e) instead of the melamine resin according to a).

3) There were 200g melamine resin according to a) with 50g chalk,

50g slate flour, 50g talc, 200g barite, 25g titanium oxide

2 and 10g Aerosil mixed. Of this mass, 450 g / m 2 were applied by spatula or by counter-rotating rollers on a Applied to the surface of a chipboard and dried with hot air. On the other face of the chipboard was then an amino synthetic resin according to d) is applied in an amount of 250 g solid resin / m and also dried with hot air. The two coating layers were cured together by pressing according to Example 1.

4) There were 200 g of melamine resin according to a) with 50 g of chalk, 50 g of slate powder, 100 g of talc, 100 g of barite, 100 g of titanium dioxide and 50 g of furfuryl alcohol and this melamine resin composition was applied analogously to Example 3 to both surfaces of a Chipboard applied, dried and hardened.

5) One side was made on a chipboard

aqueous urea resin solution according to b) in an amount of

25Og solid resin / m was applied and this coating was dried. Then it was on the other face of the plate applied a melamine resin provided with filler and pigment according to Example 1 and this top layer on a Residual moisture of 10% dried. The chipboard coated in this way was then placed in a heated platen press and the resin layers are cured. In this case, due to the higher residual moisture compared to the earlier examples, a Enrichment of the filler and pigment in the zone of the melamine resin coating layer adjacent to the chip material achieved, whereby the outer zone of the coating layer is particularly rich in resin,

6) A melamine resin solution that was obtained by that 1000g melamine resin a with 2 ml Hypersal, 2.5 ml 30% strength Hydrogen peroxide and 0.7 ml of formic acid (85%) was added in an amount of 300 g of solid resin / m on a Surface of a chipboard applied by spraying or painting. This application was dried for 10 minutes and then the same amount of melamine resin was applied to the second surface, dried again for 10 minutes and then it was pressed according to Example 1.

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Claims (16)

- ff - Claims; (1.1 Chipboard, which is at least one side with a Coating layer made of melamine resin is provided, characterized in that the coating layer consists of an im Pre-state water-soluble, homogeneous melamine resin consists, this coating layer in the fiber structure the chipboard surface engages and forms a smooth synthetic resin film on its outside. 2. Chipboard according to claim 1, characterized in that the melanin resin with an inorganic filler is offset. 3. Chipboard according to claim 1 or 2, characterized in that the melamine resin is also dye or color pigment contains. 4. Chipboard according to claim 2 or 3, characterized in that a filler on one side of the board containing melamine resin coating layer and on the other side of the board an unfilled coating layer Made of pre-water-soluble thermosetting synthetic resin, which is also incorporated into the structure of the chipboard surface engages, is provided. 5. Chipboard according to claim 2 and 3, characterized in that in the coating layer offset with filler the filler and the pigment are enriched on the inside facing the chip material, while the outside is low in fillers and pigments or practically free of fillers and pigments. 6. Chipboard according to claim 2 and 3, wherein both sides have a filled coating layer, thereby characterized in that the filler and pigment content of those located on one side of the plate The coating layer differs from that of the coating layer on the other side of the plate. 70 "IR /» 7/0739 ORIGINAL INSPECTED 7. A method for producing a chipboard according to any one of the preceding claims, characterized by combining the measures that an aqueous one for forming the coating layer on a wood chipboard A solution or a water-based paste of a water-soluble, homogeneous melamine resin is applied is that the so applied layer is then pre-dried, and that then the smoothing and curing of the predried layer to the cured coating layer with a between pressing plates Hot pressing process is carried out. 8. The method according to claim 7, characterized in that a resin solution or resin paste is used which consists of the resin and an inorganic filler. 9. The method according to claim 7 or 8, characterized in that a resin solution or resin paste is used, which also dye or. Contains color pigment. 10. The method according to claim 7, characterized in that the application of the provided for forming the coating layer Solution or paste is made by spraying on. 11. The method according to claim 7, characterized in that the application of the for forming the coating layer provided solution or paste is made by rolling or pouring. 12. The method according to claim 7, characterized in that the predrying is carried out by means of radiant heat will. 13. The method according to claim 12, characterized in that the predrying is carried out by means of infrared radiation will. 14. The method according to claim 6, characterized in that the predrying in a lleißluftofen or duct is made. 7H (IfW ₁ 7/0 73 9 15. The method according to claim 14, characterized in that the predrying in conjunction with infrared radiation is made. 16. The method according to any one of claims 7 to 15, characterized in that for producing one on both sides coated plate, the application of the material used to form the two coating layers first on one and then the other side of the plate and that smoothing and curing is carried out in a hot pressing process which treats both sides of the plate. 709847/0739