DE1037112B - Process for the production of chipboard - Google Patents

Description

si.

In the manufacture of chipboard, the required pressing time is decisive for the speed, which can be used to produce in a press system. The pressing time in turn depends on the Hardening speed of the synthetic resin used to bind the chips. Using a fast-acting hardener or a particularly fast-curing synthetic resin allows an abbreviation the pressing time, but the resin must not harden before the press is closed.

The wood chips coated with a solution of a hardenable synthetic resin and a hardening agent therefor after pouring, if necessary using a sheet metal insert and if necessary After cold pre-pressing of the chip cake, it is brought into the press heated to around 120 to 160 ° C. To retract the Spankudhen one uses stacking machines, the ten or more plates at a time Put in the open press. If this only takes about 1 minute to fill the press until closing is required, this time is sufficient, as has been found, very quickly when used acting hardener or fast hardening synthetic resin already to a hardening of the resin on the surface to effect the chip cake in the warm press. The chips on the surfaces of the chipboard are not in each case during the seizure more sufficiently glued together so that the strength in these layers is insufficient. At the When cutting and grinding such plates, the chips are very easily torn out of the surface layer. When these panels are blocked off, the barrier functions together with the top one Layer the chips slightly off the chipboard.

Alan has therefore already proposed. Chipboard from several, z. B. produce three layers of chip wires, the inner layer with a special fast-curing synthetic resin or a synthetic resin mixed with a fast-acting hardener and the outer layers are bonded with less fast curing resin or a weaker one Hardener included. This process has the disadvantage that I work with two different synthetic resins «Has to be grounded and the chipboard does not harden quickly enough.

Rs is also already known to be mixed with binders To preform wood chips and to spray the molded body obtained in this way with water before pressing. This ensures that the pressed chipboard has a smoother surface. Through the Adding water to the surface of the preformed sheet will make the resin solution in the surface layers diluted, so that the curing speed of the synthetic resin is reduced here.

Process for the production of chipboard

Applicant:

Aniline & Soda Factory in Baden

Corporation,

Ludwigshafen / Rhine

Dr. Hans Scheuermann,

Ludwigshafen / Rhein-Oggersheim,

has been named as the inventor

However, the relatively small amount of water is not sufficient to accelerate the hardening rate quickly to reduce setting synthetic resins to a sufficient extent. You also can't get the amount sprayed on Increase the water at will, otherwise the resin solution will be exposed to the heat of the pressing Surface of the chipboard migrates into the interior. so that the bond strength of the chips to the Surface of the chipboard becomes smaller.

It has now been found that synthetic resins which bind very quickly can also be used for the production of chipboard Let \ -use when layering the chips treated with these resins, if necessary cold pre-presses to the chip cake and the surface of the molded body obtained λόγ the hot pressing with a solution, in particular the aqueous solution of a hardening retarding compound, sprayed over. If aminoplasts are used as binders, solutions of Buffer salts. z. B. small amounts of a metal salt of a weak acid such as sodium acetate, secondary or tertiary sodium phosphate, sulphurous acid salts. Salts of lower or higher molecular weight Carboxylic acids, e.g. B. Soaps, as well as basic compounds. When using phenoplasts, for. B. Solutions of acids are used, which the Reduce the effect of the alkalis, which accelerate the setting of the phenoplasts. Quantity and type the buffer compound used are chosen so that the binder is not yet during the Closes the press, but hardens during pressing. Leave the appropriate amount of buffer compound Determine borrowing through a few preliminary experiments. It is useful when making thick chipboard

809 598/473

to use larger amounts of a hardening retarding compound. Together with the buffer connections can use other resins, dyes. Water repellants or other compounds be applied.

The parts mentioned in the example are parts by weight.

example

A solution of urea and formaldehyde in the molar ratio 1: 2 is l> ei a p _H of 4.5 condensed until a sample after dilution with 2 parts of water at room temperature is just beginning Harzabscheidiing. The solution, neutralized with sodium hydroxide solution, is concentrated in vacuo to a dry content of 55%. 100 parts of this solution are mixed with 10 parts of a solution

4 parts of urea, 1 part of ammonium chloride and

5 parts of water are added. Such resin solutions have a processing time of 2 to 2½ hours at room temperature. 16 parts of this synthetic resin solution are sprayed onto every 100 parts of wood chips ao with 6 to 8% moisture content. After the chip cake has been pressed in the cold, it is sprayed on both sides with 60 ccm / sqm of a 1.5% solution of secondary sodium phosphate (Na ₂ HPO ₄ · 12 aq) containing water of crystallization. In a 12-stage press with a closing time of about 1 minute, a pressing temperature of 135 ° C. and a finished chipboard thickness of 19 mm, well thermosetting press plates with excellent surface properties are obtained in a pressing time of 8 minutes.

Claims (1)

Claim. Process for the production of chipboard, characterized in that with the solution a quick-setting synthetic resin and a curing agent for the synthetic resin coated Chips are preformed, the molded body with the solution of a hardening of the synthetic resin retarding compound treated or sprayed on its surface and then hot-pressed will. Considered publications:
U.S. Patent No. 2,583,618. 809 59S / 473 8.58