DE2052312A1 - Process for the production of press bodies - Google Patents

Description

■ A f « fi ' XMWALf

.> lf F »: -;! \ (li" Heiss-Trockenverfanren "

if; ι ίι ΐτ-i «ι / KH

Dr. hc Fred F ahr η i SCPr Zurich (Switzerland)

h 1

Process for the production of compacts

The present invention relates to a method for producing pressed bodies by pressing under Applying heat by using a heat curing binder offset, lignocellulose-containing particles between press plates or in a press mold.

For example, there have long been processes for the production of synthetic panels by pressing with a binder coated wood chips between heated

109887/1080 ORIGINAL BATHROOM

Press plates have become known, whereby the average moisture content in the molding is usually around $ 12 (based on the Dry weight of the wood). Aqueous solutions of a urea-formaldehyde resin are usually used as the binding agent or a phenolic resin.

The technical problem on which the invention is based is primarily to improve the properties of the pressed body without increasing the outlay on equipment and machinery and avoiding it to bring about an increase in the cost of the manufacturing process.

This goal is achieved in the method according to the invention in that dry particles with a moisture content of at most 3 - 5 % are heated using an anhydrous and heat-resistant binder during the pressing process in such a way that the temperature inside the pressed body being formed is at least the value of 15O ⁰ C assumes.

It is advantageously based on the dry weight; the particle-related moisture content not 3 - 5 %> but at most 2 # or even less than ljo. It is also useful to remove the particles during the pressing process

10 9 8 8 7/1080 BAD original

Cerart to heat such that the temperature assumes at all points of the nascent formation in compact the value of at least ⁰ C I7O. This requirement can be met, for example, by pushing the molding, consisting of particles and binding agent, between heated press plates or placing it in a heated press mold, the active press surfaces of which have a temperature of at least 180 ° C or, in certain cases, at least 200 ° C.

Tests have shown that products manufactured according to the invention are less affected by the influence of moisture swell and also result in more favorable strength values. These effects are likely to be due to the fact that the lignocellulose-containing particles during the hot pressing as a result of the high temperature and the largely steam-free press atmosphere. The practical absence of water in the molding also has the consequence that the particles in the press one exert greater counter pressure, which makes it possible to work with get by with less raw material. The manufacture will thus more economical and the result is more stable Products.

It has already been suggested that they be produced by hot pressing Chipboard with the help of high-tension steam

109887/1080

reward. Besides that such a procedure is expensive and cumbersome, it also shows that the achievable remuneration is only very limited. That too also known quenching and tempering of Holzsρa .-, en before forming cer briquettes through a special thermal treatment is very seldom carried out for economic reasons.

The defects described do not apply to the invention Procedure because the remuneration is not in a separate procedural stage with the help of special Devices and installations are carried out, but instead take place in the course of the hot pressing, which is necessary anyway can.

Lunatic According to the new teaching, a water-free and heat-resistant binder is to be used for the process. This purpose is fulfilled, for example, by two-component binoculars, one component of which is a polyisocyanate, while the second component consists of a polyfunctional Η-active compound, such as, in particular, a polyol or a polyamine. In addition to polyurethanes, polyureas , etc. , epoxy resins or possibly anhydrous phenolic resins are also suitable.

109887/1080 ORIGINAL BATHROOM

The remuneration process that takes place during the pressing process can be accelerated by using the Particles before being mixed with binder Adds pH-lowering substance. Aqueous acetic acid and chloroacetic acid, for example, are suitable for this purpose or the ammonium or hydrazine salts of these acids. In the case of the manufacture of chipboard is sufficient it is to spray small amounts of such agents onto the chips, which are still fresh in the forest, whereupon the drying is carried out to the required level low humidity level.

The following Examples 1 and 2 explain how the process according to the invention works can be carried out.

Example 1 ;

First, fresh cut birch chips mm with a thickness of 0.5 and a moisture content of ammoniumchloracetat # 60 with an aqueous solution of 0.5 l and # 5 / £ polyethylene glycol 750 sprayed. The chips treated in this way are then dried down to 1% moisture and glued with 5,4'-diphenylmethane diisocyanate, scattered to form a fleece and covered on both sides with release paper. This molding is then placed between two press

10 9 8 8 7/1080

Plates pushed, the temperature of which is 220 ° C. With a suitable height of the fleece and a corresponding dimensioning of the pressing pressure, after a pressing time of 8 minutes, a wood chipboard 20 mm thick and a room weight of 550 kg / nP is obtained. During the pressing process, the temperature in the center of the molding increases to approx. 130 ° C.

It should also be added that the percentages used so far relate to the weight of the absolutely dry chips. This plague position also applies to "Example 2.

Example 2 :

In the case of this example, it is not a question of pressing a single-layer board, but of producing a three-layer wood chipboard, where the top layers are made from spruce chips 0.16 mm thick and the core layer from spruce chips 0.8 mm thick. These chips, which differ in their thickness, are sprayed with 1% castor oil after drying to a moisture content of 0.5 #, which has been brought to a temperature of 70 ° C. beforehand. The chips are then glued with 5% of a prepolymer, which is prepared as follows: 3 mol of one

109887/108 0 ORIGINAL BATHROOM

Isomeric mixture of 2,4- and 2,6-toluene diisocyanate are implemented by adding dropwise 1 mol of polyethylene glycol 400 at 20-40 ° C. The reaction is done by titration of isocyanate groups followed. The prepolymer can be adjusted to the desired viscosity with a little perchlorethylene can be set. The chips provided with binding agent in the manner indicated are now known per se With the help of a spreading machine, spread them in layers in such a way that a three-layer molding is created. This is covered on both sides with phenol paper and heated between heated press plates at a temperature for 8 minutes of 210 ° C and exposed to pressure. With suitable The amount of pressure can be, for example, a Create a 20 mm thick board with a density of 520 kg / m3. After pressing, the hot plates on the stack are allowed to cool down.

It has been shown that, despite the absence of water during the hot pressing, panels with unexpectedly good surfaces result. This is probably due to the fact that the anhydrous binding agent does not harden suddenly, but rather gradually.

109887/1080

In the case of the exemplary embodiments described, the pressing pressure to be applied during hot pressing is approximately J> 0 kp / cm ² . In general, in the case of the production of medium-thick chipboard with a density of approx. 400 to 750 kg / m? a maximum pressure of approx. 5 to 50 kp / em2, advantageously approx. 15 to 40 kp / cm ² , can be achieved. Medium-weight particle boards of this type are still relatively porous and are suitable for general use.

In the case of compressing dry fibers from a lignocellulose-containing material, one works with Advantage with a specific pressure of about 10 to 40 kp / cm2. The fibreboard pressed in this way have a density between 400 and 85O kg / m ^. They are called semi-hard fiberboard.

ORIGINAL BATHROOM 109887/1080

Claims (1)

P A TINTLNS P RUECHE Process for the production of pressed bodies by pressing, using heat, lignocellulose-containing particles mixed with a thermosetting binder between press plates or in a press mold, characterized in that dry particles with a moisture content of at most 5 - 5 % using an anhydrous and heat-resistant Binder are heated during the pressing process in such a way that the temperature inside the pressed body that is being formed assumes at least 150 ° C. 2) Method according to claim 1, characterized by the use of particles with a moisture content of at most 5) Method according to claim 2, characterized by the Use of particles with a moisture content not exceeding £ 1. 4) Method according to one of claims 1-3 »characterized in that the particles are heated during the pressing process in such a way that the temperature at all points of the pressed body in formation assumes at least the value of 170 ° C. 109887/1080 - ίο - 5) Method according to claim 4, using heated press plates or a heated press mold, characterized by heating the press plates or the press mold in such a way that the press surfaces have a Assume a temperature of at least 180 ° C. 6) Method according to claim 5 »characterized by such a heating of the press plates or the press mold, that the pressing surfaces assume a temperature of at least 200 ° C. 7) Method according to one or more of claims 1-6, characterized in that a polyisocyanate is used as the binder used. 8) Method according to one or more of claims 1-6, characterized in that the particles are a two-component Blndemlttel adds, the first component of which is a polyisocyanate, while the second component is made of a polyfunctional Η-active compound. 9) Method according to claim 8, characterized in that the second binder component by a polyol is formed. 10) pressed body, produced by the method according to claim 1. 109887/1080 ^ ^ BATH