DE1294003B - Process for the production of fire-retardant veneer or laminated wood panels - Google Patents

Description

The invention relates to a method of making fire retardant Veneer or pressed laminated wood panels made of dried individual veneers, which with a impregnated with diammonium phosphate impregnation solution, then dried and with glued together with a plastic adhesive using pressure and heat will.

A method for producing plywood panels is known, in the case of the individual veneer panels with the reaction components for the formation of Amino resins, such as urea-formaldehyde or melamine-formaldehyde, in the form of an impregnating solution are soaked, the z. B. 18 to 20,% inorganic salts, mainly ammonium salts, in particular ammonium phosphate and additionally alkali borate (in a ratio of approx 3: 1) as a pH buffer, should contain "and still known impregnating agents"; above However, nothing is said about the nature and nature of the latter. The single ones Impregnated veneers are then subjected to a heat treatment for partial condensation of the resins subjected and then each provided with layers of glues based on amino resins, joined together and finally glued together under pressure and heat.

The products obtained are called "fire-resistant", d. H. that they do not burn themselves. For the fire retardancy aimed at according to the invention However, the material must also be able to withstand exposure to flames over a longer period of time Withstand time without burning through charring, d. i.e., the charring rate must be as small as possible.

The known fire-retardant panels now have a relatively low Fire resistance and, above all, the disadvantage that they charred when exposed to flames Pieces of wood peel off easily and the charring process continues to advance enable. Plus, most of them show a result before they burn out the drying out of undesirable cracks; however, this disadvantage occurs the fire-retardant panels are not made of chips bonded with plastic resins have been manufactured.

The best results so far are made with particle board especially Impregnated chips with two layers of asbestos inlaid, the z. B. at a thickness of 25 mm only burn through in the course of about 30 minutes.

The invention is based on the object of the method of the opening paragraph to further develop said type in such a way that the aforementioned disadvantages are avoided grains, d. H. a method for the production of a veneer or laminated wood panel in which neither charred pieces of wood peel off under the action of a flame unwanted cracking still occurs.

The invention solves the problem in that the individual veneers with an aqueous solution containing diammonium phosphate and then impregnated with glued together with a plastic adhesive containing kaolin and diammonium phosphate will.

Using panels made in this way will be like the ones below The compilation given shows better results in terms of fire retardancy achieved than before, for which possibly the existing in the plastic adhesive Kaolin is at least partly responsible due to its heat-conducting effect.

The impregnation solution should contain 15 to 40% diammonium phosphate, with a further improvement of the fire retardancy by adding small amounts of copper sulfate of preferably 0.5 to 3% to the impregnation solution can be achieved can; it has been shown that copper sulfate appears to be within each veneer Has a heat-dissipating effect, which means that the risk of local overheating is even lower.

Another advantage of the copper sulfate addition is that on this way the resistance of the panels to rot, fungi and pests is increased. The addition of copper sulfate to the impregnation agent does indeed cause a Color deepening in the veneers, which, however, is often seen as an advantage is.

The improvement in fire retardancy achieved according to the invention is otherwise largely independent of the plastic glue used. There were many various plastic glues checked and in all cases with the addition of kaolin and diammonium phosphate to the adhesive a considerable extension of the fire retardancy time observed. However, particularly good results have been achieved with plastic adhesives known per se, such as urea-formaldehyde with melamine powder (weight ratio 4: 1), phenol-formaldehyde (if necessary with melamine powder), melamine-formaldehyde or epoxy adhesives.

The kaolin and diammonium phosphate content of the adhesive can be within quite wide limits fluctuate and among other things depends in some way on the Type of plastic adhesive and the liquid solvent and emulsifier used away.

If - as usual - an aqueous adhesive mixture is used, so the best results will be obtained with a content of 30 to 50,% plastic, 20 to 50% kaolin and 0.5 to 2.0% diammonium phosphate achieved. Preferably an approximately Adhesive mixture containing 40% plastic, 1% diammonium phosphate and 25% kaolin used.

The impregnating agents, d. H. the diammonium phosphate alone or together with copper sulphate, must be distributed as evenly as possible over the individual veneers be, and that should be at least 30%, preferably about 75 to 100% of the pore cavities of the veneers are filled with saline solution. A fire retardant effect becomes noticeable, however, at a filling level of only 150 / a.

In order to achieve a good and even impregnation of the veneers, the veneers are first placed in a drying oven to a moisture content brought less than 10% and then transferred while still hot in a vacuum container, which is evacuated and then filled with the aqueous impregnation solution; after The veneers are removed from the vacuum container again down to a moisture content from about 6 to 10%, preferably about 60%, dried.

The re-dried individual veneers are then (and preferably every second plate on both sides) coated with the plastic adhesive and the stacked veneers (with an uncoated face veneer) in one Press using of pressures between 4 and 30 kp / cm = and Glued together at temperatures between 70 and 150 ° C.

The gluing preferably takes place at temperatures in the vicinity of 120 '= C instead.

You can also increase the fire retardancy significantly if the veneers are exposed to such pressure during setting or gluing, that the thickness of the individual veneers by 10 to 5001`o, preferably by 1.0 to 30%, and mainly decreases by about 20%. By such a pressure treatment that usually pressures of about 100 to 300 kp / cm = required, panels are obtained, which not only - compared to the well-known veneer panels - improved mechanical ones Have properties and, in particular, good nail and screw strength, but also against moisture, such as direct exposure to water or a cooking process, are resistant; these plates also have improved fire-retardant properties (see table).

Finally, it should be noted that the plates, regardless of the The extent of compression during compression when exposed to a flame is also not burn on the surface and also show no noticeable smoke development, what is of great importance when used as fire protection elements should.

The following are non-limiting examples to illustrate the invention Procedure. Example 1 21 plate-shaped 1 mm thick beech wood veneers of the same size are dried in a drying oven to about 4% moisture and in a hot state placed in a vacuum container, which is largely evacuated and then with a 30% igen aqueous solution of diammonium phosphate is filled. After a short time the container will opened, the veneers taken out and in the drying oven down to a moisture content dried from about 6 to 10%.

The dried, impregnated veneers are stacked on top of each other, every second veneer panel on both sides with a 0.2 mm thick layer of one Adhesive mixture of 125 parts by weight of pheno-formaldehyde, 3 parts by weight of diammonium phosphate, 75 parts by weight of kaolin and 97 parts by weight of water is provided. The stack of veneers is then introduced into a press heated to around 125 ° C, where the veneers under a pressure of about 30 kp / cm = to produce a 25 mm thick plywood sheet are pressed together. The mechanical properties of this plate and its resistance to moisture correspond to the usual plywood panels, where the Veneers are connected by means of phenol-formaldehyde, but they will be exposed to fire do not burn spontaneously and do not develop flammable gases when heated (cf. Tabel).

Example 2 45 plate-shaped veneers 1 mm thick are coated with diammonium phosphate impregnated in the manner indicated in Example 1, but using a 20 to 25% aqueous solution of diammonium phosphate, and are used after impregnation dried to a moisture content of about 6 to 10%.

It is an adhesive made of 100 parts by weight of urea-formaldehyde, 25 parts of melamine powder, 3 parts of diammonium phosphate, 75 parts of kaolin and 97 parts Prepared water.

The 45 veneers are stacked on top of each other, with every other A 0.2 mm thick layer of the above-mentioned adhesive was applied to both sides of the plate is, after which the stack formed in a to 110 to 125 ° C, z. B. 115 ° C heated Press a pressure of about 300 kp / cm = is subjected. This not only does the veneers are firmly pressed together, but so are the individual veneers compressed so that its thickness decreases by about 50%. The stack of veneers remains in the Press under this pressure for 16 to 20 minutes; a veneer panel is obtained 25 mm thick.

This plate has very good mechanical properties. in particular in terms of nail and screw strength. Besides, the plate is also against very humid air at relatively high temperatures, such as B. under tropical conditions, resilient.

In addition, the plate has a fire resistance, which is also opposite such panels made of fire retardant materials is improved (see table). Example 3 Proceed as in Example12, but only use 15 Veneers, resulting in a compacted veneer panel with a thickness of 10 mm. This has the same mechanical properties as the plate according to Example12, but of course has a somewhat lower fire resistance due to its lower strength (see table). Example 4 34 plate-shaped 1.4 mm thick beech wood veneers of the same size were dried in a drying oven to a moisture content of about 5%, after which the veneers were placed in two vacuum containers - 17 pieces per container. The containers were largely evacuated, after which an aqueous container was placed in the first container Solution with 201 / o diammonium phosphate and 0.5% polyethylene glycol, and in the second an aqueous solution with 20% diammonium phosphate, 1.5% copper sulfate and 0.5% polyethylene glycol was filled. After a while the two containers were opened and the two of them Stack of differently impregnated veneers removed and put back into the drying oven where they were dried to a moisture content of about 6910.

By mixing 100 parts by weight of phenol-formaldehyde, 10 parts by weight of para-formaldehyde, 5 parts by weight of diammonium phosphate, 50 parts by weight of kaolin and 110 parts by weight of water, a. Adhesive produced and applied to every second panel of the two sets of veneer panels on both sides an approximately 0.2 mm thick layer of said adhesive. The two stacks formed were then placed in a press that had been heated to about 130 ° C. and subjected to a pressure of about 100 kp / cm = for about 20 minutes. Two sheets of plywood, each about 22 mm thick, were obtained. The fire retardant properties of this board are given in the table. Fire retardant effect of various panels Type of panel Panel thickness Behavior in the event of direct exposure to a butane gas burner in mm on the center of the front of the panel Ordinary plywood sheets 25 burn through after 5 min Impregnated chipboard 25 burns through after 30 minutes with the formation of holes with 2 asbestos inserts Plate according to the invention after slow charring from the front, which after play 1 penetrates 60 min or more to the back of the panel; Plate remains intact; no hole formation; no peeling According to the plate according to the invention, charring of the rear side only begins after 150 minutes; game 2 plate remains intact; no peeling; relatively insignificant Bulge; even on the front, the carbonization is limited to the flame exposure zone The plate according to the invention according to example 10 withstands the action of the flame for 50 to 60 minutes game 3 Plate according to the invention after carbonization of the rear side begins after 75 to 90 minutes game 4, without CuS04 Plate according to the invention after carbonization of the rear side began after 105 min game 4, with CuS04 In the aforementioned examples, the method according to the invention was explained in connection with the production of plywood panels from veneers. Of course, this process can also be used analogously in the manufacture of chipboard.

Claims (6)

Claims: 1. Process for the production of fire-retardant veneer or pressed plywood panels made of dried individual veneers, which are coated with a diammonium phosphate Impregnation solution impregnated, then dried and covered with a plastic adhesive Application of pressure and heat are glued together, characterized that the individual veneers are impregnated with an aqueous solution containing diammonium phosphate and then with a plastic adhesive containing kaolin and diammonium phosphate be glued together. 2. The method according to claim 1, characterized in that that the impregnation solution 15 to 40 percent by weight of diammonium phosphate and additionally contains small amounts, preferably 0.5 to 3% copper sulfate. 3. The method according to claim 1 or 2, characterized in that an aqueous adhesive mixture is used as the adhesive, the 30 to 50%, preferably 40% plastic adhesive, such as urea-formaldehyde with melamine powder (in a weight ratio of 4: 1), phenol Formaldehyde, optionally in melamine powder; Melamine formaldehyde or epoxy adhesive and 20 to 50%, preferably 25% kaolin and 0.5 to 2%, preferably 1 10/0 diammonium phosphate, contains. 4. The method according to any one of the preceding claims, characterized in that the pore cavities of the veneer panels during the impregnation up to at least 301 / o, preferably up to 75 to 100% with the impregnation salt solution. 5. Procedure according to one of the preceding claims, characterized in that the individual veneers first dried in a dryer to less than 10% moisture and then the veneers that are still hot are transferred to a vacuum container into which - after a extensive evacuation - the aqueous diammonium phosphate is filled that the veneers dried to about 6 to 10% moisture after removal from the vacuum container every second veneer is coated on both sides with the plastic adhesive and the stacked veneers with an uncoated face veneer in one Press using pressures between 4 and 30 kgf / cm2 and temperatures between 70 and 150 ° C, preferably at about 120 ° C, are glued together. 6. Procedure according to claim 5, characterized in that a increased pressure of about 100 to 300 kp / cm2 is applied.