DE2063171A1 - Process for the fire-preventive impregnation of wood - Google Patents

Description

Dipl.-Ing. W-S *** - 8 MDNCHEN 22, Dipl.-Ing. H. MITSCHERUCH IZZ ^^ uu

Dipl.-Ing. K. GUNSCHMANN Dr. rer. not. W. KDRBER

PATENT LAWYERS Kr / Ne

December 22, 1970

A / S KANAMABK

DANISH CANADIAN ENGINEER COMPANT, Ltd.

Herlufsholmve ^ 4,

4700 Naestved / Denmark

Patent application Process for the fire-preventive impregnation of wood

The invention "relates to a method of impregnation of wood to make it fireproof, the wood preferably being in the form of a thin sheet or Tape, e.g. B. has a thin sheet of veneer or wood chips and a coating formed in situ insoluble non-flammable or not highly flammable polymeric material is brought onto and into the wood.

Numerous attempts have been made to impart refractory properties to wood, as well as it to make them resistant to the growth of fungi or the infestation with termites or the influence of water. Known methods of fireproofing wood consist in impregnating wood with fire retardant salts in aqueous solution. For example, ammonium sulfate, Na or Mg sulfate, mono- or diammonium phosphate, Borates or the like can be used. The fire-preventing effect of such salts is based

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presumably, on the fact that heat bound by their decomposition and that the salts, when heated, form melts which surround the flammable substance so that it is prevented from doing so will give off flammable gases and char without flame formation.

Normally there are no difficulties in impregnating wood with the salts mentioned, as these are easy penetrate the pores and intermicellar cavities of the wood. Since these salts are soluble in water, they will easily washed out of the wood again. This is not only the case when the wood is directly exposed to water, e.g. B. when raining in Comes into contact, but also when it is exposed to natural humidity, moisture condensation or the like is. The result is that the wood is initially fire-resistant later becomes flammable again, as if it were not impregnated. Even when using a large excess of salt, up to 30% by weight, no noticeable improvement can be achieved apart from the fact that this procedure is very complex. Try to mix the salts with other substances z. B. polyethylene glycol to mix, have also not led to fully satisfactory results.

The aim of the invention is a continuous process for Impregnation of wood for the purpose of refractory, in which the refractory substance does not come out of the wood again can.

The method according to the invention is characterized in that that the wood in a dry and preferably hot State with the solution of a monomer component and optionally impregnated with a fire-retardant salt known per se and for removing the solvent by heating is dried, whereupon the wood treated in this way is treated with the solution of another Monoaier component and heated to remove the solvent and remove the monomer * components to polymerize.

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Since the polymer is insoluble, it cannot be washed out by water or other moisture. Moreover lies it is in the wood in an effective form in terms of preventing the influence of fire, while the salts are only diameter or melting from the heat of a fire to take effect. Because the polymer material all surface parts both outside as well as wrapping inside the wood, in the event of fire exposure there will be the formation of flammable gases from the wood prevent and thus significantly improve the effect that can be achieved with the known means.

Following the procedure of British Patent Specification 600 961 To make wood fireproof, it is impregnated with a polymerizable material, which is converted into an insoluble, non-flammable or not easily flammable polymeric material is transferred. However, an impregnation solution is used here, which is a mixture of monomers or other polymerizable Contains substances. It is therefore necessary to use a much more difficult heat treatment, since the impregnated wood is first dried at a relatively low temperature and only then heated to higher temperatures must be in order to achieve polymerization. If one uses drying and polymerisation in this process If you want to perform continuously in an oven, you have to work with a certain temperature cycle while you work with the inventive method only with a single high Needs to work temperature, through which a rapid evaporation of the solvent is achieved and which for a rapid polymerization is sufficient. Since the British method uses low temperatures to dry the impregnated If wood works, for example with air drying, the drying process takes a very long time. Venn one works at higher temperatures, it cannot be avoided that a polymerization to a certain degree is already in the impregnation liquid itself enters, so that there is sufficient adhesion of the polymeric material inside the wood is not guaranteed.

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2Ü63171

The first monomer component can be used together with a fire-retardant salt known per se, which can be one of the salts indicated above. This increases the fire-preventing effect, even when using small amounts of salt compared to the amounts that
are used in the known methods. This increase in effectiveness is retained because the salt is firmly incorporated into the polymeric material and is therefore not washed out
can be.

Before the wood is impregnated with the monomer solution according to the invention, the wood is hot-dried to a moisture content of, for example, 4 % . In order to achieve thorough impregnation, the monomer solution is expediently sprayed on, for example under vacuum. However can
the monomer solution preferably also at normal pressure
wood that is still in the hot state due to the previous drying can be added, which has a temperature of, for example, about 160 ° during impregnation. The monomer solution must have a minimum temperature of 80 °. Since the
Pores in the hot wood are open and the amount of air in them is very small, the pores / intermicellar spaces are completely filled with the impregnation liquid in the wood.

The first monomer component for use in the process according to the invention is, for example, phenol, a dihydroxybenzene, urea or melamine or a mixture thereof,
preferably phenol or resorcinol, suitable as the second monomer component ent e formaldehyde. Other aldehydes are also suitable, but formaldehyde has been found to be the most advantageous. A fire-retardant salt, which in some cases has a catalytic effect, can be added during the polymerization.
Boric acid, among other things, is suitable for this.

The monomer components are expediently in aqueous solution

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applied. The concentration of the first monomer solution, ζ. Β. of phenol or resorcinol, can vary to some extent. The wood per cubic meter is impregnated with about 50 kg of phenol or Eesorcin namely at a concentration of the aqueous solution of from about 7 to about 70% j · A below 7% lying concentration is too low for the ER- ^{advantageous:;} Required first monomer component. One concentration over! 70 % is too large, since the monomer component then tends to crack. A small excess is used for the second monomer component. For this purpose, preferably in a set | formaldehyde used by about 15 kg is sufficient to react completely with 50 kg of phenol or eesorcinol.

. Preferably about 20 kg of formaldehyde per cubic meter of wood are used, previously about 50 kg of phenol or eesorcinol are impregnated. The excess of formaldehyde disappears during the condensation process. If not all of the phenolic

'■ or amount of esorcinol has reacted, crystals are formed which promote a fire and thus contradict the purpose of the invention.

, The inventive method is preferably used for wood in the form of thin chips or leaves, e.g. B. veneer panels applied, but it can also, for example, for impregnation of sawdust or chips. The thin sheets of wood, like veneer panels, are treated in thicknesses of 1 to 2.5 mm, complete impregnation can be achieved. ■ After completion of the treatment, the leaves or ! Strips are glued together in the usual way, for example with a plastic adhesive that matches the waterproofing agent to wood products such as plywood j or other leaf-shaped wood surfaces, wood chips or the like produce that have particularly good fire-preventing properties. A phenol-formaldehyde or Eesorcinol formaldehyde resin is preferably used because the-; it retains its binding properties even after cooking.

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Other properties such as resistance to moisture and mold growth also become notable improved.

The inventive method can continuously with a Device are carried out, which is characterized in that it has means for moving the wood product to be treated comprises, and in the direction of movement a first drying oven or oven part, a first device for the impregnation liquid, a second drying oven or part, a second device for the impregnation liquid, has a third drying oven or oven part and a cooling device.

An expedient embodiment of a device according to the invention for the impregnation of veneer panels in the form of a continuous strip consists of one in three departments compartmentalized drying oven, means for advancing the veneer strip in one direction through the first oven part, then in the opposite direction through the second part of the furnace and again in the first direction through the third furnace part, further comprising means for applying the impregnation liquid by spraying between the first and second, as well as between the second and third furnace part. In this way a continuous working method is enabled for carrying out the process.

The invention is explained in more detail below with reference to the drawing:

Fig. 1 shows a device according to claim 5?

2 shows a device according to claim 4; Fig. 3 shows a device with only one drying oven with only a furnace part for the discontinuous implementation of the process.

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20G317 - 7 -

In each figure there is a cutting machine at the beginning of the device 1 arranged to cut wood for veneer sheets in the form of a tape, which is drawn on a roll 2 will. At the end of the device there is a second cutting machine 11 with which the veneer tape is cut into suitable Pieces 13 is cut.

According to FIG. 1, the veneer strip 12 moves from roll 2 into a first oven part 3 of the oven consisting of three compartments, in which it is dried at about 160 ° to a water content of about 4%. After passing through the drying oven, the veneer strip runs through two liquid curtains that are generated by the spray device 4. The liquid consists, for example, of a solution of 10 parts by weight of resorcinol, 4 parts by weight of borax, 4 parts by weight of boric acid and 82 parts by weight of water. The veneer tape runs through the liquid curtain in such a way that it is first sprayed on one side and then bent around a roller (not shown) when wet, whereupon it is also sprayed on the other side. The liquid not absorbed by the veneer tape is collected in a kettle 5. The temperature of the impregnation liquid is at least 80 °.

After the first impregnation, the veneer tape runs through the second section 6 of the drying oven, in which the temperature is also 160 ° and the water is removed except for a remainder of 4%.

The veneer tape, which is impregnated with resorcinol on the outside and inside is now migrates through two liquid curtains from spray device 7 of the same type as device 5. The liquid consists of a solution of 4 parts by weight of formaldehyde in 96 parts by weight of water. The spray takes place as in the first case on both sides of the veneer surface. The unabsorbed liquid will be in the Armchair 8 collected.

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After the second impregnation, the veneer tape runs through the third compartment 9 of the drying oven, which is also heated to 160 °. Here the water is evaporated and expelled. Resorcinol and formaldehyde polymerize by condensation to form a plastic that is insoluble in water Hate that envelops all of the wood substance inside and out.

After leaving the drying oven section 9, the veneer strip with a water content of approximately 4 % is cooled in device 10 to normal processing temperature, ie approximately 20 °. It is then cut into suitable pieces taking into account the setting time of the binders for use as plywood or other laminate surfaces.

In the device shown in FIG. 2, the veneer strip 12 is made in a corresponding manner as in the device according to FIG treated. However, there are three separate drying ovens 3 »6 and 9 arranged in rectification with intervening devices 4 and 7 for applying the impregnation liquids. Here, the veneer strip is immersed in kettles filled with the impregnation liquid, whereby it runs under a rotating roller.

In the device according to FIG. 3 for the discount-internal implementation of the inventive method 3, 6 and 9 are the same drying oven for the first, second and third drying stage. After the first drying (3) the veneer sheet becomes Impregnated by immersion in device 4- and lifted up on rollers 14 when wet. After the second drying (6) the veneer tape is immersed and impregnated in device 7 and lifted up on rollers 15 when wet. The cooling device 10 is only used after the third drying stage (9). The device according to Fig. 3 can be used if only one drying oven is available.

With similar embodiments as shown in the figures

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Device it is also possible to produce wood flakes in other shapes to treat. For example, you can handle wood chips that are on a conveyor belt with small holes be passed through the device. The Impregnation solution sprayed onto the chips from both sides of the conveyor belt, i.e. simultaneously from above and below will. It is also possible to treat wood flour, this on a conveyor belt made of non-absorbent Glass fiber or nylon fiber is passed through the device.

Claims ι

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Claims (1)

Patient requests Process for the fire-preventive impregnation of wood,; preferably thin veneer sheets or wood shavings, wherein a j of an insoluble non corresponds in situ formed coating, flammable or non-flammable polymeric material is applied to the outer and inner surfaces of the timber ■ in the form of thin wooden sheets or surfaces, ·, for example, characterized in that the wood is impregnated in a dry and hot preferably state with the solution of a monomer component and optionally a feuerverhütenden salt and removal of the solvent, hot dried, whereupon the wood with a solution of a second, different Monomerenkom- [component impregnated and for removal of the Solvent ^: as well as for the polymerisation of the two monomer components \ is treated hot. · Method according to claim 1, characterized in that ' as the first monomer component phenol, a dihydroxybenzene, urea or melamine or a mixture thereof, preferably Phenol or resorcinol, and formaldehyde is used as the second monomer component. ι Method according to claim 1 and 2, characterized in that that the monomer components are used in aqueous solution. Device for the continuous implementation of the method according to one of claims 1 to 3 » by means for moving the wood and then a first drying oven in the direction of movement or part (3), a first device (4) for supplying the impregnation solution, a second drying oven or part (6), a second device (7) for feeding 109827 / U78 of impregnation solution, a third drying oven or -part (9) »and a cooling device (10). ' Apparatus according to claim 4 for impregnating sheet of veneer in the form of a continuous band, marked; by a drying oven divided into three sections (3j 6, 9), Means for moving the veneer strip in one direction through the first furnace division (3)> further in the opposite direction through the second furnace compartment (6) and again in the initial sifting by the third oven compartment (9) »further characterized by devices (4 and 7) for adding the impregnation solution by spraying the wood between the first and second, as well as the second and third oven compartments. The patent attorney 109827M478