NO753613L - - Google Patents

Description

A method is known for the production of building boards from wood, cement and water, and reference should be made here to the US patent documents no. 3 164 511 and 3 271 492. The fresh mixture is transferred to a plates that are loose, the plates are stacked on top of each other

and pressed as a pack in a press to the desired plate thickness. The transfer to the boards preferably takes place in such a way that cement-encased fibers lie on the surface of the boards, respectively so that these fibers in the case of single-layer boards distribute

evenly over the entire plate thickness. This is done to obtain as high a bending strength as possible in the finished plate.

The so-called wind sifting method also belongs to the state of the art and reference should be made here to the German patent document no. 1 061 059.

A disadvantage of this'. method is that with the plates produced in this way, a relatively rough surface is obtained. Experience shows that the large chips on the surface easily swell due to climate stress, especially with boards that have been ground, and these chips therefore loosen over time. Furthermore, the rough surface is often undesirable for aesthetic reasons.

Moreover, the board type with straight chips • is not always preferable, since in building constructions the substructure is often carried out so that the same fixings are used in both directions, i.e. both in the longitudinal direction and in the transverse direction. Furthermore, chip or fiber mix-. and correspondingly also the cement distribution is equal over the entire plate cross-section. In the event of a fire, for example, the outer plate layers will therefore burn relatively quickly, and the plate burns relatively deeply, which is a disadvantage. A further disadvantage of such plates is that the relatively open, outer skin consisting of long shavings or fibers over 12mm quickly absorbs water, which leads to increased swelling. The industrial application of this invention "runs into problems when it comes to the production of the desired fibers and the question also arises of what to do with the unused, fine material that appears during the shaping of the shavings.

The new building board is distinguished by the fact that the average amount of mineral salt stored in these chips, taken up by the chips, amounts to at least 2 wt.-$ with regard to the atrore weight.

The new method avoids these disadvantages. It is distinguished by the fact that the chip mixture after chip production is divided into at least two fractions, the fine material with a particle size of 2 - 8 mm and the normal material with a chip size of 8 - 20 mm - of which at least 80$ is not larger than 12 mm -, and in that, after mixing, the chip mixture is sprinkled on a substrate by means of wind scattering where during the mineralization at least 2% by weight of the mineralizing agent, calculated on absolutely dry chips, penetrates the chips,

and during the spreading, there is at least wood evenly overlapping each other, with regard to the trespassement conditions of different layers.

By using the method, a building board is provided which has a smooth surface and whose internal structure is distinguished by the fact that the fine proportions of wood and cement are enriched at the board's surface, and the fiber dimension of a board with three layers increases steadily towards the middle of the plate thickness. The slightly reduced cement content towards the middle of the plate corresponds to the likewise reduced bonding surface to the coarse fibers present there.

With this build-up, and particularly as a result of the antifiking of cement on the surface, the resistance to external stresses is significantly increased, so that the board has significantly better resistance to, for example, climatic stresses, fungal attack, termite attack, etc.

The invention shall be explained in more detail with reference to the drawings, where Figure 1 shows a cross-section through the scattered fleece with from the center of the fleece towards both sides towards the main surfaces the removed chip or fiber length,

Figure 2 shows the calculated, percentage uptake of a mineralizing agent solution in weight-$ depending on the effective chip length, with regard to absolute dry (atro) wood weight,

figure 3 - shows the percentage by weight of expected chip fractions in dependence on the effective chip length,

figure 4 shows the progress of the space weight in the plate cross-section,

plotted over the plate thickness for a plate of the felt in figure 1,

figure 5 shows the distribution of the atro wood weight per volume unit over the plate thickness for a plate of the felt according to figure 1,

figure 6 shows the distribution of the cement weight per volume unit of atro wood over the board thickness for a board of the floret in figure 1,

figure 7 shows the average fire temperature when equal primary loads are burned in dependence on time for different wall coverings A, B and C,

Figure 8 shows the compressive strength of a plate according to

figure 4 above the plate thickness,

figure 9 shows the pure tensile strength for a plate according to figure 1 over the plate thickness, where the bending tensile strength lies between 120 and 180 kp/cm

figure 10 shows the cross-section of a plate with five

nice,

figure 11 shows the distribution of the room weight for a plate

according to figure 10, analogous to figure 4,

figure 12 shows the distribution of the wood weight of a plate according to figure 10, analogous to figure 5*

figure Ij5 shows the distribution of. the cement weight for a slab according to figure 10, analogous to figure 6, and

figure 14 shows the course of the tensile strength analogously

with Figure 9 for a plate - according to Figure 10.

The cross-section of a flor shown in Figure 1 shows that a coarse middle layer has been spread out. This middle layer moves towards the outer edges into an increasingly finer layer. The transition is continuous, which is in itself known from the wind current method.

An essential step in this method is the mineralization of the shavings. It is therefore important that the mineralizing agent, for example a mineral salt, penetrates completely into the wooden material during a specific time, preferably a maximum of 1 minute. Known mineral salts can be used as a mineralizing agent. For the present experiments, a solution of Al^SO^)-^ was used in a concentration of 14 g per liters of water. This corresponds to a weight concentration of'" 1.4%, respectively a density of 1,014 g/cm. The calculations were also based on an average yolum weight of 280 kg/m - 7. atro wood. The correct choice of chip fractions has led to a surprising result. In Figure 2, the curve a shows the amount of mineralization ice taken up by the chips,

in weight-$ of the dry shavings which. a function of the chip size. It was established that this amount asymptotically approaches a value of 5% for very coarse chips. In the case of perfectly fine shavings with a length of

0.2 mm amounts to this amount of almost 480 weight-$. Then a mineral-salt solution quantity (1.4 weight-$ig) of approx. l80 - 190 weight-$ of the shavings give optimal results in the production of such boards, contrary to previous experiences, also chip fractions with smaller shavings, for example down to approx. 0.5 tnin length, selected.

It was determined that with dry chips in a time unit of one minute and with the selected chip fractions up to 50$

more mineralizing agent solution taken up by the shavings than with shavings that, for example, have a moisture content of 80% by weight.

This effect could not be expected from the diffusion theory. In practice, it is obviously not possible to reach the conditions that are the basis for the theoretical consideration, at least not in an economic way, as experiments have shown. In practice, the Kant conditions will be completely different from those assumed in theory, since, theoretically, a complete immersion is expected, which is economically unfeasible.

In figure 3, the fractions are shown, certain choices during the plate production have led to the unexpected results. The main fraction ($64) mainly consists of a chip mixture of 5 - 12 mm in length which provides an excellent reinforcement of the plate and in this connection also ensures the corresponding strengths. The fine part (0 - 5 mm) of approx. 14$ of the total weight of shavings will be left in the outer layers. The structure of the layer, which leads to such a plate, is shown in figure 1. The smooth transition from the outermost smooth fine layer to the innermost coarse layer according to these fractions ensures the desired distribution of the stresses in the case of bending stresses. The board is built up so that the quantities of material (wood and cement) arrive where they ensure the specific properties of the board: sufficient bending strength, very high compressive strength and very good fire resistance.

In Figure 4, the distribution of the volume weights in kg/m is shown above, the plate's cross-section. It is important to note here the distribution of the amount of wood (figure 5) and the amount of cement (figure 6).

As a result of this material development, the essential advantages of such plates are ensured, namely high weather resistance and high refractoriness. The fine chips in the outer layer are better protected with three times the amount of cement in the outermost phase than the middle - inner part of the plate. By. a fire, the fine outer layers will be driven up in a finely meshed manner and will remain suspended on the rest of the plate. This prevents the penetration of air into the inner part of the plate, and the plate therefore only burns to a depth of 5 - 6 mm.

In Figure 7, the average fire temperatures for a burn-off of equal primary loads are shown schematically as a function of time for different wall coverings. Curve A relates to a building material that is completely non-combustible, curve B appears. when lining a room with normally combustible materials, and curve C shows the temperature course when lining with panels manufactured according to the present invention. Curve C has a higher ignition temperature and at the same time has a lower burning rate than the normally flammable material.

The curves have been produced in such a way that in a fitted out experimental room of approx. 8 m, a certain amount (20 kg) of wood was ignited. As the temperature increased in the room, the wall covering in the test room was also ignited, to the extent that it contained flammable components. Depending on the type of cladding and conditions during the fire, the temperature was increased as a result of the amount of heat that was released.

In figure 8, the distribution of the compressive strengths is shown

which ensures a very high wear and impact resistance.

Figure 9 shows the pure tensile strength which leads to corresponding bending tensile strengths of 120 - 180 kp/cm. In cases where even higher flexural tensile strengths are needed, another design of the plate described below will lead to the desired result. Figure 10 shows the construction of such a plate. The outer fine layers 1 and 5 take over the same protective function as for the plates in figure 1. Then follow layers 2 and 4. These only contain coarse material and give the outer zones an increased tensile strength. The central fine condition 3 ensures a very good

thrust transmission and ensures high transverse tensile strengths. This design of the board enables a saving in the material consumption of 15 - 20% wood and cement, or a corresponding increase in the strength properties. -

The distribution of the tensile strengths is shown in Figure 14.

The material distribution in a plate with 5 layers is shown in figure 11. Figure 12 shows the wood distribution in the plate cross-section and figure 13 shows the corresponding cement distribution. A plate with 5 layers according to this design will behave even better in a fire than the normal plate with 3 layers. The layers will not be torn off together at once, but separately, and you therefore get a similar effect as with glass with several layers.

Another version of the variant with 5 layers - with a different order of the straw heads - leads to an enormous improvement in the mechanical and other properties of the plate, when after the first outer fine layer a second layer with larger shavings is arranged, then the central layer is arranged with the fine material and then again arrange a layer of coarse shavings and finally the last outer fine layer. This, from a technological point of view, the best board is distinguished by the following properties: - fine outer layer with a smooth, climate-resistant and fire-resistant surface; the second and fourth layers of coarse shavings in the outer area greatly contribute to improving the sheet's flexural tensile strengths; the central fine layer is crucial for the improvement of the transverse tensile strengths, which are actually doubled compared to a design with three layers.

With the design in Figure 10, it is possible, after the first litter head and in front of the last litter head, to build in reinforcement rings 6 and 7> for example made of glass fibres, in the form of glass wool, plastic or metal mesh etc. and thus in even stronger degree increase the plate's bending tensile strengths.

The following points must also be emphasized: the difference between the volume weights in the outer layers and in the central layer corresponds at least to the ratio 1.3:1. The ratio fine goods:normal goods is 2:4 - 6, preferably 2:5.

For slabs with five layers, at least 70% of the normal goods will be placed in the second outermost layer, and the fine goods will be placed mainly in the central layer.

It is also possible to arrange, for example, an aluminum foil 8 on the transport device, and to arrange an aluminum foil 9 on the chip raw material and make a bond, with corresponding binders, in a press. With such a design, the amount of water required for setting the cement can be reduced to the theoretically necessary minimum, because the water cannot evaporate. Such surface-reinforced plates have the highest bending-tensile strength.

This design makes it possible to reduce the volume weights of the plates from 1250 kg/m and down to 600 kg/no in special versions.

It is also possible to add cement-' wood chip mix. fine, refractory components such as mica, perlite, etc., in order to further increase the plates' fire resistance.

It has been shown that you can reduce the quantity of cement additive water and achieve a better coverage of the chips by mixing the cement together with a proportion of the additive water, forming a cement milk and adding this to the mixer. This shortens the mixing time and the additive water is not extracted from the wood.

The board's unique, closed surface enables a sparing and yet effective painting, a coating with synthetic resin-bonded plaster and other coating materials.

With the help of the wind sifting method, which is known in and of itself, it is possible to color the outer layer with, for example, mineral finely ground color pigments.

A plate produced in this way is best made up of fine material fractions 2 - 8 mm and normal material fractions 8-20 mm, as chips under 12 mm should make up 50% of the normal material. The chip thickness must not exceed 0.8 mm, as this way above all ensures the good mineralization of the board.

Although wood is used in the front as chip or fiber material, you can of course also use another material, for example lint or similar instead of or together with wood. Portland cement is preferably used as a hydraulic binder. In principle, however, other cements, gypsum and similar binders can also be used.

Claims (12)

1. Building board of organic fibers or shavings and hydraulic binder, which board has at least three overlapping layers, at least one of which has coarser shavings and less binder than at least one other layer, characterized by the average amount of mineral salt taken up by the shavings and stored in the shavings at least make up 2 weight-$ of the atrore weight. 2. Building board according to claim 1, characterized in that there is a fractional band of 1 - 25 mm chip length. 3- Building plate according to claim 1, characterized by. at least 75% by weight of the chips are no longer than 12 mm. 4. Method for the production of a building board consisting of hydraulic binder cement, wood shavings and water, according to claim 1, characterized in that the chip mixture is divided into at least 2 fractions after the chip production, namely fines with a chip size of 2 - 8 mmdg normal goods with a chip size of 8 - 20 mm - of which at least 80$ is not larger than 12 mm - and after the mixture is sprinkled on a substrate by means of wind spreading, where during mineralization at least 2 weight-$ of mineralizing agent, calculated from absolutely dry shavings, penetrates into the shavings, and during laying at least 3 evenly overlapping each other,, with respect to the tresponse ratio, different layers occur. 5. Method according to claim 4, characterized in that the difference between the volume weights in the outer and inner layers at least corresponds to the ratio 1.3:1. '6. Method according to claim 4, characterized in that the ratio of fine goods: normal goods is at 2:4-6, preferably at 2:5- 7. Method according to claim 4, characterized in that, in the case of a plate with five layers, at least 70% of the normal material is laid out in the second outermost layers and mainly the fine material is brought into the central layer. 8. Method according to claim 4, characterized in that part of the fines is replaced with more refractory components, for example mica or perlite, and that these are brought to the surface of the plate during the sprinkling. 9. Method according to claim 6, characterized by the fact that in the case of a plate with five layers, the more fire-resistant materials are also placed in the central layer. 10. Method according to claim 4, characterized in that fire-resistant reinforcements are introduced in the manufacturing process after the first and before the last layer, for example in the form of glass fibres, glass fiber fleece or glass fiber mesh. 11. Method according to claim 4, characterized in that in the manufacturing process a reinforcement is placed on the means of transport, for example a foil of, for example, aluminum or plastic and a second reinforcement, in particular a foil, is placed on the finished raw material, and that connects the entire system in the press. 12. Method according to claim 4, characterized in that the cement is introduced into the mixer in the form of cement milk.