CA1141514A - Incombustible material - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An incombustible material containing at least one mineral substance, and including a first ingredient composed of a plurality of pieces constituted by fibers of cellulose and/or chips of wood shavings, with the pieces forming a network, a mass of thermosetting synthetic resin gluing the pieces of the first ingredient together, and particles of calcium sulfate, boric acid and an at least partially glass or ceramic forming mineral adhering to the fibers and/or chips.

Description

The present invention relates to an incombustible material produced with the use of mineral substan~e& and to a method for producing it.

Board-shaped structural elements of gypsum, asbestos and cement, those composed of gypsum being reserved for interior use, are used in construction in ever increasing quantities. One reason for this is that the presently preferred light-weight construction methods require such structural elements.

However, the prior art materials leave much to be desired regarding their physical characteristics, in that, for example, they tend to absorb an unduly large amount of water, and to swell to a considerable degree, they are difficult to process and have insufficient strength. The rigid compression bond between the component materials here determines the relatively low bending strength of the structural elements produced therefrom. On the other hand, structural elements containing such mineral components produced according to DIN (German Industrial ~tandard) 4102 are completely or almost completely incombustible.

In the desire to produce board-shaped structural elements with improved physical properties, cement-bound wood chip boards and gypsum fiber boards have been developed which for the most part fall into the category of completely or almost completely incombustible construc-tion materials.

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It is also known to construct synthetic resin bound wood chip board materials which attain extremely high physical strength values by virtue of their defined chip shape and the elastic synthetic resin bond. The water absorption and swelling of such materials can thus be influenced by the selection of certain resins and additives. With respect to the burn behavior of such wood chip materials, there already exist a series of methods to provide these materials with flame protection. Therefore, some of these wood chip materials also satisfy the requirements for incombustible construction materials according to DIN 4102.

Construction materials made of fibrous, granular or flaky mineral substances, such as asbestos, mica and vermiculite, are also known. In order to improve the bond with the synthetic resin, fine wood chips have sometimes also been added to these materials. Since the mineral raw materials themselves are incombustible, but do not actuate any flame or fire inhibiting reactions in the case of fire, only the amount of organic substances contained in these materials determines their classification as combustible or incombustible substances according to DIN
4102. It must, however, be considered, that the mineral raw materials contribute only very slightly to the physical strength of a product by their already mentioned compres-sive bond so that purely mineral building materials can beused only within limits.

It is an object of the present invention to provide incombustible materials which exhibit high strength values compared to prior art mineral building materials and which can also be processed easily.

In accordance with one feature of the invention, there is provided an incombustible material containing at least one mineral substance, said incombustible material comprising a first ingredient including a plurality of pieces 1~4~51~

comprising fibers of cellulose and/or chips of wood shavings, a mass of thermosetting synthetic resin gluing the pieces of the first ingredient together, and an at least partially glass or ceramic forming mineral adhering to said fibers and/or chips. Such a material thus consists not only of mineral, incombustible materials reinforced by organic fibers, but additionally contains flame inhibiting elements, such as boric acid and at least partially glass or ceramic forming minerals.

In the case of fire, not only will there occur the known fire inhibiting effect of the boric acid, but also, as appropriate tests have confirmed, the organic components, i.e. the cellulose fibers or wood chips, are vitrified or encased in ceramic, respectively, so that they do not contribute to the fire.

Due to the eleastic synthetic resin bond as well as the likewise elastic cellulose fibers or wood shaving chips, the material according to the invention exhibits very hlgh physical strength values which also permit the structural components made of such material to be used as load-bearing members of a structure. As further confirmed by experiments, these strength values also decrease only very slowly in case of fire since the content of boric acid or the surface vitrification or ceramic formation confines the attack of the flames on the structural elements at its surface.

The fact that structural elements according to the invention can be manufactured economically must also be emphasized.
One significant reason for this is that machines for pressing materials incorporating thermosetting synthetic resin already exist in large numbers and their operation is generally understood.

Finally, the method according to the invention for manufac-turing such an incombustible material is very simple and ! 51~

economical. It is carried out by intimately mixing fiber containing residual waste water clarification sludges having a water content of up to about 80%, by weight, and originating from paper, or cardboard, making or cellulose factories and/or wet wood shaving chips o~ a moisture content up to about 80%, by weight, with boron minerals, by adding concentrated (96~) sulfuric acid to the above materials while continuing to mix them, intro-ducing the resulting material into an evaporation line and subsequently combining this material with a resin and subjecting the resulting combinat-on to selected tempera-ture and pressure levels for causing the combined material and resin to be bonded together and to form a solid body.

Thus, in accordance with another feature of the invention there is provided a method for producing an incombustible material containing at least one mineral substance, said incombustible material comprising a first ingredient including a plurality of pieces comprising fibers of cellulose and/or chips of wood shavings; a mass of thermo-setting synthetic resin gluing the pieces of said firstingredient together, and particles of calcium sulfate, boric acid and an at least partially glass or ceramic forming mineral adhering to said fibers and/or chips, said method comprising: (l) forming a mixture containing an at least partially glass or ceramic forming mineral, said step of forming including providing a quantity of the first ingredient having a water content up to about 80 percent by weight and intimately mixing that quantity of the first ingredient with boron minerals which react with sulfuric acid to form calcium sulfate and boric acid; (2) adding thereto, while continuing the mixing, concentrated sulfuric acid; (3) subjecting the resulting mixture to evaporation;
and (4) subsequently combining the resulting product with resin and then bonding the product and resin into a solid body by applying pressure and heat to set the resin and obtain said incombustible material with the pieces of cellulose fibers and/or wood shaving chips being in the form of a network.

When fiber containing residual waste water clarification sludges are used, the fibrous portion of structural elements made of materials according to the invention is extremely inexpensive since this is a material which has no other industrial use. Concentrated sulfuric acid is likewise a waste product, and therefore is also inexpensive for use in the above-mentioned process.

The intimate mixing of the fibers contained in the residual waste water clarification sludg~s or of the wood shaving chips with the boron minerals which are subsequently converted into boric acid and calcium sulfate causes the boric acid particles as well as the gypsum particles to firmly adhere to the fibers or chips, respectively. It is assumed that this occurs in such a manner that the boric acid particles and the gypsum particles cover the surface of the fibers or chips only in a dot-shaped pattern. The same also applies for the other minerals which already adhere to these fibers from the preceding paper, or cardboard, or cellulose manufacture. This leaves sufficient free fiber surfaces or chip surfaces which are reached by the synthetic resin to produce a reliable bond between the fiber or chip network, which should be decisive for attaining the desired high physical strength values.

According to a further feature of the present invention, wood fibers and saw dust may be mixed in with the fiber-containing residual waste water clarification sludges and the wood shaving chips, thus producing not only a further increase in the strength values but also employing another otherwise useless material to great advantage.

The boron mineral preferably employed is colemanite; this mineral earthis relatively inexpensive and is quite well 114~5i~

suited for practicing the method according to the present invention. The resin employed according to the present invention is preferably a condensed synthetic resin, preferably urea and melamine resin, or isocyanate adhesive and thermoplastic synthetic resin adhesive.

Depending on the amount of materials added, it may be advisable to dry the mixture before employing the adhesive in order to obtain the desirable moisture content of between 3 and 10% by weight. Moreover, it may also be advisable to comminute the mixture in a mill, preferably an impact pulverizer, before adding the adhesive in order to break up possibly existing granules which are too large and which would be held together only by a compression bond.

The invention will be explained in detail with the aid of a few examples:

Example 1 The following quantities of material were introduced into a turbine mixer; 15.0 kg of shaving chips of pine wood of a thickness of 0.35-0.40 mm and a residual moisture content of about 5% by weight; 90 kg of residual waste water clarification sludge originating from a fine paper making factory and having a solids content of about 33% by weight and of approximately the following composition:
66% by weight cellulose, in the form of cellulose fibers;
25 18% by weight SiO3; 12% by weight A12O3; and 4% by weight CaO; and 85.0 of colemanite. These ingredients were mixed well for 4 to 5 minutes.

Thereafter, while the mixer continued to run, 49.0 kg of concentrated sulfuric acid (96%) were sprayed into the mixer during a period of 1 to 2 minutes, and the mixture was homogenized for an additional 2 minutes, resulting in a granular product. This granular product was evaporated and cooled, during a period of 10 minutes, then dried Si~

further to a residual moisture content of 3 to 5%, then transported to a gluing system of a type usually employed in the chip board industry, where it is glued with a mixture of glue containing approximately 55% solid resin so that 11 to 12% solid resin are applied with respect to the total weight of all ingredients, and are then shaped and hot pressed in a manner which is customary in the manufacture of wood chip boards.

The resulting board-shaped material has such strength values that it can be used for load-carrying, load supporting or reinforcing purposes in the construction industry and also in shipbuilding and for chassis construction. The material can be worked extremely well with conventional woodworking tools in the same manner as wood. It can be smoothed, cut, drilled, nailed, glued and veneered or otherwise coated.

It is of particular significance that this material, although it consists mainly of mineral substances, can be produced to have specific weights which lie below 1000 kg/m3.

Example 2 436 kg of shaving chips of pine wood, of a thickness of 0.35-0.40 mm and 1734 g of "fire protective fibers" formed by mixiny residual waste clarification sludge from fine papermaking with a boron mineral and concentrated (96%) sulfuric acid, and having the following composition:
28.0% by weight cellulose, in the form of cellulose fibers 34.8~ by weight ~3BO3, 13.8% by weight CaO, and 22.5% by weight SO3 are mixed in a fast running turbomixer, 260 g of a glue mixture being added simultaneously. The alue mixture has the following composition:
250 g raw glue (urea resin 60%) 16 g paraffin emulsion (50~O)~ 8 g paraffin, 8 g water) 26 g hardener solution (20%) (5.2 g ammonium chloride and 51~ .

and 20.8 g water) and 18 g water The mixture when finished for processing has a moisture content of 14.7~. In a scatterinq frame, 1050 g of this mixture are scattered to form a cake which is then pressed into a board in a heatable hydraulic press having dimen-sions of 26 x 26 cm with the addition of spacer strips 16 mm thick. The following pressures are used in the order stated, at a pressing temperature of 420 K.:
for 2 minutes - 3.15 N/mm for 4.5 minutes - 1.40 N/mm2 and for 0.5 minutes - 0.56 N/mm2.

Thus an incombustible mineral construction board of high strength is produced in a conventional wood chip board producing system; the high strength is attained by the reinforcement with wood chips and cellulose fibers or by the synthetic resin bond, respectively.

Example 3 In a turbomixer, 25 kg of shaving chips of pine wood and 20 kg of wood fibers and wood dust having a moisture content of 40% as well as 85 kg of colemanite are mixed for

2 to 3 minutes. Thereafter, 49 kg of concentrated sulfuric acid (96%) are sprayed onto the mixture for 1 to 2 minutes in the running mixer and the mixture is mixed further for approximately another 1 to 2 minutes. The mixture heats up to about 373 K. or more so that the drying process is initiated already in the mixer. The mixture is then discharged onto an evaporation line and, if necessary, is dried by the addition of more heat to 10 to 12% residual water content. This mixture is now gently ground in order to homogenize it and can then, if necessary, be dried some more to a residual water content of 3 to 5%. Thereafter it is brought into a gluing system of a type typically employed in the chipboard industry, and is coated with synthetic ~.",;

g resin glue in an amount such that when absoluetly dry, it constitutes 9~ , by weight, of the product.

Then the resulting composition is shaped into boards or molded bodies and pressed in the conventional manner under pressure and heat into the desired final form.

When this method is used, the resulting boards or molded bodies have a high mechanical strength and excellent, long-lasting fire protection. With such a board material, final products can be manufactured which, according to DIN 4102, can be grouped in the category of incombustible building materials.

Of course, instead of board-shaped structural elements, it is always possible to manufacture molded bodies of the materials defined in the Examples. These molded bodies, as well as the board-shaped structural elements, can also be laminated in a known manner already during pressing.

It will be understood that the above description of the present invention is susceptible to various modifications, change~ and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

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Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Incombustible material containing at least one mineral substance, said incombustible material comprising a first ingredient including a plurality of pieces comprising fibers of cellulose and/or chips of wood shavings, a mass of thermosetting synthetic resin gluing the pieces of the first ingredient together, and an at least partially glass or ceramic forming mineral adhering to said fibers and/or chips.

2. Method for producing an incombustible material containing at least one mineral substance, said incombust-ible material comprising a first ingredient including a plurality of pieces comprising fibers of cellulose and/or chips of wood shavings; a mass of thermosetting synthetic resin gluing the pieces of said first ingredient together;
and particles of calcium sulfate, boric acid and an at least partially glass or ceramic forming mineral adhering to said fibers and/or chips, said method comprising: (1) forming a mixture containing an at least partially glass or ceramic forming mineral, said step of forming including providing a quantity of the first ingredient having a water content up to about 80 percent by weight and intimately mixing that quantity of the first ingredient with boron minerals which react with sulfuric acid to form calcium sulfate and boric acid; (2) adding thereto, while continuing the mixing, concentrated sulfuric acid; (3) subjecting the resulting mixture to evaporation; and (4) subsequently combining the resulting product with resin and then bonding the product and resin into a solid body by applying pressure and heat to set the resin and obtain said incombustible material with the pieces of cellulose fibers and/or wood shaving chips being in the form of a network.

3. Method as defined in claim 2 wherein said quantity of the first ingredient is a fiber-containing residual waste water clarification sludge originating from paper or cellulose manufacture.

4. Method as defined in claim 2 or 3 wherein the first ingredient includes wood shaving chips.

5. Method as defined in claim 2 further comprising adding wood fibers and sawdust to the first ingredient.

6. Method as defined in claim 5 wherein the wood fibers and the sawdust are moistened before being added.

7. Method as defined in claim 2 wherein the boron mineral is colemanite which has a boron content greater than 42 percent by weight.

8. Method as defined in claim 3 wherein the resin is a synthetic resin glue which is hardenable by continuation of a polycondensation reaction.

9. Method as defined in claim 2 wherein the resin is an isocyanate adhesive.

10. Method as defined in claim 2 wherein the resin is a thermoplastic synthetic resin adhesive.

11. Method as defined in claim 2 further comprising drying the resulting mixture before said step of combining the resulting product with a resin.

12. Method as defined in claim 2 further comprising comminuting the resulting mixture in a mill before said step of combining the resulting product with a resin.

13. Method as defined in claim 2 wherein the sulfuric acid has a concentration of 96%.

14. Method as defined in claim 3 wherein said sludge additionally contains said at least partially glass or ceramic forming mineral.

15. Method as defined in claim 2, wherein said quantity of the first ingredient contains from about 40 water up to about 80% water.