FI64568B - ELDFAST BAUXITBLANDNINGSSKIVA - Google Patents

Description

I- rRl rt1. ANNOUNCEMENT. c, o ® * UTLÄGG NI NGSSKRI FT 64568 JS® 1451 iic-a ------------ '- ^ (51) Kv.lk.-jlin.CI.3 C 04 B 43/16 FINLAND - FINLAND (21) ****** «« "- Pw-n ^ knlnj 762 939 (22) Htkemlipllvi - AnsOknlngidag ^ q ^

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Patent and registration holder * (44) Date of filing and registration

Patent · och registerstyrelaen Ansakin utiagd och uil.skriften publicerad 31.08.83 (32) (33) (31) Claim claimed privilege — Begird prloritet 10.11.75 USA (US) 630615 (71) fiucatex S.A. Industry and Commerce, Av. Francisco Matarazzo, 58U, £ section Paulo, Brazil-Brazil (BR) (7?) James R. Roberts, Palatine, Illinois, USA (7I) Leitzinger Oy (5I *) Refractory bauxite alloy sheet - Eldfast bauxitblandningsskiva refractory bauxite-containing alloy sheet. It is particularly directed to a refractory glucocellulosic sheet containing bauxite as the main component.

In a widely used commercial process for making an alloy sheet, a slurry of fibrous cellulosic pulp is run onto a flat wire machine wire and a vacuum is created in the wet web.

This web is rolled to the desired thickness and oven dried.

The refractory alloy sheet is made in the same way using a considerable amount of the mineral ingredient in the slurry. Thus, the mineral ingredients used include gypsum, perlite, mineral fibers, glass fibers and vermiculite.

Recently, it has also been proposed to use aluminum hydrate (aluminum hydroxide) and bauxite (hydrated 2,64568 alumina) as a mineral component in such sheets. Typical alloy sheets containing these materials are disclosed in U.S. Patents 570,361, 1,907,711 and 2,108,761.

However, previous researchers have used only Aluminum Hydrate or Hydrated Alumina due to their non-combustible nature. No particular value has been assigned to the use of bauxite (hydrated alumina) lignocellulosic alloy particles as a refractory component, characterized by a physical state and chemical composition such that, although durable under normal conditions of manufacture, storage and use, is sufficient to be a relevant and often determining factor in reducing the flammability properties of the board containing it, thereby improving the fire resistance of the board.

As used herein, the term "bauxite" means alumina dihydrate of the following formula: A1203 * 2H20

The theoretical amount of bauxite hydrate water is 26% by weight. In addition, it is characterized by its durability at temperatures below about 200 ° C, i.e. at the temperatures prevailing during the manufacture, storage and use of the alloy sheets. However, under fire conditions, it is characterized by a considerable total release of hydrate water, which is converted to water vapor when the hauxite is heated to a temperature above about 200 ° C.

This water vapor, being a non-combustible gas, slows down the combustion of the alloy plate. Also, the absorption of heat from the fire as the hydrate water turns into steam further slows down the combustion of the alloy plate. As a result, alloy sheets containing bauxite have relevant and unique refractory properties that make them valuable commercial articles.

Accordingly, the main object of the present invention is to provide a refractory 64568 alloy sheet, in particular a bauxite-containing refractory sheet having a very high degree of refractory which can be easily prepared by conventional methods with inexpensive, readily available refractory components (bauxite), thus economically resistant. which are acceptable in the various tests and according to the standards required for refractory boards, which have a pleasant appearance, good surface quality and suitable qualities for machining and machining and which are not unreasonably heavy so as to cause problems during transport and use.

The above refractory bauxite alloy sheet comprises a felted dried sheet containing, as a dispersed mixture, a lignocellulosic moiety, a bauxite moiety and a binder for the bauxite and ligno-cellulosic moieties.

To be suitable for use, the bauxite component of the sheet must contain its usual amount of chemically bound hydrate water. The plate must also be characterized by considerable resistance at temperatures below about 200 ° C and an almost complete conversion of its hydrated water to the form of water vapor released at temperatures above about 200 ° C.

The mixture according to the invention is characterized in that it comprises a felted dried sheet containing as a dispersed mixture:% by weight of air-dry sheet lignocellulose particles 10 to 85 bauxite particles 65 to 20 bauxite and lignocellulose binders 5 to 25, wherein the bauxite contains at least 20% by weight chemically hydrated water, the mixture optionally further comprising vermiculite and / or clay.

4,64568

Lignocellulosic particles, which are the main constituent of the medium density alloy sheets described above, can come from a wide variety of sources. Typical sources include bagasse and trees such as eucalyptus, cotton tree, stripe, alder, douglas spruce, and pine.

When wood materials are used, they can be used as wood chips, planing chips, strips or sawdust. Whatever their source, it is first preferably reduced by defibering into 1ignocellulosic fibers and fiber bundles. This is accomplished with suitable equipment such as Bauer or Sprout-Waldron mechanical refiners. A suitable defibering system includes a standard Asplund defiberizer, in which pieces of wood are subjected to a grinding effect in a steam environment at a pressure of about 2.8 to 15.5 kp / cm 2. If desired or necessary, the fibrous product of the Asplund machine can be passed to another refiner, such as an Asplund refiner, to finally reduce the particle size, up to 10% of which remains on a 12 mesh screen, U.S. Pat. Sieve Series.

As mentioned above, the second main component of the above refractory alloy sheets is bauxite (alumina dihydrate).

This mineral is widespread in many geographical locations and is readily available as a commercially available article. It is available in a hydrated form in which it contains at least about 26% by weight of hydrated water. It is characterized by resistance to temperatures below 200 ° C and also by the ability to release hydrated water in the form of water vapor when heated to temperatures above 200 ° C. A typical sample begins to release its hydrated water at a temperature of about 250 ° C and releases all of its hydrated water at a temperature of about 450 ° C. A considerable amount of heat is required for this change and this is the factor that is important for the increase in bauxite-containing alloy sheets for fire resistance.

This behavior of bauxite (alumina hydrate) must be distinguished from that of gypsum (calcium sulphate dihydrate), which is the main constituent of gypsum board. Like bauxite, gypsum releases 64,568 of its hydrated water when heated. However, gypsum releases its hydrates at 49 ° C, while bauxite releases above 200 ° C. This leads to two serious disadvantages of gypsum board.

Unless special precautions are taken, the gypsum content of the gypsum board will release its hydrated water in the drying oven during the manufacture of the board. Thus, the plate has to be dried very slowly, which slows down the production rate and reduces the production of the mill. On the other hand, the bauxite sheet can be dried quickly at a high temperature, which increases the production speed and the production capacity of the equipment, respectively.

In use, the gypsum content of gypsum board will release its hydrate water when used in high temperature environments such as boiler rooms and other places where temperatures are very high, resulting in collapse of the board. Alloy sheets containing bauxite do not suffer from this disadvantage.

To be suitable for use in the alloy sheet just described, the bauxite must be in a state where it is compatible with the other ingredients in the sheet's raw materials. It must also be in a form in which it releases its hydrated water quickly and efficiently in the event of a fire situation. This is accomplished by providing a bauxite product having a particle size of 325 to 12 mesh to 12 to 200 mesh, U.S. Pat. Sieve Series. Screen analysis of a typical bauxite product suitable for the present purpose shows that 0.6% remains on the 35 mesh screen, 18.62% on the 120 mesh screen, and 80.72 passes through the 120 mesh screen.

When mixed with the raw materials for the production of the board, the bauxite component must also contain at least 20% by weight of chemically bound HPV water. Given that 100% pure bauxite theoretically contains 26% hydrated water, this lower value of 20% takes into account the use of impure bauxite or bauxite that is incompletely hydrated. In practice, commercial bauxite may contain 28-32% water, probably due to the additional amount of moisture absorbed or the presence of highly hydrated mineral impurities 6. 64 5 ^ 8

A bauxite product, which is well suited for the present purpose, is commercially available at a very low cost as screening waste from the production of the bauxite mineral used in the production of alumina.

The binder for the lignocellulosic and bauxite particles used in the preparation of the refractory alloy sheets described above is broadly very highly hydrated cellulose gel, starch or a mixture of the two binders. The highly hydrated cellulose gel is very interesting because it is uniquely suitable for use in a refractory sheet containing the majority of bauxite.

The gel is an excellent binder for bauxite and lignocellulosic particles. In the manufacture of the sheet, the main function of the gel is to retain the bauxite particles in the sheet preparation slurry so that they are not wasted as water leaves the forming wire. The gel helps the bauxite particles to disperse throughout the sheet raw materials and keeps them in a uniform dispersion. The gel does not adversely affect the conditions prevailing in the oven during the drying of the sheet products.

The gel also has a very small particle size and effectively and evenly covers the fine particles of lignocellulose, bauxite and clay and securely and permanently binds these together in the finished sheet.

The gel used differs from the hydrated cellulose gels of the prior art in that it is completely hydrated to a state in which it has essentially no fibrous structure. The difference becomes clear when the gels are subjected to the standard Schopper-Riegler grinding degree determination test or the TAPPI Standard T221-OS-63 test.

According to TAPPI Standard T221-OS-63, which is used to determine the degree of grinding of the various pulps which come into question here, the pulp is formed in a Williams sheet mold into a sheet with a diameter of about 15.9 cm. The sheet formed in the mold contains 1.2 g of dry mass or gel. The flow time required to form the sheet is measured and indicates the degree of hydration of the substance.

7,64568 Using this assay, it is readily possible to distinguish the highly hydrated cellulose gel binders described above from prior grade hydrated cellulosic gel products used in the manufacture of polished parchment paper and prior art composite sheet products disclosed in Robertein U.S. Patent 3,379,608. Both of these use hydrated cellulose gels with a flow time measured according to the above-mentioned TAPPI Standard T221-OS-63 of about 300 seconds.

However, according to the invention, it has been found that it is possible to hydrate the cellulose gel to a degree much higher than that characteristic of gels used either in polished parchment paper or in the blend sheets according to the above-mentioned patent. Thus, when the TAPPI standard degree of grinding of said prior art gels, determined by a run time of about 300 seconds, run times of at least 350 seconds, suitably 900 seconds, and most preferably 900-2000 seconds are used in accordance with the present invention.

Other testing methods can be used to identify and characterize the fully hydrated cellulose gel binders described above.

One such method is to determine shrinkage by drying a hand-made sheet prepared according to the TAPPI test described above. A suitable hydrated gel will form a handmade sheet that shrinks on drying to a diameter that is at least 35% smaller than the original diameter.

In the third method, the handmade sheet is dried and a small flame is applied to its lower surface. If the cellulose is sufficiently hydrated, the flame will immediately form a bubble in the plate.

In the fourth test method, 250 ml of ground pulp slurry is dried to a solid sphere. If the gel is sufficiently hydrated for the present purposes, the ball will sink when dropped into water and then remain hard without swelling for an unlimited immersion time.

The use of the fully hydrated cellulose gel binders thus characterized in the medium density densities of the invention. / 8 64568 in alloy plates is critical for several reasons.

First, the gel acts as a very effective binder that binds the lignocellulosic fibers together in the finished product. Upon drying, the gel binder shrinks considerably, pulls the particles together and irreversibly encloses them in their reinforced state. This factor is paramount in determining the increased strength of a sheet product.

The gel also acts as a binder, which very quickly affects the thickness and density of the felted sheet when introduced into the press. This allows for a fast pressing operation, i.e. requires only a pressing time of 10 seconds to three minutes, preferably 10 seconds to 60 seconds. This in turn means considerable economy, as only one relatively expensive single-hole press is needed, which can be easily adapted to the production lines of conventional equipment.

The use of the new cellulosic binder described above provides several other important advantages. The binder gives the sheet product containing it water resistance. As will be appreciated, such products contain from 5 to 40% by weight of binder and this is so strongly hydrated that it is essentially insoluble in water. This gives the alloy product a high degree of water resistance of the binder. The gel binder is excellent in this respect over conventional fibreboard binders such as thermosetting urea formaldehyde resins.

Still further, the gel is a very effective dispersant in forming fibrous slurries from which sheets are made. According to the present invention, it breaks up the wood fiber clusters contained in the slurry into separate fibers. It also thickens the sludge so that it passes through the wire at a consistency of about 5%, with a slight tendency for the light particles in the slurry to float and for the heavy particles to settle. Still further, it is responsible for forming a highly durable slurry which is converted into a finished sheet product with a completely homogeneous cross-section.

Fourth, the gel acts as a retention agent for fine particles. This is very important during the vacuum formation of the sheet as the pulp bed flows through the wire. During this step, the fine 64568 particles in the slurry tend to leave the formed sheet due to the draining of water. As a retention agent, the gel provides a valuable retention of fine ingredients in the sheet, which saves raw materials, improves the properties of the board and reduces the waste disposal problem.

Hydrated cellulose gels suitable for the intended purpose are products in which water of hydrate is added to the cellulose molecule mainly by grinding or grinding the cellulose completely in an aqueous medium. In this case, the cellulose is changed from a fluffy, fibrous state to a gel-like state, the degree of change depending on variables such as grinding time, quality of grinding equipment, presence or absence of foreign chemicals, etc.

The cellulosic gel can be prepared from a variety of sources, for example, bleached or unbleached wood or gas pulps prepared by conventional sulfate or sulfite cooking methods. If bagasse is used as a raw material, it is best to peel it before defibering. The pulps are suitable for the production of dried pulp sheets on a large commercial scale.

In preparing the gel products described above, the cellulosic pulp is completely ground and hydrated to a high degree where the fiber structure is almost completely lost. This is accomplished by breaking up the cellulosic pulp sheets into different fibers or fiber clusters, preferably by adding the dry sheets and water to a conventional wet pulp (Hydra pulper) and wet dispersing the pulp at a consistency of 1 to 10%, preferably 6 to 8%. This takes about 30 minutes.

The resulting mass is then pumped into a storage tank and fed as an adjustable stream to a selected plate or cone type refiner. Preferably, three such refiners are arranged in series with flow restricting valves arranged downstream of the last refiner to ensure a suitable residence time in the refiner. These refiners grind the pulp and hydrate it to a high degree.

The resulting partially ground and hydrated pulp is passed to a second storage tank which feeds the same standard grade refiner as the first refiner, but which is effective to supplement hydration and pulp size reduction to values that give the pulp TAPPI standard flow times of at least 350 seconds, preferably over 900 seconds. This is accomplished by an abrasion effect that almost completely degrades the fibrous structure of the pulp, introduces water into the cellulose molecules, and hydrates the pulp completely. This additional grinding and supplementary grinding greatly improves the grades of the pulp as a binder, dispersant and retention agent when used to make the refractory alloy sheets described above.

In particular, it makes the gel an "irreversible" binder. This means that an alloy sheet made using the effectively ground gel binder described above can be exposed to boiling water for several hours, with only slight softening or loosening of the adhesive bond between the bonded fibers. If the plate is dried after it has been subjected to such a cooking experiment, it is just as strong as before cooking. This same property occurs with phenolic resins when used as binders. There is no doubt about the improved water resistance of the alloy sheets according to the invention.

In order to increase or completely replace the binding effect of the hydrated cellulose gel binder in some cases, the sheet products of the invention may include 1-20% by weight of dry solids of a starch-type binder in the form of starch or tapioca starch. Tapioca starch is most preferred. Due to the low gelation temperature of about 74 ° C, tapioca starch when used uncooked does not slowly drain out of the raw materials on the wire.

Starch is added to raw materials as an uncooked, commercially available dry powder. It develops its gluing properties as it boils as the wet-formed mat passes through the oven.

The use of tapioca and corn starch in an amount of 1-3% by weight has the advantage of a slightly increased hardness of the board. The use of starch greater than 3% has the advantage of significantly reducing the drying rate in the plate oven. A significant amount of the water content of the wet plate is chemically bound by the starch as it boils.

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In addition to the above-mentioned main components of the refractory alloy sheet described above, i.e., lignocellulosic particles, bauxite particles, and a binder, certain additives may be advantageously added.

One such additive is thermally expandable vermiculite particles which are added in an amount of 10 to 50% by weight based on the weight of the air-dry sheet. The swollen vermiculite is a relatively fluffy substance and has the function of reducing the weight of the board while maintaining a high degree of fire resistance of the board.

Vermiculite can be added in the form and manner set forth in the aforementioned pending Finnish patent application 761973.

Another additive that can be advantageously added is a suitable clay, especially those known on the market as ceramic clays. These have a common sintering property when brought to elevated temperatures. To be suitable, their sintering temperatures should be below the temperature that develops when wood or other organic materials burn, preferably below about 1093 ° C. Their particle size should not exceed 50 mesl, U.S. Pat. Sieve Series.

Suitable clays suitable for use in the alloy sheets of this invention include, broadly speaking, aqueous silicates of alumina from widespread deposits. One such is trade. ' available alumina aqueous silicate containing 57% silica, 27.9% alumina and 9.8 chemically combined water. Another suitable clay product is a commercially available alumina aqueous silicate containing 63% silica, 26% alumina and 8.4% chemically combined water.

These and other clays are used in the alloy sheets according to the invention in finely divided form and in an amount of 5 to 20% by weight based on the weight of the dry sheet.

Still other additives that may be added include sizing agents, for example, an ordinary waxy adhesive used in an amount of 0.5 to 3% by weight, such as Petrolatum or Hercules Paracol wax, to improve the water resistance of the boards. Other flame retardants, such as borax, boric acid, or glass fibers, are used in an amount of 5 to 5 to increase the toughness and impact resistance, pigments, and in some cases, additional phenolic resin binders are used in an amount suitable to provide the desired properties.

In the production of the refractory bauxite alloy sheet according to the invention, the raw materials for making the sheet are first prepared by placing a predetermined total amount of water to obtain a desired raw material consistency of 6-8% in a container equipped with a mixing device. Hydra-fed cellulose gel is then added, followed by starch, if used, clay, if used, and lignocellulosic particles. Finally, a predetermined amount of bauxite is added, after the other ingredients have been thoroughly mixed and dispersed together.

The raw material thus prepared is then run on a forming wire of a flat wire machine or other conventional sheet making apparatus equipped with press rolls for pressing a wet mass sheet to a predetermined thickness.

The web is vacuum formed and pressed on rollers to a solids content of about 30% by weight, after which it is cut into sheets and transferred to a three-zone furnace.

In the first zone of the oven, a temperature of about 315-371 ° C is maintained to cook the starch content of the mat and to develop its gluing properties. In the second and third zones, where the carpet dries considerably, the temperatures are adjusted to 232 to 288 ° C and about 204 to 260 ° C, respectively.

Drying is continued to a final moisture content of the sheet of less than about 1% by weight, preferably about 1/2% by weight. This is important because if a small excess of water is present, for example the moisture content of the board is 3% by weight, this moisture condenses in the middle of the board as a "wet line". This means that the moisture content along the neutral axis of the plate can be as high as 15 to 20%. In such a case, the sheets removed from the oven are weak and can be damaged very easily in subsequent processing operations when the sheets are moved by hand or subjected to a punch press used to punch small holes in the surface of the sheet in the manufacture of the sound insulation board.

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After forming and drying, the sheets are cooled, set aside and finished to obtain the desired product and packaged for transport.

As a result of the above, uniform sheets with a moisture content of less than 1% and a desired density have been produced. In this way, for example, insulation boards with a density of 3 of about 0.22 to 0.29 g / cm 3 can be prepared. The methods commonly used for such products can also be used to produce medium density plates with densities of about 0.6 to 0.7 g / cm and true hard plates with densities of about 0.9 to 1.2 g / cm.

The bauxite-containing refractory alloy sheets described above are illustrated in the following examples, in which parts are expressed as a percentage by weight of the dry sheet.

Example 1

To prove the effectiveness of bauxite as a refractory component of wood-alloy boards, a series of boards with densities ranging from

O

0.3 and 0.9 g / cm and having the properties of an insulating sheet, medium density sheets and really hard sheets. For the purpose of the review, one plate corresponding to a commercially available specialty plate did not contain bauxite.

The lignocellulosic component of each plate was eucalyptus wood 2 fiberized in an Asplund fiberizer at a vapor pressure of about 10.6 kp / cm fiber size, of which 20% remained on a 12 mesh screen, followed by grinding in an Asplund refiner. In the case of the control plate, the ground wood contained a binder.

The bauxite component of the sheets was mineral bauxite, which in the screening analysis 0.6% remained on the 35 mesh screen, 18.6% on the 120 mesh screen and 80.7% passed through the 120 mesh screen. It contained 28 to 32% by weight of chemically combined hydrate water. Experiments show that when heated, bauxite begins to release its hydrate water at 250 ° C and has released it completely at 450 ° C.

In each case, the raw materials for making the board were prepared by first placing the entire amount of water to achieve a raw material consistency of 4 to 5% in a tank 64568 14 equipped with a mixer 11a. Hydra-fed cellulose gel binder and starch binder were then added in that order. This prevented the bauxite from adhering to the mixer.

The raw materials thus prepared were immediately run on a forming wire of a flat wire machine, whereby it formed into a wet pulp web, which was pressed on rollers to the desired thickness, cut into sheets and oven-dried. In the case of medium and very high density sheets, the sheets were wet pressed to the desired density.

The plate samples thus prepared were then subjected to the ASTM Standard Test SSA-118-b to measure the spread of flame on the surface of the plate products. The experiment involves exposing the plate samples to an alcohol flame for two minutes and recording the carbonization area in square centimeters. The carbonization range of less than 20 cm determines the fire resistance class A of the board. The results tested for the six board samples are listed in the following table, in which the mixture values are expressed as percentages by weight.

Disc number _JL _2 3 _4 _S 6

Fibrous wood 82 33 35 28 23 48

Ground wood 15

Bauxite 50 50 50 50 30

Cellulose gel * 15 20 25 20

Tapioca starch 2 13

Paracol-wax rest 1 2 2 2 2 '2 /

Density g / cm3 0.26 0.29 0.50 0.49 0.88 0.48 ''

Thickness, mm 12.7 12.7 12.7 12.7 12.7 12.7

Fracture modulus, kp / cm2 16.9 27.1 45.7 73.8 240.4 128.5

Carbon flame range, cm2 280 61.4 73.2 42.3 28.2 75.4 * TAPPI flow time 800 seconds'

Examination of the above results shows that all the plates according to the invention, i.e. plates 2-6, belong to class A, classified on the basis of the flame carbon test, while the control plate had unsatisfactory fire resistance properties. This corresponds to a regular wood fiber separator board.

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After forming and drying, the sheets are cooled, set aside and finished to obtain the desired product and packaged for transport.

As a result of the above, uniform sheets with a moisture content of less than 1% and a desired density have been produced. In this way, for example, insulation boards with a density of 3 of about 0.22 to 0.29 g / cm 3 can be prepared. The methods commonly used for such products can also be used to produce medium density sheets with densities of about 0.6 to 0.7 g / cm and true hard sheets with densities of about 0.9 to 1.2 g / cm 3.

The bauxite-containing refractory alloy sheets described above are illustrated in the following examples, in which parts are expressed as a percentage by weight of the dry sheet.

Example 1

To prove the effectiveness of bauxite as a refractory component of wood alloy boards, a series of boards with densities between 3 0.3 and 0.9 g / cm and with insulation board properties, medium density boards and really hard boards were prepared. For the purpose of the review, one plate corresponding to a commercially available specialty plate did not contain bauxite.

The lignocellulosic component of each plate was eucalyptus wood 2 fiberized in an Asplund fiberizer at a vapor pressure of about 10.6 kp / cm fiber size, of which 20% remained on a 12 mesh screen, followed by grinding in an Asplund refiner. In the case of the control plate, the ground wood contained a binder.

The bauxite component of the sheets was mineral bauxite, with 0.6% on the 35 mesh screen, 18.6% on the 120 mesh screen, and 80.7% passed through the 120 mesh screen. It contained 28 to 32% by weight of chemically combined hydrate water. Experiments show that when heated, bauxite begins to release its hydrate water at 250 ° C and has released it completely at 450 ° C.

In each case, the raw materials for making the sheet were prepared by first placing the entire amount of water to achieve a raw material consistency of 4 to 5% in a tank equipped with a mixer 11a. Hydra-fed cellulose gel binder and starch binder were then added in that order. This prevented the bauxite from adhering to the mixer.

The raw materials thus prepared were immediately run on a forming wire of a flat wire machine, whereby it formed into a wet pulp web, which was pressed on rollers to the desired thickness, cut into sheets and oven-dried. In the case of medium and very high density sheets, the sheets were wet pressed to the desired density.

The plate samples thus prepared were then subjected to the ASTM Standard Test SSA-118-b to measure the spread of flame on the surface of the plate products. The experiment involves exposing the plate samples to an alcohol flame for two minutes and recording the carbonization area in square centimeters. The carbonization range of less than 20 cm determines the fire resistance class A of the board. The results tested for the six board samples are listed in the following table, in which the mixture values are expressed as percentages by weight.

Record number _JL _J2 3 _4 _3 6

Fibrous wood 82 33 35 28 23 48

Ground wood 15

Bauxite 50 50 50 50 30

Cellulose gel * 15 20 25 20

Tapioca starch 2 13

Paracol wax emulsion 1 2 2 2 2 '2 s

Density g / cm3 0.26 0.29 0.50 0.49 0.88 0.48 '

Thickness, mm 12.7 12.7 12.7 12.7 12.7 12.7

Fracture modulus, kp / cm2 16.9 27.1 45.7 73.8 240.4 128.5

Carbon flame range, cm2 280 61.4 73.2 42.3 28.2 75.4 * TAPPI flow time 800 seconds *

Examination of the above results shows that all the plates according to the invention, i.e. plates 2-6, belong to class A, classified on the basis of the flame carbon test, while the control plate had unsatisfactory fire resistance properties. This corresponds to a regular wood fiber separator board.

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Plate No. 2 represents an improvement in fire resistance obtained by the addition of 50% bauxite. It should be noted that this and certain other tested sheets containing 50% bauxite contain about 15% of the bauxite-derived hydrate water by the weight of the dry sheet, which hydrate water is released under fire conditions.

Plate No. 3, in which tapioca starch replaces a cellulose gel binder, proves the unique retention of the latter bauxite in the plate. As will be seen, bauxite is used in a very finely divided form which tends to leach away from the forming wire with the run-off water. This fine substance remains in the sheet thanks to the cellulose gel and thus has an increased effect on the fire resistance (plate no. 4). When the tapioca starch replaces the gel (plate No. 3), a considerable amount of bauxite is wasted so that the refractory property of the obtained plate is significantly reduced, as evidenced by the considerably increased carbon range.

Plate No. 5 contains 50% combustible material and 50% bauxite. Nevertheless, its fire resistance is excellent.

Plate No. 6 contains about 70% combustible substances. Nevertheless, it has a flame carbon range limited to what is required of a Class A plate.

Example 2

The procedure of Example 1 was otherwise repeated in the same manner except that vermiculite was included in the formulas. This significantly reduced the weight of the plate.

When the plates were tested according to Example 1, the following results were obtained.

64568 16

Disc number 1 2

Fibrous wood 10 19

Bauxite 25

Vermiculite 56 35

Cellulose gel * 20 * 12 **

Tapioca starch 4 3

Savi 10 6

Density, g / cm -1 0.30 0.34

Thickness, mm 15.9 15.9 2

Fracture modulus, kp / cm 16.9 25.0 2

Flame carbon range, cm (ASTM test SSA-118-b) 70 49

Fuel effect 14.7 2.6

Applicant's lab test No. R-5551 TAPPI flow time 350 seconds TAPPI flow time 1200 seconds

Examination of the above table shows that the vermiculite will provide a sheet with 34% combustible materials, meeting fire resistance standards in the Class A narrow range. Plate No. 2 illustrates the effect of adding 25% bauxite to the raw materials of the plate instead of a certain amount of vermiculite, with the amount of combustible substances being 34%. Both the carbon range and the impact of fuel have been significantly reduced.

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Claims (15)

17 64568 A refractory bauxite-containing alloy sheet, characterized in that it comprises a felted dried sheet comprising as a dispersed mixture: a weight percent of an air-dry sheet of lignocellulose particles 10 to 85 bauxite particles 65 to 20 bauxite and lignocellulose binder at least 5 to 25% combined hydrated water, the mixture optionally further comprising vermiculite and / or clay. Alloy sheet according to Claim 1, characterized in that it contains:% by weight of air-dry sheet lignocellulose particles 20 to 65 bauxite particles 65 to 20 bauxite and lignocellulose particles binder 5 to 25. The alloy sheet of claim 1, wherein the binder comprises a member of the group consisting of hydrated cellulose gel, starch, and mixtures thereof, wherein the hydrated cellulose gel binder is in its gel-like state, characterized in that the TAPPI flow time is at least 350 seconds. Alloy plate according to Claim 3, characterized in that the binder contains starch. Mixture sheet according to Claim 1, characterized in that it contains hydrated cellulose gel as a binder. Mixture sheet according to Claim 5, characterized in that the hydrated cellulose gel binder has a TAPPI flow time of at least 900 seconds. 18 6 4 5 6 8 Mixture sheet according to Claim 5, characterized in that the hydrated cellulose gel binder has a TAPPI flow time of 900 to 2000 seconds. Alloy board according to Claim 5, characterized in that the lignocellulosic particles are wood particles. Alloy plate according to Claim 5, characterized in that the lignocellulosic particles are bagasse particles. Alloy board according to Claim 5, characterized in that the lignocellulosic particles are wood particles with a TAPPI degree of grinding of less than 750. Alloy plate according to Claim 5, characterized in that the particle size of the bauxite particles is such that they penetrate a sieve with a mesh size of 0.044 to 1.68 mm. Alloy plate according to Claim 5, characterized in that it contains 10 to 50% by weight of vermiculite. ^ A refractory bauxite-containing composite sheet according to claim 1, characterized in that it comprises a felted dried sheet containing, as a dispersed mixture:% by weight of an air-dry sheet lignocellulose particles 20 to 65 bauxite particles 65 to 20 hydrated cellulose gel binder 5-25 cellulosic cellulose having a TAPPI degree of grinding of less than 750, a particle size of the bauxite particles such that they penetrate a screen having a mesh size of 0.044 to 1.68 mm, and a hydrated cellulose gel binder having a TAPPI flow time of 900 to 2000 seconds. A composite board according to claim 13, suitable for use as a refractory core board, characterized in that it further contains a starch binder and has the following composition: 19 64568% by weight of air-dried sheet fiberized wood fibers 35 bauxite particles 50 of hydrated cellulose gel 12 of starch 3. Alloy board according to Claim 13, particularly suitable for use as a refractory core board in wall panel panels and doors, characterized in that it contains vermiculite, clay and starch as additional components, the components of the board having essentially the following proportions:% by weight 12 starch 3 swollen vermiculite 35 clay 6. 64568 20