NO793920L - FIBER MATERIALS AND PROCEDURES FOR PRODUCING THEREOF - Google Patents

Description

Fiber material and method for its production.

The present invention relates to a method for treating fibers.

Application no. 2451/77 describes a method for impregnating cellulose fibers as well as areas of application for the fibers thus treated, in particular the use of the fibers as a reinforcing fiber element in composite materials based on organic or inorganic binders or on a combination of organic and inorganic binders.

A class of the treating or impregnating agents, there

is mentioned in the above-mentioned patent application, has been shown to have particularly valuable properties, since by processing these not only cellulose fibers, but also other fiber materials, unexpected and highly desirable property improvements can be imparted. The fibers in question, which by treatment with metal oxidacylates can be modified in the desired way with

view of their properties, are cellulose fibers of any kind, animal fibers and synthetic fibers of both inorganic and organic origin, including metal fibers.

The fibers in question can be available as discrete fibers or

such as fiber bundles, or there may be "coarser" materials such as wooden fleece or wooden wool.

As main groups of fiber materials, which, according to the invention, can be advantageously treated with metal oxide acylates, the following can be mentioned:

1) Cellulose-based materials:

Chopped wood such as wood wool, wood chips, planing shavings;

cellulose fibers from the paper industry, including e.g.

mechanical pulp

semi-chemical wood pulp

all-chemical wood pulp and

other cellulose pulps of those types,

which is mentioned in the above-mentioned Danish patent

application No. 2451/77;

chemical cellulose fibers (rayon);

recycled material, e.g. newsprint, cardboard and cardboard;

plant fibres, e.g. flax, bast, coconut fibres, sisal.

2) Animal fibres, e.g. boar hair, camel hair, wool and pig bristles. 3) Synthetic organic fibres, e.g. fibers of polyamide, polyester, polyvinyl chloride. 4) Synthetic inorganic fibers (glass wool, slag wool, rock wool, kaolin wool, glass monofilaments and fibers of e.g. iron, steel, brass and aluminium).

The effect achieved by treating the fibers in question with metal oxide acylates is believed to derive primarily from the chemical reaction between reactive groups on the fiber surfaces and the metal oxide acylates, secondarily from the metal acylate groups fixed on the fiber surface by the reaction.

The effect achieved per cellulose fibre, is particularly interesting. The effect can be described as a stabilization of the cellulose fiber against the influence of the surrounding environment on a number of fiber properties. This stabilization includes a number of properties and, depending on the specific choice of metal oxide acylate, is expressed in a blocking of water absorption, an increase in alkali resistance, an increase in stiffness, thermal stability and corrosion resistance and a reduction in flammability and the achievement of antistatic properties. In both cellulose fibers and synthetic fibers, treatment with metal oxidacylates results in a significant improvement in the fibers' ability to disperse in water or solvents, as well as a significantly increased coupling effect for both organic and inorganic binders, which is of decisive importance when the fibers are used in composite materials.

One of the most important applications for a number of the above-mentioned fibers in modified form is the composite area, where the modified fibers can replace usually used mineral fibers such as asbestos. Cellulose fibres, which have been treated with metal oxide acylates, can be used in composite materials as a replacement for not only asbestos, but also glass wool, mineral fibers of the rockwool type, slag gold, kaolin wool, etc., but they can also be advantageously used in composite materials, which already include cellulose-based materials, e.g. paper and cardboard, thereby adding new and improved properties to these materials.

Mineral fibres, which have been treated with the metal oxide acylates, on the other hand, also exhibit improved properties when incorporated into composite materials, as it has been shown,

that their ability to be defibrated and uniformly distributed in the finished composite material is dramatically increased by the treatment with the metal oxide acylates.

In the case of cellulose fibres, which have been treated with suitable metal oxidacylates, a blocking or hindrance in the fibre's reaction to water is found to be one of the most significant improvements. Cellulose fibers are in themselves hygroscopic, and when water is absorbed there is primarily an expansion in volume due to swelling, a condition which will lead to unfavorable internal material stresses in a composite material. When the swelling tendency during treatment with a metal oxide acylate is reduced or completely removed, composite materials containing such fibers achieve correspondingly improved material properties.

As cellulose fibers modified with metal oxide acylates appear as discrete fibres, which do not tend to pack together, the treated fibers themselves can also be used immediately, e.g. as insulating material in cavities or as filling in pillows, bedding and the like.

Metal oxidacylates are, as mentioned in application no. 2451/77, a class of compounds, which were invented by Dr. Jacobus Rinse, and which e.g. is described in Belgian Patent No. 555,969, Dutch Patent No. 104,261, United States Patent Nos. 3,087,949, 3,243,447, 3,177,238, 3,518,287, 3,625,934, 3,546,262, 3,634,674 and 3,673,229 , Belgian Patent No. 735,548 and British Patent Nos. 1,230,412 and 1,274,718. The metal oxide acylates comprise a large group of substances, as both the metal and the acylate group can be varied within a large area. The general composition of the metal oxide acylates is assumed to be

divalent metal (R-Me-O-Me-R) linear compounds trivalent metal (O^-Me^-R^)^planar compounds tetravalent metal (Og-Me^-R^)ztetrahedron-shaped compounds!

where Me denotes a metal atom, and R denotes an acylate group,

which is an organic acid residue with at least 12" carbon atoms, andx,yogz=3-7 indicates a presumed molecular size in solution. It should be noted that metal oxide acylates can also be produced, where each molecule contains two or more different metals with possibly different valence,

and such types of compounds are also described in the above-mentioned patents.

The metal oxides tend to react with OH groups and other reactive groups, which exist as free groups on the fiber surfaces. The reaction rate is supposed to decrease with increasing complexity in the molecular structure, so that the metal oxide acylates of tetravalent metals require higher temperatures or longer time to achieve the reaction.

When choosing the metal oxide acylate to be used according to the invention, account must be taken of the desired effects in the end product and the effects that the treatment with the metal oxide acylate entails for the process technical properties of the fibres. This relationship can be illustrated by the treatment of cellulose fibres, since by appropriate choice of the combination of metal and acylate residue in the metal oxide acylate, in addition to the production of cellulose fibres, which are easily dispersible and have good coupling ability to binders, a number of additional properties can be added. Thus, e.g. fire protection is achieved by using aluminum or iron oxide phthalates:. or metal oxidacylates, where the metal is antimony, Zn- and Cu-oxidacylates impart corrosion resistance, Mg- and Fe-containing oxidacylates will usually increase the antistatic properties of the fibers, and titanium oxide phthalate will increase the stiffness of the fibers, while when using styrene-modified aliphatic acids in acylate - the rest can be achieved by improving the alkali resistance of the fibres.

As the various metal oxide acylates are fully compatible with each other, combined effects can be achieved with the correct composition of the metal oxide acylate treatment agent.

In connection with the processing of e.g. cellulose fibers and

other fibres, where an increase in the water-repellent properties is important, it is important that metal oxide acylates containing titanium exhibit a significantly greater effect with respect to hydrophobisation than other metal oxide acylates and there-

for can be used in significantly smaller concentrations and thus will enable the addition of other metal oxide acylates to achieve combination effects.

As examples of desired properties, it can be mentioned that when the final product, which is to be produced with the treated fiber,

is a composite material for electrical insulation, a minimization of the fibers' water absorption is desired, while there would be an advantage with a moderate water absorption, when the fibers are to be used in connection with inorganic binders such as e.g. cement.or gypsum.

A possible explanation for the rot resistance-improving effect that the metal oxidacylates impart to organic fibres, including cellulose fibres, may be that the free alcohol groups present on the surface of the native cellulose fiber play a significant role in the initiation of both the bacterial and the fungicidal degradation mechanisms, and that such free alcohol groups are blocked by treating the fibers with a metal oxide acylate.

According to the invention, it is of particular importance that it has been shown that a pre-treatment of the fibers with other types of wood impregnation or a treatment of the fibers with other types of wood impregnation together with the treatment with metal oxide acylates does not seem to affect the effect of the metal oxide acylate treatment. It has thus proved possible to combine a treatment with e.g. paraffin with a treatment with e.g. aluminum oxide stearate, these two treatments being applied from the same solution. It will thus also be possible to combine a treatment with metal oxide acylate with the simultaneous application of a polymer, e.g. a polyolefin, applied from the same solution. Chlorinated paraffins and other wax-type materials can also be combined with the metal oxide acylates and applied to fibers from the same solution.•

It has also been shown that e.g. cellulose fibers can be pre-treated with inorganic compounds, e.g. inorganic wood preservatives, especially the so-called "CZC"- "CCZC"-

and "CCA" types, and then treated with metal oxidacylate with good results, although in these cases provision must be made for an intermediate removal of water, if this has been used during the impregnation with an inorganic preservative. An appropriate way to remove the water is azeotropic distillation with e.g. xylene.

It has been shown that the amount of metal oxidacylate, which must usually be used to achieve the desired effect, is normally in the range from 0.5 to 8 weight percent metal oxidacylate, calculated on the weight of the fiber, since in many cases a sufficient effect is achieved by a addition between 1 and 4 percent by weight, calculated on the fiber.

In principle, the treatment of fiber materials with metal oxide acylates consists in a reaction with the metal oxide acylate on active groups sitting on the fiber surface, and therefore it is usually aimed to treat discrete fibers or fiber bundles instead of treating continuous fiber materials such as e.g. sheets, webs, etc. Synthetic organic and inorganic fibers as well as animal fibers will normally be in the desired discrete form from the manufacturer, but this is not always the case with cellulose fibers. The cellulose fibers can e.g. available as compact masses, such as raw cardboard from wood cellulose manufacturing or recycled cardboard and paper or semi-compact masses such as so-called "flash-dry" fiber from wood cellulose production or as cloths.

In such cases, where the starting material is found in such a continuous or semi-continuous form, the starting material must be subjected to a defibration process. Such a defibration process can be carried out according to the known methods, i.e. either a dry fibration, where the starting material is converted into loose fibers by beating in a flail mill or hammer mill, or a wet defibration, where a suspension of fibers in water is achieved by the combined effect of mechanical influence (stirring) and cellulose fibers' reduced cohesion in an aqueous environment. After wet defibration, the resulting suspension can be concentrated by filtering or centrifuging the main amount of water, after which the remaining part of the water can be removed by azeotropic distillation with e.g. a hydrocarbon such as toluene or xylene. In this way, the fibers are obtained

in a slurry in an organic medium, where the treatment with a metal oxidacylate can be carried out. The use of these hydrocarbons in the distillation process has the further advantage that they are immiscible with water and can thus be recovered without special precautions.

When the defibration process is carried out as dry fiberization, the dry fiberization can immediately be combined with a treatment with a metal oxidacylate, as the heat generated by the mechanical processing can serve partly to dry out the cellulose fibers to the desired degree and partly to keep the temperature at a level where the reaction between the fiber surface and the metal oxidacylate proceeds quickly, at the same time that the elevated temperature contributes to evaporation of the solvent in which the metal oxidacylate is applied. When e.g. a cellulose material is dry fibred, metal oxide acylate can also be applied immediately before the dry fiberisation, as the immediately subsequent mechanical processing and temperature increase means that the fibers will achieve the required dryness and the temperature required for the reaction with the metal oxide acylate.

The temperatures, which must be aimed at achieving a reaction between the fibers and the metal oxidacylate, will depend on the identity of the metal oxidacylate. E.g. aluminum oxide stearate reacts reasonably quickly already at temperatures between 20 and 40°C, while there e.g. with oxidacylates of titanium must be aimed for

a higher reaction temperature of the order of 40 - 80°C.

In principle, work can be done at an arbitrarily higher temperature up to approx. 200°C, as the metal oxide acylates withstand these temperatures excellently, and it will therefore often be the temperature resistance of the fibers that is decisive for the temperature at which the treatment should take place.

In addition to an application, where the fibers are dipped in or moistened with a solution of the metal oxide acylates, the metal oxide acylates can e.g. is applied by spraying, while the fibers are in an airborne state immediately after a dry defibration.

During the treatment, the amount of solution and its concentration are adjusted according to the desired degree of reaction, i.e. the amount of metal oxide acylate that is absorbed onto the fiber. The solvent is expediently a hydrocarbon or a chlorinated hydrocarbon, which for application in the liquid phase expediently has a boiling point which is higher than the reaction temperature at which the coupling process is allowed to proceed. This avoids an irregular deposition of the metal oxide acylate caused by too rapid evaporation of the solvent. On the other hand, for certain purposes it may be desirable to apply the metal oxide acylate in a solvent, which evaporates very quickly, e.g. freon; thus, as described in application no. 2451/77. When the reaction between the fibers and metaloxidacyla-

has been allowed to proceed, when work has been carried out in a solvent with a significantly higher boiling point than the reaction temperature, a filtration or centrifugation of the solvent and an evaporation of the solvent remaining on the fibers are carried out, so that the fibers are essentially free of the solvent.

It is assumed to be of significant importance for the successful reaction between the various fiber types and metal oxide acylates that the fibers are dry during treatment, as metal oxide acylates exhibit very high reactivity with water during the formation of soaps and in such circumstances would not be part of the desired chemical reaction with reactive groups on the fiber surfaces. It has been found that a suitable dryness has been achieved when the fiber materials have been dried to constant weight at moderate temperatures, e.g. 40 - 60°C.

The fibers treated with metal oxydacylate and possibly other treatment agents can then be incorporated in the usual way into composite materials with inorganic or organic binders, and it turns out in this process that they are defibrated far more easily than corresponding fibers that have not been treated with metal oxidacylate. The composite materials in question may be of the same type as the materials described in Danish patent application no. 2451/77. In such composite materials, the metal oxidacylate-treated fibers appear to be distributed in the ideal uniform manner, even in large concentrations, in contrast to the non-uniform distribution, often with lumps of non-fibrous material, which is often characteristic of the same materials, when these are not treated with metal oxidacylate.

The production of composite materials using

fibers, which are produced in accordance with the principles of the present invention, are carried out in any known way for the production of such composite materials. When e.g. the composite material is produced by wet defibration of the metal oxide-treated fibers and combination with an inorganic binder, it has proven appropriate to carry out a flocculation of the fibers together with the inorganic binder using a flocculating agent, e.g. a cationic flocculant such as Prodefloc Cl, which is a polyacrylamide product with associated quaternary ammonium groups. It has been shown that with the treated fibers a perfect "precipitation" of e.g. cement on the fiber surface and a complete retention during the subsequent dewatering. The fibers treated according to the invention can also be used as a substitute for mineral fibers in the composite materials described in Danish patent application no.

5436/76 and applications in other countries, are claiming priority from Danish patent application no. 5436/76.

It is clear that when treating the fiber material with the metal oxide acylate, any suitable impregnation method can be used, which is mentioned in Danish patent application no. 2451/77, including also pressure impregnation and pressure/vacuum impregnation, and e.g. a dry fibering process can be elegantly combined with a pressure/vacuum impregnation by suitable design of a closed apparatus.

The invention is explained in more detail in the examples below.

Example 1.

Treatment of cellulose fiber in the form of pulp fibers in sheets.

200 g of sulphate cellulose (dried to constant weight at 60°C) is broken into smaller pieces, which are suspended in a solution of 11.43 g of a 30% mineral turpentine containing aluminum oxide stearate product (Moaco C-14-70) in 2 liters of mineral turpentine, corresponding to an amount of aluminum oxide stearate of 4% by weight in relation to the amount of cellulose. The slurry is kept at 40°C with stirring for 1 hour.

The liquid phase is filtered off, and the treated cellulose is dried

for 4 hours at 100°C.

Paper sheets are produced on the basis of the treated cellulose

(250 g/m 2 ) by dispersing the cellulose in water in a blender and forming sheets on a laboratory sheet former.

The resulting sheets are loose - without any cohesive strength - and water-repellent, and they only swell slightly when immersed in a 2N NaOH solution. In contrast, the sheets of the starting material are normally continuous and strongly absorbent, and they swell to approx. the double thickness in 2N NaOH solution.

Example 2.

Production of fiber cement board.

Cellulose fibers produced as described in example 1 were used as a reinforcing element in fiber cement boards.

Sheets with a thickness of 8 mm were produced with a content of

6% cellulose fibers and 94% rapid cement as follows:

24 q of the cellulose fibers treated in the manner described in example 1 are defibrated in 2 liters of water in a blender, after which 376 g are rapidly mixed in, and the mixture is diluted to 10 litres. By adding 50 ml of a "1/4%" solution of a flocculant (Prodefloe C 1 , .. which is a strong cationic flocculant based on a high molecular weight polyacrylamide with associated quaternary ammonium groups) the cement particles are precipitated on the cellulose fibers, after which the thus flocculated suspension is formed into sheets on a laboratory sheet former. The sheets with a thickness of 8 mm were built partly in one layer and partly in two layers, four layers and eight layers respectively, as the separated materials were provided by combining the layers, and while where each time material was produced in the laboratory sheet former of approximately twice the thickness of the desired final thickness. The drained water was completely clear, and there was thus complete retention of the cement.

The sheets are pressed to a thickness of 8.5 mm, whereby excess water is removed. The boards are then cured for 1 day at room temperature, after which they are dried for 1 day at 80°C.

During curing, the sheets do not change thickness.

The resulting sheets are water-resistant and sewable and, under microscopy, show a particularly uniform fiber distribution.

Example 3.

Treatment of dry-fibred sulphate cellulose fibers with titanium oxide acylate. 50 g of sulphate cellulose fibres, which were dry-fibrated in a hammer mill and (after intermediate storage) dried to constant weight at 60°C, are treated with 400 ml of a solution in 50% mineral turpentine and 50% extraction benzine containing the for the desired treatment corresponding calculated amount of titanium oxide acylate (Moaco D-4 2-00, where the acylate is a styrene-reacted conjugated fatty acid), and paraffin with a melting point of 55 - 60°C, as the calculations take into account the fact that the fibers absorb 8 g of solvent per . grams of fiber.

After storing the moistened fibers at room temperature i

2 hours, after which reaction between the titanium oxide acylate and the fibers and drying of the fibers is carried out by keeping the fibers at 100°C for 12 hours.

The resulting fibers are loose and cottony. Paper sheets are produced from the fibers in a laboratory sheet former. The amounts of treatment agent applied and the test results are shown in the table below:

The materials produced in experiments 1 - 4 are felt-like, without strength, strongly water-freezing and only moderately swelling when immersed in 2N sodium hydroxide solution. The materials produced in experiments 5-6 show almost normal strength, moderate water repellency and moderate swelling.

Example 4.

Production of treated cellulose fibers by wet defibration and azeotropic distillation.

20 g of sulphate cellulose fibers are defibrated in 2 liters of water in a blender, after which excess water is filtered off. The filter cake, which weighs 170 g (water content 150 g), is transferred to a distillation flask, and 500 ml of xylene is added there. It is distilled there until the distillate is pure xylene - the condensation point in the vapor phase rises above 100°C. 1.4 g of Moaco C-14-70 (corresponding to 1 g of aluminum oxide stearate) is added to the slurry of cellulose fibers in xylene, which reacts spontaneously with the fibers at this temperature.

Excess xylene is removed by filtration, and the treated cellulose fibers are dried.

Paper sheets produced from the treated cellulose fibers in the same manner as described in example 1 exhibit loose and disjointed structure, water repellency and only negligible swelling in 2N NaOH solution.

Example 5.

Production of a fiber cement board from treated wood chips.

500 wood chips (of spruce/pine, starting material for the production of wood cellulose) are treated with 200 ml of a solution of 14 g of Moaco C-14-70 (content of aluminum oxide stearate 10 g)

in mineral spirits in a kneading type mixer for 10 minutes. In this way, the liquid phase is completely taken up by the wood chips. The wood chips are then dried for 6 hours at 80°C in a heating cabinet, whereby the aluminum oxide stearate reacts with the cellulose.

490 g of the thus dried wood chips are mixed with 210 g of rapid cement in a mixing machine, first dry, then with the addition of 300 ml of water. The resulting semi-dry paste is distributed in a mold and compressed to a thickness of 15 mm. The cement is cured for 10 days at room temperature and 100% relative humidity. The resulting sheet has a dense structure and a smooth surface, and it is water-resistant and seam-proof.

Example 6.

Treatment of glass wool and stone wool with aluminum oxide stearate

and production of a fiber cement board with the thus treated fibers.

200 g of white glass wool is dried to a constant weight at 80°C, after which the glass wool is moistened with a solution of 2 g of aluminum oxide stearate (2.8 g of Moaco-C-14-70) in 1.6 liters of mineral turpentine. The moistened fibers are left for 2 days at 30°C, after which they are dried at 60°C.

The impregnated glass fibers have a completely different character than the original glass fibers, in that they appear "cotton-like" and much softer, just as they do not have the normal stinging character when touched, which the original glass fibers have.

A fiber cement board is then produced with a content of

12% of the thus treated glass fibers and 88% superrapid cement.

48 g of the treated glass fibers are defibrated in 2 liters of water in a blender. The defibration is perfect, and there are no clumps of fibres, which appear when trying to defibrate the corresponding untreated glass fibres. Then 352 g of cement is mixed in, and the slurry is diluted to 10 litres. There is flocculation by adding 50 ml of a 1/4 solution of Prodefloc C1, after which a plate is formed by filtering off the water on

a laboratory sheet former. The run-off water is completely clear, which shows that the retention is complete. The filtration is carried out on a 40 mesh wire cloth. The filter cake is compressed to 8.5 mm, whereby excess water is also removed. The board is cured after 7 days of storage at room temperature and 100% relative humidity.

The manufactured boards show low porosity and, by microscopy, a particularly uniform distribution of the fibers in the cement matrix.

of 200 g Rockwool® batts, one commercial quality, which has been conventionally treated with oil and phenolic resin. However, no drying treatment of the Rockwool fibers was carried out before the impregnation with aluminum oxide stearate.

In the above examples, where cement has been used, each of the examples has been carried out with a Blaine number of approx. 2800, approx. 3200, approx. 3600 and approx. 4300. At the low Blaine numbers, significantly faster dewatering time is achieved in the laboratory sheet former than at the high Blaine numbers.

Example 7.

Treatment of cellulose fibers combined with defibration in a hammer mill.

For the treatment, a set-up consisting of a hammer mill mounted on a feeding device with an adjustable feed rate calculated for the supply of cellulose pulp in web form is used, with an application device for the treatment medium being placed immediately in front of the feeding device. The application device here is an "Air-Less" flat spray nozzle, mounted at such a distance from the pulp web, that the fan-shaped jet just moistens the web.

The supply of treatment medium is controlled by setting the dosage amount from the nozzle as well as the pulp supply speed.

Using the above setup, two types of modified cellulose fibers are produced: 1. 2500 g of sulphate cellulose is added to 5% aluminum oxide stearate by spraying a 50% solution of this in a solution of equal parts mineral turpentine and petroleum.

Before the treatment, the cellulose pulp is dried to a constant weight at 50 C for 18 hours. After the treatment, the resulting fibers are dried for 12 hours at 90°C in a heating cabinet with air renewal to remove solvent residues. 2. 2500 g of sulphate cellulose is added to a mixture of 4% aluminum oxide stearate and 4% paraffin oil. The addition is made by spraying a mixture of 1.67 parts by weight of aluminum oxide stearate in 6% solution in mineral turpentine and 1 part by weight of paraffin oil, adding 10% by weight of this mixture to the pulp.

In this case too, the fibers were dried as indicated above before and after defibration.

The addition of the treatment chemicals is a significant advantage in carrying out the defibration process. This advantage was particularly evident through the fact that the treated fibers compared to untreated ones had a significantly lower content of cellulose dust, a ratio that is immediately noticeable when handling the fibers.

Example 8.

Examination of the effect of the treatment of cellulose fibers described in example 7.

The immediate effect of the treatment of the cellulose fibers is

a reduction in the cellulose fibers' reaction to water.

This is proven in the following way:

Using the generally known technique for producing paper sheets in laboratory sheet formers, paper samples with a sheet weight of 250 g/m 2 are produced, partly from untreated fibres, partly from a mixture of 75% treated fibers and 25% untreated fibres, with an addition of untreated fibers are necessary to obtain a sheet of paper with the necessary cohesion to carry out measurements.

The measurements used are determination of the shrinkage of the paper sheet, i.e. its change in length during the transition from a completely moistened to a dry state.

The results of this study showed the following:

It will be seen that the shrinkage of the paper is significantly reduced as a result of the treatments; the measured shrinkage must essentially be attributed to the presence of the untreated fibers.

Example 9.

Investigation of treated cellulose fibers as fiber reinforcement in a cement matrix.

The modified cellulose fibers described in example 7 are used in these studies.

For the fibre-cement studies, the following composition and production method are used:

The amount used corresponds to one plate, dimension 200 x 80 x 8 mm<3>

Procedure:

A "Braun" blender with 3 speeds is used as a mixing machine. Cement and water are mixed, after which fiber is added over time

1 min., and continue to mix for 2 minutes.

Then add flocculant, 10 ml of a 0.2% solution of Prodeflock C 1, and mix for a further 0.5 minutes.

The mixture is transferred to a filter box with the length/width dimension of the intended plate. After filtering off the water, the filter cake is transferred to a mold and compressed to the final thickness while additional water is released. It was noted that the filtered water was clear, without cement particles.

The pressed plates are cured at room temperature and 100% rel. humidity for 2 weeks, after which the plates were air-dried.

The produced plates were examined for bending strength in as well

the air-dry state as in the wet state, as the wet state was achieved by immersing air-dry plates in water for 2 days.

The result of the test is the following:

It will be seen that the treatment of cellulose fiber has an effect, which, as expected, is particularly evident in the achievement of higher bending strengths in sheets in a wet state.

Claims (10)

1. Fibers in discrete form or in the form of fiber bundles or chips or shavings, characterized in that they have been treated with a metal oxide acylate in essentially dry form. 2. Fibers according to claim 1, characterized in that they are treated with an aluminum oxide acylate or a titanium oxide acylate. 3. FibreJ according to claim 1 or 2, characterized by the fact that they are inorganic fibres. 4. Fibers according to claim 3, characterized by the fact that they are synthetic mineral wool fibres. 5. Fibers according to claim 1 or 2, characterized by the fact that they are dry-fibered cellulose fibers. 6. Fibers according to any one of the preceding claims, characterized in that they are cellulose fibers which have been treated with a combination of a water vapor resistant layer such as a wax, a paraffin or a polymer, and a metal oxide acylate. 7. Process for the production of metal oxidacylate-treated fibres, characterized in that fibers in essentially dry form are brought into contact with a metal oxide acylate, and the contact is maintained for such a period of time and under such temperature conditions that a reaction takes place between the metal oxide acylate and the fibres. 8. Method according to claim 7, characterized by the fact that the fibers are cellulose fibres, which are treated with metal oxide acylate at the same time as they are dry fibred. 9. Method according to claim 7, characterized in that a continuous cellulose fiber material in essentially dry form is treated with a metal oxidacylate, and that it is defibrated immediately afterwards or at a later time. 10. Use of fibers according to any one of claims 1 - 6 in composite materials.