WO2017130147A1

WO2017130147A1 - Binding of small particles

Info

Publication number: WO2017130147A1
Application number: PCT/IB2017/050443
Authority: WO
Inventors: Michael Windsor Symons
Original assignee: Zetland Technologies Limited; Van Der Walt, Louis, Stephanus
Priority date: 2016-01-27
Filing date: 2017-01-27
Publication date: 2017-08-03
Also published as: ZA201807968B

Abstract

A method of binding small particles, which includes forming a mixture of the small particles and a first agent that is a polyvinyl alcohol, a second agent that comprises one or more of an aldehyde, glutaraldehyde and glyoxal; and a third agent that is a mineral acid.

Description

BINDING OF SMALL PARTICLES

FIELD OF THE INVENTION

THIS INVENTION relates to binding of small particles. The invention provides a method of binding small particles, and extends to an artefact obtained using the method. BACKGROUND TO THE INVENTION

THE APPLICANT IS AWARE THAT there is a number of inorganic particulate waste streams such as fly ash, which is a product of coal combustion, and gypsum dihydrate from recycled wall boards (sometimes referred to as sheetrock), as well as from flue gas de-sulphurisation in coal fired power generation. These require beneficiation, but processes in this regard are often not economically attractive.

Other inorganic wastes of which the applicant is aware include crusher dust from aggregate quarries, ultrafine dust of lime and other inorganics, including wollastonite which has good aspect ratio, and expanded perlite and exfoliated vermiculite.

Particulate waste streams are, of course, not limited to inorganic matter, and biomass (organic matter) particulate matter waste streams of which the applicant is aware include sawdust, agrifibre fines, short fibres such as coir, and others. Most construction products such as gypsum wall boards and ceilings boards, cement fibre boards, cement based roofing products, siding, tile backers and similar comprise particles that are bound by hydraulic binders. Such binders would have been calcined to produce a hemihydrate in the case of gypsum dihydrate, or a clinker in the case of Portland cement. In the case of cement, calcining temperatures in the order of 1450°C are required. It will be appreciated that calcining therefore consumes considerable amounts of energy. This is a disadvantage when it comes to beneficiation of gypsum dihydrate in particular.

In frame house construction, the frame comprises of timber studs or metal frames. In the case of both, the applicant believes that a substitute is required to minimise cost and, in the case of timber, to improve consistency, strength, dimensional stability and fire resistance. These are referred to as studs or 4 by 2's. Typically 63mm in depth, 38mm in width at appropriate lengths.

Products manufactured from biomass include medium and high density fibre board, hardboard, gypsum wall board and soft board, plywood, orientated strand board and laminated veneer lumber. Products manufactured from fibres, chips or particles are usually bound by any of urea formaldehyde, phenol formaldehyde or water dispersible isocyanates, applied to the feedstock.

In the case of hardboard, binding processes involve a lengthy period at elevated temperature and pressure to polymerise celluloses to bind, rather than by an applied binder. In the case of applied binders, binding processes involve temperatures in the range of 180°C to 220°C for between 6 and 26 seconds per millimetre thickness, in a heated press, such as a sophisticated continuous double belt press, at pressures up to 50kgs/cm². The equipment is capital intensive and formaldehyde emissions can be serious even when chemical scavengers are used. It is also noted that water in the binder converts to super-heated steam which penetrates to the board centre to accelerate resin polymerisation.

Production facilities also need to be located close to the raw material source of fibre, usually wood. There is a case for using alternative sources of fibre often having special properties or being closer to the market, lending themselves to smaller plants with less logistical costs or alternatively being classified as a waste stream. Some examples include paper mill sludge, cereal grain stovers, hemp, bamboo, coir, wetland reeds such as typha, bagasse and sawmill waste, plywood peelings and shavings.

The cost of board production may, in the simplest terms, be described as 33% energy, 33% binder, and 33% raw material and processing. There is therefore a compelling case for ambient temperature processing with very rapid binding chemistry which is not influenced by board thickness, and which for these reasons can result in rapid production from plant that may be retro utilised at ambient temperature or a low capital plant cost or size, depending on the raw material availability, seasonality or location relative to distribution points. The present invention seeks to enable this. A further important property of conventional boards is the propensity for swelling when wet or damp, the degree of water absorption, and dimensional stability. This also needs to be addressed. This invention also, ultimately, seeks to enable the production of construction elements, e.g. studs and sheets or boards pressed at room temperature or extruded profiles comprised mainly of organic or inorganic fines or small particles, without hydraulic binders such as gypsum hemihydrate or Portland Cement.

SUMMARY OF THE INVENTION

IN ACCORDANCE WITH THE INVENTION IS PROVIDED a method of binding small particles, which includes forming a mixture of the small particles and

a first agent that is a polyvinyl alcohol;

a second agent that comprises one or more of an aldehyde, glutaraldehyde and glyoxal; and

a third agent that is a mineral acid.

"Small particles" in this specification means solid particles of particle size 3mm or less, more preferably 1 mm or less, most preferably 500 micron or less, e.g. 40 micron. At the higher end of these ranges would typically be biomass and organic material, as well as sand, and at the lower end of these ranges would typically be inorganics such as fly ash and gypsum dihydrate.

As an alternative to polyvinyl alcohol, another polyol may be used. The method may, and typically does, not include any calcining step in which the small particles are subjected to calcining at high temperature.

Preferably, the mixture of the small particles and the first, second and third agents consists exclusively of the small particles and the first, second and third agents, in the sense that it does not include any additional binders, specifically not any additional hydraulic binders, and more specifically any Portland cement or gypsum hemihydrate. Optionally, an additional binder may be used however. Based on the combined mass of the first, second and third agents, the mixture may comprise from 75 to 130 parts by mass of the first agent, from 3 to 15 parts, more preferably 4 to 7 parts by mass of the second agent, and from 3 to 15 parts, more preferably 4 to 7 parts by mass of the third agent. The first agent may, in particular, comprise a fully hydrolysed polyvinyl alcohol. The fully hydrolysed polyvinyl alcohol may be in water. The fully hydrolysed polyvinyl alcohol may be in a concentration in the water that is from 3% to 15%, more preferably from 5 to 12%, most preferably from 7 or 8 to 10% by dry mass. The fully hydrolysed polyvinyl alcohol would not be foamed.

The polyvinyl alcohol used in the method of the invention is the fully hydrolysed grades such as Moliol 20/98 by Clariant, or Goshenol N types NH18, NH20, NH300 by Nippon Goshei with molecular weights in the range 125 000 to 160 000 g/mol and viscosities of 4% solution at 20°C in the range 16-30 MPa.s with a degree of hydrolysis or saponification mol% between 97 and 99.5 and an ester value of 20 ± 5mgKOH/g but molecular weights from 100 000 can be suitable. A most favourable grade is Poval 1 17 by Kururay. These grades must be dissolved in water by first dispersing them cold and then raising the temperature of the dissolution water to 95°C causing the dissolution of the polyvinyl alcohol, which is now in a molecular separated suspension in water capable of imposing considerable water resistance on the other constituents of the product once dry and at room temperature. Further waterproofness may be imposed by the use of dimethylol urea or acids such as orthophosphoric or certain salts such as ammonium chloride or sodium/ammonium bichromate, typically being added at 5% by mass on the polyvinyl alcohol in dry format. A further attribute is that the higher the drying temperature if used of the end product, the greater the insolubility of the polyvinyl alcohol. The concentration in water of the polyvinyl alcohol by mass is in the range 2 to 20% by mass, more preferably in the range 4 to 15% by mass and still more preferably in the range 5 to 12% by mass, still more preferably 8% to 10% by mass.

Alternatively, the polyvinyl alcohol may be a partially hydrolysed polyvinyl alcohol, in which case it may also be in water, typically in a concentration of 3% to 8% by mass. An example of a suitable partially hydrolysed polyvinyl alcohol is Poval 217. The method may then include a prior step of foaming the partially hydrolysed polyvinyl alcohol, by injecting compressed air into it, before mixing it with the small particles. The foam may be mixed with the small particles in a quantity that is from 5% to 15% by mass of the small particles. The second agent may comprise the aldehyde, glutaraldehyde and/or glyoxal in water. The aldehyde, glutaraldehyde and/or glyoxal may be in a concentration in the water that is from 10% to 70% by dry mass. The third agent may comprise the mineral acid in water. The mineral acid may be in a concentration in the water that is from 20% to 80%, more preferably 40% to 60% by dry mass. Preferably, the mineral acid is phosphoric acid, more preferably ortho phosphoric acid. The mixture of the small particles and the first, second and third agents may comprise the first, second and third agents, jointly, in a quantity that is 5 to 95%, more preferably 5-70%, more preferably 8-50%, more preferably 8-25%, typically 10- 15% of the weight of the small particles. A mixture of the small particles and the first agent may comprise the first agent in a quantity that is 5 to 90%, more preferably 5 to 60%, more preferably 8 to 50%, more preferably 8 to 25%, more preferably 10 to 15% of the mass of the small particles. The exact quantity may be dependent on the water content (wetness) of the small particles.

The method may include uniformly wetting the small particles with the first agent to obtain wetted small particles, and thereafter mixing the second and third agents with the wetted particles. In this regard, the fact that the small particles have been "wetted" does not necessarily mean that they were dry before. Although it is more typical that the small particles would have been dry, it is expected that the particles may already be wet, i.e. in the form of a paste or slurry. In such a case, the second and third agents may in one embodiment be pre-mixed, in a mass ratio of 1 :1 , and the resulting mixture of the second and third agents may then be mixed with the wetted small particles. Wetting may, in particular, mean that the small particles are mixed with a mass of the first agent that is from 5 to 25%, more preferably 8 to 20%, most preferably 8 to 15%, typically 10% of the mass of the small particles on a dry basis.

It follows that the small particles may be wet or dry. When the small particles are wet, weight precentages given herein based on the weight of the small particles apply to the wet small particles up to a water content of 15%. Beyond that, the weight percentages are by dry mass of the particles. It is preferred that the small particles are, at most, in a wet form in the form of a paste and not in the form of a slurry. In the case of the small particles being wood, a water content of 8% to 12% by mass is acceptable.

In another embodiment, the first, second and third agents may be pre-mixed, and the resulting mixture of the first, second and third agents may then be mixed with the small particles. This is a less typical embodiment however and is only envisaged to find application when these agents are highly dilute, and the small particles are wet. It would be advisable in such a case to mix the first second and third agents rapidly and rapidly introduce the resulting mixture into the small particles, rapidly mixing the mixture of the small particles and first, second and third agents then as well, soon after having introduced the resulting mixture into the small particles. Mixing may involve uniform wetting as hereinbefore envisaged. The composition of the resulting mixture of the first, second and third agents may be from 75 to 130 parts by mass of the first agent, from 3 to 15 parts, more preferably from 4 to 7 parts by mass of the second agent, and from 3 to 15, more preferably from 4 to 7 parts by mass of the third agent. The resulting mixture of the first, second and third agents may be prepared by mixing the second and third agents to obtain an intermediate mixture and, thereafter, mixing the intermediate mixture with the first agent to obtain the resulting mixture of the first, second and third agents.

The method may include high shear mixing of the mixture of the small particles and the first, second and third agents for from 5 to 90 seconds, more preferably 10 to 70 seconds, at ambient temperature (about 25°C).

The method may include shaping the mixture of the small particles and the first, second and third agents. Shaping may be by artificial pressure application and/or calendering and/or extrusion. The artificial pressure application may be at ambient temperature, i.e. about 25°C. The artificial pressure application may include pressing. The pressure of the artificial pressure application may be such that virtually no, i.e. no or very few, inter-particle voids remain. The artificial pressure application and/or calendering may be effected within 5 minutes, more preferably 2 to 4 minutes, most preferably 1 to 2 minutes of the mixture of the small particles and the first, second and third agents having been formed, thereby obtaining a shaped mixture of the small particles and the first, second and third agents. The artificial pressure application may be effected with non-heated plattens, i.e. the artificial pressure application may be effected at ambient temperature. In the case of calendering, speed and pressure adjusted calenders may be used. Generally, shaping of the mixture, and subsequent setting thereof, may be effected at ambient temperature, i.e. about 25°C. The small particles may be selected from organic and inorganic small particles, and mixtures thereof. In one embodiment, the small particles may be selected from gypsum dihydrate, fly ash, and mixtures thereof. A preferred embodiment is gypsum dihydrate. In other embodiments, the small particles may be selected from synthetic fibres and natural fibres. Natural fibres may include those from biomass or plant origin, such as bamboo, Sisal, kenaf, coir, flax, cotton, pulped cellulose fibre, milled dry paper waste streams, paper mill sludge, exploded or defibrated fibres such as those used in medium density fibre board mainly in the furniture industry, and the fibres of may grasses, woodchips, pieces of peeled veneer as are used in producing orientated strand board or wafer board, ply board, and mixtures of any two or more thereof. In further embodiments, the small particles may be selected from wollastonite, sand, particularly small particle size, i.e. fine, sand, e.g. desert sand, and mine tailings.

Many organic small particles are hydrophilic. Whilst these fibrous sources suggest a number of useful product developments their greatest short coming is their tendency to absorb water, and in doing so to change dimension, which could give rise to wet / dry structural instability or increased coefficient of expansion as is characteristic of fibre boards in which cellulose fibres, particularly those sourced from the soft woods, are typical. A great drawback to the use of plant fibres or cellulose is their propensity to absorb water and in so doing expand, and with a dramatic in loss in strength and binding properties. For exterior use such as in the building industry, proofness to insect or microbial attack are also necessary.

The method may therefore include pre-treatment of the small particles by surface coating or rapid immersion in or spraying with a hydrophobisation chemical in water solution, preferably a methyl potassium siliconate or similar, such as BS16 by Wacker, at a concentration in water of from 2 to 6% by mass, more usually 3 to 4% by mass, and thereafter drying the pre-treated small particles in a high carbon dioxide containing heated air stream. The hydrophobisation chemical may be used in a quantity of from 0.005% to 3%, more preferably 1 to 2% of the mass of the first, second and third agents jointly. After drying, which preferably takes place in warm air with a high CO2 content, the pre-treated small particles the particles must be able to float on water without apparent uptake, for a minimum of 24 hours. A complexation or association promoting agent can be used as a catalyst such as boric acid or borax in water at a concentration of 2 to 4% by dry mass added at up to 10 parts per 100 (10% by mass) of the polyvinyl alcohol solution causing a three dimensional cross link of the alcohol as a rigid gel. The polyvinyl alcohol, after the addition of the second and third agents, to the small particles, coats the small particles and is then gelled with the borax solution, which makes the mixture of the small particles and the first, second and third agents non- sticky, and allows for ease of spreading to a uniform thickness before pressing or calendering. Otherwise the non-stickiness facilitates handling, and when subjected to pressure or particle to particle contact the non-sticky mixture instantly bonds, allowing very rapid production of an artefact, at room temperature. Chemical reaction of the second and third agents with the first agent, as herein described, follows rapidly. The method may include allowing the mixture of the small particles and the first, second and third agents to set, thereby obtaining an artefact.

Perlite or vermiculite may be added to the mixture of the small particles and the first, second and third agents, when it is required to lower density by volume addition as a function of bulk densities in the range 100 to 350 grams per cc. Vermiculite may be added for improved behaviour in fire by its refractories and allowing the escape of water vapour in fire from decomposing coolants such as aluminum trihydrate or gypsum di-hydrate or ettringite THE INVENTION EXTENDS TO an artefact obtained according to the method of the invention.

The artefact may, in particular, be a construction element, e.g. a wall panel, roof panel, floor panel, or the like.

The method may include applying to the artefact, and the artefact may have, a paper liner, typically kraft at 200 grams per square meter specification, typically on opposite sides in use exposed sides of the artefact. THE INVENTION ALSO EXTENDS TO a binder composition comprising the first, second and third agents hereinbefore described, typically when in admixture with small particles. EXAMPLES

EXAMPLE 1 : WALL BOARD

200g/m² kraft paper lined

Cut to 100mm widths Density 0.79

Density adjustment by added perlite or Poval 217 foam

Polyvinyl alcohol Poval 1 17 is 99% hydrolysed.

Poval 217 is partially hydrolysed

EXAMPLE 3

WALL PAPER LINED 12mm

DISCUSSION

THE APPLICANT HAS SURPRISINGLY FOUND that the method of the present invention is particularly advantageous in beneficiating gypsum dihydrate which, conventionally, needs to be calcined to form the hemihydrate in order to be useful in binding applications, particularly in gypsum wall board production which usually employs the hemihydrate form. The invention therefore obviates the need for calcining, thus significantly reducing the energy requirement previously associated with gypsum dihydrate beneficiation.

As indicated in the background to the invention, construction products such as gypsum wall boards and ceilings boards, cement fibre boards, cement based roofing products, siding, tile backers and similar comprise particles that are bound by hydraulic binders. The present invention avoids the necessity for using such binders, and therefore avoids the necessity to have conducted a calcining step to produce a hemihydrate in the case of gypsum dihydrate, or a clinker in the case of Portland cement. The beneficiation of gypsum dihydrate, in particular, that is thus achieved, is regarded as being a particular advantage of the present invention.

Based on the nature of the binder composition of the invention and its use in the method of the invention, the amount of water that is conventionally required in manufacturing artefacts, and particularly construction products, of the type concerned is significantly reduced in the invention. Accordingly, drying time and energy is also significantly reduced, as is pressing and/or calendering energy, extrusion time, and the like. Furthermore, the invention, very advantageously, enables shaping and setting to take place at ambient temperature, as opposed to conventional techniques that require heat.

Reaction by acetalisation of the polyvinyl alcohol by the second and third agents takes place in the method of the invention, and results in formation of its acetal, e.g. polyvinyl gluteral or butyral or other acetal. Gaseous emissions from the reaction are negligible at room temperature. The reaction described may also be referred to as the union of an acid with an alcohol, also termed esterification, which results in the insolubility in water of the ester reaction product. In the reaction described, the acid accelerates or catalyses acetalysation, but may also esterify the alcohol, with boron being a catalyst, and the alcohol being in excess of the acetalysation reaction requirement of the polyvinyl alcohol to form its acetal, e.g. polyvinyl gluteral or butyral, the aldehyde only reacting with the two adjacent hydroxyl groups.

What the invention therefore, generally speaking, requires is cross-linking of the polyvinyl alcohol, or other polyol, with the glyoxal or other aldehydes, these reacting with the hydroxyl groups of the polyvinyl alcohol or other polyol.

Esterification results in a number of positive esters depending on the acid the choice of which influences the reaction speed. Examples are formate, citrate, lactate, proprionate, acetate, maleate and others, reacted with polycarboxylic acids, anhydrides or acid chlorides or other acids, cross linking acetalyzation forms acetates such as polyvinyl butyral in the presence of mineral acids such as hydrochloric or sulphuric or more preferably phosphoric. With the preferred reactants, a hard acetal is formed within seconds, largely depending on the acid concentration leaving water as a residue. The following is typical:

The raw material or furnish can be exactly as used at present for particle board medium or high density fibre board, orientated strand board or soft board.

In order to adjust the preparation of the binder system, the chemistry is adjusted for existing retro utilised plant, used without heat to suit the process for resination already installed, mainly by the variation of the acid concentration.

For the utilisation of alternative furnish, the control of aspect ratio, particle size distribution and layup would be engineered accordingly.

Most fibrous board products are manufactured from wood which has a composition of approximately 40-45% of cellulose, 20-30% of hemi-cellulose and 20-30% of lignin. Wood also contains fluctuating amounts of other components in small proportion such as resins, fats, comporising of mono, di and tri glycerides, waxes, tannins and sterols. Most particle board production is utilized in the furniture industry in which the board is laminated or otherwise decorated, and manufactured from ready to use furniture components or automated or semi-automated lines. Approximately 70% of the particle board manufactured is used in furniture. Approximately 85% of the board produced is bound by urea formaldehyde, which is a water based thermosetting resin, used at 10% based on the solid resin and dry chips weight of the particle board. The chips are dried to a relative humidity of approximately 1 -5% prior to blending, and the chips of the middle layer will have a lower relative humidity of approximately 2%. The resin content in the 3-layers of the boards commonly used have 10-12% of the binder in the surface layers and 7-9% in the middle layer. After blending the urea formaldehyde with the chips, they have a relative humidity of approximately 8-18%, and are pressed between the platens of a press which in the modern industry is usually a continuous process using double belt stainless belts, which are heated to a temperature between 200° and 220°C, and the dwell time of the board between the belts is between 6 & 25 seconds per millimetre thickness, depending upon the resin formulation and the density. Press pressures are approximately 1 to 2 newtons per square millimetre, but may be as high as 3.5 newtons per square millimetre, depending upon the desired board density. During the pressing operation, surface moisture turns to steam and is driven into the core of board raising the core temperature to 100°C or greater. This is referred to as "steam-shock", and is critical to the curing of the board and to minimize the dwell time of the board in the press. However even at a dwell time of 8- seconds per millimetre thickness, a 16mm thick particle board will require over 2- minutes in the press, which if it is running at a speed of 20-metres per minute, will require a press 40-meters or longer in length. These presses are very expensive. The energy required as well as the capital is very high and requires mass production to be competitive. Properties of particle board are typically a specific gravity of 650Kgs per cubic meter, and internal bond when dry of 0.5 N per square millimetre, and a thickness swell of 17% or greater when wetted. It is only those boards that comply with the EU Standard V100 that are suitable for extended exposure to moisture, and this is not possible with urea formaldehyde without the addition of a phenolic resin or an isocyanate. Board stiffness or deformation under load is often less than 12mPa.

The applicant regards the invention as herein described as being advantageous in the following ways:

· it allows pressing at room temperature; • it allows pressing boards of any thickness;

• it enables dwell time under pressure of less than 120, usually less than 60 seconds;

• it allows for biocides (polyvinyl glyoxal and aldehydes) or insecticides such as by Preventol of Bayer (gluteraldehyde or glyoxal) to be included in the aqueous binder;

• binder reaction speed is variable;

• no board spring-back or volume increase on pressure release;

• no toxic emissions;

· a competitive binder cost or lower or lower than cement or gypsum ;

• less liable to wet thickness well or water absorption;

• produces an artefact having a modulus of rupture of 12mPa as a minimum, preferably up to 20m Pa or greater;

• beneficiates major waste streams - gypsum dehydrate and fly ash;

· a wide choice of feedstock or furnish allowing greater flexibility of plant location and size, and retrofitting of existing plan using heated platens.

Claims

1 . A method of binding small particles, which includes forming a mixture of the small particles and

a first agent that is a polyvinyl alcohol;

a third agent that is a mineral acid.

2. The method according to claim 1 , wherein, based on the combined mass of the first, second and third agents, the mixture comprises from 75 to 130 parts by mass of the first agent, from 3 to 15 parts by mass of the second agent, and from 3 to 15 parts by mass of the third agent.

3. The method according to claim 1 or claim 2, wherein the first agent comprises a fully hydrolysed polyvinyl alcohol in water in a concentration of from 3% to 15% by dry mass.

4. The method according to claim 1 or claim 2, wherein the first agent comprises a foamed partially hydrolysed polyvinyl alcohol, having been prepared from partially hydrolysed polyvinyl alcohol in water in a concentration of from 3% to 8% by mass.

5. The method according to any of claims 1 to 4, wherein the second agent comprises the aldehyde, glutaraldehyde and/or glyoxal in water in a concentration of from 10% to 70% by dry mass.

6. The method according to any of claims 1 to 5 wherein the third agent comprises the mineral acid in water in a concentration of from 20% to 80% by mass.

7. The method according to any of claims 1 to 6, which includes uniformly wetting the small particles with the first agent to obtain wetted small particles, and thereafter mixing the second and third agents with the wetted particles.

8. The method according to claim 6, wherein the second and third agents are pre-mixed, in a mass ratio of 1 :1 , and the resulting mixture of the second and third agents is then mixed with the wetted small particles.

9. The method according to any of claims 1 to 8, wherein the first, second and third agents are pre-mixed, and the resulting mixture of the first, second and third agents is then mixed with the small particles.

10. The method according to claim 9, wherein the composition of the resulting mixture of the first, second and third agents is from 75 to 130 parts by mass of the first agent, from 3 to 15 parts by mass of the second agent, and from 3 to 15 parts by mass of the third agent.

1 1 . The method according to claim 9 or claim 10, wherein the resulting mixture of the first, second and third agents is prepared by mixing the second and third agents to obtain an intermediate mixture and, thereafter, mixing the intermediate mixture with the first agent to obtain the resulting mixture of the first, second and third agents.

12. The method according to any of claims 1 to 1 1 , which includes admixing with the mixture of the small particles and the first, second and third agents, a complexation or association promoting agent selected from boric acid and borax or a mixture thereof in water at a concentration of 2 to 4% by dry mass added at up to 10 parts per 100 (10% by mass) of the first agent.

13. The method according to any of claims 1 to 12, which includes high shear mixing of the mixture of the small particles and the first, second and third agents for from 5 to 90 seconds, more preferably 10 to 70 seconds, at ambient temperature.

14. The method according to any of claims 1 to 13, which includes shaping the mixture of the small particles and the first, second and third agents by artificial pressure application and/or calendering and/or extrusion.

15. The method according to claim 14, wherein the artificial pressure application is pressing.

16. The method according to claim 14 or claim 15, wherein the artificial pressure application is effected within 5 minutes, more preferably 2 to 4 minutes, most preferably 1 to 2 minutes of the mixture of the small particles and the first, second and third agents having been formed, thereby obtaining a shaped mixture of the small particles and the first, second and third agents.

17. The method according to any of claims 1 to 16, wherein the small particles are selected from organic and inorganic small particles, and mixtures thereof.

18. The method according to any of claims 1 to 17, wherein the small particles are selected from gypsum dihydrate, fly ash, and mixtures thereof.

19. The method according to any of claim 1 to 20, which includes allowing the mixture of the small particles and the first, second and third agents to set, thereby obtaining an artefact.

20. An artefact obtained according to the method of claim 19.