Patent Description:
Wood is a complex natural material comprising cellulose, hemicellulose and lignin as main components. Wood also comprises minor amounts of minerals and so-called extractives such as resins, waxes and fatty acids. Fiberboards are wood products made of wood fibers. Fiberboard industry is divided into segments like particle board, medium-density fiberboard (MDF board) and hardboard. The production of fiberboards generally includes pulping of wood chips, drying, optionally blending the fibers with binder resins, forming the fibers optionally containing binder resin into a mat and hot pressing.

The aim of pulping is to convert wood chips to fibers. Pulping usually includes a pretreatment of wood chips for softening (digesting) and mostly mechanical action (refining). The steps of digesting and/or refining generally involve a treatment of the wood chips with hot water or steam, usually under pressurized conditions. The water used for the treatment is often recirculated several times in the process. By this treatment wood ingredients are extracted into the water or steam. The extracted wood ingredients or degradation products thereof also include organic acids such as acetic acid. Hydrolysis reactions occur during this treatment, which are catalyzed by the acids present. Finally, the water is separated from the fibers obtained which are then processed further to prepare fiberboards.

The water separated is an aqueous wood extract comprising a complex mixture of wood ingredients and degradation products thereof such as e.g. hemicellulosic compounds including sugars, cellulose, lignin, resins, waxes, acetic acid and furfural. Water is usually partially removed to achieve a more concentrated aqueous wood extract. The wood extract is often disposed as waste material or used for energy recovery by incineration. More suitable uses for the wood extracts are considered such as recovery of valuable chemical substances by fractionation or use as a raw material for biofuels. However, there is still a need for appropriate potential uses for such wood extracts generated in fiberboard production.

Cement, clay, gypsum and other mineral binders are widely used in construction applications. These mineral binders, in particular cement, are usually used as the binder in concretes or mortars typically also including aggregates and/or admixtures. For use, the composition comprising the mineral binder is mixed with water and the mixture is placed and formed as desired. In the mixture a physical or chemical reaction of the mineral binder and water takes place, resulting in hardening of the mixture so that a solid building material is formed.

Plasticizers or dispersants are often used in such compositions comprising mineral binders to increase workability of the composition. Thus, plasticizers can increase plasticity or fluidity of the mixture of the mineral binder and water while in a plastic state. For this reason, the amount of water in the mixture can be reduced which is advantageous because it results in improved strength of the product obtained. Therefore, plasticizers are also called water reducers.

Examples of conventional plasticizers for mineral binders are lignin sulfonates, sulfonated naphthalene formaldehyde condensates, sulfonated melamine formaldehyde condensates, and polycarboxylate ethers, and blends thereof. Sulfonated naphthalene formaldehyde condensates, sulfonated melamine formaldehyde condensates, and polycarboxylate ethers are also called superplasticizers.

However, known plasticizers have limitations in performance, costs or availability. Therefore, there is still a need for alternatives of conventional plasticizers for mineral binders.

<CIT> relates to an additive for cementitious compositions comprising a plant extract and a surface active agent. The plant extract may be derived from wood or grasses.

<CIT> is concerned with a water-insoluble composition derived from a lignocellulose carbohydrate mixture and its use as a foaming agent.

<CIT> is related to a method for reducing water to gypsum materials by incorporating a composition selected from waste sulfite liquor, lignine sulfonate, alkali lignin and lignin material acid-precipitated from black liquor and the water-soluble soap of said acid-precipitated black liquor lignin.

<CIT> describes a mixture for accelerating curing of gypsum or cement comprising lignin sulfonate wherein the lignin sulfonate may be a waste product of sulfite pulp.

<NPL>, study the utilization of black liquors of rice straw and bagasse produced in paper and pulp industry for cement compositions.

The object of the present invention is to provide a novel plasticizer for compositions comprising mineral binders, in particular concretes, to overcome the disadvantages of the prior art discussed above. In particular, the novel plasticizer should have plasticizing properties which are comparable to those of known plasticizers. Moreover, it should be economically priced and should not impose too severe restriction in view of national regulations such as REACH, a European regulation for registration, evaluation and authorization of chemicals.

Surprisingly, this object could be achieved by a use according to claim <NUM>, that is by using a wood extract obtainable by water and/or steam extraction, for instance corresponding wood extracts generated during fiberboard production, in admixture with at least one other plasticizer as a plasticizer in a composition comprising a mineral binder.

Accordingly, the present invention relates according to claim <NUM> to the use of a wood extract obtainable by water and/or steam extraction in admixture with at least one other plasticizer as a plasticizer for a composition comprising a mineral binder, and to the corresponding composition comprising a mineral binder and a wood extract obtainable by water and/or steam extraction in admixture with at least one other plasticizer as a plasticizer.

Use of the wood extract in admixture with at least one other plasticizer in a composition comprising a mineral binder results in a good plasticizing effect by the wood extract in admixture with at least one other plasticizer which is comparable to or even better than the plasticizing effect of conventional plasticizers. Selected properties such as initial consistency, decrease of consistency over time and, especially in case of summer temperatures, too early setting and temperature development of the hardening mineral binder can be improved by incorporation of the wood extract. The wood extract is relative inexpensive so that final product costs are reduced. In addition, the wood extract is not classified as a chemical raw material so that a REACH registration is not required.

The wood extract replaces a significant part of a conventional plasticizer thereby improving selected properties such as initial plasticizing, slump-keeping over time (increased duration of workability) and retarded setting. The wood extract is used as a plasticizer in combination with a conventional plasticizer in the composition comprising a mineral binder.

Compared to the use of a conventional plasticizer, the use of the wood extract as a plasticizer in admixture with another conventional plasticizer, results in equal or better plasticizing effect, consistency is maintained and concrete stiffening and setting is retarded. These effects lead to cheaper and more efficient plasticizers, in particular for concrete, especially for use during summer time.

The invention will be described in detail in the following, wherein all statements equally apply to the use of the wood extract in admixture with at least one other plasticizer as a plasticizer and to the composition comprising the wood extract in admixture with at least one other plasticizer as a plasticizer.

A plasticizer is an additive which is used in a composition comprising a mineral binder to improve workability or fluidity of the mixture of the composition with water while being in the plastic state compared to the same mixture without such plasticizer. Plasticizers are also called water reducers or dispersants. According to the present invention, a wood extract obtainable by water and/or steam extraction is used according to claim <NUM> as a plasticizer in admixture with at least one other plasticizer in a composition comprising a mineral binder. The extraction treatment may be either water or steam extraction. It is also possible that the wood extract is obtained from sequential steam and water extractions, e.g. resulting from sequential digesting and refining steps for pulping in fiberboard production.

Wood extracts obtained as a by-product of fiberboard production are suitable for the present invention. Such wood extracts are known by the skilled person, in particular to those in the field of fiberboard production. Wood extracts are also commercially available.

The wood can be of any kind of wood or a mixture of different kinds of wood. The wood may be hardwood or softwood.

The wood extract is obtained by water and/or steam extraction of wood. The wood which is treated with water and/or steam is usually present in form of comminuted wood such as wood chips, sawdust or other wood waste, wherein wood chips are preferred. Steam as used herein means water steam. The water or steam extraction includes the treatment of wood, such as wood chips, sawdust or other wood waste, preferably wood chips, with water, preferably hot water, or steam, wherein the extraction is preferably carried under pressurized conditions, i.e. under a pressure of more than <NUM> bar.

The extraction is effected at increased temperatures, i.e. a hot water extraction, and steam extraction including steam explosion are preferred. Such treatment of wood with hot water or steam is typically used in the digesting and/or refining step for pulping of wood chips in the fiberboard production as explained above. A specific steam treatment often used in fiberboard production is the so called steam explosion. Steam explosion refers to a method where high pressurized steam is injected into a reactor filled with wood such as wood chips or saw dust. During steam injection, the temperature rises, e.g. to <NUM> to <NUM>. Subsequently, pressure is suddenly reduced and the wood undergoes an explosive decompression with degradation of hemicellulose and lignin matrix disruption as a result.

The wood extract is obtainable by water and/or steam extraction at a temperature of <NUM> to <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>.

The wood extract is obtainable by water and/or steam extraction at a pressure of <NUM> bar to <NUM> bar, preferably <NUM> bar to <NUM> bar, more preferably <NUM> bar to <NUM> bar, in particular in combination with the temperature ranges indicated above.

The water or steam extraction can be carried out in a batchwise or continuous manner. The water or steam extraction can be carried out in a cooker such as a pressurized cooker, e.g. a water or steam cooker, for instance in a digester or refiner used in fiberboard production. The water used can be recirculated. In this manner less water is required and a more concentrated wood extract is obtained. The weight ratio of water used for extraction to wood may vary in wide ranges, e.g. from <NUM>/<NUM> to <NUM>/<NUM>, but as mentioned the water/steam is often recirculated. The weight of wood refers to the dry weight.

The duration of water or steam extraction may vary in wide ranges depending on the wood used and the conditions applied. The water or steam extraction of the wood at the intended temperature may be carried out e.g. over a period of <NUM> to <NUM>, preferably <NUM> to <NUM>. Prior to this extraction at the intended temperature, a preheating of the mixture of the wood and water may be effected to arrive at the temperature intended.

By the water or steam extraction a main part or all of the hemicellulose (e.g. <NUM>-<NUM>%), usually a proportion of lignin (e.g. <NUM> to <NUM>%) and optionally a minor part of the cellulose (e.g. <NUM> to <NUM>%) are extracted from the wood. The extracted hemicellulose is mainly degraded by hydrolysis reactions. Degradation products are sugars, in particular monomeric sugars, such as pentoses and hexoses, acetic acid and optional furans such as furfural. Cellulose is usually more resistant to hydrolysis, but some degradation may also occur. Further wood ingredients which may be extracted, usually in minor amounts, are resins, fatty acids, minerals and/or waxes.

Accordingly, the wood extract usually comprises sugars, in particular monomeric sugars such as pentoses and hexoses, lignin, acetic acid and optionally cellulose or degradation products thereof, and optionally starch. The wood extract may also contain minor amounts of other wood ingredients such as resins, waxes, fatty acids and/or minerals such as sodium, potassium, calcium and magnesium ions.

The wood extract obtainable by water and/or steam extraction of wood is generally a water and/or steam extract of wood. In particular, the wood extract is obtainable by water and/or steam extraction of thermo-mechanical pulping. Accordingly, the wood extract is usually a water and/or steam extract of thermo-mechanical pulping. In thermo-mechanical pulping a thermo-mechanical pulp can be produced from wood. Thus, the wood extract is usually a by-product of thermo-mechanical pulping. The thermo-mechanical pulp obtained can be used e.g. for fiberboard production.

Accordingly, the wood extract does not include lignin sulfonates. In particular, the wood extract does generally not contain sulfur containing compounds. An exception may be sulfur compounds contained in the wood or derivatives of said sulfur compounds. The wood extract preferably comprises <NUM> to <NUM> % by weight, more preferably <NUM> to <NUM> % by weight of monosaccharides, based on the dry weight of the wood extract.

The wood extract is usually used in form of a mixture of the wood extract and water. The water content of the wood extract can be adjusted, e.g. by addition or usually by removal of water. It is possible to remove the complete water so that a water-free wood extract is obtained. Generally, however, it is preferred to use an aqueous solution or mixture of the wood extract, e.g. in view of viscosity and stability. Therefore, an aqueous wood extract containing <NUM> to <NUM> % by weight, preferably <NUM> to <NUM> % by weight, more preferably <NUM> to <NUM> % by weight of wood extract, the balance being water, is preferred. In most cases the water content of the wood extract has to be increased to the preferred concentration level, e.g. those mentioned above such as <NUM> to <NUM> % by weight, using evaporators. Standard evaporators developing temperatures above +<NUM> may be used as well as underpressure evaporators at temperatures below +<NUM> may be used.

The aqueous wood extract usually has a yellow to brown color. The aqueous wood extract is generally acidic, preferably with a pH value of not more than <NUM>, e.g. with a pH value in the range of <NUM> to <NUM>.

The water used for water and/or steam extraction is pure potable water, i.e. the water or potable water is used without adding any further components. In particular, sulfur containing compounds such as sulfides, sulfates and sulfites are not added to the water.

According to the invention, the wood extract in admixture with at least one other plasticizer as defined in claim <NUM> is used as a plasticizer in a composition comprising a mineral binder A mineral binder is a substantially inorganic material or blend which hardens when mixed with water. All mineral binders known to those skilled in the art are suitable. Typical examples of suitable mineral binders are cement, building limes, clay, gypsum, and mixtures thereof. The mineral binder is preferably at least one of cement, clay and gypsum, wherein cement is preferred.

The gypsum used as mineral binder refers to burnt gypsum or calcined gypsum in which a part or all of the hydrate water contained in the dihydrate of gypsum is removed, such as plaster of Paris or hemihydrate and anhydrite or mixtures thereof. When the gypsum is mixed with water, the dihydrate of gypsum is formed again. As to gypsum, the use of the wood extract is particularly suitable when the gypsum is used for manufacture of gypsum wallboards.

Clay is widely used as a mineral binder. When it is mixed with water, a plastic material is obtained. The clay solidifies or hardens during drying, i.e. removal of the water.

The mineral binder is preferably a cement, for instance a Portland cement or alumina cement. The cement is preferably a Portland cement or a blend of Portland cement with at least one of fly ash, granulated blast furnace slag, lime, such as limestone and quicklime, fumed silica and pozzolana. Cements usually comprise in addition calcium sulfate, such as gypsum, anhydrite and/or hemihydrate.

Cements can be classified based on the composition according to standards such as the European cement standard EN <NUM>-<NUM> or corresponding other national standards. Common cements are Portland cements, Portland-composite cements, blastfurnace cements, puzzolanic cements and composite cements. Selected materials normally added to clinker to produce blended cements, e.g. fly ashes, blast furnace slags or silicafumes, are also called "additives" and may be added separately to the cement.

When cement is mixed with water a chemical reaction occurs between the cement and water called hydration. The hydration results in hardening or curing of the mixture of cement and water.

The composition comprising a mineral binder may be a composition consisting of the mineral binder. The composition comprising a mineral binder may preferably comprise in addition one or more admixtures and/or aggregates.

Typical examples of common admixtures for mineral binders or cement additives, respectively, are grinding aids, accelerators, corrosion inhibitors, retardants and shrinkage reducing agents. These admixtures are common and well known in the field of cement industry.

Typical examples of aggregates are sand, gravel, crushed stone and quartz powder.

The composition comprising a mineral binder is preferably a mortar or more preferably a concrete, wherein the mineral binder is preferably at least one of cement, clay and gypsum, more preferably cement. Mortars and concretes include aggregates and optionally additives and admixtures. Mortars include small sized aggregates such as sand or quartz powder whereas concretes in addition to small sized aggregates such as sand or quartz powder also include coarser aggregates such as gravel or crushed stone. Typically, a composition comprising a mineral binder and aggregates having a grain size of at most <NUM> or at most <NUM>, depending on country, are considered a mortar, whereas a composition comprising a mineral binder and aggregates wherein a part of the aggregates have a grain size of more than <NUM> or more than <NUM>, respectively, are considered a concrete.

The wood extract is used in the composition in admixture with at least one other plasticizer selected from lignin sulfonates, sulfonated naphthalene formaldehyde condensates, sulfonated melamine formaldehyde condensates, and polycarboxylate ethers, preferably at least one of lignin sulfonates, sulfonated naphthalene formaldehyde condensates and sulfonated melamine formaldehyde condensates, and more preferably in admixture with lignin sulfonate and/or sulfonated naphthalene formaldehyde condensates.

The other plasticizer, in particular lignin sulfonate and/or sulfonated naphthalene formaldehyde condensates, may be e.g. sodium salt, calcium salt or magnesium salt or a mixture thereof. The other plasticizer, in particular lignin sulfonate and/or sulfonated naphthalene formaldehyde condensates, may also be in a modified form. Such common modification may e.g. include purification, e.g. to reduce the sugar content, partial desulfonation or modification of average molecular weight.

The proportion of the wood extract in admixture with at least one other plasticizer selected from lignin sulfonates, sulfonated naphthalene formaldehyde condensates, sulfonated melamine formaldehyde condensates, and polycarboxylate ethers, preferably at least one of lignin sulfonates, sulfonated naphthalene formaldehyde condensates and sulfonated melamine formaldehyde condensates, and more preferably in admixture with lignin sulfonate and/or sulfonated naphthalene formaldehyde condensate, is preferably from <NUM>% by weight to <NUM>% by weight, preferably from <NUM>% by weight to <NUM>% by weight, based on the total dry weight of the wood extract and the at least one other plasticizer.

The total amount of the wood extract and the at least one other plasticizer, preferably the total amount of the wood extract in admixture with lignin sulfonate and/or sulfonated naphthalene formaldehyde condensate, used in the composition of the invention may vary in wide ranges but is preferably from <NUM>% by weight to <NUM>% by weight, preferably from <NUM>% by weight to <NUM>% by weight, based on the dry weight of the mineral binder. The total amount of the wood extract and the at least one other plasticizer refers to the dry weight, i.e. without water.

The wood extract and the at least one other plasticizer are preferably used as an aqueous admixture. The aqueous admixture comprising the wood extract and the at least one other plasticizer, preferably comprising a mixture of the wood extract with lignin sulfonate and/or sulfonated naphthalene formaldehyde condensate, is preferably used in an amount of from <NUM>% by weight to <NUM>% by weight, preferably from <NUM>% by weight to <NUM>% by weight, based on the dry weight of the mineral binder. This is particularly preferred for a preferred aqueous plasticizer admixture comprising the wood extract and the at least one other plasticizer, preferably comprising a mixture of the wood extract with lignin sulfonate and/or sulfonated naphthalene formaldehyde condensate, which has a total dry matter content of <NUM> to <NUM>% by weight, in particular about <NUM>% by weight.

The composition may further comprise other common admixtures such as grinding aids, accelerators, corrosion inhibitors, retardants and shrinkage reducing agents and mixtures thereof. Suitable raw materials which can be added, are for instance carbohydrates, inorganic salts and aminoalcohols. Examples of inorganic salts are nitrates, nitrites, sulfates, carbonates or chlorides of alkali metals or earth alkaline metals such as sodium or calcium.

The wood extract and the at least one other plasticizer can be added to the composition separately at the same time or at different times to the composition. It is however preferred that the wood extract and at least one other plasticizer are mixed together and to add the plasticizer admixture to the composition comprising the mineral binder.

When the composition comprising the mineral binder and the wood extract in admixture with at least one other plasticizer used as plasticizer according to the invention is mixed with water. The wood extract improves workability or fluidity of the composition mixed with water, usually fresh mortar or fresh concrete, compared to the same composition but which does not contain the wood extract. Mixing of the composition with water is effected by conventional methods with which the skilled person is familiar.

Next, the invention is further explained by examples. However, the examples are for illustration only, and shall not be considered as limiting the scope of the invention.

In the following, amounts and percentages are based on weight unless otherwise indicated.

Slump in time was determined according to EN <NUM>-<NUM> (slump method), refers to water reduction and retention of consistency. Initial and final density was determined according to EN <NUM>-<NUM>. Air content (initial air and final air) in fresh concrete was determined according to EN <NUM>-<NUM>. Initial and final temperature was determined using electronic laboratory thermometer. Compressive strength of concrete was determined according to EN <NUM>-<NUM>.

The wood extract used in the examples is a wood extract obtained from a steam extraction of pine wood chips at a temperature of <NUM> and <NUM> bar, wherein the water is recirculated. The extract obtained is concentrated by water removal in an underpressure evaporator at temperatures of approximately +<NUM> to obtain an aqueous wood extract. The product obtained is a dense viscous brown liquid having a pH of about <NUM> to <NUM>. The dry content is about <NUM> % by weight, the balance being water. The main components are monosaccharides, in particular pentoses and hexoses (about <NUM>% by weight based on the dry weight). Further components are lignin, cellulose and/or degradation products thereof, starch, acetic acid, resins, waxes and minerals, in particular sodium, potassium, calcium and magnesium ions. The wood extract is commercially available as Fibro-Lep® from Fibris S.

Two commercial plasticizers admixtures (PL) were used as a control:.

Three plasticizers admixtures having the composition indicated in the following Table <NUM> were prepared. The proportions of the components are given in % by weight, based on the total weight of the plasticizer. The wood extract used is the wood extract mentioned above. In PL2 and PL3 the wood extract (dry weight) is contained in an amount of <NUM> % by weight.

Three different cement types (CM) were tested:.

The plasticizer admixtures and the cements were used to prepare standard concretes according to EN <NUM>-<NUM> (concrete class C <NUM>/<NUM> X0) according to the details given in Table <NUM> below and the properties of the concretes obtained are determined. As the consistency method the Abrams method was used. The results are given in Table <NUM> with respect to the fresh concrete properties and Table <NUM> with respect to the hardened concrete properties.

In examples <NUM> to <NUM>, the total amount of the aqueous plasticizer admixture used was <NUM> % by weight, based on the dry weight of the cement content. In examples <NUM> to <NUM>, the total amount of the aqueous plasticizer admixture used was <NUM> % by weight, based on the dry weight of the cement content.

In Table <NUM>, admixture dosage/m<NUM> refers to kg aqueous plasticizer admixture per m<NUM> concrete; Dmax refers to maximum grain size of the aggregates, w/b refers to the water/cement ratio where the binder activity is considered. For instance, for Examples <NUM>-<NUM>, the value of <NUM> is based on <NUM> water dividided by (<NUM> cement + <NUM>*<NUM> fly ash). The coefficient <NUM> considers the lower activity of the fly ash compared to the cement. The values in parenthesis for w/b refers to water to total fines ratio. For instance, the value of <NUM> for Examples <NUM>-<NUM>, is based on weight of water (<NUM>) divided by the weight of the cement mixture (<NUM> + <NUM> + <NUM>). Water (kg) refers to kg water per m<NUM> of concrete.

Plasticizer admixtures PL2 and PL3 were tested according to EN934-<NUM>: <NUM> (Water reducing admixture and retarding/water reducing admixture). As standard concrete concrete I according to PN-EN <NUM>-<NUM>:<NUM> was used for parameters P1, P2 and P3 mentioned below. For parameter P4 a reference mortar according to PN-EN <NUM>-<NUM>:<NUM> was used. The standard concrete/mortar was processed with the plasticizer admixture (test mix) and without the plasticizer admixture (reference mix). A w/c ratio of <NUM> was used for reference mix. In the test mix the amount of aqueous plasticizer admixtures was <NUM>% for PL2 and <NUM>% for PL3, based on the cement weight. The results are shown in Tables <NUM> and <NUM>. The following parameters P were determined:.

The enhancement of compressive strength after <NUM> days by PL2 and PL3 was <NUM>% and <NUM>%, respectively. The enhancement of compressive strength after <NUM> days by PL2 and PL3 was <NUM>% and <NUM>%, respectively.

Claim 1:
Use of a wood extract as a plasticizer for a composition comprising a mineral binder,
wherein the wood extract is obtainable by water and/or steam extraction at a temperature of <NUM> to <NUM>, preferably <NUM> to <NUM>, wherein the extraction is preferably carried out under pressurized conditions, and/or wherein the wood extract is obtainable by water and/or steam extraction at a pressure of <NUM> bar to <NUM> bar, preferably <NUM> bar to <NUM> bar, and wherein the water used for water and/or steam extraction is pure potable water, and
wherein the wood extract is used in admixture with at least one other plasticizer selected from lignin sulfonates, sulfonated naphthalene formaldehyde condensates, sulfonated melamine formaldehyde condensates, and polycarboxylate ethers, preferably lignin sulfonates and/or sulfonated naphthalene formaldehyde condensates