This invention relates to a composite material comprising a wood material comprising cellulose fibres, and a resin binder composition. The resin binder composition is based upon a sugar and certain salts, and the composite material is substantially free of added inorganic acid ammonium salt. The sugar and metal salt are present in the composite material in a combined amount of from about 2 to about 25 wt.%. This invention also relates to the uses of such composite materials, articles comprising such composite materials and processes for preparing articles using these composite materials and a resin binder composition. The resin binder composition has a particular application as a binder for fiberized materials, and in particular, for composite wood materials such as particle board, fibre board, HDF, MDF, chipboard and plywood.

Cellulose-based composites are major materials for the worldwide construction industry. Most buildings contain cellulose-based composites as a significant component. An important advantage of cellulose-based composites is that they typically use waste products from the pulp and timber industries and so they are significantly less expensive than virgin timber. Typically, they are constructed of wood particles which are held together with a thermoset resin, wherein the amount of resin required is typically dependent on the size of the particles; composites such as particleboard are formed of larger particles and typically require 8 wt.% of thermoset resin and composites such as fibre board are formed of smaller particles requiring 10 wt.% of thermoset resin.

The current UK market for wood products is listed in Table 1.

Table 1

(Table 1 from Timber Trade Federation Statistical Review 2010)

The majority of the conventional resins used in fibreboard are either urea-formaldehyde (UF) or phenol-formaldehyde (PF). The main concern with the use of these resins is the slow release of formaldehyde, which is a known carcinogen, often into an enclosed domestic environment.

These formaldehyde-based resins have ideal properties for board use as they are simple to prepare and inexpensive. They do not readily degrade which is an advantage in use. However, the fact that they do not degrade is also an environmental disadvantage. Fibreboard is widely used for short-term applications making it a significant environmental contaminant.

Alternatives to formaldehyde-based resins that do not release formaldehyde are available, for example methylene diphenyl diisocyanate (MDI) and polymeric methylene diphenyl diisocyanate (pMDI). However, these materials are in themselves hazardous to manufacture and handle, and are also more expensive than conventional formaldehyde based resins.

There is a need for cellulose-based composites which contain fewer, ideally no, carcinogens and are more environmentally friendly. There is, therefore, also a need for alternative resin binders which contain fewer, ideally no, carcinogens and which are more environmentally friendly.

An innovative, alternative approach is to use a resin binder composition comprising sugar and environmentally friendly salts. It has surprisingly been found that the addition of environmentally friendly salts of group I or II metal halides, such as chlorides, and sulfates or acetates into binding compositions comprising sugar decreases the swelling of wood composite boards using such binders, allowing carcinogenic or more environmentally hazardous compounds in the binder to be significantly reduced or eliminated entirely. The use of these binder compositions also reduces the tendency of such boards to delaminate.

The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

According to the present invention, there is provided a composite material comprising:

(a) a wood material comprising cellulose fibres; and

(b) a resin binder composition comprising:

(i) sugar; and

(ii) a metal salt which is a halide, acetate or sulfate salt of a group I or II metal element; wherein the sugar and metal salt are present in the composite material in a combined amount of from about 2 to about 25 wt.% and wherein the resin binder composition is substantially free of added inorganic acid ammonium salt.

Preferably, the composite material comprises wood material in an amount of from about 75 to about 98 wt.%, preferably from about 80 to about 95 wt.%, more preferably from about 85 to about 95 wt.%. An advantage of the present invention is that the resin binder composition can be present in a much lower amount than resin binders used in current fibreboards, whilst maintaining or improving the properties of the fibreboards. This means that the fibreboards may have a much higher wood material content than currently used fibreboards, leading to a reduction in resin binder material use and an overall reduction in production costs.

Advantageously, the sugar and metal salt are present in the composite material in a combined amount of from about 5 to about 20 wt.%, more preferably in a combined amount of from about 5 to about 15 wt.%.

Preferably, the composite material comprises wood material solids and resin solids in a weight ratio of from 75 to 98 : 2 to 25, such as 80 to 95 : 5 to 20, more preferably from 85 to 95 : 5 to 15.

The term“solids", as used herein, refers to the materials within the invention in a dry form (i.e. in the absence of any solvent, such as water). For example, the term“wood material solids” refers to the cellulose fibres present in the invention on a dry matter basis; the term“resin solids”, as used herein, refers to the sugar and metal salt mix of the resin of the invention on a dry matter basis; the term“sugar solids” the solids of the resin composition of the invention in a dry form (i.e., in the absence of any solvent, such as water).

Advantageously, the resin solids in the composite material comprise sugar solids : metal salt solids in a weight ratio of from 99: 1 to 34:66, for example from 98:2 to 50:50, preferably from 90: 10 to 60:40.

Advantageously, the resultant composite material comprises wood material solids : sugar solids : metal salt solids in a weight ratio of from 75 to 98 : 0.7 to 25 : 0.025 to 16.5, for example from 80 to 95 : 3 to 18 : 0.5 to 8, preferably from 85 to 95 : 3.5 to 12 : 1 to 4.5. The term“weight ratio”, as used herein, refers to the ratio of the materials within the invention in a dry form (i.e. in the absence of any solvent, such as water). Indeed, when materials are present in a defined weight ratio this can be referred to as a dry weight ratio.

Preferably, the cellulose fibres are selected from the group consisting of wood fibres, bagasse fibres, wood flour, wood particles and lignin fibres.

The cellulose fibres of the wood material may optionally be coated with a water-resistant material.

The composite material may further comprise an additive selected from flame retardants, waxes, fillers, stabilisers, anti-wear agents and blowing agents, and mixtures thereof.

Conveniently, the metal salt present in the resin binder composition is selected from the group consisting of sodium chloride, sodium sulfate, sodium acetate, potassium chloride, potassium sulfate, potassium acetate, magnesium chloride, magnesium sulfate, magnesium acetate, calcium chloride, calcium sulfate and calcium acetate, preferably wherein the metal salt is sodium chloride.

Preferably, the metal salt present in the resin binder composition is a halide or acetate of a group I or group II metal element. Conveniently, the metal salt present in the resin binder composition is a halide of a group I or group II metal element.

The metal salt in the resin binder composition may, for example, be selected from the group consisting of sodium chloride, sodium acetate, potassium chloride, potassium acetate, magnesium chloride, magnesium acetate, calcium chloride and calcium acetate, preferably the metal salt is sodium chloride.

Advantageously, the resin binder composition has no added inorganic acid ammonium salt.

Preferably, the composite material has a water content of up to about 15 wt.%, such as up to about 15, 10, 5, 2 or 1 wt.% water, for example from about 1 to about 15 wt.%, preferably from about 1 to about 10 wt.%, more preferably from about 1 to about 8 wt.%.

The composite material may further comprise a conventional formaldehyde-based or formaldehyde-free resin binder as detailed above. When comprising such conventional binders, they are included in amounts lower than currently used in existing composite wood boards.

In accordance with another aspect of the present invention, there is provided a composite article comprising the composite material as detailed above.

Preferably, the composite article is a composite wood (also known as engineered wood, man made wood or manufactured board) which includes, but is not limited to HDF (high-density fibreboard) MDF (medium-density fibreboard), particle board, chipboard and plywood. Composite wood is manufactured by binding or fixing the strands, particles, fibres, veneers or boards of wood, together using the resin binder composition described herein. Preferably, the composite article comprises wood material and resin solids in a weight ratio of from 75 to 98 : 2 to 25, such as 80 to 95 : 5 to 20, more preferably from 85 to 95 : 5 to 15.

Advantageously, the composite article comprises wood material solids : sugar solids : metal salt solids in a weight ratio of from 75 to 98 : 0.7 to 25 : 0.025 to 16.5, for example from 80 to 95 : 3 to 18 : 0.5 to 8, preferably from 85 to 95 : 3.5 to 12 : 1 to 4.5.

The composite article can be used for various applications, for example, building materials, furniture etc., in the same manner as a conventional wood-based material.

The composite wood may be coated with a water-resistant material optionally selected from the list consisting of polyvinylacetate, polyvinylalcohol or a wax selected from the group consisting of paraffin wax, beeswax, bayberry wax, candelilla wax, caranday wax, castor bean wax, shellac wax, spermaceti wax, sugar cane wax and wool wax (lanolin), and mixtures thereof.

These same water-resistant materials can be used for coating the cellulose fibres of the wood material of the composite material detailed above.

According to a further aspect of the present invention, there is provided a process for preparing a composite article comprising the steps of: a. providing a resin binder composition containing:

i. sugar;

ii. a metal salt which is a halide, acetate or sulfate salt of a group I or II metal element; and iii. no added inorganic acid ammonium salt; and

b. adding a wood material to the resin binder composition, wherein the wood material comprises cellulose fibres; and

c. pressing the composite material.

Conveniently, the resin binder composition may comprise a solvent to modify viscosity and improve the process step of adding wood material to the resin binder composition.

Preferably, the resin binder composition for use in the process has a dry solids to solvent ratio of from about 1 : 10 to about 5: 1 , such as from about 1 : 1 to about 4:1 , more preferably from about 2: 1 to 4: 1. The solvent is preferably water.

Preferably the cellulose fibres are selected from the group consisting of wood fibres, bagasse fibres, wood flour, wood particles and lignin fibres.

Advantageously, the viscosity of the resin binder composition before addition of the wood material is from about 50 to about 500 cP, such as from about 100 to about 400 cP, for example from about 200 to about 300 cP. More preferably, the viscosity is less than, or equal to, 300 cP.

Conveniently, the composition after addition of the wood material (i.e., in step (c)) is pressed at a temperature of from about 50 to about 300°C, preferably from about 100 to about 250°C, more preferably from about 150 to about 230°C.

Preferably, the composition after addition of the wood material (i.e., in step (c)) is pressed at a pressure of from about 100 to about 10,000 kNrrr ² , preferably from about 100 to about 5000 kNrrr ² , more preferably from about 100 to about 2000 kNrrr ² .

Any combination of the temperature and pressure ranges detailed above may be used when pressing the resulting composition.

When both heat and pressure are used to form the composite material according to the present invention, they may both be conveniently applied by way of a heated press.

Before pressing the composite material at elevated temperatures, the process may include a pre-press step, wherein the composite material is pressed at ambient temperature. Pre pressing the composite material aids in removing air pockets from the composite material. Advantageously, the composite material in step (c) is pressed for a time of from 1 to about 30 minutes, preferably from about 1 to about 20 minutes, more preferably from about 2 to about 10 minutes.

Conveniently, the process comprises the step of flash drying the composite material before pressing.

Preferably, the flash drying is carried out at a temperature of from about 50 to about 150°C, preferably from about 70 to about 130°C, more preferably from about 80 to about 100°C.

Advantageously, the flash drying is carried out for a period of from about 1 to about 300 seconds, preferably from about 1 to about 120 seconds, more preferably from about 1 to about 60 seconds.

As an alternative, the components of the resin binder composition, i.e., sugar, and a metal salt which is a halide, acetate or sulfate salt of a group I or II metal element, may be added separately to the wood material. After addition, these components act as a resin binder in substantially the same manner as if they were added together.

In this manner, the components of the resin binder composition may be added to the wood material in a sequential or simultaneous manner.

It is envisaged that any of the embodiments outlined above with respect to the process where the components of the resin binder composition are pre-mixed before adding to the wood material, may equally be applied to the process where the components of the resin binder composition are added separately to the wood material.

The composite articles, woods and materials prepared using the resin binder composition of the present invention may be provided with a coating (e.g., a hydrophobic coating) in order to improve their resistance to water. Alternatively, the wood fibres used in the invention may also be provided with a coating (e.g., a hydrophobic coating) in order to improve the resistance of the composite articles, woods and materials to water. For example, any of the water- resistant materials detailed above may be used for the coating.

Embodiments of this aspect of the invention includes composite articles, woods, materials and wood fibres wherein the coating of water-resistant material covers at least 50% (e.g., at least 60, 70, 80, 90, 95 or 99%, such as 100%) of the exposed surfaces of the composite article, wood, material or fibre. In this respect, the term‘exposed surfaces’, when used herein, includes references to surfaces of the composite article, wood, material or fibre that, at room temperatures and atmospheric pressure, are accessible to (externally-introduced) liquid water or water vapour.

When used herein, the term‘water-resistant mafer/a/’includes references to materials that, at a temperature of 298 K, have a solubility in water of less than 50 ppm (or less than 50 mg/L, such as less than 25, 10, 5 or 1 mg/L). Examples of water-resistant materials that may be mentioned include waxes (e.g., waxes based upon molecules containing at least 20 C-atoms, such as from 20 to 30 C-atoms), hydrophobic polymers (e.g., polyvinylacetate) and polymers such as polyvinylalcohol. Specific waxes that may be mentioned in this respect include those selected from the group consisting of paraffin wax, beeswax, bayberry wax, candelilla wax, caranday wax, castor bean wax, shellac wax, spermaceti wax, sugar cane wax and wool wax (lanolin).

The materials according to the present invention have the advantages that:

• they may be prepared entirely from renewable, natural materials (e.g., materials which are non-synthetic);

• they may be prepared entirely from materials that are non-toxic (e.g., non-toxic to humans);

• they may be completely biodegradable/compostable;

• they may biodegrade to materials that are harmless to the environment (e.g., to non-toxic materials);

• they may be prepared by simple processes (including: energy- and/or material efficient processes; processes involving a small number of steps such as one- or twostep processes; and/or one-pot processes);

• they may have mechanical properties that render them suitable for a wide variety of applications;

• they may be prepared either directly in the form required (e.g., a form not requiring further processing, such as moulding, laminating or re-casting) or in a form that is easy to manipulate;

• they may be recoverable and/or recyclable (e.g., by simple processes such as dissolution/reformation); and/or

• they may be stable to heat and/or flame resistant. In accordance with the present invention, the resin binder composition of the composite material, i.e. , the mixture of sugar and metal salt described herein can act as a resin and/or glue to bind the wood material of the composite. The skilled person would understand the term‘resin’ to mean solid or semisolid viscous substances which principally act as varnishes and/or adhesives. The skilled person would understand the term‘glue’ to mean an adhesive substance for sticking objects or materials together.

Therefore, in another aspect of the invention, there is provided a resin binder composition comprising:

a. a sugar in an amount of greater than about 40 wt.%; and

b. a metal salt which is a halide, acetate or sulfate salt of a group I or II metal element,

wherein the sugar and metal salt are present in the composition in a weight ratio of 99:1 to 0.5: 1 and wherein the composition is substantially free of added inorganic acid ammonium salt.

It will be understood by the skilled person that the resin binder composition of the invention may be a resin binder composition as detailed above, particularly in respect of the composite material, composite article and the process for preparing the composite article.

In addition, it will be appreciated that any resin binder composition of the invention may be incorporated into a composite material or a composite article and/or may be used in a process for preparing a composite material or composite article of the invention.

The term ‘resin binder composition’ is intended to refer to compositions which may, for example be applied as a dry composition or as a solution (i.e., a viscous or semi-viscous composition) and, after appropriate treatment, such as the application of pressure and/or temperature, can act as a glue or varnish.

The term‘substantially free’, when used herein in relation to added inorganic acid ammonium salt, includes references to compositions that comprise at most 5 wt.% (e.g., at most 4, 3, 2, 1 , 0.5, 0.1 or 0.01 wt.%) of added inorganic acid ammonium salt. Put differently, this includes references to compositions that comprise less than 5 wt.% (e.g., less than 4, 3, 2, 1 , 0.5, 0.1 or 0.01 wt.%) of added inorganic acid ammonium salt.

In a preferred embodiment, the resin binder has no added inorganic acid ammonium salt. The term ‘added’, when used herein in relation to inorganic acid ammonium salt, refers to inorganic acid ammonium salts purposefully added to the resin binder composition and is not envisaged to refer to any such salts already present in negligible quantities in the sugar starting material.

Preferably, the resin binder composition comprises sugar in an amount of greater than or equal to about 41 wt.%, 42 wt.%, 43 wt.%, 44 wt.% or 45 wt.%, such as from about 41 to about 80 wt.%, for example from about 41 to about 70 wt.%, preferably from about 41 to about 56 wt.%, more preferably from 41 about to about 48 wt.%.

Advantageously, the sugar and metal salt are present in the composition in a relative weight ratio of from 99: 1 to 34:66, for example from 98:2 to 50:50, preferably from 90: 10 to 60:40.

Conveniently, the sugar of the inventive composition may be derived from sugar syrup.

The term‘sugar syrup’, as used herein, refers to inter alia, processing/intermediate, final and storage syrups resulting from the processing of sugar raw materials such as sugar cane, sugar beet, sugar maple and Palmyra palm; syrups produced by dissolving solid sugars such as glucose powders, raw cane sugar (including high polarisation (HP) and very high polarisation (VHP)), refined sugars or recovery sugars; lactose syrups from whey processing; high fructose syrups, glucose syrups, glucose raffinate associated with glucose and high fructose syrup production from corn, wheat or other high starch raw materials; starch hydrolysates, directly from pure starch or from waste starch streams including wheat, corn, cassava, potato and carbohydrate hydrolysates or inulin; co-product or by-product syrups with high sugar content that result from the above processes, for example molasses, obtained when sugar is purified from sugar cane or sugar beet.

Advantageously, the sugar syrup is selected from the group consisting of process and storage syrups associated with the production of sucrose (from sugar cane, sugar beet and Palmyra palm molasses), caramel, sugar solutions produced by dissolving solid sugars, and juices of sugar containing raw materials (sugarcane, sugar beet, sugar maple, and Palmyra palm). Preferably, the sugar syrup is selected from the group consisting of process and storage syrups associated with the production of sucrose (from sugar cane, sugar beet and Palmyra palm), molasses or a sugar solution produced by dissolving solid sugars.

More preferably, the sugar syrup is process and storage syrups associated with the production of sucrose (from sugar cane, sugar beet) and sugar syrup produced by dissolving solid sugars. Preferably, the sugars of the composition are predominantly mono- and/or disaccharides, such as greater than about 90 wt.% (e.g., greater than 91 , 92, 93, 94, 95, 96, 97, 98 or 99 wt.%) of the sugars are mono- and/or disaccharides. More preferably about 100 wt.% of the sugars are mono- and/or disaccharides.

Examples of monosaccharides include glucose, psicose, fructose, sorbose, tagatose, allose, altrose, mannose, gulose, idose, galactose, talose, fucose, fuculose and rhamnose. Also included are trioses (such as ketotriose and aldotriose), tetroses (such as erythrulose, erthrose and threose) and pentoses (such as ribulose, xylulose, ribose, arabinose, xylose, lixose and deoxyribose).

Examples of disaccharides include sucrose, lactose, maltose, trehalose, turanose and cellobiose.

Advantageously, greater than about 90 wt.% (e.g., greater than 91 , 92, 93, 94, 95, 96, 97, 98 or 99 wt.%) of the sugars are a mixture of sucrose, glucose and fructose.

Preferably, the metal salt in the binder composition is selected from the group consisting of sodium chloride, sodium sulfate, sodium acetate, potassium chloride, potassium sulfate, potassium acetate, magnesium chloride, magnesium sulfate, magnesium acetate, calcium chloride, calcium sulfate and calcium acetate

Advantageously, the metal salt in the binder composition is sodium chloride.

Preferably, the metal salt present in the resin binder composition is a halide or acetate of a group I or group II metal element. Conveniently, the metal salt present in the resin binder composition is a halide of a group I or group II metal element.

The metal salt present in the resin binder composition may, for example, be selected from the group consisting of sodium chloride, sodium acetate, potassium chloride, potassium acetate, magnesium chloride, magnesium acetate, calcium chloride and calcium acetate, preferably the metal salt is sodium chloride.

Conveniently, the resin binder composition comprises the metal salt in an amount of from about 0.5 to about 50 wt.%, preferably from about 5 to about 30 wt.%, more preferably from about 6 to about 28 wt. %. The resin binder composition is preferably prepared in the form of a water-based solution. It will be obvious to those skilled in the art that different amounts of water may be added to the resin binder composition at different points in the supply chain. For example, sufficient water will need to be added to the sugar and/or metal salt to enable the solids to be dissolved and blended. If the resin is to be transported from a site of production to a site of use, then it is advantageous to minimise the amount of water transported by producing a resin with the highest possible solids content. However, once on site of use, the resin will need to be transferred from storage to the point of use and subsequently added to the wood material. During this transferring and application process it may be preferable to reduce the viscosity of the resin binder composition by the addition of further water. As any water in the resin binder composition will subsequently be removed in the production process of the composite material of the composite article, the absolute water content of the resin binder composition is not a direct indicator of the ratio of wood material : resin in the final product.

Preferably, the resin binder composition comprises water.

Advantageously, the resin binder composition is principally comprised of sugar, the metal salt and, optionally, water. That is to say, the resin binder composition comprises sugar, the metal salt and, optionally, water in a combined amount of equal to, or greater than, about 80 wt.%, such as equal to, or greater than, about 85, 90, or 95 wt.%.

Conveniently, the resin binder composition does not comprise any further component in an amount that is equal to, or greater than, the individual amounts of sugar, salt and, where present, water in the composition. That is to say, preferably the resin binder composition does not comprise any other component, except for wood material when it is incorporated into a composite material or article as defined above, in an amount that is greater than any one of these three components.

The resin binder composition may comprise water in an amount of from about 20 to about 50 wt.%, such as from about 25 to about 45 wt.%, for example from about 20 to about 40 wt.%, most preferably from about 30 to about 40 wt.%.

Preferably, the resin binder composition is substantially free of yeast and/or yeast extract. That is to say, the resin binder composition comprises at most 5 wt.% (e.g., at most 4, 3, 2, 1 , 0.5, 0.1 or 0.01 wt.%) of yeast and/or yeast extract. Put differently, this includes references to compositions that comprise less than 5 wt.% (e.g., less than 4, 3, 2, 1 , 0.5, 0.1 or 0.01 wt.%) of yeast and/or yeast extract.

Preferably, the resin binder composition is substantially free of plastics, such as polypropylene. That is to say, the resin binder composition comprises at most 5 wt.% (e.g., at most 4, 3, 2, 1 , 0.5, 0.1 or 0.01 wt.%) of plastics, such as polypropylene. Put differently, this includes references to compositions that comprise less than 5 wt.% (e.g., less than 4, 3, 2, 1 , 0.5, 0.1 or 0.01 wt.%) of plastics, such as polypropylene.

The water added to the composition of the invention is not particularly limited and includes distilled water, deionised water, pure water, tap water and industrial water. Advantageously, the water source could already contain dissolved salts, including sea water, ion exchange resin regeneration effluent or washing solutions.

Advantageously, the resin binder composition comprises the sugar in an amount greater than about 40 wt.%, the metal salt in an amount of from about 0.5 to about 50 wt.% and water in an amount of from about 20 to about 50 wt.%.

Preferably, the resin binder composition comprises the sugar in an amount of from about 41 to about 70 wt.%, the metal salt in an amount of from about 5 to about 30 wt.% and water in an amount of from about 25 to about 45 wt.%.

Most preferably, the resin binder composition comprises the sugar in an amount of from about 41 about to about 56 wt.%, the metal salt in an amount of from about 6 to about 28 wt. % and water in an amount of from about 30 to about 40 wt.%.

Advantageously, the viscosity of the resin binder composition is from about 50 to about 500 cP, such as from about 100 to about 400 cP, for example from about 200 to about 300 cP. The viscosity of the resin binder composition in the composite material may be less than, or equal to, 300 cP.

Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.

BRIEF DESCRIPTION OF FIGURES Figure 1 shows the effect of soaking the fabricated wood composite boards, having varying amounts of sodium chloride in the binder, in water at ambient temperature.

Figure 2 is an image of a 12mm composite wood article produced using a resin binder composition according to the invention.

EXAMPLES

Preparing Composite Materials

EXAMPLE 1

To prepare the resin binder composition, black treacle was mixed with water at a weight ratio of 3.33:1 after which, sodium chloride was added at an amount equivalent to 1 , 3 and 5 wt.% of the total binder composition.

To prepare the composite material, 250 g of the aqueous binder composition was sprayed onto 1000 g of wood fibre. By way of example, this delivered a final composite material composition of wood solids : sugar solids : salt solids of 88.6: 10.3: 1.1 when salt was added to 5 wt.% of the total binder composition.

The composite material was subsequently flash-dried at a temperature between 80 °C and 100 °C for approximately 30 seconds until reaching a moisture content of 4 to 10 wt.%.

1 1.0 kg of the composite material was evenly distributed within a press bed and the material was pre-pressed at ambient temperature to remove air pockets from the material and to ensure proper packing of the material. The resulting fibre mat was then transferred to a hot- press and compressed to a thickness of 15 mm at 210 °C for 10 minutes. The composite wood board was then removed and allowed to cool.

Example 2

To prepare the resin binder composition, Thick Juice was heated to 50°C and diluted with water in a ratio of 1 :0.33; to this solution crystalline NaCI was added in the ratio of 29.1 g per 133.0 g of diluted Thick Juice to produce a resin binder that consists of 7:3 sugar solids: salts solids ratio and a sugar content of 42%. This mixture was then stirred until the salt had fully dissolved and cooled to room temperature. Thick Juice (British Sugar product number 72017) is an aqueous solution of sugars, salts and other beet sugar origin compounds. It is an intermediate product in the production of beet sugar and typically contains between 65% to 70% dissolved solids, of which typically 93%-96% will be sucrose.

To prepare the composite material, 2.4 Kg of resin binder was sprayed onto 11.7 Kg of wood fibre containing ~8% moisture. This delivered a final composite material composition of wood solids : sugar solids : salt solids of 88.2:8.3:3.5. Once the material had been coated with the resin binder 0.17 Kg of paraffin wax emulsion was added by the spraying method.

The composite material was subsequently flash-dried at a temperature between 80 °C and 100 °C for approximately 30 seconds until reaching a moisture content of 4 to 10 wt.%. The flash-dried composite material was evenly distributed within a press bed and the material was pre-pressed at ambient temperature to remove air pockets from the material and to ensure proper packing of the material. The resulting fibre mat was then transferred to a hot-press and compressed to a thickness of 12 mm at 210 °C for 3 minutes. The composite wood board was then removed and allowed to cool.

Example 3

To prepare the resin binder composition, Thick Juice (British Sugar product number 72017) was heated to 50 °C and diluted with water in a ratio of 1 :0.28; to this solution NaCI was added in the ratio of 17.0 g per 128.0 g of diluted thick juice to produce a resin binder that consists of 8:2 sugar solids: salts solids ratio and a sugar content of 53%. This mixture was then stirred until the salt had fully dissolved and cooled to room temperature.

To prepare the composite material, 1.88 Kg of resin binder was sprayed onto 12.0 Kg of wood fibre (containing ~8% moisture content). This delivered a final composite material composition of wood solids:sugar solids:salt solids of 91.9:7.3: 1.8 .

The composite material was subsequently flash-dried at a temperature between 80 °C and 100 °C for approximately 30 seconds until reaching a moisture content of 4 to 10 wt.%.

The flash-dried composite material was evenly distributed within a press bed and the material was pre-pressed at ambient temperature to remove air pockets from the material and to ensure proper packing of the material. The resulting fibre mat was then transferred to a hot- press and compressed to a thickness of 12 mm at 210 °C for 3 minutes. The composite wood board was then removed and allowed to cool.

Internal Bond Strength The internal bond strength of the composite wood board at varying sodium chloride content was determined according to EN319. The sample dimensions were 50 x 50 mm and the load speed was 1.2 mm/min. The results of this analysis are provided in Table 2.

Table 2

The internal bond strength was increased by adding salt to the resin binder composition. Figure 1 also shows the effect of soaking the boards in water at ambient temperature for 30 minutes. It can be seen that in the absence of salt the boards swell significantly and delaminate, whereas the addition of salt, even at an amount of 1 wt.%, significantly decreases the swelling of the boards and decreases the level of delamination.

The above binder compositions have been found to be less expensive to produce, they maintain (or improve) the mechanical properties of fibreboards using such binder compositions and they do not require the inclusion of carcinogenic or environmentally unfriendly compounds.

Characteristics

A composite wood board having a thickness of 12 mm was prepared using a resin binder composition having a dry weight ratio of sugar solids to metal salt solids of 7 : 3, wherein the wood fibre solids to resin solids ratio is 90 : 10. The image of this board in Figure 2 shows that a uniform board was prepared using this resin binder composition.