WO2014162253A1

WO2014162253A1 - Manufacturing of sheet material and biological glue suitable for this purpose.

Info

Publication number: WO2014162253A1
Application number: PCT/IB2014/060325
Authority: WO
Inventors: Koen NEL; Jimmy BAERT
Original assignee: Spano Nv; Spano Invest Nv
Priority date: 2013-04-05
Filing date: 2014-03-31
Publication date: 2014-10-09
Also published as: EP2981399A1; BE1021591B1

Abstract

The present invention relates to a glue composition for glueing lignocellulose- containing material, comprising: water, a vegetable source of protein, a binding agent, and a source of lithium or a source of magnesium. The glue is suitable for glueing the lignocellulose-containing material for manufacturing an OSB, plywood board, fiberboard or particle board. The invention also relates to a method for manufacturing the glue composition, methods for manufacturing board materials with the glue composition, and board materials comprising the glue composition, obtainable by a method according to the invention.

Description

Manufacturing of sheet material and biological glue suitable for this purpose

The invention relates to a method for manufacturing board material on the basis of lignocellulose-containing wood material and a bio-glue suitable for this purpose; as well as to board materials obtainable with the bio-glue.

It is known to manufacture boards by pressing together lignocellulose-containing material with a urea-formaldehyde or urea-melamine-formaldehyde resin as a binding agent.

A fiberboard or particle board obtained in this manner will emit minor quantities of formaldehyde into the air during a long period of time. By reducing the amount of formaldehyde in respect to the amino compositions in the glue, the formaldehyde emission in respect to the board material can be reduced. However, it has shown that there are limits to such reduction of the formaldehyde content of the glue, as such reduction leads to a diminishing of the strength features of the board, such as the moisture and weather resistance of the board.

Alternative glue systems were proposed on the basis of polyisocyanate as a binding agent. Disadvantages of this method are the high cost price of the binding agent and the problems occurring during pressing.

In EP0013447, a glue system was presented on the basis of aminoplasts with reduced formaldehyde content with 2 to 20% soluble or dispersible protein. This glue system may reduce the formaldehyde emission, however, cannot avoid it. For obtaining beneficial strength features, a urea-formaldehyde (UF) binding agent must be applied. Moreover, a urea-melamine-formaldehyde resin must be applied as a binding agent for obtaining weather-resistant particle boards. The use of soy protein as a glueing agent for wood is already known since 1930. However, petroleum derivatives replaced soy proteins, as those had a relatively low binding strength and water resistance. Soy flour or proteins, however, are a relatively cheap raw material and are an environmentally friendly and renewable material.

Li et al. (Li K., Peshkova S., Geng X., 2004 Investigation of soy protein-Kymene® adhesive systems for wood composites. J. Am. Oil Chem. Soc. 81 , 487-491.) described the combination of soy proteins with Kymene®, a commercial polyamide-epichlorohydrin (PAE) used in the paper industry for increasing the "wet strength". However, the resin system is a very viscous material with limited shelf life, as a result only applicable for rollcoat applications.

From EP2054461 , a glue composition is known on the basis of soy flour and a polyamidoamine-epihalohydrin polymer. Soy flour functions as a binding agent, however, requires the presence of a cross-linker. These glue compositions have the disadvantage that they have a high viscosity with an interesting solids content and as a result are difficult to apply. In order to bring the composition to a manageable viscosity, water is added. However, the additional water reduces the solids content and consequently the amount of active material. Moreover, in the production of board material the water has to be removed from the final product, at the cost of time, productivity and energy.

The solids content of PAE/soy flour compositions can be increased by adding, for example, urea or glycerol. WO 2011/025911 describes an acid-treated soy flour solution, to which a significant amount of urea is added. This soy-urea glue composition can achieve a solids content of higher than 50% and thus has the advantage that less water is provided in the system. Soy-urea glues can be combined with PAE for obtaining a low-viscosity system which can be used both for MDF as, for example, particle board. However, these systems are less stable, experience a large variety in the field of physical characteristics of the board material and have a relatively low reactivity. Watery glue systems with improved reactivity are desired.

There remains a need in the industry for offering a solution to the above-mentioned problems. There is a need for a glue composition on the basis of soy flour or other vegetable flour which offers a solution to the above-mentioned problems when producing plywood, MDF or particle board.

The invention aims at providing a glue composition having high storage stability, better reactivity and good manageability. More particularly, it aims at providing a composition having a viscosity suitable for being provided on a wood mass by means of atomization or by a mechanical glue treatment. The invention also aims at providing a method in which the use of the glue composition results in board material meeting strict formaldehyde emission standards while achieving very good mechanical characteristics. In a first aspect, the invention relates to a glue composition suitable for manufacturing OSB (Oriented Strand Board), plywood board, fiberboard or particle board, as described in claim 1. The invention also provides a method for manufacturing the glue composition, according to claim 11. Further, the invention relates to methods for manufacturing board materials using this glue composition, as described in claims 16 and 17; as well as for covering these materials with a thin layer, such as veneer, paper or laminate, according to claim 18. In a third aspect, the invention relates to board material obtained according to a method of the invention, as described in claim 19 and 23.

In a last aspect, the invention relates to applications of the composition, namely as a glue for manufacturing OSB, plywood board, fiberboard or particle board; according to claim 24.

Further improvements and specifications are elaborated in dependent claims.

According to the invention, with a glue system based on a vegetable source of protein, a binding agent, such as preferably polyamidoamine-epihalohydrin, and a source of lithium or magnesium, preferably in oxide or hydroxide form, a board material can be manufactured showing a unique combination of extremely low formaldehyde emission and good mechanical strength. Further advantages are that no changes in the production process will be necessary and that raw materials can be applied which are commercially available at a low price. The bio-glue according to an embodiment of the invention can be applied as an alternative for an UF glue.

Unless otherwise defined, all terms used in the description of the invention, also technical and scientific terms, shall have the meaning as generally understood by the person skilled in the technical field of the invention. For a better evaluation of the description of the invention, the following terms will be explicitly explained.

In this document, "a" and "the" refer both to the singular and plural, unless the context clearly suggests otherwise. For example, "a segment" means one or more than one segment.

When "approximately" or "about" are used in this document with a measurable amount, a parameter, a period in time or a moment and the like, then variations are meant of +/- 20% or less, preferably +/- 10% or less, more preferably +/- 5% or less, still more preferably +/- 1% or less, and even still more preferably +/- 0.1% or less than and of the cited value, inasmuch as such variations are applied in the described invention. By this, however, it has to be understood that the amount of the value where the term "approximately" or "about" is used, is even specifically made known.

The terms "comprise", "comprising", "consist of, "consisting of, "provided with", "contain", "containing", "encompass", "encompassing", "include", "including" are synonyms and are inclusive or open terms which indicate the presence of what follows and which do not exclude or prevent the presence of other components, characteristics, elements, members, steps known from or described in the state of the art.

Citing numerical intervals by the end points encompasses all integers, fractions and/or real numbers between the end points, these end points included.

The present invention is based on the findings of the inventors that addition of lithium or magnesium to a watery, protein and binding agent-containing glue enhances the activity of the binding agent in the glue. By addition is meant that the contents are increased in respect to what is naturally present in the source of protein already.

In a first aspect, the invention relates to a bio-glue, more particularly a glue composition which is suitable for glueing lignocellulose-containing material. Due to this glue property, the bio-glue, according to an embodiment of the invention, can be employed for manufacturing lignocellulose-containing board materials. The lignocellulose-containing material consists of wood chips or fibers originating from hardwood or softwood, of known dimensions.

More particularly, the invention provides a glue composition for glueing lignocellulose-containing material for forming an OSB, plywood board, fiberboard or particle board, comprising water, a vegetable source of protein, a binding agent and a source of lithium or a source of magnesium.

In this document, the term binding agent refers to a substance which can interconnect the molecules of the vegetable source of protein; this can be in a chemically covalent manner as well as in a physical manner. Hereby, a network is formed from the protein molecules. Binding agents preferably are selected from the list of urea formaldehyde (UF), urea-melamine-formaldehyde (UMF), polymeric methylene diphenyl diisocyanate (PMDI), epoxide, polyethylene imine resin (PEI), cationic polymers, epichlorohydrin resin (pEPI), polyamidoamine resin (PAE), or mixtures thereof. Preferably, the binding agent is polymeric methylene diphenyl diisocyanate (PMDI), epoxide, polyethylene imine resin (PEI), cationic polymer, epichlorohydrin resin (pEPI), or PAE. This has the advantage that formaldehyde- containing material is avoided. Most preferably, the binding agent is PMDI or PAE. These are moisture-repellent cross-linkers. Selecting them has the advantage that the resulting board material can be applied in industry and in buildings.

In a preferred embodiment, a glue composition for glueing lignocellulose- containing material comprises water, a vegetable source of protein, a polyamidoamine-epihalohydrin polymer (PAE), and a source of lithium or a source of magnesium. The components of the watery glue composition are present in an amount and proportion suitable for glueing the lignocellulose-containing material; more particularly for manufacturing an OSB, plywood board, fiberboard or particle board.

In a preferred embodiment of a glue composition according to the invention, the source of protein has a protein content of at least 35% or 40%, preferably 45%, more preferably 50%, most preferred 60%. The protein content is measured according to known methods.

Preferably, a glue composition according to the invention is free from formaldehyde. This is beneficial for the environmental friendliness thereof.

In a preferred embodiment, a glue composition for plywood, MDF or particle board comprises: a solution of a vegetable flour, preferably soy flour in water, a binding agent, such as polyamidoamine-epihalohydrin polymer (PAE), and 1%-10%, preferably 1 %-5%, lithium oxide (Li₂0) or lithium hydroxide (LiOH), or 1%-20%, preferably 1 %-10%, magnesium oxide (MgO) or magnesium hydroxide (Mg(OH)₂), expressed on total solids content of the glue composition. More preferably, the glue composition comprises: a solution of a vegetable flour, preferably soy flour in water, polyamidoamine-epihalohydrine polymer (PAE), and 1 %-10%, preferably 1%-5%, lithium oxide (Li₂0) or lithium hydroxide (LiOH), or 1%-20%, preferably 1%-10%, magnesium oxide (MgO) or magnesium hydroxide (Mg(OH)₂), expressed on total solids content of the glue composition.

Most preferably, the glue composition comprises: a solution of a vegetable flour, preferably soy flour in water, polyamidoamine-epihalohydrine polymer (PAE), and 1%-10%, preferably 1%-5%, lithium oxide (Li₂0) or lithium hydroxide (LiOH), or 1%-20%, preferably 1%-10%, magnesium oxide (MgO) or magnesium hydroxide (Mg(OH)₂), expressed on total solids content of the glue composition.

Preferably, the source of protein is selected from soy, lupine, jatropha and wheat. For manufacturing the glue composition, preferably a source of protein is used which is in the form of a flour, concentrate or isolate.

A soy flour will be preferred. This material has a sufficiently high protein content, such that it can be employed, without further purification or enrichment, for manufacturing a glue composition according to a preferred embodiment of the invention.

Typically, soy flour has a composition consisting of 45-55 percent by weight of soy proteins. Although there are products with an even higher content of soy proteins, namely, soy protein concentrate with typically at least 65 percent by weight of protein and soy protein isolate with typically at least 85 percent by weight of protein, the use of soy flour is sufficient. This has the advantage that less production steps are required and consequently the cost price is lower. This is of importance for a competitive product, such as particle boards.

Soy flour is obtained by removing a part or the majority of the oil from the soy bean, by which a remaining flour is obtained which subsequently is ground extremely fine. The flour further preferably is denatured and possibly hydrolyzed.

Soy flour can be brought into a watery solution, wherein the solids content will be limited to less than 30%. A soy protein isolate (SPI) has a protein content of about 85%. This product has a very good water solubility. This has the advantage that it can be combined with a binding agent; preferably PAE of high molecular weight. These mostly are too viscous for being widely applicable. Preferably, a soy flour is applied in combination with a binding agent, preferably PAE of relatively low molecular weight, this is 2000-100,000 g/mol. This system is very interesting from an economic point of view and is well manageable in respect to viscosity and stability of the glue composition. In a preferred embodiment, the glue composition, more particularly the soy flour solution, according to the invention comprises a denaturation substance preferably chosen from the list of sodium hydrogen sulfite, 2-mercaptoethanol, guanidine derivatives or urea. Addition of this ingredient provides for that the protein molecules denature and in this manner the functional groups are easier approachable for the binding agent for forming a network.

In a preferred embodiment, the glue composition comprises urea. Using urea has the advantage that the solids content of the glue can be increased even further. Further, the natural formaldehyde emission is reduced.

In order to avoid the forming of ammonia from urea by the effect of urease, the glue composition, preferably soy flour solution, can be brought to at least 80°C for a certain time, urease inhibitors can be added, the glue composition can be brought into an acidic environment, or a protein-containing flour with a very low urease content can be applied. By adding urea, a functional cross-linker is added and the solids amount can be increased to above 60%. Also with high solids content, the viscosity of the urea-glue solution remains lower than 10 Pa.s. The presence of urea results in that the glue composition is better mechanically applicable. Preferably, a glue composition according to the invention has a solids content of at least 30%, preferably 35%, most preferably 40%. The advantage of the glue composition being in concentrated form is that less water has to be transported.

In a preferred embodiment of a glue composition according to the invention, the solids content of the denaturation substance, such as urea-soy flour solution, is at least 40%, preferably at least 45%, more preferably at least 50%, most preferably at least 55%. Reduction of the amount of water is advantageous for reducing transport costs. It also has the advantage that less water has to be removed during the production process of board material.

Preferably, in a glue composition according to the invention, a weight ratio of source of protein in respect to a binding agent, preferably PAE, is applied of 70:30

- 95:5; preferably 80:20 - 90: 10. More preferably, in a glue composition according to the invention a weight ratio of source of protein in respect to binding agent, preferably PAE, is applied of 70:30 - 95:5; preferably 80:20 - 90:10.

In a preferred embodiment, the weight ratio of solid matter denaturation substance - urea-soy flour solution, preferably urea-soy flour solution, in respect to solid matter/binding agent, preferably PAE, is 70:30 - 95:5; preferably 80:20 - 90:10.

In a preferred embodiment, the weight ratio of solid matter denaturation substance

- soy flour solution, preferably urea-soy flour solution, in respect to solid matter/binding agent, preferably PAE, is 70:30 - 95:5; preferably 80:20 - 90:10.

The higher the ratio, the costlier the glue composition. Moreover, the employed amount of binding agent, preferably PAE, becomes smaller. This has the consequence that the resulting board material has too little resistance against moisture. Most preferably, the ratio source of protein/binding agent is about 8. In an alternative embodiment, the soy flour is replaced by another vegetable flour, such as, for example, lupine flour, jotropha flour or wheat flour.

As a magnesium source, preferably magnesium oxide or hydroxide is applied. An amount suitable for use in a glue composition according to the invention is 1-20% MgO or Mg(OH)2; expressed in respect to the total solids content of the glue mixture.

Magnesium oxide is a white odorless solid mineral which is found in nature. Magnesium oxide is hygroscopic and reacts with water to forming magnesium hydroxide, which has low solubility in pure water. For easiness of use, preferably magnesium hydroxide is chosen.

The addition of magnesium oxide and magnesium hydroxide to the source of protein/PAE or source of protein/binding agent glue system, with preferably soy flour as a source of protein, had a positive influence on the viscosity of the glue composition, even with higher dosage. This was unexpected, as it was expected that the addition would increase the viscosity of the glue. Moreover, these glue additives had a significant positive impact on the glue reactivity. Physical parameters, such as transverse tensile strength, bending strength and Young's modulus improved in respect to a glue composition without these additives.

In a preferred embodiment, the amount of magnesium oxide and/or magnesium hydroxide to the solid matter of the soy flour/PAE or soy flour/binding agent glue mixture is 1%-20%, preferably 2% to 10%. In another preferred embodiment, the amount of lithium oxide and/or lithium hydroxide is 1 % to 10% of the total solid matter of the glue mixture. Most preferably, the amount is 1% to 5%. This concentration range has the advantage that the impact on viscosity is extremely small, that the amount of binding agent, preferably PAE, can be reduced and that the technical characteristics are improved both in variation as well as in absolute value.

The use of higher amounts of alkaline metal/alkaline earth metals allows further reducing the amount of binding agent, preferably PAE. This is economically favorable, as binding agent, preferably PAE, in solid matter is the most expensive component in the glue composition. A glue composition according to an embodiment of the invention can be employed without addition of a cross-linker, such as polymeric methylene diphenyl diisocyanate (PMDI).

Preferably, lithium hydroxide is applied as a source of lithium. An amount suitable for use in a glue composition according to the invention is 1%-10% lithium hydroxide; expressed to the total solids content of the glue mixture. Lithium oxide or hydroxide can result in a significant improvement of reactivity and mechanical characteristics with a very low dosage. This low dosage can keep the increase of viscosity within acceptable limits.

Adding other metal oxides and metal hydroxides from the group of alkaline and alkaline earth metals, already with low concentrations will lead to a fast increase of viscosity and to reduction of the pot life.

Sodium and potassium oxide or hydroxide resulted in a strongly increasing viscosity with higher dosage. The shelf life of the glue compositions was unsatisfactory. Moreover, sodium and potassium ions are undesired in respect to the combustion properties of the final product. They will lead to corrosion and fouling problems in steam plants.

Calcium hydroxide in combination with soy flour will result in lump-shaped aggregates when being used in amounts higher than 10% on dry matter basis.

In a preferred embodiment, the glue composition has a viscosity of 2 to 10 Pa.s. Glues with this viscosity can be atomized as well as mechanically provided between wood particles or on wood. The glue composition can be prepared in various manners. Either lithium or magnesium in hydroxide or oxide form is added to the soy flour solution and the polyamidoamine epoxide resin is added thereto. Or the lithium or magnesium in hydroxide or oxide form is added to a mixture of soy flour solution with polyamidoamine epoxide resin. A third possibility consists in adding the lithium or magnesium in hydroxide or oxide form to the polyamidoamine epoxide resin prior to mixing with the soy flour solution. These three systems offer similar results. However, with addition to a binding agent, preferably PAE, a reaction between products was observed. Preferably, the glue composition is produced by sequentially adding the lithium or magnesium in hydroxide or oxide form to the flour solution and only afterwards adding the polyamidoamine epoxide resin to this mixture.

A glue composition according to an embodiment of the invention is suitable for glueing lignocellulose-containing wood mass, such as wood chips, particles or fibers.

The glue composition preferably is obtained as follows: dispersing and preparing solution of vegetable source of protein in water, adding lithium or magnesium in hydroxide or oxide form to the vegetable source of protein, and subsequently to a polyamidoamine-epihalohydrin polymer; or adding lithium or magnesium in hydroxide or oxide form to a mixture of vegetable source of protein/PAE or another mixture of vegetable source of protein/binding agent; optionally adding a denaturation substance, such as urea.

In a further aspect, the invention relates to a method for manufacturing board materials, such as OSB, fiberboard, MDF, HDF or particle board, as well as for manufacturing plywood.

To this aim, a glue composition according to an embodiment of the invention is used together with a lignocellulose-containing wood mass, such as wood chips, particles, fibers or veneer. Depending on the final product, in the glueing step the lignocellulose-containing wood mass has a moisture content of 2% (particle board) up to even 160% (MDF). If necessary, the glue-treated material can be dried.

Additives can be provided on the lignocellulose-containing material, such as a hydrophobic-making agent, anti-foaming agents, fungicides and other agents inhibiting microbial decomposition. These additives can be brought onto the lignocellulose-containing material either separately or together with the glue composition. The glue composition is provided on the lignocellulose-containing material in a known manner, for example, by spraying on or mechanical glue treatment. When producing particle board, an amount of glue composition of 5% by weight to 15% by weight is applied, calculated as solid matter of glue in respect to dry weight of wood. More preferably, an amount between 6 and 12 % by weight is applied, depending on the type of product and the technical characteristics to be achieved. For manufacturing fiberboard, preferably 10 to 18% glue on wood is used.

For manufacturing an OSB, fiberboard or particle board, one preferably proceeds as follows: employing a glue composition according to an embodiment of the invention, glue-treating a wood mass with the glue composition while making use of 5%-15% solid matter of glue composition on wood, pressing of the glue-treated wood mass at a press temperature of 180°C-250°C and preferably with a pressure up to 10 N/mm² for forming the board material. The glue treatment of the wood mass can make use of various known techniques which are suitable for applying glue, such as atomizing, spraying, mechanically glue-treating by friction, immersion, spreading or applying with rollers. The wood mass is formed to a mat, after which, at a suitable temperature and pressure, the mat is solidified to a board. The mentioned temperature range can be obtained by contact with a hot surface, such as, for example, a hot press, or by hot air or steam injection, or microwaves.

Preferably, the glue treatment is performed with 6% to 8% solid matter of glue on wood. In another preferred embodiment, a pressing time of 5-12 sec/mm is sufficient; more preferably max. 7-8 sec/mm.

The process results in the cross-linking of wood, PAE binding agent and polypeptides from the source of protein. It showed a considerable improvement due to the presence of the small cations lithium or magnesium. This was unexpected, as in the literature is described that even small amounts of magnesium or calcium salts interfere with the functionality of a binding agent, such as PAE.

For obtaining a board structure, use can be made of a mold or press.

The bio-glue can be employed for manufacturing a plywood board or a fiberboard with a density higher than 400 kg/m³. Herein, one preferably proceeds as follows: employing a glue composition according to an embodiment of the invention, providing the glue on a surface to be glued, providing a second surface to be glued on the glue-treated first surface, forming the board.

The bio-glue can be employed for manufacturing light-weight fiberboards, such as insulation materials or roof underlay boards. These light-weight materials are characterized by a specific weight of 50-400 kg/m³. The method preferably comprises the steps of: providing a glue composition according to an embodiment of the invention on a fiber material, forming the glue-treated fibers to a mat and pressing the latter, at a suitable temperature, to a board.

The bio-glue can be employed for glueing thin layers to a board material. By thin layers, materials such as veneer, paper or laminate are intended. By board materials, materials in board form are understood, such as fiberboard, OSB board or plywood board. These have in common that they are lignocellulose-containing materials. The method preferably comprises the following steps: employing a glue composition according to an embodiment of the invention, applying the glue composition on a surface to be glued, bringing the glue-treated surface together with the thin layer or the board material, whereby the board material covered with a thin layer is obtained. Typically, by a thin layer a material is meant having a thickness up to 2 mm.

For pressing on thin layers, use can be made of calender rolls.

A process according to an embodiment of the invention has the advantage that boards with improved and more stable physical values are obtained in respect to the use of a composition without alkaline earth metal or alkaline metal. Or also, the pressing time for obtaining a suitable board material can be reduced. The reduction of the pressing time is of high economic importance, as it determines the capacity of a production line.

In a following aspect, the invention relates to a board material obtained by a method according to an embodiment of the invention.

Preferably, the preferred method for manufacturing the glue composition is combined with the process of glue-treating and pressing. Producing an OSB, plywood board, fiberboard or particle board comprises: adding lithium or magnesium in hydroxide or oxide form to a mixture of binding agent, preferably polyamidoamine-epihalohydrin polymer (PAE), and a vegetable flour, preferably soy flour, glue-treating a wood mass with the glue composition, making use of 5%- 10% solid matter glue composition on wood, pressing the glue-treated wood mass at a temperature of 180°C - 230°C and preferably a pressure up to 10 N/mm², for forming an OSB, plywood board, fiberboard or particle board. More preferably, the method comprises: adding lithium or magnesium in hydroxide or oxide form to a mixture of polyamidoamine-epihalohydrin polymer (PAE) and soy flour, glue-treating a wood mass with the glue composition, using 5%-10% solid matter of glue composition on wood, pressing the glue-treated wood mass at a temperature of 180°C - 230°C and preferably a pressure up to 10 N/mm², for forming an OSB, plywood board, fiberboard or particle board.

Preferably, the board is pressed with a pressing time of 5-10 sec/mm, more preferably with a pressing time below 9 sec/mm, most preferably below 7 sec/mm. Obtaining good mechanical properties, such as tensile strength, with a shortened pressing time has the advantage that the production capacity can be increased. This is of high economic importance.

Preferably, the board material shows the characteristic that the transverse tensile strength is at least 0.35 N/mm² with a board thickness of 13 to 20 mm. The inventors have found that adding said glue additive resulted in an increase of the tensile strength. This could even be realized with shortened pressing times.

Preferably, the board material has a bending strength of at least 13 N/mm² with a board thickness of 13 to 20 mm.

Preferably, the board material has a Young's modulus of at least 1600 N/mm².

The herein above-mentioned parameters of transverse tensile strength, bending strength and Young's modulus can be measured by means of EN testing methods mentioned in the EN 312 and EN 319 standards.

In an embodiment, a particle board obtained with a glue composition according to an embodiment of the invention meets at least class P2 according to EN 3 2.

In a last aspect, the invention relates to the use of a composition such as formerly described as a glue for manufacturing an OSB, plywood board, fiberboard or particle board.

Preferably, a glue composition according to the invention is used as a glue for glueing lignocellulose-containing material for forming an OSB, plywood board, fiberboard or particle board; wherein the glue preferably is a formaldehyde-free glue. When using the glue composition, it is possible to produce board material with a very low formaldehyde emission and still a sufficient mechanic strength.

Below, the invention is described by means of not-limiting examples which illustrate the invention and which are not intended or may be interpreted as limiting the scope of the invention.

EXAMPLE Example 1 A reference glue solution was obtained by mixing a 50% watery soy flour/urea solution with a 20% watery PAE solution. Herein, a weight ratio of soy flour/urea in respect to PAE was managed of 81 :19 or 90:10, expressed in percentage of solid matter soy flour/urea in respect to percentage of PAE. For comparison, the procedure was repeated, however, with an addition of 6% of lithium hydroxide, magnesium oxide or magnesium hydroxide to the amount of solid matter of glue. For verifying the impact of the form in which magnesium was added, also MgS0₄ was used as an additive. The amount of glue was 6 or 8 percent by weight (solid matter of glue to dry particle, % of solid matter). Pressing was performed at 200°C with a pressing caliber of 13 mm, resulting in a pressure build-up towards 8 N/mm² With the application of these glue compositions, particle boards having a thickness of approximately 13 mm were produced.

As a measure for the quality of the particle board, thickness (in mm), density (in kg/m³), the transverse tensile strength, bending strength and Young's modulus (in N/mm²) were determined according to EN testing methods stated in EN 312. The respective data are stated in Table 1-7 (/ = not measured).

Table 1 : 8% solid matter of glue, soy flour/PAE 81 :19, 10 seconds/mm board thickness

Table 2: 8% solid matter of glue, soy flour/PAE 81 :19, 8 seconds/mm board thickness

Thickness Density Tensile Bending Young's strength strength modulus

Ref 14.16 604 0.19 7.3 1274

+ 6% LiOH 13.36 644 0.58 9.2 1289

+ 6% Mg(OH)₂ 13.3 644 0.66 10.6 1233

+ 6% MgO 13.45 627 0.6 9.6 1218 Table 3: 6% solid matter of glue, soy flour/PAE 81 :19, 10 seconds/mm board thickness

Table 4: 6% solid matter of glue, soy flour/PAE 81 :19, 8 seconds/mm board thickness

Table 5: 8% solid matter of glue, soy flour/PAE 90:10, 10 seconds/mm board thickness

Table 6: 8% solid matter of glue, soy flour/PAE 90:10, 8 seconds/mm board thickness

Thickness Density Tensile Bending Young's strength strength modulus

Ref 13.78 585 0.26 6.1 1101

+ 6% LiOH 13.18 623 0.43 8.1 1452

+ 6% Mg(OH)₂ 13.3 610 0.38 8.2 1593

+ 6% MgO 13.5 627 0.37 8 1568 Table 7: 6% solid matter of glue, soy flour/PAE 90:10, 10 seconds/mm board thickness

From the above results, it becomes clear that the addition of LiOH, Mg(OH)₂ or MgO results in an improvement of the tensile strength in respect to the glue composition without this additive. From the comparison with MgS0₄ addition, it becomes clear that the form in which magnesium is added does play a role in obtaining an improved tensile strength. Moreover, with these additives the bending strength and Young's modulus can be increased as well. From the above data, it also becomes clear that the pressing time can be reduced.

It is presumed that the present invention is not limited to the embodiments described herein above and that some adjustments or modifications can be added to the described examples without revaluing the added claims.

Example 2

A reference glue solution was obtained by mixing a 50% watery lupine flour/urea solution with a 20% watery PAE solution. Herein, a weight ratio of lupine flour/urea in respect to PAE was managed of 85:15, expressed in percentage of solid matter soy flour/urea in respect to percentage PAE.

For comparison, the procedure was repeated, however, with an addition of 6% of magnesium hydroxide to the amount of solid matter of glue. The amount of glue was 8 percent by weight (solid matter of glue on dry particle, % solid matter).

Pressing was performed at 200°C with a pressing caliber of 13 mm, resulting in a pressure build-up towards 8 N/mm². With the application of these glue compositions, particle boards having a thickness of approximately 13 mm were produced. As a measure for the quality of the particle board, the transverse tensile strength, bending strength and Young's modulus were determined according to EN testing methods stated in EN 312. The respective data are stated in Table 8.

Table 8: 8% solid matter of glue, lupine flour/PAE 85:15, 9 seconds/mm board thickness

Example 3

In this example, a reference glue solution was prepared by mixing a 50% watery wheat protein concentrate/urea solution with a 20% watery PAE solution. Herein, a weight ratio of wheat flour/urea in respect to PAE was managed of 81 :19, expressed in percentage of solid matter soy flour/urea in respect to percentage PAE. The wheat protein concentrate was obtained after enzymatic modification and had a protein content of more than 60%.

Subsequently, glue compositions according to the invention were prepared, making use of wheat protein concentrate as vegetable raw material, urea, a 20% PAE solution and Mg(OH)₂. Pressing was performed at 200°C with a pressing caliber of 13 mm, resulting in a pressure build-up towards 8 N/mm²

With the application of these glue compositions, particle boards having a thickness of approximately 13 mm were produced.

As a measure for the quality of the particle board, the transverse tensile strength, bending strength and Young's modulus were determined according to EN testing methods stated in EN 312. The respective data are stated in Table 9.

Table 9: 8% solid matter of glue, soy flour/PAE 81 :19, 10 seconds/mm board thickness

Thickness Density Tensile Bending Young's strength strength modulus

Ref 14.38 582 0.04 5.8 1206

+ 6% Mg(OH)₂ 13.18 631 0.39 9.1 1508

+ 4% Mg(OH)₂ 13.09 621 0.41 10.2 1754

Claims

1.- A glue composition for glueing lignocellulose-containing material, comprising:

- water,

a vegetable source of protein,

a binding agent,

and a source of lithium or a source of magnesium.

2.- Glue composition according to claim 1 , wherein the binding agent is polyamidoamine-epihalohydrin polymer (PAE).

3. - Glue composition according to claim 1 or 2, wherein the source of protein has a protein content of at least 35%.

4. - Glue composition according to any of the claims 1-3, wherein the binding agent is present in a weight ratio of source of protein in respect to binding agent of 70:30 - 95:5.

5.- Glue composition according to any of the claims 1-4, wherein the source of lithium or the source of magnesium is in the form of an oxide or hydroxide.

6. - Glue composition according to claim 1-5, wherein the source of protein has been selected from soy, lupine, jatropha and wheat; preferably in the form of a flour, concentrate or isolate.

7. - Glue composition according to any of the claims 1-6, wherein the source of lithium is present in an amount of 1%-10% by weight and/or the source of magnesium is present in an amount of 1%-20% percent by weight.

8. - Glue composition according to any of the claims 1-7, wherein the glue composition has a content of solid matter of at least 30%.

9. - Glue composition according to any of the claims 1-8, with the characteristic that the composition is free from formaldehyde.

10.- Glue composition according to any of the claims 1-9, further comprising a denaturation substance chosen from the list of sodium hydrogen sulfite, 2- mercaptoethanol, guanidine derivatives or urea.

11.- Method for manufacturing a glue composition suitable for preparing an OSB, plywood board, fiberboard or particle board, comprising the steps of:

adding a source of lithium or magnesium, preferably in hydroxide or oxide form, to a vegetable source of protein and subsequently to a binding agent, preferably polyamidoamine-epihalohydrin polymer (PAE); or

- adding a source of lithium or magnesium, preferably in hydroxide or oxide form, to a vegetable source of protein or to a vegetable source of protein/binding agent blend, wherein the binding agent preferably is PAE; optionally adding a denaturation substance.

12.- Method for manufacturing an OSB board, fiberboard or particle board, comprising:

employing a glue composition according to any of the claims 1-10;

glue-treating a wood mass with the glue composition, making use of 5%- 15% solid matter glue composition on wood,

- possibly drying the glue-treated wood mass,

pressing the glue-treated wood mass at a press temperature of 180°C- 250°C for forming the board material.

13. - Method according to claim 12, wherein the glue treatment is performed with 6% to 8% of glue solid matter on wood.

14. - Method according to claim 11 or 13, wherein a pressing time of 5-12 sec/mm is sufficient.

15.- Method according to claim 14, with a pressing time of max. 7-8 sec/mm.

16.- Method for manufacturing a plywood board or a fiberboard having a density higher than 400 kg/m³, comprising the steps of:

employing a glue composition according to any of the claims 1-10,

- providing the glue on a surface to be glued of a wooden board material or wood fiber, providing a second surface of a wooden board material or a wood fiber to be glued on the glue-treated first surface, and

forming the board,

possibly repeating the above-mentioned steps.

17. - Method for manufacturing a light-weight fiberboard, such as insulation materials or roof underlay boards characterized by a specific weight of 50-400 kg/m³, comprising the steps of: providing a glue composition according to any of the claims 1-10 on a fiber material, forming the glue-treated fibers to the board.

18. - Method for providing a thin layer, such as veneer, paper or laminate, on a board material, such as a particle board, OSB board or plywood board, comprising the steps of:

employing a glue composition according to any of the claims 1-10,

- providing the glue composition on a surface to be glued,

bringing together the glue-treated surface with the thin layer or the board material.

19. - Board material obtained by a method according to any of the claims 12-18, with the characteristic that the board has a transverse tensile strength of at least

0.35 N/mm² with a board thickness of 13 to 20 mm, as measured according to testing methods described in standard EN 319.

20. - Board material according to claim 19, with the characteristic that the board has a bending strength of at least 13 N/mm² with a board thickness of 13 to 20 mm, as measured according to testing methods described in standard EN 319.

21. - Board material according to claim 19 or 20, with the characteristic that the Young's modulus of the board is at least 1600 N/mm² with a board thickness of 13 to 20 mm, as measured according to testing methods described in standard EN 312.

22. - Board material according to any of the claims 19-21 , with the characteristic that the board material meets the P2 class according to EN 312.

23. - Particle board obtained with a glue composition according to any of the claims 1-10, with the characteristic that the particle board meets at least the class P2 according to EN 312.

24.- Use of a composition according to any of the claims 1-10, as a glue for glueing lignocelluiose-containing material for forming an OSB, plywood board, fiberboard or particle board.

25.- Use according to claim 24, wherein the glue is a formaldehyde-free glue.