WO2021005266A1

WO2021005266A1 - Resin composition

Info

Publication number: WO2021005266A1
Application number: PCT/FI2020/050479
Authority: WO
Inventors: Tiina PESONEN; Peter LINGENFELTER; Seppo Havuaho; Marko Lindgren; Marika JÄNIS; John QUIBUYEN
Original assignee: Prefere Resins Finland Oy
Priority date: 2019-07-05
Filing date: 2020-07-02
Publication date: 2021-01-14
Also published as: EP3994190A1; FI129584B; FI20195614A1

Abstract

The present invention concerns a resin composition comprising a resin containing a condensate of formaldehyde, lignin-comprising phenolic component and protein isolated from cereal grains and a process for the production of such composition, as well as end- uses of the resin composition. In particular, the present invention relates to a resin composition having especially low free formaldehyde concentration and to a process for the production of such composition.

Description

RESIN COMPOSITION

Background of the Invention Field of the Invention

The present invention concerns a resin composition comprising a resin containing a condensate of formaldehyde, a phenolic component and a protein component, and a process for the production of such composition, as well as end-uses of the resin

composition. In particular, the present invention relates to a resin composition having a low free formaldehyde concentration and to a process for the production of such compositions.

Description of Related Art

The synthetic binders currently in use for the production of wood-based materials enable the production of wood-based materials with specific properties for different applications. Especially phenolic resins allow the production of materials for use in wet or outdoor areas. Phenolic resins are also widely recognized as impregnation resins.

Although these synthetically bound materials have a very low emission potential, especially when used indoors, aminoplast resins are met with skepticism in consumer circles because of their formaldehyde release. Such materials are also detrimental to the environment during subsequent disposal of the materials and products made from those. As a result, intensive investigations have been carried out in recent years on the use of natural resins based on renewable raw materials for example for certain wood-based material applications.

In addition, the availability of petrochemical raw materials, such as phenol, is limited and therefore it would be important to replace them with renewable natural raw materials such as lignin, which is obtained from wood and possesses a polyphenolic structure. At the same time, the adverse environmental impacts caused by phenol would be avoided. As alternative adhesives, soluble polymers are suitable, which polymers can be converted either thermally or by reaction with a reactive component into an insoluble form. The most common natural binders can be found in proteins, polysaccharides (such as starch derivatives), polyphenols (e.g. tannin, lignin) as well as resins and waxes.

The substitution of phenol-formaldehyde resins with renewable natural raw materials is already known. In published application WO2014/080033 a process for the production of a phenol- formaldehyde impregnation resin is disclosed, wherein phenol is replaced with lignin to an extent of 60 to 100%. In the publication, the use of mixtures of water and tetrahydrofuran, water and ammonia and water and ethyl acetate is mentioned for the dissolution of lignin.

The published patent application WO 01/59026 discloses the preparation of adhesives by copolymerization of hydrolyzed vegetable protein that has been functionalized with methylol groups and one or more co-monomers also having methylol functional groups. Preferred hydrolyzed vegetable proteins include hydrolyzed soy protein obtained from soy meal.

A disadvantage of the procedure described in WO 01/59026 is that the developed binder combinations, with swelling values of 13.6 to 57.1% after 24 hours of water storage or 30.6 to 167.7% after 2 hours of cooking, are in no way suitable for the production of swellable fiber boards with increased moisture resistance requirements. In addition, only high-molecular price-intensive hydrolyzed soy protein agricultural products are used for the co-condensation.

US 10,125,295 B2 describes one type of protein adhesive containing lignin and ground plant meal or isolated polypeptide compositions obtained from plant biomass. Other types protein adhesives described therein contain a plant protein composition and either a hydroxyaromatic/aldehyde, urea/aldehyde, or amine/aldehyde component.

A binder for the production of swell-treated materials consisting of a phenol-formaldehyde resin component and protein-containing component is known from publication

EP1318000. Significant disadvantages of the known binders for wood materials with proportionate or complete substitution of phenol-formaldehyde resins by vegetable proteins are: For the substitution high molecular weight protein products, preferably used on soybean basis, which offer no price advantage over raw materials for the production of industrial phenol- formaldehyde resins or are even more expensive and their use as binders in wood-based materials usually leads to higher process costs, especially due to longer pressing times. In addition, wood materials produced with such binders have no improved properties, especially moisture resistance, compared to wood materials with exclusive phenol- formaldehyde-resin bond. Often the addition of protein even leads to a deterioration of the properties.

Summary of the Invention

It is an object of the present invention to eliminate at least part of the problems related to prior art and achieve an improved resin composition.

Thus, the present invention concerns a resin composition comprising a resin containing a condensate of formaldehyde, a phenolic component and a protein component. At least part of the phenolic component consists of isolated lignin.

In particular, the invention concerns a resin composition having an extremely low free formaldehyde concentration. Such a feature is preferably achieved by utilizing both protein and lignin in the resin comprised in the resin composition.

The present invention also concerns a process for the production of resin compositions. In the process, formaldehyde is condensed with a protein and a material containing phenolic OH groups, at least part of which material consists of lignin, in the presence of alkaline catalyst at an elevated temperature in order to form a resin. Thus, both protein and lignin are present in the reaction mixture already during the condensation reaction of

formaldehyde resin so that they become part of the forming condensate.

The use of the above mentioned resin composition as a high quality binder, which enables the production of particulate wood materials, such as plywood, LVL ( laminated veneer lumber ), chipboard, MDF ( medium density fiberboard), HDF ( high density fiberboard) and OSB ( oriented strand board), and as an impregnation resin are also covered by the invention.

In addition, the present invention concerns an essentially phenol-free resin composition wherein the phenol has been essentially replaced by lignin and a protein component.

The invention is based on the idea that a part or all of the phenol of a phenol-formaldehyde resin is replaced by lignin and protein. Thus, a modified phenol-formaldehyde-resin into which the lignin and protein are condensed during resin production is obtained, wherein the resin has an extremely low level of free formaldehyde.

In the process the phenolic component and the protein are first brought into the liquid phase by at least essentially dissolving or dispersing them in water, in a solvent or in a solvent mixture, after which formaldehyde is added into the liquid composition thus obtained in the presence of an alkaline catalyst to bring about a condensation reaction between formaldehyde, phenolic component and protein. Alkali is being fed gradually into the liquid stage, whereby the reaction of formaldehyde with the phenolic groups can be taken to completion.

According to the invention, a resin composition having extremely low free formaldehyde concentration is accomplished, which resin composition comprises a resin containing a condensation product of formaldehyde, lignin-comprising phenolic component and protein, wherein the concentration of free formaldehyde in the resin composition is not more than 1 wt.-%, especially not more than 0.5 wt.-%, for example 0.05 to 1.0 wt.-%.

More specifically, the resin composition according to the invention is mainly characterized by what is disclosed in the independent claims.

Considerable benefits are achieved with the present invention. In embodiments of the invention, phenol in the phenol-formaldehyde resin is partially or completely replaced with lignin and protein, thus allowing for even a complete avoidance of the use of the phenol which is considered a toxic chemical. In addition to the lignin contained in the phenolic component, the protein effectively binds formaldehyde. Thus, extremely low levels of free formaldehyde are achieved. The resin composition of the present invention also has a reduced thickness swelling, whereby it does not affect the processing and use of the composition for example in board applications. Preferably, the thickness swelling of the composition after 24 hours of water storage is at a level of less than 12%.

In addition, the process of the present invention allows the control and adjustment of the reactivity of the condensation reaction between phenolic component, protein and formaldehyde. In the process, the resin can be condensed so that essentially all free formaldehyde is reacted. Thus, extremely low levels of free formaldehyde are achieved by the process according to embodiments of the invention and by the use of lignin and protein, whereby the composition can be used in many applications in which low formaldehyde levels are required. At the same time, it is possible to render the viscosity of the resin to a level allowing its use in paper impregnation applications. Such impregnated fiber sheets can be used for the production of composite veneer products, for example.

The resin composition produced by the process of the invention or a resin having the corresponding composition is thus suitable for general use as a binder or as a substitute for conventional impregnation resins e.g. in film and core papers. In addition to such uses of the binders and impregnation resins, potential applications for the compositions are as binders in various fiberboards, for example.

Brief description of the drawings

Shown in figures 1 and 2 are binding results achieved by p-LPF (protein-lignin-phenol- formaldehyde resin) binder and a reference LPF (lignin-phenol-formaldehyde resin) binder on different woods (Fig. 1 - birch, Fig. 2 - spruce).

Embodiments

In the present context, percentages refer to percentages by weight, unless otherwise stated.

By the terms“solvent” and“actual solvent” is hereby referred to a solvent other than water. The resin composition of the present invention comprises a resin containing a condensate of formaldehyde, a phenolic component and a protein component, wherein the phenolic component comprises lignin. Thus, the resin is a reaction product obtained via a polymerization reaction of these components.

According to a preferred embodiment at least 10 % by weight of the phenolic component consists of isolated lignin.

Preferably, the lignin content of the resin condensate is 10 to 50 % by weight, more preferably 10 to 30 % by weight, calculated from the total weight of the resin condensate.

The isolated lignin used in the present invention is especially lignin obtained from a biomass, such as wood or annual or perennial plants or, correspondingly, lignin obtained from other lignocellulosic material. In particular, material isolated from spent liquor obtained from cooking of biomass is used as the lignin starting material.

As examples of lignin starting material to be used, mention may be made of lignin isolated from biomass by an alkaline cooking process, such as kraft lignin (i.e. lignin from sulphate process) or soda lignin (i.e. lignin from soda pulping). The use of organosolv lignin (i.e. lignin obtained from organosolv pulping) is also possible in the process. As lignin starting materials that can be used, mention can also be made of pyrolytic lignin, steamed lignin, diluted acid lignin and alkaline oxidative lignin. Mixtures of the above-mentioned lignin starting materials may also be used as the lignin starting material. According to a preferred embodiment the molecular weight of the used lignin is in the range of 3,500 to 15, 000 Da, preferably 10,000 Da or less. Preferably, the isolated lignin used is Kraft lignin having a molecular weight of less than 10,000 Da.

In addition to lignin, the lignin starting material may also contain other materials, such as extracts or carbohydrates, such as cellulose or hemicellulose or degradation products thereof. In general, the lignin starting material comprises at least 90 weight-%, most suitably at least 95 weight-%, especially at least 98 weight-% lignin.

The lignin starting material may be in the form of a solid, such as powder. This type of lignin starting materials is represented by commercially marketed lignin products. It is also possible to use liquid stage lignin, as will be described in more detail below.

According to one embodiment the lignin is used either as a powder or an aqueous slurry having a lignin dry matter content which is most suitably over 50 weight-%, especially at least 60 weight-%, preferably at least about 70 weight-%, e.g. about 75 weight-%.

According to one embodiment, the phenolic component further comprises 0.1 to 30 % by weight, for example 5 to 20 % by weight, phenol, wherein the resin comprised in the resin composition is a condensation product of formaldehyde, protein, lignin and phenol.

According to one embodiment the resin comprised in the resin composition comprises no phenol, wherein the resin is a phenol- free resin consisting of a condensation product of formaldehyde, protein and lignin.

In one embodiment the phenol-free resin is produced by using essentially only lignin as the material comprising phenolic OH groups, wherein the resin composition comprises a condensation product of formaldehyde, lignin and protein. According to such embodiment, in practice at least 90 weight-%, preferably at least 95 weight-%, most preferably at least 98 weight-%, or even 100 weight-% of the raw material comprising phenolic OH groups is lignin.

In one application, another biomass, such as tannin, is used as the material comprising phenolic OH groups in addition to lignin, and optionally phenol.

The use of minor amounts (10 weight-%, most suitably not more than 5 weight-%, especially not more than 2 weight-%) of cresol or resorcinol or a mixture thereof is also possible in the process.

According to a preferred embodiment the protein component is isolated from cereal grains, and more preferably the protein is a low molecular weight protein selected from wheat proteins, corn proteins and mixtures thereof. Preferably, the protein has a molecular weight of 500 to 30,000 Da, in particular about 1,000 to 25,000 Da and preferably has a polydispersity of 1.0 to 2.5. According to one embodiment the protein content of the resin condensate is 1 to 20 % by weight, preferably 1 to 10 % by weight, calculated from the total weight of the resin condensate.

According to one embodiment, formaldehyde is used in the reaction as an aqueous solution having a formaldehyde concentration of 30 to 60 weight-%, typically 50 to 60 weight-%.

According to one application, technical grade formaldehyde is used. Technical grade formaldehyde starting material may among other things contain metallic impurities as well as some, typically not more than 12 weight-% methanol. According to a preferred embodiment, the formaldehyde content of the technical grade formaldehyde used is most suitably at least 95 weight-%.

The finished resin composition is most preferably in the form of an aqueous mixture in which the dry matter content with respect to the resin composition is higher than about 20 wt.-% and usually not more than about 70 wt.-%, typically the dry matter content of the resin composition is between 30 and 60 wt.-%.

According to one embodiment the resin composition has a free formaldehyde

concentration of not more than 1 weight-%, preferably less than 1 weight-%, more preferably not more than 0.5 weight-%, suitably 0.05 to 0.5 weight-%, more suitably 0 to 0.1 weight-%. This is achieved by utilizing both lignin and protein in the resin

composition, since both of these effectively bind formaldehyde. In addition, the production method of the present resin composition is significant for the low free formaldehyde concentration of the obtained resin composition.

According to one embodiment the resin composition of the present invention comprises 10 to 50 % by weight phenolic component, from which at least 10 % by weight is lignin, and 1 to 20 % weight protein.

Preferably, the resin composition comprises 50 to 100 % by weight, preferably 70 to 100 % by weight, of the resin containing a condensate of formaldehyde, a phenolic component and protein. The resin composition of the present invention may further comprise a common phenol- formaldehyde resin component which is crosslinked with the resin comprised in the resin composition. According to one embodiment, the resin composition comprises 0 to 50 % by weight, for example 10 to 30 % by weight, of a conventional phenol-formaldehyde resin.

The resin composition of the present invention is in itself already thermosetting, i.e.

addition of additives is not necessary in order to have it formulated into an adhesive or binder. The resin composition can, however, be further modified, for example by mixing it with extenders and cross-linkers. Thus, the resin composition may further comprise additives, such as fillers, extenders or cross-linking agents, or mixtures thereof, mixed with the resin of the resin composition.

Compounds that are known per se can be used as extenders, such as amide or amine compounds, such as urea, or monomeric, oligomeric or polymeric carbohydrates, such as sugars.

Compounds that are known per se can be used as cross-linkers, such as amine compounds, such as hexamethylene tetramine, or vinyl compounds, such as divinyl benzene.

The finished resin can be impregnated into the paper as such or formulated with additives and then compressed into a laminate under the influence of heat and pressure.

A paper impregnated with the resin produced by the process according to the invention or with a resin having a corresponding composition can be compacted into a laminate.

The present invention also relates to a process of preparing a resin composition. In the process formaldehyde is condensed with a protein and a material containing phenolic OH groups in the presence of alkaline catalyst in order to form a resin. In particular, the present process comprises the steps of condensing formaldehyde with a phenolic component together with a protein isolated from cereal grains, wherein at least 10 % by weight of the phenolic component consist of isolated lignin.

According to one embodiment, the production takes place by essentially dissolving or dispersing the lignin starting material and the protein in order to form a lignin-protein liquid composition. Formaldehyde, especially an aqueous solution of formaldehyde, i.e. formalin, is added to the liquid composition. The lignin, protein and formaldehyde are subsequently condensed at an elevated temperature until virtually all formaldehyde, i.e. at least 99 weight-%, more preferably at least 99.5 weight-%, most suitably at least 99.9 weight-% of the formaldehyde has reacted. The resin thus formed is recovered. According to one embodiment the protein-lignin liquid composition also comprises phenol, whereby the condensation reaction will occur between the lignin, protein, phenol and formaldehyde.

In particular, the lignin, protein, formaldehyde, and optionally phenol, are condensed at a temperature of about 50 to 90 °C until essentially all formaldehyde has reacted, whereafter the resin is collected.

According to one embodiment the protein and lignin are at least essentially dissolved at the beginning of the resin cooking into a mixture of water and solvent or water and phenol. In one embodiment all of the protein and lignin is dissolved. In one embodiment dissolution of the protein and lignin give a liquid phase containing protein and lignin which are dissolved or partially dispersed in the liquid phase. At least part of the required alkaline catalyst is included in the lignin-protein liquid composition. According to another embodiment of the present invention, both lignin and protein are dispersed to form a protein-lignin liquid composition. According to a further embodiment, the other of protein and lignin may be dissolved and the other may be dispersed, or protein and lignin may be both partly dissolved and partly dispersed. In embodiments wherein phenol is incorporated into the resin, an actual solvent is not necessarily needed since phenol is already in a liquid form, and in addition, it belongs to the group of aromatic alcohols thus being capable to replace the need for solvent. Phenol is mixed with water, whereafter the protein and lignin are dissolved or dispersed into the mixture.

The lignin, protein, formaldehyde, and optionally phenol, are most preferably condensed in liquid state. Typically that liquid state is formed by water and solvent, or optionally water and the phenol. The addition of water, and optionally solvent, at the beginning of the resin cooking makes controlling of viscosity possible during condensation to avoid excessive increase of viscosity at any reaction stage.

The catalyst can also be dosed in a number of portions, which also facilitates the control of proceeding of the condensation reactions. By dosing water and, optionally, a solvent, and the catalyst , it will be possible conduct the condensation reaction of the resin composition to a point where free formaldehyde has reacted completely or at least essentially completely.

If an actual solvent is used for dissolving or dispersing lignin and protein in addition to water, it is typically a polar liquid which is miscible with water.

As examples of the solvent, mention may be made of aliphatic and aromatic alcohols such as methanol, and aliphatic ketones such as acetone. The solvent is used in an amount sufficient to maintain a predetermined dry matter content in the mixture. In particular, the dry matter content of the mixture is adjusted to a value which allows for the further reaction of the mixture. In one embodiment, the dry matter content of the mixture is about 20 to 70 weight-%, in particular 30 to 70 weight-%.

In one application, the lignin and protein are dissolved or dispersed into a mixture of a solvent and water. Methanol or mixtures thereof, such as aqueous solution of methanol, are usually used as the solvent.

According to one embodiment the concentration of solvent in water is 0.1 to 30 weight-%, preferably 1.0 to 20 weight-%, in each case depending on the solvent used. For example, in the case of methanol, the concentration of methanol in water is usually about 1.5 to 15 weight-%, such as 1.6 to 12 weight-%.

According to one embodiment, the lignin and protein are dissolved or dispersed in a mixture of water, alkali catalyst and aliphatic or aromatic alcohol. The presence of solvent in the cooking stage allows for the resin to be condensed for a longer time without a too rapid increase in viscosity, and a low level of formaldehyde is achieved.

When lignin and protein are dissolved or dispersed in a water/methanol mixture, the resin remains soluble for a longer time and enables the control of viscosity during the

condensation reaction. This, in turn, makes it possible to react all or essentially all free formaldehyde, whereby the concentration of free formaldehyde after the reaction is not more than 1 weight-% based on the weight of the resin composition, in particular not more than 0.5 weight-%, for example 0.05 to 0.1 weight-%.

According to one embodiment, sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3), in particular as ammonium hydroxide, or a mixed catalyst system thereof, such as e.g. a mixture of sodium hydroxide and ammonia, or a mixture of sodium hydroxide and potassium hydroxide can be used as the catalyst in the reaction. Other nitrogen bases, such as organic amines, can also be used as the catalyst. The catalysts are preferably added to the mixture as aqueous solutions having a concentration that varies slightly according to the catalyst. According to one embodiment, the concentrations of sodium and potassium hydroxide, for example, are between 40 to 60 weight-%, for sodium hydroxide preferably about 50 weight-% and for potassium hydroxide preferably about 46 weight-%.

Below, the aqueous solution of sodium hydroxide is also termed”lye”.

The formation of a polymerization chain during the reaction can be influenced through the catalysts by accelerating the condensation reaction between formaldehyde, lignin, protein, and optionally phenol. The catalysts allow for the reacting of essentially all free

formaldehyde in a reasonable time, alternatively either at normal pressure or elevated pressure.

According to one embodiment the process according to the invention for the production of the resin composition involves several stages, comprising 2 to 10 stages. The process typically involves 2 to 3 stages, preferably 3 stages, in which case the addition of alkaline catalyst takes place gradually during the process in several stages. The gradual addition of alkaline catalyst enables the solids content of the mixture to be kept low during the reaction, allowing for an effective control of the viscosity. This in turn enables the viscosity of the reaction mixture to be kept low enough in order to be able to effectively carry out the condensation reaction.

’’Gradual addition” means that a longer time is used for the addition than would take if a predetermined amount is added at once (i.e. a“one-off addition” is made) without any interruption. The duration of addition is usually at least 2 times longer than would be required for a one-off addition, most suitably 5 to 100 times longer, e.g. 10 to 50 times longer.

The catalyst is usually added in two, three or more portions, in which case the reaction is allowed to proceed after the addition of one catalyst portion before the addition of the next portion.

In one application, 5 to 95 mol-%, for example 10 to 80 mol-% or 25 to75 mol-% of the total amount of catalyst are added in the first portion.

In a preferred embodiment, in the first step of the process according to the invention, lignin and protein are dissolved or dispersed into a mixture composed of water, optionally the solvent, and the catalyst, especially a water-soluble alkaline catalyst (optionally the first portion). Optionally the mixture further comprises phenol. Dissolving or dispersing takes place by stirring the mixture at room temperature (about 20 °C) or at an elevated temperature. The temperature is usually below 70 °C, most suitably below 65 °C, for example not higher than 60 °C. In one embodiment operation takes place at 30 to 50 °C, usually at 30 to 35 °C.

Dissolution or dispersion time is influenced by the chosen reaction conditions and materials, such as the lignin, protein, solvent/solvent mixture, catalyst and the dissolution or dispersion temperature being used. The dissolution or dispersion time varies between 0.5 and 2 hours, typically being about 1 hour. When the protein and lignin have been dissolved or dispersed into the mixture, the temperature of the mixture is raised typically above 60 °C, for example about 60 to 100 °C, preferably about 65 °C, and water is added (second portion). The calculated amount of formaldehyde is then added gradually while stirring the mixture typically for about 0.1 to 2 hours, preferably for about 15 to 60 minutes. After the addition of formaldehyde the temperature is raised above 80 °C, for example about 80 to 100 °C, preferably about 85 °C.

The condensation reactions between lignin, protein, formaldehyde, and optionally phenol, take place at this temperature. The reaction is continued for a period of 0.1 to 2 hours, typically for about 15 to 45 min, for example 30 min.

In a multi-stage embodiment, the second portion of the alkaline catalyst is added, the mixture is cooled to 80 °C or below, e.g. to a temperature range of 60 to 80 °C, and the condensation reaction is continued. In this way, the condensation reaction can be taken to completion, but if necessary, the second portion of the catalyst can be dosed even in more stages, for example 2 to 5, typically two stages.

After the addition of the second catalyst portion the mixture is being condensed.

Condensation takes place for a period of about 0,1 to 2 hours, e.g. about 1 hour. After this, the third portion of catalyst is optionally added and condensation is again carried out for about 0.1 to 2 hours, e.g. about 1 hour. Operation is continued in a corresponding manner, if the catalyst has been further divided into multiple proportions. After all catalyst has been added, the condensation reaction has been taken into completion.

Typically, after completion of the condensation reaction, the resin being formed is cooled to room temperature, i.e. about 20 °C, which is its typical storage temperature.

According to one embodiment the condensation reaction is continued until essentially all formaldehyde has reacted. As noted above, in a preferred application this means that at least 99 weight- % of the formaldehyde required for the reaction has reacted, more suitably at least 99.5 weight-%, for example 99.5 to 99.9 weight-%, most suitably 100 weight-%, of the formaldehyde required for the reaction has reacted. The reaction is typically continued until a predetermined viscosity is reached. The resin formed is collected. The resin is typically formulated for further use, as will be described below.“Collecting” comprises also the option that the resin is carried on for further use without isolation or without formulation.

In the process, the resin can be cooked in a non-pressurized reaction vessel, i.e. in an ordinary reactor which is operated under normal pressure, or alternatively in a pressure cooker (pressure vessel). In both cases the condensation reactor is most preferably equipped with devices for heating and cooling the reactor, as well as temperature sensors and temperature control. The non pressurized reaction vessel further most preferably comprises a condenser, such as a vertical condenser, which enables the condensation of the possibly evaporating solvent and its recycling to the reaction vessel. This also ensures that solvent for the resin is always available during the condensation reaction.

The catalyst system and dry matter influence the rate of development of the viscosity of the resin. By carrying out the condensation reaction in the manner described above, in which solvent for the lignin, such as methanol, or water is present during the reaction or phenol is used, and the catalyst is added gradually to the reaction mixture, the dry matter content can be raised without increasing the viscosity too much, i.e. above 10,000 cP.

In one application the Brookfield- viscosity of the produced resin is 20 to 10,000 cP, especially 20 to 1,000 cP, in particular 20 to 700, for example 20 to 500 cP or 200 to 700 cP.

According to a preferred embodiment the viscosity of the produced resin is on the same level as that of normal impregnation resins. A resin having a Brookfield viscosity of 20 to 50 cP is especially suited for impregnation of core paper. A resin having a Brookfield viscosity of 100 to 300 cP is in turn suited for impregnation of film paper.

According to one embodiment the finished resin composition is impregnated on film / core paper (60 to 250 g/m ). The amount of the resin composition varies between 20 to 50 % depending on the end use.

According to another embodiment the finished resin composition is used as a binder as such or it can be mixed with different additives, such as organic or inorganic fillers, extenders, crosslinking agents or water, or mixtures thereof, wherein a binder having a suitable viscosity level for bonding of wood or wood based materials is obtained.

According to what is stated above, the dry matter content of the reaction mixture with respect to the resin is typically about 20 to 70 weight-%. As required, it is possible to evaporate optionally used solvent, such as methanol, ethanol or acetone, away from the finished resin. In this way the resin becomes better suitable for various end-uses in which the presence of solvent is not allowed.

The concentration of solvent in the resin is typically 0 to 15 weight-%. The resin composition can thus also be recovered in a completely solvent-free form.

As required, optional solvents can also after evaporation be added back to the resin, or the evaporated solvent, such as methanol, ethanol or acetone, can be totally or partly replaced 15 e.g. with water in applications that do not allow the presence of said solvent at all or above a certain limit, such as e.g. over 5 weight-% based on the total weight of the resin.

For compressing, a multiple opening press can be used, in which compacting takes place under a pressure over 70 bar at about 140 to 150°C.

Alternatively, use can be made of a short cycle press, continuous press or some other method commonly used in the industry. The short cycle press used typically comprises 1 to 3 openings and its processing temperature is between 170 and 200°C.

When using a continuous press, typical process parameters include a pressure of 20 to 50 bar and a temperature of 170 to 180°C.

In the present invention, the lignin starting material, such as kraft lignin, is typically utilized as such and the reaction is conducted with protein, formaldehyde, and optionally phenol, whereby the product of the reaction consists of the reaction product between lignin, protein, formaldehyde, and optionally phenol.

The following non-limiting examples represent applications of the present technology. EXAMPLES

Example 1 - Production of resin composition comprising a resin consisting of a condensation product of protein, lignin and formaldehyde.

The resin composition was cooked in an ordinary reactor under normal pressure. The reaction involved a vertical condenser enabling the condensation of the possibly evaporating solvent back to the reaction mixture. In the first stage water I, methanol and catalyst, i.e. the first portion of the catalyst, comprising mere sodium hydroxide or sodium hydroxide in combination with either ammonia or potassium hydroxide, was dosed into the reactor. At this stage, pH of the reaction was 7 to 8.5. To this mixture was added the kraft lignin and wheat protein-containing component, whereafter the mixture was stirred for about 1 hour, keeping the temperature below 50 °C, generally between 30 and 35 °C. After stirring, the temperature of the mixture was raised to about 65 °C and water II added. Next, formalin was added into the mixture at a steady rate over a period of about 40 minutes. After the addition, the temperature of the mixture was raised to about 85 °C and the mixture was condensed for about 30 minutes. The mixture was subsequently dosed with catalyst II, i.e. the second portion of the catalyst, and the mixture was slightly cooled, to about 80 °C. The mixture was condensed at this temperature for about 1 hour. Catalyst III was added, i.e. the third portion of the catalyst, and the mixture condensed for another hour. The resin composition was finally cooled.

The following examples describe cooks conducted by the above-described process: Cooking example 1

Cooking example 2

Cooking example 3

Example 2 - Production of resin composition comprising a resin consisting of

condensation product of protein, lignin, phenol and formaldehyde.

The resin composition was cooked in an ordinary reactor under normal pressure. In the first stage water I, phenol and catalyst, i.e. the first portion of the catalyst, comprising mere sodium hydroxide or sodium hydroxide in combination with either ammonia or potassium hydroxide, was dosed into the reactor. At this stage, pH of the reaction was 7 to 8.5. To this mixture was added the kraft lignin and wheat protein-containing component, whereafter the mixture was stirred for about 1 hour, keeping the temperature below 50 °C, generally between 30 and 35 °C. After stirring, the temperature of the mixture was raised to about 65 °C and water II added. Next, formalin was added into the mixture at a steady rate over a period of about 40 minutes. After the addition, the temperature of the mixture was raised to about 85 °C and the mixture was condensed for about 30 minutes. The mixture was subsequently dosed with catalyst II, i.e. the second portion of the catalyst, and the mixture was slightly cooled, to about 80 °C. The mixture was condensed at this temperature for about 1 hour. Catalyst III was added, i.e. the third portion of the catalyst, and the mixture condensed for another hour. The resin composition was finally cooled.

The following examples describe cooking conducted by the above-described process:

Cooking example 4

Table 1. Analysis results of the resin composition according to cooking example 4.

Example 3- Binder composition and its properties

The resin composition (p-LPF resin) was used in a binder composition by mixing it with a binder composition (Prefere 24J401) and water. As a reference, a binder composition was also prepared by using lignin-phenol-formaldehyde resin (LPF resin), in which protein is not used. The veneer products have both birch veneer and spruce veneer therein.

Table 2. Binder compositions

Table 3: Production parameters of the veneer products.

The binding results of the p-LPF binder and the reference LPF binder on birch and spruce veneers are shown in figures 1 and 2. According to the results, the protein modified resin (p-LPF) has extremely low free formaldehyde concentration and its binding results corresponds to those without the protein additive. In addition, p-LPF binder functions in a same manner as LPF binder during the binding process.

Industrial Applicability

The present material can be used as binder or impregnation resin, and generally for replacement of conventional binder and impregnation resin.

In particular, the present material is useful in binder for the production of wood materials and the bonding of wood and wood-based materials. The swell-treated wood materials produced with the binder according to the invention, such as chipboard, fiberboard or OSB can after conditioning and calibrating either directly as floor, ceiling or wall panels and after coating with resin-impregnated papers, preferably with urea, melamine or phenol- formaldehyde resins, are processed into laminate flooring or panel elements.

The binder according to the present method can be used among others in the bonding of laminated veneer lumber (LVL), orient strand board (OSB), chipboard, medium density fiberboard (MDF) and high density fiberboard (HDF).

Citation List Patent Literature

WO 2014/080033

WO 01/59026

US10, 125,295 B2

EP 1318000

Claims

1. A resin composition comprising a resin containing a condensate of formaldehyde, a phenolic component and protein isolated from cereal grains, wherein at least 10 % by weight of the phenolic component consists of isolated lignin.

2. The resin composition according to claim 1, wherein the protein is a low molecular weight protein selected from wheat proteins, corn proteins and mixtures thereof.

3. The resin composition according to claim 1 or 2, wherein the protein has a molecular weight of 500 to 30,000 Da, in particular about 1,000 to 25,000 Da and preferably has a polydispersity of 1.0 to 2.5.

4. The resin composition according to any of the preceding claims, wherein the protein content of the resin condensate is 1 to 20 weight-%, preferably 1 to 10 weight-%, calculated from the total weight of the resin condensate.

5. The resin composition according to any of the preceding claims, wherein the lignin content of the resin condensate is 10 to 50 weight-%, preferably 10 to 30 weight-%, calculated from the total weight of the resin condensate.

6. The resin composition according to any of the preceding claims, wherein the isolated lignin is Kraft lignin.

7. The resin composition according to any of the preceding claims, wherein the resin is a phenol-free resin, the resin consisting of a condensation product of formaldehyde, protein and lignin.

8. The resin composition according to any of the preceding claims, wherein the

composition has a free formaldehyde concentration of not more than 1 weight-%, preferably not more than 0.5 weight-%, preferably 0.05 to 0.5 weight-%, more preferably 0 to 0.1 weight-%.

9. The resin composition according to any of the preceding claims, wherein the resin is further crosslinked with phenol-formaldehyde resin.

10. The resin composition according to any of the preceding claims, further comprising a filler, an extender and/or a cross-linking agent mixed with the resin.

11. Process of preparing a resin composition comprising the steps of condensing formaldehyde with a phenolic component together with protein isolated from cereal grains to form a resin condensate, wherein at least 10 % by weight of the phenolic component consists of isolated lignin.

12. The process according to claim 11, wherein

- formaldehyde is condensed with a protein and a material containing phenolic OH groups in the presence of alkaline catalyst in order to form a resin, and

- lignin, and optionally phenol, is used as the material containing phenolic OH

groups, and

further comprising the steps of

- dissolving or dispersing the lignin and protein in order to form a lignin-protein liquid composition,

- including at least a part of the required alkaline catalyst in the lignin-protein liquid composition,

- adding formaldehyde to the lignin-protein liquid composition, and

- condensing the lignin, protein, and optionally phenol, and formaldehyde in the liquid state until essentially all formaldehyde has reacted,

- collecting the resin thus formed.

13. The process according to claim 11 or 12, wherein the protein and lignin are dissolved or dispersed in a mixture of water and solvent or water and phenol.

14. The process according to any of claims 11 to 13, wherein the lignin is used either as a powder or an aqueous slurry having a lignin dry matter content which is most suitably over 50 weight-%, especially at least 60 weight-%, preferably at least about 70 weight-%, e.g. about 75 weight-%.

15. The process according to any of claims 11-14, wherein the protein and lignin are dissolved or dispersed by using a solvent which is a polar liquid which is miscible with water, such as an aliphatic or aromatic alcohol, such as methanol or ethanol, or an aliphatic ketone, such as acetone.

16. The process according to any of claims 11-15, wherein NaOH or KOH or ammonia or an organic amine, or a mixture of two or more substances is used as the catalyst.

17. The process according to any of claims 11-16, wherein the protein used is a low molecular weight wheat and/or com protein.

18. The process according to any of claims 11-17, wherein lignin, protein, and optionally phenol, and formaldehyde are condensed at a temperature of about 50 to 90°C until all formaldehyde has reacted, whereafter the resin is collected.

19. The process according to any of claims 11-18, wherein production of the resin composition is a multi-stage process, wherein addition of the alkaline catalyst takes place during the process in two or more stages.

20. The process according to any of claims 11-19, wherein the lignin and protein are first dissolved or dispersed into the mixture composed of water and solvent, or alternatively water and phenol, and the water-soluble alkaline catalyst (first portion), stirring the mixture at room temperature or at a slightly elevated temperature which is below 70°C.

21. The process according to any of claims 11-20, wherein after the lignin and protein have at least mainly dissolved or dispersed, the temperature of the liquid composition is raised above 60°C, for example about 65°C, and water is added, whereafter the calculated amount of formaldehyde is gradually added while stirring.

22. The process according to any of claims 11-21, wherein, after addition of

formaldehyde, the temperature is raised above 80°C, for example to about 85°C, in which temperature the condensation reaction between lignin, protein, and optionally phenol, and formaldehyde takes place.

23. The process according to any of claims 11-22, wherein the second portion of alkaline catalyst is added, the mixture is cooled to 80°C or below and the condensation reaction is continued.

24. The process according to any of claims 11-23, wherein the condensation reaction is continued until the free formaldehyde content of the resin composition is not more than 1 weight-%, e.g.0.1 to 1.0 %, preferably 0.05 to 0.5 %, more preferably 0 to 0.1 %, and its Brookfield viscosity is at least 20 cP and not more than 1000 cP.

25. The process according to any of claims 11-24, wherein the condensation reaction is conducted in a non-pressurized reaction vessel or in a pressure cooker, wherein the reactor is most suitably equipped with devices for heating and cooling the reactor, as well as temperature sensors and temperature control.

26. Use of the resin composition according to any of claims 1-10 in a binder composition in wood adhesive applications, such as adhesion of LVL, OSB, particle board, MDF and HDF.

27. Use of the resin composition according to any of claims 1-10 as an impregnation resin for impregnation of core paper, impregnation of film paper, production of plywood, LVL, chipboard or production of fiberboards, such as MDF (medium-density fiberboard) or HDF- (high- density fiberboard) boards, production of sandpaper, as beam glue, in wool resins, especially in mineral wool, such as glass wool or rock wool.