WO2021005270A1

WO2021005270A1 - An aqueous binder composition for curtain coating or extrusion coating

Info

Publication number: WO2021005270A1
Application number: PCT/FI2020/050485
Authority: WO
Inventors: Suvi Pietarinen; Saara LAAMANEN; Sanna VALKONEN; Mauno Miettinen
Original assignee: Upm-Kymmene Corporation
Priority date: 2019-07-11
Filing date: 2020-07-08
Publication date: 2021-01-14
Also published as: FI20195629A1

Abstract

An aqueous binder composition is disclosed. The aqueous binder composition can be prepared by using at least polymerizable substance, crosslinking agent, and at least one additive, wherein the aqueous binder composition has a extensional viscosity, as measured by filament break-up time, of at least 0.13 seconds, and wherein 5–99 weight-% of the polymerizable substance originates from lignin and wherein the crosslinking agent is an aldehyde. Further is disclosed a method for determining the amount of at least one additive needed for preparing an aqueous binder composition. Also different uses are disclosed.

Description

AN AQUEOUS BINDER COMPOSITION FOR CURTAIN COATING OR EXTRUSION COATING

TECHNICAL FIELD

The present disclosure relates to an aqueous binder composition. The present disclosure further relates to a method for determining the amount of at least one additive needed for preparing an aqueous binder composition. The present disclosure further relates to the use of a capillary break-up extensional rheometer and to use of the aqueous binder composition.

BACKGROUND

Lignin is a natural polymer, which can be ex- tracted from e.g. wood. As lignin is a natural biopol- ymer its use as a component in glues instead of synthetic materials has been investigated in order to come up with a more environmentally friendly adhesive composition. Especially, the ability to replace synthetic phenol in phenolic resins, such as phenol formaldehyde resin, has been the object of researches. Lignin can be used for the purpose of decreasing the amount of synthetic phenol in a resin composition. Lignin has previously been used for replacing phenol during the production of lignin- phenol-formaldehyde resin.

Resins or binder compositions can be used for the production of plywood. Plywood gluing can be per- formed e.g. by curtain coating or extrusion coating. However, depending on the manner the plywood is produced the properties of the binder composition used for the gluing purpose may vary. The inventors have recognized a need for a binder composition, especially a lignin based binder composition, having properties enabling its use for curtain coating or extrusion coating. SUMMARY

An aqueous binder composition is disclosed. The aqueous binder composition may be prepared by using at least polymerizable substance, crosslinking agent, and at least one additive. The aqueous binder composition may have an extensional viscosity, as measured by filament break-up time, of at least 0.13 seconds.

Further is disclosed an aqueous binder composition prepared by using at least polymerizable substance, crosslinking agent, and at least one additive, wherein the aqueous binder composition has an extensional viscosity, as measured by filament break-up time, of at least 0.13 seconds, and wherein 5 - 99 weight-% of the polymerizable substance originates from lignin and wherein the crosslinking agent is an aldehyde .

Further is disclosed a method for determining the amount of at least one additive needed for preparing an aqueous binder composition. The method may comprise: a) preparing an aqueous binder composition by using at least polymerizable agent, crosslinking agent, and at least one additive; b) determining the extensional viscosity, as measured by filament break-up time, of the aqueous binder composition; c) comparing the measured filament break-up time with a predetermined value to be achieved for the aqueous binder composition; and d) optionally, adjusting the amount of the at least one additive to be used for preparing the aqueous binder composition .

Further is disclosed a method for determining the amount of at least one additive needed for preparing an aqueous binder composition, wherein the method comprises: a) preparing the aqueous binder composition by using at least polymerizable agent, crosslinking agent, and at least one additive, wherein 5 - 99 weight- % of the polymerizable substance originates from lignin and wherein the crosslinking agent is an aldehyde; b) determining the extensional viscosity, as measured by filament break-up time, of the aqueous binder composition; c) comparing the measured filament break- up time with a predetermined value to be achieved for the aqueous binder composition; and d) optionally, adjusting the amount of the at least one additive to be used for preparing the aqueous binder composition.

Further is disclosed the use of a capillary break-up extensional rheometer for determining the amount of at least one additive needed in order to prepare an aqueous binder composition having properties required for curtain coating or extrusion coating of veneer in plywood production.

Further is disclosed the use of the aqueous binder composition as disclosed in the current specification for curtain coating or extrusion coating of veneer in plywood production.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the embodiments and constitute a part of this specification, illustrate various embodiments. In the drawings:

Fig. 1 presents schematically the sequence of a capillary break-up extensional rheometer measurement: filament formation (a), filament necking (b,c), and filament break-up (d) ;

Fig. 2 presents the functional principle of the capillary break-up extensional rheometer; and

Figs. 3a, 3b, and 3c present the results of example 1.

DETAILED DESCRIPTION

An aqueous binder composition is disclosed. The aqueous binder composition may be prepared by using at least polymerizable substance, crosslinking agent, and at least one additive, wherein the aqueous binder composition has a extensional viscosity, as measured by filament break-up time, of at least 0.13 seconds.

Further is disclosed a method for determining the amount of at least one additive needed for preparing an aqueous binder composition, wherein the method comprises :

a) preparing an aqueous binder composition by using at least polymerizable agent, crosslinking agent, and at least one additive;

b) determining the extensional viscosity as measured by filament break-up time, of the aqueous binder composition;

c) comparing the measured filament break-up time with a predetermined value for the filament break- up time to be achieved for the aqueous binder composition; and

d) optionally, adjusting the amount of the at least one additive to be used for preparing the aqueous binder composition.

Further is disclosed a method for determining the amount of at least one additive needed for preparing an aqueous binder composition, wherein the aqueous binder composition is a curtain binder composition or an extrusion binder composition, and wherein the method comprises: a) preparing the aqueous binder composition by using at least polymerizable agent, crosslinking agent, and at least one additive, wherein 5 - 99 weight- % of the polymerizable substance originates from lignin and wherein the crosslinking agent is an aldehyde; b) determining the extensional viscosity, as measured by filament break-up time, of the aqueous binder composition; c) comparing the measured filament break- up time with a predetermined value to be achieved for the aqueous binder composition; and d) adjusting the amount of the at least one additive to be used for preparing the aqueous binder composition based on the comparison made in c) to prepare an aqueous binder composition having an extensional viscosity, as measured by filament break-up time, of at least 0.13 seconds.

The method may be used for determining the amount of at least one additive needed for preparing an aqueous binder composition for curtain coating and/or extrusion coating. In one embodiment, the method is for determining the amount of at least one additive needed for preparing a curtain binder composition and/or an extrusion binder composition.

The inventors found out that traditional lignin-phenol-formaldehyde based binder compositions or adhesives prepared therefrom may not be suitable for curtain coating or extrusion coating as such without the addition of additive (s). The inventors surprisingly found out that determining the extensional viscosity, as measured by filament break-up time of the binder composition is an efficient manner to evaluate the suitability of the binder composition for curtain coating or extrusion coating.

b) may further comprise determining the capillary velocity of the aqueous binder composition, and c) may further comprise comparing the measured capillary velocity with a predetermined value for the capillary velocity to be achieved for the aqueous binder composition .

b) may comprise determining the extensional viscosity, as measured by filament break-up time, and the capillary velocity of the aqueous binder composition, c) may comprise comparing the measured filament break-up time with a predetermined value for the filament break-up time to be achieved for the aqueous binder composition and/or the measured capillary velocity with a predetermined value for the capillary velocity to be achieved for the aqueous binder composition. In c) , the predetermined value for the filament break-up time can be taken as at least 0.13 seconds, at least 0.17 seconds, or at least 0.2 seconds, or at least 0.25 seconds, or at least 0.30 seconds. In c) , the predetermined value for the capillary velocity can be taken as at most 2.5 mm/second, or at most 2.0 mm/second .

d) may comprise adjusting the amount of the at least one additive to be used for preparing the aqueous binder composition based on the comparison made in c) . When comparing the measured values of the filament break-up time and/or of the capillary velocity with corresponding predetermined values to be achieved for the aqueous binder composition, one is able to adjust the amount of additive, e.g. surfactant agent (s) and/or defoamer agent (s) , to be used for preparing an aqueous binder composition that has properties suitable for curtain coating and/or extrusion coating of veneer in plywood production. The inventors surprisingly found out that the measured values of the filament break-up time and/or capillary velocity of the aqueous binder composition, contrary to e.g. measured values based on shear rheological analyses, are features that efficiently describe the suitability of the prepared aqueous binder composition for especially curtain coating and/or extrusion coating.

A capillary break-up extensional rheometer, such as the one of HAAKE™ CaBER™ 1 Capillary Breakup Extensional Rheometer, manufactured by Thermo Fischer Scientific, is a device that can be used for determining extensional viscosity of a liquid sample such as an aqueous binder composition. The filament break-up time of the aqueous binder composition can be measured or determined by using the HAAKE™ CaBER™ 1 Capillary

Breakup Extensional Rheometer, manufactured by Thermo Fischer Scientific. The measurement can be conducted following the procedure described in: Willenbacher, N., Benz, R., Ewers, A., and Nijman, J. (2004), The influence of thickeners on the application method of automotive coatings and paper coatings - rheological investigations with the HAAKE CaBER 1. Rheology

Application Notes. Thermo Fisher Scientific,

(https: //assets. thermofisher . com/TFS- Assets/CAD/Application-Notes/V206-thickener- automotive-coatings-papercoatings.pdf, 13.6.2019). The operating principle of the rheometer is based on stretching a drop of fluid between two parallel plates (uniaxial extensional flow) . The upper plate is moved up rapidly (50 ms) , so the sample elongates and produces a liquid filament (Fig. 1) . The diameter of the filament 1 as the necking proceeds is measured by laser micrometer 2 as a function of time until the filament breaks-up (Fig. 2) . Long break-up time correlates with high extensional viscosity. If the surface tension of the sample is known, apparent extensional viscosity can be determined. The filament elongation and break-up are indicated as a function of time. Midfilament diameter can be measured by CaBER™:

where

s = surface tension (mN/m)

dmid = mid-filament diameter (m)

h_E = apparent extensional viscosity (Pas)

t = time (s)

For viscoelastic liquids, the break-up time increases dramatically as the polymer weight increases (Anna, S.L. and McKinley, G.H. Elasto-capillary thinning and breakup of model elastic liquids, J. Rheol. 45, 115 (2001), hereinafter referred to as Anna & McKinley, 2001) . For Newtonian liquids, i.e. liquids whose vis- cosity remains constant, no matter the amount of shear applied for a constant temperature, the filament thin- ning is linear with time. Here, equation (1) is also the slope of the curve. s/h_E may here be termed capillary velocity, so it is the absolute value of slope.

Apparent extensional viscosity can be solved based on formula (2) (Anna & McKinley, 2001) :

where

s = surface tension (mN/m)

dmid = mid-filament diameter (m)

h_E = apparent extensional viscosity (Pas)

t = time (s)

Apparent extensional viscosity is plotted as a function of Hencky strain (also known as true strain and logarithmic strain, e) (Anna & McKinley, 2001:

or as a function of Hencky strain rate (έ) :

where

d_o = initial sample diameter between the measuring plates in the beginning of the measurement (m)

dmid = mid-filament diameter (m)

t = time (s)

e = Hencky strain

έ = Hencky strain rate

Apparent extensional viscosity of Newtonian liquids is constant over Hencky strain and approximately three times its shear viscosity. For viscoelastic pol- ymer solutions, the apparent extensional viscosity in- creases as the strain increases. For adhesives, the ap- parent extensional viscosity diverges as the adhesive starts to solidify over time.

CaBER™ assumes axial symmetry of filament thinning. However, gravitational effects break this sym- metry, and cause weak axial flow downwards. Relative magnitude of the effect compared to opposing capillary forces can be described by dimensionless Bond number (Anna & McKinley, 2001) :

where

Bo = Bond number (-)

p = density (kg/m³)

g = gravitational acceleration constant (9,81 m/s²) d0 = initial sample diameter between the measuring plates in the beginning of the measurement (m)

s = surface tension (mN/m)

The gravitational effect can be neglected if Bond number is much less than 1.

Surface tension, viscosity, elasticity and mass transfer may affect the filament stretching phe- nomenon. By monitoring the dynamics of the fluid fila- ment break-up following a rapid extensional deformation of the sample, information about relaxation times, non- Newtonian flow behavior and break-up time of the fluid can be obtained .

For the quantitative measurement of the fila- ment break-up time and the capillary velocity, the ca- pillary break-up extensional rheometer device does the rapid elongation and laser measures the filament thin- ning as a function of time. The filament break-up time is the point when the filament breaks (diameter of the filament = y = 0) . Capillary velocity is the absolute value of the slope of the curve (filament diameter de- creases linearly with time) , and can be calculated from the filament thinning data.

For the qualitative measurement of the apparent extensional viscosity, the capillary break-up exten- sional rheometer device calculates the apparent extensional viscosity from filament thinning data and plots it as a function of strain.

The capillary break-up extensional rheometer can be used for determining the amount of at least one additive needed in order to prepare an aqueous binder composition having an extensional viscosity, as measured by filament break-up time, of at least 0.13 seconds.

The aqueous binder composition may have an extensional viscosity, as measured by filament break- pup time, of at least 0.13 seconds, or at least 0.17 seconds, or at least 0.2 seconds, or at least 0.25 seconds, or at least 0.28 seconds, or at least 0.30 seconds, and/or a capillary velocity of at most 2.5 mm/second, or at most 2.0 mm/second, and/or a surface tension of 30 - 40 mN/m, or 35 - 38 mN/m.

The aqueous binder composition may have an extensional viscosity, as measured by filament break-up time, of at least 0.17 seconds, or at least 0.2 seconds, or at least 0.25 seconds, or at least 0.30 seconds. The aqueous binder composition may have an extensional viscosity, as measured by filament break-up time, of at most 60 second, or at most 30 seconds.

The aqueous binder composition may have a capillary velocity of at most 2.5 mm/second, or at most 2.0 mm/second. The aqueous binder composition may have a capillary velocity of at least 0.1 mm/second, or at least 0.15 mm/second, or at least 0.2 mm/second, or at least 0.5 mm/second, or at least 0.8 mm/second, or at least 1.1 mm/second, or at least 1.2 mm/second, or at least 1.3 mm/second, or at least 1.5 mm/second.

The aqueous binder composition may have a surface tension of 30 - 40 mN/m, or 35 - 38 mN/m. The surface tension of the aqueous binder composition can be determined by pendant drop shape analysis method and De Nouy ring method. The pendant drop shape analysis may be performed in the following manner by using a device of Attension Theta optical tensiometer, Biolin Scientific: The measurements are performed at a temperature of 23 ± 2 °C. The drop is formed with a 200 mΐ micropipette and drop volumes of 3.5-4 mΐ are used. A binder composition density of 1.2073 g/cm³ is used in calculation of surface tension. Accuracy of the device is 0.01 mN/m. A micropipette of the device is filled with aqueous binder composition. A drop is formed, and a camera of the device captures 33 pictures of the drop/second. Based on drop geometry and the known aqueous binder composition density, the device determines the surface tension of the aqueous binder composition from each captured picture. Average surface tension of at least five parallel measurements is calculated .

At least part of the synthetic polymerizable substance, e.g. phenol, usually used for producing an aqueous binder composition, e.g. a phenol-formaldehyde resin, can be replaced with lignin, which is a bio-based material. E.g., 5 - 99 weight-%, or 10 - 95 weight-%, or 20 - 80 weight-%, or 30 - 70 weight-%, or 40 - 60 weight-%, of the polymerizable substance may originate from lignin. In one embodiment, at least 5 weight-%, or at least 10 weight-%, or at least 20 weight-%, or at least 30 weight-%, or at least 40 weight-%, or at least 50 weight-%, or at least 60 weight-%, or at least 70 weight-%, or at least 80 weight-%, or at least 90 weight- %, or at least 95 weight-%, or at least 98 weight-%, or about 100 weight-%, of the polymerizable substance orig- inates from lignin.

The aqueous binder composition can be formed by different manners. The aqueous binder composition can be formed by simply mixing lignin with a previously produced composition comprising crosslinking agent polymerized with e.g. synthetic polymerizable sub- stance. Alternatively, the aqueous binder composition can be formed by forming an aqueous composition com- prising lignin, synthetic polymerizable substance and crosslinking agent, and by allowing polymerization re- actions to take place between these reactant components under the influence of heating the composition. The com- position may be heated at a temperature of 30 - 150 °C for allowing polymerization reactions to take place. In one embodiment, the composition is heated at a temper- ature of 65 - 140 °C, or at a temperature of 70 - 100, or at a temperature of 75 - 85 °C or at a temperature of about 80 °C . The heating of the composition may be carried out for polymerizing the reactant components such that the viscosity of the aqueous binder composi- tion is increased. The heating can be continued until a predetermined viscosity value is formed. The predeter- mined viscosity value of the final aqueous binder com- position may vary depending on the specific application where the aqueous binder composition is to be used. The polymerization reactions may be allowed to continue un- til an aqueous binder composition with a viscosity value of 80 - 1200 cp is formed. The viscosity is measured at 25 °C using a rotary viscometer (Brookfield viscometer, plate spindle RV2, speed 50 rpm) . In one embodiment, the polymerization reactions are allowed to continue for 0.5 - 6 hours, or in 1.0 - 5 hours, or in 2 - 4 hours, or in 1.5 - 3.0 hours .

The polymerizable substance may comprise or consist of lignin and at least one compound selected from the class of phenols. In one embodiment, the polymerizable substance comprises or consists of lignin and at least one of phenol, cresol, and resorcinol. In one embodiment, the polymerizable substance comprises or consists of lignin and phenol. The polymerizable sub- stance may comprise 5 - 99 weight-%, or 10 - 95 weight- %, or 20 - 80 weight-%, or 30 - 70 weight-%, or 40 - 60 weight-%, lignin.

The crosslinking agent may be selected from a group consisting of an aldehyde, a derivative of an aldehyde, an aldehyde forming compound, and any combinations or mixtures of these. The derivative of an aldehyde may be hexamethylenetetramine, paraformaldehyde, or trioxane. Further, the crosslinking agent may be selected from a group consisting of an aromatic aldehyde, glyoxal, furfuryl alcohol, caprolactam, and glycol compounds. In one embodiment, the aromatic aldehyde is furfuryl aldehyde. In one embodiment, the crosslinking agent is an aldehyde. In one embodiment, the crosslinking agent is formaldehyde, paraformaldehyde, or a combination or mixture thereof.

The polymerizable substance may comprise or consist of lignin and at least one compound selected from the class of phenols, such as phenol, cresol, and/or resorcinol; and the crosslinking agent may be an aldehyde, a derivative of an aldehyde, an aldehyde forming compound, such as formaldehyde, paraformaldehyde, or a combination or mixture thereof.

At least one catalyst may be used for the pro- duction of the aqueous binder composition. The catalyst may be a base, such as an alkali or an alkali earth hydroxide. In one embodiment, the catalyst comprises a salt or a hydroxide of an alkali metal. In one embodi- ment, the catalyst is selected from a group consisting of sodium hydroxide, potassium hydroxide, and any mix- ture thereof. In one embodiment, the catalyst is an organic amine. The catalyst may be used in a concentra- tion of 0.1 - 15 weight-%, or 0.5 - 12 weight-%, or 3 - 10 weight-%, or 5 - 8 weight based on the total weight of the composition.

In the context of this specification, the term "lignin" may refer to lignin originating from any suitable lignin source. In one embodiment, the lignin is essentially pure lignin. By the expression "essen- tially pure lignin" should be understood as at least 70 % pure lignin, or at least 90 % pure lignin, or at least 95 % pure lignin, or at least 98 % pure lignin. In one embodiment, the essentially pure lignin comprises at most 30 %, or at most 10 %, or at most 5 %, or at most 2 %, of other components and/or impurities. Extractives and carbohydrates such as hemicelluloses can be men- tioned as examples of such other components.

The lignin may contain less than 30 weight-%, or less than 10 weight-%, or less than 5 weight-%, or less than 2 weight-% of carbohydrates. The amount of carbohydrates present in lignin can be measured by high performance anion exchange chromatography with pulsed amperometric detector (HPAE-PAD) in accordance with standard SCAN-CM 71.

The ash percentage of lignin may be less than 7.5 weight-%, or less than 5 weight-%, or less than 3 weight-%. The ash content can be determined by carbonifying and quickly burning a lignin sample so that alkali salts are not melted before the organic matter has been burned (e.g. 20 - 200 °C for 30 minutes, after which temperature is adjusted to 200 - 600 °C for 1 h, and thereafter adjusting the temperature to 600 - 700 °C for 1 hour) , and finally the lignin sample is ignited at 700 °C for 1 h. Ash content of a lignin sample refers to the mass that remains of the sample after burning and ignition, and it is presented as per cent of the sample's dry content. In one embodiment, the lignin is technical lignin. In the context of this specification, the term "technical lignin" may refer to lignin that is derived from lignin in any biomass by any technical process. Technical lignin can be received from an industrial process.

In one embodiment, the lignin is selected from a group consisting of kraft lignin, steam explosion lignin, biorefinery lignin, supercritical separation lignin, hydrolysis lignin, flash precipitated lignin, biomass originating lignin, lignin from alkaline pulping process, lignin from soda process, lignin from organosolv pulping, lignin from alkali process, lignin from enzymatic hydrolysis process, and any combination or mixture thereof. In one embodiment, the lignin is wood based lignin. The lignin can originate from softwood, hardwood, annual plants or from any combination or mixture thereof.

In one embodiment, the lignin is Kraft lignin. By "kraft lignin" is to be understood in this specifi- cation, unless otherwise stated, lignin that originates from kraft black liquor. Black liquor is an alkaline aqueous solution of lignin residues, hemicellulose, and inorganic chemicals used in a kraft pulping process. The black liquor from the pulping process comprises compo- nents originating from different softwood and hardwood species in various proportions. Lignin can be separated from the black liquor by different, techniques including e.g. precipitation and filtration. Lignin usually begins precipitating at pH values below 11 - 12. Different pH values can be used in order to precipitate lignin frac- tions with different properties. These lignin fractions differ from each other by molecular weight distribution, e.g. Mw and Mn, polydispersity, hemicellulose and ex- tractive contents. The molar mass of lignin precipitated at a higher pH value is higher than the molar mass of lignin precipitated at a lower pH value. Further, the molecular weight distribution of lignin fraction pre- cipitated at a lower pH value is wider than of lignin fraction precipitated at a higher pH value. The precip- itated lignin can be purified from inorganic impurities, hemicellulose and wood extractives using acidic washing steps. Further purification can be achieved by filtra- tion. In one embodiment, the lignin is flash precip- itated lignin. The term "flash precipitated lignin" should be understood in this specification as lignin that has been precipitated from black liquor in a con- tinuous process by decreasing the pH of a black liquor flow, under the influence of an over pressure of 200 - 1000 kPa, down to the precipitation level of lignin using a carbon dioxide based acidifying agent, prefer- ably carbon dioxide, and by suddenly releasing the pres- sure for precipitating lignin. The method for producing flash precipitated lignin is disclosed in patent appli- cation FI 20106073. The residence time in the above method is under 300 s. The flash precipitated lignin particles, having a particle diameter of less than 2 ym, form agglomerates, which can be separated from black liquor using e.g. filtration. The advantage of the flash precipitated lignin is its higher reactivity compared to normal kraft lignin. The flash precipitated lignin can be purified and/or activated if needed for the fur- ther processing.

Lignin may be derived from an alkali process. The alkali process can begin with liquidizing biomass with strong alkali followed by a neutralization process. After the alkali treatment, the lignin can be precipi- tated in a similar manner as presented above.

Alternatively, the lignin may be derived from steam explosion. Steam explosion is a pulping and ex- traction technique that can be applied to wood and other fibrous organic material.

By "biorefinery lignin" is to be understood in this specification, unless otherwise stated, lignin that can be recovered from a refining facility or process where biomass is converted into fuel, chemicals and other materials.

By "supercritical separation lignin" is to be understood in this specification, unless otherwise stated, lignin that can be recovered from biomass using supercritical fluid separation or extraction technique. Supercritical conditions correspond to the temperature and pressure above the critical point for a given sub- stance. In supercritical conditions, distinct liquid and gas phases do not exist. Supercritical water or liquid extraction is a method of decomposing and converting biomass into cellulosic sugar by employing water or liq- uid under supercritical conditions. The water or liquid, acting as a solvent, extracts sugars from cellulose plant matter and lignin remains as a solid particle.

Further, the lignin may be derived from a hy- drolysis process. The lignin derived from the hydrolysis process can be recovered from paper-pulp or wood-chem- ical processes.

The lignin may originate from an organosolv process. Organosolv is a pulping technique that uses an organic solvent to solubilize lignin and hemicellulose .

The lignin may also be lignin from an enzymatic hydrolysis process. Enzymatic hydrolysis is a process, wherein enzymes assist in cleaving bonds in molecules with the addition of elements of water. In one embodiment, the enzymatic hydrolysis comprises enzymatic hydrolysis of cellulose.

The at least one additive may be selected from the group consisting of at least one surfactant agent, at least one defoaming agent, and any combination or mixture thereof. The additive may be a surfactant agent, a defoamer agent, or their combination or mixture. Further additives, such as a hardener, a filler and/or an extender, may also be used for preparing the aqueous binder composition. The aqueous binder composition may be prepared by using e.g. two or more different surfactant agents and/or two or more different defoamer agents. The at least one additive may comprise or consists of at least one surfactant agent. The at least one additive may comprise or consists of at least one defoamer agent. The at least one additive may comprise or consists of a surfactant agent. The at least one additive may comprise or consists of a defoamer agent. I.e. at least one surfactant agent and/or at least one defoamer agent may be used as the at least one additive.

A surfactant agent, or a surface-active agent as it also may be called, may be a compound or material that lower the surface tension or the interfacial tension between e.g. two liquids, between a gas and a liquid, or between a liquid and a solid.

A defoamer agent, or an anti-foaming agent as it also may be called, may be a compound or a material, that reduces or hiders the formation of foam.

In one embodiment, at least one surfactant agent, as calculated based on a 100 % concentration of the surfactant, is used in an amount of 0.01 - 5 weight- %, or 0.05 - 1 weight-%, based on the total weight of the aqueous binder composition.

The at least one surfactant agent may be selected from a group consisting of anionic surfactant, nonionic surfactant, cationic surfactant, amphoteric surfactant, silicon surfactant, polymeric surfactant, and any combination or mixture thereof. The at least one surfactant agent may be selected from a group consisting of ethoxylates, carboxylates , alcohol alkoxylates, diols, fatty acid esters of polyols/polyhydroxy compounds, siloxanes, and any combination or mixture thereof. The surfactant agent (s) have the added utility of affecting e.g. the wetting phenomenon and surface tension of the aqueous binder composition. In curtain coating, the surfactant agent (s) may allow air to escape from the binder composition and hold the curtain together for greater distance of fall from the head. The surfactant agent (s) may affect the viscosity of the aqueous binder composition.

In one embodiment, at least one defoamer agent, as calculated based on a 100 % concentration of the defoamer agent, is used in an amount of 0.01 - 3 weight- %, based on the total weight of the aqueous binder composition .

The at least one defoamer agent may be selected from a group consisting of organic oils, vegetable paraffinic oils, silicon oils, waxes, fatty acids, soaps, esters, long chain fatty alcohols, siloxanes, alcohol alkoxylates, and any combination or mixture thereof. The defoamer agent (s) have the added utility of preventing foam generation during the use of the aqueous binder composition.

The components and their precise amounts used for producing the aqueous binder composition may vary and the choice of the different components and their amounts is within the knowledge of the skilled person based on this specification. The temperature and any other values can be controlled and adjusted if needed during the production process.

The inventors surprisingly found out that by measuring the filament break-up time and/or the capillary velocity of the aqueous binder composition one is able to produce an aqueous binder composition having properties suitable for curtain coating and/or extrusion coating of veneer in plywood production. The inventors surprisingly found out that the use of additive (s), such as surfactant ( s ) and/or defoamer agent (s), has/have the added utility of providing the formed aqueous binder composition with such suitable properties. Further, the inventors surprisingly found out that the amount of the additive (s), such as surfactant ( s ) and/or defoamer agent (s), used during the production of the aqueous binder composition beneficially affects the properties needed for forming a curtain binder composition and/or an extrusion binder composition. The inventors further surprisingly found out that the amount of surfactant agent (s) and/or defoamer agent (s) can be adjusted based in the measured values of the filament break-up time and/or the capillary velocity of the aqueous binder composition. I.e. the amount of the surfactant agent (s) and/or defoamer agent (s) can be adjusted so that a predetermined value for the filament break-up time and/or the capillary velocity is achieved for the aqueous binder composition.

In one embodiment, the aqueous binder composition is a curtain binder composition or an extrusion binder composition. I.e. the aqueous binder composition as disclosed in the current specification can be used for the production of plywood through e.g. curtain coating or extrusion coating.

Plywood is wood product that can be used for e.g. furniture and building material. Plywood is usually formed of thin wood sheets, also called veneers, on to which an aqueous binder composition or an adhesive is applied on or spread. There are different spreading methods to be used for plywood production and they can be categorized to contact and non-contact methods. Curtain coating is one of the non-contact adhesive application methods and it can be used to spread the adhesive in plywood production. Curtain coating may be considered a process that creates an uninterrupted curtain of fluid that falls onto a substrate such as a veneer. The substrate, e.g. the veneer, may be transported on a conveyor belt or calender rolls at a regulated speed through the curtain to ensure an even coat of the die. The curtain may be created by using a slit or die at the base of the holding tank, allowing the liquid to fall upon the substrate. There are two main types of curtain coaters, slot and slide applicators. Extrusion coating may be considered as coating of binder composition onto a substrate such as veneer, wherein the process comprises e.g. extruding binder composition from a slot die at temperatures up to 320 °C directly onto the moving web which may then passed through a nip consisting of a pressure roller and a cooling roll. The web is usually run faster than the speed at which the resin is extruded from the die, creating a coating thickness which is in proportion to the speed ratio and the slot gap.

The material of the veneer used for the plywood production may vary. The veneer may be made of softwood and/or hardwood. The veneer may be selected from a group consisting of pine veneer, poplar veneer, beech veneer, spruce veneer, and birch veneer. In one embodiment, the veneer is spruce veneer or pine veneer. In one embodiment, the veneer is birch veneer.

The aqueous binder composition described in the current specification has the added utility of having properties suitable for curtain coating and extrusion coating of veneer in plywood production.

The method described in the current specification has the added utility of allowing the production of e.g. a lignin containing aqueous binder composition having properties making it suitable for use in curtain coating and extrusion coating of veneer in plywood production.

The use of a capillary break-up extensional rheometer has the added utility of making it possible to provide the aqueous binder composition with an adjusted or a specified amount of at least one additive, e.g. surfactant agent and/or defoamer agent, for producing an aqueous binder composition for curtain coating and/or extrusion coating.

EXAMPLES

Reference will now be made in detail to various embodiments .

The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the embodiments based on the disclosure. Not all steps or features of the embodiments are discussed in detail, as many of the steps or features will be obvious for the person skilled in the art based on this specification.

Example 1 - Producing aqueous binder compositions and measuring their properties

In this example an aqueous lignin-phenol- formaldehyde binder composition was prepared in the following manner:

First, a preprepared aqueous binder composition was prepared. Lignin (509 g, 70 % dry matter content), phenol (594 g, 90 %) , and NaOH (43.3 g, 50 %) were mixed and dissolved in water (529 g) . The temperature was increased to 90 °C . After these components had been dissolved, formaldehyde (438 g, 37- 40 %) was added into the formed composition. The reactant components were allowed to react with each other while heating the composition at a temperature of 80 °C while simultaneously mixing the same. The polymerization reactions were stopped when the composition had reached a viscosity of 130 cP as measured at 25 °C with a rotary viscometer.

The following additives were tested:

Surfactant 1 :

- 2,5,8,11 tetramethyl 6 dodecyn-5, 8-diol ethoxylate (100 %)

Surfactant 2 :

- Ethoxylated 2 , 4 , 7 , 9-tetramethyl 5 decyn-4 , 7-diol (50- 70 %) , 2, 4, 7, 9 tetramethyldec-5-yne-4 , 7-diol (10-25 %)

Surfactant 3:

- Ethoxylated 2 , 4 , 7 , 9-tetramethyl 5 decyn-4 , 7-diol (100 %)

Surfactant 4 :

- Oxirane, methyl-, polymer with oxirane, mono (3,5,5- trimethylexyl ) ether (75-100 %) Surfactant/Defoamer 1:

2, 4, 7, 9 tetramethyldec-5-yne-4 , 7-diol (70-90 %) , ethane-1 , 2-diol (20-35 %)

Defoamer 1 :

- Organic oil defoamer

Defoamer 2 :

- Vegetable oil defoamer

Defoamer 3:

- Alcohol alkoxylate defoamer

The different additives were mixed with the prepepared aqueous binder composition to form different test samples. The surfactant agents were added at four different dosages, i.e. 0.1 %, 0.2 %, 0.4 % and 0.6 % of the weight of the aqueous binder composition. The defoamer agents were added at three different dosages, i.e. 0.03 %, 0.05 %, and 0.1 % of the weight of aqueous binder composition.

To add the additives to the aqueous binder composition sample, the average weight of a drop of each additive was determined by weighing (accuracy 0.1 mg) 10 separate drops of an additive formed with 1 ml pipette. Desired dosage of an additive was added to resin sample at the precision of a drop. After the addition, the aqueous binder compositions were mixed and stored for at least 24 h, and mixed again prior to analyses. Storage of resins allowed the additives to affect the compositions.

Having prepared the different samples, the properties of the samples were measured.

HAAKE™ CaBER™ 1 capillary break-up extensional rheometer manufactured by Thermo Fischer Scientific Inc. was used for determination of elongational properties of the samples. Plates of 6 mm were used, and thus the sample diameter was 6.0 mm. Initial and final aspect ratios defining the sample elongation were 1.00 and 2.75, respectively, so the sample initial height and final heights were 2.99 mm and 8.24 mm, respectively. System imposed axial Hencky strain (sf) was 1.01. Measurement duration was 2 s and sampling rate 4000 Hz. For each sample, at least 6 replicates were done and for each replicate 2 elongations. The filament diameter of the aqueous binder composition was measured as a function of time and the break-up time determined. The diameter was normalized for scale 0-1. Apparent extensional viscosity curves were plotted as a function of strain. Plotting was performed by V4.50 CaBER Data Analysis software. An average curve for filament elongation was calculated for each sample based on at least 5 replicates. Average apparent extensional viscosity curves were calculated for part of the experiments, and in calculations, binder composition density 1.2073 g/cm³ and surface tension determined by pendant drop method were used. Measurements were performed at a temperature of 25 ± 2 °C.

The effect of additive dosage increase was studied and working curve coefficients were computed via regression analysis (multiple linear regression, MLR) , tool available in Microsoft Excel Data Analysis Add- Inns. Regression analysis models the relationship between multiple explanatory variables and a response variable by fitting a linear equation to observed data.

The capillary velocity was calculated from the filament thinning curve, the absolute value of the slope of the curve (linearly decreasing curve) .

Results of measurements are presented in the below tables for some of the above prepared compositions. Sample 1 is a comparative sample that is produced in an otherwise similar manner as above presented but no additive was used.

Table 1. Measurement results of some prepared binder compositions

The above values for the filament break-up time and the capillary velocity for the different samples are also presented in Fig. 3a. From these results it can be seen that produced aqueous binder compositions have properties suitable for curtain coating or extrusion coating .

Table 2. Measurement results of some prepared binder compositions

The above values for the filament break-up time and the capillary velocity for the different samples are also presented in Fig. 3b. From these results it can be seen that produced aqueous binder compositions have properties suitable for curtain coating or extrusion coating .

Table 3. Measurement results of some prepared binder compositions

Samples 2 and 11 are the same as presented above in tables 1 and 2.

The above values for the filament break-up time and the capillary velocity for the different samples are also presented in Fig. 3c. From these results it can be seen that produced aqueous binder compositions have properties suitable for curtain coating or extrusion coating . Example 2 - Using the aqueous binder composition for curtain coating

The aqueous binder composition with sample number 3 as above presented (0.4 % surfactant 3 and 0.03 % defoamer 3) was used together with water and a mixture of wheat flour, soda ash, and lime for curtain coating of veneer. The flow cup viscosity of the binder composition was adjusted according to specific requirements of the process line. Uniform and durable curtain of a thickness of 1,2 - 2.5 mm, a width of 1.3 or 2,6 m and a height of 20 - 35 cm was formed. Amount of applied binder composition on the veneer was 120 - 145 g/'m². Runnability of the curtain was evaluated visually, and no ruptures occurred during continuous process.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea may be implemented in various ways. The embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims. The embodiments described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment. A composition, a method, or a use, disclosed herein, may comprise at least one of the embodiments described hereinbefore. It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item refers to one or more of those items. The term "comprising" is used in this specification to mean including the feature (s) or act(s) followed thereafter, without excluding the presence of one or more additional features or acts.

Claims

1. An aqueous binder composition prepared by using at least polymerizable substance, crosslinking agent, and at least one additive, wherein the aqueous binder composition has an extensional viscosity, as measured by filament break-up time, of at least 0.13 seconds, and wherein 5 - 99 weight-% of the polymerizable substance originates from lignin and wherein the crosslinking agent is an aldehyde.

2. The aqueous binder composition of any one of the preceding claims, wherein the aqueous binder composition has an extensional viscosity, as measured by filament break-up time, of at least 0.17 seconds, or at least 0.2 seconds, or at least 0.25 seconds, or at least 0.28 seconds, or at least 0.30 seconds.

3. The aqueous binder composition of any one of the preceding claims, wherein the aqueous binder composition has a capillary velocity of at most 2.5 mm/second, or at most 2.0 mm/second.

4. The aqueous binder composition of any one of the preceding claims, wherein the aqueous binder composition has a surface tension of 30 - 40 mN/m, or 35 - 38 mN/m .

5. The aqueous binder composition of any one of the preceding claims, wherein 10 - 95 weight-%, or 20 - 80 weight-%, or 30 - 70 weight-%, or 40 - 60 weight- %, of the polymerizable substance originates from lignin .

6. The aqueous binder composition of any one of the preceding claims, wherein the at least one additive is selected from the group consisting of at least one surfactant agent, at least one defoaming agent, and any combination or mixture thereof.

7. The aqueous binder composition of claim 6, wherein at least one surfactant agent, as calculated based on a 100 % concentration of the surfactant, is used in an amount of 0.01 - 5 weight-%, or 0.05 - 1 weight-%, based on the total weight of the aqueous binder composition.

8. The aqueous binder composition of any one of the preceding claims, wherein the aqueous binder composition is a curtain binder composition or an extrusion binder composition.

9. A method for determining the amount of at least one additive needed for preparing an aqueous binder composition, wherein the method comprises:

a) preparing the aqueous binder composition by using at least polymerizable agent, crosslinking agent, and at least one additive, wherein 5 - 99 weight-% of the polymerizable substance originates from lignin and wherein the crosslinking agent is an aldehyde;

b) determining the extensional viscosity, as measured by filament break-up time, of the aqueous binder composition;

c) comparing the measured filament break-up time with a predetermined value to be achieved for the aqueous binder composition; and

10. The method of claim 9, wherein b) further comprises determining the capillary velocity of the aqueous binder composition, and wherein c) further comprises comparing the measured capillary velocity with a predetermined value to be achieved for the aqueous binder composition.

11. The method of any one of claims 9 - 10, wherein the at least one additive is selected from a group consisting of at least one surfactant agent, at least one defoaming agent, and any combination or mixture thereof.

12. The use of a capillary break-up extensional rheometer for determining the amount of at least one additive needed in order to prepare an aqueous binder composition having properties required for curtain coating or extrusion coating of veneer in plywood production .

13. The use of claim 12, wherein the capillary break-up extensional rheometer is used for determining the amount of at least one additive needed in order to prepare an aqueous binder composition having a extensional viscosity, as measured by filament break-up time, of at least 0.13 seconds.

14. Use of the aqueous binder composition of any one of claims 1 - 8 for curtain coating or extrusion coating of veneer in plywood production.