ADHESIVE COMPOSITION COMPRISING GROUND PEA SEEDS AND AN AMINE-BASED AZETIDINIUM-FUNCTIONAL CROSS-LINKER

Abstract

The invention relates to an adhesive composition comprising: ground pea seeds comprising between 5 wt % and 40 wt % of crude proteins on the total weight of the ground pea seeds, an amine-based azetidinium-functional cross-linker, and water.

The invention also relates to an article and its preparation process, use of the adhesive composition according to the invention, and use of ground pea seeds.

Claims

1. An adhesive composition comprising: ground pea seeds comprising between 5 wt % and 40 wt % of crude proteins on the total weight of the ground pea seeds, an amine-based azetidinium-functional cross-linker, and water.

2. The adhesive composition according to claim 1, wherein the ground pea seeds belong to the genus Pisum and/or Lathyrus.

3. The adhesive composition according to claim 2, wherein the ground pea seeds belong to the species Pisum sativum.

4. The adhesive composition according to claim 1, wherein the amine-based azetidinium-functional cross-linker is polyamidoamine-epichlorohydrin (PAE), polyalkylenepolyamine-epichlorohydrin (PAPAE), amine polymer-epichlorohydrin (APE), or a combination thereof.

5. The adhesive composition according to claim 1, comprising between 5 wt % and 60 wt % of the ground pea seeds, based on the total weight of the adhesive composition.

6. The adhesive composition according to claim 1, comprising between 2 wt % and 12 wt % of the amine-based azetidinium-functional cross-linker, based on the total weight of the adhesive composition.

7. The adhesive composition according to claim 1, having a solid content of at least 20 wt %, based on the total weight of the adhesive composition.

8. The adhesive composition according to claim 1, further comprising a polyol.

9. The adhesive composition according to claim 8, wherein the polyol is glycerol or crude vegetable glycerin.

10. The adhesive composition according to claim 1, further comprising at least one additive.

11. An article comprising the adhesive composition according to claim 1 and a lignocellulosic material.

12. A process for preparing an article, comprising a step of contacting the adhesive composition according to claim 1 with a lignocellulosic material to provide lignocellulosic material impregnated with the adhesive composition.

13. The article of claim 11, wherein the lignocellulosic material is wood veneer.

14. A process comprising gluing wood veneer to the adhesive composition according to claim 1.

15. A process for improving processability of an adhesive composition comprising an amine-based azetidinium-functional cross-linker comprising adding ground pea seeds comprising between 5 wt % and 40 wt % of crude proteins on the total weight of the ground pea seeds, to the adhesive composition.

16. The adhesive composition according to claim 1, wherein the amine-based azetidinium-functional cross-linker is polyamidoamine-epichlorohydrin (PAE).

17. The adhesive composition according to claim 8, wherein the polyol is a trifunctional alcohol.

Description

[0135] The invention will be better understood in the light of the following examples, given by way of illustration, with reference to:

[0136] FIG. 1 that is a diagram illustrating the viscosity of dispersions prepared from water and micronized plant seed resources (pea flour, referred to as PF; sunflower meal, SM; heat treated sunflower meal, HT-SM; soy flour, SF1 and rapeseed meal, RM), depending on the dry content of the dispersions;

[0137] FIG. 2 that are diagrams illustrating the mechanical properties of particle boards glued with UF resin (grey) or PFG1 adhesive (black) and pressed at different press factors;

[0138] FIG. 3 that are diagrams illustrating the mechanical properties of particle boards prepared with PFG1, SF1 or SF2 adhesive compositions and pressed at different press factors;

[0139] FIG. 4 that shows picture of pea seeds (A) and sunflower seeds (B) after grinding.

EXAMPLE 1

Materials and Methods

Materials

[0140] Whole yellow pea seeds (Pisum sativum), hexane-extracted sunflower meal, hexane-extracted rapeseed meal and hexane-extracted soybean meal were purchased from Sanders (France) and ground in order to respectively obtain micronized pea flour (PF) with a diameter of Dv10-of 7 m, Dv-50-of 25 m, and Dv90 of 77 m; micronized sunflower meal (SM) with a diameter of Dv10 of 5 m, Dv50 of 30 m, and Dv90 of 427 m; micronized rapeseed meal (RM) with a diameter of Dv10 of 5 m, Dv50 of 31 m, and Dv90 of 121 m and micronized soy flour (SF2) with a diameter of Dv10 of 15 m, Dv50 of 43 m, and Dv90 of 115 m.

[0141] A laboratory grinder from Retsch model ZM 200 was used for grinding. This equipment allows to get well-defined granulometry profile characterized by the Dv (50) value (size in microns that splits the distribution with half above and half below this diameter, in volume; in other words, Dv50 is the median particle size by volume).

[0142] A ring sieve with 80 m openings and mill speed of 18000 rpm were the conditions used to obtain the target particle size distribution d50 of about 30 m.

[0143] The heat-treated sunflower meal (HT-SM) was prepared from SM which was heat treated at 150 C. during 30 min in dry conditions.

[0144] Another grade of soy flour (from hexane extracted soy beans) was also investigated. The soy flour SF1 already micronized was the commercially available soy flour grade 7B purchased from ADM and used as received. The particle size was evaluated and found to have a diameter of Dv10 of 5 m, Dv50 of 25 m, and Dv90 of 127 m.

[0145] The micronized pea, sunflower, rapeseed and soy flours have a starch content of 51.7% wt/wt, 3.9% wt/wt, 6.3% wt/wt and 5.7% wt/wt, respectively. Starch content was measured after amylolysis and by HPAEC analyses. Glucose released from starch (after amylolysis) was quantified in HPAEC-PAD (ICS-3000, Thermo Scientific Dionex) using a CarboPac PA1 column (2 mm250 mm, Thermo Scientific, USA), thermostated at 25 C. An isocratic elution of 500 mM of NaOH was used at a flow rate 0.25 mL.Math.min.sup.1. Rhamnose was used as an internal standard for calibration

[0146] Total crude proteins content of PF, SM, RM, SF1 and SF2 obtained using Kjeldahl procedure (NF EN ISO 5983-2:2009) with a nitrogen-to-protein conversion factor of 6.25 was 19.0%1.6% wt/wt, 37.0%2.3% wt/wt, 34.0% wt/wt1.9% wt/wt, 51.2%2.0% wt/wt and 48.0% +1.4% wt/wt, respectively.

[0147] The total oil content of PF, SM, RM, SF1 and SF2 was respectively 1.2% wt/wt; 1.2% wt/wt; 1.4% wt/w; 0.74% wt/wt and 2.0% wt/wt. The oil contents were measured as follows: oil was extracted with a Soxhlet extractor using n-hexane as solvent. Thereafter, the hexane was separated from oil by using a rotary evaporator at 68 C.

[0148] The moisture content of PF, SM, RM, SF1 and SF2 was respectively 7.7% wt/wt, 6.0% wt/wt, 5.0% wt/wt, 4.5% wt/wt and 6.3% wt/wt. The moisture contents were determined by placing about 1.5 g of material in an aluminum cup, the exact weight being measured with an analytical balance with 4 digits after the decimal point. Then the cup is placed in a fan ventilated oven at 105 C. for 3 h. Fan & valve aperture are set at 100% to accelerate water evaporation. The cup is weighted immediately after being removed from the oven or after conditioning in a desiccator to get sample at room temperature. Moisture content is obtained by calculating the percentage of material loss of the cup before being placed in the oven and after being placed in the oven.

[0149] Crude vegetable glycerine with a glycerol content of about 85% wt/wt was provided by Oleon (France) and used as a diluent.

[0150] The polyamidoamine-epichlorohydrin was from Ashland Water Technologies (PAE CA 1920, Wilmington, Delaware) and used as received. The PAE CA 1920 is under the form of an aqueous solution with a polymer solid content of 20% wt/wt.

[0151] Wood particles used to prepare particle boards were recycled wood (i.e. a mixture of wood from different sources) supplied by LINEX PANNEAUX (France). The wood particles were dried in an oven in order to obtain a total humidity of around 4% and stored in a closed box before being used. For gluing veneers, NEXT MDF coniferous boards were used and supplied by Panneaux de Correze (France). The NEXT MDF boards having a thickness of 19 mm and density of 730 Kg/m.sup.3 were cut in order to have specimen with dimensions of 20 cm20 cm. Wood veneer was oak with dimensions of 20 cm20 cm (length) and 0.06 cm thickness.

[0152] Urea-formaldehyde (UF) resin and hardener used to glue the veneers were respectively ADHESIVE 1274 and HARDENER 2505 purchased from AKZONOBEL.

Product Characterization

Particle Size Determination

[0153] The particle size of ground samples is measured using a Malvern laser granulometer Mastersizer 3000. Sample material is injected through the dry injection tool of the analyzer. Refractive index and model used are respectively 1.52 and Mie to determine the particle size density profile.

Rheological Analysis

[0154] The rheological properties of adhesive formulations were determined by using a Hakke Rheometer (MARSIII, Thermo, Germany). The prepared adhesive samples were placed between parallel plates, and then the shear stress and apparent viscosity under shear rate of 10 s.sup.1 were tested at 20 C.

[0155] Rheological analysis was performed on dispersions prepared from PF, SM, RM, HT-SM, SF1 (see Example 2). Typically, different amounts of micronized plant based raw materials (from 10% wt/wt to 45% wt/wt of solid) were dispersed into water at ambient temperature. After 10 min of homogenization, the viscosity was recorded.

[0156] To highlight the rheological properties depending on the plant-based source, rheological analysis was also performed on different adhesives compositions (see Example 5, Table 1).

Panel Boards Characterization

[0157] Particles boards (600 mm600 mm) are cut to get samples for, internal bond (IB) and flexural tests. Flexuraland IB tests are done respectively following standard ISO EN 310:1993 and ISO EN 319:1993 to get Modulus of Rupture (MOR), Modulus of Elasticity (MOE) and IB. Apparatus used for all these measurements is the Imal (Italia), IBX700 model. The test results are mean values with their standard deviation.

[0158] To evaluate the MOE and MOR, four test specimens with nominal dimensions of 400 mm50 mm11.5 mm were cut from the particle boards. The MOE and MOR were determined by a static, three point bending test and the values were calculated and recorded for each specimen.

[0159] To determine the internal bond strength, six test specimens with nominal dimensions of 50.0 mm50.0 mm11.5 mm were cut from test panels for each condition. The IB was calculated and recorded after each specimen was tested to failure.

Veneered Boards Characterization

[0160] Dry strength tests were conducted by delamination test after pressing step. Delamination was estimated when a failure occurred between the veneer strips and the MDF board after tearing using a cutter. For wet strength tests, the boards were soaked in water for 10 min at 20 C. Wet strength was tested immediately after soaking using a cutter. All board specimens were inspected to see whether they were delaminated after soaking.

[0161] When the specimen has not delaminated, Pass (P) was specified, and when a delamination was noticed, Fail (F) was specified.

[0162] To evaluate the dry bonding strength, Surface Soundness measurements were conducted according to European Standard EN 311:2002. First of all, each wood assembly was cut into five pieces with dimensions of 50 mm50 mm, then a circular groove (inner diameter of 35 mm) is cut 0.3 mm deep into the test samples. A steel pad was glued onto the board surface, on the cut surface portion. After the adhesive has hardened, a tensile force was applied at constant speed so that failure occurs, preferably within the surface layer; the force at failure was recorded.

Example 2

Viscosity of Micronized Plant Seed Resource Based Dispersions Depending on Their Solid Content

[0163] An adhesive composition is aimed to have a high solid content to avoid issues during pressing time at high temperature and high pressure (to prevent the blowout due to an excess of water); but limitation of water to prepare the adhesive composition can lead to a too viscous adhesive resulting in an issue during the process of injection into the wood particles. Consequently, choosing an appropriate raw material is very important to overcome both issues.

[0164] Dispersions were prepared by mixing micronized plant seed resources (pea flour, PF; sunflower meal, SM; heat treated sunflower meal, HT-SM; soy flour, SF1 and rapeseed meal, RM) into water.

[0165] The viscosity of the dispersions was evaluated according to the solid content of the raw materials into water and the results were compared (FIG. 1).

[0166] Dispersions prepared from raw materials such as soy flour SF1 and sunflower meal SM exhibited the highest viscosity. Their viscosity increased dramatically when the solid content was higher than 20% wt/wt of solid matter into water reaching to very thick dispersions (above 10000 mPa.Math.s).

[0167] The viscosity of the heat treated sunflower meal (HT-SM) and of the rapeseed meal (RM) dispersions were better than that of SF1 and SM but increased dramatically for solid contents above 25%.

[0168] However, when PF was used, the viscosity was low (inferior to or around 1000 mPa.Math.s) even at solid content equal to 35% wt/wt.

Example 3

Preparation of Particle Boards

Adhesive Composition Comprising Pea Flour

[0169] An adhesive composition for wood panels was prepared by dispersing PF into a liquid mixture made from PAE solution, crude vegetable glycerin and water. The composition of the adhesive composition was calculated based on the whole adhesive composition including the moisture.

[0170] A liquid solution was first prepared by dissolving 285 g of PAE solution and 250 g of crude vegetable glycerin used as biobased diluent and crosslinking agent into 235 g of water. 225 g of micronized pea flour was then added to the mixture and the pH of the solution was adjusted to 8 with a 10M NaOH solution. As the PAE is provided under the form of an aqueous solution (see Example 1), the weight ratio micronized pea flour/PAE is 3.6 (dry weight/dry weight).

[0171] The dispersion was mixed until formation of a homogeneous mixture in order to obtain a PF adhesive (PF.sub.G1) with a dry (or solid) content of 48.7% wt/wt.

Adhesive Compositions Comprising Soy Flour

[0172] Same procedure was used to prepare adhesive compositions from two grades of soy flour, except that micronized pea flour was replaced with micronized soy flour SF1 or SF2. The dry content of the final adhesive compositions was kept at 48.7% wt/wt.

Preparation of Particle Boards

[0173] The adhesive performances of PF.sub.G1 adhesive composition were compared to those of SF1 and SF2 adhesive compositions at lab scale. Typically, the pre-dried wood particles from LINEX PANNEAUX (as described in Example 1) were put into a 20 L stirring bowl. Then the adhesive composition was added to the wood particles. The amount of PF.sub.G1 adhesive composition or SF1 and SF2 adhesive compositions, based on the solid content, was calculated to be 6.8% wt/wt (corresponding to 0.8 wt % of PAE, on a dry weight basis) based on pre-dried wood particles. The glued wood particles were mixed during 5 min and the mats were formed using a forming box size of 20 cm20 cm.

[0174] The mats were then cold pressed by hand before being placed into a heating press at 180 C., for 144, 180 or 300 seconds corresponding to press time of 12, 15 or 25 s/mm respectively at pressure of 15 metric tons (MeT) using a CARVER hot press (platen of 20 cm20 cm) in order to obtain target boards of 12 mm thickness with a density of 650 kg/m.sup.3.

[0175] The adhesive performances of PF.sub.G1 were also compared to those of UF resin at pilot scale on particle boards. Typically, 6.8 wt % of PF.sub.G1 adhesive composition (based on solid content) was first injected onto wood particles from Linex into a particle blender (Imal, Lab Glue Blender 300) using a spray nozzle and the glued wood particles were mixed during 5 min. The impregnated particles were then weighted in order to achieve an approximately board density of 650 kg/m.sup.3. Forming box size was 600 mm600 mm to make the mat. After wood/adhesive sample addition, the mat was cold pressed by hand. The mat was then placed into a heating press from Imal (Italia) (platen of 1000 mm x 1000 mm) and pressed to a thickness of 16 mm and cured at 210 C. at different press times of 8, 10 and 12 s/mm (i.e. 96, 120 and 144 seconds). After pressing, the boards were placed in a conditioning room at 20 C. and 65% r.h. (relative humidity) for at least three days. Same procedure was used to prepare particle boards with UF used as reference. UF solution was prepared by mixing UF solution with a hardener. The amount of UF and the hardener, based on the solid content, was calculated to be 6.6% wt/wt and 0.36% wt/wt, respectively based on pre-dried wood particles.

Example 4

Preparation of Decorative Veneered MDF Boards

Adhesive Composition Comprising Pea Flour

[0176] An adhesive composition for wood veneer application was prepared by blending PF with PAE solution. The composition of the adhesive composition was calculated based on the whole adhesive composition including the moisture.

[0177] 400 g of micronized pea flour was first dispersed into 230 g of water. 375 g of PAE solution was then added to the dispersion. pH of the solution was adjusted to 8 with a 10 M NaOH solution and the whole solution was mixed until obtaining an homogeneous mixture.

[0178] As the PAE is provided under the form of an aqueous solution (see Example 1), the weight ratio micronized pea flour/PAE is 4.9 (dry weight/dry weight).

[0179] The adhesive composition named PF.sub.G2 with a solid content of 40.0% wt/wt had a viscosity of 1022 mPa.Math.s.

Veneer Preparation

[0180] The veneers were glued on pre-cut NEXT MDF boards (as described in Example 1). Using a paint roller, the adhesive composition was applied to one of the surfaces of the MDF board and then a wood veneer strip of dimensions of 20 cm20 cm was applied onto the glued MDF surface. Then the adhesive composition was applied onto the second surface of the MDF board and another wood veneer strip of dimension of 20 cm20 cm was applied onto the glued MDF surface.

[0181] The total amount of adhesive composition was calculated to be 87.5 g/m.sup.2 onto each surface. The coated wood veneer strips were then glued by hot-pressing (CARVER Heated Press) at 110 C. for different times at a pressure of 80 N/cm.sup.2.

[0182] Same procedure was done with UF resin used as reference. A mixture of UF resin and hardener, 85% and 15%, respectively was first prepared and then 87.5 g/m.sup.2 of the mixture was applied onto each surface of NEXT MDF boards. The veneer strips were then hot-pressed for different times at 110 C. and at a pressure of 80 N/cm.sup.2.

[0183] Two boards were produced for each test condition.

[0184] After pressing, these glued specimens were allowed to cool and set aside for conditioning at 20 C. and relative humidity (60%) for 3 days before further experiments.

Example 5

Particle Board Properties

Particle Boards Prepared with Pea Flour Adhesive

[0185] The mechanical properties of the particle boards prepared from the PF.sub.G1 adhesive in Example 3 were evaluated at different press factors and compared with that obtained with a UF resin used as a reference (FIG. 2). The internal bond (IB) of boards prepared with PF.sub.G1 exhibited the same value as that of the boards prepared from UF resin at press factors of 8, 10 and 12 s/mm, showing that the PF.sub.G1 adhesive had a very fast curing time. The modulus of rupture (MOR) and the modulus of elasticity (MOE) of the PF.sub.G1 adhesive were comparable to the values obtained with UF resin and were higher at a press factor of 12 s/mm.

[0186] These results show the good adhesive performances of the biobased adhesive PF.sub.G1.

Comparison of Particle Boards Prepared with Pea Flour Adhesive with Boards Prepared from Soy Flour Adhesives

[0187] Adhesive performances of the PF.sub.G1 adhesive prepared from pea flour were compared to adhesive compositions prepared from soy flour (FIG. 3). Two grades of soy flour were evaluated (SF1 and SF2). The mechanical properties (IB, MOR and MOE) of the particle boards were evaluated according to the procedure set forth in Example 1.

[0188] The internal bond of the particle boards prepared from PF.sub.G1 adhesive at a press factor of 12 s/mm was identical to that of SF1 adhesive and higher than that of SF2 adhesive. The

[0189] MOE and MOR of boards prepared with the PF.sub.G1 adhesive at a press factor of 12 s/mm were higher than the flexural moduli (MOE and MOR) of SF1 and SF2 adhesives.

[0190] Even if good mechanical properties were obtained with the soy flour-based adhesives, the use of this raw material has several limitations due to its very high viscosity. At same solid content of 48,7%, the viscosity of SF1 and SF2 adhesive compositions was respectively 2775 mPa.Math.s and 3277 mPa.Math.s while the limiting viscosity to be injected throughout nozzles was found to be around 1000 mPa.Math.s (Table 1). Increasing water amount to prepare SF1 and SF2 adhesive compositions however leads to an excess of water after resination (over 20% wt/wt of humidity, measured with a moisture analyzer).

[0191] Consequently, only the PF adhesive is a valuable raw material to prepare processable composition having good adhesive performances. Its viscosity was 828 mPa.Math.s and the humidity of glued wood particles was below 11% wt/wt (moisture analyzer).

TABLE-US-00001 TABLE 1 Viscosity of PF.sub.G1, and compositions prepared from SF1 and SF2 Viscosity (mPa .Math. s) PF.sub.G1 828 SF1 2775 SF2 3277

Example 6

Decorative Veneered MDF Board Properties

[0192] The adhesive performances of PF.sub.G2 adhesive on veneered boards prepared according to Example 4 are shown in Table 3. The bonding performances and water resistance were conducted by monitoring the delamination in dry 10 min after the pressing step or soak conditions. Good performances were expected when the specimen did not failed after delamination. The mechanical properties (delamination in dry condition 10 min after the pressing step and immediately after immersion into water and surface soundness) of the boards were evaluated according to the procedure set forth in Example 1.

[0193] The test was performed on oak strip veneered MDF boards prepared with different pressing times using UF resin (Table 2) or PF.sub.G2 adhesive (Table 3). All results are compared with UF reference.

[0194] Table 3 shows good bonding performances and water resistance of the PF.sub.G2 adhesive; good adhesion in dry and wet conditions were obtained even at low pressing time of 15 seconds (very closed to the UF reference).

[0195] The surface soundness of the veneered MDF boards was also evaluated. The values of boards laminated with oak veneer strip at a pressing time of 15 seconds where respectively 1.29% for the PF.sub.G2 and 1.43% for the UF resin. These values were similar between the PF.sub.G2 adhesive and the UF resin.

TABLE-US-00002 TABLE 2 dry and wet resistance and surface soundness of the UF resin at pressure of 80 N/cm.sup.2 Oak Dry strength Wet strength Surface Press time (10 min after (after soundness (seconds) pressing step) immersion) (N/mm.sup.2) 75 P P 1.32 65 P P 1.35 55 P P 1.08 45 P P 1.24 35 P P 25 P P 1.06 15 P P 1.43 10 P P 1.34 5 F F

TABLE-US-00003 TABLE 3 dry and wet resistance and surface soundness of the PF.sub.G2 adhesive at pressure of 80 N/cm.sup.2 Oak Dry strength Wet strength Surface Press time (10 min after (after soundness (seconds) pressing step) immersion) (N/mm.sup.2) 85 P P 1.26 75 P P 1.13 65 P P 1.55 55 P P 1.33 45 P P 1.51 35 P P 1.44 25 P P 1.39 15 P P 1.29 10 F F

Example 7

Comparison of Physicochemical Properties of Pea Flour with others Native Seeds

[0196] Yellow peas used in these examples are whole seeds that have not undergone pretreatment or other process of preparation (such as seed crushing) contrary to others vegetable raw materials usually selected to prepared biobased adhesive compositions. To confirm the interest of pea flour versus others native grains or plants, additional analysis was conducted on sunflower seeds. Their physicochemical properties were characterized and compared to pea flour.

[0197] To evaluate the properties of sunflower seeds, the first step consisted in micronization to obtain a particle size Dv10 of 206 m, Dv50 of 387 m and Dv90 of 654 m. However, the grinding of sunflower seeds was not possible due to an excess of oil amount (41.6% wt/wt) which clogged the grinder. Only agglomerates were obtained with sunflower seeds (FIG. 4B) instead of a homogeneous powder such as the powder obtained after grinding pea seeds (FIG. 4A). Due to this limitation, sunflower seeds cannot be used to produce liquid formulation.

Example 8

Water Resistance of Plywood Panels

Preparation of 5-Ply and 7-ply Plywood Panels

[0198] The PF.sub.G2 adhesive was applied to both sides of a veneer [20 cm20 cm] using an adhesive roller-coater. The targeted glue spread rate was 150 g/cm.sup.2 by face (total adhesive). 5-ply panels or -ply panels were made in such a way that the adhesive-coated veneer was stacked between two uncoated veneers with the grain directions of two neighboring veneers perpendicular to each other. The final thickness of the 5-layer and 7-layer plywood panels was 12 mm and 22 mm, respectively. Experiments were conducted on polar wood (to produce the 5-layer and 7-layer plywood) and okoume wood (to produce the 5-layer plywood).

[0199] After gluing step, the stacked veneers were hot-pressed at 1.88 Kg/cm.sup.2 and 110 C. using a CARVER hot press (platen of 20 cm20 cm) for 9 min (to produce the 5-layer plywood) or for 18 min (to produce the 7-layer plywood). Same procedure was conducted using MUF resin. 5-ply panels from polar wood and okoume wood were made with glue spread rate of 150 g/cm.sup.2 by face. The stacked veneers were hot-pressed at 1.88 Kg/cm.sup.2 and 110 C. for 9 min (to produce the 5-layer plywood) or for 18 min (to produce the 7-layer plywood). The panels made from PF.sub.G2 and from MUF adhesives were stored at ambient temperature for at least 48 h before being cut and evaluated for their water resistance.

Water Resistance of Plywood Panels

[0200] The water resistance of plywood panels was determined by a three-cycle soak based on the following procedures from the American National Standard for Hardwood and Decorative Plywood-2004 (ANSI/HPVA HP-1-2004). Three specimens (127 mm50.0 mm) from each 5-ply or 7-ply plywood panels (produced from PF.sub.G2 and from MUF adhesives) were used for the three-cycle soak test. Plywood specimens were soaked in water at 24 C. for 4 h and then dried at 50 C. for 19 h with sufficient air circulation. The criteria for interior application as described in the standard is that 95% of the specimens should not delaminate after the first soaking/drying cycle, and 85% of specimens (i.e., 2 out of 3 specimens) should not delaminate after the third soaking/drying cycle.

Results

[0201] The water-resistance of plywood bonded with the PF.sub.G2 and MUF adhesives is shown in Table 4. Results shown revealed that plywood panels bonded with the PF.sub.G2 adhesive all passed the three-cycle soak test and no specimens delaminated for all conditions (5-ply and 7-ply with poplar and okoume woods).

TABLE-US-00004 TABLE 4 water resistance of plywood panels bonded with PF.sub.G2 of MUF adhesives Number of specimens that passed the three cycle soak Pass or Wood Number of test/total specimen Fail Adhesive type plies 1st cycle 3rd cycle P PF.sub.G2 Poplar 5 3/3 3/3 P Poplar 7 3/3 3/3 P Okoume 5 3/3 3/3 P MUF Poplar 5 3/3 3/3 P Poplar 7 3/3 3/3 P Okoume 5 3/3 3/3 P

Example 9

Decorative Veneered PlywoodComparative Examples

Materials and Methods

[0202] Whole yellow pea seeds were purchased from Sanders (France) and ground in order to obtain pea flour (PF) with a diameter of Dv (10) of 7 m, Dv(50) of 25 m, and Dv(90) of 77 m (measured as described in Example 1). A pea protein concentrate powder with a protein content of 50% wt/wt (PP50) and a pea protein isolate powder with a protein content of 80% wt/wt (PP80) were purchased from MyPROTEIN (France) and used as received. The particle size of the powders PP50 and PP80 was measured as described in Example 1 and found to have a diameter of Dv(10) of 13 m, Dv(50) of 47 m, and Dv(90) of 145 m and Dv(10) of 19 m, Dv(50) of 54 m, and Dv(90) of 121 m, respectively. Total crude protein content of PF, PP50 and PP80 obtained using Kjeldhal procedure as described in Example 1 was 19.0%1.6% wt/wt, 52% +1.3% wt/wt and 78% wt/wt2%, respectively. The dry content of the PF, PP50 and PP80 was 8,8% wt/wt; 9,0% wt/wt and 6,1% wt/wt, respectively. Crude vegetable glycerine with a glycerol content of about 85% wt/wt was provided by Oleon (France) and used as diluent. Polyamidoamine-epichlorohydrin (PAE) resin Marenyl WPD 20 was from Mare SpA (Milan, Italia) and used as received. This PAE resin is an aqueous solution with a polymer solids content of 20% wt/wt. Sucrose was purchased from Fisher Scientific and used as received. The veneer strips [20 cm20 cm] with a thickness of 0.6 mm were oak and the plywood [20 cm20 cm] were 5-ply panels of poplar.

[0203] The composition of the adhesive formulations was calculated based on the whole product including the moisture.

Formulations of a 1.SUP.st .Set of Adhesive Compositions

[0204] 30% wt/wt of the protein-based raw materials PF or PP50 or PP80 were first dispersed into 70% wt/wt of PAE resin. pH of the solutions was adjusted at 8 with a 10 M NaOH solution and the whole solutions were mixed until obtaining an homogeneous mixture.

Formulations of a 2.SUP.nd .Set of Adhesive Compositions

[0205] Adhesive formulations were prepared by adding 5% wt/wt of sucrose into a mixture of 20% wt/wt glycerol and 55% wt/wt of PAE resin, based on the teaching of patent application CN110385753A. After a complete solubilization, 20% wt/wt of the protein-based raw materials PF or PP50 or PP80 were added to the blend and mixed until obtaining a homogeneous formulation.

Formulations of a 3.SUP.rd .Set of Adhesive Compositions

[0206] Adhesive formulations were prepared by adding 5% wt/wt of sucrose into a mixture of 20% wt/wt glycerol and 55% wt/wt of PAE resin, based on the teaching of patent application CN110385753A. After a complete solubilization, 20% wt/wt of the protein-based raw materials PF or PP50 or PP80 were added to the blend and mixed until obtaining an homogeneous formulation. pH of the solutions was adjusted at 8 with a 10 M NaOH solution and the whole solutions were mixed until obtaining homogeneous mixtures. The pH was adjusted in order to increase the reactivity of the PAE resin.

Working Life

[0207] The working life is defined as the amount of time the adhesive formulation remains low enough in viscosity to be easily applied to the substrate. The working life was visually assessed. The time was reported when the adhesive formulation was totally gelified after a storage at ambient temperature after the preparation.

Veneer Preparation

[0208] The veneers were glued on 5-ply plywood pre-cut in order to obtain specimens of 20 cm20 cm. Using a paint roller, the adhesive preparations were applied to the surface of the plywood and then a wood veneer strip was covered onto the glued plywood surface. The total amount of adhesives was calculated, based on the teaching of patent application CN110385753A, to have 87.5 g/m.sup.3 for the 1.sup.st set of adhesive composition and 220 g/m.sup.3 for the 2.sup.nd and 3.sup.rd set of adhesive compositions.

[0209] The coated wood veneer strips were then glued by hot-pressing (CARVER Heated Press) at 110 C. at a pressure of 80 N/cm.sup.2. After the pressing step, these glued specimens were allowed to cool and set aside for conditioning at 20 C. and relative humidity (60%) for 3 days before further experiments.

Veneered Boards Characterization

[0210] Delamination tests were conducted after pressing step. Delamination was estimated when a failure occurred between the veneer strips and the plywood due to poor interfacial adhesion. Pressing time to obtain laminated boards without delamination was reported.

Results

[0211] Three sets of adhesives formulations were prepared using PF or PP50 or PP80 respectively. For an industrial use, these formulations shall have a low viscosity to be correctly applied onto the wood veneers, a long working life to avoid gelification during the process of gluing, and be able to laminate boards at short pressing time (advantageously less than 120 seconds).

[0212] All the formulations (PF, PP50 and PP80) of the 2.sup.nd set of adhesive compositions (without NaOH) showed low viscosity and long working life (see Table 5). However, these adhesive compositions required a very long pressing time (more than 420 seconds) to laminate the boards, which is not compatible for an industrial use. Regarding the 3.sup.rd set of adhesive compositions, only formulations containing PF or PP50 showed low viscosity and long working life (see Table 5). However, these adhesive compositions required a long pressing time of 210 seconds which is also not compatible for an industrial use. Formulation containing PP80 had a too high viscosity and too short working life to be applied and therefore could not be evaluated (see Table 5).

[0213] Regarding the 1.sup.st set of adhesive compositions, only the formulation containing PF (according to the present invention) showed low viscosity and long working life (see Table 5). Only 15 seconds were needed to laminate the boards, which meets the industrial needs. Formulations containing PP50 or PP80 of the 1.sup.st set of adhesive compositions had a too high viscosity and too short working life to be applied and therefore could not be evaluated (see Table 5).

[0214] An additional evaluation was conducted with a lower amount of adhesive formulation of 87.5 g/m3 for the 1.sup.st, 2.sup.nd and 3.sup.rd set of adhesive compositions. But no laminated boards were obtained with the 2.sup.nd and 3rd set of adhesive compositions.

[0215] In addition the veneered boards glued with the adhesive composition prepared according to the formation of the 1.sup.st set containing PF (according to the invention) showed a clear aspect without any glue stain, compared to the veneered boards glued with the other tested adhesive compositions that showed glue stains, characterized by dark streaks or even blisters (see Table 6).

Conclusion

[0216] The formulation containing PF of the 1.sup.st set of adhesive compositions (according to the invention) is the best adhesive formulation as laminated boards and good surface aspect were obtained at very short press time. Indeed appropriate viscosity, long working life and best mechanical property, and clear surface aspect of the veneered boards were obtained.

TABLE-US-00005 TABLE 5 physical-chemical properties of formulations (1.sup.st 2.sup.nd and 3.sup.rd set) prepared with PF, PP50 and PP80 respectively Formulation 1.sup.st set 2.sup.nd set 3.sup.rd set Raw material PF PP50 PP80 PF PP50 PP80 PF PP50 PP80 Viscosity 1280 7400 300000 390 420 485 670 1100 270000 (mPa .Math. s) Working >180 20 5 >180 >180 >180 >180 >180 5 life (min) Pressing time 15 n.a n.a >420 >420 >420 210 210 n.a to obtain laminated board without delamination (sec) n.a = Not evaluated due to a high level of viscosity and/or too short time of working life of the adhesive formulation

TABLE-US-00006 TABLE 6 Properties of boards glued with the adhesives formulations prepared with PF, PP50 and PP80 respectively Formulation 1.sup.st set 2.sup.nd set 3.sup.rd set Raw material PF PP50 PP80 PF PP50 PP80 PF PP50 PP80 Surface Clear n.a n.a Glue Glue Glue Glue Glue n.a aspect of stains stains stains stains stains the glued veneered board