Method for preparing an activated lignin composition

Abstract

The present invention relates to a method for preparing an activated lignin composition. In addition, the present invention also relates to a method for further processing the thus activated lignin composition in a method for preparing a lignin-phenol formaldehyde resin. Such a lignin-phenol formaldehyde resin can be used in the manufacturing of laminates by replacing the traditional synthetic phenol formaldehyde resin.

Claims

1. A method for manufacturing a high pressure laminate comprising a step of preparing a core layer and a step of pressing said core layer in a press using an elevated temperature and an elevated pressure, wherein said step of preparing said core layer comprises impregnating a paper with a resin mixture and constructing a stack of resin impregnated papers, wherein said resin mixture comprises a lignin-phenol formaldehyde resin prepared with lignin methylolation and phenol methylolation steps, said step of lignin methylolation comprises: i) providing a liquid lignin having free active hydrogen positions; ii) heating said liquid lignin to a temperature in a range of 60? C. to 85? C.; iii) adding formaldehyde to said heated liquid lignin under stirring conditions, wherein the formaldehyde is added in a stoichiometric excess ratio of >1:1 relative to the lignin's free active hydrogen positions; iv) maintaining the temperature of the mixture according to iii) in a range of 60? C. to 85? C., during a time period of at least 10 minutes thereby obtaining an activated lignin composition, said step of phenol methylolation comprises: v) optionally heating said activated lignin composition of step iv) to a temperature in a range of 50? C. to 90? C.; vi) adding phenol to said activated lignin composition; vii) adjusting the temperature of the mixture of step vi) to be within the range of 60? C. to 90? C.; viii) adding formaldehyde to said mixture of step vii), ix) comprising of heating and maintaining the mixture of step viii) at a temperature in a range 50? C. to 80? C., during a period of time of at least 10 minutes, thereby obtaining said lignin-phenol formaldehyde resin.

2. The method according to claim 1, wherein optional step v) is carried out in a range of 50? C. to 85? C.

3. The method according to claim 1, wherein step vii) is carried out in a range of 60? C. to 85? C.

4. The method according to claim 1, wherein step ix) is carried out at a range of 60? ? C. to 80? C.

5. The method according to claim 1, wherein step ix) is carried out for at least 30 minutes.

6. The method according to claim 1, wherein the liquid lignin having free active hydrogen positions has a pH of at least 6.

7. The method according to claim 1, wherein the temperature according to step ii) is in a range of 65? C. to 80? C.

8. The method according to claim 1, wherein the temperature according to step iv) is in a range of 65? ? C. to 80? C.

9. The method according to claim 1, wherein the period of time according to step iv) is in a range of 15 minutes to 4 hours.

10. The method according to claim 1, wherein the addition of formaldehyde to the heated liquid lignin according to step iii) is carried out on a continuous basis over a period of time or by one or more doses of formaldehyde.

11. The method according to claim 1, wherein said lignin-phenol formaldehyde resin, prepared with lignin methylolation and phenol methylolation steps, for impregnating paper for use in said core layer is a lignin-phenol formaldehyde resin in which a resin recipe specifies that the weight of dry lignin used is equal to the weight of the dry phenol used.

12. The method according to claim 1, wherein optional step v) is carried out in a temperature in a range of 65? C. to 80? C.

13. The method according to claim 1, wherein the addition of formaldehyde according to step viii) is carried out on a continuous basis over a period of time or by the stepwise addition of two or more doses of formaldehyde.

14. The method according to claim 1, wherein the addition of formaldehyde according to step viii) occurs in a period of time between 20 and 150 minutes.

15. The method according to claim 1, wherein the temperature during step viii) is maintained in a range of 60? ? C. to 85? C.

16. The method according to claim 1, wherein the amount of formaldehyde added according to step viii) is related to the amount of phenol added according to step vi) and the amount of residual free formaldehyde in the activated lignin, the combination of the amount of formaldehyde added in step viii) together with the amount of formaldehyde residual in the activated lignin when compared with the amount of phenol charged in step vi), refers to a molar ratio Phenol: Formaldehyde in the range of 1.0:0.9 to 2.0.

17. The method according to claim 1, wherein step ix) of methylolation is maintained during a period of time between 40 and 120 minutes.

18. The method according to claim 1, wherein the mixture obtained after step ix) is cooled.

19. The method according to claim 1, wherein said lignin-phenol formaldehyde resin impregnated papers are made with saturation base kraft papers.

20. The method according to claim 1, wherein said core layer comprises a combination of prepregs made of wood fibres and said lignin-phenol formaldehyde resin impregnated papers.

21. The method according to claim 20, wherein said lignin-phenol formaldehyde resin impregnated papers are positioned as an outer-layer of the core-material while having prepregs in the middle.

22. The method according to claim 20, wherein said prepegs and lignin-phenol formaldehyde resin impregnated papers are interlaced such that said impregnated papers are positioned between said prepregs or are positioned as an outer-layer of the core-material.

23. The method according to claim 1, wherein said core layer is combined with one or more decorative layers, wherein said one or more decorative layers are positioned on one side or on both sides of the core-layers.

24. The method according to claim 23, wherein said one or more decorative layers are based on decorative papers saturated with thermosetting resin like melamine-formaldehyde resin.

25. The method according to claim 23, wherein said one or more decorative layers are coated using an acrylic resin and hardened using a UV-curable or EB-curable system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is further described in the following examples, together with the appended figures, which do not limit the scope of the invention in any way. Preferred features of each aspect of the invention are as for each of the other aspects mutatis mutandis. Embodiments of the present invention are described as mentioned in more detail with the aid of examples of embodiments, together with the appended figures, the only purpose of which is to illustrate the invention and are in no way intended to limit its extent.

(2) FIG. 1 is a graph illustrating lignin activation with variation in pH.

(3) FIG. 2 is a graph illustrating lignin activation with variation in temperature.

(4) FIG. 3 is a graph illustrating lignin activation with a comparison between Kraft lignin and sodium lignosulphonate.

(5) FIG. 4 is a graph illustrating molar mass distribution examples.

(6) FIG. 5 is a graph illustrating different charges of formaldehyde relative to Kraft lignin.

(7) FIG. 6 is a graph illustrating molar mass distribution examples.

(8) FIG. 7 is a graph illustrating activation temperature versus viscosity.

DETAILED DESCRIPTION

(9) The present invention also relates to a method for manufacturing a laminate comprising of preparing a core layer and pressing said core layer in a press using an elevated temperature and an elevated pressure, wherein a resin mixture comprising a lignin-phenol formaldehyde resin obtained according to the method according to the present invention as discussed above is used for impregnating said core layer.

(10) In an embodiment of the present method for manufacturing a laminate the core layer comprises of one or more prepregs made of wood fibres.

(11) In an embodiment of the present method for manufacturing a laminate the core layer comprises of a stack of resin impregnated papers, wherein said papers are preferably made with saturation base kraft papers.

(12) In an embodiment of the present method for manufacturing a laminate the core layer comprises of a combination of prepregs and impregnated papers, wherein said prepregs are preferably made of wood fibres and wherein the impregnated papers are preferably made with saturation base kraft papers.

(13) In an embodiment the impregnated papers are positioned as an outer-layer of the core-material, whilst having prepreg(s) in the middle.

(14) In another embodiment the prepregs and impregnated papers are interlaced, preferably in such a way that said impregnated papers are positioned between said prepregs, wherein said impregnated papers are optionally positioned as an outer-layer of the core-material.

(15) In another embodiment the core layer is combined with one or more decorative layers, wherein said decorative layer is positioned on one side or on both side of core-layers.

(16) In another embodiment one or more decorative layers are based on decorative paper saturated using thermosetting resin like melamine-formaldehyde resin.

(17) In another embodiment one or more decorative layers are coated using acrylic resin hardened using either UV-curable or EB-curable system.

(18) Method for Viscosity Measurements

(19) In the examples a Brookfield LVT was used to measure the viscosity. Once the temperature of the samples had been adjusted to 20? C., their viscosities' were measured using the appropriate spindle and rpm settings.

(20) Method for pH determination

(21) Samples were adjusted to 20? C. and their pH was measured by inserting a calibrated pH electrode/meter.

(22) Method for free formaldehyde determination (HPLC)

(23) The sample was accurately weighed out (200 mg) into a 50 ml volumetric flask and made up to the mark with methanol. Once dissolved and a homogeneous solution is formed, 2 ml are then pipette to a second 50 ml volumetric flask. This was then approximately half filled with distilled water and 2 ml of DNPH (2,4-dinitrophenolhydrazine) solution were then added. It was then filled to the mark with more distilled water and homogenised. The DNPH reacts with formaldehyde to form a derivative that is chromophoric. A small amount (circa 4 ml) is removed and passed through a 0.2 ?m filter before being readied for injection onto the HPLC column. (NB: the first 2 ml of filtrate or so go to waste, whilst the remainder goes into a sample vial that is loaded onto the HPLC carousel).

(24) The HPLC used a waters Nova-Pak C18, 4 ?m 3.9?20 mm pre-column, and a waters Nova-Pak C18, 4 ?m 4.6?150 mm main-column. The eluent was isocratic, 70% methanol:30% aqueous sodium formate buffer pH 4.5. The aqueous buffer consists of 4.3 g of sodium hydroxide plus 4.75 ml of formic acid in 2.5 litres of HPLC grade water. Both the methanol and the pH 4.5 aqueous buffer were degassed before being used as an eluent. After running the samples, the chromatograms were then evaluated and the free formaldehyde of the sample was then calculated. For each sample the determination is done twice. Note standards with formaldehyde and DNPH were also prepared and run for calibration purposes.

(25) Method for Free Phenol Determination

(26) The sample was accurately weighed out (200 mg) into a 50 ml volumetric flask and made up to the mark with methanol. Once dissolved and a homogeneous solution is formed, a small amount (circa 4 ml) is removed and passed through a 0.2 ?m filter before being readied for injection onto the HPLC column. (NB: the first 2 ml of filtrate or so go to waste, whilst the remainder goes into a sample vial that is loaded onto the HPLC carousel). The HPLC used a waters Nova-Pak C18, 4 ?m 3.9?20 mm pre-column, and a waters Nova-Pak C18, 4 ?m 4.6?150 mm main-column. The elution program was as described in Table 1.

(27) TABLE-US-00001 TABLE 1 Elution program for free phenol determination Retention aqueous sodium Type Time formate buffer of (min) methanol pH 4.5 elution 0 to 5 7% 93% Isocratic 5 to 30 100% 0% Gradient 30 to 40 100% 0% Isocratic 40 to 50 7% 93% Gradient

(28) The aqueous buffer consists of 4.3 g of sodium hydroxide plus 4.75 ml of formic acid in 2.5 litres of HPLC grade water. Both the methanol and the pH 4.5 aqueous buffer were degassed before being used as an eluent. After running the samples, the chromatograms were then evaluated and the free phenol of the sample was then calculated. For each sample the determination is done twice. Note standards with phenol were also prepared and run for calibration purposes.

(29) Method for SEC Analysis

(30) The SEC measurements were performed in 0.1 M NaOH eluent using PSS MCX 1000 & 100000 ? columns with a precolumn. The samples were diluted with 0.1

(31) M NaOH solution and filtered (0.45 ?m) prior to measurement. Molar mass distributions were calculated with the use of polystyrene sulphonate standards. A photo diode array set at 280 nm was used as the detector.

(32) Method for 2D HSQC NMR

(33) Samples were freeze dried and then dissolved in D.sub.2O (90 mg/ml). 2D (1H-13C) HSQC NMR measurements were performed using a Bruker Avarice III 600 MHz with double resonance and QCI cryoprobe. To evaluate the extent of methylolation (CH.sub.2OH) during lignin activation, the signal intensities were normalized relative to the signal from the lignin methoxy (MeO) groups.

(34) Examples 4 to 10 (Kraft Lignin Activation: Variance with pH)

(35) A 3000 ml glass reactor configured for reflux under atmospheric conditions was used. It also had an electric motor and anchor stirrer that was set to a stirring rate of 400 rpm. Furthermore the reactor was double walled, so that heating could be provided by a recirculating thermostatically controlled oil bath. The reactor also had cooling coils through which cold water could pass. This arrangement allowed good control of the experiment's temperature.

(36) To this reactor materials were added; and specifically for the Kraft Lignin Activation Examples 4-10, the materials and quantities are listed in Tables 2 and 3.

(37) Note, the data shown in Table 2 are to be regarded as raw materials for present step i), namely providing a liquid lignin having free active hydrogen positions.

(38) TABLE-US-00002 TABLE 2 Preparation of liquid lignin Step 1: Liquid Lignin Preparation Example 4 5 6 7 8 9 10 Target pH 10.0 9.0 11.0 8.0 12.0 6.0 13.0 Raw Material A Demineralised 1207.68 1243.60 1207.68 1243.68 1207.68 1267.68 1207.68 water [1] B KOH 47% [1] 76.00 40.00 76.00 40.00 76.00 16.00 76.00 C Kraft Lignin 565.32 565.32 565.32 565.32 565.32 565.32 565.32 67.22% D KOH 47% [2] 0.00 7.28 34.39 2.03 83.87 0.00 120.10 E Demineralised 151.00 143.72 116.61 148.97 67.13 151.00 30.90 water [2]

(39) TABLE-US-00003 TABLE 3 lignin activation Step 2: Lignin Activation Example 4 5 6 7 8 9 10 Target pH 10.0 9.0 11.0 8.0 12.0 6.0 13.0 Raw Material Liquid Lignin 1907.82 1886.05 1890.04 1881.60 1897.38 1894.40 1908.53 (after removal of retained sample) F Formalin 55% 73.23 72.40 72.55 72.22 72.83 72.72 73.26

(40) The following procedure was used for Examples 4-10. To the reactor, (A) demineralised water [1] and (B) KOH 47% [1] were charged. The temperature was then adjusted to 75? C., where upon (C) the kraft lignin powder was charged. This was allowed to dissolve over 1 hr at 75? C. A 100 g sample is then taken, weighed and cooled to 20? C. in an ice bath. For each example there is a target pH, these are indicated in Table 2. The pH of the sample is measured, and if necessary the pH is adjusted by the dropwise addition of KOH 47% under stirringthe amount of KOH 47% needed for this is noted and used to calculate the amounts for materials (D) KOH 47% [2] and (E) demineralised water [2]. The adjusted sample is returned to the reactor and materials (D) and (E) are then charged. The mixture is allowed to stir at 75? C. for a further 1 hr.

(41) Note, the calculations of weights for (D) and (E) are as follows:
KOH 47%[2]=(KOH 47% to adjust sample pH)/(sample)*((water[1])+(KOH[1])+(Kraft Lignin)?(sample))(D)
water[2]=2000?((water[1])+(KOH[1])+(Kraft Lignin)+(KOH[2]))(E)

(42) The temperature of the experimental example was then adjusted to 75? C. (F) Formalin 55% is then charged to the reactor, and a timer is started. Note the formalin charge is based on 96.3% liquid lignin preparation and 3.7% formalin 55%. The temperature is maintained for 4 hr and samples are taken at 10 min, 30 min, 60 min, 120 min, and 240 minfor further characterisation and analysis. These analyses and their results will discussed hereafter.

(43) Examples 11 to 15 (Kraft Lignin Activation: Variance in Temperature)

(44) Examples 11 to 15, are in line with the experimental procedures of Example 4 but with different hold temperatures for the 2.sup.nd steplignin activation.

(45) Step 1the liquid lignin preparation is performed as in Example 4, with a target pH of 10. The temperature is then adjusted to that specified in Table 4 and a retained liquid lignin sample is taken. The formalin charge (F) is then calculated and dosed to the reactor; again this is based on 96.3% liquid lignin preparation and 3.7% formalin 55%. Once charged, a timer is started, the specified temperature maintained, and samples taken at 10 min, 30 min, 60 min, 120 min, and 240 min. The samples were further characterised and analysed. These analyses and their results will discussed hereafter.

(46) TABLE-US-00004 TABLE 4 Lignin activation temperatures for examples 11 to 15 Step 2: Lignin Activation Example 11 12 13 14 15 Target lignin 98? C. 85? C. 70? C. 65? C. 60? C. activation temperature Target pH 10.0 10.0 10.0 10.0 10.0
Examples 16 and 17 (Lignosulphonate Activation)

(47) The experimental procedures in Example 16 are similar to those mentioned in Example 4 but with the kraft lignin substituted by sodium Lignosulphonate. Example 17 is a repeat of 16, but without the KOH addition; thus giving an example with lower pH. For both, the same reactor and experimental steps were used as in the previous examples. The materials used are specified in Tables 5 and 6.

(48) TABLE-US-00005 TABLE 5 Raw materials for Step 1 - liquid lignin preparation Step 1: Liquid Lignin Preparation Example 16 17 Target pH 10.0 8.4 Raw Material A Demineralised water [1] 1360.67 1360.67 B KOH 47% [1] 0.00 0.00 C Sodium lignosulphonate 412.33 412.33 92.16% D KOH 47% [2] 7.34 0.00 E Demineralised water [2] 219.66 227.00

(49) TABLE-US-00006 TABLE 6 Raw materials for Step 2 - lignin activation Step 2: Lignin Activation Example 16 17 Target pH 10.0 9.0 Raw Material Liquid Lignin 1874.32 1851.14 (after removal of retained sample) F Formalin 55% 71.94 71.05

(50) The following procedure was used for Example 16. To the reactor, (A) demineralised water [1] is charged. The temperature was then adjusted to 75? C., where upon (C) the sodium lignosulphonate powder was charged. This was allowed to dissolve over 1 hr at 75? C. A 100 g sample was then taken, weighed and cooled to 20? C. in an ice bath. The pH of the sample was measured, and then adjusted by the dropwise addition of KOH 47% under stirringthe amount of KOH 47% needed for this was noted and used to calculate the amounts for materials (D) KOH 47% [2] and (E) demineralised water [2]. The adjusted sample was returned to the reactor and materials (D) and (E) were then charged. The mixture was then allowed to stir at 75? C. for a further 1 hr.

(51) At 75? C., (F) Formalin 55% was then charged to the reactor, and a timer is started. Note the formalin charge is based on 96.3% step 1 liquid lignin preparation and 3.7% formalin 55%. The temperature is maintained for 4 hr and samples are taken at 10 min, 30 min, 60 min, 120 min, and 240 min. The samples were further characterised and analysed. These analyses and their results will discussed hereafter.

(52) For Example 17, no KOH was added. Since sodium lignosulphonate is soluble in water its natural pH was taken for the experimentthis happened to be 8.4.

(53) Example 18 (Kraft Lignin Activation: Variance in Formalin)

(54) In the previous Examples, the formalin dosing had been based on 1 g of formaldehyde (100%) for 9 g of dry lignin. In Example 18, a lower formaldehyde dosing is used; namely 1 g of formaldehyde (100%) for 12 g of dry lignin. In other respects it is like Example 4. See Tables 7 and 8 for weights of materials used.

(55) TABLE-US-00007 TABLE 7 Raw materials for Step 1 - liquid lignin preparation Step 1: Liquid Lignin Preparation Example 18 Target pH 10.0 Raw Material A Demineralised water [1] 1207.68 B KOH 47% [1] 76.00 C Kraft Lignin 67.22% 565.324 D KOH 47% [2] 0.0 E Demineralised water [2] 151.00

(56) TABLE-US-00008 TABLE 8 Raw materials for Step 2 - lignin activation Step 2: Lignin Activation Example 18 Target pH 10.0 Raw Material Liquid Lignin 1907.82 (after removal of retained sample) F Formalin 55% 54.92

(57) Again samples were taken at 10 min, 30 min, 60 min, 120 min and 240 min. The samples were further characterised and analysed. These analyses and their results will discussed hereafter.

(58) Example 20 (Lignin Phenol Formaldehyde Resin: No Lignin Activation and No Phenol Methylolation Step)

(59) To a 3000 ml reactor were charged; demineralised water 1207.68 g, KOH 47% 76.00 g, and Antifoam agent 4.00 g. The reactor was configured for atmospheric reflux and the stirrer set at 400 rpm. The batch was then adjusted to 75? C. Once 75? C. was reached, kraft lignin powder 565.32 g were charged to the reactor and allowed to dissolve over 1 hr at 75? C. A 100 g sample was then taken and cooled to 20? C. to check the quality of the dissolution and the pH (target=10). Note: If necessary the sample pH is adjusted and from this the amount of KOH required for adjustment of the rest of the batch is calculated. In this experiment no further adjustment was necessary and the sample was simply returned to the batch.

(60) A second charge of demineralised water 147 g was then charged to the reactor, and the temperature readjusted to 75? C. The batch was then held for a further 1 hr, after which time a 92.34 g sample, liquid lignin retained sample was taken. This meant that 1907.66 g of liquid lignin remained in the reactor. The lignin phenol formaldehyde resin example is intended to have a 50:50 lignin:phenol content, and 1 g formaldehyde for every 9 g of lignin. Additionally the phenol will also require further formaldehyde for cross linkingspecifically in this example at molar ratio of F/P=0.9.

(61) After performing the necessary calculations, 362.46 g of phenol 100% are charged to the reactor, followed by 262.86 g of formaldehyde 55%. The batch was then heated to 90? C. (via exothermal and oil jacket heating) for the condensation reaction to take place; samples were taken at regular time intervals after reaching 90? C.every 10 minutesuntil a total condensation time of 80 minutes was reached. The batch was then cooled and discharged from the reactor.

(62) Example 21 (Lignin Phenol Formaldehyde Resin: with Lignin Activation, but No Phenol Methylolation Step)

(63) To a 3000 ml reactor were charged; demineralised water 1207.68 g, KOH 47% 76.00 g, and Antifoam agent 4.00 g. The reactor is configured for atmospheric reflux and the stirrer set at 400 rpm. The batch was then adjusted to 75? C. Once 75? C. was reached, kraft lignin powder 565.32 g was charged to the reactor and allowed to dissolve over 1 hr at 75? C. A 100 g sample was then taken and cooled to 20? C. to check the quality of the dissolution and the pH (target=10). Note: If necessary the sample pH is adjusted, and from this the amount of KOH required for adjustment of the rest of the batch is calculated. In this experiment no further adjustment was necessary and the sample was simply returned to the batch.

(64) A second charge of demineralised water 147 g was then charged to the reactor, and the temperature readjusted to 75? C. The batch was then held for a further 1 hr, after which time a 123.93 g sample, liquid lignin retained sample was taken. This meant that 1876.07 g of liquid lignin remained in the reactor. The lignin phenol formaldehyde resin example is intended to have a 50:50 lignin:phenol content, and 1 g formaldehyde for every 9 g of lignin. Additionally the phenol will also require further formaldehyde for cross linkingspecifically in this example at molar ratio of F/P=0.9.

(65) After performing the necessary calculations, 72.01 g of formaldehyde 55% were charged to the reactor (this equates to 1 g CH2O for every 9 g of lignin). The batch was then held at 75? C. for 1 hrthis being the lignin activation step.

(66) After the lignin activation, 356.46 g of phenol 100% was charged to the reactor. A second charge of formaldehyde 55% (notemolar ratio F/P=0.9) 186.50 g was then made to the reactor. After which the batch was heated to 90? C. (via exothermal and oil jacket heating) for the condensation reaction to take place. Samples were taken at regular time intervals after reaching 90? C.every 10 minutesuntil a total condensation time of 80 minutes was reached. The batch was then cooled and discharged from the reactor.

(67) Example 22 (Lignin Phenol Formaldehyde Resin: with Lignin Activation and Phenol Methylolation Steps)

(68) To a 3000 ml reactor were charged; demineralised water 1207.68 g, KOH 47% 76.00 g, and Antifoam agent 4.00 g were charged. The reactor is configured for atmospheric reflux and the stirrer set at 400 rpm. The batch was then adjusted to 75? C.

(69) Once 75? C. was reached, kraft lignin powder 565.32 g was charged to the reactor and allowed to dissolve over 1 hr at 75? C. A 100 g sample was then taken and cooled to 20? C. to check the quality of the dissolution and the pH (target=10). Note: If necessary the sample pH is adjusted, and from this the amount of KOH required for adjustment of the rest of the batch is calculated. In this experiment no further adjustment was necessary and the sample was simply returned to the batch.

(70) A second charge of demineralised water 147 g was then charged to the reactor, and the temperature readjusted to 75? C. The batch was then held for a further 1 hr, after which time a 100.00 g sample, liquid lignin retained sample was taken. This meant that 1900.00 g of liquid lignin remained in the reactor. The lignin phenol formaldehyde resin example is intended to have a 50:50 lignin:phenol content, and 1 g formaldehyde for every 9 g of lignin. Additionally the phenol will also require further formaldehyde for cross linkingspecifically in this example at molar ratio of F/P=0.9. After performing the necessary calculations, 72.93 g of formaldehyde 55% were charged to the reactor (this equates to 1 g CH2O for every 9 g of lignin). The batch was then held at 75? C. for 1 hrthis being the lignin activation step.

(71) After the lignin activation, 361.01 g of phenol 100% was charged to the reactor and the temperature brought back to 75? C. A second charge of formaldehyde 55% (notemolar ratio F/P=0.9) 188.88 g was then made to the reactor, but this time via a peristaltic pumpso as to allow dosing over a time period of 60 minutes whilst maintaining a batch temperature of 75? C. Once the formaldehyde had be dosed, the batch was held at 75? C. for a further 60 minthis was the methylolation step.

(72) After the methylolation step, the batch was sampled (i.e. End of Methylolation Step) and then heated to 90? C. and held there for the condensation step. The batch was sampled at the beginning of the condensation and then again every ten minutes, until a total condensation time of 80 minutes had elapsed. The batch was then cooled and discharged from the reactor.

(73) Examples 23 and 24Manufacturing of HPL Compact Panels 6 mm

(74) Based on the principles and processing described in this patent, and the proof given by the earlier examples, a Lignin Formaldehyde Resin (LPF) recipe was developed using both the described lignin activation step and the phenol methylolation step. The recipe contained equal parts kraft lignin and phenol by weight (i.e. one could say that 50% of the phenol had been replaced with lignin). An alkali hydroxide was used as a catalyst. This LPF resin was Example 23.

(75) The same recipe was repeated, but without the lignin activation step and without the phenol methylolation step. In effect all ingredients were charged and the batch was taken to the condensation phase. This was Example 24.

(76) Examples 23 and 24 are analogous to Examples 22 (10 minutes condensation) and 20 (30 minutes condensation) respectively, but with proprietary recipe details. They therefore had similar free phenol and free formaldehyde.

(77) Examples 23 and 24 were used to impregnate kraft paper, using an impregnation line facility, to give comparable nominal target grammages and volatiles. These impregnated papers were then used to make 6 mm thick HPL compact panels using a laboratory press and our normal proprietary press cycle.

(78) The Table 9: below provides an overview of the Examples; 4-18, & 20-22.

(79) TABLE-US-00009 TABLE 9 an overview of the laboratory examples and the samples taken. Free- Free- Formaldehyde Example Example Target Target CH2O(g)/ Viscosity Formaldehyde if no reaction Additional number type pH T?C Lignin(g) pH {cP} (% wt.) - HPLC (% wt.)- Calc. Comments 4 Lignin Activation: 10.0 75.0 1/9 Mw Dist. (SEC) and Kraft lignin NMR (2D HSQC) on Liquid lignin 10.07 18.6 <0.05% 0.00% samples; Liquid 10 min. activation 9.90 19.2 1.55% 2.03% Lignin, 60 min 30 min. activation 9.85 18.6 1.45% 2.03% Activation, and 60 min. activation 9.82 20.4 1.27% 2.03% 120 min Activation 120 min. activation 9.70 24.0 1.13% 2.03% 240 min. activation 9.46 46.8 0.87% 2.03% 5 Lignin Activation: 9.0 75.0 1/9 Kraft lignin Liquid lignin 8.60 13.8 <0.05% 0.00% 10 min. activation 8.46 13.2 1.64% 2.03% 30 min. activation 8.38 13.8 1.66% 2.03% 60 min. activation 8.37 13.8 1.67% 2.03% 120 min. activation 8.23 13.2 1.56% 2.03% 240 min. activation 6 Lignin Activation: 11.0 75.0 1/9 Kraft lignin Liquid lignin 11.23 17.4 <0.05% 0.00% 10 min. activation 11.04 16.8 1.07% 2.03% 30 min. activation 10.98 18.0 0.91% 2.03% 60 min. activation 10.96 19.2 0.75% 2.03% 120 min. activation 10.90 22.2 0.60% 2.03% 240 min. activation 7 Lignin Activation: 8.0 75.0 1/9 Kraft lignin Liquid lignin 8.11 12.0 <0.05% 0.00% 10 min. activation 8.01 12.6 1.65% 2.03% 30 min. activation 7.98 12.0 1.65% 2.03% 60 min. activation 7.91 12.6 1.64% 2.03% 120 min. activation 7.67 13.2 1.60% 2.03% 240 min. activation 8 Lignin Activation: 12.0 75.0 1/9 Kraft lignin Liquid lignin 12.21 12.6 <0.05% 0.00% 10 min. activation 12.08 14.4 0.78% 2.03% 30 min. activation 12.04 15.0 0.57% 2.03% 60 min. activation 11.89 15.0 0.44% 2.03% 120 min. activation 11.94 17.4 0.28% 2.03% 240 min. activation 9 Lignin Activation: 6.0 75.0 1/9 it is a muddy Kraft lignin dispersion. Liquid lignin 5.98 12.0 <0.05% 0.00% 10 min. activation 5.89 10.8 2.01% 2.03% 30 min. activation 5.82 12.0 2.06% 2.03% 60 min. activation 5.88 10.2 2.02% 2.03% 120 min. activation 5.80 10.2 2.07% 2.03% 240 min. activation 10 Lignin Activation: 13.0 75.0 1/9 Kraft lignin Liquid lignin 13.09 12.0 <0.05% 0.00% 10 min. activation 12.65 12.6 0.68% 2.03% 30 min. activation 12.69 13.8 0.49% 2.03% 60 min. activation 12.68 13.2 0.32% 2.03% 120 min. activation 12.66 16.2 0.18% 2.03% 240 min. activation 11 Lignin Activation: Kraft 10.0 98.0 1/9 lignin Liquid lignin 10.2 18.0 <0.05% 0.00% 10 min. activation 9.93 20.4 1.18% 2.03% 30 min. activation 9.9 28.2 0.82% 2.03% 60 min. activation 9.84 58.2 0.66% 2.03% 120 min. activation 9.72 805.2 0.47% 2.03% 240 min. activation 12 Lignin Activation: 10.0 85.0 1/9 Kraft lignin Liquid lignin 10.2 17.4 0.07% 0.00% 10 min. activation 10.01 19.2 1.54% 2.03% 30 min. activation 9.92 22.8 1.30% 2.03% 60 min. activation 9.88 25.2 1.11% 2.03% 120 min. activation 9.81 43.2 0.94% 2.03% 240 min. activation 13 Lignin Activation: 10.0 70.0 1/9 Kraft lignin Liquid lignin 10.14 16.8 <0.05% 0.00% 10 min. activation 10.01 16.2 1.62% 2.03% 30 min. activation 9.97 18.0 1.54% 2.03% 60 min. activation 9.96 19.8 1.44% 2.03% 120 min. activation 9.84 22.2 1.28% 2.03% 240 min. activation 14 Lignin Activation: 10.0 65.0 1/9 Kraft lignin Liquid lignin 9.98 18.0 <0.05% 0.00% 10 min. activation 9.81 18.0 1.67% 2.03% 30 min. activation 9.71 17.4 1.65% 2.03% 60 min. activation 9.70 18.0 1.53% 2.03% 120 min. activation 9.57 22.8 1.41% 2.03% 240 min. activation 15 Lignin Activation: 10.0 60.0 1/9 Kraft lignin Liquid lignin 10.00 16.8 <0.05% 0.00% 10 min. activation 10.00 16.8 1.69% 2.03% 30 min. activation 9.98 12.0 1.66% 2.03% 60 min. activation 9.94 18.0 1.56% 2.03% 120 min. activation 9.86 19.2 1.46% 2.03% 240 min. activation 16 Lignin Activation: 10.0 75.0 1/9 Mw Dist. (SEC) and Sodium Lignosulphonate NMR (2D HSQC) on Liquid lignin 9.61 9.0 <0.05% 0.00% samples; Liquid 10 min. activation 9.48 9.6 1.64% 2.03% Lignin, 60 min 30 min. activation 9.38 9.6 1.58% 2.03% Activation, and 60 min. activation 9.26 9.0 1.54% 2.03% 120 min Activation. 120 min. activation 8.98 9.0 1.44% 2.03% 240 min. activation 8.51 10.2 1.38% 2.03% 17 Lignin Activation: 8.4 75.0 1/9 Sodium Lignosulphonate Liquid lignin 8.4 11.4 <0.05% 0.00% 10 min. activation 8.32 11.4 1.80% 2.03% 30 min. activation 8.33 11.6 1.79% 2.03% 60 min. activation 8.23 10.5 1.77% 2.03% 120 min. activation 8.12 11.7 1.7096 2.03% 240 min. activation 18 Lignin Activation: 10.0 75.0 1/12 Kraft lignin Liquid lignin 10.9 18.0 <0.05% 0.00% 10 min. activation 9.98 12.0 1.10% 1.54% 30 min. activation 10.01 19.2 0.98% 1.54% 60 min. activation 9.99 19.2 0.89% 1.54% 120 min. activation 9.87 21.6 0.72% 1.54% 240 min. activation 9.53 33.0 0.49% 1.54% Free- Free- formaldehyde Free- Example Example Target Target CH2O(g)/ Viscosity Formaldehyde if no reaction Phenol number type pH T? Lignin(g) pH (cP) (% wt.) - HPLC (% wt.)- Calc. (% wt.) 20 LPF Resin: no lignin activation 10.0 and no phenol metholation step Liquid lignin 9.98 18.6 0.00% 10 min. condensation 8.92 29.4 2.76% 5.71% 7.22% 20 min. condensation 8.89 33.4 1.97% 5.71% 6.34% * 30 min. condensation 8.91 37.8 1.31% 5.71% 5.68% 40 min. condensation 8.89 43.2 0.97% 5.71% 5.17% 50 min. condensation 8.90 52.8 0.73% 5.71% 4.72% 60 min. condensation 8.91 60.0 0.58% 5.71% 4.41% 70 min. condensation 8.91 66.6 0.45% 5.71% 4.07% 80 min. condensation 8.89 68.4 0.38% 5.71% 3.76% 21 LPF Resin: with lignin activation 10.0 1/9 but no phenol methylolation step Liquid lignin 10.14 19.2 0.00% 10 min. condensation 8.95 30.6 2.90% 5.71% 7.51% 20 min. condensation 8.91 33.0 2.12% 5.71% 6.70% 30 min. condensation 8.89 39.6 1.65% 5.71% 6.17% * 40 min. condensation 8.87 43.2 1.27% 5.71% 5.68% 50 min. condensation 8.85 49.2 1.03% 5.71% 5.30% 60 min. condensation 8.83 57.0 0.82% 5.71% 4.92% 70 min. condensation 8.83 67.8 0.66% 5.71% 4.57% 80 min. condensation 8.82 73.8 0.54% 5.71% 4.24% 22 LPF Resin: with lignin activation 10.0 75.0 1/9 and phenol methylolation step Liquid lignin 10.10 18.6 0.00% Methylolation 8.76 39.0 2.15% 5.71% 6.62% * 10 min. condensation 8.79 48.0 1.48% 5.71% 5.70% 20 min. condensation 8.76 55.2 1.13% 5.71% 5.17% 30 min. condensation 8.79 64.8 0.90% 5.71% 4.71% 40 min. condensation 8.79 76.2 0.71% 5.71% 4.33% 50 min. condensation 8.77 79.8 0.60% 5.71% 3.98% 60 min. condensation 8.77 81.6 0.49% 5.71% 3.71% 70 min. condensation 8.78 76.8 0.43% 5.71% 3.36% 80 min. condensation 8.76 82.8 0.34% 5.71% 3.19% * Samples from LPF Resin examples 20-22 that had their Mw distributions measured (SEC analysis). They were selected based on a free phenol normalisation = 5.7%

(80) Asidethe pH of the liquid lignins should have matched the target pH exactly; however since the amount of alkali is based on the adjustment of a small sample, and its subsequent scale up and hold for an additional hour whereby the lignin macromolecule can further open up, some tolerance was allowed. Furthermore the inventive steps of the patent can still be illustrated without compromise.

(81) TABLE-US-00010 TABLE 10 Molecular weight distribution parameters for samples taken from Examples 4 and 16. Example 4 Example 16 Mn Mw Mn Mw SEC Analysis (g/mol) (g/mol) PD (g/mol) (g/mol) PD Liquid Lignin 1802 3798 2.1 2156 9632 4.5 Activated lignin 60 min 1988 4402 2.2 2255 10316 4.6 Activated lignin 120 min 2051 4764 2.3 2300 10543 4.6

(82) TABLE-US-00011 TABLE 11 Molecular weight distribution parameters for samples taken from Examples 20 (30 min condensation), 21 (40 min condensation) & 22 (10 min condensation). Mn Mw SEC Analysis (g/mol) (g/mol) PD selection based Example 20 737 3039 4.1 on a free phenol (30 min condensation) normalisation ? 5.7% Example 21 750 3253 4.3 (40 min condensation) Example 22 749 3561 4.8 (10 min condensation)

(83) TABLE-US-00012 TABLE 12 Summary of 2D HSQC NMR analysis for Examples 4 and 16 Liquid 60 min. 120 min. Lignin activation activation Example 4 Methylol No Strong Slightly (Kraft) (CH.sub.2OH) signal signal stronger signal signal Guaiacyl unit Strong Weak Slightly G5 active signal signal weaker hydrogen signal signal Example 16 Methylol No Strong Slightly (Na (CH.sub.2OH) signal signal stronger Lignosulphonate) signal signal Guaiacyl unit Strong Weak Slightly G5 active signal signal weaker hydrogen signal signal

(84) TABLE-US-00013 TABLE 13 Examples 23 (LPF resin with activation and methylolation step) and 24 (LPF resin with only a condensation step), 6 mm HPL compact panel testing. Example 24 Example 23 No lignin EN-438 pt2 Lignin activation compliant activation and and no product methylolation methylolation specification steps step Resistance to Thickness <2% Significantly Above 2% immersion in Increase below 2% boiling water Mass <2% Significantly Above 2% increase below 2% Visual ?4 5 4
Examples 4 to 10Lignin Activation Step and Variance in pH

(85) With reference to the earlier section and Table 9 we see that for Examples 4 to 10 (wherein the sample lignin activation recipe and procedure are the same apart from a variation in potassium hydroxide concentration and the consequent pH parameter associated with it) that the formaldehyde concentration decreases with the hold time of the activation step, and that the rate of this decrease is related to how alkaline the batch is (i.e. how high the pH is).

(86) By abstracting the results from Table 9 and plotting a chart, free formaldehyde (%) verses activation time (minutes), the dependency of the reaction kinetics on pH conditions can be seen more clearly. FIG. 1 illustrates this.

(87) It can be seen that for Kraft lignin, the higher the pH is, the faster the reaction is with formaldehyde, leading to its consequent drop in concentration with time. Specifically we can note that at pH6, and therefore logically at pH's below this, there is hardly any reaction. As the pH increases the reaction kinetics improve, with the change in reaction rate appearing to be most sensitive in the region pH 8 to 12, and in particular between pH 9 and 11. Increasing the pH further from 12 to 13 results in a less dramatic rate increase.

(88) For an impregnation resin, the examples with higher charges of alkali (e.g. potassium hydroxide) are less preferred since with higher pH's it can lead to fast reaction kinetics, not only for the lignin activation but also for the methylolation and condensation reactions with phenol and formaldehyde. It is then more difficult to control the degree of condensation, and there is a greater risk of over condensing the resin. With such an over condensed resin it is then more difficult to impregnate kraft paper due to the higher molecular weight. Furthermore even if the paper is successfully impregnated, its activity is perhaps higher than desired, leading to excessive advancement of the resin curing in the impregnation line's drying section. This would lead to poor resin flow and poor HPL panel pressing. Additionally, an excessive amount of alkali (e.g. potassium hydroxide) can lead to excessive salt content within the laminate, and a potential to fail in water resistance tests; for example swelling during submergence in boiling water.

(89) Examples 4, & 11 to 15Lignin Activation Step and Variance in Lignin Activation Temperature

(90) Again, with reference to the earlier section and Table 9 we see that for Examples 4, and 11 to 15 (wherein the sample lignin activation recipe and procedure are the same apart from a variation in the lignin activation temperature) that the formaldehyde concentration decreases with the hold time of the activation step, and that the rate of this decrease is related to how high the temperature is.

(91) By abstracting the results from Table 9 and plotting a chart, free formaldehyde (%) verses activation time (minutes), the dependency of the reaction kinetics on temperature can be seen more clearly. FIG. 2 illustrates this.

(92) It can be seen that for kraft lignin, higher temperatures result in a faster reaction with formaldehyde, with its consequent drop in concentration with time. The lower temperatures, give greater control over the methylolation reaction, however below 60? C. it is perhaps too slow to be preferred for most commercial resin manufactures. At higher temperatures, the condensation reaction starts to become significant; by looking at the viscosity results from table 9, we see there is a significant increase after 85? C.indicative of chain polymerisation and molecular weight build up due to the condensation reaction. Furthermore, to illustrate this point, the viscosities from Examples 4, 11-15 after 120 mins activation have been reproduced in Table 14 below. They have also been plotted as a graph with a polynomial fit through the data points; this can be seen in FIG. 7.

(93) TABLE-US-00014 TABLE 14 Activation Temperature (? C.) vs. Viscosity after 120 min Activation (cP) Example Activation Viscosity after 120 min Number Temperature (? C.) Activation (cP) 15 60 19.2 14 65 22.8 13 70 22.2 4 75 24.0 12 85 43.2 11 98 805.2

(94) Polymerisation of the already large lignin molecules, leads to difficult paper impregnation. The resin cannot penetrate into the pores or between the fibres of the paper, or flow adequately during pressing.

(95) Therefore it is preferred to perform the lignin activation at temperatures that are advantageous to methylolation but not to condensation polymerization; i.e. between 60? C. and 85? C., and even more preferably between 65? C. and 80? C.

(96) Examples 16 & 17Activation of Sodium Lignosulphonate, and its Comparison with Example 4.

(97) Again, with reference to the earlier section and Table 9 we see that for Examples 16 and 17, a commercial sodium lignosulphonate was also tested. Sodium lignosulphonate is inherently soluble in water and requires no alkali to solubilise it. Therefore, with Example 17 no potassium hydroxide was addedthis was to test its lowest pH condition, which was pH=8.4. Example 16, had its pH adjusted to ?10 so that it can be compared to Example 4.

(98) Table 9 lists the results of the samples taken from Examples 4, 16 & 17. FIG. 3 illustrates their change in formaldehyde concentration during the activation step.

(99) In both Examples 16 and 17 there was hardly any change in viscosity, but there was some reduction in formaldehyde concentrationthis being more noticeable at pH?10. It indicates that the lignin activation can occur with other lignin raw materials, and not just with kraft lignin.

(100) SEC analysis was also performed on liquid lignin, 60 min. activation and 120 min. activation samples from Examples 4 and 16. The results can be seen in Table 10. There is some marginal increase in molecular weight during the lignin activation, but not much, and this is interpreted as more functionalization of the lignin macromolecule (i.e. introduction of methylol groups) and its associated change in hydrodynamic volume, rather than the polymerisation of the lignin. It can be seen more clearly in FIG. 4; where the molecular weight distributions of the six samples are plotted.

(101) It can also be seen how the Kraft lignin has a lower molecular weight distribution than the sodium lignosulphonate.

(102) Additional to the SEC analysis, the samples liquid lignin, 60 min. activation and 120 min. activation from Examples 4 and 16 were examined by 2D HSQC NMR. What was particularly interesting about the spectra obtained, was that signals were seen for the methylol group (CH.sub.2OH) and the aromatic active hydrogens. Table 12 shows qualitatively the most important results. From these spectra, it was confirmed that the desired methylolation of lignin, at sites with active hydrogens, does indeed occur.

(103) The signal for the methylol group (CH.sub.2OH) is absent from the spectra of the two liquid lignins (i.e. kraft [Example 4] and Sodium lignosulphonate [Example 16]). Then after the addition of formaldehyde (1 g CH.sub.2O on 9 g dry lignin) and after holding at 75? C., pH10 for 1 hour, the methylol group (CH.sub.2OH) signal can be seen with both lignin types (i.e. kraft [Example 4] and Sodium lignosulphonate [Example 16]). Furthermore, by holding at 75? C., pH 10 for an additional hour it was observed with both lignin types that the methylol group signal strengthened. It should be noted that this methylol group signal appeared to be stronger with kraft lignin (Example 4) than with lignosulphonate (Example 16); this matches the observation regarding the consumption of formaldehyde as made by HPLC analysis, at 75? C. pH 10, and as shown by FIG. 3that the kraft lignin sample reacted with formaldehyde more readily than the lignosulphonate sample did with formaldehyde.

(104) As previously stated, it was noted that in the 2D NMR HSQC spectra there were regions for the aromatic active hydrogens on lignin. These as were associated with Guaiacyl units (G) and p-Hydroxyphenyl units (H), and in particular there were regions that could be associated with; active hydrogens H2 & H6 active hydrogen G6 active hydrogens G5, H3 & H5 active hydrogen G2

(105) In the liquid lignin samples (both Kraft and lignosulphonate), the signal associated with H2 and H6 was much lower than the signals from G2 and G6. It could therefore be stated that guaiacyl units (G) were far more abundant than p-Hydroxyphenyl units (H) in both of the lignin types tested. It then followed logically that the signal for the region G5, H3 & H5 was predominantly coming from G5.

(106) In the activated lignin samples (both Kraft and lignosulphonate), we see a very strong reduction in the G5, H3 & H5 signal. This signal reduction is slightly more after 120 minutes activation than 60 minutes activation, and is more significant in the kraft lignin example than the lignosulphonate example.

(107) In summary:

(108) the lignin methylol signal seen in the 2D NMR is proportional to the amount of formaldehyde consumed in the lignin activation step the lignin methylol signal is inversely proportional to the G5, H3 & H5 signal region, which suggests that methylolation is taking place predominantly at these positions. The Lignin Activation step, is a methylolation of the lignin, which is in effect a functionalization of the lignin, with only a marginal increase in molecular weight. Since it is the lignin active hydrogens that have been methylolated in the two different lignin types, it is logical to one skilled in the art that any liquid lignin possessing active hydrogen could be used and therefore suitably activated for use in a lignin phenol formaldehyde (LPF) resin synthesis.

(109) Example 18 and its comparison with Example 4Lignin activation: 1 g CH2O on 12 g of Lignin vs 1 g on 9 g of Lignin.

(110) Building on the discussion regarding Step 2Lignin Activation, the stoichiometry of formaldehyde to lignin can be based on the mass of dry lignin that the mixture contains; and more specificallythe moles of active hydrogen sites that the said lignin contains. The formaldehyde is added in a stoichiometric excess i.e. >1:1 relative to the lignin's free active hydrogen positions so as to aid the reaction kinetics and to optionally provide a certain amount pre-dosing of formaldehyde prior phenol addition.

(111) Example 18 is an example wherein the formaldehyde has been added in a stoichiometric 1:1 molar ratio with active hydrogens.

(112) Examples 20, 21 & 22Lignin Formaldehyde Resins (LPF)

(113) The Examples 20, 21 & 22 were comparable in terms of raw materials charged, and the resin condensation stage (90? C.). The differences between these examples though were: Example 20No lignin activation step & No phenol methylolation step. i.e. Liquid lignin+phenol+formaldehyde and allowed to exotherm to the condensation temperature. Example 21Lignin activation step (1 hr 75? C.), but No phenol methylolation step.

(114) Example 22Lignin activation step (1 hr 75? C.) & phenol methylolation step (1 hr continuous formalin dosing followed by 1 hr hold, all at 75? C.).

(115) For each resin, samples were taken of the liquid lignin and at 10 minute intervals during the condensation stage. Additionally for Example 22, a sample was taken at the end of the phenol methylolation stage. The analytical results for these samples can be seen in Table 9, the parameters measured being; pH, Viscosity, Free formaldehyde % (titrino and HPLC), and free phenol %.

(116) These results were studied, with the aim of finding one sample from each of the three Examples that had a similar free phenol % results to those of the other (i.e. condensing to a specific free phenol). By normalising on a specific free phenol % content, it was then possible to run SEC analysis on these samples, and compare the three different processing routes on the resin's molecular weight distribution.

(117) The samples selected were; Example 20 (30 minute condensation) free phenol 5.68% Example 21 (40 minute condensation) free phenol 5.68% Example 22 (10 minute condensation) free phenol 5.70%

(118) Table 11 contains the numeric results from the SEC analysis for these samples; Mn, Mw & PD. They are fairly similar, however it can be seen that Example 20 has the lowest Mn, Mw and polydispersity, whilst Example 22 has the highest Mn, Mw and polydispersity. This initially would seem to suggest that the example with the lignin activation step and the phenol methylolation step would have the worst behaviour regarding HPL/CPL laminate applications.

(119) However, closer inspection of the graphical molecular weight distributions reveal features that actually support the invention and said use in HPL/CPL laminate applications. The FIG. 6 illustrates these molecular weight distributions as derived from the SEC analysis, and the 4 important regions for the following interpretation and reasoning.

(120) Block arrow 1 indicates a region of low molecular weight phenol formaldehyde resin species. However in this region it can be seen that Example22 (with the lignin activation and phenol methylolation steps) has an asymmetric peak dominated by the lowest molecular weight species, whereas Example 20 has a broader more symmetric peak indicating a shift to higher molecular weight PF species.

(121) Furthermore, with Block arrow 2 we see a region indicative of medium molecular weight PF species. This is more differentiated, even though it is a shoulder on the area assigned to lignin. It shows that Example 22 has less medium molecular weight PF species than Example 20. Therefore, it can be stated that with respect to phenol formaldehyde resin species, Example 20 is higher Mw than Example 21, which is in turn higher than Example 22.

(122) Block arrow 3 indicates the region of kraft lignin. Here Example 22 shows that the lignin component has a shift to higher Mw compared to that from Example 20. Compare this with the results from Examples 4liquid lignin, activated lignin 60 min and activated lignin 120 minthey look very similar. The lignin in Example 20 has not had time to react with the formaldehyde and so has not been activated; the resin will perform poorly since the lignin is only a filler. With the activation step, the kraft lignin is methylolated and increases marginally in Mw. This can be seen with Example 21 and even more so in Example 22, since lignin activation continues to occur also during the phenol methylolation step. This resin will perform much better in application, because the lignin is now a reactive component.

(123) Block arrow 4 indicates the region of highest Mw species from the ligninclearly as with block arrow 3 the lignin activation causes a shift to higher molecular weight due to functionalization and possibly by reaction of the lignin methylol groups with small PF resin species, which would also give rise to a cluster of reactive sites on the lignin macromolecule.

(124) Examples 23 and 24Manufacturing of HPL Compact Panels 6 mm.

(125) With reference to the earlier section and Table 13, we see that for Examples 23 and 24 there was a clear pass or fail for the 6 mm compact HPL laminates tested.

(126) The laminates were tested according to EN-438. This comprises of several tests, of which one of the most demanding tests is the resistance to immersion in boiling water. This is a good test for laminates, since failure can indicate; lack of crosslinking and cure, poor resin flow between papers on pressing, and poor impregnation of the paper.

(127) As can be seen in Table 13, Example 23 (LPF with lignin activation and phenol methylolation steps) successfully passed this test, whilst Example 24 (LPF no lignin activation or phenol methylolation steps) failed. Furthermore, Example 23 fulfilled all requirements of EN-438, such as dimensional stability at higher temperatures, flexural strength, flexural modulus and density.

(128) In summary, a clear advantage could be seen by having the lignin activation and phenol methylolation steps, with which the present inventors found that it was possible to impregnate paper and make a EN438 compliant 6 mm thickness compact HPL panel using a lignin phenol formaldehyde (LPF) resin with equal parts phenol and lignin (i.e. 50% phenol replacement).

(129) It is apparent from the experiments that by not activating the lignin through methylolation, there is insufficient reactivity towards other phenolic resin reactive species, and the panels made with such resin fail the EN-438. In this situation, the lignin is acting more as an extender or filler to the phenol-formaldehyde resin. Maximum reactivity of lignin to phenolic resin reactive species is obtained when the active hydrogen sites of the lignin are fully functionalised with methylol groups and not lost through higher temperature condensation reactions during resin cooking. This is achieved only by having a stoichiometric ratio of lignin active hydrogens to formaldehyde that has formaldehyde in excess (i.e. lignin active hydrogens:formaldehyde=1:>1. The fully methylolated lignin is then better at reacting with the other phenolic resin species and forming an infusible polymer within the laminate during final pressing; evidenced by resistance to the boiling water test. This optimal methylolation of lignin by use of the excess stoichiometric ratio, also allows for maximum use of lignin within the resin recipe whilst still fulfilling the requirements of the EN-438 Norm.

(130) When the above is combined with phenolic resin species that are predominately methylolated and of low molecular weight, paper/wood fibre penetration during impregnation is maximised as is reactivity during the high temperature/pressure press process of the laminate manufacture (either HPL or CPL).