PROCESS FOR PREPARING A BONDING RESIN

Abstract

The present invention relates to a process for preparing a bonding resin, wherein a resin prepared from lignin, phenol and formaldehyde is mixed with a resin prepared from phenol and formaldehyde to achieve a mixture useful as a bonding resin useful in the manufacture of laminates, mineral wool insulation and wood products such as plywood, laminated veneer lumber (LVL), medium density fiberboards (MDF) and particle boards.

Claims

1. A method for preparing a resin in a form of a mixture comprising the steps of: a) preparing a first resin comprising lignin, phenol, and formaldehyde; b) preparing a second resin comprising phenol and formaldehyde, wherein the second resin comprises less than 1 wt-% lignin, by weight of the second resin; c) mixing the first resin and the second resin in a weight ratio of from 0.5:10 to 10:0.5 based on weight of a mixture of the first resin and the second resin.

2. The method according to claim 1, wherein the mixing in step c) is carried out by stirring at a speed of from 20 to 1,000 rpm.

3. The method according to claim 1, wherein a duration of the mixing in step c) is at least one minute.

4. A resin in the form of the mixture obtained by the method of claim 1.

5. The method of claim 1 further comprising: manufacturing a laminate, mineral wool insulation, or wood product with the mixture of the first resin and the second resin.

6. A laminate, mineral wool insulation, or wood product manufactured using the resin according to claim 4.

7. A method for selecting an optimized resin mixture for a specific end use, the method comprising the steps of: a) defining one or more desirable properties of a resin; b) preparing a first resin comprising lignin, phenol, and formaldehyde; c) preparing a second resin comprising phenol and formaldehyde, wherein the second resin comprises less than 1 wt-% lignin, by weight of the second resin; d) mixing the first resin and the second resin in a defined weight ratio of from 0.5:10 to 10:0.5 based on weight of a mixture of the first resin and the second resin; e) a different vessel, repeating step d) with a different weight ratio; f) repeating step e) at least five times with additional different weight ratios in step d) in each repetition; g) evaluating properties of each mixture of the first resin and the second resin, said evaluation being carried out based on the properties of the mixture or based on properties of a final product prepared using each mixture of the first resin and the second resin obtained in step f); h) selecting an optimized mixture of the first resin and the second resin obtained in step f), based on the results of the evaluation carried out in step g), said selection step comprising a determination of which mixture of the first resin and second resin obtained in step f) has properties closest to the one or more desired properties of a resin defined in step a).

8. The method according to claim 2, wherein a duration of the mixing in step c) is at least one minute.

9. The method according to claim 7, wherein the mixing in step d) is carried out by stirring at a speed of from 20 to 1,000 rpm.

10. The method according to claim 9, wherein a duration of the mixing in step d) is at least one minute.

11. The method according to claim 7, wherein a duration of the mixing in step d) is at least one minute.

12. The method according to claim 5, wherein the wood product is selected from a group consisting of: plywood, laminated veneer lumber (LVL), medium density fiberboards (MDF), and particle board.

Description

EXAMPLES

Example 1

[0034] Reference phenol formaldehyde (PF) resin for plywood was prepared in a 5 L glass reactor and mixed with pitched blade stirrer. Firstly, 1116 g of molten phenol, 576 g of water and 461 g of NaOH solution (50%) were added to the glass reactor and mixed.

[0035] Secondly, 2048 g of 40% formaldehyde solution was added slowly to prevent excessive heat development. The temperature was kept constant at 60° C. for 30 minutes and was then increased to 80° C. When the viscosity had increased to approximately 200-250 cP, the temperature was set to 75° C. and 155 g of NaOH solution (50%) was added. When the target viscosity of 220-250 cP was obtained, the reaction was stopped by cooling to ambient temperature. The reaction was monitored by measuring the viscosity at 25° C. using a Brookfield DV-II+LV viscometer. [0036] The resin was analyzed and the results of the analysis are given in Table 1.

Example 2

[0037] Lignin-phenol-formaldehyde (LPF) resin was synthesized for plywood application with a phenol replacement level of 50% with lignin.

[0038] In the first step, 918 g of powder lignin (solid content 91%) and 1225 g of water were added to a 5 L glass reactor at ambient temperature and were stirred until the lignin was fully and evenly dispersed. Then, 426 g of 50% alkali solution was added to the lignin dispersion. The composition was heated to 73° C. and stirred for 60 minutes to make sure that lignin was completely dissolved in the alkaline media. Then, the temperature of the lignin composition was lowered to 45° C.

[0039] In the second step, 846 g of phenol and 1802 g of formalin solution (40%) were added into the reaction mixture. The temperature of the reaction mixture was increased to 80° C. and the reaction mixture was continuously stirred for 115 minutes. Then, 315 g of sodium hydroxide solution (50%) was added and the reaction temperature was cooled to 75° C. Then, the reaction mixture was continuously stirred at 75° C. for further 95 minutes before cooling down to room temperature. The reaction was monitored by measuring the viscosity at 25° C. using a Brookfield DV-II+LV viscometer. [0040] The resin was analyzed and the results of the analysis are given in Table 1.

Example 3

[0041] The resin blend was prepared by mixing PF resin from example 1 and LPF resin from example 2 in a ratio of 1:1 by weight. [0042] The resin blend was analyzed and the results of the analysis are given in Table 1.

TABLE-US-00001 TABLE 1 Resin properties Resin from Resin from Resin from Example 1 Example 2 Example 3 Viscosity [cP] 220 223 275 at 25° C. pH at 23° C. 12.2 11.5 11.6 Solid Content 43.6 45.5 44.7 [%] 155° C.

Example 4—Plywood Application

[0043] Birch veneers were sawn to 300×300 mm.sup.2 size and conditioned in 20° C., 65% RH prior to manufacture. Glue comprising resin from example 3 was formulated according to Table 2.

TABLE-US-00002 TABLE 2 Composition of glue for plywood boards Amount Component [wt. %] Resin from examples 3 71.5 Filler/Hardener (contains limestone, 14.2 cellulose, sodium carbonate, starch) Water 14.3

[0044] Target glue content was 165 g/m.sup.2 which were spread on one side. Pre-pressing was performed at a pressure of 1.8 MPa for 15 minutes. The close assembly time was 30 minutes. Hot pressing was performed at 127° C. with a pressure of 1.8 MPa. The total pressing time was 6 minutes 25 seconds. Prior to evaluation, all samples were conditioned according to EN636 class 3 test method. Shear strength was evaluated according to EN314 test method. Average data from 20 test specimens is presented in Table 3.

TABLE-US-00003 TABLE 3 Plywood shear strength Shear strength [N/mm.sup.2] Resin from 1.9 Example 3

[0045] In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art. However, it should be apparent that such other modifications and variations may be effected without departing from the spirit and scope of the invention.