Abstract:
A substitute for amino and phenolic resins is disclosed. It is used in the polycondensation of such resins based on formaldehyde for bonding water penetrable cellulosic particles. The substitute comprises an aqueous solution of 
     (a) either at least one aldehyde together with at least one amide and/or together with at least one phenol, or a non-resinous condensation product of formaldehyde and urea, and 
     (b) a sugar or a sugar derivative or their byproducts or a starch or its degradation products or a mixture thereof, and/or 
     (c) a raw and/or treated lignosulfonate. 
     This substitute also reduces the free formaldehyde of the resulting board without impairing the other properties thereof.

Description:
TECHNICAL FIELD 
     Background 
     Substitutes so far known in the art to substitute resin have not succeeded in substituting such high levels of resin by using lower amounts of the substitute and reducing simultaneously the free formaldehyde of the boards, without imparting any loss in bonding strength, without requiring any extra steps in the production, without changing the curing rate of the production, without causing any problems to the boilers when burning particleboard sander dust or edges from cutting saws and without reducing the tack of the resin mixture. 
     In particular, the known substituents are lignosulfonates, sodium chloride or mixtures of formaldehyde with urea and sodium chloride. It is well known that lignosulfonates may not be used for quantities higher than 10%; otherwise, board properties will be reduced. 
     It is also known that the addition of halide salt alone succeeds in substituting part of the resin with the following limitations: 
     High substitutions, higher than 6 to 8%, may not be obtained, otherwise the board properties will deteriorate. 
     Substitution is obtained in ratios 1:1, while in the case of the substitute according to the present invention it is 1.1 to 2.0:1. 
     When particleboard sander dust or edges from cutting saws are burnt in boilers, the latter are plugged within a few hours. 
     Tack is reduced when sodium chloride is added to the resin mixtures. 
     When mixtures of sodium chloride with urea and formaldehyde are used the following shortcomings are present: 
     The presence of salt in the mixture causes severe problems in the boilers when sander dust or cutting saw edges of boards are burnt. That is caused because the presence of salt reduces the melting point of the mixture and as a result a molten mass deposits in the boiler forming a glass like deposit which adheres on the boiler thus plugging it. 
     The other shortcoming of this product is the fact that tack is severely reduced, thus making it difficult to use in the plywood industry where there is a pre-press and in particleboard plants where a multi opening press is present requiring green strength of the mat. 
     The product according to the present invention overcomes all of the above shortcomings. 
     The substitute according to the present invention provides yet another advantage. Apart from substituting up to 30% of the resin by adding only 50 to 90% of the resin solids substituted, and reducing the free formaldehyde of boards, it reduces also the free formaldehyde in the production hall where workers are exposed to formaldehyde fumes. 
     The present invention relates to a substitute for amino and phenolic resins in the polycondensation of such resins based on formaldehyde for bonding water penetrable cellulosic particles thus allowing lower amounts of resin solids to be used while at the same time reducing the free formaldehyde of the resulting board without imparting any loss in bonding strength, without requiring any extra steps in the production, without changing the curing rate of the production, without causing any problems to the boilers when burning particleboard sander dust or edges from cutting saws and without reducing the tack properties of the resin mixture. 
     SUMMARY OF THE INVENTION 
     The said substitute is comprised mainly of a solution of: 
     (a) either an aldehyde together with an amide or together with a phenol, or a non-resinous condensation product of formaldehyde and urea, and 
     (b) a sugar or a sugar derivative or their byproducts or a starch or a mixture thereof, and/or 
     (c) a raw and/or treated lignosulfonate or similar products. 
     The aldehyde is preferably formaldehyde, for example in the form of paraformaldehyde, or acetaldehyde. The amide is preferably mainly urea or thiourea or their homologues or melamine, benzoguanamine or dicyandiamide or their homologues. The phenol is preferably phenol itself or resorcinol. 
     Among the sugars, sugar derivatives, their byproducts and mixtures thereof, molasses, dextrose, glucose, fructose or sucrose or mixtures thereof such as corn syrup are most preferred. Among the starches, wheat starch, modified starches, dextrin and the like are interesting. 
     Examples of raw lignosulfonates are black liquor and similar products, and example of treated lignosulfonates are sodium, calcium and ammonium lignosulfonate. 
     The substitute of the invention preferably contains 40 to 52% by weight of water. 
     The weight ratio of (a) to (b) and/or (c) is preferably 0.1 to 50.0:1, most preferably 1.0 to 15.0:1. The combination of (a) with (b) and/or (c) presents a synergistic behavior. If the single components are added alone to the resin they don not give good boards, but if they are added in combination, they exhibit an improvement in the board properties obtained. The substitute according to the present invention (calculated as 100% solids) may substitute as much as 30% of the resin solids used. Said substitute is not added in quantities equal to the quantities substituted. It is added in quantities from 50 to 90% of the amount of resin substituted (calculations referred to by weight and referring to all products as 100% solids). 
     The substitute according to the present invention may therefore, because of its synergistic behavior, substitute the resin in quantities from 110% up to 200% of its own weight. When added to lower amounts, e.g., up to 15%, there is a considerable increase in the properties of the end product. When added to higher levels, i.e., up to 30%, no difference is imparted to the properties of the end product but the free formaldehyde is considerably reduced and the amount of resin saved is considerably increased. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Bonding is effected by curing the resin mixture at elevated temperatures and pressures according to the methods well known in the art. The substitute may be used in all types of products where amino and phenolic resins are used for bonding lignocellulosic products, whether these are wood particles for particleboard production using a flat press, or a calender or wood veneers such as in plywood production. 
     It is very interesting to note that the product has also good tack. This property otherwise called &#34;green strength&#34; is desired in some types of particleboard plants, especially the plants with multi opening press and in plywood factories, especially those having a pre-press. 
     The quality of boards produced was controlled weekly for a period of six months and no reduction in the properties was observed. This proves that no polymer degradation occurs and that the ageing properties of the boards are comparable to the ones normally produced. 
     The substitute of the invention can be prepared by plain mixing of the components. In order to obtain an acceptable shelf-life of the substitute, a base is preferably added to adjust the pH to a value in the range of 6 to 14. 
    
    
     The following Examples illustrate the invention and are not intended as limitations. 
     EXAMPLE 1 
     Three samples were prepared according to the following formulations: 
     
         ______________________________________         Sample No.          1       2      3         parts by weight______________________________________Formaldehyde 100%           185        --     133Urea 100%       370        --     266Molasses 100%   --         555    156Water           445        445    445Total            1000       1000   1000______________________________________ 
    
     The above mentioned samples were prepared by plain mixing at room temperature until the solids were completely dissolved. The pH of the final products was adjusted to 7.5 to 8.0. 
     Glue formulations were then prepared as follows: 
     
         ______________________________________          Glue formulation No.          0    1        2      3          parts by weight______________________________________Urea formaldehyde resin            108.9  81.7     81.7 81.7(65% solids)Water            13.8   13.8     13.8 13.8Sample 1         --     27.2     --   --Sample 2         --     --       27.2 --Sample 3         --     --       --   27.2Ammonium chloride (20%)            7.1    7.1      7.1  7.1______________________________________ No. 0: Glue formulation is the blank and does not include any of the abov mentioned samples. No. 1: Glue formulation includes sample 1, whereby only formaldehyde and urea are included. No. 2: Glue formulation includes sample 2 whereby only molasses are included. No. 2: Glue formulation includes sample 3 whereby all three ingredients are added, namely, formaldehyde, urea and molasses. Sample 3 represents the product according to the present invention. 
    
     These glue formulations were used separately to spray a constant quantity of dried wood chips. 
     The sprayed wood chips were then formed into a mat having a normal thickness of 16 mm. These mats were then introduced into a hot press and boards were pressed at the following conditions: 
     
         ______________________________________Press temperature     200° C.Press time            9 sec/mmPressure              33 kp/cm.sup.2______________________________________ 
    
     Boards were then tested and the results are reported in the following table. 
     
         ______________________________________          Glue formulation No.           0   1        2      3______________________________________Density (kg/m.sup.3)            582    591      583  582Thickness (mm)   15.4   15.2     15.5 15.4Internal bond (kg/cm.sup.2)            7.1    6.5      5.0  7.22 hrs thickness swelling (%)            11.1   11.3     17.5 12.124 hrs thickness swelling (%)            20.3   22.5     30.3 22.3Free formaldehyde            24.1   18.3     21.8 18.7(mg/100 g dry board)Moisture content (%)            5.5    5.0      5.3  5.0______________________________________ 
    
     It can be noticed from the above mentioned table that while all three samples reduce the free formaldehyde of boards, only sample 3 including the components according to the present invention gives boards equivalent to the blank, without deterioration of the board properties. 
     EXAMPLE 2 
     This example proves the synergistic behavior existing between formaldehyde, urea and lignosulfonates. 
     For this purpose the following samples were prepared: 
     
         ______________________________________            Sample No.             1     2      3            parts by weight______________________________________Formaldehyde (100%)              100      --     133Urea (100)%        370      --     266Calcium lignosulfonate (100%)              --       555    156Water              445      445    445Total              1000     1000   1000______________________________________ 
    
     The above mentioned samples were prepared by plain mixing at room temperature until the solids were completely dissolved. The pH of the final products was adjusted to 7.5 to 8.0. 
     Glue formulations were then prepared as follows: 
     
         ______________________________________          Glue formulation No.           0   1        2      3          parts by weight______________________________________Urea formaldehyde            108.9  81.7     81.7 81.7resin (65% solids)Water            13.8   13.8     13.8 13.8Sample 1         --     27.2     --   --Sample 2         --     --       27.2 --Sample 3         --     --       --   27.2Ammonium chloride (20%)            7.1    7.1      7.1  7.1______________________________________ 
    
     These glue formulations were used separately to spray a constant quantity of dried wood chips. 
     The sprayed wood chips were then formed into a mat having a nominal thickness of 16 mm. These mats were then introduced into a hot press and boards were pressed at the following conditions: 
     
         ______________________________________Press temperature     200° C.Press time            9 sec/mmPressure              33 kp/cm.sup.2______________________________________ 
    
     Boards were then tested and the results are reported in the following table: 
     
         ______________________________________          Glue formulation No.           0   1        2      3______________________________________Density (kg/m.sup.3)            580    591      590  584Thickness (mm)   15.5   15.2     15.0 15.1Internal bond (kg/cm.sup.2)            7.0    6.3      5.4  6.92 hrs thickness swelling (%)            11.2   11.3     17.8 11.824 hrs thickness swelling (%)            20.6   22.5     29.5 23.8Free formaldehyde(mg/100 g dry board)            23.9   19.8     18.5 17.8Moisture content (%)            5.8    5.0      4.5  4.8______________________________________ 
    
     It will be noticed from the above mentioned figures that boards produced with plain lignosulfonates, sample 2, have the worst results. Boards obtained with all three components according to our present invention, sample 3, have the best results. Actually boards of sample 3 are equivalent to the blank, 0, which is the resin mixture without any substitute, while giving at the same time a reduction in the free formaldehyde of the boards. 
     EXAMPLE 3 
     In this example two samples are illustrated whereby the ratio of formaldehyde to urea is different from the one used in the previous examples. Also the weight ratio between components (a) and (b) is different from the one of examples 1 and 2. 
     The following samples were prepared: 
     
         ______________________________________              Sample No.               1    2              parts by weight______________________________________Formaldehyde (100)%  133     133Urea (100%)          177     177Molasses (100%)      156     --Dextrin glue (100%)  30      --Calcium lignosulfonate (100%)                --      186Water                504     504Total                 1000    1000______________________________________ 
    
     The above mentioned samples were prepared by plain mixing at room temperature until the solids were completely dissolved. The pH of the final products was adjusted to 7.5 to 8.0. 
     Glue formulations were then prepared as follows: 
     
         ______________________________________           Glue formulation No.            0      1      2           parts by weight______________________________________Urea formaldehyde resin             108.9     87.1   87.1(65% solids)Water             13.8      13.8   13.8Sample 1          --        21.8   --Sample 2          --        --     21.8Ammonium chloride (20%)             7.1       7.1    7.1______________________________________ 
    
     These glue formulations were used separately to spray a constant quantity of dried wood chips. 
     The sprayed wood chips were then formed into a mat having a nominal thickness of 16 mm. These mats were then introduced into a hot press and boards were pressed at the following conditions: 
     
         ______________________________________Press temperature     200° C.Press time            9 sec/mmPressure              33 kp/cm.sup.2______________________________________ 
    
     Boards were then tested and the results are reported in the following table: 
     
         ______________________________________           Glue formulation No.            0      1      2______________________________________Density (kg/m.sup.3)             573       595    587Thickness (mm)    15.1      15.4   15.2Internal bond (kg/cm.sup.2)             8.1       8.7    8.92 hrs thickness swelling (%)             10.5      10.0   9.824 hrs thickness swelling (%)             19.9      19.3   18.7Free formaldehyde(mg/100 g dry board)             46.6      39.2   34.3Moisture content (%)             5.9       5.3    5.0______________________________________ 
    
     It can be noticed from the above mentioned table that samples 1 and 2 including the substitute according to the present invention give boards equivalent to the blank, sample 0, while giving a significant free formaldehyde reduction and resin saving. 
     EXAMPLE 4 
     This is a laboratory test for plywood using a phenolic resin. 
     The following samples were prepared: 
     
         ______________________________________               Sample No.                1    2               parts by weight______________________________________Phenol (100%)         180     200Formaldehyde (100%)   80      100Molasses (100%)       120     180Ammonium lignosulfonate (100%)                 200     --Water                 420     520Total                  1000    1000______________________________________ 
    
     The samples were prepared by plain mixing at room temperature until the solids were completely dissolved. The pH of the final products was brought to 10.0 by means of addition of sodium hydroxide. 
     These samples were used in a glue formulation as follows: 
     
         ______________________________________             Glue formulation No.              0   1         2             parts by weight______________________________________Phenol formaldehyde glue (100%)               100    80        80Hardener (calcium carbonate:               60     60        60wheat flour - weight ratio 50:50)Water               107    90        90Sample 1            --     30.77     --Sample 2            --     --        30.77Wheat flour         --     --        10Total               267    260.77    270.77Viscosity (mPa.s)   1200   1300      1100______________________________________ 
    
     The above mentioned glue formulations were used to spread both sides of the core veneer for 3 ply boards. 
     Boards were then introduced in a cold press where they were pressed under the following conditions: 
     
         ______________________________________Press time           8 minutesPressure             10 kp/cm.sup.2______________________________________ 
    
     All boards gave very good tack properties. 
     They were then pressed in a hot press under the following conditions: 
     
         ______________________________________Press temperature     130° C.Press time            3.5 minutesPressure              12 kp/cm.sup.2______________________________________ 
    
     These boards were tested as follows: 
     They were immersed for 24 hours in water at 60° C. After this they were introduced in water at 20° C. for one hour and then the knife test was carried out. 
     Results were as follows: 
     
         ______________________________________Glue formulation No.          0          1       2______________________________________Grading        10/10      10/10   10/10______________________________________ 
    
     The knife test is carried out as follows: 
     Plywood samples are placed in water under pressure for 30 minutes and then in vacuum for another 30 minutes. Samples are then scraped with a knife on the surface until the top veneer comes off and the core shows up. The grading depends on the amount of fibers showing in the core after the top veneer was scraped off. 
     When gluing is satisfactory, the surface that appears after scraping with the knife must still be covered with fibers. When it is completely covered with fibers grading is 10 (excellent). As more clean spots appear and less fibers, grading is diminished. A grading of 8 is still satisfactory, and it means that the surface is mainly covered with fibers with only a few clean spots appearing. Lower grading is unsatisfactory. 
     EXAMPLE 5 
     Two samples were prepared according to the following formulations: 
     
         ______________________________________               Sample No.                1    2               parts by weight______________________________________Formaldehyde (100%)   100     140Urea (100%)           140     190Melamine (100%)       100     110Molasses (100%)       --      110Ammonium lignosulfonate (100%)                 150     --Water                 510     450Total                 1000    1000______________________________________ 
    
     The above mentioned samples were prepared by plain mixing at 25° to 30° C. until the solids were completely dissolved. The pH of the final products was adjusted to 8.5 to 10.0. 
     Glue formulations were then prepared as follows: 
     
         ______________________________________           Glue formulation No.           0        1      2           parts by weight______________________________________Kauramin 535 (63% solids)             108        92     92Hardener (1)      14.8       14.8   14.8Formic acid (20%) 4          4      4Paraffin emulsion 5.5        5.5    5.5Sample 1          --         16     --Sample 2          --         --     16Water             13         13     13______________________________________(1) The Hardener solution was:             hot water      462             urea           384             ammonium chloride                            154             TOTAL          1000 
    
     These glue formulations were used separately to spray a constant quantity of dried wood chips with 12% dry glue/dry wood. 
     The sprayed wood chips were then formed into a mat having a normal thickness of 16 mm. These mats were then introduced into a hot press and boards were pressed at the following conditions: 
     
         ______________________________________Press temperature           200° C.Press time      10 sec/mmPressure        35 kp/cm.sup.2______________________________________ 
    
     Boards were then tested and the results are reported in the following table. 
     
         ______________________________________           Glue formulation No.           0        1      2______________________________________Density (kg/m.sup.3)             686        687    685Thickness (mm)    15.9       15.7   15.7Internal bond (kg/cm.sup.2)             6.6        6.5    6.42 hrs thickness swelling (%)             3.2        3.2    2.924 hrs thickness swelling (%)             9.2        9.0    8.5V-100 (kg/cm.sup.2)             1.6        1.5    1.6______________________________________ 
    
     The V-100 test is carried out as follows: 
     The samples to be tested are placed in water at 20°±5° C. This water is warmed up in 1 to 2 hours to 100° C. The water temperature is kept at 100° C. for 2 hours. It is important that there is a space of at least 15 mm on all sides of every sample so as to make sure that water is freely introduced in the samples. The samples are then introduced for at least 1 hour in a refrigerator at 2°±5° C. Water is then allowed to drip and the wet samples are tested again for internal bond. 
     EXAMPLE 6 
     The following example will illustrate the fact that products according to our present invention may be produced by means of a variety of raw materials. 
     Samples were prepared according to the following formulations: 
     
         ______________________________________            Sample No.            1       2      3             parts by weight______________________________________Paraformaldehyde   350       --     --Precondensate 80% (1)              --        50     --Acetaldehyde 100%  --        --     130Urea 100%          150       12     200Sucrose 100%       50        100    --Molasses 100%      50        150    --Ammonium lignosulfate 100%              --        230    210Dextrin 100%       --        40     --Water              400       418    460______________________________________ (1) Precondensate containing 53 parts by weight of formaldehyde, 27 parts by weight of urea and 20 parts by weight of water 
    
     The above mentioned samples were prepared by plain mixing until the solids were completely dissolved. The pH of the final products was adjusted to 7.5 to 8.0. Glue formulations were the prepared as follows: 
     
         ______________________________________          Glue formulations No.          0     1       2       3           parts by weight______________________________________Urea formaldehyde resin(65% solids)     108.9   93      93    93Water            13.8    13.8    13.8  13.8Sample 1         --      15.9    --    --Sample 2         --      --      15.9  --Sample 3         --      --      --    15.9Ammonium chloride (20%)            7.1     7.1     7.1   7.1______________________________________ 
    
     These glue formulations were used separately to spray a constant quantity of dried wood chips. 
     The sprayed wood chips were then formed into a mat having a normal thickness of 16 mm. These mats were then introduced into a hot press and boards were pressed at the following conditions: 
     
         ______________________________________Press temperature           200° C.Press time      9 sec/mmPressure        33 kp/cm.sup.2______________________________________ 
    
     Boards were then tested and the results are reported in the following table: 
     
         ______________________________________          Glue formulation No.          0     1       2       3______________________________________Density (kg/m.sup.3)            600     610     590   580Thickness (mm)   15.8    15.9    15.7  15.6Internal bond (kg/cm.sup.2)            6.8     6.9     7.1   6.52 hrs thickness swelling (%)            10.5    10.3    10.1  9.924 hrs thickness swelling (%)            20.1    19.5    19.9  20.3Free formaldehyde            22.3    18.0    16.2  17.1Moisture content (%)            5.7     5.3     5.5   5.6______________________________________ 
    
     Boards obtained with all glue formulations are equivalent. 
     EXAMPLE 7 
     In this example four samples were prepared according to the following formulations: 
     
         ______________________________________         Sample No.         1    2        3      4          parts by weight______________________________________Formaldehyde    100    100      100  100Resorcinol      --     50       --   --Thiourea        50     --       --   --Urea            140    150      70   70Benzoguanamine  --     --       80   --Dicyandiamide   --     --       --   80Wheat starch    --     50       --   --Dextrose        --     --       --   50Glucose         --     50       --   --Fructose        --     --       50   --Modified starch*           50     --       --   --Corn syrup      60     --       --   --Molasses        --     --       50   100Black liquor    --     100      --   --Sodium lignosulfonate           100    --       150  100Water           500    500      500  500Total           1000   1000     1000 1000______________________________________ *Starch which has been hydrolysed to give a lower molecular weight and, therefore, a low viscosity 
    
     The above mentioned samples were prepared by plain mixing at 40° to 50° C. until the solids were completely dissolved. The pH of the final products was adjusted to 8.5 to 10.0. 
     Glue formulations were then prepared as follows: 
     
         ______________________________________         Glue formulation No.         0     1       2      3    4          parts by weight______________________________________Urea formaldehyde resin(65%)           108.9   87.1    87.1 87.1 87.1Water           13.8    13.8    13.8 13.8 13.8Sample 1        --      21.8    --   --   --Sample 2        --      --      21.8 --   --Sample 3        --      --      --   21.8 --Sample 4        --      --      --   --   21.8Ammonium chloride (20%)           7.1     7.1     7.1  7.1  7.1______________________________________ 
    
     These glue formulations were used separately to spray a constant quantity of dried wood chips. 
     The sprayed wood chips were then formed into a mat having a nominal thickness of 16 mm. These mats were then introduced into a hot press and boards were pressed at the following conditions: 
     
         ______________________________________Press temperature           200° C.Press time      9 sec/mmPressure        33 kp/cm.sup.2______________________________________ 
    
     Boards were then tested and the results are reported in the following table: 
     
         ______________________________________       Glue formulation No.       0     1       2       3     4______________________________________Density (kg/m.sup.3)         625     617     633   631   628Thickness (mm)         15.9    15.8    16.0  16.2  16.0Internal bond (kg/cm.sup.2)         7.0     6.9     7.1   7.2   6.82 hrs thicknessswelling (%)  12.5    12.1    13.6  13.1  12.624 hrs thicknessswelling (%)  22.5    20.7    24.7  24.0  20.9Free formaldehyde(mg/100 g dry board)         28.8    22.5    21.7  23.0  21.9Moisture content (%)         6.1     5.7     5.9   5.9   6.2______________________________________ 
    
     It can be noticed from the above mentioned table that samples 1 to 4 including the substitute according to the present invention give boards equivalent to the blank, sample 0, while giving a significant free formaldehyde reduction and resin saving. 
     EXAMPLE 8 
     Three samples were prepared according to the following formulations: 
     
         ______________________________________            Sample No.            1       2      3             parts by weight______________________________________Formaldehyde 100%  135       135    135Urea 100%          365       365    365Sucrose 100%       10        --     --Molasses 100%      --        10     --Calcium lignosulfonate (100%)              --        --     10Water              490       490    490Total              1000      1000   1000______________________________________ 
    
     The above mentioned samples were prepared by plain mixing at 25° to 30° C. until the solids were completely dissolved. The pH of the final products was adjusted to 8.5 to 10.0. 
     Glue formulations were then prepared as follows: 
     
         ______________________________________          Glue formulation No.          0    1        2      3           parts by weight______________________________________Urea formaldehyde            108.9  95.9     95.9 95.9Resin (65% solids)Water            13.8   13.8     13.8 13.8Sample 1         --     13       --   --Sample 2         --     --       13   --Sample 3         --     --       --   13Ammonium chloride            7.1    7.1      7.1  7.1(20% solution in water)______________________________________ 
    
     These glue formulations were used separately to spray a constant quantity of dried wood chips. 
     The sprayed wood chips were then formed into a mat having a nominal thickness of 16 mm. These mats were then introduced into a hot press and boards were pressed at the following conditions: 
     
         ______________________________________Press temperature           200° C.Press time      8 sec/mmPressure        35 kp/cm.sup.2______________________________________ 
    
     Boards were then tested and the results are reported in the following table: 
     
         ______________________________________          Glue formulation No.          0     1       2       3______________________________________Density (kg/m.sup.3)            575     582     579   601Thickness (mm)   15.4    15.3    15.5  15.4lnternal bond (kg/cm.sup.2)            8.3     8.7     8.9   9.52 hrs thickness swelling (%)            10.3    10.8    10.6  11.124 hrs thickness swelling (%)            20.2    21.3    20.9  21.9Free formaldehyde            60.5    39.8    41.3  38.1(mg/100 g dry board)Moisture content (%)            6.0     7.1     6.8   6.5______________________________________ 
    
     Boards obtained with all glue formulations are equivalent. Those however that include the substitute according to the present invention have lower free formaldehyde. 
     EXAMPLE 9 
     Three samples were prepared according to the following formulations: 
     
         ______________________________________            Sample No.            1       2      3             parts by weight______________________________________Formaldehyde 100%  85        85     85Urea 100%          400       400    400Sucrose 100%       32.3      --     --Molasses 100%      --        32.3   --Calcium lignosulfonate (100%)              --        --     32.3Water              482.7     482.7  482.7Total              1000      1000   1000______________________________________ 
    
     The above mentioned samples were prepared by plain mixing at 25° to 30° C. until the solids were completely dissolved. The pH of the final products was adjusted to 8.5 to 10.0. 
     Glue formulations were then prepared as follows: 
     
         ______________________________________          Glue formulation No.          0    1        2      3           parts by weight______________________________________Urea formaldehyde            108.9  81.7     81.7 81.7Resin (65% solids)Water            13.8   13.8     13.8 13.8Sample 1         --     27.2     --   --Sample 2         --     --       27.2 --Sample 3         --     --       --   27.2Ammonium chloride            7.1    7.1      7.1  7.1(20% solution in water)______________________________________ 
    
     These glue formulations were used separately to spray a constant quantity of dried wood chips. 
     The sprayed wood chips were then formed into a mat having a nominal thickness of 16 mm. These mats were then introduced into a hot press and boards were pressed at the following conditions: 
     
         ______________________________________Press temperature           200° C.Press time      8 sec/mmPressure        35 kp/cm.sup.2______________________________________ 
    
     Boards were then tested and the results are reported in the following table: 
     
         ______________________________________          Glue formulation No.          0     1       2       3______________________________________Density (kg/m.sup.3)            610     590     597   615Thickness (mm)   15.9    15.7    15.6  15.9internal bond (kg/cm.sup.2)7.9            7.9     8.1     8.3   8.42 hrs thickness swelling (%)            9.8     10.2    10.5  10.924 hrs thickness swelling (%)            20.1    21.3    20.9  21.8Free formaldehyde            40.1    15.3    17.1  16.3(mg/100 g dry board)Moisture content (%)            7.9     7.1     7.6   8.0______________________________________ 
    
     Boards obtained with all glue formulations are equivalent. Those however that include the substitute according to the present invention have a very big formaldehyde reduction and resin cost saving.