CA1248654A - Method and composition for bonding solid lignocellulosic material - Google Patents

Abstract

ABSTRACT

Wood surfaces are bonded together by heating and pressing with a bonding composition containing, on a bonding agent solids basis, from 2% to 80% of one or more sugars and from 20% to 98% of an aldehyde condensation resin, especially urea-formaldehyde or phenol-formaldehyde.

Description

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METHOD AND COMPOSITION FOR BONDING
SOLID L.IGNOCELLULOSIC MATERIAL

Field of the Invention The present invention relates to the bonding of wood surfaces, in the manufacture of composite wood products such as plywood, particle board, fiberboard and the like.

Back round of the Invention g At the present time, the major bonding systems being used in the manufacture of composite products of wood still utilize resin condensates of formaldehyde with urea or with phenol or other phenolics. As a result of general economic conditions and especially the recently increased cost of petrochemicals, there is a continuous pressure to reduce the cost involved in employing these resins in the manufacture of wood products. In addition, urea-formaldehyde resin releases formaldehyde which is carcinogenic and an eye and mucose irritant, thus creating a possible health problem.
Adhesives based on carbohydrates, such as starches or sugars, which are converted to binders by various means, have also been suggested and have been adopted to some extent. Carbohydrate binders have an important advantage in lower production costs and zero formaldehyde emission from products. On the other hand, synthetic resin binders based on the condensation of formaldehyde with urea, melamine or phenol have a significant advantage over carbohydrate binders in low curing temperature and short curing times, which are important production cost affecting factors.
Urea and melamine-formaldehyde resins cure at 212F in 13 to 45 seconds, depending on the formulation. Phenol-formaldehyde resins cure at 220F in about 90 seconds.However, carbohydrate adhesives normally need temperat:ures of at]east 280F to cure and the minimum cure time is abouttwo -1 *

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minutes. lhe higher curing temperatures and longer curing times of carbohydrate binders can be reduced by using more efficient heat transfer systems such as steam injection pressing, as disclosed in Stofko U. S. Patent No. 4~357~194~
5 but application of this heating system requires sophisticated presses and more capital investment. Thus, an improved bonding system employing carbohydrates is disclosed in Stofko U. S. Patent No. 4~357~194~ which further teaches the addition of lignin or phenolics containing lignin to the carbohydrate bonding system.
There is also a large body of art directed to forming condensation polymers utilizing carbohydrates, formaldehyde, and a member selected from the group consisting of urea, phenol and melamine. For examples of such art see U. S.
15 Patents 2 ~ 252 ~ 725; 3 ~ 284 ~ 381 and 1, 949 J 831 ~ Thus, Ford in USP 1~949~831 proposes a process for producing durable resinous or plastic substances of a saccharide, urea and formaldehyde by reacting first 63 .15V/o of a saccharide with 18 ~ 95~/o of formaldehyde and 2.1V/o of hexamethylehetetramine at 20 temperatures below 100C, followed by reacting a product of the first reaction with 15~79~/o urea at temperatures of 100-150C~ The final product is a white plastic powder suitable for molding in a press; there is no suggestion of the use of this product for bonding wood. In his related patent, 25 1~949~832~ Ford proposes reacting the condensation product of saccharide and formaldehyde with phthalic anhydride instead of with urea, the ratio of anhydride and sacharide being about 1:1, to again produce a moldable plastic powder.
Hickey et al in USP 3 ~ 284 ~ 381 propose an improvement of 30 starch adhesive for corrugated paperboard, by using amylose instead of starch. In order to increase the water-resistance, a quantity of 0~33-2.7% of urea and 0.65-2.7V/o paraforma]dehyde are added to the amylose together with other ingredients.
The preparation of this starch adhesive involves sevecal 35 steps of mixing and cooking.

-2-USP 2,252,725 describes a process for producing a glucose-phenol-formaldehyde resin in which glucose is substituted for about 30% of the phenol. Other attempts also have been made to produce a sucrose-phenol-formaldehyde resin; for example, the International Sugar Institute has conducted research and has issued a research report on the preparation of sucrose-phenol-Eormaldehyde resin for the manufacture of plywood.
Other prior proposals of some interest include the Olix USP 2,736,678, in which there is proposed the production of sugar-urea-formaldehyde resin by reacting 63.4% sugar with 18.88% formaldehyde at 100C, followed by reacting a product of the first reaction with 15.8% urea at the same temperature.
The resultant resin is proposed as an ingredient in silica-clay-starch ester adhesive, the patentee indicating that the performance of such an adhesive is enhanced by adding a small quantity, i.e. 1-8%, of such sugar-urea-formaldehyde resin to the basic composition intended for the bonding of corrugated paperboard.
Bowen in USP 2,150,148 has proposed a binder for plywood manufacture composed of urea, formaldehyde and zinc chloride.
This patent further indicates that if 0.43% of sucrose is added to the mixture before cooking the resin, some advantages are achieved over the conventional urea-formaldehyde resins.
The ~offmann USP 3,984,275 proposes a binder formulation for corrugated paperboard composed of starch, polyvinylacetate and vinyl acetate-ethylene copolymer, the ratio of the starch to the other components being 1:1. For the purpose of increasing the water-resistance of such binder, a small amount, i.e.
less than 1%, of either urea-formaldehyde or melamine-formaldehyde is added to the adhesive composition.
Another improvement of starch adhesive for corrugated paperboard appears in Bauer USP 3,019,120, where it is suggested to incorporate cyanamide or an alkaline salt thereof which improves the water-resistance of the starch adhe~sive, ;f the cyanam;de is used as a supplementary reacl-ant w;th urea-formaldehyde at h;gh alkalinity. The urea Eorll-aldehy~e represents only 0.5-5% oE the total weight oE the starch.

~Z~8654 Christ in USP 3~076~772 proposes a process for producing urea-phenol-formaldehyde resin extended by sulfite spent liquor. A special urea-phenol-formaldehyde resin of molar ratio 1 part urea, 5 parts phenol, 12 parts formaldehyde and 1.25 parts sodium hydroxide was formulated to make it compatible with sulfite spent liquor. There was about 50%
of urea-phenol-formaldehyde resin, 27~46~/o of lignosulEonic acid, 8~57% of reducing sugars and small quantities of other substances in the final product.
An analysis of these prior disclosures show that they can be classified into two groups. In the first of these groups, resins or plastic substances have been produced of either sugar-urea-formaldehyde or sugar-phenol-formaldehyde.
The basic feature of these processes is that new resins were prepared by cooking, using a definite sequence of reacting components by exposing them to elevated temperature, pressure and time. Final products are indicated to be useful as binders or plastic materials for molding. The products have a ratio of sugars to formaldehyde and urea on the order of 63 19 16~ In the formation of sugar-phenol-formaldehyde, about 30% of phenol was substituted by sucrose giving the ratio of phenol:sucrose:formaldehyde of 35 15:50; taking into account additional materials in the mixes, the sugars constitute about 8~5% of the total resin solids.
In the second group of such prior documents, smal]
amounts of carbohydrates were used as ingredients in producing urea-formaldehyde resins, or small amounts of urea-forma].dehyde resins were used as ingredients in carbohydrate binders.
Thus, 0.43% sucrose was used in cook;ng the urea-formaldehyde-zinc chloride resins according to Bowen USP 2,150,148; less than l~/o of either urea- or melamine-formaldehyde resins were used in cooking the starch-polyvinyl aceLate binder according to Hoffmann USP 3~984~275; and 0.33-5% of urea formaldehyde was used in the preparation oE starch adhesives according to Hickey USP 3,28~,381 and Bauer USP 3,019,120.

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U. S. Paten~ 4,397,756 teaches reducing formaldehyde vapor emissions from wood composite panels bonded with formaldehyde-containing adhesives. This is accomplished by using a mixture of urea and starch in conjunction with an acidic material effective as a catalyst for urea-formaldehyde resin.

Summary of the Invention It has now been determined that useful bonding agents based upon sugars and formaldehyde resins can be prepared by simple blending without the necessity of reacting the sugars with the resins at elevated temperatures prior to applying them as binders to wood surfaces if proper ratios of ingredients are used. Blends of 2V/o to 80V/o of sugars and 98U/V
to 20% of resins can be employed. Blends of 2% to 50% of sugars and 98% to 50V/o of urea or melamine-formaldehyde resin have been found to produce bonds in interior grade products virtually equal in physical properties to bonds achieved by straight urea-and melamine-formaldehyde resins at equal tota] quantity levels of addition. Similarly, blends of sugars with phenol-formaldehyde resins in the ratio of 3V/o to 80V/o of sugars and 97V/o to 20U/o of phenol-formaldehyde resins performed as well as straight phenol-formaldehyde resins at equal total quantity levels of addition. The percentages given above refer to percentages by weight based upon dry solids of the bonding agent exclusive of catalyst and buffer.
The bonding agents of the present invention are normally applied to wood surfaces as a water solution or suspension as are the resins of the prior art. The catalysts which can be used to speed up the cure of the adhesive include the catalysts used to make the lormaldehyde resin-carbohydrate condensation products of the prior art. When an acid catalyst is employed which is so acidic that it would damage the wood being bonded, it is also preLerable that a buffer be present to prevent the acid damage as disclosed in Stoko USP 4,l83,997.
The wood produc~s made in the practice of the present invent-ion are virtually Eree of or significantly lower than forn~aldehyde emissions.

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An important advantage of the present invention is that the present bonding agents are significantly less expensive than the formaldehyde condensation products of the prior art, due to the presence of the :Less-expensive carbohydrate components; at the same time, these new bonding agents in general are usable to provide excellent bonded wood products using the curing temperatures and times of the aldehyde condensation adhesives of the prior art, thereby obviating the deficiencies inherent in the use of the carbohydrate bonding agents of the prior art which required more intensive curing cycles.
For a better understanding of the invention, as well as the objects and the nature and advantages thereof, possible embodiments of the invention will now be described in more detail, it being underscood that these embodiments are intended to be merely exemplary and in no way limitative.

~etailed Description of Embodiments According to one embodiment of the invention, surfaces to be bonded are covered either by a continuous or discontinuous film, e.g. by a mist of droplets, of an unreacted blend containing one or more sugars, and an incompletely condensed aldehyde condensation resin selected from the class consisting of urea-formaldehyde, melamine-formaldehyde, phenol-Eormaldehyde and mixtures thereof, and with or without a separate catalyst and/or buffer, depending upon the nature of the ingredients and the curing system used. The total quantity of bonding agent solids is in accord with conventional practice in this art using condensation product alone. The so coated surfaces are brought into contact with other surfaces and the surfaces are consolidated by heat and pressure for a time sufficient to effect the bonding by chemical transEormation of the t:omponents.
The curing temperatures and times oE sugar-synthet;c resin binders are dependant on the ratio of sugars and synthetic resins in blencls. At the ratio oE 2-40~/o sugars, preferably at least l~, most preLerably at least 30~/O sugars, and ~8-60V/o urea-Lormalclehyde or melamine-tormaldehyde, or 4--60~/o sugars, prelerably again at least 15~/o and most preLerably a~

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least 40~/O sugars, and 96-40% of phenol-formaldehyde resins, cost savings are significant and curing temperatures and times are equal to those of straight resins. If amounts of sugars in blends are higher than indicated, either longer curing times or higher curing ~emperature or both have to be applied.
Particle boards are usually produced as three layer sandwich panels in which the central layer is of a lower density thar. the surface layers. In surface layers which are closer to hot press platens, blends of higher sugar content can be used than in the core, without the necessity of extending press times or increasing curing temperatures.
The significant advantage of blending carbohydrate binders with synthetic resins is in reducing the curing temperatures and the curing times to the levels of conventional synthetic resin binders. In practicing processes according to the present invention, advantages of both groups of adhesives are achieved; the low curing temperatures and times of the synthetic resins and the low cost and the low formaldehyde emission of carbohydrate binders are achieved.
By some mechanism which is not understood, the synthetic resins seem to perform a catalytic function for carbohydrate transformation to provide a solid bond. Sugars combine chemically with synthetic resins, which is evidenced by the fact that the condensation products of sugars and synthetic resins do not dissolve in water. At the present time, this chemical coupling cannot be explained, however, it can be concluded that dehydration of sugars to furanes and coupling thereof to lignin does not take place because a curing temperature of 212-220F is not sufficient for such transformation. Strength oE bonding of the present invention is equal to bond strength achieved by straight synthetic resins under comparable conditions.
A wide variety of sugars such as mono-di-or poly-sacharides of low molecular weight or mixtures thereoE canbe used. Preferred are low cost mixtures of sacharides - ~'2~ 54 such as molasses and wood sugars derived as by-products from wood pulping, or from wet process fiberboard production.
The preferred mixture is a blend of cane molasses and wood sugars containing lignin sulfonates such as sulEite liquor.
Molasses is the source of sugars and sulfite liquor is the source of both sugars and lignosulfonic acid catalyst. It also acts as a stabilizing agent for molasses, controlling the viscosity changes of molasses at varying temperature.
The approximate basic compositions of cane molasses and sulfite liquor and a S0%-50% mixture thereof are as follows:
Components Cane Sulfite S0/50 Blend Percent Molasses Liquor Cane Molasses and Sulfite Liquor invert sugars 32 - 18.85 reducing sugars32 22 27.87 complex sugars and other carbo-hydrates 18 20 18.85 proteins 4.17 - 2.46 lignin sulfonate - 50 20.49 ash 13.9 8 11.48 total 100 100 100 total sugars and carbohydrates 82 42 60.55 A wide range of blends of cane molasses and sulfite liquor can be used Eor example in ratios of 90% molasses and 10%
sulfite liquor to ~0% molasses and 60% sulEite liquor. Sugar containing materials such as sucrose, molasses, corn syrup, maltose base waste products from breweries or lactose based waste products Erom the dairy industry can be used either alone or in blends with wood sugars containing lignin including sodium, ammonium, calcium or magnesium based salts. ~Sugar containing materials can be use(] alone without any lignin sulfonate. In such cases acidic catalyst is u.sed co efrecL
a cure ;n a reasonably short time as ciisclosecl in ~SLoFIco ~SP
4,107,379.

-- ~ 2~ 54 The performance of such bonding agents, based on blends of sugars and synthetic resins, is dependent upon several conditions including ratio of sugars and resins for a given curing temperature and time; pH of components; resin formulation, including molar ratio of components, molecular weight and ingredients; and the amount and type of catalyst used.
As a rule the pH of the sugars should be about equal to the pH of the synthetic resins, but, depending on the urea or melamine~formaldehyde resin type, the pH of the sugars can be significantly lower or higher than the pH of the synthetic resins. If the pH of the sugars is lower than the pH of the urea- or melamine-formaldehyde resins, the sugars have a catalytic affect on the resins, speeding up curing, reducing the need for additional catalyst and shortening the curing time as well as of the storage life of blends. If the pH of sugars is equal to or higher than the pH of the resins of urea or melamine type resins, catalysts have to be added to effect a cure at times equal to that of straight resins. The storage life of such blends is about equal to that of straight resins. If the pH of the sugars is lower than the pH of the phenol-formaldehyde, precipitation of the resins and gelling takes place whih makes the blend difficult to apply.
In general, the pH of sugars for blending with synthetic resins wi]l be between 3 and 12. Low pH sugars will be used with some resins which can tolerate more acidic environment and need catalyzing, and it is desirable to catalyze them with sugars and where storage life time is of no great importance. The pll of sugars for blending with urea- or melamine-formaldehyde resins is between 3 and 9, and the p~l for blending with phenolic resins is between 5 and l2. Sugars of pH 3-5 catalyze urea-formaldehyde resins so that no additional catalyst need to be added.
There are a wide variety of synthetic formaldehyde condensation resins on the market, and these can all be used in the present invention. Variability is created by vclriable g 6~4 molar ratios of components, in~ernal catalysts and modifying agents, molecular weight and other factors. The formulation of sugars in terms of pH, catalysts and the ratio of sugars to other components has to be determind experimentally for each particular resin to make the blend compatible. Many resins have been examined and good compatibility has been achieved with all.
Blends of sugars with urea- or melamine-formaldehyde resins are catalyzed by the same catalysts as are used to catalyze the straight resins. The most widely used catalysts are ammonium chloride, ammonium sulfate, ammonium nitrate and sodium chloride. Amounts of catalysts to be used are variable depending on several factors such as the pH of the sugars, resins and wood, resin type and resin formulation.
Amounts of 0.5 to 2.5% of catalyst solids to the weight of liquid resin base are most common.
The compatibility of sugars with phenolic resins is affected by the type of phenolic resins, whether it be acidic or alkali catalyzed, pH, alkali content, molecular weight and molar ratio of phenol and formaldehyde.
Sugars can be blended with catalysts prior to blending them with synthetic resins or they can be blended with synthetic resins first stored and then shipped as such blends, and catalyst added to blends immediately prior to applying them to wood, or a catalyst solution can be applied to the wood separately.
The following examples, offered illustratively, will illustrate ways of practical application of this bonding process.

Mixed softwood shavings of 2.5% moisture contenL were sprayed with a water solution containing, based on solids, 70% of urea-formaldehyde resin (U~ resin) and 30/~ of sugars Particle-board samples of 5/8 or 3/4 inch thickress were made at conditions which are listed in Table l and the achieved physical properties of the boards are listed in r~b]~ 2.

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Samples designated by Samples No. 1, 2 and 3 were control samples made using straight urea-formaldehyde resin and Sample No. la; 2a; 3a represent data obtained on samples made using a blend of the same urea-formaldehyde resins with sugar composition specified in Table 1. It has been verified on a large number of laboratory trials of which the presented data in this example is only a small fraction, as well as on full scale production trials, that sugar/UF resin blends produce properties equivalent to straight resins at equivalent 10 conditions.

Table 1 NoO Sugars-U~ resin% to oven dry woodCatalyst Platen Press total UFsugars lignin pH % temp. time sulfon. F minutes 1 7.S RCI zerozero - NH~Cl 340 5 7.5 .75 la 7.5 5.25 1.67.59 5.5 " " "

2 5.75 Borden zeroze~o - NH4C1 370 4.5 12CllCF .75 5.75 2a 5.75 4.03 1.28.45 5.0 " " "

3 8.0 RCI zerozero 6.55 (NH4)2 375 2'45"

8.0 2 3a 8.3 5.81 2.49zero 6.55 RCI--Reichhold Chemicals Ltd; Borden=Borden Chemicals Ltd.

As is seen from these data, urea-formaldehyde resin solids represent 70% of the total and sugars solids represent 22.27 or 30'~ of the total and salt of lignosulfonic acid catalyst represents 7.87~/~ o~ the total.

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_able ~_ No. Thickness Densitx Internal ~4 hrs soaking in H20 inch Ib/ft~ bopsndi V/Othickness swell U/Owater absorbant 1 .799 45.9 114 32.3 80 la .786 45.8 112 33.3 82.2 2 .785 41.9 76 12.7 37.1 2a .800 40.9 77 23.2 72 3 .712 43.3 116 23.6 78.6 3a .730 42.8111.6 27.4 81.6 Mixed so~twood shavings o~ V/O moisture content were sprayed with a water solution containing 50% oE phenol-formaldehyde resin and 50V/o sugar formulation. Percentages are based on solid weight. Particle-boards 3/4-inch thick were made at conditions summarized in Table 3 and physical properties of boards made at these conditions are summarized in Table 4.

Table 3 No. Sugars Composition Phenol Resin Platen Press sugars lignin formaldehyde solids temperature time sulfonate p~l V/oO.D. F minutes 1 zero zero - 6.94 6.94 420 ~0 87+
2 3.49 zero 11.63.89 7.38 420 10 3 2.33 .83 11.2 3.33 6.49 420 187+

~Z~8~54 Table 4 No. Thickness Density Internal 2 hrs boiling in H20 inch lb/ft3 bond-psi V/~thickness ~/Owater absorption swell 1 .774 42.8 107 47.~ 109.3 .780 ~4.5 95 ~9.6 107.6 .776 ~2.9 93.9 27.3 91 2 .770 43.8 98 44.3 126.8 .770 4~.5 111 57.1 118.7 .764 42.8 105 ~1.95 104.8 3 .776 43.2 107 40.7 109.2 .783 43.6 113 54.9 112.5 .780 42.5 ]12 39.4 101.6 Samples pressed at 7 minutes press ~ime were hot stacked after pressing at 212F for 7 hours.

Douglas fir plywood blocks were made of 1/4 inch thick 6 x 6 inch veneers under fully controlled conditions.
A 50/50 blend of sugar composition with phenol-formaldehyde (PF) resin produced by West Coast Adhesives for the plywood industry was prepared. The sugar composition contained 61V/o sugars and 20% of sodium lignirl sulfonate. Veneers of about 5~/O moisture content were brushed with a blend of sugars and PF resin in solution in the amount of 3.785 grams per one surface which is e4ual to ~6 lb per 1000 board feet of double glue line. Assembly time was 5 minutes before, 5 minutes during and 5 to 20 minutes after prepressing at 150 psi pressure. Plywood samples were pressed at 285F press platen temperature Eor 5.5; 6.,5 and 7.5 minutes. After pressing, samples were hot stacked overnight which is a standard practice in plywood industry. To test the samples, glue lines were opened and wood failure in dry condition was determinecl.
Half of the samples were boiled in water for 4 hours fc)llowed by drying at 145F for 20 hours and then boiling in water for four hours. AEter coolin~ in the cold water glue lines were opened and wet wood Eailure determined. Obtained results are presented in Table 5.

Table 5 No.Press time pH Wood Failu~e %
Minutes Sugars Sugars Dry After boil-dry~
PF Mix S Control 5.5 - 12.0570 75 6.5 85 90 7.5 100 100 55125 5.5 10.05 11.5550 50 6.5 80 80 7.5 100 100 5525 ~.5 10.85 11.7 85 70 6.5 85 70 It has been fully verified by small scale laboratory investi~ation as well as by full scale trials in a plywood mill that blends of sugars with pheno-formaldehyde resins at a weight ratio of 50:50 produce bonding virtually equal to that achieved by the bonding produced by straight resins.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the concept and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purposes of description and not of limitation.

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Claims (27)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A bonding composition for bonding wood surfaces comprising, on a total solids basis, from 2% to 80% of one or more sugars blended with from 98% to 20% of an aldehyde condensation resin selected from the group consisting of urea-formaldehyde, melamine-formaldehyde, phenol-formaldehyde and mixtures thereof.

2. The wood bonding composition of Claim 1 consisting essentially of from 2% to 60% of sugars, 98% to 40% of urea-formaldehyde or melamine-formaldehyde and catalyst.

3. The wood bonding composition of Claim 1 consisting essentially of from 3% to 80% of sugars, 97% to 20% of phenol-formaldehyde resin, and catalyst.

4. The wood bonding composition of Claim 2 consisting essentially of 2% to 40% of sugars and 98% to 60% of urea-formaldehyde or melamine-formaldehyde.

5. The wood bonding composition of Claim 4, wherein the percentage of sugar is 15% to 40%.

6. The wood bonding composition of Claim 4, wherein the percentage of sugar is 30% to 40%.

7. The wood bonding composition of Claim 3, wherein the percentage of sugar is 4% to 60%.

8. The wood bonding composition of Claim 3, wherein the percentage of sugar is 15% to 60%.

9. The wood bonding composition of Claim 3, whereln the percentage of sugar is 40% to 60%.

10. A method of bonding wood surfaces and thereby producing a waterproof bond, which comprises providing on a surface of said wood a bonding material consisting essentially of about 2% to 80% of at least one sugar, about 98% to 20% of an aldehyde resin selected from the group consisting of urea-formaldehyde, melamine-formal-dehyde, phenol-formaldehyde and mixtures thereof, a catalyst, and optionally a buffer so that the bonding material will not decrease the pH after heating of the wood to below about 3.5, and pressing surfaces of the wood together to an elevated temperature and for a time sufficient to effect said bonding.

11. A bonded wood product made by the process of claim 10.

12. A method of bonding particulate wood surfaces and thereby producing a waterproof bonded composite wood product, which comprises providing on surfaces of said particulate wood an amount of a bonding material equal in quantity to 100% of urea-formaldahyde or melamine-formaldehyde condensation resin, and bonding material consisting essentially of about 10-70% of at least one sugar, about 90-30% of an aldehyde resin selected from the group consisting of urea-formaldehyde, melamine-formaldehyde and mixtures thereof, and optionally a catalyst, or a buffer or both so that the bonding material will not decrease the pH after heating of the wood fibers or particles to below about 3.5, and pressing surfaces of the particulate wood together to an elevated temperature and for a time sufficient to effect said bonding to produce said bonded composite wood product, said time and temperature being not substantially greater than the conventional time and temperature when using 100% of urea-formaldehyde or melamine-formaldehyde bonding resin, the resultant bonded composite wood product having a reduced formaldehyde odor compared with composite wood product made with 100% urea-formaldehyde or melamine-formaldehyde bonding resin.

13. A method according to claim 12 wherein said pressing is steam pressing carried out in the pre6ence of direct contact of the particulate and bonding material with the steam.

14. A method according to claim 12 wherein said sugar is present in an amount, based on the total quantity of bonding material, of 10-40%.

15. A method according to claim 12 wherein said sugar is present in an amount, based on the total quantity of material, of 15-40%.

16. A method according to claim 12 wherein said sugar is present in an amount, based on the total quantity of material, of 30-40%.

17. A method according to claim 12 wherein said sugar and said condensation resin are pre-mixed before application to the wood particles.

18. A method according to claim 12 wherein said sugar and said condensation resin are applied separately in series to the wood particles.

19. A method according to claim 14 wherein the total quantity of bonding material solids is about 4-12% based on the weight of the particulate wood, and pressing is carried out for less than 1 minute at about 100°-125°C.

20. A method according to claim 12, wherein said sugar comprises a mixture of lignin sulfonate and molasses.

21. A method of producing a waterproof bonded composite wood product, comprising applying to surfaces of particulate wood a bonding material consisting essentially of about 10-40% of at least one sugar and about 90-60% of an aldehyde condensation resin selected from the group consisting of urea-formaldehyde resin, melamine-formaldehyde resin and mixtures thereof, and optionally with a catalyst, or a buffer or both so that the bonding material will not decrease the pH of the particulate wood to below about 3.5 after the heating thereof, the quantity of said bonding material solids based on the weight of the wood particles being in the range of about 4-12% and equal in quantity to an amount of straight condensation resin which would be conventionally used to obtain the same degree of bonding, and pressing the particulate wood together at a temperature of about 100°-125°C. for less than about 1 minute to effect said bonding to produce said composite wood product, the resultant bonded composite wood product having a reduced formaldehyde odor compared with composite wood product made with straight urea-formaldehyde or melamine-formaldehyde condensation resin.

22. Composite wood product made according to the process of claim 12.

23. Composite wood product made according to the process of claim 16.

24. Composite wood product made according to the process of claim 18.

25. Composite wood product made according to the process of claim 20.

26. A method for reducing the quantity of urea-formaldehyde or melamine-formaldehyde bonding resin in the bonding of particulate wood surfaces, without increasing substantially the time and temperature of cure and without decreasing substantially the quality of the bond, comprising providing a bonding material comprising urea-formaldehyde condensation resin, melamine-formaldehyde condensa-tion resin or a mixture thereof as bonding agent, and in which bonding material about 10-70% of said condensation resin bonding agent has been replaced by at least one sugar, said bonding material optionally containing a catalyst, a buffer or a mixture thereof so that the bonding material will not decrease the pH after heating of the particulate wood to below a pH value of about 3.5;
providing said bonding material on surfaces of said particulate wood in an amount of about 4-12% based on the weight of the particulate wood, and equal in quantity to an amount of straight condensation resin which would be convention-ally used to obtain the same degree of bonding; and pressing the particulate wood together at a temperature of about 100°-125°C. for a time which would be conventionally used to obtain the same degree of bonding using a straight condensation resin, and thereby effecting bonding to produce said composite wood product, the resultant bonded composite wood product having a reduced formaldehyde odor and substantially equivalent bond strength compared with composite wood product made under the same conditions with straight condensation resin.

27. A method according to claim 26 wherein the quantity of condensation resin replaced by sugar is 30-40%.