WO1979000977A1

WO1979000977A1 - Method for the manufacture of adhesive products and an adhesive product manufactured according to the method

Info

Publication number: WO1979000977A1
Application number: PCT/SE1979/000098
Authority: WO
Inventors: F Edler
Original assignee: Edler & Co Faergind Ab
Priority date: 1978-04-24
Filing date: 1979-04-23
Publication date: 1979-11-29
Also published as: GB2043087A; NZ190271A; FI72338C; DK149637C; SE7808082L; IT7922141A0; NO151708B; AT365622B; SE425093B; JPS55500316A; DK551379A; FR2426720A1; NO782553L; FI782314A; ATA903179A; DK149637B; CA1117693A; CH646191A5; GB2043087B; NO151708C

Abstract

A method for the manufacture of an adhesive product suitable for use in the manufacture of wood particle board and other wood products which adhesive product includes a large proportion of the spent liquor from the sulfite pulping of lignocellulose and is readily applicable to the manufacture of particle boards using conventional apparatus and methods, and leads to the production of glued wood products of commercially acceptable properties, which meet the commercial standards for such products. According to the invention the manufactured adhesive product consists of 50-90 parts by weight of urea formaldehyde resin solids and from 10-50 parts by weight of the spent liquor dry solids basis. The adhesive product also contains as a key component from 0.2 to 4.0% by weight of ammonium ion (expressed as NH3) on a sulfite spent liquor solids basis.

Description

Title:

Method for the manufacture of adhesive products and an adhesive product manufactured according to the method.

Technical field:

The present invention relates to a method for the manufacture of an adhesive product and an adhesive product manufactured accor¬ ding to the method. More particularly the invention relates to a method for the manufacture of adhesive products including urea based condensation products with formaldehyde and with the addition of acid sulfite spent liquor. The invention particularly relates to the manufacture of such adhesive products which are generally used in connection with in a dry process produced wood particle boards , fibre boards , plywood and similar products and of which adhesive products sulfite spent liquor is a large constituent and relates also to an adhesive product of the kind mentioned .

Background Art:

Others heretofore have investigated the possibility of combining various synthetic resins , including urea formaldehyde resins (urea) or the components thereof, with various sulfite spent liquors . Among these are Hartwig et al U.S . patent 2,405,650 (cores for metal cas¬ tings) , Kei U . S . patent 2,622,979 (wet strength paper) , Walther et al U. S . patent 3,313,745 (foamed plastic bodies) . Schmidt-Hellerau U. S . patent 3,390,920 discloses the use of urea formaldehyde resin and a very minor proportion (1-5%) of sodium ? ligninsulfonate in wood particle board production . Willegger et al : U . S . patent 3, 994, 850 discloses the manufacture of wood particle- ? board using an adhesive prepared by reacting together urea, sodium base spent sulfite liquor and formaldehyde .

Technical problem :

However, none of the procedures of the foregoing references have solved successfully the problem of incorporating a large pro- portion of sulfite spent liquor in wood particle board adhesives . It has become^* axiomatic in the industry that the use of substantial quantities of these materials in the manufacture of such adhesives is to be avoided for reasons of incompatibility with the resin consti¬ tuents of the adhesives and unacceptable properties of the particle board manufactured using the adhesives .

This belief is based on the results of extensive experimental experiences and is fully justified by the molecular complexity of the two reactants, i.e. the sulfite spent liquor and the urea formaldehyde resin, as well as by the diversity of chemical reactions which poten¬ tially can occur during the preparation of the resin, the mixing of the resin with the sulfite spent liquor, and the subsequent hot pres- sing operation.

Thus, the sulfite spent liquors are incompatible with and inso¬ luble in, certain of the urea resins .

The solution: Under certain conditions urea and formaldehyde combine to form resinous condensation products containing a high proportion of mono- di- and polymethylol ureas , i. e. methylol rich products . Under other conditions the urea and formaldehyde combine to form a high propor¬ tion of methylene ureas, i. e. methylene rich products . The methylol rich products are compatible with sulfite spent liquors whereas the methylene rich products are not. Accordingly, if the urea formalde¬ hyde resin is to be combined successfully with sulfite spent liquor, it must be of the methylol rich type.

Second, when the urea formaldehyde resin is mixed with sub- stantial quantities of an untreated ammonium base sulfite spent liquor which contains ammonia in the form of ammonium lignin sulfonate, the ammonia quickly removes any free and loosely bound formaldehyde present in, or supplied by, the urea formaldehyde resin, converting it to the relatively inactive product hexamethylene tetramine. This reaction lieb rates excess lignin^*; sulfonic acids which lower the pH of the adhesive mixture, over-catalyzes the adhesive and results in excessively rapid cure and premature gelation. Conversely, when the resin is mixed with calcium, magnesium or sodium base sulfite spent liquor, no ammonia att all is present, the above noted libera- tion of lignin sulfonic acids does not occur and the adhesive will be under- catalyzed .

Accordingly, it is important that the ammonia content of the adhesive be carefully controlled. Third, variations in the pH of both the adhesive products and its components can affect materially the activity and properties of the adhesive. Too high a pH causes the adhesive to cure too slowly . Too low a pH causes it to cure too fast. Still further, in the hot press excess acidity may degrade the cellulose content of the wood to which it is applied. For these reasons it is necessary to control carefully the pH of both the sulfite spent liquor and urea formalde¬ hyde resin components of the desired adhesive product.

Advantages :

It is the general object of the present invention to provide a process for the maufacturing of an adhesive product suitable for use in the manufacture of wood particle board which product includes a large proportion of the spent liquor from the sulfite pulping of lignocellulose, is easily and simply manufactured, is readily applicable to the manufacture of particle board using conventional apparatus and methods, and leads to the production of glued wood products of commercially acceptable properties, which meet the commercial stan¬ dards for such products , and are fully competitive with related pro- ducts manufactured using conventional, more expensive, adhesives . It is another object of the invention to provide an adhesive pro¬ ducts manufactured by means of said process .

Yet another important object of the invention is the provision of a method and an adhesive product respectively which make it pos- sible to use in large proportion a very low cost waste product, sul¬ fite spent liquor, and thereby at the same time partly solvius the classic problem attending the disposition of pulp mill sulfite spent liquor while providing economies in the cost of a particle board ad¬ hesive, which in the case of the average particle board plant may be of the order of one-half million dollars annually .

Best mode of carrying out the invention :

In connection with the invention it has been discovered that the problems attending the combination of urea formaldehyde resins and sulfite spent liquors in the manufacture of a useful adhesive product may be overcome, and the foregoing objects achieved, by the provision of an adhesive product broadly comprising 50 to 90 parts by weight of urea formaldehyde resin solids and from 10 to 50 parts by weight of the spent liquor resulting from the acid sulfite pulping of lignocellulose, dry solid basis . The adhesive product also contains as a key component from 0.2 to 4.0% by weight of ammo- nium ion (expressed as NH₃) on a sulfite spent liquor solids basis . The ammonium ion may be supplied by the utilization of ammonium base sulfite spent liquor of adjusted ammonium ion content. In the event that it is desired to use another sulfite spent liquour, i.e. a calcium base, magnesium base, or sodium base sulfite spent Kquor, the ammonium ion is provided by the addition of a water soluble, ammonium salt of a strong acid in appropriate amount.

The ammonium salt has the effect of providing ammonia which combines with free formaldehyde which is present in the mixture so that the neutral product hexamethylene tetramine is formed, releasin a strong acid, and leaving a mixture of increased but controlled aci¬ dity which promotes the desired condensation or polymerization of the adhesive product during its use, as set forth hereinabove. The urea component of the adhesive product is characterized by a molar ratio of formaldehyde to urea of from 1.0 to 1.8 , and a methylol content corresponding to a Witte number of from 1.0 to 1.8. The properties of the resin thus are such as to insure compatibility with, and a desired degree of solubility in, the sulfite spent liquor as required to provide a suitable adhesive product.

The adhesive product is manufactured by simply intermixing the sulfite spent liquor and the urea formaldehyde resin in the pre¬ sence of ammonium ion under conditions of temperature, pH and vis¬ cosity which lead to the production of a mixture in which the lignin sulfonic acid component of the sulfite spent liquor and the urea for¬ maldehyde resin condense with each other to a substantial degree in a prolonged reaction. The method and the products thus is to be distinguished from the prior art methods and products manufactured by means of them wherein such condensation occurs rapid or is deli¬ berately promoted. It also is to be distinguished from the prior art processes wherein the sulfite spent liquor is reacted with urea and formaldehyde in a process including only these components .

Best mode of carrying out the invention:

In the application of the adhesive product of the invention to

OR E

OΛ.P the manufacture of glued products such as wood particle board, the adhesive is simply applied to the wood base in the usual amounts and proportions, and hot pressed, using conventional apparatus , to form the final glued, consolidated wood product.

At a preferred embodiments of the method according to the in¬ vention the same is proceeded so that the presently described adhe¬ sive product manufactured according to the method comprises, in substantially uncondensed admixture with each other, in parts by weight, on a dry solids basis :

Urea Formaldehyde Resin 50-90

Spent Liquor from the Acid Sulfite

Pulping of Lignocellulose 10-50

The adhesive product contains also from 0.2 to 4.0% by weight of ammonium ion (expressed as NH„) , on a spent liquor solid basis . As also noted above, the urea formaldehyde resin is characteri¬ zed by carefully controlled properties, particularly by its mol ratio of formaldehyde to urea from 1.0 to 1.8, its pH of from 6 to 8, and by its methylol content corresponding to a Witte number of from 1.0 to 1.8. Additionally, it should have a solids content of from 50 to 72%, preferably 55 to 65% by weight, and a viscosity of from 50 to 250 centipoises at 65% resin solids and 25° C.

With respect to the mol ratio, it is to be observed that if the mol ratio is below 1, the urea formaldehyde polymer is not sufficient- ly functional to develop the desired adhesive properties in the final product. At a mol ratio above 1.8, excessive quantities of formal¬ dehyde are present. This leads to the formation of an adhesive pro¬ duct having an objectionable odor and one which liberates excessive toxic fumes in the hot press and thereafter in service. With respect to the viscosity limit of 50 to 250 centipoises , it is to be observed that this range is below the viscosity range of the urea formaldehyde resins conventionally used in the manufacture of particle board. If the urea formaldehyde resin were to be used per se at such a viscosity, it would be unsatisfactory because of its poor tack properties . The addition of the sulfite spent liquor, as taught herein, is required in order to develop the required tack properties .

With respect to the methylol content of the urea resin, a methy¬ lol content corresponding to a Witte number of 1.0 to 1.8 is requir — .. ._ __

OM I in order to make the urea formaldehyde resin compatible with the sulfite spent liquor and in order to develop satisfactory adhesion and product performance.

Theoretically a methylol content of the urea resin, which is so low that it corresponds to a Witte number of 1.0 would not be suffi¬ cient to secure the desired reaction with the sulfite spent liquor. However, there are reasons to assume that the Witte number, which is determined as representative for the component at a state before the reaction with the other components begins, will not be adequate to the methylol content when the reaction is started. It is assumed that in the very beginning of the reaction between the two compo¬ nents new the Witte number not influenceable groups increasing the methylol content are opened so rapidly, (fractions of seconds) that the methylol content will be sufficient for the intended reaction. To obtain this it is necessary that the resin has a content of ether com¬ pounds, which can be devided into OH-groups . This condition is indicated by the fact that resin products rich of ether compunds will give an acceptable result even by a resin of the lower Witte number while resins with the lower content of ether compounds have to show higher Witte number at the state before the reaction .

The term Witte number is obtained as a result of a determination of the methylol groups in urea formaldehyde resins by reacting the resins with 2, 6- dimethyl phenol (2,6-xylenol) . It measures the methy¬ lol funtionality of the resin . It is determined as follows . A solution of 2,6-dimethyl phenol (25. Og) in 200 ml of water containing 8.0g sodium hydroxide is treated with 12.5g of the urea formaldehyde resin to be tested, with thorough mixing. The resulting reaction mixture is allowed to stand at room temperature in the dark for three days . Concentrated hydrochloric acid is added until the pH of the reaction mixture reaches 5.5-6.0. The reaction mixture is washed into a one liter flask and steam distilled until 700-750 ml of distillate has been collected.

The condenser is rinsed with a little methylene chloride and the condensate extracted with 3x100 ml of methylene chloride. The combined methylene chloride extracts are filtered through ca 20g sodium sulfate (anhydrous) and the sodium sul ate washed with

2x25 ml methylene chloride.

The methylene chloride is evaporated in vacuo until weight of the evaporating flask is obtained. The weight of dual 2, 6- dimethyl phenol is determined and subtracted from its origi¬ nal weight. The difference of these two weights is the amount of 2, 6- dimethyl phenol which has reacted with the urea formaldehyde resin and is a measure of the methylol content of the resin. It is termed herein the "Witte number" . This value is calculated by the following equation:

Weight of Recovered Xylenol _{= mne Nuffiber} 12.5 X %Solids of UF Resin

It bears a direct relationship to the methylol content of the resin, as shown by the following tabulation of typical test results in which the Witte numbers were determined for a series of urea formaldehyde resins of varying mol ratios (mols formaldehyde per mol of urea) prepared in such a manner that methylol functionality was maximized .

Mol Ratio of Urea Formaldehyde Resin Witte Number 0.9 0.76

1.2 1.17

1.3 1.30 1.4 1.38

1.5 1.47

1.6 1.57 100% dimenthylol urea 2.64

With respect to the sulfite spent liquor component of the adhe- sive product of the invention:

By the term "sulfite spent liquor" is meant the liquor resulting from the conventional acid sulfite pulping procedure in which there is about 5 to 7 % by weight total sulfur dioxide and 0.9 to 1.2 % combined sulfur dioxide . The sulfite spent liquor results from any of the conventional

^"acid sulfite lignocellulose pulping procedures . It accordingly may comprise any of the commonly produced acid sulfite spent liquors thus , whether ammonium base, calcium base, magnesium base or so¬ dium base. Specifically excluded, however, are the sulfite spent liquors resulting from the pulping of lignocellulose by the "Magnafite" , "Sodafite" and neutral sulfite semi-chemical ("NSSC") processes . These three spent liquors are inoperable for the purposes invention and are excluded by definition from the description thereo because all of them contain substantial quantities of residual sulfite ion in their concentrated liquors . As is explained in greater detail hereinbelow, this would result in an unfavourable liquor pH change if these liquors were to be used in manufactureing of the herein- described adhesives .

The sulfite spent liquors may be employed substantially in the form in which they are obtained from the liquor concentrating opera tion of the mill, without being first desugared. As thus obtained, the spent liquors generally have a solid con¬ tent of from 40 to 55 % by weight, usually 50 %+ 2 %; a viscosity of, for example, from 500 to 4000 centipoises at 25°C and 50% con¬ centration, and a pH of from 3.5 to 4.5.

If the solids content is less than about 40% by weight, the spe liquor contains too much water to be conveniently applicable to the manufacture of the adhesive products . If the liquor contains more than 55% solids, it is too viscous to handle conveniently in the plant The viscosity of the spent liquor preferably should be within a working viscosity range in which the liquor is pumpable at room tem perature and readily mixable with the urea formaldehyde resin . Higher viscosities can be handled by warming the liquor. This per¬ mits the use of liquor having viscosities as high as 15,000 centipoi¬ ses .

The proposed viscosity for the resin and the sulfite spent liquo will give components which are suitable to handle in the process and will also result in an adhesive product with the desired properties . The viscosity of the resulting product is, however, not determined by the viscosity of the components but by the total amount of water in the product. The desired content of water is obviously possible to adjust as a diversing viscosity from the recommended value of the one component can be compensated by changing the viscosity of the other component or, if the viscosity is too high by means of adding water to the mixture.

The sulfite spent liquor pH should be within the range of 3 to If the pH of the sulfite spent liquor is below 3, the adhesive in which it is contained cures too fast and gels too rapidly at room temperature for convenient handling. If the pH of the spent liquor is above about 9, the adhesive product of which it is a component cures too slowly to be used in practice. _//^,"BU The spent liquor preferably shouid be substantially free of dis¬ solved sulfur dioxide (sulfite ion) since the presence of this material has the end result of raising the pH of the adhesive to a level at which the hot press cure is too slow, adversely affecting the pro- duction and properties of wood products made with the adhesive. The spent liquors, if not neutralized, become SO₂ free, because that material is driven off during the concentration of the liquor.

As discussed hereinabove, a key component of the adhesive product of the invention, and the one responsible for the successful combination of a large proportion of sulfite spent liquor with urea formaldehyde resin, is ammonium ions used in the amount of 0.2 to 4.0% by weight (expressed as NH,) by weight on spent liquor solids . This component of the mixture has the above described function of reacting with a portion of the formaldehyde to form the relatively inactive product hexamethylene tetramine . This results in the reduction of the pH of adhesive mixture to a level at which it cures rapidly in the hot press.

If too much ammonium ion is present, the resultant high ammonia content of the adhesive reacts quickly with free or loosely combined formaldehyde in the urea formaldehyde resin to produce the stable hexamethylene tetramine, and releases large quantities of strong acids. These excessive quantities of acid in turn lower the pH of the mixture and catalyze the urea formadehyde resin to a very rapid cure. The effect of rapid-curing binder on particle board or other wood product quality is to cause soft surfaces and a general lowering of strength properties through premature cure . Water adsorption and thickness swell are also adversely affected. The period of liquid state of the binder is severely reduced, introducing a seriuos risk of gelation in plant piping and -equipment.

The ammonium ion component of the mixture is included as the water soluble ammonium salt of a strong mineral acid or organic acid (ionization constant (K.a) of 10 or greater) . Exemplary of such salts are : Ammonium lignin sulfonate

Ammonium chloride Ammonium sulfate Mono- ammonium phosphate ^ζ\, REA £_j~'

OMPI -, iPO ^' Ammonium oxalate Ammonium benzene sulfonate Ammonium mono-chloracetic acetate

It will be apparent that where the acid sulfite liquor comprises an ammonium base acid sulfite spent liquor, the ammonium salt is inherently contained in the spent liquor component of the adhesive product as ammonium lignin sulfonate. It is not necessary in this instance to add additional or extraneous ammonium salt.

In fact, since the ammonium ion content of the liquor usually exceeds that permitted in the hereindescribed adhesive products, the excess ammonium ion may be removed by treating with the pre¬ determined amount of caustic soda or other strong base driving off ammonia and leaving only the desired content of ammonium ion as a residuum. However, the removal of excess ammonia with caustic alka should be done after the removal of sulfur dioxide (on the acid side as set forth hereinabove.

If calcium, magnesium or sodium base spent liquors are employe then a sufficient amount of ammonium salt is added to result in the formation of an adhesive product containing ammonium ion in the in- dicated proportion.

In formulating the adhesive products of the invention from the above primary components, these components in predetermined pro¬ portions are simply mixed in suitable and conventional mixing equip¬ ment until a uniform mixture is obtained. The mixing is carried out at or near room temperature (10 to 30°C) in order to inhibit conden sation of the components of the sulfite spent liquor with the urea formaldehyde resin. The adhesive product of the invention is subs¬ tantially uncondensed. The condensation of the adhesive takes place in the hot press during its cure. With reference to what is stated in the foregoing the method according to the invention will be characterized by the following com ponents being chosen :

1) Urea-formaldehyde resin of the following conditions : proportions formaldehyde/urea 1.0-1.8 pH 6 - 8 viscosity preferably in the range 50-250 centi¬ poises (at Witte number 1.0-1.8 with the Witte number indicating the methylol functio¬ nality by the resin

2) Sulfite spent liquor of the following conditions : pH 3 - 4,5 viscosity preferably in the range 500-4000 centi¬ poises (at 50% dry solids basis and 25°C)

10

With the sulfite spent liquor substantially free of dis¬ solved sulfur dioxid. The sulfite spent liquor is checked according to- its content of ammonium ions which has to correspond to an amount of 0.2-4.0% by 15 weight (expressed as NH₃) on spent liquor solids .

If too much ammonium ion is present by use of a sulfite spent liquor on ammonium base the excess ammonium ion may be decreased to the predetermined amount by means of adding caustic soda or other strong base for the driving off of ammonia. 20 if the content of ammonium ion present is too low by use of a sulfite spent liquor on for example calcium, magnesium or sodium base, the ion content may be adjusted to the prescribed value by adding a water soluble ammonium salt of a strong mineral or organic acid as any of the salts ammonium lignin sulfonate, ammonium chloride, 25 ammonium sulfate, mono- ammonium phosphate, ammonium oxalate, am¬ monium benzene sulfonate or ammonium mono-chloracetic acetate;

3) Water which preferably is added as included in the components 1) and 2) by providing said components with the following dry solids content:

30 the urea-formaldehyde resin 50-72% by weight pre¬ ferably 55-65% by weight the sulfite spent liquor 40-55% by weight prefe- _₅ rably 48-52% by weight or adding of the equivalent amount of water mixing in the following proportions : the urea-formaldehyde resin 50-90 part the sulfite spent liquor 100-50 part on the compo nents dry solid basis by stirring resulting in a heat curable adhesive prod

Desired amounts of desired additives may be included in th adhesive mix. Such additives may include for example suitable o conventional proportions of waxes, oils, fungicides , fireproofin agents, surface active agents and dyes , in which case the ligni sulfonate salts serve as dispersing agents for the waxes and oils .

The finished adhesive is stable for a reasonable length of tim and may be stored and used in conventional manner.

If it is to be applied to the manufacture of wood particle board it is sprayed on wood chips, flakes fibers, shavings or other woo particles and the resultant adhesive-coated particles dry felted into a mat of the desired dimensions, using an adhesive application o the order of 5 to 10 % by weight, oven dried wood basis . The mats may be pressed in conventional presses to the desired density unde the desired press conditions of , for example 250 to 500 psi at 140 to 160°C for 2.5 to 10 minutes, depending on board thickness .

As is shown in the following examples, the resulting particle board products , have .properties which are commercially acceptable and fully competitive with the properties of particle board products made with conventional urea formaldehyde resin adhesives . The adh sives of the invention, moreover, have the significant economic ad¬ vantage of including o large proportion of low cost sulfite spent liquor, which results in significant glue cost savings to the mill which they are employed. Corresponding savings can be obtained also.

Industrial applicability: Examples

The method and the adhesive products of the invention are il¬ lustrated in the following examples, wherein the resinous adhesive products of the invention are identified as "Edler" , and the followin abbreviations are used:

SSL - sulfite spent liquor

MOR - moduls of rupture MOE - moduls of elasticity IB - internal bond The particle board products incorporating the Edler adhesives were tested by ASTM test method designated ASTM D1037-72.

Example 1

This example illustrates the commercial plant application of the adhesives of the invention to the manufacture of industrial grade wood particle board having thickness of 10, 13 and 19 mm.

Four urea formaldehyde resins were provided for use in this and the following examples . They had properties as set forth in Table 1.

TABLE I

RESIN A RESIN B RESIN C RESIN D ( Control) ( Control)

Witte Number (methylol functionality) 1.58 1.67 1.02 1.02

Mol Ratio (mols formal- dehyde/mol urea) 1.60 1.50 1.35 1.15

Solids (% by weight) 57 58 65 65.5

Viscosity at 25°C (cps) 70 70 300 140 pH 7.4 7.4 — 7.4

Dilutibility Infinite Infinite Infinite Infinite

Resins "A" and "B" were used in the formulation of the herein- described "Edler No. 1" and "Edler No. 2" adhesives , respectively. Resins "C" and "D" were used as control adhesives .

The sulfite spent liquor employed in the formulation of the Edler adhesive of this example was derived from a concentrated commercial ammonium base acid sulfite spent liquor (SO₂ free) which contained an excess of ammonium ion for the purpose of the present invention . Its ammonium ion content was adjusted to within invention limits by reacting it with a measured amount of sodium hydroxide (caustic soda) . After adjustment, the spent liquor contained 1.0% by weight of ammonium ion (expressed as ammonia) , dry solids basis .

Its other properties were as follows :

Viscosity at 25°C (cps) 15,000

In a plant run Edler type particle board adhesive were manufac tured by mixing together at ambient temperatures urea formaldehyde resin and sulfite spent liquor using the latter in amount sufficient to provide 33% by weight liquor solids , dry solids basis , in the finished adhesives . These adhesives are termed herein "Edler No. 1" and "Edler -No. 2" .

The mixing was carried out until the components were thorough ly mixed and a blend of uniform appearance obtained. During the mixing, no temperature rise or indication of condensation of the mixed constituents was observed.

The adhesives prepared in the foregoing manner were sprayed on wood chips to formulate core and face chip blends . These then were dry felted into a mat which was hot pressed to form the con¬ solidated particle board product. The forming and pressing condition were as follows :

Furnish : Core and face chip blends , about 67 % pine and 33 % fir.

Formation: Bahre-Bison air layered board, 13 mm thick

Wax Content % Adhesive Content: Face, 8.3%; Core, 8.3%. Mat moisture content: Face 10%, Core 8%. Prepress Cycle: 30 seconds Press Time: 2 minutes , 52 seconds . Time to Stops : 45 seconds . Decompression Cycle: 30 seconds (in addition to press times) .

Press Temperature: 160°C

A number of boards were made using both adhesive types, the resin "C" serving as a control. The boards were subjected to the above noted ASTM tests D1037-72 for measuring their properties , with results as given in Table II .

"BU

OM TABLE II

Adhesive Resin Percent Density MOR cont

Designation Type SSL g/cm i kPa

Control

Sample Resin Averages C 0 0,75 17354

Edler No. 1

Sample Resin Averages A 33 0,77 16858

cont. -

Adhesive MOE Internal % Water Thickness

Designation kPa bond kPa Absorption Swell mm

Control

Sample Averages 2620xl0³ 993 23.0 0.84

Edler No. 1 .

Sample Averages 2703x10^s 972 18.9 0.79

The foregoing procedure was repeated in the manufacture of wood particle boards having thicknesses of 10 and 19 mm respectively.

The urea formaldehyde resin designated resin "C" in Table I again was used as a control.

Edler No. 2 adhesive was prepared by mixing sulfite spent liquor with resin "B" (Table I) in amount sufficient to provide 33% by weight spent liquor solids, dry adhesive basis . Like the sulfite spent liquor employed in the manufacture of the above described 13 millimeters particle board, the spent liquor employed in the pro¬ duction of the 10 and 19 mm particle boards presently under consi¬ deration comprised a commercial concentrated ammonium base acid sulfite spent and SO„ free liquor originally containing excess ammo¬ nium ion, but adjusted by reaction with sodium hydroxide in amount predetermined to fix the final ammonium ion value at 0.4% by weight (expressed as ammonia) on a total spent liquor solids basis .

The other properties of the adjusted sulfite spent liquor were as follows :

Viscosity at 25°C (cps) 1200 pH 6.95

Solids (% by weight) 50.2 Both the control resinous adhesive and the resinous adhesive of the invention were sprayed onto wood particles which were then dry formed into a mat and the mat hot pressed, all under the follo¬ wing forming and pressing conditions : Furnish : Core and face chip blends, about 67% pine and 33% fir.

Formation: Bahre-Bison air-layered board, thicknesses as shown.

Wax Content: 1% Adhesive Content: Face 8%, Core 8% Mat moisture content: Edler 10%; Control 9.6% Prepress Cycle: 30 seconds Press Time: 19 mm, 4,5 minutes ; 10 mm , 2,5 minutes

Time to Stops : 19 mm, _.65 seconds; 10 mm, 35 seconds

Decompression Cycle: 19 mm, 40 seconds; 10 mm,

20 seconds (in addition to press times)

Press Temperature: 19 mm, 160°C; 10 mm, 154°C

Several test samples of the resulting particle boards were sub¬ jected to the conventional ASTM tests with averaged test results as follows :

TABLE III

Adhesive Resin % Density MOR MOE V cont.

Designation Type SSL g/cm kPa kPa

Control

Sample

Averages C 0,76 19237 2875xlO^c

Edler No. 2

Sample

Averages B 33 0,79 18548 3034X10¹-

Control

Sample

Averages C 0,76 20133 3199xlO

Edler

No . 2 Sample

Averages B 33 0,75 17031 3082x10^{^}

ύ- t cont.

Adhesive Internal Water Panel thickness/ Designation Bond kPa Adsorption % thickness swell mm

Control

Sample

Averages 986 29,7 10/0,84

Edler No. 2

Sample

Averages 800 24,6 10/0,79

Control

Sample

Averages 972 ^" 22,9 19/0,91

EdlerNo . 2

Sample

Averages 738 18,9 19/0,76 The above tests demonstrate clearly that the adhesives of the invention containing 1/3 by weight sulfite spent liquor may be used in the production of wood particle boards of commercially acceptable properties, which compare favorably with the properties of the control boards made with straight urea formaldehyde resin adhesives . This indicates that the rheological and curing properties of the adhe¬ sives of the invention are fully compatible with normal particle board manufacturing procedures and may be utilized without requiring pro¬ cess changes or causing reductions in plant capacity.

In these respects, the performance of the spent liquor- con tai- ning adhesives of the invention compares favorably with the perfor¬ mance of straight urea-formaldehyde resin adhesives which have been carefully adjusted over several years of operation to the particular requirements of particle board manufacturing techniques . In fact, particle boards made using the adhesives of the invention demon- strate significantly improved water resistance qualities over those made with commercial resins o the same class .

By way of contrast, failure to duplicate such performance has been observed in the past when testing other resin-sulfite spent liquor compositions . These tests not only produced particle board of inferior physical properties , but, because of unfavorable rheological properties of the adhesive, caused immediate plant shutdown due to inability to produce a mat possible to form and handle in a approp¬ riate way . Example 2

This example illustrates the preparation of the adhesive pro ducts of the invention containing from 10-50% of sulfite spent liquor and the properties of such products . In a laboratory study, a series of urea formaldehyde resin- sulfite spent liquor adhesives was prepared using the procedure out lined in Example 1. The adhesives containing respectively 10 %, 30 and 50 % by weight, dry solids basis, of sulfite spent liquor. The adhesives were applied to wood chips which then were laid up into mats and hot pressed into particle boards, the properties of which were tested. The properties of the experimental boards then were compared with those of control boards made similary, but containing no sulfite spent liquor.

The commercial resinous urea formaldehyde particle board adhe sives used as controls had the properties set forth in Table I of Example 1 under the headings "Resin C" and "Resin D", respectivel

The urea formaldehyde resin component of the test adhesive of this example had the properties listed in the columns headed "Resin A" and "Resin B" of Table I of Example 1. The sulfite spent liquor component of the test adhesive comprised a substantially sulf dioxide free, concentrated sodium base acid sulfite spent liquor to which sufficient ammonium sulfate had been added to produce a resu tant spent liquor product containing 0.425% by weight ammonium ion, expressed as ammonia based on spent liquor solids . The other properties of the sulfite spent liquor were as follows

Viscosity cps (at 25°C) 830

Solid Content (% by weight) 50 pH 6.8

The forming and pressing conditions employed in the manu¬ facture of the board products were as follows :

Furnish : Douglas Fir Chips

Formation : Air Felted mat

Adhesive Content: 7% total solids

Mat Moisture Content: 9.5%

Press Time: 4 minutes , 4 1/2 minutes,

5 minutes, 4 1/2 minutes average

Press Temperature: 163°C

Board Thickness : ^{19 mm} Board Density: 0.73+0.15 Upon being tested, the particle board products demonstrated the following properties :

Control Adhesive Edler Adhesives

Spent Liquor Solids % 10 % 30 % 50 %

Resin Component

Resin A

MOR 20837 21237 21719 19996

IB 779 758 690 462

Resin D

MMOORR 21650 22202 21099 16755

IB 779 814 772 379

It is to be noted that the Edler adhesvie compositions containing up to 50 % sulfite spent Hquor solids had commercially acceptable pro¬ perties for some purposes . Also it is notable that resins with Witte numbers in the range of 1.0 to 1.8 give good Edler adhesives .

Example 3

This example illustrates the effect on particle board properties of incorporating in the adhesive products of the invention more than the stipulated amount of ammonium ion, i. e. more than 4.0 % by weight ammonium ion (expressed as NH₃) dry solids basis, based on spent liquor solids .

Urea formaldehyde resin, commercial high ammonium content sulfite spent liquor, and 1 % by weight wax were thorougly mixed and blended at ambient temperature, using sufficient of the sulfite spent liquor to provide 33 % sulfite spent liquor solids in the resul¬ ting adhesive product, dry weight basis . The ammonium base sulfite spent liquor contained 5.7 % by weight ammonium ion (expressed as ammonia) dry spent liquor solids basis . Its other properties and the properties of the test resin, designated "Resin E" , as well as those of a commercial urea formaldehyde resin used as a control and de¬ signated "Resin F" are given in Table IV below.

-BU t^-UT

OMPI

« ' . wn-o _*y. ^* * TABLE IV

Resin Resin F Sulfite Waste

Property E (Control) Liquor

Mol Ratio 1 :1.8 1:1.3

Solids (by weight) 65 65 52

Viscosity at 21°C (cps) 400 295 3000 pH 7.4 7.5 7.2

Witte Number 1.72 1.02

Water Solubility Infinite Infinite Infinite

Ammonia Content (% by weight) 5.7 %

Resin E was used in the manufacture of "Edler adhesive No. 3" Resin F was used as a control.

Two sets of 10 mm wood particle boards were manufactured with the above two adhesive products, using the following forming and pressing conditions :

Furnish : Core and face chip blends, about 67 % pine and 33 % fir.

Formation : Bahre-Bison air-layered boards at thickness shown .

Wax Content: 1 % Adhesive Content: Face 8.3 %; Core 8.3 % Adhesive pH: Control 7.8; Edler 4.4 Mat. moisture content: Control 8.5 %; Edler 9.5 % Prepress Cycle: 30 seconds Press Time: 2 3/4 minutes Time to Stops : 45 seconds Decompression Cycle: 40 seconds (in addition to press time)

Press Temperature: .. 154°C

Testing the board products gave the values set forth in Table below :

c.v - Λ TABLE V

Panel cont.

Adhesive Resin SSL Thickness Density Precure Designation Type %_ mm g/cm3 ^•mm

Control Average Resin F 0 10 0,75 0

Edler No. 3 Average Resin E 33 10 0,74 0,79

cont. . . Internal Water Thickness

Adhesive MOR MOE Bond Adsorp- Swell Designation kPa kPa kPa tion % mm

Control Average 18617 2758x10^s 662 26,8 9,71

Edler No. 3

Average 9687 1855x10° 276 33,7 1,04

Table V clearly shows the undesirable effect on board perfo- mance properties generally of including high levels of ammonia in the sulfite spent liquor. Both strength values and properties of water resistance are sharply reduced. . The high ammonia content, rapid-curing binder causes soft board surfaces and general lowering of strength properties through premature cure. Also, the working life of the binder is greatly reduced, introducing a serious risk of gelation in plant piping and equipment.

Example 4 This example illustrates the application of various categories of

SOft free sulfite spent liquor to the manufacture of the herein- described adhesive products . The spent liquors tested were:

A concentrated commercial sodium base acid sulfite spent liquor to which sufficient ammonium sulfate had been added to provide an ammonium ion content (expressed as NH₃) of 0.4 %, spent liquor solids basis .

A concentrated commercial calcium base spent liquor which had been desugared and contained an ammonium ion content (expressed as NHo) of 0.34 % by weight, dry solids basis. A concentrated high-ammonia, ammonium base, commercial sulfit spent liquor which had been partially reacted with caustic soda to a residual ammonium ion content (expressed as NH„) of 0.46 % of dry solids basis .

The properties of these sulfite spent liquors are given i a Table VI . The pH of each was adjusted to about 7.0 before incor¬ porating it into the adhesive.

TABLE VI

Sulfite Spent ^"Viscosity Ammonia % Solids % PH Liquor 25°C (cps) by weight by weight 25°

Ammonium sulfate modified sodium base 300 0.4 50.3 4.80

Desugared _ calcium base 1066 0.34 51.9 3.79

Caustic soda treated ammonium base 740 0.46 48.7 7.12

A commercial straight urea formaldehyde particle board adhesive was used as a control and designated "Resin D" (Table I) .

The urea formaldehyde resin employed in the formulation of the test adhesives was "Resin B" and had the physical properties set forth in Table I of Example 1.

The adhesives were formulated as set forth in the preceeding examples . They were sprayed onto wood particles which then were laid up into mats and hot pressed under the following forming and pressing conditions .

Furnish : Douglas Fir Wood Parti

Formation : Dry Felted

Wax Content: 0 %

Adhesive Content: 7 %

Mat Moisture Content: 9 %

Board Thickness : 3/4"

Press Time: 2 boards , 4,5 minutes;

2 boards, 5 minutes

Time to Stops : 70 seconds The resulting particle boards were tested under ASTM test method D1037-72 with results given in Table VII, the results being averages of tests carried out on four specimens from each board.

TABLE VII

Adhesive Adhesive Characterized Resin Designation by Content of: Type MOR I Inntte. rnal Bond

Edler No. 4 Ammonium sulfate modified sodium base B 19133 655

Edler No. 5 Desugared calcium base B 18892 627

Edler No. 6 Caustic soda treated ammonium ' base B 19616 669

Control none D 20306 772

The strength values of the test boards thus are substantially the full equivalent of those of the control board and are well within commercially acceptable limits .

Example 5

This example illustrates the application of a magnesium base acid sulfite spent liquor in the formulation of the adhesive products of the invention.

The urea formaldehyde resin used in the formulation of the adhesive was that indentified as "Resin B" in Table I hereinbefore. It had a solids content of 58 % by weight, a Witte number of 1.67, and a mol ratio of 1.50.

The sulfite spent liquor employed was a commercial magnesium base acid sulfite spent liquor containing 47 % solids .

The control was a commercial particle board urea formaldehyde resin having a mol ratio of 1.25, which contained no sulfite spent liquor (Resin G) .

The 67/33 (resin to spent liquor solids) core and face adhesive products (Edler No. 7 and 7a) were prepared by mixing the urea formaldehyde resin and sulfite spent liquor, together with ammonium sulfate as the source of ammonium ion, in the following proportions : Board core layer: 320.7g Resin B ;

58.5 % solids , pH 7.0

198.6g magnesium base acid sulfite spent liquor;

47 % solids, pH 4.5

8.5g ammonium sulfate

Board face layer: 329.3g Resin B ; 58.5 % solids, pH 7.0

203.9g magnesium base acid sulfite spent liquor;

47 % solids, pH 4.5 3.0g ammonium sul

The resinous adhesives were sprayed on wood particles using applications of 11.5 % in the face and 7 % in the core, dry solids bas The adhesive coated particles then were felted into mats and pressed into 17.5 mm boards in conventional manner, using a press pressure of 3500 kPa a press closing time of 30-40 seconds, a press cycle of 3.5 minutes, and a press temperature of 177°C.

The properties of the resulting panels were tested (ASTM D1037-72) with results as given below, which are averages for five panels allowed to reach equilibrium under ambient conditions of the atmosphere for 48 hours prior to testing:

TABLE VIII

Adhesive Resin g/cm kPa kPa cont

Designation Type Density MOR IB

Control Resin G 0.68 15397 600

Urea formaldehyde Magnesium Base Sulfite spent liquor (Edler No . 7 and 7a) Resin B 0.73 18299 640

- cont.

Adhesive 2 Hour 2 Hour

Designation Thickness Swell Water Adsorption .

Control 16.1 % 91.6 %

Urea formaldehyde Magnesium Base Sulfite spent Liqour (Edler No. 7 and 7a) 17.6 % 77 .2 %

- ΪJ C

^"'.• Example 6

This example illustrates the application of magnesium based sul¬ fite spent liquors to the adhesive products of the invention, but under somewhat different conditions, in particular using a spent liquor of lower pH than those set forth in Example 5.

Wood particle boards were prepared using the same control resin (Resin G) as used in Example 5 and similar core and face test adhe¬ sives (Edler No. 8 and 8a) which, however, contained 50 % rather than 47 % spent liquor solids, in the ratio of 67/33 urea formaldehyde resin to sulfite spent liquor solids , dry weight basis . The adhesive formulations employed in the core and face layers of the board were as follows :

Core layer 320.7g Resin B

(Table I) urea formaldehyde resin

58 % solids, pH 7.0

186.7g magnesium base acid sulfite spent liquor, 50 % solids , pH 3.2

2.5g ammonium sulfate

Face layer 329.3g Resin B urea formaldehyde resin, 58 % solids, pH 7

191.7g magnesium base acid sulfite spent liquor, 50 % solids, pH 3.2

2.8g ammonium sulfate

In the manufacture of the particle boards, the same amount of adhesive, the same manufacturing procedure, the same control resin and the same board thickness were used as are set forth in Example

5. The press cycle was three minutes and twelve seconds at 177°C.

The test results (five panel average) were as follows :

TABLE IX

Adhesive Resin g/cm kPa kPa cont Designation Type Density MOR IB

Control Resin G 0.68 15396 600

UF Resin- Magnesium Base SSL (Edler No. 8 and 8a) Resin B 0.71 17196 630 cont.

Adhesive 2 Hour Thickness 2 Hour Water Designation Swell Adsorption

Control 16.1 % 91.6 % UF Resin- Magnesium Base SSL (Edler No. 8 and 8a) 16.3 % 84.5 %

In a manner similar to the foregoing, urea formaldehyde-sulfite spent liquor adhesives are made and wood particle boards and other glued wood producrs are manufactured therefrom using as a source of ammonium ion, in place of ammonium sulfate: ammonium chloride, mono-ammonium phosphate, ammonium oxalate, ammonium benzene sul- phonate and ammonium monochloracetic acetate.

Example 7

This example illustrates the effect of incorporating in the adhesive products of the invention a low mol ratio, low Witte number urea formaldehyde resin .

A urea formaldehyde resin-sulfite spent liquor adhesive was prepared using the procedure outline in Example 1. The urea formal¬ dehyde resin component of the test adhesive had the following pro¬ perties :

Witte number 0.76

Mol Ratio .90

(mol formaldehyde)

(mols urea )

Solids (% by weight 65

Viscosity at 25°C . (cps) 70 pH 7.3

Dilutibility Infinite

The sulfite spent liquor component of the test adhesive had the properties of the sulfite spent liquor described in Example 2. The forming and pressing conditions employed in the manufac¬ ture of the board product were as described in Example 2.

Upon being tested, the particle board products demonstrated the following properties : MOR 9522

IB 152

This example clearly shows the undersirable effect of using low mol ratio, low Witte number urea formaldehyde resin. Both the modu- les of rupture, (MOR) and the internal bond (IB) are well below the minimum National Particle Board Association standards for wood particle board products (MOR-11032; IB-414) .

Claims

Claims :

1. Method of manufacture of an adhesive product more particularly manufacturing of an adhesive product including urea-formaldehyde resin with addition of acid sulfite spent liquor CHARACTERIZED BY

5 the following components being provided:

1) Urea-formaldehyde resin of the following conditions : propor¬ tions formaldehyde/urea 1.0 - 1.8 pH 6 - 8 viscosity preferably in the range 50 -250 centipoise o (at 65 % dry solids basis and 25° C)

Witte number indicating the methylol 1.0 - 1.8 content in the resin.

2) Sulfite spent liquor of the following conditions : 5 pH 3 - 9 preferably 3.5 - 4.5 viscosity preferably in the range 500 - 4000 centipoi

(at 50 % dry solids basis and 25°C) 0 The content of ammonium ion in the sulfite spent liquor has to be 0.2 - 4.0 % by weight (expressed as NH„) by weight on spent liquor solids .

3) Water which preferably is added as included in the compo- ments 1) and 2) by providing said components with the fol- 5 lowing dry solids content: the urea-formaldehyde resin 50 - 72 % by weigh preferably 55 - 65 % by weigh the sulfite spent liquor 40 - 55 % by weigh 0 preferably

48 - 52 % by weigh or adding of the equivalent amount of water in an other way.

Thorough mixing in the following proportions: the urea-formaldehyde resin 50 - 90 parts 5 the sulfite spent liquor 10 - 50 parts on the components dry solid basis by stirring resulting in a heat curable adhesive product.

2. Method according to claim 1 , CHARACTERIZED BY the sulfite 0 spent liquor is checked according to its content of ammonium ion which has to be 0.2 - 4.0 % by weight (expressed as NH„) by weigh on spent liquor solids . In connection with too high content of ammo- nion ion by use of a sulfite spent liquor on ammonium base the ex¬ cess ammonium ion may be decreased to the predetermined amount by means of adding caustic soda or other strong base for the dri- ving off of ammonia. If the content of ammonium ion present is lower by use of a sulfite spent liquor on for example calcium, magnesium or sodium base, the ion content may be adjusted by adding a water soluble ammonium salt of a strong mineral or organic acid as any of the salts ammonium lignin sulfonate, ammonium chloride, ammonium- sulfate, mono-ammonium phosphate, ammonium oxalate, ammonium benzene sulfonate or ammonium mono-chloracetic acetate.

3. Method according to claim 1 or 2, CHARACTERIZED BY the spent liquor used comprising at least one spent liquor on calcium base, magnesium base, sodium base or ammonium base.

4. Method according to claim 3, CHARACTERIZED BY the spent liquor comprising a calcium base acid sulfite spent liquor to which is added a sufficient amount of water soluble ammonium salt of a strong acid to provide said content of ammonium ion.

5. Method according to claim 3, CHARACTERIZED BY the spent hquor comprising a magnesium base acid sulfite spent hquor to which is added a sufficient amount of a water soluble ammonium salt of a strong acid to provide said content of ammonium ion.

6. Method according to claim 3, CHARACTERIZED BY the spent liquor comprising a sodium base acid sulfite spent liquor to which is added a sufficient amount of a water soluble ammonium salt of a strong acid to provide said content of ammonium ion .

7. An adhesive product manufactured by the method according to any of the claims 1 - 6, CHARACTERIZED BY it comprising a sub¬ stantially uncondensed admixture of urea-formaldehyde resin 50 - 90 parts spent liquor form the acid sulfite pulping of lignocellulose 10 - 50 parts by weight dry solid basis the adhesive product containing from 0.2 to 4.0 % by weight ammonium ion (expressed as NH₃) on a spent liquor solids basis .