FI72338C - Procedure for manufacturing adhesive products. - Google Patents

Description

luS * - »· I NOTICE OF PUBLICATION

tBJ (11) UTLÄGGNINGSSKRIFT 723 38 C (45) 13 /: \ '‘v’. ’:. '' {(51) Kv.lk.4 / lnt.CI.4 C 09 J 3/16 (21) Patent application - Patentansökning 782314 (22) Filing date - Ansökningsdag 24.07.78 (F «) (23) Starting date - Giltighetsdag 24.07 * 78 (41) Has become public - Blivit offentlig 25. 10.79

National Board of Patents and Registration Date of display and publication - 30.01.87

Patent and registration authorities '' Ansökan utlagd och utl.skriften publieerad (86) Kv. application - Int. ansökan (32) (33) (31) Privilege claimed — Begärd priority 24.04.78 USA (US) 899237 (71) AB Edler S Co. FärgIndustri, Brobacken 16, Lerum, Sweden-Sweden (SE) (72) Folke J. Edler, Västra Frölunda, Sweden-Sweden (SE) (74) Leitzinger Oy (54) Method for producing adhesive products - Förfarande för tillverkning av limprodukter is a method of making adhesive products. More specifically, the invention relates to a process for preparing adhesive products having the components of formaldehyde, sulfite liquor and water. The invention relates in particular to the manufacture of adhesive products which are generally used in connection with the manufacture of dry-process particle board, fibreboard, plywood board and the like and in which the proportion of sulphite liquor is high and to adhesive products of this quality.

The possibility of combining various synthetic resins, including urea resins (urea) or their components with sulphite liquor, has been studied in the past. These are disclosed in U.S. Patents 2,405,650 (cores for metal casting), 2,622,979 (wet strength paper) and 3,313,745 (foam details).

U.S. Patents 3,390,928 describe the use of urea resin and sodium lignin sulfonate, the latter being used in very small amounts (1-5%) in the manufacture of particle board.

U.S. Patent 3,994,850 discloses the manufacture of particle board using an adhesive prepared by reacting urea, soda-black liquor and formaldehyde with each other.

However, the above-mentioned methods have not been able to successfully produce a chipboard adhesive rich in sulfite liquor. Professional circles must avoid the manufacture of particle board adhesives and because the resin components of adhesives do not react with each other and the properties of particle boards made using such an adhesive are not satisfactory.

This notion is based on empirical results and is fully justified by the complex molecular structure of the two reactants, i.e. sulphite lye and urea resin, as well as the various chemical reactions that can potentially occur during resin preparation, mixing with resin sulphite lye and subsequent resin.

Thus, for example, sulfite liquor does not react with and is insoluble in certain urea resins.

However, urea and formaldehyde can be combined into condensation products containing a large amount of mono-, di- and polymethylolecarbamide products, i.e. rich in methylol. Urea and formaldehyde can also be combined with each other to form methylene-rich products with a high methylene urea content. Methylol-rich products can react with sulfite liquor, while methylene-rich products cannot. Thus, if it is desired to successfully combine the urea resin with a sulfite liquor, it must be of the methylol-rich type.

Second, if the urea resin is mixed with substantial amounts of untreated ammonized sulfite liquor containing ammonium in the form of ammonium lignin sulfonate, ammonium is rapidly removed from any free or loosely bound formaldehyde that may be in or added to the urea resin to form a relatively inactive product, hexamine. This reaction releases excess lignin sulfonic acids, which lowers

II

3 72338 pH of the adhesive mixture and overcatalyzed the adhesive, resulting in too fast curing and too early gel formation. Conversely, if the resin is mixed with a calcium, magnesium or sodium-alkalized sulphite liquor and no ammonium is present, the above-mentioned release of lignin sulfonic acids does not occur and the adhesive becomes undercatalyzed.

It is therefore important that the ammonium content of the adhesive is closely monitored.

Third, changes in the pH and adhesive product and its component can significantly affect the strength and properties of the adhesive. Too experimental pH causes the adhesive to cure too slowly. Too low a pH will cause the adhesive to cure too quickly. In addition, an excess of acid in the adhesive may age-age the cellulose to be treated. For these reasons, it is necessary to carefully monitor the pH of the sulfite liquor and urea resin components of the desired adhesive product.

The main object of the present invention is to provide a process for the production of an adhesive product suitable for the production of wood products comprising a large proportion of sulphite lye from wood pulp sulphite soup and easy and simple to produce and for example for the production of particle board using conventional equipment and methods. have commercially acceptable properties that use the marketing standards of such products and are fully competitive with similar products made using ordinary, more expensive adhesive products.

Another object of the invention is to provide an adhesive product made by the method according to the invention and having said properties.

In addition, it is an important object of the invention to provide a method and an adhesive product which allow the use of a very inexpensive waste product, namely sulphite liquor as a major component, solving the classical problem of using sulphite waste liquor in cellulose mills, while achieving economic advantages in the production of adhesives for particle board and the like. for example, in a medium-sized particle board factory, it can be of the order of 2 million. savings in SEK / year.

The object of the invention is achieved by carrying out the method according to the features set forth in claim 1 and with an adhesive having the features set forth in claim 6.

In the context of the invention, it has been found that the problem of providing a compound between urea resins and sulphite liquor in the preparation of a useful adhesive product can be solved and said objects achieved by preparing an adhesive product containing approximately 50 to 90 parts by weight of solid urea resin and 10 to 50 parts by weight. sulphite waste liquor from the sulphite pulp of the wood pulp, calculated as a key component 0.2 to 4.0% by weight of ammonium ions (expressed as NH3) based on the dry weight of the sulphite liquor. Ammonium ions can be added using an ammonized sulfite tube with a precisely controlled ammonium ion content. In case it is desired to use another sulphite lye, such as calcium, magnesium or sodium alkalized sulphite lye, ammonium ions can be added by adding a suitable amount of a water-soluble ammonium salt of a strong acid.

The addition of the ammonium salt adds ammonium associated with the free formaldehyde in the mixture to form a neutral product, hexamethylenetetramine, and the strong acid is released, leaving an elevated but controlled acidity, which promotes the desired condensation or polymerization of the adhesive product as mentioned above.

The urea components of the adhesive product are characterized by a molar ratio of formaldehyde to urea of 1.0 to 1.8 and a methylol content corresponding to a Witte number of 1.0 to 1.8. The properties of the resin are thus such as to ensure that it can react with sulphite lyes and achieve the desired degree of solubility in sulphite lyes in just the amount required to provide a suitable adhesive product.

5 72338

The adhesive product is prepared simply by mixing sulfite broth and urea together in the presence of ammonium ions in appropriate proportions at temperature conditions, pH and viscosity, resulting in a mixture in which the lignin sulfonic acid component of the sulfite liquor and urea condense with each other in a substantial amount. The process and the product thus differ considerably from the hitherto known processes and the products prepared according to them, in which such condensation takes place rapidly and is deliberately accelerated. The process according to the invention also differs considerably from the production processes used hitherto, in which the sulphite lye reacts with urea and formaldehyde in a process in which only these three components are present.

When the product according to the invention is used in the manufacture of glued products, such as particle board, the glue is simply applied to the wood material in the usual quantities and proportions and hot pressing is carried out, using conventional equipment to produce the final glued and pressed wood product.

In a preferred embodiment of the process according to the invention, the process is such that the adhesive product described herein, prepared by the process according to the invention, contains, expressed as a percentage by weight of dry matter, a non-condensable mixture as follows:

Urea 50 - 90

Sulphite waste liquor from sulphite cellulose cooking 10 to 50

The adhesive also contains 0.2 to 4.0% by weight of ammonium ions (expressed as NH3) based on the dry weight of the sulfite liquor.

As also mentioned above, the urea resin is characterized by closely controlled properties, in particular a molar ratio of formaldehyde to urea of 1.0 to 1.8, a pH of 6 to 8 and a methylate content corresponding to a Witte number of 1.0 to 1.8. . In addition, the dry matter content must be 50 to 72%, preferably 55 to 65% by weight and the viscosity 50 to 250 centipoise at a dry matter content of 65% resin and at a temperature of 25 ° C.

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With respect to the molar ratio, it should be noted that if it is less than 1, then the urea resin polymer is not effective enough to develop the desired adhesion properties of the final product.

When the molar ratio is above 1.8, too much excess formaldehyde is present. This results in the formation of an adhesive product which has an unpleasant odor and which releases too much toxic gases during hot pressing and later use of the product.

With respect to viscosity times of 50 to 250 centipoise, it should be noted that this range is below the viscosity range of urea resins commonly used in the manufacture of particle board. If the urea resin were not used at normal viscosity, the result would be unsatisfactory due to its poor adhesion properties. As described herein, the addition of sulfite liquor requires the achievement of desired adhesion properties.

As for the methylol content, it is necessary that the concentration corresponds to a Witte number of 1.0 to 1.8 in order to react the urea resin with the sulphite liquor and to achieve satisfactory adhesion and product quality.

Theoretically, a urea formaldehyde resin having a methylol content as low as a Witte number of 1.0 does not have high enough hydrophilicity to react with sulfite liquor. However, it can be reasonably assumed that the Witte number measured in the first component before any reaction with the second component has begun is not essential to the methylol content once the reaction has begun. Namely, it can be assumed that, immediately related to the fact that when the reaction between the two components begins, new hydrophilic groups which do not affect the Witte number are opened at a high rate (in a fraction of a second), the methylol content is sufficient for the intended reaction. In this case, the resin must contain ether compounds which can be cleaved into OH groups. This can be seen from the fact that ether-rich resin products also give a satisfactory result even at a low Witte value, while less ether-rich resins may require a higher Witte number in the initial state.

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The Witte number is obtained by determining the methylol groups of urea resins by the reaction of the resins with 2,6-dimethylphenol (2,6-xylenol). It indicates the methylol potency of the resin and is determined as follows.

A solution of 2,6-dimethylphenol (25.0 g) in 200 ml of water containing 8.0 g of sodium hydroxide is treated with 12.5 g of the urea resin to be tested to obtain a uniform mixture. The resulting reaction mixture is allowed to stand for three days at room temperature in the dark. Concentrated hydrochloric acid is then added until the pH of the reaction mixture reaches 575 to 6.0. The reaction mixture is washed in a 1 liter flask and is therefore steam distilled until 700 to 750 ml of distillate are obtained.

The condenser is rinsed with a small amount of methylene chloride and the condensate is extracted 3 times with methylene chloride. The combined methylene chloride extract is filtered through about 20 g of anhydrous sodium sulfate and this is washed twice with 25 ml of methylene chloride.

The methylene chloride is evaporated in vacuo until the weight of the evaporation flask remains unchanged. The weight of the remaining 2,6-dimethylphenol is measured and its initial weight is subtracted. The difference between the two weights is the amount of 2,6-dimethylphenol which has reacted with the urea resin and is a measure of the methylol content of the resin. This value is called the Witte number. This value is calculated from the following formula: _Weight of xylenol recovered ___ = w .. t 12.5 x percentage of dry matter of urea-formaldehyde resin This value is directly related to the methylol content of the resin, as can be seen from the following table of typical test results for Witte numbers urea-formaldehyde resins with varying molar ratios (moles of formaldehyde per mole of urea) and treated to maximize the effect of methylol.

8 72338

Molar ratio of urea 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% dimethylol urea 2.64

Regarding the sulfite component of the adhesive product according to the invention, the following is stated:

By the term "sulphite waste liquor" is meant the liquid obtained by conventional treatment of the pulp with acid sulphite containing a total of about 5-7% by weight of sulfur dioxide and 0.9-1.2% of sulfur dioxide containing the compound.

Sulphite lye is formed in any conventional method by treating wood pulp with acid sulphite. Thus, it can usually be formed from waste liquors, i.e. either ammonified calcium, magnesium or sodium alkalized waste liquors.

However, a specific exception is waste liquors obtained from the treatment of wood pulp with "Magnafite": 11a, "Sodafite": 11a and semi-chemical processes ("NSSC") with neutral sulphite.

These three waste liquors are disadvantageous for the purposes of the invention and will not be described in this specification because they all contain significant amounts of sulfite ion residues in their concentrates.

As will be explained in detail below, an unfavorable change in pH will result if these lyes are used in the manufacture of the adhesive products disclosed herein.

Sulphite liquors can be used in roughly the form in which they are obtained from the plant concentration process without sugar removal.

In the form in which the sulphite lyes are obtained, they generally have a dry matter content of 40 to 55% by weight, usually 50% + 2%, a viscosity of, for example, 500 to 4000 centipoise> <9 72338 at a temperature of 2 5 ° C and a concentration of 50% and a pH of 3, 5 - 4.5.

If the dry matter content is less than 40% by weight, the sulfite broth contains too much water to be very suitable for the manufacture of adhesive products. If the sulphite liquor contains more than 55% dry matter, it is too slow-flowing to be comfortably handled in the factory.

The viscosity of the sulfite liquor must most suitably be in a useful range where the sulfite liquor can be pumped at room temperature and easily mixed with the urea resin. Higher viscosities can be controlled by heating the waste liquor. This allows the use of a sulphite liquor with a viscosity of up to 15,000 centipoise.

It should be noted that the proposed viscosity of the resin and sulfite liquor provides suitable processing conditions for the components and the final product having the desired properties. However, the latter do not depend solely on the viscosity of the components, but on the water content. However, as can be readily appreciated, this can be controlled so that the deviation of the viscosity of the second component from the recommended values can be compensated by changing the viscosity of the second component or when the viscosity is too low by adding water to the mixture.

The pH of the sulfite liquor must be in the range of 3-9.

If the pH of the sulfite liquor is lower than 3, the adhesive hardens too quickly and gels too quickly at room temperature to be handled comfortably. If the pH of the sulfite liquor is higher than 9, the adhesive product cures too slowly to be useful.

The sulphite liquor must be approximately free of dissolved sulfur dioxide (sulphite ions), as the presence of this substance results in an increase in the pH of the adhesive to a level where curing during hot pressing occurs too slowly, adversely affecting production and wood products using this adhesive. properties. Sulphite liquors, if not neutralized, become free of sulfur dioxide because this substance is removed upon concentration of the sulphite liquor.

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As mentioned above, ammonium ions, when used in an amount of 0.2 to 4.0% by weight (expressed as NH 4) of the sulphite liquor dry matter, form a key component of the adhesive product of the invention and provide a successful compound containing a large amount of sulphite liquor together with urea resin. This component of the mixture has the function described above to react with a portion of formaldehyde to form a relatively inactive product, hexamethylene tetramine. This results in a decrease in the pH of the adhesive mixture so that it reaches a level where the mixture hardens rapidly during hot pressing.

If too much ammonium ions are present, the large amount of ammonium in the adhesive result a reacts rapidly with the free or soluble combined formaldehyde of the urea resin to form a stable hexamethylenetetramine and release large amounts of strong acid. These excess acids, in turn, lower the pH of the mixture and catalyze the urea resin so that it cures very rapidly.

The effect of the fast-curing binder on the quality of the wood products in question is that the surfaces become soft and, in general, the strength properties deteriorate as a result of premature curing. Water absorption and swelling also have an adverse effect. The flow time of the binder is stably limited, creating a serious risk of gel formation in the plant's pipelines and equipment.

The ammonium ion component of the mixture is a water-soluble ammonium salt of a strong inorganic or organic acid (ionization factor (Ka) 10 or higher). Examples of such salts are:

Ammoniumligniinisulfonaatti

Ammonoiumkloridi

Ammonium sulfate

Monoammonium phosphate

ammonium oxalate

Ammoniumbensoiisulfonaatti

Ammonium acetate monochloroacetic acid li 11 72338

It is clear that when the acid sulphite lye is ammonia-containing sulphite lye, the ammonium salt belongs to the sulphite lye component of the adhesive product in the form of ammonium lignin sulphonate. In this case, it is not necessary to add any other ammonium salt.

When the ammonium ion content of the sulfite liquor ultimately usually exceeds that contained in the adhesive products described herein, excess ammonium ions can be removed by treating the sulfite liquor with a predetermined amount of sodium hydroxide or some other strong base that forces ammonia away and leaves only the desired ammonium ion residue. Removal of excess ammonia with base must be performed after the sulfur dioxide (on the acid side) has been removed as described above.

If calcium, magnesium or sodium alkalized sulphite lyes are used, a sufficient amount of ammonium salt is added to give an adhesive product containing the indicated amount of ammonium ions.

When assembling the assembly of the adhesive products according to the invention by means of the above-mentioned primary components, it is stated that these components are simply mixed in predetermined amounts in a suitable mixing machine of the usual type until a uniform mixture is obtained. Stirring is performed at approximately room temperature (10-30 ° C) with the urea resin components of the sulfite liquor to prevent condensation. The adhesive product of the invention is substantially non-condensable.

Condensation of the adhesive occurs during hot pressing during curing.

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Considering what has been previously described, the process according to the invention is characterized in that the components are selected as follows: 1) 50 to 90 parts by weight on a dry weight basis of urea formaldehyde resin having the following properties: molar ratio formaldehyde / urea 1.0 to 1.8 pH 6 to 8 viscosity preferably in the range of 50 to 250 centipoise (measured at a dry matter content of 65% and at 25 ° C) the methyl content of the resin corresponds to a Witte number of 1,0 to 1,8 2) 10 to 50 parts by weight on a dry weight basis of sulphite lye having the following characteristics : pH 3-9, preferably 3.5 to 4.5 viscosity 500 to 15,000 centipoise, most preferably in the range 500 to 4000 centipoise (measured at 50% dry matter content and 25 ° C) the ammonium ion content is 0.2 to 4 .0% by weight (expressed as NH3) based on the dry weight of the sulphite liquor, and 3) water is mixed together with the dry contents of components 1) and 2): urea formaldehyde resin 50 to 72% by weight, preferably 55 to 65% by weight. % sulfite solution 40-55 % by weight, preferably 48 to 52% by weight.

When the components are mixed, a thermosetting absorbent product is obtained.

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Desired amounts of the desired additives may be included in the adhesive product mixture. Such additives may include, for example, in suitable or customary amounts, waxes, oils, fungicides, flame retardants, surfactants and dyes, the lignin sulfonate salts acting as dispersants for waxes and oils.

The finished adhesive product is stable for a moderate period of time and can be stored and used in the usual way.

If used in the manufacture of particle board, it is sprayed on wood chips, cutter chips, fibers, planed chips and other wood particles and the resulting glue-coated particles are dried to a felt mat of the desired size using an adhesive addition of the order of 5-10% by weight of kiln-dried wood. The mats can be pressed in standard presses to the desired tightness under the desired pressure conditions, 2

e.g. at a pressure of about 17 to 18 kg / cm and a temperature of 140 to 160 ° C

2.5 to 10 minutes, depending on the thickness of the plate.

As can be seen from the following examples, the resulting particleboard products have properties that are commercially acceptable and competitive with the properties of particleboard products made using urea resin adhesive. However, the adhesive products according to the invention have the considerable economic advantage of containing a large proportion of inexpensive sulphite waste liquor, which results in considerable cost savings for the plant using it. Similar savings can also be made for other glued wood products, such as plywood and fibreboard.

eXAMPLES

The preparation method and adhesive products according to the invention are illustrated in the following examples, in which the resin-based adhesive products according to the invention are identified as "Edler" and the following abbreviations are used: 14 72338 SSL sulphite waste liquor MOR tensile strength MOE elastic modulus IB internal bond

Particleboard products in which the Edler adhesive formed an ingredient were tested according to ASTM testing methods, designated ASTM D 1037-72.

Example 1 This example illustrates the factory use of the adhesive products according to the invention in the production of particle boards of industrial grade with a thickness of 10, 13 and 19 mm.

Four urea resins were used in this and the following examples. Their properties are shown in Table I.

Table I

Resin A Resin B Resin C Resin D

(revision)

Witte number (methylol function: 1.58 1.67 1.02 1.02

Molarity ratio (moles of formaldehyde / moles of urea) 1.60 1.50 1.35 1/15

Dry matter (% by weight) 57 58 65 65.5

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

Dilutability unlimited unlimited unlimited unlimited unlimited

Resins A and B were used for the "Edler No. 1" adhesive composition disclosed herein, respectively. Resins C and D were used as control resins.

The sulfite liquor used in the Edler adhesive composition in this example was derived from a concentrated commercial acid sulfite liquor (free of SO 2) containing ammonium ions to achieve the purpose of the invention. The concentration of ammonium ions was adjusted to within the limits indicated by the invention by reacting said ions with a measured amount of sodium hydroxide (soda liquor) is 72338. After adjustment, the sulfite liquor contained 1.0% by weight of ammonium ions (expressed as ammonia) on a dry weight basis.

Other characteristics were as follows:

Viscosity (cps) at 25 ° C 15,000 pH 7.35

Dry matter content (% by weight) 52.0

Under factory conditions, an Edler-type particle board adhesive was prepared by mixing together, at ambient temperature, a urea resin and a sulfite liquor in a sufficient amount to give a solution dry matter content of 33% by weight in the finished adhesive products. These adhesive products are referred to herein as "Edler No. 1" and "Edler No. 2".

Stirring was always continued until the components were thoroughly mixed and a uniform appearance was obtained. No increase in temperature or any indication of condensation was observed during mixing.

Adhesives prepared as described above were sprayed onto the wood chips to form mixtures for the core material and the surface material of the particle boards. These were then felted in a dry state to methoxy, which was hot pressed to form a compacted particle board product. The conditions during formation and compression were as follows:

Contribution: Mixtures for heart and surface, approximately 67% as seen and 33% as spruce

Target: Bahre-Bison air-laminated board, thickness 13 mm

Wax content: 1%

Adhesive content: Surface 8.3%, heart 8.3%

Carpet moisture content: Surface 10 5, heart 8%

Pre-compression time: 30 seconds

Compression time: 2 minutes 52 seconds

Stop time: 45 seconds

Pressure reduction step: 30 seconds (in addition to the pressing time)

Compression temperature: 160oc 16 72338

Several sheets were prepared using both types of adhesives and resin C served as a control. The plates were subjected to the aforementioned ASTM tests D1037-72 to determine the properties shown in Table II.

Table II

Adhesive j Resin- Percent- Density MOR MOE »Indoor% water Thickness type ti SSL g / cm kPa kPa adsorpt. denial fading _i________kPa___nm_

Tarkxs- Rartei 0 0.75 L7354 2620x103 993 23.0 0.84 pain test average

Edler No. 1 Test Resin 33 0.77 L6858 2703x10 972 18.9 0.79

tus A

average j

The above procedure was repeated for the production of particle boards with thicknesses of 10 mm and 19 mm, respectively.

The urea resin, denoted C in Table I, was again used as a control.

Edler No. 2 adhesive was prepared by mixing sulfite liquor with B-resin (Table I) in an amount sufficient to make the solids of the solution 33% by weight of the constituent content of the adhesive product. Consistent with the sulphite liquor used in the preparation of the above-mentioned 13 mm thick particle boards, a sulphite liquor was used in the preparation of 10 and 19 mm thick particle boards, which in this case is a real commercially concentrated, ammonised acid sulphite lye free of bogs and initially excess ammonium ions, but adjusted by reaction with sodium hydroxide to a predetermined amount so that the final ammonium value became 0.4% by weight (expressed as ammonia) of the total corresponding dry matter content of the sulfite liquor.

Il 17 72338

Other characteristic features of sulfite liquor were as follows:

Viscosity (cps) at 25 ° C 1200 pH 6.95

Dry matter (% by weight) 50.2

Both of the resin adhesives used as a control and the resin adhesives of the invention were sprayed onto the wood particles, which were then formed in a dry state into a mat which was hot-pressed under the following forming and pressing conditions:

Contribution: Mixtures for heart and surface about 67% pine and 33% spruce

Target: Bahre-Bison air-laminated sheets with the thicknesses mentioned above

Wax content: 1%

Adhesive content: Surface 8%, heart 8%

Carpet moisture content: Edler 10%, check 9.6%

Pre-compression time: 30 seconds

Compression time: 19 mm, 4.5 mi, 10 mm 2.5 minutes

Stop time: 19 mm, 65 seconds, 10 mm 35 seconds

Pressure reduction step: 19 mm 40 seconds, 10 mm 20 seconds (in addition to the pressing time)

Compression temperature: 19 mm 160 ° C, 10 mm 154 ° C

Several test examples of the obtained particle boards were subjected to standard ASTM tests, giving the following average test results: 18 72338

Table III

Glue. Resin Percent Density MOR MCE Internal% Water Thickness type ti SSL g / αη kPa kPa nen adsorpt. displacement kuma kPa nm

.. .......... I - '....' '' »-“ '1 f 1' 'I ". I I

Verification test c 0 0.76 19237 2875x103 986 29.7 10 / 0.84 average

Edler No. 2, Test B 33 0.79 18548 3034x10 800 24.6 10 / 0.79 average

Verification test c Q o, 76 20133 3199x103 972 22.9 19 / 0.91 average

Edler No. 2. B 33 0.75 17031 3082x103 738 18.9 19 / 0.76 average

It is clear from the above that the adhesive products according to the invention, which contain 1/3 of their weight of sulphite liquor, can be used in the production of particle boards with commercially acceptable properties which are advantageous compared to control boards prepared using urea resin adhesives alone. This shows that the rheological and curing properties of the adhesives according to the invention are fully consistent with the usual manufacturing processes for particle board production and these adhesives can be utilized without having to make any changes in the manufacturing process or without reducing the production capacity of the factory.

The sulphite lye adhesive products according to the invention are advantageous in these respects compared with the results obtained with urea resin adhesives alone, which, based on many years of manufacturing experience, have been carefully adapted to the specific requirements of particle board technology and other wood gluing technology. After all, it has thus been shown that particle boards made using the adhesives of the invention had significantly better water resistance properties than particle boards made using the same class of commercial adhesives.

Experiments with other adhesive compositions based on sulfite liquor have shown that they do not reach the same level as the adhesives of this invention. These experiments not only yielded particle boards with poorer physical properties, but also resulted in production interruptions due to the unfavorable rheological properties of the adhesive, as it has proved impossible to obtain a mat that can be formed and treated satisfactorily.

Example 2 This example relates in more detail to the preparation of adhesive products according to the invention containing 10 to 50% sulphite liquor and the properties of such products.

In a laboratory-scale study, a series of urea formaldehyde resin and sulfite liquor adhesive products were prepared using the method described in Example 1. The adhesives contained 10, 30 and 50% by weight of sulfite liquor, respectively, calculated on its dry weight. The adhesives were applied to the wood chips, which were then formed into a mat and hot-pressed into chipboard, the properties of which were tested. The properties of the experimentally prepared chipboards were then compared with the properties of similarly prepared control chipboards in which the adhesive used did not contain sulphite lye.

The commercial urea resin adhesives for particle board used for inspection purposes had the properties shown in Table I of Example 1 under the headings "Resin C" and "Resin D", respectively.

In this example, the urea resin component of the test adhesive had the properties shown in the columns entitled "Resin A" and "Resin B" in Table I of Example 1. The sulphite component of the test adhesive was a substantially sulfur dioxide-free concentrated sodium alkaline sulphite lye to which sufficient ammonium sulphate had been added to obtain a sulphite lye product containing 0.425% by weight of ammonium ions, expressed as ammonia from the sulphite liquor dry matter.

The other properties of the sulphite liquor were as follows:

Viscosity (cps) at 25 ° C 830

Dry matter content (% by weight) 50 pH 6.8

The forming and pressing conditions in the manufacture of particle board were as follows:

Stake: Douglas Spruce

Formation: Air-laid carpet

Adhesive content: 7% of the total dry matter

Carpet moisture content: 9.5%

Compression time: 4, 4.5 and 5 minutes, average 4.5 minutes

Compression temperature: 163 ° C

Plate thickness: 19 mm

Specific gravity of the plate: 0.75 + 0.15

When tested, particleboard products had the following properties:

Inspection adhesive_ _Edler adhesive_

Sulphite liquor, dry matter O% 10% 30% 50%

resin components

Resin A

MOR 20837 21237 21719 19996 IB 779 758 690 462

Resin D

MOR 21650 22202 21099 16755 IB 779 814 772 379 21 72338

It is noted that Edler adhesive compositions containing up to 50% sulfite lye by dry weight had commercially acceptable properties for many purposes. It also turns out that resins with a Witte number in the range of 1.0 to 1.8 give good Edler adhesives.

Example 3 This example demonstrates the effect of showing the properties of particle board when the adhesive products of the invention contain more than a specified amount of ammonium ions, i.e., more than 4% by weight of ammonium ions (expressed as NH 4) from the dry matter of sulfite liquors.

Urea resin, a commercial grade sulfite liquor having a high ammonium ion content and 1% by weight of wax was thoroughly mixed at ambient temperature, using sufficient sulfite liquor so that the sulphite liquor content of the obtained adhesive product was 33% by dry weight of the adhesive product. The ammonified sulfite liquor contained 5.7% by weight of ammonium ion and (expressed as ammonia) the dry matter weight of the sulfite liquor. The other properties of the solution and the properties of the test resin labeled "Resin E" and the corresponding values of the commercial urea resin used in the test and labeled "Resin F" are shown in Table IV below.

Table IV

Properties Resin E Resin F Sulphite- _ (check) bogie__

Molar ratio 1: 1.8 1: 1.3 ---

Dry matter (% by weight) 65 65 52

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

Average score 1.72 1.02 ---

Water solubility unlimited unlimited unlimited

Ammonium content (% by weight) --- --- 5.7% E-resin was used in the preparation of "Edler Adhesive No. 3". F-resin was used as a control.

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Two batches of 10 mm thick particle board were prepared using the two adhesive products mentioned above, the formation and compression conditions being as follows:

Input: Mixtures for heart and surface, about 67% pine and 33% spruce

Target: Bahre-Bison air-laid plate in the specified thicknesses

Wax content: 1%

Adhesive content: Surface 8.3%, heart 8.3%

Adhesive pH: Revision 7.8, Edler 4.4

Carpet moisture content: Check 8.5%, Edler 9.5%

Pre-compression time: 30 seconds

Compression time: 2.75 minutes

Stop time: 45 seconds

Pressure reduction step: 40 seconds (in addition to the pressing time)

Compression temperature: 154 ° C.

When tested, the particleboards gave the values shown in the following Table V: 23 72338

Table V

T Density Pre-press

Llima Resin- Present- Plate / cm $ tus mm extension ...

type ti SSL thickness mm

Verification test average Resin F O 10 0.75 0

Edler No. 3 Testing Average Resin E 33 10 0.74 0.79 cont .... Glue MOR MOE Internal% Water Thickness kPa kPa nen si- aBsorpt. swelling dos kPa e.g.

Verification test average 18617 2758x10 ^ 662 26.8 9.71

Edler No. 3 test average 9687 1855x1ο · 5,276 33.7 1.04

Table V clearly shows the undesired effects of the general properties of the sheets when the ammonium content of the sulfite liquor is at high levels. Both strength and water resistance properties were strikingly reduced. The high ammonium content, which causes rapid curing, results in soft surfaces of the sheets and a continuous decrease in strength properties due to early curing of the sheet. The shelf life of the adhesive is also considerably shortened, which means a serious risk of jelly forming in the pipelines and equipment of the factory.

Example 4 This example illustrates the use of different grades of sulfur dioxide-free sulfite lyes in the manufacture of the adhesive products described herein. The sulphite lyes to be tested were as follows: Concentrated sodium alkaline acid sulphite lye to which sufficient ammonium sulphate had been added to give an ionic content of 0.4% (expressed as NH 4) of the dry matter weight of the sulphite lye.

Concentrated commercial calcium alkalized sulphite liquor from which sugar had been removed and containing ammonium ions (expressed as NH4) in an amount of 0.34% by weight of the dry matter of the sulphite liquor.

Concentrated ammonized commercial sulphite liquor with a high ammonium content, which has been partially reacted with soda liquor so that the residual ammonium content (expressed as NH 4) was 0.46% by weight of the sulphite liquor dry matter.

The properties of these sulfite lyes are shown in Table VI. The pH was adjusted to 7.0 before being allowed to form part of the adhesive.

Table VI

Sulphite liquor Viscosity Ammonia- Dry matter Ρ ^ 0

___ (cps) at 25 ° C ki,% by weight Weight ° 25 C

Sodium base, modified with ammonium sulphate 300 0.4 50.3 4.80

Calcium base, sugar removed 1066 0.34 51.9 3.79

Ammonium base, treated with sodium hydroxide solution 740 0.46 48.7 7.12

Commercial urea resin adhesive for particle board was used as a control and was labeled "Resin D" (Table I).

The urea resin used in the composition of the test adhesives was "Resin B" having the physical properties shown in Table I of Example 1.

The adhesive products had the same configurations as in the previous examples. They were sprayed onto wooden parts, which were then formed into worms and these were hot pressed under the following forming and pressing conditions:

Input: Douglas spruce wood particles

Formation: Dry felted

Wax content: 0%

Adhesive content: 7%

Moisture content of the carpet: 9% 25 72338

Plate thickness: 19 mm

Squeezing time: 2 plates, 4.5 minutes

Stop time: 70 seconds

The prepared chipboards were tested according to ASTM Test Method D-1037-72, and the results are shown in Table VII, where the values are the averages of the tests performed using four examples of each chipboard grade.

Table VII

Adhesive Characteristic of the adhesive Resin-MOR Internal _______type__binding__

Edler No. 4 Sodium base, modified B 19133 655 with ammonium sulphate

Edler No. 5 Calcium base, sugar B 18892 627 removed

Edler No. 6 Ammonium base, treated with B 19616 669 sodium hydroxide solution

Amendment None D 20306 772

The strength values of the tested particleboards are thus approximately exactly equal to the strength values of the inspection boards and are within very commercially acceptable limits.

Example 5 This example illustrates the use of a magnesium alkalized acid sulphite broth having the composition of the adhesive products of the invention.

The urea resin used in the composition of the adhesive product is identified in "Resin B" in Table I above. It had a dry matter content of 58% by weight, a Witte ratio of 1.47 and a molar ratio of 1.50.

The sulfite liquor used was a commercial magnesium alkalized acid sulfite liquor with a dry matter content of 47%.

The control was a commercial grade urea resin with a molar ratio of 1.25 to 26,733,38 and no sulphite lye (Resin G).

Adhesive products for the core and the surface (Edler Nos. 7 and 7a) with a ratio (ratio of resin to sulfite liquor) of 67:33 were prepared by mixing urea resin and sulfite liquor together with ammonium sulfate as a source of ammonium ions, in the following amounts:

Plate core layer: 320.7 g of resin B, 58.5% dry matter content, pH 7.0 198.6 g magnesium alkalized crude sulphite lye, 47% dry matter content, pH 4.5 8.5 g ammonium sulphate

Plate surface layer: 329.3 g of resin B, dry matter content 58.5%, pH 7.0 203.9 g magnesium-alkalized acid sulphite lye, dry matter content 47%, pH 4.5 3.0 g ammonium sulphate

The resin adhesive was sprayed on the surface of the wood particles, using 11.5% for the surface layer and 7% for the core, calculated as dry matter, for coating. The adhesive-coated wood particles were then felted into worms and pressed into 17.5 mm thick sheets in the usual manner using a pressure of 3500 kPa and a pre-sealing time of 30-40 seconds, a pressing step of 3.5 minutes and a pressing temperature of 177 °. C.

The properties of the obtained plates were tested (ASTM D1037-72) and the results are shown in Table VIII below, which are the averages of five plates given a 48-hour recovery time under ambient atmospheric conditions to equalize stresses before being tested.

27 72338

Table VIII

Thickness Water ab-swelling sorption 2

Resin- Density MOR IB during 2 hours Glue_type_g / cm ^ kPa_kPa during,% during,%

Amendment Resin G 0.68 15397 600 16.1 91.6

Urea-formaldehyde, magnesium-alkali sulphite lye (Edler Nos. 7 and 7a) Resin B 0.73 18299 640 17.6 77.2

Example 6 This example illustrates the use of magnesium alkalized sulphite lyes in the adhesive products of the invention, but under a few different conditions, in particular with regard to the use of sulphite lye having a pH lower than the pH of the sulphite lyes of Example 5.

Particleboards were prepared in which the control resin was the same (resin G) as used in Example 5 and the test adhesives for the core and the surface layer were also similar (Edler Nos. 8 and 8a), but with a dry matter content of 50% instead of 47%, in a weight ratio of 67:33, urea formaldehyde resin and sulfite liquor. The compositions of the adhesives used for the core and surface layer of the particle board were as follows:

Core layer: 320.7 g of resin B

(Table I) urea formaldehyde resin 58% dry matter, pH 7.0 186.7 g magnesium alkylated acid sulphite alkaline, 50% dry matter, pH 3.2 2.5 g ammonium sulphate

Surface layer: 329.3 g of resin B, urea formaldehyde resin, 58% dry matter, pH 7 191.7 g magnesium-alkalized acid sulphite lye, 50% dry matter, pH 3.2 2.8 g ammonium sulphate

Particleboards were prepared using the same amount of glue, the same manufacturing method, the same inspection resin, and the same board thickness as reported in Example 5. The compression step lasted 3 minutes 28 72338 12 seconds at 177 ° C. Experimental results (average of five plates were as follows:

Table IX

Thickness Water ab-swelling sorption 2

Resin Density MOR IB 2 hours after-Li ima_type g / cm ^ kPa after kPa,% keen,%

Amendment Resin G 0.68 15396 600 16.1 91.6

Urea-formaldehyde, crude alkali sulphite lye (Edler Nos. 8 and 8a) Resin B 0.71 17196 630 16.3 84.5

In the same manner as described above, adhesive products of urea resin-sulfite lye were prepared and chipboard and other glued wood products were prepared using these, where the source of ammonium ions instead of ammonium sulfate may be: Ammonium chloride, monoammonium phosphate, ammonium oxalate ethanesulfonate

Example 7 This example illustrates the use of a urea resin having a low molar ratio and a low Witte number in adhesive products.

The adhesive product was prepared using the procedure described in Example 1, in which the urea resin component of the adhesive had the following properties:

Witte number 0.76

Molar ratio 0.90 (moles of formaldehyde) (moles of urea)

Dry matter (% by weight) 65

Viscosity (cps) at 25 ° C 70 pH 7.3

Dilutability unlimited 29 72338

The sulfite liquor component of the tested adhesive product had the same properties as shown in Example 2.

The forming and compression conditions used in the preparation of the sheet product were the same as shown in Example 2.

In the test, the particleboard products had the following properties: MOR 9522 IB 152 This example clearly shows an adverse effect when using a urea formaldehyde resin with a low molar ratio and a low Witte number. Both the tensile strength (MOR) and the internal bond (IB) are well below the minimum value set by the National Particle Board Associations for particle board products (MOR 11032, IB 414).

Claims (3)

A process for the preparation of an adhesive comprising components of formaldehyde resin, sulphite liquor and water, characterized in that between 1) 50-90 parts by weight (dry weight) of urea formaldehyde resin having the following properties: molar ratio formaldehyde / urea 1.0 - 1.8 pH 6 - 8 viscosity most preferably in the range of 50 - 250 centipoises (measured at 65% dry matter content and 25 ° C) resin's methylol content corresponds to the Witte's 1.0 - 1.8 2) 10 - 50 parts by weight (dry weight) sulfite liquor having the following properties: pH 3 - 9, most preferably 3.5 - 4.5 viscosity 500 - 15000 centipoises, most preferably in the range 500 - 4000 centipoises (measured at 50% dry matter content and 25 ° C) content of ammonium ions 0.2 - 4.0% by weight (stated as NH 3) calculated on the dry weight sulfite liquor, and 3. water, wherein the components 1) and 2) dry matter contents are: urea formaldehyde resin 50-72% by weight, preferably 55-65% by weight sulphite liquor 40-55% by weight, preferably 48-52% by weight. 2. A process according to claim 1, characterized in that the sulfite liquor is ammonium sulfite liquor, whose ammonium ion content is adjusted to a value of 0.2 - 4.0 wt.% By the addition of sodium liquor or some other strong base to remove ammonia. Process according to claim 1, characterized in that the sulfite liquor is calcium, magnesium or sodium-based sulfite liquor, whose ammonium ion content is adjusted to the value 0.2 - 4.0 wt.% By the addition of a water-soluble ammonium salt of a strong mineral or organic acid, such as e.g.