DE19653627A1 - Production of alkali-condensed phenol-urea-formaldehyde resin used e.g. for lignocellulosic material - Google Patents

Abstract

A process for the production of an alkali-condensed phenol-urea-formaldehyde (PUF) resin with a mol ratio of P:F:U = 1:(1.5-3.5):(0.3-2.5), comprising: (a) preparation of a PF condensate by alkaline condensation of P and F up to a viscosity of 100-5000 mPa.s; (b) production of a PF resin by further condensation to a viscosity of more than 5000 mPa.s; and (c) reaction of the PF resin with urea. The novelty is that stage (b) is carried out in an extruder. Also claimed is a PUF resin obtained by this process. Preferably stage (b) is carried out in an extruder at 90-150 deg C, preferably in a continuous single- or twin-screw mixer, a twin-screw continuous kneader or a continuous multi-screw kneader. Stages (a)-(c) may be carried out continuously. The PF resin is produced in stages (a) and (b) by starting with 60-90% of the total amount of formaldehyde required, and then reacted in stage (c) with the remaining 10-40% F and the urea, possibly in the form of a UF precondensate. The PF resin obtained in stage (b) has a viscosity of more than 5000 to 100,000 mPa.s. The final PUF resin has a solid content of 40-70 wt% and a mol ratio of (phenol):(alkali hydroxide) = 1:(0.4-1.2), which may be reduced to 1:(0.9-1.5) before processing by adding more alkali hydroxide.

Description

The present invention relates to an improved method of manufacture of an alkaline condensed phenol-urea-formaldehyde resin characterized in that a step is carried out in an extruder is such a resin per se and its use as a binder for lignocellulosic materials.

Phenol-urea-formaldehyde resins, hereinafter also called phenolic resins have long been used as binders in the wood-based panel industry in the manufacture of e.g. B. chipboard used.

Binder based on aqueous solutions of alkaline condensed phenol resins for the gluing of cut, grown wood, such as Wood fibers, wood shavings, wood veneers or wooden strips to match the wood materials, such as fiberboard, chipboard, plywood and Blockboards are generally known. Usually in the manufacture of the wood-based materials, the binders on the divided, grown wood applied and together at elevated temperatures pressed until the binder has hardened.  

To achieve a high level of economy in the production of wood materials, for example, binders are desired

• - Which have a not too high viscosity, because otherwise when opening carry the binder onto divided, grown wood technical Difficulties arise and especially in the case of wood chips and Wood fibers the binder is not evenly distributed,
• - The when gluing the divided, grown wood, z. B. at Hot press, harden as quickly as possible, d. H. a sufficiently high Possess reactivity, and
• - with which wood-based materials with a generally advantageous property shaft profile, d. H. sufficient mechanical stability and at least conditional moisture resistance.

Particularly short production times for hot pressing can be achieved with such Phenolic resins achieve a relatively high level of curing accelerating alkali hydroxide and already a high degree of condensation exhibit. The possibility of increasing the degree of condensation, however, will limited by the fact that the viscosity increases with increasing degree of condensation of the binder increases, which leads to technical difficulties when applying of the binder on the divided, grown wood.

From DE-A 2 944 178 it is known that the viscosity of the binder based on a phenolic resin with a high degree of condensation can reduce that the solids content of the resins by dilution lowered with water. The pressing times can, however, be taken with this measure barely shorten me, because the advantage of the high degree of condensation will compensated here by the higher water content.  

EP-A 0 146 881 describes rapidly curing, aqueous binders for Chipboard based on a phenol-formaldehyde resin with a viscosity of more than 300 mPa.s (measured at 20 ° C), an alkali content of 2 to 12 wt .-%, a high degree of condensation and a formaldehyde hyd fraction of 20 to 25 wt .-% described. The binders will be obtained by mixing phenol and formaldehyde in aqueous alkaline media um condensed and at the end of the condensation reaction 2 to 30 wt .-% Urea, based on the aqueous solution of the phenol-formaldehyde Kon addition of resin.

EP-A 0 282 903 describes low-viscosity aqueous binders for Chipboard based on a phenol-formaldehyde condensation resin and Urea with a dry content of 38 to 65 wt .-% and one Content of dimethylol and / or trimethylol urea from 0 to 5% by weight, which harden particularly quickly when they are processed into chipboard. After the local manufacturing instructions are the aqueous solution of the phenolic Formaldehyde condensation resin immediately after its manufacture urine added substance and then the mixture with dimethylol urea mixes.

EP-A 0 282 910 discloses that an addition of 0.2 to 3% by weight of sulfite and / or hydroxymethanesulfinate to those in EP-A 0 282 903 described binders the increase in viscosity during the Storage of the resin slows down.

DE 44 09 512 describes a process for the production of highly reactive aqueous binders for wood materials made of cut, grown wood described in which A) an aqueous solution of a phenol-formaldehyde Kon Densationsharzes with a solids content of 40 to 55 wt .-%, one Viscosity of 0.5 to 5 Pa.s and a proportion of 0.8 to 1.5 mol  equivalents, based on the phenol, of an alkali hydroxide and B) urea mixed together in the form of an aqueous solution or as a solid are, according to the method claimed there, the mixture of Components A) and B) at most 96 h before applying the bandage by means of the divided, grown wood and its gluing to wood materials are mixed together.

DE-C-43 00 035 describes a process for producing highly reactive Urea-modified phenolic resins as binders for medium-layer chips the production of chipboard, which is characterized in that phenol and formaldehyde are condensed so far under alkaline conditions, that after the addition of 30 to 50% by weight of urea, based on the phenolic Formaldehyde condensation resin, modified phenolic resins result that a solids content of 50 to 70% by weight, alkali contents of 2 to 8% by weight (calculated as NaOH) and viscosities of maximum 5000 mPa.s / 20 ° C have and that this highly reactive urea-modified, relative low-alkali phenolic resins prior to processing to provide sufficient So fast alkali leaching of the phenolic resin on the chip ge is added that a total alkali content of the resin solution of 7 to 13% by weight (calculated as NaOH) results.

This is in the light of the prior art described above the invention has for its object a further improved method for Production of an alkaline condensed phenol-urea-formaldehyde resin to make available that on the one hand compared to the previously available Ver available processes faster, easier and therefore economical is advantageously feasible and also comparatively storage stable, low-alkali and reactive products.  

Accordingly, the present invention relates to a process for producing an alkaline condensed phenol-urea-formaldehyde resin with a molar ratio of phenol: formaldehyde: urea of 1: (1.5 to 3.5): (0.3 to 2.5), the process comprising the following stages a) to c):

• a) Preparation of a phenol-formaldehyde condensation resin by alkali condensation of phenol and formaldehyde up to a viscosity from 100 to 5000 mPa.s,
• b) Preparation of a phenol-formaldehyde resin by further condensation of the phenol-formaldehyde condensation resin produced in stage a) to a viscosity of more than 5000 mPa.s, and
• c) reacting the phenol-formaldehyde resin obtained in step b) with Urea,

which is characterized in that the condensation according to stage b) in an extruder is carried out.

A special feature of the method according to the invention is that by using an extruder in stage b) also highly viscous solution gene of a phenol-formaldehyde condensation resin with no problems a "stuck" of the reactor can be processed, wherein in In the present case, the term "highly viscous" for solutions of a phenolic Formaldehyde condensation resin with a viscosity of approximately 5000 to about 300,000 mPa.s, preferably about 10,000 to about 100,000 mPa.s, and especially about 20,000 to about 50,000 mPa.s stands.

It should be noted that with conventional condensation in the Stirred kettle solutions of a phenol-formaldehyde condensation resin with a Viscosity of more than approximately 50,000 mPa.s only with more accuracy Reaction management and complex monitoring of the condensation, e.g. B. regarding heat dissipation, can be processed.  

The temperature at which the condensation in the extruder according to stage b) is preferably about 90 to about 150 ° C, preferably at about 100 to about 140 ° C and especially at about 110 to about 130 ° C.

As already described above, the condensation in step b) is always carried out continuously in the extruder. Steps a) and c) can be carried out either batchwise or continuously. This means that stages a) to c) can be carried out as follows in accordance with the process according to the invention:

• 1st stage a): discontinuous - stage b): continuous - stage c): discounted continuous;
• 2nd stage a): continuous - stage b): continuous - stage c): discounted continuous;
• 3rd stage a): discontinuous - stage b): continuous - stage c): con continuous; and
• 4. Stages a) to c): in each case continuously,

the variant, corresponding to stages a) to c), each being continuous be carried out, is preferred.

The continuous and / or discontinuous process steps are generally in a manner known per se what z. B. dwell times and Reactors used carried out (see. Ullmanns Encyklopadie der Technical Chemistry, 5th edition, Verlag Urban & Schwarzenberg, Mün chen / Berlin 1979, volume 18, pp. 245-257, especially pp. 249-252). The Continuous production of the phenol-formaldehyde resins becomes special favorable in a continuous, consisting of several individual reactors  flowed reaction system made in DE-A 1 720 306 is described.

With regard to the Ex that can be used in the present method there are no restrictions. In general, extruders, like in Ullmann’s Encyclopedia of Chemical Engineering, 4th edition, Verlag Urban and Schwarzenberg, Munich / Berlin 1972, Volume 2, P. 295ff. are described, used. To be mentioned in particular are continuous single-shaft mixers, such as B. single screw extruder, FRENKEL mixers, plasticizers, extractors, votators and co-kneaders; con Continuous twin-screw mixer (twin screw extruder), such as B. the same extruders with common twin screws, COLOMBO screws pointing extruders, extruders with ZSK screws, holo-flite twin screw extruders, counter rotating twin screw extruders Extruders, LEISTRITZ kneading pumps, PASQUETTI twin screw Extruders, extruders with cotruder screws, MAPRÉ twin screws extruders, a GETECHA kneading extrusion press, a WELDING-ENGINEERS Ma machine, ANGER tandem extruder and ZIMMERMANN-JANSEN extruder; Two-shaft continuous kneader, such as. B. DSM twin-shaft mixer, ECK mixing truder, FCM kneader and LIST all-phase devices; and continuous more wave kneader, such as B. Four-screw extruders and planetary roller extruders.

In a further preferred embodiment, the present relates Invention a method as described above, initially in Stages a) and b) a phenol-formaldehyde resin by reacting phenol with an initial amount of 60 to 90% of the total amount used ten formaldehyde is produced and then in step c) according to Stages a) and b) produced phenol-formaldehyde resin with a residual amount from 10 to 40% of the total amount of formaldehyde used and with Urea is implemented.  

The peculiarity of this embodiment of the method according to the invention can be seen in the fact that the phenol initially only with part of the Total amount of formaldehyde is implemented, which is generally at about 60 to about 90%, and preferably about 70 to about 100% about 85% of the total amount of formaldehyde used is [(stages a) and b)], and then in stage c) that in stages a) and b) phenol-formaldehyde resin obtained with a residual amount of generally about 10 to about 40%, and preferably about 15 to about 30% of the total amount of formaldehyde used and with urea, preferably at about 30 to about 70 ° C.

The remaining amount of formaldehyde can be added together with or immediately are added before the urea and then reacted, or else also used in the form of a urea-formaldehyde precondensate and be implemented.

The solids content, which according to the method for measuring the solids content, after 1 g of the substance in a weighing glass according to DIN 12 605 with a Diameter of 35 mm at a temperature of 120 ° C for 2 hours are dried, determined, of the phenolic Urea-formaldehyde resin is preferably about 40 to about 70% by weight, more preferably about 45 to about 65% by weight and especially about 50 to about 60% by weight.

The viscosity of the resins produced in this way is determined in accordance with DIN 53 019. The viscosity is measured on a solution of the phenolic resin set to a solids content of 48% by weight in a rotary viscometer at 20 ° C. and a shear rate of 41 s⁻ ¹ , the sample being beforehand for 20 s at a shear rate of 41 s⁻ ^{1 was} sheared. The viscosities of the phenol-urea-formaldehyde resins measured in this way are preferably approximately 500 to approximately 5,000 mPa.s, more preferably approximately 500 to approximately 1500 mPa.s and in particular approximately 500 to approximately 1000 mPa.s.

The molar ratio of phenol to formaldehyde in the resin according to the invention is generally 1: (about 1.5 to about 3.5), preferably 1: (about 2 to about 3.0) and especially 1: (about 2.2 to about 2.8).

In addition to the abovementioned phenol, up to 2 mol% of phenol derivatives can also be used, in particular those whose use does not significantly change the property profile of the resins compared to those which are composed exclusively of phenol. Suitable phenol derivatives include, for example, homologs of phenol, such as C ₁ -C ₆ -alkylphenols, for example m-, o- and p-cresol, the xylenols and resorcinol.

The solutions of the phenol-formaldehyde resins also contain an alkali hydroxide, especially sodium or potassium hydroxide. The alkali content of the phenol-urea-formaldehyde resin obtained is preferably about 0.4 to about 1.2, more preferably about 0.7 to about 0.9 molar equivalents based on the phenol.

The total amount of the alkali metal hydroxide can already be the mixture of Starting products, preferably in the form of a 40 to 60 wt .-% aqueous Solution. However, it is advisable to mix the Starting products only a part of the total amount of alkali hydroxide, generally about 35 to about 45% by weight before condensation in stage a) and add the remaining part during the (further) con addition reaction in step a) and / or b).  

The molar ratio of phenol: urea in the resin is in general 1: (about 0.3 to about 2.5), preferably 1: (about 0.7 to unge about 2.0) and especially 1: (about 1.2 to about 1.8).

In general, the phenol-urea-formaldehyde resin according to the invention is produced as follows:
In step a), the phenol and, if appropriate, the phenol derivatives are initially introduced together with part of the alkali metal hydroxide and either the total amount of formaldehyde or a starting amount of formaldehyde, as defined above, is metered in and at temperatures in the range from about 70 to about 120 ° C, working at temperatures above 100 ° C at elevated pressure, preferably at a temperature from about 80 to about 100 ° C, condensed to a viscosity of about 500 to about 5000 mPa.s continuously or discontinuously. Subsequently, the phenol-formaldehyde condensation resin obtained in stage a) according to stage b) in an extruder, preferably with further addition of alkali metal hydroxide, at temperatures from about 90 to about 150 ° C., preferably about 100 to about 130 ° C., until condensed to a viscosity of about 5000 mPa.s or above, the upper limit for the viscosity of the phenol-formaldehyde resin obtained in step b) being about 300,000 mPa.s, preferably about 100,000 mPa.s and especially at about 50,000 mPa.s.

In stage c) either urea and formaldehyde or, according to a further embodiment, the formaldehyde as a urea form aldehyde precondensate (e.g. 4.95 mol formaldehyde; 1.24 mol urea) and the remaining amount of urea added as urea and with the in Step b) phenol-formaldehyde resin obtained usually at temperatures  from about 30 to about 70 ° C to a preferred viscosity about 100 to about 5000 mPa.s, more preferably about 500 to about 1500 and especially about 500 to about 1000 mPa.s implemented.

The phenol-urea-formaldehyde resin thus obtained can then be in the form its aqueous solution obtained according to the invention at room temperature be stored.

Before processing, this resin solution is given a suitable amount Alkali lye added, preferably as much alkali hydroxide added the ratio of phenol: alkali hydroxide is 1: 0.9 to about 1.5, preferably 1: 1.2 to about 1.5.

The present invention further relates to an alkaline condensed phenol-urea-formaldehyde resin with a molar ratio of phenol: formaldehyde: urea of 1: (approximately 1.5 to approximately 3.5): (approximately 0.3 to approximately 2.5) , producible by means of a process which comprises the following stages a) to c):

• a) Preparation of a phenol-formaldehyde condensation resin by alkali condensation of phenol and formaldehyde up to a viscosity from 100 to 5000 mPa.s,
• b) Preparation of a phenol-formaldehyde resin by further condensation of the phenol-formaldehyde condensation resin produced in stage a) to a viscosity of more than 5000 mPa.s, and
• c) reacting the phenol-formaldehyde resin obtained in step b) with Urea,

characterized in that the condensation according to stage b) is carried out in an extruder,
and the use of the phenol-urea-formaldehyde resin according to the invention or produced according to the invention as a binder for lignocellulosic materials, such as. B. wood shavings from grown and / or recycled wood, hemp, flax, straw, z. B. for the production of chipboard or insulation boards for example for car interiors.

In the following the use according to the invention is based on the application example when gluing wood as a lignocellulosic material described.

The use of the phenol-urea-formaldehyde resin according to the invention is generally carried out by adding an aqueous solution thereof divided, for example machined or grained, grown and / or recycled wood and glue it. Gluing is cheaper wise, by cutting the divided, grown wood provided with the solution at temperatures from about 100 to about 250 ° C, preferably at compresses about 105 to about 225 ° C. Under these conditions the phenol-urea-formaldehyde resin hardens quickly and you get Wood materials with a favorable property profile.

The solution can additionally accelerate the hardening reaction Potassium carbonate in amounts from about 2 to about 8, preferably from about 4 to about 6% by weight based on the solution will.

In addition, the solution can be insecticides and / or microbicides such. B. Han commercially available fungicides, which are preferably immediately before be mixed into the application.  

The water resistance of wooden materials such as chipboard or fiberboard can be increased by adding a commercially available, aqueous paraf find dispersion is added.

The resin produced according to the invention is particularly suitable for production of wood-based materials such as plywood or blockboards and especially of Fibreboard and chipboard, which are made by gluing cut, grown wood such as wood fibers, wood chips, wood veneers or wood egg most can be obtained with the resin.

The production of such wood materials is known per se and is u. a. in H.-J. Deppe, K. Ernst, Paperback of chipboard technology, 2nd edition, Verlag Leinfelden 1982, in Ullmann's Encyclopedia of Technical Chemistry, 4th edition, volume 12, pp 709 to 727, and in DE 44 09 512, the Content related to the manufacture of wood-based materials using Phenolic resins are fully included in the present application is described in detail.

The invention will now be described in more detail on the basis of a few exemplary embodiments are explained.

Examples Example 1 (continuous / discontinuous / continuous operation)

9.8 kg of water, 27.7 kg of phenol were placed in a stirred tank cascade (0.295 kmol), 46.1 kg 40% formaldehyde (0.615 kmol) and 6.75 kg 50% Sodium hydroxide solution (0.084 kmol) per hour through a mixing section into a stirrer introduced and at a temperature of 100 to 101 ° C at a  Residence time from 20 min to a viscosity of 70 mPa.s siert.

The product was then passed through a tube bundle heat exchanger passed, wherein it was cooled to 80 ° C and a viscosity of 100 mPa.s. The residence time in the tube bundle heat exchanger was 40 min.

Then the phenol-formaldehyde condensation resin got into one second stirred kettle and was there again with 8.1 kg of 50% sodium hydroxide alkali (0.101 kmol) per hour and at 80 ° C within Condensed for 90 min to a viscosity of 300 mPa.s.

In another (third) stirred kettle, the product was removed within Condensed for 45 min at 75 ° C to a viscosity of 700 mPa.s.

When leaving the stirred tank cascade, a sample of the primary solution cooled to 20 ° C had the following characteristics:

Viscosity: 820 mPa.s
Solids content: 47%
Alkali content: 7% by weight
Gel time (100 ° C without hardener): 32 min

The alkali content of the resin was in this and the other example by titration of the product obtained with 0.25 molar sulfuric acid to determined at the equivalence point.

The time of gelation in this and the other example was determined as follows:
20 g of the product obtained were weighed into a test tube. The test tube with the product was placed in a water bath (round-bottom flask), which was heated to a temperature of 100 ° C. The product was stirred until it solidified using a warmed glass rod located in the round bottom flask. The gelation time, which is the time elapsed until the product gelled since the start of stirring, was measured using a stopwatch and is given here in minutes.

The primary solution was pumped into an extruder via a gear pump. With a resin throughput of approximately 100 kg / h, there was a residence time of 5.2 min in the extruder. The reaction temperature was kept at 120 ° C. The characteristics of the phenol-formaldehyde condensation product obtained were:

Viscosity at 20 ° C: 30,000 mPa.s
Gel time: 11 min.

The product, cooled to 50 ° C., solidified with 27.3 kg of urea and 8.6 kg formaldehyde-urea precondensate (4.95 mol formaldehyde: 1.24 mol Urea), the urea via a special feed screw and the formaldehyde-urea precondensate via a pipeline were metered in continuously.

After the product had cooled to 20 ° C, it had the following characteristics:

Viscosity: 720 mPa.s
Solids content: 55% by weight
Alkali content: 5% by weight
Gel time (100 ° C without hardener): 15 min.

Example 2 (discontinuous / continuous / continuous operation)

98 kg of water, 277 kg of phenol (2.95 kmol), 461 kg of 40% formaldehyde (6.15 kmol) were placed in a 1 m ³ stirred tank. The mixture was heated to 40 ° C. and 148.5 kg of 50% sodium hydroxide solution (3.71 kmol) were added in three stages at 40 ° C., 55 ° C. and 85 ° C. within 30 minutes while simultaneously removing the heat of reaction. The mixture was then heated to 100 ° C. and condensed under reflux at this temperature for a further 50 min. The mixture was then cooled to 85 ° C. and condensed to a final viscosity of 500 to 700 mPa.s. After reaching this viscosity, the mixture was cooled to 40 ° C.

A sample of the phenol-formaldehyde condensation product cooled to 20 ° C had the following characteristics:

Viscosity: 750 mPa.s
Solids content: 46.5% by weight
Alkali content: 7% by weight
Gel time: 28 min.

In a further stage, the primary solution stored in an intermediate container was pumped into an extruder via a gear pump. With a resin throughput of 100 kg / h, there was a residence time of 5.2 min in the extruder. The reaction temperature was kept at 120 ° C. The characteristics of the phenol-formaldehyde condensation product obtained were:

Viscosity at 20 ° C: 32,000 mPa.s
Gel time: 10 min.

The product, cooled to 50 ° C., solidified with 295 kg of urea and 107 kg of 40% formaldehyde are added, the urea having a special feed screw and 40% formaldehyde via a pipe were metered in continuously.

After the product had cooled to 20 ° C, it had the following characteristics:

Viscosity: 580 mPa.s
Solids content: 54% by weight
Alkali content: 5% by weight
Gel time (100 ° C without hardener): 14 min.

Claims (12)

1. A process for producing an alkaline condensed phenol-urea-form aldehyde resin with a molar ratio of phenol: formaldehyde: urea of 1: (1.5 to 3.5): (0.3 to 2.5), the The process comprises the following stages a) to c):

• a) producing a phenol-formaldehyde condensation resin by alkaline condensation of phenol and formaldehyde up to a viscosity of 100 to 5000 mPa.s,
• b) producing a phenol-formaldehyde resin by further condensing the phenol-formaldehyde condensation resin produced in step a) up to a viscosity of more than 5000 mPa.s, and
• c) reacting the phenol-formaldehyde resin obtained in stage b) with urea,

characterized in that the condensation according to stage b) is carried out in an extruder. 2. The method according to claim 1, characterized in that the con densify according to stage b) in an extruder at a temperature of 90 to 150 ° C is carried out. 3. The method according to claim 1 or 2, characterized in that in Stage b) as an extruder, a continuous single-shaft mixer, a con  continuous two-shaft mixer, a two-shaft continuous mixer or a continuous multi-shaft kneader is used. 4. The method according to any one of the preceding claims, characterized records that stages a) to c) each carried out continuously will. 5. The method according to any one of the preceding claims, characterized records that first in stages a) and b) a phenol-formaldehyde resin by Um put phenol with a starting amount of 60 to 90% of Total amount of formaldehyde used is produced and then in stage c) the phenolic obtained in stages a) and b) Formaldehyde resin with a residual amount of 10 to 40% of the total amount of formaldehyde used and reacted with urea becomes. 6. The method according to any one of the preceding claims, characterized records that in stage c) the urea and the remaining amount of form aldehyde used in the form of a urea-formaldehyde precondensate will. 7. The method according to any one of the preceding claims, characterized records that the alkaline condensed phenol-urea-formaldehyde resin has a solids content of 40 to 70 wt .-%. 8. The method according to any one of the preceding claims, characterized records that the alkaline condensed phenol-urea-formaldehyde resin a molar ratio of phenol: alkali hydroxide of 1: (0.4 to 1.2) owns.   9. The method according to any one of the preceding claims, characterized records that the phenol-formaldehyde resin produced in step b) a Has a viscosity of more than 5,000 to 100,000 mPa.s. 10. The method according to any one of the preceding claims, characterized records that the alkaline condensed phenol-urea-formaldehyde resin so much alkali hydroxide is added before processing that the ratio of phenol: alkali hydroxide is 1: (0.9 to 1.5). 11. Alkaline-condensed phenol-urea-formaldehyde resin with a molar ratio of phenol: formaldehyde: urea of 1: (1.5 to 3.5): (0.3 to 2.5), which can be produced by a process which the following Stages a) to c) include:

• a) producing a phenol-formaldehyde condensation resin by alkaline condensation of phenol and formaldehyde up to a viscosity of 100 to 5000 mPa.s,
• b) producing a phenol-formaldehyde resin by further condensing the phenol-formaldehyde condensation resin produced in step a) up to a viscosity of more than 5000 mPa.s, and
• c) reacting the phenol-formaldehyde resin obtained in stage b) with urea,

characterized in that the condensation according to stage b) is carried out in an extruder. 12. Use of the alkaline condensed phenol-urea-formaldehyde-har zes according to claim 11, or one using a method according to one of claims 1 to 10 prepared alkaline condensed Phenol-urea-formaldehyde resin as a binder for lignocellulosi materials.