DE4226329A1 - Lignin-modified binder mixts. prodn., useful for mfg. e.g. nonwoven textiles etc. - Google Patents

Abstract

The binders (I) are produced by (i) pre-reacting low mol. wt. lignin obtd. by the organosolv process (L) with phenol in the wt. ratio (1:20)-(3:1) at 100-180 deg.C. then adjusting to acid pH and (ii) condensing at 60-120 deg.C. with 0.2-0.9 mol. formaldehyde per mol. phenol. Also claimed are lignin-phenol novolaks (I) obtd. by this process, and process for producing binder mixts. (II) by intensively mixing (I) with a phenolic novolak (III) in the wt. ratio (10:90)-(90:10) at 100-200 deg.C., then cooling, possibly drying, and finely milling or granulating the mixt.. Alternatively, (I) and (III) are mixed in the same. wt. ratio, pref. (30:70)-(70:30), in a solvent, esp. MeOH, EtOH, iso-PrOH, acetone, furfuryl alcohol or ethylene glycol. Pref. (III) are obtd. by condensn. of phenols, cresols and bisphenols with formaldehyde, and pref. solvent (see above) is furfuryl alcohol. Amt. of hardener (pref. HMTA) is 4-14 wt.%, and (II) can also contain lubricants, release agents, fillers and glass fibres etc..

Description

The invention relates to new binders Conversion of low molecular weight lignin from the Organosolv process with phenol and formaldehyde be preserved. These new binders are as such or mixed with conventional Phenolic novolaks for the production of curable Molding compounds and high temperature resistant molding materials, refractory and carbon materials just as suitable as friction linings and textile fleeces.

While one used to be carbon-forming Binder for carbon materials, sintered masses and refractory products mainly tars or pitches, which among other things polycyclic hydrocarbons included as a starting material for good Has used carbon formation today synthetic resins especially furan and phenolic resins, as Binder meaning. They are free from in the resin state toxic polycyclic hydrocarbons such as B. Benzo-a-pyrene, and develop such in pyrolysis  only to a very small extent. You also avoid at elevated temperatures smoke and soot development and improve the quality and the at the same time Processability of the refractory materials. These are resins however, compared to tar-based binders, it is quite expensive. Meanwhile, the by-product falls Obtaining pulp in large quantities is a phenolic Polymer, the lignin, as part of the so-called Black liquors or sulfite liquors in which it is considered Phenolate is dissolved.

A small part of this lignin is called Binder for press plates of low quality, than Dispersant, as foam stabilizer, as Stabilizer for asphalt emulsions or for others Purposes.

Most of the resulting lignin, however, is there so far it can not be disposed of otherwise, burned and thus serves as a cheaper source of energy for the Pulping, although as a high quality, renewable raw material for coal or Products manufactured from mineral oil-derived raw materials would be conceivable.

Despite intensive investigations, none has so far suitable method found, which makes it possible, for. B. Binder mixtures based on phenolic resins through lignin resins while maintaining the To replace quality features or even to stretch.  

That from the pulping or Kraft process The sulfonated lignin obtained is in itself inert, but can be reacted with phenol Reactivated and present by the presence of an acid subsequent reaction with formaldehyde to form a resin be implemented that is miscible with phenolic resin. Sulfonated lignin, which in the presence of a base with Formaldehyde reacted and then with phenol has been condensed, is also suitable as Extender for phenolic resins (Sundstrom, D.W .; Klei, H.E .; Biotech. Bioeng. Symp. 12, 45-56 (1982).

However, it was found that the described sulfonated lignin derivatives not in any amount can be mixed with the phenolic resins as they have a very high viscosity and with increasing Lignin has a strong adhesive force in the resin mixture decreases. A phenolic resin that is 10% Contains lignosulfonic acid derivative already shows none satisfactory properties more and is relative sensitive to moisture.

Similar to these lignosulfonic acid resin mixtures Resins also behave in the same way Use of Kraft Lignin or Alkali lignin fractions can be produced.

It has also been tried to partially through phenolic resins To replace Organosolv lignin. Under comparative In mild conditions, this lignin becomes chemically almost unchanged from the wood used in two stages drained.  

With steam and an alcohol / water mixture pretreated wood chips are in a first Step with an alcohol / water mixture at almost 200 ° C and leached high pressure. It becomes a lignin slightly acidic solution obtained. The partial leached wood chips are then with treated with a cooking liquor, e.g. B. from one Methanol / water / NaOH mixture exists, and with a small amount of a catalyst is added. Out this second continuous leaching one falls with wood constituents, in particular with low molecular weight lignins, hemicelluloses and Cellulose saturated alkaline solution. This becomes the alcohol contained distilled up to 90% and receive the so-called black liquor. From both Fractions can contain the lignin in powder form be separated. It is in ketones, such as B. acetone, or in special alcohols, such as. B. Furfury alcohol, soluble and miscible in this form with a novolak.

A mixture of lignin to phenolic novolak in the ratio of 1: 1 and textile fibers as filler for Production of textile fleece results in one Solid resin content of approx. 30% (based on the Weight of the total mixture) Cold and hot bending strength compared to conventional phenolic novolacs. Take the strength decreases even more with increasing lignin content.

Try the properties of Organosolv lignin through different pre-reaction procedures to improve with phenol and formaldehyde led to  no noteworthy success. It can be done this way although resin mixtures are obtained, which are used for Manufacture of pressed and composite panels, as well as Gluing wooden veneers are suitable; high quality Products such as high temperature resistant molding materials refractory products and especially friction linings, cannot be made with it, however, because the desired property profiles of these products, such as e.g. B. in carbon yield and strength Requirements do not meet.

It is therefore an object of the invention To provide binder mixture, the Organosolv lignin in large quantities as inexpensive and at the same time contains high quality raw material, whereby the Binder mixture the requirements described above fulfilled and its quality that of the usual binder mixtures containing lignin. It is further object of the invention, a method through which the new Binder mixtures can be produced.

The task is solved by a method for Production of a lignin phenol novolak according to one Method according to claims 1 to 3, and by a produced by this process Lignin phenol novolak according to claim 4, which as Binder for the production of curable Molding compounds, molded articles, molding compounds, textile fleeces, refractory masses and friction linings according to claim 17 can be used. In particular, the solution is given the task by making one  Binder mixture consisting of the lignin-phenol novolak according to the invention and a conventional phenolic novolak, according to a method according claims 5 to 8 and its special Design according to claims 9 and 10, and by producing the above products, possibly using hardeners according to the claims 13 to 16.

That in the Organosolv process under comparatively mild conditions sulfur-free lignin has, because its chemical structure by the The process conditions affect only slightly has been changed to a relatively low medium Molecular weight. The bulk of the after Organosolv process by leaching isolated lignins has an average molecular weight of about 500 to 3,000, while only small amounts of average molecular weights have from 18,000 to 20,000 and higher. In the strong alkaline black liquor of the second leaching stage are only lignins with average molecular weights of contain about 1,000 to 4,000. By simple Technical measures can also include fractions lower average molecular weight can be obtained.

It has now been found that in the Organosolv process resulting lignin fractions with low medium Molecular weight by pre-reaction with a phenol and subsequent condensation with an aldehyde high quality resins that can be modified in simple way with a phenolic novolak and possibly other additives are mixed to binders can, which are incorporated into molding compounds, after  Curing a particularly good bond between the lignin-modified binders and the added Fillers result.

Moldings produced in this way surprisingly have in contrast to previously known Organosolv-lignin-phenol novolak binder mixtures good mechanical, thermal and electrical Features that those of conventional, not Modified phenolic resins produced molded parts correspond. Particularly good properties are shown when using the invention Binder mixtures for the production of Refractory compounds because they have high green strength and surprisingly to high carbon yields to lead.

For modification, they are preferably in powder form isolated lignins reacted with phenol and formaldehyde.

Resins with particularly good properties obtained when in particular lignins with molecular weights implemented less than 2000.

To produce the binder according to the invention the separated lignin fraction in a ratio of 1:20 to 3: 1 with phenol, based on the weight fraction of the in the solution contained lignins, spiked and at a Temperature in the range of 100 to 180 ° C thermal treated. The pH of the solution is then increased set a value less than 4. As acids for Regulation of the pH or as catalysts for  Novolak condensation can use all common acids be used. This is particularly preferred Purpose oxalic acid used. After that, 0.2 to 0.9 moles of formaldehyde added per mole of phenol and the following condensation carried out at 90 to 100 ° C. The novolak thus obtained is known per se Separated by distilling off the water, possibly washed and dried again, ground and powdered.

In this way it becomes a lignin phenol novolak get the as such to produce high quality Molding and molding compounds can be processed. He but can also be done using a known method phenol novolak produced and mixed Refractory compounds, hardenable molding compounds, friction linings or Textile nonwovens are processed.

For the production of the invention Binder mixtures by mixing one conventional phenolic novolaks with that described above Lignin-phenol novolak are the two novolaks in Weight ratio 10:90 to 90:10, preferably 30: 70 to 70: 30 mixed intensively.

These mixtures can be in a solvent such as e.g. B. methanol, ethanol, isopropanol, acetone, Furfuryl alcohol, ethylene glycol or other im Weight ratio of 30:70 to 70:30, preferably 45: 55 to 55: 45. As Solvent furfuryl alcohol is preferably used, since it is not only effective as a solvent, but  also as a reaction partner in special cases can serve the curing.

As Novolak, everyone is in the acidic medium for this purpose manufactured condensation products based on Phenols, cresols and bisphenols with formaldehyde in a molar ratio of phenol to formaldehyde of 1: 0.8 to 1: 0.2 can be used.

The mixing of the two novolaks can in itself done in a known manner. It has a favorable effect if this under the influence of high shear forces Temperatures from 100 to 200 ° C, preferably 130 to 160 ° C. For this purpose, the premixed Novolak mixture to be placed on heated rollers.

After a rolling time of about 2 to 10 minutes, a coherent roller skin is formed, which is peeled off can be and after cooling to a granulate with a grain size smaller than 2 mm is ground.

The raw mixture can also be just as well in itself known and usually for such processes used heatable devices, such as. B. in Twin screw extruder, trough or bowl kneader or mix in a co-kneader. The temperature will adjusted so that a good mixing of the individual components with each other, but neither a decomposition of the material used premature curing of the resin mixture takes place.  

This work process becomes a homogeneous product get that after cooling to room temperature, possibly can be dried and pulverized and that excellent as a binder or Binder component for molding compounds, curable Molding compounds, refractory compounds, friction material or Textile fleece is suitable.

For further processing, this Binder mixture 4 to 14% by weight of a hardener, preferably hexamethylenetetramine. Reactive resins such as are also suitable as hardeners Epoxy resins, phenolic resoles, amino resins or their Mixtures. In addition, 0.05 to 1.2 wt .-% of a Lubricants and release agents, 4 to 90% by weight fillers, but also 0 to 20 wt .-% fiber materials, such as. B. Glass fibers are added.

Me stearate are preferred as lubricants and release agents (Me = Al, Ca, Mg, Li, Zn) in an amount of 0.1 to 0.8% by weight and wax in an amount of 0.1 too up to 0.8% by weight, in particular amide wax, ester wax, Montan wax or paraffin wax, added. For Improvement of the rolling behavior of the thermoset Molding material is preferably chalk as a filler mixed in.

The examples given below are for further explanation of the invention, however, they are intended not limited to this.  

Examples example 1

3 kg phenol, 2 kg lignin from the Organosolv process with a sintering point of approx. 110 ° C and a average molecular weight of approx. 1100 will be 50 g Oxalic acid added and at a temperature of 150 ° C. Held for 2 hours.

Then it is cooled to 100 ° C and at this Temperature and under reflux 1.45 kg formalin (45%) added dropwise over the course of 2 1/2 hours. It will continued boiling until the free Formaldehyde content of the reaction solution less than 0.3% is.

Then water and monomers are distilled off until the Free phenol content in the resin melt <0.5% and the resulting lignin-phenolic resin is one Has a melting point of approx. 90 ° C.

The resin is discharged and fine after cooling crushed, pulverized in a baffle mill and homogeneously mixed with 6% hexamethylenetetramine.

Example 2

760 g of powder resin according to the invention from Example 1 is with a mixture of 2 kg steel wool, 1 kg brass shavings, 700 g coke, 320 g graphite, 320 g polyaramid fiber (2 mm), 180 g glass fiber (2 mm),  1 kg barium sulfate and 500 g magnesium oxide intensive mixed.

The mixture is used in the usual way to produce Friction pads used. The coefficient of friction, determined on Test specimens, which 30 seconds per millimeter Layer thickness pressed at 170 ° C and at 10 hours Post-cured at 200 ° C is approximately 0.40.

Example 3

70 parts by weight of textile fiber mixture are with 30 parts by weight of the powder resin according to the invention from Example 1 intimately mixed. For production of Nonwoven becomes the material of an aerodynamic Subjected to fleece formation and on a perforated screen filed. The uncured so obtained Textile nonwoven fabric is placed in a heating cabinet at approx. Pre-hardened at 120 ° C and then in a press at 180 ° C pressed into sheets of 250 mm × 250 mm.

The panels obtained in this way are in terms of strength (Load and deflection) and smell with Production plate material compared, where a Standard powder resin Phenol-Novolak-Hexamethylenetetramin-Basis for use came.

Compare in strength

No differences  

Comparisons in the odor test (Ford odor test)

Grade 1.9 to 2.3 when using powder resin according to of the invention, marks 2.2 to 2.6 for the material from the Production with unmodified powder resin (the Odor quality increases with decreasing marks).

Example 4

5 kg phenol, 5 kg lignin fraction from the Organosolv process, with a melting point of 80 to 82 ° C according to DIN ISO 10082 and an average molecular weight from about 800 to a temperature of 150 ° C brought and held there for 2 hours.

It is then cooled to 100 ° C, 100 g of oxalic acid added and at this temperature as well as below Reflux 2.4 kg formalin (45%) over the course of Added dropwise for 3 hours. It continues to boil at reflux until the free formaldehyde content of the reaction solution is less than 0.3%.

Then water and monomers are distilled off until the content of free phenol in the resin melt <0.5% and the resulting lignin-phenol resin is one Has a melting point of approx. 90 ° C according to DIN ISO 10082.

The resin is discharged and after cooling crushed.  

Example 5

3 kg of resin according to the invention from Example 4 are mixed with 3 kg phenol novolak resin with a melting point after DIN ISO 10082 from 80 ° C in 4 kg anhydrous Furfuryl alcohol dissolved. The solution contains less than 0.2% water.

Example 6

11.14 kg of a mixture of various types of dolomite Grainings are made with 60 g hexamethylenetetramine and 800 g Resin solution according to the invention from Example 5 homogeneous mixed.

After pressing into molded bodies, the cold compressive strength is approximately 80 N / mm ² .

The resin-bonded moldings are then up to heated to a temperature of 180 ° C and hardened. You then have a strength that is so great that it is well transported and installed in units can be.

The dolomite bodies could also be stored well without decay. The determined cold bending strength is around 22 N / mm ² for the hardened moldings.

Tempering tests carried out in parallel up to 1000 ° C on the basis of shaped bodies, a carbon content was obtained  of 54% based on the resin content of the resin solution Example 5.

Example 7

4 kg of resin from Example 4 are ground and with 2 kg Phenolic novolak with a melting point according to DIN ISO 10082 at approx. 85 ° C, 750 g hexamethylenetetramine, 18 g Montan wax, 60 g amide wax, 10 g calcium stearate and 7 kg softwood flour intimately mixed and to 100 to Rollers heated at 130 ° C abandoned.

The mass is in a rolling time of about 3 to 4 Minutes compacted into a coherent rolled skin and homogenized.

The resulting rolled skin is pulled off and after the Cool down to a granulate of <2 mm.

The granules are molded in the pressing process molded and hardened. The physical values of the Shaped bodies lie over the frame of the Phenolic resin molding compounds of type 31 according to DIN 7708. Die molded parts thus produced are characterized by a good surface.

Claims (22)

1. A process for the preparation of a binder for molding compositions and moldings, characterized in that low molecular weight lignin from the Organosolv process

• a) is pre-reacted with phenol in a weight ratio of 1:20 to 3: 1 at temperatures of 100 to 180 ° C. and
• b) after setting an acidic pH with 0.2 to 0.9 mol of formaldehyde per mol of phenol is condensed at temperatures from 60 to 120 ° C.

2. The method according to claim 1, characterized characterized in that low molecular weight lignin the Organosolv process with a medium one Molecular weight from 500 to 3000 is implemented. 3. The method according to claim 1, characterized characterized in that low molecular weight lignin  the Organosolv process with a medium one Molecular weight from 600 to 1200 is implemented. 4. Lignin phenol novolak made according to a Method according to claims 1 to 3. 5. A process for the preparation of a binder mixture, characterized in that

• a) a lignin-phenol novolak according to claim 4 is mixed intensively with a phenol novolak in a weight ratio of 10:90 to 90:10 at a temperature of 100 to 200 ° C and
• b) the cooled, possibly dried, homogeneous mixture is finely ground or granulated.

6. Process for producing a Binder mixture according to claim 5, characterized characterized that a lignin phenol novolak according to claim 4 with a phenol novolak in Weight ratio 30:70 to 70:30 at one Temperature from 100 to 200 ° C mixed intensively becomes. 7. The method according to claims 5 and 6 for Production of a binder mixture, thereby characterized in that the intensive mixing at 130 to 160 ° C takes place. 8. The method according to claims 5 to 7 for Production of a binder mixture, thereby  characterized that the intensive mixing under the influence of high shear forces in a kneader or extruder. 9. Process for producing a Binder mixture, characterized in that a lignin phenol novolak according to claim 4 with a phenol novolak in a ratio of 10:90 and 90:10 in a group solvent Methanol, ethanol, isopropanol, acetone, Furfuryl alcohol and ethylene glycol in Weight ratio 30: 70 to 70: 30 solved becomes. 10. Process for producing a Binder mixture according to claim 9, characterized characterized that the to be used Weight ratio of lignin novolak to Phenol novolak 45: 55 to 55: 45. 11. Binder mixture, prepared according to the Claims 5 to 10. 12. Binder mixture, prepared according to the Claims 5 to 10, characterized in that for its hardening or hexamethylenetetramine reactive resins such as B. phenol resoles, Epoxy resins or nitrogenous polymers be used.   13. Use of the binder mixture according to Claims 11 and 12 for the production of curable Molding compounds. 14. Use of the binder mixture according to the Claims 11 and 12 for the production of Textile fleeces. 15. Use of the binder mixture according to Claims 11 and 12 for the production of refractory masses. 16. Use of the binder mixture according to Claims 11 and 12 for the production of Friction linings. 17. Use of the lignin phenol novolak according to Claim 4 as a binder for the production of curable molding compounds. 18. Use of the lignin phenol novolak according to Claim 4 as a binder for the production of Molded articles. 19. Use of the lignin phenol novolak according to Claim 4 as a binder for the production of Molding compounds. 20. Use of the lignin phenol novolak according to Claim 4 as a binder for the production of Textile fleeces.   21. Use of the lignin phenol novolak according to Claim 4 as a binder for the production of refractory masses. 22. Use of the lignin phenol novolak according to Claim 4 as a binder for the production of Friction linings.