DE4226330A1 - Binders for moulding materials, etc. - Google Patents

Abstract

Binder mixts. (I) for moulding materials and mouldings are claimed. (I) are obtd. by homogeneously mixing and pre-reacting (A) 5-60 wt.% lignin or lignin fraction from the organosolve process with (B) 40-95 wt.% phenolic novolak, by applying high shear forces in a kneader or extruder, and then possibly mixing with a hardener (C). Prodn. comprises (i) mixing (A) and (B) as above at 100-200 deg.C and (ii) milling the cooled, possible dried, homogeneous mixt. obtd. to give granules with particle size below 2 mm. More specifically (A) is lignin obtd. from the wood of conifers or deciduous trees, with mol. wt. 800-4000, pref. 800-1500, and sinter pt. 80-120 deg.C. (C) is hexamethylenetetramine (HMTA), or a reactive resin, e.g. phenolic A-stage resin or epoxy resin, or a UF or MF resin.

Description

The invention relates to new binders homogeneous mixing under the influence of high shear forces from suitable synthetic resins with up to 60% lignin the Organosolv process and, if necessary, with a Hardening agents can be obtained. These new binders are for the production of curable molding compounds and high temperature resistant molding materials such as refractory Products and carbon materials, as well suitable, such as friction linings and textile fleeces.

While formerly in the field of carbon-forming Binders for carbon materials and refractories Products mainly tars or pitches has used, among others, polycyclic Containing hydrocarbons are gaining today synthetic resins, especially furan and phenolic resins, meaning as a binder. They are free in the resin state of toxic polycyclic hydrocarbons such as e.g. B. Benzo-a-pyrene and develop such in the Pyrolysis only to a very minor extent. they also avoid at elevated temperatures  Smoke and soot development and improve the quality and the processability of the refractory materials. However, synthetic resins are compared to tar-derived binders are relatively expensive.

From EP 2 48 980 A1 binders for known high temperature resistant molding materials from such a phenolic resin with a molar Ratio of phenol and formaldehyde from 1: 0.2 to 1: 0.55.

Attempts have been made to make the binder cheaper made the expensive phenolic resin with inexpensive, to stretch cross-linkable substances. As such were Residues from the production of dimethyl terephthalate (DE-PS-27 23 792, DE-OS-36 20 473 and EP 2 49 959 A1) or from the bisphenol A synthesis (DE-A 40 15 440) used.

However, these synthesis residues are only limited Amounts accessible. Residues from the Dimethyl terephthalate production also have one high viscosity and are therefore difficult to mix. Though can be added by adding solvents or oils Workability can be improved, but when heated these volatile components are mostly released again and can cause unwanted smoke and Cause soot formation.

Binder mixtures in which a Part of the phenolic resin replaced by lignin sulfonic acid has been. That from the pulp or  Kraft process-derived sulfonated lignin is in itself slow to react, but can for this purpose Reaction with phenol in the presence of an acid reactivated and by subsequent reaction with Formaldehyde can be converted into a suitable resin, 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 negatively affect the processing properties and with increasing lignin content the adhesive strength of the Resin mixture decreases sharply. A phenolic resin that is 10% Contains lignosulfonic acid derivative already shows none satisfactory properties more and is before all relatively 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. This chemically Evenly occurring sulfur-free lignin is in Ketones such as acetone and alcohols such as e.g. B. methanol,  soluble and in this form with a phenolic novolak miscible. A mixture of 1: 1 lignin too Phenol novolak with a solid resin content of approx. 2% (based on the weight of the test rod Quartz sand) a strong drop in the cold bending strength and the heat resistance compared to one Mixture that contains only phenolic resin as a binder. Both strengths decrease with increasing lignin content even more.

Try the properties of Organosolv lignin by upstream reactions with phenol and Improving formaldehyde did nothing noteworthy success. It can be done this way though Resin mixtures are used to produce Pressed and composite panels, as well as for gluing Wood veneers are suitable; quality products, such as high temperature resistant molded materials, refractory Products and especially friction linings can use it however cannot be made because the physical Property profile of the products obtained in generally not enough.

It is therefore an object of the invention To provide binder mixture, the Organosolv lignin in larger quantities than 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 solution to the problem is one Binder mixture, which by homogeneous mixing under the influence of high shear forces from 5 to 60% Lignin or a lignin fraction from the Organosolv process with 40 to 95% of a synthetic resin is obtained. If necessary, this can Binder mixture mixed with a curing agent will. Organosolv lignin fractions are preferred made of coniferous or deciduous woods with medium molecular weights between 600 to 4000, especially with those of 800 to 1500 used. As synthetic resins can Phenol novolaks can be used. This can be used for hardening Resin mixture with hexamethylenetetramine or with reactive Resins such as B. phenol resoles, epoxy resins or nitrogen-containing polymers.

The resin mixtures according to the invention can, after they in a heatable mixer, such as. B. in one Twin screw extruder, trough or bowl kneader, at increased temperature intensely under the influence of high Shear forces have been mixed to produce curable molding compounds, textile fleeces, refractory compounds but can also be used for friction linings.

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.

Depending on the process control, this lignin falls either in a mixture with hemicelluloses and others Degradation products from the wood pulp or as pure Lignin obtained after drying as a powder can be. Lignin of this quality Connections with molecular weights less than 5000 before.

It has now been found that low molecular weight lignin with an average molecular weight of 600 to 4000 as it can be obtained by the Organosolv process, in in a special way under the influence of high shear forces Phenolic novolaks can be mixed, being a Binder is obtained without chemical Implementation for the production of curable molding compounds, Textile fleeces, friction linings and refractory materials can be used.

Lignin fractions with are particularly suitable average molecular weights from 800 to 1500 and one Sintering point from 80 to 120 ° C. These factions can in a manner known per se from the lignin fractions of the Organosolv process are separated or fall into a 2-step process directly in basic, alcoholic solution. These low molecular weight Lignins can be in dissolved form or as dried Powder with a phenolic novolak at elevated temperature mixed under the action of high shear forces and under Addition of a hardener at lower temperatures and if necessary together with additional  Processing aids processed into a binder be a particularly good one after curing Association between the Lignin-phenol novolak binder mixture and the has added fillers. Molded parts with this mixture of binders are produced Surprisingly, 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 equal. Particularly good properties are shown when using the invention Binder mixtures for the production of Refractory compounds because they are insensitive to moisture are, have high shelf life and too high Green stability and surprisingly too high Lead carbon yields.

For the production of the invention Binder mixtures are 5 to 60 wt .-% powdered organosolv lignin and 40 to 95% by weight of a phenolic novolak premixed.

After mixing the raw materials, the obtained Mixture at a temperature of 100 to 200 ° C, especially at 130 to 160 ° C, by exposure to high Homogenized shear forces. This is preferably in known and for such processes Usually used heatable devices, such as e.g. B. in twin screw extruder, trough or Trough kneader or carried out in a co-kneader. The  Temperature is set so that a good one Mixing the individual components together takes place, but at the same time the lignin material partially reacted with the phenolic resin, however neither decomposition of the material used nor the resin mixture cures prematurely.

This work process becomes a homogeneous product get that after cooling to room temperature, Possibly can be powdered dry and that excellent as a binder or binder component for molding compounds, curable molding compounds, refractory Masses, friction materials or textile fleeces are suitable.

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: 0.9 to 1: 0.2 and a melting point of 50 to Can be used at 110 ° C. To work gently, you can Mixtures of low and high melting novolaks Find use.

For further processing, this Binder mixture 4 to 15% 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 additional amounts of 10 to 60 wt .-%. Furthermore can 0.05 to 1.2 wt .-% of a sliding and Release agent, 4 to 6 wt .-% fillers, but also  0 to 20 wt .-% fiber materials, such as. B. glass fibers be 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.

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

example 1

Softwood lignin from the Organosolv process, made with an average molecular weight of 1000 and a sintering point of approx. 105 ° C a phenolic novolak with a melting point of DIN 150 10 082 from 80 to 85 ° C in a ratio of 1: 1 intensive mixed.

0.3% calcium stearate is added to the premix and using on a twin screw extruder high shear forces at 110 to 150 ° C and homogenized granulated to 2 mm after cooling. The granules is finely ground on a baffle plate mill and after grinding with 7% hexamethylenetetramine (very fine, powdery) intimately mixed.  

Example 2

Hardwood lignin made from the Organosolv process with an average molecular weight of 900 and one Sintering point of 110 ° C is with a phenolic novolak a melting point according to DIN 150 10 082 from 75 to 80 ° C intensively mixed in a ratio of 1: 2.

The premix is made up with 0.3% by weight calcium stearate provided on a twin-screw extruder Use of high shear forces at 110 to 1450 C. homogenized and after cooling to 2 mm granulated. The granulate is on a Baffle plate mill finely ground and after grinding with 6.5% by weight hexamethylenetetramine (very fine, powdery) intimately mixed.

Example 3

3 kg of powder resin according to the invention from Example 1 with 2 kg phenol novolak with a melting point of 80 up to 85 ° C according to DIN 150 10 082, 450 g Hexamethylenetetramine, 15 g montan wax, 50 g amide wax and 3.8 kg Soft wood flour mixed intimately and at 100 to 130 ° C given heated rollers.

The mass increases in a rolling time of about 3 minutes compacted 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 are significantly above the scope of the Phenolic resin molding compounds of type 31 according to DIN 7708. With that manufactured molded parts are characterized by good Surface.

Example 4

70 parts by weight of textile fiber mixture with 30 Parts by weight of the powder resin from Example 1 intimately mixed. For the production of nonwoven, the Material subjected to aerodynamic fleece formation and placed on a perforated screen. The so won Unhardened textile fleece is in one Warming cabinet preheated at approx. 120 ° C and then in one Press at 180 ° C for sheets of 250 mm × 250 mm pressed.

The panels obtained in this way are in terms of strength (Load and deflection) and smell with Production board material compared to that unmodified phenolic resin powder resin for Application came.

The comparison of the strength showed no differences.

In the smell test (according to Ford) received the so obtained products according to the invention grades from 1.6 to 2.1,  while lignin-free products scores from 2.4 to 2.8 achieved (the smell quality increases with decreasing Grading).

Example 5

70 parts by weight of textile fiber mixture with 30 Parts by weight of the powder resin from Example 2 intimately mixed. For the production of nonwoven, the Material subjected to aerodynamic fleece formation and placed on a perforated screen. The so won Unhardened textile fleece is in one Warming cabinet preheated at approx. 120 ° C and then in one Press at 180 ° C for sheets of 250 mm × 250 mm pressed.

The panels obtained in this way are in terms of strength (Load and deflection) and smell with product compared onsplatteplatte material in which unmodified Phenolic resin-based powder resin was used.

The comparison of the strength showed no differences.

In the smell test (according to Ford) received the so obtained Products according to the invention scores from 1.6 to 2.0.

Example 6

1.0 kg of powder resin according to the invention from Example 2 is with a mixture of 3 kg steel wool, 1.5 kg Brass chips, 1 kg coke, 0.5 kg graphite,  0.5 kg polyaramid fiber (2 mm), 0.5 kg glass fiber (2 mm), 1.5 kg barium sulfate, 0.3 kg hexamethylenetetramine (finest, powdery) and 0.7 kg magnesium oxide intensely mixed.

The mixture is made in the usual way used by friction linings. The coefficient of friction is determined Test specimens, which take 30 seconds per mm layer thickness 170 ° C pressed and post-cured at 200 ° C for 10 hours was 0.38 to 0.41.

Example 7

9,500 g of a mixture of various magnesites Grain is made with 125 g of powder resin according to the invention from Example 1 and 125 g of powder resin according to the invention from Example 2 and 300 g of a 70% strength aqueous solution Phenol resol (phenol-formaldehyde ratio 1: 1.5) homogeneously mixed.

After pressing into shaped bodies, one results Cold compressive strength of 83 N / mm².

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 they are well transported and in appropriate units in the Steel mill can be installed.

The determined cold bending strength lies with the hardened moldings at approx. 19 N / mm².  

In a parallel test, moldings up to 1000 ° C were annealed and their carbon content determined. The Carbon content was approximately 58% based on the amount of resin used (powder resin plus resin content of Liquid resin).

Claims (15)

1. Binder mixture for the production of molding compounds and moldings made by 5 to 60 % Lignin or lignin fraction from the Organosolv process with 40 to 95% by weight Phenolic novolak under the action of high shear forces homogeneously mixed in a kneader or extruder, pre-reacted and then optionally with a Hardening agents are added. 2. Binder mixture according to claim 1, characterized characterized in that it is obtained from conifers Contains lignin. 3. Binder mixture according to claim 1, characterized characterized in that it is obtained from hardwoods Contains lignin. 4. Binder mixture according to claims 1 to 3, characterized in that for its manufacture Lignin with an average molecular weight of 800 to 4000 is used.   5. binder mixture according to claims 1 to 3, characterized in that for its manufacture Lignin with an average molecular weight of 800 to 1500 and a sintering point of 80 to 120 ° C Is used. 6. Binder mixture according to claims 1 to 5, characterized in that for its hardening Hexamethylenetetramine or reactive resins, such as. .B. Phenolic resoles or epoxy resins can be used. 7. binder mixture according to claims 1 to 5, characterized in that for its hardening Urea or melamine formaldehyde resins be used. 8. A method for producing a binder mixture according to claims 1 to 7, characterized in that

• a. 5 to 60% by weight of lignin or lignin fraction from the Organosolv process are homogeneously mixed with 40 to 95% by weight of a phenolic resin at a temperature of 100 to 200 ° C by the action of high shear forces and
• b. the cooled, possibly dried, homogeneous mixture is ground into granules with a grain size of less than 2 mm.

9. The method according to claim 8 for producing a Binder mixture, characterized in that mixing takes place at 130 to 160 ° C. 10. Production of a binder mixture according to one Process according to claims 8 and 9, characterized characterized in that a mixture of phenolic resin low and high melting phenolic novolaks be used. 11. Use of a binder mixture according to the Claims 1 to 10 for the production of curable Molding compounds. 12. Use of a binder mixture according to the Claims 1 to 10 for the production of Textile fleeces. 13. Use of a binder mixture according to Claims 1 to 10 for the production of Refractory materials. 14. Use of a binder mixture according to the Claims 1 to 10 for the production of Friction linings. 15. Use of a binder mixture according to Claims 1 to 10 for the production of Carbon and graphite materials.