DE4331656C2 - Binder mixture - Google Patents

Description

The invention relates to a binder mixture for works fabrics based on wood and / or cellulose, used as contains essential component lignin.

Lignins are by-products of the pulp made of wood and when saccharifying wood. On due to their compulsive seizure from natural, after growing raw materials and their polymeric structure make an interesting building block variant for Po polymers and binders. There are a variety of Try lignin as an inexpensive polymeric building block use and thus dispose of, such. B. by a construction of lignin in phenol-formaldehyde condensation pro products, by condensation with formaldehyde, by combination nation with isocyanates or through diverse chemical Modifications (see Encyclopedia of Polymer Science and Engineering, 2nd edition, vol. 8 (1987) pages 795 to 852).

So z. B. according to DD 134 363 sulfite waste liquor or therefrom lignin sulfonate produced together with formaldehyde condensed. A mixed condensate is obtained, in the phenol is partially replaced by lignin sulfonate. Wood materials made with it are only conditional weatherproof.

According to WO92 / 18552, the combination known per se of phenol resoles with lignin improved in that the low molecular weight lignin from the Organosolv process ren is used. This lignin can additionally be phenolated or methylolated. Nevertheless, they are with these binders achieved strengths in particular re after water storage not satisfactory. That is, the large-scale utilization of the solutions found failed due to the low reactivity of the  Lignins that either receive low strengths products or too long curing times.

It is therefore an object of the invention to provide a further possibility possibility of using lignin as a building block in bandages to provide means in which these binders Sufficient storage stability and room temperature a short curing time at curing temperature gene and in which the end products obtained have good strength have values.

The task is solved by a binding agent mix according to claims 1 to 4 and a method its manufacture according to claims 5 to 6. Das Binder mixture is suitable as a binder for Materials based on wood and / or cellulose, ins especially for the production of chipboard and textile read according to claims 7 to 9 and as an amplifier resin for rubber and rubber mixtures according to claim 10th

It has been found that reactivity and therefore the economic applicability of lignin in simple cher way can be increased by the fact that lignin by Be methylolated with formaldehyde and so with Lignin modified with methylol groups with a phenol Resol and a di- or polyisocyanate combined is set. With such a binding agent mix consisting of 45 to 85 wt .-% methylolated Lignin, 5 to 25% by weight of phenol resole, 10 to 30% by weight of one Di- or polyisocyanate and 0 to 15 wt .-% accelerator means are z. B. with chipboard curing times achieved as previously used for this Urea resins were reserved. In contrast to with  Urea resin bound boards are however used by us dung of the binder mixture according to the invention Strength of the plates after water storage essential improved, so that a classification accordingly chipboard in group V 100 (water-resistant) is appropriate.

The binder mixture is in the simplest case Mixture of the three in solid powdered form lying components: modified with methylol groups tes lignin, resol and di- or polyisocyanate.

A major simplification is, however, the modified lignin and the resol not as a solid to isolate the fabric, position resulting aqueous, alkaline solutions with each other and with a liquid di or polyiso cyanate and, if necessary, a hardening accelerator and the binder mixture within its processing time of up to 7 hours (at room temperature) to process.

Surprisingly, no demix occurs during this time and a reaction of the isocyanate groups with Water is negligible. Even with the Aus hardening of the binder mixture at a higher temperature preferably the reaction of the binder components takes place ten with each other, so the presence of water does not bother.

Modified with methylol groups, so-called methylolated, Lignin is obtained through the implementation known per se lignin with formaldehyde in alkaline aqueous  Solution, the pH in the range of 8 to 14, be is preferably in the range from 9 to 11.

Any lignin can be used as lignin, regardless of the raw material source and the manufacturing method. As is known, different lignins different molecular sizes and reactivities ha ben, this is also from the different methylo lignins to be expected. So z. B. methylo bagasse lignin or methylolated lignin the Organosolv process is much more reactive as methylolated kraft lignin.

Lignin is a polymeric product with an average molecular weight of 5,000 to 10,000. A molar amount is therefore not appropriate. However, since lignin generally consists of phenylpropane units with occasional methoxy groups, structural units of the general formula C ₉ H ₇ O ₂ . H ₂ O. Define (OCH ₃ ) _0.94 . The ratio of formaldehyde to lignin used is therefore based on this structural unit. It is (structural unit lignin: mol-formaldehyde) in the range from 1: 0.7 to 1: 1.5, the reactivity of the lignin modified in this way generally increasing with increasing degree of methylolation.

The preparation of the alkaline reaction mixture Lignin and formaldehyde take place at elevated temperature, preferably at a temperature in the range from 50 to 90 ° C. The reaction time depends on the pH value the solution and the reactivity of the Li used gnins. It is in the range of 3 to 10 hours. The  The reaction product is a methylolated lignin in alkane aqueous solution. It can e.g. B. by spray drying obtained in the form of a solid powder and with solid resole and solid isocyanate to a powder resin be mixed. But Re is preferred action solution not worked up, but after the Cooling with an aqueous resole solution, preferably with a cooled, not further processed reaction onsolution from the alkaline condensation of phenol with formaldehyde and with a di- or polyisocyanate mixed.

Decisive for the appropriate mixing ratio are the solutions of methylolated lignin in the solutions and resol, d. that is, it will be 45 to 85 parts by weight modified reaction solution containing lignin the methylolation reaction with a 5 to 25 parts by weight of resol containing reaction solution the resol condensation reaction is mixed. Subsequently or at the same time 10 up to 30 parts by weight of a liquid di- or polyisocya nats and possibly 1 to 15 parts by weight of an accelerator, preferably mixed in an ester.

The resols used according to the invention are those which by condensing phenol with formaldehyde under catalytic effect of alkali or alkaline earth hydro xiden were made, the water resistance the hardened binders and the ones with them presented materials is improved if both the Resole as well as the methylolated lignins under kata lytic effects of alkaline earth hydroxides instead of Alkali hydroxides were prepared.  

As di- and polyisocyanates for solid binders tel-mixtures solid at room temperature and for liquid Binder mixtures liquid isocyanate compounds set. Examples of solid isocyanates are Diisocya natonaphthalene, 4,4 ', 4 "-triisocyanato-triphenylmethane or tris (4-isocyanatophenyl) thiophosphate. Examples for liquid isocyanates are isophorone diisocyanate, To luole diisocyanate or hexamethylene diisocyanate. Prefers the isomer mixture of diisocyanato is used diphenylmethyans (MDI), which is both adequate Processing time as well as quick curing time of the binder mixture according to the invention made possible light.

Although the binder mixture according to the invention at he high temperature (120 to 200 ° C) even without accelerator niger has a good curing speed often, especially when using less reactive Kraft lignin or to achieve particularly short press and curing times, an additional acceleration desirable.

It has been found that such an acceleration in simply by adding 1 to 1.5% by weight of one Esters can be reached. All esters can be used aliphatic mono-, di- or polycarboxylic acids with 1 up to 6 carbon atoms with mono- or polyhydric alcohols 1 to 5 carbon atoms, but also lactones.

Examples are esters of ants, vinegars, propions, Oxal, gamma chlorine butter, milk, wine or epsilon Oxycaproic acid with alcohols such as methanol, ethanol, Propanol, glycol or glycerin.  

The preferred esters are gamma-butyrolac clay, triacetin and propylene carbonate.

EXAMPLES example 1

30 parts by weight of bagasse lignin (powder with 95% solids substance) with stirring to 60 parts by weight of water given and slowly with 8 parts by weight of 30% sodium hydroxide lye mixed. A pH of 13 is established. This solution is heated to 60 ° C and with 3.5 parts by weight of paraformaldehyde (96%) added (mo ratio of structural unit lignin: formaldehyde 1: 0.71).

The solution is stirred for 8 hours at 60 ° C and then cooled down.

Example 2

Analog to Example 1, Kraft lignin is methylolated.

Example 3

94 parts by weight of phenol are mixed with stirring 40 parts by weight of a methanol-water mixture (20/80) and 55 parts by weight of parformaldehyde (96%) mixed. The mixture is heated to the boiling point. In four 15 minute intervals will total 20 parts by weight 30% sodium hydroxide solution added, the reaction mixture  held under reflux for a further 60 minutes and then cooled down.

Example 4

The aqueous solution of the methylolated lignin from Bei game 1 (MBL) and from example 2 (MKL) is resolved with Solution from Example 3 (PF) and diisocyanato-diphenylme than (mixture of isomers) (MDI) mixed. The time to Processing the mixture at room temperature more than 5 hours. The mixtures have a pH from 12 to 12.5.

The mixtures are mixed with wood chips (pinus radiata) and pressed at 190 ° C and a pressure of 2.3 N / mm ² to chipboard of dimensions 400 × 350 × 12 mm.

The density and the transverse tensile strength are determined of plates a. dry and b. after water storage (2 hours in boiling water, then 16 hours at 105 ° C dried), varying the mixture ratio Ratios of the binder component, the binder quantity and the pressing time.

The values obtained can be found in the following days bark 1 to 3.  

Table 1

Different mixing ratios of the binder components (binder content 11%, pressing time 7.5 minutes at 190 ° C)

Table 2

Different binder content (mixing ratio MBL / PF / MDI = 46/24/30, pressing time 7.5 minutes at 190 ° C)

a. methylolated bagasse lignin

b. methylolated kraft lignin (MKL / PF / MDI = 46/24/30)

Table 3

Different pressing times (binder content: 11%, MBL / PF / MDI ratio = 46/24/30)

a. methylolated bagasse lignin

b. methylolated kraft lignin (MKL / PF / MDI = 46/24/30)

Example 5

Chipboard is produced analogously to Example 4 and tested. However, methylolated kraft lignin becomes a set and the hardening of the binder mixture (pH 10.5 to 11) by adding ester nigt.

Table 4 shows the values obtained with different proportions of the individual binder components: (pressing time 7.5 minutes at 190 ° C.):

Claims (10)

1. Binder mixture consisting of
45 to 85% by weight of lignin modified with methylol groups
5 to 25 wt .-% resole, produced by alkaline-catalyzed condensation of phenol with formaldehyde
10 to 30 wt .-% of a di- or polyisocyanate. 2. Binder mixture according to claim 1, characterized ge indicates that the modifi with methylol groups graced lignin and the resol in aqueous solution available. 3. Binder mixture according to claims 1 and 2, characterized in that it is 1 to 15 wt .-% Contains esters as accelerators. 4. Binder mixture according to claim 3, characterized ge indicates that the ester is triacetin.   5. Process for the preparation of binder mixture according to claims 1 to 4, characterized in net that 45 to 85 wt .-% methylolierter lignin, 10 up to 25% by weight of resol, 10 to 30% by weight of a di- or polyisocyanate and optionally 1 to 15 % By weight of esters are mixed together. 6. Process for the preparation of binder mixture according to claims 1 to 4, characterized in net that lignin and formaldehyde in proportion (Structural unit lignin: mol aldehyde) of 1: 0.7 to 1: 1.5 in aqueous alkaline solution a pH in the range of 9 to 14 several For hours at temperatures in the range of 50 be treated up to 90 ° C that after cooling this reaction solution 45 to Containing 85 parts by weight of modified lignin Reaction solution with a 5 to 25 parts by weight of Re sol-containing aqueous alkaline resole solution and with 10 to 30 parts by weight of a liquid Di- or polyisocyanate and if necessary with 1 to 15 Parts by weight of an ester are mixed. 7. Use of the binder mixture according to the An claims 1 to 4 as binders for materials Base of wood and / or cellulose. 8. Use of the binder mixture according to the An Proverbs 1 to 4 for the production of chipboard. 9. Use of the binder mixture according to the An Proverbs 1 to 4 for the production of textile fleece. 10. Use of the binder mixture according to the An  sayings 1 to 4 as reinforcing resin for rubber and Rubber compounds.