DE1165844B - Process for the manufacture of rubber products mixed with lignin products as reinforcing fillers - Google Patents

Description

Process for the manufacture of using lignin products as a reinforcing filler mixed rubber products It is known for the production of lignin-reinforced Rubber vulcanizates Lignin in alkaline solution with aqueous rubber dispersions to be mixed and precipitated together with the rubber using diluted acids. The washed out and dried coagulate was then mixed with the usual additives mixed on the rubber mixing roller and further processed in the usual way and vulcanized.

Lignin or its metal compounds have also been found in hydrated, d. H. the solid rubber when swollen in water or aqueous solutions mixed on the mixing roller, preferably so that first a mixture with a high Lignin component was produced and the dried mixture with further rubber components and the usual additives and processed in the usual way and was vulcanized.

For the processes described above, primarily »alkali lignin« was used. used, which in the alkaline wood digestion with the so-called black liquor accrues. In contrast, sulphite lignin, which is used in acid sulphite digestion of the wood so-called sulphite waste liquor is contained, so far little and used with little success.

In contrast to alkali lignin, sulfite lignin is in its original state Condition could not be precipitated with dilute acids and could therefore not easily be can be used for coagulation together with rubber dispersions.

It was therefore used for the joint coagulation of sulfite lignin with rubber milk, part of the sulfonic acid groups through controlled hydrolysis the sulfite lignin is split off and the lignin is thereby made acidic.

As a basic rubber material for lignin fillers one has so far besides Natural rubber only the synthetic rubber types based on butadiene-styrene, Butadiene-acrylonitrile and chlorobutadiene are used.

It has now been found that the binding of lignin products, in particular of sulfite lignin on rubber and thus the rubber-reinforcing effect can be significantly improved if the lignin products in copolymers, graft or block polymers are mixed in by polymerizing them containing tertiary amino groups Vinyl compounds in rubber have been obtained.

These are rubber polymers for mixing according to the invention particularly suitable in the vinyl containing tertiary amino groups links Vinyl pyridine, 2-methyl-5-vinyl pyridine and 2-vinyl-5-ethyl pyridine, but also vinyl quinoline and vinyl pyrrolidine and alkyl derivatives thereof, N-vinyl pyrrolidone, acrylic acid or methacrylic acid esters of alcohols bearing tertiary amino groups have been.

It is best to suggest those for mixing with lignin products Copolymers in dispersion form with the aqueous solutions or dispersions of the Lignin products mixed and coagulated.

Vulcanizing agents and other rubber auxiliaries are known in the art Way added to the aqueous lignin-containing polymer dispersions or the dry polymer-lignin mixtures incorporated on the rubber mixing roller.

When using the method of the invention, lignin can come in handy in any form and quantity, be it as alkali lignin, be it as sulfite lignin or as modified products thereof.

The purer forms, i.e. H. Lignin products that are as free from reducing sugars and hemicelluloses as well as ash components can be used directly be mixed into the dry polymer on the mixing roller. Because of the better ones However, if possible, the powder should be distributed in water, aqueous solutions or be swollen in a plasticizer.

A particular advantage of the method according to the invention is that that one also heavily contaminated lignin, such as. B. sulphite waste liquor, in its original State or as> thick liquor «. Due to the content of the rubber molecules of tertiary amino groups is, on the one hand, the mixture from the rubber dispersion and the lignin solution so stabilized that the rubber dispersion is not already at Mixing in the sulphite liquor coagulates prematurely, on the other hand the in the Sulphite liquor contained Lignosulfonic acids selectively on the rubber bound. The precipitation is preferably carried out in an acidic medium. The pH of the precipitation bath should be below 5 if possible. To achieve easily filterable Coagulate and a clear serum is recommended to coagulate in the heat and possibly brief boiling of the rubber-lignin coagulate after the precipitation.

Depending on the tertiary nitrogen atom content of the rubber polymer on the one hand, the origin and the degree of condensation of the lignin and its content of reactive hydroxyl and sulfonic acid groups on the other hand are in the Coagulation of the rubber polymer with certain amounts of lignin constituents bound.

When using 2-methyl-5-vinylpyridine as a copolymerization component or nitrogen carriers in the rubber polymer and spruce wood sulphite liquor the binding capacity for lignin constituents about 250 g per mole of tertiary nitrogen.

For optimal utilization of the tertiary nitrogen atoms in the rubber polymer should therefore be used in the rubber-lignin dispersion provided for joint coagulation not less than 250 g of lignin constituents per 1 mole of tertiary nitrogen.

When using small amounts of plasticizer - less than 5 parts per 100 parts of dry rubber substance - and processing on the mixing roller should the content of tertiary nitrogen atoms is 2 percent by weight of the dry polymer substance and accordingly the lignin content is not significant to 35% by weight of the final product must be exceeded, otherwise the mixture will be difficult to process on the roller leaves.

Larger amounts of plasticizer are beneficial at the same time Coagulation added or, if lignin powders are used, used to swell them.

Plasticizers that can be used are all those commonly used in rubber processing Products are used.

However, plasticizers with polar ones are particularly suitable Groups.

Due to the polar character of those to be used according to the invention Polymers and their mixtures with lignin are those with other polar rubber types, such as B. butadiene acrylonitrile rubber and chlorobutadiene, very well tolerated.

The deformation and vulcanization of the proposed according to the invention Process produced rubber-lignin mixtures or the production of rubber articles it is made in the manner customary for solid rubber mixtures or aqueous dispersions Way. Since lignin-rubber mixtures generally vulcanize somewhat more slowly, it is advisable to use more or more effective accelerators. As the mixes, especially when using sulphite lignin, the can be somewhat acidic Mixture advantageous basic substances such. B. magnesium oxide, triethanolamine or hexamethylenetetramine is added.

The invention is explained in more detail using the following examples.

Example 1 75 parts by weight of a 20% strength aqueous dispersion of a Graft polymer made from 600/0 natural rubber milk and 2-methyl-5-vinylpyridine (85:15, based on dry weight) were mixed with 25 parts by weight of spruce wood suifitablauge mixed homogeneously.

100 parts by weight of the rubber-lignin mixture were added to about Heated to 70 C and then treated with 100 parts by weight of 5% acetic acid while stirring and then briefly boiled. The coagulate obtained in this way was washed free of acid and dried at 40 ° C. The dried coagulate gave a quantitative ratio of 30 parts by weight of lignin per 100 parts by weight of graft polymer.

The following vulcanization additives were then mixed in on a mixing roller: parts by weight of lignin + graft polymer (coagulate) 130.0 stearic acid. . . . . . ............. 1.0 triethanolamine .................. 3.0 sulfur ........... ........... 2.5 zinc oxide (red seal) 5, 0 dibenzothiazyl disulfide ......... 1.5 diphenylguanidine ............... 0.5 This mixture was vulcanized in a mold under the heating press for 20 minutes at 132 "C 7u of a 6 mm thick rubber sheet. The following values were obtained when testing the vulcanizate: tensile strength, kg / cm2 ......... 190 Elongation at break,% ................. 362 Module at 300% elongation 154 Hardness, ° Shore .................. 66 Impact elasticity,% .............. 55.5 notch toughness, kg / cm ........... 12 Example 2 The cocoagulate made from sulfite as in Example 1 Lignin and the graft polymer containing 2-methyl-5-vinylpyridine were not dried in this case, but finely dispersed again after thorough washing by vigorous stirring of pre-vulcanized nature rubber in relation to wet and dry Lignin + graft polymer (Dispersion), parts by weight. . . . . 715 100 Pre-vulcanized natural rubber milk, parts by weight. . . . . . . . . . . 165 100 mixed and produced from it by pouring the mixture onto a glass plate and letting it dry, a 0.8 mm thick film.

Claims (3)

During the test, this gave the following values: tensile strength, kg / cm2 ............ 164 Elongation at break,% ................. 440 at 200 ° / o elongation ..... 63 Module at 3000 / o elongation .............. 95 at 400% elongation ............. 150 claims : 1. Process for making blended with lignin products as reinforcing filler Rubber products, in that the lignin products are mixed into those copolymers, graft or block polymers that are polymerized by of tertiary Amino group-containing vinyl compounds in rubber have been received. 2. The method according to claim 1, characterized in that graft polymers are used in their production vinyl pyridine or its methyl or ethyl derivatives as tertiary amino group-containing vinyl compounds have been used. 3. The method according to claims 1 and 2, characterized in that that the mixing takes place in that the sulphite liquor with the tertiary amino groups containing rubber is precipitated together in an aqueous dispersion. Documents considered: British Patent Specification No. 752780, 778 102, 793 149; French Patent No. 1,154,139; Rubber and Gummi (1956), 9, 8, WT 205 -Wo 206; Rubber and Plastics Age (London, 1957,) 38, 6, 502/503.