CS254154B1 - Organic vulcanization accelerators - Google Patents

Abstract

The elimination of emissions of harmful substances, especially carbon disulfide and carbonyl sulfide, during the processing of raw rubber mixtures is achieved by using as organic vulcanization accelerators mixtures of normal and basic zinc salts of O,O'-diesters of thionethiolphosphoric acids, especially O-2-ethylhexyl-O'-n-butyl ester of thionethiolphosphoric acid, together with thiazole and/or dithiocarbamate compounds, in a vulcanization system, usually containing sulfur, zinc oxide and stearic acid. The solution will be used in rubber technology, especially in the production of so-called technical rubber.

Description

The invention relates to organic accelerators for the vulcanization of rubber mixtures which do not release substances harmful to health.

Optimal use of the properties of individual rubbers is represented by rubber mixtures based on their mutual combinations, often combinations of two different types. The resulting mixtures and vulcanizates combine the excellent properties of the starting elastomers. Technically, rubber mixtures based on EPDM rubbers with other diene rubbers, especially butadiene styrene, butadiene, butadiene acrylonitrile, butyl rubbers and polyisoprene rubbers, both natural and synthetic, and others, are of particular importance.

The terpolymer of ethylene, propylene and another suitably selected diene, e.g. dicyclopentadiene, hexadiene, ethylidenenorboron, etc., briefly referred to as EPDM rubber, is characterized by relatively high thermo-oxidative resistance, including resistance to ozone, due to the absence of unsaturated double bonds in the main chain. These properties predetermine it for the production of high-performance vulcanizers from the field of so-called technical rubber, such as sealing profiles, roofing and insulating foils, hoses, cables and insulated wires, etc., which maintain their excellent physico-mechanical properties for a long time during exploitation.

However, unsaturated double bonds, as a result of the copolymerization of ethylene and propylene with a non-conjugated diene, remain in the side pendant groups, distributed along the main chain, and allow EPDM rubbers and their combinations with other rubbers to be vulcanized using elemental sulfur and/or suitable sulfur donors, e.g. TMTD, DTDM, etc.

Diene rubbers with higher and higher unsaturation compared to EPDM rubbers contain double bonds in the main chain; they vulcanize faster than EPDM, but are less resistant to degradation effects, especially oxidation.

Due to the relatively low unsaturation, sulfur vulcanization of EPDM rubber blends with diene rubbers activated with ZnO and stearic acid requires the presence of organic accelerators.

Conventional sulfur vulcanization systems, the main components of which are thiazole accelerators (most often 2-mercaptobenzothiazole (2-MBT), benzothiazyl disulfide or Znsof 2-MBT, or sulfenamide derivatives, N-cyclohexylbenzothiazyl sulfenamide or N-tert.butylbenzothiazyl sulfenamide) activated by thiuram sulfides (most often tetramethylthiuram disulfide or tetraethylthiuram disulfide) and/or dithiocarbamates (most often Zn-salt of dimethyl, diethyl, or ethylphenyldithiocarbamic acid), provide the desired properties to raw mixtures and also to the respective vulcanizates, however, during the preparation and processing of the mixture, i.e. during mixing, extrusion and especially vulcanization, they release relatively high concentrations of chemical pollutants that worsen the working environment of rubber plants. The exhalates mainly contain carbon disulfide, carbonyl sulfide, etc.

In addition, many of the above-mentioned commonly used organic accelerators, added to the mixture or in mixtures formed in situ, above certain concentrations that exceed their solubility in the mixture or vulcanizate at a given temperature, bloom to the surface and, in particular, visually degrade the surface of the respective vulcanizate.

These disadvantages are practically eliminated according to the invention by using a mixture of normal and basic zinc salts of O,O'-diesters of thionethiolphosphoric acid, especially O-2-ethylhexyl-O'-n-butyl esters of thionethiolphosphoric acid, which have so far been used as additives to motor lubricating oils, together with thiazole and dithiocarbamate vulcanization accelerators, in a sulfur vulcanization system for mixtures based on a combination of ethylene rubbers with EPDM rubbers, which does not release substances harmful to health.

The invention is based on the finding that if a known mixture based on a combination of diene rubbers with EPDM rubbers is used as organic accelerators for vulcanization of Zn salts of O,O'-diesters of thionethiolphosphoric acid in an amount of 0.5-4.0 parts together with thialose compounds (0.5-3.0 parts) and/or dithiocarbamate compounds (0-2.0 parts) in vulcanization systems that usually contain sulfur and/or sulfur donor, zinc oxide and stearic acid, there is practically no release of substances harmful to health. The reason is the appropriate structure of the zinc salt of diesters of thionethiolphosphoric acids present. The parts are parts by weight based on 100 parts by weight of rubber.

The advantages of using the accelerator mixture according to the invention are illustrated by the following examples: Example 1

Mixture composition: parts by weight.

SBR 1702 100

EPDM (ENB-type, 24% oil vapor) 35

ZnO 5

Stearic acid 2

Paraffin 9

Phenylbetanaphthylamine 2

Carbon black, FEF, N-539 145

Aromatic oil 45

Sulfur 2.00

Benzthiazyl disulfide 1.25

Zinc diethyldithiocarbamate 0.25

Zinc 0-2-ethylhexyl-0'-n-butylthionate phosphate 1.25 .254154 is mixed in two stages in a Banbury mixer with a volume of 170 1. The mixture is shaped into endless strips and processed by extrusion and continuous vulcanization on lines with microwave heating or using a shear head. The vulcanizate has the following properties:

Hardness 70 Sh A Tensile strength 10 MPa Complaint 250% Permanent compression set at 70 °C after 144 h 15% Example 2 Composition mixture: parts wt. Styrene butadiene rubber 25.00 Polyisoprene rubber 44.00 Ethylene propylene rubber, 24% oil vapor 38.00 Fact 10.00 Zinc oxide 5.00 Stearic acid 2.00 Paraffin 4.00 Phenylbetanaphthylamine 2.00 Carbon, FEF, N-539 80.00

Floated kaolin 56.00 Aromatic oil 54.00 Sulfur 1.20 Tetramethylthiuram sulfide 0.30 Benzthiazyl disulfide 1.50 Triethanolamine 0.30 O-2-ethylhexyl-O'-n-butylthiothiol- zinc phosphate 3.00

is mixed in two stages in a 147 liter high-pressure low-speed kneader. Sulfur, tetramethylthiuram disulfide, is added to the kneader in the second stage. After being discharged from the kneader, the mixture is processed into endless strips, in which it is further processed on continuous vulcanization lines. Sealing profiles and frames are produced from the mixture. The mixture has the following properties after vulcanization:

Hardness 60 Sh A Tensile strength 6 MPa Complaint 450 % Permanent compression set at 70 °C after 144 h 25 %

SUBJECT

Claims (1)

5 6 is mixed two-stage on a Banbury type kneader with a volume of 170 l. The blend and forms the endless strip doforms and is processed by extrusion and continuous vulcanization with alebos microwave and shear heads. The vulcanizate has the following characteristics: Hardness 70 Sh A Tensile strength 10 MPa Elongation 250% Permanent deformation at 70 ° C after 144 h 15% Example 2 Composition composition: parts wt. Styrene Butadiene Rubber 25.00 Polyisoprene Rubber 44.00 Ethylene Propylene Rubber, 24% Vapor. oil 38,00 Faktis 10,00 Zinc oxide 5,00 Stearic acid 2,00 Paraffin 4,00 Phenylbeta-naphthylamine 2,00 Carbon black, FEF, N-539 80,00 Kaolin float 56,00 Aromatic oil 54,00 Sulfur 1,20 Tetramethylthiuram sulfide 0.30 Benzothiazyl disulfide 1.50 Triethanolamine 0.30 Zinc O-2-ethylhexyl-O'-n-butylthionothioate 3.00 is stirred in a 147 liter high pressure low speed kneader for two stages. Sulfur, tetramethylthiuramide disulfide, is added to the second stage. The mixture is discharged from the kneader to form non-strips, in which the vulcanization is continued on the lines. Sealing profiles and frames are produced from the blend. The composition has the following properties after vulcanization: Hardness 60 Sh A Tensile strength 6 MPa Elongation 450% Permanent compression at 70 ° C for 144 h 25% SUBSTANCE Use of a mixture of normal and basic O, O'-diester thionothio-phosphate salts acids in an amount of 0.5 to 4.0 parts, in particular O-2-ethylhexyl-O'-n-butyl ester thionothiophosphoric acid together with thiazole compounds in amounts of 0.5 to 3% and / or dithiocarbamate compounds in our up to 2.0 parts by weight, as organic vulcanization accelerators in a sulfur vulcanization system for blends of base and ethylene propylene rubbers, parts being parts by weight of 100 parts by weight of rubber.