FR2680795A1 - PROCESS FOR PRODUCING MOLDED MASSES LIABLE TO BE VULCANIZED AND MASSES MOLDED THUS PRODUCED - Google Patents

Abstract

a) Process for the manufacture of moldings capable of being vulcanized and molding compounds thus produced. b) The process is characterized in that simultaneously using 3-thiocyanotopropyltrialkoxysilanes of general formula (CF DRAWING IN BOPI) in which R represents an alkyl of 1 to 8 C atoms, it is possible to reduce at least up to half the amount of accelerators of the thiuram and / or dithiocarbamate class, relative to the amount initially used in the vulcanizable molding mass free of organosilicon compounds.

Description

Process for producing molded masses which can be

  The invention relates to a process for the production of vulcanizable moldable masses and the molding compositions produced thereby.The problem of the emission of volatile carcinogenic N-nitrosamines during processing, Vulcanisation and storage of rubber products10 has been a growing concern for the rubber processing industry in recent years. The first legal regulations, such as the "Technical Guidelines for Dangerous Substances" (TRGS 552) for the Federal Republic of Germany Therefore place upper limits on volatile N-nitrosamine levels in the workplace air and, if these limits are exceeded, provide for significant restrictions in the production process of a company. rubber processing industry has been working diligently to replace in its rubber mixes n-nitrosamines and where it is not possible, at least to reduce them quantitatively.25 As has been learned from various publications 1) and 2) nitrosamines are formed under the effect of temperatures which are necessary for the composition, processing and vulcanization of rubber mixtures, by decomposition of components of the mixture yielding in particular secondary amines and by reaction of these amines with

NO, ubiquitous in nature.

  1) Schuster R, Nabholz F, M Gm Under, "Rubber, vulcanized rubber, synthetic materials 2" (1990) 95; 2) W Hoffmann: About the production problem

  of rubber articles free of N-nitrosamine.

  Presentation at the regional group DKG

  from South and South West Germany, April 1990.

  Vulcanization accelerators currently used mainly in the rubber industry, the class of Fulfenamides, thiurams, dithiocarbonates are one of the sources

main amines.

  The efforts of the rubber-processing industry are therefore the result of the need to exchange these toxic accelerators, as nitrosamine trainers, against non-toxic compounds, or at least to reduce their quantity without having to undergo major modifications in

the technical aspect of rubber.

  The object of the invention is a process for the production of vulcanizable molded bodies, consisting of one or more natural or synthetic rubbers, or synthetic materials, which are vulcanized with sulfur or sulfur and accelerators, fillers and other usual components, using at least one accelerator, which belongs to the class of

  thiurams and / or dithiocarbonates, which are

  in that by simultaneously using 3-

  thiocyanotopropyltrialkoxysilanes of the general formula (RO) 3 Si (CH 2) 3 SCN (I). in which R represents an alkyl of 1 to 8 C atoms, it is possible to reduce by at least half the amount of thiuram and / or dithiocarbonate accelerators, as compared with the amount initially used in the mass of molding

  vulcanizable free of organosilicon compounds.

  The subject of the patent application includes

  also the vulcanizates thus produced.

  Accelerators include:

  Tetramethylthiuramedisulfide (TMTD).

  Tetramethylthiuramemonosulfide (TMTM).

  Zinc N-dimethyldithiocarbamate (MDMC).

  N-diethyldithiocarbamate zinc (ZDEC).

  Zinc N-ethylphenyl dithiocarbamate (ZEPC).

  They are used according to the state of the art in amounts of 0.2 to 10 phr (parts per cent

parts of rubber).

  The decrease is preferably 20 to% of the initial amount, in some cases

  it is even 100% (see Example 2).

  It turned out that one succeeds according to the invention.

  to reduce the amount of accelerators involved, while there is no need to suffer technical losses from the usual values. The manufacture of molded masses and their

  vulcanization is done according to the known method.

  Other components are also known

  such as plasticizers, stabilizers, activator

  pigments, pigments, anti-aging protectors and

processing aids.

  The molding compositions generally contain the known silicate clear fillers (for example clays, kaolin, precipitated and pyrogenic silicas, silicates, etc.) with BET surfaces of between 1 and 1000 m 2 / g, preferably 5 to 300 m 2 / g. with the hydroxyl groups from which the groups

  trialkoxysilyl compounds of the invention react

  by releasing an alcohol, which leads to a chemical bond between the filler and the silane But known carbon blacks are also used as

loads.

  The thiocyanatesilane according to formula (I) is added to the vulcanizable molding compound, generally in amounts of 0.1 to 20 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts of rubber or synthetic material,

  directly in form already linked to the load.

  In addition to the decrease obtained according

  the amount of accelerator, the use of the organosilicon compound of formula (I) also leads to a decrease in the viscosity of the moldable masses which can be vulcanized and thus to a

  better aptitude for processing.

  Suitable rubbers and plastics for the process of the invention are the low-double-bonded rubbers such as EPDM and

EVA, but also the NBR, NR and SBR.

  The examples below demonstrate the advantages of the compounds of the invention over the state of the art and show that it is possible to largely dispense with toxic accelerators forming nitrosamines, while retaining at least

the usual state of the art.

  Test Standards for Evaluation Test Method Unit Mooney Viscosity Tensile Strength Tensile Strength Shore Shore Compression Set

DIN 53523/524

DIN 53504

DIN 53504

DIN 53505

ASTM D 395

  In the examples of use, the following names and abbreviations, meaning is given here: Keltan 578 N 765 N 660 Ultrasil VN 3 Suprex Clay Chalk Omya Sunpar 150 Si 264 DEG

CBS

  TMTD Rhenocure CUT ZDBC EPDM Company DSM Black Furnace with a surface area of 34 m 2 / g Furnace black with a surface of 36 m 2 / g precipitated silica with a BET surface of 175 m 2 / g Sodium silicate Calcium carbonate Plasticizer paraffinic 3-thiocyanatopropyltriethoxysilane Diethylene glycol Benzothiazyl-2-cyclohexylsulfenamide Tetramethylthiuramidesulfide Copper dialkyldithiophosphate Zinc dibutyldithiocarbamate M Pa M Pa M Pa Example 1: Decrease of TMTD using Si 264 in an EPDM cable jacket mix

1 2

  Keltan 578 100 100 Ultrasil VN 3 25 25 Chalk Omya 50 50 Suprex Clay 125 125 Zn O RS 5 5 Stearic acid 2 2 Sunpar 150 30 30

DEG 2 2

If 264 2

CBS 2 2

TMTD 1 0.5

  Rhenocure CUT 2.5 2.5 Sulfur 1.5 1.5 Rheometer: 160 C D-D (Nm) 10.63 11.27 max min t 90% t 1% 4.0 3.3 Mooney Viscosity

ML 4 (1000 C) (ME) 78 58

  Vulcanization data: 1600 C, t 95% Tensile strength M Pa 10.3 11.1 Module 300% M Pa 3.2 6.0 Hardness Shore 74 78 Compression Set 22 h / 70 C% 26.3 19, 4 70 h / 1000 C% 73.2 67.5 The example shows that, thanks to the Si 264 (mixture n 2), in spite of a 50% reduction of the quantity of thiuram one obtains at least the state of the

  technical, or even better in part.

  Example 2: Replacement of TMTD by use of Si 264 in a coating of

EPDM hydraulic hose.

1 2

Keltan 578 100 100

N 765 75 75

N 660 100 100

  Suprex Clay 90 90 Zn O RS 5 5 Stearic acid 1 1 Sunpar 150 100 100 Si 264 1

MBT 1.5 1.5

ZDBC 0.8 0.8

TMTD 0.7 -

  Rhenocure CUT 0.7 0.7 Sulfur 4 4 Rheometer: 160 CD mx-D min (Nm) 9.93 13.05 max min Vulcanization data: 1600 C, t 95% Tensile strength M Pa 10.1 10 , 8 Module 100% M Pa 7.5 9.6 Shore Hardness 86 86 Oil Storage ASTM No. 2 (70 h / 1600 C) Tensile Strength M Pa 3.4 4.3 Module 100% M Pa 2 4.3 Increasing elongation 110 110 In Example 2, using Si 264, the TMTD can be completely abandoned without decreasing

  characteristics of the vulcanizate.

Yr 2680795

Claims (1)

R E V E N D I C A T IONS   1) Process for the production of vulcanizable molded compositions consisting of one or more natural or synthetic rubbers or synthetic materials which are vulcanized with sulfur or sulfur donors and accelerators conventional fillers and other components, using at least one accelerator, which belongs to the class of thiurams and / or dithiocarbamates,   characterized in that by simultaneously using   3-thiocyanotopropyltrialkoxysilanes of the general formula (RO) 3 Si (CH 2) 3 SCN ().   in which R represents an alkyl of from 1 to 8 carbon atoms, it is possible to reduce by at least half the amount of thiuram and / or dithiocarbamate accelerators relative to the amount initially used in the molding composition.   vulcanizable free of organosilicon compounds.   ) Vulcanizable molding compounds,   are manufactured in accordance with the method of claim 1.