DE1254341B - Process for plasticizing sulfur modified polychloroprene - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C08d

German KL: 39 b-4/01

* t /

Number 1254341

File number: D 43299IV d / 39 b

Filing date. 7 January 1964

Opening day 16 November 1967

Under the name "sulfur-modified polychloroprene latex" every synthetic rubber latex was understood, through homo- or copolymerization of 2-chloro-1,3-butadiene has been produced in the presence of sulfur. Furthermore means "Softening" the breakdown of the sulfur-modified polychloroprene into a more plastic product

For peptizing or softening sulfur-modified products Polychloroprene latex are already known numerous agents (see for example the British Patent specification 529 838)

In Russian works tetramethyl and tetraethylthiuram disulfide are already used for the same purpose, furthermore the piperidine and ammonium salt of hexamethylenedithiocarbamic acid been used

The invention is a method for Softening sulfur modified polychloroprene by treating a polychloroprene latex with tetraalkylthiuram disulfides, if appropriate in mixture with a secondary amine or a Dialkyl dithiocarbamate, which is characterized is that you also have water-soluble inorganic Thiosulfates, sulfides or dithionites or mixtures thereof are used

The ammonium and alkali metal salts of these inorganic compounds are expediently used. As Alkahmetallsalze the Natrmmsalze are preferably used The Verbmdungen be m amounts of 5%> in particular 1 ° / o ^{oa <it} uses less of the weight of dry rubber in latex.

The preferred secondary amine is diethylamine used

When carrying out the claimed process, the water-soluble inorganic salts can be added to the latex at any stage of softening, preferably before the remaining monomers are removed. The water-soluble inorganic compounds are added to the latex in the form of an aqueous 2-5% solution. Emulsifiers are also used for easier mixing with the latex and to avoid coagulation. The reaction is expediently carried out under an inert atmosphere, such as nitrogen. The treatment temperature harbors preferably between room temperature and 5O ⁰ C, although higher temperatures can be used, the pH of the latex harbors 8 to 12.3, preferably 10.5 to 12.3

Preferably the freshly made, sulfur-modified Polychloroprene latex treated.

The amount by weight of the tetraalkyltbiuram disulfide used in the latex is between 0.1 and Method for softening with sulfur
modified polychloroprene

Applicant.

The Distillers Company Limited,

Edinburgh (Great Britain)

Representative.

Dr W Schalk, Dipl-Ing. P Wirth,

Dipl.-Ing. G. E. M Dannenberg

and Dr. V. Schmied-Kowarzik, patent attorneys,

Frankfurt / M., Gioße Eschenheimer Str. 39

Named as inventor:

Anthony Archibald Sparks,

Epsom Downs, Surrey;

Robert Charles Moore, Sutton, Surrey

(Great Britain)

Claimed priority
Great Britain January 18, 1963 (2405),
dated March 29, 1963 (12453)

Percent by weight, preferably 1 to 5 percent by weight, that of the dialkyldithiocarbamate between 0.1 and 3.0 percent by weight, each based on the solids content of the latex.

The following examples illustrate the invention

Examples 1 to 3

Ahren by known Emulsionspolymensationsverf a polychloroprene latex having a pH value of 11.3 was at 40 ⁰ C prepared wherein em small proportion of sulfur (0.5 to 0.6 weight percent, based on the monomers) in the alkaline emulsion was present, a Wood resin was used as a soap and potassium persulfate as a polymerization initiator. The polymerization was terminated at the desired conversion by adding the plasticizers listed in the table. Immediately after this addition, a dilute aqueous solution of sodium dithioma or sodium thiosulfate was added in an amount of

709 688/436

1.0% based on the weight of dry rubber was added

Samples were taken from the plasticized latex after 1, 3, 5 and hours and the rubber was isolated and the Mooney viscosity determined

The results in Table 1 show a comparison

to a sample in which sodium dithionite or sodium thiosulfate have been omitted. The results clearly show the acceleration of softening with sodium dithiomite or sodium thiosulphate.

Table 1 Plasticizers 1 hour Mooney viscosity (ML-4/100 ° C
after a plasticization of 5 hours >
.Γ ) 8 hours example 142 3 hours 90 84 2% tetraethylthiuram disulfide 43 94 31 30th Control
sample 2% tetraethylthiuram disulfide / 1%
Sodium dithiomite 86 35 65 54 1 2% tetraethylthiuram disuffide / 1%
Sodium thiosulfate 115 69 79 75 2 2% tetraethylthiuram disulfide / 0.5%
Diathylaimn 84 86 68 65 Control
sample 2% tetraethylthiuram disulfide / 0.5 ° / ₀
Dietamine + 1% sodium dithionite 72 3

Example 4

It became the same polychloroprene latex as in the Examples 1 to 3 used.

Then the latex was eme mixture of 2.4% tetraethylthiuram disulfide and 0.12% dimethylammomumdimethyldithiocarbamate, based on the weight of the dry polychloroprene added. Afterward one of the following alkali metal salts was added to the latex samples in one concentration of 1% based on the weight of dry rubber is added.

From the peptized latex were after 1, 5 and Samples taken 12 hours and the Mooney viscosity of the polymer obtained is determined. The results in Table 2 show a comparison with a sample in which the alkali metal salts are omitted became.

Tabel

Control sample Mooney viscosity (ML-4/100 ° C) according to 5 hours 12 hours Plasticizer added to the latex Tetraathylthiuramdisuhid / Dimethylammoniumdimethyldithio- a plasticization of carbamate 1 hour 90.5 77 Tetraethylthiuram disulfide / dimethylammoniumdunethyldithio- carbamate / 1.0% sodium thiosulfate 128 75 60 TetraathylthiuramdisuMd / Dunethylammomumdimethyldithio- carbamate / 1.0% sodium dithiomite 88 33 cores sample Tetraethylthraram disulfide / Dimethylammoniumdnnethyldithio- taken carbamate / 1.0% sodium sulfide 45 75.5 60 88.5

Claims (2)

Patent claims: 1. Method of plasticizing sulfur modified polychloroprene by treatment a polychloroprene latex with tetraalkylthiuram disulfides, optionally mixed with a secondary amine or a dialkyldithiocarbamate, characterized in that there are also water-soluble inorganic Thiosulfates, sulfides or dithionites or mixtures thereof are used 2. The method according to claim 1, characterized in that the ammonium or alkali salts the water-soluble inorganic thiosulphates, sulphides or dithionites are used. Considered publications:
British Patent No. 529 838,
Soviet Rubber Technology, Vol. 20 (1961), Issue 5, pp. 2 to 5. 709 688/436 11.67 © Bundesdruckerei Berlin