DE1807298A1 - Process for the production of sulfur-modified polychloroprenes which have no tendency to cyclization - Google Patents

Description

1807298 FARBENFABRIKEN BAYER AG

b5, Nov. 1968

LEVERKUSEN-i * T «iwwk Pateat department

Process for the production of sulfur-modified polychloroprenes, which have no tendency to cyclization.

The copolymerization of 2-chloro-butadiene-1.3 (chloroprene) is known with sulfur in the presence of emulsifiers and activators in aqueous emulsion (see USP. 2.264.173). The so obtained Polymers are insoluble in benzene and are converted into benzene-soluble chloroprene polymers through chemical degradation. This chemical breakdown - peptization - is caused, for example, by tetraethylthiuram disulfide (see USP 2,234,215). the Peptization can be carried out in the latex state (see USP. 2,831,842) or in a drying cabinet (see Chem. Eng. Process 43 (1947) No. 8 S 391-398 carry out.

During the peptization in the latex phase, the polymer emulsion becomes stirred at a certain temperature with the peptizer and then the polymer is isolated from the latex by freeze coagulation (see USP. 2,187,146) and dried in a drying cabinet.

In the case of peptization in a drying cabinet, polymer degradation also takes place, combined with a decrease in viscosity.

Is carried out with the polymer obtained by the degradation methods a polymer stability test by storing the samples for several days at an elevated temperature and then the Mooney viscosity (see ASTM-D-927-49 T) is measured, a different behavior of the polymers is found.

The Mooney value is given as the viscosity at 100 ° C and after 4 · running time of the rotor. The whole procedure is called the Mooney Stability Test denotes and gives a statement about the polymer stability. What is desired is a polymer behavior, with the Samples show a decrease in their Mooney viscosity.

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Is the heat treatment of the polymers during the degradation phase in the If the drying cabinet or latex is too strong, a cyclization phase can follow the breakdown. This can be determined the increase in Mooney viscosity.

The polymer viscosity drops during peptization in the latex phase depending on the residence time of the latex at higher temperatures. There is a particular danger here that one continues the degradation too far and, through the subsequent drying process in the cabinet dryer, arrives at polymers that are necessary for technical Purposes too low Mooney viscosities and on the other hand the Mooney stability test by cyclization processes Show Mooney viscosity increase.

If the polymer is only broken down in the cabinet dryer, where both breakdown and drying take place, a decrease in the Mooney viscosity with increasing residence time of the polymer in the drying cabinet is observed at the same time, but this must be determined very precisely, because if the residence times in the cabinet dryer are too long, the polymers tend to cyclize, if the residence times are too short, the polymer is only insufficiently degraded.

The present invention is based on the object of preventing the cyclization of sulfur-containing chloroprene polymers by choosing suitable working-up conditions. The invention is based on the following observation:

Wildly the peptization in the latex phase is carried out up to Mooney viscosity values which are in the technically interesting range, the Mooney viscosity drops even further in the subsequent drying phase in the cabinet dryer and polymers are obtained which In addition to a Mooney viscosity that is too low, they also have inadequate polymer stability, recognizable by the increase in viscosity when the polymers are stored at elevated temperatures (see Example V of Table 1).

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If, on the other hand, insufficient peptization is carried out in the latex phase, polymers are obtained which, in addition to those for technical Purposes that are too high in viscosity also show poor processing properties (see Example VI, Table 1).

If the polymer is only broken down in the cabinet dryer (see Example I in Table 1), it is found that with increasing residence time of the polymer in the cabinet dryer, the Mooney viscosity falls, goes through a minimum and then rises again. Products with good polymer stability are only obtained if the polymer residence time in the cabinet dryer is precisely selected. This must be chosen so that one is 30 to 10 Mooney viscosity units before the viscosity minimum possible at the selected temperature. Since the residence time range is very narrow, this method is technically difficult to carry out. Similar results are obtained if only a short pre-peptization is carried out in the latex phase and the main degradation is carried out in a drying cabinet (Example II of Table 1).

Polymers with the desired Mooney viscosity that do not contain any Show a tendency towards cyclization and decrease somewhat in the Mooney stability test, expressed by a decrease The Mooney viscosity is reached if, after the polymerization, a prepeptization is first carried out in the latex phase, peptization being carried out until the Mooney viscosity of the polymer i «latex is 6o-3o units before the viscosity minimum and then the Mooney viscosity of the polymer in the drying cabinet is like this sets that "at 30 to 10 units before the viscosity minimum possible at the selected temperature. (Example III and IV of Table 1.) This process prevents too much energy from being used to achieve the desired viscosity allows the drying and chemical degradation of the polymer to act on the polymer sample in the drying cabinet. In the latex phase only a pre-peptization is carried out and the actual viscosity setting is achieved in the drying cabinet.

Table 1 shows the breakdown of sulfur-modified polychloroprene shown schematically in the drying cabinet and in the latex phase. At the beginning of the degradation phase, the polymer viscosity is in the Mooney viscosity range of about 160-180 Mooney units. By breaking down in the

Cabinet dryer (S) the Mooney viscosity decreases steadily as the residence time increases, goes through a minimum and increases again with a long residence time in the drying cabinet (Fig. I. Ji, />,% S) The position of the minimum depends on the residence time also depends on other parameters, such as the amount of sulfur in the polymerization batch, the conversion achieved and the amount of peptizing agents.

The degradation in the latex phase (L) is followed by minimal degradation in the cabinet dryer (MS), since the polymers obtained by freeze coagulation still have to be dried and the drying conditions cannot be chosen so gently that further degradation can be completely ruled out.

The invention accordingly relates to a method of production Sulfur-modified chloroprene homo- and copolymers with a specified Mooney viscosity through the polymerization of chloroprene and up to 20% by weight, based on chloroprene, of an ethylenically unsaturated comonomer in the presence of from 0.1 to 2% by weight, based on monomers, sulfur, optionally in the presence of regulators in an aqueous emulsion, addition of 0.5 to 5% by weight, based on the polymer Peptizing agent, prepeptization of the polymer in the latex phase, coagulation of the latex obtained and separation of the polymer with subsequent drying, which is characterized by that after the addition of the peptizing agent, a pre-peptization is carried out in the latex phase to Mooney viscosity units, which 60-3o units are before the viscosity minimum and that, after the polymer has been separated off from the latex, drying is carried out at temperatures between 80-170 ° C. until a Mooney viscosity of 30-10 Mooney viscosity units is achievable Minimum is set.

The polymers produced by the process described above, have some excellent properties. They can be masticated very easily on the roller and do not need any additional ones Vulcanization accelerator.

The polymerization process used to produce the sulfur-modified Polychloroprene is known per se. All customary emulsifiers can be used, such as, for example, water-soluble salts, in particular Alkali salts of long-chain fatty acids, resin acids disproportionated

BATH ORIGINAL

Abietic acids, arylsulfonic acids and their formaldehyde condensation products, Alkyl and aralkyl sulfonates or sulfates, oxyethylated alcohols and phenols.

The usual activators for the polymerization are used Free radical forming catalysts, such as hydrogen peroxide, cumene hydroperoxide, water-soluble salts of peroxydosulfuric acid, 2,2 «-azobisisobutyronitrile, salts of formamidinesulfinic acid and Combinations of potassium persulfate and / 9-anthraquinone sulfonic acid. The last compound is also known as the silver salt.

The general procedure is to add the aqueous solution of the catalyst to an aqueous emulsion which contains monomers and the emulsifier. In general, the polymerization is carried out in the pH range 7-13 at temperatures between ⁰ C to 60 υ and issue the emulsion so that their total monomer content at 3o-6o wt.% Is the weight of the total emulsion.

To influence the molecular weight of the polymers, in the presence of regulating substances such as dialkylxanthogen disulfides or Mercaptans are polymerized. As ethylenically unsaturated comonomers, which can be copolymerized with chloroprene are: acrylonitrile, methacrylonitrile, ethyl acrylate, 2,3-dichlorobutadiene and «£ -chloroacrylonitrile.

After a certain monomer conversion has been reached, the Polymerization by stoppers, stabilizers or by removing the unreacted monomers by steam distillation cancel (see USP. 2,467,769).

Phenothiazine, p-tert.-butylpyrocatechol, are used as a stopper, Sodium dialkyldithiocarbamate, sterically hindered phenols or aromatic amines as stabilizers.

A peptizer is added to the latex for peptization and stirred at a temperature between 4o and 7o C and a pH value between pH = 7.5 and pH = 12. As a peptizer if you use tetraalkylthiuram sulfide such as tetraethylthiuram disulfide, or combinations of diisopropylxanthogen disulfide and Arylguanidines such as diorthotolylguanldine. These are in the form of a

ORIGIN * ¹

loo , 6 Weight .Parts ο , 01 Il η 0 η M. 12ο Il Il

aqueous emulsion stirred into the latex. The right choice The pH value, concentration of the peptizing agent and peptizing temperature play an important role in setting the properties of the polymers obtained. after the The desired Mooney viscosity is reached in the latex phase, the pH of the latex is below pH = 8 by adding Acetic acid adjusted. The latex is then worked up by freeze coagulation. The polymer tape is both dried and chemically degraded in the drying cabinet Viscosity decreased.

Attempt a

For the production of the sulfur-modified polychloroprene is an emulsion prepared according to the following approach:

Chloroprene

sulfur p-tert. Butyl catechol

Desalinated water

Sodium salt of a disproportionated abietic acid 4.5

Sodium salt of the condensation product of β- naphthalenesulfonic acid

Caustic Soda Tetrasodium Pyrophosphate

The sulfur is dissolved in the chloroprene and stirred into the aqueous phase. Thereafter, the temperature is increased to 49 ⁰ C and treated at intervals of 6o minutes with an activator solution of the following components:

Potassium persulfate 0.04 parts by weight

/? - Anthraquinone sulfonic acid o, oo4 ""

Desalinated water 1.3 ⁿ " /

When the monomer conversion is around 65-70% , the latex is mixed with a stopper solution consisting of the following components:

Chloroprene 0.5 parts by weight Phenothiazine o, o65 ^{w M}

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BATH ORIGINAL.

o, 7 Il Il o, 4 Il ti o, 5 It η

Then the latex is made of unreacted monomers Steam treatment freed. The latex thus obtained is in ■ split up several proportions and degraded the polymer for this purpose using various methods.

Example I.

The latex obtained according to experiment A is mixed with 2.5 parts by weight of tetraethylthiura disulfide with 20 % acetic acid and adjusted to pH = 7-7.5 and then immediately precipitated by freeze coagulation and dried in a drying cabinet with various residence times (Example I;

Example II

The latex obtained according to Experiment A is adjusted to pH 11 with 20% acetic acid, 2.5 parts by weight of tetraethylthiuram disulfide are added and the mixture is peptized at 45 ° C. for 30 minutes. The ptl value of the latex is then adjusted to pH values less than β with acetic acid and the polymer is precipitated by freeze coagulation and then dried in the drying cabinet for such a residence time that a Mooney viscosity is obtained which is in the technically interesting range.

Example III

The latex obtained according to experiment I is made up with 20% acetic acid pH 11 adjusted with 2.5 parts by weight of tetraethylthiuram disulfide added and peptized at 45 ° C. for 15 h. The pH of the latex is then adjusted to less than 8 with acetic acid and the polymer precipitated by freeze coagulation and then expressed with a minimal amount of heat, through a short residence time in the Drying cabinet dried.

Example IV

The latex obtained according to Experiment A is adjusted to pH = 11 with 20% acetic acid, 2.5 parts by weight of tetraethylthiuram disulfide are added and the mixture is peptized at 45 ° C. for 35 h. The pH of the latex is then adjusted to pH less than 8 with acetic acid and the polymer is precipitated by freeze coagulation and then dried with a minimal amount of heat.

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Example V Q

The latex obtained after the test Λ is adjusted with acetic acid to pH = 2O $ 11, mixed with 2.5 parts by weight of tetraethylthiuram disulfide and 6o peptized h at 45 ⁰ C. The pH of the latex is then adjusted to pH less than B with acetic acid, and the polymer is precipitated by freeze coagulation and then dried with a minimal amount of heat.

Example VI

The latex obtained according to experiment A is adjusted to pH = 11 with 2o fe acetic acid, treated with 2.5 parts by weight of tetraethylthiuram disulfide and peptized at 45 ° C. for 5 h. The \ H value of the latex is then adjusted to a pH of less than 8 with acetic acid and the polymer is precipitated by freeze coagulation and then dried with a minimal amount of heat.

Attempt B

The following emulsion is produced and emulsion polymer ^{at 49 0 C}

sated:

Chloroprene

sulfur 2.3-dichlorobutadiene p-tert. Butyl catechol

Desalinated water

Sodium salt of a disproportionate abietic acid 4.5 ^{n M}

Sodium salt of the condensation product of β- naphthalenesulfonic acid and formaldehyde 0.7 " ^w

Caustic soda 0.4 "" Tetrasodium pyrophosphate 0.5 " ⁿ

The sulfur is dissolved in the chloroprene and stirred into the aqueous phase. The temperature is then increased to 49 ⁰ C using an activator solution made up of the following components:

Potassium persulfate o, o4 ^{M n}

β- anthraquinone sulfonic acid o, oo4 ^{w M}

Desalinated water 1.3 ⁿ "

97 6th Weight .Parts O, Il • I 3 oil Il •1 O, Il η 12o •1 Il

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With a monomer conversion of about 65-7o "ί , the latex is mixed with a stopper solution made from the following components:

Chloroprene 0.5 parts by weight Phenothiazine o, o7o ""

Then the latex is made of unreacted monomers Freed steam treatment.

The latex obtained in this way is divided into several parts. Example VII

The latex obtained according to experiment B is adjusted to pH = II with 20% acetic acid, 2.5 parts by weight of tetraethylthiuram disulfide are added and the mixture is peptized at 47 ° C. for 30 hours. The pH of the latex is then adjusted to a pH of less than 8 with acetic acid and the polymer is precipitated by freeze coagulation and then dried with a minimal amount of heat.

Example VIII

The latex obtained by Experiment B is set with 2o% acetic acid to pH = 11 and treated with 2.5 parts by weight Tetraäthylthiuraadisulfid and 4o peptized h at 47 ⁰ C. The pH of the latex is then adjusted to a H value of less than 8 with acetic acid and the polymer is precipitated by freeze coagulation and then dried with a minimal amount of heat.

Of the polymers obtained by freeze coagulation and drying the Mooney viscosity (see ASTM D 927-49T) is measured. The polymer is then stored at 60 ° C. and at intervals of 1, 2 and 3 days - a sample is taken and the Mooney viscosity measured again.

The Mooney value is given as the viscosity at 100 ° C and below 4 minutes running time of the rotor. The above-described measurement is referred to below as the Mooney stability of the crude polymer.

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* Table 2 Dismantling Dismantling in Mooney viscosity 0 1 2 f 3 attempt example in latex cabinet After days Ho Io3 77 66 . (H) Stay . 56 54 48 47 time (min.) '29 52 54 6o O 2.25 "72 89 115 113 I d, O 2.83 . 47 55 56 58 eat O 3.56 O 3.97 65 6o 52 43 0.5 2.54 43 38 33 3o II 29 39 48 53 A. 15th 2.25 97 91 83 75 Λ III 35 2.25 52 43 38 33 IV 6o 2.25 46 4o 4o 39 V 5 2.25 VI 3o 2.25 B. VII 4o 2.25 B. VIII

The following can be seen from the examples in Table 2. Leads to the degradation of sulfur-modified polychloroprene by only the cabinet dryer so does the polymer viscosity with increasing V _e rweilzeit in a drying oven off passes through a minimum, and increases again. Polymers which have a desired Mooney viscosity and which in the Mooney stability test do not yet cyclize on storage at 40 ° C., detectable by an increase in viscosity, but rather show slight degradation, are obtained only with a very specific residence time (Example 13) , detectable by the decrease in Mooney viscosity. _t At too low residence polymers are obtained with too high a Mooney viscosity at too long a residence time strongly cyclizing Polymers.

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ßAO ORfGJNAL

If you carry out a very short prepeptization according to Example II and build on the desired Mooney viscosity by correct If the residence time is selected down, the polymers show a relatively long residence time, which is still in the cabinet dryer little tendency towards cyclization.

If, on the other hand, the degradation is carried out in the latex phase (Example III and IV) so far that a polymer viscosity in the latex is obtained which is about 6o to 3o Mooney viscosity units before the viscosity minimum, then polymers with the desired Mooney viscosity are obtained which, in the Mooney stability test, show no tendency towards cyclization, but still degrade.

If, on the other hand, the degradation in the latex phase is carried out too far (Example V), polymers with Mooney viscosities which lie outside the technically interesting range, but on the other hand show strong cyclization tendencies in the Mooney stability test.

If, according to Example VI, there is only a very slight degradation in the Latex phase through and, in contrast to Example II, only uses a short residence time in the cabinet dryer, so polymers are obtained ■ it too high Mooney viscosity, which is of no technical interest. In addition, their viscosity drops sharply on storage.

It is particularly easy to obtain polymers with the desired Mooney viscosity and no tendency to cyclization if you follow the polymerization a degradation by leptizing agents in the Performs latex phase, the polymer in the latex state being reduced to at least 6o to 3o Mooney viscosity units before the viscosity minimum. A very gentle drying process is then carried out in a cabinet dryer, with the polymer on Mooney viscosities are reduced, which are 3o to Io units before the viscosity minimum.

To determine the scorch behavior, which is an eminent When the sulfur-modified polychloroprene plays a role in the technical processing, these are made with the following components mixed on the roller:

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loo parts by weight of polychloroprene, 29 parts by weight of semi-active furnace black, 0.5 parts by weight of stearic acid, 2 parts by weight of phenyl- / ί-naphthylamine, 4 parts by weight magnesium oxide, 5 parts by weight zinc oxide.

Thereafter, the mixtures at ⁰ C Hl be exposed to a stepped heating and the moduli at 3oo t'o determined elongation. Technically well usable polymers should not show any scorch, expressed by an increase in the moduli during step heating.

Table 3

example Mooney viscosity module
time
5 « i
η in kg
in Mii
lo ' cm "after
ι. at i .'Jo
15 « O 2 i following heating '
⁰ O elongation d. sample
5o » I. 29 2 3 6th ² i 13th II 47 2 3 5 4 y 12th III 65 2 2 2;
1 2 IV 43 2 2 2 2 V 29 2 3 Io VII 52 2 2 VIII 46 2 2 2

Table 3 clearly shows that only those polymers have no tendency to undesired scorch, which show no tendency to cyclization. It's about those polymers which were obtained by prepeptization in the latex phase to Mooney viscosities, diu 6o to 3o units in front of the viscosity mini-aura and the gentle Drying in the cabinet dryer have been reduced to Mooney viscosities, the 3o to Io units before the viscosity miniraura.

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Claims (1)

Claim Process for the production of sulfur-modified chloroprene homo- and copolymers with a given Mooney viscosity, which have no tendency to cyclization by polymerization of chloroprene and up to 20% by weight, based on chloroprene, of an ethylenically unsaturated cotnonomer in the presence of 0.1 to 2% by weight based on monomers, sulfur,% optionally in the presence of regulators, in aqueous emulsion, the addition of O, 5 to 5 wt. based on polymer of a peptizer, Vorpeptisierung of polymer in the latex phase, coagulation of the obtained latex and-separation of the polymer followed by Drying, which is characterized in that, after the addition of the peptizing agent, a pre-peptization is carried out in the latex phase to Mooney viscosity units which are 6o to 3o units before the viscosity minimum and that, after the polymer has been separated off from the latex, drying is carried out at temperatures between 8o - 17o c until a Mooney visco sity is set from 3o to Io Mooney viscosity units before the attainable minimum. - 13 - 009823/1749 ft Blank page