DE2166126A1 - METHOD FOR PREVENTING THE POLYMERIZATION OF CONJUGATED SERVICES IN SOLVENTS AT HIGH TEMPERATURES - Google Patents

Description

JAPAN SYIiTHETIC RUBBER COMPANY LIMITED, 1, Kyobashi, 1-chome, Chuo-ku, Tokyo, Japan.

Methods of preventing conjugated dienes from polymerizing,

The invention relates to a method for preventing polymerization conjugated dienes and, in particular, a method for preventing the polymerization of conjugated dienes in organic ones Solvents at relatively high temperatures.

They are methods of extractive distillation or absorption by solvents for separating and refining butadiene or- Isoprene is known in high yield, or from C, «hydrocarbon fractions of split heavy oil containing butadiene, butane, butylene and isobutylene as main components, or of Cc hydrocarbon fraction, the pentane, pentene, Contains isoprene and piperylene as main components.

Solvents such as acetonitrile are used for such processes (ACN), iJ-methylpyrrolidone (NMP), dimethylformamide (DMF), Dimethylacetamide (DMAC) and furfural were used.

Usually it is known of the conjugated dienes given above that the same can be carried out at normal temperature by means of oxygen or the like, which is present in the solvents, are easily oxidizable and tend to polymerize on prolonged standing to build. When separating or refining by means of

- 2 - 30 9 8 17 / ι 1 2 i

Beriln office

f »in ijfoi.hfir: aüöfiO i // iitJß2'Jii2
t; Invention Berlin

nto: W. Mtl-i.iner, Berliner R.ink AG, Dt.pka " Mie, Kurt (ir.itemJamm130.Knnto-Nr. 9f> 7li>

Po.Uiclkkcmto: W Muiaü .-. Er, Berlin

BAD ORfGINAL.

In conventional extractive distillation or absorption processes, a solvent-containing butadiene or isoprene is inevitably subjected to temperatures above the boiling point of the C 1-4 or CU hydrocarbon fractions, for example above 70 ^{° C.} As a result, the polymerization of butadiene or isoprene in the solvent is accelerated and the polymerization product is deposited. Such a polymer deposition gives rise to numerous difficulties. For example, a thin polymer film is formed on the inner wall of the device, the outlets are clogged, and the extraction efficiency is reduced _9, making continuous operation for several hours difficult.

From DT-OS 1,816,82,6 it is known to stabilize a solution of butadiene in dimethylformamide at excess pressure and a temperature of 155 ° C. with 2,4-dinitroaniline in the presence of iron rust. Another known method for preventing the polymerization of butadiene in a solvent at elevated temperatures consists in adding furfural, benzaldehyde or aromatic nitro compounds to the butadiene solution which may come into contact with rust; (DT-OS 1 543 06-n _e

The previous .. ¹ :,}] suggestions that the technology could fall back on have not yet led to fully satisfactory results.

The object of the invention was to find an improved method for preventing the polymerization of conjugates Serve in solvents at elevated temperature. ■

For this purpose, a method is proposed in German patent application P 21 12 705.9-42, which is characterized by that a solvent containing the conjugated diene as an inhibitor eii organic phosphoric acid ester of the general Formula:

3 0 9 a I 7/1 1 2 3

BATHROOM OPlIGINAL,

-3- 2186126

O
R ₂ -O-P = O

is added, where R 1, R ₂ and R _{7 are} phenyl groups or ring-substituted phenyl groups whose substituents are alkyl, phenyl or halogen radicals; Mean alkyl groups, halogen-substituted alkyl groups or allyl groups.

The invention gives another equivalent proposal:

The subject of the invention is a method for preventing polymerization conjugated dienes in solvents at high temperatures, which is characterized in that at least one Compound from the group: pyridine, nucleus-substituted derivatives of pyridine, the substituents of which are alkyl groups, Quinoline, ring-substituted derivatives of quinoline, the substituents of which are alkyl groups, and anthracene, one of the conjugated diene-containing solvents can be added as an inhibitor.

Possible solvents here are ACN, NMP, DMF or DMAC for the purpose of extracting the conjugated diene.

Examples of compounds which represent alkyl groups in the core substituent of the pyridine are: picolines such as 2-methyl-pyridine, 3-methyl-pyridine, and 4-methyl-pyridine; Lutidines such as 2,3-dimethylpyridine, 2,4-dimethylpyridine, 2-ethylpyridine, and 3-ethylpyridine; Collidines, such as 2-methyl-4-ethylpyridine, 2-methyl-ip-ethylpyridine, 2-propylpyridine, 2-isopropylpyridine and 2, k , 5-trimethylpyridine; and parvoline, like. 2,3,4,5-tetramethylpyridine and 2-butylpyridine _v Examples of compounds whose alkyl groups are substituted in the nucleus of the quinoline are: alkylquinolines, such as 2-methylquinoline, 3-methylquinoline, 2,3-dimethylquinoline, 3,4 -Dimethylquinoline, 2-ethylquinoline and 4-ethylquinoline.

3098 17/1123 BAD ORIGINAL

These polymerization inhibitors can either be used to prevent the polymerization of conjugated dienes are used at high temperatures or are used for chain transfer of the polymerization, thereby preventing the generation of any solvent insoluble polymer.

These polymerization inhibitors are found to be very effective when used individually. The effect of preventing the polymerization of conjugated dienes, which is achieved by adding these compounds according to the invention, however, it is increased significantly when the connections are combined with a larger number of connections, e.g. Sodium nitrate, potassium nitrate, sodium sulfide, phenolic compounds and aromatic amine compounds are commonly used find application as polymerization inhibitors or antioxidants for unsaturated compounds. This arises from the fact that the polymerization inhibitors can be classified into two types from the point of view of their mechanism, i. Free radical reaction inhibitor and peroxide decomposer and it is contemplated that polymer production The reference is made to the two-stage radical initiation and radical growth. Thus it does what is according to the invention Method possible, the effect of preventing the polymerization of conjugated dienes in a solvent at increased Remarkably prevent temperatures by relying on the synergistic effect of the two substances that are different Have polymerization inhibition capabilities. The combined use of different inhibitors proves found to be particularly effective in preventing the polymerization of isoprene.

The known polymerization inhibitors or antioxidants for unsaturated compounds, which in combination with the Inhibitors according to the invention are used are:

(1) NaNO ₂ , KNO ₂ , Na ₃ S, methylene blue, and mercaptobenzothiazole;

(2) Pjaenol compounds, e.g., hydroquinone, such as 2,5-di-tert-butyl-hydroquinone and 2,5-di-tert-amylhydroquinone, phenols,

such as o-phenyl-phenol, 2,6-di-tert-butyl-p-phenylphenol,

309817/1123

butylated hydroxytoluene and p-methoxyphenol; Cresols, such as 2,6-di-tert-butyl-p-cresol, Brenz catechins, such as di-ter <t.-. butylpyrocatechnins and p-tert.-butylpyrocatechol, bisphenols, such as Z ^ '- methylenebis ^ -methyl-b-tert.-butylphenol) and 4.4 ^t -methylene bis (2,6-di-tert.-butylphenol); Naphthols such as alpha-naphthol, β-naphthol, 1,1'-methylenebis-2-naphthol; and aminophenols such as ρ-aminophenol and 2,6-di-tert-butylalpha-dimethyleneamine-p-cresol and

(3) Aromatic amine compounds, for example _o p, p ^f -diaminodiphenyltnethan, N-phenyl-alpha-naphthylamine, N-phenyl-ß-naphthylamine, p-isopropoxydiphenylamine, 4,4 ^I -dimethoxydiphenylamine, Ν, Ν ¹ -diphenyl-p -phenylenediamine, N, N ¹ -diphenyläthylendiamiri, NjN'-di-o-tolyläthylenediamine, N, N ^f -naphthylenediamine, octyldiphenylamine (mono- and di * ·) and 2,4-diaminotoluene.

According to the present invention, the effect of preventing the polymerization of butadiene and isoprene is sufficiently achieved even in the presence of iron rust which is generally believed to lead to the polymerization of dienes. In this way, the application is more expensive than equipment SpezialstöhLe material out switch t and v ird possible to maintain it / continuous operation over an extended period out.

The amounts of the polymerization inhibitors to be added can be changed in accordance with the kind and water content of the solvent and the operating conditions used. Usually, however, the purpose is achieved by first adding the inhibitors, e.g. pyridine, quinoline, anthracene, the nucleus-substituted derivatives of pyridine and quinoline, etc. in an amount of 0.01 to 1050, preferably 0.05 to 5 wt. on the weight basis of the solvent, and then adding the second inhibitors, zE>. Sodium nitrite, phenol compounds, aromatic amine compounds, etc., in a Me ^ -g * - ¹ of 0.0 (J! To 5%, preference ':; we Lie 0.005 to 1> o aui der üewiciiUJgruridLn ^ c: Λαα L-isungsmLtt ^ Li,

■ J ü ί)> i i 7 / M 2 3 BAD ORIQINAt

These inhibitors classified according to the above two groups can be added individually or in combination to the to achieve the desired effect.

The invention is explained in more detail on the basis of exemplary embodiments explained.

example 1

There v / earth 70 parts by weight _o ^ 5 water-containing acetonitrile with 3iner CV-Kohlenwanserstoff fraction of the composition shown in Table I blended. Each of the mixtures obtained is treated with different inhibitors for 70 hours in the presence of iron oxide in a hermetically sealed vessel at a temperature of 120 ^° C. under a pressure of 5 kg / cm. The results are given in Table II.

Table I. Bes canceled L1

AL Leu

Methyl acetylene isobutane isobutene ! -But

1,3-butadiene n- but an 1 trans-2-butene cis-2-butene vinylacetylene ethylacetylene!, 2-butadieri

Salary (wt. ^F ; Q

0.002 0.019

2.605

22.096

33,847

2,400

4,541

1.690

0, ü4 |

0.0075

0.001

100.0Ou

J {) ^C J b I 7 / I] 2

BATH

Table II

2166176

No . Polymerization inhibitor
1. Inhibitors% by weight 2 _β inhibitors 1.0 no ppm Condition n _e
the warmth
implementation polymer
salary
Weight % 1 no 1.0 Sodium nitrite polymer
stores
himself off 10.6 2 no 1.0 p-tert-butyl
catechin 100 small amount
docile
White 4.2 3 no Sodium nitrite 100 becomes white 7.3 4th Pyridine U 100 clear 0.5 VJl Quinoline I) 100 clear 1.2 6th Anthracene 100 clear 0.5

example

There are 80 parts of acetonitrile and containing 5% by weight of water
20 parts of butadiene introduced into a hermetically sealed vessel. The mixtures obtained are treated with various inhibitors under heat for 70 hours in the presence of iron oxide at a temperature of 120 ^° C. and a pressure of 5 kg / cm. The results are shown in Table III below.

309817/1123

Table III

No. Polymerization Inhibitor

I. Inhibitor wt. % 2. Inhibitor ppm

State after
Heat treatment Polymer content
Weight % becomes white polymer
deposit 10.4 becomes minor
White 3.2 well 4.1 η η η 2.2 clear 0.7 Il 0.8 η 0.5 η 0.4 pretty white 1.7 clear 0.1 clear 0.4 clear 0.8 becomes minor white 1.5 clear 1.0

O CC OO

no

no

no

Pyridine 0.5

"0.5

»1.0

alpha picoline 1.0

2-methyl-5-ethyl-1.0
pyridine

Quinoline 0.5

"0.5

^M 1.0

2-methylquinone 1.0

Anthracene 0.5

^M. 1.0

no

Sodium nitrite

p-tert-butylbenzatechin 200

no
Sodium nitrite

p-tert-butyl catechol 200

Sodium nitrite 100 »100

no

Sodium nitrite 100

p-tert-butyl catechol 200

Sodium nitrite 100

no

Sodium nitrite 100

Experiments are carried out under the same conditions as described above with the exception that the solvent acetonitrile is replaced by DMF, NMP or DMAC. In any case, the addition of 100 ppm sodium nitrite alone leads to a whitening of the solution in 70 hours, while the use of only pyridine, quinoline or anthracene (0.5% by weight ) keeps the solution clear for 70 hours later. The transparency of the solution is maintained for even longer periods of time by the combined application of 100 ppm sodium nitrite and one of the inhibitors.

Example 3

There are 70 parts of acetonitrile containing 5 wt.% Water, and 30 parts isoprene mixed with addition of the different,
inhibitors shown below. The corresponding mixtures are reacted in the presence of iron oxide at 120 ^° C. and the properties of the products are investigated. The results are given in Table IV below.

Table IV,, . _ ... (see p. 10)

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309817/1123

Table IV

Mr. Polymerization Inhibitor

I.Inhibitoren wt.% 2.Inhibitoren

12 Ahthracene

It η η

State after ppm heating 24 h 48 h

1 no 0.5 no 200 polymer
filing
tion polymer
deposit polymer
deposit 2 η 0.5 Sodium nitrite 200 slight
gig white Polymer off -
storage clear 3 It 1.0 p-tert-butyl
catechol quite.
cloudy M. 4th Pyridine 1.0 no 200 clear quite
cloudy VJl η 0.5 Sodium nitrite 100 η Polymerabi. 6th η 0.5 η 200 slight
gig white clear 7th η 1.0 p-tert-butyl
catechol pretty much
cloudy ; ^M. 8th Quinoline 1.0 no 200 clear quite.
cloudy 9 η Sodium nitrite 100 η 10 N H 200 slight
gig white 11 η p-tert -butyl-
catechol

0.5 no 200 quite. Polymer- 100 cloudy storage 0.5 Sodium nitrite 200 clear clear 1.0 It H η 1.0 p-tert-butyl minimally

Pyrocatechin gig white cloudy

Experiments under the same conditions as in experiments 4, 5, 8, 9, 12 and 13 are indicated in Table IV with except that acetonitrile is replaced by N-methylpyrrolidone or dimethylformamide is replaced. The conditions then correspond to those of experiments 4, 8 and 12 a slight cloudiness observed in 24 hours while

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309817/1123

under the conditions corresponding to those according to experiments 5, 9 and 13, the extraction solutions remain clear.

Example 4

Tests are carried out under the same conditions as in the example 6 with the exception that 0.5% by weight of pyridine and 100 ppm of sodium nitrite were used as inhibitors will.

Operation is continued for 5 days, but the extraction solution shows no changes and remains clear «If Replacing pyridine with quinoline or anthracene results in results similar to those obtained with pyridine.

If there is no pyridine, quinoline, anthracene or sodium nitrite, the extraction solution begins to turn white and cloudy in 10 hours and a light orange-colored polymer separates out in 20 hours.

Example 5

Under the same conditions as specified in Example 8, test solutions are prepared with the addition of various inhibitors specified in Table IX and the mixtures are ^{reacted in the presence of iron oxide at 120 °} C. and the properties of the products are then tested. The results are given in Table V.

- 12 "

309817/1123

Table V

No. Polymerization Inhibitor

1. Inhibitors wt.% 2.Inhibitoren ppm state after heating 24 h 48 h

1 2-methylpyridine 0.5 no 200 2 It 0.5 Sodium nitrite 100 3 Il 1.0 η 200 4th Il 1.0 p-tert-butyl
catechol 5 2,3-dimethyl
pyridine 0.5 no 200 6th Il 0.5 Sodium nitrite 100 7th η 1.0 It 200 8th It 1.0 p-tert-butyl
catechol 9 2-methyl-d-ethyl
pyriäin 0.5 no 200 10 Il 0.5 Sodium nitrite 100 11 Il 1.0 η 200 12th η 1.0 p-tert-butyl
catechol 13th 2-methylquinoline 0.5 no 200 14th It 0.5 Sodium nitrite 100 15th η 1.0 η 200 16 "V 1.0 p-tert-butyl
catechol 17th 4-ethylquinoline 0.5 no 200
100
200 18th
19th
20th Il
It
It 0.5
1.0
1.0 Sodium nitrite
It
p-tBrt -Butyl-
catechol

rather cloudy clear

Polymer deposit clear

It

slightly white rather cloudy

rather cloudy

clear η

Polymer deposition

clear η

slightly white rather cloudy

rather cloudy

clear η

slightly white rather cloudy clear

slightly white

rather cloudy

clear η

Clear polymer deposit

It

rather cloudy polymer appearance

clear η

rather cloudy

Clear polymer deposit

Il

slightly white rather cloudy

Claims (7)

Claims 1. Method of preventing the polymerization of conjugates Serves in solvents at high temperatures, characterized in that at least one compound from the group: Pyridine, nucleus-substituted derivatives of pyridine, the substituents of which are alkyl groups, quinoline, nucleus-substituted Derivatives of quinoline, the substituents of which are alkyl groups, and anthracene, a conjugated diene containing Solvent can be added as an inhibitor. 2. The method according to claim 1, characterized in that a known polymerization inhibitor or antioxidant for unsaturated compounds is used as the second polymerization inhibitor is added. 3. The method according to claim 1 or 2, characterized in that as nucleus-substituted derivatives of the pyridines picolines, such as 2-methylpyridine, 3-methylpyridine and 4-methylpyridine; Lutidines such as 2,3-dimethylpyridine, 2,4-dimethylpyridine; 2-ethyl pyridine and 3-ethylpyridines! collidines, such as 2-methyl-4-ethylpyridine, 2-methyl-5-ethylpyridine, 2-? Ropylpyridine, 2-isopropylpyridine and 2,4,5-trimethylpyridine; and parvolins such as 2,3,4,5-tetramethylpyridine and 2-butylpyridine can be used. 4. The method according to claim 1 or 2, characterized in that as nucleus-substituted derivatives of quinoline alkylquinolines, such as 2-methylquinoline, 3-methylquinoline, 2,3-dimethylquinoline, 3,4-dimethylquinoline, 2-ethylquinoline and 4-ethylquinoline, can be used. 5. The method according to claim 2, characterized in that the second polymerization inhibitor sodium nitrite, potassium nitrite, Sodium sulfide, a phenolic compound or an aromatic amine compound. - 14 - .30 9817/1123 6. The method according to claim 5, characterized in that the polymerization inhibitor is sodium nitrite. 7. The method according to any one of the preceding claims, characterized in that the solvent isoprene as conjugated Dien contains. -Inn P. F .. Meissner 3098 17/1123