DE1265409B - Process for stabilizing polyolefins - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY GERMAN WTWW ^ PATENT OFFICE

EDITORIAL

Int. α .:

German KL:

Number:
File number:
Registration date:
Display day:

C08f

1,265,409
F28654IVc / 39b
June 10, 1959
April 4th 1968

Numerous high polymer compounds suffer from oxygen at higher temperatures, especially when exposed to light, a degradation. The physical properties of the Starting product, such as its strength, elongation or hardness, drop so much that it is for technological Purposes can no longer be used. Stand to prevent such degradation Numerous coating agents are now available, which are known as stabilizers.

So z. B. for high and low pressure polyolefins phenols and phenol derivatives, e.g. B. based on 4,4'-dioxydiphenylmethane or -dimethylmethane, described as particularly effective anti-aging agents. In addition, aminophenols and sulfur-containing phenol derivatives obtained by condensation of alkylphenols with monosulfur dichloride or disulfur dichloride are mentioned in various patents.

However, the above-mentioned anti-aging agents - insofar as they are phenol derivatives - the disadvantage that the stabilizing effect is insufficient in some cases, while the sulfur-containing Phenol derivatives at the high processing temperatures, such as those found in particular with polypropylene, decompose many times and discolor the plastic.

There has now been a method for stabilizing polyolefins by a mixture of a) one Phenol derivative and b) an organic sulfur compound found, characterized in that is that as b) symmetrical thioethers of the general formula

R —S —R

where R is an aliphatic radical with 4 to 5 or 21 to 25 carbon atoms or unsymmetrical Thioether of the general formula

R - S - R '

where R is an alkyl radical having 4 to 25 carbon atoms, R 'is a hydroaromatic hydrocarbon, represents a benzene, thiophene, naphthalene radical or a higher condensed nucleus or compounds the general formula

R - S - (RO »- S - R

used, where R is a hydrocarbon radical with 4 to 25 carbon atoms and R 'is a hydrocarbon radical with η = 1 to 20 or an optionally alkylated thiophene, naphthalene, process for stabilizing polyolefins

Applicant:

Farbwerke Hoechst Aktiengesellschaft
formerly Master Lucius & Brüning,
6000 Frankfurt

Named as inventor:
Dr. Claus Heuck, 6238 Hofheim;
Dr. Otto Mauz, 6231 Niederhofheim;
Dr. Jakob Winter, 6233 Kelkheim;
Dr. Felix Schulde, 6232 Neuenhain

Anthracene nucleus or a hydrogenated nucleus or the groups

(CH2) 2 * ~ O (CH2) 2

means.

These thioethers, which z. B. in a simple and known manner from alkyl halides and sodium sulfide can be produced show, when used alone, the two different polyolefins no or only a slight anti-aging effect.

However, if these thioethers are combined with a phenolic anti-aging agent, this occurs a synergistic effect that unexpectedly reduces the anti-aging effect of the phenolic bodies elevated.

In the case of stabilizers or anti-aging agents, one can therefore use the current state of the art Knowledge distinguishes two types of connections based on their effectiveness:

a) the substances with a special effect as antioxidants,

b) the substances which themselves are not or only slightly effective as antioxidants, but in a mixture with compounds of group a) are able to significantly increase the effectiveness (so-called Co-stabilizers).

The antioxidants cause the chain reaction of auto-oxidation to break off by reducing the Catch the resulting radicals and render them harmless. These are antioxidants mostly of phenolic structure.

The substances of group b) with synergistic effectiveness did not apply on their own

809 537/596

or only low anti-aging effect; however, they increase the effect of those mentioned in group a) Antioxidants to a very considerable extent. You can get this that gradually due to the oxidation are consumed, regenerate and in the given case pro-oxidative traces of metal compounds render harmless by forming salts or chelates.

As phenolic components, alkylated phenols, condensation products of mono- and Dialkylphenols with aldehydes and ketones, such as o-cresol, tert-butylphenol, nonylphenol, nonylp-cresol, used with formaldehyde, propionaldehyde, acetone or cyclohexanone.

The phenolic component is now used to reinforce the stabilizing effect as a co-stabilizer a thioether added. In the simplest case, the thioether can be built symmetrically,

R —S —R

where R is an aliphatic radical having 4 to 5 or 21 to 25 carbon atoms.

The thioether can also be asymmetrical according to the formula

R - S - R '

be built, where R is an aliphatic radical from C4 to Caä and R 'is a hydroaromatic hydrocarbon, represents a benzene, thiophene, naphthalene or a more highly condensed nucleus. Furthermore, several sulfur atoms, which are separated by carbon atoms, can also be used. be contained in the molecule. These compounds have the general formula

20th

35

where R denotes hydrocarbon radicals with 4 to 25 carbon atoms and R ' denotes a hydrocarbon radical with η = 1 to η = 20 or an optionally alkylated thiophene, naphthalene, anthracene nucleus or a hydrogenated nucleus or the group

- (CHa) ₂ -O- (CHa) ₂ -

represents.

Such compounds are obtained in a known manner by using dialkyl halides, such as dichloromethane, 1,2-dichloroethane, 1,3-dichloropropane, 1,4-dichlorobutane or / ί, / J'-dichlorodiethyl ether, Bis (chloromethyl) naphthalene, bis (chloromethyl) thiophene, dichloropentamethylbenzene, 1,4-di (chloromethyl) benzene, with mercaptans.

Particularly effective for stabilizing polyolefins such as polyethylene, polypropylene, polybutene and polymethylpentene, are those thioethers that are long-lasting in terms of compatibility aliphatic hydrocarbon radicals such as octyl, dodecyl and carry octadecyl residues.

The total amount of anti-aging agents + co-stabilizer required is generally for normally stressed fittings 0.001 to 5%, preferably 0.05 to 1%. The relationship of the two components should be 5: 1 to 1: 5 parts by weight, preferably 1: 1.

The great advantage of using such mixtures of antioxidants from group a). and the specified co-stabilizers of group b) is not only due to the observed increase in Stability of the polyolefins, but also in the possibility of reducing the dosage of such Mixtures with regard to possible discoloration of the plastics.

The following table ^{lists the embrittlement times measured at 140 °} C. for polypropylene, which in each case contains 0.5% of the stabilizer combination listed in a ratio of 1: 1. The embrittlement time is the time in days after which a 1 mm thick polyolefin press film breaks when it is bent.

The process according to the invention can be particularly advantageous for low-pressure homopolymers or low pressure copolymers z. B. are manufactured according to the Ziegler process (cf. R a f f- Allison, Polyethylene, [1956], pp. 72 to 81).

example 1
Stabilization of polypropylene

Embrittlement in days at 140 ^° C. and a total stabilizer concentration of 0.5% (0.25% by weight of a condensation product of nonylphenol and acetone and 0.25% of the synergist listed in the table).

The following results were obtained:

Co-stabilizer

Embrittlement
in days at 140 C.

Color according to
Tempering

1,2-bis (octadecylmercapto) ethane

1,4-bis (octadecylmercapto) butane

Bis (octadecylmercapto) diethyl ether

1,2,4,5-tetramethyl-2,4-di (dodecylmercapto) benzene

For comparison:

Condensation product

Nonylphenol

+ Acetone

(without co-stabilizer)

0.25
0.25
0.25
0.25

27 20th 38 20th

0.25
0.50

4 to p

unchanged,
colorless

unchanged,
colorless

unchanged,
colorless

unchanged,
colorless

unchanged,
colorless

continuation

Co-stabilizer concentration
% Embrittlement
in days at 140 ^° C Color according to
Tempering 1,4-bis (octadecylmercapto) butane
Bis (octadecylmercapto) diethyl ether 0.50
0.50 1
2 to 3 unchanged,
colorless
unchanged,
colorless

As can be seen from the table, the new stabilizer system makes the polypropylene extraordinary well stabilized against embrittlement. The addition of the synergistic co-stabilizer leads to a multiple increase in the stabilization time.

Similar values are obtained if 0.25 percent by weight of 2,6-di-tert-butyl-p-cresol or condensation products of camphene and phenols with 0.25 percent by weight of the co-stabilizers listed in the table above for stabilization of propylene or polyethylene are used.

B e i s ρ i e 1 2

0.25 percent by weight of sulfur-containing co-stabilizers, as listed in the following table, were each together with 0.25 percent by weight of a condensation product of nonylphenol and acetone in a low-boiling solvent, such as. B. methylene chloride or acetone, dissolved and mixed with the propylene powder. The wet powder was dried in vacuo at 50 ⁰ C and then pressed under the following conditions into 1 mm thick circular plates: Temperature 200 ⁰ C, 10 minutes of contact pressure (5 to 10 atm), 2 minutes pressing pressure (100 atm). Several strips, each 10 mm wide and 100 mm long, are punched out of each plate, hung freely in a drying cabinet and ^{tempered at 140 °} C. with admission of air. As a measure of the thermal stability of the embrittlement time was determined, the time in days, after which the sample strips break when bent through 180 ⁰ C ie.

The results are listed in the following table (abbreviation = Ph. K. = Phenolic Component).

Co-stabilizer concentration
% Phenol. Rod.
(Ph. K.) concentration
% Embrittlement time
in days at 140 ^° C Ethyl a-naphthyl sulfide
Ethyl a-naphthyl sulfide
p-Tolyl-a-naphthyl sulfide
p-Tolyl-a-naphthyl sulfide
1,5-di (dodecylmercapto) naphthalene
1,5-di (dodecylmercapto) naphthalene 0.5
0.25
0.5
0.25
0.5
0.25 Ph. K.
Ph. K.
Ph. K.
Ph. K. 0.25
0.25
0.25
0.5 1
15th
1
13th
4th
35
4th

It is clear from the table that the sulfur-containing compound alone has practically no the combination with a relatively weak phenolic stabilizer, on the other hand, is a very good one Shows stabilizing effect (synergism).

It is known that under certain circumstances the combination of a phenol derivative acts synergistically with an organic sulfur compound to stabilize polyolefins, however, the question remains. unanswered what organic sulfur compounds with phenol derivatives result in a particularly strong and lasting effect. For example, it can be shown that the mixture of a condensation product of nonylphenol and acetone with diethyl sulfide or the mixture of diisobornyl-p-cresol with diethyl sulfide show a less good stabilizing effect than the corresponding phenol alone.

attempt

stabilizer

Concentration in
Weight percent

Embrittlement time
in days
at 18O ⁰ C

Condensation product from nonylphenol and acetone

Diisobornyl-p-cresol

CH ₃

0.5

Comparative example
Comparative example

continuation

attempt
No.

Stabilizer concentration in
Weight percent

Embrittlement time
in days
at 180 ^° C

C ₂ H ₅ -SC ₂ H ₅ diethyl sulfide

Bis (octadecylmercapto) diethyl ether

Condensation product

Nonylphenol and acetone

+ Diethyl sulfide

Condensation product

Nonylphenol and acetone

+ Bis (octadecylmercapto) diethyl ether

Diisobornyl-p-cresol

+ Diethyl sulfide

Diisobornyl-p-cresol

+ Bis-octadecylmercaptoJ diethyl ether 0.5
0.5

0.25
0.25

0.25
0.25

0.25
0.25

0.25
0.25

Comparative example Comparative example

Comparative example

inventive example

Comparative example

inventive example

The examples given show that diethyl sulfide in combination with the two phenolic Stabilizers do not result in synergism. The faster embrittlement in experiment no.5 compared to no.1 and Trial No. 7 versus No. 2 is on reducing the phenolic component of 0.5 attributable to 0.25 percent by weight. The superiority of the stabilizer mixtures according to the invention also compared to the mixtures described in Belgian patent 571035 is evident from the comparative test set out in the table below.

Stabilizers concentration
in percent by weight Embrittlement time
in days at 140 ° C Color according to
Tempering Condensation product
Nonylphenol and acetone
+ Thio-bis- (4-hydroxy-2-methyl-5-tert-butylphenol)
Condensation product
Nonylphenol and acetone
+ Dibutyl sulfide 0.25
0.25
0.25
0.25 } »
}> ² Brown
unchanged,
colorless;

The testing was carried out at 140 ⁰ C in a convection oven to polypropylene plates.

It follows that the mixture of the condensation product of nonylphenol and acetone with thio - bis - (4 - hydroxy - 2 - methyl - 5 - tert - butylphenol) the stabilizer effectiveness of the invention Mixture slightly surpasses, but a very disadvantageous discoloration the test plates gives rise to.

This shows that a very careful selection of the organic sulfur compound is required in order to achieve the desired synergism on the one hand, but on the other hand no new disadvantages to exchange.

Claims (1)

Claim: Process for stabilizing polyolefins by means of a mixture of a) a phenol derivative and b) an organic sulfur compound, characterized in that b) symmetrical thioethers of the general formula R —S —R 45 55 60 where R is an aliphatic radical having 4 to 5 or 21 to 25 carbon atoms or unsymmetrical thioethers of the general formula R - S - R ' where R is an alkyl radical having 4 to 25 carbon atoms, R 'is a hydroaromatic hydrocarbon, represents a benzene, thiophene, naphthalene radical or a higher condensed nucleus or compounds of the general formula R-S - (R ') n -S -R used, where R is a hydrocarbon radical with 4 to 25 carbon atoms and R 'is a hydrocarbon radical with η = 1 to 20 or an optionally alkylated thiophene, naphthalene, anthracene nucleus or a hydrogenated nucleus or the groups - (CHs) ₂ - O - (CHa) ₂ - means. Considered publications: Austrian patents No. 203 211,203209, 202774. 809537/596 3.68 Q Bundesdruckerei Berlin