DE1149165B - Stabilizing polyolefins - Google Patents

Description

Stabilizing polyolefins It is known that the disadvantageous Influence of heat, oxygen and light on polyolefins, through which, among other things the mechanical and electrical properties of the plastics are impaired, by adding stabilizers. The known stabilizers are sufficient not yet meeting the requirements, as their duration of action is quite limited and as they tend to discolour in many cases.

From the German Auslegeschrift 1108 427 it is also known that one polymers of propylene with reaction products of alkylphenols with ketones, d. H. Stabilize mixtures of multiply methylated 2- (2'-hydroxyphenyl) -chromane can. However, the stabilizing effect of these compounds leaves something to be desired.

It has now been found that 5,7,8-trimethyl-6-hydroxychroman, the in the 2-position by one or two aliphatic hydrocarbon radicals with together up to 14 carbon atoms or a divalent aliphatic hydrocarbon radical is substituted by up to 11 carbon atoms, optionally mixed with known polyolefin stabilizers, a particularly effective one, not to discolour is a tending stabilizer for polyolefins.

The production of the stabilizers used according to the invention is among others from VogelKnobloch, chemistry and technology of vitamins, Enke-Verlag Stuttgart (1955), Volume 1, pp. 279 ff., Known.

You can z. B. the stabilizers by condensation of trimethylhydroquinone with an alkylene bromide using zinc chloride in an inert solvent, such as gasoline or cyclohexane.

The stabilizers used according to the invention are similar to natural ones Tocopherols built up, which have long been used to stabilize fats and fatty acids Serve luxury foods. But this did not foresee that the more simply constructed synthetic trimethylhydroxychromans very well stabilizing in polyolefins works.

The following compounds are used, for example, as stabilizers Consideration: 2-isobutyl-2, 5,7, 8-tetramethyl-6-hydroxychroman, 2,2-pentamethylene-5,7,8-trimethyl-6-hydroxychroman, 2-N-ethylpentyl-5,7,8-trimethyl-6-hydroxychroman, 2-nonyl-2,5,7,8-tetramethyl-6-hydroxychroman, 2-tridecyl-2,5,7,8-tetramethyl-6-hydroxychromane, 2-tohexenyl-2,5,7,8-tetramethyl-6-hydroxychromane.

Polyolefins that are made with the help of these hydroxychroman compounds Can stabilize against the influence of light, heat and oxygen, are z. B. branched and linear polyethylene, polypropylene, copolymers of ethylene and propylene or polyisobutylene.

The stabilizers are expediently in amounts from 0.01 to 5 percent by weight, based on the amount by weight of polyolefin, is used. Advantageous are above all amounts of 0.05 to 2 percent by weight. Prove to be particularly effective the compounds can also be used together with other known stabilizing agents, such as compounds of the type of 2,2'-alkylene-bis- (4-alkyl-6-tert-butylphenol), thiodicarboxylic acid esters or thiolactams.

You can use the stabilizers in the usual way, for. B. with the help of a Screw press or a kneader or by mixing the powdered polyolefins with a solution of the stabilizer. With those mentioned in the examples Parts are parts by weight.

Example 1 100 parts of polypropylene (intrinsic viscosity = 3.15) in a mixer intimately with 0.1 part 2 - - ethylpentyl - 5,7,8 - trimethyl -6 - hydroxychroman mixed and then rolled at 190 "C with access to air. The Polymer is gradually degraded in the process. Its melt viscosity decreases, until it starts to drip off the rollers. The time until draining starts is 64 minutes. at is the same polypropylene with no additive the time 6 to 10 minutes.

In analogous experiments with 2-tridecyl-2,5,7,8-tetramethyl-6-hydroxychroman, 2-isohexenyl-2, 5,7, 8-tetramethyl-6-hydroxychromane and 2,2-pentamethylene-5,7,8-trimethyl-6-hydroxychromane take 78, 53 and 65 minutes to become liquid.

Are 100 parts of the polypropylene with an analog experiment a mixture of 0.1 part of 2-tridecyl-2,5,7,8-tetramethyl-6-hydroxychroman and 0.25 Parts of thiodilauryl ester stabilized, then the time until the start of dripping 96 minutes.

Example 2 0.1 part of 2-nonyl-2,5,7,8-tetramethyl-6-hydroxychromane are dissolved in 15 cm3 of acetone and mixed with 100 parts of polypropylene powder (intrinsic viscosity 1 = 3.15) mixed. After drying, the mixture is at 190 ° C. with admission of air rolled. The time to become liquid is 58 minutes. With the same polypropylene without addition it is 6 to 10 minutes.

Is also used to stabilize the polypropylene 0.25 part of dilauryl thiodipropionate is the time it takes to become liquid 83 minutes.

On the other hand, it takes the polypropylene to become liquid only 16 or 14 or 26 or 28 minutes if you replace a 5,7,8-trimethyl-6-hydroxychroman 0.1 part of a according to the information in Example 1 of the German Auslegeschrift 1108 427 produced reaction product from nonylphenol and acetone (A) or from nonylphenol and mesityl oxide (B) or a mixture of 0.1 part A and 0.25 part thiodipropionic acid dilauryl ester or from 0.1 part B and 0.25 part thiodipropionic acid dilauryl ester.

Example 3 100 parts of polyisobutylene (Fikentscher K value 211) are mixed well with 0.1 part of 2-tridecyl-2,5,7,8-tetramethyl-6-hydroxychroman (I) and rolled at 170.degree. C. on a rolling mill A sample is taken every 20 minutes and the K value is determined The same test is carried out with polyisobutylene and 0.1 01o 2-nonyl-2,5,7,8-tetramethyl-6-hydroxychroman (11) and with unstabilized polyisobutylene. The results are compiled in the table. Rolling time K-value to K-value g K-value Minutes without addition with 0.101, (I) | with 0s1 O / o (II) 0 211 211 211 20 202 212 206 40 202 206 205 60 199 202 198 80 187 202 198 100 184 196 196 120 148 196 193

Claims (1)

PATENT CLAIM: Use of 5,7,8-trimethyl-6-hydroxychromane, that in the 2-position by one or two aliphatic hydrocarbon radicals with together up to 14 carbon atoms or a divalent aliphatic hydrocarbon radical is substituted by up to 11 carbon atoms, optionally mixed with known polyolefin stabilizers, as stabilizers for polyolefins. Documents considered: German Auslegeschrift No. 1108 427.