DE1195047B - Molding compounds made from propylene polymers and stabilizer mixtures - Google Patents

Description

Molding compounds made from propylene polymers and polypropylene stabilizer mixtures is known to be used during processing into molded articles, for example by extrusion and injection molding, because of the high temperatures required, a strong thermal Subject to stress that leads to partial degradation of the polypropylene. As is known, degradation of polypropylene and copolymers of propylene occurs also when such polymers are exposed to light and for a long time exposed to elevated temperatures. It is known to have such a Degradation through the addition of stabilizers, in particular through alkylidene-bis (alkylphenols), Thiobis (alkylphenols) and substituted benzophenones, push back very strongly can.

It is also known to use polypropylene with mixtures of dialkyl thiodipropionates and at least one compound from the group of 2- (2'-hydroxyphenyl) -2, 4, 4-trimethyldialkylchromane, 4- (2'-hydroxyphenyl) -2,2,4-trimethyldialkylchroman or the alkylidene bis (alkylphenols) to stabilize.

From the French patent 1 269 406 molding compounds are from Polypropylene known as a stabilizer is a mixture of thio-bis (carboxamides) and thio-bis (alkylphenols). As examples of thio-bis (carboxamides) however, only N, N'-dilauryl-thio-bis- (propionic acid amide) and N, N, N ', N'-tetra-n-hexyl-thio-bis- (propionic acid amide) called. Individual compounds of thiobis (carboxamides) that are different from carboxylic acids derive with four or more carbon atoms are in this French patent but not listed by name. The stabilizing effect of mixtures Thio-bis (carboxamides) of the type mentioned in the French patent specification and alkylidene-bis (alkylphenols) against the harmful effects of elevated temperatures of oxygen and of light on propylene polymers leaves something to be desired (cf. the comparative experiments in Examples 1 to 3 of the following description).

It has now been found that molding compounds made from propylene polymers optionally in a mixture with other polyolefins and stabilizer mixtures (a) alkylidene-bis- (alkylphenols) or thio-bis- (alkylphenols) and (b) thio-bis- (carboxamides) a particularly good resistance to the damaging effects of light and heat if they are thio-bis- (carboxamide) thio-bis- (butyric acid-N-methyl-N-cyclohexylamide) contain.

Compared to the dialkyl thiodipropionates, said thiodicarboxamide is used less easily saponified, resulting in a somewhat longer effectiveness of the stabilizer combination guaranteed. The thio-bis- (carboxamide) shows only a very small amount by itself stabilizing effect for propylene polymers, but increases the effectiveness of the alkylidene-bis- (alkylphenols) and thio-bis- (alkylphenols) synergistically extraordinary strong. It is particularly noticeable for the effect of the stabilizer combination that Propylene polymers stabilized in this way under severe thermal stress discolour very little, while propylene polymers that only contain alkylidene-bis- (alkylphenols) or thio-bis- (alkylphenols) are very stabilized under the same conditions strongly discolor. This fact is all the more surprising as propylene polymers, which only contain thio-bis (carboxamides), with high thermal stress also strongly discolour.

The stabilized molding compositions according to the invention also discolor in the case of strong thermal stress, significantly less than those with mixtures stabilized from dialkyl thiodipropionates and alkylidene-bis (alkylphenols) are.

Suitable alkylidene-bis (alkylphenols) are, for example, 2,2'-methylene-bis- (4-methyl-6-tert.-butylphenol) and 2,2'-methylenebis (4-ethyl-6-tert-butylphenol). You can after known Process, for example, by reacting a corresponding alkylphenol with Formaldehyde, acetaldehyde, acetone or methyl ethyl ketone in the presence of acids, z. B. hydrochloric acid.

Suitable thio-bis (alkylphenols) are, for example, 4,4'-thio-bis (6- tert. -butyl-3-methylphenol), 2,2'-thio-bis- (5-tert-butylphenol), 2,2'-thio-bis- (5-isoamylphenol), 4,4'-thio-bis- (2-methyl-5-tert-butylphenol) and 2,2'-thio-bis- (3-tert-butyl-5-methylphenol).

The compounds can be prepared in a known manner, for example from phenols and disulfur dichloride obtained in the presence of aluminum chloride.

Propylene polymers for the purposes of the invention are in particular high molecular weight Homopolymers of propylene, as well as high molecular weight copolymers of propylene with ethylene, for example, which polymerizes more than 50 percent by weight of propylene contain. The stabilizers can be used in the high molecular weight propylene polymers usual way, e.g. B. in screw presses and multi-shaft disc kneaders, be added. The weight ratio of the thio-bis (carboxamide) to alkylidene-bis (alkylphenol) or thio-bis- (alkylphenol) is generally between 10 in the molding compounds: 1 and 0.5: 1, preferably between 3: 1 and 1: 1.

The total amount of the stabilizers can be within wide limits can be varied. It is generally between about 0.02 and 3 percent by weight, preferably between 0.1 and 1 percent by weight, based on the total weight of the Molding compound.

The molding compounds can contain the usual additives, such as dyes, fillers, Pigments, as well as other stabilizers, e.g. B. W stabilizers incorporated will. Other polyolefins, such as polyethylene, poly-isobutylene, can also be used and polybutene- (I), can be added.

The parts mentioned in the following examples are parts by weight; the molecular weights given therein were determined according to U b b e 1 h o d e (DIN 51562) certainly.

Example 1 In each 99.65 parts of polypropylene, which has the intrinsic viscosity ii = 3.4 and has a molecular weight of 540,000, mixtures of 0.1 parts each become 4,4'-thio-bis- (3-methyl-6-tert-butylphenol) and 0.25 parts of the specified thio-bis (butyric acid-N-methyl-N-cyclohexylamide) incorporated in the usual way. The molding compositions obtained are used for testing Kneaded in air in a commercially available plastograph at 220 ° C. for 1 hour. The plastograph shows the viscosity of the molten molding compound plotted against time. The viscosity of the molding compositions is at the beginning of kneading 2500 plastograph units and decreases within 1 hour of kneading to the value given in the table, column 3. Also in this table are in column 4 information on the discoloration of the stabilized molding compounds is given, which occur during 1 hour of kneading in the plastograph. This information is in Iodine scales were made and were determined by colorimetric comparison of the staining of the kneaded molding compounds with an iodine color scale, as described in DIN 53403 is described.

In addition, column 5 of the table below shows the molecular weights of the molding compositions after kneading for one hour. Plasto- g Ver graph- Thio-bis- (carboxamide) in iodine- a- scale weight share 1 y, y'-thio-bis- (butter- acid-N-methyl- N-cyclohexylamide) .. 1120 7 373 000 2 *) y, y'-thio-bis- (butter- acid-N-stearylamide) 1,100 8,375,000 *) The polypropylene stabilized with the γ, γ'-thio-bis- (butyric acid-N-stearylamide) containing stabilizer mixture has a much stronger tendency to yellow in daylight than the polypropylene, the y, y'-thio-bis- (butyric acid - N - contains methyl-N-cyclohexylamide).

Comparative experiment For comparison, molding compositions made of 99.65 each were used Parts of polypropylene, which has molecular weight 540,000 and intrinsic viscosity ? = 3.4 had, and mixtures of 0.25 parts each of thio-bis (propionic acid lauryl ester) and 0.1 part of 4,4'-methylenebis (3-methyl-6-tert-butylphenol) or 4,4'-thio-bis (3-methyl-6-tert-butylphenol) each kneaded for 1 hour at 220 "C. in the same plastograph. The viscosity of the molten molding compound drops to 720 plastograph units, the molecular weights to 325,000, and molding compounds are obtained which have a discoloration of 30 parts of iodine scale exhibit.

Example 2 In 99.65 parts of polypropylene, which is the intrinsic viscosity 71 = 3.4 and has a molecular weight of 540,000, a mixture of 0.1 part of methylene-bis- (3 - methyl -6- tert. - butylphenol) and 0.25 parts of y, y'-thio-b i s- (butyric acid-N-methyl-N-cyclohexylamide) incorporated in the usual way. The molding compound is, as indicated in Example 1, checked. The viscosity of the molding compound drops to 1060 within 1 hour of kneading Plastograph units, the molecular weight to 430,000. The discoloration is after kneading 6 iodine scale parts.

If only 0.1 part of methylene-bis (3-methyl-6-tert. -butylphenol) or 0.25 part of y, y'-thio-bis- (butyric acid-N-methyl-N-cyclohexylamide) incorporated, molding compositions are obtained whose viscosities are otherwise the same Kneading conditions to 85 resp.

40 plastograph units and their molecular weights to 80,000 resp. 29,000 are falling. The discoloration is then 85 or 160 iodine scale parts.

Example 3 In 99.65 parts of polypropylene, which is the intrinsic viscosity r = 3.4 and the molecular weight 540,000, it is incorporated in the usual way Mixture of 0.1 part of 4,4'-butylidene-bis- (3-tert-butyl-6-methylphenol) and 0.25 Divide thio - bis - (butyric acid-N-methyl-N-cyclohexylamide). The molding compound obtained is kneaded in a commercially available plastograph at 220 ° C. in air for 1 hour. The viscosity of the molding compound at the start of kneading is 2500 plastograph units and drops to 1280 plastograph units during kneading.

The discoloration of the molding compound after kneading is 5 parts of iodine scale, the molecular weight of polypropylene 440,000.

If you use instead of thio-bis- (butyric acid-N-methyl-N-cyclohexylamide) the same amount of thiobis (butyric acid lauryl ester), the molding compound is under otherwise the same conditions with one hour kneading in the plastograph so far, that their viscosity corresponds to only 1080 plastograph units. The discoloration the molding compound in this case corresponds to 6 iodine scale parts. The molecular weight of the polypropylene is only 314,000 after kneading.

Claims (1)

Claim: Molding compounds made from propylene polymers, if appropriate in a mixture with other polyolefins, and stabilizer mixtures of (a) alkylidene-bis- (alkylphenols) or thio-bis (alkylphenols) and (b) thio-bis (carboxamides), d a d u r c it is noted that it is called thio-bis (carboxamide) thio-bis (butyric acid-N-methyl-N-cyclohexylamide) contain. Documents considered: French patent specification No. 1,269,406.