DE1169662B - Process for stabilizing low pressure polyolefins - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C08f

German class: 39 b -22/06

Number: 1169 662

File number: P 24593 IV c / 39 b

Filing date: March 11, 1960

Opening day: May 6, 1964

The invention relates to stabilizing low pressure polyolefins, i. H. Polyolefins that by polymerization or copolymerization of olefinic hydrocarbon compounds, in particular Olefins with up to 10 carbon atoms in the molecule, e.g. B. ethylene and propylene Pressures less than 500 atmospheres have been obtained.

Such low pressure processes are e.g. B. in British Patents 799 392, 799 823 and 801 031.

The subject of patent 1 065 170 is a process for stabilizing polyolefins or copolymers of low molecular weight olefins, which contain a polyolefin produced by the low-pressure polymerization process as the main component, against oxidative degradation in the heat, whereby, according to the invention, the solid dry polymers up to I ⁰ J ₀ , preferably 0.2 to 0.6%, based on the polymer, of an organic phosphite of the general formula

R'O

RO

P-OR "

optionally in a mixture with a known stabilizing agent and / or antioxidant is incorporated and where R 'and R "represent the same or different hydrocarbon groups, the Can be alkyl, cycloalkyl, aryl, alkaryl or aralkyl radicals.

It has now been found that a surprising stabilizing effect occurs when it is known Stabilizing agents phenolic antioxidants optionally containing sulfur or nitrogen atoms be used.

The phenolic compounds known as antioxidants, when used alone, have the disadvantage on that they cause pronounced discoloration of the colorless or light-colored Ziegler polyolefins and are therefore completely unsuitable for certain uses of the polyolefins. It it is clear that the problem of discoloration with dark colored, especially black Ziegler polyolefins does not appear.

Stabilizing low pressure polyolefins with phosphites also in conjunction with others Antioxidants are known from Belgian patent 554,304. The phosphite-containing ones mentioned Antioxidants have, among other things, their own processes for stabilizing low-pressure polyolefins

Addendum to the patent: 1 065 170

Applicant:

Shell Internationale Research Maatschappij N.V., The Hague

Representative:

Dr.-Ing. F. Wuesthoff, Dipl.-Ing. G. Pulse and
Dipl.-Chem. Dr. rer. nat. E. Frhr. v. Bad luck man,
Patent Attorneys, Munich 9, Schweigerstr. 2

Named as inventor:
Robert Nobbs Haward, Bowden, Cheshire,
Christopher Carteret Gosselin,
Flixton, Manchester (Great Britain)

Claimed priority:

Great Britain March 13, 1959 (8785),

dated October 13, 1959 (34 666)

to prevent the degradation of the polymers and, to a certain extent, also the discoloration from Z. B. to inhibit low-pressure polyethylene at elevated temperature. In contrast, receives However, when using phenolic compounds as stabilizers, in general one Discoloration of light-colored polymers. So these antioxidants are used to stabilize light Polymers hardly usable. In contrast, the phosphites are useful and cause only slight discoloration. These facts were known. But like the Belgian patent specification 304 can be seen, has the mixture of Ziegler polyethylene and an organic phosphite after hot rolling a color number from 53 to 60, while the same non-stabilized polyethylene then a color number of 47 and, if a phenolic compound is added after hot rolling, a color number from about 12 to 20. The color number is therefore when a phenolic stabilizer is used

409 588/465

significantly worse from that of a non-stabilized mass. It follows that from a stabilizing Light colored Ziegler polyolefin with a phenolic compound was not recommended.

Nevertheless, it was surprisingly found that when phenolic compounds are added an improved color number is obtained for a phosphite antioxidant.

The one in Belgian patent specification 554 304

called antioxidants such as glycidyl polyether or io half about 100 ° C or

are generally useful. As examples of particularly suitable phenolic compounds these groups include 4,4'-thio-bis- (3-methyl-6-tert-butylphenol), called the N-stearyl-p-aminophenol and the N-lauryl-p-aminophenol.

The additives mentioned are with the polymer z. B. mixed in a powder mixer and then the resulting mixture at elevated temperature z. B. by grinding at a temperature of

Tin alkyl esters, which can be used in addition to the phosphites, have compared to the Phenolic compounds used according to the invention have the disadvantage that they are in the case of metal compounds reduce the "electrical" properties of the polymer, in the case of polyethers, the Adversely affect the color of low-pressure polyolefins.

In general, a total amount of up to about 3% will generally suffice to stabilize the polyolefins about 0.1 to 2% of the additives mentioned, based on the weight of the low-pressure polyolefin. The amount of the organic is advantageously

the amount of by extrusion or mixer according to Banbury

Phosphite about 0.1 to 1.0%
phenolic antioxidant by mixing in one
mechanically processed.

Particularly preferred organic phosphites used according to the invention are the trialkyl phosphites, z. B. trilauryl and trioctyl phosphite, and certain aryl phosphites, e.g. B. the tri- (nonylphenyl) phosphite.

The invention is explained in more detail with reference to the following examples, the percentages being based on based on the weight of the polyolefin.

example 1

A Ziegler polyethylene (density 0.945, intrinsic viscosity 2.75, melt index 0.20)

0.5% · Mixtures of one or more organic phosphites, e.g. B. alkyl or Alkylaryl phosphites, together with one or more phenolic antioxidants in the Polyolefins be present.

Examples of the organic phosphites which can be used according to the invention are: tri- (hexyl) phosphite, Tri - (2 - ethylhexyl) - phosphite, tri - (lauryl) - phosphite, tri (octyl) phosphite, tri- (p-isopropylphenyl) phosphite, Tri- (p-tert-butyl-phenyl) -phosphite, di- (p-tert-butylphenyl) -monophenylphosphite, Tri- (n-octyl) -phosphite, tri- (n-nonyl) -phosphite, tri- (nonyl-phenyl) -phosphite, tri- (stearyl) -phosphite and tri- (cyclohexyl) -phosphite.

The use of the phenolic antioxidants used according to the invention is with rubber and polymers in general, including polyolefins, are already known. Examples of phenolic Antioxidants are e.g. B. in Industrial and Engineering Chemistry, Vol. 41, 1949, No. 7, p. 1442 until 1447. As mentioned in the documents on which the patent 1 065 170 is based, this has been proven Such phenolic antioxidants as such are suitable for use in natural-colored and light-colored Ziegler polyolefins as unsuitable, and it is a particular advantage of the invention Stabilization that the presence of the organic phosphite the discoloration by the phenolic Can prevent antioxidants. In addition, with the phenolic antioxidant a particularly effective stabilizer combination is present.

Preferred phenolic antioxidants are as follows: 4,4'-thio-bis- (3-alkyl-6-tert-alkylphenols) and N-acyl-p-aminophenols, also 2,6-di-tert-butyl-

about 0.01 to 25 with 0.05% 4,4'-thio-bis- (3-methyl-6-tert-butyl-phenol)

In a mill with two rollers for 5 minutes at a surface temperature of the rollers of about 160 ^° C., then for a further 10 minutes before it was pressed into foils ^{in a press heated to about 180 ° C.} Additional batches of the same polyethylene were made up in the same manner except that various amounts of trilauryl phosphite were added to the plastic material prior to milling for 10 minutes. The results are compiled in the following table, the color ratings being obtained in a normal reflection test and the rating 60 being the transparent or white polymer and the rating indicating the completely black polymer.

additive 0.05% 4,4'-thio-bis (3-methyl- Colours
valuation 6-tert-butyl-phenol) 36 0.1% 0.2% Trilauryl phosphite + 0.05% 50 0.3% 4,4'-thio-bis (3-methyl- 53.5 0.4% 6-tert-butyl-phenol) 53.5 0.5% 53.5 54

Example 2

There were three further approaches of the polyethylene used in Example 1 with (a) 0.5% trilauryl phosphite, (b) 0.5% trilauryl phosphite and 0.02% 4,4'-thio-bis- (3-methyl-6-tert-butyl-phenol) or (c) 0.05% 4,4'-thio-bis (3-methyl-6-tert-butyl-phenol)

Grind 4-methylphenol, 2,2'-methylene-bis (5-isopropylphenol) 60, the grinding being carried out as in Example 1 and 2,2'-methylenebis (4-methyl-6-tert-butylphenol), was made. Samples from each batch were made

then tested by extrusion at 220 ⁰ C and injection ^{molding at 240 and 280 0} C and the color rating, intrinsic viscosity number and the melt index

although also z. B. Di-o-cresylolpropane, 2,4-dimethyl-6-tert-butylphenol, Phenols of the group of bis (2-hydroxy-3,5-dialkylphenyl) alkanes and the ent

speaking, optionally alkyl-substituted 3-cyclo-65 determined after processing. The basal molars alkyl compounds, especially bis- (2-hydroxy viscosity, was found in the 0.1% solution in decalin 3-tert-butyl-5-methylphenyl) methane and bis (2-hydroxy-S-A-methylcyclohexyl-S-methylpheny ^ -methane

determined at 120 ° C. The test results are compiled in the following table.

additive

Physical properties after processing

extruded at 22O ⁰ C

grand- I color molar | Viscosity!

sprayed at 240 ⁰ C

colour

basal molars
viscosity

Melt index

molded at 28O ⁰ C

colour

basal molars
viscosity

Melt index

0.5 7o trilauryl phosphite 54 2.60 0.31

0.5% trilauryl phosphite + 0.02% 4,4'-thio-bis- (3-methyl-6-tert-butyl-phenol) 56 2.71 0.28

0.05% thio-bis- (3-methyl-6-tert-butyl-phenol) 53.5 2.28 0.24

Example 3

A sample of Ziegler polyethylene (density 0.950, intrinsic viscosity 1.52, melt index 2.6) was made by grinding the polyethylene for 15 minutes in a mill with two rollers at a surface temperature of the mill of about 160 ° C and then pressing the material Shaped into foils in a press heated to about 180 ^{° C.} The following table shows the results obtained on the one hand with the addition of a phenolic antioxidant alone and on the other hand with the stabilizer mixture of a phenolic antioxidant and an organic phosphite used according to the invention.

additive

0.5% trilauryl phosphite

0.05% 4,4'-thio-bis- (3-methyl-6-tert-butyl-phenol)

0.05% 4,4'-thio-bis- (3-methyl-6-tert-butyl-phenol) + 0.5% trilauryl phosphite

0.1% N-stearyl-p-aminophenol

0.1% N-stearyl-p-aminophenol + 0.5% trilauryl phosphite

Color rating

38 36

45 35.5

44

35

40

45 53.5

55
49

2.51

2.50
2.47

0.33

0.26
0.13

53
44

1.89

1.74

2.13

1.24

1.76

Claims (2)

Patent claims: 1. Process for stabilizing low pressure polyolefins or copolymers of low molecular weight olefins with organic phosphites the general formula R'O, R'O ' ; p -or " wherein R 'and R "are identical or different hydrocarbon groups represent, which mean alkyl, cycloalkyl, aryl, alkaryl or aralkyl radicals, in a mixture with known stabilizers according to patent 1065170, thereby characterized as being known stabilizers phenolic antioxidants optionally containing sulfur or nitrogen atoms be used. 2. The method according to claim 1, characterized in that the phosphite in an amount from 0.1 to 1 percent by weight and the phenolic antioxidant in an amount of 0.01 up to 0.5 percent by weight, based in each case on the polymer, is used. Considered publications:
Belgian patent specification No. 554 304 409 588/465 4.6Φ © Bundesdruckerei Berlin