GB1574114A

GB1574114A - Stabilized polyolefins

Info

Publication number: GB1574114A
Application number: GB1806878A
Authority: GB
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1977-05-06
Filing date: 1978-05-05
Publication date: 1980-09-03
Also published as: CA1087794A; FR2389652B1; JPS6228171B2; DE2819875A1; BE866776A; FR2389652A1; DE2819875C2; JPS53140346A

Description

(54) STABILIZED POLYOLEFINS (71) We, BORG-WARNER CORPORATION, a Corporation duly organised and existing under and by virtue of the laws of the State of Delaware, of 200 South Michigan Avenue, Chicago, Illinois 60604, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to stabilized olefin polymers. More particularly it relates to such olefins polymers as are stabilized against deterioration which ordinarily results from prolonged exposure to ultraviolet light. Still more particularly, it relates to the stabilization of olefin polymers by means of small proportions of certain additives.

Ultraviolet light has a degradative effect on olefin polymers, the severity of which is dependent on the particular polymer and the geographical location of exposure. The degradation may take the form of discoloration, loss of tensile and impact strength, distortion of mitial flexibility, dimensional change, surface craze, cracking, powdering or increased electrical conductivity. All of these effects may result from the breaking of carbon-to-carbon bonds in the polymer chain followed by immediate oxidation of the chain fragments.

It is well known that the addition of certain materials to an olefin polymer will impart a degree of stabilization to that polymer with respect to its resistance to the destructive forces of ultraviolet radiation. These materials, in one instance, function as preferential acceptors of incident ultraviolet radiation because they have a much higher affinity for such radiation than does the olefin polymer. It appears that they absorb harmful radiation and dissipate it as harmless energy.

They thus form a protective shield for the polymer in which they are present.

Although there are many types of ultraviolet stabilizers, an important class includes the 2-hydroxyphenylbenzotriazoles. They offer strong intensity and broad ultraviolet stabilization with a fairly sharp wavelength limit close to the visible region. They absorb light at 280390 mm.

Olefin polymers which are stabilized by an ultraviolet stabilizer frequently contain also an oxidation inihibitor. This is especially so where it is important to achieve light stable polymer compositions. A wide variety of antioxidants are available.

McNally, U.S. Patent Specification No. 4,000,101, teaches the combined use of certain phenolic antioxidants, pentaerythritol diphosphites and ultraviolet stabilizers, in olefin polymers. The compositions there disclosed, however, contain a rather complex polythiopolyphosphite as the principal polymer additive.

Mills, U.S. Patent Specification No. 3,988,293, shows the particular combination of 2- hydroxy - 4- n- octoxybenzophenone and distearyl pentaerythritol diphosphite as a stabilizer for olefin polymers.

U.S. Patent Specification No. 4,064,100 teaches the combination of stearyl pentaerythritol diphosphite with a wide variety of other polymer additives including 2,(2' - hydroxy - 5' - methyl phenyl)benzotriazoles.

U.S. Patent Specifications Nos. 3,285,855 and 3,644,482, show (4 - hydroxy 5 - alkylphenyl)alkanoic acid esters of monohydric and polyhydric alcohols and refer to their combined use with "synergizing stabilizers (UV absorbers, phosphites, dialkyl thiodipropionates, and the like." Gilles, U.S. Patent Specification No.

3,531,483 contains a similar statement, applicable to the hydroxyphenylalkenyl isocyanurates.

It has been found that the effectiveness of certain 2hydroxyphenylbenzotriazoles as ultraviolet stabilizers in olefin polymers is unexpectedly enhanced by the presence of small proportions of a dialkyl pentaerythritol diphosphite and certain phenolic ester oxidation inhibitors. The combination of these three additives is effective to extend the useful life of polypropylene, for example, by many hours.

The 2-hydroxyphenylbenzotriazoles contemplated for use herein are those which conform to the structural formula

where R, is C1-C10 alkyl or halogen (preferably chlorine), R2 is C,--C,, alkyl, halogen (preferably chlorine) or hydrogen, and X is chlorine or hydrogen Illustrative examples of such 2-hydroxyphenylbenzotriazoles include 2(2' hydroxy - 3',5' - ditertiarybutylphenyl)5 - chlorobenzotriazole ("Tinuvin" 327), 2 - (2' - hydroxy - 3',5' - dimethylphenyl)benzotriazole, 2 - (2' - hydroxy - 5' tertiarybutylphenyl)benzotriazole, 2 - (2' - hydroxy - 5' - amylphenyl)5 chlorobenzotriazole, 2 - (2' - hydroxy - 3' - tertiarybutyl - 5' methylphenyl)benzotriazole ("Tinuvin" 326), 2 - (2' - hydroxy - 5 methylphenyl)benzotriazole ("Tinuvin" P), 2 - (2' - hydroxy - 3',5' dimethylphenyl)5 - chlorobenzotriazole, 2 - (2' - hydroxy - 3',5' ditertiaryoctylphenyl)benzotriazole ("Tinuvin" 328), 2 - (2' - hydroxy - 3',5' dichlorophenyl)benzotriazole, and 2 - (2' - hydroxy - 3'- methyl- 5'tertiaryoctylphenyl)benzotriazole.

Many of the benzotriazoles used in accordance with this invention are available under the trademark designation "Tinuvin" 326, "Tinuvin" 327, "Tinuvin" 328 and "Tinuvin" P ("Tinuvin" is a Registered Trademark). They may be prepared by coupling an aromatic diazo compound with an aromatic amine, followed by oxidation of the coupled intermediate. An illustrative preparation is as follows:

Other methods of preparation are set out in U.S. 3,004,896 (Heller et al.) and U.S.

3,189,615 (Heller et al.).

These benzotriazoles suitably are used, for the purposes of this invention, in concentrations ranging from 0.01 percent to 5.0 percent. Best results are obtained at concentrations of from 0.1 percent to 0.5 percent, based on the olefin polymer.

The dialkyl pentaerythritol disphosphite component of the combination of the invention may be either the spiro or the caged isomer, i.e.,

/0CH /CH20 /CH20\ ROP aC\ I POR or (RO)2POCll2CCH20P 'RO CH2O OCH2 C1120 SPIRO CAGED or it may be a mixture, in any proportion, of the two. R in the above equation is an alkyl group of 8-20 carbon atoms. Such a mixture results from the reaction of an alcohol, as the source of R with diphenyl pentaerythritol diphosphite, which in turn may be prepared by the reaction of triphenyl phosphite with pentaerythritol.

The alkyl group preferably is stearyl, i.e. C18H37; other illustrative alkyl radicals include decyl, dodecyl, tetradecyl, hexadecyl and eicosyl radicals.

A preferred form of such dialkyl pentaerythritol diphosphite is that in which the disphosphite is mixed with a small amount of the alcohol from which the diphosphite is prepared, e.g. stearyl alcohol. This is especially preferred where the alkyl groups are large, e.g. hexadecyl, stearyl or eicosyl, and where it is desirable to ensure the friable nature of the solid product. The presence of 510% of stearyl alcohol, for example, imparts to distearyl pentaerythritol diphosphite, a decidely friable character. This is desirable because it permits the product to be handled more conveniently. The usual method of preparing such a product involves simply using an excess of the alcohol, e.g. stearyl alcohol, in the reaction with diphenyl pentaerythritol disphosphite.

The proportions of dialkyl pentaerythritol diphosphite suitably used herein range from 0.05 percent to 1.0 percent, based on the olefin polymer.

The phenolic ester oxidation inihibitors contemplated herein are those embraced by the structural formula

where R and R' are C1-C10 alkyl, R" is C1-C10 alkyl or hydrogen, n is 1--4, and A is the residue of an alkanol or alkane polyol. Illustrative examples of A include

A contains 2-24 carbon atoms. Preferably, A is C18Hs7. The proportion of antioxidant used in the stabilized olefin polymers of this invention suitably is from 0.01 percent to 3.0 percent, based on the olefin polymer.

The stabilizing ingredients may be added to the olefin polymer in any conventional manner. They may, for example, be blended into the polymer as dry powders, or they may be dissolved in one or more solvents and sprayed onto finely divided polymers particles, or they may be blended as a melt in an extruder, or they may be mixed on a roll mill, or in a Banbury mixer.

Other additives can also be added to the olefin polymer including fillers, pigments and antistatic agents. Metal stearates, for example, are commonly added as lubricants, or as neutralizers, or to impart a measure of heat stability to the polymer composition.

The olefin polymer compositions contemplated herein can be converted, for example by extrusion, injection molding or blow molding, into a variety of molded objects. filaments, films or sheets.

The efficacy of these polymer compositions is shown by data obtained from Weather-Ometer testing using a xenon arc as a source of ultraviolet radation. The test samples are held by clamps and the atmosphere in the Weather-Ometer is maintained at a temperature of 110"F. For 20 minutes of each hour of the test period a thin spray of water is applied to the samples to simulate rainfall. Test samples are prepared by compression molding the indicated polymer compositions to form an 0.003-inch thick film.

The test samples are removed from the Weather-Ometer at periodic intervals, usually every 100 hours, and analyzed for carbonyl content by means of infrared curves. That is, the area under the peak at 5.8 microns is taken as a quantitative measure of the carbonyl content of the test sample. When the test sample is shown to have developed an increase of 0.1 percent in carbonyl content, it is regarded as having failed and the hours of exposure until such failure is a measure of the efficacy of the test sample as an ultraviolet stabilizer.

Each of the test samples, except for No. 1, contained 100 parts of polypropylene, 0.05 parts of calcium stearate and 0.1 part of octadecyl 3(4 hydroxy - 3,5 - diteriarybutylphenyl)propionate. Sample No. 1 contained only 100 parts of polypropylene and 0.05 parts of calcium stearate. The test results are as follows: Test Sample UV Stabilizer'"' PhosphitelbM Hours to Failure {c) ~ ~ 140 2 470 3 0.15 920 4 0.30 1150 5 0.15 0.15 1780 (a) 2(2' - hydroxy - 3',5' - ditertiarylbutylphenyl)5 - chlorobenzotriazole.

(b) distearyl pentaerythritol diphosphite.

(c) contains no antioxidant.

The olefin polymers which are benefited by the above combination of stabilizing additives include homopolymers and copolymers of monoolefins; preferably those monoolefins having 1--4 carbon atoms. Illustrative examples include polyethylene (both low density and high density), polypropylene, polyisobutylene, and copolymers of ethylene, propylene and isobutylene. EPDM polymers are also contemplated.

WHAT WE CLAIM IS: 1. A polymer composition, stabilized against deterioration due to ultraviolet radiation, comprising an olefin polymer and stabilizing amounts of (1) a 2hydroxyphenylbenzotriazole of formula:

wherein R, is C,--C,, alkyl or halogen, R2 is C,--C,, alkyl, halogen or hydrogen, and X is chlorine or hydrogen; (2) a dialkyl pentaerythritol diphosphite wherein the alkyl groups each contain 8-20 carbon atoms; and (3) a phenolic ester oxidation inhibitor of formula:

where R and R' are C,--C,, alkyl, R" is C,--C,, alkyl or hydrogen, n is an integer from 1 to 4 and A is the residue of an alkanol or alkane polyol.

2. A polymer composition according to claim 1 in which the olefin polymer is a polymer of propylene.

3. A polymer composition according to claim 2 in which the olefin polymer is nolypropylene.

4. A polymer composition according to any one of claims 1 to 3 in which component (1) is 2,(2' - hydroxy - 3',5' - ditertiarylbutylphenyl)5 chlorobenzotriazole.

5. A polymer composition according to any one of claims 1 to 4 in which component (2) is distearyl pentaerythritol diphosphite.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

The test samples are removed from the Weather-Ometer at periodic intervals, usually every 100 hours, and analyzed for carbonyl content by means of infrared curves. That is, the area under the peak at 5.8 microns is taken as a quantitative measure of the carbonyl content of the test sample. When the test sample is shown to have developed an increase of 0.1 percent in carbonyl content, it is regarded as having failed and the hours of exposure until such failure is a measure of the efficacy of the test sample as an ultraviolet stabilizer.

Each of the test samples, except for No. 1, contained 100 parts of polypropylene, 0.05 parts of calcium stearate and 0.1 part of octadecyl 3(4 hydroxy - 3,5 - diteriarybutylphenyl)propionate. Sample No. 1 contained only 100 parts of polypropylene and 0.05 parts of calcium stearate. The test results are as follows: Test Sample UV Stabilizer'"' PhosphitelbM Hours to Failure {c) ~ ~ 140

2 470

3 0.15 920

4 0.30 1150

5 0.15 0.15 1780 (a) 2(2' - hydroxy - 3',5' - ditertiarylbutylphenyl)5 - chlorobenzotriazole.

(b) distearyl pentaerythritol diphosphite.

(c) contains no antioxidant.

The olefin polymers which are benefited by the above combination of stabilizing additives include homopolymers and copolymers of monoolefins; preferably those monoolefins having 1--4 carbon atoms. Illustrative examples include polyethylene (both low density and high density), polypropylene, polyisobutylene, and copolymers of ethylene, propylene and isobutylene. EPDM polymers are also contemplated.

WHAT WE CLAIM IS: 1. A polymer composition, stabilized against deterioration due to ultraviolet radiation, comprising an olefin polymer and stabilizing amounts of (1) a 2hydroxyphenylbenzotriazole of formula:

wherein R, is C,--C,, alkyl or halogen, R2 is C,--C,, alkyl, halogen or hydrogen, and X is chlorine or hydrogen; (2) a dialkyl pentaerythritol diphosphite wherein the alkyl groups each contain 8-20 carbon atoms; and (3) a phenolic ester oxidation inhibitor of formula:

where R and R' are C,--C,, alkyl, R" is C,--C,, alkyl or hydrogen, n is an integer from 1 to 4 and A is the residue of an alkanol or alkane polyol.
2. A polymer composition according to claim 1 in which the olefin polymer is a polymer of propylene.
3. A polymer composition according to claim 2 in which the olefin polymer is nolypropylene.
4. A polymer composition according to any one of claims 1 to 3 in which component (1) is 2,(2' - hydroxy - 3',5' - ditertiarylbutylphenyl)5 chlorobenzotriazole.
5. A polymer composition according to any one of claims 1 to 4 in which component (2) is distearyl pentaerythritol diphosphite.
6. A polymer composition according to any one of the preceding claims in

which from 0.01 to 5.0% by weight of component (1) is present, based on the weight of the olefin polymer.
7. A polymer composition according to claim 6 in which from 0.1 to 0.5% by weight of component (1) is present.
8. A polymer composition according to any one of the preceding claims in which from 0.05 to 1.0% by weight of component (2) is present based on the weight of the olefin polymer.
9. A polymer composition according to any one of the preceding claims in which from 0.01 to 3.0% by weight of component (3) is present, based on the weight of the olefin polymer.
10. A polymer composition according to claim 1 substantially as hereinbefore described in Test Sample 5.
11. A process for stabilizing an olefin polymer against deterioration due to ultraviolet radiation by the preparation of a polymer composition as claimed in any one of the preceding claims, comprising adding to the olefin polymer stabilizing amounts of (1) a 2-hydroxyphenylbenzotriazole of formula:

where R, is C1-C10 alkyl or halogen, R2 is C1-C10 alkyl, halogen, or hydrogen, and X is chlorine or hydrogen; (2) a dialkyl pentaerythritol diphosphite wherein the alkyl groups each contain 8-20 carbon atoms; and (3) a phenolic ester oxidation inhibitor of formula:

where R and R' are C,--C,, alkyl, R" is C,--C,, alkyl or hydrogen, n is low4, and A is the residue of an alkanol or alkane polyol.