CA1087794A

CA1087794A - Stabilized polyolefins

Info

Publication number: CA1087794A
Application number: CA302,309A
Authority: CA
Inventors: Leo L. Valdiserri; Elyse M. Bullock
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1977-05-06
Filing date: 1978-05-01
Publication date: 1980-10-14
Also published as: GB1574114A; BE866776A; DE2819875C2; JPS6228171B2; JPS53140346A; FR2389652A1; FR2389652B1; DE2819875A1

Abstract

STABILIZED POLYOLEFINS

Abstract of the Disclosure An ultraviolet stabilizer for olefin polymers. It is a combination of a 2-hydroxyphenylbenzotriazole, a dialkyl pentaerythritol diphosphite and a phenolic ester oxidation inhibitor.

Description

~ ) 77014-M

1087~794 Stabilized Polyolefins This invention relates as indicated to stabilized polyolefins.
More particularly it relates to such polyolefins as are stabil;zed against deterioration which ordinarily results from prolonged exposure to ultra-violet light. Still more particularly, it relates to the stabilization of polyolefins as ab~ve by means of small proportions of certain additives.
, ---- , -- . .

- Background of the Invention 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 initial : ~ -flexibility, dimensional change, surface craze, cracking, po~dering or `~
increased electrical conductivity. All of these e~fects 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 radia-ion. 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 280- -- 390 mm.

10~7 794 . .
Olefin polymers which are stabilized by an ultraviolet stabilizer frequently contain also an oxidation inhibitor.
This is especially so where it is important to achieve light stable polymer compositions. A wide variety of antioxidants are available.
McNally, U.S. 4,000,101 (Dec. 28/76) 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. 3,988,293 (Oct. 26/76) shows the particular combination of 2-hydroxy-4-n-octoxybenzophenone and distearyl pentaerythritol diphosphite as a stabilizer for olefin ~:
~ polymers.
S The specification of ~.S. Patent No. 4,064,100 issued December 20, 1977 (I. Hechenbleikner) teaches the combination of distearyl pentaerythritol diphosphite with a wide variety of ;~ ~ ~ other polymer additives including 2-(2'-hydroxy-5'-methyl phenol) ~; benzotriazoles.
Dexter et al., U.S. 3,285,855 (Nov. 15/66) and U.S.
3,644,482 (Feb. 22/72) show (4-hydroxy-S-alkylphenyl)alkanoic acid ' esters o~ monohydric and polyhydric alcohols and refer to their combined use with "synergizing stabilizers ( W absorbers, phos~hites, dialkyl thiodiproprionates, and the like." Gilles, U.S. 3,531,483 (Sept. 29/70) contains a similar statement, applicable to the hydroxy-phenylalkeneyl isocyanurates.
Summary of the Invention It has been found that the effectiveness of certain

2-hydroxyphenylbenzotriazoles as ultraviolet stabilizers in olefin polymers is ~nexpectedly enhanced by the presence of small propor-tions 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 ho~rs.

` ~ ) 77014-M
1~)87794 .
Description of the Preferred Embodiments The 2-hydroxyphenylbenzotriazoles contemplated herein are those which conform to the structural formula X ~

where Rl is lower alkyl or halogen (preferably chlorine), R2 is lower 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-~'-tertiary-~ butylphenyl)benzotriazole, 2-(2'-hydroxy-5'-amylphenyl)5-chlorobenzotriazole, ,s 2-(2'-hydroxy-3'-tertiarybutyl-5'-methylphenyl)benzotriazole (Tinuvin 326), 2-(2'-hydroxy-5-methylphenyl)benzotriazole (Tin win P), 2-(2'-hydroxy-3',5'-dimethylphenyl)5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-ditertiaryoctyl-~henyl)benzotriazole (Tinuvin 328), 2-(2' hydroxy-3',5'-dichlorophenyl)benzo-triazole, and 2-(2'-hydroxy-3'-methyl-5'-tertiaryoctylphenyl)benzotriazole.
The term "lower alkyl" denotes an alkyl group having 1-10 carbon atoms.
Many of the benzotriazoles of this invention are available under the trademark desi~nation Tinuvin 32~, Tinuvin 327, Tinuvin 328, Tinuvin P, etc. (See abo~e.) 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: -2 H ~ HO ~

t ~ 77014-M

R ~ N \ ~

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 are used, for the purposes of this invention, in concentrations ranging from about 0.01 percent to about 5.0 percent.
Best results are obtained at concentrations within the range of from about 0.1 percent to about 0.5 percent, based on the olefin polymer.
The dialkyl pentaerythritol diphosphite component of the combination of the invention may be either the spiro or the caged isomer, i.e., , .
~OC~ ~CH2C ~CH20~
~ ROP \ / C \ / POR or(RO)2POCH2C \ CH20 - P

" OCH2 CH2 " CH20 . ~ . .
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.

) ~ 77014-~1 ~)87794 A preferred form of such dialkyl pentaerythritol diphosphite is that in which the diphosphite is mixed with a small amount of the alcohol from which the diphosphite is prepared, e.g., stearyl alcohol. T~lis is especially preferred where the alkyl groups are large, i.e., hexadecyl, stearyl, eicosyl, etc., and where it is desirable to insure the friable nature of the solid product. The presence of 5-lOX of stearyl alcohol, for example, imparts to distearyl pentaerythritol diphosphite, a decidedly 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 diphosphite.
- The relative proportions of dialkyl pentaerythritol diphosphite used herein range from about 0.05 percent to about 1.0 percent, based on the olefin polymer.
The phenolic ester oxidation inhibitors contemplated herein are those embraced by the structural formula , , . . . - .
,,,. _ _ . `.

H0 ~ CH2fHC00- - A
R' R"
n - where R and R' are lower alkyl, i.e., alkyl of 1-10 carbon atoms, R" is lower alkyl or hydrogen, n is 1~4, and A is the residue of an alkanol or alkane polyol. Illustrative examples of A include l 2 ~ CH
- CH2 1 CH2' C18H37~ CH2CH2, CH2CHCH2 and (CH3)2c \ 2

3 j 77014-M

A contains 2-24 carbon atoms. Preferably, A is C18H37. The relative pro-portion of antioxidant used in the stabilized polyolefins of this invention range from about 0.01 percent to about 3.0 percent, based on the olefin polymer.
These 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 polymer particles, or they may be blended as a melt in an extruder, or they may be mixed on a roll mill, or in a ~anbury mixer.
Other additives can also be added to the olefin polymer including fillers, pigments, ant,static agents and the like. 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 con-verted by extrusion, injection moiding, blow molding and the like into a variety of molded objects, filaments, films, sheets, etc.
The efficacy of these polymer compositions is shown by data obtained from Weather-Ometer testing using a xenon arc as a source of ultraviolet radiation. The test samples are held by clamps and the atmosphere in the Weather-Ometer is maintained at a temperature of 110F.
For 20 minutes of each hour of the test period a thin spray of water is applied to the samples to simulate rain-fall. 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 ) 77014-~1 10~7794 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-ditertiarybutylphenyl)propionate. Sample No. 1 contained only 100 parts of polypropylene and 0.05 parts of calcium stearate. The ` test results are as follo~s:

Test Sample UV Stabilizer(a) Phosphite( )Hours to Failure .,' ' (c) _ _ 140 ~, 2 ---- ---- 470 3 0.15 ---- 920 , 0.1~ 0.15 1780 (a3 2(2'-hydroxy-3',5'-ditertiarybutylphenyl)5-chlorobenzotriazole.
(b) distearyl pentaerythritol diphosphite.
(c) contains no antioxidant.

The olefin polymers which are benefitted 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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A polymer composition stabilized against deterioration in the presence of ultraviolet radiation com-prising an olefin polymer and stabilizing amounts of (1) a 2-hydroxyphenylbenzotriazole having the structural formula wherein R1 is lower alkyl or halogen, R2 is lower 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 having the structural formula where R and R' are lower alkyl, R" is lower alkyl or hydrogen, n is 1-4, and A is the residue of an alkanol or alkane polyol.

2. The polymer composition of claim 1 characterized in that the olefin polymer is a polymer of propylene.

3. The polymer composition of claim 1 characterized in that the olefin polymer is polypropylene.

4. The polymer composition of claim 1 characterized in that component (1) is 2,(2'-hydroxy-3',5'-ditertiarybutyl-phenyl)5-chlorobenzotriazole.

5. The polymer composition of claim 1 characterized in that component (2) is distearyl pentaerythritol diphosphite.

6. A method for stabilizing an olefin polymer against deterioration in the presence of ultraviolet radiation comprising adding stabilizing amounts of (1) a 2-hydroxyphenylbenzotriazole having the structural formula where R1 is lower alkyl or halogen, R2 is lower 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 having the structural formula where R and R' are lower alkyl, R" is lower alkyl or hydrogen, n is 1-4, and A is the residue of an alkanol or alkane polyol.