JPS6228171B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyolefins stabilized as indicated. More particularly, the present invention relates to such polyolefins that are stabilized against degradation that normally results from prolonged exposure to ultraviolet light. Still more particularly, the present invention relates to the stabilization of the aforementioned polyolefins by small proportions of certain additives. Ultraviolet radiation has a degrading effect on olefin polymers, the severity of which depends on the geographic location of exposure of a particular polymer. Deterioration can take the form of discoloration, loss of tensile and impact strength, distortion of initial flexibility, dimensional changes, surface cracking, splitting, powdering or increased conductivity. All of these effects can result from the breaking of carbon-to-carbon bonds in the polymer chain, followed by immediate oxidation of the chain fragments. When certain substances are added to olefin polymers,
It is well known that a degree of stabilization is imparted to polymers with respect to their resistance to the destructive forces of ultraviolet radiation. These substances are, in one example,
Functions as a preferential receptor for incident ultraviolet radiation. This is because these materials have a much higher affinity for such radiation than olefin polymers. These materials absorb harmful radiation,
It then appears to dissipate it as harmless energy. These substances therefore form a protective shield over the polymer in which they are present. Although many types of UV stabilizers exist, an important class includes the 2-hydroxyphenylbenzotriazoles. They provide strong, dense and broad UV stabilization with a fairly sharp wavelength limit close to the visible range. They absorb light between 280 and 390 nm. Olefin polymers stabilized with UV stabilizers often also contain oxidation inhibitors. This is especially the case when it is important to obtain a photostable polymer composition. A wide variety of antioxidants are available. US Pat. No. 4,000,101 to McNally teaches the use of a combination of certain phenolic antioxidants, pentaerythritol diphosphites, and ultraviolet light stabilizers in olefin polymers. However, the compositions disclosed therein contain a rather complex polythiopolyphosphite as the main polymeric additive. US Pat. No. 3,988,293 to Mills shows a particular combination of 2-hydroxy-4-n-octoxybenzophenone and distearyl pentaerythritol diphosphite as a stabilizer for olefin polymers. No. 696,637, filed June 18, 1976, discloses distearylpentaerythritol diphosphite and a wide range of other polymeric additives, such as 2-(2'-hydroxy-5'-methylphenol). ) teaches combinations with benzotriazoles. U.S. Patents 3,285,855 and 3,644,482 to Dexter et al.
refers to (4-hydroxy-5-alkylphenyl)alkanoic acid esters of monohydric and polyhydric alcohols and refers to them as “phase stabilizers (UV absorbers, phosphites, dialkylthiodipropionates, etc.)”. U.S. Pat. No. 3,531,483 to Gilles contains a similar description applicable to hydroxyphenyl alkenyl isocyanurates. Certain 2-hydroxy as UV stabilizers in olefin polymers It has been found that the effectiveness of phenylbenzotriazole is unexpectedly enhanced by the presence of small proportions of dialkyl pentaerythritol diphosphite and certain phenol ester oxidation inhibitors. The combination is effective in extending the service life of polypropylene, e.g. by many hours. The 2-hydroxyphenylbenzotriazole considered here has the structural formula (wherein R ₁ is lower alkyl or halogen, preferably chlorine, R ₂ is lower alkyl, halogen, preferably chlorine or hydrogen, and
is chlorine or hydrogen). An example of such a 2-hydroxyphenylbenzotriazole is: 2-(2'-hydroxy-3'.5'-di-t-butylphenyl)-5
-Chlorobenzotriazole (Tinuvin327), 2
-(2′-hydroxy-3′・5′-dimethylphenyl)
Benzotriazole, 2-(2'-hydroxy-
5'-t-butylphenyl)benzotriazole,
2-(2'-hydroxy-5'-aminophenyl)-5
-chlorobenzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)benzotriazole (Tinuvin326), 2-(2'hydroxy-5-methylphenyl)benzotriazole (Tinuvin P), 2 −(2′-hydroxy-3′・5′−
dimethylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3', 5'-di-t-octylphenyl)-benzotriazole (Tinuvin328), 2-(2'-hydroxy-3', 5′−
dichlorophenyl)benzotriazole and 2
-(2'-hydroxy-3'-methyl-5'-t-octylphenyl)benzotriazole. The term "lower alkyl" refers to an alkyl group containing 1 to 10 carbon atoms. Many of the benzotriazoles of the present invention are trademarks.
Tinuvin326, Tinuvin327, Tinuvin328, Tinuvin
Available at P etc. (see above). They can be prepared by coupling aromatic diazo compounds with aromatic amines and then oxidizing the coupled intermediate. An example of manufacturing is as follows: Other manufacturing methods are described in US Pat. No. 3,004,896 (Heller et al.) and US Pat. No. 3,189,615 (Heller et al.). These benzotriazoles are used for purposes of this invention at concentrations ranging from about 0.01% to about 5.0%. Best results are obtained at concentrations within the range of about 0.1% to about 0.5%, based on the olefin polymer. The dialkyl pentaerythritol diphosphites of the combination of the invention may be in the spiro or caged isomer, i.e. or a mixture of these two in any ratio. In the above formula, R is an alkyl group having 8 to 20 carbon atoms. Such mixtures result from the reaction of alcohol as R source with diphenylpentaerythritol diphosphite. Diphenylpentaerythritol diphosphite can be produced by the reaction of triphenylphosphite and pentaerythritol. The alkyl group is preferably stearyl, i.e. C ₁₈ H ₃₇
Examples of other alkyl groups are decyl, dodecyl, tetradecyl, hexadecyl and eicosyl groups. A preferred form of such dialkyl pentaerythritol diphosphite is one in which the diphosphite is mixed with a small amount of the alcohol from which it was prepared, such as stearyl alcohol. This is particularly preferred when the alkyl group is large, ie hexadecyl, stearyl, eicosyl, etc., and when it is desired to ensure the brittle nature of the solid product. stearyl alcohol is
For example, the presence of 5-10% imparts critical brittle properties to distearyl pentaerythritol diphosphite. The reason this is desirable is that it allows the product to be handled more conveniently. The usual method of preparing such products consists in simply using an excess of alcohol, such as stearyl alcohol, in the reaction with diphenyl pentaerythritol diphosphite. The relative proportions of dialkyl pentaerythritol diphosphite used herein range from about 0.05% to about 1.0%, based on the olefin polymer. The phenol ester oxidation inhibitor considered here has the structural formula (wherein R and R' are lower alkyl, i.e., alkyl having 1 to 10 carbon atoms, R'' is lower alkyl or hydrogen, n is 1 to 4, and A is the remainder of the alkanol or alkane polyol. An example of A is:

[Formula] C ₁₈ H ₃₇ , CH ₂ CH ₂ , CH ₂ CHCH ₂ and

[Formula] A contains 2 to 24 carbons. Preferably, A is
_{C18H37 .} The relative proportions of antioxidants used in the stabilized polyolefins of the present invention range from about 0.01% to about 3.0%, based on the olefin polymer.
It is. These stabilizer components can be added to the olefin polymer by any conventional method. They can be incorporated into the polymer as a dry powder, for example, or they can be dissolved in one or more solvents and sprayed onto the finely divided polymer particles, or they can be incorporated as a melt in an extruder. or they can be mixed in a roll mill or Banbury mixer. Other additives may also be added to the olefin polymer, such as fillers, pigments, antistatic agents, etc. For example, metal stearates are commonly added as lubricants, as neutralizing agents, or to impart a degree of thermal stability to polymer compositions. The olefin polymer compositions contemplated herein can be formed into various shaped articles, filaments, films, sheets, etc. by extrusion, injection molding, blow molding, and the like. The efficacy of these polymer compositions is demonstrated by data obtained from weatherometer tests using a xenon arc as the ultraviolet radiation source. The test specimen is held in a clamp and the ambient air in the Weatherometer is maintained at a temperature of 110°C (43.3°C). For 20 minutes of each hour of test time, a thin spray of water is applied to the sample to simulate rain. Test samples are compression molded from the polymer compositions shown to form films 0.003 inches (0.076 mm) thick. Test samples are removed from the Oedarometer at periodic intervals, usually every 100 hours, and analyzed for carbonyl content by an infrared curve. That is, take the area under the peak at 5.8 microns as a quantitative measure of the carbonyl content of the sample. When a test sample is shown to have produced a 0.1% increase in carbonyl content, it is considered a failure, and the exposure time until such failure is a measure of the effectiveness of the test sample as a UV stabilizer. . Test samples other than No. 1 contained 100 parts polypropylene, 0.05 part calcium stearate, and 0.1 part octadecyl 3-(4-hydroxy-3.5-di-t-butylphenyl) propionate. Sample No. 1 contained only 100 parts polypropylene and 0.05 parts calcium stearate. The test results are as follows:

Examples of olefin polymers that benefit from the above combinations of stabilizer additives are homopolymers and copolymers of monoolefins, preferably those of monoolefins having 1 to 4 carbon atoms. Examples of these are polyethylene (both low density and high density), polypropylene, polyisobutylene, and copolymers of ethylene, propylene and isobutylene. EPDM polymers are also conceivable.

Claims (1)

[Claims] 1. (1) Structural formula of an olefin polymer and a stabilizing amount (In the formula, R ₁ is lower alkyl or halogen,
R ₂ is lower alkyl, halogen or hydrogen and X is chlorine or hydrogen)
-hydroxyphenylbenzotriazole, (2) dialkylpentaerythritol diphosphite (each alkyl group contains 8 to 20 carbon atoms), and (3) structural formula Phenol ester oxidation with (wherein R and R′ are lower alkyl groups, R″ is lower alkyl or hydrogen, n is 1 to 4, and A is the residue of an alkanol or alkane polyol) A polymer composition stabilized against degradation in the presence of ultraviolet radiation, characterized in that it consists of an inhibitor. 2. Claim 1, characterized in that the olefin polymer is a polymer of propylene. 3. The polymer composition according to claim 1, wherein the olefin polymer is polypropylene. 4. Component (1) is 2-(2'-hydroxy-3 '・5'-dit
-butylphenyl)-5-chlorobenzotriazole
The polymer composition described in . 5. The polymer composition according to claim 1, wherein component (2) is distearyl pentaerythritol diphosphite.