Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-08-22
2004-09-07
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S091000, C524S100000, C524S108000, C524S291000, C524S342000, C524S349000, C524S359000, C524S502000, C524S612000
Reexamination Certificate
active
06787591
ABSTRACT:
The invention relates to synergistic stabilizer compositions comprising Hindered Amine Stabilizers (HAS), phenolic antioxidants, and, if appropriate, UV-absorbers, for thermoplastic polymers, especially for polyolefin pipes and other polyolefin molding materials, which are in prolonged contact with water.
The usability and lifetime of thermoplastic polymers and especially—often partially crosslinked-polyolefin pipes, geotextiles and other molding materials which are in prolonged contact with water such as is influenced by numerous parameters such as mechanical properties, density, molar mass and mass distribution of the polymer. Depending on the final use and the specific conditions (temperature, stress, and environmental influences) during the use, a lifetime of up to several decades should be guaranteed. New trends for lifetime expectancy are more than 50 years. In case of their use for water transportation, special requirements must be fulfilled which can be reached by addition of appropriate stabilizers and stabilizer conditions. Their contribution can be determined under accelerated test conditions at elevated temperatures by hot water storage. As important technical criteria oxidation induction time (OIT) and mechanical stability are used to assess the stabilization of polyolefin pipes or other polyolefin-based molding materials. OIT-tests are still established and are used as technically important criteria despite the fact that extrapolations of OIT-data are discussed since a long time to be often too optimistic compared to conventional oven aging results. Effects in the polymer matrix e.g. change in cristallinity, free volume, morphology, and coefficient of diffusion and reaction kinetics cause changes in the degradation mechanism. Nevertheless, especially in the PE-MD- and PE-HD-sector OIT-limits of at least 30 minutes at T=210° C. are required.
Another technical criterion which must fulfill certain technical requirements is color determined as yellowness index (YI).
Further technical criteria to judge the quality of resins used for contacts with water is the remaining stabilizer content after hot water storage (95° C.) which is part of the standard test program of the involved resin producers and manufacturers of finished articles.
The following publications refer to the above mentioned problems:
1) Higuchi, Y.; Nishimura, H.; Tamamura, H.; Harada, T. Osaka Gas Co., Ltd., Japan. Proc. Int. Gas Res. Conf. (1998), (Vol. 3), 67-75.
2) Advanced extraction resistant long-term thermal stabilizers for polyolefin pipes. Schmutz, Th.; Kramer, E.; Zweifel, H.; Dörner, G. Ciba Specialty Chemicals, Inc., Basel, Switz. J. Elastomers Plast. (1998), 30(1), 55-67.
One of the decisive criteria preventing rapid oxidative degradation of thermoplastic polymers is the use of long-term stabilizers. Their efficiency is depending on the compatibility, the solubility, the mobility and the migration of additives in the pipe resin.
Superior long-term thermal stability of thermoplastic materials such as polyolefin pipes and other molding polyolefin materials can be achieved using sterically hindered phenols or piperidine-based sterically hindered amine stabilizers (HAS) (F. Gugumus, Polym. Degrad. Stab. 44, 299, (1994)). Also combination of both stabilizer types are used and are therefore basically state-of-the-art. Combinations of phenolic antioxidants with phosphite are described in H. Zweifel in “Stabilization of Polymeric Materials”, Springer, Berlin, Heidelberg, New York, 1998, p. 71-75. DE-A-196 37 181 discloses stabilizing mixtures of phenolic antioxidants, sterically hindered amines and organic phosphites or phosphonites.
As already pointed out earlier there is a certain technical need to improve stabilizer systems used in polymer substrates for extended contact with extracting media with regard to long term stability of the system (problems with migration, stability to hydrolysis).
It has now been found that appropriate combinations of special phenol-based stabilizers with certain hindered amine stabilizers lead to superior long-term thermal stabilization in polyolefin pipes and generally in polyolefin-based moldings to be utilized under extractive conditions of water after hot water storage.
Also multiple combinations of the special phenol-component with conventional sterically hindered phenols and certain sterically hindered amines show superior effects. The instant stabilizer combinations offer surprisingly the possibility to outperform the state of the art.
Object of the instant invention are stabilizer compositions for thermoplastic polymers comprising
a) at least one sterically hindered amine, one of which must be the polymer of epichlorhydrin and 2,2,4,4-tetramethyl-7-oxa-3, 20-diaza-20-(2,3-epoxi-propyl)-dispiro-[5.1.11.2]-heneicosane-21-one (LS 1), the others being poly-{[6[1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidyl)-amino]-hexamethylene-[4-(2,2,6,6-tetramethylpiperidyl)-imino]} (LS 2) or poly-(N-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidyl-succinate) (LS 3), and
b) at least one phenolic antioxidant,
wherein the overall weight ratio of component(s) a) to the overall weight ratio of component(s) b) is from 10:1 to 1:5.
Preferred are stabilizer compositions wherein component b) is selected from the compounds (AO 1) to (AO 8),
bis-[3,3-bis-(4′-hydroxy-3′-tert.butylphenyl)-butanoic acid]-glycolester (AO 1),
tetrakismethylene(3,5-di-tert.butyl-4-hydroxyphenyl)-hydrocinnamate (AO 2), octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate (AO 3), 4,4′,4″-[(2,4,6-trimethyl-1,3,5-benzenetriyl)tris(methylene)]-tris[2,6-bis(1,1-dimethylethyl)-phenol] (AO 4),
1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[[4-(1,1-dimethylethyl)-3-hydroxy-2,6-dimethylphenyl]methyl] (AO 5),
phenol, 4,4′,4″-(1-methyl-1-propanyl-3-ylidene)tris[2-(1,1-dimethylethyl)-5-methyl (AO 6), phenol, 2,6-bis[[3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]octahydro-4,7-methano-1H-indenyl]-4-methyl (AO 7), or
benzenepropanoic acid, 3-(1,1-dimethylethyl)-4-hydroxy-5-methyl-, 2,4,8,10-tetraoxa-spiro[5.5]undecane-3,9-diylbis(2,2-dimethyl-2,1-ethanediyl)ester (AO 8).
Preferred are also stabilizer compositions wherein component b) is compound (AO 1), (AO 2) or (AO 3) or any mixture thereof, especially preferred are compositions wherein component b) is a mixture of compound (AO 1) and (AO 2) in a weight ratio of 5:1 to 1:5, more preferably of 2:1 to 1:2.
Very good stabilizing properties are also achieved with stabilizer compositions wherein an additional UV-absorber as further component c) is
methanone, [2-hydroxy-4-(octyloxy)phenyl]phenyl (UV 1) or
phenol, 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methyl (UV 2) or a 2-hydroxybenzophenone, a 2-(2-hydroxyphenyl)-benzotriazole, a 2-(2-hydroxyphenyl)-1,3,5-benzotriazine, an oxanilide, a cinnamate or a salicylate,
and wherein the weight ratio of component(s) a): component(s) b): component(s) c) is from 5:1:1 to 1:5:5.
The compounds (LS 1) to (LS 3), (AO 1) to (AO 8), (UV 1) and (UV 2)are commercially available products of the following chemical structure, as far as known:
A further object of the instant invention is a method of use of said stabilizer compositions for the stabilization of thermoplastic polymers, especially polyolefins, which are in prolonged contact with extracting media like water, in concentrations of 0.001% to 2.000%, preferably 0.020% to 0.20% by weight, based on the polymer.
Another object of the instant invention is a process of stabilizing thermoplastic polymers, especially polyolefins, which are in prolonged contact with extracting media like water, by incorporating 0.001% to 2.000%, preferably 0.020% to 0.20% by weight, based on the polymer, of said stabilizer compositions.
Suitable thermoplastic polymers to be stabilized according to the instant invention are for example the followi
Koch Harald
Kröhnke Christoph
Lichtblau Alexander
Zäh Matthias
Bisulca Anthony A.
Clariant Finance (BVI) Limited
Sanders Kriellion A.
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