Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-12-18
2003-02-04
Lambkin, Deborah C. (Department: 1613)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C503S209000, C427S150000, C548S260000
Reexamination Certificate
active
06515051
ABSTRACT:
BACKGROUND OF THE INVENTION
The benzotriazoles have long been an important class of UV absorbers and have gained wide commercial importance and acceptance for many industrial applications. The prior art is replete with references to their manufacture and utility. However, as requirements become ever more stringent and demanding, the search for still more stable and durable benzotriazoles continues. The gradual phase out of HAPS solvents, such as xylene, because of environmental concerns and their replacement with non-HAPS solvents, such as esters, ethers or ketones, and increased durability requirements for automotive coatings make this search more urgent. Indeed, the automotive industry is most concerned about UVA losses from automotive paints and coatings as seen in the publication by J. L. Gerlock et al., Proc. 36th Annual Tech. Sym. (Cleveland Coating Society), May 18, 1993.
Vysokomol Soedin, Ser. A, 18(3), 553 (1976) describes the linear dependence of hydrogen bond strength and photostability in benzotriazoles.
J. E. Pickett et al., Angew. Makromol. Chem. 232, 229 (1995) describe the photodegradation of benzotriazole UV absorbers in poly(methyl methacrylate) films. Structural variation generally caused only small differences in the rates of degradation unless the substitution disrupted the intramolecular hydrogen bonds which are critical for stability. Pickett et al. did not test any benzotriazoles containing both electron withdrawing and electron donating groups as in the instant invention.
J. Catalan et al., J. Am. Chem. Soc., 114, 964 (1992) and H. J. Heller, Eur. Polymer J. Suppl. 1969, 105 both suggest that a bulky substituent such as tert-butyl ortho to the hydroxy group on the phenyl ring will increase stability in highly polar systems.
The prior art leads one to the conclusion that strengthening the hydrogen bond leads to a more stable benzotriazole, but does not teach how this can be accomplished. The instant invention discloses benzotriazoles which exhibit enhanced durability, but surprisingly this enhanced durability is not always related to greater hydrogen bond strength. Indeed, compounds with enhanced durability often have weaker, not stronger hydrogen bonds.
U.S. Pat. Nos. 4,226,763; 4,278,589; 4,315,848; 4,275,004; 4,347,180; 5,554,760; 5,563,242; 5,574,166 and 5,607,987 describe selected benzotriazoles, substituted in the 3-position of the hydroxyphenyl ring by an &agr;-cumyl group, which show very good durability in automotive coatings. These benzotriazoles represent the present state of the art. The instant invention is directed at preparing benzotriazoles which exhibit still better durability and low loss rates from the prior art benzotriazoles.
U.S. Pat. Nos. 5,278,314; 5,280,124; 5,436,349 and 5,516,914 describe red-shifted benzotriazoles. These benzotriazoles are substituted in the 3-position of the phenyl ring with an &agr;-cumyl group and at the 5-position of the benzo ring by thio ethers, alkylsulfonyl or phenylsulfonyl moieties. Red-shifting the benzotriazoles is desirable for spectral reasons. A group at the 5-position which is also electron withdrawing provides additional benefits in low loss rates and durability as found in the instant invention. Missing from these patents are any alkylsulfones with seven or fewer carbon atoms. When such sulfonyl substituents are combined with specifically &agr;-cumyl moieties, extremely durable compounds result which, due to the bulk of the &agr;-cumyl moiety have sufficiently low volatility to be useful in coating and other polymer systems.
The presence of an &agr;-cumyl or phenyl group ortho to the hydroxy group on the phenyl ring exerts a surprisingly large positive effect on benzotriazole photostability in coatings and photographic gel systems. The magnitude of this effect, particularly when compared to a tert-butyl group in that position, is well beyond prediction. The combination of both an electron withdrawing group on the benzo ring and an &agr;-cumyl or phenyl group on the phenyl ring in the same molecule leads to extremely desirable properties in coating systems when high UV absorber permanence is critical.
Novel compounds meeting these parameters as being extremely stable in aggressive use environments constitute a first portion of this invention.
The presence of the electron withdrawing moiety at the 5-position of the benzo ring has a powerful stabilizing effect on benzotriazoles in general and is observed in other polymer systems such as polycarbonate and poly(vinyl chloride) substrates as well. However, the effect of having an &agr;-cumyl or phenyl group ortho to the hydroxy moiety on the phenyl ring is much smaller to non-existent in some polymer systems such as polycarbonate or poly(vinyl chloride) even though critical for coating systems as described above.
In addition to being more photostable, the compounds of this invention are red-shifted, absorbing strongly in the 350-400 nm wavelength range. While such red-shifting is desirable in that a greater portion of the UV spectrum is absorbed, this can also introduce color if the absorption beyond 400 nm is significant. This can limit the use of such compounds, particularly in systems such as polycarbonate glazing applications or present difficulties in various pigmented systems.
It is found that the nature of the substituent ortho to the hydroxyl group on the phenyl ring has an unexpected impact on color imparted to the substrate by the benzotriazole. Thus, relatively subtle differences in substitution on the phenyl ring can have a large impact on the resulting color and the applicability of the benzotriazole in specific color sensitive applications. There are striking differences between havinghydrogen, alkyl or &agr;-cumyl at this 3-position.
Furthermore, it is found that, when the 5-position of the benzo ring is substituted with a trifluoromethyl group, the resulting benzotriazole not only exhibits the same or greater enhanced stability when incorporated into thermoplastic resins, but also imparts less color than related benzotriazoles substituted at the 5-position with other electron withdrawing moieties such as sulfonyl or carbonyl. These trifluoromethyl compounds also absorb strongly in the 350-400 nm wavelength range despite the low color and are extremely compatible in a wide range of substrates such as acrylic resins, hydrocarbons, polycarbonates and poly(vinyl chloride).
There are a multitude of general references to benzotriazoles having in the 5-position of the benzo ring electron withdrawing groups such as esters, amides, sulfones and the like that are not substituted in the 3-position of the phenyl ring by an &agr;-cumyl or phenyl moiety. In many of these references the broadly described compounds are unexemplified and no teaching or appreciation taught of the positive effect on photostability described in this invention. In any event, the vast majority of these structures fall well outside the scope of instant invention. Perfluoroalkyl, specifically trifluoromethyl, is an ideal substituent for the 5-position of the benzo ring. The prior art relevant to this substituent is very limited and exemplifies none of the instant compounds. As a result, said prior art naturally fails to point out the important advantages regarding stability, color and compatibility achievable with the 5-trifluoromethyl substituted benzotriazoles of this invention. The general, unexemplified references to alkyl substituted with halogen are acknowledged, but are clearly irrelevant to the instant invention.
German Offen. 1,670,951 describes inter alia the use of methylene (or alkylidene) bis-benzotriazoles substituted with electron withdrawing groups in polymeric resins. Especially useful are the asymmetrical compounds where only one benzotriazole moiety is substituted. Such asymmetric compounds have considerably less color.
German 116,230 provides a method of preparing benzotriazole N-oxide intermediates which can be converted into dyes and light stabilizers. The N-oxide of 5-trifluoromethyl-2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole is disclosed. This
Debellis Anthony
Detlefsen Robert E.
Iyengar Revathi
Ravichandran Ramanathan
Suhadolnik Joseph
Ciba Specialty Chemicals Corporation
Hall Luther A. R.
Lambkin Deborah C.
Stevenson Tyler A.
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