Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-11-11
2002-02-05
Hoke, Veronica P. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C548S260000, C558S412000, C558S413000, C558S422000, C568S707000, C568S712000, C568S718000
Reexamination Certificate
active
06344505
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to mono-, bis-, and mixtures of mono- and bis-benzotriazolyldihydroxybiaryl compositions which are particularly useful as stabilizers for photodegradable polymers against the degradative action of ultraviolet (UV) light.
2. Description of Related Art
Stabilization of polymers by incorporation of ultraviolet light stabilizers in polymer films, coatings, fibers, and molded articles to provide protection against the degradative action of light, moisture, or oxygen has been an active area of research in recent years. Incorporation of a absorber into the degradable polymer has been one of the most widely used methods of stabilizing these polymers. Of the multitude of UV absorber compositions capable of providing stabilization, 2-(2-hydroxyaryl)benzotriazoles have generally been the most effective.
To perform its stabilizing role effectively, a stabilizer should have permanence within the photodegradable polymer. Without permanence, the degradable polymer would rapidly deteriorate when exposed to ultraviolet light. Many stabilizers suffer from high material losses during polymer processing caused by their relatively high volatility. They also suffer from the effects of material losses caused by poor retention within the polymer matrix after being incorporated into a degradable polymer. Poor retention, which is in general a consequence of the limited compatibility of the stabilizers with the polymer, may cause the stabilizer to migrate to the surface by a phenomenon generally referred to as “blooming.” To compensate for the losses, the use of higher levels of the stabilizer may be. possible in some cases. The presence of high levels of stabilizers in a polymer, however, negatively impacts the physical properties of the polymer causing it to fail prematurely.
Attempts in the past to improve the permanence of stabilizers within the polymer matrix by increasing the molecular weight of the stabilizer have met with limited success.
For example, a successful attempt to oligomerize a suitable benzotriazole precursor to produce a high molecular weight material having reduced volatility has been described in U.S. Pat. No. 5,547,753. Other attempts to reduce volatility by converting benzotriazoles to higher molecular weight oligomers and polymers have generally resulted in a decreased retention of the stabilizers within the degradable polymer due to the incompatibility of the high molecular weight stabilizers with the degradable polymer to which they are added.
Increasing the molecular weight of a benzotriazole stabilizer by joining two benzotriazole compounds with an alkylene bridging group thereby decreasing volatility has been attempted. The preparation of alkylene or aralkylene bridged benzotriazoles are described in U.S. Pat. Nos. 5,237,071; 5,229,521; 4,937,348; 4,859,726; and Czechoslovakian Pat. No. 141,206 and some uses thereof are disclosed in U.S. Pat. Nos. 5,001,177; 4,812,498; 4,684,680; 4,684,679; 4,681,905; and 3,936,305. While bridged benzotriazole stabilizers have somewhat reduced volatility, their usefulness as stabilizers for degradable polymers has been limited because of their relative incompatibility.
Other attempts to increase the molecular weight of the stabilizer without introducing incompatibility by using an anchor group have been tried in the past without great success. For example, U.S. Pat. No. 4,319,016 describes the preparation of an ultraviolet light absorbing material from the reaction of a benzotriazole, formaldehyde, and melamine. It is stated therein that if the benzotriazole is present in amounts greater than 0.5 mole per mole of melamine, the compatibility of the resulting compound with a resin or solvent tends to be reduced. These compounds are sulfur containing benzotriazoles (i.e. thio-, sulfinyl-, and sulfonyl-substituted benzotriazoles) which have high molecular weight and low volatility. These benzotriazole stabilizers, however, have the disadvantage of being yellow, partly as a result of a shift of absorption to longer wavelengths and tailing into the visible spectrum. In addition, coatings and articles incorporating these sulfur containing benzotriazoles also exhibit an unacceptably high level of yellowness, particularly in clear coatings. This makes the sulfur containing benzotriazoles unsuitable for coatings applications.
U.S. Pat. Nos. 5,104,782, 5,294,530 and 5,360,692 contain a generic disclosure of a bis-triazolylbiaryl diol structure for silver halide color photographic film. However, actual compounds were neither disclosed nor exemplified.
With the exception of the isolated attempts summarized above to overcome the deficiencies of the existing stabilizers, the problems of high volatility and poor retention still remain largely unsolved.
It is therefore an object of this invention to provide novel benzotriazole UV absorbers which have the required low volatility without sacrificing compatibility and permanence. It will be apparent from the description below that the benzotriazoles of the present invention are efficient UV stabilizers, have very low volatility, good compatibility, and high permanence, providing protection at long wavelengths without yellowing.
SUMMARY OF THE INVENTION
The present invention is a composition of matter comprising a benzotriazole compound selected from the group consisting of a (2H-benzotriazol-2-yl)-biaryldiol compound, a bis-(2H-benzotriazol-2-yl)-biaryldiol compound, an N-oxide thereof, and a mixture thereof. We have discovered that (2H-benzotriazol-2-yl)-biaryldiols, bis-(-2H-benzotriazol-2-yl)-biaryldiols, and particularly a mixture thereof have the required low volatility without sacrificing compatibility with the polymer to which they are added, so that loss of the stabilizer either through volatilization during processing or through migration of the stabilizer to the surface of the polymer and eventual loss is minimized or prevented entirely.
This invention also provides a composition of matter comprising an azo compound selected from the group consisting of a (2-nitroarylazo)biaryldiol compound, a bis-(2-nitroarylazo)biaryldiol compound, and a mixture thereof.
This invention also provides a process for preparing a bis-benzotriazole compound, which comprises: oxidatively dimerizing a monomeric benzotriazole having an unsubstituted 4,6-position, a position para- or ortho- to the hydroxy group.
This invention also provides a process for preparing an azo compound, comprising: contacting a 2-nitroaryldiazonium salt and a biaryl diol at a temperature, pH, and length of time sufficient to produce an azo compound selected from the group consisting of (2-nitroarylazo)-biaryldiol, bis-(2-nitroarylazo)-biaryldiol, and a mixture thereof.
This invention is also a process for preparing a benzotriazole compound by reductive cyclization of an azo-compound, said process comprising: contacting a reducing agent and an azo compound selected from the group consisting of a (2-nitroarylazo)-biaryldiol, a bis-(2-nitroarylazo)-biaryldiol, and a mixture thereof, optionally in the presence of a catalyst, at a temperature and for a length of time sufficient to produce a benzotriazole selected from the group consisting of a (2H-benzotriazol-2-yl)-biaryldiol, a bis-(2H-benzotriazol-2-yl)-biaryldiol, an N-oxide thereof, and a mixture thereof.
This invention is also a degradation stable composition, comprising: (i) a degradable polymer; and (ii) a stabilizingly effective amount of a benzotriazole selected from the group consisting of a (2H-benzotriazol-2-yl)-biaryldiol compound, a bis-(2H-benzotriazol-2-yl)-biaryldiol compound, an N-oxide thereof, and a mixture thereof.
Finally, this invention is a method of stabilizing a degradable polymer, said method comprising: adding to said degradable polymer a stabilizingly effective amount of a benzotriazole selected from the group consisting of a (2H-benzotriazol-2-yl)-biaryldiol compound, a bis-(2H-benzotriazol-2-yl)-biaryldiol compound, an N-oxide thereof, and a mixture thereof.
The advantages of this invention in
Sassi Thomas P.
Stephen John F.
Valentine, Jr. Donald H.
Cytec Industries Inc.
Hoke Veronica P.
Pennie & Edmonds LLP
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