Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-05-03
2001-07-31
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S110000, C524S300000, C524S487000, C428S423100, C428S480000, C428S500000
Reexamination Certificate
active
06268415
ABSTRACT:
This invention pertains to stabilized adhesive compositions containing an effective amount of a benzotriazole substituted in the ortho position of the hydroxyphenyl ring by &agr;-cumyl or phenyl, such as 2-(2-hydroxy-3-&agr;-cumyl-5-tert-octylphenyl)-2H-benzotriazole having enhanced solubility and durability.
BACKGROUND OF THE INVENTION
Adhesives are made up of various components such as polymers, tackifiers, waxes and oils. Adhesive formulations based on these ingredients are susceptible to degradation. The consequences of degradation are discoloration, loss of elongation, loss of tensile strength, loss of tack and change in viscosity, molecular weight and molecular weight distribution. Degradation can be caused by prolonged exposure to sunlight. Sunlight contains invisible ultraviolet (UV) radiation with wavelengths between 290 and 400 nm. This radiation is responsible for the initiation of photodegradation.
Absorption of UV light by chromophores present in the adhesive formulation transforms the chromophores into their excited states which can undergo further undesired reactions. Some polymers contain strongly absorbing chromophores as a major part of their structures. Other polymers contain unintentional impurities such as ketones and hydroperoxide moieties and catalyst residues which act as chromophores. Absorption of UV radiation by these chromophores eventually results in bond cleavage, chain scission and/or crosslinking reactions.
Photostabilization of adhesives can be achieved by the addition of UV absorbers which convert the absorbed energy into harmless heat. An ideal UV absorber should be extremely photostable and have strong absorption over the UV range from 290 to 400 nm, but particularly the range of 350 to 400 nm. Classes of UV absorbers include the salicylates, cyanoacrylates, malonates, oxanilides, benzophenones, s-triazines and benzotriazoles.
Salicylates, cyanoacrylates, malonates and oxanilides absorb UV light primarily at the lower wavelengths of the UV range. These compounds have little to no absorption in the range of 350 to 400 nm which make them unsuitable for the instant applications. Benzophenones absorb over the lower half of the UV range, and they tend to be prone to yellowing upon light exposure due to photodegradation. Recently, it has been shown photochemically that benzophenones decompose prematurely in ethylene-vinyl acetate encapsulants which lead to the production of polyenic chromophores. This color generation from light yellow to brown is not only highly undesirable and unsightly in adhesive systems, but also can results in a loss of adhesive properties. By contrast, selected benzotriazole UV absorbers are particularly useful because of their increased photostability.
Some polymers such as polycarbonates, polyesters and aromatic polyurethanes contain strongly absorbing chromophores as a major and integral part of their structures. Poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) are particular examples the latter of which absorbs into the red UV region and especially need red-shifted benzotriazoles for UV protection. U.S. Pat. No. 5,294,473 and WO 98/34981 teach the use of coatings containing UV absorbers including some benzotriazoles in stabilizing PEN films. Adding an adhesive UV screening layer containing the benzotriazoles, especially those described in the instant invention, further protects such polymers in multilayered constructions and articles.
The description, preparation and uses of the 2H-benzotriazole UV absorbers are described in U.S. Pat. Nos. 3,004,896; 3,055,896; 3,072,585; 3,074,910; 3,189,615; 3,230,194; 4,127,586; 4,226,763; 4,278,589; 4,315,848; 4,383,863; 4,675,352; 4,681,905 and 4,853,471.
Selected benzotriazoles with just hydrogen or halogen at the 5-position of the benzo ring are photostable and soluble in adhesive formulations. One such benzotriazole is 2-(2-hydroxy-3-&agr;-cumyl-5-tert-octylphenyl)-2H-benzotriazole as described in U.S. Pat. Nos. 5,554,760; 5,563,242; 5,574,166 and 5,607,987. These patents are incorporated herein by reference. While the absorbance of this benzotriazole is not red-shifted toward longer UV wavelengths, it is very photostable and is amazingly soluble in adhesives making it especially well-suited for the instant applications.
It is known in the art that the concomitant use of a hindered amine light stabilizer with a UV absorber such as a benzotriazole provides excellent stabilization in many polymer compositions as summarized by G. Berner and M. Rembold, “New Light Stabilizers for High Solids Coatings”, Organic Coatings and Science and Technology, Vol. 6, Dekkar, New York, pp 55-85.
The effect of UV light on laminated articles that are exposed to the sun or other sources of UV light are of great concern to the manufacturers of such articles. Over time, constant or repeated exposure to UV light can result in dye and/or pigment fade for dyes and/or pigments used in such articles and in the degradation or breakdown of the adhesives, polymers or other materials used in the construction of the articles. The aforementioned fading and degradation shorten the useful life of the articles in question, making protection from UV light exposure an issue of great importance to the manufacturers of such articles.
Molecules known as UV absorbers are generally known in the art. However, due to the differences discussed above between the various UV absorber classes, it is the benzotriazoles and articles containing them which will be discussed here. Due to the incompatibility and low solubility of certain benzotriazoles, a need exists for a benzotriazole that is highly soluble and which is very photostable.
In addition, articles which incorporate the selected benzotriazoles of the instant invention are useful in protecting interior structures, textiles and fabrics from UV induced photodegradation such as in automotive applications.
International application WO 97/32225 describes the use of PEN films having reflective and polarizing elements for use as optical films.
U.S. Pat. No. 5,770,114 discloses stabilized compositions containing soluble benzotriazoles that are used in electrochromic devices. This patent discloses that 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole is effective in stabilizing such electrochromic devices against degradation from UV radiation, but that it is not soluble enough in aprotic solvents, e.g. propylene carbonate, to provide suitable protection for electrochromic devices for very long periods of time. This indicates that the acceptable benzotriazole UV absorbers must also exhibit excellent solubility in substrates and solvents in order to be acceptable.
Articles which would benefit from the incorporation of the instant, highly soluble and photostable benzotriazole include, but are not limited to:
(a) Retroreflective Sheets and Signs and Conformable Marketing Sheets as seen in WO 97/42261; and U.S. Pat. No. 5,387,458 which is incorporated herein by reference;
(b) Solar Control Films of Various Construction as seen in British 2,012,668; European 355,962; and U.S. Pat. Nos. 3,290,203; 3,681,179; 3,776,805 and 4,095,013 which are incorporated herein by reference;
(c) Corrosion Resistant Silver Mirrors and Solar Reflectors as seen in U.S. Pat. No. 4,645,714 which is incorporated herein by reference;
(d) Reflective Print Labels as seen in U.S. Pat. No. 5,564,843 which is incorporated herein by reference;
(e) UV Absorbing Glasses and Glass Coatings as seen in U.S. Pat. Nos. 5,372,889; 5,426,204; 5,683,804 and 5,618,626 which are incorporated herein by reference;
(f) Electrochromic Devices as seen in European 752,612 A1; and U.S. Pat. Nos. 5,239,406; 5,523,877 and 5,770,114 which are incorporated herein by reference;
(g) Films/Glazings as seen in WO 92/01557; Japanese Nos. 75-33286; 93-143668; 95-3217 and 96-143831; and U.S. Pat. No. 5,643,676 which is incorporated herein by reference;
(h) Windscreens and Intermediate Layers as seen in Japanese Nos. 80-40018; 90-192118; 90-335037; 90-335038; 92-110128 and 94-127591; and
(i) Optical Films as se
Hall Luther A. R.
Iyengar Revathi
Ravichandran Ramanathan
Renz Walter
Suhadolnik Joseph
Ciba Specialty Chemicals Corporation
Hall Luther A. R.
Sanders Kriellion
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