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
2001-02-13
Szekely, Peter A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C548S259000
Reexamination Certificate
active
06187845
ABSTRACT:
This invention pertains to stabilized adhesive compositions containing an effective amount of a benzotriazole UV absorber having enhanced solubility, durability and absorption in the 350 to 400 nm range.
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-tiazines 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.
Although benzotriazoles with just hydrogen at the 5-position of the benzo ring are photostable and useful in adhesive formulations, they lack a red-shifted absorbance toward longer UV wavelengths which would be most useful in giving added protection to the substrates. U.S. Pat. Nos. 5,319,091 and 5,410,071 described the preparation of benzotriazoles substituted at the 5-position of the benzo ring with alkyl- or aryl-sulfonyl moieties. It is taught in U.S. Pat. No. 5,280,124 that by introducing a higher alkyl or aryl sulfoxide or sulfone at the 5-position of the benzo ring of the benzotriazole, the resulting benzotriazole exhibits enhanced absorption in the near visible range (over 350 nm). Such sulfone substituted products were shown to be useful in automotive coatings applications. Copending patent applications Ser. Nos. 08/961,127 and 09/234,880 teach that an electron withdrawing moiety at the 5-position of the benzo ring of the benzotriazole is advantageous for similar reasons. Additionally, these copending patent applications teach that such an electron withdrawing group dramatically increases the photostability of these benzotriazole UV absorbers in automotive coatings. Quite surprisingly, these red-shifted benzotriazoles are amazingly soluble in adhesives making them 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 benzotriazole UV absorbers represent a special class of commercial UV absorbers as described above. Only a few references refer to substitution on the benzo ring by an aryl or alkyl sulfoxide or sulfonyl moiety.
U.S. Pat. No. 3,218,332 discloses benzotriazoles substituted at the 5-position of the benzo ring by a lower alkyl sulfonyl moiety. However, this patent deals with putting reactable groups, namely alkenyl groups, at the 3-position on the phenyl ring and is of little relevance to the instant application. U.S. Pat. Nos. 5,268,450 and 5,319,091 disclose polymer compositions and a process for the production of substituted aryl thio and aryl sulfonyl benzotriazoles which are covalently bound to polymers, such as poly(phenylene sulfide), RYTON®, Phillips Petroleum. U.S. Pat. No. 5,280,124 discloses benzotriazoles with only higher alkyl or aryl sulfonyl or sulfonyl moieties at the 5-position of the benzo ring which are useful for protecting thermoset automotive coatings. The copending patent applications mentioned above teach the use of certain electron withdrawing groups including some sulfonyl groups at the 5-position of the benzo ring for the stabilization of automotive coatings.
Japanese Patent No. 92-352228 discloses the use of 5-ethylsulfonyl benzotriazoles with the 3-position of the phenyl ring being unsubstituted or substituted by methyl for the UV protection of dust proof poly(vinyl chloride) resin films. These compounds when studied in the instant adhesive compositions were found to be quite insoluble and totally useless for the instant adhesive compositions. By contrast, when a tertiary alkyl group is inserted at the 3-position of the phenyl ring, the solubility of the thus substituted benzotriazole in adhesive composition is surprisingly enhanced.
The instant compounds exhibit enhanced broadened absorption characteristics particularly in the long wavelength UV region (over 350 nm) when compared with compounds of the prior art. Additionally, the instant compounds have surprising and unexpectedly high solubility in adhesives making them especially well suited for use in adhesive formulations.
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 articl
Iyengar Revathi
Ravichandran Ramanathan
Renz Walter
Suhadolnik Joseph
Wood, Jr. Mervin Gale
Ciba Specialty Chemicals Corporation
Hall Luther A. R.
Szekely Peter A.
LandOfFree
Stabilized adhesive compositions containing highly soluble,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stabilized adhesive compositions containing highly soluble,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stabilized adhesive compositions containing highly soluble,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2614524