Stock material or miscellaneous articles – Composite – Of polycarbonate
Reexamination Certificate
2000-11-03
2003-03-25
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polycarbonate
C428S413000, C428S419000, C428S423100, C428S447000, C428S474400, C428S480000, C428S492000, C428S500000, C428S532000, C560S085000, C560S140000, C568S325000, C568S333000, C568S332000
Reexamination Certificate
active
06537670
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to bis(alkyleneoxybenzophenone) compositions which are particularly useful as stabilizers for photodegradable polymers against the degradative action of ultraviolet (UV) light.
BACKGROUND
It is well known that UV light or radiation, particularly from sunlight, can cause degradation of polymers. Often this results in the embrittlement or yellowing of polymers, which may be in the form of molded articles, extruded articles, polymer films, fibers, tapes, coatings, and the like. This degradation can be inhibited by the incorporation of stabilizers which retard photooxidative degradation on weathering.
Derivatives of benzophenones, benzotriazoles, triazines, benzoxazinones and other compounds have been widely used for the protection of such polymeric materials. The effectiveness of such UV absorbers is reduced if they readily migrate and/or volatilize out of the polymeric substrate, during manufacture and/or use of said substrate. Loss of the absorbers by these mechanisms may be particularly high in certain types of articles, such as stabilized thin films, or in capstock applications. In the latter approach, a thin layer with a very large concentration of the absorber is applied to the top of a molded article by any of several means, in order to protect that article from UV light-induced degradation. The high concentration of absorber in a thin layer, processed at relatively high temperatures, gives a higher likelihood that loss of the absorber will occur. Certain properties of the absorbers themselves are likely to cause greater loss from the substrates during manufacture and/or use. These properties include high volatility, low compatibility with the polymer, water solubility, as well as other characteristics. Absorbers with low volatility (usually those with higher molecular weight), and high polymer solubility/compatibility will be more likely to stay in the polymer during manufacture and throughout the lifetime of the polymer. Of course, these absorbers should also possess other characteristics that are important for effectiveness as stabilizers, such as low initial color in the polymer and prevention of tensile strength reduction during weathering. They should not cause adverse effects, such as significant reduction of molecular weight of the polymer.
One approach that has been taken to reduce the loss of absorbers from polymeric substrates has been to increase their molecular weight, either by using an absorber with attached high molecular weight groups, or by adding a group which will bind two or more absorbing nuclei in the same molecule, thus increasing molecular weight. U.S. Pat. No. 4,278,589 provides an example of the former approach, and describes benzotriazoles with large groups attached at the 3- and 5-positions. Of the latter approach, benzophenones, benzotriazoles and other molecules have been dimerized to reduce volatility. U.S. Pat. Nos. 5,108,835 and 4,948,666 describe articles with capstock layers stabilized by 2-hydroxyphenylbenzotriazoles which are bridged by various groups. One structure encompassed by the description is a 2-hydroxyphenylbenzotriazole bridged by a methylene group in the 3-position. These materials have relatively low volatility, as measured by the high temperature required for 10% of the materials to volatilize during Thermogravimetric Analysis. This temperature, known as the TGA T-10% value, is approximately 365° C. for the methylenebis{(5-tert-octyl-2-hydroxyphenyl)benzotriazole} known commercially as LA-31, Mixxim BB-100 or Tinuvin 360 (supplied by Asahi Denka, Fairmount Chemical and Ciba Specialty Chemicals, respectively), versus a TGA T-10% value of 245° C. for the non-dimerized (5-tert-octyl-2-hydroxyphenyl)benzotriazole known commercially as CYASORB® UV-5411. Also described have been 2,4-dihydroxybenzophenones which are dimerized by attachment through the 4-oxygen by an ether bond to two carbons of an aliphatic group. Compounds of this type have been described in U.S. Pat. Nos. 3,580,927 and 3,666,713 and CZ Appl. 135,115, JP Sho 47-48888, JP Sho 44-26456 and GB 1, 296,240. Capstock articles stabilized by some of these compounds, and a method for preparing the same are described in U.S. Pat. Nos. 5,445,872 and 5,306,456. Descriptions of benzotriazoles and benzophenones bridged by attachment of other groups may be found in U.S. Pat. Nos. 5,589,529 and 4,859,726 (for benzotriazoles) and JP Sho 57-12643 (for benzophenones). Many of the compounds described above, while solving the problem of volatility, have other limitations, including low solubility and high initial color when processed into the plastic substrate.
Benzophenone carbonates in which the aryloxy group is directly bonded to the carbonate carbonyl group have been described and studied as light stabilizers. (See, e.g., CA 78: 58083, CA 84: 75151, CA 83: 180163 and CA 83: 60222). In contrast, the compounds of the present invention have aliphatic spacer groups between the aryloxy group and the carbonyl group. U.S. Pat. No. 5,644,485 describes 2-hydroxy-4-(2-hydroxyethoxy)benzophenone esters and their use as stabilizers. This patent, however, requires at least two carbonyl groups in the moiety bridging the at least two benzophenones. This patent does not describe the situation wherein only one carbonyl is present in the bridging moiety. EP 446740 A2 describes poly(benzophenones) attached to ester groups, with an aliphatic spacer between the aryloxy group and the ester. This patent does not describe the situation wherein poly(benzophenones) are attached to carbonate groups. Therefore a need remains for compositions that stabilize polymeric materials against degradation caused by exposure to UV light, while simultaneously demonstrating low volatility, low color and high solubility. The present invention provides such compositions.
SUMMARY OF THE INVENTION
The present invention is directed to a new class of bisbenzophenone compounds, in which two alkyleneoxybenzophenone molecules are linked by a bridging group. It has been surprisingly discovered that such bisbenzophenone compounds of the invention exhibit unexpected beneficial characteristics including low volatility, low initial color and excellent solubility and stabilizing effects on polymers. As examples of such bridging groups may be mentioned, carbonate, oxalate, ester, acetal and ketal groups. More specifically, the new bis benzophenone compounds of the present invention have the following general formula I:
wherein
each X, Y, Z, X′, Y′ and Z′ is independently selected from hydrogen, hydrocarbyl, functional hydrocarbyl, alkyl, aryl, aralkyl, alkaryl, alkoxyl, aroxyl, carboxyl, carboalkoxy, cyano, hydroxyl, halogen, or an S, N or P atom substituted for a carbon atom of the ring;
each R and R′ is independently selected from hydrocarbylene or functional hydrocarbylene; and
L is selected from a carbonyl group, a dicarbonyl group or hydrocarbylene.
Preferred in the present invention is the compound of Formula I wherein X, Y, Z, X′, Y′ and Z′ are hydrogen, R is (CH
2
)
2
, and L is a carbonyl group, as described in Formula III.
The present invention is further directed to a process for producing the bis benzophenone compounds. The compounds may in general be prepared via a number of procedures, but preferably by reacting a hydroxyfunctional benzophenone with a carbonyl compound such as a carbonate or an oxalate, followed by removal of alcohol byproduct. Further preferred process conditions are disclosed below.
The present invention is also directed to a polymeric article comprising a polymeric material and from about 0.01% to about 15% of a light stabilization composition comprising such bis benzophenone compounds.
The present invention is further directed to a method for preparing multilayer plastic articles, wherein such polymeric articles comprise a polymeric material and from about 0.01% to about 15% of a light stabilization composition comprising such bis benzophenone compounds.
The novel bis benzophenone compounds of the pre
Cytec Technology Corp.
Jubinsky James A.
Kiliman Leszek
Negron Liza
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