EP0041555A4

EP0041555A4 - Novel secondary and tertiary amines and the use thereof in compositions and in stabilization of polymers against ultraviolet light degradation.

Info

Publication number: EP0041555A4
Application number: EP19810900159
Authority: EP
Inventors: Pyong-Nae Son
Original assignee: BF Goodrich Corp
Current assignee: Goodrich Corp
Priority date: 1979-12-10
Filing date: 1980-11-06
Publication date: 1982-04-22
Also published as: EP0041555A1; GR71618B; JPS56501681A; BE886428A; BR8008958A; ES497599A0; ES8203344A1; WO1981001706A1

Abstract

Novel compounds, compositions and methods for stabilization of ultraviolet light sensitive polymers against photodegradation. The novel secondary and tertiary amines of this invention can be represented by the following structural formula: (FORMULA) with R and R' being independently selected from the group consisting of alkyl, hydroxy substituted alkyl, aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl; R1 and R2 being independently selected from hydrogen, alkyl, aralkyl; R3 and R4 being independently selected from alkyl of 1 to 4 carbon atoms and capable of collectively forming a cycloalkyl substituent; A and A' being independently selected from the group consisting of alkylene of 1 to 12 carbon atoms; and m is 0-4; n is 1-3. The above compounds are especially suitable in the stabilization of polyolefins (i.e. polypropylene) against the degradative forces of ultraviolet light.

Description

NOVEL SECONDARY AND TERTIARY AMINES AND THE USE THEREOF IN COMPOSITIONS AND IN STABILIZATION OF POLYMERS AGAINST ULTRAVIOLET LIGHT DEGRADATION

BACKGROUND OF THE INVENTION The Field of the Invention - This invention relates to novel compounds, compositions containing such compounds and methods for the stabilization of UV sensitive polymers. More specifically, this invention is directed to novel secondary and tertiary amines, stabilized polymer compositions containing such novel compounds and methods for the UV stabilization of photodegradable polymers. Description of the Prior Art - Polymers have in the past and continue to provide an attractive -substitute for the more traditional types of structural materials (e.g. wood or metals) because of relatively inexpensive materials and fabrication cost. As polymers continue to find new applications in, for example, the fabrication of automotive parts and building materials, they must also become more durable and capable of withstanding prolonged exposure to a variety of degradative forces. Degradation of polymers can be caused by exposure to light, heat, moisture and/or air. Such degradation is usually manifest by either a partial or total loss of structural integrity, changes in light transmission properties, changes in color, loss or reduction of flexibility and/or resiliency, or any combination of the above phenomena. Those attempting to avoid polymer degradation have generally selected from among three possible approaches: (a) elimination or reduction of the degradative forces; (b) isolation of the sensitive material from the degradative forces; or (c) modification of the polymer composition to enhance its resistance to the degradative forces. The latter approach is generally preferable since it does not require elaborate engineering nor structural changes in the polymer product environment.

As one might readily expect, the problems associated with the stabilization of different polymeric materials are affected to a greater extent by the functionality of the polymer and any unsaturation that may be present along the backbone or the side chains of such materials. For example, where the polymer contains unsaturation along its backbone and/or side chains, it is highly sensitive to oxidative degradation. Materials that are suitable to prevent oxidative degradation of dienic or unsaturated polymers do not necessarily have similar beneficial effects when incorporated within a polymeric materials lacking such unsaturation. Similarly stabilizers which are effective for polyolefins, such as polyethylene, may have little, if any, stabilizing effect upon dienic polymers or polymers having unsaturation along their backbone or side chain. There are a variety of additives which have been disclosed in the past as suitable for enhancing polymer resistance to one or more degradative forces described hereinabove. These additives (hereinafter collectively referred to as "stabilizers") can usually be physically combined with or engrafted upon the environmentally sensitive polymer thereby prolonging its useful life in its hostile degradative environment. It is not uncommon for polymers to contain a variety of stabilizer materials, (i.e. a stabilizer package), each being present for prevention on a particular degradative reaction. One of the more difficult to control of the degradative forces is the irradiation of polymers by ultraviolet light. The impact of such irradiation will, of course, vary depending upon the intensity and duration of exposure and thus, may manifiest itself only after a prolonged interval. The irradiation of polymers with ultraviolet light can oftentimes cause crosslinking of these materials, thereby reducing its resiliency and/or impact resistance. Changes in color and opacity are often effected by prolonged exposure of polymers to UV irradiation. While many materials are known and commercially available as stabilizers against ultraviolet light degradation, the degree of protection afforded by such agents is generally concentration dependent and may be geared to a particular limited class of material. The prior art is replete with technical articles and patents directed to resolving this complex problem, see for example, "Photodegradation, Photooxidation and Photostabilization of Polymers", B. Ranby & J. Raybeck, John Wiley & Sons, New York City (1975) at page 369 et seq. A number of hindered amine stabilizers had been previously disclosed as suitable in the prevention of photodegradation of polyolefins, such as polyethylene and polypropylene, see for example, U. S. Patents 4,006,207 and 4,104,248. Each of the above references discloses a piperdinyl functional compound which is suitable in the light stabilization of synthetic materials, such as polypropylene and polyethylene. In the case of the ' 207 patent, the stabilizer is a polyurea having piperdinyl functional moieties appended from its backbone. The '248 patent is similar in its disclosure in that the piperidinyl functional moieties are appended from a polymer backbone composed of alkalene groups. While each of the foregoing stabilizer materials would appear to be attractive from the standpoint of low mobility, (due to its size) the presence of other components of the polymer backbone tends to increase the amount by weight, in relation to polymer, of such stabilizer that must be present in order to insure a sufficient number of stabilizer functional groups to adequately protect the ultraviolet light sensitive polymer against degradation. In contrast to the above approach, it would be preferable to somehow bind, either physically or chemically, stabilizer functional groups within the host material so as to achieve both the requisite amount of stabilization and the immobility or affixation of stabilizer necessary to prevent extraction thereof upon contact of the stabilized composition with solvents or exposure of the polymer to elevated temperatures.

In summary, the stabilization of polymers against changes in their physical, chemical and/or electrical properties can be readily achieved by the incorporation of one or more stabilizer compounds within the environmentally sensitive material. The specific stabilizer materials which have been discussed herein- above are effective to a degree in the prevention of UV degradation of many widely used polymeric materials. However, such stabilization with the aforementioned materials can apparently result in some alteration in the stabilized polymer properties due to the amount of materials which must be included therein to achieve the desired degree of protection of the host polymer from the degradative agent.

SUMMARY OF THE INVENTION Accordingly, it is the object of this invention to remedy the above as well as related deficiencies in the prior art.

More specifically, it is the principal object of this invention to provide a novel stabilizer material suitable for enhancing the resistance of ultraviolet light sensitive polymers to photodegradation.

Another object of this invention is to provide stabilized polymeric compositions which are resistant to photodegradation by ultraviolet light and yet possess processing characteristics essentially equivalent to the unstabilized material. Another object of this invention is to provide a method for extending the useful life of environmentally sensitive polymers by enhancement in their resistance to photodegradation by ultraviolet light.

The above and related objects are achieved by providing a composition containing a stabilizer compound of the following formula:

with R and R' being independently selected from the group consisting of alkyl, hydroxy substituted alkyl, aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl; R₁ and R₂ being independently selected from hydrogen, alkyl, aralkyl; R₃ and R₄ being independently selected from from alkyl of 1 to 4 carbon atoms and capable of collectively forming a cycloalkyl substituent;

A and A' being independently selected from the group consisting of alkylene of 1 to 12 carbon atoms; and m is 0 - 4 n is 1 - 3.

In the preferred embodiments of this invention, the amount of stabilizer compounds which can effect satisfactory stabilization of ultraviolet light sensitive polymers is in the range of about 0.1 to about 5 parts by weight of stabilizer per 100 parts by weight of polymer. DESCRIPTION OF THE INVENTION

INCLUDING PREFERRED EMBODIMENTS

The novel compounds of this invention can be routinely prepared using standard equipment, techniques and readily available starting materials. In a typical synthesis of such materials, stoichiometric quantities of an appropriately substituted piperidone and a primary amine are reacted with one another in an alcoholic medium in the presence of a catalyst such as platinum. The reaction vessel in which such synthesis is carried out is pressurized and hydrogen introduced therein while the temperature of the reaction mass is elevated (preferably to the refluxing temperature of the alcohol). After the consumption of hydrogen gases essentially ceases, the reaction mass is cooled and filtered. The starting materials which can be used in the synthesis of such novel compounds are either commercially available or can be prepared from readily available materials using standard equipment and techniques. For example, appropriately substituted piperazine and piperidone is commercially available from Aldrich Chemical Co. Representative piperazine and piperidone reactants which are suitable for use in the synthesis of the compounds of this invention are N,N'-bis (3-aminopro- pyl) piperazine, N,N'-bis (3-aminopropyl) -2, 5-dimethyl piperazine, 2, 2,6, 6-tetramethyl-4-piperidone and 1,2,2,6, 6-pentamethyl-4-piperidone.

Similarly, the primary amines which are suitable for use in the synthesis of the novel compounds of this, invention are readily available from Dow Chemical Co. or Union Carbide Corp. Representative of the amine reactants which are suitable for use in the synthesis of the compounds of this invention are diethylenetriamine, triethylenetetramine, tetraethylene- pentamine, 3,3-diamino-N-methyldiproρylamine, 3,3- diamino-N-ethyldipropylamine and 3, 3-diamino-N-proρyl- dipropylamine.

As noted hereinabove, the reaction is preferably carried out in the presence of a suitable catalyst, such as platinum. Catalyst concentration is preferably in the range of from about 0.01g to 0.10g of 10% Pt on carbon, per 0.1 mole piperidone reactant.

In the preferred embodiments of this invention, the novel compounds can be represented by the following structural formulae:

wherein R, R' , A, A' , R, , R₂ and m are the same as previously defined.

Typical compounds falling within the scope of the foregoing formulae are bis [3-(2, 2, 6, 6-tetramethylpiperidin-4-yl) aminopropyl]methylamine, bis [3-(2, 2, 6,6- tetramethylpiperidin-4-yl) aminopropyl] ethylamine, bis [3- (2,2,6,6-tetramethylpiperdin-4-yl) aminopropyl] propyl amine, N,N*-bis [3- (2, 2, 6, 6-tetramethylpiperidin-4- yl) aminopropyl] piperazine, N,N'-bis [3-(2, 2, 6, 6-tetra- methylpiperidin-4-yl) aminopropyl] -2, 5-dimethylpiperazine, N,N' -bis [3- (2, 2, 6, 6-tetramethylpiperidin-4-yl) amino- propyl] -2,3,5, 6-tetramethylpiperazine, bis [2-(2, 2, 6, 6- tetramethylpiρeridin-4-yl) aminoethyl] amine, N ¹ N ⁸ - bis (2, 2, 6 , 6-tetra methylpiperidin-4-yl) -3 , 6-diazaoctane-

1, 8-di-amine, N ¹ ,N ^{1 1} -bis (2 , 2 , 6 , 6-tetramethylpiperidin-4- yl) -3 , 6 , 9-triazaundecane-l, 11-diamine, bis [3- ( l , 2 , 2 , 6 , 6- pent amethylpiperidin-4-yl) aminopropyl] methylamine ,

N,N'-bis [3-(l, 2,2,6,6-pentamethylpiperidin-4-yl) amino- propyl] piperazine, N 1,N8-bis (1, 2,2,6, 6-pentamethylpiperidin-4-yl)-3,6-diazaoctane -1,8-diamine, N ¹ ,N ^{1 1}-bis (1,2,2,

6, 6-pentamethylpiperidin-4-yl)-3,6, 9-triazaundecane-l, 11-diamine.

Ultraviolet light sensitive polymers of the compositions of this invention can include any polymeric material that manifests some degradation upon exposure to UV irradiation. Virtually all polymeric materials are sensitive, at least to some degree, to photodegradation by ultraviolet light. The term "photodegradation", as used herein with reference to ultraviolet light sensitive polymeric materials, is intended to be inclusive of any photo-induced change in the physical, chemical and/or electrical properties of the polymer or articles prepared therefrom.

Representative of the above UV sensitive polymeric materials are the polyurethanes, PVC resins, ABS resins, polystyrene, polyacfylonitrile, polymethacrylate, polycarbonates, phenol-formaldehyde resins, polyepoxides, polyesters, and polyolefins (especially homopolymers and copolymers of polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers), and the like. In the preferred stabilized compositions of this invention, the ultraviolet light sensitive polymers are derived from α- monoolefin monomers such as ethylene, propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-l- pentene, and the like. The stabilized polymeric compositions prepared from the above materials can contain, in addition to the stabilizers and polymers described hereinabove, a variety of optional ingredients. Such optional ingredients can include metal oxides, such as zinc, calcium and magnesium oxides; fatty acids, such as stearic, lauric and salts thereof; fillers such as calcium and magnesium carbonate, calcium and barium, sulfonates, aluminum silicates, asbestos, and the like; plasticizers and extenders, such as dialkyl and diaryl organic acids, such as diisobutyl, diisooctyl, diisodecyl and dibenzyl oleates, stearates, sebacates, azelates, phthalates, and the like; ASTM Type 2 petroleum oils, paraffinic oils, castor oil, tall oil, glycerine, and the like; antioxidants, such as 2,6-di-t- butyl-para-cresol, 2,2'-methylene-bis-(4-ethyl-6-t-butyl phenol), 2, 2' -thio-bis-(4-methyl-6-t-butyl phenol), 2, 2'- methylene-bis-(6-t-butyl-4-methyl phenol), 4,4'-butyli- dene-bis-6-t-butyl-m-cresol, 2-(4-hydroxy-3, 5-di-t- butylanilino-4, 6-bis-(octylthio)-1,3 ,5 triazine, hexa- hydro-1,3 ,5-tris-[β-(3, 5-di-t-butyl-4-hydroxyphenyl)- propionyl]-s-triazine, tris (3, 5-di-t-butyl-4-hydroxy- benzyl) isocyanurate, tetrakis-[methylene-3-(3'5'-di-t- butyl-4'-hydroxyphenyl) propionate] methane, distearylthiodipropionate, dilaurylthiodipropionate, tri- (nonylphenyl) phosphite, tin thioglycolate, and the like; and other ingredients such as pigments, tackifiers, flame retardants, fungicide and the like.

Optional compounding ingredients which are especially suitable for use in combination with the above stabilized compositions are the antioxidants. The inclusion within the composition of an antioxidant, in addition to the UV stabilizer, confers upon the polymer compositions stability against two of the more environmentally hostile degradative forces. Typically, antioxidants can be present within the polymer composition at a concentration within the range of from about 0.1 to about 10 parts by weight per 100 parts by weight polymer, and preferably from about 0.2 to about 5 parts by weight per 100 parts by weight polyer. Generally, the phenolic antioxidants are preferred for use in conjunction with the UV stabilizers of this invention. This combination of UV stabilizer and phenolic antioxidants is especially suitable for use in conjunction with polyolefins; that is, in an environment in which the polyolefin is subjected to a plurality of degradative forces, including heat, oxygen and ultraviolet light.

The photodegradable polymers of the compositions of this invention can be compounded with the various stabilizers and additives described hereinabove in accord with standard mixing techniques and equipment; such as in a Banbur.y mixer, Henschel mixer, a rubber mill, an extruder mixer or other equivalent device. The various components of such a composition may be physically and intimately blended either in the absence of, or in the presence of, a common solvent; or in a solvent which is capable of dissolving the polymer component of the composition yet substantially incapable of dissolving the stabilizer ingredients. Typical of such solvents/dispersing agents include hexane or benzene. Subsequent to intimately dispersing the various components of the composition within one another, the dispersing agent (if any) can be removed by selective evaporation and the resultant resin compounded and recovered. The resin compound may thereafter be formed into useful products by a variety of molding techniques. The ultraviolet light stability of the compositions prepared in the above manner can be evaluated by exposing a sample thereof to a Xenon or Carbon arc light in a Weather-Ometer operated at a temperature of about 60°C. Degradation of similarly prepared samples is determined by measurement of the difference in tensile strength after exposure to UV light. Where the tensile strength of the sample is reduced to fifty percent (50%) of its original value, the sample is regarded as degraded. The protocol used in such evaluation is generally recognized as an accepted method for evaluation of photodegradation of plastics and correlate with other more elaborate techniques. Degradation of the sample can also be monitored periodically, by measuring the carbonyl absorption band at 1720cm¹, using an IR spectrophotometer. The relatively rapid formation of carbonyl sites indicates photodegradation occurring within the sample. This test procedure is also a recognized method for evaluation of the efficacy of such UV stabilizers and is fully described in the open literature, see for example "Photodegradation, Photooxi- dation and Photostabilization of Polymers", by Ranby & Raybeck, John Wiley & Sons, New York City (1975) at page 125 et seq; and U.S. Patent 3,909,493. Photodegradation of the sample can also be visibly manifest as cracking of the sample upon prolonged heating at 180°C. Oxidative degradation and thermal stability of the sample can be verified by monitoring the time required to effect discoloration and/or embrittlement of the sample in a standard aging oven maintained at 149 °C.

THE EXAMPLES The Examples which follow further define, describe and illustrate the preparation and evaluation of the compounds and stabilized compositions of this invention. Apparatus and procedures used in both the preparation and evaluation of such compounds and compositions are standard or as hereinbefore described. Parts and percentages appearing in such Examples are by weight unless otherwise stipulated.

EXAMPLE I

Preparation of bis [3-(2, 2, 6, 6-tetramethyIpiper- idin-4-yl) aminopropyl]methylamine: Into a 110 ml autoclave are charged 15.5 grams (0.1 mole) of 2,2,6,6- tetramethyl-4-piperidone, 30 mis of methanol, 7.3 grams

(0.05 mole) of 3 ,3'-diamino-N-methyldipropylamine, and

0.05 grams of 10% platinum catalyst on carbon. The reaction mass is heated to about 80°C and the autoclave pressurized with hydrogen to about 800 psi. After about 3 hours, the reaction is terminated, the reaction mass is cooled and the catalyst was separated from the reaction product by filtration. The methanol medium is fractionated from the filtrate yielding a clear syrup product which is 99% pure by gas chromatographic techniques . The desired product has a boiling point between 227.5 and 228.9°C at 1.0 mm Hg. Elemental analysis yields the following results:

Calculated for C₂₅H₅₃N₅: C,70.86; H,12.61; N, 16.53.

Found: C70.90; H,12.86; and N,16.35.

EXAMPLE II Preparation of N,N'-bis[3-(2, 2, 6 , 6-tetramethyl- piperidin-4-yl) aminopropyl] piperazine: Into a 110 ml autoclave are charged 15.5 grams (0.1 mole) of 2,2,6,6- tetramethyl-4-piperidone, 25 mis methanol, 5.0 grams (0.025 mole) of N,N' -bis (3-aminopropyl) piperazine, and 0.05 grams of 10% platinum on carbon. The reaction mass is heated to about 80°C and the autoclave pressurized with hydrogen to about 800 psi. After about 3 1/2 hours, the reaction is terminated, the reaction mass cooled and the catalyst was separated therefrom by filtration. The resultant product is fractionated for removal of 2,6,6,6- tetramethyl-4-piperidonol. 8.9 grams of a tan solid product is isolated from the pot residue. The melting point of this product is 95 to 96 °C. Elemental analysis of the product yields following results:

Calculated for C₂₈H₅₈N₆:C,70.24,H,12.21, and

N,17.55. Found: C, 69.94;H, 12.30; N,17.40 EXAMPLE III

Preparation of bis [2- (2,2, 6 , δ-tetramethylpiper- idin^-yl) aminoethyl] amine : Into a 110 ml autoclave are charged 22.5 grams (0.145 mole) of 2, 2, 6, 6-tetramethyl-4- piperidone, 35 mis of methanol, 4.8 grams (0.047 mole) of diethylenetriamine, and 0.07 grams of 10% platinum on carbon. The reaction mass is heated to about 80°C, and the autoclave pressurized with hydrogen to about 1500 psi. After about 4 1/2 hours the reaction is terminated, the reaction mass is allowed to cool and the catalyst was separated from the reaction mass by filtration. The filtrate is thereupon concentrated on an evaporator. The concentrate is fractionated under reduced pressure for removal of 2,2,6,6-tetramethyl-4-piperidonol and the desired product isolated from the remaining fraction, boiling point 168 - 172°C @ 0.002mm Hg, total yield 12.9 grams or 72% based upon diethylenetriamine content of the charge. Elemental analysis yields the following results: Calculated for C₂₂H₄₇N₅: C, 69.23;H,12.42;N,18.35. Found: C,68.41; H,12.38; N,18.03.

EXAMPLE IV Preparation of N ¹,N⁸-bis(2,2, 6-tetramethyl- piperidin-4-yl)-3, 6-diazaoctane-l, 8-diamine: Into a 110 ml autoclave are charged 16.25 grams (0.105 mole) of 2, 2,6,6-tetramethyl-4-piperidone, 25 ml of methanol, 7.31 grams (0.05 mole) of triethylenetetramine, and 0.60 grams of 10% platinum on carbon. The above mixture is heated to 60°C, and the autoclave pressurized with hydrogen to about 1500 psi. After two hours, the reaction is terminated, cooled, and filtered to remove the catalyst. The filtrate is thereupon concentrated on an evaporator. The concentrate is fractionated under reduced pressure to remove 2,2,6,6-tetramethyl-4-piperidinol and to collect the desired product which boils at 220°C/0.7 mm Hg. The total weight of the desired product is 12.60 grams (59.2% yield based on triethylenetetramine). Elemental analysis gives the following results:

Calculated for C₂₄H₅₂N₆: C, 67.87; H, 12.34; N,19.79.

Found: C, 67.93; H, 12.32; N, 19.77.

Each of the foregoing compounds are evaluated for the stabilization of polypropylene with the following results:

* All samples are 20 mil plaques and contain 0.10 phr of. Good-rite 3125. Good-rite 3125 is 3,5- di-tert-butyl-4-hydroxy-hydrocinnamic acid triester with 1,3, 5-tris(2-hydroxyethyl-s- triazine)-2,4,6( IH,3H,5H)-trione.

**

A time to reach 50% of the original tensile strength. ***

2-Hydroxy-4-n-octoxybenzophenone

The foregoing Description and Examples have been provided as illustrative of the invention and not intended to delineate its scope which is set forth in the following claims.

Claims

1. Compounds of the formula

with R and R' being independently selected from the group consisting of alkyl, hydroxy substituted alkyl, aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl; R₁ and R₂ being independently selected from hydrogen, alkyl, aralkyl; R₃ and R₄ being independently selected from alkyl of 1 to 4 carbon atoms and capable of collectively forming a cycloalkyl substituent;

Compounds of the formula

wherein R is selected from the group consisting of alkyl, hydroxy substituted alkyl, aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl;

R₁ and R₂ being independently selected from hydrogen, alkyl, aralkyl; R₃ and R₄ being independently selected from alkyl of 1 to 4 carbon atoms and capable of collectively forming a cycloalkyl substituent;

3. Compounds of the formula

wherein R' is independently selected from the group consisting of alkyl, hydroxy substituted aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl; R₁ and R₂ being independently selected from hydrogen, alkyl, aralkyl;

R₃ and R₄ being independently selected from alkyl of 1 to 4 carbon atoms and capable of collectively forming a cycloalkyl substituent;

4. A composition comprising a polymer which is sensitive to photodegradation by ultraviolet light a a UV stabilizer effective amount of a compound of the formula

with R and R' being independently selected from the group consisting of alkyl, hydroxy substituted alkyl, aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl; R₁ and R₂ being independently selected from hydrogen, aIky1, araIky1; R₃ and R₄ being independently selected from alkyl of 1 to 4 carbon atoms and capable of collectively forming a cycloalkyl substituent;

5. A composition comprising a polymer which is sensitive to photodegradation by ultraviolet light and a UV stabilizer effective amount of a compound of the formula

wherein R is selected from the group consisting of alkyl, hydroxy substituted alkyl, aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl; R₁ and R₂ being independently selected from hydrogen, alkyl, aralkyl; R₃ and R₄ being independently selected from alkyl of 1 to 4 carbon atoms and capable of collectively forming a cycloalkyl substituent;

6. A composition comprising a polymer which is sensitive to photodegradation by ultraviolet light and a UV stabilizer effective amount of a compound of the formula

A and A' being independently selected from the group consisting of alkylene of 1 to 12 carbon atoms; and m is 0 - 4 n is 1 - 3,

7. A method for the stabilization of polymers which are sensitive to photodegradation by ultraviolet light, said method comprising incorporating within such photosensitive polymer a stabilizer effective amount of a compound of the formula

with R and R' being independently selected from the group consisting of alkyl, hydroxy substituted alkyl, aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl; R₁ and R₂ being independently selected from hydrogen, alkyl, aralkyl;

8. A method for the stabilization of polymers which are sensitive to photodegradation by ultraviolet light, said method comprising incorporating within such photosensitive polymer a stabilizer effective amount of a compound of the formula

9. A method for the stabilization of polymers which are sensitive to photodegradation by ultraviolet light, said method comprising incorporating within such photosensitive polymer a stabilizer effective amount of a compound of the formula

wherein R' is independently selected from the group consisting of alkyl, hydroxy substituted aryl, amino or hydroxy substituted aryl, aralkyl and amino or hydroxy substituted aralkyl; R₁ and R₂ being independently selected from hydrogen, alkyl, aralkyl; R₃ and R₄ being independently selected from alkyl of 1 to 4 carbon atoms and capable of collectively forming a cycloalkyl substituent;