Method for preparing light-absorbing polymeric compositions

Details Method for preparing light-absorbing polymeric compositions Method for preparing light-absorbing polymeric compositions

1999-05-26

2001-03-06

Tucker, Philip (Department: 1712)

Compositions

Light transmission modifying compositions

C252S587000, C252S589000, C528S271000, C528S272000, C525S418000, C525S419000, C525S450000, C525S471000, C525S534000, C525S535000, C525S540000

Reexamination Certificate

active

06197223

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an improved method for preparing light-absorbing polymeric compositions, which are useful as powders or pellets for incorporation into a variety of thermoplastic resins such as cellulose esters, polyesters, polyolefins, polycarbonates, polyamides, etc. by conventional melt or solution blending techniques. The colored thermoplastic resins thus produced have good clarity, good color development, excellent fastness to light and are useful for a variety of end uses where nonhazardous, nonmigrating, or nonextractable colorants are needed.
It is well-known that thermoplastic polymers may be colored by adding pigments or solvent dyes (e.g., see Thomas G. Weber, Editor,
Coloring of Plastics,
John Wiley & Sons, New York, 1979). The use of pigments, however, is accompanied by undesirable properties such as opacity, dullness of color, low tintorial strength, etc. Also, difficulties in uniformly blending the insoluble pigments with the thermoplastic resin are often encountered. Also useful for coloring thermoplastic polymers are the solvent dyes (K. Venkataraman, Editor,
The Chemistry of Synthetic Dyes,
Vol. 8, Academic Press, New York, 1978, pp. 81-131), which provide compositions having improved clarity, brightness in hue and high tinctorial strength, but which may lead to dye migration, extraction, etc. from the colored thermoplastic polymer. These problems are of particular concern when solvent dyes are used to color flexible polymers such as polyvinyl chloride, polyethylene and polypropylene which have low glass transition temperatures.
Plastics, paints, printing inks, rubber, cosmetics, and similar materials are typically colored by organic pigments when superior brilliance and tinctorial strength are important. Toxicity considerations have presented chronic problems relative to the use of organic pigments since some have been shown to be potential carcinogens and to cause contact dermatitis.
Plastics are also colored by using color concentrates consisting of physical admixtures of polymers and colorants (usually solvent dyes). However, the use of such physical admixtures to color polymeric materials such as polyester, e.g., poly(ethylene terephthalate) and blends thereof, present a number of problems, including:
Colorant migration during drying of the colored polyester pellets.
Colorant migration during extrusion and colorant accumulation on dies which can cause shutdowns for clean-up. Such colorant migration and accumulation result in time consuming and difficult clean-up, particularly when a polymer of another color is subsequently processed on the same equipment.
Colorants may not mix well, for example, when using two or more color cencentrates to obtain a particular shade.
Colorants may diffuse or exude during storage and use of the colored polymeric material.
The colored polymeric compositions which are prepared by the process of this invention eliminate or minimize the aforementioned problems associated with the use of conventional dyes and pigments.
PRIOR ART
To attempt to overcome some of the problems mentioned above, particularly as relates to coloring polyesters, colored polyester compositions have been prepared by copolymerizing relatively low amounts of monomeric colorants during the polymer preparation (U.S. Pat. Nos. 5,194,571; 5,106,942; 5,102,980; 5,032,670; 4,892,922; 4,740,581; 4,403,092; 4,359,570; 4,267,306 and WO92/07913). However, the preparation of these colored polymers require dyes having outstanding thermal stability since the colorants are exposed to very high temperatures for prolonged periods of time necessary for polyester formation, thus severely circumscribing the selection of efficacious colorants. For example, only the nonazo type colorants have been shown to have the adequate thermal stability for copolymerization into polyesters, since azo type compounds do not have the resquite thermal stability for copolymerization.
Furthermore, it is known to prepare polymeric dyes by reacting dyes containing reactive hydroxy and amino groups with organic di-acid chlorides in solvents (U.S. Pat. Nos. 2,994,693; 3,403,200; 4,619,990; 4,778,742; 5,401,612). Although this method of polymer preparation allows the use of a wide range of chromophoric classes, including azo compounds, as colorant monomers, the polymerization reaction in each case involves the use of very reactive organic di-acid chlorides which are toxic and involve difficult to handle inorganic halogen compounds in their preparation and have accompanying problems of hydrolysis in the presence of water which causes serious handling and storage problems. The hydrolysis product (HCl) is particularly corrosive and makes storage of these compounds difficult. Furthermore, since the di-acid chlorides will react with water, the monomeric dyes must be specially dried to avoid side reactions in the polymer preparation.
In a similar attempt to prepare polymeric dyes using relatively low temperatures, polyurethanes have been prepared by reacting dyes bearing two hydroxyalkyl group with aliphatic and aromatic isocyanates (U.S. Pat. 5,194,463). However, the organic isocyanates themselves are extremely toxic and present difficult handling problems. They also are reactive with water and thus the reaction requires specially dried monomeric dyes. Also, the colored polyurethanes as a class do not have excellent thermal stability.
It is further known to prepare colored condensation polymers by reacting a polymerizable lactone or a hydroxyalkanoic acid with a dye containing reactive hydroxy group (U.S. Pat. No. 4,933,426). The procedure again requires relatively high reaction temperatures and prolonged times and use a large excess of the lactone reactant. The method is further hindered by the fact that some lactones are suspected carcinogens.
Light-absorbing polymeric compositions have also been produced by free radical polymerization of vinyl functionalized light-absorbing monomers (U.S. Pat. Nos. 5,310,837; 5,334,710; 5,359,008; 5,434,231 and 5,461,131).
Finally, it is known that one may color plastics, in particular polyolefins, with low melting, cross-linked colored polyester compositions containing residues of terephthalic acid, isophthalic acid, or both, a low-molecular weight trimethylol alkane, i.e., 1,1,1-trimethylol propane and a copolymerizable colorant, said colorant being present at a level of 0.1-25% by weight (U.S. Pat. No. 4,116,923). Difficulties are encountered, however, in preparing these highly cross-linked colored polymers as extreme care with regard to the temperature, amount of vacuum, the level of colorant present, and the reaction time, is necessary in order to attempt to reproduce the same quality of cross-linked colored polyester composition. Further, these colored polyester compositions are brittle or low melting and may cause deterioration in physical properties of themoplastic polymers when added in quantities sufficient to produce a high level of coloration.
Practice of the Invention
This invention relates to a method for preparing a light absorbing linear polymeric having Formula I
wherein A comprises the residue of a diacidic monomer comprising about 1 to 100 mole % of at least one light-absorbing monomer having a light absorption maximum between about 300 nm and about 1200 nm and wherein the remaining portion of A comprises the residue of a non-light absorbing monomer which does not absorb significantly at wavelengths above 300 nm or has a light absorption maximum below 300 nm and wherein B is a divalent organic radical selected from C
2
-C
12
alkylene, C
3
-C
8
cycloalkylene, C
1
-C
4
alkylene-C
3
-C
8
-cycloalkylene-C
1
-C
4
alkylene, C
1
-C
4
alkylene-arylene-C
1
-C
4
alkylene, C
2
-C
4
alkylene-O—C
2
-C
4
alkylene, and C
2
-C
4
-alkylene-L-arylene-C
2
-C
4
alkylene and C
2
-C
4
alkylene-(L—C
2
-C
4
alkylene)
1-4
, wherein L is a linking group selected from-O—, —S—, —SO
2
—, —NH—, —N(C
1
-C
6
alkyl)—, —N(aryl)—, —N(SO
2
C
1
-C
6
alkyl)—, —N(SO
2
aryl)—, —SO
2
N(C
1
-C
6
alkyl)— and combinations thereof; wherei

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