Dip-dyeable polycarbonate process

Details Dip-dyeable polycarbonate process Dip-dyeable polycarbonate process

2001-11-07

2004-06-15

Einsmann, Margaret (Department: 1751)

Bleaching and dyeing; fluid treatment and chemical modification

Nontextile, dyeing process or product, including inorganic...

C008S509000, C008S510000, C008S512000, C008S514000, C008S515000, C008S516000

Reexamination Certificate

active

06749646

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to plastic articles and more particularly to colored articles, and to a process for their preparation.
SUMMARY OF THE INVENTION
A process for tinting of articles molded from a polymeric resin is disclosed. Preferably, the article is molded from polycarbonate and the process entails immersing the molded article in a dye bath that contains water, dye, a carrier and an optional surfactant. The carrier is a compound conforming to
R
1
[—O—(CH
2
)
n
]
m
OR
2
  (i)
wherein R
1
and R
2
independently denote H or C
1-18
alkyl, benzyl, benzoyl or phenyl radical which may be substituted in the aromatic ring by alkyl and or halogen, preferably R
1
=butyl, R
2
=H, n is 2 or 3 and m is 2 to 35. The method is especially useful in the manufacture of tinted lenses.
BACKGROUND OF THE INVENTION
Articles molded of polycarbonate are well known. The utility and method for making colored articles that are prepared from pigmented polycarbonate compositions are well known. Also known are processes for dyeing articles molded of resins, including polycarbonates, and including lenses that have been tinted by immersion in special pigmenting mixtures. Among the advantages attained by such tinting of lenses, mention has been made of reduced light transmission and mitigation of glare.
U.S. Pat. No. 4,076,496 disclosed a dye bath composition suitable for dyeing hard-coated polarized lenses; the composition of the bath included a dye and as a solvent, a mixture of glycerol and ethylene glycol, optionally with a minor proportion of water or other organic solvent.
U.S. Pat. No. 5,453,100 disclosed polycarbonate materials that are dyed by immersion into a mixture of dye or pigment dissolved in a solvent blend. The blend is made up of an impregnating solvent that attacks the polycarbonate and allows the impregnation of the dye or pigment and a moderating solvent that mitigates the attack of the impregnating solvent. The impregnating solvent thus disclosed includes at least one solvent selected from dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether and propylene glycol monomethyl ether. PCT/CA99/00803 (WO 0014325) disclosed tinting plastic articles by immersion in an aqueous dispersion and exposing the dispersion and immersed article to microwave radiation. JP 53035831 B4 disclosed polycarbonate moldings that are dyed in aqueous dispersion containing dispersed dyes and diallyl phthalate, o-phenylphenol or benzylalcohol. Also, JP 55017156 disclosed aliphatic polycarbonate lenses that are colored with a liquor containing dyes and water. JP 56031085 (JP-104863) disclosed compositions containing a disperse dye in an aliphatic ketone and polyhydric alcohol said to be useful in coloring polycarbonate films at room temperature. JP2000248476 disclosed a molded polycarbonate bolt that was dyed with a solution containing dyes, an anionic leveling agent and then treated with a solution containing thiourea dioxide.
U.S. Pat. No. 4,812,142 disclosed polycarbonate articles dyed at a temperature of 200° F. or above in a dye solvent having a boiling point of at least 350° F., and U.S. Pat. No. 3,514,246 disclosed immersing molded polycarbonate articles in an emulsified dye liquor which contains a water insoluble dyestuff, an oil-soluble surface active agent dissolved in an aliphatic hydrocarbon solvent and water. The procedure was repeated with similar results where the surfactant was replaced by a poly(oxyethylene) derivative. U.S. Pat. No. 3,532,454 disclosed dyeing of polycarbonate fibers with a dye composition that contains at least one of alkoxyalkylbenzyl ether, alkylene glycol di-benzyl ether, benzoic acid alkoxyalkyl ester or phenoxy acetic acid-alkoxyalkyl ester. U.S. Pat. No. 3,630,664 disclosed a dye bath that required the presence of a carbonate conforming to a specific formula, e.g. ethyl-benzyl-carbonate.
DETAILED DESCRIPTION OF THE INVENTION
The inventive method and the dye bath composition of this invention are useful for dyeing plastic articles molded of a variety of resinous molding compositions. The suitable resins include both thermoplastic and thermosetting compositions. Among the suitable resins, mention may be made of (co)polyesters, (co)polycarbonates (including aromatic and aliphatic polycarbonate such as allyldiglycol carbonate e.g., trade name CR-39), polyesterpolycarbonate copolymers, styrenic copolymers such as SAN and acrylonitrile-butadiene-styrene (ABS), acrylic polymers such as polymethylmethacrylate and ASA, polyamide, and polyurethane and blends of one or more of these resins. Particularly, the invention is applicable to polycarbonates, and most particularly to thermoplastic aromatic polycarbonates.
The molding compositions useful in molding the articles that are suitable for use in the inventive process may include any of the additives that are known in the art for their function in these compositions and include at least one of mold release agents, fillers, reinforcing agents in the form of fibers or flakes most notably metal flakes such as aluminum flakes, flame retardant agents, pigments and opacifying agents such as titanium dioxide and the like, light-diffusing agents such as polytetrafluoroethylene, zinc oxide, Paraloid EXL-5136 available from Rohm and Haas and crosslinked polymethylmethacrylate minispheres (such as n-licrospheres from Nagase America) UV-stabilizers, hydrolytic stabilizers and thermal stabilizers.
Articles to be dyed in accordance with the inventive process may be molded conventionally by methods that have long been practiced in the plastics arts and include articles molded by compression molding, injection molding, rotational molding, extrusion, injection and extrusion blow molding, and casting, the method of molding the articles is not critical to the practice of the inventive process. The molded articles may be any of a vast variety of useful items and include computer face-plates, keyboards, bezels and cellular phones, color coded packaging and containers of all types, including ones for industrial components, residential and commercial lighting fixtures and components therefor, such as sheets, used in building and in construction, tableware, including plates, cups and eating utensils, small appliances and their components, optical and sun-wear lenses, as well as decorative films including such films that are intended for use in film insert molding.
Polymer resins particularly suitable in the present context include one or a mixture of two or more resins selected from the group consisting of polyester, polycarbonate, polyesterpolycarbonate copolymer, acrylonitrile-butadiene-styrene (ABS), polyamide, polyurethane, polymethylmethacrylate and styrenic copolymer. While styrenic copolymers, most notable styrene-acrylonitrile copolymers are thus suitable, the inventive process is not applicable for tinting of homopolystyrene.
According to the present invention, the molded article to be tinted, preferably a lens, is immersed in the dyeing bath mixture for a time and at temperature sufficient to facilitate at least some impregnation, or diffusion, of the dye into the bulk of article thus effecting tinting thereof. For tinting articles made of aromatic polycarbonate the immersion may be carried out at a temperature of about 90 to 99° C. and the immersion time is typically less than 1 hour, most preferably in the range of 1 to 15 minutes. However, due to the efficiency of dye up-take, thermoplastic resins that have low heat distortion temperature may be dyed at lower temperatures than polycarbonate. For example, polyurethanes, SAN and polyamide may be readily dyed using the solution composition that is typically used for tinting polycarbonate, heated to only about 60° C., 90° C. and 105° C., respectively. The tinted article is then withdrawn at a desired rate, including a rate sufficient to effect a tinting gradient, the portion of the article that remains in the mixture longest is impregnated with the most dye so that it exhibits the darkest color tint.
The dyeing b

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