HK1095368B - Method of dyeing a plastic article - Google Patents

Description

Method for dyeing plastic products

Technical Field

The invention relates to a method for dyeing plastic products. A plastic article (e.g., a molded article of thermoplastic polycarbonate) is at least partially immersed in a dye bath comprising one or more dyes, water, at least one carrier (e.g., ethylene glycol butyl ether), and a glycol (e.g., diethylene glycol).

Background

Colored plastic articles can be prepared by incorporating (e.g., by compounding) pigments and/or dyes directly into the polymeric material from which the article is made. This direct bonding method allows the colorant to be adequately dispersed throughout the plastic article. Direct bonding is not particularly suitable for producing molded articles that are only slightly colored or tinted (e.g., less than opaque), such as in the case of sunglasses. It is often difficult to properly and sufficiently disperse the small amounts of colorant required to produce slightly colored or tinted plastic articles by direct blending methods.

While a masterbatch of dye and resin may be used to better control the amount of dye blended during compounding and/or extrusion processing, the preparation of the masterbatch requires additional steps. In addition, the masterbatch resin is subjected to at least two heating cycles (one during the preparation of the masterbatch and the other during the preparation of the dyed molded article), which results in deterioration of the physical properties of the final molded article.

In general, it is known to prepare coloured plastic articles by applying a dye composition to the surface of the plastic article. Such dyeing methods are more suitable for producing slightly colored or tinted molded articles because only small, controllable amounts of colorant are incorporated into their surfaces. The dye composition may be aqueous or non-aqueous.

In view of environmental problems related to the use of organic solvents, attention has recently been paid to the development of dyeing methods using aqueous dye compositions. Methods of dyeing plastic articles with aqueous dye compositions generally have several disadvantages including, for example, uneven and/or insufficient dyeing of the articles, inconsistent degrees of dyeing between different batches of the same plastic articles.

It would be desirable to develop new methods of dyeing plastic articles that use aqueous dye compositions and, as a result, form uniform and well-dyed articles. Additionally, it is expected that such new methods may also provide dye consistency over time.

Summary of The Invention

According to the present invention, there is provided a method of dyeing a plastic article comprising:

(a) providing a plastic article comprising at least one polymer selected from the group consisting of thermoplastic polymers and thermosetting polymers;

(b) immersing at least a portion of the molded article in a dye bath comprising:

(i) at least one dye;

(ii) water;

(iii) at least one carrier represented by the following general formula I,

I

R-O-(CH₂)_n-OH

wherein R is selected from the group consisting of straight or branched C₁-C₁₈Alkyl, benzyl, benzoyl and phenyl, n is 2 or 3,

(iv) selected from straight or branched C₂-C₂₀Aliphatic diol, poly (C)₂-C₄Alkylene glycol), a diol of at least one of alicyclic diol having 5 to 8 carbon atoms in the ring, monocyclic aromatic diol, bisphenol and hydrogenated bisphenol;

(c) maintaining said portion of said molded article in said bath for a period of time at least sufficient to form a dyed plastic article;

(d) removing the dyed molded article from the bath.

Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about".

Brief description of the drawings

FIG. 1 is a graph showing the percentage% transmission (% T) and percentage% haze (% H) of dyed plastic articles as a function of the amount of carrier in the dye bath;

FIG. 2 is a graph showing the percent transmittance (% T) and percent haze (% H) of dyed plastic articles as a function of the diol content of the dye bath;

detailed description of the invention

The dye bath used in the process of the invention comprises at least one carrier according to formula I, as described hereinbefore. Straight or branched chain alkyl groups from which R of formula I may be selected include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups and structural isomers thereof (e.g., isopropyl, isobutyl, tert-butyl, and the like).

With further regard to formula I, R may also be selected from benzyl, benzoyl and phenyl, each of which may be independently and optionally substituted with 1 to 5 substituents selected from halogen (e.g., chloro, bromo and fluoro), straight or branched chain C₁-C₉Alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl), aryl (e.g., phenyl).

In one embodiment of the invention, with respect to formula I, n is 2 and R is selected from n-butyl, isobutyl and tert-butyl. In a particularly preferred embodiment of the invention, n is 2 and R is n-butyl.

The carrier is generally present in the dye bath in an amount of less than or equal to 30 wt.%, preferably less than or equal to 25 wt.%, more preferably less than or equal to 20 wt.%. The carrier is also generally present in the dye bath in an amount of at least 10 wt.%, preferably at least 15 wt.%, more preferably at least 17 wt.%. The carrier may be present in the dye bath in an amount ranging between any combination of these upper and lower values, inclusive. For example, the carrier is typically present in the dye bath in an amount of 10 to 30 wt%, more preferably 15 to 25 wt%, and more typically 17 to 20 wt%. These weight percentages are in each case based on the total weight of the dye bath.

The dye bath may also comprise C selected from linear or branched C₂-C₂₀Aliphatic diol, poly (C)₂-C₄Alkylene glycol), alicyclic diols having 5 to 8 carbon atoms in the ring, monocyclic aromatic alcohols, bisphenols and hydrogenated bisphenolsAt least one diol. Straight or branched C₂-C₂₀Examples of aliphatic diols include, but are not limited to, ethylene glycol, propylene glycol, 1, 3-propanediol, 1, 2-and 2, 3-butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, dodecanediol, tridecanediol, tetradecanediol, pentadecanediol, hexadecanediol, heptadecanediol, octadecanediol, nonadecanediol, and eicosanediol.

Poly (C) from which diols (iv) can be selected₂-C₄) Examples of alkylene glycols include, but are not limited to, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol and higher glycols, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol and higher propylene glycols, dibutylene glycol, tributylene glycol, tetrabutylene glycol, pentabutylene glycol and higher butylene glycols. Cycloaliphatic diols having 5 to 8 carbon atoms which can be used as diol (iv) include, but are not limited to, cyclopentanediol, cyclohexanediol, cyclohexanedimethanol, cycloheptanediol, and cyclooctanediol. Examples of monocyclic aromatic diols useful as diol (iv) include, but are not limited to: benzene diols such as 1, 2-dihydroxybenzene and 1, 3-dihydroxybenzene; c₁-C₄Alkyl-substituted benzene diols such as 4-tert-butyl-benzene-1, 2-diol, 4-methyl-benzene-1, 2-diol, 3-tert-butyl-5-methyl-benzene-1, 2-diol and 3, 4, 5, 6-tetramethyl-benzene-1, 2-diol; halogenated benzene diols such as 3, 5-dichlorobenzene-1, 2-diol, 3, 4, 5, 6-tetrabromo-benzene-1, 2-diol and 3, 4, 5-trichloro-benzene-1, 2-diol; and C₁-C₄Alkyl-and halogen-substituted benzene diols, such as 3-bromo-5-tert-butyl-benzene-1, 2-diol, 3, 6-dichloro-4-methyl-benzene-1, 2-diol, 3, -bromo-4, 5-dimethyl-benzene-1, 2-diol and 3-chloro-4, 6-di-tert-butyl-benzene-1, 2-diol.

The bisphenols and hydrogenated bisphenols useful as diol (iv) may be represented by the following general formula II,

general formula II

In formula II: r₁And R₂Each independently selected, and each of p and q is independently selected from C₁-C₄Alkyl (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl), chlorine, and bromine; p and q are each independently an integer from 0 to 4; x-is selected from-O-, -S (O)₂)-、-C(O)-、-CH₂-、-CH＝CH-、-C(CH₃)₂-and- (CH)₃)(C₆H₅) -a divalent linking group; while

Represents a benzene ring or a cyclohexane ring. An example of a bisphenol that may be used as diol (iv) is 4, 4' -isopropylidenediphenol (i.e., bisphenol a). An example of a hydrogenated bisphenol which can be used as diol (iv) is 4, 4' -isopropylidenebicyclohexanol.

In a preferred embodiment of the present invention, the diol (iv) is a poly (C) selected from the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol and mixtures thereof₂-C₄Alkylene) glycols. Particularly preferred diols are ethylene glycol and diethylene glycol.

The content of diol in the dye bath is generally less than or equal to 20% by weight, preferably less than or equal to 15% by weight, more preferably less than or equal to 12% by weight. The content of diol in the dye bath is also generally at least 1% by weight, preferably at least 5% by weight, more preferably at least 10% by weight. The diol may be present in the dye bath in an amount ranging between any combination of these upper and lower values, inclusive of the upper and lower values. For example, the diol is typically present in the dye bath in an amount of from 1 wt% to 20 wt%, more typically from 5 wt% to 15 wt%, and more typically from 10 wt% to 12 wt%. These weight percentages are in each case based on the total weight of the dye bath.

The dye contained in the dye bath may be selected from the group consisting of a fixed dye, a photochromic dye, and combinations thereof. The term "fixed dye" as used herein and in the claims refers to a dye that does not substantially change color when exposed to (or shielded from) Ultraviolet (UV) light. The term "photochromic dye" as used herein and in the claims refers to a dye that can reversibly change color upon exposure to ultraviolet light, as known to those skilled in the art. Typically, photochromic dyes will convert to a colored, open or active form (within a particular portion of the visible spectrum) when exposed to ultraviolet light of a particular wavelength. Upon removal of the ultraviolet light source, the open/activated photochromic dye returns to a non-colored, blocked/activated form, or to a form that is at least less colored than the activated form.

Fixed dyes that may be included in the dye bath include, for example, fabric dyes and disperse dyes, as well as dyes known in the art to be suitable for coloring plastic articles, such as thermoplastic polycarbonate articles. Examples of suitable Disperse dyes include, but are not limited to, Disperse Blue #3, Disperse Blue #14, Disperse Yellow #3, Disperse Red #13, and Disperse Red # 17. The classification and naming of The immobilized Dyes is set forth herein in accordance with The third edition of The color Index (1971) published jointly by Society of Dyes and Colors and The American Association of Textile Chemistsand Colors (1971), which is incorporated herein by reference. Dyes can generally be used as a single dye component, or as one component of a dye mixture, depending on the desired color. Thus, the term fixed dye as used herein includes mixtures of fixed dyes.

A class of fixed Dyes known as Direct Dyes can be used in the practice of the present invention. Examples of Direct Dye include, but are not limited to, Solvent Blue 35, Solvent Green 3, and Acridine orange base. However, it has been observed that Direct Dyes generally do not color (tint/dye) plastic articles as strongly as disperse Dyes (described above).

Also suitable fixed dyes include, for example, water-insoluble azo, diphenylamine and anthraquinone compounds. Particularly suitable examples include acetate dyes, dispersed acetate dyes, disperse dyes and dispersol dyes, such as those disclosed in The Colour Index, third edition, volume 2, The Society of Dyers and colourists, 1971, pages 2479 and 2187-2743, each of which is incorporated herein by reference in its entirety. Preferred Disperse dyes include Dystar's Palanil Blue E-R150 (anthraquinone/Disperse Blue) and DIANIX Orange E-3RN (azo dye/Cl Disperse Orange 25). In the process of the present invention, it has been observed that phenol red and 4-phenylazophenol do not provide the desired level of coloration when the plastic article is a thermoplastic polycarbonate.

In the practice of the present invention, it has been observed that fixed dyes known as direct dyes or those known as acid dyes can provide less desirable levels of coloration when the plastic article is a thermoplastic polycarbonate. However, it has been observed that acid dyes are effective with nylon

Another class of suitable fixed dyes that may be used in the method of the present invention include non-migrating fixed dyes (i.e., fixed dyes that have been chemically modified to minimize or eliminate migration from a plastic article to which the fixed dye has been incorporated). A specific class of non-migratory fixed dyes can be represented by the following general formula III,

III

R₅- (Polymer constituent-Y)_t

In formula III: r₅Represents an organic dye group (or chromophore group); the polymer moieties are independently selected for each (t) from poly (C)₂-C₄Alkylene oxide), such as homopolymers of polyethylene oxide and polypropylene oxide, poly (ethylene oxide-propylene oxide) copolymers, and diblock or higher block copolymers of ethylene oxide and propylene oxide; (t) may be an integer from 1 to 6; (Y) is independently selected for each (t) from hydroxyl, primary amine, secondary amine, and thiol groups. Polymer compositionThe molecular weight of the moiety may be, for example, 44 to 1500. (Y) dye groups from which one may choose include, but are not limited to, nitroso, nitro, azo (e.g., monoazo, disazo, and trisazo), diarylmethane, triarylmethane, xanthene, acridine, methine, thiazole, indamine, azine, oxazine, and anthraquinone dye groups. Non-migratory fixed dyes of the general formula III are described in more detail in us patent nos. 4284729, 4640690 and 4812141.

Non-migrating fixed dyes have been found to be useful when dyeing plastic articles by imbibition or diffusion (e.g., by immersion) according to the methods of the present invention. When incorporated into a plastic article by imbibition, excess non-migrating fixed dye may be washed off the plastic article with a minimal amount of imbibed non-migrating fixed dye being lost from the plastic article. Non-migratory fixed dyes (e.g., as represented by formula III) have been found to be particularly useful in the process of the present invention when dyeing (e.g., by dipping) plastic articles made from thermoplastic polyurethanes.

Photochromic dyes that may be used in the method of the present invention include those dyes known to those skilled in the art. Suitable types of photochromic dyes include, but are not limited to: spiro (indoline) phenoxazines and spiro (indoline) benzoxazines (e.g., as described in U.S. patent No. 4818096); chromenes such as benzopyrans and naphthopyrans (e.g., as described in U.S. patent No. 5274132), and benzopyrans having a substituent at the 2-position of the pyran ring and having an optionally substituted heterocyclic ring such as a benzothiophene ring or a benzofuran ring fused to the benzene moiety of the benzopyran (e.g., as described in U.S. patent No. 5429774). Other types of photochromic dyes include, for example, fulgides and fulgimides (fulgimides), such as 3-furyl and 3-thienyl fulgides (fulgies) and fulgimides (for example, as described in U.S. Pat. No. 4931220). The relevant disclosure of said patent with respect to photochromic dyes is incorporated herein by reference.

In the process of the present invention, photochromic dyes or mixtures thereof may be used alone or in combination with one or more fixed dyes. Typically, photochromic dyes are imbibed into thermoplastic articles, such as thermoplastic polycarbonate articles, resulting in dyed plastic articles that do not readily change color upon exposure to or shielding from ultraviolet light. While not intending to be bound by any theory, it is believed based on the present information that the photochromic dye is entrapped in the thermoplastic polymer matrix in an open or closed form. Photochromic dyes are imbibed into plastic articles made from thermosetting polymers such as thermosetting polycarbonates or thermosetting polyurethanes, and generally result in dyed plastic articles having photochromic properties.

The amount of dye in the dye bath may vary widely. The dye should generally be present in the dye bath in an amount sufficient to form a dyed plastic article having a visually discernable color effect and/or photochromic effect when exposed to ultraviolet light, for example, in the case of photochromic dyes.

The actual amount of dye in the dye bath will depend on the solubility of the dye in the mixture of water, carrier and glycol. The solubility of the dye in the dye bath may also be affected by the temperature of the bath. In the case where the dye is not completely soluble in the bath, the dye bath is considered to contain a saturated amount of dye. The level of dye in the bath may be maintained at a saturation level during the dyeing operation by adding more dye than is required to achieve saturation in the bath (e.g., by adding to a bag filter through which the dye bath is continuously passed). The amount of dye in the bath (e.g., the amount of saturation) can be determined periodically or continuously by, for example, thermogravimetric analysis or spectrophotometric analysis.

The dye is typically present in the dye bath in an amount of less than or equal to 15 weight percent, more typically less than or equal to 5 weight percent, more typically less than or equal to 1 weight percent, and even more typically less than or equal to 0.5 weight percent. The dye is also generally present in the dye bath in an amount of at least 0.001% by weight, preferably at least 0.005% by weight, more preferably at least 0.01% by weight. The amount of dye in the dye bath may vary between any combination of these upper and lower values, inclusive of the recited values. For example, the dye is typically present in the dye bath in an amount of from 0.001 wt% to 15 wt%, more typically from 0.005 wt% to 5 wt%, more typically from 0.01 wt% to 1 wt%, and more typically from 0.01 wt% to 0.5 wt%. In one embodiment, the dye is present in the dye bath in an amount of 0.03% by weight. These weight percentages are in each case based on the total weight of the dye bath.

In a preferred embodiment of the invention, the dye bath contains: 0.001 to 0.5% by weight of the dye; 65 to 75 wt% water; 15 to 25 weight percent of the carrier; 1 to 15% by weight of the diol. These weight percentages are in each case based on the total weight of the dye bath.

The water content in the dye bath is generally less than or equal to 85% by weight, preferably less than or equal to 80% by weight, more preferably less than or equal to 75% by weight. The water content in the dye bath is generally at least 50% or 51% by weight, preferably at least 60% by weight, more preferably at least 65% by weight. The amount of water in the dye bath may vary between any combination of these upper and lower values, inclusive. For example, the water is typically present in the dye bath in an amount of 50 or 51 wt% to 85 wt%, more typically 60 wt% to 87 wt%, and even more typically 65 wt% to 75 wt%. These weight percentages are in each case based on the total weight of the dye bath. Preferably, the water used is deionized or distilled water.

In one embodiment of the present invention, the dye bath may further comprise a surfactant (or emulsifier) different from any one of the carrier and the glycol. Suitable surfactants in the present invention are readily dispersible upon pouring into water and then form a milky white emulsion upon stirring. The surfactant may be selected from at least one of the following: an anionic surfactant; an amphoteric surfactant; and a nonionic surfactant selected from the group consisting of poly (C)₂-C₄Alkoxylation) C₁₄-C₁₈Unsaturated fatty acid, poly (C)₂-C₄Alkoxylated) phenols and poly (C)₂-C₄Alkoxylation) C₁-C₉At least one of alkyl substituted phenols.

Examples of anionic surfactants useful in the present invention include, for example, amine or alkali metal salts of carboxylic, sulfamic or phosphoric acids, such as sodium lauryl sulfate, ammonium lauryl sulfate, lignosulfonates, sodium ethylenediaminetetraacetic acid (EDTA) and acid salts of amines, such as laurylamine hydrochloride or ammonium salts of poly (oxy-1, 2-ethanediyl), alpha-sulfo-omega hydroxy ethers and phenol 1- (methylphenyl) ethyl derivatives.

Amphoteric surfactants that may be present in the dye bath include, for example, dodecyl sulfobetaine; dihydroxyethyl alkyl betaine; amido betaines based on coconut oil acid; disodium N-dodecylaminopropionate; or the sodium salt of a dicarboxylic acid coconut derivative.

Poly (C)₂-C₄Alkoxylation) C₁₄-C₁₈Examples of unsaturated fatty acids include ethoxylated, propoxylated and/or butoxylated tetradecene carboxylic acids. Poly (C)₂-C₄Alkoxylated) phenols include ethoxylated, propoxylated and/or butoxylated phenols. Poly (C)₂-C₄Alkoxylation) C₁-C₉Examples of alkyl substituted phenols include octylphenoxy polyethenoxy ethanol and poly (oxy-1, 2-ethanediyl), styrenated alpha-phenyl-omega-hydroxy.

The optional surfactant (emulsifier) may be used in an amount of less than or equal to 5 wt%. Preferably, the optional surfactant is present in the dye bath in an amount of from 0.5 wt% to 5 wt%, more preferably from 1 wt% to 4 wt%. These weight percentages are in each case based on the weight of the dye bath.

The dye bath further comprises a performance enhancing additive selected from, for example, at least one (compound or substance) of ultraviolet stabilizers, fluorescent whitening agents, mold release agents, antistatic agents, heat stabilizers, infrared absorbers, and antibacterial agents. The inclusion of one or more of these optional performance enhancing additives in the dye bath may be used to enhance the physical properties/attributes of the dyed plastic article. In addition to the dye, optional additives may also be diffused, impregnated, or otherwise absorbed into the body of the plastic article when the plastic article is immersed in the dye bath. For example, inclusion of an ultraviolet stabilizer in the dye bath may improve the ultraviolet resistance of the dyed plastic article. It may be more advantageous to include a release agent in the dye bath when the plastic article is selected from thermoplastic pellets and/or thermoplastic strands that will be later used to prepare molded articles, as will be discussed further herein. The optional performance enhancing additives may be selected from known additives used in the preparation of thermoplastic and thermoset molded plastic articles.

The types of UV (ultraviolet) stabilizers (or absorbers) that may be used in the dye baths of the present invention include, but are not limited to, salicylic acid ultraviolet absorbers, benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, and mixtures thereof. More specific examples of benzotriazole uv absorbers include, but are not limited to: 2- (2 '-hydroxy-5' -methylphenyl) benzotriazole (may)Available from Ciba of Tarrytown, new york); 2- (3 ' -5 ' -di-tert-butyl-2 ' -hydroxyphenyl) -5-chlorobenzotriazole (may beCommercially available from Ciba); 2- (2 ' -hydroxy-3 ' -5 ' -di-tert-amylphenyl) benzotriazole (may beCommercially available from Ciba); phenylpropionic acid, 3- (2H-benzotriazol-2-yl) -5- (1, 1-dimethylethyl) -4-hydroxy-, C_7-9Branched alkyl ester (may)Commercially available from Ciba); 2- (3 ', 5 ' -bis (1-methyl-1-phenylethyl) -2 ' -hydroxyphenyl) benzotriazole (mayTo be provided withCommercially available from Ciba); 2- [ 2-hydroxy-3-dimethylbenzylphenyl-5- (1, 1, 3, 3-tetramethylbutyl)]-2H-benzotriazole (may bePurchased); poly (oxy-1, 2-ethanediyl), alpha- [3- [3- (2H-benzotriazol-2-yl) -5- (1, 1-dimethylethyl) -4-hydroxyphenyl]-1-oxopropyl radical]-omega-hydroxy and poly (oxy-1, 2-ethanediyl), alpha- [3- [3- (2H-benzotriazol-2-yl) -5- (1, 1-dimethylethyl) -4-hydroxyphenyl]-1-oxopropyl radical]-omega- [3- [3- (2H-benzotriazol-2-yl) -5- (1, 1-dimethylethyl) -4-hydroxyphenyl]-1-oxopropyl radical]A mixture of (may)1130 available from Ciba); and 2- [4- [ 2-hydroxy-3-tridecyloxypropyl group]Oxygen gas]-2-hydroxyphenyl]-4, 6-bis (2, 4-dimethylphenyl) -1, 3, 5-triazine and 2- [4- [ 2-hydroxy-3-dodecyloxypropyl]Oxygen gas]-2-hydroxyphenyl]-4, 6-bis (2, 4-dimethylphenyl) -1, 3, 5-triazine (which may beCommercially available from Ciba). An example of a commercially available benzophenone UV stabilizer is 2-hydroxy-4 (N-octyloxy) -benzophenone (which may beCommercially available from Great Lakes chemical core of West Lafayette, ind).

Other examples of commercially available uv stabilizers that can be used in the present invention include, but are not limited to: 2-ethylhexyl p-methoxycinnamate stabilized with butylated hydroxytoluene (hereinafter "BHT") (commercially available as Uvinul MC 80 from BASF of Mount Olive, N.J.); unstabilized 2-ethylhexyl p-methoxycinnamate (available as Uvinul MC 80N from BASF); 2' -ethylhexyl 2-cyano-3, 3-diphenylacrylate (commercially available as Uvinul 539T from BASF); 2-hydroxy-4- (N-octyloxy) benzophenone (commercially available as Cyasorb UV-501 from Cytec in West Paterson, N.J.); 2- (2 ' -hydroxy-3 ' -5 ' -di-tert-amylphenyl) benzotriazole (available from Cytec as Cyasorb UV-2337); and 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole (available from Cytec as Cyasorb UV-5411 PA).

Another class of UV stabilizers which may be used in the process of the present invention includes UV stabilizers modified with at least one poly (oxyalkylene) chain. Such poly (oxyalkylene) chain-modified UV stabilizers are characterized by: once imbibed (or diffused) into the plastic, they have low migration properties (e.g., they do not readily leach out of the plastic into which they are imbibed). The poly (oxyalkylene) chain may be of C_2-20Alkylene oxides (e.g., ethylene oxide, propylene oxide, and butylene oxide) react to form homopolymers, copolymers, or block copolymers. The poly (oxyalkylene) groups may be substituted by hydroxy, C₁-C₂₀Alkyl ether radical or C₁-C₂₀And (4) blocking ester groups. Poly (oxyalkylene) chain modified uv stabilizers are described in more detail, for example, in U.S. patent No. 6602447B 2.

The optical brighteners which may be included in the dye bath of the process of the present invention typically absorb light at wavelengths equal to or less than 450 nm and emit light at higher wavelengths, for example, at wavelengths equal to or less than 550 nm, preferably equal to or less than 525 nm. Preferably, the emitted light is in the blue region of the visible spectrum (e.g., the emitted light has a wavelength of at least about 400 nanometers and at most about 525 nanometers). Most preferably, the emitted light does not exceed about 500 nanometers.

Classes of optical brighteners that can be used in the present invention include, but are not limited to, benzoxazole derivatives and stilbene derivatives. Examples of commercially available benzoxazole derivatives that may be used in the present invention include, but are not limited to:

2, 2' - (2, 5-thiophenediyl) bis [ 5-tert-butylbenzooxazole](may beCommercially available from Ciba); such as(from Bayer of Pittsburgh, Pa.)Benzoxazole derivatives of the class;(Clariant from Muttenz, Switzerland); and(from Clariant). An example of a commercially available stilbene derivative is 4, 4' -bis (2-benzoxazolyl) stilbene (which may be substituted with a substituentAvailable from Eastman of Kingsport, tenn). Other types of optical brighteners that can be used in the present invention include, but are not limited to: derivatives of 4, 4 '-diiminostilbene-2-2' -disulfonic acid; coumarin derivatives (e.g., 4-methyl-7-diethylaminocoumarin); and bis- (styryl) biphenyl.

Types of release agents that may be included in the dye bath include, but are not limited to, hydrocarbon-based release agents, fatty acid amide-based release agents, alcohol-based release agents, fatty acid ester-based release agents, silicone-based release agents, and mixtures or combinations thereof. Examples of hydrocarbon-based mold release agents include synthetic waxes, polyethylene waxes, and fluorocarbons. Fatty acid-based mold release agents that may be used include, for example, stearic acid and hydroxystearic acid. Fatty amide-based mold release agents that may be used include, for example, stearamide, ethylene bis stearamide, and alkylene bis fatty amide. Examples of the alcohol-based mold release agent include stearyl alcohol, cetyl alcohol, and polyhydric alcohols such as polyethylene glycol and polyglycerol. An example of a fatty acid ester based release agent that may be included in the dye bath is butyl stearate.

Antistatic agents that may be included in the dye bath of the present process include, but are not limited to, nonionic antistatic agents, such as those containing fluorocarbon groups and silicone oils, such as BAYSILONE 01A (available from Bayer AG, germany). Other examples of antistatic agents that may be used in the present invention include dioctadecyl hydroxylamine, triphenylamine, tri-N-octylphosphine oxide, triphenylphosphine oxide, pyridine N-oxide, and ethoxylated sorbitan monolaurate.

Types of thermal (or heat resistant) stabilizers that may be included in the dye bath of the present process include, but are not limited to, phenol stabilizers, organic thioether stabilizers, organic phosphide stabilizers, hindered amine stabilizers, epoxy stabilizers, and mixtures thereof. Specific examples of heat stabilizers include, but are not limited to, 2, 6-di-tert-butyl-p-cresol, o-tert-butyl-p-cresol, tetrakis (methylene-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate) methane, beta-naphthylamine, p-phenylenediamine, and thiodiethylene bis (3, 5-di-tert-butyl) -4-hydroxyhydrocinnamate, which is commercially available from Ciba specialty Chemical under the trade name IRGANOX 1035 heat stabilizer.

Infrared (IR) absorbers useful in the methods of the present invention include dyes that absorb in the infrared region of the spectrum. Examples of commercially available infrared absorbers include CYASORB IR-99, IR-126, and IR-165, which are commercially available from Glendale Protective Technologies, Inc., Lakeland, Fla.

Antimicrobial agents that may be included in the dye bath of the present method include, for example, substances having antimicrobial activity against microorganisms, such as pathogenic microorganisms. The term "antimicrobial agent" as used herein and in the claims also includes preservatives, disinfectants and antifungal substances. Alternatively, the antimicrobial agent may be used in a pre-activated form, e.g., in a form that does not have antimicrobial activity until an initiating event occurs, such as the action of a microorganism on the pre-activated substance.

Examples of antimicrobial agents that may be included in the dye bath include, but are not limited to: quinolones such as nalidixic acid, pipemidic acid, cinoxacin, ciprofloxacin, norfloxacin, ofloxacin, pefloxacin and enoxacin; aminoglycosides such as gentamicin, kanamycin, amikacin, sisomicin, tobramycin, and netilmicin; macrolides such as erythromycin, clarithromycin, and azithromycin; polypeptides such as bacitracin, mupirocin, thyroxine (thyrothicin), gramicidin and tyrosine; lincomycins such as lincomycin and clindamycin; and antimycobacterial agents such as rifampicin and fusidic acid. Other examples of antimicrobial agents that may be used in the dye bath include: 10, 10' -oxybisphenoxyarsine; 2-n-octyl-4-isothiazolin-3-one; 2, 4, 4 '-trichloro-2' -hydroxydiphenyl ether (also named 5-chloro-2- (2, 4-dichlorophenoxy) -phenol, and commonly known as Triclosan); n-butyl-1, 2-benzisothiazolin-3-one; n- (trichloromethylthio) phthalic acid dimethylamide.

If performance enhancing additives are used, they are generally present in the dye bath in a specified amount totaling less than or equal to 15% by weight, preferably less than or equal to 5% by weight, more preferably less than or equal to 1% by weight. The performance enhancing additives are also typically present in the dye bath in an amount totaling at least 0.001 wt.%, preferably at least 0.005 wt.%, more preferably at least 0.01 wt.%. The total amount of performance enhancing additive in the dye bath may vary between any combination of these upper and lower values, inclusive of the recited values. For example, the performance enhancing additives may be present in the dye bath in an amount totaling from 0.001 to 15 wt.%, more typically from 0.005 to 5 wt.%, more typically from 0.01 to 1 wt.%. These weight percentages are in each case based on the total weight of the dye bath.

The method of the present invention relates to dyeing plastic articles. The plastic article may comprise at least one polymer selected from thermoplastic and/or thermoset polymers. In one embodiment of the invention, the plastic article comprises a polymer selected from at least one of (co) polyesters, (co) polycarbonates, polyester polycarbonate copolymers, acrylonitrile-butadiene-styrene (ABS) copolymers, polyamides, polyurethanes, polyalkyl (meth) acrylates (e.g., polymethylmethacrylate), and styrene copolymers (e.g., styrene acrylonitrile copolymers). The (co) polyesters, (co) polycarbonates, polyesterpolycarbonate copolymers may be aliphatic or aromatic polymers (e.g., containing bisphenol a residues). These described polymers may be thermoplastic polymers, thermosetting polymers, or combinations thereof, as the case may be.

As used herein and in the claims, the term "thermoplastic polymer" and similar terms refer to a polymer having a softening or melting point and being substantially free of a three-dimensional crosslinked network formed by covalent bonds between chemically active groups (e.g., active hydrogen atoms and free isocyanate groups). Thermoplastic polymers that may be used in the present invention include those known to those skilled in the art, such as thermoplastic (co) polyesters, thermoplastic (co) polycarbonates, thermoplastic polyester polycarbonate copolymers, thermoplastic acrylonitrile-butadiene-styrene (ABS) copolymers, thermoplastic polyamides, thermoplastic polyurethanes, thermoplastic polyalkyl (meth) acrylates, and thermoplastic styrene copolymers.

The term "thermosetting polymer" and similar terms as used herein and in the claims refers to a polymer having a three-dimensional cross-linked network structure formed by covalent bonds between chemically reactive groups (e.g., between an active hydrogen atom and a free isocyanate or oxirane group, or an unsaturated group such as an allyl group). Thermosetting polymers generally do not have a melting point. Thermosetting polymers that can be used in the present invention include those known to those skilled in the art, such as thermosetting (co) polyesters, thermosetting (co) polycarbonates, thermosetting polyester polycarbonate copolymers, thermosetting polyamides, thermosetting polyurethanes, and thermosetting polyalkyl (meth) acrylates.

Preferred thermosetting polymers include thermosetting polycarbonates. One preferred thermoset polycarbonate is a polymer of a polymerizable composition comprising a polyol (allyl carbonate) monomer such as CR-39 diethylene glycol bis (allyl carbonate) monomer available from PPG Industries, Inc.

The plastic article may contain additives known to those skilled in the art. Such additives include, but are not limited to: a release agent; a filler; reinforcing agents in the form of fibers or flakes (e.g., metal flakes, such as aluminum flakes); a flame retardant; a pigment; and masking agents such as titanium dioxide; light diffusers such as polytetrafluoroethylene, zinc oxide, Paraloid EXL-5136 available from Rohm and Haas, and crosslinked polymethylmethacrylate microspheres (such as n-siliconspheres from Nagase America); a UV stabilizer; a hydrolysis stabilizer; a heat stabilizer; and an antibacterial agent. In one embodiment, the plastic article contains at least one of pigments, crosslinked polymethylmethacrylate microspheres, glass microspheres, and metal flakes.

The plastic article may be a molded plastic article prepared by methods well known in the art. Molding methods include, for example, compression molding, injection molding, rotational molding, extrusion, injection and extrusion blow molding, casting. The molded plastic article can be selected from the group consisting of shaped articles, films (e.g., less than 30 mils (762 micrometers) thick), sheets (e.g., greater than or equal to 30 mils (762 micrometers) thick). Examples of shaped molded articles include optical lenses, sun visors, and window glass (e.g., windows for vehicles such as cars, trucks, and aircraft, windows for residential and commercial buildings). Other examples of molded plastic articles include: a computer panel; a keyboard; a bezel and a mobile phone; all types of colored barcoded packages and containers; home and business lighting fixtures and components thereof; sheets, for example, sheets used in buildings and structures; tableware, including plates, cups and tableware; small appliances and their components; and decorative films, including films used in film insert molding.

In one embodiment of the invention, the plastic article is selected from thermoplastic pellets and/or thermoplastic strands. Thermoplastic pellets and strands can be prepared by methods well known in the art, such as extrusion or melt spinning. The thermoplastic pellets and/or strands are dyed and then further processed. In one embodiment of the present invention, dyed thermoplastic pellets and/or strands are melted (e.g., in an extruder) to form a molten dyed thermoplastic composition, and the molten dyed thermoplastic composition is then added (e.g., injected) into a mold. The contents of the mold are allowed to cool, the mold is opened, and the dyed molded article is removed from the mold.

The method of further processing the dyed thermoplastic pellets and/or strands differs from the direct blending method described previously and these differences are advantageous. For dyed thermoplastic pellets and/or strands, the dye is already present in the thermoplastic polymer (rather than being added separately to the polymer), which allows for better control and better reliability in producing molded articles having the desired and repeatable level of dyeing.

In the method of the present invention, the plastic article (e.g., lens) to be dyed is at least partially immersed in a dye bath for a time and at a temperature at least sufficient to facilitate impregnation (diffusion or imbibition) of at least some of the dye into the bulk of the plastic article, thereby effecting dyeing (or tinting). The time and temperature used will generally depend on the composition of the plastic article. Thermoset plastic articles are generally more resistant to heat than thermoplastic articles (e.g., the former has a higher heat distortion temperature than the latter). Accordingly, thermoset plastic articles can generally be immersed in a dye bath at a higher temperature than the thermoplastic article.

The impregnation time is generally less than or equal to 8 hours, more generally less than or equal to 4 hours, and even more generally less than or equal to 1 hour. The immersion time is also typically at least 5 seconds, more typically at least 30 seconds, and even more typically at least 1 minute. The immersion time may range between any combination of these upper and lower values, inclusive. In embodiments of the invention, the immersion time is typically from 5 seconds to 8 hours, more typically from 15 or 30 seconds to 4 hours, more typically from 1 minute to 1 hour (e.g., from 1 minute to 15 minutes).

During impregnation of the plastic article, the temperature of the dye bath is typically at least room temperature (e.g., 25 ℃) and below the boiling point and/or decomposition temperature of the dye bath. The temperature of the dye bath is maintained at 25 ℃ to 99 ℃, e.g., 60 ℃ to 97 ℃, or 70 ℃ to 95 ℃. As previously mentioned, the time and temperature of the impregnation depends at least in part on the type of plastic article to be dyed. For example, for thermoplastic aromatic polycarbonate plastic articles, dyeing may be effected at a temperature of from 90 ℃ to 99 ℃ and the dipping time is typically less than 1 hour, more typically in the range of from 1 minute to 15 minutes. In some cases, the dye can be absorbed into soft plastic articles, such as soft thermoplastic articles, more quickly and efficiently, in which case a lower dye bath temperature is generally sufficient. For example, plastic articles made from thermoplastic polyurethane or thermoplastic styrene-acrylonitrile copolymer (SAN) can be readily dyed with the same dye bath composition as used to color thermoplastic aromatic polycarbonates, but at temperatures of 60 ℃ and 80 ℃, respectively.

The colored (or dyed) plastic article is then removed from the dye bath. The dyed plastic article can be removed from the dye bath rapidly or at a slower rate (e.g., at a rate sufficient to effect a gradient tint). When forming a dyed plastic article having a color gradient, portions of the article remaining in the dye bath for longer periods of time are impregnated with more dye, thus exhibiting a greater degree of coloration (relative to those portions removed from the dye bath first).

The dye bath may be prepared by mixing together the dye, water, carrier, glycol, optional surfactant, and optional performance enhancing additive in any order. For example, the carrier and diol can be mixed together with the dye and then either added to the water or added to the mixture. In one embodiment, the dye bath is formed by: (i) preparing a mixture of water, carrier and glycol; (ii) adding a dye to the filter; (iii) the mixture is passed over the dye and through a filter, thereby forming a dye bath. The dye bath, or at least a portion of the dye bath, is then typically passed continuously through a filter. Optionally, the mixture of water, carrier and glycol can be heated, for example, to 25 ℃ to 99 ℃, or 60 ℃ to 97 ℃, or 70 ℃ to 95 ℃, and then the heated mixture contacted with the dye in a filter.

The filter to which the dye is added may be any suitable filter known to those skilled in the art. A preferred filter type is a bag filter. Preparing and maintaining the dye bath in this manner ensures that the level of dye in the bath is maintained substantially at the saturation level (as discussed above). In addition, continuous passage of the dye bath through the bag filter may be used to remove particulate impurities (e.g., undissolved dye particles) therein that can foul dyed plastic articles prepared by immersion in the dye bath.

In another embodiment, the dye bath is continuously added to and continuously removed from the impregnation tank (or vessel). Typically, the impregnation tank is part of a circuit comprising an inlet in fluid communication (via an inlet pipe) with a pump in fluid communication with the outlet of the tank via an outlet pipe. The circuit may optionally comprise at least one filter in the line with the inlet and/or outlet pipe, for example a bag filter as described hereinbefore. Preferably, the inlet and outlet of the immersion tank are located below the level of the dye bath in the tank.

The immersion tank inlet may comprise a plate (e.g., a diffuser or a diffuser plate) having a plurality of holes. The dye bath is continuously fed into the impregnation tank through a plate having a plurality of holes to increase the level of turbulent mixing within the impregnation tank and improve the efficiency and uniformity of dyeing the plastic articles impregnated therein. The holes in the diffuser plate may be any suitable shape, for example, circular, elliptical, polygonal, or combinations thereof. The holes of the diffuser plate typically have a diameter of 0.79 mm to 12.70 mm, for example, 3.17 mm to 6.35 mm. The diffuser plate may have any suitable configuration, for example, it may be flat, concave, or convex.

The scope of the method of the present invention includes other steps by which the composition of the dye bath is adjusted, for example, by replacing the initial dye or dyes with the subsequent dye or dyes. In one embodiment of the present invention, the dye and optional performance-enhancing additive are separated from the other components of the dye bath (e.g., water, carrier, glycol, and optional surfactant). This separation is advantageous for the environment, since it makes it possible to reuse the non-dyeing components of the dye bath, for example, with another dye or dyes or with one or more fresh dyes, or as a cleaning composition for cleaning the dyed plastic articles removed from the dye bath. In addition, the dye separation process may be carried out if the dyes of the dye bath have been damaged, for example by oxidation or denaturation (for example due to overheating caused by temperature peaks).

The dye separation process may be carried out by contacting a dye bath with activated carbon particles and separating therefrom a substantially dye-free liquid containing water, carrier, glycol and optionally surfactant in approximately the same relative proportions as before the separation step. The dye-free liquid is then mixed with another dye or dyes to form a different dye bath. The dye bath may be contacted with the activated carbon by continuously passing the dye bath through a bed or column containing the activated carbon.

The activated carbon is generally capable of retaining substantially all of the dye bath, preferably less than a minimum amount of the organic liquid components of the dye bath (e.g., carrier, glycol, and optional surfactant). However, the organic liquid component may evaporate somewhat, requiring adjustment of the dye-free liquid by subsequent addition of an evaporating component. It has been found that when the dye separation step is carried out with a dye bath containing the dye, water, carrier and glycol (which does not contain the optional surfactant and optional performance enhancing additive), substantially no organic liquid component remains on the activated carbon. This result is very surprising, since the use of activated carbon for the separation of organic compounds from aqueous compositions is known. Thus, it is expected that both the dye and a significant amount of the organic liquid component in the dye bath will be retained, but surprisingly this is not observed in this case.

In one embodiment of the present invention, the method further relates to a dye separation method comprising:

(i) contacting the dye bath with activated carbon particles to form a mixture of the dye bath and the activated carbon particles;

(ii) separating a dye-free liquid comprising water, carrier and glycol from the mixture;

(iii) at least one dye is optionally added to the dye-free liquid, thereby forming another dye bath.

As discussed previously, the dye bath may be contacted with the activated carbon particles by passing the dye bath through a bed or column containing the activated carbon particles. The dye-free liquid separated by the dye separation method is substantially free of dye, e.g., contains an undetectable amount of dye by spectrophotometric analysis. The activated carbon particles typically have a particle size of 200 mesh (e.g., a particle size of 0.075 mm). An example of a commercially available activated Carbon particulate that can be used in the present invention is Filtrasorb 200 activated Carbon from Calgon Carbon Corporation.

The amount of activated carbon required to effect dye separation depends in part on the temperature of the dye bath. In general, the amount of activated carbon required to achieve dye separation is: decreases with decreasing temperature of the dye bath; increasing with increasing temperature of the dye bath. In an embodiment of the invention, the dye bath is contacted with activated carbon at 25 ℃.

The one or more dyes optionally added to the dye-free liquid are selected from the group consisting of fixed dyes, photochromic dyes, and combinations thereof. The fixed dyes and photochromic dyes that may be added include those classes and examples previously described. The dye added to the dye-free liquid may be the same type of dye as removed from the dye bath, in which case the other dye bath is a fresh or renewed dye bath. Alternatively, the dye added to the dye-free liquid may be different from the dye removed from the dye bath, in which case the other dye bath is a new or different dye bath.

The dye separation process may also include adding other materials to the dye-free liquid and/or other dye bath. Such other materials include, for example, surfactants and/or performance enhancing additives, each of which may be selected from those classes and examples previously described.

After removal from the dye bath, the dyed plastic articles are typically washed to remove excess dye bath material therefrom. The rinsing step is typically accomplished by contacting at least a portion of the surface of the dyed article with a rinsing composition comprising water and optionally a carrier represented by formula I and/or a glycol. The water of the cleaning composition may be deionized or distilled water. The carrier and glycol that may be present in the rinse composition, as described above with respect to the dye bath, may each be selected from those classes and examples described above. For example, in one embodiment, the carrier is ethylene glycol monobutyl ether and the glycol is diethylene glycol. Preferably, the rinse composition consists of water, a carrier of formula I and a glycol (as described above with respect to glycol (iv) of the dye bath).

The rinse composition may be contacted with the surface of the dyed plastic article by, for example, dipping (immersion), spraying, and/or curtain coating. After contact with the surface of the dyed plastic article, the rinse composition may be recycled for rinsing additional dyed articles. After many wash cycles, dyes typically accumulate in the recycled wash composition. Accumulated dye may be removed from the recycled rinse composition by contacting the recycled rinse composition with activated carbon particles, as described previously with respect to the dye separation process. The dye-free recycled cleaning composition can then be used to clean other dyed articles after separating the accumulated dye from the recycled cleaning composition.

The rinse composition typically has a water content of from 50 (or 51) wt% to 100 wt%, more typically from 60 wt% to 87 wt%, and still more typically from 65 wt% to 75 wt%. These weight percentages are in each case based on the total weight of the cleaning composition.

If present, the carrier and/or glycol content of the cleaning composition may be selected from those ranges and amounts previously described with respect to the dye bath. For example, the carrier is typically present in the cleaning composition in an amount of from 10 wt.% to 30 wt.%, more typically from 15 wt.% to 25 wt.%, and even more typically from 17 wt.% to 20 wt.%. These weight percentages are in each case based on the total weight of the cleaning composition. For example, the diol is typically present in the cleaning composition in an amount of from 1 wt.% to 20 wt.%, more typically from 5 wt.% to 15 wt.%, and even more typically from 10 wt.% to 12 wt.%. These percentages are in each case based on the total weight of the cleaning composition.

After washing, the dyed plastic articles are usually dried. Drying can be accomplished by wiping the washed dyed plastic article with a dry cloth and/or by standing at room temperature (25 ℃). Alternatively, the washed dyed plastic article may be dried by exposure to elevated temperatures (above 25 ℃), for example, temperatures of 50 ℃ to 100 ℃. In addition, hot air (e.g., at a temperature of 50 ℃ to 100 ℃) may be passed over the surface of the washed dyed plastic article.

The present invention is described in more detail in the following examples, which are intended to be illustrative only, since numerous modifications and variations will be apparent to those skilled in the art. All parts and percentages are by weight unless otherwise indicated.

Examples

In the following examples, each dye bath was prepared by mixing deionized water, carrier and glycol together in a mixing tank to form a liquid mixture having a total weight of 26986 grams. The liquid mixture was passed continuously at a temperature of 95 ℃ into a bag filter which had been filled with 50 g of dye. The heated mixture containing the dye is circulated from the mixing tank through a bag filter and back into the mixing tank for a period of time sufficient to saturate the mixture of water, carrier and glycol with the dye to form a dye bath. The dye bath was recirculated to the mixing tank through small openings (4.8 mm diameter) to enhance turbulent mixing of the dye bath during dyeing operations.

To form the saturated dye bath, the initial cycle was performed for about 60 minutes. The dye bath was then continuously circulated through the system at a temperature of 95 c at a rate of 72 liters/minute.

In the following examples, the amount of dye in the dye bath is estimated to be a specified amount greater than zero, less than or equal to 0.1% by weight, based on the total weight of the dye bath (calculated from the known weights of water, carrier, glycol and dye used). Typically, a small amount of dye was observed to be present in the bag filter after each experiment was completed. A dye bath was prepared as described above containing 70 wt.% deionized water, 18 wt.% ethylene glycol monobutyl ether (as the carrier) and 12 wt.% diethylene glycol (as the glycol), these weight percents being based on the total weight of deionized water, carrier and glycol. The liquid mixture was passed through a bag filter which had 50 g of MacroLEX Blue3R dye in it. After cycling at 95 ℃ for 60 minutes, the dye bath was analyzed spectrophotometrically (at 95 ℃) and found to contain 0.03 weight percent dye based on the total weight of the dye bath.

Examples 1 to 5

In the following examples, the water and carrier content was varied while maintaining the diol content between 10 and 11 parts by weight. The dyes used in examples 1-5 are all MacroLEX Blue3R dye, available from Bayer Chemicals Corporation. The parts by weight of water, carrier and glycol in the dye bath compositions of examples 1-5, based on 100 parts by weight, are summarized in table 1 below.

TABLE 1

(a) The carrier is ethylene glycol monobutyl ether.

(b) The diol used is diethylene glycol.

Clear test specimens of molded thermoplastic polycarbonate having dimensions of 5 cm by 7.5 cm by 0.25 cm were immersed in a dye bath for 3 minutes. The thermoplastic polycarbonate used was a bisphenol A based MAKROLON 2600 homopolycarbonate having MFR values of 10 to 12 g/10 min (determined according to ASTM D1238) available from Bayer Polymers LLC. The test specimens had a percent transmittance of 90.6% and a percent haze of 0.8 (both measured according to ASTM D1003) prior to dyeing. After removal from the dye bath, the dyed plastic articles were rinsed with methanol and deionized water and manually wiped dry with a soft cloth. In each of the examples, the dyed plastic articles were observed to be uniformly dyed. The physical properties of the dyed articles were measured and are summarized in table 2 below.

TABLE 2

(c) Percent transmittance and percent haze were determined according to ASTM D1003.

The percent transmittance and percent haze data for table 2 are plotted as a function of weight parts of the carrier and are shown in figure 1. The data show that as the carrier content is increased, the percent transmittance decreases and the percent haze increases. Dye baths containing from 15 to 25 parts by weight of carrier provide the desired combination of low percent transmission and low percent haze.

Examples 6 to 11

In examples 6-11, the ratio of water to carrier was maintained in the range of 3.3 to 3.5 while varying the content of glycol. The dyes used in examples 6-11 were all MacroLEX Blue3R dyes, available from Bayer Chemicals Corporation. Dye baths of examples 6-11 were prepared in substantially the same manner as in examples 1-5 using the same equipment. The parts by weight of water, carrier and glycol in the dye bath compositions of examples 6-11, based on 100 parts by weight, are summarized in table 3 below.

TABLE 3

The transparent thermoplastic polycarbonate specimens having the same dimensions, composition and physical properties as the specimens described in examples 1-5 were used. The transparent thermoplastic polycarbonate test piece was dyed under the same conditions as described in examples 1 to 5. In each example, the dyed plastic articles were observed to be uniformly dyed. The physical properties of the dyed articles were measured and are summarized in table 4 below.

TABLE 4

The percent transmittance and percent haze data for table 4 are plotted as a function of the weight fraction of diol, and are shown in figure 2. The data show that as the diol content increases, the percent transmittance increases and the percent haze decreases. The dye bath containing about 7 to 10 parts by weight of the carrier provides the best combination of low percent transmission and low percent haze.

It was observed that a dye bath containing water, diol and dye (without carrier) resulted in the formation of undyed thermoplastic polycarbonate articles. It was observed that a dye bath containing water, carrier and dye (not containing diol) resulted in the formation of a thermoplastic polycarbonate article that was not uniformly dyed.

The invention has been described with reference to specific details of embodiments thereof. Such detailed description should not be taken as limiting the scope of the invention, except to the extent and extent that the appended claims are included.

Claims (27)

1. A method of dyeing a plastic article comprising:

(a) providing a plastic article comprising at least one polymer selected from the group consisting of thermoplastic polymers and thermosetting polymers;

(b) immersing at least a portion of the plastic article in a dye bath, the dye bath comprising:

(i) at least one dye;

(ii) water;

(iii) at least one carrier represented by the following general formula I,

I

R-O-(CH₂)_n-OH

wherein R is a straight or branched chain C₁-C₉Alkyl, n is 2 or 3, and

(iv) a diol which is a poly C selected from the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol and mixtures thereof₂-C₄An alkylene glycol;

(c) maintaining said portion of said plastic article in said dye bath for a period of time at least sufficient to form a dyed plastic article;

(d) removing the dyed plastic article from the bath; wherein

The dye bath is formed by the steps of:

(i) preparing a mixture of water, the carrier and the glycol,

(ii) the dye is added to the filter and,

(iii) passing the mixture over the dye and through the filter, thereby forming the dye bath; and is

The dye bath was passed continuously through the filter.

2. The method of claim 1, wherein the plastic article comprises a polymer selected from at least one of a polyester, a polycarbonate, a polyester polycarbonate copolymer, a polyamide, a polyurethane, a polyalkyl (meth) acrylate, and a styrene copolymer.

3. The method of claim 1, wherein the dye bath comprises:

0.001 to 0.5 weight percent of the dye;

65 to 75 weight percent water;

15 to 25 weight percent of the carrier; and

1 to 15% by weight of the diol,

these weight percentages are in each case based on the total weight of the dye bath.

4. The method of claim 1, wherein the temperature of the dye bath is maintained at 25 ℃ to 99 ℃.

5. The method of claim 1, wherein n is 2.

6. The method of claim 5, wherein R is selected from the group consisting of n-butyl, isobutyl, and tert-butyl.

7. The method of claim 1, wherein the dye bath further comprises a surfactant selected from at least one of the following surfactants: an anionic surfactant; an amphoteric surfactant; and a nonionic surfactant selected from the group consisting of poly C₂-C₄Alkoxylation of C₁₄-C₁₈Unsaturated fatty acid, poly C₂-C₄Alkoxylated phenols and poly-C₂-C₄Alkoxylation of C₁-C₉At least one of alkyl substituted phenols.

8. The method of claim 7, wherein the surfactant is present in an amount of from 1 to 15 wt%, based on the total weight of the dye bath.

9. The method of claim 1, wherein the diol is diethylene glycol.

10. The method of claim 1, wherein the dye is selected from the group consisting of fixed dyes, photochromic dyes, and combinations thereof.

11. The method of claim 10, wherein the dye is a water insoluble fixed dye selected from the group consisting of azo dyes, diphenylamine dyes, and anthraquinone dyes.

12. The method of claim 10, wherein the dye is a fixed dye selected from the group consisting of disperse dyes, non-migrating fixed dyes, and combinations thereof.

13. The method of claim 10, wherein the photochromic dye is selected from the group consisting of spiroindolinophenoxazines, benzopyrans, naphthopyrans, organometallic dithizonates, fulgides, and fulgimides.

14. The method of claim 1, wherein the dye bath further comprises at least one of a uv stabilizer, a fluorescent whitening agent, a mold release agent, an antistatic agent, a thermal stabilizer, an infrared absorber, and an antimicrobial agent.

15. The method of claim 1, wherein the plastic article comprises at least one of a pigment, crosslinked polymethylmethacrylate microspheres, glass microspheres, and metal flakes.

16. The method of claim 1, wherein the plastic article comprises a thermoplastic polycarbonate selected from at least one of a thermoplastic aromatic polycarbonate and a thermoplastic aliphatic polycarbonate.

17. The method of claim 1, wherein the plastic article is a molded article comprising a thermoset polycarbonate.

18. The method of claim 17, wherein the thermosetting polycarbonate is a polymer of a polymerizable composition comprising a polyol allyl carbonate monomer.

19. The method of claim 1, wherein the plastic article is a molded article selected from shaped articles.

20. The method of claim 1, wherein the plastic article is a molded article selected from the group consisting of a film and a sheet.

21. The method of claim 19, wherein the molded article is a shaped article selected from a lens.

22. The method of claim 19, wherein the molded article is a shaped article selected from the group consisting of optical lenses, sun visors, and window glass.

23. The method of claim 1, wherein the plastic article is selected from the group consisting of thermoplastic pellets and thermoplastic strands.

24. The method of claim 23, further comprising:

melting at least one of the dyed thermoplastic pellets and the dyed thermoplastic strands to form a molten dyed thermoplastic composition; and

adding the molten dyed thermoplastic composition to a mold to form a dyed shaped molded article.

25. The method of claim 1, further comprising:

(i) contacting the dye bath with activated carbon particles to form a mixture of the dye bath and activated carbon particles;

(ii) separating a dye-free liquid comprising water, the carrier and the diol from the mixture;

(iii) optionally adding at least one dye to the dye-free liquid, thereby forming another dye bath.

26. The method of claim 1, further comprising: contacting at least a portion of the surface of the dyed plastic article removed from the dye bath with a cleaning composition comprising water, and optionally at least one of the carrier (iii) and the glycol (iv).

27. The method of claim 2, wherein the styrene copolymer is an acrylonitrile-butadiene-styrene copolymer.