Patent Publication Number: US-2013249137-A1

Title: Solvent application of boron pyrromethene dye to polymer prior to injection molding

Description:
FIELD 
     Methods for preparing polymer materials including dye compounds are described. 
     BACKGROUND 
     Typically, plastic articles incorporating dye compounds are formed by injection molding, extrusion, or other methods by dissolving or dispersing the dye into white mineral oil and then mixing precursor plastic pellets with the dye/mineral oil. However, this method was not thought to be suitable for dyes which are less soluble or substantially insoluble in mineral oil, including porphyrin dyes (e.g., platinum octaethylporphyrin) and boron pyrromethene dyes. 
     SUMMARY 
     Methods comprising injection molding a polymer-dye mixture into an article, the polymer-dye mixture comprising a polymer, a dye compound, and a solvent, wherein the solvent is not mineral oil, are provided. 
     Methods comprising contacting a dye compound with a polymer in the presence of a solvent to form a polymer-dye mixture, wherein the solvent is not mineral oil, are also provided. 
    
    
     DETAILED DESCRIPTION 
     The embodiments described herein generally relate to methods for incorporating dye compounds into various polymer materials. In some cases, organic solvents that are sufficiently compatible with both the dye compound and the polymer material may be utilized to dissolve, disperse, or suspend dye compounds, which may then be applied to the polymer material. Such methods may be useful for dye compounds which may not be compatible with (e.g., soluble in) solvents used in current methods. Other advantages of methods described herein include simplified manufacturing processes and the use of minimal solvent (e.g., organic solvent), surfactant, or water, thereby reducing the amount of waste. In some cases, the method may be performed without need for a heated drying step, which typically adds time and complexity to manufacturing processes. Methods described herein may be useful in the manufacture of various articles, including articles for protective eyewear, by methods including injection molding, extrusion, casting, spin coating, and the like. 
     Methods described herein may be particularly advantageous in that the dye compounds may be evenly dispersed within or throughout a polymer material (e.g., polymer pellet, polymer powder) while substantially maintaining the structural integrity, morphology, and/or other physical or chemical characteristics of the polymer material. For example, some embodiments involve the use of polymer pellets, and undesired dissolution or softening of the pellets may be minimized or prevented using methods described herein. In some cases, the method may reduce or prevent the overloading of polymers with dye compounds. 
     In some cases, the method involves contacting a dye compound with a polymer in the presence of a solvent to form a polymer-dye mixture. The polymer-dye mixture typically includes a polymer, a dye compound, and a solvent, wherein the solvent is not mineral oil. In some cases, the polymer-dye mixture contains the dye compound dispersed on or within the polymer. In some cases, the polymer-dye mixture contains the dye compound formed as a coating on the polymer. In some cases, the dye compound is formed as a film on the polymer. In some cases, the method involves injection molding a polymer-dye mixture into an article. 
     Methods described herein may be useful in a wide range of applications, including the fabrication of articles including optical filters. For example, articles produced using methods described herein may be useful as optical filters having the ability to substantially block or absorb emissions having a particular wavelength or that are within a particular wavelength range, while simultaneously allowing other emissions to be transmitted through the article. In some embodiments, the optical filter may be included in eyewear, namely, lenses, eyeglasses, goggles, visors, and the like. For example, the article may be laser protective eyewear fabricated using a boron pyrromethene compound and an optically transparent, high-strength ballistic material such as polycarbonate. The article may be capable of blocking or absorbing hazardous laser radiation (e.g., laser radiation at about 532 nm), while simultaneously allowing other visible light to be transmitted through the article. 
     Solvents used in the methods described herein may be selected to be sufficiently compatible with the dye compound such that combination of the dye compound with the solvent may produce stable mixtures, solutions, dispersions, emulsions, and the like. In some cases, the dye compound may be substantially dissolved in the solvent to form a solution. In some cases, the dye compound may be sufficiently soluble and/or sufficiently dispersible in the solvent such that a relatively homogeneous mixture may be formed. In some embodiments, the dye compound may be sufficiently dispersed within the solvent such that scattering or the formation of undesired precipitates or aggregates is minimized. The ability to formulate stable solutions, dispersions, or mixtures containing dye compounds may also aid in the ability to homogeneously coat the dye compounds onto, or disperse the dye compounds on or within, polymer materials. 
     In one set of embodiments, the solvent may be selected to be sufficiently compatible with polycarbonate pellets. Polycarbonate is a widely used thermoplastic polymer and exhibits high impact-resistance, low scratch-resistance, optical transparency, and high light transmission. In some cases, the solvent may be selected to form a stable dispersion of the dye compound, such that the dye compound may be relatively evenly applied to (e.g., dispersed within, coated on) polycarbonate pellets. In some cases, the solvent (e.g., an oil) may not substantially dissolve or soften the polycarbonate pellets, and/or the solvent may prevent overcoating of the polycarbonate pellets with the dye compound. The polycarbonate-dye material may then be processed to form molded objects without adversely affecting the desirable properties of polycarbonate. 
     The solvent may also be selected to be suitable for use in processing methods such as injection molding. For example, the solvent (e.g., oils) may have a relatively high boiling point such that it does not evaporate or degrade when subjected to high temperatures used during typical thermoforming, injection molding, or other manufacturing processes. In some cases, the solvent may be an organic solvent having a relatively high boiling point. For example, the solvent may have a boiling point of between about 100° C. and about 500° C. In some cases, the solvent may have a boiling point of about 100° C., about 200° C., about 300° C., about 400° C., or about 500° C. The solvent may be a small molecule (e.g., DMF, xylene, various oils), oligomer, or polymer (e.g., polysiloxanes). The solvent may also be selected to be relatively non-toxic and non-hazardous to the environment. 
     Examples of solvents include polysiloxanes, ethers (e.g., glycol ethers), carbonate esters, and esters of organic acids. In some cases, the solvent is an ester of an organic acid such as a dicarboxylic acid, citric acid, or phthalic acid. The dicarboxylic acid may be adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, or the like. In one embodiment, the solvent is an ester of adipic acid. In another embodiment, the solvent is an ester of sebacic acid. Some specific examples of solvents include, but are not limited to, diethylene glycol monoethyl ether (DEGME), 1,4-dioxane, p-xylene, siloxane polymers such as polydimethylsiloxane (e.g., Dow 210H), Dow 705 penta-phenyl trisiloxane, and Dow 710 phenyl-methyl polysiloxane, dimethylformamide, dibutyl phthalate, propylene carbonate, 1-phenoxy-2-propanol, triethyl citrate, bis(2-ethylhexyl) adipate (BEHA), or bis(2-ethylhexyl) sebacate (BEHS). In one set of embodiments, the solvent is BEHA. Those of ordinary skill in the art would be able to select which solvents are suitable for use in methods described herein. For example, in order to determine the compatibility of a dye compound in a solvent, a small sample of dye compound may be combined with a small amount of solvent, and the resulting mixture may be analyzed (e.g., visually analyzed). The solvent may also be evaluated for its compatibility with a polymer material, such as polycarbonate, by contacting the polymer material with the solvent and observing changes, if any, in the properties of the polymer material. 
     Various dye compounds may be utilized in the context of the embodiments described herein. The dye compound may be an organic compound, a metal-containing compound (e.g., organometallic compounds), an oligomer, a polymer, or the like. In some cases, the dye compound may be a negatively charged compound. In some embodiments, the dye compound is a polar compound. In some cases, the dye compound may be a positively charged compound. In some cases, the dye compound may be a neutral compound. In some cases, the dye compound may be a salt. Some examples of dye compounds include, but are not limited to, boron pyrromethene compounds, boron azapyrromethene compounds, porphyrin compounds, boron furanopyrrole compounds, and the like. 
     In one set of embodiments, the method may involve contacting a dye compound with a polymer in the presence of a solvent to form polymer-dye mixture. The dye compound may be a boron pyrromethene containing an electron-withdrawing group, such as a nitro group. In another set of embodiments, the dye compound may be a boron pyrromethene containing an electron-donating group, such as a catechol group. In some cases, the boron pyrromethene compound may be a boron pyrromethene compound having an absorbance from about 400 nm to about 800 nm (e.g., about 532 nm). The polymer-dye mixture may then be processed via injection molding. 
     Various polymers may be suitable for use in the methods described herein. In some embodiments, the polymer may be a substantially optically transparent polymer such as polycarbonate. Other examples include, but are not limited to, polyethylene, polypropylene, poly(vinyl chloride), poly(methyl methacrylate), poly(vinyl benzoate), poly(vinyl acetate), polystyrene, cellulose, poly(vinyl pyrrolidinone), polyamide, polyacrylamide, epoxys, silicones, poly(vinyl butyral), polyurethane, nylons, polyacetal, polycarbonate, polyesters, polyethers, cyclic olefin polymers, copolymers such as polyester-polycarbonate, acrylonitrile-butadiene-styrene (ABS), crosslinked polymers such as polystyrene-poly(divinyl benzene), polyacrylamide-poly(methylenebisacrylamide), polybutadiene copolymers, combinations thereof, and the like. 
     In an illustrative embodiment, the method involves combining the dye compound (e.g., boron pyrromethene) with an oil (e.g., BEHA), and then adding the dye-containing oil to a quantity of polycarbonate pellets. The mixture may be shaken and/or stirred for a period of time to substantially uniformly coat the dye-containing oil on the polycarbonate pellets. The resulting dye-polycarbonate material may then be processed via injection molding or extrusion to form articles containing the dye compound. 
     The concentration of dye compound in the solvent may be varied to suit a particular application. In some embodiments, about 5 mg, about 10 mg, about 15 mg, about 20 mg, about 25 mg, about 30 mg, about 35 mg, about 40 mg, about 45 mg, about 50 mg, about 55 mg, about 60 mg, about 65 mg, about 70 mg, about 75 mg, about 80 mg, about 85 mg, about 90 mg, about 95 mg, or about 100 mg of dye compound per 0.5 mL solvent may be used. Additionally, the ratio, by weight, of dye compound to polymer may also be varied to suit a particular application. In some embodiments, the ratio of dye compound to polymer may be about 1:1, about 1:2, about 1:3, about 1:4, about 1:5, about 1:10, about 1:20, about 1:30, about 1:40, about 1:50, about 1:100, about 1:500, about 1:1000, about 1:2000, or less, by weight. In one set of embodiments, the ratio of dye compound to polymer is about 1:5, by weight. In another set of embodiments, the ratio of dye compound to polymer is about 1:2000, by weight. Those of ordinary skill would be able to select the appropriate amounts of dye compound, solvent, and polymer suitable for use in a particular application. 
     In an illustrative embodiment, the method may be carried out using about 25 mg of dye compound and 100 g polycarbonate pellet in 0.5 mL of solvent. 
     Having thus described several aspects of some embodiments of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only. 
     Example 1 
     In the following example, a series of oils were studied for use as solvents in the application of boron pyrromethene dyes to polycarbonate pellets, as summarized in Table 1. The solvents were combined with either Pt(II) octaethylporphine (PtOEP) or 1,3,5,7,8-pentamethyl-2,6-diethylpyrromethene-BF 2  (PM567), two known dyes, and the solubility and fluorescence of the dyes in the solvents were observed. To determine the solubility of the dye in the solvent, about 1 mg of dye was added to about 0.5 ml of the solvent and the combination was mixed. If necessary, the combination was heated to dissolve the dye. Polycarbonate pellets were then added to the solvent and dye, and the resistance of the polycarbonate pellets to the solvents was also evaluated. If the dyes were sufficiently soluble in the solvent and the polycarbonate pellets were sufficiently resistant to the solvent, the mixture was molded into a plaque. Generally, the dye was dissolved in a solvent, and the dye/solvent was added to a quantity of resin pellets (SABIC OQ2720 bisphenol-A-carbonate). The mixture was shaken/stirred to roughly uniformly coat the dye-containing solvent on the pellets, which were then processed via injection molding. Test plaques (50 mm squares, 2.2 mm thickness) were molded using a MiniJector injection molding machine. Molding temperatures were generally around 500° F. The loadings were generally about 25 mg of dye, with 500 uL solvent and 100 g polycarbonate pellets. Amounts varied depending on dye and desired optical density of the finished article. 
     As shown in Table 1, a number of the solvents tested were compatible with PtOEP and PM567 and did not dissolve, swell, or craze polycarbonate pellets when left in the solvent for two weeks. Solvents in which at least one of the dyes was soluble, partially soluble, mostly soluble, or soluble with heat, and in which the polycarbonate pellets had good or excellent resistance were considered to be suitable for use in methods described herein, such as diethylene glycol monoethyl ether (DEGME), 1,4-dioxane, DOW 705 penta-phenyl trisiloxane, dimethylformamide, propylene carbonate, 1-phenoxy-2-propanol, triethyl citrate, bis(2-ethylhexyl) adipate (BEHA), and bis(2-ethylhexyl) sebacate (BEHS). 
     In addition, the fluorescence under 365 nm irradiation of the dye/solvent mixtures was observed visually, as aggregates or crystals of dyes often display decreased fluorescence relative to dye monomers in the solvent. Thus, observance of moderate to high dye fluorescence may be an indication of good dissolution of the dye in the solvent. 
     Some of the solvent/polymer/dye mixtures were molded into plaques and their optical properties observed. Although Dow 705 pentaphenyl trisiloxane was able to dissolve PM567 with heat, it was not used in molding experiments due to potential interference with overcoating processes of the molded articles. The remaining candidates were tested in molding experiments and while all performed well relative to mineral oil, BEHA gave molded samples with the best optical properties. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Results for various oils used as solvent in application 
               
               
                 of boron pyrromethene dyes to polycarbonate pellets. 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Boiling 
                 Resistance of 
                   
                   
                   
                   
               
               
                   
                 Point 
                 Polycarbonate 
                 Solubility 
                 Fluor. of 
                 Solubility 
                 Fluor. of 
               
               
                 Solvent 
                 (° C.) 
                 to Solvent 
                 of PtOEP 
                 PtOEP 
                 of PM567 
                 PM567 
               
               
                   
               
               
                 DEGME 111-90-0 
                 192-202 
                 Good 
                 Partially 
                 Moderate 
                 Soluble 
                 High 
               
               
                   
                   
                   
                 soluble 
               
               
                 1,4-dioxane 
                 101 
                   
                 Partially 
                 Low 
                 Soluble 
                 High 
               
               
                   
                   
                   
                 soluble 
               
               
                 p-xylene 
                 138 
                 Poor 
                 Mostly 
                 Low 
                 Soluble 
                 High 
               
               
                   
                   
                   
                 soluble 
               
               
                 Dow 210H (PDMS) 
                 &gt;200  
                   
                 Insoluble 
                 None 
                 Below 
                 None 
               
               
                   
                   
                   
                   
                   
                 desired 
               
               
                   
                   
                   
                   
                   
                 level of 
               
               
                   
                   
                   
                   
                   
                 solubility 
               
               
                 Dow 705 penta- 
                 245/0.5 
                 Excellent 
                 Below 
                 Very 
                 Soluble 
                 High 
               
               
                 phenyl trisiloxane 
                 mm Hg 
                   
                 desired 
                 high 
                 with heat 
               
               
                   
                   
                   
                 level of 
               
               
                   
                   
                   
                 solubility 
               
               
                 Dow 710 (phenyl- 
                   
                 Excellent 
                 Insoluble 
                 High 
                 Below 
                 High 
               
               
                 methyl 
                   
                   
                   
                   
                 desired 
               
               
                 polysiloxane) 
                   
                   
                   
                   
                 level of 
               
               
                   
                   
                   
                   
                   
                 solubility 
               
               
                 Mineral oil (light) 
                 &gt;180  
                 Excellent 
                 Below 
                 Very 
                 Below 
                 High 
               
               
                   
                   
                   
                 desired 
                 high 
                 desired 
               
               
                   
                   
                   
                 level of 
                   
                 level of 
               
               
                   
                   
                   
                 solubility 
                   
                 solubility 
               
               
                 Dimethylformamide 
                 153 
                   
                 Partially 
                 Very low 
                 Soluble 
                 Low 
               
               
                   
                   
                   
                 soluble 
               
               
                 Dibutyl phthalate 
                 340 
                 Poor 
                 Partially 
                 High 
                 Soluble 
                 High 
               
               
                   
                   
                   
                 soluble 
               
               
                 Propylene 
                 240 
                 Good 
                   
                   
                 Soluble 
                 High 
               
               
                 carbonate 
               
               
                 1-phenoxy-2- 
                 243 
                 Good 
                   
                   
                 Soluble 
                 High 
               
               
                 propanol 
               
               
                 Triethyl citrate 
                 235/150 
                 Excellent 
                   
                   
                 Soluble 
                 High 
               
               
                   
                 mmHg 
               
               
                 BEHA (103-23-1) 
                 417 
                 Excellent 
                 Partially 
                 Moderate 
                 Soluble 
                 High 
               
               
                   
                   
                   
                 soluble 
                   
                 with heat 
               
               
                 BEHS (122-62-3) 
                 256/0.6 
                   
                 Partially 
                 High 
                 Soluble 
                 High 
               
               
                   
                 mm Hg 
                   
                 soluble 
                   
                 with heat 
               
               
                   
               
            
           
         
       
     
     What is claimed: