INFRARED ABSORBING POLYCARBONATE EYE PROTECTIVE LENS

Abstract: Infrared-absorbing polycarbonate eye protective lenses are prepared from a polycarbonate resin having a meltflow value of about 12 to 120 and being substantially free of acidic and basic impurities and a bis(p-dialkylamino­ phenyl) [N,N-bis(p-dialkylaminophenyl)-p-aminophenyl]­ aminium salt.

Description: INFRARED ABSORBING POLYCARBONATE EYE PROTEC?rVE LENS The present invention relates to near infraredabsorbing polycarbonate eye protective lenses. More particularly, it relates to a composition for, and a method of preparation of, a polycarbonate eye protective lens, having near infrared absorbing properties, comprising a polycarbo natfr resin having a meltflow value of about 12 to 120 and is- substantially free of acidic and basic impurities and an infrared-absorbingly-effective amount of a- bis(p-dialkyl- aminophenyl)- [N,N-bis Cp-dialylaminophenyI) -p-aminophenyli - aminium salt (I) EMI1.1 wherein R and R' represent lower (C1-C4) alkyl groups and X is an anion. Suitable eye protective lenses are essential for various purposes, such as welding goggles, to protect against glare from arc welding, torch burning, and the like. Such lenses must filter out or absorb invisible but harmful radiation, such as the near infrared components of the incident radiation. Nevertheless, they must permit an adequate transmission of the visible components of the incident radiation. Moreover, to be commercially useful, they must have an adequately long service life before excessive degradation of the components thereof by the incident radi ation, such as by ultraviolet light. Glass eye protective lenses are relatively easy to make and are readily available. Glass lenses, however, are heavy, and they are quite susceptible to scratching and pitting. As a result, they are subject to reduced vision and loss of eye protection. Moreover, pitting causes a loss of impact resistance. The American National Standards Institute (ANSI) (Standard Z87.1-1979) recommends that glass lenses be replaced when pitted. Polycarbonate is a very useful plastic substrate for eye protective lenses, exhibiting good optical properties and impact resistance Also polycarbonates may be readily made mar resistant by the application of various mar-resistant coatings. Heretofore, however, it has not been possible to make polycarbonate lenses, having near infrared absorbing properties-, because it has not been pos visible to incorporate infrared-absorbing compounts into the substrate. The American National Standards Institute presently does not recommend the use of anti-glare polycarbonate lenses for the aforementioned welding applications, because of this lack of infrared absorption. The difficulty in making near infrared-absorbing polycarbonate lenses has been twofold. First, the processing temperatures (550-675 F) of polycarbonates, which usually have meltflow values (ASTM D-1238) of about 2 to 9, have been too high for the infrared absorber compounds to survive processing. Secondly, most polycarbonates have contained basic or acidic impurities which have destroyed the infrared absorbers by interaction therewith. The present invention provides a means for the preparation of eye protective polycarbonate lenses which meet or exceed the requirements of the American National Standards Institute. In accordance with the invention, a polycarbonate resin is utilized which has a meltflow value of about 12 to 120 and which is substantially free of acidic or basic impurities. Polycarbonate resins having these characteristics may be processed at temperatures of 480550 F at which the infrared absorbing compounds (I) are thermally stable. The polycarbonate resins, useful in the present invention, may be homopolymers or copolymers so long as they meet the requirements set forth above. An example of a suitable polycarbonate resin is MarlonO Polycarbonate M-39 (Mobay). The infrared absorber compounds, useful in the present invention, are bis(p-dialkylaminophenyl)[N,N-bis- (p-dialkylaminophenyl)-p-aminophenyl]aminium salts, represented by (I), which are readily prepared by the oxidation ofN,N,N',N'-tetraarylenediamines with silver salts, as described in U S. Patent 3,251,881. Suitable silver salts are those solnble in acetone or other organic solvent medi um. The anion of the silver salt provides the anion (XI) of the aminium salt. Silver salts of halogen-containing acids are preferred and include the perchlorate (C104 ), hexafluoroantimonate (SbF6 ), hexafluoroarsenate (AsF6 ), fluoroborate (BF4 ), r trichloroacetate (CC13CO2 ), trifluoro- acetate (CF3CO2 ), and the like. Other suitable silver salts include picrates, benzenesulfonates, ethanesulfonates, etc. The preferred infrared absorber compound for the purposes of the present invention is bis(p-di-n-butylaminophenyl)- N ,N-bis (p-di-n-butylaminophenyl) -p-aminophenyl aminium hexafluoroantimonate (II) EMI3.1 Alternatively but preferably the infrared absorber is prepared in situ in the polymer in accordance with U. S. 3,631,147 by reacting equimolar amounts of a diimonium salt of the formula EMI4.1 with a polyamine of the formula EMI4.2 wherein R and R' are individually C1 -C4 alkyl groups and X is an anion. Exemplary anions include perchlorate, hexafluoroantimonate, hexafluoroarsenate, fluoroborate, trichloroacetate, trifluoroacetate, picrate, benzenesulfonate, ethanesulfonate, phosphate, sulfate, chloride and the like. Similar suitable infrared absorber compounds are described in U. S. Patents 3,251,881; 3,484,467; 3,575,871; and 3,670,025. In principle the lenses will permit varying amounts of visible transmission while meeting the required absorption of both infrared and ultraviolet radiation. The degree of visible transmission is related to the shade of the lens, which may vary from about 1.2 (light) to 14 (very dark). Shade of the lens is related to the optical density by the formula: optical density (O.D.) = 3 [Shade No. - 11 7 where optical density = log 100 and T = % transmittance T In the above shade range, percent transmittance varies from about 82% (shade 1.2) to .00027% (Shade 14). While the invention is applicable to the preparation of lenses covering the entire range of shades, it is preferred to prepare lenses in the range of about 1.7 to 3 (55 to 8.58 visible transmittance). The maximum permissible transmittance of infrared radiation in the region 700-2800 nanometers, in accordance with the American National Standard Z87.1-1979, varies from 25% for a shade 1.5 lens to 0,3 for a shade 14 lens. The composition will generally contain an ultraviolet ray absorber compound to protect the infrared absorber from deterioration and to protect the eye from incident ultraviolet radiation. In the following example, 2,4diacetoxybenzoic acid was used, although the particular ultraviolet absorber used is not critical and does not constitute a critical feature of the invention Any UV absorber which is compatible with the substrate and which provides the desired degree of absorption of ultraviolet radiation may be used. The lenses of the present invention are preferably green shade. This may be accomplished by the incorporation of a green dye such as C.I. Acid Green 25. The particular dye used is not critical, nor is the color of the lens, it being within the skill of the art to determine suitable dyes or colors Green shade lenses are merely conventional. Green shade polycarbonate lenses are made, in accordance with the present invention, by the incorporation into the polycarbonate substrate of a mixture of an infrared absorber, an ultraviolet ray absorber, and a dye in conventional proportions, as shown in the accompanying example. The shade of the lens, in general, is determined by the amount of the mixture which is incorporated into the substrate; larger amounts are added for darker shades. The particular COIibi- nation used is not critical and will depend on the particular infrared absorber, UV ray absorber, and dye used. The preferred infrared absorber is particularly suitable because of its thermal stability under processing conditions. Polycarbonate lenses are attractive because of their light weight and because of the inherent excellent impact resistance of the polymer. Another attractive feature of poIyzarbonate lenses.is the ability to render them mar resistant by application of a mar-resistant coating. This can be accomplished by- a number of means. Suitable mar-resistant coatings are described in U. S. Patent Nos, 4,017,456; 4,018,941; 4,021,405, and other such patents. The lenses may be made in conventional manner by dry blending the additive mixture with the polycarbonate resin (granular) followed by extrusion at 680-5500F and pelletizing. The dried pellets are then conventionally injection molded at 480-5500F into lenses of the'desired shape and thickness, usually round and about 125 mils. The lenses may then be cleaned and provided with a mar-resistant coating, as described in the aforementioned patents. The following example is illustrative of the present invention Example 1 Infrared Absorbing Polycarbonate Eye Protective Lens To 100 pounds of pulverized polycarbonate (MarlonO M-39; Mobay), having a meltflow value of 19, was added 42 grams of a mixture containing 21.09 grams of N,N,N',N'-tetrakis(p-dibutylaminophenyl)-p-benzoquinonebis (imoniunhexafluoroantimonate), 13.95 grams of N,N,N',N' -tetrakis (p-dibutylaminophenyl) -p-phenylene diamine, 6.03 grams of 2,4-diacetoxybenzoic acid, and 0.92 gram of C.I. Acid Green 25. The mixture was blended and extruded at 480-550 F. and pelletized. The dried pellets were then injection molded at 480-5500F.into 125-mil thick lenses having a green shade of 2.0 (29-43% luminous transmittance). The lenses exhibited excellent ultraviolet ray and infrared absorption and met or exceeded the requirements of ANSI Z87.1-1979 for polycarbonate eye protective lenses. A transmittance curve for the lens is shown in Figure 1. Example 2 The procedure of Example 1 is repeated using 35.04 grams of bis (p-dibutylaminophenyl) tN,N-bis(p-dibutyl- aminophenyl) -p-aminophenyl aminium hexafluoroantimonate in place of the combination of the iminium compound and the diamine.

Claims: WHAT IS CLAIMED IS 1. An infrared absorbing eye protective lens comprising a polycarbonate resin having a meltflow value of about 12 to 120 and being substantially free of acidic and basic impurities, and an effective infrared-absorbing amount of a bis- (p-dialkylaminophenyl) [N, N-bis (p-dialkylamino- phenyl)p-aminophenyl]aminium salt represented by the formula: EMI8.1 wherein R and R' are individually C1-C4 alkyl groups and X is an anion selected from perchlorate, hexafluoroantimonate, hexafluoroarsenate, fluoroborate, trichloroacetate and trifluoroacetate; said lens exhibiting a transmittance of infrared radiation in the region 700 to 2800 nanometers not exceeding 25 percent, and having a luminous transmittance of from about .00027'to about 82 percent, and wherein the lens optionally contains an ultraviolet ray absorber and/ or a green dye. 2. the lens of Claim 1 wherein said aminium salt is bis (p-di-n-butylaminophenyl) [N,N-bis (p-di-n- -butylaminophenyl) -p-aminophenyl1 aminium hexafluoroantimonate. 3. The lens of Claim 1 or Claim 2 wherein said ultraviolet ray absorber compound is present and is 2,4 -diacetoxybenzoic acid. 4. The lens of Claim 1 wherein said green dye is present and is C. I. Acid Green 25. 5. The lens of Claim 1 wherein the aminium salt is prepared in situ from an essentially equimolar mixture of EMI9.1 wherein R and R' are individually C1-C4 alkyl groups and X is an anion selected from perchlorate, hexafluoroantimonate, hexafluoroarsenate, fluoroborate, trichloroacetate and trifluoroacetate. 6. A composition comprising a polycarbonate resin having a meltflow value of about 12 to 120 and being substantially free of acidic and basic impurities and a bis(p dialkylaminophenyl) EN,N-bis(p-dialkylaminophenyl) -p-amino- phenyl]aminium salt of the formula EMI9.2 wherein R and R' are individually C1-C4 alkyl groups and X is an anion selected from perchlorate, hexafluoroantimonate, hexafluoroarsenate, fluoroborate, trichloroacetate and trifluoroacetate. 7. The composition of Claim 6 further containing an ultraviolet ray absorber compound. 8. The composition of Claim 7 wherein the ultraviolet ray absorber compound is 2,4-diacetoxybenzoic acid. 9. The composition of Claim 6 or Claim s wherein each R and R' is n-butyl and X is hexafluoroantimonate. 10. The composition of Claim 6 wherein the aminium salt is prepared in situ from an essentially equimolar mixture of EMI10.1 wherein R and R' are individually C1-C4 alkyl groups and X is an anion selected from perchlorate, hexafluoroantimonate, hexafluoroarsenate, fluoroborate, trichloroacetate and trifluoroacetate.

Inventors: TUCKER, ROBERT J., WHITE, WILLARD C.
Applicants: AMERICAN CYANAMID COMPANY
Application year: 1981
Main classification: G02B1
IPC codes: G02B1, C08K5