Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-08-20
2004-06-22
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S162000, C524S261000, C524S262000, C524S263000, C524S267000, C524S269000, C524S316000
Reexamination Certificate
active
06753367
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to flame retardant polycarbonate compositions with improved weathering performance, said compositions comprising one or more cyanoacrylic esters. The invention also relates to methods for improving the flame retardancy and weathering performances of polycarbonate compositions. Finally, the invention further relates to articles manufactured from flame retardant polycarbonate compositions comprising cyanoacrylic ester(s).
BACKGROUND OF THE INVENTION
Fire proof, fire resistant and/or flame retardant materials are increasingly desired in applications where exposure of various plastics to heat or flame is possible or likely. For most polymer compositions, it is necessary to add materials to the composition that impart flame retardance to the final article. Flame retardant materials, and additives for imparting this property, are especially useful in applications such as housings and insulations for electrical and electronic devices. Examples of materials which have been used to impart such flame retardance are brominated resins, antimony oxide fillers, and organic phosphates. Flame retardancy has been predominantly provided by halogenated flame retardant additives, especially bromine- and chlorine-based flame retardant additives which are incorporated into various plastic compositions.
As pointed out by various environmental groups, a well-known and potentially serious drawback with regard to the use of such halogenated flame-retardant additives is the potential release of harmful or toxic gas when the composition is heated to elevated temperatures. Therefore, flame retardant systems, which are environmentally friendly, are preferred over halogen based systems.
Cyanoacrylic esters are known as additives for use in plastics for imparting various properties. For example, some cyanoacrylic esters are suitable as light stabilizers. U.S. Pat. Nos. 5,821,380 and 3,215,725; and DE-A 41 22 475 teach 2-cyanoacrylic esters of novel formulae for use in plastics and/or paints for the purpose of stabilizing said paint or plastic against the action of light, oxygen and heat. The cyanoacrylic esters and compositions of U.S. Pat. Nos. 5,821,380 and 3,215,725 and DE-A 41 22 475 are suitable for use in the polycarbonate compositions of the present invention. The cyanoacrylic esters and compositions of U.S. Pat. Nos. 5,821,380 and 3,215,725 are incorporated herein by reference.
Certain polysiloxanes are known to impart fire resistance to many plastics, including polycarbonate materials. These polysiloxanes are normally used in combination with a sulphonate salt.
Underwriters Laboratories has developed a variety of flammability and flame retardance tests for materials which are to be used with or near electricity. The UL rating is very influential and a polymer composition which does not have a UL flame rating will not be purchased for applications which require flame retardance. The UL flame test is designated UL-94 and a composition so tested can receive a rating of V-0 (most flame retardant), V-1, or V-2 (least flame retardant), depending on the results of the test.
What is desirable is a non-chlorine and non-bromine flame-retardant polycarbonate composition with improved weathering.
BRIEF SUMMARY OF THE INVENTION
The inventors surprisingly found that the use of cyanoacrylic ester UV-absorbers in ecological friendly polycarbonate materials significantly improves the flame characteristics. Superior flame retardant properties are obtained versus comparable polycarbonate formulations without a UV-absorber and with a benzotriazole based UV-absorber. This specification describes a non-chlorine and non-bromine flame-retardant polycarbonate composition with improved weathering.
The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a flame retardant polycarbonate composition of the present invention comprising, inter alia, one or more cyanoacrylic ester(s).
In particular, the present invention provides polycarbonate compositions exhibiting flame retardancy, improved weathering performance, visual clarity, and reduced toxicity on exposure to elevated temperatures, relative to the emissions from the heating of conventional flame retardant polycarbonate compositions.
More particularly, the present invention provides polycarbonate compositions with flame retardancy meeting the UL-94-V0 rating without the use of chlorine-containing or bromine-containing additives, said compositions comprising, one or more commercially available sulphonate salts, one or more commercially available siloxanes, and one or more commercially available cyanoacrylic esters, such as but not limited to, Uvinul 3035, Uvinul 3030, or Uvinul 3039 available from BASF.
DETAILED DESCRIPTION OF THE INVENTION
The flame retardant polycarbonate compositions of the present invention containing one or more cyanoacrylic esters are visually clear, free of chlorine and bromine, and further incorporate one or more synergistic flame retardants. Useful synergistic flame retardants are salt based flame retardants, such as alkali metal or alkaline earth metal salts of inorganic protonic acids as well as organic BrÖnsted acids comprising at least one carbon atom. These salts should not contain chlorine and/or bromine. Preferably the salt based flame retardants are sulphonates and even more preferably they are selected from the group consisting of potassium diphenylsulfon-3-sulphonate (KSS), potassium-perfluorobutane-sulphonate (Rimar salt) and combinations comprising at least one of the foregoing. Other synergistic flame retardants are phenylpolysiloxanes, such as poly(phenylmethyl siloxane) and octaphenyltetracyclosiloxane.
In one embodiment of the present invention, there is provided a transparent, fire resistant, low combustion toxicity, polycarbonate composition comprising (a) polycarbonate and (b) a cyanoacrylic ester. In another embodiment, the polycarbonate composition further comprises (c) a sulphonate salt and/or (d) a siloxane.
By “low combustion toxicity” herein is meant the absence of bromine- and/or chlorine-based additives that can contribute to the toxicity of fumes emitted upon combustion.
In a preferred embodiment, the present invention provides a transparent polycarbonate composition comprising (a) a bromine-free and chlorine-free polycarbonate, (b) a cyanoacrylic ester, (c) a potassium sulphonate salt, and (d) a phenyl-siloxane having a molecular weight of about 120 to 150,000, but most preferably a low molecular weight of 120 to 1,500. The phenyl-siloxanes useful in the present invention can include, but are not limited to, poly(methylphenylsiloxane) such as “PD5” and “SR476” available from GE Bayer Silicones or comparable materials from Dow Corning Corporation.
The sulphonate salts useful in the present invention can include, but are not limited to, alkali and earth alkali metal sulphonate salts, such as potassium-perfluorobutane-sulphonate, available from 3M and Bayer, and potassium-diphenylsulfon-3-sulphonate, available from Seal Sands.
The cyanoacrylic esters useful in the present invention can include, but are not limited to, Uvinul 3030, Uvinul 3035 and Uvinul 3039, available from BASF.
The present invention is directed to a method to improve the flame retardance and weathering performance of polycarbonate compositions. Thus, in one embodiment the present invention provides a composition comprising (a) polycarbonate present at 89 to 99.9 weight percent; (b) at least one cyanoacrylic ester present at 0.01 to 0.5 weight percent; (c) at least one sulphonate salt present at 0.01 to 0.5 weight percent; and (d) at least one siloxane present at 0.01 to 1.0 weight percent.
Heat stabilizers can be used in the compositions of the present invention, including for example, tris(2,4-di-tert-butylphenyl)phosphite, such as Irgaphos 168 from Ciba.
Also useful herein are release agents such as, but not limited to, pentaerythritol tetrastearate (PETS), known as Loxiol, from Henkel.
In an important feature of the present composition, the polycarbona
Goossens Johannes Martinus Dina
Verhoogt Hendrik
General Electric Company
Oppedahl & Larson LLP
Szekely Peter
LandOfFree
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