Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-09-18
2002-09-10
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...
C524S145000, C524S451000
Reexamination Certificate
active
06448316
ABSTRACT:
This invention relates to a polymer mixture which comprises an aromatic polycarbonate (A); a styrene (or styrene derivative and/or (meth)acrylate) containing polymer or copolymer and/or a styrene (or styrene derivative and/or (meth)acrylate) containing graft polymer (B); phosphorous compound(s) which are phosphate or phosphonate or oligomeric or poly-phosphate based flame-retardant(s) (C); specific inorganic additive(s) (D); and further flame retardant(s) or anti-drip agent(s) (E): and optionally, other additives.
Polymer mixtures which comprise an aromatic polycarbonate, a styrene-containing copolymer and/or graft polymer, for example, ABS, and a flame-retardant arc known, for example, from U.S. Pat. Nos. 4,692,488, 5,204,394, and 5,061,745. According to this prior art an organic phosphate ester, for example, triphenyl phosphate, tricresyl phosphate, diphenylcresyl phosphate, and/or oligomeric phosphates, can be used as a flame-retardant for such mixtures. Tetrafluoroethylene polymers are often used in combination with such phosphate esters to provide flame retardant mixtures and mouldings which can achieve a flammability rating of UL-V0 in the UL-94 vertical burning test typically at a thickness of 1.6 mm, together with good impact strength. In other prior art other additives may assist anti-dripping or flame retardancy such as aramid fibres (U.S. Pat. No. 5,272,193).
However thermoplastic moulding compounds of the type described in the prior art have the disadvantage that if a UL-V0 flammability rating is required in thinner sections or thinner moulded articles—and it is generally more difficult to achieve flame retardancy in thinner sections—then it is not clear that such compositions could achieve such performance and still retain other useful properties.
Increasing the level of the phosphate flame retardant additive may not be successful in achieving the desired flame retardant rating at lower than typical thicknesses and will in any case reduce other useful properties such as impact strength and/or heat distortion temperature (HDT) significantly.
The present invention also relates to moulding compounds and articles formed or moulded from the polymer mixtures or compounds according to the invention. The polymer mixture according to the invention comprises the following constituents:
(A) aromatic polycarbonate(s), and
(B) styrene-containing polymer(s)/copolymer(s) and/or styrene-containing graft polymer(s), (or substituted styrene analogues/derivatives), and/or (meth) acrylate based polymer(s), copolymer(s), graft polymer(s) (where ‘(meth)acrylate’ is understood to encompass either or both of acrylate, methacrylate) and
(C) phosphorous compound(s) based on phosphate ester(s) and/or oligomeric phosphate(s), and/or polyphosphate(s) or phosphonate ester(s), and
(D) inorganic additive(s) selected from talc, kaolin, mica, and magnesium hydroxide and
(E) further flame-retardant(s) and/or anti-drip agent(s) selected from tetrafluorethylene polymers or copolymers, polyvinylidenedifluoride, other fluoropolymers, red phosphorous, aramid fibre or powder or polyimide fibre or powder; and, optionally, other additives.
In the discussion of compositions references arc to parts by weight per 100 parts of (A)+(B), as defined above—except where ‘%’ is used which, then describes weight % of the total of (A)+(B)+(C)+(D)+(E) components.
In the prior art, many flame retardant polycarbonate based moulding compounds also containing styrene and/or (meth)acrylate based polymers are reported to exhibit UL94-V0 rating at thicknesses of 1.5 mm or 1.6 mm, or greater and arc based on compounds containing (A), (B), (C), and (E) as defined above. Within the present invention it is surprising to achieve UL94-V0 flame retardancy performance at thicknesses substantially below this thickness level simply by the incorporation or addition of the particular stated inorganic additives (D).
The compositions of the present invention are specifically designed for use in thin wall mouldings and in particular to those mouldings or parts where, in some portion of the mouldings or assembled parts, & same retardancy to meet the requirements of UL-94-V0 performance at a thickness lower than 1.5 mm is required or desired. In particular, UL-V0 performance at or below 1.2 mm, 1.1 mm, 1.0 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, and/or any thickness or range within these thicknesses can surprisingly be achieved with retention of useful other properties, by addition or incorporation of the stated inorganic additive (D) to mixtures of (A), (B), (C), and (E), as defined herein. The formulations will also be able to achieve UL-V0 performance at thicknesses greater than these.
Compositions for achieving UL-V0 performance at thicknesses of 1.5 mm or greater are well known, as mentioned above. However recent trends in thin wall mouldings for many applications require or desire UL-V0 flammability performance in some parts or sections of the moulding or assembled parts at thicknesses less than 1.5 mm and for example at thicknesses of 1.2 mm or 1.1 mm or 1.0 mm or 0.9 mm or 0.8 mm or 0.7 mm or 0.6 mm or 0.5 mm or 0.4 mm or at thicknesses in between or below such values. In addition, the absence of chlorine or bromine contain flame retardants is desired due to environmental reasons or regulations and the compositions of the present invention arc designed to allow flame retardancy in such thin sections as described without the use of chlorine or bromine based flame retardants.
The compositions of the present invention are designed for flame retardant mouldings, or mouldings in which some portion require or desire such flame retardancy for use in parts and housings of electronic equipment, business machines, including computers, monitors, keyboards, printers, fax machines, telephones, office automation or audio-visual equipment and particularly in portable or compact or lightweight items or versions such as notebook computers, palm-top or hand-held computers, or electronic diaries or personal organisers, mobile telephones, cameras and video cameras, portable audio items and related ancillary equipment.
In many such applications, in addition to flame retardancy there will also be other requirements such as impact strength (as often measured by the Notched Izod Impact test) and/or a certain level of heat resistance, as for example commonly measured by HDT (heat distortion temperature).
The actual specifications will of course vary according to the different applications and indeed different models of the applications. However, the compositions of the invention are designed to exhibit flame retardancy associated with a UL-V0 rating according to the UL94 V test at thicknesses below 1.5 mm as described and also show reasonable impact strength and reasonable HDT for use in such applications as measured via the notched izod impact test (ISO 180-1A) and the HDT test (ISO 75 at 1.8 MPa).
It is known in polycarbonate based compositions and compositions based on blends containing polycarbonate and styrenic and/or (meth)acrylate based polymers, copolymers or graft copolymers that phosphate ester based flame retardants will reduce properties such as impact strength and HDT. The greater the loadings of such additives generally the greater the fall off in these properties. Higher loadings of such phosphates can impart flame retardant performance up to a point, but very high loadings such as for example more than 16 parts or 17 or 18 or 18.4 or more parts by weight (per 100 parts by weight of (A)+(B), as described herein) are not particularly effective for use in thin wall mouldings such as those which are the subject of this present invention since either impact strength and/or HDT becomes too low and very high phosphate loadings can give other problems in migration of the phosphate and relatively poor chemical resistance.
The use of inorganic fillers or additives in moulding compounds is well known and they are routinely used for providing reinforcements or stiffness and/or lowering cost. In many publications
Capitelli Joseph Angelo
Davies Martin Thomas
Fernyhough Alan
Hirano Yasuo
Ives Peter John
Mitsubishi Engineering-Plastics Corporation
Szekely Peter
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