Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-09-03
2004-05-18
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S101000, C524S492000, C524S493000, C524S494000, C524S463000
Reexamination Certificate
active
06737455
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to thermoplastic polyester compositions, and in particular to halogen-free, flame retardant thermoplastic polyester compositions.
BACKGROUND OF THE INVENTION
Thermoplastic polyester compositions, such as poly(alkylene terephthalates) have valuable characteristics including strength, toughness, high gloss and solvent resistance. Polyesters therefore have utility as materials for a wide range of applications, from automotive parts to electric and electronic appliances. Because of their wide use, particularly in electronic applications, it is desirable to provide flame retardancy to polyesters. One particular set of conditions commonly accepted and used as a standard for flame retardancy is that which is set forth in Underwriter's Laboratories, Inc. Bulletin 94 which proscribes certain conditions by which material are rated for self-extinguishing characteristics. Another set of conditions commonly accepted and used (especially in Europe) as a standard for flame retardancy is the so-called Glow Wire Test (GWT), the International standard IEC 695-2-1/2.
Numerous flame retarding agents for polyesters are known, but many contain halogens, usually bromine. Halogenated flame retardant agents are however less desirable because of the increasing demand for ecological friendly ingredients. Alternative flame retarding agents have therefore been developed, based on for instance Nitrogen and/or Phosphorus compounds. A general disadvantage of these flame retardant ingredients in polyesters is the negative effect on properties as impact and color stability upon oven aging.
Several N-containing compounds, combined with P-containing compounds have been described as flame retardants for polyesters. JP 03-281652 to Mitsubishi Petrochemical, for example, discloses FR polyester compositions comprising 100 parts of a polyester resin, 30-250 parts of a filler, 5-50 parts of melamine cyanurate, and 5-50 parts of a P-containing FR compound. JP 06-157880 to Akzo Kashima, Mitsubishi Petrochemical, describes a polyester (100 parts) with 30-250 pts of a filler, 5-50 parts of melamine cyanurate and 5-50 parts of an aromatic phosphate. JP11209587 to Kaneka discloses a polyester composition with a) 20-59% Glass and mineral filler in a ratio of 3/2-1/4, b) melamine cyanurate and c) 15-32% P-compound with P-compound/Melamine cyanurate ratio of 1/1-1/3, and d) 0.01-2% Fluoro resin.
Above mentioned literature/patents are suitable for the intended flame-retardant properties, but none of them describes potential limitations of the claimed composition ingredients and the claimed amounts for practical use. Not only good flame retardancy is needed but a combination of good flame retardant properties with good ductility and color stability upon oven aging. The herewith described invention overcomes the described deficiencies.
BRIEF SUMMARY OF THE INVENTION
Non-halogenated flame retardants for polyesters, based on N- and P-containing compounds, are described in the literature. Although good FR-properties can be obtained upon high enough amounts of the FR-ingredients, the materials lack good mechanical properties as impact and/or have insufficient color stability upon heat aging. Desirable enhanced properties and deficiencies can be overcome by the proper choice of the P-compound and the right amounts of N- and P-compounds in relation which each other and in relation with the type and amount of the present polyester. Good balance of ductility, flame retardancy and color stability upon oven aging can be obtained by a flame retardant polyester composition comprising, based on the total composition,
(a) A poly(ethylene terephthalate) with a molecular weight of at least 50,000 or a blend of poly(ethylene terephthalate) with another polyester, taking into account that the ratio poly(ethylene terephthalate)/other polyester should be at least 55/45.
(b) A combination of at least one N-containing compound, selected from the group of triazine, guanidine, or (iso)cyanurate compounds, and at least one P-containing compound, selected from the group of BPA-diphosphates or phosphoramides with the proviso that the ratio of the total amount of P- and N-containing compounds over the total polyester amount should be between 0.3 and 0.6 and the ratio of the P-containing compound over the N-containing compound should be higher than 0.8.
(c) An anti-dripping agent in an amount of 0.01-2 weight percent of the total composition.
(d) A reinforcing filler in an amount of 0-40 weight percent of the total composition.
DETAILED DESCRIPTION OF THE INVENTION
A halogen-free, flame retardant polyester composition comprises, based on the total composition,
(a) A poly(ethylene terephthalate) with a molecular weight of at least 50,000 or a blend of poly(ethylene terephthalate) with another polyester, taking into account that the ratio poly(ethylene terephthalate)/other polyester should be at least 55/45.
(b) A combination of at least one N-containing compound, selected from the group of triazine, guanidine, or (iso)cyanurate compounds, and at least one P-containing compound, selected from the group of BPA-diphosphates or phosphoramides with the proviso that the ratio of the total amount of P- and N-containing compounds over the total polyester amount should be between 0.3 and 0.6 and the ratio of the P-containing compound over the N-containing compound should be higher than 0.8.
(c) An anti-dripping agent in an amount of 0.01-2 weight percent of the total composition.
(d) A reinforcing filler in an amount of 0-40 weight percent of the total composition.
The flame retardant polyester composition includes a flame retarding quantity of one or a mixture of nitrogen-containing compounds, selected from the group of triazine, guanidine, or (iso)cyanurate compounds. Examples of such compounds are the 1,3,5-triazine compounds as for instance 2,4,6-triamine-1,3,5-triazine (melamine), melam, melem, melon, ammeline, ammelide, 2-ureidomelamine, acetoguanamine, benzoguanamine, diaminephenyltriazine or mixtures thereof. Especially salts/adducts of these compounds with (iso)cyanuric acid (as eg melamine cyanurate), boric acid, and/or phosphoric acid (including the so called melamine polyphosphate) can be used in the composition. Preferred compounds include the cyanuric acid derivatives of 1,3,5-triazine-compounds as melamine cyanurate.
The nitrogen-containing compounds are used in combination with one or more phosphorous-containing compounds as described below, since the combination appears to impart better flame retardant properties than where either component is used alone.
A suitable class of phosphorous compounds is the class of diphosphates of the general structure (OR1)(OR2)P(═O)—OXO—P(═O)(OR3(OR4) (optionally including some oligomeric higher phosphates), for instance made out of POCl3, a diphenol compound HO—X—OH with X is a group with at least 2 aryl unit (such as bisphenol A), and mono-hydroxy compound(s) ROH (R1, R2, R3, R4 might be equal or different), such as phenol. Other suitable phosphorus compounds are phosphoramides such as tetraxylyl piperazine diphosphoramide.
The phosphoramides have the following general structure:
wherein R1 is an amine residue, and R2 and R3 are independently an alkoxy residue, aryloxy residue, aryloxy residue containing at least one alkyl or one halogen substitution or mixture thereof, or amine residue. It is preferred that the phosphoramide have a glass transition point of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C.
Another phosphoramide comprises a phosphoramide having a glass transition temperature of at least about 0° C., preferably of at least about 10° C., and most preferably of at least about 20° C., of the formula:
wherein each A is independently phenyl, 2,6-dimethylphenyl, or 2,4,6-trimethylphenyl.
The composition may further optionally comprise various fillers and other additives known in the art, particular glass fibers in an amount of up to about 40 weight percent, and 0.01 to about 2.0 weight perce
Aouraghe Tieb
de Wit Gerrit
Gosens Johannes Cornelis
Oppedahl & Larson LLP
Rajguru U K
Sergent Rabon
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