Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-08-30
2004-03-23
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S127000, C524S138000, C524S139000, C524S492000, C524S430000, C524S437000, C524S497000, C524S445000, C524S449000
Reexamination Certificate
active
06710108
ABSTRACT:
BACKGROUND OF 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 set forth in Underwriters Laboratories, Inc. Bulletin 94, which proscribes certain conditions by which materials 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 Glow Wire Test (GWT), performed according to the International standard IEC 695-2-1/2.
Numerous flame retardants for polyesters are known, but many contain halogens, usually bromine. Halogenated flame retardant agents are less desirable because of the increasing demand for ecologically friendly ingredients. Also, polyester compositions with halogenated flame retardants typically display poor color stability upon aging under ultraviolet light.
There is a need for polyester compositions having the combination of good flame retardant properties and good color stability upon ultraviolet light aging without the use of halogenated flame retardants and without sacrificing mechanical properties. The compositions taught herein overcome the described deficiencies.
SUMMARY OF INVENTION
The above-described and other drawbacks and disadvantages of the prior art are alleviated by a composition comprising a poly(butylene terephthalate); a nitrogen-containing flame retardant selected from the group consisting of triazines, guanidines, cyanurates, isocyanurates, and mixtures comprising at least one of the foregoing nitrogen-containing flame retardants; and a phosphorus-containing flame retardant selected from the group consisting of diphosphates, phosphoramides, and mixtures comprising at least one of the foregoing phosphorus-containing flame retardants; wherein the weight ratio of the total of the phosphorus-containing flame retardant and the nitrogen-containing flame retardant to the poly(butylene terephthalate) is greater than 0.70.
Other embodiments, including a method of preparing the compositions, are described below.
DETAILED DESCRIPTION
One embodiment is a composition comprising a poly(butylene terephthalate); a nitrogen-containing flame retardant selected from the group consisting of triazines, guanidines, cyanurates, isocyanurates, and mixtures comprising at least one of the foregoing nitrogen-containing flame retardants; and a phosphorus-containing flame retardant selected from the group consisting of diphosphates, phosphoramides, and mixtures comprising at least one of the foregoing phosphorus-containing flame retardants; wherein the weight ratio of the total of the phosphorus-containing flame retardant and the nitrogen-containing flame retardant to the poly(butylene terephthalate) is greater than 0.70.
Preferred poly(butylene terephthalate) polyesters are obtained by copolymerizing a glycol component at least about 70 mole %, preferably at least about 80 mole %, of tetramethylene glycol, and an acid component comprising at least about 70 mole %, preferably at least about 80 mole %, of terephthalic acid, or polyester-forming derivatives thereof. The preferred glycol component may contain up to about 30 mole %, preferably up to about 20 mole % of another glycol, such as ethylene glycol, trimethylene glycol, 2-methyl-1,3-propane glycol, hexamethylene glycol, decamethylene glycol, cyclohexane dimethanol, neopentylene glycol, and the like, and mixtures comprising at least one of the foregoing glycols. The preferred acid component may contain up to about 30 mole %, preferably up to about 20 mole %, of another acid such as isophthalic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 4,4′-diphenyl dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, sebacic acid, adipic acid, and the like, and polyester-forming derivatives thereof, and mixtures comprising at least one of the foregoing acids or acid derivatives.
A preferred poly(butylene terephthalate) may have a number average molecular weight of about 10,000 atomic mass units (AMU) to about 200,000 AMU, as measured by gel permeation chromatography using polystyrene standards. Within this range, a number average molecular weight of at least about 20,000 AMU may be preferred. Also within this range, a number average molecular weight of up to about 100,000 AMU may be preferred, and a number average molecular weight of up to about 50,000 AMU may be more preferred.
The poly(butylene terephthalate) may be present in the composition at about 20 to about 60 weight percent, based on the total weight of the composition. Within this range, it may be preferred to use at least about 25 weight percent, even more preferably at least about 30 weight percent of the poly(butylene terephthalate). Also within this range, it may be preferred to use up to about 55 weight percent, more preferably up to about 50 weight percent, yet more preferably up to about 45 weight percent of the poly(butylene terephthalate).
In one embodiment the composition may contain a second polyester resin that is not a poly(butylene terephthalate). For the second polyester, suitable resins include those derived from a C
2
-C
10
aliphatic or cycloaliphatic diol, or mixtures thereof, and at least one aromatic dicarboxylic acid. Preferred polyesters are derived from an aliphatic diol and an aromatic dicarboxylic acid having repeating units of the following general formula:
wherein n is an integer of from 2 to 6, and R is a C
6
-C
20
divalent aryl radical comprising a decarboxylated residue derived from an aromatic dicarboxylic acid.
Examples of aromatic dicarboxylic acids represented by the decarboxylated residue R are isophthalic acid, terephthalic acid, 1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenyl ether, 4,4′ bisbenzoic acid, and the like, and mixtures thereof. All of these acids contain at least one aromatic nucleus. Acids containing fused rings can also be present, such as in 1,4-, 1,5-, or 2,6-naphthalene dicarboxylic acids. Preferred dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acids, and the like, and mixtures comprising at least one of the foregoing dicarboxylic acids.
The aliphatic or alicyclic polyols include glycols, such as ethylene glycol, propylene glycol, butanediol, hydroquinone, resorcinol, trimethylene glycol, 2-methyl-1,3-propane glycol, 1,4-butanediol, hexamethylene glycol, decamethylene glycol, 1,4-cyclohexane dimethanol, or neopentylene glycol.
Also contemplated herein are the above polyesters with minor amounts, e.g., about 0.5 to about 30 percent by weight, of units derived from aliphatic acids and/or aliphatic polyols to form copolyesters. The aliphatic polyols include glycols, such as poly(ethylene glycol). Such polyesters can be made following the teachings of, for example, U.S. Pat. No. 2,465,319 to Whinfield et al., and U.S. Pat. No. 3,047,539 to Pengilly.
Block copolyester resin components are also useful, and can be prepared by the transesterification of (a) straight or branched chain poly(alkylene terephthalate) and (b) a copolyester of a linear aliphatic dicarboxylic acid and, optionally, an aromatic dibasic acid such as terephthalic or isophthalic acid with one or more straight or branched chain dihydric aliphatic glycols. Especially useful when high melt strength is important are branched high melt viscosity resins, which include a small amount of, e.g., up to 5 mole percent based on the terephthalate units, of a branching component containing at least three ester forming groups. The branching component can be one that provides branching in the acid unit portion of the polyeste
de Wit Gerrit
Govaerts Luc
Talibuddin Sapna Halim
General Electric Company
Oppedahl & Larson LLP
Rajguru U. K
Seidleck James J.
LandOfFree
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