Compositions – Fire retarding – For solid synthetic polymer and reactants thereof
Reexamination Certificate
1994-05-12
2001-02-20
Anthony, Joseph D. (Department: 1714)
Compositions
Fire retarding
For solid synthetic polymer and reactants thereof
C252S604000, C252S610000, C524S410000, C524S411000, C524S412000
Reexamination Certificate
active
06190581
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to flame proofed or fire retarded polymer and resin compositions including polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). In particular flame retarding concentrates or pellets to be added to PET and PBT are prepared from hydrated sodium antimonate and at least one polymer.
BACKGROUND OF THE INVENTION
A wide variety of flame proofing or fire retarded polymer compositions are known. In the case where the polymer is a polyester such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) it was known to flame retard with brominated polystyrene and an antimony compound. It was further known that a dry rather than a wet or hydrated antimony compound was required for addition to PET or PBT. Japanese Patent Application No. 64-83995 (TEIJIN LTD.) discloses a flame retardant composition of brominated polystyrene with an auxiliary antimony compound and a brominated dioctyl phthalate.
Other patents relating to flame proofing and fire retarding compositions and the state of the art include: U.S. Pat. No. 3,723,139; U.S. Pat. No. 3,816,367; U.S. Pat. No. 3,892,667; U.S. Pat. No. 3,897,389; U.S. Pat. No. 3,951,905; U.S. Pat. No. 4,035,333; U.S. Pat. No. 4,338,243; U.S. Pat. No. 4,362,658; U.S. Pat. No. 4,713,407; U.S. Pat. No. 4,729,854; U.S. Pat. No. 4,786,663; U.S. Pat. No. 4,814,130; U.S. Pat. No. 4,983,660; U.S. Pat. No. 5,021,495; U.S. Pat. No. 4,034,439; U.S. Pat. No. 5,115,010; U.S. Pat. No. 5,177,132 and U.S. Pat. No. 5,258,434.
Yet in spite of what was previously known concerning useful means for fire proofing or flame retarding polyester and polymer compositions, a need still existed to provide a means to use lower amounts or employ simplified processes than had previously been used.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a flame retarding concentrate suitable to add to a polymer and/or resin composition comprising dehydrated sodium antimonate and at least one polymer. Produced in a vented extruder a preferred concentrate in pellet form comprises dehydrated sodium antimonate and a sodium ionomer polymer and an antioxidant to be blended with either PET or glass-filled PET.
A general process for flame retarding a resin or polymer composition comprises the steps:
(1) mixing 10 to 90 parts by weight sodium antimonate having a moisture content of about 2.9% with 10 to 90 parts of a homopolymer or copolymer having a molecular weight greater than 150,000;
(2) processing the antimonate/polymer mixture in a vented or vacuum extruder or high shear blender at a temperature of at least 150° C. to produce a flame retarding concentrate with a moisture content below 0.2%; and
(3) compounding the concentrate in a resin or polymer composition.
A preferred process for flame retarding a polyethylene terephthalate or other resin composition comprises the steps:
(1) dehydrating a mixture of alkyl tertabromophthalate and/or tribromophthalate and brominated polystyrene and hydrated sodium antimonate in an extruder,
(2).adding the dehydrated mixture to the resin composition, and
(3) dispersing through an extruder in the presence of glass fibers to prepare a flame retarded resin composition.
A most preferred process for flame retarding a glass-filled polyethylene terephthalate composition comprises the steps:
(1) dehydrating and pelletizing a mixture of di-2-ethyl hexyl tetrabromophthalate and hydrated sodium antimonate and brominated polystyrene and an antioxidant,
(2) combining the dehydrated pellets with polyethylene terephthalate and glass fiber, and
(3) blending the ingredients to prepare a flame retarded polyethylene terephthalate composition.
DETAILED DESCRIPTION OF THE INVENTION
Antimony compounds have been widely used to flame retard polymeric compositions such as thermoplastic resins. Use of an antimony synergist has at times caused deterioration of the polymer or resin, attributed to pH or the use of hydrated antimony compounds. Antimony compounds have been employed in combination with brominated compounds such as brominated dioctyl phthalate, brominated polystyrene, etc. But in contrast with what had previously been known about such combinations, it has now been discovered that a novel process allows the preparation of a dehydrated concentrate or pellet using hydrated sodium antimonate and at least one polymer at lower temperatures than previously believed to be required. A preferred process in a vented extruder processes a combination of an antioxidant and an alkyl tetrabromophthalate and/or tribromophthalate and brominated polystyrene and sodium antimonate in polyethylene terephthalate and similar polymers and resins and combinations thereof.
Using the process of the invention objectional quantities of water can be removed from hydrated sodium antimonate in the presence of at least one polymer and optionally an antioxidant at a temperature as low as 150° C. What is meant by objectional quantities of water is that when the concentrate is placed within a PBT formulation there is no evidence of hydrolysis of the esters. The anhydrous mixture as a concentrate can be produced as extruded pellets along with an antioxidant in less than five minutes at about 250° C.
While the prior art teaches that temperatures of 600 to 1000° C. are required to remove water of crystallization from sodium antimonate it has been discovered that readily available polymers, such as polyethylene and polypropylene, facilitate dehydration at temperatures below 500° C.
A hydrated sodium antimonate suitable for the practice of the invention is available from Elf Atochem North America, Inc. and others. To be fully effective in the presence of polyethylene terephthalate (PET) it was believed that the water of crystallization had to be removed as was previously known from U.S. Pat. No. 4,786,663 and U.S. Pat. No. 5,258,434. Whereas these references teach that the sodium antimonate needs to be heated above 500° C. for one hour, it has now been discovered that water vapor equivalent to the water of crystallization can be removed at temperatures of about 250° C. in less than five minutes. Removal of water had been monitored by the intensity of peaks at 5.30 and 2.65 A° C. when subjected to x-ray diffraction. As long as the hydrated structure was present the 5.30 peak was just slightly higher than the 2.65 peak, but the decrease in the 2.65 peak to approximately half indicated elimination of the hydrated structure.
But in contrast to the complex methods and high temperature requirements of the prior art, it has now been discovered that water vapor removal can be measured and recorded during the compounding and pelletizing process.
Brominated polystyrene is obtained from Ferro Corp. under the Tradename PYROCHECK* 68PB, while other sources include Great Lakes Chemical and Ethyl Corp. The brominated polystyrene can be dispersed most conveniently in polyethylene terephthalate by the addition of di-2-ethyl hexyl tetrabromophthalate. Other suitable alkyl substitutions for the tetrabromophthalate other than ethyl hexyl are; n-octyl, isooctyl, dimethyl, ethyl heptyl and ethyl octyl. With pellets produced by the process of the invention it was a surprising result to find that a mixture of brominated polystyrene and di-2-ethyl hexyl tetrabromophthalate could be extruded and pelletized below 250° C. with-or without incorporation of an antioxidant. And even more surprising was the discovery that water of crystallization was removed when hydrated sodium antimonate was included in the mixture, even at temperatures as low as 150° C. It appears that the process of the invention involves synergy, since less energy or lower temperatures appear to be required in the production process for the flame retarding concentrate or pellet.
A preferred alkyl tetrabromophthalate is PYRONIL* 45 flame retarding agent (*Registered Trademark of Elf Atochem). Inferior performance is obtained with trisubstituted rather than tetrasubstituted materials in terms of final flame retarding properties since it is a function of degree
Duffin, Jr. Robert J.
Touval Irving
Anthony Joseph D.
Brookes Anne E.
Laurel Industries, Inc.
LandOfFree
Dehydrated antimonate/polymer pelletizing process does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dehydrated antimonate/polymer pelletizing process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dehydrated antimonate/polymer pelletizing process will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2562406