Patent Grant
5071897
Reference is made to copending application Ser. No. 07/497,155, filed 3-21-90 which is a continuation-in-part of application Ser. No., 07/353,713, filed May 18, 1989, now abandoned. The present invention relates to injection moldable flame retardant reaction products of biphenol and organosilicon material which have been melt extruded with certain crystallization accelerators. Prior to the present invention, as shown by copending application 07/497,155, polymeric reaction products of biphenol and organosilicon material were provided consisting essentially of chemically combined groups of the formula, ##STR1## where R.sup.1 is selected from the same or different C.sub.(1-13) monovalent hydrocarbon radicals, and C.sub.(1-13) monovalent hydrocarbon radicals substituted with monovalent radicals inert during condensation, R.sup.2 is a member selected from the class consisting of, ##STR2## Y is a member selected from the class consisting of --C(CH.sub.3).sub.2 --, --CH.sub.2 --, --SO.sub.2 --, --S--, --O--, ##STR3## R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.6, R.sup.8, R.sup.9, and R.sup.10 are members selected from the class consisting of the same or different radicals consisting of hydrogen and C.sub.(1-13) monovalent hydrocarbon radicals included within R.sup.1 radicals, and n is an integer equal to 1 to 4 inclusive. The preferred form of the organosilicon materials of formula (1) is poly(silyloxytetraalkylbiphenyleneoxides consisting essentially of chemically combined groups of the formula, ##STR4## where R is selected from the same or different C.sub.(1-8) alkyl radicals, and R.sup.1 is as previously defined. Polymeric reaction products included within formula (1), referred to hereinafter as "polyaryloxysiloxanes" or "PAS resins", have been found to crystallize only slightly, or not at all, when cooled rapidly from their melts. The PAS resins can be converted by injection molding to transparent, amorphous articles having good mechanical properties and excellent resistance to burning. However, their upper use temperature is restricted to temperatures somewhat below their glass transition temperature, which can be about 145.degree. C. It has been known that semi-crystalline polymers can retain their high modulus, and thereby their useful physical properties well above their glass transition temperatures, if the polymer is filled with glass fiber or other particulate fillers. Experience has shown that improvements in the crystallinity of molded polymeric materials are desirable to improve the non-sag and non-drip behavior of the molded article. In addition, the semi-crystalline state tends to increase resistance to environmental attack by solvents and gaseous penetrants. Accordingly, efforts have been made to provide PAS resin compositions which will crystallize rapidly from their melts in such operations as injection molding. It has been found that PAS resins having IV's in the range of 0.5 to 2.0 dl/gm can form amorphous, glassy solids when rapidly cooled from their melts. Upon heating amorphous PAS resin from room temperature at a rate of 20.degree. C./min, the resin passes through its glass transition temperature, crystallizes and then melts. For example, if the glass transition temperature of a particular PAS resin is 146.degree. C., the crystallization peak rate can occur at 205.degree. C. with a total crystallization heat release of 17.5 J/gm. The resin can then melt with the peak melting rate occurring at about 270.degree. C. with an observed total melting heat absorption 17.2 J/gm. Although PAS resins will crystallize when heated from their amorphous, glassy condition, they crystallize rather slowly while cooling from the molten state. In order to provide melt extruded PAS pellets which can be converted to crystalline injection molded parts, a crystallization enhancement method is required. The present invention is based on the discovery that if PAS resin is melt extruded with an effective amount of a crystallization accelerator, including a siloxane having the formula, ##STR5## hereinafter referred to as "DXODS", where R.sup.1 is as previously defined, and p is a whole number equal to 0 to 10 inclusive, the resulting melt extruded blend can undergo rapid crystallization during cooling from the molten state following injection molding. It has been further found other commercially available materials such as glyceryl tribenzoate and isopropylated triphenyl phosphate also can be used as crystallization accelerators when melt extruded in effective amounts with PAS. There is provided by the present invention, melt extruded injection moldable flame retardant blends of polymeric reaction products of biphenols and organosilicon materials consisting essentially of chemically combined groups of formula (1) and an amount of a compatible additive which is effective for enhancing the rate and broadening the temperature region at which crystallization of the polymeric reaction product of biphenols and organosilicon materials can occur from the melt during cooling. (A) effecting reaction between a biphenol of the formula, (B) recovering from (A), the polymeric reaction product of the biphenol and difunctional organosilicon material, Some of the organosilanes of formula (5) which can be used to make PAS resins used in the present invention are organosilanes, such as ##STR7## Some of the organosilazanes which can be used as difunctional organosilicon material in making PAS resins are for example, difunctional silazanes shown by Martellock, U.S. Pat. No. 3,243,404 and Rochow, Chemistry of the Silicones, Second Edition 1951, John Wiley & Sons New York, Table 10, page 186 which are incorporated herein by reference. For example there can be used hexamethylcyclotrisilazane, and octamethylcyclotetrasilazane. The PAS resins having condensed groups of formula (2), are preferably made by effecting reaction between a tetraalkylbiphenol of the formula, ##STR8## and a difunctional organosilicon material as previously defined, including an organosilane of formula (5), where R and X are as previously defined. Radicals included by R of formulas (2) and (6) are alkyl radicals, such as methyl, ethyl, propyl, butyl, pentyl and hexyl; radicals included by R.sup.1 are, for example, R radicals as previously defined, and substituted R radicals, such as trifluoropropyl, cyanoalkyl, such as cyanoethyl and cyanopropyl; alkenyl radicals such as vinyl and propenyl; cycloaliphatic radicals, such as cyclopentyl, and cyclohexyl. R.sup.1 also can be aryl radicals, such as phenyl, xylyl, tolyl, naphthyl and anthryl; and halogenated aryl radicals, such as chlorophenyl and bromo-tolyl, as well as nitroaryl radicals, such as nitrophenyl and nitrotolyl. Radicals included within X of formula (5) are for example halo, such as chloro, amino, amido, imido, ureido, alkoxy and acyloxy. The PAS resins having condensed units of formula (1) have been found to be flame retardant. The PAS resins having condensed units of formula (2) can have a molecular weight in the range of about 5,000 to about 1,000,000 and an intrinsic viscosity of from about 0.1 to 6.0 dl/gm at 25.degree. in chloroform. Crystallization accelerators can be utilized at from 1 to 40 parts by weight of crystallization accelerator, per 100 parts by weight of PAS. In addition to the siloxanes of formula (3), commercially available materials which are often used as compatible flame retardants or as plasticizers in non-crystalline resins can be used. There are included by these commercially available materials, dioctyl phthalate and tricresyl phosphate. In addition to crystallization accelerators, the PAS resin can be blended with inert fillers, such as glass fiber, mica, clay, talc, titanium dioxide and silica; a proportion of from about 1 to about 200 parts of weight of filler, per 100 parts of PAS resin can be used. In order that those skilled in the art will be better able to practice the present invention, the following examples are given by way of illustration and not by way of limitation. All parts are by weight unless otherwise indicated.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4397973 | Scott et al. | Aug 1983 | |
| 4954549 | Lewis et al. | Sep 1990 |
