Plastic Compositions

The prior art considered in conjunction with the preparation of this application is as follows: U.S. Pat. Nos. 1,979,145; 2,130,990; 2,186,367; 2,263,444; 2,329,033; 2,488,499; 2,738,351; 2,797,246; 2,930,815; 3,385,819; 3,549,591; 3,560,441; 3,649,591; 3,658,634; 3,666,692; 3,697,456; 3,686,320; 3,717,609; 3,763,243; 3,787,506; German Pat. No. 891,549; German Pat. No. 1,139,636; German Pat. No. 2,054,522; Japanese Pat. No. (72) 14,500 (and as cited in Volume 77, Chemical Abstracts, column 153737k, 1972); Chemical Abstracts, Volume 13, column 4485; Chemical Abstracts, Volume 31, column 70459; Chemical Abstracts, Volume 52 (1958), column 4543-4544; Journal of the Chemical Society, pages 2972-2976 (1963); Journal of the American Chemical Society, Volume 57 (1935), pages 572-574 and Volume 76 (1954) page 2993; Journal of the Science of Food and Agriculture, Volume 20 (1969), pages 748-754; and Philippine Journal of Science, Volume 34 (1927), page 159. All of these publications are to be considered as incorporated herein by reference.

The present invention relates to plastic compositions containing polystyrene polymer. More specifically, the present invention covers plastic compositions containing a three component system which consists of polystyrene, certain bis-phenoxy compounds (hereinafter defined) as flame retardants for said plastic compositions, and an enhancing agent (hereinafter defined) for said flame retardants.

Polystyrenes and utility thereof are known in the art as exemplified by Polystyrene, W. C. Teach and G. C. Kiessling (Reinhold Plastics Applications Series), Reinhold Publishing Corporation, N.Y., 1960 and Modern Plastics Encyclopedia 1972-1973, Vol. 49: No. 10A, Oct. 1972, pages 97-99, 161 and 271-272 and which publications are in toto incorporated herein by reference.

The need for flame retarding polystyrenes has also been recognized in the art as exemplified by U.S. Pat. No. 3,347,822 and 3,422,048 and Modern Plastics Encyclopedia, ibid, pages 221, 222 and 456-458 and which publications are in toto incorporated herein by reference.

The prior art has specifically recognized the problems of finding suitable flame retardants for polystyrene in view of the fact that polymer systems differ substantially in both flammability characteristics and physical properties and there is no predictability whatsoever from one system to another. Thus in the Norris et al paper entitled "Toxicological and Environmental Factors Involved in the Selection of Decabromodiphenyl Oxide as a Fire Retardant Chemical", Applied Polymer Symposium No. 22, 195-219 (1973), the authors state: "A growing recognition of the huge annual toll taken by fire is resulting in more stringent flammability requirements for synthetic polymers in a variety of applications. Because of economic constraints and the need to produce flame resistant polymers without total replacement of existing and manufacturing processes, increased flame resistance is generally achieved by incorporation of a fire retardant chemical in the finished product. This chemical is usually based on bromine, chlorine, phosphorus, or nitrogen and may either be chemically reacted or physically blended into the product. Since polymer systems differ markedly in both flammability characteristics and physical properties, selection of a suitable flame retardant depends on a variety of factors that severely limits the number of acceptable materials.

"A general class of synthetic polymers that require flame retardancy because of their use in electrical and high temperature applications, but pose severe problems in selecting a suitable flame retardant are the high performance thermoplastic resins such as thermoplastic polyesters, polyphenylene oxides, and acrylonitrile-butadiene-styrene (ABS) terpolymers. Some of the most important criteria for an acceptable flame retardant in these applications are:

1. It must be as effective as possible to minimize both cost and effect on polymer properties. Use levels may range up to 15% by weight.

2. It must have sufficient stability to withstand conditions encountered during polymer processing and use. Processing conditions (blending, extrusion, and molding) often involve temperatures exceeding 300.degree. C. The flame retardant must tolerate these conditions without degradation or volatilazation. Also, attention must be given to hydrolytic stability and oxidative degradation, particularly under extended service at high temperatures.

3. It must be compatible with the base polymer and exert minimal adverse effect on those properties that give the polymer its value. Some of these critical properties are tensile strength, impact strength, heat deflection temperature, shear strength, and flexural modulus.

4. Finally, the flame retardant must not interfere with attainment of desired product esthetics and form.

"Because of the stringest thermal stability requirements, only a very few compounds have been identified which can meet the necessary performance and economic criteria."

The resultant disadvantages in the utilization of various prior art materials as flame retardants, in general, for plastic compositions include, without limitation, factors such as thermal migration, heat instability, light instability, non-biodegradable, toxicity, discoloration, the large amounts employed in order to be effective, and the unpredictable end results obtained when using the same material in different plastics (note, for example, in Modern Plastics Encyclopedia, ibid, page 650, wherein octabromobiphenyl is suitable for use in polyolefins as a flame retardant therefor, but is not shown for use (or functionally equivalent) as such for the other 27 compositions listed such as ABS; polycarbonates, polystryrene, acrylics and polyurethanes). Thus, it can be seen that the field of flame retardancy is highly sophisticated and consequently requires substantial research effort to achieve a particular desired end result.

In conjunction with the rendition of polystyrene plastics flame retardant the aforegoing discussion is particularly applicable. Furthermore, it is important that, in addition to the retention of good physical characteristics, three characteristics (one of which is critical) of the product (polystyrene) be within certain limitations in order to provide a functional flame retarded product. These three characteristics are (1) light stability (as measured, for example, by .DELTA. E color values, hereinafter defined), (2) flame retardancy (as measured, for example, by UL-94, hereinafter defined, and which is a critical characteristic and limitation), (3) thermal stability (as measured, for example, by certain ASTM tests for decomposition and migration, hereinafter defined). This characteristic of flame retardancy is not an arbitrary item but is a criteria which is strictly adhered to in the polystyrene plastic art and hereinafter explained in more detail, with particular reference to the examples contained herein.

In conjuction with the foregoing discussion, the prior art in general suggests the use of halogen-containing materials as "potential" or "possible" flame retardants for plastic materials. However, the prior art also recognizes that any material must be adjudged on a case by case basis because of the unpredictable results of the end product when any additive is incorporated therein. For example, with reference to the use of a halogenated fire retardant in U.S. Pat. No. 3,658,634, attention is directed to the fact that the patentee specifically points out the disadvantages in the use of a halogen-containing fire retardant. In Column 1, lines 14-17, the patentee states: "Therefore, if it is possible to impart fire-retardancy to the thermoplastic polymers without deteriorating the useful properties of the thermoplastic polymers, they can be widely used in the field of inertia, construction and electric industries." In Column 1, lines 26-32, the patentee states: "--the compounds containing chlorine or bromine atoms to be used as fire-retardant agents, are generally sublimated and therefore, the fire retardant agents are sublimated and lost in the process for producing fire-retardant polymers or in after-finishing processes; accordingly, deteriorations of fire-retardancy or difficulties in use tend to occur more often than not."

In Column 1, lines 39-44 the patentee states: "--the compounds containing chlorine or bromine atoms to be used as fire-retardant agents are unstable in most cases when exposed to ultraviolet rays." In Column 1, lines 59-64 the patentee states: "However, as a matter of fact, only very few fire-retardant polymers can be used in actual practice although they are said to have fire-retardant effects, because there are restrictions such as the conditions employed in production attributable to the properties of the fire-retardant agent, or to the properties of the polymers into which they are to be incorporated."

It can be seen, then, from the foregoing discussion and quoted subject matter that the field of flame retardancy is highly sophisticated, unpredictable and requires substantial research to produce an end product (plastic composition) which meets the necessary criteria for utilitarian purposes, particularly under the present day government standards. Thus, there is always a demand for a material which will function as a flame retardant in polystyrene and concurrently will not, by incorporation therein, adversely effect the chemical and/or physical and/or mechanical properties of the resultant polystyrene containing plastic composition (herein also referred to as "polystyrene plastic composition") and also have utility.

The prior art problem of providing a flame retarded polystyrene composition having desired chemical, physical and mechanical properties, in addition to functional utility, has now been substantially solved by the present invention and the above-described disadvantages substantially overcome.

Accordingly, one of the main objects of the present invention is to provide polystyrene plastic compositions which are flame retarded.

Another object of the present invention is to provide a unique three component system for polystyrene plastic compositions which will not substantially adversely effect the chemical and/or physical and/or mechanical properties of said compositions.

A salient object of the present invention is to provide a polystyrene plastic composition which has a certain defined flame retardancy property.

A further object of the present invention is to provide a flame retardant and an enhancing agent which are economical and easy to incorporate into polystyrene plastics without being degraded or decomposed as a result of normal blending or processing operations.

It has been found that the foregoing objects can be obtained by the use of a unique three component system, which consists of (a) polystyrene compounds (hereinafter defined), (b) certain bis-phenoxy compounds (hereinafter defined), and (c) an enhancing agent (hereinafter defined) to subsequently provide flame retarded plastic compositions which exhibit outstanding chemical, physical and mechanical properties.

It is to be understood that the term "flame retarded" as used herein refers and is restricted to a limited definition and that is the reduction in flammability of the plastic composition which contains the three component system. The criticality of this flame retardancy is more specifically set forth herein, with particular reference being made to page 21 herein regarding UL-94 classification (sometimes referred to herein as "values").

The particular class of bis-phenoxy compounds used in the present invention compositions have the formula ##STR2##

In Formula I above, Z is bromine, m and m' are each an integer having a value of 5, and alkylene is a straight chain carbon group having from one to six carbon atoms and includes, without limitation, groups such as --CH.sub.2 --; --(CH.sub.2).sub.2 --; --(CH.sub.2).sub.3 --; --(CH.sub.2).sub.4 --; --(CH.sub.2).sub.5 --; and --(CH.sub.2).sub.6 --

It is to be understood that all the compounds falling within Formula I above and as heretofore defined are generically described herein as "bis-phenoxy compounds".

Representative, but without limitation, of said bis-phenoxy compounds are the following: ##STR3##

1,1-bis(2,3,4,5,6-pentabromophenoxy) methane ##STR4##

1,2-bis(2,3,4,5,6-pentabromophenoxy) ethane ##STR5##

1,3-bis(2,3,4,5,6-pentabromophenoxy) propane ##STR6##

1,4-bis(2,3,4,5,6-pentabromophenoxy) butane ##STR7##

1,5-bis(2,3,4,5,6-pentabromophenoxy) pentane ##STR8##

1,6-bis(2,3,4,5,6-pentabromophenoxy) hexane

Compounds of Formula II through VII above, designated as "bis-phenoxy compounds," have been found to be uniquely suitable for polystyrene, particularly "high impact polystyrene". However, it was surprising to find that "other bis-phenoxy compounds" were not found suitable in polystyrene as hereinafter disclosed in the examples. These "other bis-phenoxy compounds" include the following: ##STR9##

1,2-bis(2,4,6-tribromophenoxy) ethane ##STR10##

1,3-bis(2,4,6-tribromophenoxy) propane ##STR11##

1-(2,3,4,5,6-pentabromophenoxy),

2-(2,4,6-tribromophenoxy) ethane ##STR12##

1,1-bis(2,4,6-tribromophenoxy)methane ##STR13##

1,4-bis(2,4,6-tribromophenoxy)butane

It is to be specifically understood that those compounds of Formulae VIII thru XII do not fall within the term "bis-phenoxy compounds" used herein, but do fall within the term "other bis-phenoxy compounds".

In general, the bis-phenoxy compounds are prepared by reacting a halogenated phenol with a halogenated alkane at elevated temperatures in the presence of a basic material such as alkali metal hydroxides, carbonates, bicarbonates, oxides and hydrides. The preferred alkali metals are potassium and sodium. Where one desires to increase, for example, ease of handling the reaction mass, solvents such as ketones (e.g. acetone, methyl ethyl ketone, and methyl iso-butyl ketone), alcohols (e.g. methanol, ethanol, iso-propyl alcohol, butyl alcohol and glycols), or aqueous solvents (e.g. water, a mixture of water and alcohol and a mixture of water and ketone) can be employed. The desired end product i.e. the bis-phenoxy compounds, can be recovered from the reaction mass via various methods known to those skilled in the art. Where the end product requires recovery via crystallization, various aromatic solvents, such a benzene, toluene, xylene, dichlorobenzene and the like, can be used.

Specifically, the bis-phenoxy compounds are prepared according to the following reactions: ##STR14##

In the above reaction, X is halogen, preferably bromine, and alkylene is the same as herein defined.

The above reaction is conducted at temperatures ranging from the freezing point of the initial reaction mass to the boiling point hereof. Preferably the temperatures are from about 40.degree. C. to about 200.degree. C. and more preferably from about 50.degree. C. to about 175.degree. C. It is to be understood that the reaction can be conducted under sub-atmospheric (e.g. 1/10-8/10 atmospheres) pressure. Preferably, the reaction is carried out at atmospheric pressure.

The above-described processes can be carried out with conventional, readily available chemical processing equipment. For example, a conventional glass-lined vessel provided with heat transfer means, a reflux condenser and a mechanical stirrer can be advantageously utilized in practicing any of the preferred embodiments of the invention described in preparing the bis-phenoxy examples set forth herein.

The amount of bis-phenoxy compound employed in the present invention compositions is any quantity which will effectively render, in conjunction with the enhancing agent, the polystyrene containing composition flame retardant. In general, the amount used is from about 1% to about 25% by weight, based on the total weight of the composition. Preferably, the amount employed is from about 5% to about 20% by weight. It is to be understood that any amount can be used as long as it does not substantially adversely effect the chemical and/or physical and/or mechanical properties of the end plastic composition. The amount utilized, however, is such amount which achieves the objectives described herein.

The second component of the three component system, and which is critical therefor, are certain compounds which when used with the bis-phenoxy compounds promote a cooperative effect therebetween and thus enhance the flame retardancy of the resultant plastic composition as compared to the flame retardancy of either one component used separately. These "enhancing agents" comprise the oxides and halides of groups IVA and VA of the Periodic Table, i.e. oxides and halides of antimony, bismuth, arsenic, tin, lead, germanium, e.g. antimony oxychloride, antimony chloride, antimony oxide, stannic oxide, stannic chloride, arsenous oxide, arsenous chloride, and the like; and organic and inorganic compounds of phosphorus, nitrogen, boron, and sulfur, e.g., triphenyl phosphate, ammonium phosphate, zinc borate, thiourea, urea, stannic sulfide, and the like and oxides and halides of titanium, vanadium, chromium, manganese, iron, niobium, molybdenum copper, zinc, magnesium, e.g. titanium dioxide, titanium chloride, vanadanium pentoxide, chromic bromide, manganous oxide, molybdenum trioxide, ammonium molybdate; and hydrates of the above, e.g., stannic oxide hydrate, lead hydrate; and combinations thereof. The preferred enhancing agents are the oxides of antimony, arsenic and bismuth. However, any compound which on decomposition, as by ignition, yields these oxides would be suitable. Thus some organic antimonates are preferred. The enhancing agents disclosed in U.S. Pat. No. 3,205,196 are also suitable for use.

U.S. Pat. No. 3,205,196, column 2, states that "Antimony oxide is the antimony compound that is presently preferred for use in the present invention. However, many antimony compounds are suitable, inorganic antimony compounds include antimony sulfide sodium antimonite, potassium antimonite, and the like. Many organic antimony compounds are suitable such as the antimony salts of organic acids and their pentavalent derivatives disclosed in copending application Ser. No. 688,143, filed Oct. 4, 1957, now U.S. Pat. No. 2,996,528. Compounds of this class include antimony butyrate, antimony valerate, antimony caproate, antimony heptylate, antimony caprylate, antimony pelargonate, antimony caprate, antimony cinnamate, antimony anisate, and their pentavalent dihalide derivatives. Likewise the esters of antimonous acids and their pentavalent derivatives disclosed in copending application Ser. No. 688,108, filed Oct. 4, 1957, now U.S. Pat. No. 2,993,924, such as tris(n-octyl) antimonite, tris(2-ethylhexyl) antimonite, tribenzyl antimonite, tris(.beta.-chloroethyl) antimonite, tris(.beta.-chloropropyl) antimonite, tris(.beta.-chlorobutyl) antimonite and their pentavalent compounds are the cyclic antimonites such as trimethylolpropane antimonite, pentaerythritol antimonite, and glycerol antimonite. The corresponding arsenic and bismuth compounds can also be employed."

It is to be understood that such patents as U.S. Pat. Nos. 3,205,196; 2,996,528 and 2,993,924 are to be considered as incorporated herein by reference for all intents and purposes. Without limitation, preferred enhancing agents include Sb.sub.2 O.sub.3, SbCL.sub.3, SbBr.sub.3, SbI.sub.3, SbOCl, As.sub.2 O.sub.3, As.sub.2 O.sub.5, ZnBO.sub.4, BaB.sub.2 O.sub.4.sup.. H.sub.2 O, 2.sup.. ZnO.sup.. 3B.sub.2 O.sub.3.sup.. 3.sup.. 5H.sub.2 O and stannic oxide hydrate. The more preferred enchancing agent is antimony trixoide.

The amount of enhancing agent employed in the present invention compositions is any amount which when used with said bis-phenoxy compounds will promote a cooperative effect therebetween. In general, the amount employed is from about 0.5% to about 15%, preferably from about 1% to about 10%, by weight, based on the total weight of plastic composition. Higher or lower amounts can be used as long as the desired end result is achieved.

The third critical component of the three component system is the polystyrene polymer. It is to be understood that the term polystyrene as used herein means polymers containing more than 60% styrene (phenylethylene, vinyl benzene, styrol, cinnamene) C.sub.6 H.sub.5 CH.dbd.CH.sub.2 or other unsaturated aromatic monomers comprised of variously substituted styrene derivatives. This term also includes rubber modified impact-resistant polystyrene and styrene-acrylonitrile copolymers (sometimes referred to in the trade as SA or SAN).

Thus the polystyrene used in the present invention compositions is any polystyrene herein defined and which one so desires to flame retard. It is to be understood that the polystyrene used can be a "virgin" material, i.e. substantially free of additives such as stabilizers, plasticizers, dyes, pigments, fillers, and the like, or the polystyrene can have additives (such as those mentioned and described herein) already contained therein or added concurrently with or after the addition of the bis-phenoxy compounds and enhancing agents.

The bis-phenoxy compounds and enhancing agents can be incorporated into the polystyrene at any processing stage in order to prepare the present invention plastic compositions. In general, this is undertaken prior to fabrication either by physical blending or during the process of forming polystyrene per se. Where one so desires, the bis-phenoxy compounds and/or enhancing agents may be micronized into finely divided particles prior to incorporation into the polystyrene.

It is also within the scope of the present invention to employ other materials in the present invention compositions where one so desires to achieve a particular end result. Such materials include, without limitation, adhesion promoters; antioxidants, antistatic agents; antimicrobials; colorants; flame retardants such as those listed on pages 456-458, Modern Plastics Encyclopedia, ibid., (in addition to the new class of flame retardants described herein); heat stabilizers; light stabilizers; pigments, plasticizers; preservatives; ultraviolet stabilizers and fillers and additives.

In this latter category, i.e. fillers, there can be mentioned without limitation, materials such as glass; carbon; cellulosic fillers (wood flour, cork and shell flour); calcium carbonate (chalk, limestone, and precipitated calcium carbonate); metal flakes; metallic oxides (aluminum, beryllium oxide and magnesia); metallic powders (aluminum, bronze, lead, stainless steel and zinc); polymers (comminuted polymers and elastomerplastic blends); silica products (diatomaceous earth, novaculite, quartz, sand, tripoli, fumed colloidal silica, silica aerogel, wet process silica); silicates (asbestos, kaolimite, mica, nepheline syenite, talc, wollastonite, aluminum silicate and calcium silicate); and inorganic compounds such as barium ferrite, barium sulfate, molybdenum disulfide and silicon carbide.

The above mentioned materials, including filler, are more fully described in Modern Plastics Encyclopedia, ibid, and which publication is incorporated herein (in toto) by reference.

The amount of the above described materials employed in the present invention compositions can be any quantity which will not substantially adversely effect the desired results derived from the present invention compositions. Thus, the amount used can be zero (0) percent, based on the total weight of the composition, up to that percent at which the composition can still be classified as a plastic. In general, such amount will be from about 0% to about 75% and more specifically from about 1% to about 50%.

With reference to the present invention plastic compositions described herein, one of the critical features thereof is the unusually high flame retardancy thereof. The significance of flame retardancy of plastic compositions is well recognized in the art as heretofor mentioned. However, recent developments in conjunction with the use of flame retardant plastic compositions as judged by the Consumer Product Safety Commission, require a UL-94 value (hereinafter discussed) of V-0 in order to produce a commercially acceptable article of manufacture. The Consumer Product Safety Commission is continuing to set mandatory standards in the field where the plastic compositions are utilized and since about 1970 have increased in criticality of UL value of plastic compositions. In reacting to the Consumer Product Safety Commission's mandatory standards in this area, the producers of (plastic composition) articles of manufacture are now requiring that said articles have a V-0 value in order to meet new mandatory standards which are anticipated to be activated by federal legislation shortly. Thus, the significance of a plastic composition having a V-0 value is well recognized in the art; note Modern Plastics, Sept. 1974, pages 74- 77 and which publication is to be considered as incorporated herein by reference.

In conjunction with the present invention plastic compositions described herein, an important feature thereof is the light stability thereof. The significance of light stability of plastic compositions is recognized in the art, e.g. the publication entitled "The Measurement of Appearance" by Mr. Richard S. Hunter (Hunter Associates Laboratory, Inc., 9529 Lee Highway, Fairfax, Va.) 1973. Mr. Hunter has been associated with the efforts of defining appearance and color since the 1930's and was for many years an associate of Gardner who is another authority in this field. The following paragraphs from Mr. Hunter's book are set forth in order to demonstrate this light stability significance.

The Judd-Hunter system "of scales for color difference was based on Judd's uniform chromaticity scales triangle. Judd made an instrumental study of a number of woolen swatches rated by dyers for their acceptabilty as commercial color matches to standard. The NBS unit of color difference was designed by Judd to be the maximum difference commercially acceptable in the textile trade as represented by these dryers at the time when the study was carried out (Judd, 1939). The NBS Unit generally referred to today is not Judd's 1939 unit, but the Hunter 1942 version of the Judd unit with 100 units falling between black and white."

"Since 1942 this unit has been used in terms of a number of the opponent color scales. In a color scale which is already uniform in its visual spacing of lightness and chromaticity, and which has 100 units between black and white as well as rectangular coordinates for chromaticity, color difference in approximate NBS units can be specified in units of that system. The color difference becomes the distance between the two colors in that color space. With rectangular coordinates, the formula is:

Similarly if only the chromaticity component of difference is desired, the formula is:

"Following Judd's proposed unit of color difference, Hunter proposed the measurement of much the same quantity by a photoelectric tristimulus method in 1942. In the next year, Scofield proposed a quantity which was quite a bit easier to compute. Scofield used the reciprocal of the square root of reflectance instead of the reciprocal of the fourth root of reflectance as a multiplier in adjusting reflectance values for uniform lightness scale intervals. This is the only difference between the Scofield and the Judd-Hunter formulas for color difference. (Scofield, 1943)."

"In 1948, Hunter started to develop a tristimulus instrument which would read chromaticity dimensions of opponent colors directly. He was seeking to improve the precision and usefulness of results of the tristimulus reflectometers previously used. The R.sub.d scales developed in the period 1948 and 1950 did not have a uniform lightness readout but did have direct reading visually uniform a and b scales. The L scales, in which there is approximate perceptual uniformity in all three dimensions, were created in the period 1950-1952 but were not described in a formal publication until 1958. These two sets of Hunter Color Difference Meter scales enjoy wide use because of the fact that they can be read directly from a tristimulus instrument with high precision, and offer instrumental computation of color difference by the .DELTA.E formula given above."

"NBS Unit of Color Difference is defined as: the unit of color difference of the National Bureau of Standards. The unit is about four times as great as the smallest difference observable under ideal conditions. Differences of less than one unit are usually not important in commercial transactions. In Munsell terms, one NBS unit is equivalent to about 0.1 Value step, 0.15 Chroma step, or 2.5 Hue step at Chroma 1."

"Hunter further investigated the use of L', .alpha.', .beta.' for color difference measurement. He recognized at this time (which no other color-difference scale before or since has recognized) that perceived color difference will depend on the proximity of the specimens compared and on their glossiness. Accordingly, the 1942 Hunter color difference equation includes factors to account for these variables. It is this equation, with selected constants, that defines the widely used NBS unit of color difference."

"High precision is almost always essential for useful color difference measurements. Only with precise instruments is it possible to measure color differences as small as those the eye can see. Instrument accuracy is also normally a requisite because spectrally inaccurate instruments, even though precise, will give visually inaccurate color difference measurements wherever there are spectral differences between the specimens involved. The ease of obtaining and interpreting values of color difference is another factor which may effect the selection of a procedure."

"Twenty years ago, color difference scales were in demand to serve as a basis for setting one-number tolerances for fading and acceptability of matches. The Index of Fading and NBS unit were used as units."

"Today, the concept of color difference is more refined. One number tolerances are seldom used. Instead, color difference tolerances are designed as boundaries in color space within which acceptable colors must fall. The boundaries do not necessarily correlate with perceptibility of difference but rather with the limits of acceptability. The standard color, furthermore, may not be in the center of the bounded region but may be displaced to one side. For example, where subsequent yellowing may occur, the tolerance for the yellow-blue dimensions might be +0.1, -0.8 units."

"Color difference specifications are tighter today and tolerances are smaller. The specification usually treats the color dimensions separately so that a complete specification would contain nine numbers: The three numbers that describe the desired color, and the six numbers that describe the individual plus and minus tolerances. Such tolerances can be reduced to graphs which not only show acceptability but provide a guide to the formulation correction needed to correct an off shade. When the question of acceptability becomes a question of sorting objects according to shade, a graphical chart showing the classification of color values can be quite helpful."

"Although color measurements are frequently used for identification, sorting and recording of color values, the primary uses of tristimulus instruments all involve measurements of fairly small color differences. The most frequent uses of these small color difference measurements are to establish closeness to standard and to give guidance for the adjustment of color mismatches. They are also used in the study of deterioration in a product as a result of exposure and use."

"Spectrophotometers and tristimulus instruments made up the majority of color appearance measuring instruments in use in industry. Spectrophotometers give wavelength-by-wavelength analyses of the reflecting properties of objects, while tristimulus instruments by the use of filters which approximate the Standard Observer functions of the eye, give measurements of color in X, Y, Z terms, or in L, a, b values. Spectrophotometers are essential where color formulation is involved, and metamerism must be controlled. However, tristimulus colorimeters and reflectometers provide precise and less expensive means for the routine measurement of color and adjustment of small color differences."

In view of the foregoing quoted subject matter, it can thus be seen that a change in .DELTA.E value of 1 unit constitutes a real change. Note also Japanese patent application (publication 122,456, of 1974) which shows that achieving a color change in .DELTA.E of only 2.3 is significant as it pertains to a polycarbonate polymeric composition; (this value is substantially the same as those .DELTA.E values obtained in polycarbonate tests and which results thereof are shown in Table VIII herein, i.e. 2.3 versus 2.5 over the control). Both of these publications (i.e. the Japanese patent 122,456 and the Hunter book) are to be considered as incorporated herein by reference. It is to be noted also that a lower .DELTA.E value is more desired and the higher .DELTA.E value is least desired. This .DELTA.E value is not an abstract value, however, since one must compare it with the .DELTA.E values of the "control" plastic composition. One of the desired .DELTA.E values would be where both the .DELTA.E values of the "control" plastic composition " without additives"-(i.e. without flame retardant and enhancing agent) and the plastic composition with said additives are substantially the same or the latter has a lower value.

The following examples are presented to demonstrate the uniqueness of the present invention compositions as contrasted to other plastic compositions containing the same (present invention) bis-phenoxy compounds, "other bis-phenoxy compounds" and prior art compounds with or without an enhancing agent. These examples also show unpredictability, via the end results, in using any halogenated material, much less the same material, in several different plastics.

Referring to Example I, this example sets forth the comparison of a polystyrene plastic (HIPS) with seven other polymer systems and includes substantial detail with particular reference to physical properties including flammability.

Referring more specifically to Example II, this compares a related polymer system (acrylonitrile-butadiene-styrene [ABS]), having incorporated therein the "other bis-phenoxy compounds" (Formulae VIII and IX, page 13), and an enhancing agent with four other polymers containing the same "other bis-phenoxy compounds" and enhancing agent. The four comparative polymers are polyacrylonitrile, polypropylene, nylon and polymethylmethacrylate. As will be seen from the results hereinafter set forth, the four other polymers had no flame retardant efficacy when incorporating the "other bis-phenoxy compounds" and enhancing agents, whereas the ABS system did and so demonstrated an unexpected and substantial flame retardant efficacy.

In conjunction with the results set forth in Table XV it can readily be seen that while the "other bis-phenoxy compounds" (Formulae VII and IX, page 13) were effective in an ABS system, these same compounds were not effective in polystyrene polymers, which is somewhat related to the ABS polymer.

The results, thus, are another indication of the unpredictability of additives in polymer systems and correspond to the subject matter set forth in "Modern Plastic Encyclopedia", ibid., regarding the use of octabromobiphenyl in one polymer but not shown for use (or functionally equivalent) in numerous other materials.

Solid samples of eight different plastic compositions separately containing certain prior art compounds, the present invention bis-phenoxy compound and "other bis-phenoxy compounds", all with or without the herein described enhancing agents, are prepared according to the procedure set forth hereinafter, and are subjected to the following tests in order to ascertain comparative properties of the resultant plastic compositions:

Regarding item (a) above, i.e. light stability, the results obtained via the "Visual" rank include any color changes which occurred in the molded materials tested from a combination of processing and exposure to the xenon arc.

Each of the aforementioned Tests are standard test in the art and are utilized collectively in order to ascertain the efficacy of a polymeric system as an overall flame retardant composition for commercial application. All of these Tests are to be considered as incorporated herein by reference.

The different polymers utilized along with trade names and corresponding suppliers are listed below.

The concentration of the additives (i.e. prior art compounds (designated PAC), present invention bis-phenoxy compounds (designated BPC) or "other bis-phenoxy compounds" (designated OBPC), with or without an enhancing agent (designated EA) and the respective Table Nos. listing the pertinent data are shown below. The Table numbers are shown in parenthesis.

All percentages (%) shown are on a weight basis, based on the total weight of the plastic composition.

The identification of the prior art compounds (PAC) listed as A, B, C, D, E and F in the Tables are shown below:

The present invention bis-phenoxy compounds (BPC) listed in the Tables under Present Invention, as II, III, VII, etc. correspond to those compounds listed on pages 11 and 12 of this specification.

The "other bis-phenoxy compounds" (OBPC) listed in the Tables under such title, as VIII, IX, X etc. correspond to those compounds listed on pages 13 and 14 of this specification.

The control (base resin) is the particular designated polymer without the PAC, BPC, OBPC, or EA.

The plastic materials which are subject to the above described tests, are prepared in the following manner. With the exception of "base resin", the particular additive (PAC, OBPC or BPC, and the antimony trioxide enhancing agent where indicated) is incorporated into the plastic by adding both to a Brabender mixer ("Plastic-Corder", Torque Rheometer, Model PLV-150, C. W. Brabender Instruments Inc., South Hackensack, N.J.). The mixer is equipped with a pair of roller type blades positioned within a head provided with heat transfer means.

The resultant mixture is heated to about 245.degree. C.; at this temperature, it is in a molten state. The percentages by weight of each component utilized in the respective formulations are listed in the Tables. Each formulation is discharged from the mixer and upon cooling solidifies and is ground into chips. The chips are subjected to injection molding in a one (1) ounce Newbury Injection Molder, Model HI 30 RS, manufactured by Newbury Industries, Inc., Newbury, Ohio by placing said chips therein and utilizing a 60 second molding cycle with a ram pressure of 2000 psi. The chips contained in said molder are subjected to heat transfer means supplied thereto in order to melt said chips, and the melted chips are then rammed into a mold in order to provide solid samples (after cooling) for testing.

Portions of the solid samples of each respective formulation prepared according to the above described procedure are subjected to two different flammability tests, i.e. UL 94 and ASTM D-2863-70. The UL 94 is, in general, the application of a burner to a test specimen (strip) for a certain period of time and observation of combustion, burning, and extinguishment. This procedure is fully set forth in Underwriters' Laboratories bulletin entitled UL 94, Standard for Safety, First Edition, Sept. 1972 and which is incorporated herein by reference. ASTM No. D-2863-70 is a flammability test which correlates the flammability of a plastic specimen to the avialable oxygen in its immediate environment; this correlation is stated as an Oxygen Index, O.I., level predicated upon the percent oxygen in the gaseous medium which is required to just provide a steady state of continuous burning of the plastic specimen. This ASTM method is fully described in 1971 Annual Book of ASTM Standards-- Part 27, published by the American Society for Testing and Materials, 1916 Race Street, Philadelphia, Pa.; this publication is to be considered as incorporated (in toto) herein by reference. The UL 94 test is the more critical test as it is the test generally used to determine the suitability of thermoplastics for commercial applications.

The results of all of this comparative testing are shown in Tables I through XIV.

Samples of each formulation are subjected to temperature (thermal) stability tests via the use of thermal gravimetric analysis (TGA). This test employs the use of a "Thermal Balance," model TGS-1, Perkin-Elmer Corporation, Norwalk, Conn. and an electrical balance, Cahn 2580 model, Cahn Instrument Company, Paramount, Calif. The conditions of this TGA test are listed in the following Tables.

Samples of each formulation are also subjected to light stability tests via the use of a "Weather-Ometer", model 25/18 W. R., Atlas Electrical Devices Company, Chicago, Ill. Utilizing an operating temperature of 145.degree. F. and a 50% relative humidity, each sample is subjected to the indicated number of hours of "simulated daylight" via the use of a Xenon arc. This Test shows whether there is any significant discoloration in any sample tested and the end results are set forth in .DELTA.E values.

Referring to Tables I through XIV in general, it is readily apparent that the incorporation of additives in polymer systems is highly unpredictable. Even in the same polymer, "structurally related" prior art compounds, "other bis-phenoxy compounds" and the present invention bis-phenoxy compounds produced completely different results. However, out of all the data shown therein it is clear that the combination of the present invention bis-phenoxy compounds and enhancing agent result in an unexpected, superior, flame retarded polystyrene plastic composition which has commercial application.

Specifically, Table I shows the results of testing a polystyrene polymer containing 12% PAC, OBPC, or BPC and 4% EA. The polystyrene/BPC/EA combination is the only one of the OBPC or BPC which produced V-0(UL-94) and, in general color values .DELTA.E, on an overall average basis, substantially closer to the control (without additives). Thus these BPC compounds, as a class, are unique; note the HB values of the OBPC. While B, C and D yielded a V-0(UL-94) composition, the .DELTA.E Values were excessively high and thus nonapplicable for most commercial uses. A and E show non-efficacy (HB ratings like the control) thereof as flame retardants and again point out the non-predictability of additives incorporated in either the same or various polymers. (The inclusion of data, relating to where no enhancing agent is used, is presented to show non-efficacy of BPC at low concentrations and the large quantities required to produce efficacy-- note Table III.)

Regarding Formulation Nos. 1- 10 in Table XV, a virgin polyacrylonitrile plastic material, (T-61 polymer crumb, a product of American Cyanamid and characterized as a copolymer of 93% by weight acrylonitrile and about 7% by weight methyl methacrylate) is utilized as the base resin in order to prepare 10 formulations (plastic compositions). With the exception of formulation No. 1, the particular "other bis-phenoxy compound" (and the antimony trioxide enhancing agent where indicated) is incorporated into the plastic (which is dried to remove moisture therefrom) by adding both to a Waring blender which contains acetone as a dispersing liquid. The resultant mixture, after blending for 3 minutes, is poured into evaporation dishes and the acetone evaporated, first at room temperature (20.degree.-25.degree. C.) for 60 minutes and followed by oven drying at 60.degree. C. for one hour.

The percentages by weight of each component utilized in the respective formulations are listed in Table XV. Each formulation is discharged from the evaporation dish and is ground into powder. The powder is subjected to compression molding in a Wabash press by placing said powder between two platens, the bottom of which contains four equal size depressions three inches by five inches by 1/8 inch deep. The top platen is then placed over the bottom platen and heat transfer means supplied thereto in order to melt said powder and thus provide solid samples (after cooling) for testing. The temperature and ram pressure utilized are respectively 100.degree. C. and 30 tons.

A polypropylene plastic material, (Hercules Pro-Fax.RTM. 6523 grade of polypropylene) is utilized as the base resin in order to prepare 13 formulations (plastic compositions)-- Nos. 11-23 shown in Table XV. With the exception of formulation No. 11, the particular "other bis-phenoxy compound" (and the antimony trioxide enhancing agent where indicated) is incorporated into the plastic and solid samples prepared according to the procedure set forth in Example I.

A virgin nylon 6 plastic material, (Zytel.RTM. 211, a product of E. I. du Pont de Nemours and Co., Wilmington, Del. is utilized as the base resin in order to prepare 7 formulations (plastic compositions)-- Nos. 24- 30 shown in Table XV. With the exception of formulation No. 24, the particular "other bis-phenoxy compound" (and the antimony trioxide enhancing agent where indicated) is incorporated into the plastic and solid samples prepared according to the procedure set forth in Example I.

Regarding Formulation Nos. 31-33 in Table XV, a virgin polymethylmethacrylate plastic material, Plexiglas.RTM. V (811) a commercially available product of Rohm and Haas Company, Philadelphia, Pa. and being substantially free of additives, is utilized as the base resin in order to prepare 3 formulations (plastic compositions). With the exception of formulation No. 31, the particular "other bis-phenoxy compound" (and the antimony trioxide enhancing agent where indicated) is incorporated into the plastic and solid samples prepared according to the procedure set forth in Example I.

Referring to Formulation Nos. 34-37 in Table XV, an acrylonitrile-butadiene-styrene (ABS) polymer plastic material, Marbon TP-2098, a product of Marbon Division, Borg-Warner Corporation, Washington, W. Va., and which is a slight process variation of their commercially available "T" grade ABS polymer, is utilized as the base resin in order to prepare four (4) formulations (plastic compositions). These formulations, Nos. 34-37, are prepared in accordance with the procedure described in ASTM D-1897-68.

Portions of the samples of each respective formulation (Nos. 1-37, Table XV) prepared respectively according to the above described procedures are then subjected to two different standard flammability tests, i.e. UL 94 and ASTM D-2863-70, i.e. Oxygen Index, O.I.

The results of these flammability tests are shown in Table XV.

Referring to Table XV, the "other bis-phenoxy compound" formula VIII or IX relates to the structural formulae heretofor set forth; and the UL 94 values are on a graduated scale wherein the highest degree to lowest degree of flame retardancy is respectively SE-0 (V-0), SE-1 (V-1), SE-2 (V-2), SB (HB) and Burns.

The results shown in Table XV demonstrate the unexpected and completely unpredictable and superior results and the unique effectiveness of the plastic composition containing the three component system which consists of the "other bis-phenoxy compounds", an enhancing agent and acrylonitrile-butadiene-styrene (ABS) polymer as compared to the use of such "other bis-phenoxy compound" with or without an enhancing agent in a polyacrylonitrile polymer, a polymethlmethacrylate polymer, a nylon polymer, and a polyolefin such as polypropylene polymer, the latter four of which polymers show substantially no increase in flame retardancy via the use of said "other bis-phenoxy compounds", with or without an enhancing agent.

Specifically referring to the polyacrylonitrile polymer compositions Nos. 1-10, formulation No. 1 (the control) has an UL value of SB. In Nos. 2-10, the use of the particular "other bis-phenoxy compound" (with or without the enhancing agent) results, within experimental accuracy, in no increase in flame retardancy via incorporation of 2% , 5%, or 10% of the "other bis-phenoxy compound" per se.

Regarding the use of an enhancing agent in formulation Nos. 5 and 6, the results obtained therefrom show that there is no increase in flame retardancy. Thus, for example, No. 1 (control) has an UL value of SB and Nos. 5 and 6 (which have different enhancing agent levels, 5% versus 10%) have also an UL value of SB. In viewing the results of No. 3 (5%-0%) and No. 5 (5%-5%), it can be seen that even the use of the enhancing agent does not increase flame retardancy in a polyacrylonitrile polymer.

With reference to the polypropylene polymer compositions Nos. 11 thru 23, it can readily be seen from the UL 94 values that the incorporation of the particular "other bis-phenoxy compound" therein resulted in substantially little, if any, increase in flame retardancy as compared to the control, considering the experimental accuracy. Even the use of an enhancing agent did not result in an increase in flame retardancy, note No. 12-SB and No. 13-SB. Predicated upon this data, it is thus seen that the incorporation of the "other bis-phenoxy compounds" (with or without an enhancing agent) in a polypropylene results in no flame retardant efficacy.

Specifically referring to the nylon polymer compositions--Nos. 24-30, formulation No. 24 (the control) had an UL value of SB. In Nos. 25-28, the use of the particular "other bis-phenoxy compound" results in no increase in flame retardancy via incorporation of 10% (SB versus SB) of the "other bis-phenoxy compound" per se.

Regarding the use of an enhancing agent in formulation Nos. 26, 27, 29, and 30, the results obtained therefrom show there is substantially little, if any, increase in flame retardancy. Thus, for example, No. 1 (control) has an UL value of SB and Nos. 26 and 29 also have an UL value of SB. While Nos. 27 and 30 each have an UL value of SE-2, this is not considered a significant increase and thus even the use of the enhancing agent does not result in flame retardancy efficacy.

With reference to the polymethylmethacrylate polymer compositions Nos. 31, 32 and 33, it can readily be seen from the UL values, i.e. all SB, that the incorporation of the particular "other bis-phenoxy compound" therein results in no increase in flame retardancy as compared to the control. Even the use of an enhancing agent did not result in an increase in flame retardancy. Consequently, it can readily be seen that the incorporation of the "other bis-phenoxy compounds" in a polymethylmethacrylate results in no flame retardant efficacy.

The most unexpected and outstanding results in flame retardancy were obtained via the incorporation of the particular "other bis-phenoxy compounds" and enhancing agents in an acrylonitrile-butadiene-styrene (ABS) polymer. Referring specifically to formulation Nos. 34 through 37, the control (formulation No. 34) had an UL value of HB(SB). Notwithstanding the incorporation of 15% (No. 35) of the particular "other bis-phenoxy compound" per se in the ABS polymer, there still results an UL value of SB. Use of the enhancing agent with both "other bis-phenoxy compounds" formulae VIII and IX, in formulation Nos. 36 and 37 results in an extraordinary and unexpected UL value change from SB (No. 35) to SE-0 (No. 36) and SE-0 (No. 37). In view of these results, it was quite unexpected that the ABS polymer system, having incorporated therein the particular "other bis-phenoxy compounds" and enhancing agent would show such superior flame retardant efficacy based on the results obtained from the performance of the other four (4) polymers, i.e. polyacrylonitrile, polypropylene, nylon and polymethylmethacrylate polymer systems having the same "other bis-phenoxy compounds" and enhancing agents incorporated therein. By the same token and with particular reference to the results disclosed in Example I, the "other bis-phenoxy compounds" (formulae VIII and IX) did not exhibit any flame retardancy efficacy (HB) in polystyrene (HIPS) at the "12/4" level (Table I) whereas the present invention bis-phenoxy compounds exhibited superior and unexpected efficacy (V-0) at the same level of usage. Consequently, it can readily be seen that it is not possible to predict the efficacy and/or functionality of any halogen-containing material (which may be suggested as a flame retardant) in any polymeric system until one actually conducts a substantial research program thereon and ascertains certain properties of the "flame retarded" system and its utility.

The procedure of Examples I and II are repeated except that the enhancing agent used in zinc borate instead of antimony oxide. Substantially the same results are obtained using zinc borate as those using antimony oxide.

The (present invention) bis-phenoxy compounds described herein are subjected to toxicity tests and it is found that these compounds are not toxic orally, not irritating to the eye and not irritating to the skin, all as measured by the guidelines of the Federal Hazardous Substances Act. Furthermore, rat feeding studies indicate these materials are not biologically persistent, an important property to minimize ecological imbalance.

In summary, the results shown on Tables I through XV are reviewed with the aforementioned criteria, i.e. UL-94 rating V-0 and physical properties, and are presented in Table XVI in terms of whether there is commercial utility, (taking into consideration most importantly V-0 rating and then mechanical properties) i.e. similar to those results shown for octabromobiphenyl in Modern Plastics Encyclopedia, ibid. Table XVI sets forth more vividly the difference between the present bis-phenoxy compounds, other bis-phenoxy compounds and the prior art and also the different results obtained when different polymers have the same additives incorporated therein; and also confirming those specific observations regarding the difference in polymer systems as noted by the Norris et al paper, ibid.

In view of the foregoing Examples and remarks, it is seen that the plastic compositions, which incorporate a three component system (including the bis-phenoxy compounds), possess characteristics which have been unobtainable in the prior art. Thus, the use of bis-phenoxy compounds and enhancing agents in polystyrene as flame retardants therefor is quite unique since it is not possible to predict the effectiveness and functionality of any particular material in any polymer system until it has actively undergone incorporation therein and the resultant plastic composition evaluated according to certain criteria such as UL-94 and various ASTM Standards. Furthermore, it is necessary, in order to have commercial utility, that the resultant flame retarded plastic composition possess characteristics such as being non-toxic and not biologically persistent. Use of the bis-phenoxy compounds and an enhancing agent in polystyrene has accomplished all of these objectives.

Thus, in order to meet the needs and standards of commerce, it is necessary that a successful candidate fulfill all of the requirements outlined above, not just a selected group. It was totally unexpected that the specific class of bis-phenoxy compounds meet these requirements in all aspects contrary to the expectations of the suggested teachings of the prior art.

The above examples have been described in the foregoing specification for the purpose of illustration and not limitation. Many other modifications and ramifications will naturally suggest themselves to those skilled in the art based on this disclosure. These are intended to be comprehended as within the scope of this invention.