US3319203A

US3319203A - Filler for fluorescent ballast

Info

Publication number: US3319203A
Application number: US101530A
Authority: US
Inventors: Joseph P Haughney
Original assignee: Sherwin Williams Co
Current assignee: Sherwin Williams Co
Priority date: 1961-04-07
Filing date: 1961-04-07
Publication date: 1967-05-09
Anticipated expiration: 1984-05-09

Description

y 1957 J. P. HAUGHNEY FILLER FOR FLUORESCENT BALLAST Filed April 7, 1961 H R.N WW wH p B Y //AWI W ,W

ATTORNEY;

United States Patent 3,319,203 FILLER FOR FLUORESCENT BALLAST Joseph P. Haughney, Chicago, Ill., assignor to The Sherwin Williams Company, Cleveland, Ohio, a corporation of Ohio Filed Apr. 7, 1961, Ser. No. 101,530 7 Claims. (Cl. 336--96) This invention relates as indicated to a filler composition which is especially adapted for use in a transformer, and to a method for reducing the noise level of transformer elements. For exemplary purposes, the invention will be described with reference to a fluorescent ballast which includes transformer means.

In the early development of fluorescent lights, starting was achieved by the application of sufiicient starting volt age. This voltage could be reduced if means were provided for preheating the cathodes whether by separate heating circuits, or by incorporating starting preheat in a ballast circuit design. Recent demands for instant starting have necessitated the development of more sophisticated ballast elements which while satisfactory for their intended purpose are, nevertheless, subject to operation noises or ballast hum. While much of the noise can be eliminated by proper mounting of the ballast, for many purposes the noise level is still objectionable.

It has now been found that a transformer having the elements thereof encased in a specially compounded resinous polyester composition is especially useful for installations where minimum transformer hum can be tolerated.

In the annexed drawings:

FIG. 1 is a transformer circuit of a typical fluorescent ballast and gas tube circuit.

FIG. 2 is an illustration of a ballast in accordance with the present invention.

Briefly stated, the present invention is in an electrical transformer including a core of a plurality of thin patterned sheets of iron in laminar form and having insulated copper wire wound thereabout, said transformer being immersed in a filler comprising a co-polymer of a vinyl substituted aromatic hydrocarbon and a polyester for-med from (I) a mixed organic acid consisting of (a) from 10% to 40% by equivalent weight of a dibasic unsaturated aliphatic acid and (b) from 90% to 60% by equivalent weight of a saturated organic acid, and (II) a C to C aliphatic glycol, the amount of (II) being from 140% to 180% of the amount in terms of equivalents theoretically required to react with all of the acid of component (I). These polyesters have an acid value of from to 20.

In FIG. 1 there are shown two gaseous tubes 10 and 11 arranged to be energized by current flowing from the

secondary windings

12 and 13, respectively, of the transformer 19. A single primary winding coil section 14, energized rfom a source of alternating current supply 9, e.g. 110 v. A.C., is used for energizing the secondary

winding coil sections

12 and 13, and all coils are mounted on a single core structure 15. Core structure 15 is formed of a plurality of patterned iron lamina 18 with

coil windings

12, 13 and 14 made of insulated or varnished copper wire and wound on central leg 21.

To obtain a lagging current in the circuit for tube 10, shunt means 21 in the core structure between central leg 22 and outer legs 18 may be used. Any other means such as a choke may also be used. A leading current 3,319,203 Patented May 9, 1967 for lamp 11 is secured by means of condenser 20 in series in the circuit.

The foregoing electrical components are contained within a suitable box 16 having a divider 17 therein. Box 16 and divider 17 may be of any suitable material, e.g. metal, cardboard, etc.

FIG. 2 shows a ballast in accordance with the present invention having the component parts therein embedded in a co-polymerized unsaturated polyester in accordance with the present invention.

It has been found that the transformer hum usually associated with devices utilizing copper wire wound soft iron patterned lamina cores as transformers is substantially eliminated by encasing the transformer as well as the other circuit elements in the co-polymers hereof. These materials have a dielectric strength which is sulficient for use in such electrical apparatus without promoting malfunction thereof due to leakage of currents through the resinous material.

The filler compositions of the present invention are composed of two essential ingredients, one of which is, at once, a solvent for the other and co-polymerizable therewith upon the application of suitable initiators or catalysts, with or without heat. The solvent material, therefore, is generally an aromatic hydrocarbon, preferably of the monocyclic variety characterized by having at least one hydrogen atom thereof replaced with a vinyl substituent. There may be two such vinyl substituents in the molecule and, additionally, one or more of the remaining nuclear hydrogen atoms may be replaced with an alkyl group containing from one to three carbon atoms, or a halogen substituent group. Thus, the solvent material may be selected from the group which includes such notable examples as styrene, di-vinyl benzene, vinyl toluene, alpha methyl styrene, and the like.

The second essential component of the filler compositions of the present invention is, as indicated above, an unsaturated polyester which is co-polymerizable with any one of the solvent materials containing a vinyl substituent such as mentioned above. These unsaturated polyesters differ from the usual unsaturated polyesters primarily in respect of the fact that a large excess of glycol is used in their preparation, and the resulting unsaturated polyester has an acid value well below those normally encountered in unsaturated polyesters.

In general, these polyesters are the result of the interaction of an unsaturated dibasic acid and a glycol, the amount of glycol being substantialy in excess of that which is required to react with the acidic component. A portion of the unsaturated dibasic acid in the polyesters hereof is, however, replaced with a saturated di'basic acid, or a mixture of such saturated dibasic acid with an aliphatic C C mono-carboxylic acid.

For the purposes of this invention and, as is customary in the art of manufacturing polyesters, the aromatic dibasic carboxylic acids are regarded as saturated. Even though the benzene nucleus does contain unsaturated linkages, these unsaturated linkages do not behave in the environment of esterification in the same manner as ethylenic unsaturation in an aliphatic chain.

Hence, the acidic portion of the polyester reaction may be composed of an unsaturated dibasic acid and a saturated dibasic acid, with or without additional mono-basic unsaturated aliphatic acid. The unsaturated aliphatic 'dibasic acid may, therefore, be selected from maleic acid or its anhydride, and fumaric acid. The saturated dibasic 3 acid component may be phthalic acid, its anhydride, isophthalic acid tetrachlorophthalic acid or its anhydride,

sebacic acid, adipic acid, pimelic acid, or the like.

The ratio of unsaturated dibasic acid to saturated dibasic acid is within the range of from 10% to 40% by equivalent weight of unsaturated dibasic acid to from 90% to 60% by equivalent weight of saturated acid.

As indicated above, a portion of the saturated dibasic acid may be replaced with a mono-carboxylic acid, the extent of this replacement may not exceed 50% by eqivalent weight of the saturated dibasic acid component. As indicated above, the mono-carboxylic acid contains from 16 to 18 carbon atoms and is characterized by ethylenic unsaturation. Thus, the acids which are included within the scope hereof include palmitolenic, oleic, iso-oleic, petrolesic, erucic, linoleic, linolenic, elaeostearic acid, clupanodonic. acid, linseed oil fatty acids, rape seed oil fatty acids, tall oil fatty acids, and thelike.

The mixture of acids is cooked with a large excess of a polyol over that which is theoretically required to react with all of the carboxylic acid groups in the aforementioned acidic portion of the esterification mass. This excess amounts to from 40% to 80% excess, or 140% to 180% of the amount in terms of equivalent weight required to neutralize all of the acid.

The polyol used in these filler compositions is a C -C glycol and preferably a C -C alkylene glycol. Specific examples of such glycols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, hexamethylene glycol, 2,3-dihydroxybutane, octylene glycol, and the like.

The polyesters of the present invention maybe produced by any of the conventional esterification procedures, for example, either the solvent type cook or the fusion type cook. In the solvent type cooking procedure water of esterification may be removed azeotropically with a refluxing solvent. Alternatively, the esterification may be conducted under fusion temperatures in the range of 325 F. to 525 F. Cooking is continued until an acid value of from to 20 is secured. Usually from 2 to 18 hours are required to achieve acid values of this low magnitude.

The polyesters produced in accordance herewith are soluble in the vinyl substituted aromatic hydrocarbon solvents previously mentioned, and because of their unsaturated nature, are radially co-polymerizable therewith. These polyesters are conveniently dissolved in such vinyl substituted aromatic hydrocarbon solvents to the extent of from 50 to 80% solids. Normally a small amount of mono-tertiary butyl hydroquinone, for example 0.001% based on the total weight of solution is included to inhibit polymerization during storage. Upon the inclusion of from .05%"to 3% by weight of a free-radical polymerization catalyst, such as benzoyl peroxide, cumene hydroperoxide, and the like. These composed polymerizable solutions of vinyl aromatic hydrocarbon and polyester may be caused to solidify with or withoutthe application of heat in the range of from room temperature to 225 F. by adding a small amount of such a free radical polymerization catalyst to'the composition. The composition in the liquid state may be poured into the ballast case containing the component parts of fluorescent ballast, completely covering the same, and filling all of the void space within the ballast case. Upon completion of the co-polymerization reaction, there is obtained a composite ballast case member such as shown in FIG. 2 having the component parts completely embedded in a c-o-polym- 'erized resinous material as aforesaid, and in which the noise level of the transformer under normal conditions of operation is substantially inaudible.

It becomes convenient at this point to illustrate a manher of making the co-polymerizable position of the present invention by giving specificillustration examples thereof. It is to be understood, however, that these examples are for illustrative purposes only to serve as a guide to those skilled in the art to whom numerous other'examples useful in accordance herewith will become readily apparent in view of these teachings.

Example I The following ingredients in the amount indicated were reacted together to produce a co-polymerizable unsaturated polyester ballast composition having properties listed below:

Equiv.

Diethylene Glycol. Base Input Manufacturing Loss- Bace Yield Styrene Yield, Total Solids, percent..- Viscosity, centipoises Pounds per gallon Acid Value Excess Polyol (based on equiv. wt.) percent; Acids (based on equiv. wt):

Saturated/unsaturated Saturated/fatty acids This polyester was produced by heating the diethylene glycol to a temperature of 250 F. The phthalic anhydride was then added, and the temperature raised from 400-425 F. in one hour. This was held untilan acid number of from 17-20 was secured. Thereupon the heat was allowed to drop spontaneously to 370 F. At this point the maleic anhydride was added, the temperature maintained at 370 F. until the acid number reached a value of from 10-13. The total hold time at this temperature is from 8-10 hours and will vary from batch to batch. The heat is removed and the temperature allowed to fall to 200 F. whereupon the styrene containing a small percentage of tertiary-butyl-hydroquinone was added. The product was then filtered.

This co-polymerizable material can be cured by admixing therewith a free radical polymerization catalyst to produce a clear polyester-styrene co-polymer ballast resin. Alternatively, this resin may have added thereto from 1-3 times its weight of silica, and the entire mass gelled by the addition of 1% by weight of the resin of cumene hydroperoxide.

Example 11 The following example was carried out using the same procedure as set forth in Example I, the following ingredients in the amounts indicated were reactedto produce a product having the characteristics enumerated below:

Name Gms. Mols E quiv.

Maleic Anhydride 88 0. 9 1. 8 Phthalie Anhydride 293 1. 8 3.6 Diethylene G1yco1 501 4 72 9. 45 Base Input 882 Manufacturing Loss. Bace Yield 777 Styrene 333 Yield, TotaL- 1,110

Solids, percent 70 Viscosity, centipoises. Pounds per gallon" 9.62 Acid Value- 13. 0 Excess Polyol (based on equiv. wt.) percent- 74 Acids (baced on equiv. Wt):

Saturated/unsatmated 67/33 Saturated/fatty acids 100/0 The resin thus produced may be used in precisely the same manner as the resin of Example 1.

Example Ill The following ingredients in the amounts indicated were reacted to produce an unsaturated polyester-styrene composition capable'of being co-polymerized to a solid resinous co-polymer upon the addition of a suitable'catalytic agent. The product had the characteristics enumerated below:

Solids, percent Viscosity, centipoises Pounds per gallon" Aoid Value Excess Polyol (based on equiv. wt.) percent- Acids (based on equiv. wt.):

Saturated/unsaturated Saturated/fatty acids This resin 'was also produced by the fusion process in accordance with which the polyol is heated to 250 F., the isophthalic acid added and the temperature raised to 425 F. This temperautre is held for a period varying from 2-3 hours until an acid value of 17-20 is secured. The temperature may be raised as high as 450 F. to shorten this time. The reaction temperature is then spontaneously dropped to from 350 F. to 370 F. at which point the maleic anhydride is added. A small amount, i.e. 0.1% by weight of the acid anhydride of hydroquinone may be added along with the unsaturated acid to inhibit oxidation during the cook. Any other means for inhibiting oxidation during the cook may be employed. Thereupon the temperature of the reaction mass is raised to 400-420 F. where it is held until an acid value of from 5-9 is secured. A light blow of carbon dioxide or other inert gas through the reaction mass at a rate of about cubic feed per minute will assist in arriving at this acid value. The total time at the temperature of 400-420 F. varies from 7-10 hours.

The foregoing resinous material may be used with or without the inclusion of a pigment or resin filler, e.g. calcium carbonate, silica, sand, clay, and the like and cured by the addition of 1% to 2% by weight of the resin of methyl ethyl ketone peroxide as a free radical polymerization catalyst. In making the transformers of the present invention, the co-polymerizable styrene-unsat urated polyester composition is poured into a commercial fluorescent ballast case containing electrical components such as those illustrated in FIGS. 1 and 2 and under the influence of the catalyst is permitted to co-polymerize in place. Ballasts so modified with the resin of this invention was found to produce noise at such a level as to be inaudible in comparison with the same ballast prior to filling.

Example IV The following materials were interacted by the fusion process to produce a co-polymerizable composition useful as a transformer filler, having the characteristics enumerated below:

Manufacturing Loss Base Output Styrene Solids, percent Viscosity, centipoises. Pounds per gallon- Acid Value Excess Polyol (based on eq Acids (based on equiv. wt.):

Saturated/unsaturated Saturated/fatty acids The polyester was produced by heating tall oil fatty acids, isophthalic acid, diethylene glycol, and maleic anhydride to 450 F. in a period of 1.5 to 2 hours. This temperature was held for about 8 hours after which it was reduced to from 400-420 F. At an acid value of about 15, 5 grams of hydroquinone were added, and the cook held at this temperature until an acid value of from 5-10 was obtained. The styrene was added at a temperature of about 200 F. along with 0.01% by Weight of the styrene of tertiary-butyl-hydroquinone. Thereafter, the resultant co-polymerizable composition was filtered. The composition c-ould then be used in the manners previously described with satisfactory results.

amounts indicated to produce a co-polymerizable composition having the properties enumerated below:

Name Gms. Mols Equiv Malcic Anhydride Isophthalic Acid 2, 225 Tall Oil Fatty Acids 4, 740 Diethylene Glycol 3, 580 Pentaerythritol 61 Epoxidized Soya Bean Oil 50 Base Input 12,417 Manufacturing Loss ,8 Base Output 10, 555 Styrene 5, 3 Yield 16, 238

Solids, percent 65 Viscosity T-U Pounds per gallon 8. 55 Acid Value 5. 0 Excess Polyol (based on eq v. wt 44 Acids (based on equiv. wt):

Saturated/unsaturated 72/28 Saturated/fatty acids 63/37 To cook this polyester, the tall Oil fatty acids, diethylene glycol and isophthalic acid were heated to a temperature of 450 F. in about two hours time. The reaction mass was held to this temperature for an additional three to four hours until an acid value of 17-20 was obtained. At this point the maleic anhydride and pentaerythritol were added along with 5 grams of hydroquinone. The cook is held at a temperature of 440-450 F. and blown with an inert gas, e.g. carbon dioxide at the rate 015.20 cubic feet per minute for a period of from 5-8 hours until an acid value of 6-8 is reached.

The cook is now cooled to 200 F. and thinned with the styrene containing a small amount of tertiary-butylhydroquinone as a polymerization inhibitor. Addition of 1% by weight of the resin of a peroxide type free radical polymerization catalyst overcomes the effect of the inhibitor and permits the co-polymerizable material to undergo polymerization. Before solidification has occurred, the co-polymerizable mass including the catalyst is poured into the casing containing the transformer and such other electrical components as may be present, filling the casing completely and allowed to completely copolymerize with or without the application of heat. The resultant transformer containing the compositions hereof exhibits a very greatly reduced noise level or transformer hum. Instead of styrene, alike quantity of vinyl toluene provides a co-polymerizable composition useful in accordance herewith. A satisfactory formulation for copolymerizable compositions is as follows:

Grams The polymerizable compositions of Examples I to V 300 Inert powdered or granular filler 700 Accelerator, e.g. 6% cobalt naphthenate-mineral spirits solution 3 Free radical polymerization catalyst 3 The foregoing examples illustrate procedures by which co-polymerizable compositions useful in accordance herewith may be produced. Any of the ingredients in these illustrative examples may be replaced in part or in whole with any one of the equivalent materials mentioned in a discussion preceding the examples to provide additional examples of co-polymerizable compositions useful herein. The resultant co-polymerizable compositions have viscosities which make them especially adapted for use in filling cases containing transformers and other electrical components, particularly those characterized by an alternating current hum.

Other modes of applying the principles of this invention may be employed instead of those specifically set forth above, changes being made as regards the details herein disclosed provided the elements set forth in any of the following claims, or the equivalent of such be employed.

It is, therefore, particularly pointed'out and distinctly claimed as the invention:

1. In combination in an alternating current transformer having reduced transformer hum characteristics, a filler comprising a co-polymer of a vinyl substituted aromatic hydrocarbon and an unsaturated polyester formed from (I) a mixed organic acid consisting of (a) from 10% to 40% by equivalent weight of a dibasic unsaturated aliphatic acid selected from the group consisting of maleic acid, maleic anhydride and fumaric acid, and (b) from 90% to 60% by equivalent weight of a saturated organic acid selected from the group consisting of phthalic acid, phthalic anhydride, iso-phthalic acid, and mixtures thereof with an ethylenically unsaturated C C aliphatic monocarboxylic acid not in excess of 50% by equivalent weight of the saturated organic acid, and (II) a C to C alkylene glycol, the amount of component (II) being from 140% to 180% of the amount in terms of equivalents theoretically required to react with all the acid of component (I), said polyester having an acid value of from 5 to 20.

2. In combination in an alternating current transformer having reduced transformer hum characteristics, a filler comprising a co-polymer of from 25 to 100 parts by weight of a mono-vinyl substituted monocyclic aromatic hydrocarbon and 100 parts of an unsaturated polyester formed from (I) a mixed organic acid consisting of (a) from to 40% by equivalent weight of a dibasic unsaturated aliphatic acid selected from the group consisting of maleic acid, maleic anhydride and fumaric acid, and (b) from 90% to 60% by equivalent weight of a saturated organic acid selected from the group consisting of phthalic acid, phthalic anhydride, iso-phthalic acid, and mixtures thereof with an ethylenically unsaturated G -C aliphatic monocarboxylic acid not in excess of 50% by equivalent weight of'the saturated organic acid, and (II) a C to C alkylene glycol, the amount of component (n) being from 140% to 180% of the amount in terms of equivalents theoretically required to react with all the acid of component (I), said polyester having an acid value ,of from 5 to 20.

3. In combination in an alternating current transformer having reduced transformer hum characteristics, a filler comprising a co-polymer of from 25 to 100 parts by weight of styrene and 100 parts of an unsaturated polyester formed from (I) a mixed organic acid consisting of (a) from 10% to 40% by equivalent weight of maleic anhydride, and (b) from 90% to 60% by equivalent weight of a saturated organic acid selected from the group consisting of phthalic acid phthalic anhydride, iso-phthalic acid, and mixtures thereof with an ethylenically unsaturated C C aliphatic mono-carboxylic acid not in excess of 50% by equivalent weight of the saturated organic acid, and (II) diethylene glycol, the amount of diethylene glycol being from 1 40 to 180% of the amount in terms of equivalents theoretically required to react with all the acid of component (I), said polyester having an acid value of from 5 to 20. I

4. In combination in an alternating current transformer having reduced transformer hum characteristics, a filler comprising a co-polymer of from 25 to 1 00 parts by weight of styrene, and 100 parts by weight of anunsaturated polyester formed by cooking together at a temperature of from 350 F. to 525 F. to an acid value in the range of from 5 to 20, about a one molar proportion of maleic anhydride, a one molar proportion of isophthalic acid, and a 2.0 molar proportion of tall oil fatty acids, and about 5 moles of diethylene glycol.

5. A fluorescent ballast having reduced hum characteristics comprising a transformer including a core of a plurality of thin patterned sheets of iron in laminar form and having insulated copper Wire wound thereabout, said transformer lbeing immersed in a solid filler comprising a co-polymer of a vinyl substituted aromatic hydrocarbon and an unsaturated polyester formed from (I) a mixed organic acid consisting of (a) from 10% to 40% by equivalent weight of a dibasic unsaturated aliphatic acid selected from the group consisting of maleic acid, maleic anhydride and fumaric acid, and (b) from to 60% by equivalent Weight of a saturated organic acid selected from the group consisting of phthalic acid, phthalic anhydride, iso-phthalic acid, and mixtures thereof with an ethylenically unsaturated C -C aliphatic monocarboxylic acid not in excess of 50% by equivalent weight of the saturated organic acid, and (II) a C to C alkylene glycol, the amount of component (II) being from 140% to 180% of the amount in terms of equivalents theoretically required to react with all the acid of component (I), said polyester having an acid value of from 5 to 20.

6. A fluorescent ballast having reduced hum characteristics comprising a transformer including a core of a plurality of thin patterned sheets of iron in laminar form and having insulated copper wire wound thereabout, said transformer being immersed in a solid filler comprising a co-polymer of from 25 to parts by weight of styrene, and 100 parts of an unsaturated polyester formed by cooking together at a temperature of from 350 F. to 525 F. to an acid value in the range of from 5 to 20, about a one molar proportion of maleic anhydride, aone molar proportion of iso-phthalic acid, and a 2.0 molar proportion of tall oil fatty acids, and about 5 moles of diethylene glycol. I

7. The method of reducing transformer hum in a fluorescent ballast including a core of a plurality of. thin patterned sheets of iron in laminar form and having insulated copper Wire wound thereabout, which comprises the step of immersing said transformer in a co-polymerizable filler composition comprising a 50% to 80% solids solution in a vinyl substituted aromatic hydrocarbon of an unsaturated polyester formed from (I) a mixed organic acid consisting of (a) from 10% to 40% by equivalent weight of a dibasic unsaturated aliphatic acid selected from the group consisting of maleic acid, maleic anhydride and fumaric acid, and (b) from 90% to 60% by equivalent weight of a saturated organic acid selected from the group consisting of phthalic acid, phthalic anhydride, iso-phthalic acid, and mixtures thereof with an ethylenically unsaturated C C aliphatic monocarboxylic acid not in excess of 50% by equivalent weight of the saturated organic acid, and (II) a C to C alkylene glycol, the amount of component (II) being from to 180% of the amount in terms of equivalents theoretically required to react with all the acid of component (I), said polyester having an acid value of from 5 to 210, and copolymerizing said filler composition in situ to provide a composite filler fluorescent ballast.

(References on following page) References Cited by the Examiner FOREIGN PATENTS UNITED STATES PATENTS 515,805 8/ 1955 Canada.

Foster 260 22 OTHER REFERENCES Nischk et a1. 260-76 5 Chatfield, Varnish Constituents, Leonard Hill Limited, Robitschek et a1. 260 -76 London, 1953 3rd Edition, 868 pages, pp. 266-271 and Sample 260-22 288 of interest (Copy in Scientific Library) TP 938 C53. Knobel 336-400 LEON J. BERCOVITZ, Primary Examiner. Hart 260 -22 Herbst 336 96 1o MILTON STERMAN, Examiner. Le Bras et a1. 260-122 R. W. GRIFFIN, Assistant, Examiner.

Claims

1. IN COMBINATION IN AN ALTERNATING CURRENT TRANSFORMER HAVING REDUCED TRANSFORMER HUM CHARACTERISTICS, A FILLER COMPRISING A CO-POLYMER OF A VINYL SUBSTITUTED AROMATIC HYDROCARBON AND AN UNSATURATED POLYESTER FOMED FROM (I) A MIXED ORGANIC ACID CONSISTING OF (A) FROM 10% TO 40% BY EQUIVALENT WEIGHT OF A DIBASIC UNSATURATED ALIPHATIC ACID SELECTED FROM THE GROUP CONSISTING OF MALEIC ACID, MALEIC ANHYDRIDE AND FUMARIC ACID, AND (B) FROM 90% TO 60% BY EQUIVALENT WEIGHT OF A SATURATED ORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF PHTHALIC ACID, PHTHALIC ANHYDRIDE, ISO-PHTHALIC ACID, AND MIXTURES THERE-