US2743309A - Thixotropic unsaturated alkyd resin compositions and members produced therewith - Google Patents

Description

United States Patent THIXOTROPIC UNSATURATED ALKYD RESIN COMPOSITIONS AND MEMBERS PRODUCED THEREWITH No Drawing. Application November 19,

Serial No. 321,492

7 Claims. (Cl. 174-437) This invention relates to thermosetting polyester resins and cast members produced therewith.

In making electrical insulating members, it is often desirable to employ resinous materials that may be cast to a predetermined shape. members are particularly critical in building line traps or tuned filters of the type set forth in the following application copending herewith: Edward W. Lindsay and Ralph E. Marbury. Serial No. 344,812, filed March 26, 1953. in such electrical traps, heavy copper conductors are wound into coils wherein the turns of the conductors may be separated by air gaps of the order of from inch to a few inches at most. These traps are placed in highvoltage, high-amperage circuits. When high amperage currents pass through the conductors, the conductors are attracted to one another with considerable force. Therefore, the insulating material applied to the conductors to space them apart and maintain them in proper position must have high compressive strengths even at elevated temperatures of the order of 100 C. to which these line U traps may be subjected. In many instances, these line traps are placed in exposed locations where they are subjected to rain and weathering. Consequently, the cast resinous materials must withstand weathering and have very low moisture absorption.

The dielectric characteristics of the insulating materials employed in building these line traps are equally critical with the physical properties required. The electrical loss factor should not exceed 0.l for the Whole range of expected operating temperatures. The loss factor is the product of power factor and dielectric constant. The power factor should be low and is desirably not over 0.02 for frequencies of 30 to 300 kilocycles. A low dielectric constant of the order of less than 4 is equally desirable. other falls with changes in temperature. The increase in both power factor and dielectric constant with temperature increase should be low.

in building line traps, it is highly desirable to have a resin that may be poured into molds having crevices or openings of substantial size, that is, up to M4 inch in width, without the resin in the liquid state escaping hrough such crevices in any significant amount. The resinous composition should be such that when catalyzed, i t will set at room temperature in several hours. In order to be able to pour the resin into elongated molds that may be as much as 10 feet in length and only 2 or 5 inches in transverse dimensions and with many corners to fill, one must have a resinous composition of a low viscosity. it will be appreciated that these factors require an unusual resinous composition.

The object of this invention is to provide a completely reactive polyester composition that will thermoset at room temperature in several hours to produce cast resinous members having high strength, low moisture absorption, and low electrical losses.

A further object of the invention is to provide thermo- Such cast resinous insulating However, the one may rise while the set resinous members having characteristics enabling their use in line traps.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

We have discovered a novel resinous composition having unusual characteristics. In particular, this resinous composition may be introduced into long molds of up to ten feet in length, for example, having transverse dimensions of only a few inches such that the resinous composition will fill the mold completely, and the resinous composition possesses thixotropic properties such that a ew seconds after being introduced into the mold, the resinous composition will not exude through substantial sized crevices of the order of up to /4 inch. The resinous composition will thermoset at room temperature in several hours to produce a strong cast member having outstanding dielectric properties.

More particularly, the resinous composition comprises essentially (1) from 59% to 63% by weight of a resinous material comprising (a) from 25% to 38% by weight of at least one unsaturated aryl compound selected from the group of monostyrene and simple alkyl substitution derivatives thereof, such, for example, as paramethyl styrene and alphamethyl styrene and (b) from to 62% by weight of a polyester resin dissolved in the unsaturated aryl compound (the composition of the polyester resin will be disclosed hereinafter), (2) from 37% to 41% by weight of a finely divided mica filler, the filler may include small amounts of up to 20% of the weight of the mica, of at least one of the group consisting of silica, glass fibers, nylon fibers, fibers of acrylonitrile resins, polyethylene tercphthalate fibers, or other synthetic resinous fiber, and powdered glass, the tiller being thoroughly admixed in the resinous material, the mixture of (1) and (2) having a viscosity of 1500:200 centipoises, and (3) a catalyst equal to at least 0.5% of the weight of the resinous material but not exceeding 5% thereof, the com position of the catalyst being set forth hereinafter.

The polyester resin ([9) of the composition above is the reaction product of at least one glycol selected from the group consisting of ethylene glycol, 1,2-propylene glycol, and Lil-propylene glycol, and a mixture of 1 mol of at least one unsaturated acid from the group consisting of fumaric acid, maleic acid, and maleic anhydride, and from 0.1 to l mol of a dicarboxylic acid selected from at least one of the group consisting of phthalic anhydride, diglycolic acid, and dicarboxylic acids having a chain of from 2 to 7 carbon atoms between terminal carboxyl groups, the mols of the glycol being equal to at least the mols of the mixture of acids but not exceeding a 20% excess of the mols of the acids. The glycols and mixture of acids are heated to a temperature of from 200 C. to not in excess of 250 C. for a period of time not over 10 hours at this temperature until the reaction product has a viscosity of from O to Q on the Gardner-Holdt scale when measured as a solution containing 65% of the polyester resin and 35% by weight of monostyrene. The acid number of the resin will be between 30 and 60.

In order to promote room-temperature curing of the resinous material comprising the solution of the unsaturated aryl compound and polyester resin, a mixture of catalysts is selected, the mixture comprising at least 0.1% of a metal drier, particularly cobalt and lead driers, such, for example, as cobalt naphthenate, cobalt linoleate and lead octoate, and the balance comprising at least 0.3% of at least one peroxide catalyst selected from the group consisting of methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, methyl amyl ketone peroxide, tert-butyl hydroperoxide, hydroxyheptyl peroxide, and 1-hydroxycyclohexyl hydroperoxide-l.

The finely divided mica filler is preferably powdered to :pass 100-mesh screen. We have secured good results with 3.25-rnesh ,mica. .Added glass fibers may he in lengths not exceeding an average of from /2 inch to inch. Nylon, acrylonitrile and other synthetic resin fibers may be of :similar .lengths. The diameter of .glass fibers is of the order of 0.002 inch and finer. The syntheticresin .fibers may beof about 1.5 denier. The .resinous fibers will be hereinafter designated as fibers of synthetic resins, Up' to 20% of the weight of .thesmica may 'comprise :silica of 100 mesh fineness or :the fibrous additives or both.

The following examples illustrate :the preparation of the resinous :compositiorrsof the "invention:

Example 1 Into a reaction vessel, there were charged the following ingredients:

7 Mols Fumaric acid 1.4 Phthalic anhydride 1 Propylene glycol 2.65

Temp. range, C. Time at temp, Hrs.

Viscosity measurements on the reaction product were :run

from time to time until a solution comprising 65% of the reaction product and monostyrene :had a viscosity of P on the Gardner-Holdt scale. The "final acid number of the polyesterlresin was ,53. The .reaction product was cooled rapidly from the final temperature, and there was added 0.03% by weight of hydroquinone. A composition was prepared by taking .61 .parts by weight of arnixture of 65% of the polyesterzof Example I dissolved'in 35% by Weight of monostyrene. The .61 parts of solution were then placed ina Banbury-type amixer,.and 39 .parts of 325,-meshmica was :added to the resin solution. The Banbury mixer was evacuated, and the mica and solution were thoroughly -admixed. The composition was 30f .fairly thin consistency when subjecte to stirring. However, .it possessed :notable thixotropic properties such that when permitted to stand .for a short period of time, .it became quite thick and flowed with considerable difficulty. The viscosity of this mixture was approximately 1500 .centipoi'ses. ,In order to cast .members from the mixture of resin andmica, there was added 01% ofa cobalt naphthenate and 0.5% ,ofmethylcthyl ketone peroxide dissolved in dimethyl phthalate. The peroxide content of the solution comprised 60%. ;At room temperature (25 C. the resinous composition gelled in 110 minutes. Members produced by introducing the composition into molds were tested for their electrical properties and had a 100 kilocycle .power factor of 0.0082 at .20" C. while thepower factor at 115 C. was 0.0215. The dielectric constant at ,100 kilocycles at 20 C. was 3.63 and .at 115 C. it was 3.99. It is expected that line trap temperatures will not exceed about 105 C.

Example-.11

Into a reaction vessel similar to thatused in Example I, P

there were introduced the following:

Propylene glycol 6.6

The reaction was carried out essentially as set forth in Power .Factor Dielectric-Constant Temp C.

Cycles 100 kc. (SO-Cycles 10mm,

The compositions :disclosed herein have been .introduced into split steel molds several feet long having several dozen openings through which passed some thirty turns ofcopper conductor about '1 inch in diameter, there .being numerous fissures, cracks and crevices the full length of :the mold and particularly at the openings through which the copper conductors pass. The catalyzed resinous composition disposed in a large steel .drum was readily introduced therefrom by means of a pump and a hose into the mold, and satisfactory .filling of the mold was secured. Very little of the polyester resin exuded through the numerous openings. In .a matter of several hours at 25 C., the resinous composition gelled and it was fully thermoset in several more hours.

The room-temperature curing .resins disclosed herein have a number of particularly desirableproperties which provide for exceptional results when used for casting purposes. When .poured into casting molds, the fluid polyester resin compositions exhibit thixotropic properties so that they rapidly thicken and are retained in place without material leakage even though the molds ,contain many crevices and fissures. The cast resin compositions begin to thicken and in a few hours reach the gel state. By contrast, a polyester resin composition requiring heating to cause curing, will initially thin out when heat is applied and a considerablequantity thereof will seep out of'the fissured and creviced mold, before suficient gelat'ion takes place to prevent such loss. We have found further that room temperature curing polyester resin compositions react more slowly so that exothermiciheat due to polymerization results both ina lower temperature gradient and in a much lower maximum temperature in the reacting composition than with oven cured polyester compositions. By using the polyester compositions of this invention, we have produced polyester castings many 'feet inlength free from cracks, voids or'other flaws.

When line traps prepared with the resins of this composition were subjected to short-circuit tests, the resinous compositions were found to withstand the heavy forces applied thereto without any difiiculty. The electrical properties of the resinous insulators in these line traps were not affected appreciably by exposure to weather.

It will be understood that the compositions disclosed herein are critical, and the proportions may notbe departed from substantially Without resulting in serious degradation of the desirable electrical and physical properties.

We claim as our invention:

1. A resinous composition which may be castin molds having sizable .crevices without substantially leaking out and will cure in the molds to a thermoset body in several hours at room temperature, comprising essentially '(1) from 59% to 63% by weight of a resinous material comprising "(a') from 25% to 38% by weight of at least one unsaturated aryl compound selected from the group consisting of monostyrene and simple alkyl substitution derivatives thereof, and (b) from 75% to 62% by weight of a polyester resin soluble in the unsaturated aryl compound, the polyester resin being the reaction product of at least one glycol selected from the group consisting of ethylene glycol, 1,2-propylene glycol and 1,3-propylene glycol and a mixture of one mol of at least one unsaturated acid from the group consisting of fumaric acid, maleic acid and maleic anhydride, and from 0.1 mol to 1 mol of a dicarboxylic acid se lected from at least one of the group consisting of phthalic anhydride, diglycolic acid and dicarboxylic acids having a chain of from 2 to 7 carbon atoms between terminal carboxyl groups, the mols of the glycol being equal to at least the mols of the mixture of acids but not exceeding a 20% excess of the mols of the acids, the resinous material having a viscosity of from O to Q on the Gardner-Holdt scale, (2) from 37% to 41% by weight of a finely divided filler comprising essentially mica alone to render the composition thixotropic, the filler being thoroughly admixed in the resinous material and the mixture of (1) and (2) having a viscosity of 15001-200 centipoises, and (3) a catalyst equal to at least 0.5% of the weight of the resinous material but not exceeding 5% thereof, the catalyst comprising at least 0.1% of a metal drier and the balance being at least 0.3% of at least one peroxide catalyst selected from the group consisting of methyl ethyl ketone peroxide, methyl amyl ketone peroxide, methyl isobutyl ketone peroxide, tert-butyl hydroperoxide, hydroxyheptyl peroxide and l-hydroxycyclohexyl hydroperoxide-l, the cured resinous castings of the composition having high strength and low electrical losses.

2. A resinous composition suitable for casting in molds having crevices without appreciable leakage, and which will cure to a thermoset casting in several hours at room temperature, comprising essentially (1) from 59% to 63% by weight of a resinous material comprising essentially (a) from 25% to 38% by weight of monostyrene and (b) from 75% to 62% by weight of a polyester resin soluble in the monostyrene, the polyester resin being the reaction product of 1.4 mols of fumaric acid, 0.8 to 1.2 mols of phthalic anhydride and from 2.2 to 2.8 mols of propylene glycol, the acids and the glycol being admixed and heated to a maximum temperature of 250 C. to an acid number of about 55, the resinous material having a viscosity of about P on the Gardner-Holdt scale, (2) from 37% to 41% by weight of a divided mica, the mica being thoroughly admixed in the resinous material and the mixture of (1) and (2) having a viscosity of 1500x200 centipoises, and (3) a catalyst equal to at least 0.5 of the weight of the resinous material, but not exceeding 5% thereof, the catalyst comprising at least 0.1% of a metal drier and the balance being at least 0.3% of at least one peroxide catalyst selected from the group consisting of methyl ethyl ketone peroxide, methyl amyl ketone peroxide, isobutyl ketone peroxide, tert-butyl hydroperoxide, hydroxyheptyl peroxide and l-hydroxycyclohexyl hydroperoxide-1, the cured resinous castings of the composition having high strength and low electrical losses.

3. A resinous composition suitable for casting in molds having crevices without appreciable leakage, and

which will cure to a thermoset casting in several hours at room temperature, comprising essentially 1) from 59% to 63% by weight of a resinous material comprising essentially (a) from 25% to 38% by weight of monostyrene and (b) from to 62% by weight of a polyester resin soluble in the monostyrene, the polyester resin being the reaction product of 1 mol of fumaric acid, from 0.15 to 0.25 mol of adipic acid and 1.1 to 1.24 mols of propylene glycol, the acids and the glycol being admixed and heated to a maximum tempera ture of 250 C. to an acid number of about 55, the resinous material having a viscosity of about P on the Gardner-Holdt scale, (2) from 37% to 41% by weight of a finely divided filler comprising essentially mica of an average fineness to pass a mesh screen to render the composition thixotropic, the filler being thoroughly admixed in the resinous material and the mixture of 1) and (2) having a viscosity of 1500:200 centipoises, and (3) a catalyst equal to at least 0.5 of the weight of the resinous material, but not exceeding 5% thereof, the catalyst comprising at least 0.1% of a metal drier and the balance being at least 0.4% of at least one peroxide catalyst selected from the group consisting of methyl ethyl ketone peroxide, methyl amyl ketone peroxide, isobutyl ketone peroxide, tert-butyl hydroperoxide, hydroxyheptyl peroxide and l-hydroxycyclohexyl hydroperoxide-l, the cured resinous castings of the composition having high strength and low electrical losses.

4. The fully cured, thermoset resinous member composed of the composition of claim 1.

5. In an electrical line trap device comprising an electrical conductor and insulating supports for maintaining the electrical conductor in position, the insulating supports comprising a fully cured, thermoset resinous composition cast about portions of the electrical conductor, the resinous composition composed of the composition of claim 1.

6. In an electrical line trap device comprising an electrical conductor and insulating supports for maintaining the electrical conductor in position, the insulating supports comprising a fully cured, thermoset resinous composition cast about portions of the electrical conductor, the resinous composition composed of the composition of claim 2.

7. In an electrical line trap device comprising an electrical conductor and insulating supports for maintaining the electrical conductor in position, the insulating supports comprising a fully cured, thermoset resinous composition cast about portions of the electrical conductor, the resinous composition composed of the composition of claim 3.

References Cited in the file of this patent UNITED STATES PATENTS 2,537,375 Simon et a1. Jan. 9, 1951 2,610,959 Nordlander Sept. 16, 1952 2,677,067 Johnson et al. Apr. 27, 1954 FOREIGN PATENTS 500,339 Belgium Jan. 15, 1951 500,343 Belgium Ian. 15, 1951

Claims (2)

1. A RESINOUS COMPOSITION WHICH MAY BE CAST IN MOLDS HAVING SIZALBE CREVICES WITHOUT SUBSTANTIALLY LEAKING OUT AND WILL CURE IN THE MOLDS TO A THERMOSET BODY IN SEVERAL HOURS AT ROOM TEMPERATURE, COMPRISING ESSENTIALLY(1) FROM 59% TO 63% BY WEIGHT OF A RESINOUS MATERIAL COMPRISING (A) FROM 25% TO 38% BY WEIGHT OF AT LEAST ONE UNSATURATED ARYL COMPOUND SELECTED FROM THE GROUP CONSISTING OF MONOSTYRENE AND SIMPLE ALKYL SUBSTITUTION DERIVATIVES THEREOF, AND (B) FROM 75% TO 62% BY WEIGHT OF A POLYESTER RESIN SOLUBLE IN THE UNSATURATED ARYL COMPOUND, THE POLYESTER RESIN BEING THE REACTION PRODUCT OF AT LEAST ONE GLYCOL SELECTED FROM THE GROUP CONSITING OF ETHYLENE GLYCOL, 1,2-PROPYLENE GLYCOL AND 1,3-PROPYLENE GLYCOL AND A MIXTURE OF ONE MOL OF AT LEAST ONE UNSATURATED ACID FROM THE GROUP CONSISTING OF FUMARIC ACID, MALEIC ACID AND MALEIC ANHYDRIDE, AND FROM 0.1 MOL TO 1 MOL OF A DICARBOXYLIC ACID SELECTED FROM AT LEAST ONE OF THE GROUP CONSISTING OF PHTHALIC ANHYDRIDE, DIGLYCOLIC ACID AND DICARBOXYLIC ACIDS HAVING A CHAIN OF FROM 2 TO 7 CARBON ATOMS BETWEEN TERMINAL CARBOXYL GROUPS, THE MOLS OF THE GLYCOL BEING EQUAL TO AT LEAST THE MOLS OF THE MIXTURE OF ACIDS BUT NOT EXCEEDING A 20% EXCESS OF THE MOLS OF THE ACIDS, THE RESINOUS MATERIAL HAVING A VISCOSITY OF FROM 0 TO Q ON THE GARDNER-HOLDT SCALE, (2) FROM 37% TO 41% BY WEIGHT OF A FINELY DIVIDED FILLER COMPRISING ESSENTIALLY MICA ALONE TO RENDER THE COMPOSITION THIXOTROPIC, THE FILLER BEING THOROUGHLY ADMIXED IN THE RESINOUS MATERIAL AND THE MIXTURE OF (1) AND (2) HAVING A VISCOSITY OF 1500+200 CENTIPOISES, AND (3) A CATALYST EQUAL TO AT LEAST 0.5% OF THE WEIGHT OF THE RESINOUS MATERIAL BUT NOT EXCEEDING 5% THEREOF, THE CATALYST COMPRISING AT LEAST 0.1% OF A METAL DRIER AND THE BALANCE BEING AT LEAST 0.3% OF AT LEAST ONE PEROXIDE CATALYST SELECTED FROM THE GROUP CONSISTING OF METHYL ETHYL KETONE PEROXIDE, METHYL AMYL KETONE PEROXIDE, METHYL ISOBUTYL KETONE PEROXIDE, TERT-BUTYL HYDROPEROXIDE, HYDROXYHEPTYL PEROXIDE AND 1-HYDROXYCYCLOHEXYL HYDROPEROXIDE-1, THE CURED RESINOUS CASTINGS OF THE COMPOSITION HAVING HIGH STRENGTH AND LOW ELECTRICAL LOSSES.

5. IN AN ELECTRICAL LINE TRAP DEVICE COMPRISING AN ELECTRICAL CONDUCTOR AND INSULATING SUPPORTS FOR MAINTAINING THE ELECTRICAL CONDUCTOR IN POSITION, THE INSULATING SUPPORTS COMPRISING A FULLY CURED, THERMOSET RESINOUS COMPOSITION CAST ABOUT PORTIONS OF THE ELECTRICAL CONDUCTOR, THE RESINOUS COMPOSITION COMPOSED OF THE COMPOSITION OF CLAIM 1.