CA1224595A - Two-part, low-viscosity epoxy resin composition - Google Patents
Two-part, low-viscosity epoxy resin compositionInfo
- Publication number
- CA1224595A CA1224595A CA000442307A CA442307A CA1224595A CA 1224595 A CA1224595 A CA 1224595A CA 000442307 A CA000442307 A CA 000442307A CA 442307 A CA442307 A CA 442307A CA 1224595 A CA1224595 A CA 1224595A
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- Canada
- Prior art keywords
- epoxy resin
- resin composition
- dicarboxylic acid
- anhydride
- hardener
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Abstract of the Disclosure A two-part, low-viscosity epoxy resin potting composition cures to a tough, semi-flexible, thermoset state affording good electrical insulation, good resistance to thermal and mechanical shock, and the cured product does not deteriorate upon prolonged exposure to tropical environment. These properties are attained by employing as the hardener part of the composition a mixture of liquid carboxyl-terminated polyester, low-melting cycloaliphatic anhydride, and imidazole catalyst. The hardener part of the composition is surprisingly resistant to decarboxyla-tion during storage.
Description
-l- 1224595 TWO-PART, LOW-VISCOSITY EPOXY RESIN COMPOSITION
Technical Field The invention concerns a two-part, low-viscosity epoxy resin potting composition which provides cured, electrical-insulating products that are "semi-flexible", that is, have a Shore D hardness of less than 90, and hence have good resistance to thermal and mechanical shock.
Background Art Epoxy resin compositions are known which have sufficiently low viscosity to be used for potting elect tribal components and cure to a tough, semi-flexible, thermoses state providing good electrical-insulating properties at temperatures as high as 155C, good resistance to thermal and mechanical shock, and good flame retardancy. However, it is believed that the cured products of every prior potting composition having those attributes gradually deteriorate from exposure to the sort of hot, humid environment that prevails in the tropics.
United States MOLLY, Levi. G, requires retention of at least ninety percent of the original Shore D hardness after exposure to 71~C at 95% RHO for 120 days while retaining a volume resistivity value greater than 1 x 1012 ohm-cm.
An epoxy resin potting composition which cures to a tough, semi-flexible, therlrloset state providing good electrical-insulating properties is disclosed in US.
Patent No. 3,523,143 (Queuing), Preferred compositions of the Queuing patent are marketed in two parts. One part come proses liquid polyglycidyl ether of bisphenol A. The other part comprises a mixture of likelihood carboxyl-terminated polyp ester of dicarboxylic acid and polyalkylene glycol, low-melting cyclic dicarboxylic acid android, and a catalyst.
Cured products ox the working examples of the Queuing patent would no-t meet the aforementioned MIX specification.
Technical Field The invention concerns a two-part, low-viscosity epoxy resin potting composition which provides cured, electrical-insulating products that are "semi-flexible", that is, have a Shore D hardness of less than 90, and hence have good resistance to thermal and mechanical shock.
Background Art Epoxy resin compositions are known which have sufficiently low viscosity to be used for potting elect tribal components and cure to a tough, semi-flexible, thermoses state providing good electrical-insulating properties at temperatures as high as 155C, good resistance to thermal and mechanical shock, and good flame retardancy. However, it is believed that the cured products of every prior potting composition having those attributes gradually deteriorate from exposure to the sort of hot, humid environment that prevails in the tropics.
United States MOLLY, Levi. G, requires retention of at least ninety percent of the original Shore D hardness after exposure to 71~C at 95% RHO for 120 days while retaining a volume resistivity value greater than 1 x 1012 ohm-cm.
An epoxy resin potting composition which cures to a tough, semi-flexible, therlrloset state providing good electrical-insulating properties is disclosed in US.
Patent No. 3,523,143 (Queuing), Preferred compositions of the Queuing patent are marketed in two parts. One part come proses liquid polyglycidyl ether of bisphenol A. The other part comprises a mixture of likelihood carboxyl-terminated polyp ester of dicarboxylic acid and polyalkylene glycol, low-melting cyclic dicarboxylic acid android, and a catalyst.
Cured products ox the working examples of the Queuing patent would no-t meet the aforementioned MIX specification.
-2- 557-2702 If a cycloaliphatic android were substituted for the tetrapropenyl succinic android used in most of the working examples of the Queuing patent, the cured products might be sufficiently resistant to a hot, humid environment to meet the MIX
specification. However, the android would tend to decarboxylate gradually during storage at ordinary room temperatures, as evidenced by evolving gas.
Some cycloaliphatic androids such as tetrahydro-phthalic android by themselves have high melting points but in admixture with other cyclic dicarboxylic acid androids can provide low-melting android mixtures as taught in US. Patent No. 3,078,235 (Bowman et at.).
Disclosure of Invention The present invention concerns a two-part, low-viscosity epoxy resin potting composition which cures to a tough, semi-flexible, thermoses state providing good electrical-insulating properties at 155C, good resistance to thermal and mechanical shock, and also satisfactory resistance to deterioration upon prolonged exposure to tropical environment.
As in the Queuing patent, one part of the novel composition comprises liquid polyglycidy] ether of bisphenol A and the other part is a hardener comprising a mixture of liquid carboxyl-terminated polyester of dicarboxylic acid and polypropylene glycol having no more than one ester group per 500 average molecular weight, 1~4595 -pa- 557-2702 cyclic dicarboxylic acid android having a melting point of less than 40C, and a catalyst, wherein the cyclic dicarboxylic acid android primarily comprises low-melting cycloaliphatic android, and the catalyst is an imidazole.
Also as in the Queuing patent, there are approximately 0.9 to 1.3 epoxy groups for each android group of the android plus each carboxyl group of the polyester.
, .~., The epoxy resin colnposition of the present invent lion differs from that of the Queuing patent in that the cyclic dicarboxylic acid android primarily comprises low-melting cycloaliphatic android and the catalyst is an imidazole.
Mixtures of low-mel~ing cycloaliphatic android and imidazole, when stored at ordinary room temperature in admixture with the carboxyl-terminated polyester, are surprisingly resistant to decarboxylation and should remain fully effective after being stored a year or more at ordinary room temperatures.
Many uses for electrical-insulating potting come positions require flame retardancy, even though known flame-retarding additives tend to impair certain electrical-insulating properties. Where lame retardancy is important, the composition of the present invention preferably also includes a bromina-ted compound in an amount providing at least 5 parts, preferably at least 10 parts, of bromide per 100 parts by weight of total interactive ingredients of the novel potting composition. The brominated compound may either be an inert filler material such as decabromodiphenyl ether or a viscous delineate such as pentabromodiphenyl ether. Preferably the novel potting composition also contains up to one part of antimony trioxides per part by weight of bromide.
Inert Miller may comprise at least lo by weight of the total composition in order to provide optimum resistance to thermal and mechanical shock. At least half of the inert filler should be inorganic because this economically enhances flame retardancy and also has a mechanical reinforcing effect. Preferred inorganic fillers include calcium and magnesium silicates, calcium carbonate, talc, silica, and mica.
To provide a composition having both 10% or more filler content and desirably low viscosity, each of the liquid polyglycidyl ether arid the liquid carboxyl-terminated polyester Schloss have a viscosity not exceeding ~224595 20,000 cups at 25C oven lower viscosities are preferred and, to this end, the dicarboxylic acid used in making the polyester preferably is aliphatic or cycloaliphatic and desirably has ethylenic unsaturation. Malefic android is especially useful. However, any dicarboxylic acid may be used as long as the viscosity of the polyester does not exceed 20,000 cups at 25C.
The low-melting cycloaliphatic android may be provided either by a single cycloaliphatic android which by itself has a melting point below 40C or by a mixture of one or more cycloaliphatic androids and one or more other cyclic dicarboxylic acid androids, some of which by themselves have melting points above 40C, but which together have a melting point below 40C as taught in Us Patent No. 3,07~,235 (cowman et at.). useful cycle-aliphatic androids include hexahydrophthalic android, MOP. 35C; methylhexahydrophthalic android, MOP. <-15C;
tetrahydrophthalic android, MOP. 10~C; methyltetrahydro-phthalic android, MOP. 63C; endomethylene-tetrahydro-phthalic android ("Nadir" android) MOP. 120C; andmethylenclomethylenetetrahydropllthalic android ("Methyl Nadir" anhydricle) Pi <-15C. Other cyclic dicarboxylic acid androids which may be blended with one or more of the cycloaliphatic androids in compositions of the pro-sent invention include phtllalic android, MOP. 130C; but the anhyclride mixture shallowly be primarily cycloaliuhatic.
If the low-melting cycloaliphatic android or its mixture with other cyclic dicarboxylic acid androids were to have a melting point much higher than 40C, it would tend to crystallize and then need to be heated to provide a homogeneous liquid before being blended with the polyglycidyl ether. To insure against crystallization, the melting point of the low-melting cycloalipha-tic android or android mixture is desirably less than 20C.
For ease of Mooney, the viscosities of the polyglycidyl ether portion and the hardener portion of the two-part epoxy resin potting composition of the invention l~X~595 -5_ 557-2702 should be approximately the same, and inert filler should comprise no more than 70% by weight of each part. Usually inert filler comprises no more than 50% by weight of the total compost it ion since its viscosity might otherwise be too high to impreg-Nate minute interstices such as the spaces between the wires of an electrical coil. For good impregnation, the individual filler particles preferably are quite fine (e.g., less than 30 micrometers) and have a cubic or equi-axial shape, as opposed to needle-like or plate-like particles. Because exceedingly fine particles tend to produce unduly increased viscosities, a preferred particle size range is from 5 to 20 micrometers.
Preferred imidazole catalysts include imidazole, 2-ethylimidazole, and 2-ethyl-4-methylimidazole. The imidazole catalyst preferably is used in an amount from 0.2 to I by weight of the polyglycidyl ether. At lesser amounts, the curing rate tends to be too slow. At greater amounts, the composition obtained by mixing the hardener and polyglycidyl ether parts might have undesirably short pot life.
Although the epoxy resin composition of the invention is primarily useful for potting electrical components, it may be used as a dipping composition, and for such use, it should include a thixotropic filler.
When used for potting electrical components, the process involves preparation of the subject composition, and, after mixing, pouring same onto the electrical device to impreg-Nate and cover substantial portions thereof, and heating the device and the mixture with which it is impregnated and covered to cure the mixture to a tough, semi-flexible, thermoses state.
aye- 1224595 557-2702 In the following examples, all parts are by weight.
A two-part liquid epoxy resin composition was prepared as follows:
Resin Part A
195 grams liquid polyglycidyl ether of bisphenol A having an epoxy equivalent of 175-210 and a viscosity of 11,000 - 15,000 centipoises at 25C.
1~24595 104.8 grams calcium carbonate having an average particle size of 10 micrometers ("Gamma-Sperse"
255 from Georgia warble Co.) 86.2 grams decabromodiphenyl ether 14 grams antimony trioxides To the polyglycidyl ether in a vessel with a turbine type mixer, the calcium carbonate was mixed in, followed by the brominated compound and the antimony trioxides After being uniformly mixed, this material was set aside as Resin Part A.
Hardener Part B
128.4 grams acid-terminated divester of two moles of rnaleic android and one mole of polypropylene ylycol having an average molecular weight of 1025 (Example III of So 3,523,143) 110.~ cruelness rnethylhexahydrophthalic android 1.1 grams 2-ethyl-4-me~hyl imidazole 0.02 gram silicone anti-foam agent (DB-100, Dow Corning) 358.1 grams calcium carbonate ("Gamma-Sperse"~255) The acid-terminated divester was charged to a mixing vessel into which the android was mixed, followed by the imidazole and the silicone fluid. Finally the calcium carbonate ways aided an-l us orlrlly mixed into the batch to provide Hardener Part B.
Two parts of Resin Part A and three parts of Hardener Part B when blended had a viscosity of 20,000 cups at 25C and a gel time of 17 minutes at 121C. After decoration, the blended material was poured into molds and cured for four hours in a 120C oven. After cooling, the cured specimens were tested.
*I trade Clark Property Test Method Value Specific Gravity 1.71 Thermal 1/8" (3.2 mm) Olyphant Pass 10 cycles shock insert, test temp. cycle 130C to -55C
[M. Olyphant, Jr.; National Conference on the Application of Electrical Insular lion sponsored jointly by NEMO and Am.
10 Inst. of Electrical Engineers, 1958, Paper No. 85; pup 1118-35.]
Flame United States EDITED Pass Retardancy Method 2021 1/8" (3.2 mm) (non-burning) thickness US Subject 94 V-O rating 1/4" (6.4 mm) thickness Moisture united States FED-STD-406 0.0125%
Absorption Method 7031 1" by 3" by 1/8"
(2.5 by 7.5 by 0.3 cm) specimens, 24 hour immersion Hydrolytic 168 his. in scaled contailler Stability a 120C and 17 psi (117 IcPa) water vapor, 5" by 1/2" by 1/4"
(13 by 1.3 by 0.6 cm) specimens Hardness, before 81 Shore D
Hardness, after 79 Shore D
Volume Resistivity, before >1015 ohm-cm Volume Resistivity, after 1012 ohm-cm dielectric 1/8" (3.2 mm) specimen 340 volts/mil Strength 500 v/sec rate of rise (13.6kV/mm) -8- ~2~4595 The above Hydrolytic Stability test method is believed to be more rigorous than is the above-cited US. MOLLY, Rev. G.
another cured specimen 2" by 2" by 1" (5 by 5 by 2.5 cm) was immersed in water and heated in a sealed vessel at 125C or 28 days. This caused surface blistering, and the Shore D hardness was reduced from an initial value of 85 to 55. These test results indicate that cured products of this example have extraordinarily good hydrolytic stability for a semi-flexible cured product of an epoxy resin composition.
Cured specimens of Example 1 were also tested for dissipation factor and dielectric constant. The following results (averages of two tests) show that dissipation factor when measured at low frequencies is poor at high temperatures, a common characteristic of cured epoxy resin products which have good flame retardancy.
dissipation Factor Dielectric Constant (%) Tampa loo 1 10 100 100 1 10 100 ( C) tlzkHz kHz ktlz Ho kHzkHz kHz 24 2.22.2 2.1 2.1 5.14.84,7 4.6 106 >20 Lo 5.9 I 8.76.86.3 6.0 130 >20 >20 8.0 4.4 NT 7.26.5 6.1 25155 >20,>20 14 4.1 NT 8.36.5 6.0 NT = not tested Examples 2-5 Four two-part liquid epoxy resin compositions were Prepared silnilar to aye ox example I except that all fillers were omitted. In three of the your, other cycloaliphatic androids were substituted for the methylhexahydropllthalic android. Each composition was cured and tested for hydrolytic stability as in Example 1.
- 9- 1~:24~;95 Example Android Shore D
2 Methylhexahydroph~halic Before, 78-79 After, 76
specification. However, the android would tend to decarboxylate gradually during storage at ordinary room temperatures, as evidenced by evolving gas.
Some cycloaliphatic androids such as tetrahydro-phthalic android by themselves have high melting points but in admixture with other cyclic dicarboxylic acid androids can provide low-melting android mixtures as taught in US. Patent No. 3,078,235 (Bowman et at.).
Disclosure of Invention The present invention concerns a two-part, low-viscosity epoxy resin potting composition which cures to a tough, semi-flexible, thermoses state providing good electrical-insulating properties at 155C, good resistance to thermal and mechanical shock, and also satisfactory resistance to deterioration upon prolonged exposure to tropical environment.
As in the Queuing patent, one part of the novel composition comprises liquid polyglycidy] ether of bisphenol A and the other part is a hardener comprising a mixture of liquid carboxyl-terminated polyester of dicarboxylic acid and polypropylene glycol having no more than one ester group per 500 average molecular weight, 1~4595 -pa- 557-2702 cyclic dicarboxylic acid android having a melting point of less than 40C, and a catalyst, wherein the cyclic dicarboxylic acid android primarily comprises low-melting cycloaliphatic android, and the catalyst is an imidazole.
Also as in the Queuing patent, there are approximately 0.9 to 1.3 epoxy groups for each android group of the android plus each carboxyl group of the polyester.
, .~., The epoxy resin colnposition of the present invent lion differs from that of the Queuing patent in that the cyclic dicarboxylic acid android primarily comprises low-melting cycloaliphatic android and the catalyst is an imidazole.
Mixtures of low-mel~ing cycloaliphatic android and imidazole, when stored at ordinary room temperature in admixture with the carboxyl-terminated polyester, are surprisingly resistant to decarboxylation and should remain fully effective after being stored a year or more at ordinary room temperatures.
Many uses for electrical-insulating potting come positions require flame retardancy, even though known flame-retarding additives tend to impair certain electrical-insulating properties. Where lame retardancy is important, the composition of the present invention preferably also includes a bromina-ted compound in an amount providing at least 5 parts, preferably at least 10 parts, of bromide per 100 parts by weight of total interactive ingredients of the novel potting composition. The brominated compound may either be an inert filler material such as decabromodiphenyl ether or a viscous delineate such as pentabromodiphenyl ether. Preferably the novel potting composition also contains up to one part of antimony trioxides per part by weight of bromide.
Inert Miller may comprise at least lo by weight of the total composition in order to provide optimum resistance to thermal and mechanical shock. At least half of the inert filler should be inorganic because this economically enhances flame retardancy and also has a mechanical reinforcing effect. Preferred inorganic fillers include calcium and magnesium silicates, calcium carbonate, talc, silica, and mica.
To provide a composition having both 10% or more filler content and desirably low viscosity, each of the liquid polyglycidyl ether arid the liquid carboxyl-terminated polyester Schloss have a viscosity not exceeding ~224595 20,000 cups at 25C oven lower viscosities are preferred and, to this end, the dicarboxylic acid used in making the polyester preferably is aliphatic or cycloaliphatic and desirably has ethylenic unsaturation. Malefic android is especially useful. However, any dicarboxylic acid may be used as long as the viscosity of the polyester does not exceed 20,000 cups at 25C.
The low-melting cycloaliphatic android may be provided either by a single cycloaliphatic android which by itself has a melting point below 40C or by a mixture of one or more cycloaliphatic androids and one or more other cyclic dicarboxylic acid androids, some of which by themselves have melting points above 40C, but which together have a melting point below 40C as taught in Us Patent No. 3,07~,235 (cowman et at.). useful cycle-aliphatic androids include hexahydrophthalic android, MOP. 35C; methylhexahydrophthalic android, MOP. <-15C;
tetrahydrophthalic android, MOP. 10~C; methyltetrahydro-phthalic android, MOP. 63C; endomethylene-tetrahydro-phthalic android ("Nadir" android) MOP. 120C; andmethylenclomethylenetetrahydropllthalic android ("Methyl Nadir" anhydricle) Pi <-15C. Other cyclic dicarboxylic acid androids which may be blended with one or more of the cycloaliphatic androids in compositions of the pro-sent invention include phtllalic android, MOP. 130C; but the anhyclride mixture shallowly be primarily cycloaliuhatic.
If the low-melting cycloaliphatic android or its mixture with other cyclic dicarboxylic acid androids were to have a melting point much higher than 40C, it would tend to crystallize and then need to be heated to provide a homogeneous liquid before being blended with the polyglycidyl ether. To insure against crystallization, the melting point of the low-melting cycloalipha-tic android or android mixture is desirably less than 20C.
For ease of Mooney, the viscosities of the polyglycidyl ether portion and the hardener portion of the two-part epoxy resin potting composition of the invention l~X~595 -5_ 557-2702 should be approximately the same, and inert filler should comprise no more than 70% by weight of each part. Usually inert filler comprises no more than 50% by weight of the total compost it ion since its viscosity might otherwise be too high to impreg-Nate minute interstices such as the spaces between the wires of an electrical coil. For good impregnation, the individual filler particles preferably are quite fine (e.g., less than 30 micrometers) and have a cubic or equi-axial shape, as opposed to needle-like or plate-like particles. Because exceedingly fine particles tend to produce unduly increased viscosities, a preferred particle size range is from 5 to 20 micrometers.
Preferred imidazole catalysts include imidazole, 2-ethylimidazole, and 2-ethyl-4-methylimidazole. The imidazole catalyst preferably is used in an amount from 0.2 to I by weight of the polyglycidyl ether. At lesser amounts, the curing rate tends to be too slow. At greater amounts, the composition obtained by mixing the hardener and polyglycidyl ether parts might have undesirably short pot life.
Although the epoxy resin composition of the invention is primarily useful for potting electrical components, it may be used as a dipping composition, and for such use, it should include a thixotropic filler.
When used for potting electrical components, the process involves preparation of the subject composition, and, after mixing, pouring same onto the electrical device to impreg-Nate and cover substantial portions thereof, and heating the device and the mixture with which it is impregnated and covered to cure the mixture to a tough, semi-flexible, thermoses state.
aye- 1224595 557-2702 In the following examples, all parts are by weight.
A two-part liquid epoxy resin composition was prepared as follows:
Resin Part A
195 grams liquid polyglycidyl ether of bisphenol A having an epoxy equivalent of 175-210 and a viscosity of 11,000 - 15,000 centipoises at 25C.
1~24595 104.8 grams calcium carbonate having an average particle size of 10 micrometers ("Gamma-Sperse"
255 from Georgia warble Co.) 86.2 grams decabromodiphenyl ether 14 grams antimony trioxides To the polyglycidyl ether in a vessel with a turbine type mixer, the calcium carbonate was mixed in, followed by the brominated compound and the antimony trioxides After being uniformly mixed, this material was set aside as Resin Part A.
Hardener Part B
128.4 grams acid-terminated divester of two moles of rnaleic android and one mole of polypropylene ylycol having an average molecular weight of 1025 (Example III of So 3,523,143) 110.~ cruelness rnethylhexahydrophthalic android 1.1 grams 2-ethyl-4-me~hyl imidazole 0.02 gram silicone anti-foam agent (DB-100, Dow Corning) 358.1 grams calcium carbonate ("Gamma-Sperse"~255) The acid-terminated divester was charged to a mixing vessel into which the android was mixed, followed by the imidazole and the silicone fluid. Finally the calcium carbonate ways aided an-l us orlrlly mixed into the batch to provide Hardener Part B.
Two parts of Resin Part A and three parts of Hardener Part B when blended had a viscosity of 20,000 cups at 25C and a gel time of 17 minutes at 121C. After decoration, the blended material was poured into molds and cured for four hours in a 120C oven. After cooling, the cured specimens were tested.
*I trade Clark Property Test Method Value Specific Gravity 1.71 Thermal 1/8" (3.2 mm) Olyphant Pass 10 cycles shock insert, test temp. cycle 130C to -55C
[M. Olyphant, Jr.; National Conference on the Application of Electrical Insular lion sponsored jointly by NEMO and Am.
10 Inst. of Electrical Engineers, 1958, Paper No. 85; pup 1118-35.]
Flame United States EDITED Pass Retardancy Method 2021 1/8" (3.2 mm) (non-burning) thickness US Subject 94 V-O rating 1/4" (6.4 mm) thickness Moisture united States FED-STD-406 0.0125%
Absorption Method 7031 1" by 3" by 1/8"
(2.5 by 7.5 by 0.3 cm) specimens, 24 hour immersion Hydrolytic 168 his. in scaled contailler Stability a 120C and 17 psi (117 IcPa) water vapor, 5" by 1/2" by 1/4"
(13 by 1.3 by 0.6 cm) specimens Hardness, before 81 Shore D
Hardness, after 79 Shore D
Volume Resistivity, before >1015 ohm-cm Volume Resistivity, after 1012 ohm-cm dielectric 1/8" (3.2 mm) specimen 340 volts/mil Strength 500 v/sec rate of rise (13.6kV/mm) -8- ~2~4595 The above Hydrolytic Stability test method is believed to be more rigorous than is the above-cited US. MOLLY, Rev. G.
another cured specimen 2" by 2" by 1" (5 by 5 by 2.5 cm) was immersed in water and heated in a sealed vessel at 125C or 28 days. This caused surface blistering, and the Shore D hardness was reduced from an initial value of 85 to 55. These test results indicate that cured products of this example have extraordinarily good hydrolytic stability for a semi-flexible cured product of an epoxy resin composition.
Cured specimens of Example 1 were also tested for dissipation factor and dielectric constant. The following results (averages of two tests) show that dissipation factor when measured at low frequencies is poor at high temperatures, a common characteristic of cured epoxy resin products which have good flame retardancy.
dissipation Factor Dielectric Constant (%) Tampa loo 1 10 100 100 1 10 100 ( C) tlzkHz kHz ktlz Ho kHzkHz kHz 24 2.22.2 2.1 2.1 5.14.84,7 4.6 106 >20 Lo 5.9 I 8.76.86.3 6.0 130 >20 >20 8.0 4.4 NT 7.26.5 6.1 25155 >20,>20 14 4.1 NT 8.36.5 6.0 NT = not tested Examples 2-5 Four two-part liquid epoxy resin compositions were Prepared silnilar to aye ox example I except that all fillers were omitted. In three of the your, other cycloaliphatic androids were substituted for the methylhexahydropllthalic android. Each composition was cured and tested for hydrolytic stability as in Example 1.
- 9- 1~:24~;95 Example Android Shore D
2 Methylhexahydroph~halic Before, 78-79 After, 76
3 Hexahydrophthalic Before, 76-77 After, 73-74
4 Mixture of 95 parts of Before, 77-78 methyltetrahydrophthalic After, 77 android and 5 ports of phthalic android Methylendomethylenetetra- Before, 79 hydrophthalic After, 74-75
Claims (17)
1. A two-part, low-viscosity thermosetting epoxy resin composition which cures to a tough, semi-flexible, thermoset state, one part comprising liquid polyglycidyl ether of bisphenol A, the other part comprising a mixture of liquid carboxyl-terminated polyester of dicarboxylic acid and polypropylene glycol having no more than one ester group per 500 average molecular weight, cyclic dicarboxylic acid anhydride having a melting point of less than 40°C, and a catalyst, there being approximately 0.9 to 1.3 epoxy groups for each anhydride group of the anhydride plus each carboxyl group of the polyester, characterized in that the cyclic dicarboxylic acid anhydride primarily comprises low-melting cycloaliphatic anhydride, and the catalyst is an imidazole.
2. An epoxy resin composition as defined in Claim 1 wherein the low-melting cycloaliphatic anhydride is a mixture of cyclic dicarboxylic acid anhydrides, at least one of which has a melting point above 40°C.
3. An epoxy resin composition as defined in Claim 1 and further including a brominated compound in an amount providing at least 5 parts of bromine per 100 parts by weight of total interactive ingredients.
4. An epoxy resin composition as defined in Claim 3 wherein the brominated compound provides at least 10 parts of bromine per 100 parts of total interactive ingredients.
5. An epoxy resin composition as defined in Claim 4 and further including up to one part of antimony trioxide per part by weight of bromine.
6. An epoxy resin composition as defined in Claim 5 wherein the brominated compound is an inert filler.
7. An epoxy resin composition as defined in Claim 6 wherein the brominated compound is decabromodi-phenyl ether.
8. An epoxy resin composition as defined in Claim 7 and further including nonbrominated inert inorganic filler in an amount such that inert filler provides 10 to 70% by weight of the total composition.
9. An epoxy resin composition as defined in Claim 8 wherein the inert filler comprises at least 20% by weight of the total composition.
10. An epoxy resin composition as defined in Claim 9 wherein at least half of the inert filler by weight is inorganic.
11. An epoxy resin composition as defined in Claim 1 wherein each of the liquid polyglycidyl ether and the liquid carboxyl-terminated polyester has a viscosity not exceeding 20,000 cps at 25°C.
12. A hardener for curing polyglycidyl ether of bisphenol A to a tough, semi-flexible, thermoset state, said hardener comprising a mixture of liquid carboxyl-terminated polyester of dicarboxylic acid and polypropylene glycol having no more than one ester group per 500 average molecular weight, cyclic dicarboxylic acid anhydride having a melting point of less than, 40°C, and a catalyst, characterized in that the dicarboxylic acid anhydride primarily comprises a low-melting cycloaliphatic anhydride and the catalyst is an imidazole.
13. A hardener as defined in Claim 12 wherein the viscosity of the liquid carboxyl-terminated polyester does not exceed 20,000 cps at 25°C.
14. A hardener as defined in Claim 13 wherein inert filler comprises 10 to 70% by weight of total hardener plus filler.
15. A hardener as defined in Claim 14 wherein the inert filler includes a brominated compound.
16. A hardener as defined in Claim 15 wherein the brominated compound is decabromodiphenyl ether.
17. Method of encapsulating an electrical device in electrical insulation characterized by the steps of (a) preparing a two-part, low-viscosity composi-tion, one part of which comprises liquid polyglycidyl ether of bisphenol A and the other part of which comprises a mixture of liquid carboxyl-terminated polyester of dicarboxylic acid and polypropylene glycol having no more than one ester group per 500 average molecular weight, cyclic dicarboxylic acid anhydride which is primarily cycloaliphatic and has a melting point of less than 40°C and in all amount less than the weight of the polyester, and an imidazole catalyst, there being approximately 0.9 to 1.3 epoxy groups for each anhydride group of the anhydride plus each carboxyl group of the polyester, (b) mixing the two parts together, (c) promptly after mixing, pouring the mixture onto the electrical device to impregnate and cover substantial portions of the device, and (d) heating the device and the mixture with which it is impregnated and covered to cure the mixture to a tough, semi-flexible, thermoset state.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US44717582A | 1982-12-06 | 1982-12-06 | |
| US447,175 | 1982-12-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1224595A true CA1224595A (en) | 1987-07-21 |
Family
ID=23775297
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000442307A Expired CA1224595A (en) | 1982-12-06 | 1983-11-30 | Two-part, low-viscosity epoxy resin composition |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1224595A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0307665A2 (en) * | 1987-09-15 | 1989-03-22 | International Business Machines Corporation | Encapsulation composition and use thereof |
| US4985475A (en) * | 1987-03-09 | 1991-01-15 | Minnesota Mining And Manufacturing | Encapsulant compositions for use in signal transmission devices |
| US20120208924A1 (en) * | 2009-07-14 | 2012-08-16 | Abb Research Ltd | Epoxy resin composition |
-
1983
- 1983-11-30 CA CA000442307A patent/CA1224595A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4985475A (en) * | 1987-03-09 | 1991-01-15 | Minnesota Mining And Manufacturing | Encapsulant compositions for use in signal transmission devices |
| EP0307665A2 (en) * | 1987-09-15 | 1989-03-22 | International Business Machines Corporation | Encapsulation composition and use thereof |
| EP0307665A3 (en) * | 1987-09-15 | 1989-09-13 | International Business Machines Corporation | Encapsulation composition and use thereof |
| US20120208924A1 (en) * | 2009-07-14 | 2012-08-16 | Abb Research Ltd | Epoxy resin composition |
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