DE1165851B - Use of branched-chain polyesters for curing epoxy resins - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 08 g

German KL: 39 b -22/10

Number:
File number:
Registration date:
Display day:

M 46282IV c / 39 b
17th August 1960
March 19, 1964

The curing of epoxy resins with polyesters is known from US Pat. No. 2,683,131. In the polyesters described in this patent specification have an acid number of at least 150, are low molecular weight, as can be derived from the specified acid number and the functionality of the polyester, and are reaction products of a dicarboxylic acid with a polyhydric alcohol.

The subject of the invention is the use of branched-chain, terminal carboxyl groups holding polyesters with an average molecular weight of 1500 to 17000, with on average 2.1 to 3.0 carboxyl groups per molecule, an acid number of 15 to 125, a hydroxyl number of less than 10, which are free of unsaturated groups in the backbone chain, which are not more than half related on the total amount of acids and alcohols, contained on aromatic rings and made up of one Dicarboxylic acid, a dihydric alcohol and either a polyhydric alcohol with at least three non-tertiary hydroxyl groups or a polybasic acid with at least 3 carboxyl groups for curing epoxy resins - with an average of at least 1.3 epoxy groups in the molecule - in the heat or, if necessary, together with conventional catalysts normal temperature.

The polyester does not gel when heated in the absence of air. Preferably contains its chain practically no ether oxygen, in the presence of which the hardened moldings are less resistant against moisture and thus less resistant to electrical breakdown, although these The effect is smaller when the ether oxygen is bound directly to an aromatic ring.

The epoxy resin to be cured must contain at least an average of 1.3 epoxy groups per molecule. These epoxy groups must be separated by a chain of at least 2 carbon atoms, the chain containing no double bonds.

Epoxy resins such as the diglycidyl ethers of resorcinol and bisphenol A, which usually contain more than 1.3 but slightly less than 2.0 epoxy groups per average molecular weight, but sometimes also more than 2.0 epoxy groups, are particularly valuable. The diglycidyl ethers of glycerine can also be used. A commercially available epoxy resin that can be used according to the invention is, for. B. the condensation product of 1,1,2,2-tetrakis (4-hydroxyphenyl) ethane and epichlorohydrin with an average of about 3 glycidyl ether groups in the molecule. Also monomeric polyepoxides, such as limonene, use branched-chain polyesters
for curing epoxy resins

Applicant:

Minnesota Mining and Manufacturing Company, St. Paul, Minn. (V. St. A.)

Representative:

Dr.-Ing. H. Ruschke, patent attorney,
Berlin 33, Auguste-Viktoria-Str. 65

Named as inventor:

Kurt August Kurka, Roseville, Minn.,

Herbert Marvin Bord, Stillwater Township, Minn.

(V. St. A.)

Claimed priority:

V. St. ν. America August 18, 1959

(No. 834 407)

dioxide, dicyclopentadiene dioxide, vinylcyclohexenedioxide and S ^ -epoxy-o-methylcyclohexylmethyl-S ^ -epoxy-o-methylcyclohexanecarboxylate, can be hardened.

Other epoxy compounds associated with the carboxyl-terminated and branched polyesters Chain has been converted into solid, tough, flexible molded parts that are used for electrical insulation are epoxidized novolaks.

Through the reaction between the epoxy groups and the terminal carboxyl groups of the polyester, which is caused by the application of heat or at least considerably accelerated, becomes the Molding compound in a solid, tough, temperature-resistant, practically infusible and insoluble Molded part transferred. The proportions in the masses are chosen so that approximately one epoxy group comes to every carboxyl group of the polyester. When a large excess of one type of group is present, the strength and other properties of the molded part may be impaired. However, in the presence of an agent that reacts one epoxy group with another catalyzed, a considerable excess of epoxy groups may be contained in the original mass,

409 539/580

3 4

without affecting the cured product. Knife applied to a slightly adhesive base sheet,

The mass of a crosslinking agent Fuei epoxy resins, the pre-heated for 2 hours in a 120 ⁰ C

z. B. a polycarboxylic anhydride, containing an oven. The mixture hardened in the process

the acid-terminated polyester only in a pliable, non-tacky, 0.02 cm film

a very small amount of starch needs to be present, which after cooling from the non-adherent

and then acts to increase toughness. has been peeled off the document. The hardened film

A catalyst can be incorporated into the mass, which had the following electrical properties:

to cure them at room temperature. As a catalytic dielectric strength

Tertiary amines volts / cm '338 600 are particularly preferred

and their salts in an amount of about 0.1 to 2.0%, ™ specific volume resisted, '

but also up to about 5% of the total weight of the ohm · cm 2 5 · 10 ¹²

^M * ^ss . ^e -. ", ..., power factor O, 'o83

With certain uses for the ent- Dielectric constant 5.98

standing molding, which require a particularly high flexibility, monoepoxides can be mixed in the 15 The last two values were at 30 ⁰ C and masses. Typical useful mono periods measured per second. A strip of epoxy are dodecene oxide, octylene oxide, dipentene film lost only 11% of its weight when it was placed in acetone, ether, vinylcyclohexene monoxide for 24 hours at room temperature. It is also possible to use the electrical properties and the solvent epoxidized long chain olefins, e.g. B. epoxidized 20 strength of this film are excellent.
To mix in olefins having 16 to 18 carbon atoms. A 1.9 cm wide strip of the cured film

The polyester to be used according to the invention was tested with the Instron Tensile Tester with a branched chain and terminal carboxyl starting bracket spacing of 2.5 cm and a group must on average at least 2.1 carb crosshead speed of 2.5 cm per minute contained in the molecule. Preferred must 25 seeks and yielded a tensile strength of 25 kg / cm ² when they averaged more than 2.2 carboxyl groups an elongation at break of 250% · Another sample contained when the cured product was a high of the uncured mixture by coating strength and toughness should own. The average number of carboxyl groups distributed with the knife on a fleece made of randomly distributed polyethylene terephthalate fibers must not be more than 3.0 to saturation, otherwise the polyester gels below 30, some of which are stretched prematurely by pulling. But if a tetravalent acid had become. The non-stretched fibers were on or a tetravalent alcohol is used, their crossing points fused together in order to give the average number of carboxyl groups the fabric good cohesion, not more than about 2.3, if a premature The weight of the uncoated web was Gelation should be avoided. For acids and 35.9 g / m ² . The coated fleece was 1 hour with alcohols that contain even more functional groups at 95 ° C and then 2 hours at 150 ° C to a solid, molecule, the average number of flexible, reinforced, electrically insulating film of free carboxyl groups per molecule must be hardened smaller,
but in no case may it be less than 2.1. Example 2

If the polyester has an acid number of less than 40

than 15, that is, if its average molecular weight is a blend of 215.5 kg of polyester B produced weight is more than 17,000, calculated from the conversion of adipic acid, isophthalic acid, average degree of polymerization above propylene glycol, trimethylolpropane and triphenyl about 100, is its reaction rate with phosphite as a catalyst and 46.7 kg of liquid epoxy Epoxy compound small, and the reaction product 45 resin, which with toluene to a resin content of 90% is not completely diluted to a tough, infusible, was refluxed for 4 hours hardened insoluble state, even when heated, after which the viscosity of the partially reversed Time is heated. When the acid number was higher, the mixture was 1300 ocP at 65 ° C. For this than 125, so if the average molecular weight was 5.2 kg of tris (2,4,6-dimethylaminomethyl) weight is less than 1500, calculated from its 50 phenol and given so much toluene that the solution had an average degree of polymerization of less than 40% solids content. A light, highly porous one than 10, the cured product is harder and less fiberglass fabric was through the solution flexible than is desired for most purposes. drawn, the excess through a pair of dosing

The hydroxyl number of the polyester must not exceed 10 bars, and was then 12 minutes

and should preferably be less than 5. A 55 ^{heated to 260 0} C, being a pliable one, not

A higher hydroxyl number results in a sticky insulating film of about 0.13 mm thickness formed with the epoxy compound

Moldings of relatively poor quality. became.

. -I ₁ The dielectric strength of these reinforced

^{Example 1} insulation film was 236,000 V / cm. A strip of the

A mixture of 326 g of polyester A, which lost only 7% of its weight through 60 insulating film when it was soaked in toluene for 24 hours at room temperature (mixture of 72 to 80% 2-ethyl suberic acid, 12 bis, and another strip absorbed only 0.5% 18% 2,5-diethyladipic acid and 6 to 10% n-sebacin- of its weight when soaked in water for 24 hours at room acid), propylene glycol, glycerin and triphenylphosphate temperature,
phit was recovered as a catalyst, 84 g of liquid 65 A pressure-sensitive adhesive coating, epoxy resin and 8 g of tris (2,4,6-dimethylaminomethyl) - were applied to the reinforced insulating film, a phenol was mixed with toluene to a solids content Wire thinned by 70% and obtained by coating with the ends and the like.

Example 3

A mixture of 100 parts by weight of liquid epoxy resin and 170 parts of polyester D, prepared by reacting "isosebacic acid", neopentyl glycol, trimethylolpropane and p-toluenesulfonic acid as a catalyst, had a viscosity of 14,300 cP at 23 ^° C. After adding 3.7 parts tris (2,4,6-dimethylaminomethyl) phenol was very rubbery 2stündiges obtained by heating at 13O ⁰ C, a tough molding. The bulk of this example is particularly useful for embedding electrical devices.

Example 4

A solid Epoxyharzkondensationsprodukt of epichlorohydrin and bisphenol A was used in this example had a Durransschen softening point of about 43 ⁰ C and an epoxy equivalent of about 345th

375 g of solid epoxy resin, which was also diluted to 90% solids content, were added to 1010 g of polyester F, prepared by the reaction of "isosebacic acid", isophthalic acid, propylene glycol, trimethylolpropane and triphenyl phosphite, which had been diluted to 90% solids content with toluene had been. This mixture was heated to 150 ° C until the measured at 82 ⁰ C viscosity had reached 14 00OcP. The mixture was cooled, diluted to 80% solids content with toluene and layered with a knife on loosely woven glass fiber cloth of 0.1 mm thickness until saturation. After _{drying for 2–2} minutes at 80 ° C and 4 minutes at 175 ° C to partially cure the mixture, the resin-treated cloth was bonded to polyethylene-coated paper and rolled up. The treated cloth was somewhat sticky in this state, very pliable, and the resin was 90% soluble in toluene in this hardened state.

One inch wide strips were cut from the roll and wound onto a copper spiral with a half-lap. The strip fused well and was firmly bonded to itself on the copper after being cured ^{in an oven at 150 ° C for 1 hour.} The dielectric strength was 394,000 V / cm. The strip insulation had excellent resistance to transformer oils and a variety of solvents such as toluene, heptane and mineral spirits.

A roll of the resin treated glass cloth was stored at room temperature for 9 months and was still pliable. When it was wound on a copper spiral and ^{cured at 150 °} C. for 1 hour, it gave the same electrical insulation as was obtained with a freshly produced strip.

Comparative experiment

For comparison, Example 1 of U.S. Patent 2,683,131 was followed up by attempting to produce cantilevered cured films for experimental purposes. Sample Nos. 1, prepared from 10 parts of the acidic polyester and 20 parts of a commercially available bisphenol type epoxy resin was cast into a 0.9 cm thick film and heated for 18 hours 15O ⁰ C. After peeling off the backing, the film was cut into strips approximately 0.65 cm long and tested for tensile strength in an Instron Tensile tester with an initial clamp spacing of 2.5 cm and a crosshead speed of 5 cm per minute. The average tensile strength was 460 kg / cm ² with an elongation at break of only 3 to 5%. This test shows that the cured product of Example 1 of U.S. Patent 2,683,131 is suitable for the purposes to which the products according to the invention can be put, is way too brittle.

Similarly, the second sample of the example of the above United States patent was cut using a conventional epoxy resin 1.9 cm in length. The cured product had a tensile strength of 4.8 kg / cm ² with an elongation at break of 10 to 12%. It was found to be too soft and weak to be used as an electrical insulating material.

The strongly acidic polyesters of U.S. Patent 2,683,131 also exercise on metals such as those in U.S. Patent No. 2,683,131 Electrical engineering used has a corrosive influence.

A wide variety of other carboxyl terminated and branched chain polyesters became cured products according to the invention with compounds containing epoxy groups implemented. As the dicarboxylic acid for the production of these polyesters, besides those mentioned in detail above Acids o-phthalic acid, azelaic acid, and hexachloroendomethylene tetrahydrophthalic anhydride used. Other dihydric alcohols that can be used are 1,4-butanediol, ethylene glycol and 2,2-bis- [4- (2-hydroxypropoxy) phenyl] propane. In addition to glycerine and trimethylolpropane, pentaerythritol was used; it can also be polybasic carboxylic acids, such as Trimesic acid, citric acid, trimellitic acid, benzene tetracarboxylic acid and tricarbalylic acid are used will.

Crepe paper, impregnated with the composite compositions according to the invention and by short Hardened by heating gives an electrically insulating material of good solvent and moisture resistance. Clear, tough, flexible films can also be produced from these compositions, which are generally known as Packaging material or for other non-electrical purposes.

Claims (1)

Claim: Use of branched-chain polyesters containing terminal carboxyl groups an average molecular weight of 1500 to 17,000, with an average of 2.1 to 3.0 carboxyl groups per molecule, an acid number from 15 to 125, a hydroxyl number below 10, those in the backbone chain are free of unsaturated groups, which are not more than half, based on the total amount of acids and alcohols, on aromatic rings and those of a dicarboxylic acid, a dihydric alcohol and either one polyhydric alcohol with at least three not tertiary hydroxyl groups or a polybasic acid with at least 3 carboxyl groups for curing epoxy resins - with an average of at least 1.3 epoxy groups in the molecule - in the heat or possibly together with conventional catalysts at normal temperature. Considered publications:
German Auslegeschrift No. 1 054 705;
U.S. Patent No. 2,683,131. 409 539/580 3.64 © Bundesdruckerei Berlin