DE1259488B - Stabilization of the thixotropy in epoxy resin coating agents - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C09d

German KL: 22 g-10/01

Number: 1 259 488

File number: G 30964IV c / 22 g

Filing date: November 18, 1960

Opening day: January 25, 1968

The invention relates to thixotropic coating agents based on epoxy resins with fillers, which retain their thixotropic properties over long periods of time.

Epoxy resins are well known and consist of a polyether derivative of a polyvalent organic Alcohol compound, this derivative containing 1,2-epoxy groups and from the class selected from polyhydric alcohols and phenols having at least two phenolic hydroxyl groups. U.S. Patent 2,324,483, for example, describes epoxy resin compositions made from the reaction product of phenols having at least two phenolic hydroxyl groups and one epihalohydrin, e.g. B. Epichlorohydrin. The product has at least two epoxy groups and becomes hot by mono- or polybasic carboxylic acids or acid anhydrides, e.g. B. phthalic anhydride, to a hardened infusible mass. The use of organic nitrogen base or amine-like substances for curing epoxy resins is also well known and is described, for example, in U.S. Patent 2,444,333 described. Such substances often provide rapid hardening of the resin masses even at room temperature.

To delay the rapid hardening by the amine hardeners and at the same time the softening agents To obtain properties of these substances, one often has boron trifluoride complexes with an organic one Base, which are also well known, is used. These shocks are carried out in a conventional manner Addition of an ether solution of a boron trifluoride-ether complex to an ethereal solution or, as desired, to a basic amine. You can do it too by simply passing boron trifluoride gas through an ethereal solution of a base. To be favoured: Alkyl ethers, e.g. B. methyl, ethyl, propyl, butyl ethers and others, or mixed alkyl or aryl, alkaryl and Aralkyl ethers. The amines that can be used include: methylamine, ethylamine, propylamine, butylamine, Aniline, diethylaniline, toluodine, chloroaniline, nitroaniline and piperidine. Usable according to the invention are also complexes which, as indicated above, with boron trifluoride and other substances, e.g. B. phenolic and etherate complexes. Such substances are commercially available.

In order to provide thixotropic resin compositions which adhere to the material to be coated with a uniform and noticeable strength, especially at the edges and corners, such epoxy resins are filled with various fillers which cause the thixotropy. However, it has been found, although such finely divided fillers the thixotropy of stabilizing the thixotropy in
Epoxy resin coating agents

Applicant:

General Electric Company,

Schenectady, N. Y. (V. St. A.)

Representative:

Dipl.-Ing. M. Licht and Dr. R. Schmidt,

Patent Attorneys, 8000 Munich 2, Theresienstr. 33

Named as inventor:

Joseph Rosenberg,

Walter Niels Larsen, Erie, Pa. (V. St. A.)

Claimed priority:
V. St. v. America November 20, 1959
(854223)

Coating compounds promote that they lose their thixotropic property after a certain time and are therefore unusable if they are not used immediately after manufacture.

Unexpectedly it has now been found that the thixotropy of coating agents made from epoxy resins, Hardeners and thixotropic fillers can be stabilized by adding small amounts of a polyalkylene glycol clogs. Usually the addition of polyalkylene glycols is between about 0.06 and about 6.0 parts by weight for every 100 parts by weight of the epoxy resin.

There are already hardenable coating compounds made of epoxy resin and hardeners, which in addition to pigments, Fillers and the like that can also contain polyglycols are known. These known coating compositions have however, consistently no thixotropic character.

The ethoxylin resins used in the coating agents have more than one epoxy group per molecule. You can react by a multivalent

709 720/500

Alcohol or phenol, e.g. B. hydroquinone, resorcinol, glycerine and the condensation products of phenols with ketones, e.g. B. bis- (4-oxyphenyl) -2,2-propane, can be prepared with epichlorohydrin. Also epoxidized Olefins and other known epoxy resins can be used.

As the hardener, the above-mentioned commercially available boron trifluoride amine complex can be used. Of course, other hardeners can be used during the preparation and normal storage of the coating agent does not cause excessive hardening.

In order to bring about the desired degree of thixotropy in the coating agents, any known, the thixotropy inducing filler can be used. The finely divided, silicon-containing ones are preferred Fillers, e.g. B. sublimed silicon oxide, finely divided silicon dioxide, silicon dioxide powder, a finely divided, precipitated silica and diatomaceous earth. Other known inactive or non-thixotropic fillers, e.g. B. coarser silicon dioxide fillers, ground glass fibers of about 0.8 to about 1.6 mm in length and still other substances can be used in conjunction with the thixotropic or active fillers are used.

The polyalkylene glycols that can be used include, for. B. polyethylene glycol, polypropylene glycol, or polybutylene glycol.

Usually about 1 to 10 parts of the thixotropic filler is used for every 100 parts by weight of epoxy along with up to

ίο about 200 parts of other desired fillers, as required, using milled glass fibers in an amount of about 1 to 30 parts, hardener in an amount of about 1 to 10 parts and polyalkenylene glycol in one Amounts from about 0.06 to 6.0 parts are included.

The following examples are intended to describe various coating agents that can be used. All information relate to units of weight. In all examples, commercial liquid epoxy resin was used with a Epoxy equivalent of 190 used.

Examples 1 to

example

2 I 3

Epoxy resin

Boron trifluoride monoethylamine complex

Silicon dioxide (particle size less than 177 μ) ..

Lithium aluminum silicate

Sublimated silica

Milled glass fiber of 0.8 mm length

Glycerin

Polyethylene glycol (molecular weight 400) ....
Polyethylene glycol (molecular weight 500,000)

100

50

7th
0.12

100

50

3.5
7th

0.06

100

100

25th

4th 7th

100

25th 4th 7th

The materials of the examples given were mixed with one another in the following way: The epoxy resin and the curing agent were added by adding the curing agent to about 10 parts of the epoxy resin combined approximately 80 to 90 ° C until solution was achieved. This mixture then became the rest of the resin was added and the total mixture was ground on a 3-roller roller. The rest of the ingredients was subsequently mixed with the first part, and then the whole mixture was again ground on a 3-roller roller. This mixture can be made in any order will. _

The stability of the thixotropy of the coating agent can be made recognizable by the following method will:

Steel plates about 7.6 cm ² and 0.08 cm thick were immersed in the mixtures of Examples 1 to 5 on different days. The resulting coatings were immediately cured at 150 ° C for 3 hours. The thickness of the coatings was measured at the same point with a micrometer to determine the decrease in the thixotropic properties of the mixture with age.

The results of the tests are shown in Table I.

Table I.

Age of the crowd
when pulling over Thickness of the coating (mm) 1 2 example 5 the sample plate 0.81 0.84 3 0.76 (Days) - - 0.81 0.76 - 0 - - - - 0.71 3 0.61 - - 0.84 - 7th - - 0.81 0.81 10 0.43 - - - 0.84 17th 0.28 - - - - 24 - 0.94 - - - 31 - 0.86 0.84 0.84 - 35 - - 0.84 - 0.76 45 - 0.91 - 0.79 - 48 - - 0.81 - 0.81 62 - 0.81 - - - 68 - U.N 0.76 - 86 just 0.79 105

From this information it can be seen that in the masses which did not contain polyethylene glycol, the The thickness of the coating decreased rapidly, so that the measurements with such compounds were discontinued after 31 days

became. On the other hand, in the case of the compositions containing polyethylene glycol, the thickness of the coating with the Age of the masses only slowly or not at all. A polyethylene glycol addition to such masses has an effect than to the effect that the thixotropic properties are still present even when the mass is older.

Example 6

As above, a composition was prepared which, in parts by weight, consisted of 100 parts of epoxy resin, 3 parts Boron trifluoride monoethylamine complex, 50 parts of silicon dioxide below 177 microns particle size, 3 parts sublimed silica, 7 parts ground glass fiber 0.8 mm in length and 6 parts of polyethylene glycol (molecular weight 600). Even after The original coating thickness of 1.1 mm was retained for 8 days.

The following examples are intended to illustrate the implementation of the process according to the invention Describe the use of other hardeners. All data relate to weight units.

Examples 7-10

Epoxy resin 100 100 100 100

Dicyandiamide

Pyromellitic anhydride - - 30 30

Silicon dioxide
(Particle size below
177 μ) 50 50 50 50

Sublimated silica 3 3 3 3

Milled glass fibers
0.8 mm long ....

Polyethylene glycol
(Molecular weight 400)

If the specified substances were combined and cured as in the previous examples, so

example 9 7th 100 100 100 - 4th 4th 30th - - 50 50 50 3 3 3 7th 7th 7th 6th

the resistance of the coatings was shown in Table II.

Table II

OTage

ITag.

5 days

12 days

(In millimeters) 9 7th 8th 1.1 0.9 1.2 0.56 0.86 1.2 - 0.38 1.22 __ 0.25 1.17

1.17
1.09

The coating agents are suitable for many purposes. For example, electrical Coils, which have so far been cumbersome by applying foils or wrapping them with ribbons were isolated and subsequently impregnated with various liquid resin compositions, now immediately dipped, hardened and used. This immersion process enables the rotor and stators to be isolated , whereby the use of slot linings, slot wedges, locking rails and the like. becomes superfluous. In addition, the substances can be used without worrying about the starch the coatings made of these materials become uneven and sink if they are not immediately complete hardened.

Claims (1)

Claim: Use of polyalkylene glycols in coating agents made from an epoxy resin, one only at higher temperature effective hardener for the epoxy resin, a thixotropic resulting active Filler and optionally an inactive filler, in amounts of 0.06 to 6 parts by weight per part by weight of epoxy resin as a means of stabilizing the thixotropic. Considered publications: German Auslegeschrift No. 1 062 008;
Austrian patent specifications No. 209 571, 210 144 to 210147.