DE1040235B - Process for curing resinous polyepoxy compounds by phenol-aldehyde condensation products - Google Patents

Description

GERMAN

It is known per se, di- or polyhydric phenols, such as bisphenol or resorcinol, with, for example Epichlorohydrin or another halohydrin in an alkaline medium to resinous polyepoxides to implement of different high molecular weight, which generally more than one Have epoxy group in the molecule.

However, polyepoxides of this type with a low molecular weight below 600 are difficult to produce into curable, technically usable and especially suitable for casting and adhesive purposes products.

Various types of hardeners have been tried for this purpose, for example Amines. However, these hardeners have the disadvantage that they are poisonous and cause severe skin irritation can evoke. Anhydrides of polybasic carboxylic acids, such as phthalic anhydride, have have the disadvantage that when they are used, ester groups are formed in the cured product. Such groups adversely affect the chemical resistance of the cured polyepoxy resin.

It has now been found that these low molecular weight polyepoxides can be cured quickly and safely can, if you add them together with 10 to 40 percent by weight, based on the polyepoxide, a heat-fusible, resinous phenol-aldehyde condensation product treated at elevated temperature, the fusible condensation process for hardening resinous polyepoxy compounds by phenolic

aldehyde condensation products

Applicant:

NV De Bataafsche Petroleum
Maatschappij, The Hague

Representative: Dr. K. Schwarzhans, patent attorney,
Munich 19, Romanplatz 9

Claimed priority:
Netherlands 28 October 1955

Pieter Bruin and Hendricus Anthonius Oosterhof,

Amsterdam, Netherlands),
have been named as inventors

It is also known to use polyepoxides in addition to the actual curing agent dicyandiamide

product of bivalent or higher, optionally ₃₀ ethers derived from formaldehyde condensation products, such as substituted phenols, all of which phenol-formaldehyde condensates are to be added. Since the

free OH groups in the phenols through ether formation have been eliminated, exercise these additives

no more hardening effect, but they serve

Hydroxyl groups are in the m-position and which are unsubstituted in at least one place.

The cured products erfmdungsgemäß produced are not brittle, but tough and hard, and ₃₅ just as another resin component in addition to the Poiyepsie also an excellent withstand thermal oxides show.

speed. They also only soften at high temperatures. The hardening of the starting materials according to the invention

(Heat distortion temperature). medium considered low molecular weight poly,

Is used, however, a Kondensationsproduki epoxides with a molecular weight below 600 mitals curing agent stän- p-of a phenol with ₄₀ Phenolaldehydkondensaten means of the novolak type is

therefore quite surprising, and the process leads to novel and valuable hardened products. In In many cases, an accelerator can be dispensed with entirely.

The heat fusible resins used in the present invention may be substituted or unsubstituted

Digen OH groups is derived, for example from p-cresol, the cured product remains at the curing temperature soft and brittle at room temperature, which indicates insufficient curing.

It is known per se, high molecular weight and therefore solid polyepoxides with phenol-formaldehyde condensation products to cure, for which, however, only resins of the resol type come into question. In contrast, the unsubstituted dihydric phenols. If they are substituted by a further OH group, this should be in the m-position with respect to

Hardening of such high molecular weight polyepoxides at 50 the other O Η groups are, as in phloroglucinol.

Use of novolak resins, d. H. fusible phenol aldehyde condensates, only slowly and incompletely, even if an accelerator is used in addition.

However, other substituents such as Alkyl groups or halogen atoms, in any vacant position in the di- or polyhydric phenol to be available. The new hardeners conduct themselves

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preferably from resorcinol, while formaldehyde is preferably used as the aldehyde. It is particularly expedient to use 20 to 30 percent by weight of the hardening agent.

Curing is generally conducted at temperatures between 80 and 22O ⁰ C, preferably between 110 and 150, performed ° C. It is usually heated until hardening has taken place, which can be seen from the insolubility of the hardened product in methyl ethyl ketone. The heating is usually less than 48 hours, preferably less than 24 hours. The lower the temperature used, the longer it is heated.

If extremely rapid curing is to take place, it is advisable to add an accelerator, especially an amine. The amounts of accelerator to use can be very low, preferably less than 1 percent by weight, calculated on the mixture.

In addition to the hardening agents, the hardened product prepared according to the present invention can be added, if desired various other substances may also be incorporated; e.g. fillers. Pigments, dyes, plasticizers and other resins or resin-forming substances.

The products produced according to the invention can be used for many purposes, in particular for the production of castings, as embedding compounds for electrotechnical parts or components and for the production of layer material. The hardenable products are also very suitable as adhesives.

The following describes the production of the new curing agents and low molecular weight polyepoxy resins explained in more detail, for these processes, however, no protection is given in the context of the present invention claimed.

A. Manufacture of resorcinol-formaldehyde resin

A solution of 1100 g of resorcinol (10 moles) in 1100g of water was heated in a round bottom flask to 100 ⁰ C. Then 470 g of 37% formaldehyde (5.8 mol) were added over the course of 20 minutes. As a result of the heat released by the reaction, the temperature rose to about 110 ° C. The mixture was refluxed for one hour and then the water was distilled off, first at normal pressure and then in vacuo up to a mass temperature of 140 ° C. The resin yield was about 1200 g.

B. Manufacture of one derived from resorcinol
Epoxy resin

A solution of 440 g of resorcinol (4 mol) in 1480 g of epichlorohydrin (16 mol) was heated to 80.degree. Of the 715 g of a 47% sodium hydroxide solution required for the overall reaction, 5 g were initially used was added to the solution, thereby starting the reaction and increasing the temperature over the course of time rose from 10 minutes to about 125 ° C. The temperature then dropped again. Then the rest became the sodium hydroxide solution added over the course of 3 hours, the temperature of the reaction mixture was kept at 100 ° C. During the reaction, the concentration of water was increased by distilling off an azeotropic mixture of water and epichlorohydrin was kept low. The epichlorohydrin was again returned to the reaction vessel after separation.

After all the caustic soda had been added. the excess epichlorohydrin was distilled off first at normal pressure and then in a vacuum up to a temperature of the mass of 160 ° C. Then was heated for one hour while maintaining a temperature of the mass of 160 ° C, the The residue was taken up in 1400 ecm of toluene and the salt formed during the reaction was filtered off.

The toluene was distilled off up to a mass temperature of 170 ^° C., initially at normal pressure and then in vacuo. The residue was

ίο again heated to 170 ° C in vacuo for 1 hour and, after adding 1% of a filter aid, filtered at 100 ° C. The yield was 840 g. The received Epoxy resin had an average number of 1.9 epoxy groups per molecule and a molecular weight from about 290.

C. Preparation of one of diphenylol propane
derived epoxy resin

A solution of 228 g of diphenylolpropane (1 mol) in 925 g of epichlorohydrin (10 mol) was heated to 105.degree heated, whereupon 168 g of a 50% sodium hydroxide solution were slowly added over the course of 3 hours with stirring became. Subsequent treatment was the same as above for making one epoxy resin derived from resorcinol is described. The yield was 325 g. The final product obtained had an average of 1.9 epoxy groups per molecule and a molecular weight of about 380.

example 1

Castings made from mixtures of the epoxy resins prepared according to B or C with that obtained according to A. Hardening agents were examined for their properties.

The mixtures specified in more detail in the table below were ^{cured at 140 °} C. for 20 hours. The degree of hardening of the hardened compositions obtained was determined in such a way that the proportion of a certain amount of a finely pulverized hardened mixture which was soluble in boiling methyl ethyl ketone was determined. The results are compiled in the following table.

Parts of the
Resorcinol Parts of the
Resorcinol Parts of the
Diphenylene Extract Shape-
aldehyde-
50 ^Har2es JLVvJvI WaI
derived
Epoxy resin propane
derived
Epoxy resin barer
percentage 40 60 8.0 35 65 - 4.6 30th 70 - 3.0 55 25 75 - 1.4 20th 80 - 6.1 50 - 50 19.4 40 - 60 7.7 35 65 5.0 ⁶⁰ 30 .—. 70 3.6 25th 75 2.2 20th - 80 3.7 15th - ■ 85 13.9

The above values show that in both cases the best hardening is achieved with a mixing ratio of 75 parts of epoxy resin to 25 parts of resorcinol formaldehyde resin is achieved.

There were other properties of using the above mixing ratios

obtained compositions checked. For this purpose the mixtures were made up by heating Cured 140 ° C for 24 hours. Some of the so

Cured products were subjected to post-curing by heating to 200 ° C during further Subject to hours.

Mix Heat deformation After 24 hours 90 98 j 119 128 Hardness (according to rock well, After 24 hours 75 Electr. Dielectric relationship temperature at 140 ° C
and then
2 hours. E-scale) at 140 ° C
and then
2 hours. Loss factor constant (ASTM D 648 45 T, at 200 ° C at 200 ° C at 450 kHz at 450 kHz 18.5 kg / cm ² ) After 24 hours
at 140 ° C After 24 hours
at 140 ° C After 24 hours
at 140 ° C Nadi 24 hours
at 140 ° C 71 72 25/75 Resorcinol form aldehyde resin 0.028 4.7 + Resorcinol Epoxy resin 73 Resorcinol form 25/75 aldehyde resin + Diphenylene 0.024 4.2 propane epoxy resin

All hardened products are very tough.

Example 2

75 parts of the polyepoxy resin produced by the process described under C were mixed with 25 parts of the resorcinol-formaldehyde resin obtained according to method A cured. After heating for 20 hours Good curing of this mixture was achieved at 140 ° C. When using 0.5 percent by weight triethanolamine, calculated on the mixture, the same degree of hardness (determined by extracting with boiling methyl ethyl ketone) after only one hour of heating to 140 ° C.

35

Claims (4)

PATENT CLAIMS: 40 1. Method of curing resinous polyepoxy compounds by phenol aldehyde condensation products, characterized in that polyepoxides with a molecular weight below 600 by 10 to 40%, based on polyepoxide, resinous phenol-aldehyde condensation products which are meltable in the heat based on dihydric or higher, optionally substituted phenols, all of which are hydroxyl groups in m-position and which are unsubstituted in at least one place, at elevated temperature hardened. 2. The method according to claim 1, characterized in that the curing takes place at 80 to 220 ° C. 3. The method according to claim 1 and 2, characterized in that the hardening with one in the Heat fusible resorcinol-formaldehyde resin is carried out. 4. Modification of the method according to claim 1 to 3, characterized in that during curing an amine is also used in an amount below 1 percent by weight. Considered publications:
U.S. Patent Nos. 2,521,911, 2,458,796. © 809 640/490 9.