DE2237550C3 - Process for the preparation of liquid modified epoxy resins - Google Patents

Description

of the reactants) of a catalyst of the formula
R ₁ OH R ₁ OH

CH,

R "—CH ₂ - —Ο - C-

CH ₃

and η is on average <1, with about 20-80% by weight of one optionally with up to about 10% by weight (based on the drying oil) maleic acid, maleic anhydride or fumaric acid and with at least one saturated aliphatic polyhydric alcohol with 2–6 hydroxyl groups in an amount approximately 1–1.5 times that of maleic acid, maleic anhydride or fumaric acid, modified drying oils in the presence of approximately 0.1–1.5% by weight (based on the total weight

RO

OR

NR ₁ OH

R ₁ OH

wherein M is titanium, aluminum or silicon, Ri is a ethylene, propylene or isopropylene group and R darsteilen an aliphatic radical having 1-6 carbon atoms or a phenyl group, at about 200 to 250 ⁰ C up to the clearing point-stage reacted.

2. The method according to claim 1, characterized in that the catalyst with at least one Borate is modified in a ratio of 1: 2 to 2: 1.

According to the invention, liquid modified epoxy resins are prepared by reacting a drying agent Oil with a diepoxide in the presence of a metal chelate catalyst. The drying oil can by reaction with maleic acid, maleic anhydride or fumaric acid and with a polyhydric alcohol can be modified to increase the drying speed. The catalyst can be modified by mixing or reacting it with a borate.

An epoxy resin can be liquid or solid, depending on the epoxy equivalent weight. A solid epoxy resin can be used for Coatings are used by applying a solution to an object and evaporating it Solvent (cf. AU-PS 2 05 972) or by melting a catalyzed powder on the object. However, it is not feasible to use a solid epoxy resin as an embedding and casting resin compound, because a solvent cannot escape from the depths of the casting and the resin melts would tend to polymerize prematurely.

Liquid epoxy resins would therefore be much more suitable as casting and embedding compounds than solid resins, but it does has been difficult until now to control the flexibility of liquid epoxy resins.

Plasticizers have been tried, but they precipitate and the resin gradually becomes less flexible. Flexible hardeners have also been tried, but they are expensive and do only one thing small area flexibility.

While drying oils easily with solid epoxy resins can be made compatible (see CA-PS 5 18 956 and AU-PS 2 05 972) attempts to dry

working oils into liquid epoxy resins to make them making it flexible, did not result in the production of a clear resin.

It has been found that a certain class of metal chelate catalysts are capable of drying oils

fts diepoxides to react to form liquid modified epoxy resins, which are curable under Achieving a wide range of flexibility from almost liquid to rigidly solid. The modified

Epoxy resins of the invention are useful as embedding and casting compounds for the formation of topcoats and for purposes for which other epoxy resins are used. They are very stable and can withstand several Months of gel formation when at room temperature be stored in a tightly closed container. According to the invention there is about 20-80% by weight of at least one diglycidyl ether of a diphenol of the formula

C ^ -C, -

-CH ₂ -ER'-CH ₂ -CHOH- CH ₂ ^ R'-CH ₂ -CH

-CH,

in the R 'a diphenol residue from the groups

- O

wherein

R "—CH ₂ - —O

O-

CH ₃

- C - CH ₃

and η is on average <1, with about 20-80% by weight of one optionally with up to about 10% by weight (based on the drying oil) maleic acid, maleic anhydride or fumaric acid and with at least one saturated aliphatic polyhydric alcohol with 2–6 hydroxyl groups in an amount approximately 1–1.5 times that of maleic acid, maleic anhydride or fumaric acid, modified drying oils in the presence of approximately 0.1–1.5% by weight (based on the total weight of the reactants) of a catalyst of the formula

R ₁ OH

RO

NR ₁ OH

R ₁ OH

wherein M is titanium, aluminum or silicon, Ri is a ethylene, propylene or isopropylene group and R represents an aliphatic radical having 1-6 carbon atoms or a phenyl group, is reacted at about 200 to 250 ⁰ C up to the clearing point level. The reaction should preferably be carried out under inert conditions

Protective gas atmosphere, for example nitrogen, are carried out in order to exclude oxygen, which is the Resin thickened by reaction with the drying oil Diepoxide, drying oil and catalyst become under under non-hydrolyzing conditions (to obtain the epoxy functionality) ^{heated to about 200-250 0} C until the clear point stage is reached (that is, the point at which a sample that has been cooled to room temperature is clear and not cloudy), which in about 1/2 to 1/2 hour is reached. Lower temperatures require reaction times that are too long and higher temperatures lead to the gelling of the drying oil. The reaction can continue beyond the clear point level, if higher Viscosities are desired. Lack of clarity can also occur when certain hardeners, for example polyamides, are used. This can can be eliminated by heating above the clear point level for about 1/2 hour.

The liquid modified epoxy resin thus formed can then be mixed with known reactive ones Diluents, fillers, thixotropic agents, reinforcing materials, pigments, etc. A curing agent can be mixed in and the resin becomes poured onto a carrier or in a mold and hardened.

π is on average <1 and preferably about 0. These low values for η are required when the diepoxide is liquid, which is necessary when that modified epoxy resin product is said to be liquid. It should be noted that η is an average and that approximately 75-98% of commercially available diglycidyl ethers have an exact value of / 1 = 0 and the remaining 2-25% higher values for π . The preferred diphenol is bisphenol A (4,4'-dioxydiphenyldimethyl methane). Examples of other suitable ones Diphenols are resorcinol, which produces less viscous resins than bisphenol A, hydroquinone and Pyrogallol.

The drying oils do not have any functional hydroxyl groups (which could etherify with the epoxy groups). They are typical natural products, triglycerides of mixed unsaturated fatty acids. While natural drying oils are preferred because of their availability, drying oils can also be produced synthetically by stoichiometric conversion of an unsaturated fatty acid of the formula Ci ₇ HiCOOH, where χ 28-33 is with a polyoxy compound with 2-4 hydroxyl groups. Glycerin is that preferred polyoxy compound. But it can also pentaerythritol, trimethylolethane, trimethylolpropane, Ethylene glycol, etc. and mixtures of polyoxy compounds can be used.

Suitable drying oils are linseed oil, oitici-

caöl, perilla oil, tung oil, dehydrated castor oil,

Safflower oil and fish oil. Flaxseed oil either raw or

Refined over alkali is preferred because of the good quality drying properties.

If the epoxy resin is cured with a curing agent, it is not necessary to use a modified one to use drying oil. But if the resin is cured by exposing it to oxygen, that is Desire to use a modified drying oil that dries faster because of the Presence of further double bonds.

The drying oil can be modified by treating it with up to about 10% by weight (based on the drying oil) maleic acid, maleic anhydride or fumaric acid and with at least one saturated aliphatic polyhydric alcohol having 2-6 hydroxyl groups in an amount equal to the 1 - 1.5 times that of maleic acid, maleic anhydride or fumaric acid. The presence of up to about 1.5% (based on the drying oil) of an ester interchange catalyst such as lime (CaO) is desirable to accelerate the reaction. The reaction components are ^{heated to approximately 230 °} C. until an acid value of less than 14 is reached. This is usually reached in about 1/2 to 2 hours. The Acid Value is the number of milligrams of KOH required to neutralize 1 gram of the feed. It should be <14 in order to avoid excessively high viscosities when the modified drying oil is reacted with the diepoxide. The reaction should be carried out under an inert gas, for example nitrogen, in order to prevent thickening of the drying oil by oxygen. ·

Maleic anhydride and pentaerythritol are preferred because they can produce good results and because they are readily available. Other suitable polyhydric alcohols are dipentaerythritol, trimethylolethane, Trimethylol propane, glycerin and ethylene glycol.

A suitable catalyst is isopropyl triethanolamine titanate. It is preferred because it is easy to process is. Butyltriethanolamine aluminate and phenyltriethanolamine silicate are also suitable.

To avoid local gel formation, which could occur with an unmodified catalyst, the catalyst is preferably modified by adding at least one borate in a proportion Metal chelate to borate from 1: 2 to 2: 1 (see US-PS 28 09 284 and 2941981). The catalyst and borate can be used as a mixture or after a pre-reaction to produce a To form connection. It can be heated for about 1 hour or until no more alcohol escapes. This compound is preferred over the use of a mixture of the ingredients.

Suitable borates are compounds of the following formulas:

R ₅ O OR ₅ OR ₅ \
O
/ /
O
\ /
O-B ^ BO
/ \ /
O \ /
O \ /
B.
\ R,
/ \

■ ο ο ο

B B

I ι

-ί) Ö -

R ₄ R ₄

N O

OBR ₁ R ₄

R ₁ ON

wherein R5 is an aliphatic or cycloaliphatic radical having 1 to 6 carbon atoms or an alkyl group optionally containing one to 4 carbon atoms substituted phenyl group and Ri has the meaning given above, namely an ethylene, Is propylene or isopropylene group.

R3 is a divalent radical derived from a saturated aliphatic polyhydric alcohol having 2-6 hydroxyl groups with two removed. R <is hydrogen or R. The open oxygen bonds are represented by R3 or a monovalent radical derived from a monohydric alcohol in which a Hydroxyl group is removed - selected from the saturated and unsaturated aliphatic and aromatic Alcohols and phenol - saturated.

The preferred borate is a mixture of trimeta and triparacresol borate because it gives good results and does not generate volatile by-products as e.g. B. is the case with methyl borate. Other examples are Di-n-hexylene glycol biborate, trihexylene glycol biborate, Trioctylene glycol borate and methyl borate.

The epoxy products of this invention are curable because of their epoxy functionality. They have epoxy equivalent weights of less than 8,000, preferably less than 5,000 for increased epoxy functionality, and therefore they cure faster and more completely. Their minimum epoxy equivalent weight is expressed as the epoxy equivalent weight of the diepoxide divided by the percentage of diepoxide in the compound. Their softening points are below 35 ° C and mostly below 10 ⁰ C.

The following examples serve to illustrate the invention.

example 1

A reaction kettle was charged with 300 g of a diglycidyl ether of bisphenol A (n = 0.15), 300 g of crude linseed oil and 6 g of isopropyltriethanolamine titanate. The charge was heated to 210-220 ⁰ C with stirring for 1 hour and 45 minutes. A clear bead of the liquid modified epoxy resin was achieved. The epoxy equivalent weight was 400-420.

Example 2

Example 1 was repeated using the diglycidyl ether of resorcinol, tung oil and butyltriethanolamine aluminate. A resin of lower viscosity became

obtained with an epoxy equivalent weight of 320-330.

Example 3

Example 1 was repeated using a diglycidyl ether of hydroquinone, perilla oil and phenyltriethanolamine silicate A liquid modified epoxy resin was obtained having an epoxy equivalent weight from 330-340.

Example 4

A mixture was prepared from 605 g of linseed oil refined via alkali, 605 g of liquid diglycidyl ether of bisphenol A with an epoxy equivalent weight of 175-210 (/ 7 = 0.15) and 20 g of the reaction product of isopropyltriethanolamine titanate with a mixture of trimeta and triparacresol borate the mixture was heated to 230-240 ⁰ C and at periodic intervals of about 5 minutes drops were removed and cooled to room temperature, to determine whether they remain clear. After heating for about an hour, the drops removed from the mixture were found to remain clear on cooling to room temperature. The heating of the mixture was stopped so that the mixture could cool to room temperature. Here the mixture consists of a liquid epoxy resin compound modified with drying oil. This compound had an epoxy equivalent weight of 420-430. It is stable when stored in a tightly closed container at room temperature for 3 months.

Example 5

A mixture was prepared from 605 g of alkali-refined linseed oil, 605 g of the liquid diglycidyl ether of resorcinol having an epoxy equivalent weight of 175-210 (tj = 0.12-0.15) and 20 g of trihexylene glycol biborate and isopropyltriethanolamine titanate from 230-240 ⁰ C, and at periodic intervals of about 5 minutes each drops were removed and cooled. After heating for about one hour, it was found that the drops removed from the mixture remain clear on cooling to room temperature. The mixture was then heated for an additional 30 minutes. Then they were allowed to cool to room temperature. The mixture contained a drying oil modified liquid epoxy resin compound having an epoxy equivalent weight of 420-430. This connection is stable when stored for three months in a tightly closed container at room temperature.

Example 6

Example 4 was repeated with the exception that O

a mixture of the diglycidyl ether of bisphenol A and resorcinol 50:50 was used instead of the diglycidyl acid before bisphenol A, soybean oil instead of an alkali refined linseed oil and trioctylene glycol biborai instead of trimetaparacresol borate The results are the same with the exception of:

ίο epoxy equivalent weight of 425-435.

Example 7

Example 4 was repeated with the exception that safflower oil was used instead of linseed refined via alkali men oil and butyl borate was used instead of trimeta paracresol borate. The results are the « same.

Example 8

Example 4 was repeated with the exception that tung oil was used instead of linseed oil refined via alkali and an azeotropic mixture of 32% methanol and 68% methyl borate in place of trimeta paracresol borate has been used. The results are the same.

Example 9

A maleic anhydride modified (maleinized) linseed oil was prepared by mixing 8000 g of pre-alkali refined linseed oil, 410 g of maleic anhydride, 560 g of pentaerythritol, and 2 g of lime. This mixture was gegeber in a vessel and under the protection of an inert gas at 230 ⁰ C for a time period Fuei heated which was sufficient to reduce the acid value to less than the fourteenth The! Took about 1.3 hours. Then 65 g of de: modified oil were mixed with 1 g of isopropyltriethanolamine titaniumate and 20 g of a diglycidyl ether which had an epoxy equivalent weight of 175-210 and was based on bisphenol A and epichlorohydrin. The Mi research was heated to 230 ⁰ C and removed in Intervaller drops of the mixture to room temperature cooled door After about an hour wurdi found that the cooled droplets remained clear and the heating was interrupted. The mixture was cooled to room temperature and consisted of a liquid, drying oil-modified epoxy resin compound with remarkable room temperature stability (the compound could be stored in a tightly sealed container at room temperature for more than 3 months). Nonetheless, the compound was curable in the various ways usual for liquid epoxy resin compounds.

Claims (1)

Patent claims: I. Process for the production of liquid modified epoxy resins, characterized in that that about 20-80% by weight of at least one diglycidyl ether of a diphenol of the formula CH ₂ CH-CH ₂ -ER-CH ₂ -CHOH-CH ₂ Ii-R-CH ₂ -CH- -CH, in the R 'a diphenol residue from the groups C)