RU2509783C1 - Method of producing curing agent for medium-molecular weight epoxy resins - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to curing agents for epoxy resins and compositions based thereon. Disclosed is a method of producing an organosilicon curing agent for medium-molecular weight epoxy resins by reacting, for 2-3 hours at temperature of 80-100°C in the presence of an alkaline catalyst, an amine-containing organosilicon compound (I), an organosilicon compound with a phenyl group at the silicon atom (II) and an organosilicon compound containing two methyl groups at the silicon atom (III) with molar ratio of components I:II:III = 1.0:(0.5-1.0):(0.5-2.0) and total content of alkoxy groups to the total number of silicon atoms of 1-1.5.

EFFECT: simple method of producing organosilicon curing agents that are stable during storage, which enable to obtain paint coatings with good adhesion to different substrates and improved physical and mechanical properties.

1 cl, 3 tbl, 14 ex

Description

The invention relates to the field of production of hardeners for epoxy resins and compositions based on them.

The use of organosilicon amine hardeners for epoxy oligomers can significantly increase the adhesion of coatings to hydrophilic substrates, in particular to aluminum. The most common of these hardeners in our country was ASOT-2 [2283331, 2284342, 2174136], obtained by complete hydrolysis and partial condensation of AGM-9 in cyclohexanone [TU 6-02-1250-83].

The main disadvantage of ASOT-2 is its inability to use it in compositions with low- and medium-molecular epoxy resins, such as the widely used E-40 resin. We can also note the short storage time of ASOT-2 (up to 6 months) and the presence of sufficiently toxic cyclohexanone as a solvent in its synthesis.

The closest in technical essence is the method for producing organosilicon hardeners by reacting 3-aminopropyltriethoxysilane (analogue of the product AGM-9) with diphenylsilanediol, or with α, ω-diphenylsiloxanediol, or with methylphenylsilanediol, or with α, ω-methylphenylsiloxanediol at a temperature of 90-105 ° C , with distillation of ethyl alcohol and subsequent exposure at 140 ° C [RF patent 2230068, 2004].

The disadvantages of the method include: 1) the raw material for the hardener (silane and α, ω-siloxane diols) has a limited storage time, 2) when implementing the proposed method, to avoid homopolycondensation of the hydroxyl-containing components with each other, it is necessary to introduce them for a very long time ( by dropping) and 3) distillation of ethyl alcohol takes at least 1.5-2 hours.

The technical task of the invention is the development of a more efficient, fast and simple method for the synthesis of organosilicon amine hardeners of epoxy oligomers (resins) of average molecular weight from available, convenient raw materials. At the same time, high physical and mechanical properties of coatings obtained using such hardeners should be maintained.

The technical problem is solved by our method of producing an organosilicon hardener for epoxy resins by reacting, when heated to a temperature within 80 ÷ 100 ° C, an amine-containing organosilicon compound of the general formula

, $${[RSi{(OR\text{'}\text{'})}_a{O}_{(3-a)/2}]}_{n\mathrm{one}}\left(I\right)$$

,

where R is 3-aminopropyl or N- (2-aminoethyl) -3-aminopropyl,

R ′ is methyl or ethyl; a = 1.0 ÷ 3.0, n ₁ = 1 ÷ 9,

with an organosilicon compound containing a phenyl group at a silicon atom, of the general formula

, $${[(C_6{H}_5)Si{(OR\text{'}\text{'})}_b{O}_{(3-b)/2}]}_{n2}\left(II\right)$$

,

where R ′ is methyl or ethyl, b = 1.0 ÷ 3.0, n ₂ = 1 ÷ 9,

and with an organosilicon compound containing two methyl groups on a silicon atom, of the general formula

, $${[{(C{H}_3)}_{2}Si{(OR\text{'}\text{'})}_c{O}_{(2-c)/2}]}_{n3}\left(III\right)$$

,

where R ′ is methyl or ethyl; c = 0 ÷ 2.0, n ₃ = 1 ÷ 6,

with a molar ratio of components I: II: III of 1.0: (0.5 ÷ 1.0) :( 0.5 ÷ 2.0),

and the total number of alkoxy groups in the starting components with respect to the total number of silicon atoms equal to 1.0 ÷ 1.5.

The process is carried out for 2-3 hours under the action of an alkaline catalyst selected from a series of potassium, sodium or tetraalkylammonium hydroxide or siloxanolate, with a content of 0.05-0.5% of the total mass of organosilicon components, followed by neutralization of the catalyst with trimethylchlorosilane or glacial acetic acid and filtering the product from the precipitate.

The invention is illustrated by the following examples.

Example 1. In a flask equipped with a stirrer, a thermometer and a reflux condenser, 55.25 g of 3-aminopropyl-triethoxysilane, 42.98 g of phenylethoxysiloxane [(C ₆ H ₅ ) Si (OC ₂ H ₅ ) _1.16 O _0, are charged ₉₄ ] ₅ and 18.5 g of octamethylcyclotetrasiloxane. While stirring, a solution of 0.58 g of potassium hydroxide in 5 grams of ethyl alcohol is added to the reaction mass and it is heated to 85 ° C. After that, the reaction mass is stirred for 2 hours, then cooled to 50 ° C and the catalyst is neutralized by the addition of an equimolar amount of trimethylchlorosilane. The precipitate of potassium chloride is filtered off. 113.5 g of aminoethoxy-siloxane hardener are obtained in a yield of 97% by weight. The hardener formula can be represented in a simplified form {[NH ₂ (CH ₂ ) ₃ Si] [(C ₆ H ₅ ) Si] [(CH ₃ ) ₂ Si] (OC ₂ H ₅ ) _4.16 O _1.94 } m where m≈1.

The amount of active amine groups is determined in the obtained product by titration; if necessary, the structure is refined by NMR spectroscopy from ¹ H and ²⁹ Si nuclei.

Example 2. In a flask equipped with a stirrer, thermometer and reflux condenser, load 44 g of aminomethoxysiloxane [NH ₂ (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) O] _n , where n≈9, 49.5 g phenyltrimethoxy silane; and 37 g octamethylcyclotetrasiloxane. With stirring, a solution of 0.06 g of NaOH in 1 g of ethyl alcohol is added to the reaction mass and heated to a temperature of 80 ° C. After this, the reaction mass is stirred for 3 hours, then cooled to 50 ° C and the alkali is neutralized by the addition of an equimolar amount of glacial acetic acid. The precipitate of sodium acetate is filtered off. 128 g of aminomethoxysiloxane hardener are obtained with a yield of 98% by weight. The hardener formula can be represented as {[NH ₂ (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si] [(C ₆ H ₅ ) Si] [(CH ₃ ) ₂ Si] ₂ (OCH ₃ ) ₄ O ₃ } _m where m≈1.

In the obtained product, the amount of active amine groups is determined by titration and, if necessary, the structure is refined by NMR spectroscopy from ¹ H and ²⁹ Si nuclei.

Examples 3-7. The synthesis is carried out according to a similar scheme, changing the starting materials, their ratio and temperature. The composition of the starting materials, their amount, the temperature of the reactions, as well as the characteristics of the obtained products are presented in table 1.

The following are examples of the use of the obtained organosilicon hardeners in varnish compositions based on epoxy resin E-40 in comparison with the prototype (organosilicon diamine obtained by condensation of 3-aminopropyltriethoxysilane with methylphenylsilanediol).

Example A. 38.6 g of epoxy resin E-40 is dissolved in 30.9 g of mixed solvent R-5 [GOST 7827-74] and 30.5 g of the aminoethoxysiloxane hardener obtained in Example 1 are added.

Example BJ Compositions are prepared analogously to example A, changing the ratio of components and type of hardener.

Example 3 (prototype). 33.3 g of epoxy resin E-40 is dissolved in 33.4 g of toluene and 33.3 g of silicone hardener are added according to the prototype (α, ω-di (-3-aminopropyl) oligomethyl-phenylsiloxane).

The compositions of the examples of specific performance AZ are presented in table 2.

Table 3 shows the physicochemical and operational properties of the varnish coatings obtained from the compositions of Examples A-3 and cured for 2 hours at 120 ° C.

As can be seen from examples of specific performance, coatings obtained using organosilicon hardeners by the proposed method are not inferior, but in some properties, and superior to coatings obtained using a hardener according to the prototype.

The proposed method in comparison with the prototype allows to simplify the synthesis - to exclude the stage of distillation of a low molecular weight by-product, the use of inert gas, to carry out the process at a lower temperature, and also to reduce the duration of the process by about half. In contrast to the prototype, where the main reaction of the synthesis is the polycondensation of silane or siloxanediol with 3-aminopropyltriethoxysilane, which has the above disadvantages, in the proposed method, the main reaction is the catalytic rearrangement and co-oligomerization of siloxanes, that is, practically the redistribution of siloxane and silicon ether bonds between silicon atoms equilibrium state. In this case, the equilibrium state is reached relatively quickly (as was established by NMR ²⁹ Si - in 2-3 hours), therefore, special methods for controlling the synthesis are not required.

Claims (1)

A method of obtaining an organosilicon hardener for epoxy resins of medium molecular weight, characterized in that the amine-containing organosilicon compound of the general formula is reacted
$${[RSi{(OR\text{'}\text{'})}_a{O}_{(3-a)/2}]}_{n\mathrm{one}},\left(I\right)$$

where R is 3-aminopropyl or N- (2-aminoethyl) -3-aminopropyl,
R ′ is methyl or ethyl; a = 1.0-3.0; n ₁ = 1-9;
with an organosilicon compound containing a phenyl group at a silicon atom, of the general formula
$${[(C_6{H}_5)Si{(OR\text{'}\text{'})}_b{O}_{(3-b)/2}]}_{n2},\left(II\right)$$

where R ′ is methyl or ethyl; b = 1.0-3.0; n ₂ = 1-9;
and with an organosilicon compound containing two methyl groups at the silicon atom, of the general formula
$${[{(C{H}_3)}_{2}Si{(OR\text{'}\text{'})}_c{O}_{(2-c)/2}]}_{n3},\left(III\right)$$

where R ′ is methyl or ethyl; c = 0-2.0; n ₃ = 1-6;
with a molar ratio of components I: II: III of 1.0: (0.5-1.0) :( 0.5-2.0),
and the total number of alkoxy groups in the starting components equal to 1.0-1.5 with respect to the total number of silicon atoms, and the reaction is carried out for 2-3 hours at a temperature of from 80 to 100 ° C and in the presence of an alkaline catalyst selected from the series potassium, sodium or tetraalkylammonium hydroxide or siloxanolate, taken in an amount of 0.05-0.5% of the total mass of organosilicon components, followed by neutralization of the catalyst and filtering the product from salt precipitate.