CS268957B1 - Fast epoxide hardener - Google Patents

Abstract

The solution is a fast hardener for epoxy resins, which is prepared by homogenizing 10 to 95 parts by weight of an amine hardener and 5 to 90 parts by weight of an accelerating plasticizer with the following composition by weight: 3 to 50 parts by weight of bisphenol A, 20 to 85 parts by weight of diallyl ether of bisphenol A, 5 to 25 parts by weight of monoallyl ether of bisphenol A, 2 to 10 parts by weight of allylated monoallyl ether of bisphenol A and 3 to 18 parts by weight of allylbisphenol A.

Description

The invention relates to rapid hardeners based on modified aliphatic polyamines.

The pot life of compositions made from epoxy and aliphatic polyamines at normal temperature is several minutes to several hours. The curing time is usually 48 to 72 hours. The final properties are therefore achieved after several days. The smaller the number of primary active hydrogens in the hardener, the slower the post-curing. The lower the ambient temperature has the same effect. The advantage of slow curing is the suppression of shrinkage. In many cases, faster curing is required, even at the cost of slight shrinkage. This can be achieved by increasing the temperature or using a fast hardener. ,

For successful curing of epoxy resins with aliphatic polyamines, a minimum temperature of 18 °C is recommended. At lower temperatures, a curing accelerator must be used, although the reaction of the epoxy group with amines forms a secondary hydroxyl group, which also accelerates. Any acceleration of curing is simultaneously associated with a shortening of the workability time. When curing with amine adducts or aminoamides, it may be necessary to accelerate curing even at laboratory temperature. This causes a higher molecular weight and a lower concentration of primary amine groups. However, excessive acceleration can lead to inhomogeneity of the cured mass and greater internal stress in it, '

Hydrogen atom donors, such as alcohols, phenols, acids or water, usually have an accelerating effect. However, they usually have too low boiling points and therefore cannot be used in larger quantities, or they have a higher molecular weight, but then they are solid and must be dissolved for dosing, e.g. bisphenol A.

Users prefer two-component systems to three-component systems because of the lower probability of errors. For curing aliphatic polyamines at room temperature, common accelerators are triethanolamine, benzoic and salicylic acids, and cresol.

It has now been found that for curing at temperatures below 10 °C and general acceleration of the curing reaction of epoxy resins and liquid epoxy elastomers, amine hardeners can be modified by adding 5 to 90 wt. % of an accelerating plasticizer consisting by weight of 3 to 50 parts of bisphenol A, 20 to 85 parts of diallyl ether of bisphenol A, 5 to 25 parts of monoallyl ether of bisphenol A, 2 to 10 parts of allylated monoallyl ether of bisphenol A and 3 to 18 parts of allylbisphenol A.

The rapid hardeners according to the invention are prepared by mixing the individual components (sometimes it is necessary to use elevated temperatures, e.g. 70 °C) or as solutions of products of a suitably controlled reaction of allyl chloride with bisphenol A. Other bisphenols can also be used, e.g. bisphenol F, in addition to p.p.-isomers, also o;p- and o,o-isomers of bisphenol, or derivatives of bisphenols. Sometimes it is appropriate to add an inert plasticizer or diluent to the accelerator for better processability.

New rapid hardeners are usually yellow to brown liquids with a viscosity of 20 to 1000 mPa.s/25 °C. Due to the higher average molecular weight, they can be used in larger quantities than previously known accelerators. They have a lower toxicological hazard for workers in production and during use. They are not washed out with water. Their effectiveness is comparable to m-cresol. In addition, they increase resistance to dry heat. The acceleration of hardening and plasticization increases with the amount used. As starting amine hardeners, e.g. diethylenetriamine, dipropylenetriamine, triethylenetetramine, tetraethylenepentamine, trimethylhexamethylenediamine, pentaethylenediamine. their adducts. modifications and mixtures. Acceleration and plasticization have also been found with other polyamines. e.g. isophoronediamine. They are usually used in an amount of 90 to 160% of theory based on the content of epoxy groups.

The epoxy resins used are usually palm type with an average molecular weight of 300 to 600 and may also contain fillers, pigments and additives regulating the mechanical properties.

CS 268957 81 chemical and technological properties Liquid epoxy elastomers have an average molecular weight of 500 to 1000. They include products based on epoxy resins or compounds with an average molecular weight of 170 to 500 and polymeric fatty acids or carboxylic oligomers with an average molecular weight of 500 to 1500.

Example 1

4 types of accelerating plasticizers were used. Their probable composition in wt. % Is this: type A 8 C D bisphenol A 7 15 25 40 bisphenol A allyl ether 70 45 40 35 bisphenol A monoallyl ether 10 20 18 15 allylated monoallyl ether of bisphenol A 8 5 4 . 3 allylbisphenol A 5 15 13 7

The accelerating effect was monitored in the reaction of an epoxy resin with an average molecular weight of 394 with dipropylenetriamine containing 14.7 wt. % of accelerating plasticizer at 23 °C. 140 g of resin and 21.8 g of modified dipropylenetriamine (100 % of theory) were weighed into a PVC crucible. Immediately after weighing, the mixture was homogenized by stirring on a 5 cm high wooden base. The temperature was read with a thermometer with a division of 1 °C. The temperature increase in 15 minutes, the amount of OH groups of the tested substance in mol/100 g, the ultimate tensile strength T (MPa) and the elongation t (%) determined 28 days after casting are given in the table:

modifier + °C OH T t - 8 - 39 3 A 11 0.161 50 4 B 13 0.335 50 4 C 13.5 0.397 42 3 0 ' 14 0.468 30 3

Example 2

According to the procedure given in Example 1, . . . · composition K1 (127.5 g of epoxy resin with an average molecular weight of 384 + 36 g..... diethylstriamine containing 62.5 wt. % of accelerating plasticizer type . . . B) · .........

L (150 g of the same resin + 16.4 diethylenetriamine).

The temperature increase over 5 minutes at an ambient temperature of 25 °C and the determined tensile strength and ductility after 28 days are given in the table:

composition + °C T (MPa) t (%) K1 13 58 8 L 3 36 4

Example 3 • Compositions K1 and L from example 2 were prepared from raw materials tempered to 12 °C and after 5 minutes of mixing at 23 °C they were placed in spaces with temperatures of 23, 10 and 3 °C. The gelation times determined in minutes are °C ' 23 10 composition K1 <11 130 240 composition L

240 more than 8 hours

CS 268957 Bl 3

Example 4. The effect of the amount of type C was investigated for compositions P1, P2, P3 and P4 (32 g dibutyl phthalate - 113 g epoxy resin with an average molecular weight of 588 and 8.4 or 14.2 or 37.4 or 48.4 g diethylenetriamine containing 0 or 30.4 or 77.5 or 82.6 wt. % type C. The last line shows the use of 160% of the hardener theory. The following table shows the evaluation As in example 2.S

composition °c T t P.I. 4 37 5 P2 9 31 6 P3 15 6 8 P4 19 4 17 P2 8 32 15

Example 5

The influence of the rapid hardener according to the invention on the course of the formation of epoxy rubber is shown by the composition R1 (140 g of a cap epoxy elastomer with an average molecular weight of 800 + 14 g of trimethylhexamethylenediamine) R2 (140 g of the same elastomer + 16.8 g of trimethylhexamethylenediamine containing 16.7 wt. % of an accelerating plasticizer of type B. The values found are for composition R1 +7 °C/10 minutes 3 MPa 60%

R2 10 3.5 61

Example 6

The effect of thermo-oxidative aging (4 days, 125 °C) was verified for compositions T (120 g of epoxy resin with an average molecular weight of 588 ♦ 38.8 g of ethylenetriamine containing 22.7 wt. % of accelerator type B. The loss is given in wt. %:

+ °C/10 minutes ^{That 1} or ^T 4 *4 u type 8 14.5/5 minutes 35 5 26 3 0.8 benzyl alcohol 19 43 5 3 2 10.4 dibutyl phthalate 6 37 6 9 2 3.3 bisphenol A diallyl ether 6 64 5 44 4 1.3

Example 7

_Composition Z (140 g of epoxy resin with an average molecular weight of 392 * 21.8 dipropylenetriamine containing 13 wt. % accelerator) was monitored at 25 °C. After 10 minutes, temperature increases were determined, and after 28 days, mechanical values - tensile strength T (MPa), elongation t (%) and tensile product (MPa.%) were determined:

accelerator ♦°C T t product type 8 11.5 83 8 664 triethanolamine 11 63 6 378 tricresol 12 77 2.5 193 PRE D M £ T W I N A I'M CLIMBING

Rapid hardener for epoxy resins, usable even at temperatures below 10 °C, containing 10 to 95 wt. % amine hardener and 5 to 90 wt. % accelerating plasticizer, characterized by.

Claims (2)

Rapid hardener for epoxy resins, usable even at temperatures below 10 °C, containing 10 to 95 wt. % amine hardener and 5 to 90 wt. % accelerating plasticizer, characterized by. 4 CS 268957 Bl that it consists by weight of 3 to 50 parts of biaphenol A, 20 to 85 parts of diallyl ether of biaphenol A, 5 to 25 parts of monoallyl ether of biaphenol A. 2 to 10 parts of allylated monoallyl ether of bisphenol A and 3 to 18 parts of allylbisphenol A.