DE1543307C - Hardening of epoxy resins - Google Patents

Description

The invention relates to the use of a new class of non-staining hardeners, which in Deliver room temperature colorless, transparent, flexible, hardened epoxies.

So far, polyamines, acid anhydrides, or polyamides are mainly used as hardeners for epoxy resins Polysulfide polymers have been used. In the areas of application of potting adhesives as well as the coating, however, hardeners in particular are required which give the hardened resins flexibility to lend. In this context, of the conventional hardeners mentioned, the "polyamides and polysulfide polymers have been used as agents for imparting flexibility to the epoxy resins been. However, these connections increase the physical strength, such as tensile and tensile strength Flexural strength, decreased in the hardened products; since it is also very difficult to be alone To obtain resins of sufficient strength by curing at room temperature, there is still heating for post-curing necessary. Furthermore, many of the conventional hardeners have a coloring effect as such, and the cured products are noticeably dark or cloudy, which indicates the further influence of the during curing exothermically developed heat or the heat treatment for post-curing.

It has been found that epoxy resins can be completely colorless and transparent at room temperature Resins of excellent flexibility can cure without impairment The mechanical strength takes place when using certain modified spiroacetaldiamines as hardeners used.

The invention accordingly relates to the use of viscous reaction products of spiroacetal diamines the general formula

H ₂ N-R '

O-CH ₂

0-CH ₂

CH ₂ O.

CH ₂ O

R-NH ₂

in which R is hydrogen, a methyl or ethyl residue and R 'denotes a straight-chain or branched alkyl radical having 1 to 6 carbon atoms, with an epoxide or Acrylonitrile for curing epoxy resins.

The reaction product of spiroacetal diamines with epoxides used as hardener according to the invention or acrylonitrile; very resistant, so that no discoloration during storage, during or after curing discoloration occurs and, in combination with ordinary epoxy resins, gives hard, strong, practically colorless, transparent, hardened moldings. . ■

Some examples of Spiroacetaldiamine of the formula given above, which can be used for the preparation of the hardeners used according to the invention include

3,9-bis (aminomethyl) -2,4,8,10-tetraoxa-

spiro- [5,5] -undecane,
3,9-bis (2-aminoethyl) -2,4,8,10-tetraoxa-

spiro- [5,5] -undecane,
3,9-diethyl-3,9-bis (2-aminoethyl) -

2,4,8,1 () -tctraoxa-spiro- [5,5] -undecane,
3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxa-

spiro-f 5,5] -iindccan,

3,9-bis (4-aminobutyl) -2,4,8,10-tetraoxa-

spiro- [5,5] -undecane or
3,9-bis- (1,1-dimethyl-4-aminobutyl) -

2,4,8,10-tetraoxa-spiro- [5,5] -undecane.

These spiroacetaldiamines can easily be found according to known processes, such as those of the German patent 1 092 029 or U.S. Patent 2 996 517, according to which formyl nitrile and

ίο Pentaerythritol in the presence of an acidic catalyst to the intermediate 3,9-bis (cyanoalkyl) -2,4,8,10-tetra-oxa-spiro- [5,5] -undecane are implemented, which is then reduced catalytically. You can also by reacting aminoaldehyde acetal with Pentaerythritol can be prepared directly in the presence of an acidic catalyst.

To form the adducts of the spiroacetaldiamines • all epoxides with at least one oxyrane group can be used can be used in the molecule.

The epoxy or acrylonitrile adducts of the Spiroacetaldiamine can by heating a mixture of spiroacetal diamine and epoxy or acrylonitrile in the presence or absence of solvents. will be. '. . .

Some examples of the solvents suitable for this purpose are methanol, ethanol, butanol, benzene, Toluene, xylene, dioxane ,. Ethylene glycol monomethyl ether or ethylene glycol monoethyl ether.

The heating to carry out the reaction of spiroacetal diamines with epoxy or acrylonitrile is usually continued until the mixture of reactants is a homogeneous viscous liquid forms. The reaction temperature can be above the melting point of the diamines or around the The boiling point of the epoxy or acrylonitrile. In general, temperatures are in the range between 20 and 150 ° C proved to be appropriate.

When reacting with epoxides, the spiroacetaldiamines are expediently used in an amount greater than this

40. as 0.25 ,. preferably 0.5 to 6 mol of spiroacetal diamine per oxyrane groups of the epoxide, and in the reaction with acrylonitrile the spiroacetal diamines are used in a molar ratio of 0.25 to 10, preferably 0.5 to 6 mol per mol of acrylonitrile. ₍

The reaction product of spiroacetal diamine and V Epoxy or acrylonitrile can be isolated in the form of a viscous liquid. In addition, the obtained reaction mixtures containing excess spiroacetaldiamine and solvent, provided it is applied was used directly as a hardener for epoxy resins without fractional distillation will.

The amount in which the hardeners used according to the invention are used per polyepoxide, depends on the number of active hydrogen atoms in the respective hardener and the number of der.im used Polyepoxide present from oxyrane groups. In general, it is appropriate to use equivalents To use amounts by weight of spiroacetal diamine adducts (or their reaction mixtures) and polyepoxide. However, the properties of the hardened products are affected by defects that are less than 20% make up the optimal amount of hardener according to the invention, not impaired.

f> 5 From the German patent I 092 029 it is already known, free spiroacetal diamine: 3,9-bis- (aminoethyl) -2,4,8,10-tetroxaspiro- [5,5] diindecane, to be used as a hardener for epoxy resins. In contrast

The hardener used according to the invention is not free spiroacetal diamine, but around viscous reaction products between spiroacetal diamine and epoxy or acrylonitrile. With Epoxy resin compositions cured by these viscous reaction products have greater flexibility and toughness than the epoxy resins cured using free spiroacetal diamine (see Example 9, bending tests in Table 10).

There are further advantages of the epoxy or acrylonitrile modified spiroacetal diamines of the invention in this,

1. that they represent colorless and transparent viscous liquids, which in contrast to the solid materials, such as the free spiroacetal diamines, are easy to handle,

2. That with them - in contrast to the free spiroacetal diamines, which are based on their basic Form carbonates easily when lying in the air - this carbonate formation is strong is degraded,

3. that they have a very high boiling point and do not cause skin irritation when they evaporate,

4. that they are extremely stable, e.g. B. after storage for 3 months at room temperature do not show any discolouration and if stored for a long time below 5 ° C no separation or crystallization of unreacted spiroacetal diamine components occurs,

5. that they are due to their very low hygroscopicity and the excellent compatibility with epoxy resins neither causes so-called »amine brushing« nor efflorescence,

6. that they provide colorless and transparent resins that do not turn brown,

7. That they are tough, flexible, heat shock resistant resins

deliver and have the same or better mechanical, elastic, chemical properties compared with the other conventional room temperature hardeners,

that curing can be carried out completely at room temperature without heating or post-curing is necessary, but the curing treatment can be shortened by heating can.

In addition, other components such as extenders, fillers, reinforcers can be added in an appropriate manner or provide pigments, depending on the requirements of the particular application.

The invention is to be explained in more detail by the following examples.

Various types of adducts were made from spiroacetal diamines by the following procedure and epoxies.

In a four-necked flask with a stirrer, reflux condenser, dropping funnel and thermometer were 109.6 g (0.4 mol) of 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxa-spiro- [5.5] -undecane and added to 45 bis Heated to 55 ° C. The melt obtained was dripped from the dropping funnel over the course of 2 hours 30.0 g (0.2 mol) of phenyl glycidyl ether and kept the mixture at this temperature for a further 2 hours. It became a colorless, transparent, viscous liquid, the mixture of reaction product and unreacted 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxa-spiro- [5,5] -undecane receive. After storage below 5 ° C for 24 hours or after storage for 3 months at room temperature there was no evidence of separation or crystallization.

The amines and epoxides used are listed in Table 1. All adducts made transparent ones and viscous liquids.

Table 1

Spiroacetal diamine Epoxy ratio of attempt Diamine to epoxy 3,9-bis (3-aminopropyl) -2,4,8,10-tetra- Phenyl glycidyl ether (Mole) 1 oxaspiro [5.5] undecane 2/1 the same Allyl glycidyl ether 2 the same . the same 1/1 3 the same Butyl glycidyl ether 2/1 4th the same the same 1/1 5 the same Glycidyl ester of C _{9 -C 11 fat} - 2/1 6th acids with a to a sec. or 1/1 tert. C-atom bonded carb oxyl group the same the same 7th the same S ^ -Epoxy-o-methylcyclohexyl- 2/1 8th methyl-3,4-epoxy-6-methyl- 2/1 cyclohexyl carboxylate the same Poly (phenylglycidyl) ether 9 3,9-bis (4-aminobutyl) -2,4,8,10-tetraoxa- Phenyl glycidyl ether 2/1 10 spiro- [5.5] undecane 2/1 3,9-bis (aminoethyl) -2,4,8,10-tetraoxa- Butyl glycidyl ether 11th spiro- [5.5] undecane 2/1 3,9-bis (2-aminoethyl) -3,9-diethyl- the same 12th 2,4,8,10-tetraoxa-spiro- [5,5] -undecane 1/1

For example

Theoretical amounts of the adducts given in Table 1 were with a poly (phenylglycidyl ether) mixed and 50 g of the mixtures in a room with air conditioning (temperature 20 ± 1 ° C, relative Humidity 65%). The exothermic maxima and pot lives observed in this way are shown in Table 2 at the same time as those of comparison resins that were hardened with triethylenetetramine - a typical one Hardener for room temperature curing - and at the same time with those of resins specified with a Typical polyamide had been cured to give flexibility to epoxy resins.

Table 2 Service life Exothermic attempt Amount of (Min.) (° C) Hardener *) 40 97 1 60 65 61 2 60 65 103 3 50

IO

attempt Amount of
Hardener *) Service life
(Min.) Exothermic
maximum
("O 4th 60 55 68 5 50 55 115 6th 70 70 46 7th 55 70 82 8th 60 85 75 10 55 50 92 11th 50 55 103 12th 60 65 71 Triethylene tetramine 10 124 polyamide 50 39

*) Parts by weight / 100 parts by weight of poly (phenylglycidyl ether).

*) Parts by weight / 100 parts by weight of poly (phenylglycidyl ether).

Example 2

Heat deformation tests according to ASTM D 648-56 and bending tests according to ASTM D 790-49 T were carried out on the carried out in Table 2 specified epoxy resin systems. The results are shown in Table 3.

table

Harder

Attempt 1,
Attempt 2,
Attempt 3
Attempt 4
Attempt 5
Trial 6
Trial 7

Trial 8.
Attempt 9.
Attempt 10
Attempt 11

Attempt 12

Triethylenetetramine

polyamide

Parts by weight /

100 parts by weight

Poly (phenyl

glycidyl ether)

60
60
50
60
50
70
55
60

55
50

60
10

Hardness condition

r.t.

3h / 80 ° C

r.t.

3h / 80 ° C

r.t.

3h / 80 ° C

r.t.

3h / 80 ° C

r.t.

3 h / l 20 ° C

r.t.

3 h / 100 ° C

r.t.

3h / 80 ° C

r.t.

r.t.

r.t.

3h / 80 ° C

r.t.

r.t.

3 h / 100 ° C

3h / 65 ° C heat

deformation temperature Γ C)

75 52 55 75 77 74 65 52 75 58 55 79 74

55 70 65 55 79 64

Piping test

max. elongation max. strength module (mm) (kg / mm ² ) ■ (kg / mm ² ) 31.3 14.4 388 29.2 12.2 298 20.0 10.0 290 - 10.8 311 - 11.0 290 29.6 11.0 287 33.7 11.4 292 10.7 309 21.0 10.0 295 - 11.5 313 34.2 10.8 320 - 10.7 310 28.5 11.2 290 31.7 11.4 296 25.0 10.1 250 29.5 12.0 320 25.0 10.5 ■ 301 31.1 11.0 310 29.1 11.1 300 4.6 9.15 388 15.6 13.7 320 20.7 9.85 242

r.t. = Room temperature.

- = test pieces did not break during the bending test.

B e i s ρ i e 1 3 65 the following test samples and test methods are given

turns:

The heat shock resistance was measured on 80 g of a mixture of poly (phenylglycidyl

some epoxy resin adduct systems tested. There was aether) and hardener in a vessel of 70 mm

Diameter and 30 mm depth together with a spring-spring metal pad with a diameter of 2.54 cm deformed and cured for 14 days at room temperature. The thermal cycles were these test specimens given by adding them alternately to boiling water and ice water. The duration the cycle of each heating and cooling was 30 minutes. Resilience to the thermal shock of these test samples was determined according to the degree of caused by the thermal cycling Jumps measured.

Table 4 shows that the invention obtained moldings showed superior resistance to thermal shock, and not only against the one with triethylenetetramine, but also against one with one Polyamide hardened resin.

Combination test 1. Table 4 2. 3. 4th Test pieces after 6th every cooling cycle 8th. 9., 10. ratio piece cycle Cycle- cycle cycle cycle cycle cycle cycle TT " A. Estimates of the A. A. A. 5. A. 7th A. A. A. Harder 70 1 A. A. A. A. cycle A. cycle A. A. A. 2 A. A. A. A. A. A. A. A. A. A. Experiment 6 .. 3 C. D. D. D. A. D. A. D. D. D. 55 1 C. D. E. A. A. 2 A. A. A. B. D. E. D. Trial 7 3 B. B. B. B. B. B. B. B. 70 1 A. A. A. A. D. A. A. B. B. (15% over 2 A. A. A. A. B. A. B. A. A. A. Trial 7 shot) 3 C. C. C. C. A. C. A. C. C. C. 60 1 B. C. C. C. : a C. A. C. C. C. 2 A. A. A. A. c A. C. A. A. A. Attempt 4 , 50 1 A. A. A. A. C. A. C. A. A. A. 2 A. A. Attempt 5 E *) E. E. E. A. E. A. E. E. E. 9 1 E. E. E. E. E. E. E. E. Triethylene 2 E. E. E. E. E. E. E ■ E. E. E. tetramine 50 1 E. E. E. E. E. E. E. E. E. E. 2 E. E. polyamide E. E.

Criteria for estimating:

C: small cracks.

A: No cracks at all. D: considerable cracks.

B: few cracks. E: large cracks.

*) Large cracks were observed during curing.

Example 4

Impact tests were carried out using a Sharpy impact tester accordingly the Japanese Industrial Standard K-6911 carried out on epoxy resins, which with the from Example 2 selected hardeners had been hardened. Test samples cured for 14 days at room temperature and those cured by machine were used the in F i g. 1 specified size was given. Those obtained in the impact resistance test Results are given in Table 5. Unit = mm.

Table 5
(Mean values of 6 test pieces)

Harder Station wagon
nations. Hardening
1_ · Impact resistance ratio at (kg / cm / cm ² ) 5th attempt 4 60 r.t., 14 days 14.3 Attempt 5 50 r.t., 14 days 15.7 *) Triethylene tetramine 9 r.t., 14 days 4.3 55 polyamide 50 65 ° C, 8.9 3 hours

*) No breakage occurred in the test apparatus used.

Example 5

Harder Station wagon
national
ratio Hardening
at Impact resistance
(kg / cm / cm ² ) Trial 6
Trial 7 70 '
55 rt, 14 days
rt, 14 days 14.4
. 15.7 *)

*) No breakage occurred in the test apparatus used.

The tensile strength and the modulus of elasticity in tension were measured in tests carried out according to the Japanese Industrial Standard K-6911 at 21 ° C, relative humidity 65% and carried out at a cross-head pulling speed of 5 mm / min became. The in F i g. Test samples shown in FIG. 2 were machine formed from a sheet shown in FIG

109 512/392

a glass mold has been cured at 120 ° C for 30 minutes was (Table 6).

Table 6
(Average of 3 to 6 test pieces)

Harder Station wagon
national
ratio tensile strenght
(kg / mm ² ) Tension
elasticity
module
(kg / mm ² ) Trial 6 70 7.15 232 Trial 7 55 6.52 194 Attempt 4 60 7.15 235 Attempt 5 50 7.30 216 Triethylene
tetramine 9 5.09 273 polyamide 50 6.89 237

*) Parts / 100 parts poly (phenyl glycidyl ether).

Example 6

Various types of adducts were prepared in the manner shown below. The used Amines are given in Table 7. The molar ratio of acrylonitrile to amine is 1: 1 or 1: 2. The adducts obtained were transparent and viscous liquids.

53 g (1 mol) of acrylonitrile were added dropwise at a temperature between 45 and 55 ° C. over the course of one hour to 274 g (1 mol) of 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxa-spiro- [5,5] -undecane contained in a flask was. The mixture was kept stirring for an additional 60 minutes, the adduct in shape a transparent and viscous liquid.

Table 7

Spiroacetal diamine ratio of sample Amine too
Acrylonitrile 3,9-bis (3-aminopropyl) - (Mole) 13th 2,4,8,10-tetraoxa- 1: 1 spiro- [5.5] undecane 3,9-bis (3-aminopropyl) - 14th 2,4,8,10-tetraoxa- 2: 1 spiro- [5.5] undecane 3,9-bis (4-aminobutyI) - 15th 2,4,8,10-tetraoxa- 1: 1 spiro- [5,5] undecari 3,9-bis (2-aminoethyl) - 16 2,4,8,10-tetraoxa- 2: 1 spiro- [5.5] undecane 3,9-bis- (1,1-dimethyl- 17th 4-aminobutyl) - 1: 1 2,4,8,10-tetraoxa- spiro- [5.5] undecane 3,9-diethyl-3,9-bis (2-amino- 18th ethyl) -2,4,8,10-tetraoxa- 2: 1 spiro- [5.5] undecane

40

45

Example 7

40 to 30 parts by weight of the product obtained were 100 parts by weight of poly (phenylglycidyl ether) given, 500 g of the mixture obtained were added in an air-conditioned laboratory 20 ± TC and relative humidity of 65% and the exothermic reaction with gel formation observed. The exothermic peak and the pot life is for the corresponding compounds in Table 8, in which these values for comparison compounds, i.e. H. for triethylenetetramine and for a polyamide are included.

Table 8 shows that the moldings obtained according to the invention have the property that the time for gel formation is twice as long as that of the conventional hardeners, although that exothermic maximum was close to the same temperature. This feature then turned out to be special Proven valuable when the compound is used for castings, as the pot life is longer than when the usual conventional connection.

Table 8

Harder Amount of
Resin *) gel
educational
time**)
(Min.) Exo
thermes
maximum
CQ Time until
Achievement of the
exotherms
Maximum
(Min.) Trial 13 63 130 178 150 Attempt 14 49 70 200 90 Attempt 15 63 100 170 120 Attempt 16 42 65 189 90 Attempt 17 78 105 165 124 Attempt 18 54 70 180 92 Triethylene no
tetramine 9 30th 200
to 210 60 polyamide 50 48 157 72

*) Parts by weight / 100 parts by weight of poly (phenylglycidyl ether). **) Time between the time the hardener is added and the point in time at which the compound reaches too high a viscosity for practical use.

55

Example 8

The results of the heat distortion tests performed according to the test methods described in ASTM D 648-56 and the bending tests performed according to the test methods specified in ASTM D 790-49 T, are given in Table 9.

The moldings obtained according to the invention have the same color as the uncured epoxy resin. The color of the resins cured with the conventional hardeners was usually yellow or yellowish brown.

table

12th

Harder

Heat distortion temperature

( ⁰ C) bending test

Strength (kg / mm ² ) Young's modulus
(kg / mm ² )

Maximum stretch before

the breakage of the sample

(mm)

Trial 13

Attempt 14

Attempt 15

Attempt 16

Attempt 17

Attempt 18

Triethylenetetramine

Triethylenetetramine 3 hours

hardened at 100 ^{° C}

Polyamide 3 hours

cured at 65 ° C

69.5 80.7 65.0 72.1 70.1 71.0 55.0

78.0 64.0

11.6 12.4 11.0 12.1 11.5 12.2 9.15

298
297
295
290
293
300
388

320

242

32.3 25.0 30.0 24.2 31.3 25.0 4.6

15.6 20.7

Example 9

The aim of the following experiments is to show that the resins obtained with the adduct of 3,9-bis- (3 - aminopropyl) - 2,4,8,10 - tetraoxa - spiro - [5,5] - undecane and epoxy according to the invention have been cured have better properties than the resins prepared with 3,9-bis- (3-aminopropyl) -2,4,8,10-tetraoxaspiro- [5,5] -undecane have been hardened.

Table 10 shows that the flexibility of the resins cured with the adducts is greatly improved. the Evidence of this fact can easily be found in the maximum elongation data; H. the value of Elongation before the specimen is broken under the bending load. The values for the comparison compounds, d. H. for triethylenetetramine and for a polyamide are also given.

Table 10 a) Flexural tests at room temperature curing

Harder Amount of hardener ■ Strength
(kg / mm ² ) Bending test
modulus of elasticity
(kg / mm ² ) Maximum elongation before
the breakage of the sample
(mm) ATU *) 35
60
60
50
10 12.9
14.4
10.0
11.0
9.15 312
388
290
290
388 19.3
31.3
20.1
does not break
4.6 Attempt 1
Attempt 2
Attempt 3
TTA **)

b) Bending tests with high temperature hardening

Amount of hardener strength Bending test Maximum elongation before
the breakage of the sample Harder (kg / mm ² ) modulus of elasticity (mm) -35 12.6 (kg / mm ² ) 21.8 ATU 30 minutes at 8O ⁰ C ... 60 12.2 288 29.7 Experiment 1 3 hours at 8O ⁰ C 60 10.8 298 does not break Experiment 2 3 hours at 8O ⁰ C 50 11.0 311 29.6 Experiment 3 3 hours at 8O ⁰ C 10 13.7 287 15.6 TTA 3 hours at 100 ^° C 50 9.85 320 20.7 Polyamide 3 hours at 65 ° C 242

*) 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxa-spiro- [5,5] -undecane. **) triethylenetetramine.

Claims (1)

13 14 Claim: Use of viscous reaction products of spiroacetal diamines of the general formula R 0-CH ₂ CH, OR CCC H ₂ NR '0-CH ₂ CH ₂ OR- NH ₂ in which R is hydrogen, a methyl or ethyl radical having 1 to 6 carbon atoms, with an epoxide and R 'a straight-chain or branched alkyl radical or acrylonitrile for curing for epoxy resins. 1 sheet of drawings