Mannich Type Hardeners based on MXDA
1. Introduction

meta-Xylylenediamine(MXDA) is an aliphatic diamine having benzene ring and a useful raw material for epoxy resin hardeners. It has unique properties different from those of the conventional aliphatic amines or aromatic amines. MXDA may be used as an epoxy resin hardener by itself, but they are preferably modified into the forms of blends, adducts, or polyaminoamide by treatment with adequate chemicals in order to improve properties, workability and safety. Among those hardeners, Mannich type hardeners based on MXDA are used for ambient temperature and especially lower temperature cure epoxy resin systems with many advantages.

2. Properties of MXDA

MXDA has been manufactured by ammoxidation of pure meta-xylene into isophthalonitrile, followed by hydrogenation of the nitrile. MXDA is colorless liquid with low viscosity. The properties of MXDA are shown Table 1.

Table 1.Properties of MXDA

Physical Properties
Appearance
Colorless liquid
Molecular weight
136.1
Color (Gardner)
1 max
Specific gravity (20°C/ 68°F)
1.052
Viscosity (cps at 20°C/ 68°F)
6.8
Freezing point
14.1°C/ 57.4°F
Boiling point (760mmHg)
273°C/ 523°F
Flash point (COC)
139°C/ 282°F
Amine value
824
Active Hydrogen Equivalent Weight
34
Solubility
Soluble
water, ether, benzene
TSCA Registry CAS No.
1477-55-0
EINECS No.
216-032-5

3. Mannich reaction

Mannich reaction is aminomethylation of carbonyl compounds and other acidic CH compounds by the aldol condensation of active methylene groups with formaldehyde and ammonia or primary or secondary amines.
Mannich type hardeners based on MXDA are prepared with MXDA, phenol and formaldehyde, shown in Scheme 1.


Scheme 1. Mannich reaction

3-1.Preparation of Mannich type hardeners based on MXDA

In a four-necked flask, equipped with a stirrer, a thermometer, a nitrogen gas inlet, a dropping funnel and measuring reservoir of the condensation water surmounted by a reflux condenser, phenol and MXDA were stirred and heated 80°C(176°F) under nitrogen gas stream. 37% formalin was added slowly dropwise, while the temperature was controlled to keep 80°C(176°F) through 90°C(194°F). The temperature was raised to 100°C(212°F) and kept for one hour. Then the water was distilled off during two hours at up to 150°C(302°F) and the reaction was continued for one hour at 150°C(302°F). The reaction mixture was cooled to 80°C(176°F), while nitrogen gas stream was stopped. If necessary, accelerator and diluent were added and stirred. The hardener was obtained.

4. Advantages of Mannich type hardeners based on MXDA

Mannich type hardeners based on MXDA have the following advantages;
-Lower viscosity of the hardeners than other hardeners
-Cure fast at ambient temperature and lower temperature
-Give glossy, flat and hard surface
-Give excellent water and chemical resistant surface

5. Contents of free phenols and MXDA, and viscosity of Mannich type hardeners based on MXDA

Mannich type hardeners based on MXDA include free phenol and MXDA in themselves. Contents of free phenol and MXDA, and viscosity in several compositions of Mannich type hardeners based on MXDA, which were prepared with MXDA, phenol or p-tert-butylphenol or p-nonylphenol or o-cresol, and formaldehyde, are given in Table 2. While molar ratio of phenol increases, free phenol increases, therefore, free MXDA decreases, and viscosity of the hardener decreases. While molar ratio of formaldehyde increases, Mannich reaction proceeds to the preparation of higher molecular compounds, therefore, free phenol decreases, free MXDA decreases, and viscosity of the hardener increases.

Table 2. Contents of free phenol and MXDA, and viscosity of Mannich type hardeners based on MXDA

Molar ratio *1
Free phenols *2 (wt.%)
Free MXDA *2 (wt.%)
Viscosity (ps.25°C)
P
B
N
OC
P
B
N
OC
P
B
N
OC
70100
90100
100100
110100
3.6
8.0
11
 
  
7.7
11
13		  
10
13
19
0.9
5.3
7.5
 
26
21
21
 
  
16
15
12		  
13
13
8
19
16
15
 
860
870
850
 
  
3600
2600
2720		  
1300
1000
1100
258
145
150
 
10067
10090
100110
17
 
9.0
21
12
7.1
26
16
11
  
 
5.4
29
 
18
22
15
13
18
13
11
  
 
13
22
 
3300
92
930
19000
110
550
3760
  
 
445

P:Phenol B:p-t-Butylphenol N:p-Nonylphenol OC:o-Cresol
*1 Molar ratio : Phenols/ Formaldehyde/ MXDA = 60/ 110/ 100 = 60110
*2 measured with HPLC method

6. Comparison of MXDA with IPDA and DETA as Mannich type hardeners with phenol

6-1. Formulations and physical properties of hardeners

As shown Table 3, Mannich type hardener based on MXDA for non-solvent system has lower color number and lower viscosity compared with hardeners based on IPDA or DETA.

Table 3. Formulation and properties of Mannich type hardener based on MXDA

Hardener No.
A
B
C
Kind of Amines
MXDA
IPDA
DETA
Molar ratio
10067
10067
10067
Properties
 Color
 Viscosity
 Amine Value
 Active H Eq. Wt.
  
(Gardner)
(ps, 25°C)
 
 		  
2-3
22
463
70		  
8
1800
408
78		  
9
54
806
40

6-2. Properties of coating film cured at 20°C or 8°C

Coating film cured with Mannich type hardeners based on MXDA for non-solvent system with liquid type DGEBA(Diglycidyl ether of bisphenol-A) shows a excellent appearance, shorter drying time, harder surface, and better chemical and solvent resistances than hardeners based on IPDA or DETA.

Table 4. Properties of coating film cured with Mannich type hardener based on MXDA

Hardener No.
A
B
C
phr/ epoxy resin *1
37
41
21
Curing condition
(day/ °C)
7/ 20
14/ 8
7/ 20
14/ 8
7/ 20
14/ 8
Appearance *2
  
Gloss
Clarity		  
Ex
Ex		  
Ex
Ex		  
Ex
Ex		  
Ex *3
Ex		  
F
F		  
G
F
Physical properties
  
 
1:00
1:20
3:00		 1:00
2:50
24 up		 1:00
2:00
4:00		 0:50
3:00
7:00		 1:00
5:00
24 up		 2:30
24 up
24 up
RCI drying time (hr:min)
Set-to-touch
Dust free
Dry through
Pencil hardness *4 3H
4H
4H
 		 3H
3H
3H
3H		 2H
2H
2H
 		 F
H
H
2H		 H
2H
2H
 		 B
B
B
HB *5
1 day
4 days
7 days
14 days
Impact (cm) *4
1/2" x 300g		 Dir.
Rev.
20
10 Failure
 10 Failure
10 Failure		 10 Failure
10 Failure		 10 Failure
10 Failure *6
10
10 Failure
 10 Failure
10 Failure
Chemical resistance *2
 (1W)
10% Caustic soda aq.
Ex
G
Ex
G
F
F
5% Sulfuric acid
5% Acetic acid
aq.
aq.
G
Ex
F
F
F
F
G
Ex
P
P
F
P
Methanol
Toluene
F
G
P
G
G
G
P
P
F
P
P
P
Salt spray 5% NaCl
14 days
G
G
G
Ex
P
F

*1: Epon 828 (EEW = 190)
*2: Ex; excellent, G; good, F; fair, P; poor
*3: Wrinkle
*4: JIS K5400
*5: Sticky
*6: After testing, many cracks occurred on the coating films.

7. Mannich type hardener based on MXDA either with p-t-butylphenol or p-nonylphenol

7-1. Formulation and physical properties of hardeners

Table 5. Formulation and properties of Mannich type hardener based on MXDA

Hardener No.
D
E
Kind of phenols
p-t-butylphenol
p-nonylphenol
Formulations (parts)
7B10090 *1
7N10090 *2
Benzyl alcohol
Nikanol Y-50 *3
100
 
15
15
  
100
15
15
Properties
Free phenols
Free MXDA
Viscosity
Amine Value
Active H Eq. Wt.		  
(%)
(%)
(ps, 25°C)
 
 		  
9.2
12
44
291
124		  
12
10
41
235
154

*1 p-t-butylphenol/ Formaldehyde/ MXDA = 100/ 90/ 100
*2 p-nonylphenol/ Formaldehyde/ MXDA = 100/ 90/ 100
*3 Low viscosity xylene-formaldehyde resin as non-reactive diluent, manufactured by Mitsubishi Gas Chemical Co., Inc.
Color (Gardner): <1, Viscosity: 50cps/ 25°C

7-2. Properties of coating films

Table 6. Properties of coating film cured with Mannich type hardener based on MXDA

Hardener No.
D
E
phr/ pigmented epoxy resin *1
65
81
Curing condition
7 days/ 20°C 72%RH
Properties
RCI drying time (hr:min)
Set-to-touch
Dust free
Dry through
  
 
1:30
3:00
5:00		  
 
1:45
4:15
6:15
Pencil hardness *2
1 day
4 days
7 days		  
2H
3H
4H		  
H
2H
2H
Erichsen cupping *(mm)2
0.3
2.4
DuPont impact *2Dir.(cm)
1/2" x 300gRev.(cm)
10 Failure
10 Failure
10 Failure
10 Failure
Chemical resistance(1 W)
10% Caustic soda (aq.)
5% Sulfuric acid (aq.)
Methanol
Toluene
Salt spray 5% NaCl 14 days
  
F
F
P
P
F		  
F
F
F
P
F

*1: Epon 828 (EEW = 190)
*2: JIS K5400

8. Formulation and properties of Mannich type hardener based on MXDA for heavy-duty paint

8-1. Formulation and physical properties of hardeners

Properties of Mannich type hardener based on MXDA for heavy-duty paint are given in Table 7. The hardener was prepared with higher molar ratio of formaldehyde to MXDA than non-solvent system.

Table 7. Formulation and properties of Mannich type hardener based on MXDA

Hardener No.
 F
G
Commercial *1
Molar ratio
150200
200240
  
Properties
NVM
Free phenol
Free MXDA
Viscosity
Amine Value
Active H Eq. Wt.
 (%)
Soln. (%)
Soln. (%)
(ps, 5°C)
 
 		 70 *2
5.0
2.7
7760
256
215		 50 *2
5.7
0.8
26
162
441		 50 *3
-
-
34
140
290

*1:DETA-Epon 1001 adduct
*2:Solvent xylene/ ethoxyethanol = 1/ 1 (wt. ratio)
*3:Solvent butanol/ xylene = 1/ 1 (wt. ratio)

8-2. Properties of coating film cured with Mannich type hardener based on MXDA

Coating film cured with Mannich type hardeners based on MXDA with pigmented epoxy resin based on solid type DGEBA (Diglycidyl ether of bisphenol-A) shows a better result of low temperature curing property, shorter drying time, and better chemical and solvent resistances for several months than commercial hardener.

Table 8. Properties of coating film cured with Mannich type hardener based on MXDA

Hardener No.
F
G
Commercial
phr/ pigmented epoxy resin *1
9.5
27.9
18.4
Curing condition
1+7 days/ 5°C 80%RH
Properties *2
Water spotting resistance *3
 G G P
Walkability *4
Undercoat
Topcoat		 Ex
F		 Ex
G		 Ex
F
RCI drying time (hr:min)
Set-to-touch
Dust free
Dry through		 0:00
4:30
16:00		 0:00
3:30
18:00		 0:00
4:00
19:00
Pencil hardness *5
1 day
4 days
7 days		 <6B
3B
2B		 <6B
2B
B		 <6B
3B
2B
Crosscut adhesion *5 ( / 100)
100
100
100
Erichsen cupping *5 (mm)
7.8
9
8.8
DuPont impact *5 Dir.(cm)
1/2" x 500g Rev.(cm)
40
10 Failure
40
10 Failure
50
10 Failure
Recoatability
Ex
Ex
Ex
Chemical resistance
20% Caustic soda (aq.) 5 months
10% Sulfuric acid (aq.) 3 weeks
Methanol 6 months
Toluene 6 months
60°C Warm water 4 months
Salt spray 5% NaCl 500hrs.
 G
P
G
G
G
Ex		 G
F
Ex
Ex
G
G		 P
P
F
P
P
P

*1: Pigmented epoxy resin based on Epon1001X-75 (EEW = 1580)
*2: 150µm for undercoat and after 24hrs. 150µm for topcoat
*3: After 24hrs. of curing, 10mm diameter water is placed on the coating film
*4: After 16hrs. of curing, stand on the coating film
*5: JIS K5400

9. Mannich type hardeners based on MXDA on Chemical Substances Lists

Listed in Table 9 are Mannich type hardeners based on MXDA on Chemical Substances Lists, ENCS(Japan), TSCA(USA), DSL(Canada), NLP(EC), ECL(Korea) and AICS(Australia). The lists cover 1979 through May 2, 1997.

Table 9. Mannich type hardeners based on MXDA on Chemical Substances Lists

 
Chemical Name
CAS Registry

No.
ENCS

[Japan]
TSCA

(EPA)

[USA]
DSL

(NDSL)

[Canada]
NLP

[EC]
ECL

[Korea]
AICS

(RLN)

[Australia]
1
 Xylylenediamine-Resol polycondensate  
7-1167
          
2
 Formaldehyde, polymer with 1,3-benzenedimethanamine and phenol
57214-10-5
  
YES
        
3
 Reaction product of p-tert-butyl-phenol with formaldehyde and with m-xylylenediamine    
(P95-78)
        
4
 Xylylenediamine-Alkyl(C1-16)-phenol-Formaldehyde polycondensate
160994-58-1
7-654
      
9312-13174
  
5
 Formaldehyde, reaction product with 1,3-benzenedimethanamine, p-tert-butylphenol, nonylphenol and trimethyl-1,6-hexanediamine
116912-33-5
    
YES
    
YES
6
 Formaldehyde, polymer with 1,3-benzenedimethanamine, 4-(1,1-dimethylethyl)phenol, nonylphenol and C, C, C-trimethyl-1,6-hexane-diamine
104242-08-2
  
YES
(YES)
      
7
 Formaldehyde, polymer with 1,3-benzenedimethanamine, 4-(1,1-dimethylethyl)phenol, octylphenol and C, C, C-trimethyl-1,6-hexane-diamine
72441-90-8
  
YES
(YES)
    
YES
8
 Formaldehyde, oligomeric reaction products with phenol and m-phenylenebis(methylamine)
57214-10-5
      
500-137-0
    
9
 Formaldehyde, oligomeric reaction products with 4,4’-Isopropyliden-diphenol and m-phenylenebis-(methylamine)
161278-17-7
      
500-607-5
    
10
 Paraformaldehyde, oligomeric reaction products with 4-tert-butylphenol, 4-nonylphenol, m-phenylenebis(methylamine) and trimethylhexane-1,6-diamine
161278-27-9
      
500-618-5
    

Safety Precautions:

MXDA, can cause severe skin and eye irritation and can cause burns with prolonged contact. Wear protective clothing and equipment, such as chemical goggles, rubber gloves, splash apron and a respirator, especially when using in an area with poor ventilation. Do not get products on skin or in eyes. Do not breathe the vapors.

Consult appropriate Material Safety Data Sheets for additional details before handling the product.

Storage:

Product should be kept in tightly closed containers in a cool, dry, ventilated place. These products will have a minimum shelf life of one year if properly stored in unopened containers. They should be kept away from open flame and ignition sources.

Important:

The information accumulated herein is believed to be accurate but is not warranted to be, whether originating with Mitsubishi Gas Chemical America or not. Recipients are advised to confirm in advance of need that the information is current, applicable and suitable to their circumstances.