Wood Adhesives 2013, 11 Oct. 2013 in Toronto
Effects of Synthetic Process of MelamineUrea-Formaldehyde (MUF) Resins on
Chemical Structure before and after cure
Shin-ichiro TOHMURA (FFPRI)
Atsuhiro IWATAKE (DAIKEN Corporation)
Kohta MIYAMOTO (FFPRI)
Forestry and Forest Products Research Institute, Tsukuba, JAPAN
Formaldehyde emission grade in Japan (since 2003)
FE
Grade
(JIS, JAS)
Formaldehyde Conc.
( by Dessicator
method)
AVG.
MAX.
Limitation of finish materials in
The Building Code
Ventilation above
0.7 times/h
Ventilation between
0.5 and 0.7 times/h
F☆☆☆☆
≦0.3mg/L
≦0.4mg/L
F☆☆☆
≦0.5mg/L
≦0.7mg/L
Within the 5 times
of floor area
Within the 2 times of
floor area
F☆☆
≦1.5mg/L
≦2.1mg/L
Within the 0.8
times of floor area
Within the 0.3 times
of floor area
F☆S
(only for GL)
≦3.0mg/L
≦4.2mg/L
Banned
F☆
≦5.0mg/L
(only for PW)
≦7.0mg/L
Banned
Out of regulation
HWPW
PB
MDF
F☆☆☆☆
F☆☆☆
E1
CARB-P2
CARB-P1
F☆☆☆☆
F☆☆☆
CARB-P2
E1
CARB-P1
F☆☆☆☆
CARB-P2
F☆☆☆
CARB-P1
E1
The ≒ E1333 values (ppm)
Formaldehyde emission criteria in the world
0.25
0.2
0.15
0.1
0.05
0
Production of major wood adhesives in Japan
(ton)
350,000
300,000
UF
MUF
PF
API
250,000
200,000
150,000
100,000
50,000
2008
2006
2004
2002
2000
1998
1996
0
How to make a low formaldehyde emission MUF
Factors of MUF synthesis
 F/M/U molar ratio
 Temperature schedule
 Timing of 2nd U and M addition
 Order of addition
 pH control
 End point
 And so on….
 Too many factors too many secrets
Former findings
 Primary factor is M/U/F molar ratio
F/(M+U) is higher, Methylol group in the
resin, bond performance, and formaldehyde
emission are higher.
 F/(M+U) affects chemical structure and
cured structure also.
Most of former studies : F/(M+U) > 1.3
How is further lower F/(M+U) case?
Experimental design
MUF resin synthesis
 Fix the final F/(M+U)=1.125 (F☆☆☆☆)
Exp.1. Mixing method of MF, UF, M and U
Exp.2. Addition timing of M and U
Resin characterization and properties
 Chemical structure of MUF resins before
and after cure
 Bonding properties
Chemical structure 13C-NMR Analysis
α-500 JEOL
Solution 13C-NMR
Chemagnetics CHX 300
Solid CP/MAS 13C-NMR
Experiment1 – Mixing method
85  C, pH9-9.5, 30min
 ADD pH 6.5, 85  C, 60min
60  C, pH 8.5
Sample
ID
Mixture Method
(Final component M/U/F=1/3/4.5)
Viscosity
(c.P)
Resin I
UF(U/F=3/3) + MF(M/F=1/1.5)
2800
Resin II
MF(M/F=1/3) + UF(U/F=3/1.5)
5000
Resin III
MF(M/F=1/4.5) + U(3)
2400
Resin IV
UF(U/F=3/4.5) + M(1)
190
Resin V
MUF(M/U/F=1/3/4.5)
176
Final F/(M+U)=1.125
MUF resins – Appearance
Resin I UF-MF
Resin II MF-UF
Resin III MF-U
Clear
Resin IV UF-M
Resin V MUF
Bonding performance evaluation
Plywood Manufacture
3ply red melanti plywood （Total thickness: 5mm ）
MUF/Flour/Water/NH4Cl＝100/20/10/2
Spread: 265g/m2
Hot Press: 120C, 8.0kg/cm2, 45s/mm
Tensile Shear Strength test (JAS for plywood)
Dry
Wet Boil 2h, Cold water 1h
Wet Boil 4h, dry at 60C 20h, Boil 4h, Cold water
Plywood Shear Strength Test Result
Shear Strength (MPa)
1.6
1.4
dry
boil 2hour
boil 2cycle
1.2
1.0
0.8
0.6
0.4
0.2
0.0
MUF①-1 MF-UF
MUF①-2 MF-U
MUF② UF-M
MUF③
UF-MF
MUF④
MUF
Resin I Resin II Resin III Resin IV Resin V
Solution 13C-NMR Resin structure Analysis
（Total Urea carbonyl group =1）
Substance
and structure
Chemical
Shift
Resin I
UF-MF
Total Metylene
44.5-47.5
0.62
0.66
0.38
0.50
0.35
Total Methylol
63.0-64.5
0.63
0.78
0.93
0.74
1.25
Dimethylene
ether
67.0-68.5
0.20
0.11
0.17
0.33
0.30
157.5-161.0
1.00
1.00
1.00
1.00
1.00
Total Melamine 164.5-167.5
0.83
0.93
0.78
0.81
0.84
Total Urea
Resin II Resin III Resin IV Resin V
MF-UF
MF-U
UF-M
MUF
Relationship between Me/Mo and shear strength
Shear Strength (Mpa)
1.6
1.4
R² = 0.9479
1.2
dry
boil 2hour
boil 2cycle
1.0
0.8
R² = 0.7974
0.6
0.4
R² = 0.9016
0.2
0.0
0
0.5
1
Me/Mo
1.5
(Methylene / Methylol)
Cured MUF – Solid CP/MAS13C-NMR Analysis
Curing condition: 120 C for 7 min
Resin I
Resin II
Resin III
Resin IV
Resin V
200
150
100
50
Chemical shift(ppm)
0
Summery of Experiment 1
 Chemical structure
 Some difference in the solution 13C-NMR spectra
among pre-cured MUF resins, but no difference
was found on the solid state13C-NMR spectra of
cured MUF resins.
 Bond performance
The Methylene/Methylol (Me/Mo) ratio in MUF
resin strongly correlated to plywood share
strength, supporting the former findings.
Practical Problem of MUF Resin for Board Making
 When a MUF resin is applied to a MDF manufacturing
line in industry, pipe stacking is one of the main problems
hindering productivity.
Tack ability
Pipe stacking
?
Gel time
Long Pressing time
Productivity
To improve productivity, the contradiction of both faster
pressing time and lower tack ability of resin must be resolved.
Experiment 2– Addition timing of M and U
Initial F/M/U = 4.5 / 0.8 / 2 (F/(M+U)=1.60)
80  C, 10min, pH9.5  pH6.5 80  C 30min  pH8.5
Sample
ID
MUF1
MUF2
MUF3
MUF4
MUF5
MUF6
2nd
addition
M/U
0.2 / 1
0.2/ 0
0.2 / 0
0.5 / 1
0.5 / 0
0.5 / 0
3rdaddition
U
0
0
1
0
0
1
Final
F/M/U
4.5 / 1 /
3
4.5 / 1 /
2
4.5 / 1 /
3
4.5 / 1.3
/3
4.5 / 1.3
/.2
4.5 / 1.3
/3
F/(M+U)=
1.125
1.5
1.125
1.046
1.363
1.046
Solution 13C NMR analysis and characterization results
Chemical Chemical
Structure85
Shift
MUF1
MUF2
MUF4
MUF5
M/U
=0.2/1
M/U
=0.2/0
M/U
=0.5/1
M/U
=0.5/0
Methylene
45-48
0.15
0.6
0.24
0.30
Methylol
63-65
1.26
1.87
1.09
1.90
Free
Triazine
165-167
0.84
1.19
0.84
1.33
Water Miscibility (%)
106
169
69
104
Gel time (s)
195
185
233
188
F/(M+U) molar ratio
1.125
1.5
1.046
1.363
Solid state 13C-CP/MAS NMR of Low M proportion
Curing condition: 120 C for 7 min
Methylene
(Cross-linked)
MUF 1
(F/(M+U)=1.125)
MUF 3
(F/(M+U)=1.125)
MUF 2
(F/(M+U)=1.5)
90
70
50
Chemical shift (ppm)
30
Methylene
(Linear)
Solid state 13C-CP/MAS NMR of High M proportion
Methylene
(Cross-linked)
MUF 4
(F/(M+U)=1.046)
Methylene
(Linear)
MUF 6
(F/(M+U)=1.046)
MUF 5
(F/(M+U)=1.363)
90
70
50
Chemical shift (ppm)
30
Additional U is provably taken into the network structure.
Conclusions
 The chemical component of MUF resin differed
depending on the course of melamine addition by
solution 13C-NMR analysis, while the molar ratio of the
methylene/methylol (Me/Mo) ratio in MUF resin strongly
correlated to plywood shear strength, supporting the
former findings.
 For the solid-state 13C-NMR analysis, we found no
difference in the structure of cured MUF resins with the
same final M/U/F molar ratio, even if the course of
melamine and/or urea late addition differed.
Thank you for your attention!
Any Question?