Effects of Synthetic Process of Melamine-

Urea-Formaldehyde (MUF) Resins on

Chemical Structure before and after cure

Shin-ichiro TOHMURA (FFPRI)

Atsuhiro IWATAKE (DAIKEN Corporation)

Kohta MIYAMOTO (FFPRI)

Wood Adhesives 2013, 11 Oct. 2013 in Toronto

Forestry and Forest Products Research Institute, Tsukuba, JAPAN

FE

Grade

(JIS, JAS)

Formaldehyde Conc.

( by Dessicator

method)

Limitation of finish materials in

The Building Code

AVG. MAX. Ventilation above

0.7 times/h

Ventilation between

0.5 and 0.7 times/h

F☆☆☆☆ ≦0.3mg/L ≦0.4mg/L Out of regulation

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☆

(only for PW) ≦5.0mg/L ≦7.0mg/L Banned

Formaldehyde emission grade in Japan (since 2003)

0

0.05

0.1

0.15

0.2

0.25

E1

CA

RB

-P1

F☆☆☆

CA

RB

-P2

F☆☆☆☆

CA

RB

-P1

E1

CA

RB

-P2

F☆☆☆

F☆☆☆☆

CA

RB

-P1

CA

RB

-P2

E1

F☆☆☆

F☆☆☆☆

HWPW PB MDF

Th

e ≒

E133

3 v

alu

es (

pp

m)

Formaldehyde emission criteria in the world

0

50,000

100,000

150,000

200,000

250,000

300,000

350,0001

99

6

199

8

200

0

200

2

2004

200

6

200

8

UF MUF

PF API

(ton)

Production of major wood adhesives in Japan

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

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.

Former findings

Most of former studies : F/(M+U) > 1.3

How is further lower F/(M+U) case?

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

Experimental design

Chemical structure of MUF resins before

and after cure

Bonding properties

MUF resin synthesis

Resin characterization and properties

Chemical structure 13C-NMR Analysis

Chemagnetics CHX 300

Solid CP/MAS 13C-NMR

α-500 JEOL

Solution 13C-NMR

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

Experiment1 – Mixing method 85 C, pH9-9.5, 30min

ADD pH 6.5, 85 C, 60min

60 C, pH 8.5

Final F/(M+U)=1.125

Resin I UF-MF Resin II MF-UF Resin III MF-U

Resin IV UF-M Resin V MUF

Clear

MUF resins – Appearance

Plywood Manufacture

3ply red melanti plywood （Total thickness: 5mm ）

MUF/Flour/Water/NH4Cl＝100/20/10/2

Spread: 265g/m2

Hot Press: 120C, 8.0kg/cm2, 45s/mm

Dry

Wet Boil 2h, Cold water 1h

Wet Boil 4h, dry at 60C 20h, Boil 4h, Cold water

Tensile Shear Strength test (JAS for plywood)

Bonding performance evaluation

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

MUF①-1 MUF①-2 MUF② MUF③ MUF④

Sh

ear

Str

en

gth

(M

Pa

) dry boil 2hour boil 2cycle

UF-MF MF-UF MF-U UF-M MUF

Resin I Resin II Resin III Resin IV Resin V

Plywood Shear Strength Test Result

Solution 13C-NMR Resin structure Analysis （Total Urea carbonyl group =1）

Substance

and structure

Chemical

Shift

Resin I

UF-MF

Resin II

MF-UF

Resin III

MF-U

Resin IV

UF-M

Resin V

MUF

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

Total Urea 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

R² = 0.9479

R² = 0.7974

R² = 0.9016

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 0.5 1 1.5

Sh

ear

Str

en

gth

(M

pa)

Me/Mo

dry

boil 2hour

boil 2cycle

Relationship between Me/Mo and shear strength

(Methylene / Methylol)

Cured MUF – Solid CP/MAS13C-NMR Analysis

050100150200

Chemical shift(ppm)

Resin I

Resin II

Resin III

Resin IV

Resin V

Curing condition: 120 C for 7 min

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.

Summery of Experiment 1

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

Practical Problem of MUF Resin for Board Making

?

To improve productivity, the contradiction of both faster

pressing time and lower tack ability of resin must be resolved.

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

Experiment 2– Addition timing of M and U

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

Structure85

Chemical

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

30507090Chemical shift (ppm)

MUF 1

(F/(M+U)=1.125)

MUF 3

(F/(M+U)=1.125)

MUF 2

(F/(M+U)=1.5)

Solid state 13C-CP/MAS NMR of Low M proportion

Methylene

(Cross-linked)

Methylene

(Linear)

Curing condition: 120 C for 7 min

30507090

Chemical shift (ppm)

MUF 4

(F/(M+U)=1.046)

MUF 6

(F/(M+U)=1.046)

MUF 5

(F/(M+U)=1.363)

Methylene

(Cross-linked)

Methylene

(Linear)

Solid state 13C-CP/MAS NMR of High M proportion

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.

Any Question?

Thank you for your attention!