Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~:~25~30
-- 1 --
A Formaldehyde ~inder
Boards such as particleboard, chipboard and
the like are prepared from lignocellulosic materials
using adhesives. The preferred adhesives(or glues) are
based on formaldehyde, such as urea-formaldehyde, me-
lamine-formaldehyde, phenol-formaldehyde ~nd resorcinol-
formaldehyde resins or mixtures thereof. It is a well-
known fact that boards prepared using these adhesives
have a formaldehyde odour which is both harmful and un-
pleasant. Formaldehyde is emitted both during the pro-
duction of such boards and during their storage and final use.
Many methods of avoiding the emission of form-
aldehyde have been proposed, but all of them are either
ineffective or reduce the properties of the boards or
require complicated application procedures. Some of these
procedures involve spraying or spread coating the warm
boards coming out of the press with various solutions,
such as solutions of urea andtor ammonia or of ammonium
salts. Generally, these types of methods are not desi-
rable for industrial application because they require
additional process steps and anyway are not very efficient.
Other methods involve the use of very complica-
ted mixtures of a large number of components, some ofwhich are natural glues. These products also are not
very efficient. One handicap thereof is the fact that
the properties of natural products are not constant.
iLZ25630
-- 2 --
Another way of reducin~ the content of free form-
aldehyde involves the use of an aqueous suspension of urea
prills coated with a special wax. This method, too, requi-
res a separate feeding line, because the product is not
S added to the adhesive rormulation itself.
An object of the present invention is to pro-
vide a formaldehyde binder which effectively reduces the
formaldehyde odour ~Jithout reducing the properties Or
the board, withou~ changing the reactivity Or the
10 adhesive formulations and without requirin~ any additio-
nal steps in the production Or particleboard, plywood or
blockboard.
The invention provides a rormaldehyce binder
when for use in boards prepared from lignocellulosic ma-
15 terials using adhesives based on formaldehyde,which com-
prises a solution Or
(a) at least one or~anic hydroxy compound with the excep-
tion of Cl 4 monohydric aliphatic alcohols and
(b) at least one amide
20 in water. The formaldehyde binder can also contain (c) an or-
ganic compound which acts as a solvent for (a) and (b) and
also reacts with formaldehyde and/or (d) an inorganic com-
pound soluble in water. The organic compound (c) is prefer-
ably a Cl 4 monohydric aliphatic alcohol. The inorganic com-
25 pound (d) is preferably a halide salt. Even if the individualcomponents are not soluble in water, they may dissolve in wa-
ter if a mixture thereof is heated in water to 70 C.
Preferably the organic hydroxy compounds [com-
30 ponent (a)] are soluble in water or in lower monohydric
aliphatic alcohols. Examples Or such prererred hydroxy
compounds are the dihydric, trihydric and pentahydric
alcohols containing up to 6 carbon atoms, the mono-
saccharides containing up to G carbon atoms, the di-
.
~2Z56~0
3saccharides containing up to 12 carbon atoms and the po-
lysaccharides having an Ostwald viscosity up to 200 mPas
at 25 C and a concentration corresponding to 37 % refrac-
tion. Other ex~mples of preferred hydroxy compounds are the
aromatic alcohols and phenols, which preferably are used
alone or in combination with one or more of the above-men-
tioned dihydric, trihydric and/or pentahydric alcohols and/
or monosaccharides, disaccharides and/or polysaccharidesO
The phenols and aromatic alcohols can be monohydric or
polyhydric phenols and monohydric or polyhydric aromatic
alcohols containing one benzene ring.
Specific examples of suitable organic hydroxy
compounds are monoethyleneglycol, diethyleneglycol,
glycerine, pentaerythritol, fructose, mannose, sorbitol,
dextrose, sucrose, maltose, lactose, dextrin, phenol,
resorcinol, hydroquinone and the like.
Preferably the amides [component (b)] used in the
formaldehyde binder of the invention are likewise soluble
in water or in lower monohydric aliphatic alcohols. Parti-
cularly preferred are the aliphatic amides containing up
to 6 carbon atoms and the aromatic amides containing one
benzene ring.
Suitable examples of amides are urea, thiourea,
formamide, acetamide, benzamide, oxamide, succinamide,
malonamide and the like.
If desired, to enhance solubility,the formaldehyde
binder of the invention can additionally contain additives
[component (c)] which are lower monohydric aliphatic alco-
hols such as methanol, ethanol, isopropanol and the like.
A cheaper and more efficient formaldehyde binder
.,
1~25630
-- 4
is obtained if inorganic compounds [component (d)] which
are preferably halide salts, more preferably halides of
alkali metals or alkaline earth metals, such as sodium
chloride, potassium chloride and calcium chloride3 are added.
The ratio of organic hydroxy compound r cor.lponent
(a) and component (c), if present] and inorganic compound
[component (d), if present] to amide [component (b)]
is preferably 10:100 to 400:100, particularly 10:100 to
200:100, by weight. The formaldehyde binder of the inven-
tion can be added to the usual ~lue formulations in quanti-
tie8 varying from 1 to 10 %, preferably 3 to 7 %, of form-
aldehyde binder solids, based on the weight of the liquid
resin containing 65 % by weight of resin solids.
The formaldehyde binder of the invention may
contain 20 to 80 % by weight, preferably 50 to 70 % by
weight, of the active ingredients [components (a) and (b)
and components (c) and/or (d)~ if present]. The water con-
tent of the formaldehyde binder depends on the solubilityof the active ingredients and the amount of water which can
be tolerated in the glue formulations.
The formaldehyde binder of the invention can be
produced by simply adding the active ingredients and
water to a mixer and mixing until the active ingredients
are dissolved. This can be done at room temperature or
at an elevated temperature up to 70 C.
The formaldehyde binder of the invention may be
used whenever boards are prepared from lignocellulosic
materials using adhesives based on formaldehyde, such
as urea-formaldehyde, melamine-formaldehyde, phenol-
formaldehyde or resorcinol-formaldehyde resins or mix-
~225630
tures thereof.
When using the formaldehyde binder o~ the invention,
it is possible to produce boards actually containing
less than 10 mg Or free formaldehyde per 100 g of the dry
board, as determined by the F.~.S.Y.P. (Fédération Euro-
péenne des Syndicats des Fabricants de Panneaux de Par-
ticules) perforator method No. EN 120.
The amount of the free formaldehyde reduction
depends on many factors and, therefore, can vary widely.
If the emission of free formaldehyde is high (higher
than 50 mg of formaldehyde per 100 grams of dry board),
the reduction can be as high as up to 60 to 85 %. If the emission
of free formaldehyde is relatively low, i.e. 20 to 5C mg
of free formaldehyde pèr 100 g of the dry board, the
maximum reduction is usually 50 to 60 %. The amount of
reduction obtained also depends on the amount of form-
aldehyde binder used: The more formaldehyde binder is
used, the lower is the amount of free formaldehyde.
When the active ingredients of the formaldehyde
binder are used in combination with each other, the free
formaldehyde reduction is surprisingly much higher than
the sum of the effects of the separate components, and
they have no adverse effect on the reactivity of the
glue formulation or the properties of the boards.
The following examples illustrate the invention.
Parts and percents are by weight.
~%~630
-- 6 --
Example l
In this example the organic compound con-
taining hydroxyl groups is glycerine and the amide is
urea. Here, there is illustrated the synergistic be-
haviour of these two compounds. Various glue formula-
tions are prepared and each is used subsequently in
order to produce particleboard.
The control does not include any of the
components of the formaldehyde binder according to the
invention. Sample 1 includes both glycerine and urea,
sample 2 includes only glycerine and sample 3 includes
only urea.
It is noticed from the tables reported here
below that glycerine when used on its own (sample 2)
is a very efficient formaldehyde binder, but urea
(sample 3) gives a poorer formaldehyde reduction and
lower mechanical values and water resistance, however,
when urea is used in combination with glycerine (sample
l), it gives values that are equivalent to those of
glycerine on its own.
We may therefore use a cheaper and less
efficient product (urea) and make it react as effec-
tively as a more expensive and more efficient product
(glycerine). The efficiency refers to formaldehyde
absorbing capacities as well as to maintaining good
mechanical properties and water resistance without
changing the reactivity of the glue formulation and
without the need to introduce any special apparatus
for its use.
Formaldehyde reduction actually is in this
630
case 46 %.
The formulations of the various samples used
are as follows:
l 2 3
parts byparts by parts by
weight weight weight
Glycerine (100 ~) 270 590
Urea (100 %) 320 - 59
Water 410 410 410
1000 1000 1000
% solids 59 59 59
The glue formulations used are as follows:
Control 1 2 3
grams grams gramsgraJns
Urea-formalde-
hyde resin 65 %3077 3077 3077 3077
(Molar ratio
F:U 1.27:1)
Hardener 400 400 400 400
(Ammonium chloride
15 %)
Paraffin emulsion 250 250 250 250
50 %
Ammonia 25 Baumé 5 5 5 5
Sample l - 308 - -
Sample 2 - - 308
Sample 3 - ~ ~ 308
Water 268
Total 4 44 44 44
Gel time in secs. 68 68 71 62
~2Z5630
-- 8 --
Single-layer boards are prepared in the
laboratory by spraying each of these formulations onto
25 kgs wood chips. Boards are pressed at 10, and 9 and
8 secs./mm. The thickness of the boards is 17.3 mms.
The temperature of the press is 200 C and the pressure
is 35 kg/cm . The dimensions of the boards produced
are 40 x 56 cms.
The results obtained are reported in the
following table and are average values.
Control 1 2 3
Density (kg/m3) 683 669 663 657
Bending strength (Ntmm ) 19.9 18.1 17.3 16.3
Tensile strength (N/mm ) 0.73 0.72 0.71 0.63
2 hr. thickness swelling (%) 5.2 4.9 4.5 5.4
24 hr. thickness swelling (%) 51.449.9 47.4 53.1
Free formaldehyde 15. 8 8. 5 8.7 11.7
(mg/100 g dry board)
Example 2
This is another example illustratin~ the
synergistic behaviour of glycerine and urea in reducing
the free formaldehyde of particleboards while main-
taining the mechanical properties of the boards and thewater resistance as well.
The control does not in^lude any of the com-
ponents of the formaldehyde binder according to the
invention. Sample 1 contains both components of the form-
aldehyde binder according to the invention and sample
2 contains only one of the two components (the most
efficient of the two components).
It is noticed here again that only sample 1 gives free
formaldehyde that is below 10 mg/100 g. dry board (which is the desir-
~2ZS~
- g
ed level for Elclass) and is the only one to have ab-
solutely equivalent mechanical properties and water
resistance. Formaldehyde reduction actually is 34 %.
The formulations of the various samples used
are as follows:
1 2
parts by_weight parts by weight
Glycerine (100 %)128 128
Urea (100 %) 424
Water 448 872
1000 1000
% solids 55.2 12.8
The glue formulations used are as follows:
Control 1 2
grams ~rams grams
_
Urea formaldehyde
resin 65 % 3077 3077 3077
(Molar ratlo
F:U = 1.27:1)
Hardener 400 400 400
(Ammonium chloride
15 %)
Paraffin emulsion250 250 250
50 %
Ammonia 25 Baumé 5 5 5
Sample 1 - 268
Sample 2 - - 268
Water 268
Total 4000 4000 4000
Gel time in secs.66 67 69
-" ~225630
-- 10 --
Single-layer boards are prepared in the
laboratory by spraying each of these formulations onto
25 kgs wood chips. Boards are pressed at 10, 9 and 8
secs./mm. The thickness of the boards is 17.3 mms.
5 The temperature of the press is 200 ~C and the pressure
is 35 kg/cm . The dimensions of the boards produce~
are 40 x 56 cms.
The results obtained are reported in the
following table and are average values.
Control 1 2
Density (kg/m3) 685 684 687
Bending strength (N/mm2) 20. 7 20. 6 19.4
~ensile strength (~/mm2) 0.740.73 0.67
2 hr. thickness swelling (%) 11.0 7.9 8.6
24 hr. absorption (%)23.5 23.2 23.7
Free formaldehyde 14.3 9.5 12.3
(mg/100 g dry board)
Example 3
This example illustrates the efficiency of mono-
ethyleneglycol together with urea as a formaldehyde
binder.
Two formulations are prepared: the control
without any of the ingredients of the formaldehyde
binder according to the invention and sample 1 which
includes both monoethyleneglycol and urea.
Boards are produced from these two glue
formulations and it is proved here, too, that with
the formaldehyde binder according to our invention
we obtain with a urea-formaldehyde resin that gives
: , .
~225630
-- 11 --
normally boards classified as E 2 (control), boards
classified as E 1 (sample 1).
The formaldehyde reduction is in this case
37 %.
The formulation of sample 1 used is as follows:
Sample 1
partæ by weight
Monoethyleneglycol 100 % 360
Urea 100 % 365
Water 275
1000
15 % solids 72.5
The glue formulations used are as follows:
Control
grams grams
Urea formaldehyde resin 65 % 3077 3077
(Molar ratio F:U - 1.27:1)
Hardener 400 400
(Ammonium chloride 15 %)
Paraffin emulsion 50 % 250 250
Ammonia 25 Baumé 5 5
Sample 1 - 268
Water 268
Total 4000 4000
30 Gel time in secs. 66 60
Single-layer boards are prepared in the
laboratory by spraying each of these formulations onto
25 kgs wood chips. Boards are pressed at 10, 9 and
~2;2S63~1
- 12 -
8 secs./m~. The thickness of the boards is 17.3 mms.
The temperature of the press is 200 C and the pressure
is 35 kg/cm2. The dimensions of the boards produced are
40 x 56 mms.
The results obtained are reported in the
following table and are average values.
Control
Density (kg/m3) 685 684
Bending strength (N/mm2) 20.7 20.2
Tensile strength (N/mm2) 0.74 0.74
2 hr.thickness swelling (%) 11.0 8.6
24 hr. absorption (%) 23.~22.6
Free formaldehyde 14.3 9.0
(mg/100 g dry board)
Example 4
In this example we are illustrating the
synergistic behaviour of monoethyleneglycol and urea.
Boards are prepared from three different
formulations: the control wherein no ingredients of
the formaldehyde binder according to the invention
are used, sample 1 wherein both ingredients
of the formaldehyde binder of the present invention are
used and sample 2 wherein only one ingredient is used.
It is obvious from the results obtained and
reported here in below that sample 1 containing both
ingredients is much more effective than sample 2 con-
taining only one ingredient (the most efficient of
the two ingredients).
12Z5630
The formaldehyde reduction obtained in this
case is 32 %.
The formulations of the various samples used
are as follows:
parts by weight parts by weight
Monoethyleneglycol 100 %230 580
Urea 100 % 350
Water 420 420
1000 1000
% solids 58 58
The glue formulations are as follows:
Control 1 2
gramsgramsgrams
Urea formaldehyde 3077 3077 3077
20 resin 65 %
(Molar ratio F:U = 1.27:1)
Hardener 400 400 400
(Ammonium chloride 15 %)
Paraffin emulsion 50 % 250 250 250
Ammonia 25 Baumé 5 5 5
Sample 1 - 268
Sample 2 - - 268
Water 268
Total 4 4 4
Gel time in secs. 70 71 76
Single-layer boards are prepared in the
laboratory by spraying each of these formulations onto
25 kgs wood chips. Boards are pressed at 10, 9 and
lZZ5630
- 14 -
8 secs./mm. The thickness of the boards is 17.3 mms.
The temperature of the press is 200 C and the pressure
is 35 kg/cm2. The dimensions of the boards produced
are 40 x 56 mms.
The results obtained are reported in the
following table and are average values.
Control 1 2
10 Density (kg/m3) 688 688 687
Bending strength (N/mm2)17.6 17.6 17.5
Tensile strength (N/mm2)0.55 0.60 0.56
2 hr. thickness swelling (%) 6.7 4.9 4.7
24 hr. absorption (%) 20.1 20.1 19.5
15 Free formaldehyde 15.0 10.3 12.3
(mg/100 g dry board)
Example 5
In this example the use of a resin of diffe-
rent molar ratio is illustrated as well as variouslevels of addition of the formaldehyde binder itself.
The formaldehyde binder used has the follo-
wing formulation:
parts by weight
Glycerine 100 % 270
Urea 100 % 318
Water 412
1000
% solids 58.8
The glue formulations used in the varioussamples are as follows:
i
~22S~;30
- 15 -
Control 1 2 3
grams grams grams grams
Urea formaldehyde resin 65 % 30773077 3077 3077
(Molar ratio F:U = 1.4:1)
Hardener 293 380 380 380
(Ammonium chloride 15 % )
Paraf~in emulsion 50 % 250 250 250 250
Ammonia 25 Baumé 5 5 5 5
Formaldehyde binder - 154 215 375
Water 375 134 73
Total 4000 4000 4000 4087
Gel time in secs. 73 73 72 75
Single-layer boards are prepared in the
15 laboratory by spraying each of these formulations onto
25 kgs wood chips. Boards are pressed at 10, 9 and
8 secs./mm. The thickness of the boards is 17.3 mms.
The temperature of the press is 200 C and the pressure
is 35 k~/cm2. The dimensions of the boards produced
20 are 40 x 56 cms.
The results obtained are reported in the
following table and are average values.
Control 1 2 3
Density (kg/m3) 680 687 685 688
Bending strength (N/mm2)22.022.5 22.3 21.6
Tensile strength (N/mm2)0. 610.63 o .66 0 ~ 6
2 hr. thickness swelling (%)10.1 9. 3 8.8 9.5
24 hr. thickness swelling (%)20.6 21.8 21.0 21.5
Free formaldehyde 22.2 13.0 10.1 9.5
(mg/100 g dry board)
It is noticed that the mechanical properties
122563
- 16 -
and water resistance of the boards are equivalent andthe formaldehyde reduction is 41 % in case of sample 1,
55 % in case of sample 2 and 57 % in case of sample 3.
Example 6
In this example six different types of poly-
alcohols are illustrated, two different types of amides,
one additive and a variation in the ratio of alcohol
to amide covering a range from 57.5/100 to 385/100.
The various types of formaldehyde binder used
are as follows:
- ~ZZ5630
-- 17 --
o o o o o o r~
~D I I ~ I ~ I ~0 ~ I C- O
o
o o o o o ~ ~
Ll~ I I I I I J ~ Ir~ I ~ O ~D
r~,-~ 0C~
f
g
O O O O r~
J ~ I I O I I I 1~ I t-- O ~O ~
Ln ~ l~t O Ln
O
o o o ol o ~ ,1
~ II ~ I I I o I ~ ~ o ~o
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I r~ I I I I I O I ~ O ~
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~` ~ ' ~ .
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O ~ ,~ S ~ O ~ c~ O bO O
x a) ~ ~ 0 rl
~ rl O r~ ~ O al ~ s ~d O a) ,~
~ 3 ~d
. I .
1 225630
- 18 --
All above-mentioned figures are in parts by
weight.
The glue formulations used in the various
samples are as follows:
... .
;630
-- 19 --
U~
O O r- =r c~
~D ~ ~ O Lr~ I I I O I
h O 1-~ N r~ ~1
~0 ~ ~r
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E~ t-- O O t-- J N
U~ ~ ~-- O U~ ~ I I I I O I I ~ ~D
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t- O O t-
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~2256:~0
- 20 -
Single-layer boards are prepared in the
lab-oratory by spraying each of these formulations onto
25 kgs wood chips. Boards are pressed at 10, 9 and
8 secs./mm. The thickness of the boards is 17.3 mms.
The temperature of the press is 200 C and the pressure
is 35 kg/cm2. The dimensions of the boards produced
are 40 x 56 cms.
The results obtained are reported in the
following table and are average values.
. .
~225630
-- 21 --
O
s t-- ~ ar~
CP~ O ~D ~ 0
~1 ) a~ ~J ~1 ~r
~D
N
r~ ~ L~ ~ OC
L~ O`\ O ~D O C~
U~ 0
~D
~ 1 ~ O
O o o ~ J
3 ~ t~J r~ 3
~D
Lr ~ U~ CO O
U~ O~ O U~ CJ~ ~1
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co ~1 ~ ~
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0~ 0 ~D 0~
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e e ~ ,1
.~ ~ ~ ~ o
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" :
Z5~i30
- 22 -
The above-mentioned results prove that all
samples used have values equivalent to the control and
that the formaldehyde reduction is of the order of 32
to 47 %
Example 7
In this example three different types of
organic compounds containing hydroxyl groups are
exemplified by means of dextrin, phenol and resor-
cinol.
One monohydric alcohol acting as an additive
other than methanol is also illustrated, namely ethyl
alcohol.
The various types of formaldehyde binder
used are as follows:
l 2 3 4
20 Monethyleneglycol 230
Dextrin - 140
Phenol - - 130
Resorcinol - - - 130
Methanol - 140 130 130
25 ~thanol 80 - - -
Urea 350 350 370 370
Water 340 370 370 370
1000 1000 1000 1000
% solids 66 63 63 63
All above-mentioned figures are in parts by
weight. The formaldehyde binder samples are used in
this example to substitute a part of the resin used.
lZ25630
- 23 -
The glue formulations actually used are as
follows:
Control 1 2 ~ 4
grams grams grams grams grams
-
5Urea formaldehyde 3077 2770 2770 2770 2770
resin (Molar ratio
F:U = 1.27:1)
Hardener 400 500 400 450 400
(Ammonium chloride
15 % solution)
Paraffin emulsion 50 % 250 250 250 ~50 250
Ammonia 25 Baum~ 5
~ormaldehyde binder
Sample 1 - 307 - - -
15 Sample 2 ~ ~ 37
Sample 3 - ~ ~ 37
Sample 4 - ~ ~ ~ 307
Water 268
Total 4 3827 3727 37773727
Gel time in secs.65 64 62 63 63
Single-layer boards are prepared in the
laboratory by spraying each of these formulations onto
25 kgs wood chips~ Boards are pressed at 10, 9 and
8 secs./mm. The thickness of the boards is 17.3 mms.
The temperature of the press is 200 C and the pressure
is 35 kg/cm . The dimensions of the boards pressed
are 40 x 56 cms.
The results obtained are reported in the
following table and are average values.
~Z~5~30
-- 24 --
C~ t- ~'
O O O ~ ~ O
~1
r-
O ~ ~ o~
O O ~ ~ o~
O ~ ~ r~
L~
t~ ~ N
Ln O~ O ~ ~ O~ O
~I CJ~
~o
U~
oo a~ o
a~
~D
~1
O U~
~ ' ~ O O ~ O
O O C~
C~ C-
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Z Z;
S S ~q ~ ~ O
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q s s ~ ~o s
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~ ~ ~ s ~ a) ~0 ~
a) a) a~ ~ 3 h Ei O
~5630
- 25 -
The above-mentioned results prove that all
samples have values that are equivalent to the control
sample that contains no formaldehyde binder even though
the latter substitutes an equivalent amount of urea-
formaldehyde resin in the formulation. The formaldehydereduction varies in this example from 24 to 37 %.
Example 8
In this example one type of formaldehyde
binder is used and the resin is based on phenol-
melamine-urea formaldehyde resin.
The formaldehyde binder used has the follo-
wing formulation:
parts by wei~ht
Monoethyleneglycol 300
Urea 33
Water 370
1000
The glue formulations used are as follows:
Control
grams grams
25 Phenol-melamine-urea-formal-
dehyde resin 63 % 5600 5600
Hardener (solution in water
of 15.5 % ammonium chloride) 840 840
Paraffin emulsion 50 % 150 150
30 Formaldehyde binder - 560
Total 6590 7150
Gel time in secs. 73 79
- ~ Z S ~ 3
- 26 -
Single-layer boards are prepared in the
laboratory by spraying each of these formulations onto
25 kgs wood chips. Boards are pressed at 10, 9 and
8 secs./mm. The thickness of the boards is 17.3 mms.
The temperature of the press is 200 C and the pressure
is 35 kg/cm . The dimensions of the boards produced
are 40 x 56 cms.
The results obtained are reported in the
following table and are average values.
Control
Density (kg/m3) 705 695
Bending strength (N/mm ) 26.2 25.9
Tensile strength (N/mm2)0.27 0.26
Tensile strength V100 (N/mm2) 2.7 2.6
2 hr. thickness swelling (%) 7.1 6.2
24 hr. thickness swelling (%) 12.0 11.3
Free formaldehyde
(mg/100 g dry board) 12.8 7
Formaldehy~ reduction (%) - 45
The above-mentioned results prove that the
formaldehyde binder according to the present invention
can be used also for phenol-melamine-urea-fo~E~dehyde resins
reducing considerably the free formaldehyde emission
without adversely affecting the properties of the
boards.
3o
. , :
225630
-- 27 --
Example 9
In this example the formaldehyde binder used
includes an inorganic compound [component (d)], illu-
strated in this case by sodium chloride.
The formaldehyde binder used has the follow-
ing formulation:
Parts by weight
Monoethyleneglycol 100 % 270
10 Urea 100 % 318
Sodium chloride 100 % 50
Water 362
Total 1000
% solids . 63.8
The glue formulations used in the various
samples are as follows:
Control
grams grams
Urea-formaldehyde resin
(Molar ratio F:U=1.27:1)3077 2770
Hardener
25 ( Ammonium chloride 15 %
solution) 400 450
Paraffin emulsion 50 %250 250
Ammonia 25 Baumé 5
Formaldehyde binder - 307
30 Water 26~ -
Total 4000 3777
Gel time in secs. 65 64
,
lZ2563~)
- 28 -
Single-layer boards are prepared in the laboratory by
spraying each of these formulations onto 25 kg wood chips.
Boards are pressed at 10, 9 and 8 secs/mm. The thickness
of the boards is 17.3 mms. The temperature of the press is
200 C and the pressure is 35 kg/cm2. The dimensions of the
boards pressed are 40 x 56 cms.
The results obtained are reported in the follow-
ing table and are average values.
Control
Density (kg/m3) 695 699
Bending strength (N/mm ) 19.9 19.5
Tensile strength (N/mm2) 0.71 0.73
2 hr. thickness swelling (%) 7.0 6.6
2Y hr. thickness swelling (%) 20.5 20.8
Free formaldehyde
(mg/100 g dry board) 17 9.5
Formaldehyde reduction (%) - 44
The results prove that the sample including the
formaldehyde binder gives values that are equivalent to the
control sample in spite of the fact that the formaldehyde
binder substitutes a part of the urea-formaldehyde resin in
the formulation. The formaldehyde reduction is 44 %.
3o
