Note: Descriptions are shown in the official language in which they were submitted.
10918~
FIELD OF TIIE INVF,NTION
The present invention rela~es to aqueous solu-
tions of melamine-formaldehyde resins and methods for their ;~
preparation, and, more particularly, to etherified melamine-
formaldehyde resins having long shelf lives and comparatively
low contents of free formaldehyde. The melamine-formaldehyde
resins are of particular utility as binders for glass fiber mats
in the manufacture of various items.
OBJECTS OF THE INVENTION
.
It is an object of this invention to provide
etherified melamine-formaldehyde resins and methods for their
preparation.
Another object of this invention i5 to provide
etherified melamine-formaldehyde resins that have prolonged
-,"i
shelf lives.
Another object is to provide in accordance with
one aspect of this invention etherified melamine-formaldehyde
resins that have low residual free formaldehyde.
Another object of this invention is to provide
etherified melamine-formaldehyde resins that nave high water
compatibility.
Another object of this invention is to provide
a method for the preparation of etherified melamine-formaldehyde
resins that can reproducibly be controlled.
Another object of this invention is to provide
etherified melamine-formaldehyde resins that are especially
suitable for use as binders for glass fiber mats.
.
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f~ ~
1091836
SU~ RY OF THE~ VEMTION
Briefly, these and other objects are achieved
by conducting a reaction in a plurality of distinct
. ~tages, including: ' ' .
~1) condensing a basic aqueous solution
l ' of melamine and formaldehyde at elevated tempera-
;' tures, to a controlled degree, in the presence of
a polyol and triethanolamine;
~2) etherifying the aqueous condensate
0 by cooling and acidification;
:~¦ ' (3~ terminating the etherification by
¦ neutralizing ths cooled acidic solution with a base;j ¢omprised, at least in part, of triethanolamine;
. (4) stabilizing the neutralized solution
by heating it to an elevated temperature for a con-
'3; trolled period of time; and
, ~ . ~ . .
5) adjusting the free formalaehyde con-
~ tent of the stabilized solution by the addition
.'i' r of urea.
The resins obtained by the practice of this
' invention are characterized by a particularly high
..
. ' formaldehyde-melamine molecular ratio (designated here-
Inafter as "F/M ratio"), by good water compatibility, by
a shelf life at ambient temperatures at least equal to
~1; two months, and by a content of free formaldehyde less
3 than 6% by weight. ~
`'~ . The term "water compatibility" is here defined
~¦ as the lar~est amount of water ~by vo'lume) that can be
i added to 100 volumes of an agitated a~ucous resin solution
'`'1 .
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'I .
., -- 2 -- .
1091836
at 25C before the first appearance of turbidity.
The term "shelf life at ambient temperatures"
denotes the ability of an aqueous resin solution, when
stored at ambient temperatures between 15C and 25C,
to maintain both a viscosity, measured at 2SC, of less
than 800 centipoise ,and a water compatibility greater
than or equal to 1,200. The aqueous resin solutions
w,hich are the obiect of this invention have useful shelf
lives of at least two months.
These resins, together with a suitable sizing,
are particularly suitable for use as a binder for glass
fiber mats, The aqueous solutions of this invention
provide excellent properties for glass iber mats, such
as improved stress resistance and flexibility.
DESCRIPTION OF THE PPIOR ART
The preparation of etherified melamine-formal-
dehyde resins is known in the prior art as disclosed,
for example, in German patent application No. 2,005,166,
published for public inspection on February 5, 1970.
This application discloses a process for the alkaline
condensation of melamine with formaldehyde in the presence
of a polyol, by which process practically anhydrous ether-
ified tetramethylolmelamines or tetramethylolmelamines
in alcohol solution are obtained.
The process of this German application can be
distinguished from the instant invention in that the,
~nstand invention provides substantially higher P/M
ratios, the ratio of moles diol to moles melamine i~
higher, the ratio of moles of triethanolamine to melamine
~ ' ' , '
1091~336
i5 higher and the alkaline condensation is conducted
at lower temperatures. Further, the instant invention
relies substantially on polyols or etherification
whexeas the German disclosure primarily utilizes mono-
hydric alcohols for this purpose.
Another prior art method for the preparation
of resins of the type with which this invention i5 con-
cerned is described in U. S. Patent 2,577,767 in which
triethanolamine is also included in the reactive melamine-
formaldehyde-polyol mixture. In this process, an initial
reaction is conducted at a relatively high temperature
~80C), the reacting mixture is acidified to a pH of
between 0.5 and 1.5 at eleva~ed temperatures ~72-82C),
and a ~inal step includes increasing the pH of the resin
, .
to about 6.3 with sodium hydroxide, also at elevated t~n-
peratures (70C). The process disclosed in this patent
i~ conducted under rather ex~reme conditions of pH and
temperature, making it difficult, at very best, to exer-
! cise reproducible control over residual formaldehyde,1 20 viscosities and shelf life of the resins as can be done
¦ in the practice of the instant invention.
'¦ DETAILED DESCRIPTION OF TEIE INVENTION
; First Stage - Conden~ation
. .
The melamine employed in this invention can be
of technical quality, but must have a purity of greater
than 99% by weight, with the maiority of particles le5s
¦ than 160 microns in diameter to permit facile dissolution
- ~n the reaction environment.
While either formaldehyde or its polymers (such
. as paraformaldehyde) can be used in the practice of this
~ ' ' ' . .
4 _
109i83~ .
-
.invention, 36% by weight aqueous solu~ion of formalde-
hyde preferably is employed due to its comm~rcial avail-
ability and its comparatively low cost. These solutions
; . ~hould not contain more than 10% ~maximum) methanol ~y
weight. Preferably, this content will be less than 1%
in order to avoid the presence of methoxy groups in the
etherified resin. In practice, etherification is pre-
ferably achieved solely by a polyol or triethanolamine
rather than by monofunctional alcohol.
The F/M ratio will range between 5 and ll, but
preferably between 6.5 and 10. Values lower than 5 cause
`I a lo~s in glass fiber mat properties ~particularly stress
~ésistance) and further result in low water compatibility
:~i value~. Values higher than 10 yield final aqueous solu-
! tions with low dry extracts which have little industrial
;. I
. . use. The successive values 5, 6.5, 10 and 11 of the F/M
,;~ ratio correspond appreciably to the dry extracts which
, are 52, 50, 44 and 41% respectively, if one uses as a
I source of formaldehyde an aqueous solution of 36% by
j 20 weight.
-¦ . The alkaline condensation reaction is éffected
; at a p~ ranging between 8.5 and 9.5 and preferably between
. ' 8.8 and 9.2. This pH is obtained by addition of triethan-
olamine to the reacting environment.
~ he quantity of triethanolamine will range
between 0.2 and 0.6 and preferably between 0.3 and 0.4
~ molecule per molecule o~ melamine. This ratio will be
.
designated hereinbelow by the ratio TEA/Mo These quanti-
t~es are largely in excess in relation to that re~uircd
' . .'
,~
0 5_
10~1836
for adjustment of the reacting p~i at the values indicated.
~heir purpose is to provide resins ~as already mentioned)
with high water compatibility.
Also included with aqueous condensation reac-
tants is a polyol, such as ethylene glycol, in an amount
corresponding to a polyol/me~amine molar ratio of from
about 3 to about 5, and preferably from about 3.5 to about
.. . . .
4Ø
he reaction is preferably conducted as follows:
- First, the required quantities of formaldehyde,
polyol and triethanolamine are mixed and then, with vigor- -
OU5 agitation, the mixture is brought to the desired reac-
tion temperature, ranging between 60C and 70C, and pre-
I ~erably b~tween 63c ana 68c.
! Second, the melamine is gradually added over a
~ period of ten to fiftéen minutes while maintaining the
j ~ desired reaction temperature and solution agitation for
¦ a further period of thirty to ninety minutes. Tempera-
tures of at least 60C are necessary to dissolve the mela-
-¦ 20 mine at a practical rate.
At the appropriate time (as discussed below),
the reaction is stopped by cooling the mixture to a tem-
perature ranging between 20C and 40C, and preferably
between 33C and 37C.
The reaction is stopped by rapid cooling at a
precise moment which is determined by the cloud point of
~he-rcacting mix that is measured and monitored during
~heLreaction.
his cloud point is indicative of thc extent
.
.
- 6 -
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: j .
- 109i836
.
of the alkaline condensation. It is measured by suc-
cessivc samplings of test pieces from the reacting
~nvironment at regular time intervals. These test pieces
are cooled while agitating them and the temperature at
which a cloud i5 produced is noted. This cloud point
temperature, rather low at the beginning of the reaction,
rises as the reaction proceeds.
The alkaline condensation reaction is stopped
by rapid cooling when the cloud point appears between
40 and 65C, and preferably between 45 and 55C, which
: i5 produced at the end of a time period usually in a
range of from 30 to 90 minutes.
I the reaction is stopped at a cloud point
le~s than 40C, the cooled reacting environment then
presents a high ~iscosity which makes it difficult to
maintain homogeneity by agitation. At the other extreme,
, ,
one cannot surpass a cloud point temperature higher than
' that of the reaction without causing the reacting environ-
- ment to opacify at the reacting temperature. For example,
~; 20 if the temperature of the reaction is 70C, it would be
very difficult to measure a cloud point temperature higher
than 65C because of the small temperature difference
betweén the test and reaction temperatures.
1 Second Stage - Etherification
i In this stage, the methylolmelamines obtained
in phase 1 are etherified with one or several of the
polyols that were previously introduced into the reacting
en~ironment. These polyols can be selected from, for
; example, ethylene glycols, diethylene glycol, triethylene
'''I ' . .
`I , ' '.
1 i
'",1
- ~
iO9i836
, , .
glycol, glycerol, saccharose and d-glucose. The pr~-
~erred diol, because of its price and availability is
ethylenc glycol.
Control over viscosities can be exercised by
using mixtures of polyols. For example, by using a mix-
ture of ethylene glycol and saccharose, the viscosity
of the final resin will increase with an increased use
:- of saccharose.
The total quantity of the one or several polyols ~
10 used should range between 3.0 and 5.0, and preferably ~--
between 3.5 and 4.0 moles per mole of melamine. This
ratio will be designated hereinbelow by the ratio P/M.
An lnsufficient ~uantity of polyol will diminish the resin's
water compatibility. On the other hand, exceeding this
ratio i5 not use~ul because it does not further increase
,.;
water compatibility.
The acid used for lowering the pH of the con-
densation phase to that o~ the etherification should pre-
~? ferably be a concentrated acid to avoid lowering the final
ary extract of the aqueous resin solution. Examples of
suitable acids are sulfuric, hydrochloric, orthophosphoric,
nitric, formic or monochloracetic.
Immediately after the alkaline condensation,
::~,
the mixture is cooled, as described above, ~nd, while
maintaining the obtained temperature constant, the envir-
onment is acidified to a p~I selected with regard to th~
chosen temperature, the pll range being 1.5 to 3Ø It
~s under these conditions of temperature and p}I that the
atherification reaction is effected.
.
'~'
,
- 8 -
~ .
The conditions should range between 25°C
for a pH of 1.5 to 40°C for a pH of 3.0, or preferably
33°C for a pH of 1.8 to 37°C for a pH of 2.2.
If etherification is conducted at a pH and/or
a temperature that is too high, the resin will have a
viscosity which is too high. It will also reduce shelf
life and hinder use of the resin soon after preparation.
On the other hand, if the pH and/or temperature of ether-
ification is too low, the viscosity of the resin will
be low, its water compatibility will be very good, ut
the values of stress resistance for the glass fiber mats
will be undersirably low.
After acidification, the temperature of the
cloud point at which the reacting environment, previously
opaque, becomes clear, is determined. The etherification
reaction is then continued for a certain time at the same
temperature before stopping it by neutralization.
The time periods before and after the moment
when the reacting environment becomes clear will be
called hereinafter "opaque phase" and "clear phase" of
etherification.
The following conditions should be respected
for the etherification pahse: The acid should be added
very regularly and for a period between 25 and 35 minutes,
preferably between 28 and 32 minutes.
It has been found that the total duration of
etherification is substantially constant, and that by
final viscosity of the aqueous resin solution is appre-
- 9 -
i09i83~
ciably increased. On the other hand, the acid should
be added slowly enough to permit adequate mixing and to
maintain a constant temperature despite any heat released
by the acid addition. -~
The total duration of etherification, counted
f~om the outset of the acid addition, should range be-
tween 50 and 180 minutes for a cloud point ranging be-
tween 40 and 65C, respectively, and preferably between
105 and 135 minutes for a cloud point ranging bet~leen 45
10 and 55C respectively. These duration Iimits are under-
stood to be true in the context of the previously defined
values o f pH and temperature.
For the pH and temperature values indicated
hsr~inabove for the cloud point, it has been established
that the minimal duration of the opaque phase is 50 min-
utes, measured from the beginning of the acid flow.
If, on the other hand, at pH and temperature
values indicated hereinabove for the cloud point, a total
duration of 180 minutes is surpassed, it has been estab-
20 lished that the viscosity of the resins becomes too greatand that their water compatibility falls below 1,200
immediateiy after manufacture. Further, it can be shown
that when these resins are maintained at storage tempera-
tures, there is a rapid increase in their viscosity and
an equally rapid lessening of their water compatibility.
After their manufacture, the resins of the pre-
sent invention have low viscositics ranging betwecn about
30 and about 200 centipoise.
It should be remembered that to obtain the
,
-- 10 --
iV~1836
minimal shelf life of two months and a water compatibi-
lity of at least 1,200, the viscosity of the resins
~hould not be higher than 800 centipoise. As is known,
dur~ng storage the resins tend to increase their viscos-
ity and to diminish their water compatibility.
Third Stage - Neutralization
of Etherified Resin
Upon completion of the etherification and
reaching an appropriate cloud point, as mentio~ed above,
the aqueous resins are neutralized to a pH of about 7.0
to 7.5. The base employed for neutralization should be
triethanolamine. Minimally, triethanolamine should be
present at a ratio of 1/3 mole per mole of melamine; the
rest of the neutralizing agent can be a base such as a
solution o 5G% by weight sodium hydroxide.
It has been established that the total neutral-
ization by soda yields resins not easily miscible in
water and precipitation occurs due to the neutralization.
The purpose of neutralizing with triethanolamine is to
Lmprove the water compatibility of the resin.
Fourth Stage - Stabilization
- This stage of preparation of the resins of this
invention is one in which the reacted mix is held at ele-
vated temperatures of 50C to 90C, and preferably between
70C and 85C, for a period of time of about two to five
hours. This holding period ~herein referred to as "sta-
bilization") is important because it improves two proper-
t~es of glass fiber mats held together with a binder pre-
pared from the-aquc~us resin solutions. It has been found
that increasing the duration of this stabilization stage
109i~36 . :~:
', '' ~-
increases the flexibility index and stress resistance
of the glass fiber mats.
The 1exibility index and stress resistance
were determined in accordance with the following:
Sixty rectangular test pieces measuring 25 x
S cm were cut from a glass fiber mat. On thirty of these
test pieces, stress resistance was measured and the aver-
age of these measurements taken.
The other thirty test pieces were each sub- -
jected one time to folding under the following condi-
tions. A metal plate was used which was 35 cm long and
S cm wide, of 2 mm thickness, and supplied with two
hin~es which permit folding it into two half-plates,
each 12.5 cm long. Each flat mat test piece was placed ~ -
on the unfolded plate and two other plates measuring
12.5 x S cm were applied over the mat~ The test piece
was maintained tightly closed and flat between the plate
supplied with hinges and the two half-plates completely
folded 180 around the hinge. The distance between the
two halves of the test pieces after folding was 10 mm,
the test piece always being maintained between the plates,
as described. The stress resistance of the thirty test
pieces was measured and the average of these measurements
taken. The loss of traction resistance after folding
was then calculated in percentage.
The flexibility index is a numbcr on a scale
of 0 to 10 which was determined in accordance with the
following table:
,
- 12 -
1091~336
Loss of Stress Resistance Flexibility
after Folding in % Index
-
0 to 4 10
4 to 10
10 to 20 8
20 to 30 7
3~ to 40 6
40 to 50 ~ 5 `
50 to 60 4
60 to 70 3
70 to 80 2
80 to gO
90 to 100 0
A ~mall lessening in percentage o~ free for-
maldehyde of the aqueous resin solution and a gradual
increase in its viscosity is observed during the stabil-
ization stage. Since this may be detrimen~al to the
shelf life of the resin solution, the stabilization is
l~mited to the above-mentioned temperature ranges of 50C
to 90C, and preferably of 70C to 85C, for a period of
time not to exceed two to five hours.
Under these conditions, the aqueous resin
solution remains water compatible at a ratio of at least
12 times its volume.
If the duration of the stabilization period
surpasses five hours, for the indicated temperature values,
the resin acquires an undesirably high viscosity. If the
8tabilization is interrupted before two hours, the desired
improvement in flexibility of glass fiber mats is not
obtained.
- 13 -
1091836
.
Fifth Stage - Reduction
of Free Formaldéhyde
Th~ percentage of free formaldehyde of the
aqueous rcsin solutions after the stabilization stage is
even higher than the initial F/M ratio and is on the order
of 6 to 12% or more. Such amounts of free formaldehyde
are undesirable because, among other reasons, the vapors
emitted during final curing irritate the eyes and respir-
atory systems of the operators.
Thus, the principal objective of the fifth ,-
~tage is to reduce the content of free formaldehyde to
6% or less. The irritating vapors emitted at these con-
centrations are tolerable to the worker~.
Further, when the ~ormaldehyde content of the
resin is reduced to 6~ or less, the stress re~istance o
the resin-bonded glass fiber mats increases and the rate
at which the viscosity of the stored aqueous resin solu-
tions increases is minimized, thereby contributing to a
prolonged shelf life.
The free formaldehyde content is reduced in the
fifth phase by adding urea in a ratio of 0.6 to 1.6, and
preferably 0.8 to 1.2 moles of urea per molc of melamine
while the resin is heated to temperaturés as existed in
the stabilization stage. The free formaldehyde content
of the stabilized resin is a function of the initial F/M
ratio and therefore the molecular ratio of urea to mela-
mine is referred to here as the U/M ratio.
.
109183~i
EX~MPLE 1
Stage I
562 g of an aqueous solution o~ 36% formaldehyde
and 0.5% methanol, 248 g of ethylene glycol and 49.5 g of
triethanolamine were introduced into a one-liter reactor
~upplied with a reflux condenser, an agitator and a
thermometer. The solution was heated to 65C and 126 g
of melamine were added in twelve minutes during agitation.
The condensation reaction was continued at 65C until a
cloud point of 50C was obtained, at which time the tem-
. perature was rapidly lowered to 35C.
Stage II
,
Etherification was commenced by adding 56 g of
concentrated sulfuric acid over a thirty-minute period
until a pH o 2 was reached. Etherification continued
at 35C for one hour and thirty minutes.
Stage III
At the end of etherification, the p~ of the
environment was adjusted to 7.2 by adding 49.5 g of tri-
ethanolamine and 50 g of a 50% solution of sodium hydroxide.
- Stage IV
The temperature was then brought to 70C and
the resin allowed to stabilize for five hours.
Stage V
At the end of five hours, 48 g of urea were
introduced and the resin cooled to a temperature of
about 60C.
- The rcsin obtained presented the following~
charactcristics:
. .
- 15 -
.. . . . . ..
1(~9~836 - :
- F/M ratio - 6.75
- P/M ratio ~ 4
- TEA/M - 0.33
- Number o molecules of triethanolamine, added
after etherification, per molecule of melamine:
0.33
- U/M ratio = 0.8
- Dry extract: 50.1%
- Viscosity: 94 centipoise - -~
- Free formaldehyde: 1.9
- Water compatibility: infinite ~2,000)
- pH: 7. 2
- After two months' storage: Infinite water com-
patibility (~2,000) and a v~scosity of 160 cen-
tipoise
PreParation of S~zing
An aqueous dispersion of starch paste was pre- -
pared from potatoes, as modified by ethylene oxide
treatment, having a concent~ation of 8% calculated in
the form of anhydrous starch. Steam was bubbled in this
dispersion until its temperature reached 98C and was -
continued for twenty minutes. After cooling to 25-30C,
the paste was ready to be used.
An aqueous solution of the preceding melaminé-
formaldehyde resin corresponding to a dry weight of 1.2
kg was mixed with 110 Xg of the paste
MLxed with the preceding mixture was an emul-
sion of a homopolymer of polyvinyl acetate, which poly-
vinyl acetate was plasticized by dibutyl phthalate to
the extent of 50~ of plasticizer p~r weight of resin.
1.378 kg of a 58% emulsion, based on the dry weight of
the plasticizcd homopolymcr~ was mixed with 1.378 kg
- - 16 -
1091836
(or an equal weight) of water and the resulting mixture
added to the mixture of starch and melamine-formalde-
hyde resin formed in the preceding step.
The diluted emuision was added to the preceding
mix. The total was homogenized by agitation or ten
minutes and constituted the concentrated sizing.
; When used, this concentrated sizing was diluted
by a quantity of water such that the sizing finally used
had a dry extract of 2.2%.
Preparation of a Glass Fiber Mat
A mat of unbonded discontinuous glass fibers
(hereinafter called "uncured mat") was used. This mat
was obtained by distributina in regular fashion on a
conveyor belt of metallic cloth discontinuous glass
fibers obtained by steam attenuation of molten glass
streams which flow from holes placed at the lower sec-
tion of a platinum bushingO These glass fibers have an
~verage diameter of about 16 microns. The uncured ma~
used had a weight of 80~5g/m2.
The uncured mat, in the form of a continuous
ribbon placed between two conveyor belts of metallic
cloth, was immersed in the preceding prepared sizing.
The excess sizing retained by the uncured mat
was extracted, always in a continuous fashion, by means
of a bin with a depression placed below the lower belt.
The deprcssion was regulated in the bin so that the mat
retained, after drying, 20~ by weight of dry binder in
proportion to the total weigkt of glass and dry binder.
The uncured mat, sized and dried, was then con-
- 17 -
109i83~
tinuously passed for two minutes in an air circulation
ov~n heated to 145C.
The finished mat was found to have a stress
resistance of 5.5 kg/cm and a flexibility index of 7.
EXAMPLE 2
A melamine-formaldehyde resin was prepared
according to the operative mode of Example 1, using
the following quantities of materials:
- formaldehyde at 36% 666 g
- ethylene glycol 248 g :
- triethanolamine 49.5 g
- melamine 126 g ~,
- concentrated sulfuric acid 56 g ;
- aqueous solution of sod~um 50 g
hydroxide at 50%
- urea 48 g ;
- triethanolamine 49.5 g
The resin obtained had the following charac-
teristics:
- 20 - F/M ratio: 8.0
- P/M ratio: 4.0
- TEA/M ratio: 0.33
- Number of molecules of triethanolamine, added
after etherification, per molecule of melamine:
0.33
- U/M: 0.8
- Dry.extract: 47.8%
- - Viscosity: 70 centipoise
. - Free forma~dchyde: 4.0~
, - Water compatibility: infinite ~2,000)
- pH: 7.2
- 18 -
, lOgl83~ " `,
- After two months' storage: Infinite water com-
patibility (~2,000) and a ~iscosity of 130
centipoise.
By u~ing the preceding resin, a paste was pre-
pared that was applied on the uncured mat which was then
dried in an oven according to the method described in
Example 1.
The stress resistance of the final mat was
5.6 kg/cm and the flexibility index was 7.
EXAMPLE 3 f
A melamine-formaldehyde resin was prepared
according to the method of Example 1, using the quan-
t~ties of materials set forth below:
- ~ormaldehyde at 36% 750 g
- ethylene glycol 248 g
- triethanolamine 49.5 g
- melamine 126 g
- concentrated s~lfuric acid 5~ g .
- triethanolamine 49.5 g
- aqueous solution of sodium 50 g
hydroxide at 50%
- .urea 48 g
The characteristics of this resin were as fol-
lows: .
- F/M ratio: 9.0
- P/M ratio: 4.0
- TEA/M ratio: 0.33
- Number of triethanolamine moleculesJ added after
etherification, per molecule of melamine: 0.33
3n U/M ratio: 0.8
- Dry extract: 45.6%
-- 19 --
109183~
- Viscosity: 52 centipoise
- Free formaldehyde: 5.4%
- Water compatibility: infinite (~2,000)
_ p~ 7.2
- After two months' storage: In~inite water com-
patibility ~2,000) and a viscosity of 100 cen-
tipoise.
By using the preceding resin, a sizing was
prepared th~t was applied to the uncured mat which was
then dried in an oven according to the method described
in Example 1.
Ths finished mat had a stress resistance of
5.9 ~g/cm and a flexibility index of 8.
~XAMPLE 4
. A formaldehyae-melamine resin was prepared -:
according to the method of Example 1, using the follow-
ing quantities of materials:
- formaldehyde at 36~ 6b6.5 g
- ethylene glycol 198.5 g
- triethanolamine 39.5 g
- melamine 101.0 g
- concentrated sulfuric acid45.0 g
- triethanolamine 39.5 g
- aqueous solution of sodium40.0 g
hydroxide at 50% .
urea 38.5 g
The characteristics of this resin were as fol-
lows: ~ -
- F/M ratio: 10.0
- P/M ratio: 4.0
- TEA/M ratio: 0.33
- 20 -
.
1091836
,
- Number of triethanolamine molecules, added aftcr
ethexification, per molecule of melamine: 0.33
- U/M ratio: 0.8
- Dry extract: 43.2%
- Viscosity: 44 centipoise
- Free formaldehyde: 5.7
- Water compatibility: infinite (~2,000)
- pH: 7.2
,
- After two months' storage: Infinite water com-
- - patibility (~2,000) and a viscosity of 92 cen-
tipoise.
A sizing was prepared by using the preceding
resin and then a mat manufactured according to the
method of Example 1. This mat had a stress resistance
o~ 6.2 kg/cm and a ~lexibility index o~ 7.
. * * *
If the stress resistances of the mats obtained
in Examples 1, 2, 3 and 4 are compared, the relationshi~ -
between a rise in stress resistance with increasing F/M
, . .
ratios can be seen.
Stress Resis-
Example F/M Ratio tance (kg/cm)
1 6~75 5.5
,
2 8.0 5.6
3 9.0 5.9
4 ------ - 10.0 - 6.2
- --- EXAMPLE 5
An alkaline condensation with formaldehyde and
~e~amine was conducted in a reaction vessel at 65C with
vigorou~ .ag~a~ion,.using the following quantities of
mater-ia~s~
- 21 -
~091836
` ::
- ethylene glycol 248 g (4 mol.)
- tricthanolamine 49.5 g ~0.33 mol.)
- melamine 126 g (1 mol.)
- formaldehyde see below
~ he aqueous solution of formaldehyde at 36%
containing 0. 5% methanol was placed in a reactor.
Glycol and triethanolamine were added and the mixture
heated to reaction temperature. The melamine was then
added in twelve minutes. ;~
, 10 For i~creasing quantities of agueous formalde-
hyde solutions, the following determinations were made: -
- P/M ratio 2.5 - Even after three hours at 65C,
the reacting en~ironment remained cloudy. Continuous
heating resulted in solidification of the resin. ~ -
- F/M ratio 2.9 - At the end of ninety minutes at
65C, the reacting mixture was clear. Operations were
continued corresponding to ~tages 2-5 according~to the
conditions indicated in Example 1. The final resin had
no water compatibility.
- F/~ ratio 4.0 - The reacting environment of the
alkaline condensation became clear after fifty minutes
at 65C. Preparation was finished according to the
method of Example 1. Tne resin obtained had a water
compatibility of only 1,000.
A sizing was prepared with the last resin and
a glass fiber mat manufactured according to the methods
of Example 1. The stress resistance of this mat was
only 4.2 ~g/cm
This example shows that the d~sadvantageous
.
~ - 22 -
1091~36 . ~:
.
results of an F/M ratio < 5.0 are lack of desired wa-ter
co~patibility of the resins and weakening of the stress
resistance of the glass fiber mat.
E%AMPLE 6
Three resins were prepared according to the
conditions indicated in Example 1, except that the
cloud point was 12C for all the preparations. Further,
the temperature of alkaline condensation was varied ;
from one preparation to the other. The following
results were obtained:
First Preparation
Condensàtion at a temperature of 60C for
forty-fl~e minutes, The resin had a viscos~ty of 14
cent~poise and a water compatibility higher than 2,000.
Second Preparation
Condensation at a temperature of 65C for
thirty-five minutes, The resin had a viscosity~of 12
centipoise and a water compatibility higher than 2,000.
Third Preparation
Condensation at a temperature of 70C for
twenty-three minutes. The resin had a viscosity of 11
centipoise and a water compatibility higher than 2,000.
However, at the end of only fifteen days'
storage, these three resins had such increased viscosi-
ties that they had the consistency of a gel.
This example shows the necessity of a sufficiently
high cloud point in order to obtain a good shelf life
of the resins. One should also note, by comparison
with Example 1, that the viscosity is reduced when the
- 23 -
~ .
1091836
-
temperature of the cloud point is lowered.
EXAMPLE 7 i.
A melamine-formaldehyde resin was prepared
according to the method of Example 4, using the follow-
ing quantities of material:
- formaldehyde 665.5 g
- ethylene glycol 198.5 g
- triethanolamine 39.5 g
- melamine 101.0 g
,10 - concentrated sulfuric acid 45.0 g
, - triethanolamine 39i5 g ~ .
- aqueous solution of sodium 40.0 g
hydroxide at 50% . .
- ur~a 57.5 g
The method was varied from that of Example 4
in that the alkaline condensation was continued to a
cloud point of 62C instead of 50C, in that the time
~therification duration was increased to three hours
and ten minutes instead of two hours, and in that the
stabilization phase was altered to three hours at 85C
instead of five hours at 70C.
~ he characteristics of this resin were the
same as those of the resin of Example 4 except for the
following: -
- U~M ratio: 1.2
- Dry extract: 43.3%
- Viscosity: ~0 centipoise
- Free formaldehyde: 4.5%
- Water compatibility: 1,900
- 24 -
, . .
~091836
- After two months' storage: Water compatibility ~ -
was 1,400 and viscosity was 210 centipoise.
A ~i~ing was prepared with the preceding resin
and the method of Example 1 used to manufacture a mat. -~
The mat had a stress resistance of 6.7 kg/cm and a
flexibility index of 6.
This example shows the possibility of prepar-
ing a resin according to the invention by stopping the
alkaline condensation at a cloud point of 62C. It
further shows that the total etherification duration
should be adjusted in function of the cloud point value.
EXAMPLE 8
A resin was prepared according to Example 4
except that a TEA/M ratio of 0.1 instead of 0.33 was
u~d at the time of the alkaline condensation.
The obtained resin had practically no water
compatibility (~50) and a viscosity of 275 centipoise.
, This example illustrates, by comparison with
Example 4, the disadvantage of using, at the time of
alkaline condensation, a TEA/M ratio that is too low,
and also illustrates the importance of the role of tri-
ethanolamine in imparting ~ood viscosity and high water
compatibility to the resin.
- EXAMPLE 9
A resin was prepared according to the method
of Example 4, but sodium hydroxide was used as catalyst
for the alkaline condensation instead of triethanolamine.
The quantities of materials used were as follows:
- formaldehyde at 36% 666.5 g (8 mol.)
- 25 -
~09i836
- ethylene glycol 198.5 g t3.2 mol.)
- S0~ agueous solution of 1 ml
sodium hydroxide
- melamine 101 g ~0.8 mol.)
- concentrated sulfuric acid 10 ml
- triethanolamine 39.5 g (0.264 mol.) ~ .
- 50% aqueous solution of 7 ml
sodium hydroxide
The resin obtained after the etherification
10 phàse and neutralization had practically no water com- :
patibility ~ 100). If the resin is stabilized by heat-
ing under the conditions of Example 4, it is transformed
into a gel.
Thi example shows, as did Example 8, the ' .
important role o the triethanolamine introduction
during the alkaline condensation phase. This introduc-
tion of triethanolamine results in good viscosity and
suitable water compatibility which canno,t be obtained
with sodium hydroxiae.
EXAMPLE 10
This example illustrates the use of a certain
variety of different polyols based on ethylene glycol
in the synthesis of the resins of the present invention.
The preparations are made according to all the
conditions described in Example 1, except for the nature ,-
and ~uantities of polyols and for certain particulari-
ties for each polyol which are indicated in the follo~-
~ng table: .
.
- 26 -
1091836
Nature & Quantity . Results and
of polY ~ mol Particu].arities Observations
Glycerol: 4 mol 3 hr. stabiliza- Water compat-
tion at 75C ibility: 2,000
. IStage IV)
. Viscosity:
- - - 90 centipoise :
Stable 2
months' storage
10 Diethyleneglycol: Water compati-
.4 mol bility: 2,000
- Viscosity:
94 centipoise
Stable 2
months' storage
. .
d-gluco~e: 0.4 Cloud point of Water compati-
-47C obtained bility: 2,.~00
Ethylene glycol 3.0 ater 70 minutes
-at 65C ~Stage I) Viscosity:
112 centipoise
Stable 2
months' storage
Triethylene glycol Cloud point o Water compati-
4 mol 47C obtained bility: 2,000
after 120 min-
utes at 65C Viscosity:
(Stage I) 98 centipoise -~
Stable 2
- months' storage
EXAMPLE 11
. Three melamine-formaldehyde resins were pre-
pared according to the general method of ~le preceding
examples, using the following quantities of matérials:
formaldehyde at 36% 583O3 g (7 mol)
- triethanolamine 4~.5 g ~0.33 mol)
- melamine 126.0 g ll mol)
- 27 -
1(~91836 `
- concentrated sulfuric acid 56.0 g
- triethanolamine 49.5 g (0.33 mol)
- 50% aqueous solution of 50.0 g .
sodium hydroxide
- urea 48.0 g (0.8 mol) ~`
The alkaline condensations were made at 65C~:
and discontinued at a cloud point of 52C. The etheri-
fications were made at a pH of 2 and a temperature of
30C.
These three preparations differ by the mix
of polyols used: -~
Preparations
Mix of Polyol A B C
Sucrose ~saccharose) 342 g 171 g 86 g
Ethylens glycol 0 124 g 186 g
Resin A was etheri~ied only forty minutes
bQcause its viscosity was already very high. Resins - s
B and C were etherified for a total period of ninety
minutes.
After neutralization, the three preparations
were stabilized for five hours at 70C. 95 g of water
had to be added to Resin A during heating because of
its thickness.
The characteristics of the resins finally
obtained were as follows~
'A - B C
F/M ratio 7.0 7.0 . 7.0
Molecular ratio:
Sucrose/melamine 1.0' 0.5 0.25
Ethylene glycol/ 2.0 3.0
melamine
TEA~M ratio 0.33 0.33 0-33
- 28 - .
8:~6 -:
A B C
Number of molecules of 0.33 0.33 0,33
triethanolamine added
after ctherification,
per molecule of melamine
U/M ratio 0.8 0.8 0.8
Dry extxact (~) 57.3* 55.6 54.0
~*includes water added
during stabilization)
Vlscosity in centipoise 2,100 1,100 125
Water compatibility 1,800 2,000 2,000
This example illustrates the possibility of
obtaining resins of viscosities that are very different
and that can be regulated as desired by adding varying
r~lative proportions of sucrose and ethylene glycol.
In ~stablishing the relative proportions of the two
polyols in the threè r~sins, A, B and C, above, it wa~,
considered that the sucrose, including eight hydroxyl
alcoholic groups per molecule, should be employed in
molecular ~uantities four times less than the diol.
Finally, it is evid~nt that only low portions of sucrose
- can furnish useful resins for general practice.
ExAMæLE 12
Three resins were prepared according to Example
1 except for the quantities of ethylene glycol.
Resin A was prepared using a P/M ratio of 2Ø
During the etherification phase; a solidifying of the
resin was observed which could not be stabilized by the
addition of water.
Resin B was prepared using a P/M ratio of 2.5.
There was no solidification during etheriflcation, but
the final resin had a water compatibility of only 1,000.
.
- 29 -
i09~:836
.
~ sin C was prepared using a P/M ratio of 3Ø
No difficulty was encountered in the prepaxation of
thi~ resin ~nd an infinite water compatibility (~2,000)
was obtained.
This example shows the necessity of using a
P/M ratio of at least 3.0 in order to obtain good water
compatibility.
EXAMPLE 13 ~;
Two resins were prepared under the conditionc~
, 10 described in Example 1, except those concerning pH and
temperature of the etherification phase.
Etherification of Resin A took place at a pH
of 4 and a temperature of 40C. The obtained resin
pre~entea normal viscosity and water compatibility the
day after its manufacture. However, twenty days later,
the viscosity of the resin had no increased that it was
a type of gel at ambient temperature.
Etherification of Resin B took place at a pH
of l.S and a temperature of 20C. The day after its
manufacture, the resin presented a water compatibility
higher than 2,000 and a viscosity of 15 centipoise.
After two months' storage, the water compatibility was
hlgher than 2,000 and the viscosity was 40 centipoise.
A sizing was prepared with Resin B and a glass
fiber mat manufactured according to the specifications
of Example 1. Stress resistance for the mat was only
4.0 kg/cm.
By comparison with the results indicated in
Example 1, the present example shows the disadvantages
30 -
1091836 .
encountered if one departs from the defined pH and
temperature values during the etherification stage.
EXAMPLE 14
Two resins wcre prepared according to the
specifications of Example 4, except for the duration
of the etherification phase.
Resin A - The total duration of etherifica-
tion, acid flow included, was only sixty minutes for
a cloud point of 50C instead of ninety minutes for
this same cloud point. The final viscosity of the
resin was only 23 centipoise, and its water compati-
billty was higher than 2,000
A ~izing was pxepaxed with Resin A and a
glass fiber mat manufactured according to Example 1.
The stress resistance of the mat was only 4.9 kg/cm.
Resin B - The total duration of etherifica-
tion was prolonged to 180 minutes for a cloud point
which is always 50C. The resin obtained presented a
viscosity of 285 centipoise and a water compatibility
of 1,500. After two months' storage, viscosity of
Resin B was 1,050 centipoise and water compatibility
was 600.
This example shows, by comparison with the
xesults of Example 4, the disadvantages encountered
~n not conforming, for the etherification reaction,
to the limits indicated for its total duration for a
given cloud point.
~XAMPLE i5
A resin was preparcd according to Example 4,
- 31 -
10~1~36
.
except that 60 g of aqucous solution of hydrochloric
acid at 35.5% were used instead of 45 g of concentrated
~ulfuric acid.
The characteristics of this resin, apart
from the molecular ratios of the different reactors
which are those of Example 4, were:
- Dry extract: 43.3% . ---
- Viscosity: 35 centipoise
- ~ree formaldehyde: 5.5%0 . - Water compatibility: infinite ( 2,000) -- Viscosity: 30 centipoise - - -
- After two months' storage: Infinite water com-
patibility ~72,000) and a viscosity of 55 centi-
poise.
~ A 5i21ng was prepared with this resin and a
mat manufactured in accordance with the specifications
of Example 1. The m~t was found to have a stress resis-
tance of 6.0 kg~cm ana a flexibility index of 7.
Analogous results are obtained wit~ orthophos-
phoric, nitric, formic or monochloracetic acids if thesame methods and stoichiometric proportions are used.
This example shows that various acids can be
used interchangeably in the practice of the present
~nvention.
EXAMPL~ 16
A resin was prepared according to Example 4,
cxcept that ne~tralization was effected--to a p~I of 7.2
~fter eth~ri~ication solely by an aqueous solution of
.
50% sodium hydroxide instëad:of-using 0.33 mol. of tri-
ethanolamine and 40 g of 50% aqueous solution of sodium
- 3i -
lO~i836
hydroxide. During stabilization at 70C ~Stage IV),
~olidif~cation of the resin occurs after two hours.
This resin cannot be solubilized by the addition of
watex.
This example shows the necessity of using,
at least in part, triethanolamine for the neutraliza-
tion of the resin after the etherification phase. It
shows, in comparison with Example 8 and 9, that tri-
ethanolamine plays an essential role in obtaining
water compatibility, not only during Stage I (catalyst
of the alkaline condensation), but also at the end of
Stage II ~etherification~ at the time of its neutrali-
zation.
XAMPLE 17
l'hls example shows the improvements obtained
by stabilization (Stage IV).
Four resins were prepared according to Example
1, exc~pt that the etherification temperature was 30C
for all preparations instead of 35C.
Duration of the stabilization phase (Stage IV)
was varied by increasing it from one preparation to the
next.
With each resin, a sizing was prepared and a
glass fiber mat manufactured according to Example 1.
~he results obtained are set forth in the fol-
lowing table: '
- 33 -
1~183~;
-
ST~BILIZATION
Nonë ---I hour 4 hours 5 hours
~tress resistance 4.2 4.6 4.8
of glass fiber mats
~n kg/cm
Flexibility index S 6 8
o glass fiber mats
Viscosity of aqueous 41 53 115 245
This example shows the very rapid increase in
10 viscosity after about four hours of stabilization and
demonstrates that the duration of stabilization must
be limited in order to obtain usable resins.
EXAMPLE 18
This example illustrates the improvements
obtained by the addition of urea to the resins after
the stabilization phase.
A resin was prepared according to Example 4,
but no urea was added at the end of manufacture. A
sizing was prepared from the resin and a glass fiber
mat manufactured according to Example 1.
In the following table, the results obtained
are compared to the results of Example 4:
Resin ofResin with
Example 4No Urea
Free formal~ehyde (%) 5.7 11.0
Stress resistance of glass 6.2 . 5.7
fiber mat in ~g/cm
Viscosity after manufacture 44 . 55
in cen ipoise
Viscosity two months after 92 185
manufacture in centipoise
* .
i4 -
1091836
The resins of the instant invention are advan-
tag~ous for binding mats of thin glass fibers, particu-
larly those of a thickness less than 4 mm. The resins
~mpart good qualities of flexibility and stress resis-
tance.
