Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~15~)~89
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BACKGROUND OF T~E INVENTlON
T~IS INVENTION relates ~o a novel process for preparingaminoplast resins, mQre particularly, advanced etherified
methylolguanamine resins, to the resins made by the new process,
snt to théir use in coating compositions.
Etherified methylolguanamine resins are, in general, well known,
commercially available materials ant are used in numerous fields of
application, especially iD liquid or powder coating compositions.
They are prepared by reacting a guanamine with formaldehyde or a
formaldehyde donor such as paraform under neutral or basic conditions
to form the methylolated guanamine and etherifying this with an
alkanol under acid conditions ( see, for example, British Patent
Specification No. 1 026 696). Such materials are often blended
with an alcoholic hydroxyl group-containing resin, such as an alkyd,
polyester, acrylic resin, or polyepoxide, and cured at elevated
-~emperatures in the presence o an acid ca~alyst, or, when larger
proportions of an acid catalyst are used, at room temperature.
Carboxyl-containing resins have also been used as the coreactant.
For certain applications, such as in the formulation of powder
coatings, it is preferred that the etherifiet methylolguanamine
resin is a non-sticky solid at room temperature or at slightly
elevated temperatures. Many commercially available etherified
methylolguanamine resins are sticky, high viscosity liquids at
ordinary temperatures, and so cannot be used in powder coatings,
Purther, it is known that while, when butanol is used as the
etherifying alcohol, the resultant resin in fully compatible with
a wide range of co-reactants and solvents, such compatibility
'~
115{~889
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i8 not always achieved when a lower alcohol is used. However,
complete elimination of butanol from the resin is not easy to
achieve, and its presence, either remaining after etherification or
liberated by the curing process, makes the resin unpleasant to
handle without very effective ventilation.
We have now found a novel method of making`etherified
methylolguanamine resins which are solid at ambient and slightly
elevated temperatures, which are fully compatible with a wide range
of co-reactants and solvents, and which do not contain butanol or
liberate it on curing.
It is known, from British Patent Specification Nb. 948 853,
to prepare a modified aminoplast resinous composition by
i. forming a partially polymerised aminotriazine resin
comprising an aldehyde, especially formaldehyde, and an aminotriazine,
which is usually melamine but may be a guanamine,
ii. adding a small unt of an ~m;notriazine to the partially
polymerised aminoplast resin ( which i8 unetherified),
iii. heat-treating the resulting syrup for a short period, and
iv. cooling the hot syrup, and then blending there*ith a small
unt of one or more amines.
The product is used alone to form laminates from glasscloth.
British Patent Specification No. 1 048 710 describes the
reaction of benzoguanamine and formaldehyde to form a monomeric
reaction product which is then treated with melamine and a
polymerisation catalyst i6 added. The product is likewise unetherified.
In the process now provided, a monomeric, highly methylated, methyl-
olated guanamine i8 heated with an advancement agent, which may be an
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Aminotriazine, urea, a cyclic urea, or a biscarbamate, under neutral
or slightly acid conditions. The term "atvancement" is used herein
in its conventional sense to mean a process iD which an essentially
linear, i.e., not substantially crosslinked, product of higher
molecular veight is produced. In the present process, part of the
etherifying methanol is eliminated.
DETAILED DISCLOS~RE
Accordingly, this invention provides a process for the preparation
of an advanced methylated, methylolated guanamine resin which
comprises reaction of a methylatet methylolated guanamine of the
formula
RlOC~2 ~ N 20R
N ~ N ~ ~ N
R OCH2 ~ \ CH20R
where
R represents an alkyl group of 1 to 16, and preferably 1 to 4,
carbon atoms, a phenyl group, or a group of formula
Rloc~ N ------ ~ CH ORl
2 \ ~ 2 II
N ~ N N
R10CH2~ \ C}120Rl
each Rl represents a hydrogen atom or a methyl group with the proviso
that, on average, at least 70% of the total number of groups R
on the methylated methylolated guanamine of formula I are methyl
groups, and
115{)889
R represents an alkylene group of from 2 to 16, and preferably 2 to S,
carbon atoms or a phenylene group,
at a pH of from 2.5 to 7, with 0.1 to 1 mole, per gram equivalent of
guanamine residue in the compound of formula I, of an advancement agent of gen-
eral formula III
R4 - NH - R3 NH - R5 III
where
either R represents a carbonyl group and R and R each represent a
hydrogen atom or together represent an alkylene chain having from 2 to 4 carbon
atoms which may be substituted by one or two hydroxyl groups, for example a group
of the formula -fH-ICH- or -CH2-CHCH2-
OH OH OH
or R represents a residue of formula
-CO - O - R - O - CO - IV
or
R7
N =~=~55 ~ N
~ N
where
R represents an alkylene group of 2 to 20 carbon atoms or an arylene
group of 6 to 12 carbon atoms, and
R represents an alkyl group of 1 to 16 carbon atoms, a phenyl group,
or an amino group (NH2-),
and R and R each represent a hydrogen atom.
This advancement may be effected in the presence or absence of
. ~.
, j _~
~J ~.
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an acid catalyst, preferably at a pH of 4~to 7. Acids which may be
used as the catalyst include formic acid, phosp~oric acid, and aromatic
sulphonic acids, especially toluene~-sulphonic acid. The amount
of the advancing agent of formula III, and thè reaction conditions,
may be varied according to the physical properties sought in the
final product, more advancement agent and a longer reaction time
generally leading to higher molecular weight materials, these having
higher melting temperature ranges. Preferably, the reaction is
effected with 0.2 to 0.7 mole of advancing agent of formula III per
gram equiYalent of guanamine residue in the compound of formula I,
but as little as~e.g., 0.125 le may be used successfully.
Preferably, too, the mixture i8 heated in the presence or absence of an
inert solvent at from 80 to 120C for from 2 to 6 hours. The product
may be purified by removal of solvent if present and, if desired,
by re val of the acid using conventional methods, including
neutralisation. Often, however, it is not necessary to remove the acid,
since it does not usually interfere with, and may indeed help, the
later cùring reactions. The product preferably melts within the
range 50 to 130C, especially w~thin the range 60 to 90C.
The etherified methylolated guanamines of formula I used as
starting materials for the novel process are known materials,
their prepsration baving been described in, for example, British
Patent Specification No.1 026 696 and We~t German Offenlegungsschrift
~o. 2 03i 035,
They are normally prepared by reaction of a guanamine of
general formula
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N ~ N VI
2 N ~ ~ NH2
~bere R8 represents an alkyl group of 1 to 16 carbon atoms, a
phenyl group, or a group of formula
N ~ N
NH2 ~ N J ~ NH2 VII
where R2 is as hereinbefore tefined,
with at least 4 moles, and especially 4.5 to 7 moles, of
formaldehyte per gram equivalent of guanamine residue in the
guanamine of formula VI, under alkaline conditions, the methylolation
being substantially complete after ~ to 4 bours at 50 to 100C.
The mixture is then treated with at least 4 les of methanol per
gram equivalent of guanamine residue in the guanamine of formula
VI and acidified. An exces6 of methanol is preferred, this excess
serving as a solvent for the reaction. Acidification is effected
using a strong acid, such as hydrochloric acid, which is preferably
added in an amount sufficient to reduce the pH to within the range
1.5 to 4, and the reaction is carried out at any temperature from
20C to the boiling temperature of the mixture.
The reactant of formula I may, for example, be a methylated
octamethylolatipoguanamine or a methylated octamethylolsuccino-
~15(3`~89
guanamine, but preferably it is a methylated tetramethylol-
benzoguanamine or a ~methylated tetramethylolacetoguanamine. As the
advancement agent of formula III there may be used, for example, urea,
melamine, ethylene dicarbamate, 1,4-butylene dicarbamate, and
1,2-dihydroxyethyleneurea ( i.e., 4,5-dihydroxyimidazolidin-2-one)
but preferably benzoguanamine, acetoguanamine, ethyleneurea ( i.e.,
imidazolidin-2-one), or 1,3-propyleneurea (i.e., hexahydro-2H-
pyrimidin-2-one).
The products of the present invention are suitable for use in
a variety of coatings applications. They may, for example, be
dissolved in an organic solvent or a mixture of organic solvents
and blented with pigments, co-reactants, or other polymerisable
materials as paints for application to woot or metals or as inks
for application to paper or card. Alternatively, they may, if
desired, be mixed with pigments, fillers, polymerisable materials,
or co-reactants, ground to a fine powder, typically having a particle
size within the range 0.015 to 500 ~m, and used as powder coatings.
Suitable co-reactants contain two or more free alcoholic
hydroxyl groups per average molecule and may be any of those used
conventionally with guanamine resins, including alkyds, polyesters,
hydroxyl-containing epoxide resins, and hydroxyl-containing acrylic
resins. There also may be used ( although in general they are
less preferred~being less reactive towards the advanced methylated,
methylolated resins of this invention) resins containing two or
more free carboxylic acid groups per average molecule. Yet further
suitable co-reactants comprise resins containing at least two amide
groups (-CONH2) per average molecule, such as copolymers of styrene
1150889
g
and/or (meth)acrylic acid esters with minor proportions of
(meth)acrylamide and (meth)acrylic acid as described in British
Patent Specification No~ 1 026 696.
The coatings may be applied by means conventional for
liquid or powder coating compositions and, after drying if necessary,
they may be cured at room temperature or by heating, usually
within the range 35 to 300C, especially from 100 to 200C or
225C, to give a coating having a very good gloss, colour, hardness,
and resistance to grease, staining, and detergents.
This invention therefore also provides a process for coating
a surface which comprises applying to the surface an advanced
~ethylated, methylolated guan~m;ne resin prepared by the novel
process, optionally with a compound containing at least two alcoholic
hydroxy groups or at least two carboxylic acid groups or amide
groups per average lecule, and causing the resin to form a hard,
cross-linked coating, usually by heating.
The invention will be further illustrated in the following
Examples, in which all parts are by weight ( unless otherwise
specified). Softening points are recorded as determined by means
of a ~ofler bench.
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EXA~LE 1
A. Preparation of a methylated, methylolated guanamine resin
Methanol (387.2g), paraformaldehyde (444.6g; 91% pure),
benzoguanamine ~841.5g), and aqueous sodium hydroxide solution
(54.0 ml; 20% w/w) were stirred and heated together for one hour
at 70C. A further quantity of paraformaldehyde (444.6g) and of
sodium hydroxide solution (54.0 ml; 20Z w/w) were adted, and
heating was continued at 70C for one hour.
The mixture was cooled to 45-50C, and concentrated hydrochloric
acid was added to bring the pH of the mixture to 8.6-8.8 (approximately
2.5 ml was required) Methanol (2475g) was added, and the ~ixture
was cooled to 36C.
Concentratet .hyarochloric acid (67.5 ml) was added, and the mixture
was stirred at 40C for 2 hours. The mixture was adjusted to
pH 8.6-8.8 with 20% sodium hydroxide solution (approximately
117 ml) and the mixture was distilled under a water pump vacuum
to remove aqueous methanol. When the temperature of the distillation
residue reached 70C, water (100 ml) was added and distillation
was continued until the residue reached a temperature of 100-110C.
This residue was then ~ooled to 90C and filtered to remove sodium
chloride. The filtrate comprised a highly methylated tetramethylol-
benzoguanamine resin (1550g), a colourless clear liquid having
a refractive index n2 of 1.5700-1.5750 and a viscosity at 25C
of 20.-25 Pas. Its degree of methylation (i.e., the
proportion of groups Rl which are methyl groups) was 82.5%~
B. Advancement
This resin (104.54g) and benzoguanamine (27.81g, i.e., 0.51
115(i~9
mole per gram equivalent of guanamine resitue in the resin) were
mixed and stirred at 100C for 15 minutes. Toluene~-sulphonic acid
(0.4 ml of a 50% solution in methanol) was added and the mixture,
which had a pH value of 5.0, was stirred at 100C for a further 2
hours, all volatile materials being removed as they formed. At
the ent of this heating the residue hat a softening point of 60C.
The product was substantially of formula
~L~2--N ~N J~ N-CII2-NII--~N --~NI~
3 CH2 n
N _ ~ N
CH30CH2 1 11
N ~ N ~ ¦ CH2
CH20CH3
CH30CH2
VIII
where
n represents an integer of average value 0.8, as determined by
vapour pressure osmometry, and
R9 and R10 each represent a phenyl group.
EXANPLE 2
A. Preparation of a methylated, ~eth~lolated cuanamine resin_
Acetoguanamine (600g) and methanolic formaltehyde solution (939g;
44% methanol, 46% formaldehyte, 10% water) were mixet with 57.6 ml of
889
20% agueous sodium hydroxide solution ant heated to 70C. Ater 1
hour, paraformaldehyte (474.2g; 91Z formaldehyde) and 57.6 ml of
20~ aqueous sodium hydroxide solution were added and the reaction was
continued for a further hour. The solution was neutralised with
hydrochloric acid, then methanol (2640g) was added and the solution
was cooled to 37C. Hydrochloric acid (72ml) was adted, and the
reaction was continued for a further 2 hours. After neutralising
the mixture with 20Z aqueous sodium hydroxide solution, excess of
methanol and water were removed by distillation under reduced
pressure. The product, a highly methylated tetramethylolacetoguanamine,
which was filt~red to remove sodium chloride, was a viscous liquid.
Its degree of methylation was approximately 80%.
B. Advancement
To 689 parts of the above liquid was added 1~2.5 parts of
acetoguanamine (i.e., O.S mole per gram equivalent of guanamine
residue in the resin) and the mixture was heated to 120C. After
15 minutes, 1.3 parts of toluene~-sulphonic acid solution (50%
in methanol) was added; reaction was continued at 120C until the
product had a softening point of 75C. The catalyst was neutralised
with N-benzyldimethylamine and the product was allowed to solidify
in a tray.
The product was substantially of formula VIII, in which R9
and R10 each represent a methyl group and n has a calculsted
average value of 1Ø
EXAMPLE 3
Example 2 was repeated but only 1~8 parts of acetoguanamine
werç used, instead of 162.5 parts, in the advancement reaction, i.e.,
.llS~`889
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0.33 mole per gram equivalent of guanamine residue in the resin.
Heating was continued~for lO hours at 120C, and the product then
had a softening point of 7SC. This product is of formula VIII, in
which R9 and R10 each represent a methyl group and- n has a calculated
average value of 0.66.
E~A~LE 4
Example 2 was repeated, the 162.5 parts of acetoguanamine
employed in the advancement reaction being replaced by 243 parts of
benzoguanamine, i.e., 0.5 mole per gram equivalent of guanamine
residue in the resin. The reaction was continued until the product
had a softeniDg point of 60C.
This product is of formula VIII, in which R9 represents a methyl
group, R10 represents a phenyl group, and n has a calculated average
value of lØ
EXAMPLE 5
The product of each of Exæmples 1, 2, and 4 was mixed with
an equal weight of either a solid~hydroxyl-containing polyester
resin (hydroxyl content 3.4 equiv.lkg) prepared in a conventional
manner from cyclohexanedimethanol, trimethylolpropane, neopentyl
glycol, and dimethyl terephthalate, or a solid, hydroxyl-containing
acrylic resin (hydroxyl content 1.91 equiv./kg) prepared in a
conventional manner from 70% of methyl methacrylate and 30% of
2-hydroxyethyl methacrylate. ~br ease of application the mixtures
were dissolved in xylene/n-butanol (1:1 by volume) to give a 50%
solution. The solutions were applied by means of a wire-wound rod to
glass or metal plates to give a coating 37.5 ~m thickness. The
coatings were cured for 15 minutes at 180 or 200C. After being
llSU~389
conditioned overnight at 65% relative humidity and 15.5C their
hsrdness (Persoz) was measured, and they were tested for acetone
rub resistance by rubbing 20 times with a swab of cotton wool soaked
in acetone. The results obtained are recorded in Table I.
TABLE I
Protuct Co-reactant Cure Hardness Acetone
of Temp C (Persoz) Resistance
Example ¦ _
1 Polyester 180 312 no effect
1 Acrylic 180 274 no effect
1 Polyester 200 289 no effect
1 Acrylic 200 286 no effect
2 Polyester 180 270 slight softening
2 Acrylic 180 256 no effect
2 Polyester 200 255 slight softening
2 Acrylic 200 263 no effect
4 Polyester 180 289 softening
4 Acrylic 180 291 no effect
4 Polyester 200 301 slight softening
4 Acrylic 200 256 no effect
EXAMPLE 6
A highly methylated tetra~ethylolbenzoguanamine resin was
prepared as described in Part A of Example I. A 104.5g portion of
this resin was advanced by stirring with 14.9g of 1,3-propyleneurea
115~9
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(i.e., 0.50 mole per gram equivalent of guanamine residue in the
resin) at 100C for 15 minutes, adding toluene~-sulphonic acid
(0.4 ml of a 50% solution in methanol) to bring the pH to 5.2, and
heating for a further 4 hours at 100C, all volatile materials
being re ved as they formed. The product had a softening point
of 65C. The catalyst was neutralised with N-benzyldimethylamine.
EXAMPLE 7
The procedure of FY~mple 6 was repeated, there being used
6.95g of benzoguanamine ( i.e., 0.125 mole per gram equivalent of
guanamine resitue in the resin) in place of the propyleneurea. The
softening point of the product was 67C.
EXAMPLE 8
Example 6 was repeated, there being used 14.2g of ethyleneurea
(90% pure, the balance being water), i.e., 0.50 mole per gram
equivalent of the guanamine residue in the resin, in place of the
1,3-propyleneurea. The softening point of the product wa~ 55C.
EXAMPLE 9
Example 6 was repeated, there being used 13.5 g of melamine,
i.e., 0.36 mole per gram equivalent of the guanamine residue in the
resin in place of the 1,3-propyleneurea. The softening point of the
product, which was opaque, was 74C.
EXAMPLE 10
Example 6 was repeated, there -being used in place of the
1,3-propyleneurea, 8.9g of urea ( i.e., 0.50 mole per gram equivalent
of the guanamine residue in the resin) The softening point of the
product was 60C.
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EXAMPLE 11
Example 6 was repeated, but in place of the 1,3-propyleneurea
there was used 17.6 g of 1,2-dihydroxyethyleneurea (i.e., 0.50 mole
per gram equivalent of the guanamine residue in the resin). The
product had a softening point of 70C.
EXAMPLE 12
Powder coating compositions were made from the products
of Example 6 and 7. The components of each composition are listed
in Table II.
TABLE II
Component Parts in Mixture
Product of Exa=ple 6 5~ _ C _
Product of Example 7 _ 50 _ 55
Polyester I 240 240 _
Polyester II _ 200 200
Polyacrylic resin (a
commercially-available 5 5 5 5
flow additive)
Benzoin (as flow 3 3 3 3
additive)
Titanium dioxide 200 200 175 175
Polyester I denotes "Uralac P2115", an oil-free, hydrosyl group-
115(J~89
containing branched polyester available from Synthetic Resins Ltt.,
Speke, Liverpool, England, which has the following properties:
acid value less than 10 mg KOH/g; hydroxyl value 30-40 mg KOH/g;
softening point ( measured according to ASTM E28-67 without stirrer)
110-120C.
*~ Polyester II tenotes BA 530, available from BIP Chemicals Ltd.,
Oldbury, Worley, ~orcestershire, England, which has an acid value
of approximately 7.5 mg KO~/g, a hydroxyl value of 90-110 mg KOH/g,
and a softening point, measured according to 8S 2782 Method 103A,
of 90-97C.
Mixing was effected by dry blending, followed by hot-melt
extrusion in a Buss Ko-Kneader using a barrel temperature of 95C
and a screw t~mperature of 40C. (Buss Ko-Kneader is a trademark).
The extrudate was cooled to ambient temperature, crushed, ant
ground to a particle size below 75 ~m, the bulk of the msterial
hsving a particle size between 20 and 75 ~m.
The gel time~ of these mixtures at 180C were:
Mixture A 9 mi~utes;
Mixture B 7 minutes;
Mixture C 8~ minutes;
Mixture D 7 minutes.
The mixtures were sprayed onto steel panels or onto chromate-
treated aluminium panels using an electrostatic powder sprayer, and
cured by heating for 20 minutes at 200C, giving costings 50 ~m
thick. These coatings were then tested as follows:
~ EMK resistance" was determined by giving the panels 20
double rubs with a cotton wool swab soaked in ethyl methyl ketone
- 18 -
"Fle~;bility" was detenmined by bending the panels around
mandrels of decreasing diameter to find the smallest diameter
around which the panels could be bent without cracking the
coating.
"Gloss" was determined by the method of BS 3900 Part D2
(1967~ using a 60 angle of incidence,
The result~ are given in Table III~
TABLE III
Misture EMK Flexibility Gloss Appearance
resistance
A Unaffected 3m~ 60% hard, glossy,
. . . slight "orange
B Unaffected 1.5 m~ 22Z even matt
C Unaffected 12 ~ 40% hard, glossy,
. slight "orange
. D ~tfecce~ 20Z hard, s=ooth ? even .
