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Claims  |
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What is claimed is:
1. A powderous composition of matter useful in preparing coatings having a
non-glossy surface consisting essentially of;
(a) at least one cross-linkable saturated polyester resin;
(b) a cross-linking agent comprising masked isocyanate groups in an amount
sufficient to cross-link said resin; and
(c) a catalytic amount of a salt of an at least bivalent metal ion and an
organic acid anion selected from carboxylic and acetylacetonate anions.
2. The composition as defined in claim 1, wherein the amount of
cross-linking agent is such that the number of functional groups therein
is about stoichiometrically equivalent to the number of reactive groups
within the cross-linkable resin.
3. The composition as defined in claim 1, wherein the cross-linkable resin
has a melting point of between about 50.degree. and about 130.degree. C.
4. The composition as defined in claim 1, wherein the cross-linkable resin
is a polyester resin the hydroxyl number of which is between about 40 and
about 200.
5. The composition as defined in claim 1, wherein the cross-linkable resin
is a polyester resin the acid number of which is between about 0 and 10.
6. The composition as defined in claim 1, wherein the cross-linkable resin
is a polyester resin which is a co-condensation product of a carboxylic
acid component comprising at least one aromatic dicarboxylic acid and an
alcohol component comprising at least one diol.
7. The composition as defined in claim 6, wherein the acid component
further comprises at least one carboxylic acid selected from the group of
saturated aliphatic dicarboxylic acids, saturated aliphatic polycarboxylic
acids containing at least three functional groups and aromatic
polycarboxylic acids containing at least three functional groups.
8. The composition as defined in claim 6, wherein the alcohol component
further comprises at least one polyol containing at least three functional
groups.
9. The composition as defined in claim 6, wherein the aromatic dicarboxylic
acids comprise 8 to 12 carbon atoms.
10. The composition as defined in claim 9, wherein the aromatic acids are
phthalic acids.
11. The composition as defined in claim 7, wherein the polycarboxylic acids
comprise 3 to 4 carboxylic acid groups.
12. The composition as defined in claim 7, wherein the polyester resin is a
reaction product of polyethylene terephthalate with a tricarboxylic acid
having a hydroxyl number of between about 100 and about 180, an acid
number of between 0 and about 10, and a melting point of between about
80.degree. and about 110.degree. C.
13. The composition as defined in claim 1, wherein the cross-linking agent
has a melting point of between about 70.degree. and about 130.degree. C.
14. The composition as defined in claim 1, wherein the cross-linking agent
is an agent which is obtainable by reacting a reaction product of a polyol
with a diisocyanate with an amount of .epsilon.-caprolactam which is
stoichiometrically equivalent to the free isocyanate groups in the
reaction product.
15. The composition as defined in claim 14, wherein the cross-linking agent
is obtainable by reacting diethylene glycol with isophorone diisocyanate
and then with .epsilon.-caprolactam in a molar ratio of 1:2:2.
16. The composition as defined in claim 1, wherein the salt of the at least
bivalent metal ion and the organic acid anion is a salt wherein the
organic acid anion is derived from a carboxylic acid containing from 2 to
about 25 carbon atoms or from acetylacetonic acid and which is mixed with
the cross-linkable resin and the cross-linking agent.
17. The composition as defined in claim 16, wherein the organic acid anion
comprises from about 6 to about 22 carbon atoms.
18. The composition as defined in claim 17, wherein the organic acid anion
is selected from the group consisting of undecanoate, stearate,
phthalates, naphthenates and acetylacetonate.
19. The composition as defined in claim 1, wherein the at least bivalent
metal ion is derived from a metal selected from the group consisting of
calcium, zinc, magnesium, lead, and aluminum.
20. The composition as defined in claim 1 or 2, wherein the by weight ratio
between the at least bivalent metal and the cross-linkable saturated resin
is between about 0.1:100 and 1.5:100.
21. The composition as defined in claim 20, wherein the by weight ratio
between the at least bivalent metal and the cross-linkable saturated resin
is between about 0.3:100 and about 1.0:100.
22. The composition as defined by claim 1 further comprising an adjuvant
selected from the group consisting of fillers, spreading agents,
catalysts, coloring agents, pigments and admixtures thereof.
23. A coating composition comprising the composition of matter as defined
by claim 22.
24. The coating composition as defined by claim 23, which comprises a
powder paint.
25. A polymer comprising the cross-linked reaction product of the
composition of matter as defined by claim 1.
26. A coated substrate, the coating comprising the cross-linked polymer as
defined by claim 25.
27. A process for preparing the composition of matter defined by claim 1,
which comprises the steps of:
(a) mixing the components to form a powdery mixture;
(b) heating the resulting mixture to a temperature sufficiently high to
form a liquid mixture which is below the temperature at which the
cross-linking reaction occurs;
(c) cooling the resulting liquid mixture to form a solid mixture; and,
(d) grinding the solid mixture into a powder.
28. The process of claim 27, wherein mixed with the components of step (a)
is at least one adjuvant component selected from the group consisting of
pigments, spreading agents, catalysts, fillers and coloring agents.
29. The composition of matter as defined in claim 1, wherein the
cross-linkable resin has a melting point of between about 50.degree. and
about 130.degree. C., and wherein the cross-linking agent has a melting
point of between about 70.degree. and about 130.degree. C.
30. A composition of matter useful in preparing coatings having a
non-glossy surface comprising:
(a) at least one cross-linkable saturated polyester resin which is a
co-condensation product of a carboxylic acid component comprising at least
one aromatic dicarboxylic acid and an alcohol component comprising at
least one diol;
(b) a cross-linking agent comprising masked isocyanate groups in an amount
sufficient to cross-link said resin;
(c) a catalytic amount of a salt of an at least bivalent metal cation and
an organic acid anion selected from carboxylic and acetylacetonate anions;
and,
(d) at least one derivative of the polyester resin which is infusible at
150.degree. C., which is a crystalline fraction of a crystallizable
saturated polyester or a cross-linked reaction product of the saturated
polyester and the cross-linking agent.
31. The composition as defined in claim 30, wherein the infusible polyester
resin derivative is a crystallized fraction of the polyester which is
obtained by subjecting at least a part of the crystallizable polyester to
a thermal treatment at a temperature of between about 100.degree. to about
140.degree. C. for a period of time sufficient to transform at least part
of the polyester into a crystalline state.
32. The composition as defined in claim 31, wherein the period of time is
from about 1 to about 24 hours.
33. The composition as defined in claim 31, wherein the crystallized
fraction of the polyester has been crystallized in the presence of about
0.2 to about 1% by weight of asbestos.
34. The composition as defined in claim 30, wherein the by weight ratio
between the amount of the derivative of the polyester which is infusible
at 150.degree. C. and the amount of the polyester which is fusible at
150.degree. C. is between about 0.1:100 and about 20:100.
35. A process for preparing a composition of matter comprising at least one
cross-linkable saturated resin, a cross-linking agent comprising masked
isocyanate groups in an amount sufficient to cross-link said resin, and a
catalytic amount of a salt of an at least bivalent metal cation and an
organic acid anion selected from carboxylic and acetylacetonate anions,
with said organic acid anion of the salt component being derived from a
cross-linking agent the functional groups of which are acid or acid
anhydride groups, which process comprises the steps of:
(a) reacting at least part of the cross-linking agent with an active
inorganic compound of the at least bivalent metal at a temperature of
between about 170.degree. and about 220.degree. C.;
(b) mixing the components to form a powdery mixture;
(c) heating the resulting mixture to a temperature sufficiently high to
form a liquid mixture which is below the temperature at which the
cross-linking reaction occurs;
(d) cooling the resulting liquid mixture to form a solid mixture; and,
(e) grinding the solid mixture into a powder.
36. The process as defined in claim 35, wherein the reacting is effected
for a period of between about 1 and about 3 hours.
37. The process as defined in claim 35, wherein the active inorganic
compound is a hydroxide or an oxide.
38. A process for preparing a composition of matter comprising at least one
cross-linkable saturated resin, a cross-linking agent comprising masked
isocyanate groups in an amount sufficient to cross-link said resin, a
catalytic amount of a salt of an at least bivalent metal cation and an
organic acid anion selected from carboxylic and acetylacetonate anions,
and a crystalline fraction of a saturated crystallizable polyester resin,
which process comprises the steps of
(a) heating at least part of the crystallizable polyester to a temperature
of between about 100.degree. and about 140.degree. C. for a period of time
sufficient to transform at least part of the crystallizable polyester into
a crystalline fraction which is infusible at 150.degree. C.;
(b) mixing the components of the composition to form a powdery mixture;
(c) heating the resulting mixture to a temperature sufficiently high to
form a liquid mixture which is below the temperature at which the
cross-linking reaction occurs;
(d) cooling the resulting liquid mixture to form a solid mixture; and,
(e) grinding the solid mixture into a powder.
39. The process as defined in claim 38, wherein the period of time for
heating the crystallizable polyester is from about 1 to about 24 hours.
40. The process as defined in claim 38, wherein the reaction is effected in
the presence of about 0.2 to about 1% by weight of asbestos. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to saturated cross-linked compositions and
their preparation and, particularly to powderous binders for paints and
coatings containing such compositions.
Description of the Prior Art
In the painting industry, powderous compositions are conventionally used,
wherein the binder may consist of a polyester resin or an epoxide resin
usually in combination with a cross-linking agent. If the polyester resin
is used in combination with a cross-linking agent, wherein the functional
groups are acid anhydride- and/or acid groups or masked isocyanate groups,
or a cross-linking agent which is a compound derived from hexamethylol
melamine, the number of hydroxyl groups predominates over the number of
carboxyl groups within the polyester. If the cross-linking polyester is
used without a cross-linking agent, it polycondensates with itself during
the final utilization, and consequently the contents in hydroxyl groups
and in carboxyl groups are more or less equal. If in the composition, the
binder comprises a cross-linkable epoxide resin, the latter is combined
with a cross-linking agent wherein the functional groups are acid
anhydride- and/or acid groups.
The powderous painting compositions usually contain a certain amount of
pigments and specific adjuvants such as spreading agents, catalysts, and
coloring agents. The ratio between the amount of pigment and the amount of
binder varies within a large range. The preparation of the compositions
usually comprises separately preparing the binder and the cross-linking
agent, optionally mixing the same at a temperature which is lower than the
temperature at which the two components may react with each other, mixing
the compounds of which the binder is comprised with the adjuvants by
melting at a relatively low temperature, grinding the resulting mixture,
and selecting a fraction of a certain particle size.
Then the final composition is distributed in powderous form onto a metal
article, usually by means of an electrical pistol, then the coated article
is heated in an oven to a temperature which favorizes the melting and
spreading of the composition and the subsequent cross-linking of the
binder. In this way, a smooth and glossy coating which exhibits favorable
physical properties may be obtained. Yet, more and more, the painting
industry requires compositions which, after baking, are able to provide a
textured, non-glossy, mat or satin surface. A conventional process for
achieving this purpose usually comprises introducing at least one mineral
component, the particle distribution of which is chosen depending on the
desired effect, into the composition in addition to the pigment. This
process has important disadvantages in several aspects, namely: a high
content of materials which are opposite to a good spreading of the binder,
and at the upper limit may cause a lack of cohesion of the film or paint,
poor mechanical properties, considerable defects with regard to adherence,
and a poor resistency against solvents or aging.
The German Patent Application No. 2,351,176 discloses a composition for
powderous coatings which comprises a saturated thermoplastic polyester
resin which includes particles of cellulose esters which are intended to
provide a mat and textured surface upon melting. Yet, this composition is
not cross-linked. It necessitates a high baking temperature and its
cellulose ester content is very high, which renders the resulting coating
sensitive to the usual solvents. Therefore, the industry is in need of
compositions which can be used as powderous binders in paints, and provide
the cross-linked coating having a textured, non-glossy surface which does
not exhibit the defects and insufficiencies of the heretoknown
compositions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide powderous compositions
which are useful as paint binders and which permit to obtain a paint
coating having a non-glossy and textured surface.
It is a further object of the present invention to provide such a
composition which yields such a coating which exhibits an excellent
resistency against solvents.
It is a further object to provide such a composition which yields a coating
that exhibits a long life time and an excellent behaviour under the
influence of atmospheric agents and/or under ultraviolet irradiation.
It is still a further object of the present invention to provide such a
composition, which yields a coating which exhibits good mechanical
properties, in particular, a good resistency against folding, bending,
beating, shock and a good resiliency.
It is a further object of the present invention to provide such a
composition which provides for a strong adherence and cohesion of the
resulting coating.
It is yet a further object of the present invention to provide such a
composition which does not require temperatures of above 220.degree. C.
for forming the cross-linked coating.
In order to accomplish the foregoing objects according to the present
invention, there is provided a powderous homogeneous saturated
cross-linkable binder composition adapted for coatings having a non-glossy
surface comprising:
(a) at least one cross-linkable resin selected from the group consisting of
saturated polyester resins and epoxide resins;
(b) a cross-linking agent wherein the functional groups are selected from
the group consisting of acid groups and acid anhydride groups and, in case
the cross-linkable resin is a saturated polyester resin, also masked
isocyanate groups; and,
(c) having associated therewith a salt of an at least bivalent metal ion
and an organic acid anion selected from the group consisting of carboxylic
anions and acetylacetonate.
The metal salt of the organic acid may either be a separate compound which
is admixed with the cross-linkable resin and the cross-linking agent or
the organic acid anion thereof may be derived from at least part of such
cross-linking agent molecules, wherein the functional groups are acid- or
acid anhydride groups. The composition may further comprise a polyester
derivative which is infusible at 150.degree. C. and which may be a
crystalline fraction of a crystallizable saturated cross-linkable
polyester or a reaction product of a saturated cross-linkable polyester
and the cross-linking agent.
According to the present invention, there are further provided powderous
coatings and paint compositions comprising the above binding compositions
and suitable adjuvants such as pigments, fillers, spreading agents,
coloring agents, catalysts, and the like, which yield a mat, non-glossy
coating having a textured surface.
According to the present invention, there are further provided processes
for preparing the above compositions and for preparing a non-glossy
coating therefrom
Other objects, features and advantages of the present invention will become
apparent to those skilled in the art from the detailed description which
follows.
DETAILED DESCRIPTION OF THE INVENTION
The saturated cross-linkable resins which are used within the present
invention are selected from saturated polyester resins and epoxy resins.
The polyester resins which may be part of the compositions according to the
present invention are known products which are prepared according to
conventional methods by reacting a carboxylic acid containing at least two
carboxylic groups or their lower alkyl esters with an alcohol containing
at least two hydroxy groups, whereby the ratio between the acid and the
alcohol is chosen depending on the desired acid number and hydroxy number
of the polyester resin. Suitable carboxylic acids comprise aromatic and
saturated aliphatic dicarboxylic acids containing up to 12 carbon atoms,
and optionally in admixture therewith, aromatic and saturated aliphatic
polycarboxylic acids containing up to 12 carbon atoms. Among these
carboxylic acids, aromatic dicarboxylic acids such as phthalic acids,
e.g., terephthalic acid is preferred.
These aromatic dicarboxylic acids or mixtures thereof may be used as such
or in admixture with saturated aliphatic dicarboxylic acids, such as
adipic acid or sebacic acid. Furthermore, saturated polycarboxylic acids
which contain more than two functional groups may be combined with
dicarboxylic acids in order to obtain a partially branched polyester, yet
without rendering the polyester infusible. Examples of suitable carboxylic
acids containing more than two functional groups are tri- or
tetracarboxylic acids, e.g., aromatic tricarboxylic acids, such as
trimellitic acid or its anhydride or pyromellitic acid, or lower aliphatic
acids, such as butene tetracarboxylic acid.
Suitable alcohols comprise aliphatic diols, such as lower alkylene diols,
e.g., ethylene glycol, propylene glycol, butane diols, neopentyl glycol,
or hydrogenated bisphenol A, and diols containing ether bridges, such as
di- or trimers of the above lower alkylene diols or mixtures thereof, and
optionally lower dihydroxy aryl compounds, e.g., a diethylene glycol-,
dipropylene glycol-, or dihydroxy diethyl ether of bisphenol A. The above
diols or mixtures thereof can be used within the polyesters according to
the present invention. Furthermorre, polyols which contain more than two
functional groups may be combined with the above diols. Suitable such
polyols are lower alkyl tri- to hexaols, such as glycerine, trimethylol
propane, pentaerythritol, and trihydroxy ethyl isocyante. Evidently, the
amount of polyacids and/or polyols containing more than two functional
groups have to be limited such, that these compounds do not cause an
elevated degree of cross-linking and consequently, formation of an
infusible product. The maximum proportion of monomers having more than two
functional groups is determined as a function of the advancement of the
reaction according to the theory of Flory (for the subject matter, see T.
Alfrey, Mechanical Behavior of High Polymers, Intescience Publishers,
volume VI, page 268).
Generally spoken, the saturated polyesters, which are used within the
composition of the present invention, are solid substances, the softening
point of which as determined by the ball-and-ring method is in the range
of between about 50.degree. and about 130.degree. C., and which exhibit a
hydroxyl number of from about 40 to about 200, preferably from about 50 to
about 180, and an acid number of less than 10.
The epoxide resins which may be used within the present invention are known
condensation products of epihalohydrins, such as epichlorohydrin, with
diphenols which are prepared according to conventional processes. Suitable
diphenols are lower aryl- and lower diaryl alkylene compounds containing
two phenolic hydroxyl groups, e.g., lower di(hydroxyphenol) alkylenes,
such as 2,2-di(4-hydroxyphenol) propane. The epoxide resins which are used
within the compositions of the present invention are solid substances, the
melting point of which as determined by the ball-and-ring method is in the
range of between about 50.degree. and about 120.degree. C., and which
exhibit an epoxy value of from about 400 to about 1,500.
The cross-linking agents which are used within the compositions according
to the present invention are known compounds which contain functional
groups which are capable of reacting with the reactive groups within the
above resins.
In the event that an above defined saturated polyester resin is used as a
resin component, the functional groups within the cross-linking agent
comprise:
(a) acid anhydride- and/or acid groups; and,
(b) masked isocyante groups. Suitable cross-linking agents containing acid
anhydride- and/or acid groups comprise reaction products of an aliphatic
diol containing from 2 to about 10, preferably 2 to about 8, carbon atoms
with a polycarboxylic acid or an anhydride derivative thereof containing
at least one carboxylic acid group and at least one acid anhydride group,
or at least three carboxylic acid groups, two of which are susceptible of
forming an anhydride group. Examples of suitable polycarboxylic acids and
their anhydride derivatives comprise lower saturated or unsaturated
aliphatic or aromatic tri- and tetracarboxylic acids or their anhydrides,
such as tricarballylic acid, trimellitic acid anhydride, pyromellitic acid
dianhydride, and butane tetracarboxylic acid.
Examples of such cross-linking agents are disclosed in the French Patent
Application No. 75.42685, the disclosure of which is hereby incorporated
by reference. It trimellitic acid anhydride is used as a reactive compound
for preparing the cross-linking agent, the molar ratio between the
trimellitic acid anhydride and the aliphatic diol may vary between about
2/1 and about 2/1.8. The reaction between the diol and the trimellitic
acid anhydride is effected at a temperature of between about 180.degree.
and 250.degree. C. until the water formation has stopped.
The cross-linking agents containing masked isocyanate groups comprise
reaction products of diisocyanates, preferably cyclic diisocyanates
containing up to 15 carbon atoms, e.g., aromatic diisocyanates such as
tolylene diisocyanate or non-aromatic diisocyanates such as isophoron
diisocyanate, and polyols, preferably lower alkyl di- to hexa-ols, such as
ethylene glycol, trimethylol propane and pentaerythritol which are further
reacted with c-caprolactam, for example the commercially available
isophoron diisocyanate reaction product ADDUCT B 1065 (manufacturer,
VEBA). These products are prepared according to conventional methods,
usually by progressively adding the polyol to the isocyanate which has
been heated to a temperature of between about 80.degree. and 100.degree.
C. under an atmosphere of neutral gas and under sufficient cooling to
maintain a temperature of below 100.degree. C. inside the reactor, then
maintaining the reaction mixture at a temperature of about 100.degree. C.
for one hour after the addition of polyol has been finished, and then
progressively introducing into the reaction mixture an amount of solid
.epsilon.-caprolactam which is stoichiometrically equal to the number of
remaining free isocyanate groups in such a manner that the temperature
within the reactor does not exceed 125.degree. C. The reaction mixture is
then maintained at 125.degree. C. for another hour, then the resulting
viscous product is cooled in order to obtain a solid substance, the
softening point of which as determined by the ball-and-ring method is
between about 70.degree. and about 130.degree. C.
In the event that an above defined epoxide resin is used as a resin
component within the composition according to the present invention, the
corresponding cross-linking agent is a cross-linking agent as defined
above, wherein the functional groups are acid anhydride and/or acid
groups.
Further to the above defined saturated cross-linkable resins and
cross-linking agents, the compositions according to the present invention
comprise, associated with the resin and the cross-linking agent, a
carboxylic acid salt or an acetylacetonate of an at least bivalent metal
ion, which may either be a separate compound admixed with the above
components or may be part of a cross-linking agent molecule.
In the case that the carboxylic salt of the at least bivalent metal ion is
a separate compound, there are no particular limitations or requirements
with regard to the organic acid from which the carboxylate anions within
the salt of at least the bivalent metal ion are derived.
For example, aliphatic, aromatic or cycloalkyl monoor polycarboxylic acids
containing from 2 to about 25, preferably from about 6 to about 20 carbon
atoms, can be used. The polycarboxylic acids preferably contain 2 to 4
carboxylic groups. Particularly preferred organic acid anions are the
anions of undecanoic acid, stearic acid, acetylacetonic acid, naphthenic
acids or phthalic acids.
According to a preferred embodiment of the present invention, the organic
acid anion is provided by a functional group of such a cross-linking agent
wherein the functional groups are acid anhydride and/or acid groups.
According to this embodiment, the organic salt of the at least bivalent
metal ion is obtained by reacting at least a part of said cross-linking
agent with an active inorganic compound of the at least bivalent metal.
Preferably, said inorganic metal compound is the oxide or the hydroxide of
said metal. Prior to its reaction with the cross-linking agent, the active
inorganic metal compound is dried at a temperature at which it does not
lose its activity. For example, the compound may be dried at about
120.degree. C. for about 2 hours.
According to this embodiment of the present invention, at least a part of
the cross-linking agent is reacted with said active metal compound. The
reaction may be carried out as follows: The cross-linking agent is
introduced into a reactor provided with an agitating means and a heating
means and is molten at a temperature of between about 170.degree. and
about 220.degree. C., preferably of between about 180.degree. and about
200.degree. C. Then the inorganic active metal compound which has been
dried as is described above is introduced. Subsequently, this temperature
is maintained, and the content of the reactor is agitated for a period of
time of preferably more than 1 hour. The resulting product is then poured
from the reactor, cooled and ground. According to an embodiment of this
process, it is possible to react only a portion of the cross-linking agent
with the metal compound. In this case, said portion preferably is less
than 50% by weight of the total amount of cross-linking agent within the
composition.
There are no restrictions as to what type of the at least bivalent metal
ion is used in the organic acid metal salt. Preferred are bivalent or
trivalent ions of readily available metals. For practical and economical
reasons, the following metals are the most preferred: calcium, zinc,
magnesium, lead, and aluminum. The amount of the above defined metal salt
in the composition according to the present invention preferably is
equivalent to a by-weight ratio between the metal ion and the saturated
cross-linkable resin of from about 0.1/100 to about 1.5/100, preferably
from about 0.3/100 to about 1.0/100.
According to another embodiment of the present invention, in addition to at
least one of the above saturated polyesters, the cross-linking agent and
the above defined organic metal salt associated therewith, the composition
further comprises an organic fraction which is infusible at 150.degree. C.
and is obtained from at least one of the above polyesters or from a
mixture of at least one of the above polyesters and the above
cross-linking agents.
According to the first variant of this embodiment, said organic fraction
which is infusible at 150.degree. C. is a crystalline fraction of a
saturated crystallizable and cross-linkable saturated polyester of the
composition. The term "a crystallizable and cross-linkable saturated
polyester" as used in this specification is meant to connote a polyester
which does not contain any double bonds which are copolymerizable with
vinylic monomers, and which is obtained by reacting at least one
symmetrical diol, which is selected from the group consisting of
unsubstituted straight chain lower alkylene glycols, such as ethylene
glycol, trimethylene glycol, butane-1,4-diol, and hexamethylene glycol,
and lower alkylene glycols containing two lower alkyl substituents fixed
to the same carbon atom, such as neopentyl glycol, or mixtures thereof,
with at least one symmetrical saturated dicarboxylic acid such as succinic
acid, terephthalic acid and the like.
According to the above cited, difunctional reactants are replaced by tri-
or polyfunctional reactants containing hydroxy groups or carboxylic groups
such as trimethylpropane, trimellitic acid anhydride butane,
tetracarboxylic acid and the like. The maximum proportion of
polyfunctional reactants is determined by means of the theory according to
Flory. The crystallizable polyesters are prepared according to
conventional polycondensation methods, usually at a temperature of above
180.degree. C. Cooling of the resin rapidly to ambient temperature yields
an amorphous and vitreous resin, the softening point of which is between
about 70.degree. and about 130.degree. C., as determined according to the
ball-and-ring method. Subsequently, a partial or complete crystallization
of the resin is caused by a thermal treatment at a temperature of between
about 80.degree. and about 150.degree. C., preferably of between about
100.degree. and 130.degree. C. during a period of time of usually between
about 1 and about 20 hours, preferably between about 2 and about 10 hours.
In order to accelerate the crystallization and to modify the dimensions of
the crystals, a compound which is susceptible of promoting the
crystallization, such as microcrystals of a polyester of the same type or
finely divided solids in the form of fibers or fine particles, such as
asbestos, may be introduced into the resin in the molten state prior to
the thermal treatment. According to a further method, the crystallization
of the resin is promoted by cooling it slowly from its polycondensation
temperature to ambient temperature, for example, by pouring the liquid
resin into containers forming a relatively thick layer, e.g., the
thickness of which is in the range of about 50 to about 150 mm. The
occurrence of a crystalline phase can be proved, e.g., by enthalpic
differential analysis (AED). The thus obtained crystallized product is
cooled and ground.
Of course, according to a preferred embodiment of the present invention,
the saturated cross-linkable polyester may be a saturated cross-linkable
and crystallizable resin yet which has not been subjected to the treatment
which is needed for its crystallization.
This saturated cross-linkable and crystallizable resin would then be
included in the above cited general definition of the resins.
According to the secondly mentioned variant of this embodiment, said
fraction which is infusible at 150.degree. C. is a cross-linked fraction
which is obtained from the reaction of at least one of the above saturated
polyesters and the cross-linking agents used within the composition. The
cross-linked fraction is prepared by melting the polyester, or at least
one of the polyesters used in the composition and mixing the molten
polyester with the cross-linking agent or at least one of the
cross-linking agents used in the composition as defined above at a
temperature of between about 90.degree. and about 180.degree. C.,
preferably between about 110.degree. and about 150.degree. C., for a
period of time of between about 1 and about 30 minutes. The progressing of
the cross-linking can be determined by determining the mixture which
contains any components which are insoluble in boiling chloroform. As soon
as insoluble components occur, the resulting mixture is rapidly poured
from the reactor and cooled, and then is coarsely ground.
The by-weight ratio between the amount of the organic fraction which is
infusible at 150.degree. C. and the amount of fusible polyester resin
according to the present invention may vary within a wide range, e.g.,
from about 0.1 to about 90 parts per 100 parts of fusible resin depending
on the desired effect. However, the preferred ratio is from about 1 to
about 20 parts per 100 parts of resin which is fusible at 150.degree. C.
The compositions according to the present invention can be cross-linked by
polyaddition and/or polycondensation at a temperature of between about
160.degree. and about 220.degree. C., and the cross-linking time may vary
within a period of between about 5 and about 40 minutes. The by-weight
ratio between the saturated resin and the cross-linking agent may vary
depending on hydroxyl numbers in case of a polyester resin or the epoxy
value in case of an epoxy resin and the number of acid and/or anhydride
equivalents or isocyanate equivalents in the cross-linking agent. Usually,
such a by-weight ratio is chosen which provides for an overall equilibrium
within the final compositions between the number of active functional
groups of the saturated resin and the number of active functional groups
of the cross-linking agent.
Powderous painting formulations which comprise the composition according to
the present invention may further contain conventional adjuvants which are
well known in the painting industry e.g., such as, pigments, coloring
agents and fillers. Furthermore, conventional spreading agents may be
incorporated, e.g., such as, acrylic polymers or silicon oils.
For prparing powderous painting formulations according to the present
invention, the coarsely powdered components of the binding composition are
thoroughly mixed with the adjuvants and fillers by melting the mixture in
a conventional mixer, such as a mixer of the tradename Banbury or Buss, at
an elevated temperature not exceeding 120.degree. C., e.g., at a
temperature of between about 60.degree. and about 120.degree. C.,
preferably of between about 80.degree. and about 110.degree. C. Then the
mixture is cooled and finely ground, e.g., to a particle size of between
about 20 and about 100 microns, and then is passed through a sieve. The
resulting mixtures can be applied to previously de-fatted thermally
resistant materials, such as metal or ceramical objects, by means of
conventional methods, e.g., by a fluid bed technique or by electrostatical
pulverizing. Subsequently, the cross-linking is effected at a temperature
of between about 150.degree. and about 220.degree. C. for a period of
between about 5 and about 40 minutes. The average thickness of the
resulting coating on the support material is usually between about 30 and
about 70 microns.
From the compositions according to the present invention, cross-linked
coatings which exhibit a textured non-glossy surface may be obtained. The
gloss, or brilliance, of the coating is determined by measuring the
reflected portion of an incident light, and is expressed as the percentage
of the intensity of the reflected light in the normal direction of
reflection relative to the intensity of a light which is incident under an
angle of 60.degree., by means of a reflection apparatus from Gardner
Laboratories.
A gloss value of 0% corresponds to a black body and a gloss value of 94%
corresponds to an opalin.
The composition of the present invention provides a coating having a
textured surface, the gloss value of which as defined before is between
about 5 and about 60%, more particularly, between about 5 and about 35%.
The surface of the resulting coating exhibits a structure which is
different from what is usually called in the art an "orange peel" and what
is due to a poor tension of the sheet. In comparison with the composition
according to the present invention, if all other conditions are the same,
the prior art coatings which contain a system resin-cross-linking agent as
a binder but does not contain an organometal salt as defined above,
exhibit a gloss value of between 75 and 85% in a white color, which may
decrease to 65% in the case of an "orange peel" and poor tension of the
sheet of pain, whereby the aspect of the surface is wrinkly and not
textured as it is in the case of the compositions according to the present
invention.
The invention will now be further demonstrated by the following
non-limiting examples, which are representative only and wherein the
amounts are expressed in parts by weight, unless stated otherwise.
EXAMPLE 1
Preparation of cross-linking resins
(A) Preparation of polyester resins (resin [A]):
In the Table I below, the molar composition of various resins which were
used within the compositions according to the present invention, their
acid number, their hydroxyl number and their melting point are given.
The resins were prepared according to conventional methods, e.g., by
reacting the components at a temperature of 200.degree. C. under nitrogen
atmosphere, until the product showed the desired analytical data. Then the
resins were continuously poured onto a cooled metal band in a layer of 4
mm thickness and the resulting sheets were coarsely ground.
(B) Preparation of the crystallized resin (resin [Al]):
100 parts of a resin [A] were molten at 200.degree. C. in a reactor, then
0.6 parts of asbestos were incorporated. After homogenizing the mixture,
the resin was poured into metal boxes in a layer of 50 mm thickness, and
the boxes were kept in an oven at a temperature of 120.degree. C. for 5
hours. After this thermal crystallizing treatment, the resulting resin,
which was infusible at 150.degree. C., was crushed and coarsely ground.
TABLE I
__________________________________________________________________________
(Compositions and analytical data of the polyester resins which are used
within the composition)
Components (parts by moles) Characteristics of the resins
Tereph-
Trimellitic Trimethyl- Melting
thalic
acid Ethylene
Propylene
Neopentyl
ol Penta
Acid Hydroxyl
point
Resin
acid anhydride
glycol
glycol
glycol
propane
erythritol
number
number
(.degree.C.)
__________________________________________________________________________
A 1 0.33 2 .ltoreq.5
150 78
A1 1 0.33 2 .ltoreq.5
150 160
B 1 1 0.33 .ltoreq.5
180 75
C 1 1.15 0.15 .ltoreq.5
180 85
D 1 1 0.07 .ltoreq.5
50 101
__________________________________________________________________________
(C) Preparation of cross-linking agents wherein the functional groups are
an anhydride:
The following two cross-linking agents (Products E and F of Table II below)
were prepared.
Table II composition of a cross-linking agent containing anhydride groups.
TABLE II
______________________________________
Cross-linking
Cross-linking
agent E agent F
______________________________________
trimellitic acid anhydride
3 moles 2 moles
ethylene glycol 1.5 moles 1.5 moles
______________________________________
The trimellitic acid anhydride was first introduced into a reactor which
had previously been swept with nitrogen, then the ethylene glycol was
progressively added whilst maintaining the temperature in the reactor by
means of external cooling. Two hours after the addition had been
completed, the water formation had stopped. The resulting product was
cooled and ground.
The analytical data of the products are given in the following Table III:
Table III analytical data of cross-linking agents containing anhydride
groups.
TABLE III
______________________________________
Cross-linking
Cross-linking
agent E agent F
______________________________________
acid number in aqueous medium
513 403
acid number in alcoholic medium
364 250
melting point (ball-and-ring)
110.degree. C.
115.degree. C.
______________________________________
(D) As a cross-linking agent wherein the functional groups are masked
isocyanate groups, the commercial product ADDUCT B 1065.sup.+ was used.
The melting point of this cross-linking agent (product G) is 80.degree. C.
EXAMPLE 2
In this example, the following powderous painting compositions were
prepared, the compositions of which are given in Table IV below.
TABLE IV
______________________________________
(Painting compositions)
Composition (.degree.C.)
Components
1 2 3 4 5 6 7 8
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