The present invention relates to a hydroxylated and/or carboxylated polyester resin with
specific composition, particularly characterized by compositions specifically selected from polyol
5 components and polyacid components free of any unsaturated fatty monoalcohol or monoacid,
particularly with no oil content for resins in a solvent medium with high solids content of at least 60%, preferably of at least 62%, more preferentially from 65 to 90% by weight and viscosity
suitable for coatings with high solids content and high covering power, particularly for coatings
for metal foils, commonly also called "coil coatings."
10 The present invention relates to improving, through the specific structure of the binding
resin used, the solids content with a weight content of at least 60%, preferably of at least 62%
and more preferentially from 65 to 90%, even more preferentially from 70 to 85%, while
maintaining a viscosity of the coating composition suitable for the final application, particularly
for the application to metal foils otherwise also called "coil coating application." This viscosity
15 (Brookfield) must be less than 1000 mPa.s at the application temperature ranging from 15 to
35"C, the Brookfield viscosity being measured according to the ISO 3219 method. Regarding
the target resin, it must have a viscosity of less than 15 000 mPa.s in solution in an organic
solvent at 25"C with a resin content (solids content) of 80% by weight. Regarding the covering
power of the final composition of this coating, it is preferably greater than 400 m' per kg of
20 coating for a thickness of 1 ~- Specifically, an increase of at least 10% and preferably from 10 to
20% of the covering power is obtained with a coating composition comprising said resin
compared with a common polyester resin.
Compositions containing polyester, as defined according to the present invention, have
the specific goal of improving the covering power of paints (yield) and meet a real need in the
25 paint market, particularly for the coating of metal foils.
The present invention first relates to a hydroxylated or carboxylated polyester resin with
a specific structure obtained from specific compositions of polyol components A) and polyacid
components B).
It also relates to said resin in solution form in an organic solvent of said resin, particularly
30 at a resin content relative to the weight of said solution ranging from 65 to 90%, preferably from
70 to 90% and more preferentially from 72 to 85%.
The invention also covers a crosslinkable composition comprising said resin, particularly
a coating composition and more particularly a coating composition for metal foils ("coils").
2
The use of said resin or a solution of said resin as binder in a coating composition in an
organic solvent medium is also covered, particularly for crosslinkable coatings and more
particularly to increase the covering power of said coating_
The invention further relates to the finished product which is a coating that results from
5 the use of said resin or of a solution of said resin or of a crosslinkable composition containing it,
particularly having increased (improved) covering power relative to other common polyester
resins.
The first subject of the invention relates to a polyester resin bearing at least two
functions from among hydroxyl and/or carboxyl, said resin having as components:
10 A) a polyol component comprising:
a1) at least one C3 to Cs dial bearing (additionally) at least two lateral C2 to C4 alkyl
substituents, particularly with said alkyls being different, preferably said dial being a
C3 or c, dial,
a2) at least one C3 to c. dial, bearing at least one lateral methyl substituent, particularly
15 two lateral methyl substituents, preferably said dial being a C3 or C4 dial,
zo B)
a3) optionally, at least one linear C2 to c. dial, bearing no lateral (alkyl) substituent,
a4) optionally, at least one polyol with functionality > 2 and preferably with functionality
of 3 or 4, more preferentially of 3
and
a polyacid component comprising:
b1) at least one aromatic diacid or its anhydride, preferably representing from 20 to 75%
by weight of said resin,
b2) at least one linear C4 to C10, preferably C4 to C,, aliphatic diacid
b3) optionally, at least one cycloaliphatic diacid
2.5 preferably with the b1/b2 molar ratio ranging from 1/1 to 4/1, said resin being free of any
unsaturated fatty monoacid and of any unsaturated fatty monoalcohol.
The term "a c. dial" where n is the number of carbons, means that it has n linked carbon
atoms (connected in a chain) besides the lateral substituents that are not counted in said
number n.
30 More particularly and preferably, said dial a1) is 2-butyl-2-ethyl-1,3-propanediol.
According to a preferred option, the two components a3) and a4) are present as
essential components with the other components a1 ), a2) and a3) as defined above.
Said dial a1) may represent at least 3%, preferably at least 5% by weight of said resin.
More particularly, said dial a1) may represent from 3 to 25%, preferably from 5 to 20%, more
35 preferentially from 5 to 15% by weight of said resin.
- ---------------------,
3
Specifically, when a3) is present, the a1/(a1 +a2+a3) molar ratio varies from 0.1 to 0.4
and preferably from 0.1 to 0.3. More specifically, when a3) and a4) are present, the a1/
(a1 +a2+a3+a4) molar ratio varies from 0.1 to 0.4 and preferably from 0.1 to 0.3.
Like Dial a2), it may be selected from among: neopentyl glycol (2,2-dimethyl-1 ,3-
5 propanediol) or dimethyl butanediol and preferably be neopentyl glycoL The content by weight
of said polyol a2) is preferably less than 75% by weight of said polyol component A).
According to a specific composition of said resin, polyol a4) is present in addition to a1),
a2) and a3) in said polyol component A), with the structure of said polyester resin being
branched. A branched polyester resin structure here means that said polyester resin bears
10 polyesters grafts on its main chain.
According to a specific composition of said resin, the acid component B) of said resin
comprises (in addition to diacids b1) and b2)) at least one cycloaliphatic dicarboxylic acid b3) or
its anhydride.
As aromatic diacid b1) or its anhydride, isophthalic acid, terephthalic acid, and phthalic
15 anhydride may be cited.
As linear aliphatic diacid b2), adipic acid, succinic acid, and sebacic acid may be cited.
As cycloaliphatic diacid b3), cyclohexane dicarboxylic acid and hexahydrophthalic acid
may be cited.
Said resin has a hydroxyl index or a carboxyl index or a global hydroxyl + carboxyl index
20 that may range from 10 to 200, preferably from 15 to 175 (in mg KOH/g).
The OH index is measured according to the ISO 2554 method and the acid index
according to the ISO 2114 method.
According to a specific option, said resin is a hydroxylated resin.
The glass transition temperature of said resin, measured by DSC at 1 O"C/min, (2nd
25 passage) may vary from -1 o·c to so·c, preferably from o•c to 30"C, with a calculated number
average molecular weight Mn ranging from 500 to 1 0 000, preferably from 1 000 to 1 0 000. The
Mn value is calculated from the measured hydroxyl index and the measured acid index, which
allow calculation of an equivalent mass M"' per function (OH or carboxyl or sum of the two if
both are present) and number average functionality of the resin, this average functionality fm
30 being calculated from:
where x, is the number of moles of component i (acid or alcohol) and
f; is the functionality of said component i
the equivalent mass M"' is defined by M"' = 56 000/(loH+I, •• )
35 So Mncalculated= Meq*fm
---------------------,
4
The second subject of the invention relates to a resin solution comprising at least one
resin as defined above according to the invention and an organic solvent of said resin,
particularly with a content of said resin over the total weight of resin + solvent (total solution
weight) greater than 60%, preferably from 65 to 90%, more preferentially from 70 to 90% and
5 even more preferentially from 72 to 85%.
As organic solvent suitable for preparing said resin solution, said solvent may be
selected from among methyl esters or ethyl esters of C2 to c. monocarboxylic acids or esters of
said monocarboxylic acids with methoxy or ethoxy monoethers of c, to C4 dials, particularly
methoxy propyl acetate or among methyl or ethyl diesters of c. to C6 carboxylic diacids,
10 terpenes, polyhydroxyalkanoates, methyl or ethyl esters of fatty acid oils or esters of lactic acid
with c, to c, alcohols, aromatic solvents such as xylene or other aromatic solvents that are
distillation fractions of hydrocarbons including 9 carbon atoms with boiling point (b.p.) ranging
from 155 to 180"C like Solvarex'" 9 or distillation fractions of aromatic hydrocarbons including 10
carbon atoms with b.p. ranging from 180 to 193"C like Solvesso'"150 NO, optionally in mixtures
15 with glycol monoethers such as butyl glycol (or butoxyethanol).
Preferably, said solvent is selected from among aromatic solvents, as defined above,
alone or in mixtures with glycol monoethers, such as for example the mixture of a C9 distillation
fraction with b.p. ranging from 155 to 180"C like Solvarex'" 9 with butylglycol. The content by
weight of said resin in said solution may vary from 60 to 90%, particularly from 62 to 90%, more
20 particularly from 65 to 90% and even more particularly from 70 to 90% or between 70 and 90%
and more preferentially from 72 to 85%. Said solvent may be the preparation solvent for said
resin if prepared by polycondensation in a solvent medium or a dissolution solvent after
preparation by bulk polycondensation. The solids content may be adjusted by extra addition of
solvent if the resin is prepared at the start in a solvent. Said solvent may be a mixture of at least
25 two solvents among those cited.
Said resin may be prepared by polycondensation reaction between the polyol
component A) with the acid component B) as defined above. The reaction may take place in a
solvent medium or when melted in bulk, as is already known to a person skilled in the art. When
the reaction is conducted in the presence of a solvent as azeotropic carrier to remove the water,
30 the solvent chosen preferentially is xylene.
The reaction is advantageously conducted in the presence of a catalyst. As catalyst,
alkyl titanates may be used like, for example, isopropyl titanate, butyl titanate, 2-ethyl-hexyl
titanate or tin derivatives like, for example, tin oxide, tin oxalate, monobutyl tin oxide. The
quantities of catalyst used are comprised between 100 and 5000 ppm relative to all of the
35 monomers and preferably from 500 to 1500 ppm still relative to all of the monomers.
5
Another important subject of the invention is a crosslinkable binder composition, which
comprises as binder at least one polyester resin or a resin solution as defined above according
to the invention.
More particularly, said composition comprises at least one organic solvent as defined
5 above, with the content of said resin ranging from 60% to 90%, preferably from 62 to 90%, more
preferentially from 65 to 85%, and even more preferentially from 70 to 85% relative to the total
weight of the resin together with the solvent .
Said composition is preferably a coating composition, particularly for metal foils (also
known as "coil" application). This composition may apply to:
10 finishing coatings,
primer coatings,
backer coatings. These are coatings for the internal portion of the metal foil not exposed
to poor weather or light.
Said crosslinkable composition, as well as said resin, may further comprise at least one
15 crosslinking agent bearing groups that react with the hydroxyl and/or carboxyl groups borne by
said resin. More specifically, said crosslinking agent is selected from among melamine or a
polyisocyanate, particularly a blocked polyisocyanate or a polyanhydride or a polysilane,
particularly a polysilane blocked by alkoxy when said resin is hydroxylated or said crosslinking
agent is selected from among polyepoxides or polyols when said resin is carboxylated.
20 According to a specific preference, said composition is a coating composition in an
organic solvent medium; particularly a paint or varnish composition, more particularly for metal
surfaces (or "coils").
Said composition may be pigmented and in this case it additionally comprises at least
one pigment. More particularly, it comprises said resin, an organic solvent and a pigment.
25 Another specific subject covered by the present invention relates to the use of said resin
or of a solution of said resin as defined above according to the invention as binder in coating
compositions in an organic solvent medium, particularly in crosslinkable coating compositions.
According to a first option, said use relates to coatings compositions with "singlecomponent"
behavior for metals, particularly for metal foil (called "coil") coating. "Single-
3D component" behavior means that, in spite of the presence of two reagent components (resin
and crosslinking agent), the crosslinkable composition remains stable when stored in ambient
conditions. This is the case for blocked crosslinking agents like blocked isocyanates or blocked
alkoxy silanes, which cannot react without prior unblocking by heating or hydrolysis. In the same
way, melamines are suitable as crosslinking agents for this type of composition with
35 hydroxylated polyesters because the reaction only takes place after prior heating. More
-----------------------,
6
particularly, such a coating composition with single-component behavior may comprise a
hydroxylated resin as defined according to the invention, a preferred organic solvent as defined
above and a crosslinking agent chosen from among blocked isocyanates (polyisocyanates },
silanes blocked by alkoxy or melamines. A coating composition of this type with "singles
component" behavior may be used for the coating of metal foils (also called "coils").
More particularly, a primer, top-coat, backer or single-coat coating may be concerned.
According to another specific use, powdered coatings may also be concerned.
According to another specific use, "two-component" coatings are concerned. A "twocomponent"
coating composition means that the crosslinking reaction starts when said resin is
10 mixed with the crosslinking agent and consequently, said mixing (addition of the crosslinking
agent) occurs at the moment of final application.
Preferably, said use of said resin or of said resin solution relates to a pigmented coating
for increasing the covering power (yield) of said coating.
The last subject of the invention relates to the final product obtained, which is a coating,
15 which results from the use of at least one resin or of at least one resin solution as defined above according to the invention or of a coating composition as also defined according to the invention. More particularly and preferably, said coating is a metal foil (also called "coil") coating.The examples outlined below are presented as illustrations of the invention and of its
performance qualities and do not in any way limit the invention. The resin according to the invention (example 3) is diluted in pure Solvarex® 9 and in a
Solvare~ 9/butylglycol mixture (70/30) for the resin of comparison test 3.
Table 6: Compositions and characteristics of the resins (without solvent, catalyst and azeotropic
carrier) according to the invention (example 3) and comparison test 3 4) Application of resins in paints for metal foil
4.1) Metal foil and application conditions for the coating/packaging before tests
The sheeting used for the tests is galvanized steel sheeting 0. 75 millimetres thick,
5 pretreated with a solution of chromate.
The paiht is applied using a Bar Coater applicator. Three types of application are made:
primer coating,
top-coat coating,
backer coating.
10 The thickness of the top-coat coating and the backer coating on the metal sheeting is 20
!Jm.
In the case of the top-coat coating, the paint is applied on a metal sheeting coated with a
primer coating 5 !Jm thick.
The resulting coated sheeting is put in a ventilated oven.
15 Table 7 below gives the crosslinking conditions depending on the type of coating, at The method for resistance to the solvent indicated consists in making back and forth
movements on the coated sheeting with a Taber abraser device impregnated with said solvent
and noting the time (in s) after which degradation in the coating is observed.
5 The yield is calculated according to the following formula from the dry paint density, the
solids content and the coat thickness:
Yield (in g/m2
) = 100 multiplied by "dry paint density (g/m3
)" multiplied by "the thickness
of the coat of paint (m)" and the result divided by "the solids content of the paint(%)".
The covering power (in m2/g/(J) is equal to the inverse of the yield (in g/m2
) divided by the
10 thickness of the coat.
Yield (in g/m2
) = 100 multiplied by "dry paint density (g/m3
)" multiplied by "the thickness
of the coat of paint (m)" and the result divided by "the solids content of the paint (%)".In a 1 liter thermostated beaker at ambient temperature, in this order, the compounds
(1 ), (2), (3), (4), (5), (6), (7), (B), (9) and (1 0) are added. This mixture is stirred using a
Disperrnat stirrer, then dispersed for 30 minutes at 3500 rpm in the presence of glass beads to
facilitate pigment dispersion. After removing the beads for sieving, with stirring at 1000 rpm, the
rest of the binder (11) and compounds (12), (13) and (16) are added. Still with stirring at 1000
rpm, the viscosity of the paint is adjusted due to the addition of (14) and (15).
The satin paint obtained presents the following characteristics (Table 9).

Claims
1. A polyester resin bearing at least two functions from among hydroxyl and/or carboxyl,
characterized in that it includes the components:
5 A) a polyol component comprising:
a 1) at least one C3 to C6 dial bearing at least two lateral C2 to c., alkyl substituents,
particularly with said alkyls being different, preferably said dial being a C3 or c. dial,
a2) at least one C3 to Ca dial, bearing at least one lateral methyl substituent, particularly
two lateral methyl substituents, preferably said diol being a C3 or c. dial,
10 a3) optionally, at least one linear C2 to c. dial, bearing no lateral (alkyl) substituent,
15
and
B)
a4) optionally, at least one polyol with functionality > 2 and preferably with functionality
of 3 or 4, more preferentially of 3
a polyacid component comprising:
b1) at least one aromatic diacid or its anhydride, preferably representing from 20 to 75%
by weight of said resin,
b2) at least one linear c. to C10 , preferably C4 to Ca, aliphatic diacid.
b3) optionally, a cycloaliphatic diacid
preferably with the b1/b2 molar ratio ranging from 1/1 to 4/1 , said resin being free of any
20 unsaturated fatty monoacid and of any unsaturated fatty monoalcohol.
2. The polyester resin as claimed in claim1, characterized in that said dial a1) is 2-butyl-2-
ethyl-1 ,3-propanediol.
3. The resin as claimed in claim1 or 2, characterized in that said dial a1) represents from 3
to 25%, preferably from 5 to 20%, more preferentially from 5 to 15% by weight of said resin.
25 4. The resin as claimed in one of claims 1 to 3, characterized in that a3) is present and in
that the a1/(a1 +a2+a3) molar ratio varies from 0.1 to 0.4, preferably from 0.1 to 0.3.
5. The resin as claimed in one of claims 1 to 4, characterized in that said polyol a2) is a dial
selected from among: neopentyl glycol (2,2-dimethyl-1 ,3-propanediol) or dimethyl butanediol
and preferably is neopentyl glycol.
30 6. The resin as claimed in claim 5, characterized in that the content of weight of said polyol
a2) is less than 75% by weight of said polyol component A).
7. The resin as claimed in one of claims 1 to 6, characterized in that said polyol a4) is
present in addition to a1 ), a2) and a3) in said polyol component A), with the structure of said
polyester resin being branched.
20
8. The resin as claimed in one of claims 1 to 7, characterized in that the acid component B)
of said resin comprises at least one cycloaliphatic carboxylic diacid b3) or its anhydride.
9. The resin as claimed in one of claims 1 to 8, characterized in that said resin has a
hydroxyl index or a carboxyl index or a global hydroxyl + carboxyl index ranging from 10 to 200,
5 preferably from 15 to 175 mg KOH/g.
10. The resin as claimed in one of claims 1 to 9, characterized in that said resin is
hydroxylated.
11. The resin as claimed in one of claims 1 to 10, characterized in that it has a glass
transition temperature measured by DSC at 10"C/min, from -to•c to 50"C, preferably from o·c
10 to 30"C and a (calculated) Mn ranging from 500 to 10 000, preferably from 1000 to
10 000.
12. A resin solution, characterized in that it comprises at least one resin as defined
according to one of claims 1 to 11 and an organic solvent of said resin.
13. The resin solution as claimed in claim 12, characterized in that the content by weight of
15 said resin relative to the total resin + solvent weight is greater than 60% and varies preferably
from 65 to 90%, preferentially from 70 to 90%, and even more preferentially from 72 to 85%.
14. A crosslinkable binder composition, characterized in that it comprises as binder at least
one polyester resin as defined according to one of claims 1 to 11 or a resin solution as defined
according to claim 12 or 13.
zo 15. The composition as claimed in claim 14, characterized in that it comprises at least one
organic solvent with the content of said resin ranging from 60% to 90%, preferably from 62 to
90%, more preferentially from 65 to 85%, and even more preferentially from 70 to 85% relative
to the total resin + solvent weight.
16. The composition as claimed in either of claims 14 and 15, characterized in .that it is a
zs coating composition, particularly for metal foils.
17. The composition as claimed in claim 16, characterized in that it further comprises at
least one crosslinking agent bearing groups that react with the hydroxyl and/or carboxyl groups
borne by said resin.
18. The composition as claimed in claim 17, characterized in that said crosslinking agent is
30 selected from among melamine or a polyisocyanate, particularly a blocked polyisocyanate or a
polyanhydride or a polysilane, particularly a polysilane blocked by alkoxy when said resin is
hydroxylated or said crosslinking agent is selected from among polyepoxides or polyols when
said resin is carboxylated.
21
19. The composition as claimed in one of claims14 to 18, characterized in that it is a coating
composition in an organic solvent medium, particularly a paint or varnish composition, more
particularly for metal surfaces.
20. The composition as claimed in one of claims 14 to 19, characterized in that it additionally
5 comprises at least one pigment.
21. The use of a resin as defined according to one of claims 1 to 11 or a resin solution as
defined according to claim 12 or 13, as binder in coating compositions in an organic solvent
medium, particularly in crosslinkable coating compositions.
22. The use as claimed in claim 21, characterized in that coating compositions with "single-
10 component" behavior for metal, particularly for metal foil ("coil") coating are concerned.
23. The use as claimed in claim 21 or 22, characterized in that a primer, top-coat, backer or
single-coat coating is concerned.
24. The use as claimed in claim 21 or 22, characterized in that powdered coatings are
concerned.
15 25. The use as claimed in claim 23 or 24, characterized in that "two-component" coatings
are concerned.
26. The use as claimed in one of claims 21 to 25, characterized in that said coating is
pigmented and in that said use relates to the increase of the covering power of said coating.
27. A coating characterized in that it results from the use of at least one resin as defined
20 according to one of claims 1 to 11 , of a resin solution as defined according to claim 1.2 or 13 or
of a coating composition as defined according to one of claims 14 to 20.
28. The coating as claimed in claim 27, characterized in that it is a metal foil ("coil") coating.