Coating resin composition

This invention offers a coating resin composition which exhibits excellent drawing processability, processability and hardness and forms a coat having good processability, hardness, scuff resistance, impact resistance, stain resistance and blocking resistance even in clear or low pigment concentration. Disclosed herein is a coating resin composition containing a polyester resin (A) which has a glass transition point of 10-80.degree. C., reduced viscosity of not less than 0.2 dl/g and specific gravitity of 1.21-1.30 and mainly comprises aromatic dicarboxylic acid including terephthalic acid, 2-methyl-1,3-propanediol and/or 1,3-propanediol and alkylene glycol with 5-10 carbon atoms and/or alicyclic glycol and a hardener (B) which is reactive with said polyester resin (A).

FIELD OF THE INVENTION 
The present invention relates to a coating resin composition which has 
excellent processability and hardness, gives a coat having an appearance 
with excellent gloss and vividness, has a prominent drawing processability 
and exhibits good hardness, processability and scuff resistance in clear 
or low pigment concentrations. 
BACKGROUND OF THE INVENTION 
With regard to the paint used as a resin for precoated metal sheets, there 
are many paints including copolymerized polyester resin, alkyd resin, 
vinyl resin and silicon resin paints and they are used in a form of a 
solvent system, aqueous dispersion system or powder paint. However, in any 
of those cases, there is no product which satisfies all of the requested 
properties and it is unavoidable that, when one property is given the top 
priority, other properties will become unsatisfactory whereby it is the 
real fact that there is a limit upon actual use. 
Moreover, there has been a demand of drawing processability in recent years 
not only for two-piece food/beverage cans but also for precoated metal 
sheets because of giving high added-value. In the meanwhile, clears, color 
clears and metallic paints with high ornamental value as well as deep 
color paints with low pigment concentrations have been investigated. 
However, any of them does not have sufficient property at present whereby 
various problems have been left unsolved or their practical utilization 
has been delayed. 
For example, in the Japanese Kokai Patents Sho-57/57,746 and 
Sho-63/108,081, investigations were made for giving both hardness and 
processability but sufficient effects are not achieved in any of them. In 
the Japanese Kokoku Patent Sho-62/21,830, coating resin compositions 
mainly comprising terephthalic acid and alkylene glycol were investigated 
but their gloss retention (GR) is poor upon drawing processing and, 
therefore, they have not been actually used. In turn, the product showing 
a relatively good processability has insufficient hardness and, especially 
in the case of clear or low-pigment products, hardness, scuff resistance 
and stain resistance are considerably insufficient. Further, alkali 
resistance, weather resistance and gasket resistance are insufficient too. 
Another coating resin composition mainly comprising terephthalic acid and 
alkylene glycol has been also known from the Japanese Kokoku Patent 
Sho-61/34,754. Again, its drawing processability is insufficient and, in 
the case of clear or low-pigment products, hardness, scuff resistance and 
stain resistance are considerably insufficient. 
In the Japanese Kokai Patent Hei-07/18,169, a coating resin composition 
mainly comprising isophthalic acid, orthophthalic acid and long-chain 
glycol is disclosed and, although the resulting product exhibits good 
weather resistance, alkali resistance and processability, its drawing 
processability is insufficient and its hardness, stain resistance and 
scuff resistance are poor. 
In said Japanese Kokai Patent Hei-07/18,169, a coating resin composition 
mainly comprising isophthalic acid, orthophthalic acid and alkylene glycol 
is investigated as well and, although the reuslting product exhibits good 
processability, weather resistance and alkali resistance, its hardness, 
blocking resistance pressure-mark resistance and stain resistance are 
considerably insufficient. Further, in spite of its low glass transition 
temperature (Tg), its drawing processability is insufficient. 
In the Japanese Kokai Patent Sho-59/91,118, polyester in which 
2-methyl-1,3-propanediol is used is known. Its object is to reduce the 
cost and to improve the workability upon polymerization by the use of 
2-methyl-1,3-propanediol in place of neopentyl glycol and the product is a 
polyester having a lower molecular weight wherein a large amount of tri- 
or higher functional polyols are jointly used. Therefore, large amount of 
aliphatic dicarboxylic acid is copolymerized for achieving a 
processability but it does not give a sufficient result but 
processability, stain resistance, weather resistance, etc. are poor 
whereby the product is entirely unsuitable for coating resins. 
In the polyester resins for precoated metal sheets, drawing processability 
is insufficient and there is a problem of reduction of gloss in the 
processed area even in the case of polyesters of low Tg having a good 
processability. Thus, if one wants to prepare clear or low-pigment 
concentrations having good hardness, it is usually necessary to make Tg 
not lower than 40.degree. C. whereby the coat becomes considerably hard 
and good processability and impact resistance are not achieved. On the 
other hand, if one wants to achieve good processability and impact 
resistance, hardness will be reduced whereby good scuff resistance is not 
afforded and, in addition, problems such as blocking and pressure mark are 
resulted. 
SUMMARY OF THE INVENTION 
Under such circumstances, the present inventors have carried out intensive 
studies on coating resin which exhibits excellent drawing processability, 
shows good hardness, scuff resistance, blocking resistance, gasket 
resistance, pressure-mark resistance, processability and impact resistance 
even in clear or low-pigment concentrations and has good appearance, gloss 
and stain resistance of the coat and have found that the polyester resin 
having a glass transition point of 10-80.degree. C. and a reduced 
viscosity of not less than 0.2 dl/g in which acid components are mainly 
composed of aromatic dicarboxylic acids including terephthalic acid while 
glycol components are composed of 25-100 molar % of 
2-methyl-1,3-propanediol and/or 1,3-propanediol and 0-75 molar % of 
alkylene glycol having five to ten carbon atoms and/or alicyclic glycol 
where the total amount of said glycols is not less than 50 molar % 
exhibits wonderful coat properties having an excellent drawing 
processability, showing good hardness, gasket resistance, pressure-mark 
resistance, processability and impact resistance even in clear low-pigment 
concentrations and further having gloss, vividness and stain resistance 
whereby the present invention has been achieved. 
Thus, the present invention relates to a coating resin composition 
characterized in that, in said composition, polyester resin (A) of a glass 
transition point of 10-80.degree. C., a reduced viscosity of not less than 
0.2 dl/g and a specific gravity of 1.21-1.30 having acid components which 
comprise 10-70 molar % of terephthalic acid where the total amount of 
terephthalic acid and other aromatic dicarboxylic acids is 80-100 molar % 
and the amount of other dicarboxylic acids is 0-20 molar % and further 
having glycol components which comprise 25-100 molar % of 
2-methyl-1,3-propanediol and/or 1,3-propanediol and 0-75 molar % of 
alkylene glycol having five to ten carbon atoms and/or alicyclic glycols 
where the total amount of said glycols is not less than 50 molar % is 
compounded with a hardener (B) which is able to react with said polyester 
resin (A) in such a ratio that (A)/(B) is from 95/5 to 60/40 by weight. 
DETAILED DESCRIPTION OF THE INVENTION 
In the acid components which are copolymerized with the polyester resin (A) 
of the present invention, the amount of terephthalic acid is 10-70 molar % 
or, preferably, 20-60 molar % and the total amount of terephthalic acid 
and other aromatic dicarboxylic acids is 80-100 molar % or, preferably, 
90-100 molar % and that amount of other dicarboxylic acids is 0-20 molar 
%. When the amount of terephthalic acid is more than 70 molar %, good 
solubility in solvents is not achieved while, when it is less than 10 
molar %, processability and hardness are not well-balanced. When the total 
amount of aromatic dicarboxylic acids is less than 80 molar %, it is not 
possible to afford good hardness, stain resistance, blocking resistance, 
pressure-mark resistance, alkali resistance and weather resistance. 
Examples of the aromatic dicarboxylic acid which are other than 
terephthalic acid and are copolymerizable with the polyester resin (A) of 
the present invention are isophthalic acid, orthophthalic acid and 
2,6-naphthalenedicarboxylic acid. Among those, the joint use of 
terephthalic acid with isophthalic acid is preferred especially in terms 
of well-balanced drawing processability, processability, impact resistance 
and hardness. 
Examples of the other carboxylic acids which are copolymerizable with the 
polyester resin (A) of the present invention are aliphatic dicarboxylic 
acids such as succinic acid, glutaric acid, adipic acid, sebacic acid, 
dodecanedicarboxylic acid and azelaic acid; and alicyclic dicarboxylic 
acids such as 1,2-cyclohexanedicarboxylic acid, 
1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid and 
the use of alicyclic dicarboxylic acids is preferred. Polycarboxylic acids 
such as trimellitic acid anhydride and pyromellitic acid anhydride may be 
used therewith provided that they do not affect the merit of the 
invention. 
The glycol components which are copolymerizable with the polyester resin 
(A) of the present invention comprise 25-100 molar %, preferably 30-90 
molar % or, more preferably, 50-90 molar % of 2-methyl-1,3-propanediol 
and/or 1,3-propanediol and 0-75 molar %, preferably 10-50 molar %, of 
alkylene glycol having 5-10 carbon atoms and/or alicyclic glycol where the 
total amount of said glycols is not more than 50 molar %. 
When the amount of 2-methyl-1,3-propanediol and/or 1,3-propanediol is less 
than 25 molar %, good drawing processability is not resulted and, in the 
case of clear or hyperchromic state, hardness, stain resistance, blocking 
resistance and pressure-mark resistance are insufficient. Good result is 
not obtained when glycol other than 2-methyl-1,3-propanediol and 
1,3-propanediol is used as a hardening component having three or less 
carbon atoms in a main chain. For example, if ethylene glycol is used, 
good alkali resistance and weather resistance are not achieved, vanish 
stability is no good and deterioration in processability with a lapse of 
time is resulted. When neopentyl glycol is used, all of drawing 
processability, processability, hardness and stain resistance become 
insufficient. When 1,3-propanediol is used, joint use with alkylene glycol 
having 5-10 carbon atoms in which the carbon numbers at the main chain are 
5 or more and there is alkyl group on a side chain such as 
3-methyl-1,5-pentanediol is preferred particularly in terms of vanish 
stability and deterioration in processability with a lapse of time. In the 
polyester resin (A) of the present invention, it is preferred to 
copolymerize with alkylene glycol having 5-10 carbons and/or alicyclic 
glycol. As a result of such a copolymerization, a plasticity can be 
resulted and both processability and impact resistance can be improved. 
Especially when polyester having high glass transition point is required, 
it is recommended to use the alicyclic glycol in terms of processability 
and impact resistance. 
Specific examples of the alkylene glycol having 5-10 carbon atoms used in 
the present invention are 1,5-pentanediol, 1,6-hexanediol, 
3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 1,9-nonanediol, 
1,10-decanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol and 
1,2-cyclohexanedimethanol. Particularly preferred examples in terms of 
physical properties of the applied coat are 1,6-hexanediol and 
1,5-pentanediol. 
Specific examples of the alicyclic glycol used in the present invention are 
1,4-cyclohexandimethanol, 1,3-cyclohexanedimethanol, 
1,2-cyclohexanedimethanol and hydrogenated bisphenol A. Particularly 
preferred one in terms of physical properties of the applied coat is 
1,4-cyclohexanedimethanol. 
Incidentally, multivalent polyols such as trimethylolethane, 
trimethylolpropane, glycrol and pentaerythritol may be used together 
therewith provided that they do not deteriorate the merit of the 
invention. 
Further, dicarboxylic acid or glycol containing sulfonic acid metal 
sulfonates such as metal salt of 5-sulfoisophthalic acid, 
4-sulfonaphthalene-2,7-dicarboxylic acid and 
5-(4-sulfo-phenoxy)isophthalic acid or metal salt of 
2-sulfo-1,4-butanediol and 2,5-dimethyl-3-sulfo-2,5-hexanediol may be used 
in an amount of not more than 5 molar % of the total acid or glycol 
components. 
It is preferable that the acid value of the polyester resin (A) used in the 
present invention is 20-350 equivalents/10.sup.6 g or, more preferably, 
50-250 equivalents/10.sup.6 g in terms of hardening ability and physical 
properties of the coat. As a result of such an acid value, hardening 
ability is improved and hardness, scuff resistance and stain resistance 
are further improved. It is not desirable that the acid value is more than 
350 equivalents/10.sup.6 g because it results in a reduction of 
processability. 
A preferred method for giving the acid value to the polyester resin is 
that, after the polyester resin is polymerized, trimellitic acid 
anhydride, phthalic acid anhydride, pyromellitic acid anhydride, succinic 
acid anhydride, 1,8-naphthalic acid anhydride, 1,2-cyclohexanedicarboxylic 
acid anhydride, etc. are subjected to an after-addition at ordinary 
pressure to give the acid value. 
The polyester resin (A) used in the present invention has a glass 
transition point of 10-80.degree. C. or, preferably, 15-60.degree. C. When 
the glass transition point is lower than 10.degree. C., it is not possible 
to give sufficient hardness, scuff resistance, stain resistance and 
drawing processability while, when it is higher than 80.degree. C., 
processability and impact resistance are reduced. 
In the polyester resin (A) used in the present invention, the reduced 
viscosity is not less than 0.2 dl/g or, preferably, not less than 0.3 dl/g 
or, more preferably, not less than 0.4 dl/g. When the reduced viscosity is 
less than 0.2 dl/g, it is not possible to give sufficient processability, 
drawing processability, hardness and impact resistance. 
In the polyester resin (A) used in the present invention, the specific 
gravity is 1.21-1.30 or, preferably, 1.22-1.28. When the specific gravity 
is less than 1.21, a good balance between good hardness and drawing 
processability as well as processability is not resulted and, in addition, 
stain resistance is poor too. When the specific gravity is more than 1.30, 
it is not possible to afford a good solubility in solvents. 
In the polyester resin (A) used in the present invention, the preferred 
number-average molecular weight is not less than 3,000 or, more 
preferably, not less than 8,000. When it is less than 3,000, 
processability, hardness and impact resistance are reduced. With regard to 
a hydroxyl value, it is preferably 30-500 equivalents/10.sup.6 g or, more 
preferably, 30-250 equivalents/10.sup.6 g. When the hydroxyl value is more 
than 500 equivalents/10.sup.6 g, then the higher said value, the lower the 
processability and impact resistance. When the hydroxyl value is less than 
30 equivalents/10.sup.6 g, the reaction with a hardener is poor whereby 
hardness and stain resistance are reduced. 
The coating resin composition of the present invention is used by 
compounding the polyester resin (A) with a hardener (B) which is reactive 
with (A). In that case, the compounding ratio of the polyester resin (A) 
to the hardener (B) in terms of (A)/(B) by weight is from 95/5 to 60/40. 
Preferably, the ratio of (A)/(B) is from 90/10 to 70/30. When the amount 
of (A) in terms of said ratio is more than 95/5, hardness of the coat, 
stain resistance, blocking resistance and pressure-mark resistance are 
lowered while, when it is less than 60/40, processability and impact 
resistance are lower and that is not preferred. 
Examples of the hardener (B) which is reactive with the polyester resin (A) 
are alkyl-etherized aminoformaldehyde resins, epoxy resins and isocyanate 
compounds. 
Alkyl-etherized aminoformaldehyde resin is a condensation product of 
formaldehyde or paraformaldehyde (which is previously alkyletherized with 
alcohol having 1 to 4 carbon atom(s) such as methanol, ethanol, 
n-propanol, isopropanol and n-butanol) with urea, N,N-ethyleneurea, 
dicyandiamide, aminotriazine, etc. and is, for example, methoxylated 
methylol-N,N-ethyleneurea, methoxylated methyloldicyandiamide, 
methoxylated methylolbenzoguanamine, butoxylated methylolbenzoguanamine, 
methoxylated methylolmelamine, butoxylated methylolmelamine, mixedly 
methoxylated/butoxylated methylolmelamine and butoxylated 
methylolbenzoguanamine. In terms of processability and stain resistance, 
it is particularly preferred to use methoxylated methylolmelamine or 
mixedly methoxylated/butoxylated methylolmelamine together with 
butoxylated methylolmelamine. 
Examples of epoxy compound are diglycidyl ether of bisphenol A and 
oligomers thereof, diglycidyl ether of hydrogenated bisphenol A and 
oligomers thereof, diglycidyl orthophthalate, diglycidyl isophthalate, 
diglycidyl terephthalate, diglycidyl p-hydroxybenzoate, diglycidyl 
tetrahydrophthalate, diglycidyl hexahydrophthalate, diglycidyl succinate, 
diglycidyl adipate, diglycidyl sebacate, ethylene glycol diglycidyl ether, 
propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 
1,6-hexanediol diglycidyl ether and polyalkylene glycol diglycidyl ethers, 
triglycidyl trimellitate, triglycidyl isocyanurate, 
1,4-diglycidyloxybenzene, diglycidylpropylene urea, glycerol triglycidyl 
ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl 
ether, pentaerythritol tetraglycidyl ether, and triglycidyl ether of 
glycerol alkylene oxide adduct. 
The isocyanate compound includes aromatic and aliphatic diisocyanates and 
polyisocyanates with three or more valencies. They may be either low- or 
high-molecular compounds. Examples are tetramethylene diisocyanate, 
hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane 
diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene 
diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, 
or trimers of those isocyanate compounds, and compounds having terminal 
isocyanate group which are prepared by the reaction of excessive amount of 
those isocyanate compounds with low-molecular active hydrogen compounds 
such as ethylene glycol, propylene glycol, trimethylolpropane, glycerol, 
sorbitol, ethylenediamine, monoethanolamine, diethanolamine and 
triethanolamine or with high-molecular active hydrogen compounds such as 
polyester polyols, polyether polyols and polyamides. 
The isocyanate compound may be a blocked one. Examples of an agent for 
blocking the isocyanate are phenols such as phenol, thiophenol, 
methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, 
nitrophenol and chlorophenol; oximes such as acetoxime, methyl ethyl 
ketoxime and cyclohexanone oxime; alcohols such as methanol, ethanol, 
propanol and butanol; halogen-substituted alcohols such as ethylene 
chlorohydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as 
tert-butanol and tert-pentanol; lactams such as epsilon-caprolactam, 
delta-valerolactam, gamma-butyrolactam and beta-propiolactam; aromatic 
amines and imides; active methylene compounds such as acetylacetone, 
acetoacetates and ethyl malonate; mercaptans; imines; ureas; diaryl 
compounds; and sodium bisulfite. Blocked isocyanates can be prepared by 
subjecting the above-mentioned isocyanate compounds and blocking agent 
therefor to a reaction of addition by a suitable method which has been 
known in the art. 
Those cross-linking agents may be used together with known hardeners or 
accelerators which are selected depending upon the type. 
Sufficient effect is resulted even when the paint composition per se of the 
present invention is applied on a metal sheet followed by baking but, if 
there is a demand of, for example, improvement of corrosion resistance, 
epoxy resin, polyester resin, urethane resin, etc. may be used as a primer 
coating agent too. 
Baking temperature of the paint composition of the present invention may be 
freely selected depending upon size and thickness of the steel sheet, 
ability of the baking furnace, hardening property of the paint, etc. In 
the manufacture of the paint composition, mixers such as roll mill, ball 
mill and blender are used. Roller coating, roll coater, spray coating, 
electrostatic coating, etc. may be suitably selected in conducting a 
coating. 
Depending upon the object and the use, additives including pigments such as 
titanium oxide, carbon black, organic color pigments and inorganic color 
pigments; dyes; body pigments such as aluminum flakes, silica, talc and 
barium sulfate; glass fiber; colloidal silica; wax; etc. may be added to 
the paint composition of the present invention.

EXAMPLES 
The present invention will now be further illustrated by way of the 
following examples. In the examples, the term "part(s)" means that/those 
by weight. Incidentally, each of the measurements was conducted by the 
following methods. 
1. Reduced Viscosity .eta.sp/c (dl/g). 
Polyester resin (0.10 g) was dissolved in 25 ml of a mixed solvent of 
phenol and tetrachloroethane (6:4 by weight) and the measurement was 
conducted at 30.degree. C. 
2. Number-average Molecular Weight. 
Measurement was conducted by means of gel permeation chromatograph (GPC) 
using an standard sample of polystyrene as a standard. Tetrahydrofuran was 
used as a solvent. 
3. Glass Transition Point. 
Measurement was conducted using a differential scanning calorimeter (DSC) 
at a temperature rising rate of 20.degree. C. per minute. The sample (5 
mg) was placed in a container made of aluminum and used after being 
crimped. 
4. Acid Value. 
Sample (0.2 g) was precisely weighed and dissolved in 20 ml of chloroform. 
Then measurement was conducted by titrating with 0.01N ethanolic solution 
of potassium hydroxide. Phenolphthalein was used as an indicator. 
5. Specific Gravity. 
A 500 ml measuring cylinder in which an aqueous solution (ca. 20%) of 
calcium chloride was placed was adjusted to 30.+-.0.05.degree. C., a 
sample (polyester resin) without oil and foams was placed therein and 
specific gravity of calcium chloride solution was adjusted so that the 
sample was located at the middle of the measuring cylinder. The specific 
gravity of the calcium chloride solution at that time was measured by a 
hydrometer and was defined as the specific gravity of the sample. 
6. Gloss. 
A 60.degree.-reflectivity of coated surface of steel sheet was measured. 
7. Hardness. 
Measurement was conducted in accordance with JIS K-5400 using a 
high-quality pencil (as regulated by JIS S-6006) on a coated surface of 
steel sheet and the judgment was done by checking the state of scratches. 
8. Stain Resistance. 
8-1. Stain Resistance Against Felt-tip Pen. 
Lines were drawn using a red felt-tip pen on the coated surface of steel 
sheet, the sheet was allowed to stand for two hours, the lines were wiped 
off with ethanol and the marks, if any, after wiping were checked and 
evaluated in a five-grade system in which 5 was for no mark noted while 1 
was for all marks clearly remained. 
8-2. Resistance Against Gaskets. 
Gasket for doors of refrigerators was stuck on the coated surface of steel 
sheet by means of magnet, allowed to stand at 70.degree. C. for 96 hours, 
detached from the surface, then the coated surface was wiped with old 
cloth and the marks, if any, after wiping were checked and evaluated in a 
five-grade system in which 5 was for no mark noted, 4 for slight marks 
noted, 3 for some marks noted and 1 for all marks clearly remained. 
9. Processability. 
The coated steel sheet was bent down to an extent of 180.degree. and cracks 
at the bent area were observed under a small 10-power magnifier and 
evaluated. The evaluation "3T" means the case where three sheets having 
the same thickness as that of the bent sheet were sandwiched between the 
bent area while the evaluation of "0T" means the case where bending of 
180.degree. was conducted without sandwiching the sheet. 
10. Drawing Processability. 
Wax was applied on the coated surface of steel sheet and the sheet was made 
into a square can (60 mm side length and 45 mm depth) using a pressing 
machine. Gloss of the side of the can was compared and evaluated with that 
of the bottom of the can by means of naked eye. 
5: almost no change in gloss; 4: slight decrease in gloss; 3: decrease in 
gloss; 1: significant decrease in gloss with partial peeling. 
11. Impact Resistance. 
Evaluation was conducted by treating the coated steel sheet with a Du Pont 
type impact resistance tester under the condition of 40 cm height and 500 
g load. 
5: no crack; 4: slight whitening due to cracks; 3: cracks generated; 1: 
significant cracks generated. 
12. Blocking Resistance. 
Two coated steel sheets in which a coated side of one sheet and a back side 
of another were faced were heated with a heat press at 60.degree. C. and 5 
kg/cm.sup.2 for one hour, then restored to ambient temperature, torn off 
softly and the evaluation was conducted. 
5: no mark noted; 4: marks noted slightly; 3: marks noted; 2: marks noted 
significantly; 1: tearing impossible. 
13. Scuff Resistance. 
Coated surface of steel sheet was strongly scratched with a nail and 
generation of scratch was evaluated by naked eye. 
5: no scratch; 4: slight scratch noted; 3: scratch noted; 1: significant 
scratch noted. 
Synthetic Example (A) 
Dimethylterephthalic acid (388 parts), 388 parts of dimethylisophthalic 
acid, 714 parts of 2-methyl-1,3-propanediol, 104 parts of 1,6-hexanediol 
and 0.41 part of tetrabutyl titanate were placed in a reactor equipped 
with a stirrer, a condenser and a thermometer and a transesterification 
was conducted by raising the temperature from 160.degree. C. to 
230.degree. C. during four hours. Then the system was gradually 
depressurized to 5 mmHg over 20 minutes. After that, polycondensation was 
carried out at not higher than 0.3 mmHg and at 260.degree. C. for 40 
minutes. The resulting copolymerized polyester (A) was subjected to an 
analysis by means of NMR etc. and found to comprise acid components 
consisting of terephthalic acid and isophthalic acid in 50:50 molar ratio 
and glycol components consisting of 2-methyl-1,3-propanediol and 
1,6-hexanediol in 85:15 molar ratio. Its reduced viscosity was 0.45 dl/g, 
glass transition temperature was 40.degree. C., acid value was 13 
equivalents/10.sup.6 g, specific gravity was 1.24, number-average 
molecular weight was 11,000 and hydroxyl value was 151 
equivalents/10.sup.6 g. The result is given in Table 1. 
Polyester resins (B)-(N) having compositions shown in Tables 1-3 were 
synthesized according to a method of the above Synthetic Example. 
Polyester (O) was synthesized by a dehydrating condensation in a nitrogen 
stream under ordinary pressure. (G)-(O) are polyesters for comparison. 
EXAMPLE 1 
(Evaluations by Formulation With White Color) 
To a solution of 100 solid parts of polyester resin (A) were added 125 
parts of titanium oxide, 12.5 solid parts of methylated melamine (trade 
name: Sumimal M40S; manufactured by Sumitomo Chemical Co., Ltd.), 12.5 
solid parts of butylated melamine (trade name: Super Beckamine J-820; 
manufactured by Dainippon Ink & Chemicals, Inc.), 2.5 parts of 10% 
solution of p-toluenesulfonic acid in benzyl alcohol and 0.5 part of 
Polyflow S (manufactured by Kyoeisha Chemical Co., Ltd.) and the mixture 
was dispersed for five hours by a glass beads type high-speed shaker to 
give a coating composition. 
The coating composition was applied to a zinc plated iron shee (thickness: 
0.5 mm; precoated with a primer paint of a polyester type) to make the 
coat thickness 18 .mu.m and then baked at 230.degree. C. for one minute. 
The resulting coat exhibited good processability and hardness and, in 
addition, showed excellent drawing processability and stain resistance. 
The test result is given in Table 4. 
EXAMPLE 8 
(Evaluation by a Deep Color Formulation) 
To a solution of 100 solid parts of polyester resin (A) were added 10 parts 
of carbon black, 20 solid parts of M40S (mentioned already), 15 solid 
parts of J-820 (mentioned already), 10 parts of a 10% solution of 
p-toluenesulfonic acid in benzyl alcohol, 0.5 part of Polyflow-S 
(mentioned already) and 0.5 part of a dispersing agent and the mixture was 
dispersed for five hours in a glass beads type high-speed shaker to give a 
coating composition. 
This coating composition was applied on a zinc plated iron sheet 
(thickness: 0.5 mm; precoated with a primer paint of a polyester type) to 
a coat thickness of 18 .mu.m and baked a 230.degree. C. for one minute. 
The resulting coat exhibited excellent gloss and showed good 
processability, hardness and scuff resistance. It also had very good 
blocking resistance and impact resistance. When it was exposed to outdoor 
circumstances for one year, it still maintained gloss with a retaining 
rate of not less than 90%. The test result is given in Table 4. 
Coating compositions of Examples 2-13 and Comparative Examples 1-18 having 
compositions as shown in Tables 4-10 were similarly prepared, applied and 
baked. Test results of the resulting coated steel sheet are given in 
Tables 4-10 where the formulation ratio of the compositions are given on a 
solid basis. 
TABLE 1 
______________________________________ 
Polyester Resins 
A B C D E F 
______________________________________ 
Composition (molar %) 
Acid Components 
Terephthalic acid 50 30 29 19 30 30.0 
Isophthalic acid 50 68 68 79 69 69.3 
Trimellitic acid 1 1 1 
Trimellitic acid 1 2 1 1 0.7 
(added later) 
Diol Components 
2-Methyl-1,3-pro- 85 85 100 64 31 
panediol 
1,3-Propanediol 65 
1,5-Pentanediol 15 37 
1,6-Hexanediol 15 
3-Methyl-1,5- 35 
pentanediol 
1,4-Cyclohexane- 36 
dimethanol 
1,4-Butanediol 32 
Reduced Visco- 0.45 0.50 0.60 0.55 0.58 0.35 
sity (dl/g) 
Glass Transition 40 45 47 55 25 21 
Temp (.degree. C.) 
Specific Gravity 1.24 1.26 1.26 1.24 1.26 1.25 
Acid Value 13 91 190 88 93 62 
(Eq/10.sup.6 g) 
Number-Average 11000 12800 16500 18500 19000 8000 
Mol. Wt. 
Hydroxyl Value 151 161 76 114 60 205 
(Eq/10.sup.6 g) 
______________________________________ 
TABLE 2 
______________________________________ 
Polyester Resins for Comparison 
G H I J K 
______________________________________ 
Composition (molar %) 
Acid Components 
Terephthalic acid 50 40 50 41 29 
Isophthalic acid 50 60 49 59 69 
Trimellitic acid 1 
Trimellitic acid 1 1 
(added later) 
Diol Components 
2-Methyl-1,3-propanediol 10 85 
1,5-pentanediol 15 
1,6-Hexanediol 50 16 90 
3-Methyl-1,5-pentanediol 15 
Ethylene Glycol 50 85 
Neopentyl Glycol 84 
Reduced Viscosity (dl/g) 0.42 0.45 0.48 0.62 0.15 
Glass Transition Temp 15 50 56 9 32 
(.degree. C.) 
Specific Gravity 1.25 1.28 1.21 1.20 1.26 
Acid Value (Eq/10.sup.6 g) 10 13 90 88 95 
Number-Average Mol. Wt. 11000 11000 12000 16500 2000 
Hydroxyl Value (Eq/10.sup.6 g) 177 175 122 77 1003 
* 
______________________________________ 
Notes 
*: Stability of varnish was poor. 
TABLE 3 
______________________________________ 
Polyester Resins for Comparison 
L M N O 
______________________________________ 
Composition (molar %) 
Acid Components 
Terephthalic acid 47 
Isophthalic acid 50 71 42 80 
Orthophthalic acid 49 21 
Sebacic acid 11 
Adipic acid 20 
Trimellitic acid 1 
Trimellitic acid (added later) 
Diol Components 
2-Methyl-1,3-propanediol 85 84 
1,5-Pentanediol 15 
1,6-Hexanediol 75 
3-Methyl-1,5-pentanediol 
Ethylene Glycol 55 
Neopentyl Glycol 25 45 
Pentaerythritol 16 
Reduced Viscosity (dl/g) 0.45 0.35 0.50 0.11 
Glass Transition Temp (.degree. C.) 41 10 45 -10 
Specific Gravity 1.26 1.20 1.25 1.22 
Acid Value (Eq/10.sup.6 g) 89 12 10 232 
Number-Average Mol. Wt. 11000 8100 12800 1500 
Hydroxyl Value (Eq/10.sup.6 g) 187 238 151 1875 
** 
______________________________________ 
Notes 
**: Conducted under ordinary pressure. Thus, dehydration and 
polymerization were conducted under ordinary pressure until the acid valu 
became 232 equivalents/10.sup.6 g (13 mg KOH/g). 
TABLE 4 
______________________________________ 
Examples 
1 2 3 4 5 
______________________________________ 
Composition (Solid parts): 
Polyester resin A B B C D 
100 100 100 100 100 
Aminoformaldehyde resin (1) 12.5 12.5 12.5 12.5 
Aminoformaldehyde resin (2) 12.5 12.5 12.5 12.5 
Blocked isocyanate (3) 25 
p-Toluenesulfonic acid 0.25 0.25 0.25 0.25 
Dibutylene dilaurate 0.50 
Titanium oxide 125 125 125 125 125 
Polyflow-S 0.5 0.5 0.5 0.5 0.5 
Properties of Coat: 
Gloss (%) 91 91 90 92 90 
Processability (T) 2 2 1 2 2 
Hardness H H F H H-2H 
Drawing Processability 5 5 5 5 5 
Gasket Resistance 5 5 5 5 5 
Felt-Tip Marker Resistance 4 5 3 5 5 
______________________________________ 
(1) Sumimal M40S (methoxymethylolmodified melamine manufacture by Sumitom 
Chemical) 
(2) Super Beckamine J820 (butoxymethylolmodified melamine manufactured by 
Dainippon Ink & Chemicals) 
(3) IPDI B1530 (manufactured by Daicel Huls) 
TABLE 5 
______________________________________ 
Examples 
6 7 
______________________________________ 
Composition (Solid parts): 
Polyester resin E F 
100 100 
Aminoformaldehyde resin (1) 12.5 12.5 
Aminoformaldehyde resin (2) 12.5 12.5 
p-Toluenesulfonic acid 0.25 0.25 
Titanium oxide 125 125 
Polyflow-S 0.5 0.5 
Properties of Coat: 
Gloss (%) 90 92 
Processability (T) 0 0 
Hardness H H 
Drawing Processability 5 5 
Gasket Resistance 5 5 
Felt-Tip Marker Resistance 5 5 
______________________________________ 
(1) Sumimal M40S (methoxymethylolmodified melamine manufacture by Sumitom 
Chemical) 
(2) Super Beckamine J820 (butoxymethylolmodified melamine manufactured by 
Dainippon Ink & Chemicals) 
TABLE 6 
______________________________________ 
Examples 
8 9 10 11 12 13 
______________________________________ 
Composition (Solid parts): 
Polyester resin A B C D E F 
100 100 100 100 100 100 
Aminoformaldehyde resin (1) 20 20 20 20 20 20 
Aminoformaldehyde resin (2) 15 15 15 15 15 15 
p-Toluenesulfonic acid 1 1 1 1 1 1 
Carbon black 10 10 10 10 10 10 
Polyflow-S 0.5 0.5 0.5 0.5 0.5 0.5 
Dispersing agent 0.5 0.5 0.5 0.5 0.5 0.5 
Properties of Coat: 
Gloss (%) 95 94 95 96 92 93 
Processability (T) 1 1 1 1 0 0 
Hardness F H H H F F 
Scuff Resistance 4 5 5 5 5 5 
Impact Resistance 5 5 5 5 5 5 
Blocking Resistance 5 5 5 5 4 4 
______________________________________ 
(1) Sumimal M40S (methoxymethylolmodified melamine manufacture by Sumitom 
Chemical) 
(2) Super Beckamine J820 (butoxymethylolmodified melamine manufactured by 
Dainippon Ink & Chemicals) 
TABLE 7 
______________________________________ 
Comparative Examples 
1 2 3 4 5 
______________________________________ 
Composition (Solid parts): 
Polyester resin G H I J K 
100 100 100 100 100 
Aminoformaldehyde resin (1) 12.5 12.5 12.5 12.5 12.5 
Aminoformaldehyde resin (2) 12.5 12.5 12.5 12.5 12.5 
p-Toluenesulfonic acid 0.25 0.25 0.25 0.25 0.25 
Titanium oxide 125 125 125 125 125 
Polyflow-S 0.5 0.5 0.5 0.5 0.5 
Properties of Coat: 
Gloss (%) 88 80 93 90 93 
Processability (T) 4 3(*) 5 0 7 
Hardness H H HB B F 
Drawing Processability 2-3 2-3 2 2 2 
Gasket Resistance 5 5 2 2 2 
Felt-Tip Marker Resistance 5 5 2 2 4 
______________________________________ 
(1) Sumimal M40S (methoxymethylolmodified melamine manufacture by Sumitom 
Chemical) 
(2) Super Beckamine J820 (butoxymethylolmodified melamine manufactured by 
Dainippon Ink & Chemicals) 
(*): Deterioration in processability with lapse of time was noted. The 
processability immediately after coating was 3T but, when the coated shee 
was allowed to stand at room temperature for three months, deterioration 
proceeded down to 6T. 
TABLE 8 
______________________________________ 
Comparative Examples 
6 7 8 9 
______________________________________ 
Composition (Solid parts): 
Polyester resin L M N O 
100 100 100 100 
Aminoformaldehyde resin (1) 12.5 12.5 12.5 12.5 
Aminoformaldehyde resin (2) 12.5 12.5 12.5 12.5 
p-Toluenesulfonic acid 0.25 0.25 0.25 0.25 
Titanium oxide 125 125 125 125 
Polyflow-S 0.5 0.5 0.5 0.5 
Properties of Coat: 
Gloss (%) 92 90 90 89 
Processability (T) 5 2 4 7 
Hardness F HB F HB 
Drawing Processability 3 2 2 1 
Gasket Resistance 5 2 3 3 
Felt-Tip Marker Resistance 5 2 3 2 
______________________________________ 
(1) Sumimal M40S (methoxymethylolmodified melamine manufacture by Sumitom 
Chemical) 
(2) Super Beckamine J820 (butoxymethylolmodified melamine manufactured by 
Dainippon Ink & Chemicals) 
TABLE 9 
______________________________________ 
Comparative Examples 
10 11 12 13 14 
______________________________________ 
Composition (Solid parts): 
Polyester resin G H I J K 
100 100 100 100 100 
Aminoformaldehyde resin (1) 20 20 20 20 20 
Aminoformaldehyde resin (2) 15 15 15 15 15 
p-Toluenesulfonic acid 1 1 1 1 1 
Carbon black 10 10 10 10 10 
Polyflow-S 0.5 0.5 0.5 0.5 0.5 
Dispersing agent 0.5 0.5 0.5 0.5 0.5 
Properties of Coat: 
Gloss (%) 94 83 95 93 93 
Processability (T) 3 3(*) 4 1 5 
Hardness HB H B B F 
Scuff Resistance 2 5 2 2 2 
Impact Resistance 3 3 2 5 1 
Blocking Resistance 5 5 2 2 3 
______________________________________ 
(1) Sumimal M40S (methoxymethylolmodified melamine manufacture by Sumitom 
Chemical) 
(2) Super Beckamine J820 (butoxymethylolmodified melamine manufactured by 
Dainippon Ink & Chemicals) 
(*) Deterioration in processability with lapse of time was noted. The 
processability immediately after manufacture was 3T but, when the coated 
sheet was allowed to stand at room temperature for three months, 
deterioration proceeded down to 6T. 
TABLE 10 
______________________________________ 
Comparative Examples 
15 16 17 18 
______________________________________ 
Composition (Solid parts): 
Polyester resin L M N O 
100 100 100 100 
Aminoformaldehyde resin (1) 20 20 20 20 
Aminoformaldehyde resin (2) 15 15 15 15 
p-Toluenesulfonic acid 1 1 1 1 
Carbon black 10 10 10 10 
Polyflow-S 0.5 0.5 0.5 0.5 
Dispersing agent 0.5 0.5 0.5 0.5 
Properties of Coat: 
Gloss (%) 95 94 92 92 
Processability (T) 4 1 4 6 
Hardness HB B HB HB 
Scuff Resistance 4 2 2 3 
Impact Resistance 3 3 2 2 
Blocking Resistance 5 2 4 3 
______________________________________ 
(1) Sumimal M40S (methoxymethylolmodified melamine manufacture by Sumitom 
Chemical) 
(2) Super Beckamine J820 (butoxymethylolmodified melamine manufactured by 
Dainippon Ink & Chemicals) 
[MERIT OF THE INVENTION] 
In the coating composition of the present invention, both hardness and 
processability/stain resistance can be maintained in a high level. 
Moreover, the surprising fact is that the composition exhibits an 
excellent drawing processability which has not been available in prior art 
and, even in clear or low pigment concentration, appearance of the coat is 
excellent and all of good processability, hardness, scuff resistance, 
impact resistance, stain resistance and blocking resistance are available. 
Thus, the composition is able to meet with a demand for high quality in 
the field of home electric appliances including outdoor use and of cans 
for food and beverages. In addition, the polyester resin used in the 
present invention can be used not only as a paint composition but also, 
with or without known hardeners, as an adhesive for various materials such 
as plastic film (e.g. polyethylene terephthalate film) and metal sheet 
(e.g. iron and tinplate) and as a binder for various pigments.