Powder coating composition

A powder coating composition containing a vehicle which comprises about 50 to about 98% by weight of a polycondensate obtained by a polycondensation of a polyol component comprising at least about 30 mol% 2-methylbutane-1,3-diol and a polycarboxylic acid component comprising at least about 50 mol% terephthalic acid and/or dimethyl terephthalate and about 2 to about 50% by weight of a crosslinking agent. The powder coating composition has a good storage stability (or powder stability) and also the boiling water resistance, the smoothness, the gloss, the flexibility, the adhesiveness, etc., in particular of a film thereof is quite excellent.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a thermosetting polyester-type powder 
coating composition containing, as a vehicle a poly-condensate obtained 
from 2-methylbutane-1,3-diol (isopentyl glycol) (hereinafter referred to 
as "IPG", for simplicity) and terephthalic acid (hereinafter referred to 
as "TA", for simplicity) or dimethyl terephthalate (hereinafter referred 
to "DMT", for simplicity) as an essential ingredient. 
2. The Description of the Prior Art 
Recently, a powder coating which does not contain an organic solvent which 
causes air pollution, has been strongly desired from a social standpoint, 
and such a coating which does not use an organic solvent has been 
seriously considered. Various materials such as an acrylic resin, an epoxy 
resin or the like have been proposed as a vehicle of a powder coating. 
However, disadvantages exist because an acrylic resin type powder coating 
is expensive and has poor chemical resistance. Further the inherently bad 
smell of the acrylic acid is generated on curing. An epoxy resin type 
powder coating has poor weatherability and ultraviolet light resistance. 
Recently a polyester type powder coating composition has been rapidly 
investigated and various reports thereon have been published. However, use 
of IPG as an essential polyol component has not been reported, and reports 
merely have been that a polyol other than IPG can be used. For example, a 
vehicle for a powder coating comprising (a) 70 to 99% by weight of a 
polycondensate obtained from 40 to 55 mole % of aromatic dicarboxylic 
acids (e.g., TA or DMT), 15 to 50 mole % of hydrogenated bisphenols and 5 
to 40 mole % of aliphatic diols (e.g., ethylene glycol, propylene glycol 
or butylene glycol) and (b) 1 to 30% by weight of an amino resin is 
described in Japanese Patent Publication No. 6615/73. However, this 
conventional polyester type powder coating is not sufficiently 
satisfactory from the standpoint of storage stability and with respect to 
various properties such as smoothness, gloss, adhesiveness, boiling water 
resistance, etc. of a film obtained therefrom (see Comparative Example 2 
described hereinafter). 
Generally, it is desired for a powder coating to have sufficient storage 
stability (or powder stability) that blocking (or caking) after the 
production thereof does not occur. To achieve the above purpose, the 
softening point of the base resin must be high. On the other hand, since 
the flow properties of a powder coating on coating or curing must be good, 
the softening point of the base resin should be low. Thus, opposing 
requirements must be satisfied. Further, it is desirable for the mixing 
with a pigment to be easy in preparing a powder coating and pulverizing 
and screening of the powder coating desirably, should also be easy. The 
flowability on curing of a powder coating thus prepared preferably should 
also be good, curing to form a film should also occur at a temperature 
which is, relatively, not so high and pinholes, blisters, etc. should do 
not occur. Thus, coating should have a good smoothness, gloss, 
flexibility, chemical resistance, stain resistance and water resistance. 
SUMMARY OF THE INVENTION 
Therefore, a primary object of the present invention is to provide a novel 
and useful powder coating composition. 
Another object of the present invention is to provide a powder coating 
composition containing, as a vehicle, a polycondensate obtained from IPG 
and TA and/or DMT. 
Still another object of the present invention is to provide a powder 
coating composition, specifically, having excellent storage stability. 
A further object of the present invention is to provide a powder coating 
composition exhibiting excellent film properties such as boiling water 
resistance, smoothness, gloss and adhesiveness. 
The above objects of the present invention will be apparent from the 
foregoing descriptions. 
It has now been found that where a polycondensate obtained from IPG and TA 
or DMT is used as a vehicle for a powder coating, a powder coating 
composition having various excellent properties such as no occurrence of 
blocking during storing; excellent flowability on curing; excellent 
smoothness, good gloss, good flexibility, good adhesiveness, good stain 
resistance, good chemical resistance, good salt spray resistance and 
excellent boiling water resistance of the surface of the coating formed; 
etc. can be obtained. Since a powder coating composition having excellent 
flowability on curing can be obtained, one of the characteristics of the 
present invention is that a coating having a thin film thickness can be 
obtained. Thus, it is a surprising and novel discovery that the storage 
stability of the powder coating obtained and the various film properties 
such as boiling water resistance, smoothness, gloss, flexibility, 
adhesiveness or the like can be remarkably improved by using essentially 
IPG (2-methylbutane-1,3-diol; 
##STR1## 
selected from aliphatic diols, as a polyol component for a polyester. 
Accordingly, this invention provides a powder coating composition which 
comprises a vehicle comprising 
(a) about 50 to about 98% by weight of a polycondensate having a softening 
point of about 80.degree. to 150.degree. C. obtained from 
(i) a polyol component comprising at least about 30 mol% 
2-methylbutane-1,3-diol and 
(ii) a polycarboxylic acid component comprising at least about 50 mol% 
terephthalic acid and/or dimethyl terephthalate, and 
(b) about 2 to about 50% by weight of a crosslinking agent. 
THE DETAILED DESCRIPTION OF THE INVENTION 
The polycondensate used in the present invention can be obtained using a 
conventional polycondensation method employing the following starting 
materials. It is essential to use in the polycondensate IPG as a polyol 
component and TA and/or DMT as a polycarboxylic acid component, but other 
conventional diols, other triols or higher polyols and/or other 
polycarboxylic acids can be used in combination therewith in the 
polycondensation reaction. 
In this case, the IPG content in the polyol component must be at least 
about 30 (mole/mole) %, preferably at least about 40 (mole/mole) % and the 
TA and/or DMT content in the polycarboxylic acid component must be at 
least about 50 (mole/mole) %, preferably at least about 55 (mole/mole) %. 
Where the IPG content is below about 30 (mole/mole) % or the TA and/or DMT 
content is below about 50 (mole/mole) %, the film properties, especially 
smoothness of the film surface, of the powder coating obtained deteriorate 
remarkably. As used herein the term (mole/mole) % for the IPG and for the 
TA and/or DMT content refers respectively to the ratio of moles of IPG to 
total moles of IPG and other polyol components and to the ratio of moles 
of TA and/or DMT to the total moles of TA and/or DMT with other 
polycarboxylic acid components, respectively, expressed in mole %. 
Suitable examples of other diols which can be used in the diol component 
include diols having 2 to 20 carbon atoms such as ethylene glycol, 
propylene glycol, butylene glycols (-1,2; -1,3; and -2,3), 1,5-pentane 
diol, diethylene glycol, dipropylene glycol, triethylene glycol, hexane 
diols, nonane diols, decane diols, pentadecane diols, neopentyl glycol, 
cyclohexane diol, cyclohexane dimethanol, hydrogenated bisphenols or the 
like and suitable examples of triols or higher polyols which can be used 
include triols having 3 to 15 carbon atoms such as glycerin, 
trimethylolethane, trimethylolpropane, 1,2,6-hexane triol, or the like, 
and higher polyols having 4, 5, or 6 hydroxy groups and containing 3 to 15 
carbon atoms such as erythritol, pentaerythritol, dipentaerythritol or the 
like. 
Examples of polycarboxylic acids other than TA or DMT which can be used in 
the polycarboxylic acid component include aromatic polycarboxylic acids 
having 8 to 12 carbon atoms and 2 to 4 carboxyl groups such as isophthalic 
acid, dimethyl isophthalate, phthalic anhydride, trimellitic acid, 
pyromellitic acid or the anhydride thereof or the like; aliphatic 
polycarboxylic acids having 4 to 12 carbon atoms and 2 or 3 carboxyl 
groups such as succinic acid, adipic acid, sebacic acid, 1,10-decane 
dicarboxylic acid, azelaic acid or the like; or the like. 
The polycondensation reaction proceeds easily in the presence or absence of 
a catalyst. Catalysts suitable for the polycondensation reaction include 
known esterification or transesterification catalysts, e.g., metal oxides 
such as zinc oxide, lead oxide, antimony oxide or titanium oxide, organic 
or inorganic metal salts such as zinc acetate, calcium acetate, cobalt 
acetate, manganese acetate, lead acetate, stannous oxalate, zinc 
naphthenate, zirconium naphthenate, aluminum sulfate or lead nitrate, 
organic metal compounds such as dibutyl tin oxide, tetrabutyl zirconate, 
tetrabutyl titanate, tetrabutoxy titanate, or tributyl antimony, metal 
halides such as zinc chloride, titanium tetrafluoride, or aluminum 
chloride, acids such as sulfuric acid, phosphoric acid or p-toluene 
sulfonic acid, and ion exchange resins. 
Further, in order to prevent side-reactions such as ether formation, weak 
alkaline materials such as alkali metal salts (e.g., lithium acetate, 
potassium acetate, sodium acetate, etc.), alkaline earth metal salts 
(e.g., calcium acetate, calcium naphthenate, etc.), amines (e.g., 
triethylamine, trimethyl amine, etc.) or the like can be added. 
These catalysts can be used either individually or as a combination 
thereof. The catalyst is usually used in an amount of about 0.001 to about 
1% by weight, preferably about 0.01 to about 0.5% by weight, based on the 
weight of the polycarboxylic acid component. 
Usually, the polycondensation is carried out at a temperature of about 
100.degree. to about 250.degree. C. under reduced pressure, atmospheric 
pressure or super atmospheric pressure, preferably at atmospheric 
pressure, for about 2 to about 20 hours in an inert atmosphere, preferably 
by bubbling an inert gas such as carbon dioxide or nitrogen through the 
esterification mixture. During the course of the reaction, water (methanol 
in the case of using DMT) is formed and reduces the rate of reaction. It 
is desirable, therefore, to remove the water (or methanol) produced from 
the reaction system as soon as possible, e.g., by bubbling an inert gas 
through the esterification mixture, etc. Near the end of the 
polycondensation reaction, the esterification mixture is generally 
subjected to a reduced pressure treatment. The reduced pressure treatment 
is usually carried out at a temperature of about 150.degree. to about 
230.degree. C. under a pressure of about 1 to about 50 mmHg abs. for about 
1 min. to about 20 hrs. and provides the advantages of distilling off 
unreacted polyols, increasing the molecular weight of the polycondensate 
obtained and elevating the softening point of the polycondensate. 
The completion of the polycondensation reaction is based on the softening 
point of the polycondensate (or polyester). The reaction is completed when 
the softening point of the polycondensate reaches a desired point within 
about 80.degree. to about 150.degree. C. Where the softening point of the 
polycondensate is below about 80.degree. C., the storage stability 
deteriorates and, on the other hand, where the softening point is higher 
than about 150.degree. C., film properties such as smoothness of the film 
surface, Ericksen depression, etc., are not good and it is not suitable as 
a vehicle for a powder coating. 
The polycondensate thus obtained is a polyester wherein at least about 30 
mole % of the polyol component is an IPG repeating (structural) unit and 
at least about 50 mole % of the polycarboxylic acid component is a 
terephthalic acid repeating unit. 
Any crosslinking agent which is a compound capable of carrying out a 
crosslinking reaction with the polycondensate can be added to the 
polycondensate. Preferred crosslinking agents are amino resins and blocked 
polyisocyanates. For example, amino resins are methylolated amino 
compounds such as methylolated melamine (e.g., hexamethylol melamine, 
etc.), methylolated urea, methylolated benzoguanamine or the like obtained 
by a condensation of amino compounds (such as melamine, urea, 
benzoguanamine or the like) and formaldehyde, or alkoxides (such as 
tetrabutoxymethylbenzoguanamine, hexamethoxymethylmelamine or the like) of 
these methylolated compounds and aliphatic alcohols (such as methanol, 
ethanol, propanols, butanols or the like having 4 or less carbon atoms). 
These materials are generally the so-called melamine-formaldehyde resins, 
urea-formaldehyde resins, benzoguanamine-formaldehyde resins or the like. 
Further, as blocked polyisocyanates, polyisocyanate compounds obtained 
from phenols, caprolactams, aliphatic alcohols or the like and the 
tolylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate 
or the like and condensation products of diisocyanates and trimethylol 
propane condensate can be used. 
The amount of each of the polycondensate and the crosslinking agent blended 
in the present invention is important and the amount is such that a 
coating having excellent properties can be obtained and storage stability 
as a powder coating can be maintained. More precisely, the amount of the 
polycondensate employed is about 50 to about 98% by weight, preferably 
about 60 to about 96% by weight, and the amount of the crosslinking agent 
employed is about 2 to about 50% by weight, preferably about 4 to about 
40% by weight. A powder coating composition using a vehicle comprising 
such a polycondensate and a crosslinking agent can also contain 
conventional additives such as a pigment, a flow agent, a cure accelerator 
or the like and such can be mixed uniformly at a temperature not lower 
than the softening point of the vehicle, preferably not lower than the 
melting point of the vehicle. After cooling to room temperature (about 
20.degree.-30.degree. C.), the resulting mixture is pulverized with a 
pulverizer to obtain a coating composition in a powder form. Generally, 
where the additives are added to the vehicle, the additives may be added 
to the vehicle in a molten state and kneaded, or, after blending the 
additives with the vehicle as a solid, the resulting blend may be heat 
melted and kneaded. 
Generally known inorganic or organic pigments can be used as a pigment, and 
examples thereof include powders of titanium dioxide (titanium white), 
zinc oxide, carbon black, ferric oxide, aluminum, phthalocyanine blue, 
phthalocyanine green, or the like. The amount of the pigments used will 
vary greatly depending upon the kind of pigment, the size of the pigment 
particles or the size distribution thereof. However, the amount of the 
pigment is generally up to about 200 parts, preferably up to 100 parts, by 
weight based on 100 parts by weight of the vehicle. 
A flow agent is used to improve the flowability of the powder coating on 
heating and curing the powder coating to form a coating, and examples 
thereof include "Modaflow" (trade name, a product of Monsanto Co.), 
"L-5310" (trade name, a product of Union Carbide Co.) or the like which 
are commercially available. The amount thereof is up to about 3 parts, 
preferably up to 1.5 parts, by weight based on 100 parts by weight of the 
vehicle. 
A cure accelerator is used to promote the curing reaction on heating the 
powder coating to form a cured coating, and examples thereof include 
conventional cure accelerators such as tertiary amines (e.g., 
triethanolamine, dimethylaminoethyl methacrylate or pyridine, etc.), 
organic tin compounds (e.g., dibutyl tin oxide, dibutyl tin dilaurate, 
dibutyl tin dichloride, etc.) or the like. The amount thereof is up to 
about 10 parts by weight based on 100 parts by weight of the vehicle. 
The vehicle to which the above described additives are uniformly blended 
is, after cooling, pulverized using conventional techniques to obtain a 
coating composition in a powder form. In this case, the size of the 
particles of the powder coating is generally about 100 microns or less, 
preferably 75 microns or less. The minimum size of the particles is 
generally about 10 microns. Where the particles have a size above about 
100 microns, a coating having a smooth surface cannot be obtained.

The present invention is illustrated in greater detail by reference to the 
following Examples. However, the present invention is not to be construed 
as being limited to these Examples only. Unless otherwise indicated, all 
parts, percents, weights, ratios and the like are "by weight". 
EXAMPLE 1 
Into a 3-liter inner volume glass reactor equipped with an agitator, a 
thermometer, a condenser and inert gas inlet and outlet tubes were charged 
9.05 moles of IPG, 2.25 moles of trimethylol propane, 10 moles of TA and 4 
g of dibutyl tin oxide and the mixture was stirred at 150.degree. to 
230.degree. C. at atmospheric pressure for 4.5 hours. After distilling off 
the theoretical amount of water produced, the contents in the reactor were 
cooled to 210.degree. C. and the polycondensation was completed at a 
pressure of 15 mmHg abs. for 1.5 hours. The number average molecular 
weight of the polycondensate obtained was 3,400, the acid value thereof 
was 5.0 and the softening point thereof was 110.degree. C. 
10 parts of hexamethoxymethylmelamine, 45 parts of titanium dioxide and 0.5 
part of "Modaflow" (as defined before) were added to 100 parts of the 
polycondensate and the mixture was melt kneaded at 140.degree. C. for 20 
min. with heated rollers. After cooling to room temperature (about 
20.degree.-30.degree. C.), the resulting blend was pulverized and sieved 
to obtain powders having an average particle diameter of 45 microns. 
The powders were coated on a mild steel sheet (0.8 mm.times.50 mm.times.150 
mm) using an electrostatic spray-coating method and cured at 200.degree. 
C. for 30 min. to obtain a cured film having a thickness of about 60 
microns. The properties of the powders and the film obtained are shown in 
the Table below. 
EXAMPLE 2 
In the same type of glass reactor as was used in Example 1 were charged 8.8 
moles of IPG, 2.5 moles of trimethylol propane, 8.0 moles of TA and 3 g of 
tetrabutoxy titanate and the mixture was stirred at 150.degree. to 
230.degree. C. under atmospheric pressure for 5 hours. After distilling 
off a theoretical amount of water produced, 2.0 moles of isophthalic acid 
were added thereto and the mixture was stirred at 150.degree. to 
230.degree. C. at atmospheric pressure for 2 hours. The temperature in the 
reactor was reduced to 210.degree. C. and the polycondensation reaction 
was completed at a pressure of 15 mmHg abs. for 1 hour. The number average 
molecular weight of the polycondensate was 3,200, the acid value thereof 
was 4.6 and the softening point thereof was 104.degree. C. 
90 Parts of the polycondensate together with 10 parts of 
tetrabutoxymethylbenzoguanamine, 45 parts of titanium dioxide and 0.5 part 
of "Modaflow" (as defined before) were melt kneaded at 140.degree. C. for 
20 min. with heated rollers. After cooling, the resulting blend was 
pulverized and sieved to obtain powders having an average particle 
diameter of 40 microns. 
The powders were coated in the same manner as in Example 1. 
The properties of the powders and the film obtained are shown in the Table 
below. 
EXAMPLE 3 
Into the same type of glass reactor as was used in Example 1 were charged 
10.4 moles of IPG, 1.0 mole of trimethylol ethane, 9.0 moles of TA, and 3 
g of tetrabutoxy titanate and the mixture was stirred at 150.degree. to 
230.degree. C. at atmospheric pressure for 5 hours to distill off the 
theoretical amount of water produced. After reducing the temperature of 
the contents in the reactor to 140.degree. C., 1 mole of adipic acid was 
added thereto and the mixture was stirred at 150.degree. to 190.degree. C. 
at atmospheric pressure for 2 hours and the polycondensation reaction was 
completed at a pressure of 15 mmHg abs. for 30 minutes. The number average 
molecular weight of the polycondensate was 3,100, the acid value thereof 
was 7.5 and the softening point thereof was 95.degree. C. 
75 Parts of the polycondensate, 25 parts of .epsilon.-caprolactam-blocked 
isophorone diisocyanate, 45 parts of titanium dioxide and 0.5 part of 
"Modaflow" (as defined before) were melt kneaded with an extruder. After 
cooling, the resulting blend was pulverized and sieved to obtain powders 
having an average particle diameter of 45 microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
EXAMPLE 4 
Into the same type of glass reactor as was used in Example 1 were charged 
9.5 moles of IPG, 1 mole of trimethylol propane, 10 moles of DMT and 5 g 
of zinc acetate and the mixture was stirred at 150.degree. to 230.degree. 
C. at atmospheric pressure for 9 hours to distill off the methanol formed. 
The polycondensation reaction was completed at a pressure of 15 mmHg abs. 
for 2 hours. The number average molecular weight of the polycondensate 
obtained was 3,700, the acid value thereof was 7.7 and the softening point 
thereof was 110.degree. C. 
92 Parts of the polycondensate, 8 parts of hexamethoxymethylmelamine, 45 
parts of titanium dioxide, 0.5 part of "Modaflow" (as defined before) and 
0.5 part of phthalic anhydride were melt kneaded at 140.degree. C. for 20 
min. with heated rollers. After cooling, the resulting blend was 
pulverized and sieved to obtain powders having an average particle 
diameter of 45 microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
EXAMPLE 5 
Into the same type of glass reactor as was used in Example 1 were charged 
6.0 moles of IPG, 2.5 moles of 1,3-butane diol, 2.0 moles of trimethylol 
propane, 10 moles of DMT and 3 g of tetrabutoxy titanate and the mixture 
was stirred at 150.degree. to 210.degree. C. at atmospheric pressure for 9 
hours to distill off the methanol formed followed by completion of the 
polycondensation reaction at a pressure of 15 mmHg abs. for 1 hour. The 
number average molecular weight of the polycondensate obtained was 3,000, 
the acid value thereof was 4.5 and the softening point thereof was 
99.degree. C. 
65 Parts of the polycondensate obtained above, 45 parts of 
.epsilon.-caprolactam-blocked isophorone diisocyanate, 45 parts of 
titanium dioxide and 0.5 part of "Modaflow" (as defined before) were melt 
kneaded. After cooling, the resulting blend was pulverized and sieved to 
obtain powders having an average particle diameter of 45 microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
EXAMPLE 6 
58 Parts of the polycondensate obtained in Example 1, 52 parts of 
.epsilon.-caprolactam-blocked isophorone diisocyanate, 45 parts of 
titanium dioxide and 0.5 part of "Modaflow" (as defined before) were melt 
kneaded. After cooling, the resulting blend was pulverized and sieved to 
obtain powders having an average particle diameter of 45 microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
EXAMPLE 7 
Into the same type of glass reactor as was used in Example 1 were charged 
11.5 moles of IPG, 10.0 moles of TA and 4 g of dibutyl tin oxide and the 
mixture was stirred at 150.degree. to 230.degree. C. at atmospheric 
pressure for 8 hours followed by a completion of the polycondensation 
reaction at a pressure of 15 mmHg abs. for 2 hours. The number average 
molecular weight of the polycondensate obtained was 3,500, the acid value 
thereof was 6.8 and the softening point thereof was 102.degree. C. 
70 Parts of the polycondensate obtained above, 30 parts of 
hexamethoxymethylmelamine, 55 parts of titanium dioxide and 0.5 part of 
"L-5310" (as defined before) were melt kneaded. After cooling, the 
resulting blend was pulverized and sieved to obtain powders having an 
average particle diameter of 45 microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
EXAMPLE 8 
Into the same type of glass reactor as was used in Example 1 were charged 
4.0 moles of IPG, 1.2 moles of trimethylol propane, 6.0 moles of 
hydrogenated bisphenol A, 10 moles of TA and 4 g of tetrabutoxy titanate 
and the mixture was stirred at 150.degree. to 230.degree. C. at 
atmospheric pressure for 8 hours followed by a completion of the 
polycondensation reaction at a pressure of 15 mmHg abs. for 1 hour. The 
number average molecular weight of the polycondensate obtained was 3,000, 
the acid value thereof was 8.5 and the softening point thereof was 
102.degree. C. 
60 Parts of the polycondensate obtained above, 40 parts of 
hexamethoxymethylmelamine, 55 parts of titanium dioxide and 0.5 part of 
"Modaflow" (as defined before) were melt kneaded. After cooling, the 
resulting blend was pulverized and sieved to obtain powders having an 
average particle diameter of 45 microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
EXAMPLE 9 
Into the same type of glass reactor as was used in Example 1 were charged 
8.0 moles of IPG, 1.0 mole of propylene glycol, 1.0 mole of 
pentaerythritol, 9.5 moles of TA and 3 g of dibutyl tin oxide and the 
mixture was stirred at 150.degree. to 230.degree. C. at atmospheric 
pressure for 8 hours followed by a completion of the polycondensation 
reaction at a pressure of 15 mmHg abs. for 1 hour. The number average 
molecular weight of the polycondensate obtained was 3,200, the acid value 
thereof was 6.4 and the softening point thereof was 105.degree. C. 
75 Parts of the polycondensate, 25 parts of hexamethoxymethylmelamine, 45 
parts of titanium dioxide and 0.5 part of "Modaflow" (as defined before) 
were melt kneaded. After cooling, the resulting blend was pulverized and 
sieved to obtain powders having an average particle diameter of 45 
microns. 
The powders obtained above were coated in the same manner as in Example 1 
to obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
EXAMPLE 10 
Into the same type of glass reactor as was used in Example 1 were charged 
10.4 of IPG, 1.0 mole of pentaerithritol, 6.0 moles of TA, 4.0 moles of 
isophthalic acid and 3 g of tetrabutyl titanate and the mixture was 
stirred at 150.degree. to 230.degree. C. at atmospheric pressure for 9 
hours followed by a completion of the polycondensation reaction at a 
pressure of 15 mmHg abs. for 1 hour. The number average molecular weight 
of the polycondensate obtained was 3,200, the acid value thereof was 5.7 
and the softening point thereof was 96.degree. C. 
75 Parts of the polycondensate, 25 parts of hexamethoxymethylmelamine, 55 
parts of titanium dioxide and 0.5 part of "Modaflow" (as defined before) 
were melt kneaded. After cooling, the resulting blend was pulverized and 
sieved to obtain powders having an average particle diameter of 45 
microns. 
The powders obtained above were coated in the same manner as in Example 1 
to obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
COMATIVE EXAMPLE 1 
Into the same type of glass reactor as was used in Example 1 were charged 
8.8 moles of neopentyl glycol, 2.23 moles of trimethylol propane, 8.0 
moles of TA and 3 g of dibutyl tin oxide and the mixture was stirred at 
150.degree. to 230.degree. C. at atmospheric pressure for 5 hours. The 
temperature in the reactor was decreased to 210.degree. C. and the 
polycondensation reaction was completed at a pressure of 15 mmHg abs. for 
2 hours. The number average molecular weight of the polycondensate 
obtained was 3,400, the acid value thereof was 8.7 and the softening point 
thereof was 111.degree. C. 
90 Parts of the polycondensate obtained above, 10 parts of 
hexamethoxymethylmelamine, 45 parts of titanium dioxide and 0.3 part of 
"Modaflow" (as defined before) were melt kneaded at 140.degree. C. for 20 
min with heated rollers. After cooling, the resulting blend was pulverized 
and sieved to obtain powders having an average particle diameter of 45 
microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
As is apparent from the results in the Table below, where IPG is not used 
as a polyol component, the storage stability of a powder coating obtained 
specifically is poor and various properties of gloss, appearance, 
flexibility and cross hatch adhesion after testing of resistance to 
boiling water of the film are also inferior. 
COMATIVE EXAMPLE 2 
Into the same type of glass reactor as was used in Example 1 were charged 
6.1 moles of hydrogenated bisphenol A, 4.3 moles of 1,3-butylene glycol 
and 9.6 moles of TA and the mixture was stirred at 180.degree. C. for 6 
hours and 220.degree. C. for 10 hours and then 240.degree. C. for 8 hours 
at atmospheric pressure. 
The number average molecular weight of the polycondensate obtained was 
3,500, the acid value thereof was 7.3 and the softening point thereof was 
100.degree. C. 
95 Parts of the polycondensate obtained above, 5 parts of 
hexamethoxymethylmelamine, 45 parts of titanium dioxide and 0.5 part of 
"Modaflow" (as defined before) were melt kneaded. After cooling, the 
resulting blend was pulverized and sieved to obtain powders having an 
average particle diameter of 45 microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powders and the film obtained are shown in the Table 
below. 
As is apparent from the results in the Table, where IPG is not used as a 
polyol component, various properties of storage stability of the powder 
coating at 40.degree. C., gloss, appearance and cross hatch adhesion after 
testing for resistance to boiling water of the film are inferior 
specifically. 
COMATIVE EXAMPLE 3 
35 Parts of the polycondensate obtained in Example 5, 65 parts of 
.epsilon.-caprolactam-blocked isophorone diisocyanate, 45 parts of 
titanium dioxide and 0.5 part of "Modaflow" (as defined before) were melt 
kneaded. After cooling, the resulting blend was pulverized and sieved to 
obtain powders having an average particle diameter of 45 microns. 
The powders obtained were coated in the same manner as in Example 1 to 
obtain a film. 
The properties of the powder and the film obtained are shown in the Table 
below. 
As is apparent from the results in the Table below where the polycondensate 
content in the vehicle is below 50 mole %, various properties of gloss, 
appearance, flexibility, impact resistance and cross hatch adhesion after 
testing for resistance to boiling water of the coating deteriorated 
specifically. 
Table 
__________________________________________________________________________ 
Example No. 
Property of Powders: 
1 2 3 4 
__________________________________________________________________________ 
Storage stability *1 
(a) No blocking 
No blocking 
No blocking 
No blocking 
(b) No blocking 
No blocking 
No blocking 
No blocking 
Properties of Film: 
Film Thickness *2 (.mu.) 
about 60 
about 40 
about 25 
about 60 
Gloss *3 96 97 98 96 
Appearance of 
No orange 
No orange 
No orange 
No orange 
Film Surface *4 
peel peel peel peel 
Cross Hatch 
Adhesion *5 100/100 
100/100 
100/100 
100/100 
Flexibility 
(conical mandrel) *6 
.phi.4 .phi.4 .phi.4 .phi.4 
(mm) 
Impact 
Resistance *7 (cm) 
50 50 50 50 
Erichsen 
Depression *8 (mm) 
9 8 10 9 
Salt 
Spray Test *9 
Pass Pass Pass Pass 
Boiling 
Water Test *10 
No change 
No change 
No change 
No change 
Cross Hatch 
Adhesion after 
Boiling Water Test 
100/100 
100/100 
100/100 
80/100 
Example No. 
5 6 7 8 9 10 
__________________________________________________________________________ 
No blocking 
No blocking 
No blocking 
No blocking 
No blocking 
No blocking 
about 60 
about 60 
about 70 
about 70 
about 60 
about 60 
94 94 96 95 95 97 
No orange 
No orange 
No orange 
No orange 
No orange 
No orange 
peel peel peel peel peel peel 
100/100 
100/100 
100/100 
100/100 
100/100 
100/100 
.phi.6 .phi.6 .phi.4 .phi.6 .phi.6 .phi.4 
50 50 50 40 40 50 
6 8 8 6 6 8 
Pass Pass Pass Pass Pass Pass 
No change 
No change 
No change 
No change 
No change 
No change 
80/100 90/100 100/100 
100/100 
80/100 100/100 
Comparative Example No. 
1 2 3 
__________________________________________________________________________ 
Trace of blocking 
No blocking No blocking 
Trace of blocking 
Trace of blocking 
No blocking 
about 60 about 70 about 60 
85 87 84 
Orange peel Orange peel Orange peel 
100/100 100/100 100/100 
.phi.8 .phi.6 .phi.10 
40 40 20 
6 7 2 
Pass Pass Pass 
No change No change No change 
60/100 60/100 60/100 
__________________________________________________________________________ 
Notes 
*1 : About 20g of powder was charged into a glass vessel and allowed to 
stand under the conditions below to observe blocking or caking of the 
powder. (a) : 35.degree. C. .times. 1 week (b) : 40.degree. C. .times. 1 
week 
*2 : Cure conditions 180.degree.-200.degree. C. .times. 30 min.) 
*3 : Gloss 60.degree. spectral value according to ASTM Method D-523 
*4 : The surface of the film coated on the mild steel sheet was visually 
observed as to whether the surface was flat. 
*5 : Cross Hatch Adhesion Test according to ASTM Paint Test Manual, 
Edition 13, page 319 (1972) (Cross Section : 1mm .times. 1mm .times. 100) 
*6 : According to ASTM Method D-522 
*7 : Du Pont Typing Machine (1/2 inch .times. 500 g) 
*8 : Using Erichsen film tester, a hemispherical ball having a diameter o 
20mm was gradually pressed against the film surface and the depression 
(depth) of the hemispherical ball when the film broke was measured. 
*9 : An aqueous NaCl solution of a concentration of about 5% was 
continuously sprayed on the film surface at room temperature (about 
20-25.degree. C.) for 500 hrs. and the change of the film surface was 
observed. The expression "pass" means that no change was observed on the 
surface. 
*10 : A mild steel sheet having the film coated thereon was immersed in a 
boiling water (100.degree. C.) for 2 hrs. and the change of the film 
surface was observed. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.