Particulate vinyl polymer and water-base coating composition using the same

A particulate vinyl polymer is provided. At least 95 wt. % of its particles have a minor axis A and a major axis B, which are in a relationship of 1.ltoreq.B/A.ltoreq.1.5 and individually range from 30 .mu.m to 400 .mu.m. The polymer has an acid value of from 30 to 150 mg KOH/g. This particulate vinyl polymer is excellent in workability such as the solubility in aqueous medium, and is useful as a raw material for water-base coating compositions having superb dispersion of a pigment and excellent waterproofness.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a particulate vinyl polymer and also to a 
water-base coating composition using the particulate vinyl polymer. More 
specifically, this invention is concerned with a particulate vinyl polymer 
excellent in workability such as the solubility in an aqueous medium and 
also with a water-base coating composition which can form coating films 
excellent in waterproofness, adhesion and the like and which also has 
excellent pigment dispersibility and is hence suited for paints, inks and 
the like. 
2. Description of the Related Art 
From the environmental viewpoint, there is an ever-increasing demand for 
water-base coating compositions in recent years, leading to the 
development of a wide variety of products. 
In an emulsion, dispersion or the like of a polymer, the polymer is 
contained in a form distributed in water. The emulsion, dispersion or the 
like therefore does not exhibit any substantial increase in viscosity even 
when the molecular weight of the polymer becomes higher. This makes it 
possible to use a polymer of high molecular weight, leading to the 
advantage that a water-base coating composition capable of forming a 
coating film of excellent physical properties can be formulated. Numerous 
water-base coating compositions have hence been developed to date. 
Whenever dispersion of a pigment at a high concentration is needed, 
however, it is indispensable to rely upon the action that an associated 
polymer surrounds the pigment to prevent its re-agglomeration. In an 
emulsion, dispersion or the like in which a polymer is contained in a form 
dispersed in water, it has however been difficult to fully prevent such 
re-agglomeration of a pigment, thereby failing to obtain sufficient 
pigment dispersibility. To surround the pigment for the prevention of its 
re-agglomeration, it is needed that the polymer must be contained in a 
form dissolved in water.. To this end, the development of water-soluble 
polymers has been proceeded with in various ways. 
Typical examples of such water-soluble polymers include polyvinyl alcohols 
and sodium salts of polyacrylic acids. These water-soluble polymers are 
however accompanied by many practical inconveniences, because even after 
their formation into coating films, they are prone to dissolution in water 
and the coating films are thus re-dissolved and damaged by a slightest 
adverse cause such as exposure to water droplets. 
To overcome the above inconveniences, a technique was developed. According 
to this technique, a polymer containing acidic groups such as sulfonic or 
carboxylic groups is poured into an aqueous medium containing a volatile 
base so that the polymer is neutralized into a salt and is hence rendered 
soluble in water. In the course of drying subsequent to coating, the 
volatile base is allowed to evaporate so that the polymer becomes 
insoluble. Water-base coating compositions based on this technique have 
been put on the market in recent years. 
The above water-base coating compositions are however accompanied by the 
drawback that the dissolution of a polymer in an aqueous medium containing 
a volatile base takes time. It has accordingly been attempted to enhance 
the solubility of a polymer by increasing its acid value or comminuting it 
into fine particles. A coating film which has been formed from a polymer 
with an increased acid value however involves the problem that it has low 
waterproofness and cannot avoid deteriorations such as whitening. A 
comminuted, that is, fine particulate polymer, on the other hand, is 
accompanied by the problem that it tends to scatter around as dust upon 
handling and hence reduces workability. 
Illustrative polymer particles having dust-free property include polymer 
powder such as those disclosed in Japanese Patent Laid-Open No. 
242807/1990. They can be obtained by salting out fine particles, which 
have been produced by emulsion polymerization, and then collecting them by 
filtration. Such polymer powder however has irregular particle shapes and 
hence are poor in free-flowing property. When a worker attempts to take 
the polymer powder out of a bag to charge them into an aqueous medium, for 
example, the polymer powder does not flow out of the bag at a uniform 
rate, resulting in irregular charging into the aqueous medium. Upon 
dissolution of the polymer powder, polymer aggregates may be formed, 
resulting in the problems that the polymer powder may not be dissolved 
well and the workability is lowered. 
It has also been attempted to blend a dispersion, emulsion or the like of a 
polymer having good waterproofness in an aqueous polymer solution. When 
dispersion of a pigment at a high concentration is needed, however, it is 
difficult to achieve both pigment dispersibility and waterproofness while 
holding a good balance therebetween. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide a particulate vinyl polymer, 
which has good free-flowing and dust-free properties and is hence easy to 
handle. 
Another object of this invention is to provide a particulate vinyl polymer, 
which is highly soluble in an aqueous medium and is useful as a raw 
material for a water-base coating composition capable of forming a coating 
film having excellent dispersion of a pigment and superb waterproofness. 
A further object of this invention is to provide a water-base coating 
composition, which is usable as mixtures with aqueous dispersions of a 
wide variety of polymers and can form coating films having excellent 
waterproofness and outstanding dispersion of a pigment. 
In one aspect of the present invention, there is thus provided a 
particulate vinyl polymer. At least 95 wt. % of its particles have a minor 
axis A and a major axis B, which are in a relationship of 
1.ltoreq.B/A.ltoreq.1.5 and individually range from 30 .mu.m to 400 .mu.m. 
The polymer has an acid value of from 30 to 150 mg KOH/g. This particulate 
vinyl polymer is excellent in workability such as the solubility in 
aqueous medium, and is useful as a raw material for water-base coating 
compositions having superb pigment dispersion and waterproofness. 
The particulate vinyl polymer according to this invention is excellent in 
workability such as the solubility in aqueous medium, and is useful as a 
raw material for water-base coating compositions having superb dispersion 
of a pigment and excellent waterproofness.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The particulate vinyl polymer according to this invention has an acid value 
of 30-150 mg KOH/g as expressed in terms of the milligrams of KOH required 
to neutralize 1 g of the vinyl polymer when an aqueous solution of the 
vinyl polymer is titrated with a solution of KOH in ethanol by using as a 
reference the color transition point of phenolphthalein. Acid values 
smaller than 30 mg KOH/g tend to result in a reduction in the solubility 
in an aqueous medium, whereas acid values greater in excess of 150 mg 
KOH/g are apt to lead to the formation of a coating film of reduced 
waterproofness. The preferred acid value is in a range of 40-90 mg KOH/g. 
Further, at least 95 wt. % of particles of the particulate vinyl polymer 
are required to have a minor axis A and a major axis B, which are in a 
relationship of 1.ltoreq.B/A.ltoreq.1.5 and are individually in the range 
of 30-400 .mu.m. B/A ratios greater than 1.5 (B/A&gt;1.5) lead to 
insufficient free-flowing property, so that when a worker attempts to take 
the particulate vinyl polymer out of a bag to charge it into an aqueous 
medium, for example, the particulate vinyl polymer does not flow out of 
the bag at a uniform rate, resulting in irregular charging into the 
aqueous medium and upon dissolution of the particulate vinyl polymer, 
aggregates of the polymer are formed, the polymer may not be dissolved 
well and the workability is lowered. Such large B/A ratios are therefore 
not preferred. The preferred B/A ratio range from 1 to 1.1, both inclusive 
(1.ltoreq.B/A.ltoreq.1.1). As described above, it is also required that at 
least 95% of the particles of the particulate vinyl polymer individually 
have a minor and major axes A and B in the range of 30-400 .mu.m. If 
either the minor axis A or the major axis B is smaller than 30 .mu.m, the 
particulate vinyl polymer tends to scatter around as dust and hence to 
lower the workability. If either the minor axis A or the major axis B 
becomes greater than 400 .mu.m, on the other hand, the dissolution 
velocity in aqueous media is lowered. Preferably the minor and major axes 
A and B are each in a range of 70-250 .mu.m. 
In the present invention, it is important that at least 95 wt. % of the 
particulate vinyl polymer meets the above-described configurational 
conditions, because proportions smaller than 95% significantly impair the 
workability and the dissolution velocity in aqueous media. 
The particulate vinyl polymer according to the present invention preferably 
comprises (a) 30-90 wt. % of methyl methacrylate, (b) 0-30 wt. % of an 
aromatic vinyl compound, (c) 4-30 wt. % of an acidic-group-containing 
vinyl compound and (d) 0-66 wt. % of a further vinyl monomer 
copolymerizable with methyl methacrylate (a), the aromatic vinyl compound 
(b) and the acidic-group-containing vinyl compound (c). 
Methyl methacrylate (a) is a component to impart hardness to the vinyl 
polymer and is used in a proportion of 30-90 wt. %. Proportions of methyl 
methacrylate (a) smaller than 30 wt. % tend to result in lower hardness, 
while its proportions greater than 90 wt. % tend to lead to reduced 
solubility in aqueous media. Proportions of methyl methacrylate (a) 
outside the above range are therefore not preferred. 
The aromatic vinyl compound (b) is effective in imparting waterproofness to 
a resulting coating film. The aromatic vinyl compound (b) can be 
polymerized in a proportion up to 30 wt. % as needed. More preferably, it 
is used in a range of 0-20 wt. %. Proportions of the aromatic vinyl 
compound (b) greater than 30 wt. % are not preferred because such high 
proportions tend to lower the solubility in aqueous media. Specific 
examples of the aromatic vinyl compound (b) include styrene, 
.alpha.-methylstyrene, p-methylstyrene and benzyl (meth)acrylate. Among 
these, styrene is particularly preferred. 
The acid-group-containing vinyl compound (c) serves to provide the vinyl 
polymer with acidic groups. It is a compound containing one or more acidic 
groups, such as a carboxylic acid or sulfonic acid, and is used in the 
range of 4-30 wt. % so that the resulting vinyl polymer has an acid value 
of 30-150 mg KOH/g. As examples of the acid-group-containing vinyl 
compound (c), vinyl compounds containing one or more carboxylic group are 
preferred because they can provide vinyl polymers good in the 
dispersibility in aqueous media, waterproofness and pigment 
dispersibility. Specific examples of the acidic-group-containing vinyl 
compound (c) include monobasic acids such as acrylic acid, methacrylic 
acid and crotonic acid; dibasic acids such as fumaric acid, maleic acid 
and itaconic acid; and their partial esterification products. Among these, 
methacrylic acid is especially preferred. It is possible to use two or 
more of these compounds in combination. 
Further, the further vinyl monomer (d) copolymerizable with the above 
monomers (a) to (c) is used in the range of 0-66 wt. % and can be chosen 
as desired from those containing at least one polymerizable vinyl group in 
accordance with the application purpose. Specific examples of the vinyl 
monomer (d) include C.sub.1-18 -alkyl (meth)acrylates such as ethyl 
(meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl 
(meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 
lauryl (meth)acrylate, and stearyl (meth)acrylate; hydroxyalkyl 
(meth)acrylate such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl 
(meth)acrylate; glycol di(meth)acrylates such as ethylene glycol 
di(meth)acrylates and butylene glycol di(meth)acrylates; alkylaminoalkyl 
(meth)acrylates such as dimethylaminoethyl (meth)acrylate; 
dimethylaminoethyl (meth)acrylate methyl chloride; allyl (meth)acrylate; 
trimethylolpropane tri(meth)acrylate; vinyl acetate; vinyl propionate; and 
(meth)acrylonitrile. 
Further, the particulate vinyl polymer according to the present invention 
preferably has a second-order transition temperature of 
10.degree.-150.degree. C., more preferably 30.degree.-100.degree. C., and 
most preferably 35.degree.-100.degree. C., as measured by DSC 
(differential scanning calorimetry). Second-order transition temperatures 
lower than 10.degree. C. tend to lead to insufficient antifouling property 
and reduced blocking resistance, whereas second-order transition 
temperatures higher than 150.degree. C. are apt to result in friable 
coating films. On the other hand, the weight average molecular weight of 
the particulate vinyl polymer as measured by GPC (gas permeation 
chromatography) is preferably in a range of 6,000-100,000, with a range of 
8,000-60,000 being more preferred. Weight average molecular weights 
smaller than 6,000 tend to result in friable coating films whereas weight 
average molecular weights greater than 100,000 are inclined to lead to 
reduced water solubility. 
As a polymerization process upon production of the particulate vinyl 
polymer according to this invention, a known process such as suspension 
polymerization, solution polymerization or bulk polymerization can be 
applied. Suspension polymerization is however particularly preferred, for 
example, for the ready availability of the acid value and particle shape 
specified in the present invention and also from the viewpoint of 
productivity. When suspension polymerization is applied, the particulate 
vinyl polymer according to the present invention can be easily obtained by 
separating a solid polymerization product from a dispersion medium such as 
water subsequent to the polymerization. Filtration is a preferred method 
for separating it. 
Further, a particulate vinyl polymer--which is obtained by the one-shot 
monomer charging process that monomers are charged at once in a 
polymerization system and their polymerization is then initiated--is 
superior in both waterproofness and pigment dispersibility to that 
obtained by charging monomers in several portions into a polymerization 
system while allowing their polymerization to proceed or by dropping 
monomers into a polymerization system over several hours while allowing 
the polymerization to proceed. This advantage appears to be attributed to 
the copolymerizability of the monomers. 
As a dispersant for the suspension polymerization, it is possible to use a 
known water-soluble high-molecular substance such as polyvinyl alcohol 
having a saponification degree in a range of 70-100% or poly[sodium 
(meth)acrylate]. Although no particular limitation is imposed on a solvent 
for the solution polymerization insofar as it can dissolve the monomers 
employed in the present invention and also the resulting polymer, its 
illustrative examples include alcohols such as methanol, ethanol, 
isopropyl alcohol and n-butanol; glycols such as "Ethyl Cellosolve" (trade 
name for ethylene glycol monoethyl ether; product of Union Carbide 
Corporation), "Cellosolve Acetate" (trade name for ethylene glycol 
monoethyl ether acetate; product of Union Carbide Corporation), "Butyl 
Carbitol" (trade name for diethylene glycol monobutyl ether; product of 
Union Carbide Corporation) and propylene glycol methyl ether; acetate 
esters such as ethyl acetate and butyl acetate; and ketones such as methyl 
ethyl ketone and methyl isobutyl ketone. 
As a polymerization catalyst, it is possible to use a conventionally known 
initiator as needed depending on the application purpose, for example, an 
azo initiator such as azobisisobutyronitrile or a peroxide initiator such 
as benzoyl peroxide. 
To regulate the molecular weight of the vinyl polymer, a chain transfer 
agent such as n-dodecyl mercaptan or .alpha.-methylstyrene dimer can be 
used as needed. 
The particulate vinyl polymer obtained as described above can be used as a 
water-base coating composition (A) by dissolving it in an aqueous medium. 
In this case, a base--which is employed to neutralize 50-100% of acidic 
groups in the particulate vinyl polymer to form a salt, thereby imparting 
water solubility to the particulate vinyl polymer and dissolving it in the 
aqueous medium--preferably has a boiling point not higher than 200.degree. 
C. If the acidic groups in the particulate vinyl polymer are neutralized 
only to less than 50%, the polymer is dispersed in the aqueous medium so 
that the resulting water-base coating composition tends to have 
insufficient pigment dispersibility. On the other hand, use of a base 
having a boiling point higher than 200.degree. C. for neutralization tends 
to result in a coating film of reduced waterproofness. It is preferred to 
neutralize 70-100% of the acid groups in the particulate vinyl polymer. 
No particular limitation is imposed on the method for dissolving the 
particulate vinyl polymer in an aqueous solvent. It is possible to 
dissolve the particulate vinyl polymer in a short time by charging it into 
an aqueous medium, which contains a volatile base and has been heated to 
50.degree. C. or so, and stirring the resulting mixture. 
Illustrative examples of the volatile base include ammonia, triethylamine, 
propylamine, diethylamine, tripropylamine, dibutylamine, amylamine, 
1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, 
2-diethylaminoethanol, 1-amino-2-propanol, 2-amino-1-propanol, 
3-amino-1-propanol, 1-dimethylamino-2-propanol, 
3-dimethylamino-1-propanol, 2-propylaminoethanol, ethoxypropylamine, 
aminobenzyl alcohol, and morpholine. 
The water-base coating composition (A) can be obtained by dissolving the 
particulate vinyl polymer of this invention usually at a concentration of 
15-35 wt. % preferably at a concentration of 20-30 wt. % in an aqueous 
medium. 
The particulate vinyl polymer according to the present invention can also 
be used as a water-base coating composition (B) by mixing (I) an aqueous 
solution of the particulate vinyl polymer solution in an aqueous medium 
with (II) an aqueous dispersion of another polymer. 
With respect to the aqueous particular vinyl polymer solution (I) in the 
above case, the acidic groups of the particulate vinyl polymer can be 
neutralized by a base as in the case of the water-base coating composition 
(A). It is unnecessary to neutralize all the acidic groups. Usually, 30% 
or more of the acidic groups are neutralized. As exemplary bases usable 
for the neutralization, the above-exemplified volatile bases can be 
mentioned. 
No particular limitation is imposed on the type of the polymer in the 
aqueous dispersion (II) insofar as a polymer having a weight average 
molecular weight of 200,000-2,000,000 is employed. Illustrative usable 
polymers include acrylic resins, alkyd resins, urethane resins, epoxy 
resins, polyester resins, vinyl resins such as polyvinyl chloride and 
polyvinyl acetate, and cellulose resins such as nitrocellulose and 
cellulose acetate butyrate. 
The second-order transition temperature of the polymer contained in the 
aqueous dispersion (II) is preferably 120.degree. C. or lower, with 
30.degree.-120.degree. C. being more preferred, because second-order 
transition temperatures higher than 120.degree. C. tend to result in a 
coating film susceptible to cracking. Further, weight average molecular 
weights lower than 200,000 tend to result in coating films having 
insufficient toughness, whereas weight average molecular weights higher 
than 2,000,000 are inclined to lead to coating films prone to cracking. 
For the production of the aqueous polymer dispersion (II), various methods 
can be adopted, including (a) a method making use of emulsion 
polymerization, (b) a method of neutralizing with a base a solution of a 
polymer containing acidic groups such as carboxyl groups in a hydrophilic 
organic solvent, said solution having been prepared by dissolving the 
polymer in the hydrophilic organic solvent or by solution-polymerizing the 
polymer in the hydrophilic organic solvent, and then dispersing the 
thus-neutralized solution in water, and (c) a method of dissolving the 
polymer in a hydrophilic organic solvent and then dissolving the resulting 
solution in surfactant-containing water under high shear force. Of these, 
the aqueous polymer dispersion prepared by emulsion polymerization is 
particularly preferred for its good waterproofness. 
The water-base aqueous composition (B) can be prepared by mixing (I) the 
aqueous solution of the particulate vinyl polymer and (II) the aqueous 
dispersion of the polymer at a (I)/(II) ratio of from 5/95 to 95/5 in 
terms of polymer solid. Mixing ratios smaller than 5/95 tend to make it 
difficult to form a tough coating film which does not form cracks without 
using any film-forming aid, while mixing ratios greater than 95/5 are 
inclined to lead to coating films reduced in waterproofness. Mixing ratios 
outside the above range are therefore not preferred. No particular 
limitation is imposed on the mixing method of (I) the aqueous solution of 
the vinyl polymer with (II) the aqueous dispersion of the polymer. They 
can be mixed together at room temperature, or they can be mixed together 
after heating them. Further, the aqueous polymer dispersion (II) is 
usually employed at a polymer concentration of 25-60 wt. %. 
The particulate vinyl polymer according to the present invention can also 
be used as a water-base coating composition (C) by mixing (III) an aqueous 
solution of the particulate vinyl polymer in an aqueous medium with (IV) 
an aqueous dispersion of a urethane polymer. 
The second-order transition temperature of the particulate vinyl polymer 
employed in the above case is preferably 20.degree.-110.degree. C. as 
measured by DSC. The weight average molecular weight of the vinyl polymer 
as measured by GPC is preferably 6,000-30,000, more preferably 
8,000-25,000. Weight average molecular weights lower than 6,000 tend to 
result in various drawbacks such as friable coating films, whereas weight 
average molecular weights higher than 30,000 have tendency of leading to 
poor compatibility with the urethane polymer. 
To obtain the aqueous solution (III) of the particulate vinyl polymer, the 
acidic groups in the vinyl polymer are neutralized using a base to form a 
salt so that water solubility is imparted to the vinyl polymer, and the 
vinyl polymer is then dissolved in an aqueous medium. It is unnecessary to 
neutralize the entire acidic groups of the vinyl polymer. In general, 30% 
or more of the acidic groups are neutralized. As examples of the base used 
in the neutralization, the above-described volatile bases can be 
mentioned. 
The aqueous dispersion of the urethane polymer, on the other hand, can be a 
self-emulsifiable emulsion obtained by extending with water or a polyamine 
such as a di- or tri-amine a urethane prepolymer, which is composed of (e) 
an aliphatic or alicyclic diisocyanate, (f) a diol compound having a 
number average molecular weight of 500-5,000 and (g) an 
acid-group-containing diol and has an NCO/OH equivalent ratio of 1.1-1.9, 
either after or while neutralizing the urethane prepolymer with a tertiary 
amine. 
Illustrative examples of the aliphatic or alicyclic diisocyanate (e) 
include aliphatic diisocyanates such as hexamethylenediisocyanate and 
2,2,4-trimethylhexanediisocyanate; C.sub.4-18 -alicyclic diisocyanates 
such as isophoronediisocyanate, 1,4-cyclohexanediisocyanate and 
4,4'-dicyclohexylmethane diisocyanate; and modified products of these 
diisocyanates (carbodiimido-, urethodiono- and urethoimino-containing 
modified products). Particularly preferred examples are hexamethylene 
diisocyanate and isophorone diisocyanate. Two or more of these 
diisocyanates can be used in combination. Aromatic diisocyanates cannot be 
used for their excessive reactivity with water upon extension with water 
or a polyamine. 
The diol compound (f) whose number average molecular weight is 500-5,000 is 
a compound which has a number average molecular weight of 500-5,000 and 
usually contains hydroxyl groups at terminals thereof. Number average 
molecular weights smaller than 500 result in friable coating films while 
number average molecular weights greater than 5,000 lead to coating films 
lacking in flexibility. Specific examples of the diol compound (f) include 
those obtained by (co)polymerizing alkylene oxides such as ethylene oxide 
and propylene oxide or heterocyclic ethers such as tetrahydrofuran, for 
example, polyethylene glycol, polypropylene glycol, polytetramethylene 
ether glycol and polyhexamethylene ether glycol; polyethylene adipate, 
polybutylene adipate, polyneopentyl adipate, poly-3-methylpentyl adipate, 
polyethylene/butylene adipate, and polyneopentyl/hexyl adipate; 
polylactone diols such as polycaprolactone diol; and polycarbonate diols. 
Also usable are water-soluble polyester diols obtained by copolymerization 
of sodium 5-sulfoisophthalate with diethylene glycol or polyethylene 
glycol. Two or more of these diol compounds can be used in combination. 
The acid-group-containing diol (g) is a diol compound containing one or 
more acidic group such as carboxylic and/or sulfonic groups. Specific 
examples include dimethylolalkanoic acid esters such as dimethylol 
acetate, dimethylol propionate and dimethylol butyrate. Two or more of 
these diol compounds can be used in combination. Among these, particularly 
preferred is dimethylol propionate. 
A urethane prepolymer synthesized from one or more of these compounds is 
required to have an NCO/OH equivalent ratio of 1.1-1.9. NCO equivalent 
ratios smaller than 1.1 result in urethane polymers whose viscosities are 
too high to permit smooth dispersion in water. NCO equivalent ratios 
greater than 1.9, on the other hand, are prone to gelation upon extension 
with water or a polyamine. 
Upon synthesis of the urethane prepolymer, a polyhydroxy compound of a low 
molecular weight can be added. Examples of such a low-molecular 
polyhydroxy compound include glycols mentioned above as raw materials for 
polyester diols, and low-mole alkylene oxide adducts thereof; and 
trihydric alcohols such as glycerin, trimethylolethane and 
trimethylolpropane, and low-mole alkylene oxide adducts thereof. The lower 
molecular polyhydroxy compound is used suitably in an amount of 20 wt. % 
or less based on the diol compound (f). Use of the low molecular 
polyhydroxy compound in amounts greater than 20 wt. % tend to result in 
friable coating films. 
The urethane prepolymer obtained as described above is dispersed in water 
by extending it with water or a di- or a tri-amine either after or while 
neutralizing its acidic groups, which have originated from the 
acid-group-containing diol, with a tertiary amine. 
The amine employed for the neutralization is required to be tertiary. A 
primary or secondary amine is not suited because it reacts with the 
remaining isocyanate. Specific examples of the tertiary amine include 
trialkylamines such as trimethylamine and triethylamine; 
N-alkylmorpholines such as N-methylmorpholine; and N-alkylalkanolamines 
such as N-dimethylethanolamine. Two or more of these tertiary amines can 
be used in combination. In general, they can be used in an amount of 0.5-1 
equivalent per equivalent of acidic groups in the urethane prepolymer. 
As the polyamine employed for the amine extension, a diamine or triamine is 
usually used. Specific examples include hexamethylenediamine, 
isophoronediamine, hydrazine and piperazine. Two or more of these amines 
can be used in combination. 
The water-base coating composition (C) can be prepared by mixing (III) the 
aqueous solution of the particulate vinyl polymer with (IV) the aqueous 
dispersion of the urethane polymer at a (III)/(IV) ratio of from 5/95 to 
95/5 in terms of polymer solid. Blending percentages of the particulate 
vinyl polymer not greater than 5% cannot fully exhibit the advantages of 
the aqueous solution of the particulate vinyl polymer, that is, good 
pigment dispersibility and little insoluble aggregates. On the other hand, 
blending percentages of the particulate vinyl polymer greater than 95% 
cannot fully bring about the advantages of the aqueous dispersion of the 
urethane polymer, that is, good film-forming ability and good adhesion to 
plastic films. No particular limitation is imposed on the manner of mixing 
between (III) the aqueous solution of the particulate vinyl polymer and 
(IV) the aqueous dispersion of the urethane polymer. The aqueous solution 
(III) of the particulate vinyl polymer is used generally at a 
concentration of 20-35 wt. %. Further, the aqueous dispersion (IV) of the 
urethane polymer is employed generally at a concentration of 25-45 wt. %. 
When the particulate vinyl polymer according to this invention is used as 
the water-base coating compositions (A) to (C), it is possible to 
incorporate additives such as defoaming agents, pigment dispersants and 
antiseptics. 
Illustrative methods for coating the water-base coating compositions (A) to 
(C), which make use of the particulate vinyl polymer of this invention, 
include, but are not specifically limited to, spray coating, roller 
coating, blade coating, air-knife coating, flow casting, brushing, and 
dipping. 
The present invention will hereinafter be described specifically by the 
following examples, in which all designations of "part" or "parts" and "%" 
are by weight. Incidentally, minor and major axes of particles will be 
indicated by "A" and "B" respectively. 
The following methods and standards were employed for the testing and 
evaluation of particulate vinyl polymers. 
Solubility Test of Particulate Vinyl Polymers in Aqueous Medium 
In a 300-ml flask equipped with a stirrer, a thermometer and a reflux 
condenser and permitting both heating and cooling, 50 g of a particular 
vinyl polymer were charged along with deionized water in an amount 
determined by the below-described formula. Stirring was then initiated at 
200 rpm by a single-blade agitator. After a 28% aqueous ammonia in an 
amount determined by the below-described calculation formula was then 
added over 5 minutes, the contents were heated to 50.degree. C. and the 
stirring was continued. From the time required for the dissolution of the 
particulate vinyl polymer, the solubility of the particulate vinyl polymer 
in the aqueous medium was evaluated. 
Amount (g) of aqueous ammonia to be 
added=(A.times.50.times.17)/(1,000.times.56.1.times.0.28) 
[A: the acid value of the polymer (mg KOH/g)] 
Amount (g) of deionized water to be added=150-(the amount of aqueous 
ammonia to be added.times.0.72) 
Solubility 
Excellent: Dissolution was completed in less than 60 minutes after heated 
to 50.degree. C. 
Good: Dissolution was completed in less than 90 minutes after heated to 
50.degree. C. (practically usable down to this solubility level). 
Poor: Ninety minutes or longer were needed until full dissolution after 
heated to 50.degree. C. 
Insoluble: Dissolution was uncompleted even after 180 minutes had elapsed 
after heated to 50.degree. C. 
Evaluation of Pigment Dispersibility and Waterproofness of Water-Base 
Coating Compositions 
Pigment Dispersibility 
Twenty parts of carbon black ("#100", trade name; product of Degussa Inc.) 
were added to 100 parts of an aqueous solution of a particulate vinyl 
polymer, said aqueous solution having had the same composition as the 
sample employed in the above solubility test, and the resulting mixture 
was mixed for 2 hours in a planetary ball mill (manufactured by FRITCH 
INC.) to disperse the pigment. The water-base coating composition with the 
pigment dispersed therein was left over at room temperature for 100 days 
and the settling behavior of the pigment was visually observed. 
Excellent: No settling of the pigment was observed even after 100 days had 
elapsed after left over. 
Good: Settling of the pigment was observed on the 20th days after left 
over. 
Poor: Settling of the pigment was observed on the 2nd day after left over. 
Waterproofness 
Twenty parts of carbon black ("#100", trade name; product of Degussa Inc.) 
were added to 100 parts of an aqueous solution of a particulate vinyl 
polymer, said aqueous solution having had the same composition as the 
sample employed in the above solubility test, and the resulting mixture 
was mixed for 2 hours in a planetary ball mill (manufactured by FRITCH 
INC.) to disperse the pigment. The water-base coating composition with the 
pigment dispersed therein was coated on a glass plate to give a solid film 
thickness of 80 .mu.m. After drying the coating composition for 20 minutes 
in a drying furnace controlled at 50.degree. C., the resultant coating 
film was immersed in water of 20.degree. C. for 10 days, during which 
damages to the coating film were visually observed. 
Excellent: No damage to the coating film was observed even after 10 days 
had elapsed after its immersion. 
Good: Damages to the coating film, such as whitening and blisters, were 
observed on the 10th day after its immersion. 
Poor: Damages to the coating film, such as whitening and blisters, were 
observed in 5 hours after its immersion. 
Example 1 
Production of Particulate Vinyl Polymer (P-1) 
In a polymerizer equipped with a stirrer, a thermometer and a reflux 
condenser and permitting both heating and cooling, 200 parts of deionized 
water were added to 0.6 part of polyvinyl alcohol (saponification degree: 
80%, polymerization degree: 1,700), followed by stirring to completely 
dissolve the polyvinyl alcohol. The stirring was then interrupted once to 
add 70 parts of methyl methacrylate (hereinafter abbreviated as "MMA"), 10 
parts of styrene (hereinafter abbreviated as "St"), 10 parts of n-butyl 
acrylate (hereinafter abbreviated as "n-BA") and 10 parts of methacrylic 
acid (hereinafter abbreviated as "MAA"). Stirring was resumed, and 0.5 
part of azobisisobutylonitrile (hereinafter abbreviated as "AIBN") and 4 
parts of n-dodecylmercaptan (hereinafter abbreviated as "n-DM") were then 
added. The contents were heated to 75.degree. C. and were reacted for 3 
hours while maintaining the reaction temperature at 75.degree.-80.degree. 
C. The reaction mixture was then heated to 95.degree. C., at which the 
reaction mixture was held for 1 hour to complete the reaction. The 
reaction mixture was thereafter filtered through a mesh having an opening 
of 30 .mu.m, whereby a particulate vinyl polymer was obtained. The polymer 
so obtained had an acid value of 65 mg KOH/g, a weight average molecular 
weight of 12,000 and a second-order transition temperature of 87.degree. 
C. With respect to 1,000 particles of the resultant particulate vinyl 
polymer, their shapes were checked using a microscope. The percentage of 
particles, which had a minor axis A and a major axis B in the range of 
30-400 .mu.m and satisfied the relationship of B/A.ltoreq.1.5, was at 
least 99%. Further, the percentage of particles, which had a minor axis A 
and a major axis B in the range of 30-400 .mu.m and satisfied the 
relationship of B/A.ltoreq.1.1, was 97%. 
Examples 2-5 and Comparative Examples 1-4 
Production of Particulate Vinyl Polymers (P-2 to P-9) 
In each Example, a vinyl monomer composition was polymerized using a 
radical polymerization initiator and a chain transfer agent in a similar 
manner to Example 1. The compositions and characteristic values of the 
resultant particulate vinyl polymers (Examples 2-5: P-2 to P-5; 
Comparative Examples 1-4:P-6 to P-9) are presented in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Parti- 
culate Polymerization 
Chain trans- 
vinyl 
Vinyl monomer initiator 
fer agent 
polymer 
MMA St n-BA 
nBMA 
EHA MAA AA AIBN 
BPO n-DM 
MeSt 
__________________________________________________________________________ 
P-2 65 10 18 0 0 7 0 0.4 0 7 0 
P-3 51 0 0 0 29 20 0 0.5 0 4 0 
P-4 50 24 6 10 0 10 0 0 2 0 2.1 
P-5 49 5 0 37 0 6 3 0.8 0 3 0 
P-6 80 0 15.6 
0 0 4.4 0 0.5 0 6 0 
P-7 42 3 0 0 30 25 0 0.4 0 5 0 
P-8 73 0 0 15 0 12 0 0.3 0 0.1 0 
P-9 40 35 0 0 12 13 0 0 3 0 3 
__________________________________________________________________________ 
Parti- Weight- 
Second-order 
culate average 
transition 
Particles of 
Particles of 
vinyl 
Acid value 
molecular 
tempera- 
specified 
specified 
polymer 
[mgKOH/g] 
weight 
ture [.degree.C.] 
shape I [%] 
shape II [%] 
__________________________________________________________________________ 
P-2 45.5 8500 68 at least 99% 
97% 
P-3 130.0 11000 50 at least 99% 
98% 
P-4 65.2 21000 87 at least 99% 
98% 
P-5 63.0 16000 72 at least 99% 
97% 
P-6 28.7 8500 72 at least 99% 
96% 
P-7 163.0 10000 50 at least 99% 
97% 
P-8 78.3 120000 
98 at least 99% 
98% 
P-9 84.5 17000 80 at least 99% 
97% 
__________________________________________________________________________ 
Particles of specified shape I: 
The percentage of particles having a minor axis A and a major axis B in the 
range of 30-400 .mu.m and satisfying the relationship of 
1.ltoreq.B/A.ltoreq.1.5. 
Particles of specified shape II: 
The percentage of particles having a minor axis A and a major axis B in the 
range of 30-400 .mu.m and satisfying the relationship of 
1.ltoreq.B/A.ltoreq.1.1. 
Abbreviations: 
10 nBMA: n-butyl methacrylate 
EHA: ethylhexyl acrylate 
AA: acrylic acid 
BPO: benzoyl peroxide 
MeSt: .alpha.-methylstyrene dimer 
Comparative Example 5 
Production of Particulate Vinyl Polymer (P-10) 
Following the procedures of Example 1, the same vinyl monomer composition 
as that employed in Example 1 was polymerized and the polymerization 
suspension was dried by warm wind of 40.degree. C., so that a particulate 
vinyl polymer (P-10) was obtained. The polymer so obtained had an acid 
value of 65 mg KOH/g, a weight average molecular weight of 12,000 and a 
second-order transition temperature of 87.degree. C. With respect to 1,000 
particles of the resultant particulate vinyl polymer, their shapes were 
checked using a microscope. The percentage of particles, which had a minor 
axis A and a major axis B in the range of 30-400 .mu.m and satisfied the 
relationship of B/A.ltoreq.1.5, was 93.5%. 
Example 6 
Production of Particulate Vinyl Polymer (P-11) 
In a polymerizer equipped with a stirrer, a thermometer and a reflux 
condenser and permitting both heating and cooling, 100 parts of 
isopropanol, 65 parts of MMA, 10 parts of St, 12 parts of n-BA, 13 parts 
of MAA, 2 parts of AIBN and 3 parts of n-DM were charged and stirred. The 
contents were heated to 80.degree. C., followed by the initiation of a 
reaction. While adding 0.2 part of AIBN at every hour, the reaction 
mixture was maintained at the same temperature for 9 hours. The reaction 
was then terminated, whereby a solution of a vinyl polymer in isopropanol, 
whose solid content and viscosity were 51% and 10,000 cps, was obtained. 
The solution was depressurized while heating it at 70.degree. C., so that 
isopropanol was distilled off and the polymer was obtained in a solid 
form. The polymer in the solid form was heated to 200.degree. C. and while 
being maintained in the molten form, the polymer was poured into water of 
20.degree. C. under vigorous agitation to form the polymer into 
particles. The particles were then filtered through a mesh having an 
opening of 30 .mu.m, whereby a particulate vinyl polymer was obtained. The 
polymer so obtained had an acid value of 85.5 mg KOH/g, a weight average 
molecular weight of 13,000 and a second-order transition temperature of 
84.degree. C. With respect to 1,000 particles of the resultant particulate 
vinyl polymer, their shapes were checked using a microscope. The 
percentage of particles, which had a minor axis A and a major axis B in 
the range of 30-400 .mu.m and satisfied the relationship of 
B/A.ltoreq.1.5, was 96.0%. 
Comparative Example 6 
Production of Particulate Vinyl Polymer (P-12) 
In a polymerizer equipped with a stirrer, a thermometer and a reflux 
condenser and permitting both heating and cooling, 100 parts of 
isopropanol, 65 parts of MMA, 10 parts of St, 12 parts of n-BA, 13 parts 
of MAA, 2 parts of AIBN and 3 parts of n-DM were charged and stirred. The 
contents were heated to 80.degree. C., followed by the initiation of a 
reaction. While adding 0.2 part of AIBN at every hour, the reaction 
mixture was maintained at the same temperature for 9 hours. The reaction 
was then terminated, whereby a solution of a vinyl polymer in isopropanol, 
whose solid content and viscosity were 51% and 10,000 cps, was obtained. 
The solution was depressurized while heating it at 70.degree. C., so that 
isopropanol was distilled off and the polymer was obtained in a solid 
form. The solid polymer was formed into slender rods of 3 mm in diameter 
by a twin-screw kneader. Those slender rods were chopped by a pelletizer 
under conditions satisfying the relationship of B/A.ltoreq.1.5, whereby a 
particulate vinyl polymer was obtained. The polymer so obtained had an 
acid value of 85.5 mg KOH/g, a weight average molecular weight of 13,000 
and a second-order transition temperature of 84.degree. C. With respect to 
1,000 particles of the resultant particulate vinyl polymer, their shapes 
were checked. The percentage of particles, which had a major axis B of 400 
.mu.m or longer, was at least 99%. 
Comparative Example 7 
Production of Particulate Vinyl Polymer (P-13) 
In a polymerizer equipped with a stirrer, a thermometer and a reflux 
condenser and permitting both heating and cooling, 100 parts of 
isopropanol, 65 parts of MMA, 10 parts of St, 12 parts of n-BA, 13 parts 
of MAA, 2 parts of AIBN and 3 parts of n-DM were charged and stirred. The 
contents were heated to 80.degree. C., followed by the initiation of a 
reaction. While adding 0.2 part of AIBN at every hour, the reaction 
mixture was maintained at the same temperature for 9 hours. The reaction 
was then terminated, whereby a solution of a vinyl polymer in isopropanol, 
whose solid content and viscosity were 51% and 10,000 cps, was obtained. 
The solution was poured into a vat and while being heated at 70.degree. 
C., depressurized, so that isopropanol was distilled off and the polymer 
was obtained in a bulk form. The bulk polymer was then ground by a grinder 
so that particles having a major axis B not greater than 400 .mu.m 
(B.ltoreq.400 .mu.m) accounted for at least 98%, whereby a particulate 
vinyl polymer was obtained. The polymer so obtained had an acid value of 
85.5 mg KOH/g, a weight average molecular weight of 13,000 and a 
second-order transition temperature of 84.degree. C. With respect to 1,000 
particles of the resultant particulate vinyl polymer, their shapes were 
checked using a microscope. Seventy percent of the particulate vinyl 
polymer satisfied the relationship of B/A.ltoreq.1.5. Further, particles 
having a minor axis A and a major axis B not greater than 30 .mu.m 
accounted to 30%. 
Evaluation Tests 
The workability of each of the particulate vinyl polymers (P-1) to (P-13), 
its solubility in an aqueous medium and its properties as a water-base 
coating composition were evaluated in accordance with the evaluation 
standards described above. The results are presented in Table 2. 
TABLE 2 
__________________________________________________________________________ 
Evaluation of aqueous 
Particu- 
Workability Solubility 
coating composition 
late vinyl 
Free flowing 
Dust-free 
in aqueous 
Pigment 
Water 
polymer 
property 
property 
medium 
dispersion 
Proofness 
__________________________________________________________________________ 
Example No. 
Example 1 
P-1 Good Good Excellent 
Excellent 
Excellent 
Example 2 
P-2 Good Good Excellent 
Excellent 
Excellent 
Example 3 
P-3 Good Good Excellent 
Excellent 
Good 
Example 4 
P-4 Good Good Good Excellent 
Excellent 
Example 5 
P-5 Good Good Excellent 
Excellent 
Good 
Example 6 
P-11 
Good Slightly 
Excellent 
Excellent 
Good 
good 
Comparative 
Example 
No. 
Comp. Ex. 1 
P-6 Good Good Insoluble 
No data available due 
to lack of solubility 
in aqueous medium 
Comp. Ex. 2 
P-7 Good Good Excellent 
Excellent 
Poor 
Comp. Ex. 3 
P-8 Good Good Insoluble 
No data available due 
to lack of solubility 
in aqueous medium 
Comp. Ex. 4 
P-9 Good Good Insoluble 
No data available due 
to lack of solubility 
in aqueous medium 
Comp. Ex. 5 
P-10 
Poor Good Excellent 
Excellent 
Excellent 
Comp. Ex. 6 
P-12 
Good Good Poor Good Good 
Comp. Ex. 7 
P-13 
Poor Poor Excellent 
Good Good 
__________________________________________________________________________ 
Examples 8-10 
Production of Particulate Vinyl Polymers (P-14 to P-16) 
In each Example, a vinyl monomer composition was polymerized using a 
radical polymerization initiator and a chain transfer agent in a similar 
manner to Example 1. The compositions and characteristic values of the 
resultant particulate vinyl polymers (P-14 to P-16) are presented in Table 
3. 
TABLE 3 
__________________________________________________________________________ 
Parti- 
culate Polymerization 
Chain trans- 
vinyl 
Vinyl monomer initiator 
fer agent 
polymer 
MMA St n-BA 
nBMA 
EHA MAA AA AIBN 
BPO n-DM 
MeSt 
__________________________________________________________________________ 
P-14 52 0 0 0 34 14 0 0.4 0 4 0 
P-15 60 17 0 10 0 10 3 0 2 0 2.1 
P-16 42 5 0 37 0 18 0 0.8 0 3 0 
__________________________________________________________________________ 
Parti- Weight- 
Second-order 
culate average 
transition 
Particles of 
Particles of 
vinyl 
Acid value 
molecular 
tempera- 
specified 
specified 
polymer 
[mgKOH/g] 
weight 
ture [.degree.C.] 
shape I [%] 
shape II [%] 
__________________________________________________________________________ 
P-14 91.0 11000 37 at least 99% 
98% 
P-15 88.6 21000 100 at least 99% 
97% 
P-16 117.4 16000 79 at least 99% 
98% 
__________________________________________________________________________ 
Synthesis Example 1 
Preparation of Aqueous Polymer Dispersion (II-1) 
In a polymerizer equipped with a stirrer, a thermometer and a reflux 
condenser and permitting both heating and cooling, were charged 100 parts 
of deionized water, 2 parts of polyoxyethylene nonylphenyl ether 
containing 35 oxyethylene units, 1 part of sodium lauryl sulfate and 0.5 
part of potassium persulfate. Stirring was then initiated and the contents 
were heated to 70.degree. C., followed by the dropwise addition of a 
mixture of 57 parts of MMA, 25 parts of n-butyl methacrylate, 15 parts of 
n-BA and 3 parts of MAA over 4 hours. The resulting mixture was then 
heated to 80.degree. C., at which the reaction mixture was held for 2 
hours to complete the reaction so that an aqueous polymer dispersion was 
obtained. The polymer so formed had a second-order transition temperature 
of 52.degree. C. and a weight average molecular weight of 1,000,000. The 
aqueous dispersion had a solid content of 50% and a viscosity of 3,000 
cps. 
Synthesis Example 2 
Preparation of Aqueous Polymer Dispersion (II-2) 
By a preparation process similar to that of Synthesis Example 1, was 
polymerized a mixture of vinyl monomers consisting of 85 parts of St, 14 
parts of ethylhexyl acrylate and 1 part of MAA. A polymer whose 
second-order transition temperature and weight average molecular weight 
were 67.degree. C. and 500,000 was obtained. An aqueous dispersion so 
obtained had a solid content of 50% and a viscosity of 800 cps. 
Synthesis Example 3 
Preparation of Aqueous Polymer Dispersion (II-3) 
In a polymerizer equipped with a stirrer, a thermometer and a reflux 
condenser and permitting both heating and cooling, were charged 25 parts 
of isopropanol, 42 parts of MMA, 23 parts of St, 28 parts of n-BMA, 7 
parts of MAA and 0.1 part of AIBN. The contents were then heated to 
80.degree. C., at which the contents were held for 7 hours while charging 
0.1 part of AIBN every hour. The reaction mixture was then cooled to 
50.degree. C., followed by the gradual charging of 3.1 parts of 28% 
aqueous ammonia and 150 parts of deionized water. The resulting mixture 
was then heated to 95.degree. C. over 3 hours, whereby isopropanol was 
distilled off to about 1% of its initial charge to obtain an aqueous 
polymer dispersion. A polymer whose second-order transition temperature 
and weight average molecular weight were 76.degree. C. and 350,000 was 
obtained. An aqueous dispersion so obtained had a solid content of 40% and 
a viscosity of 200 cps. 
Synthesis Example 4 
Preparation of Aqueous Polymer Dispersion (II-4) 
In a 1,000-ml reaction vessel equipped with a stirrer, a thermometer and a 
condenser, were charged 13 parts of dimethylolpropionic acid, 80 parts of 
N-methyl-2-pyrrolidone, 100 parts of polytetramethylene glycol and 5 parts 
of trimethylol propane. The contents were heated to 90.degree. C. so that 
they were converted into a solution. Next, 48 parts of isophorone 
diisocyanate were added and after stirring it for 10 minutes, 0.1 part of 
dibutyl tin dilaurate was added. The resulting mixture was then heated to 
95.degree. C., at which a reaction was conducted for 1 hour. 
After the hydrophilic-group-containing oligomer so obtained was neutralized 
with 5 parts of triethylamine, 300 parts of deionized water were added, 
followed by stirring for 1 hour to obtain an aqueous dispersion. A polymer 
whose second-order transition temperature and weight average molecular 
weight were 40.degree. C. and 220,000 was obtained. An aqueous dispersion 
so obtained had a solid content of 29% and a viscosity of 8,000 cps. 
Example 11 
Weighed in a beaker were 60 g of a 25%-solid aqueous solution (I-1) of the 
particulate vinyl polymer (P-1; neutralization degree of the acidic 
groups: 100%), which had been produced according to the process described 
above under the Solubility Test, and 120 g of the aqueous polymer 
dispersion (II-1). They were gently mixed with a stick so that a liquid 
blend formulation [a water-base coating composition (B)] was prepared. In 
this case, the ratio of the aqueous solution (I-1) of the particulate 
vinyl polymer to the aqueous polymer dispersion (II-1) was 20:80 in terms 
of polymer solid. No precipitate was observed upon an elapsed time of 24 
hours after the blending, whereby good compatibility of the particulate 
vinyl polymer (P-1) as a solution was confirmed. The liquid blend 
formulation was coated on a glass plate to give a solid film thickness of 
80 .mu.m. When dried in an environment controlled at 15.degree. C. and 60% 
RH, the liquid blend formulation so coated became tack-free in 2 minutes 
so that a transparent coating film free of cracks was formed. Even when 
the coating film was rubbed with a nail, no damages such as scratches were 
observed on the coating film. Further, two glass plates coated in the 
above-described manner were provided. Those glass plates were superposed 
one over the other with their coated sides maintained in a contiguous 
relationship and were then left over for 2 days in an environment 
controlled at 30.degree. C. and 70% RH. No cohesion between the coating 
films was observed. After a further glass plate also coated in the 
above-described manner was immersed for 20 hours in deionized water of 
30.degree. C., the coated glass plate was pulled out of the deionized 
water and then left over for 1 hour in a room controlled at 15.degree. C. 
and 60% RH. No changes were observed on its coating film. 
Examples 12-18 and Comparative Examples 8-10 
In each Example, a liquid blend formulation was prepared and evaluated as 
in Example 11. The results are presented in Table 4. Symbols assigned to 
represent the results of the respective evaluation tests have the 
following meanings: 
Compatibility 
Solution 
S: No precipitate was observed. 
IS: Precipitate was observed. 
Coating film 
C: The coating film was transparent, indicating good compatibility. 
VSH: The coating film was slightly opaque, indicating somewhat poor 
compatibility. 
SH: The coating film was more opaque than the VSH rank, indicating lower 
quality in compatibility than the VSH rank. 
H: The coating film was more opaque than the SH rank, indicating lower 
quality in compatibility than the SH rank (quality level of no practical 
utility). 
Film-Forming Ability 
A glass plate was coated to give a solid thickness of 80 .mu.m, follower by 
drying in in environment controlled at 15.degree. C. and 60% RH. 
Good: A good coating film free of cracks was formed. 
Poor: Cracks were formed in the coating film. 
Abrasion Resistance (Toughness of Coating Film) 
A glass plate was coated to give a solid thickness of 80 .mu.m, followed by 
drying in an environment controlled at 15.degree. C. and 60% RH. The 
coating film so formed was then rubbed with a nail. 
Good: No damages such as scratches were observed on the coating film. 
Poor: The coating film was damaged, for example, scratched or crazed. 
Blocking Resistance 
Two glass plates were each coated to give a solid film thickness of 80 
.mu.m, followed by drying in an environment controlled at 15.degree. C. 
and 60% RH. The glass plates were superposed one over the other with their 
coated sides maintained in a contiguous relationship and were then left 
over for 2 days in an environment controlled at 30.degree. C. and 70% RH. 
Good: No cohesion was observed between the coating films. 
Poor: The coating films cohered. 
Waterproofness 
A glass plate was coated to give a solid film thickness of 80 .mu.m, 
followed by drying in an environment controlled at 15.degree. C. and 60% 
RH. The glass plate was immersed for 2 days in warm water of 40.degree. C. 
and was then pulled out of the warm water. The glass plate was thereafter 
left over for 1 hour in a room controlled at 15.degree. C. and 60% RH. 
Good: No changes were observed on the coating film. 
Poor: The coating film was subjected to a certain damage such as whitening. 
TABLE 4 
__________________________________________________________________________ 
Example/Compara- 
tive Example No. 
Example 12 
Example 13 
Example 14 
Example 15 
Example 16 
__________________________________________________________________________ 
Aqueous soln. of particu- 
I-1(P-1) 
I-2(P-2) 
I-14(P-14) 
I-15(P-15) 
I-1(P-1) 
late vinly polymer (polymer) 
Workability 
Free flowing 
Good Good Good Good Good 
of property 
particulate 
Dust-free 
Good Good Good Good Good 
vinyl property 
polymer 
Solubility of particulate 
Excellent 
Excellent 
Excellent 
Good Excellent 
vinyl polymer in aq. medium 
Aqueous dispersion of polymer 
II-2 II-4 II-3 II-1 II-4 
I/II (solid ratio of polymer) 
50/50 20/80 40/60 50/50 20/80 
Compatibility 
Solution 
S S S S S 
Coated film 
C C C C C 
Film-forming property 
Good Good Good Good Good 
Abrasion resistance 
Good Good Good Good Good 
Blocking resistance 
Good Good Good Good Good 
Waterproofness Good Good Good Good Good 
__________________________________________________________________________ 
Example/Compara- 
tive Example No. 
Example 17 
Example 18 
Comp. Ex. 8 
Comp. Ex. 9 
Comp. Ex. 10 
__________________________________________________________________________ 
Aqueous soln. of particu- 
I-16(P-16) 
I-11(P-11) 
I-14(P-14) 
I-6(P-6) 
I-7(P-7) 
late vinly polymer (polymer) 
Workability 
Free flowing 
Good Good Good Good Good 
of property 
particulate 
Dust-free 
Good Slightly 
Good Good Good 
vinyl property good 
polymer 
Solubility of particulate 
Excellent 
Excellent 
Excellent 
Insoluble 
Excellent 
vinyl polymer in aq. medium 
Aqueous dispersion of polymer 
II-2 II-3 II-2 No data 
II-4 
I/II (solid ratio of polymer) 
8/92 35/65 3/97 available 
10/90 
due to 
lack of 
solubili- 
ty in 
aqueous 
medium 
Compatibility 
Solution 
S S S No data 
IS 
Coated film 
VSH VSH C available 
H 
Film-forming property 
Good Good Poor due to Good 
Abrasion resistance 
Good Good Poor lack of 
Good 
Blocking resistance 
Good Good Good solubili- 
Good 
Waterproofness Good Good Good ty in Poor 
aqueous 
medium 
__________________________________________________________________________ 
Examples 19-21 and Comparative Example 11 
Production of Particulate Vinyl Polymers (P-17 to P-20) 
In each Example, a vinyl monomer composition was polymerized using a 
radical polymerization initiator and a chain transfer agent in a similar 
manner to Example 1. The compositions and characteristic values of the 
resultant particulate vinyl polymers (Examples 19-21: P-17 to P-19, 
Comparative Example 11: P-20) are presented in Table 5. 
TABLE 5 
__________________________________________________________________________ 
Parti- 
culate Polymerization 
Chain trans- 
vinyl 
Vinyl monomer initiator 
fer agent 
polymer 
MMA St n-BA 
nBMA 
EHA MAA AA AIBN 
BPO n-DM 
MeSt 
__________________________________________________________________________ 
P-17 45 10 38 0 0 7 0 0.4 0 5 0 
P-18 68 0 0 15 0 14 0 0.4 0 4 0 
P-19 60 20 0 0 7 10 3 0 2 0 2.5 
P-20 40 3 0 0 25 32 0 0.4 0 5 0 
__________________________________________________________________________ 
Parti- Weight- 
Second-order 
culate average 
transition 
Particles of 
Particles of 
vinyl 
Acid value 
molecular 
tempera- 
specified 
specified 
polymer 
[mgKOH/g] 
weight 
ture [.degree.C.] 
shape I [%] 
shape II [%] 
__________________________________________________________________________ 
P-17 45.5 9000 32 at least 99% 
96% 
P-18 91.0 11000 110 at least 99% 
97% 
P-19 88.2 17000 92 at least 99% 
97% 
P-20 208.5 10000 65 at least 99% 
98% 
__________________________________________________________________________ 
Synthesis Example 5 
Preparation of Aqueous Urethane Polymer Dispersion (IV-1) 
In a 1,000-ml reaction vessel equipped with a thermometer, a stirrer and a 
condenser, were charged 13 parts of dimethylolpropionic acid, 80 parts of 
N-methyl-2-pyrrolidone and 100 parts of polytetramethylene glycol (number 
average molecular weight: 1,900). The contents were heated to 90.degree. 
C. Next, 48 parts of isophorone diisocyanate were added and after stirring 
it for 10 minutes, 0.1 part of dibutyl tin dilaurate was added. The 
resulting mixture was then heated to 95.degree. C., at which a reaction 
was conducted for 1 hour. 
After the hydrophilic-group-containing urethane polymer so obtained was 
neutralized with 10 parts of triethylamine, 300 parts of deionized water 
were added, followed by stirring for 1 hour to extend the polymer with 
water. The resultant mixture was a stable aqueous dispersion, whose solid 
content and viscosity were 29.2% and 5,000 cps. 
Synthesis Example 6 
Preparation of Aqueous Urethane Polymer Dispersion (IV-2) 
In the same reaction vessel as that employed in Synthesis Example 5, were 
charged 6 parts of dimethylolpropionic acid, 40 parts of 
N-methyl-2-pyrrolidone and 100 parts of polypropylene glycol (number 
average molecular weight: 1,850). The contents were heated to 90.degree. 
C. Next, 48 parts of isophorone diisocyanate were added and after stirring 
it for 10 minutes, 35 parts of hexamethylene diisocyanate were added. The 
resulting mixture was stirred for 10 minutes, followed by the addition of 
0.1 part of dibutyl tin dilaurate. The mixture so obtained was heated to 
95.degree. C. and was then reacted for 1 hour. 
After the hydrophilic-group-containing urethane polymer so obtained was 
neutralized with 5 parts of triethylamine, 300 parts of deionized water 
were added, followed by stirring for 1 hour to extend the polymer with 
water. The resultant mixture was a stable aqueous dispersion, whose solid 
content and viscosity were 30.2% and 1,000 cps. 
Synthesis Example 7 
Preparation of Aqueous Urethane Polymer Dispersion (IV-3) 
In the same reaction vessel as that employed in Synthesis Example 5, were 
charged 6 parts of dimethylolpropionic acid, 40 parts of 
N-methyl-2-pyrrolidone and 42 parts of polyethylene glycol (number average 
molecular weight: 2,200). The contents were heated to 90.degree. C. Next, 
48 parts of isophorone diisocyanate were added and after stirring it for 
10 minutes, 35 parts of hexamethylene diisocyanate were added. The 
resulting mixture was stirred for 10 minutes, followed by the addition of 
0.1 part of dibutyl tin dilaurate. The mixture so obtained was heated to 
95.degree. C. and was then reacted for 1 hour. 
After the hydrophilic-group-containing urethane polymer so obtained was 
neutralized with 10 parts of triethylamine, 300 parts of deionized water 
were added, followed by dispersion in water. The dispersion so obtained 
was added with 8 parts of isophoronediamine, followed by stirring for 1 
hour so that the urethane polymer was extended with the diamine. The 
resultant mixture was a stable aqueous dispersion, whose solid content and 
viscosity were 30.2% and 1,000 cps. 
Example 22 
Weighed in a beaker were 60 g of a 25%-solid aqueous solution (III-1) of 
the particulate vinyl polymer (P-1; neutralization degree of the acidic 
groups: 100%), which had been produced according to the process described 
above under the Solubility Test, and 120 g of the aqueous urethane polymer 
dispersion (IV-1). They were gently mixed with a stick so that a liquid 
blend formulation [a water-base coating composition (C)] was prepared. In 
this case, the ratio of the aqueous solution (III-1) of the particulate 
vinyl polymer to the aqueous urethane polymer dispersion (IV-1) was 30:70 
in terms of polymer solid. No precipitate was observed upon an elapsed 
time of 24 hours after the blending, whereby good compatibility of the 
particulate vinyl polymer (P-1) as a solution was confirmed. The liquid 
blend formulation was coated on a glass plate to give a solid film 
thickness of 80 .mu.m. When dried, the liquid blend formulation so coated 
turned to a transparent coating film so that the particulate vinyl polymer 
was confirmed to have good compatibility with the urethane polymer in the 
coating film. Twenty parts of "Carbon Black #100" (trade name; product of 
Degussa Inc.) were added to 100 parts of the polymers in the liquid blend 
formulation. The resulting mixture was mixed for 2 hours in a planetary 
ball mill (manufactured by FRITSCH INC.) so that the pigment was 
dispersed. The resultant pigment dispersion was then left over for 3 days 
at room temperature. No settling of the pigment was observed. Further, the 
liquid blend formulation was coated on a polyester film ("Lumirror E-35", 
trade name; product of Toray Industries, Inc) to give dry film thickness 
of 20 .mu.m, followed by drying. A adhesive cellophane tape (product of 
Nichiban Co., Ltd.) was pressed against the coating film and was then 
peeled off. The coating film was not stuck off onto an adhesive layer of 
the cellophane tape. 
Examples 23-28 and Comparative Examples 12-14 
In each Example, a liquid blend formulation was prepared and evaluated as 
in Example 22. The results are presented in Table 6. Symbols assigned to 
represent the results of the respective evaluation tests have the 
following meanings: 
Compatibility 
The symbols have the same meanings as described above with respect to Table 
4. 
Pigment dispersibility 
Good: No settling of the pigment was observed three days later. 
Poor: Setting of the pigment was observed three days later. 
Adhesion 
Good: Not stuck off onto the adhesive layer of the cellophane tape. 
Poor: Stuck off onto the adhesive layer of the cellophane tape. 
TABLE 6 
__________________________________________________________________________ 
Example/Compara- 
tive Example No. 
Example 23 
Example 24 
Example 25 
Example 26 
Example 27 
__________________________________________________________________________ 
Aqueous soln. of Particulate 
III-1(P-1) 
III-1(P-1) 
III-17(P-17) 
III-18(P-18) 
III-19(P-19) 
vinly polymer (polymer) 
Workability 
Free flowing 
Good Good Good Good Good 
of property 
particulate 
Dust-free 
Good Good Good Good Good 
vinyl property 
polymer 
Solubility of particulate 
Excellent 
Excellent 
Excellent 
Excellent 
Excellent 
vinyl polymer in aq. medium 
Aqueous dispersion of polymer 
IV-1 IV-2 IV-3 IV-2 IV-3 
III/IV (solid ratio of polymer) 
70/30 25/75 85/15 50/50 20/80 
Compatibility 
Solution 
S S S S S 
Coated film 
C C C C C 
Film-forming property 
Good Good Good Good Good 
Pigment dispersibility 
Good Good Good Good Good 
Adhesion Good Good Good Good Good 
__________________________________________________________________________ 
Example/Compara- 
tive Example No. 
Example 28 
Comp. Ex. 12 
Comp. Ex. 13 
Comp. Ex. 14 
__________________________________________________________________________ 
Aqueous soln. of Particulate 
III-11(P-11) 
III-6(P-20) 
III-6(P-20) 
III-1(P-1) 
vinly polymer (polymer) 
Workability 
Free flowing 
Good Good Good Good 
of property 
particulate 
Dust-free 
Good Good Good Good 
vinyl property 
polymer 
Solubility of particulate 
Excellent 
Insoluble 
Excellent 
Excellent 
vinyl polymer in aq. medium 
Aqueous dispersion of polymer 
IV-1 No data 
IV-2 IV-1 
III/IV (solid ratio of polymer) 
25/75 available 
30/70 3/97 
due to 
lack of 
solubili- 
ty in 
aqueous 
medium 
Compatibility 
Solution 
S No data 
IS S 
Coated film 
VSH available 
H C 
Film-forming property 
Good due to Good Poor 
Pigment dispersilbility 
Good lack of 
Poor Poor 
Adhesion Good solubili- 
Good Good 
ty in 
aqueous 
medium 
__________________________________________________________________________ 
The particulate vinyl polymer according to the present invention is 
excellent in workability such as the dissolution in an aqueous medium and 
also superb in pigment dispersibility and waterproofness, and is 
industrially very valuable as a raw material for water-base coating 
compositions. 
The water-base coating composition (A) can form a coating film excellent in 
both waterproofness and pigment dispersion. The above advantageous effects 
of the particulate vinyl polymer according to this invention are marked in 
a water-base coating composition free of any organic solvent, because no 
conventional particulate vinyl polymer, when coated without any organic 
solvent, can achieve excellent waterproofness and superb pigment 
dispersion at the same time. 
According to the water-base coating composition (B), a crack-free tough 
coating film can be formed without using any organic solvent. This coating 
film has a glass transition point Tg higher than room temperature, is 
excellent in antifouling property, blocking resistance and waterproofness, 
and also has good drying property. Further, the aqueous solution of the 
particulate vinyl polymer of this invention has broad compatibility with 
aqueous dispersions of various polymers so that mere blending of the 
aqueous solution and the aqueous dispersions permits their hybridization. 
A wide variety of water-base coating compositions can be easily developed 
as commercial products. 
The water-base coating composition (C) has good pigment dispersibility, 
does not form much insoluble agglomerates upon coating, and can form a 
tough coating film having good adhesion to a plastic film. Further, the 
water-base coating composition (C) can be prepared by simply blending an 
aqueous dispersion of a urethane polymer with an aqueous solution of a 
vinyl polymer. A wide variety of commercial products can therefore be 
developed.