Patent Description:
In recent years, coatings with paints are performed so as to prevent dirt in various uses including: electric appliances, such as portable telephones, personal computers, televisions, and plasma displays; transportation equipment, such as motor vehicles and trains; and further various everyday necessities.

As a paint with excellent antifouling property, generally, a composition using an additive which contains fluorine in a molecule (Patent Document <NUM>) is known. However, because the material is expensive, and from the standpoint of environmental issues, fluorine-free additives are required. From the same standpoint of environmental issues, water-based (water-soluble, water-dispersible) materials are also attracting attention as paints to be used.

As a fluorine-free paint additive, a polyether-modified silicone is widely used as paint additive for reasons of surface leveling property, defoaming property, etc. (Patent Document <NUM>). However, a polyether-modified silicone imparting excellent antifouling performance is not known.

On the other hand, as a polyether-modified silicone for enhancing an emulsifying property for cosmetics, a siloxane-branched polyether-modified silicone produced by addition reaction of a polyoxyalkylene compound and a silicone compound to an organohydrogenpolysiloxane is known (Patent Document <NUM>). However, the document does not disclose applications for paints at all. <CIT> discloses a production method of a liquid high-purity polyhydric alcohol derivative-modified silicone or a composition thereof, the method comprising: a capturing step of bringing into an impurity-containing composition containing a liquid polyhydric alcohol derivative-modified silicone and hydrophilic impurities originating from a polyhydric alcohol derivative, the polyhydric alcohol derivative being a hydrophilic modifier of the polyhydric alcohol derivative-modified silicone, into contact with solid particles capable of capturing the hydrophilic impurities, and then capturing the hydrophilic impurities with the solid particles; and a separating step of separating the polyhydric alcohol derivative-modified silicone and the solid particles. <CIT> discloses a liquid organopolysiloxane having fluidity at at least <NUM>, a silicon-bonded glycerin derivative group, and a crosslinked structure comprising a carbon-silicon bond at the crosslinking portion. <CIT> discloses silicone material that is a organopolysiloxane or acid-neutralized salt thereof that contains a side-chain bonded hydrophilic group having tertiary-amine structure and is represented by formula: -CqH2q-O-CH<NUM>-CH(OH)-CH<NUM>-N(RQ1)(RQ2), wherein q is a number ranging from <NUM> to <NUM>, RQ1 and RQ2 are a halogen-substituted or non-substituted monovalent hydrocarbon group or alkanol group, at least one of RQ1 and RQ2 has a hydroxyl group, but total number of hydroxyl groups in RQ1 and RQ2 is <NUM> or less, and any of RQ1 and RQ2 does not have a nitrogen atom in the group. <CIT> discloses a co-modified organopolysiloxane having a viscosity at <NUM> of not more than <NUM>,<NUM> mPa·s, a group that has a siloxane dendron structure, and a hydrophilic group.

The present invention has been made in view of the circumstance. An object of the present invention is to provide: a paint additive and a paint composition, particularly a water-based paint, with small environmental load and imparting excellent antifouling performance.

To achieve the object, the present invention provides an additive for water-based paint, comprising a siloxane-branched polyether-modified silicone shown by an average composition formula (<NUM>) R<NUM>aR<NUM>bR<NUM>cSiO(<NUM>-a-b-c)/<NUM> and having a weight-average molecular weight in a range of <NUM> to <NUM>,<NUM>,
wherein in the formula (<NUM>) each R<NUM> is identical to or different from one another and represents an organic group selected from an alkyl group, an aryl group, and an aralkyl group having <NUM> to <NUM> carbon atoms, and an organic group shown by a general formula (<NUM>) -CmH<NUM>-O-(C<NUM>H<NUM>O)d(C<NUM>H<NUM>)eR<NUM>;.

Such an additive for water-based paint can have little environmental load and impart excellent antifouling performance.

Moreover, the additive for water-based paint preferably further comprises a solvent.

Such an additive for water-based paint can have more excellent workability.

Further, the present invention provides a water-based paint composition comprising the additive for water-based paint.

Such a paint composition, particularly a water-based paint, contains the paint additive which successfully reduces environmental load and imparts excellent antifouling performance.

Furthermore, the inventive water-based paint composition preferably comprises a resin selected from the group consisting of urethane resins, acrylic resins, amide resins, phenolic resins, epoxy resins, melamine resins, urea resins, alkyd resins, polyimide resins, polyalkylene resins, polyvinyl chloride, polystyrene, polyvinyl acetate, and alloys of the resins.

Such various resins can be employed in the inventive water-based paint composition.

In this case, the resin is preferably a urethane resin or an acrylic resin.

These resins are preferable because of good compatibility with the additive for water-based paint containing the siloxane-branched polyether-modified silicone.

In addition, the inventive water-based paint composition is preferably used for antifouling paint.

The inventive water-based paint composition can exhibit excellent antifouling property without impairing various paint properties, such as defoaming property and leveling property.

Further, the present invention provides a coating layer formed from the water-based paint composition.

The inventive coating layer can be applied to various base materials, and exhibits excellent antifouling property.

The use of the inventive additive for water-based paint containing the siloxane-branched polyether-modified silicone makes it possible to provide the water-based paint composition and coating layer with small environmental load and excellent antifouling property.

As described above, there have been demands for the development of a paint additive, as well as a paint composition and particularly a water-based paint, with small environmental load and imparting excellent antifouling performance.

The present inventor has diligently investigated to achieve the above object and consequently found that a siloxane-branched polyether-modified silicone imparts excellent antifouling performance to a paint, and completed the present invention.

Specifically, the present invention is an additive for water-based paint, comprising a siloxane-branched polyether-modified silicone shown by an average composition formula (<NUM>) R<NUM>aR<NUM>bR<NUM>cSiO(<NUM>-a-b-c)/<NUM> and having a weight-average molecular weight in a range of <NUM> to <NUM>,<NUM>,
wherein in the formula (<NUM>) each R<NUM> is identical to or different from one another and represents an organic group selected from an alkyl group, an aryl group, and an aralkyl group having <NUM> to <NUM> carbon atoms, and an organic group shown by a general formula (<NUM>) -CmH<NUM>-O-(C<NUM>H<NUM>O)d(C<NUM>H<NUM>O)eR<NUM>;.

However, the present invention is not limited thereto but defined in the claims.

The siloxane-branched polyether-modified silicone contained in the additive for water-based paint of the present invention is shown by an average composition formula (<NUM>) R<NUM>aR<NUM>bR<NUM>cSiO(<NUM>-a-b-c)/<NUM>. In the formula (<NUM>), each R<NUM> is identical to or different from one another and represents an organic group selected from an alkyl group, an aryl group, and an aralkyl group having <NUM> to <NUM> carbon atoms, and an organic group shown by a general formula (<NUM>) -CmH<NUM>-O-(C<NUM>H<NUM>O)d(C<NUM>H<NUM>O)eR<NUM>. Each R<NUM> represents a group shown by a general formula (<NUM>) -CmH<NUM>-O-(C<NUM>H<NUM>O)f(C<NUM>H<NUM>O)g-R<NUM>. Each R<NUM> represents an organosiloxane shown by the following general formula (<NUM>)
<CHM>.

R<NUM> represents a hydrocarbon group having <NUM> to <NUM> carbon atoms, or an organic group shown by R<NUM>-(CO)-. R<NUM> represents a hydrogen atom, a hydrocarbon group having <NUM> to <NUM> carbon atoms, or an organic group shown by R<NUM>-(CO)-. R<NUM> represents a hydrocarbon group having <NUM> to <NUM> carbon atoms. R<NUM> in the general formula (<NUM>) is the same as R<NUM> in the formula (<NUM>). "a", "b", and "c" respectively satisfy <NUM>≤a≤<NUM>, <NUM>≤b≤<NUM>, and <NUM>≤c≤<NUM>. "d" and "e" respectively represent integers satisfying <NUM>≤d≤<NUM> and <NUM>≤e≤<NUM>. "f" and "g" respectively represent integers satisfying <NUM>≤f≤<NUM>, <NUM>≤g≤<NUM>, and f+g being <NUM> to <NUM>. "m" represents an integer satisfying <NUM>≤m≤<NUM>. "h" represents an integer satisfying <NUM>≤h≤<NUM>. "n" represents an integer satisfying <NUM>≤n≤<NUM>.

Further, the siloxane-branched polyether-modified silicone satisfies the following expression (I), <MAT> and the following expression (II), <MAT>.

R<NUM> in the formulae is an alkyl group, an aryl group, and an aralkyl group having <NUM> to <NUM> carbon atoms. R<NUM> is preferably an alkyl group, an aryl group, and an aralkyl group having <NUM> to <NUM> carbon atoms. R<NUM> is particularly preferably a methyl group, an ethyl group, a propyl group, a hexyl group, an octyl group, a dodecyl group, a phenyl group, and a <NUM>-phenylpropyl group. Preferably, <NUM>% or more of R<NUM>'s are methyl groups.

Alternatively, R<NUM> may be an alkoxy group, an ester group, an alkenyl ether residue, or an alkenyl ester residue shown by the general formula (<NUM>) -CmH<NUM>-O-(C<NUM>H<NUM>O)d(C<NUM>H<NUM>O)e-R<NUM>. Herein R<NUM> in the formula (<NUM>) is a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms, or an organic group shown by R<NUM>-(CO)-, and preferably a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms, or an organic group shown by R<NUM>-(CO)- because of availability. R<NUM> is a hydrocarbon group having <NUM> to <NUM> carbon atoms, and preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms because of availability.

"d", "e" and "m" are respectively integers satisfying <NUM>≤d≤<NUM>, <NUM>≤e≤<NUM>, and <NUM>≤m≤<NUM>, and preferably integers satisfying <NUM>≤d≤<NUM>, <NUM>≤e≤<NUM>, and <NUM>≤m≤<NUM> because of availability. Incidentally, when the polyoxyalkylene moiety in the formula (<NUM>) is composed of both ethyleneoxide units and propyleneoxide units, the polyoxyalkylene moiety may be any of a block polymer and a random polymer of these two units.

R<NUM> is a group shown by the general formula (<NUM>) - CmH<NUM>-O-(C<NUM>H<NUM>O)f(C<NUM>H<NUM>O)g-R<NUM>. Herein R<NUM> in the formula (<NUM>) represents a hydrogen atom, a monovalent hydrocarbon group having <NUM> to <NUM> carbon atoms, or an organic group shown by R<NUM>-(CO)-, and preferably a hydrocarbon group having <NUM> to <NUM> carbon atoms, an organic group shown by R<NUM>-(CO)-, or a hydrogen atom because of availability. R<NUM> is as defined above.

"f" and "g" are respectively integers satisfying <NUM>≤f≤<NUM> and <NUM>≤g≤<NUM>, and preferably integers satisfying <NUM>≤f≤<NUM> and <NUM>≤g≤<NUM> because of availability. Further, f+g is an integer satisfying <NUM> to <NUM>, and preferably an integer satisfying <NUM> to <NUM>. If f+g is smaller than <NUM>, the antifouling property lowers. If f+g is larger than <NUM>, the synthesis is hindered. "m" is as defined above.

Incidentally, like the formula (<NUM>), when the polyoxyalkylene moiety in the formula (<NUM>) is composed of both ethyleneoxide units and propyleneoxide units, the polyoxyalkylene moiety may be any of a block polymer and a random polymer of these two units.

R<NUM> is an organosiloxane shown by the following general formula (<NUM>).

R<NUM> is as defined above. "h" is an integer satisfying <NUM>≤h≤<NUM>, and preferably an integer satisfying <NUM>≤h≤<NUM>. "n" is an integer satisfying <NUM>≤n≤<NUM>, and preferably <NUM> because of availability. If "h" is larger than <NUM>, the synthesis is hindered, and the compatibility with a resin is lowered as the water-based paint composition in some cases.

"a", "b", and "c" respectively satisfy <NUM>≤a≤<NUM>, preferably <NUM>≤a≤<NUM>, <NUM>≤b≤<NUM>, preferably <NUM>≤b≤<NUM>, and <NUM>≤c≤<NUM>, preferably <NUM>≤c≤<NUM>. If "a" and "b" deviates from the range, the compatibility is unstable as the water-based paint composition. Further, if "c" is below <NUM>, the antifouling property as the water-based paint composition decreases, and if more than <NUM>, the compatibility is unstable as the water-based paint composition.

Further, the siloxane-branched polyether-modified silicone shown by the formula (<NUM>) has a weight-average molecular weight of <NUM> to <NUM>,<NUM>, preferably <NUM>,<NUM> to <NUM>,<NUM>, and particularly preferably <NUM>,<NUM> to <NUM>,<NUM>, in terms of polystyrene according to GPC. When the weight-average molecular weight is less than <NUM>, the antifouling property lowers. When the weight-average molecular weight is more than <NUM>,<NUM>, the resulting silicone has such high viscosity that it is difficult to handle, and further the compatibility with a resin is lowered as the water-based paint composition in some cases.

The siloxane-branched polyether-modified silicone contained in the inventive additive for water-based paint can be obtained by a known method. For example, as described in Patent Document <NUM> (<CIT>), the siloxane-branched polyether-modified silicone can be easily synthesized by subjecting an organohydrogenpolysiloxane to addition reaction with an alkenyl group-containing organosiloxane and an alkenyl group-containing polyoxyalkylene compound in the presence of a platinum or rhodium catalyst.

The siloxane-branched polyether-modified silicone shown by the formula (<NUM>) satisfies the following expression (I), <MAT> and the following expression (II), <MAT>.

Further, the expression (I) is preferably <MAT>.

If the value of the expression (I) is smaller than the range, the compatibility with other component(s) in the water-based paint composition is impaired, and this causes segregation or lowers the leveling property (forming spots). If the value is larger than the range, the antifouling property consequently lowers. Further, if the value of the expression (II) is larger than the range likewise, the compatibility with other component(s) in the water-based paint composition is impaired, and this causes segregation and lowers not only the leveling property (forming spots) but also lowers the antifouling property.

Moreover, the inventive additive for water-based paint may be the siloxane-branched polyether-modified silicone only, or may further contain a solvent in addition to the siloxane-branched polyether-modified silicone. When the inventive additive for water-based paint contains a solvent and is added to a water-based paint composition, homogenizing by stirring becomes easier. Further, the paint additive may contain other components as necessary.

As the solvent which may be blended to the inventive additive for water-based paint, for example, it is possible to use one explained in the description of the water-based paint composition described below. Preferable ones are water, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, propylene glycol monomethyl ether acetate, butyl acetate methyl ethyl ketone, methyl isobutyl ketone. Furthermore, when the inventive additive for water-based paint contains a solvent, for example, the water-based-paint additive may be a <NUM> to <NUM>% solution of the siloxane-branched polyether-modified silicone, preferably <NUM> to <NUM>% solution, and further preferably <NUM> to <NUM>% solution.

Furthermore, the present invention provides a water-based paint composition containing the additive for water-based paint. The water-based paint composition is used particularly for antifouling paint.

The addition amount of the siloxane-branched polyether-modified silicone (that is, the effective component contained in the inventive additive for water-based paint) is <NUM> to <NUM> parts by mass, preferably <NUM> to <NUM> parts by mass, of <NUM> parts by mass of the inventive water-based paint composition. With these ranges of the addition amount, dirt prevention corresponding to the addition amount is surely obtained, which is cost effective.

The inventive water-based paint composition preferably contains a resin. The resin is not particularly limited, and is selected from the group consisting of urethane resins, acrylic resins, amide resins, phenolic resins, epoxy resins, melamine resins, urea resins, alkyd resins, polyimide resins, polyalkylene resins, polyvinyl chloride, polystyrene, polyvinyl acetate, and alloys of the resins. The resin is preferably a urethane resin or an acrylic resin in view of the compatibility with the water-based-paint additive containing the siloxane-branched polyether-modified silicone.

The addition amount of the resin is <NUM> to <NUM> parts by mass, preferably <NUM> to <NUM> parts by mass, of <NUM> parts by mass of the inventive water-based paint composition. With the resin content being <NUM> parts by mass or more, there is no fear of decrease of mechanical strength.

The inventive water-based paint composition can be optionally blended with other well-known components in the industry as appropriate, such as a curing agent, a dilution solvent, a ultraviolet absorber, a polymerization initiator, a polymerization inhibitor, a neutralizing agent, a stabilizer (a light-resistant stabilizer, a weather-resistant stabilizer, a heat-resistant stabilizer), an antioxidant, a leveling agent, a defoaming agent, a viscosity adjuster, a precipitation-inhibitor, a pigment, a dye, a dispersant, an antistatic agent, an anti-fog agent, and a rubber.

Isocyanate compounds usable in aqueous systems are useful as the curing agent. Examples thereof include aliphatic isocyanate (hexamethylene diisocyanate derivative, Bayhydur XP <NUM> manufactured by Covestro AG), etc. The amount of the curing agent is not particularly limited, and may be <NUM> to <NUM> parts by mass, preferably <NUM> to <NUM> parts by mass, of <NUM> parts by mass of the inventive water-based paint composition.

Examples of the dilution solvent include water, alcohols, esters, aliphatic hydrocarbons, aromatic hydrocarbons, ketones. Preferable are water, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, propylene glycol monomethyl ether acetate, butyl acetate methyl ethyl ketone, and methyl isobutyl ketone. Particularly preferable are water, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, and dipropylene glycol ethyl ether. The amount of the dilution solvent is not particularly limited, and may be <NUM> to <NUM> parts by mass, preferably <NUM> to <NUM> parts by mass, of <NUM> parts by mass of the inventive water-based paint composition.

The inventive water-based paint composition has a viscosity (<NUM>, B-type viscometer) of, for example, <NUM> to <NUM>,<NUM> mPa·s, preferably <NUM> to <NUM>,<NUM> mPa·s, in consideration of the coatability, film thickness, etc..

Further, the present invention relates to a coating layer using the water-based paint composition.

Various methods to be applied for typical paints are available as the coating method with the water-based paint composition for obtaining the inventive coating layer. Specifically, examples thereof include spray coating, spin coating, roll coating, curtain coating, brushing, electrostatic coating, anionic and cationic electrodeposition coating, dipping, etc. In addition, the curing method after coating is not particularly limited and examples thereof include (heat) curing particularly at <NUM> to <NUM>, more preferably <NUM> to <NUM>.

Moreover, examples of base materials to which the coating layer is applied (materials to be coated) include: plastics such as polystyrene resins, acrylic resins, acrylonitrile-styrene-butadiene resins (ABS), polypropylene, ethylene-propylene resins, polycarbonate resins, Noryl resins, nylon resins, polyester resins, and blends (alloys) of these resins with, for example, polyolefins, fillers, and reinforcement materials, such as glasses and carbon fibers; thermosetting resins, such as epoxy resins, unsaturated polyester resins, and urethane resins; inorganic materials, such as glasses, mortars, asbestos-cement slates, and rocks; metals, such as iron (and alloys), copper (and alloys), aluminum (and alloys), and magnesium (and alloys); combustible materials, such as papers and vinyl fabrics; etc..

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited thereto. Incidentally, in a case where multiple repeating units, each of which is shown in the parentheses, are included in the structural formulae described below, these units are arranged at random.

In a reactor, <NUM> of organohydrogensiloxane shown by the following structural formula (I), <NUM> of organosiloxane shown by the following structural formula (i), and <NUM> of isopropyl alcohol were mixed, and <NUM> of isopropyl alcohol solution of <NUM>% by mass chloroplatinic acid was added. This mixture was allowed to react at <NUM> for <NUM> hours. <CHM>
<CHM>.

Then, <NUM> of polyoxyalkylene compound of the following structural formula (a) was added, and the reaction was further continued for <NUM> hours.

CH<NUM>=CHCH<NUM>O(C<NUM>H<NUM>O)<NUM>H. structural formula (a).

After completion of the reaction, the obtained solution was heated under reduced pressure to distill the solvent to give a compound (A) of organopolysiloxane shown by the following structural formula in a yield of <NUM>%. <CHM>
<CHM>
        Rb = -C<NUM>H<NUM>O(C<NUM>H<NUM>O)<NUM>H.

The obtained compound (A) had a value of <NUM> in the expression (I), a value of <NUM> in the expression (II), and a weight-average molecular weight of <NUM>,<NUM>.

A compound (B) of the following formula was obtained in a yield of <NUM>% as in Synthesis Example <NUM>, except that <NUM> of organohydrogensiloxane shown by the following structural formula (II) was used instead of one in the structural formula (I) in Synthesis Example <NUM>, the addition amount of organosiloxane of the structural formula (i) was changed to <NUM>, and polyoxyalkylene compound of the structural formula (b) was used in place of one in the structural formula (a) and added in an amount of <NUM>.

CH<NUM>=CHCH<NUM>O(C<NUM>H<NUM>O)<NUM>H. structural formula (b).

Rc = -C<NUM>H<NUM>O(C<NUM>H<NUM>O)<NUM>H.

The obtained compound (B) had a value of <NUM> in the expression (I), a value of <NUM> in the expression (II), and a weight-average molecular weight of <NUM>,<NUM>.

A compound (C) of the following formula was obtained in a yield of <NUM>% as in Synthesis Example <NUM>, except that <NUM> of organohydrogensiloxane shown by the following structural formula (III) was used instead of one in the structural formula (I) in Synthesis Example <NUM>, the addition amount of organosiloxane of the structural formula (i) was changed to <NUM>, and polyoxyalkylene compound of the structural formula (c) was used in place of one in the structural formula (a) and added in an amount of <NUM>.

CH<NUM>=CHCH<NUM>O(C2H4O)<NUM>(C<NUM>H<NUM>O)<NUM>H. structural formula (c).

Rd = -C<NUM>H<NUM>O(C<NUM>H<NUM>O)<NUM>(C<NUM>H<NUM>O)<NUM>H.

The obtained compound (C) had a value of <NUM> in the expression (I), a value of <NUM> in the expression (II), and a weight-average molecular weight of <NUM>,<NUM>.

A compound (F) of the following formula was obtained in a yield of <NUM>% as in Synthesis Example <NUM>, except that <NUM> of polyoxyalkylene compound of the structural formula (d) was used in place of one in the structural formula (c) in Synthesis Example <NUM>.

CH<NUM>=CHCH<NUM>O(C<NUM>H<NUM>O)<NUM>H. structural formula (d).

Re = -C<NUM>H<NUM>O(C<NUM>H<NUM>O)<NUM>H.

The obtained compound (F) had a value of <NUM> in the expression (I), a value of <NUM> in the expression (II), and a weight-average molecular weight of <NUM>,<NUM>.

A mixture was prepared by mixing <NUM> of Bayhydrol A <NUM> (aqueous dispersion of <NUM>% acrylic resin manufactured by Covestro AG), <NUM> of water, <NUM> of Bayhydur XP <NUM> (isocyanate-based curing agent for aqueous system, manufactured by Covestro AG), and <NUM> of dipropylene glycol methyl ether. To <NUM> of this mixture, <NUM> of <NUM>% dipropylene glycol methyl ether solution of the compound (A) obtained in Synthesis Example <NUM> was added as the additive for water-based paint. Then, the resultant was mixed by using a dispersion mixer until uniform to prepare a water-based paint composition. After being left standing for <NUM> minutes, the obtained water-based paint composition was coated on glass using an applicator so as to have the thickness of <NUM>, and heated and cured at <NUM> for <NUM> minutes to form a coating layer (<NUM>). The obtained coating layer (<NUM>) was subjected to various evaluations as follows.

The water-based paint composition was uniformly mixed by using a dispersion mixer and left standing for <NUM> minutes. Then, the state of the water-based paint composition was observed.

The surface state of the coating layer on the glass was visually observed.

A line was drawn with a marker pen on the coating layer on the glass, and rubbed with tissue paper. The easiness for erasing the line was evaluated in this event.

A coating layer (<NUM>) was formed and the various properties thereof were evaluated as in Example <NUM>, except that <NUM>% dipropylene glycol methyl ether solution of the compound (B) was used instead of <NUM>% dipropylene glycol methyl ether solution of the compound (A) in Example <NUM>.

A coating layer (<NUM>) was formed and the various properties thereof were evaluated as in Example <NUM>, except that <NUM>% dipropylene glycol methyl ether solution of the compound (C) was used instead of <NUM>% dipropylene glycol methyl ether solution of the compound (A) in Example <NUM>.

A coating layer (<NUM>) was formed and the various properties thereof were evaluated as in Example <NUM>, except that <NUM>% dipropylene glycol methyl ether solution of the compound (F) was used instead of <NUM>% dipropylene glycol methyl ether solution of the compound (A) in Example <NUM>.

A coating layer (<NUM>) was formed and the various properties thereof were evaluated as in Example <NUM>, except that <NUM>% dipropylene glycol methyl ether solution of the compound (A) in Example <NUM> was not added.

A coating layer (<NUM>) was formed and the various properties thereof were evaluated as in Example <NUM>, except that <NUM>% dipropylene glycol methyl ether solution of a compound (D) of the following formula (the value in the expression (I): <NUM>, the value in the expression (II): <NUM>, weight-average molecular weight: <NUM>,<NUM>) was used instead of <NUM>% dipropylene glycol methyl ether solution of the compound (A) in Example <NUM>.

Rb = -C<NUM>H<NUM>O(C<NUM>H<NUM>O)<NUM>H. compound (D).

A coating layer (<NUM>) was formed and the various properties thereof were evaluated as in Example <NUM>, except that <NUM>% dipropylene glycol methyl ether solution of a compound (E) of the following formula (the value in the expression (I): <NUM>, the value in the expression (II): <NUM>, weight-average molecular weight: <NUM>,<NUM>) was used instead of <NUM>% dipropylene glycol methyl ether solution of the compound (A) in Example <NUM>. <CHM>
<CHM>.

Rb = -C<NUM>H<NUM>O(C<NUM>H<NUM>O)<NUM>H.

A coating layer (<NUM>) was formed and the various properties thereof were evaluated as in Example <NUM>, except that <NUM>% dipropylene glycol methyl ether solution of a compound (G) of the following formula (the value in the expression (I): <NUM>, the value in the expression (II): <NUM>, weight-average molecular weight: <NUM>,<NUM>) was used instead of <NUM>% dipropylene glycol methyl ether solution of the compound (A) in Example <NUM>. <CHM>
<CHM>.

A coating layer (<NUM>) was formed and the various properties thereof were evaluated as in Example <NUM>, except that <NUM>% dipropylene glycol methyl ether solution of a compound (H) of the following formula (the value in the expression (I): <NUM>, the value in the expression (II): <NUM>, weight-average molecular weight: <NUM>,<NUM>) was used instead of <NUM>% dipropylene glycol methyl ether solution of the compound (A) in Example <NUM>. <CHM>
<CHM>.

Rf = -C<NUM>H<NUM>O(C<NUM>H<NUM>O)<NUM>(C<NUM>H<NUM>O)<NUM>H.

The following Table <NUM> shows the results of Examples <NUM>, <NUM>, <NUM>, and <NUM> and Comparative Examples <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

As shown in Table <NUM>, it was revealed that the coating layers (<NUM>), (<NUM>), (<NUM>), and (<NUM>) formed from the water-based paint compositions using the inventive additives for water-based paint exhibited excellent antifouling property without impairing compatibility, defoaming property, and leveling property.

Claim 1:
An additive for water-based paint, comprising a siloxane-branched polyether-modified silicone shown by an average composition formula (<NUM>) R<NUM>aR<NUM>bR<NUM>cSiO(<NUM>-a-b-c)/<NUM> and having a weight-average molecular weight in a range of <NUM> to <NUM>,<NUM>,
wherein in the formula (<NUM>) each R<NUM> is identical to or different from one another and represents an organic group selected from an alkyl group, an aryl group, and an aralkyl group having <NUM> to <NUM> carbon atoms, and an organic group shown by a general formula (<NUM>) -CmH<NUM>-O-(C<NUM>H<NUM>O)d(C<NUM>H<NUM>O)eR<NUM>;
each R<NUM> represents a group shown by a general formula (<NUM>) -CmH<NUM>-O-(C<NUM>H<NUM>O)f(C<NUM>H<NUM>O)g-R<NUM>;
each R<NUM> represents an organosiloxane shown by the following general formula (<NUM>)
<CHM>
R<NUM> represents a hydrocarbon group having <NUM> to <NUM> carbon atoms, or an organic group shown by R<NUM>-(CO)-;
R<NUM> represents a hydrogen atom, a hydrocarbon group having <NUM> to <NUM> carbon atoms, or an organic group shown by R<NUM>-(CO)-;
R<NUM> represents a hydrocarbon group having <NUM> to <NUM> carbon atoms;
R<NUM> in the general formula (<NUM>) is the same as R<NUM> in the formula (<NUM>);
"a", "b", and "c" respectively satisfy <NUM>≤a≤<NUM>, <NUM>≤b≤<NUM>, and <NUM>≤c≤<NUM>;
"d" and "e" respectively represent integers satisfying <NUM>≤d≤<NUM> and <NUM>≤e≤<NUM>;
"f" and "g" respectively represent integers satisfying <NUM>≤f≤<NUM>, <NUM>≤g≤<NUM>, and f+g being <NUM> to <NUM>;
"m" represents an integer satisfying <NUM>≤m≤<NUM>;
"h" represents an integer satisfying <NUM>≤h≤<NUM>; and
"n" represents an integer satisfying <NUM>≤n≤<NUM>, and wherein the siloxane-branched polyether-modified silicone satisfies the following expression (I) and the following expression (II), <MAT> and <MAT>