JP7754615B2 - Sealant composition - Google Patents

Description

The present invention relates to a sealant composition.

Conventionally, compositions containing urethane resins have been used for applications such as sealants, etc. Furthermore, the sealants are often coated with a water-based resin (water-based paint).
For this reason, sealant compositions are required to have good adhesion to water-based paints.

For example, U.S. Patent No. 5,999,949 describes a curable silyl-containing polymer composition comprising:
a) at least one hydrolyzable silyl-containing polymer;
Compositions containing b) at least one silicone-containing paint adhesion promoter; and c) optionally at least one component selected from the group consisting of fillers, plasticizers, thixotropes, antioxidants, UV stabilizers, adhesion promoters, cure catalysts, moisture scavengers, pigments, dyes, surfactants, solvents, and biocides are described that provide improved adhesion to paints, coatings, and other surface treatments.

Special Publication No. 2010-531383

Under these circumstances, the present inventors prepared and evaluated a sealant composition with reference to Patent Document 1, and found that such a sealant composition may have poor adhesion to a water-based paint.
Therefore, an object of the present invention is to provide a sealant composition that has excellent adhesion to water-based paints.

As a result of intensive research aimed at solving the above problems, the present inventors have found that the desired effects can be obtained by including 12 parts by mass or more of silica in a sealant composition per 100 parts by mass of a urethane prepolymer having an isocyanate group.
The present invention is based on the above findings and solves the above problems by specifically providing the following configurations.

[1] A sealant composition containing 12 to 50 parts by mass of silica per 100 parts by mass of a urethane prepolymer having an isocyanate group.
[2] The sealant composition according to [1], which is a one-component or two-component type.
[3] A two-component type having a first component and a second component,
the first liquid contains the urethane prepolymer,
the second liquid contains a curing agent that reacts with the urethane prepolymer,
The sealant composition according to [1], wherein at least one of the first liquid and the second liquid contains the silica.
[4] The sealant composition according to any one of [1] to [3], wherein the silica has a pH of 7.0 or less.
[5] The sealant composition according to any one of [1] to [4], wherein the silica has a specific surface area measured by the BET method of 60 to 250 m ² /g.
[6] The sealant composition according to any one of [1] to [5], wherein the silica includes hydrophilic silica.

The sealant composition of the present invention has excellent adhesion to water-based paints.

The present invention will be described in detail below.
In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
Unless otherwise specified, the production method of each component is not particularly limited in this specification. For example, a conventionally known method may be used. Furthermore, commercially available products may be used as each component.
In this specification, unless otherwise specified, each component may be used alone or in combination of two or more substances. When a component contains two or more substances, the content of the component means the total content of the two or more substances.
In this specification, better adhesion to a water-based paint may be referred to as better effects of the present invention.

[Sealant composition]
The sealant composition of the present invention (the composition of the present invention) is a sealant composition containing 12 to 50 parts by mass of silica per 100 parts by mass of a urethane prepolymer having an isocyanate group.

Conventionally, silica has been used in sealant compositions as a thixotropic agent to impart thixotropy to the composition.
Since a high content of the thixotropic agent in a sealant composition deteriorates workability, the content of the thixotropic agent in a sealant composition is generally low. For example, in Patent Document 1, the content of the thixotropic agent is 4.2 phr relative to the hydrolyzable silyl-containing polymer (a).

In response to the above, the present inventors have discovered that the silica contained in a sealant composition has the function of improving adhesion to aqueous paints. Furthermore, they have found that by using silica in an amount of 12 parts by mass or more per 100 parts by mass of a urethane prepolymer having an isocyanate group, the silica can exert the above function and provide excellent adhesion to aqueous paints.
Each component contained in the composition of the present invention will be described in detail below.

<Urethane prepolymer>
The urethane prepolymer contained in the composition of the present invention is not particularly limited as long as it is a urethane compound having at least one isocyanate group in one molecule.
In one preferred embodiment, the urethane prepolymer has a plurality of isocyanate groups (preferably two isocyanate groups).
The urethane prepolymer preferably has an isocyanate group at the molecular end.
As the urethane prepolymer, a conventionally known one can be used, for example, a reaction product obtained by reacting a polyisocyanate compound with a compound having two or more active hydrogen-containing groups per molecule (hereinafter abbreviated as "active hydrogen compound") such that the number of isocyanate groups is in excess relative to the active hydrogen-containing groups.
In the present invention, the active hydrogen-containing group refers to a group containing active hydrogen, and examples of the active hydrogen-containing group include a hydroxy group, an amino group, and an imino group.

(Polyisocyanate compound)
The polyisocyanate compound used in producing the urethane prepolymer is not particularly limited as long as it has two or more isocyanate groups in the molecule.
Examples of polyisocyanate compounds include aromatic polyisocyanate compounds such as toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), and triphenylmethane triisocyanate;
aliphatic (the aliphatic includes linear, branched and alicyclic) polyisocyanates, such as hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate (NBDI), transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), bis(isocyanatomethyl)cyclohexane (H ₆ XDI), and dicyclohexylmethane diisocyanate (H ₁₂ MDI);
These carbodiimide-modified polyisocyanates are exemplified.

The polyisocyanate compounds may be used either alone or in combination of two or more.
Among these, aromatic polyisocyanates are preferred, TDI and MDI are more preferred, and TDI is even more preferred, because they have excellent weather resistance.

(active hydrogen compounds)
The compound having two or more active hydrogen-containing groups in one molecule (active hydrogen compound) used in producing the urethane prepolymer is not particularly limited. Examples of the active hydrogen-containing group include a hydroxyl (OH) group, an amino group, and an imino group.

Suitable examples of the active hydrogen compound include polyol compounds having two or more hydroxyl (OH) groups per molecule, and polyamine compounds having two or more amino and/or imino groups per molecule. Of these, polyol compounds are preferred.

The polyol compound is not particularly limited as long as it has two or more OH groups. Specific examples of polyol compounds include polyether polyols; polyester polyols; polybutadiene polyols, hydrogenated polybutadiene polyols; low-molecular-weight polyhydric alcohols; and mixed polyols thereof. Among these, polyether polyols are one preferred embodiment.

The polyether polyol is not particularly limited as long as it is a compound having a polyether main chain and two or more hydroxy groups. A polyether is a group having two or more ether bonds, and a specific example thereof is a group having a total of two or more structural units -R ^a -O-R ^b -. Here, in the above structural unit, R ^a and R ^b each independently represent a hydrocarbon group. The hydrocarbon group is not particularly limited. For example, a linear alkylene group having 1 to 10 carbon atoms is exemplified.
Examples of polyether polyols include polyoxyethylene diol (polyethylene glycol), polyoxypropylene diol (polypropylene glycol), polyoxypropylene triol, ethylene oxide/propylene oxide copolymer polyol, polytetramethylene ether glycol (PTMEG), polytetraethylene glycol, and sorbitol-based polyols.
The number average molecular weight of the polyether polyol is preferably 500 to 20,000, from the viewpoint that the viscosity of the urethane prepolymer obtained by the reaction with the polyisocyanate compound has appropriate fluidity at room temperature. In the present invention, the number average molecular weight is a polystyrene-equivalent value obtained by the GPC method (gel permeation chromatography method, solvent: tetrahydrofuran (THF)).
The active hydrogen compounds may be used either alone or in combination of two or more.

When producing the urethane prepolymer, it is preferable to use a polyoxyalkylene monool, in which some of the terminal hydroxy groups are blocked with hydrocarbon groups, such as polypropylene glycol monobutyl ether, in combination with the active hydrogen compound, from the viewpoint of being able to appropriately adjust the modulus of the resulting cured product.
The hydrocarbon group is not particularly limited, and examples thereof include alkyl groups.
Examples of the polyoxyalkylene monool include polypropylene glycol monobutyl ether, one end of which is blocked with an alkyl group, obtained by ring-opening addition polymerization of a cyclic ether compound such as propylene oxide using an alcohol such as butanol as an initiator.
From the viewpoint of being able to appropriately adjust the modulus of the resulting cured product, the number average molecular weight of the polyoxyalkylene monool is preferably 1000 to 8000, more preferably 2000 to 5000. In the present invention, the number average molecular weight can be a polystyrene-equivalent value obtained by a GPC method (solvent: tetrahydrofuran (THF)).

When producing the urethane prepolymer, the amount of the polyoxyalkylene monool is preferably 0 to 30% by mass, and more preferably 10 to 20% by mass, of the total amount of the active hydrogen compound and the polyoxyalkylene monool, from the viewpoint of being able to appropriately adjust the modulus of the resulting cured product.

From the viewpoints of achieving superior effects of the present invention, excellent curing properties, and the ability to appropriately adjust the modulus of the resulting cured product, the urethane prepolymer preferably contains a urethane prepolymer obtained by reacting (or formed by reacting) at least a polyether polyol with an aromatic polyisocyanate compound, and more preferably contains a urethane prepolymer obtained by reacting a polyether polyol with the above-mentioned polyoxyalkylene monool and an aromatic polyisocyanate compound.

From the perspective of achieving superior effects of the present invention, the content of isocyanate groups in the urethane prepolymer (isocyanate group content) is preferably 1.0 to 5.0 mass% of the total amount of urethane prepolymer.

The method for producing the urethane prepolymer is not particularly limited. For example, a polyisocyanate compound is used so that 1.5 to 2.5 moles of isocyanate groups react with 1 mole of the active hydrogen-containing group (e.g., hydroxy group) of the active hydrogen compound (when the polyoxyalkylene monool is used in addition to the active hydrogen compound, the total mole of the active hydrogen-containing group of the active hydrogen compound and the hydroxy group of the polyoxyalkylene monool is 1 mole), and the urethane prepolymer can be produced by mixing and reacting them.
The urethane prepolymers may be used either alone or in combination of two or more.

In one preferred embodiment, the urethane prepolymer does not contain silicon.

<Silica>
The silica (silicon dioxide) contained in the composition of the present invention is not particularly limited.
In the present invention, silica is believed to function as an adhesion promoter for water-based paints.
Examples of the silica include conventionally known silica, specifically hydrophobic silica and hydrophilic silica.

(hydrophilic silica)
Examples of hydrophilic silica include natural silica obtained by finely grinding quartz, silica sand, etc.; and synthetic silica such as dry silica and wet silica.
Among synthetic silicas, dry silica can be obtained by burning a silane gas such as silicon tetrachloride in an oxygen-hydrogen flame.
An example of wet silica is precipitated silica, which is obtained by neutralizing sodium silicate with a mineral acid to precipitate silica in a solution.
The silica preferably contains hydrophilic silica, from the viewpoint of achieving better effects of the present invention.

(hydrophobic silica)
Examples of hydrophobic silica include the above-mentioned hydrophilic silica that has been surface-treated with a reactive organosilicon compound (e.g., silicone oil, silane coupling agent, chlorosilanes, etc.) to be hydrophobic.

(BET specific surface area of silica)
The specific surface area of the silica measured by the BET method (BET specific surface area) is preferably 60 to 250 ^{m 2} /g, more preferably 170 to 230 m ² /g, from the viewpoint of achieving the effects of the present invention.
The BET specific surface area of the silica can be determined according to the BET method.

(pH of silica)
From the viewpoint of achieving superior effects of the present invention, the pH of the silica is preferably 7.0 or less, and more preferably 3.0 to 5.0.
The pH of the silica can be determined by dispersing silica in a mixed liquid of 50 parts by mass of water and 50 parts by mass of methanol to prepare a dispersion having a silica concentration of 4% by mass, thoroughly stirring the dispersion, and measuring the pH of the dispersion with a pH meter at 23°C, and the obtained pH can be used as the pH of the silica.

(Combination of BET specific surface area of silica and pH)
From the viewpoint of achieving superior effects of the present invention, the silica preferably has a BET specific surface area of 60 to 250 ^{m 2} /g and a pH of 7.0 or less, and more preferably has a BET specific surface area of 170 to 230 ^{m 2} /g and a pH of 3.0 to 5.0.

<Silica content>
In the present invention, the content of the silica is 12 to 50 parts by mass per 100 parts by mass of the urethane prepolymer having an isocyanate group.
In the present invention, by setting the content of the silica to 12 to 50 parts by mass per 100 parts by mass of the urethane prepolymer, it is possible to achieve both the effects of the present invention and excellent workability of the sealant composition.
When the content of the silica is 12 parts by mass or more per 100 parts by mass of the urethane prepolymer, the effect of the present invention (adhesion to water-based paint) is excellent.
From the viewpoint of achieving superior effects of the present invention, the content of the silica is preferably 15 to 40 parts by mass, more preferably 20 to 35 parts by mass, and even more preferably 23 to 30 parts by mass, per 100 parts by mass of the urethane prepolymer.
The content of the silica is preferably 12 to 30 parts by mass, more preferably 15 to 25 parts by mass, per 100 parts by mass of the urethane prepolymer, from the viewpoint of excellent workability and achieving both the effects of the present invention and workability at a high level.

The compositions of the present invention can be one-part or two-part.

(Two-component adhesive composition)
When the composition of the present invention is a two-part type, the two-part adhesive composition can have a first part and a second part (curing agent in a broad sense).

When the composition of the present invention is a two-part type having a first part and a second part,
the first liquid contains the urethane prepolymer,
the second liquid contains a curing agent (curing agent in the narrow sense) that reacts with the urethane prepolymer (the isocyanate group thereof),
One preferred embodiment is one in which at least one of the first liquid and the second liquid contains the silica.

・Second liquid (hardener in the broad sense)
The second liquid (hardening agent in the broad sense) may contain a hardening agent (hardening agent in the narrow sense) that reacts with the urethane prepolymer (the isocyanate group contained in the urethane prepolymer).
Examples of curing agents (curing agents in the narrow sense) that react with the urethane prepolymer (or with isocyanate groups in the urethane prepolymer) include compounds having multiple active hydrogen-containing groups in one molecule. The curing agent in the narrow sense refers to a compound that substantially reacts with the urethane prepolymer to cure the adhesive composition. Meanwhile, the second liquid (curing agent in the broad sense) is only required to contain at least the curing agent in the narrow sense.
The curing agent in the narrow sense includes, for example, the same active hydrogen compounds as those usable in producing the urethane prepolymer.
From the viewpoint of achieving superior effects of the present invention, the curing agent in the narrow sense preferably contains a polyol compound, more preferably contains a polyether polyol or a polybutadiene polyol, and even more preferably contains a polyether polyol.
The polyether polyol is the same as above.

In the case of two-component systems, the urethane prepolymer can be used in an amount such that the number of isocyanate groups per mole of active hydrogen-containing groups (e.g., hydroxyl groups) in the narrowly defined curing agent is, for example, 1.5 to 2.5 moles.

(Silica content in two-component type)
When the composition of the present invention is a two-component type, the content of the silica relative to the total amount of the polyol compound constituting the urethane prepolymer and the curing agent (in the narrow sense) contained in the second liquid is preferably 3 to 20 mass %, and more preferably 5 to 10 mass %, from the viewpoint of achieving better effects of the present invention.

(Other optional ingredients)
The composition of the present invention may further contain various additives, such as a room-temperature-curable resin other than the urethane prepolymer (e.g., a crosslinkable silyl group-containing organic polymer), a plasticizer, a solvent such as a paraffinic hydrocarbon, a catalyst (e.g., a curing catalyst), calcium carbonate, balloons (e.g., resin balloons), an antioxidant, an antioxidant, a silane coupling agent, a pigment, an ultraviolet absorber, a flame retardant, a surfactant, a leveling agent, a dispersant, a dehydrating agent, and an antistatic agent, as needed, provided that the object of the present invention is not impaired.
It is preferable that the plasticizer does not have reactivity with the urethane prepolymer or the hardener in the narrow sense. The same applies to the solvent.
When the composition of the present invention is a two-liquid type, it can be appropriately selected whether the above-mentioned optional components are added to the first or second liquid.

Calcium Carbonate From the viewpoint of excellent workability, the composition of the present invention preferably further contains calcium carbonate.
The calcium carbonate is not particularly limited, and examples thereof include heavy calcium carbonate, precipitated calcium carbonate (light calcium carbonate), and colloidal calcium carbonate.
The calcium carbonate may be surface-treated with at least one treating agent selected from the group consisting of, for example, fatty acids, resin acids, urethane compounds, and fatty acid esters.

The calcium carbonate content is preferably 20 to 400 parts by mass, and more preferably 100 to 300 parts by mass, per 100 parts by mass of urethane prepolymer or narrowly defined curing agent.

Curing Catalyst The curing catalyst is not particularly limited as long as it is a compound that can promote the reaction of an isocyanate group, and specific examples include zinc catalysts such as zinc octoate; carboxylic acids such as 2-ethylhexanoic acid and oleic acid; phosphoric acids such as polyphosphoric acid, ethyl acid phosphate and butyl acid phosphate; bismuth catalysts such as bismuth octoate; tin catalysts such as dibutyltin dilaurate and dioctyltin dilaurate; and tertiary amine catalysts such as 1,4-diazabicyclo[2.2.2]octane, 2,4,6-tris(dimethylaminomethyl)phenol (e.g., DMP-30), and compounds containing a dimorpholinodiethyl ether structure.

The content of the curing catalyst is preferably 0.05 to 5 parts by mass per 100 parts by mass of the urethane prepolymer or the curing agent in the narrow sense.

Plasticizer The plasticizer is not particularly limited as long as it can improve the mixability of the urethane prepolymer or reduce the hardness of the resulting cured product.
Specific examples of the plasticizer include terminally esterified polyfunctional polyethers; diisononyl phthalate (DINP); diisononyl adipate, dioctyl adipate, isodecyl succinate; diethylene glycol dibenzoate, pentaerythritol esters; butyl oleate, methyl acetylricinoleate; tricresyl phosphate, trioctyl phosphate; propylene glycol adipate polyester, butylene glycol adipate polyester, and the like. These may be used alone or in combination of two or more.
The content of the plasticizer is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, per 100 parts by mass of the urethane prepolymer or the hardener in the narrow sense.

The balloon (hollow body) is not particularly limited, but the hollow body preferably has an outer shell made of a resin or glassy material, because this provides a superior effect of the present invention. For example, a thermally expandable resin hollow body can be obtained by encapsulating a liquid inside the hollow body and heating it to expand the resin that forms the outer shell and vaporize the liquid inside.

Examples of resins that make up the outer shell of the above-mentioned hollow resin body include thermosetting resins such as phenolic resin and urea resin; and thermoplastic resins such as polystyrene resin, polyvinylidene chloride resin, and (meth)acrylonitrile (co)polymer. Of these, at least one resin selected from the group consisting of phenolic resin, urea resin, polystyrene, polyvinylidene chloride, and (meth)acrylonitrile (co)polymer is preferred.

Examples of the thermoplastic resin include homopolymers of compounds such as halogen-containing compounds, such as vinyl chloride and vinylidene chloride; nitrile compounds, such as acrylonitrile and methacrylonitrile; acrylate compounds, such as benzyl acrylate and norbornane acrylate; methacrylate compounds, such as methyl methacrylate, norbornane methacrylate and trimethylolpropane trimethacrylate; styrene-based monomers; vinyl acetate; butadiene; vinylpyridine; and chloroprene; and copolymers of these compounds.
Among these, from the viewpoint of weather resistance and heat resistance, acrylonitrile copolymers (for example, copolymers of acrylonitrile and methacrylonitrile, copolymers of acrylonitrile and vinyl monomers such as butadiene copolymerizable with acrylonitrile or styrene) and polyvinylidene chloride resins are preferred.

Examples of the liquid that can be contained in the hollow resin body include hydrocarbons such as n-pentane, isopentane, neopentane, butane, isobutane, hexane, and petroleum ether; and chlorinated hydrocarbons such as methyl chloride, methylene chloride, dichloroethylene, trichloroethane, and trichloroethylene.
The balloon is preferably coated with calcium carbonate for the reason that it has excellent workability.

(Manufacturing method)
When the composition of the present invention is a one-component type, the method for producing it is not particularly limited, and it can be produced, for example, by a method of mixing a urethane prepolymer, silica, and other optional components that can be used as needed.

When the composition of the present invention is a two-component type, the method for producing it is not particularly limited, and it can be produced, for example, by a method in which the first liquid and the second liquid are placed in separate containers and mixed under a nitrogen gas atmosphere in each container.
In addition, the two-component type may be used by mixing the first and second components.

(Base material)
Examples of substrates to which the composition of the present invention can be applied include plastics, rubber, metals, and mortar.

The method for applying the composition of the present invention to a substrate is not particularly limited. For example, conventionally known methods can be used.

The composition of the present invention can be cured by moisture or other factors. For example, the composition of the present invention can be cured by aging under conditions of 5 to 90°C and 5 to 95% RH (relative humidity).

Uses of the compositions of the present invention include, for example, construction sealants.
Since the composition of the present invention has excellent adhesion to water-based paints, water-based paints (e.g., paints containing water and water-soluble resins) can be applied to the composition of the present invention or to a cured product of the composition of the present invention. The water-based paint is not particularly limited. For example, conventionally known paints can be used.

The present invention will be explained in more detail below using examples. However, the present invention is not limited to these examples.

(Preparation of first liquid ^*1 containing urethane prepolymer)
The PPG, plasticizer (diisononyl adipate, trade name DINA, manufactured by J-Plus Corporation), and polyisocyanate compound (toluene diisocyanate, trade name TDI-80, manufactured by Mitsui Chemicals, Inc.) shown in the column 1 liquid ^*1 in Table 1 were used (the above components were used in the amounts shown in Table 1, units are parts by mass).
The PPG shown in the column for Solution 1 ^*1 in Table 1 used 45 parts by mass of polyoxypropylene diol (Excelnol 3020, number average molecular weight 3,200, manufactured by AGC) and 25 parts by mass of polyoxypropylene triol (Excelnol 5030, number average molecular weight 5,100, manufactured by AGC) as the active hydrogen compounds (compounds having two or more active hydrogen-containing groups per molecule), as well as 10 parts by mass of polyoxypropylene butyl ether (trade name Newpol LB-3000, manufactured by Sanyo Chemical Industries, Ltd., having one hydroxy group, number average molecular weight 3,000).
The PPG and the plasticizer were placed in a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet tube, and heating/cooling device under a nitrogen gas flow, and the mixture was heated to 120°C and stirred for 20 hours to dehydrate. Then, while stirring, the polyisocyanate compound was added in an amount such that the equivalent ratio (NCO groups/OH groups) of the isocyanate groups in the polyisocyanate compound to the total hydroxy groups in the PPG (a mixture of the polyoxypropylene diol, etc.) was 2.0. The mixture was then heated and stirred at 80 to 90°C for 18 hours to react, producing a urethane prepolymer having isocyanate groups. The resulting isocyanate group-containing urethane prepolymer had an isocyanate group content of 3.0% by mass as determined by titration, and was a viscous liquid at room temperature (23°C).

In this example, the urethane prepolymer prepared as described above, containing the plasticizer, was used as it was as the first liquid in <Production of Composition> described below.
In this specification, the first liquid prepared as described above contains 90 parts by mass of the urethane prepolymer and 10 parts by mass of the plasticizer.

(Preparation of second liquid)
The components shown in the column for second liquid (hardening agent in a broad sense) in Table 1 below and silicas 1 to 3 were used in the compositions (parts by mass) shown in the same table, and these were mixed with a stirrer to prepare second liquid.
In this example, the second liquid prepared as described above was used as it was in the next <Preparation of Composition> to prepare a two-liquid sealant composition.

<Production of Composition>
The first and second parts prepared as described above were used in the combinations shown in Table 1 and mixed to prepare sealant compositions (also simply referred to as compositions).

<Evaluation>
Each of the compositions prepared as described above was evaluated for adhesion to water-based paint (paint adhesion) and workability. The results are shown in Table 1.
- Adhesion to water-based paints (paint adhesion)
(Preparation of Sealant)
Each composition prepared as described above was poured into an aluminum channel (depth 30 mm × height 10 mm × width 100 mm) and left to cure for 3 days under conditions of 23°C and 55% RH (relative humidity).

(Application of water-based paint)
A water-based paint (self-emulsifying cationic emulsion. The interface between the emulsion particles is in an ionized state of the amines in the polymer skeleton. Product name: Water-based Milk Sealer Eco, manufactured by SK Chemical Co., Ltd.) was applied with a brush to the surface of the above-mentioned cured sealant, and the paint was cured and hardened for 7 days at 23°C and 55% RH (relative humidity) to prepare a test specimen after paint curing.

(Method for evaluating paint adhesion)
Each test specimen obtained as described above was subjected to a cross-cut test (25 squares) and an X-cut test in accordance with JIS K5600-5-6:1999 "General test methods for paints, Part 5: Mechanical properties of coating films, Section 6: Adhesion (cross-cut method)."
In the above-mentioned cross-cut test, 25 cross-cuts (2 mm apart) were made, and a peel test was carried out using transparent pressure-sensitive adhesive tape. After the peel test using the tape, the number of paint cross-cuts remaining on the surface of the sealant of each test specimen was evaluated.
In the X-cut test, the paint of each test specimen was cut into a cross (X shape) with a cutter to a depth of about 1 mm, and an opening was created to scrape off the sealant on the back of the paint at the intersection of the cuts, and the paint was peeled off with a finger to determine the strength of adhesion (bite) between the paint and the sealant.

(Evaluation criteria)
Adhesion to water-based paint (paint adhesion) was evaluated according to the following criteria.
If 0 to 7 squares remained in the cross-cut test and there was no adhesion in the X-cut test, the adhesion to the water-based paint was evaluated as poor, and this was indicated by "X."
If 0 to 7 squares remained in the cross-cut test and there was a slight adhesion in the X-cut test, the adhesion to the water-based paint was evaluated as being slightly excellent, and this was indicated by "Δ".
If 8 to 20 squares remained in the cross-cut test and there was some adhesion in the X-cut test, the adhesion to the water-based paint was evaluated as very good, and this was marked as "good."
When 21 to 25 squares remained in the cross-cut test and there was strong adhesion in the X-cut test, the adhesion to the water-based paint was evaluated as particularly excellent, and this was marked with "Excellent".

Workability (measurement of viscosity of each composition)
The viscosity (unit: Pa·s) at 1 rpm of each of the compositions prepared as described above was measured using a Brookfield viscometer under conditions of 23° C. and 50% RH.

(Evaluation criteria)
The workability (workability) of the sealant composition was evaluated according to the following criteria.
In the present invention, when the viscosity of each composition measured as described above was less than 5,500 Pa·s, the sealant composition was evaluated as having excellent workability.
Specifically, when the viscosity of each composition measured as described above was less than 2500 Pa·s, the workability was evaluated as very good, and this was marked with "Excellent".
When the viscosity was 2500 Pa·s or more and less than 3500 Pa·s, the workability was evaluated as good and this was marked as "◯".
When the viscosity was 3500 Pa·s or more and less than 5500 Pa·s, the workability was evaluated as being somewhat good, and this was indicated by "Δ".
On the other hand, when the viscosity was 5,500 Pa·s or more, the workability was evaluated as poor and this was marked as "X."

Details of each component shown in the second liquid (hardening agent in a broad sense) column in Table 1 are as follows.
Curing agent (PPG): A mixture of 65 parts by mass of polyoxypropylene diol (Excelnol 3020, number average molecular weight 3,200, manufactured by AGC) and 35 parts by mass of polyoxypropylene triol (Excelnol 5030, number average molecular weight 5,100, manufactured by AGC).

Plasticizer: Terminally esterified multifunctional polyether, trade name Sunflex GPA-3000, manufactured by Sanyo Chemical Industries, Ltd. Note that GPA-3000 does not have a hydroxy group.
Solvent: Paraffin hydrocarbon. Product name: Merveille 40, manufactured by Showseki International Co., Ltd.
Curing catalyst: bismuth octylate, trade name Pucat 10, Nikka Octix Zinc 8% EH, manufactured by Nippon Chemical Industries Co., Ltd.

Calcium carbonate: a mixture of 125 parts by mass of Super SS (unsurface-treated heavy calcium carbonate, manufactured by Maruo Calcium Co., Ltd.) and 15 parts by mass of MC Coat S-20 (fatty acid-surface-treated heavy calcium carbonate, manufactured by Maruo Calcium Co., Ltd.).
Surface-treated calcium carbonate: Product name MS-900 (calcium carbonate surface-treated with a fatty acid. Manufactured by Maruo Calcium Co., Ltd.)

Balloon: A hollow acrylonitrile copolymer body coated with calcium carbonate. Product name: MFL-SE100, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.

Details of each component shown in columns 1 to 3 of Table 1 are as follows.
Silica 1: Product name RY-200S, manufactured by Nippon Aerosil Co., Ltd. Dry silica. Hydrophobic silica. pH 4.5-6.5. BET specific surface area 65-95 m ² /g.
Silica 2: Product name QS-102, manufactured by Tokuyama Corporation. Dry silica. Hydrophilic silica. pH 4.0-4.5. BET specific surface area 180-220 ^{m 2} /g.
Silica 3: Tokusil 928 (trade name), manufactured by Tokuyama Corporation. Wet silica. Hydrophilic silica. pH 6.6. BET specific surface area 195 m ² /g.

As is clear from the results shown in Table 1, Comparative Example 1, which contained no silica, and Comparative Examples 2 and 3, which contained less silica than the specified range, had poor adhesion to the water-based paint.
Comparative Example 4, in which the silica content was higher than the predetermined range, had poor workability.

In contrast, the sealant composition of the present invention had excellent adhesion to water-based paints.
Furthermore, the sealant composition of the present invention is also excellent in workability, and it is possible to achieve both the effect of the present invention (adhesion to water-based paint) and excellent workability.

Claims (4)

A sealant composition comprising an adhesion promoter that improves adhesion to aqueous resins and a urethane prepolymer having an isocyanate group,
the adhesion imparting agent is made of hydrophilic silica fine particles,
the pH of the hydrophilic silica fine particles is 3.0 to 5.0;
The hydrophilic silica microparticles are contained in an amount of more than 13.5 parts by mass and less than 22.5 parts by mass per 90 parts by mass of the urethane prepolymer having an isocyanate group (excluding those containing ureylene group-containing organic group-bonded silica microparticles). The sealant composition according to claim 1, which is a one-component or two-component type. It is a two-component type having a first component and a second component,
the first liquid contains the urethane prepolymer,
the second liquid contains a curing agent that reacts with the urethane prepolymer,
The sealant composition according to claim 1 , wherein at least one of the first liquid and the second liquid contains the silica. The sealant composition according to any one of claims 1 to 3, wherein the silica has a specific surface area measured by the BET method of 60 to 250 m ² /g.