JP5460640B2 - Curing agent for polyurethane resin paint - Google Patents

Description

  The present invention relates to a curing agent suitable for a polyurethane resin paint.

Buildings, civil engineering structures, and the like are painted with various paints for the purpose of protecting the frame and improving aesthetics. Among these, polyurethane resin paints are widely used because they are excellent in coating film properties such as weather resistance, water resistance, and chemical resistance and are relatively inexpensive in terms of price.
Such a polyurethane resin paint is usually composed of a main component mainly composed of polyol and a curing agent mainly composed of polyisocyanate, and is distributed as a two-component paint. Among these, polyisocyanates having an isocyanurate structure or an allophanate structure are used as the polyisocyanate in the curing agent.

  However, in recent years, in urban areas and the like, oily pollutants are floating in the atmosphere due to exhaust gas from automobiles and the like. In the coating film of a general polyurethane resin paint as described above, there is a problem that rain streak contamination is likely to occur due to such oily contaminants and the aesthetics are greatly impaired.

  On the other hand, a technique for increasing the stain resistance of the polyurethane resin paint is described in, for example, WO94 / 06870 (Patent Document 1). The paint described in Patent Document 1 is obtained by mixing a silicate compound such as methyl silicate with a polyurethane resin paint.

  In consideration of the actual commercial form of the paint described in Patent Document 1, etc., the silicate compound as described above must be mixed with either the main agent or the curing agent. Among these, since the main component side contains a large number of various additives in addition to the resin and the pigment, it is difficult to ensure the stability of the silicate compound. For this reason, it is usually desirable to mix the silicate compound on the curing agent side. However, in a mixture of an isocyanate compound and a silicate compound, phase compatibility or cloudiness may occur due to insufficient compatibility. Such a problem is likely to occur particularly in a low temperature environment.

WO94 / 06870 Publication

  This invention is made | formed in view of this situation, and it aims at improving the compatibility in the hardening | curing agent for polyurethane resin coating materials containing an isocyanate compound and a silicate compound.

  As a result of diligent research in view of the problems of the prior art as described above, the present inventors have come up with a curing agent in which an isocyanate compound having a specific chemical structure and a specific silicate compound are combined. It came to complete.

That is, the present invention has the following characteristics.
1. (A) Polyisocyanate having an isocyanurate structure obtained by reaction of a monoalcohol having m carbon atoms (where m is an integer of 2 to 12) and an isocyanate compound, and (B) two or more alkoxyls having different carbon numbers A tetraalkoxysilane condensate containing a mixture of groups,
When the average carbon number of the alkoxyl group in the component (B) is n,
0 ≦ m−n ≦ 2
A curing agent for polyurethane resin paints, which is excellent in compatibility in a low temperature environment, characterized by satisfying
2. (A) Polyisocyanate having an allophanate structure obtained by reaction of a monoalcohol having m carbon atoms (where m is an integer of 2 to 12) and an isocyanate compound, and (B) two or more alkoxyl groups having different carbon numbers. Containing tetraalkoxysilane condensate,
When the average carbon number of the alkoxyl group in the component (B) is n,
0 ≦ m−n ≦ 2
A curing agent for polyurethane resin paints, which is excellent in compatibility in a low temperature environment, characterized by satisfying
3. (A) Polyisocyanate having an isocyanurate structure and an allophanate structure obtained by reaction of a monoalcohol having m carbon atoms (where m is an integer of 2 to 12) and an isocyanate compound, and (B) two types having different carbon numbers Containing a tetraalkoxysilane condensate in which the above alkoxyl groups are mixed,
When the average carbon number of the alkoxyl group in the component (B) is n,
0 ≦ m−n ≦ 2
A curing agent for polyurethane resin paints, which is excellent in compatibility in a low temperature environment, characterized by satisfying
4). The component (B) is a tetraalkoxysilane condensate in which a methoxy group and a butoxy group are mixed. To 3. A curing agent for polyurethane resin paints having excellent compatibility in a low temperature environment.

In the present invention, the compatibility can be dramatically improved by combining specific two components. Therefore, a uniform and transparent curing agent for polyurethane resin paints can be obtained.
In particular, the curing agent of the present invention can sufficiently prevent the occurrence of phase separation or cloudiness in a low temperature environment. Therefore, the coating operation in a cold district or the like is not hindered, and a stable coating performance can be expressed in coating properties such as contamination resistance.

  Hereinafter, it explains in detail with the best form for carrying out the present invention.

  The curing agent for polyurethane resin paints of the present invention has an isocyanurate structure and / or an allophanate structure obtained by the reaction of (A) a monoalcohol having m carbon atoms (where m is an integer of 1 to 12) and an isocyanate compound. A mixture of polyisocyanate (hereinafter referred to as “component (A)”) and (B) a tetraalkoxysilane condensate (hereinafter referred to as “component (B)”) in which two or more types of alkoxyl groups having different carbon numbers are mixed. It is.

In the present invention, when the average carbon number of the alkoxyl group in the component (B) is n,
0 ≦ mn ≦ 6 (preferably 0 ≦ mn ≦ 4, more preferably 0 ≦ mn ≦ 2)
(A) component and (B) component which satisfy | fill are used in combination.
In the present invention, compatibility can be dramatically improved by combining such specific components. Therefore, a uniform and transparent curing agent can be obtained.
In particular, the curing agent of the present invention can sufficiently prevent the occurrence of phase separation or cloudiness in a low temperature environment. Therefore, the coating operation in a cold district or the like is not hindered, and a stable coating performance can be expressed in coating properties such as contamination resistance.
The average carbon number of the alkoxyl group in the component (B) is a value obtained by dividing the total number of carbon atoms constituting the alkoxyl group in the component (B) by the total number of alkoxyl groups in the component (B).

  (A) component in a hardening | curing agent is a component which forms a coating film by the crosslinking reaction with the polyol contained in a main ingredient. This (A) component is obtained by reaction of a C1-C12 monoalcohol and an isocyanate compound.

  The monoalcohol can be used without particular limitation as long as it has 1 to 12 carbon atoms. Specifically, methanol, ethanol, n-propanol, isopropyl alcohol, n-butyl alcohol, n-amyl alcohol, n-hexyl alcohol, 2-ethyl-1-hexanol, n-heptanol, isoheptyl alcohol, n-octanol , 2-octanol, n-nonanol, n-decanol, n-undecyl alcohol, n-dodecyl alcohol and the like.

  As the isocyanate compound, diisocyanate is usually used. Among these, aliphatic diisocyanates and alicyclic diisocyanates are preferable because they are excellent in yellowing resistance. Specifically, as the isocyanate compound in the component (A), for example, ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, undecamethylene diisocyanate, 1,3-diisocyanatocyclobutane, 1,3-diisocyanatocyclohexane, 1 , 3-diisocyanatomethylcyclohexane, isophorone diisocyanate and the like. Among these isocyanate compounds, one or more selected from hexamethylene diisocyanate, 1,3-diisocyanatomethylcyclohexane, and isophorone diisocyanate are particularly preferable.

The component (A) has an isocyanurate structure or an allophanate structure in its skeleton. By having such a structure, stability when mixed with an aliphatic hydrocarbon solvent can be enhanced. Therefore, it is suitable for a weak solvent polyurethane resin coating.
Furthermore, in this invention, what has both an isocyanurate structure and an allophanate structure is preferable. By having such a structure together, the stability when mixed with an aliphatic hydrocarbon solvent can be further improved. Therefore, it is preferable for a weak solvent polyurethane resin coating.

The manufacturing method of (A) component should just follow a well-known method. Specifically, for example, a method in which a monoalcohol and an isocyanate compound are isocyanurated in the presence of a catalyst, a part or all of the hydroxyl group of the monoalcohol is reacted with a part of the isocyanate group in the isocyanate compound, and allophanate And a method of forming allophanate by the presence of a catalyst.
In addition, according to a method in which a part or all of the hydroxyl group of the monoalcohol is reacted with a part of the isocyanate group in the isocyanate compound to urethanize and then isocyanurated in the presence of a catalyst, Allophanatization can be performed simultaneously.

The component (B) in the present invention is localized on the surface in the course of forming the coating film, and can make the coating film surface hydrophilic.
In addition, the average condensation degree of (B) component is 1-100 normally, Preferably it is about 4-20.

The present invention is particularly effective when a tetraalkoxysilane condensate in which two or more types of alkoxyl groups having different carbon numbers are mixed is used as the component (B).
As such a combination of alkoxyl groups, a combination of a methoxy group having 1 carbon atom and an alkoxyl group having 2 to 12 carbon atoms, or a combination of an ethoxy group having 2 carbon atoms and an alkoxyl group having 3 to 12 carbon atoms, This is suitable in terms of expressing stain resistance at the initial stage of coating film formation. Among these, it is a combination of a methoxy group and an alkoxyl group having 2 to 12 carbon atoms (preferably 3 to 10 carbon atoms), and more than 5 equivalent% (preferably 5 to 50 equivalent%) of the total alkoxyl group. ) Is an alkoxyl group having 2 to 12 carbon atoms (hereinafter referred to as “B-1” component).

  The component (B-1) can be produced by the following method, but is not limited thereto.

(1) General formula Si (OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ )
(Wherein R _{1 to} R ₄ are a mixture of a methyl group and an alkyl group having 2 to 12 carbon atoms), and the tetraalkoxysilane is condensed so as to have an average degree of condensation of 1 to 100. . The condensation method is a known method. In this case, other alkyl silicates can be mixed and condensed during the condensation.
Specific examples of the compound represented by the above general formula include, for example, monoethoxytrimethoxysilane, monobutoxytrimethoxysilane, monopentoxytrimethoxysilane, monohexoxytrimethoxysilane, dimethoxydiethoxysilane, dimethoxydibutoxysilane. Or the condensates thereof.

(2) The tetramethoxysilane condensate is reacted with an alcohol having 2 to 12 carbon atoms to transesterify 5 equivalent% or more (preferably 5 to 50 equivalent%) of the methoxy group in the tetramethoxysilane condensate. Examples of the alcohol having 2 to 12 carbon atoms in this method include ethanol, n-propanol, isopropyl alcohol, n-butyl alcohol, n-amyl alcohol, n-hexyl alcohol, 2-ethyl-1-hexanol, and n-heptanol. , Isoheptyl alcohol, n-octanol, 2-octanol, n-nonanol, n-decanol, n-undecyl alcohol, n-dodecyl alcohol and the like.

The mixing ratio of the component (A) and the component (B) can be appropriately set in consideration of the mixing ratio with the main agent, the type and content of the polyol in the main agent, and the like. Usually, the weight ratio of component (A): component (B) may be within the range of 90:10 to 10:90 (preferably 80:20 to 20:80).
In the present invention, the component (A) and the component (B) may be usually used and mixed one by one, but a plurality of types of components in either one or both of the components (A) and (B) Can also be used. In this case, if at least one combination satisfies the conditions of the present invention, an effect of improving compatibility can be obtained.

The curing agent of the present invention can be mixed with a solvent within a range that does not impair the effects of the present invention. Examples of usable solvents include aliphatic hydrocarbon solvents such as n-hexane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, terpin oil, and mineral spirits. And aromatic hydrocarbon solvents such as toluene, xylene, solvent naphtha, and the like, and ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and the like.
Moreover, various additives can also be mixed as needed.

The curing agent of the present invention is used by mixing with the main agent immediately before coating.
The main agent is not particularly limited as long as it contains at least a polyol, and a known material can be appropriately used in the field of polyurethane resin coatings.

Examples of the polyol include polyether polyol, polyester polyol, acrylic polyol, silicon-modified acrylic polyol, fluorine-containing acrylic polyol, silicone-containing acrylic polyol, fluorine-containing polyol, and silicone-containing polyol. These may be either soluble or dispersed. Of these, the use of one or more selected from acrylic polyols, silicon-modified acrylic polyols, fluorine-containing polyols, and silicone-containing polyols is preferable in that the weather resistance of the coating film can be improved.
The hydroxyl value of the polyol is usually about 15 to 100 KOHmg / g. Moreover, the weight average molecular weight of a polyol is about 5000-200000 normally.

A coloring pigment can also be mix | blended with a main ingredient. Examples of such colored pigments include titanium oxide, zinc oxide, carbon black, ferric oxide (bengala), yellow iron oxide, ultramarine blue, cobalt green and other inorganic pigments, azo-based, naphthol-based, pyrazolone-based, Organic pigments such as anthraquinone, perylene, quinacridone, disazo, isoindolinone, benzimidazole, phthalocyanine, and quinophthalone can be used.
It is also possible to use extender pigments such as heavy calcium carbonate, clay, kaolin, talc, precipitated barium sulfate, barium carbonate, white carbon, diatomaceous earth.

  In addition, various additives that can be usually used in paints can be blended in the main agent. Examples of such additives include plasticizers, antiseptics, antifungal agents, antialgae agents, antifoaming agents, leveling agents, pigment dispersants, antisettling agents, antisagging agents, catalysts, curing accelerators, dehydration agents Agents, matting agents, ultraviolet absorbers, light stabilizers and the like.

  In mixing the main agent and the above-described curing agent, the ratio of the polyisocyanate in the curing agent to the polyol in the main agent is 0.7 to 2.0 (preferably 0.8 to 1.5 in terms of NCO / OH ratio). ) Is preferable. At this time, if the NCO / OH ratio is less than 0.7, the crosslinking rate of the coating film becomes low, the curability and durability become insufficient, and contaminants sink into the molecules with a coarse coating film density. Even if the coating film is washed, it is difficult to remove the pollutant, and it tends to be inferior in contamination recovery. When the NCO / OH ratio is larger than 2.0, unreacted isocyanate remains and deteriorates the initial drying property, resulting in stickiness of the surface called tack and easily causing contaminants to adhere physically. Become.

Furthermore, in the mixing of the main agent and the curing agent, the tetraalkoxysilane condensate in the curing agent is 1.0 to 50.0 weight in terms of SiO _{2 with} respect to 100 parts by weight of the resin solid content of the polyol in the main agent. The range of parts (preferably 2.0 to 30.0 parts by weight) is suitable. When the tetraalkoxysilane condensate is less than 1.0 part by weight, the coating film does not exhibit hydrophilicity, so that the stain resistance is insufficient. On the other hand, when it exceeds 50.0 parts by weight, the appearance of the cured coating film is deteriorated or cracks are likely to occur in the coating film.

In addition, SiO ₂ conversion is the weight remaining as silica (SiO ₂ ) when a compound having a Si—O bond such as alkoxysilane or silicate is completely hydrolyzed and then baked at 900 ° C. It is a representation.
In general, alkoxysilanes and silicates have a property of reacting with water to cause a hydrolysis reaction to form silanol, and further causing a condensation reaction between silanols or between silanol and alkoxy. When this reaction is performed to the ultimate, silica (SiO ₂ ) is obtained. These reactions are RO (Si (OR) ₂ O) _n R + (n + 1) H ₂ O → nSiO ₂ + (2n + 2) ROH
(R represents an alkyl group. N is an integer.)
It is expressed by the reaction formula. The SiO ₂ conversion in the present invention is the conversion of the amount of the remaining silica component based on this reaction formula.

  Examples are given below to clarify the features of the present invention.

(Synthesis example)
As a catalyst, 52 parts by weight of n-butyl alcohol and 100 parts by weight of methyl silicate (hereinafter referred to as “tetraalkoxysilane condensate (1)”) having a weight average molecular weight of 1000, an average degree of condensation of about 8 and a non-volatile content of 100% After adding 0.03 part by weight of dibutyltin dilaurate and mixing, a demethanol reaction was performed at 75 ° C. for 8 hours to synthesize a tetraalkoxysilane condensate (2).
This tetraalkoxysilane condensate (2) has a transesterification rate (ratio of butoxy groups to all alkoxyl groups) of 38 equivalent%, and the average number of carbon atoms of the alkoxyl group is 2.2. The remaining silica ratio was 43% by weight.

Example 1
A curing agent (1) was obtained by uniformly mixing 30 parts by weight of polyisocyanate (1), 40 parts by weight of tetraalkoxysilane condensate (2) and 30 parts by weight of Solvesso 100 (manufactured by Exxon Chemical).
As the polyisocyanate (1), an isocyanurate structure-containing polyisocyanate (reaction product of hexamethylene diisocyanate and n-butyl alcohol, nonvolatile content: 100% by weight, NCO content: 21% by weight) was used.

(Low temperature stability)
The said hardening | curing agent (1) was put into the transparent container, and after leaving it to stand in -20 degreeC environment for 2 hours, the external appearance was observed visually. The evaluation is as follows.
◎: No abnormality ○: Almost no abnormality ×: Cloudiness or phase separation

(Contamination resistance)
Non-aqueous dispersion type acrylic polyol (hydroxyl value 50KOHmg / g, weight average molecular weight 80000, glass transition temperature 35 ° C, solid content 50% by weight, medium: mineral spirit) A paint was prepared by uniformly mixing (1) at a weight ratio of 82:18.
Next, “SK # 1000 primer” (manufactured by SK Kaken Co., Ltd.) was applied to an aluminum plate of 300 mm × 150 mm × 1 mm so that the dry film thickness was 30 μm, and the standard state (temperature 23 ° C., relative humidity) 50%) for 8 hours, the paint obtained by the above method was applied to a dry film thickness of 40 μm, and dried for 7 days in a standard state to prepare a test specimen.
This test body was bent at 45 ° at 1/3 of the long side, and the wide area was set up vertically so as to face south in Ibaraki City, Osaka, and exposed outdoors for 3 months. The evaluation was performed by visually observing the presence or absence of rain streak on the vertical surface. The evaluation is as follows.
◎: Rain-stained dirt is not observed ○: Rain-stained dirt is slightly observed △: Rain-stained contamination is observed x: Significant rain-stained contamination is observed

(Table 1)
────────────────────────────
│ │Example 1│Example 2│Example 3│Comparative Example 1│
────────────────────────────
│Low temperature stability│ ○ │ ◎ │ ○ │ × │
│Contamination resistance │ ◎ │ ◎ │ ◎ │ × │
────────────────────────────

(Example 2)
A curing agent (2) was obtained by uniformly mixing 30 parts by weight of polyisocyanate (2), 40 parts by weight of tetraalkoxysilane condensate (2) and 30 parts by weight of Solvesso 100 (manufactured by Exxon Chemical).
As polyisocyanate (2), polyisocyanate having both isocyanurate structure and allophanate structure (reaction product of hexamethylene diisocyanate and n-butyl alcohol, non-volatile content of 100% by weight, NCO content of 21% by weight) is used. did.
The test was performed in the same manner as in Example 1 except that the curing agent (1) was changed to the curing agent (2).

(Example 3)
A curing agent (3) was obtained by uniformly mixing 30 parts by weight of polyisocyanate (3), 40 parts by weight of tetraalkoxysilane condensate (2) and 30 parts by weight of Solvesso 100 (manufactured by Exxon Chemical).
As polyisocyanate (3), allophanate structure-containing polyisocyanate (reaction product of hexamethylene diisocyanate and n-butyl alcohol, non-volatile content: 100% by weight, NCO content: 21% by weight) was used.
The test was performed in the same manner as in Example 1 except that the curing agent (1) was changed to the curing agent (3).

(Comparative Example 1)
A curing agent (4) was obtained by uniformly mixing 30 parts by weight of polyisocyanate (4), 40 parts by weight of tetraalkoxysilane condensate (1), and 30 parts by weight of Solvesso 100 (manufactured by Exxon Chemical).
As polyisocyanate (4), isocyanurate structure / allophanate structure combined polyisocyanate (reaction product of hexamethylene diisocyanate and 2-octanol, nonvolatile content: 100% by weight, NCO content: 21% by weight) was used. .
The test was performed in the same manner as in Example 1 except that the curing agent (1) was changed to the curing agent (4).

Claims (4)

(A) Polyisocyanate having an isocyanurate structure obtained by reaction of a monoalcohol having m carbon atoms (where m is an integer of 2 to 12) and an isocyanate compound, and (B) two or more alkoxyls having different carbon numbers A tetraalkoxysilane condensate containing a mixture of groups,
When the average carbon number of the alkoxyl group in the component (B) is n,
0 ≦ m−n ≦ 2
A curing agent for polyurethane resin paints, which is excellent in compatibility in a low temperature environment, characterized by satisfying (A) Polyisocyanate having an allophanate structure obtained by reaction of a monoalcohol having m carbon atoms (where m is an integer of 2 to 12) and an isocyanate compound, and (B) two or more alkoxyl groups having different carbon numbers. Containing tetraalkoxysilane condensate,
When the average carbon number of the alkoxyl group in the component (B) is n,
0 ≦ m−n ≦ 2
A curing agent for polyurethane resin paints, which is excellent in compatibility in a low temperature environment, characterized by satisfying (A) Polyisocyanate having an isocyanurate structure and an allophanate structure obtained by reaction of a monoalcohol having m carbon atoms (where m is an integer of 2 to 12) and an isocyanate compound, and (B) two types having different carbon numbers Containing a tetraalkoxysilane condensate in which the above alkoxyl groups are mixed,
When the average carbon number of the alkoxyl group in the component (B) is n,
0 ≦ m−n ≦ 2
A curing agent for polyurethane resin paints, which is excellent in compatibility in a low temperature environment, characterized by satisfying   The polyurethane resin excellent in compatibility in a low temperature environment according to any one of claims 1 to 3, wherein the component (B) is a tetraalkoxysilane condensate in which a methoxy group and a butoxy group are mixed. Curing agent for paint.