JP2007169360A - Stock solution for coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stock solution for coating composition for forming a film which is excellent in weather resistance and durability, on the surface of various substrates such as a metal, a plastic, paper or the like, useful for coating, especially useful for rustproof paint, excellent in storing stability by solving conventional problems that the solution is unstable in a weakly acidic to neutral region when the solution contains silica in high concentration. <P>SOLUTION: The stock solution comprises the silica dispersion with 10-30 wt.% concentration of silica, wherein the silica dispersion is obtained by dispersing silica particles having ≤30 nm of an average primary particle diameter in the aqueous medium to have a secondary average particle diameter of ≤200 nm, and the solution contains 0.01-10 pts.wt of amino acid or its salt per 100 pts.wt of the silica particle. The solution is preferably applied to the preparation of the rustproof paint. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a stock solution for a coating composition for use in forming a film having excellent weather resistance and durability on the surface of various substrates such as metal, plastic, paper, etc. It relates to stock solutions useful for preparation.

  Conventionally, in coating compositions, silica has been added to a resin serving as a binder to improve the film properties. For example, the addition of silica in a rust-preventing paint improves the adhesion between the steel sheet and the surface-treated resin coating layer, and contributes to the formation of a dense and stable metal corrosion product in a corrosive environment. It is said to exhibit rust prevention properties (see, for example, Patent Documents 1 and 2).

  In this case, the silica is mixed into the composition in the form of a silica dispersion in which silica is dispersed in a solvent such as water. For example, in the use of a rust preventive paint, it is used by mixing the silica dispersion in an organic solvent or a water-soluble resin.

  As such a silica dispersion, so-called wet silica such as dry silica made by burning silicon tetrachloride as a raw material in an oxyhydrogen flame, precipitated silica made by neutralizing sodium silicate and gel silica is excellent. In addition, silica dispersions using such silica have attracted attention.

  However, since the dry silica and wet silica have strong cohesiveness, it is difficult to disperse them in a solvent with good dispersibility. For this reason, silica dispersions produced using these silicas are generally poorly stable, particularly in the weakly acidic to neutral regions that are encountered in the preparation of coating compositions such as paints. The silica dispersion liquid is inferior in stability and impractical because silica sedimentation or gelation occurs within a few days.

  Under such circumstances, as an improvement in stability under acidic conditions, colloidal silica treated with an aqueous solution of basic aluminum chloride, or an aluminum particle in an acidic silicic acid solution is allowed to grow to grow particles. Those containing an aluminum compound are known (see, for example, Patent Documents 3 and 4).

  However, although the silica dispersion obtained by these methods has stability under acidic conditions due to the presence of aluminum, it contains not only corrosive ions such as chloride ions but also metal impurities such as alkali such as sodium. Since the amount is large, there is a problem that the range of use is limited in applications where the presence of impurities is not preferred.

  In addition, when preparing a coating composition such as a paint, it is necessary to store it in a high concentration state that is diluted and used at the time of preparation, that is, in the state of a “stock solution” from the viewpoint of distribution cost, storage location, etc. There has been a growing demand for the problems of sedimentation and gelation of silica in the silica dispersion.

Japanese Patent Laid-Open No. 11-158649 JP 2000-15176 A Japanese Patent No. 2767646 JP-A-63-123807

  Therefore, the object of the present invention is that there is no residue of impurity ions such as sodium ions and chloride ions, which is a problem with conventionally used colloidal silica, and the silica concentration is 10% by weight or more. Another object of the present invention is to provide a coating composition stock solution comprising a silica dispersion in which the silica particles are highly dispersed even in a high dispersion, and the storage stability is long in a weakly acidic to neutral range.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, the silica dispersion containing an amino acid or a salt thereof does not gel during long-term storage and exhibits excellent storage stability such that silica particles do not settle, and coating compositions such as paints It has been found that it can exhibit excellent stability even in a pH change from weak acidity to neutrality, which is an environment encountered in the preparation of products, and can solve all of the above objects, and has completed the present invention. It was.

  That is, the present invention comprises a silica dispersion in which silica particles having an average primary particle size of 30 nm or less are dispersed in an aqueous medium so that an average secondary particle size (average aggregated particle size) is 200 nm or less. The dispersion liquid has a silica concentration of 10 to 30% by weight, and contains 0.01 to 10 parts by weight of an amino acid or a salt thereof with respect to 100 parts by weight of silica particles. It is.

  The present invention also provides a rust-preventing paint characterized by using the above coating composition stock solution as a component.

  The coating composition stock solution of the present invention contains an amino acid or a salt thereof in a silica dispersion in which silica particles are finely dispersed, and thus exhibits excellent dispersion stability and storage stability at high concentrations.

  And in the use of various coating compositions for imparting gas barrier properties, corrosion resistance, hydrophilicity, glossiness, liquid absorption, insulation, etc. to the surface of metal, plastic, paper, etc. It can be used effectively as a stock solution when preparing a coating composition, and a stable coating composition can be obtained even after preparation.

  In addition, when dry silica or wet silica (hydrous silica) is used as silica, it is preferable because it does not contain corrosive ions such as chloride ions. In addition to the property, it is possible to capture a metal ion eluted on the metal surface with an amino acid or a salt thereof and form a dense film, so that it is possible to obtain a rust-preventing paint having an extremely high rust-preventing property.

(silica)
In the present invention, known silica can be used without particular limitation. Moreover, these silica can also be used individually or in mixture of multiple types. Among the silicas, dry silica obtained by burning a silane-based gas such as silicon tetrachloride in an oxyhydrogen flame, and wet silica obtained by neutralization with an acid such as sodium silicate are particularly preferable.

That is, the above-mentioned dry silica and wet silica have a structure forming secondary agglomerated particles in which primary particles are gathered, and therefore, in a coating composition to which this is added, adhesion and workability are good. A film can be obtained.
The average primary particle diameter of the silica used in the present invention is preferably 30 nm or less. When silica having an average primary particle size larger than 30 nm is used, precipitates are likely to be deposited in the stock solution, resulting in poor storage stability.

It is preferable that the specific surface area of the silica used for this invention exists in the range of 50-400 m < ² > / g from the point of a rust prevention effect.

(Amino acid or its salt)
Moreover, in this invention, an amino acid is a compound which has an amino group and a carboxyl group in the same molecule, and a well-known amino acid is used without a restriction | limiting in particular. Some amino acids have optical isomers, but in the present invention, there is no difference in effect due to optical isomers, and any isomer can be used alone or in racemic form.

  If the amino acid used for this invention is illustrated concretely, the amino acid represented by following General formula (1) is preferable.

_{H 2 N-R-COOH (} 1)
In the general formula (1), R represents an arbitrary substituent, preferably a substituent having 10 or less carbon atoms, and more preferably a substituent having 8 or less carbon atoms. When the carbon number is larger than 10, the solubility in water is lowered, which is not preferable.

  Specific examples include glycine, alanine, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, phenylalanine, tryptophan, tyrosine, proline, glutamine, glutamic acid, asparagine, aspartic acid, lysine, arginine, histidine, etc. Among them, lysine, arginine, and histidine are particularly preferable from the viewpoints of dispersibility and storage stability of the silica particles in the coating composition stock solution.

  In the present invention, salts of the above amino acids such as acetates, formates, lactates and phosphates can also be used.

(Stock solution)
In the present invention, the concentration of silica in the silica dispersion constituting the coating composition stock solution is preferably 10 to 30% by weight, more preferably 10 to 25% by weight. That is, when the silica concentration in the silica dispersion is as high as 10% by weight or more, the effect of the present invention is particularly remarkable when the amino acid or a salt thereof is added. Cost can be reduced. Moreover, the raise of the viscosity of the stock solution for coating compositions can be suppressed by setting it as 30 weight% or less.

  In the present invention, the silica dispersion is prepared by atomizing the silica so that the average secondary particle diameter is 200 nm or less. By dispersing the finely divided silica particles, good storage stability can be obtained.

  In addition, the secondary particle diameter as used in the field of this invention is a value of the volume reference | standard arithmetic mean diameter measured with the light-scattering diffraction type particle size distribution measuring apparatus.

  The dispersion medium used in the stock solution for a coating composition of the present invention is mainly composed of water, but may contain a small amount of an organic solvent such as a low boiling point solvent such as lower alcohol or ethyl acetate. In that case, the organic solvent is preferably 20% by weight or less, more preferably 10% by weight or less, based on the total dispersion medium.

  In the present invention, the addition amount of the amino acid or salt thereof is such that the stock solution for coating composition can be stably produced without thickening and gelling, and the viscosity of the obtained stock solution for coating composition is lowered, and In order to improve the storage stability of the stock solution, it is preferably 0.01 to 10 parts by weight, particularly 0.02 to 5 parts by weight, based on 100 parts by weight of silica.

  That is, when the added amount of the amino acid or a salt thereof is less than 0.01 parts by weight, the effect of suppressing aggregation between silica particles is insufficient, which is not preferable. When the amount exceeds 10 parts by weight, the effect is small even if added in a large amount, and in some cases, aggregation of silica particles is promoted.

  Since the pH, viscosity, and storage stability of the coating composition stock solution with respect to the addition amount of amino acid or salt thereof are slightly different depending on the type of amino acid to be added, the optimum addition amount is selected from the range of the addition amount by experiment in advance. It is preferable.

  In the present invention, in order to improve the storage stability and dispersibility of the stock solution, an acid as a pH adjusting agent or a surfactant such as a silane coupling agent or an antifungal agent within the range not impairing the effects of the present invention. A small amount of an agent may be added.

  The coating composition stock solution of the present invention maintains dispersion stability over a long period of time even if it is weakly acidic to neutral, that is, pH 5-8.

(Method for producing undiluted solution)
In the present invention, the stock solution may be obtained by uniformly dispersing silica particles and an amino acid or a salt thereof in an aqueous medium, but in order to disperse silica as high as possible, a solution obtained by the following steps is preferable. Used for.

  That is, a method in which silica and an amino acid or a salt thereof are predispersed in an aqueous medium and then the predispersed liquid is atomized is preferable. Specifically, the preliminary dispersion is prepared by adding silica directly to a solution in which an amino acid or a salt thereof is mixed in an aqueous medium, mixing and dispersing, and after adding and dispersing silica in the aqueous medium. And a method of mixing and dispersing an amino acid or a salt thereof, a method of mixing and dispersing a liquid in which silica particles and an amino acid or a salt thereof are dispersed in an aqueous medium, and the like.

  The disperser used for the preliminary dispersion is not particularly limited, and specifically, a general stirrer having propeller blades, turbine blades, paddle blades, etc., a high-speed rotary radial stirrer such as a disper mixer, a homogenizer, a homomixer, an ultra Dispersers such as high-speed rotary shear type agitators such as mixers, colloid mills, planetary mixers, and suction type dispersers, and further, composite type dispersers combining the above high-speed rotary shear type agitators, propeller blades and paddle blades, and planetary Examples thereof include a composite disperser in which a mixer and a high-speed rotation centrifugal radiation stirrer or a high-speed shear stirrer are combined.

  Moreover, the method in particular of atomizing the preliminary liquid mixture obtained by said method is not restrict | limited, The method using a well-known atomization apparatus is employ | adopted. Specifically, the atomization method using wet media type | mold dispersers, such as a sand mill and a bead mill, an ultrasonic homogenizer, a high-pressure homogenizer, etc. are mentioned.

(Other conditions)
In the present invention, in order to produce more stably without causing thickening or gelation during the production of the coating composition stock solution, it is preferable to control to a temperature range of 45 ° C. or less, particularly 20 to 40 ° C. .

  The method for controlling the temperature range is not particularly limited, and a known cooling means that does not affect the composition of the liquid is employed without any particular limitation. For example, by appropriately selecting cooling means such as installation of a jacket type cooler outside each dispersion tank, installation of cooling piping inside each dispersion tank, installation of a heat exchanger at each equipment inlet or outlet piping section, etc. Apply.

(Anti-rust paint)
The amino acid or salt thereof contained in the anticorrosive paint prepared using the stock solution for the coating composition of the present invention can be easily coordinated to the metal surface, thereby passivating the metal surface. Effective for zinc-based coated steel. The rust preventive paint of the present invention is mixed with an organic binder for the purpose of film formation.

  As the organic binder, various known binders used for preparing paints can be used. Specific examples of the binder include a polyurethane resin, a polyester resin, a polyacrylic resin, a melamine resin, and an epoxy resin. Moreover, the binder which mixed 2 or more types of the said binder can also be used.

  In the rust-preventing paint of the present invention, the ratio of the organic binder to the silica is not particularly limited as it is generally used in known paints. For example, the blending ratio is 100 to 2,000 parts by weight, preferably 150 to 1,000 parts by weight, and more preferably 180 to 500 parts by weight with respect to 100 parts by weight of silica.

(Other additives)
The rust preventive agent of the present invention can contain any known additive as long as the effect of the present invention is not significantly reduced. Examples of typical additives include surfactants, pH adjusters, antifoaming agents, and antifungal agents.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In addition, the physical-property measurement and rust-proof evaluation of the coating composition undiluted | stock solution were performed with the following method.

(1) Viscosity measurement After collecting 300 g of the coating composition stock solution in a 500 ml container and placing it in a thermostatic bath at 30 ° C. for 10 minutes, the coating composition was used at 60 rpm using a B-type viscometer (manufactured by Tokimec, BL). The viscosity of the stock solution was measured. The change in viscosity over time was determined by measuring the viscosity of the resulting coating composition stock solution that had been aged for 30 days at 25 ° C. in the same manner as described above.

(2) pH measurement 300 g of the coating composition stock solution was collected in a 500 ml container, and the pH of the coating composition stock solution was measured using a pH meter (H-22, manufactured by Horiba, Ltd.).

(3) Measurement of average secondary particle size After diluting the undiluted solution with ion-exchanged water so that the silica concentration of the undiluted solution for coating composition is 10% by weight, a light scattering diffraction type particle size distribution analyzer (Beckman Coulter) Manufactured by Coulter LS-230), the volume-based arithmetic average diameter was measured, and this value was adopted as the average secondary particle diameter.

  In the measurement, the refractive index of water (dispersion medium) 1.332 and the refractive index of silica 1.458 were input as parameters.

(4) Rust prevention evaluation The coating composition stock solution and water-soluble polyurethane resin (Daiichi Kogyo Seiyaku Co., Ltd., Superflex 110) are mixed so that the water-soluble polyurethane resin is 200 parts by weight with respect to 100 parts by weight of silica. A rust-proof paint having a silica concentration of 5% by weight and a resin solid content of 10% by weight was obtained.

  As the metal plate to be treated with the anticorrosive paint, a 150 mm × 70 mm × 0.8 mm hot-dip alloyed galvanized steel plate was degreased using acetone, then washed and dried. Next, the above-mentioned rust preventive paint was applied to a steel plate with a # 3 bar coater, and baked with a drier kept at 150 ° C. to prepare a test piece.

  Evaluation was made by immersing the test plate in a 5% by weight aqueous sodium chloride solution, removing the remaining drops, leaving it in a humid atmosphere at 35 ° C. and a relative humidity of 85% for 120 hours, and visually observing the degree of corrosion of the test piece. The following criteria were used.

5: No occurrence of red rust, 4: Rust generation area less than 5%, 3: Rust generation area from 5% to less than 10%, 2: Rust generation area from 10% to less than 15%, 1: Rust generation area from 15% to 25% Less than 0: Rust generation area 25% or more Example 1
While gradually adding fumed silica having a specific surface area of 300 m ² / g (manufactured by Tokuyama, Leolosil QS-30) to ion-exchanged water, the liquid temperature was maintained at 30 ° C. By dispersing with LR-2), a silica slurry having a silica concentration of 12% by weight was obtained. This silica slurry and lysine aqueous solution were mixed and dispersed so that lysine was 0.1 parts by weight with respect to 100 parts by weight of silica to obtain a premixed solution. The liquid temperature during the preliminary mixing was maintained at 30 ° C. This premixed solution was atomized using a high-pressure homogenizer (Nanomizer, Nanomizer, LA-31) at a treatment pressure of 80 MPa to obtain a stock solution. Table 1 shows the physical properties and evaluation results.

Example 2
A stock solution was obtained in the same manner as in Example 1 except that histidine was used as an amino acid. Table 1 shows the physical properties and evaluation results.

Example 3
A stock solution was obtained in the same manner as in Example 1 except that arginine was used as the amino acid. Table 1 shows the physical properties and evaluation results.

Example 4
A stock solution was obtained in the same manner as in Example 2 except that the silica concentration was 16% by weight and the amount of histidine to be added was 0.2 parts by weight. Table 1 shows the physical properties and evaluation results.

Example 5
A stock solution was obtained in the same manner as in Example 3 except that fumed silica (manufactured by Tokuyama, Leoroseal QS-09) having a specific surface area of 90 m ² / g was used as silica. Table 1 shows the physical properties and evaluation results.

Example 6
Commercially available sodium silicate and ion-exchanged water were charged into the reaction vessel so that the concentration of sodium silicate was 5% by weight. The temperature of the reaction vessel was set to 40 ° C., neutralization reaction (up to a neutralization rate of 50%) was performed using 22 wt% sulfuric acid, and then the temperature of the reaction solution was set to 95 ° C. The sulfuric acid was added to the reaction solution until the neutralization rate reached 100%. Filtration and washing operations were repeated on the produced silica to obtain a silica cake (silica content 15% by weight). Next, while gradually adding ion-exchanged water to the wet silica cake, the liquid temperature is maintained at 30 ° C., and the mixture is dispersed with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2), whereby a silica concentration of 12% by weight is obtained. A silica slurry was obtained. This silica slurry and lysine aqueous solution were mixed and dispersed so that lysine was 0.1 parts by weight with respect to 100 parts by weight of silica to obtain a premixed solution. The liquid temperature during the preliminary mixing was maintained at 30 ° C. This premixed solution was atomized using a high-pressure homogenizer (Nanomizer, Nanomizer, LA-31) at a treatment pressure of 80 MPa to obtain a stock solution. Table 1 shows the physical properties and evaluation results.

Example 7
A stock solution was obtained in the same manner as in Example 6 except that glycine was used as the amino acid. Table 1 shows the physical properties and evaluation results.

Example 8
A stock solution was obtained in the same manner as in Example 6 except that cysteine was used as the amino acid. Table 1 shows the physical properties and evaluation results.

Example 9
A stock solution was obtained in the same manner as in Example 6 except that lysine was used as the amino acid. Table 1 shows the physical properties and evaluation results.

Example 10
A stock solution was obtained in the same manner as in Example 6 except that histidine was used as the amino acid. Table 1 shows the physical properties and evaluation results.

Example 11
A stock solution was obtained in the same manner as in Example 6 except that arginine was used as the amino acid. Table 1 shows the physical properties and evaluation results.

Comparative Example 1
A stock solution was obtained in the same manner as in Example 1 except that lysine was not added. Table 1 shows the physical properties and evaluation results.

Comparative Example 2
A stock solution was obtained in the same manner as in Example 1 except that it was not atomized with a high-pressure homogenizer. Table 1 shows the physical properties and evaluation results.

  The coating composition stock solution obtained in Example 1 was the same as the stock solution obtained in Comparative Example 1 in which no amino acid was added, and the coating composition stock solution obtained in Comparative Example 2 that was not subjected to high-pressure atomization. It can be seen that the stability is larger than that. In Comparative Example 2, since the average secondary particle diameter is 31 μm and the dispersion state is poor, it is considered that the storage stability is small compared to the highly dispersed stock solution.

Claims (3)

It consists of a silica dispersion in which silica particles having an average primary particle size of 30 nm or less are dispersed in an aqueous medium so that the average secondary particle size is 200 nm or less. The silica dispersion has a silica concentration of 10 to 30% by weight. And 0.01-10 parts by weight of an amino acid or a salt thereof with respect to 100 parts by weight of silica particles. The stock solution for a coating composition according to claim 1, wherein the pH of the stock solution is 5-8. A rust preventive paint comprising the coating composition stock solution according to claim 1 as a component.