JPH04234461A - Additive for water-base coating composition, and coating composition - Google Patents

Abstract

PURPOSE: To obtain an additive for aq. coating adapted to a coating compsn. used in a transport vehicle to make rheology proper to impart excellent coating properties and appearance by adding a specific amt. of essentially hydrophilic colloidal silica and a specific amt. of a crosslinking agent.

CONSTITUTION: 50-99 wt.% of essentially hydrophilic colloidal silica (e.g.; fumed silica) and 0.1-50 wt.% of a crosslinking agent substantially containing 2-25 wt.% of a surfactant (e.g.; nonionic fluorinated hydrocarbon polymer) pref. soluble or dispersible in water are contained.

COPYRIGHT: (C)1992,JPO

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention mainly applies to water-based
erborne) Relates to rheology control additives used in paints. Paintability and final appearance are important properties, especially in paints used on transportation vehicles.

0002

BACKGROUND OF THE INVENTION The rheology of coating compositions greatly influences the important properties mentioned above. In the case of spray coating compositions, the general rheology requirements for solvent and water-based coatings are similar to each other, but the specific requirements are distinct. These differences are primarily due to the fact that water is a solvent with a very slow evaporation rate. Also water and oil-based (so
Due to the vast differences in chemistry between solvents commonly used in paint compositions (bent borne), many of the rheology control additives used in the latter compositions cannot be is not suitable for

The general rheology requirement is that the paint has a high viscosity in the low shear rate range and a low viscosity in the high shear rate range. The former is necessary to improve resistance to settling and denting, and to ensure good metal piece controllability. Furthermore, the coating composition should have little elasticity in the high shear rate range.

Additives are commonly used to achieve proper rheology in coating compositions. However, there are few additives suitable for use in water-based paints used in transportation vehicles. U.S. Patent No. 4,416,94
No. 1 and No. 4,429,066 describe that colloidal silica works well together with crosslinking agents as rheology control additives for oil-based paint systems. Also, Cabot Corp. Instructions by “Cab-O
-Sil Properties and Fu
nctions'' describes the use of additives to adjust the viscosity of an aqueous dispersion of fumed silica. U.S. Pat. No. 4,416,941 also describes the use of colloidal silica in water-based color coating compositions. Surprisingly, the crosslinking agents described below greatly improve the action of colloidal silica in water-based paints, thereby improving the paintability and appearance of the paint.

[0005]

SUMMARY OF THE INVENTION The present invention is an additive for aqueous coating compositions comprising colloidal silica and a water-soluble or water-dispersible surfactant containing about 1-25 wt% fluorine. Concerning additives.

The additives of the invention improve the coatability and appearance of water-based paints. The additives of the invention may be used in coating compositions for painting automobiles, trucks and buses. Additives may also be used in a variety of waterborne coating compositions, including undercoats, primers, sealers, color coats, base coats, and clear coats.

The additives of the present invention improve pseudoplastic rheology in aqueous coating compositions, thereby improving coatability and final appearance. The additives of the present invention are also used at levels of about 0.1 to 30 wt% based on the weight of the coating composition. The rheology imparted to the paint by the additives of the invention makes it possible to form attractive, defect-free coatings using conventional equipment, especially spray coating. In the case of metallic coating compositions, the additives of the invention improve good flake control. Good flake control means that the iridescent pigment, typically aluminum flakes, is evenly distributed parallel to the substrate. This alignment of the pigments improves the shine of the paint, avoids mottling, and creates a good flop. Additionally, the additives of the invention retard pigment settling, thereby improving paint stability and performance.

The silica (silicon dioxide) used in the additive of the present invention has a particle size of about 0.001 to 100 microns and a surface area of about 50 to 500 m2/g. An example of such colloidal silica is fumed silica, or pyrogenic silica. This silica is formed by hydrolysis of silicon tetrachloride vapor in a hydrogen and oxygen flame. Moreover, this silica is generally 98 wt% or more, preferably 98 wt% or more, and preferably 98 wt% or more.
It has a SiO2 content of 9.6 wt% or more.

The additive of the present invention also contains a crosslinking agent that interacts with the fumed silica to greatly increase the viscosity of the coating composition in the low shear rate range. This component of the additive is a water soluble surfactant containing 1-25 wt% fluorine.

The additive of the present invention is mainly used in water-based paints. The coating composition may use latex or water soluble or dispersible resins or combinations thereof as a binder. Coating compositions based on latex or water-soluble resins may be thermoplastic or thermosetting. Also, the coating composition may or may not be modified.

[0011] Commonly used coating compositions are based on acrylic resins. Suitable properties of the acrylic latex binder supplied for use include solids content 20-60%, pH ~10, weight per gallon (8.0-9.0). .1g/
cm3), minimum coating film formation temperature 0 to 70℃, SWORD (
Sward) Hardness 25-110, glass transition temperature 50℃
, molecular weight 150,000-3,000,000, number average molecular weight 30,000-60,000, oxidation index 5 based on solid
~35, volatile organic solvent content 0-20%, particle size 5
It is 0 to 150 nm. A particularly preferred acrylic latex is Neoc, sold by ICIResins.
ryl A-622, Neocryl A-640, N
eocrylA-6037, Johnson Wax
Joncryl J-537, J sold by
oncryl J-538, NL Industry
Arolon 860-w sold by ies
-45. The resin used in the pigment grinding process may also be an acrylic latex. The preferred properties of this latex provided for use are the same as for the acrylic latex binder described above.

The additives of this invention may be used in a variety of coating compositions. The additives of the invention are suitable for use in undercoats, ie primers, fillers, sealers. Additionally, the additives of the present invention can be applied to color coats, base coats,
It is also effective in top coat compositions including clear coats.

The additives of this invention are particularly useful in waterborne basecoats. In such systems, the color is contained in a base coat that is overcoated with a clear coat. The clear coat helps protect the underlying base coat and creates a high gloss finish.

Example 1 An 8 wt % aqueous dispersion of fumed silica was formed in an Eiger model VSE mini motor mill. The fumed silica had a particle size of 12 nm and a surface area of 200 m2/g. The silica was ground to a size of less than 20 microns. A part of this crushed base is 2wt
% silica concentration with deionized water. The viscosity distribution of this dispersion was measured before and after addition of the fluorine-containing surfactant (Figure 1). Measurements were performed on a Bohlin VOR at 25° C. using a 30 mm parallel plate geometry.

A fluorine-containing surfactant was added to the dispersion to an active level of 0.2 wt%. In this case, the viscosity in the low shear rate region was greatly increased due to the interaction between the surfactant and colloidal silica. The following description is a description of surfactants. It is non-ionic and about 50
wt% ethylene oxide linkage, about 10 to
It contains 20 wt% fluorine and has a molecular weight of about 20,000.

Examples 2-4 illustrate the use of the rheology control additives of this invention in actual coating compositions.

Example 2: Formation of a Base Coat Formation of an Acrylic Polymer Modified with Glycidyl Esters of Tertiary C10 Fatty Acids A 5-liter three-necked round-bottomed flask was equipped with a stirrer, thermometer, condenser, and nitrogen inlet. , monomer inlet installed, 680g methoxypropanol and 20g
of methyl ethyl ketone was charged. The mixture was brought to reflux and the temperature was adjusted to 140-141°C by adding 5.0 g of methyl ethyl ketone. 333g propenolic acid, 847 methyl-
2-Methyl-2-propionate, 450 g 2-ethylhexyl-2-methylpropionate, 180 g
isobornyl-2-methyl-2-propionate, 2
A monomer solution containing 7 g of Surfynol 440 was formed. A reaction initiation solution containing 36 g of t-butyl peroxobenzoate and 76 g of methoxypropanol was also formed. These monomer solutions and reaction starter solutions were added to the flask at a uniform flow rate over a period of 2 hours. After the addition is complete, add 35.
0g of methoxypropanol is flushed and 15g of t
A solution containing -butyl peroxobenzoate and 40 g of methoxypropanol was added over 10 minutes. The reaction was then held at reflux for 135 minutes. After reflux, 475 g of glycidyl esters of tertiary C10 fatty acids were added to the flask, heated to reflux temperature and allowed to react until constant acid number. The reaction is cooled and
Then 43g of methoxypropanol and 588g
of ethanol was added to the resin, which reduced the viscosity. The properties of the resin are viscosity Z5-Z6, solids content 60-61%, oxidation index 53-56 based on solids.

Formation of component A (aluminum base) 44
．． 0g of the above acrylic resin was added to 19.0g of butoxyethanol. This mixture was stirred until a homogeneous solution was formed. Then 38.0 g of commercially available oil-based aluminum paste was added to the resin solution. The resulting slurry was stirred until a smooth, uniform slurry was formed. This aluminum base is 49.8
wt% volatile organic solvent, 38.4wt% solid material,
Contains 24.3 wt% aluminum pieces.

Formation of Component B (Neutralized Base) To 300 g of deionized water was added 8.0 g of a 30% aqueous ammonia solution. The solution was thoroughly stirred before adding 100.0 g of acrylic resin. The resulting mixture was stirred until the solution became clear to slightly cloudy. The non-volatile content of this base was 14.8 wt%, the water content was 74.9 wt%, and the volatile organic oil content was 9.8 wt%. The final pH of this dispersion was 9.2.

Formation of component C (transparent resin latex) 48
．． 0g hydrophilic colloidal silica, 10.0g antifoam, and 1865g acrylic latex (Neoc
ryl A-622) was mixed in advance. This mixture was then ground in a horizontal mill until the particle size was less than 8 microns. Then 260 g of deionized water was added to the above slurry under stirring to form a homogeneous latex solution. Silica content is 2.2wt%
, the volatile organic substance content is 8.9 wt%,
The solid material content was 28.3 wt%.

Formation of component D (pigment base) 80 g of N
eocryl A-6037 and 30% of 2.1g
Ammonia water, 23.9g of transparent red oxide,
A pigment slurry was formed containing 0.2 g of defoamer. The components mentioned above were mixed together and pre-dispersed using a Cowles blade. The mixture was then ground in a horizontal mill until the desired particle size was obtained. 70.
A drop solution containing 0g of grinding resin and 2.0g of aqueous ammonia was added to the grinding section. The resulting pigment paste was reduced with stirring in a solution containing 5.75 g deionized water and 19.2 g butoxyethanol. The resulting pigment base had a pH of 9.2, 48 wt.
% solid matter content, 9.4wt% volatile organic matter content, 36.2wt% binder content, 11.8wt
% pigment content, and water content of 42.0 wt%.

Formation of component E (surfactant base) 48g
2.0 g of polymeric nonionic fluorocarbon surfactant was added to 100 g of deionized water. The mixture was stirred to form a slightly cloudy solution.

Example 3: Formation of water-based red metallic base coat

[Table 1]

The composition of Table 1 above was used to form a red metallic basecoat. The order of addition was as shown in Table 1. The entire solution was stirred after each component was introduced. The base coat is sprayed onto the primed panel with an epoxy primer. The base coat was sprayed onto the panel using conventional spray equipment until the base coat was covered. The base coat was allowed to flow along the panel for 30 minutes and then a clear coat was applied with an isocyanate-based clear paint. The final properties (including appearance properties) of the base coat after being applied with a conventional polyurethane clear coat are as shown in Table 2 below.

[0025]

[Table 2]

Example 4: Formation of water-based silver metallic base coat

[Table 3]

The composition of Table 3 above was used to form a silver metallic basecoat. The order of addition was as shown in Table 3. The entire solution was stirred after each component was introduced. The base coat is sprayed onto the primed panel with an epoxy primer. The base coat was sprayed onto the panel using conventional spray equipment until the base coat was covered. The base coat was allowed to flow along the panel for 30 minutes and then a clear coat was applied with an isocyanate-based clear paint. The final properties (including appearance properties) of the base coat after being applied with a conventional polyurethane clear coat are as shown in Table 4 below.

[0028]

[Table 4]

Although the present invention has been described above in detail with reference to specific examples, the present invention is not limited to such examples, and various embodiments are possible within the scope of the present invention. will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between silica particle size and dispersion viscosity.

Claims (10)

[Claims] Claim 1: An additive for water-based paints comprising substantially 50 to 99 wt% of hydrophilic colloidal silica and 0.1 to 50 wt% of a crosslinking agent. 2. The additive according to claim 1, wherein the crosslinking agent is a water-soluble or water-dispersible surfactant. 3. The additive according to claim 2, wherein the surfactant contains substantially 2 to 25 wt% fluorine. 4. The additive of claim 1, wherein the crosslinking agent has an ethylene oxide linkage and substantially 5,000 to 50
1. An additive which is a nonionic fluorinated hydrocarbon polymer having a weight average molecular weight of 0.000 and containing substantially 2 to 25 wt% fluorine based on the weight of the fluorinated hydrocarbon polymer. 5. A coating composition comprising a water-soluble binder resin, hydrophobic silica, and a crosslinking agent. 6. The coating composition according to claim 5, wherein the crosslinking agent contains substantially 2 to 25 wt % fluorine. 7. The additive of claim 5, wherein the crosslinking agent has an ethylene oxide linkage and substantially 5,000 to 50
1. An additive which is a nonionic fluorinated hydrocarbon polymer having a weight average molecular weight of 0.000 and containing substantially 2 to 25 wt% fluorine based on the weight of the fluorinated hydrocarbon polymer. 8. A coating composition comprising an acrylic latex binder resin, hydrophilic silica, and a crosslinking agent. 9. The coating composition according to claim 8, wherein the crosslinking agent contains substantially 2 to 25 wt % fluorine. 10. The additive of claim 8, wherein the crosslinking agent has an ethylene oxide linkage and a
1. An additive which is a nonionic fluorinated hydrocarbon polymer having a weight average molecular weight of 0,000 and containing substantially 2 to 25 wt% fluorine based on the weight of the fluorinated hydrocarbon polymer.