JPS583518B2 - Thickener for water-based paints - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in thickeners for water-based coatings.

The water-based paint as used in the present invention refers to a product obtained by stirring and kneading component resins with pigments and/or metal powders, stabilizers, and solvents.

Moreover, the neutralization rate refers to the degree of neutralization of carboxyl groups in the resin used in the water-based paint.

For example, when 100% of the carboxyl groups in the resin are neutralized, the neutralization rate is said to be 100%.

In recent years, laws regarding water, air, noise, etc. have been enacted in order to protect the environment, and organic solvents emitted from paint booths have become a problem as they pollute the air, and the amount of water-based paints with low organic solvent content has decreased over the years. It is on the rise.

Now, one of the methods for applying this water-based paint is a method in which a water-dispersion paint, a water-based emulsion paint (both with a neutralization rate of 80% or less) and a thickener are brought into contact with each other at the time of painting or on the painted surface.

This coating method can be easily applied even in high humidity atmospheres, so it is attracting attention as a promising coating method that will further develop in the future.There are many types of thickeners used in this coating method. However, any material that dissolves and swells the dispersed particles in the paint can be used.

In particular, amines are promising as thickeners because they have the property of rapidly thickening paints even in small amounts.

However, when an object coated with a water-based paint using a low-boiling point amine is placed in a drying oven, the amine on the surface of the object evaporates rapidly and the viscosity of the water-based paint decreases.
Painting defects such as sagging and metal unevenness are likely to occur on the surface of the object to be painted.

In addition, objects coated with water-based paints using high-boiling point amines do not have the above-mentioned coating defects during painting and drying, but even after drying, there are amines may remain.

Such a coating film is easily dissolved in a solvent, and also tends to have problems in water resistance, weather resistance, hardness, etc.

For example, when a water-based paint is applied to the exterior of a car using a high-boiling point amine, the paint film deteriorates due to the amine remaining in the paint film as a result of exposure to sunlight, rain, sulfur dioxide, etc. in the air. promoted.

Note that the thickening effect of water-based paints differs depending on the type of amine, but in general, amines increase the viscosity by about 1000 times when used at about 1% to 100 parts of the paint, but solvents other than amines increase the viscosity by about 100 times per 100 parts of the paint. When used at 1%, the thickening effect is as low as 10 times or less.

In view of the above, the present inventors have developed the present invention as a result of intensive research into the development of thickeners for water-based paints.
This is what I propose here.

The thickener for water-based paints of the present invention is characterized by comprising an amine or aqueous ammonia whose boiling point is below the paint baking temperature and an organic solvent whose boiling point is above the paint baking temperature.

In addition to ammonia water, examples of amines whose boiling point is below the paint baking temperature include diethylamine (boiling point 55.5
℃), triethylamine (boiling point 89 to 90℃), etc., and organic solvents with a boiling point higher than the paint baking temperature include:
For example, butyl cellosolve, butyl carbitol, etc. are commonly used, but if the ratio of the two is mixed, if the ratio of amine is too high, an amine odor will be felt when painting, and if the ratio of amine is low, the thickening effect will be poor. Therefore, a suitable ratio of amine to organic solvent is 1:5 to 15.

The present invention will be specifically explained below using examples in which a thickener for water-based paints is used for coating water-based paints.

Example 1 Using a hand-blown double-headed spray gun shown in the side view of FIG. 1 and the front view of FIG. Thor and a thickener at a blending ratio of 1:10 (on an anhydrous basis) were simultaneously coated.

As shown in the figure, the water-based paint A shown in Table 1 is supplied from the hose 2 of a hand-blown double-headed spray gun 1, the thickener is supplied from the hose 3, and the trigger 4 is pulled to supply air from the air hose 5. Water-based paint A and thickener were simultaneously atomized and jetted from nozzles 6 and 7, respectively, and a vertically erected test piece (not shown) was coated under the coating conditions shown in Table 2 below. After drying, the test piece was The painted surface was visually observed and judged according to the following criteria.

In addition, when the painted test piece was subjected to a water resistance test at 40°C, blistering occurred after 600 hours.

Reference Example 1 Coating was carried out in the same manner as in Example 1 except that the thickener in Example 1 was replaced with 10% aqueous ammonia.

After drying, the coated surface of the test piece was visually observed and evaluated according to the same criteria as in Example 1.

The results are shown in Table 4.

Reference Example 2 Coating was carried out in the same manner as in Example 1, except that the thickener in Example 1 was replaced with 30% ethanolamine water.

After drying, the coated surface of the test piece was visually observed and evaluated according to the same criteria as in Example 1.

The results are shown in Table 5.

In addition, when the painted test piece was subjected to a water resistance test at 40°C, pristle occurred in 192 hours.

Reference Example 3 Coating was carried out in the same manner as in Example 1 except that the thickener used in Example 1 was replaced with butyl carbitol.

After drying, the coated surface of the test piece was visually observed and evaluated according to the same criteria as in Example 1.

The results are shown in Table 6.

Reference Example 4 All the same as Example 1 except that the thickener of Example 1 was not used and only water-based paint A was applied at a painting booth humidity of 55 to 60%.
After coating and drying, the test piece was subjected to a water resistance test at 40°C, and blistering occurred after 600 hours.

The following observations will be made regarding the above examples and reference examples.

Please refer to FIG. 3, which is a graph of the viscosity of the water-based paint when 10 to 59 cc of the thickener used in the Examples and Reference Examples was added to 300 cc of the water-based paint A.

Reference Example 1: Water-based paint A thickened during painting due to the use of ammonia water as a thickener (see Figure 3), but as soon as the test piece was placed in a drying oven ( 1
The ammonia water in the wet coating film evaporated within minutes) and the viscosity decreased rapidly.

As a result, coating defects and sagging occurred as shown in Table 5.

Reference example 2... Thickener ethanolamine (boiling point 170.
(8°C), the coated surface was in good condition with no sagging during painting and drying.

However, in the water resistance test, compared to Example 1 and Reference Example 4, blistering occurred quickly and was extremely poor.

Reference example 3: The use of the thickener butyl carbitol thickens the water-based paint, but as shown in Figure 3, the thickening effect is inferior to that of solvents with amine groups, so the water-based paint already sag before drying. occured.

Reference Example 4: Since no thickener was used, no solvent remained in the coating film, and the water resistance test was the best.

However, painting is difficult unless the humidity is 60% or less.

Example 1: By using a mixture of ammonia water and butyl carbitol as a thickener, the ammonia water increases the viscosity of the water-based paint during painting (see Figure 3), so there is no sagging, and it is easy to use during setting and drying. Even if water evaporates in the initial stage or aqueous ammonia evaporates in the drying oven, the thickening effect of butylcarbitol can prevent the generation of sag.

In other words, during setting and drying, the high boiling point organic solvent prevents sagging even if water and aqueous ammonia evaporate, and no solvent remains in the coating after drying, so the reference example was used in the water resistance test. It was found that the same effect as 4 can be obtained.

As mentioned above, the thickener for water-based paints of the present invention can be used at the time of painting or after forming the painted surface, so that it can be used during painting or after forming the painted surface.
There are no coating defects during either setting or drying, and since ammonia water, amines, etc. do not remain in the coating film, a coating film with excellent water resistance, light resistance, hardness, etc. can be obtained. Inventions have extremely great industrial value.

[Brief explanation of the drawing]

Figure 1 is a side view of the hand-blown double-headed spray gun used in the examples, Figure 2 is a front view of the same, and Figure 3 shows the thickening effect of the water-based paint by the thickener used in the examples and reference examples. This is a graph to compare. In the figure, 1... double-headed spray gun for hand blowing, 2,
3...Hose, 4...Trigger, 5...
... Air hose, 6.7 ... Represents a nozzle.

Claims (1)

[Claims] 1. Additives applied simultaneously with the paint during painting or by spraying onto the painted surface after painting of water-based paints of the water-dispersion type or water-based emulsion type that contain resins with a degree of neutralization of carboxyl groups in the resin of 80% or less. A viscosity agent consisting of an amine or aqueous ammonia whose boiling point is below the baking temperature of the paint and an organic solvent which is soluble in water and whose boiling point is above the baking temperature of the paint and has the property of thickening the paint when mixed with the paint. A thickener for water-based paints characterized by containing: