JPH0360845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to spray coating of polyurethane paint,
It relates to a method of spraying polyurethane formulations, such as spray lining of polyurethane elastomers.

(Prior Art and Problems) Traditionally, the spray coating method for polyurethane paints involves uniformly mixing in advance a base material mainly composed of a compound having at least two active hydrogen groups, a solvent, a pigment, etc., and a polyisocyanate. Spray painting is done using air spray or airless spray. This spray coating usually does not use a urethanization catalyst due to pot life issues, so curing after coating is slow and an extremely long curing period is required. At normal temperatures (20 to 25°C), curing for more than one week was required, but in winter, curing for more than 10 days was required. Furthermore, as a characteristic required for paints, adducts, prepolymers, and other derivatives of non-yellowing or non-yellowing polyisocyanates such as hexamethylene diisocyanate, water-added diphenylmethane diisocyanate, isophorone diisocyanate, and xylene diisocyanate must be used. As a result, the reaction rate was slow and a long curing time was essential. In addition, in order to shorten the curing period, a small amount of urethane catalyst is sometimes used in the main ingredient of polyurethane paints, but after mixing with polyisocyanate, the pot life is inevitably shortened, which interferes with stable painting work. Ori,
It has been difficult to achieve both quick reaction curing (short curing period) and long pot life.

Polyurethane elastomer has good abrasion resistance and durability, and is highly elastic, making it suitable for floors, aquariums, tennis courts,
It is used for lining swimming pools, etc., and can be applied by pouring with a trowel or spatula, or by spraying to achieve a uniform and beautiful finish. Even with this spray application, as with the urethane paint described above, it was difficult to achieve both shortening of the curing period (short reaction curing) and long pot life.

In order to achieve both the above-mentioned curing period and pot life, a double-headed spray gun is used, and a method of spraying while mixing with a device equipped with a polyol or polyisocyanate metering pump and a mixing device is also used. . In the former method, the polyol component and polyisocyanate component are injected from two spray nozzles, collided, and mixed while spraying. To shorten the curing period, it is possible to add a urethanization catalyst to the polyol component side, but each It is not used in general spray painting methods because there are restrictions on the spray amount ratio of the components, poor mixing conditions, and other restrictions on spray conditions.

In the latter case, a urethanization catalyst can be added to the polyol component to shorten the curing period, and the mixing and spraying properties are good, but the equipment is large-scale and expensive, and it is not suitable for on-site coating. Furthermore, if a mixture of a polyol component and a polyisocyanate component to which a urethanization catalyst has been added is sprayed for a long period of time, the sprayed matter will adhere to the air cap and nozzle of the spray gun due to the turbulence of the spray air. There was a problem in that the deposits rapidly solidified due to the urethanization catalyst and prevented uniform spraying.

It is also known, as described in JP-A-59-170153, to spray paints containing polyols and polyisocyanates with a carrier gas containing a vaporized tertiary amine. However, this method requires a device to vaporize the tertiary amine, and also requires heating or other means to maintain the tertiary amine in a vapor state in the carrier gas, making the work complicated. There were other problems.

As mentioned above, conventional spraying methods for polyurethane compounds have been used to shorten the curing period and
Although it has been difficult to achieve both a long pot life and good sprayability, the present invention has solved the problem by the following means as a result of intensive studies.

(Means for Solving the Problems) The method of spraying a polyurethane compound of the present invention involves bringing a liquid material containing a urethanization catalyst as an essential component into contact with compressed air in a quantitative supply device, and dispersing it in the form of mist droplets in the compressed air. Then, by spraying a compound containing a compound having at least two active hydrogen groups in the molecule and polyisocyanate as essential components with the compressed air, the compound and the urethanization catalyst are uniformly mixed and cured in a short time. It is characterized by this.

As the urethanization catalyst in the present invention, general urethanization catalysts can be used without particular limitation. Examples include organic tins, organic leads, and amines. These urethanization catalysts may be used alone or in combination of two or more.

Further, as the liquid material containing the urethanization catalyst as an essential component in the present invention, the above-mentioned urethanization catalyst is dispersed or dissolved in a solvent, process oil, plasticizer, etc. to be used. Further, the liquid urethanization catalyst may be used as it is.

The quantitative supply device for supplying the liquid material containing the urethanization catalyst as an essential component into compressed air in the present invention can be any quantitative supply device, but representative devices include a lubricator and a micro lubricator. etc. can be used.
In addition, the amount of liquid material containing a urethanization catalyst as an essential component to be supplied into the compressed air may be determined by taking into account the setting of the curing period, the type of urethanization catalyst, the concentration of the mixture, etc. However, it is preferably supplied in a range of 0.1 cc/min to 300 c.c./min. By bringing the liquid material, which requires the urethanization catalyst, into contact with compressed air in the metering supply device, the liquid material, which requires the urethanization catalyst, is dispersed in the compressed air in the form of droplets.

Furthermore, the quantitative supply device used in the present invention may be installed anywhere from the compressed air supply section of the compressed air generating device such as a compressor to the spray gun, but between this point the urethanization catalyst is supplied as the essential component. It is preferable to make sure that there are no areas where the liquid substance may remain. The pressure of the compressed air may be any pressure that does not interfere with spraying, and is preferably 2 to 5 kg/cm ² .

As the compound having at least two active hydrogen groups in the molecule in the present invention, all compounds that are generally used in polyurethane paints, polyurethane lining materials, etc. and can react with isocyanates can be used, such as polyether polyol, polyester polyol, polyacrylic polyol, polyether polyester polyol,
Examples include liquid diene polymer polyols, modified products and derivatives thereof. In addition, depending on the required properties, these compounds may include organic pigments, inorganic pigments, extender pigments, polyhydric alcohols, amines, antifoaming agents, dispersants, antisettling agents, flow regulators, thixotropic agents, slip agents, fillers, Oil, plasticizer, inorganic reinforcing agent, organic reinforcing material, antioxidant, ultraviolet absorber, conductivity imparting agent, antistatic agent, surfactant, water repellent,
Dyes, various solvents, etc. can be added.

As the polyisocyanate in the present invention,
Mention may be made of the usual aromatic, aliphatic and cycloaliphatic ones, such as hexamethylene diisocyanate, hydrated diphenylmethane diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate. and modified products, derivatives, crude forms thereof, and isocyanate prepolymers obtained by reacting the above-mentioned isocyanates with polyhydric alcohols or polyols, etc.
Furthermore, if necessary, these diluted with a solvent or the like can also be used.

Although any conventional air spray gun can be used as the spray device in the present invention, airless spray guns cannot be used for the purpose of the present invention.
However, an air assisted airless spray gun, which is an intermediate spray gun between an air spray gun and an airless spray gun, that is, a gun that pressurizes the spray liquid like an airless spray system and sprays using compressed air is the object of the present invention. It can be used because it matches.

(Effects of the Invention) According to the present invention, a liquid material containing a urethanization catalyst as an essential component is supplied into compressed air in a larger amount than in conventional spraying methods, and active hydrogen groups are added to the molecule at least. 2. By spraying a compound containing a unique compound and polyisocyanate as essential components with the compressed air, the compound and the urethanization catalyst are uniformly mixed.
This has made it possible to achieve both short-time reaction curing (short curing period) and long pot life, which were previously considered difficult to achieve. Needless to say, it is possible to obtain a beautiful and uniformly coated product similar to that achieved by the conventional spray method. Furthermore, according to the present invention, the mixture of polyol component and polyisocyanate component is uniformly mixed with the finely divided urethanization catalyst only after it is ejected from the spray gun. This eliminates problems such as adhesion of the formulation and interference with uniform spraying due to rapid reaction solidification.

(Examples and Comparative Examples) Examples and Comparative Examples of the present invention will be described below, but the present invention is not limited to these Examples.

Example 1 An aluminum plate was coated by the spray method according to the present invention under the following conditions, and the progress of reaction curing of the coating film was measured by changes in adhesion and hardness of the coating film. The pot life of the compounded paint was also measured using a viscosity cup. The measurement results are shown in FIGS. 1, 2, and 3.

(1) Paint composition used (parts by weight) Acrylic polyurethane paint Urethane top #
8000 (Asia Kogyo Co., Ltd.) 15 Hardening agent (non-yellowing polyisocyanate) 3 Thinner 16 (2) Spray conditions (a) Spray gun W-71-2G (Iwata Painting Machine Co., Ltd.) (b) Urethane catalyst required Mixture of liquid as components Part by weight dibutyltin dilaurate (urethanization catalyst) 1 xylene 100 (c) Lubricator L-150 (Koganei Seisakusho Co., Ltd.) is used as a quantitative supply device for the liquid whose essential component is urethanization catalyst. The amount of compressed air supplied into the air was adjusted to 1 c.c./min.

(d) Spray air pressure 3.5Kg/cm ² (e) Spray amount of acrylic polyurethane paint
130±10g/m ² 〃 Ejection amount
150c.c./min (f) Drying conditions: Standing at room temperature (20-25℃) (3) Surface treatment of the object to be coated The aluminum plate was degreased with toluene.
When spraying under the above conditions, it was confirmed that the urethanization catalyst solution was coming out of the spray gun together with the spray air, and then spraying was carried out to obtain a uniform and beautiful coated aluminum plate. The coating film of this coating has exactly the same finish as the conventional general spray method, and the pot life of the paint formulation is the same as that of the conventional general method that does not use a urethanization catalyst, and is very good. Ta.

Example 2 10 parts by weight of triethylamine was added to cellosolve acetate as a liquid material that required a urethanization catalyst.
An aluminum plate was coated by spraying under the same conditions as in Example 1, except that a solution of 100 parts by weight was used. The progress of reaction curing of the coating film was measured by the adhesion of the coating film and changes in curing, and the results are shown in FIGS. 1 and 2. The pot life of the paint formulation is also shown in FIG. The coating film of this painted product had the same finish as the conventional general spray method, and the pot life of the paint formulation was very good, the same as that of the conventional general method that does not use a urethanization catalyst.

Comparative Example 1 An aluminum plate was coated under all the same conditions as in Example, except that a liquid material containing a urethanization catalyst as an essential component, that is, a urethanization catalyst xylene solution, was not supplied into compressed air as in a conventional general spraying method. The results of measuring the progress of reaction curing of the coating film based on the adhesion and hardness changes of the coating film are shown in the first table.
As shown in Fig. 2. The pot life of the paint formulation is also shown in FIG. The finish condition of this coated product was the same as in the example, and the pot life of the paint formulation was long and good, but the progress of reaction curing of the paint film was extremely slow, and a long curing period was required. It was hot.

Comparative Example 2 As a conventional spraying method, a small amount of a urethane catalyst is added to a polyurethane paint to accelerate the rate of reaction and curing of the paint film. As this comparative example, 0.1% by weight of the urethanation catalyst dibutyltin dilaurate was blended into the polyurethane paint, and the other conditions were the same as in Example 1.
Spray painted on aluminum plate. The progress of reaction curing of the coating film was measured by changes in adhesion and hardness of the coating film, and the results are shown in FIGS. 1 and 2. The pot life of the paint formulation is also shown in FIG.

Although the finished state of this coated object is the same as in the example, the pot life of the paint formulation is extremely short and the workability of the spray paint is poor. In addition, the progress of reaction curing of the coating film is faster than that of Comparative Example 1, but
It is much slower than in the example and requires a curing period.

Testing methods for paint films and paint formulations (1) Adhesion measurement by grid test (Figure 1)
A grid cut was made on the coating film according to the grid test method of JIS K-5400, cellophane tape was pasted on the surface, and the cellophane tape was peeled off to examine the peeling status of the coating film. Evaluation was based on the JIS K-5400 grid test evaluation point method.

(2) Hardness measurement by pencil scratch test (Figure 2)
According to the JIS K-5400 pencil scratch test method,
Pencil hardness was measured.

(3) Measurement of pot life using viscosity cup (Figure 3)
These are the results of measuring the flow time of the paint formulation using a viscosity cup (type NK-2). In spray painting, it has traditionally been said that a time range of 20 to 25 seconds is suitable for spraying.

Measurement conditions: Temperature: 25°C Test results of paint film and pot life of paint formulations From Figures 1 and 2, it can be seen from Figures 1 and 2 that the reactive hardening rate of the paint film in the example reached practical strength in a significantly shorter time than in the comparative example. I understand. Furthermore, as shown in Figure 3, the pot life of the paint formulation in the example is the same as that of the non-catalyzed formulation (comparative example 1), although the reaction curing rate of the coating film is extremely fast. .

[Brief explanation of drawings]

FIG. 1 is a graph showing the test results of the adhesion measurement by the grid test of the examples of the present invention and the comparative examples;
Figure 2 is a graph showing the test results of the hardness measurement by the pencil drag test of the examples of the present invention and comparative examples, and Figure 3 is the graph showing the measurement results of pot life of the examples of the present invention and comparative examples. This is a graph.

Claims (1)

[Claims] 1 A liquid material containing a urethanization catalyst as an essential component,
The composition is brought into contact with compressed air in a quantitative supply device to be dispersed in the form of mist in the compressed air, and the composition containing a compound having at least two active hydrogen groups in the molecule and polyisocyanate as essential components is sprayed with the compressed air. A method for spraying a polyurethane compound, characterized by uniformly mixing the compound and a urethanization catalyst and curing the compound in a short period of time.