JPS61106677A - Thick-coat paint composition - Google Patents

Abstract

PURPOSE:The titled compsn. of high critical skimming film thickness and critical sagging film thickness suitable for coating a lower portion of an automobile body, obtd. by mixing a resin, pigment and solvent in such a manner as to give a predetermined proportion between solids of the pigment and the resin, non-volatiles content, viscosity and thixotropic index. CONSTITUTION:A resin such as polyester or melamine resin, a pigment such as talc or silica and a solvent such as arom. hydrocarbon solvent are mixed in such a manner as to give a proportion of a solid in the pigment to that in the resin of 65-75, non-volatiles content of 60-80%, viscosity of 3,000-4,500CPS at 20 deg.C and thixotropic index of 3-8, each based on the paint to be prepd. to obtain the purpose thick-coat paint compsn. It is pref. to use as a part of the pigment fine CaCO3 powder, bentonite, etc. in order to give additional thixotropic property and also pref. to compound these components in such a proportion that the specific surface area of the total pigment components in 100g of the paint is 600-700m<2>.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a high film thickness type paint, and more specifically, a high film coated on the lower surface of a car body, etc., to protect the car body from the impact of pebbles etc. thrown up while driving. This relates to thick paint. Note that the a-thickness type paint of the present invention can also be used for chemical plants, building materials, etc.

[Prior Art] The paint film may be damaged by I#J impact from pebbles etc. thrown up while driving, and the car body may corrode from that area.

In order to prevent such problems, it is effective to increase the thickness of the coating film. However, with ordinary liquid paints, increasing the film thickness causes problems such as sagging or bubbling (foaming), and there is a limit to the film thickness that can be applied at one time.

To resolve these problems, JP-A-56
-There is a high viscosity paint as seen in Publication No. 167766, which prevents dripping by applying with hot airless.
This is preferable because a coating film with a high thickness can be obtained without forming wrinkles or the like.

[Problems to be solved by the invention] Conventional high film thickness paints have high viscosity and are difficult to apply using normal painting methods.
It was also painted using a hot airless method that discharged the paint at high pressure. However, this method has problems with the stability of the paint because the paint composition gradually reacts because the paint is heated.

In addition, it was necessary to constantly circulate the paint between the spray gun and the pressure pump so that the paint was at a uniform temperature, and the circulation hose not only hindered the painting process but also used a lot of heat energy.

Furthermore, conventional cold airless paints can be applied with higher viscosity than normal air spray paints, and can be applied with a certain degree of film thickness. However, its coating viscosity is up to 1500-2500:1”, CP S
/ 20 'C & fi W ffi $5 ':'・
4ゞ181ゝBecause of problems such as sagging and underpainting, a paint that can provide a film thick enough to protect the car body and that causes fewer problems during painting has not yet been developed.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a high film thickness type paint that can be applied without cold air and which solves the above-mentioned problems without impairing painting workability.

[Means to solve the problem] Cold airless means that 100 to 150
This is a method of applying a high pressure of kg/cm 2 and discharging it from a fine slit at the tip of a spray gun to atomize and paint. Hot airless is a painting method similar to cold airless, except that the paint is heated to lower its viscosity.

In this cold airless method, as the viscosity of the paint increases, the particle size of the atomized paint increases, and when it is applied to the object, air is drawn in, leaving bubbles in the paint film. These bubbles then expand during baking and drying, resulting in coating film defects called wrinkles. Furthermore, if the viscosity becomes even higher, coating may become impossible.

In cold airless coating, as mentioned above, there is a close relationship between the viscosity of the paint and the quality of the paint film, and in general, the lower the viscosity at the time of painting, the better. However, as a result of extensive research, the present inventors have discovered that the viscosity of the paint at the moment it exits the fine slit at the tip of the spray gun is an important factor for maintaining the quality of the paint film. That is, the most desirable paint is one that has a low viscosity at the moment it is discharged from the spray gun, but increases in viscosity after being applied to the object to be coated, and the present invention provides such a paint.

That is, the high film thickness coating composition of the present invention is a solution type coating mainly composed of a resin, a pigment, and a solvent, in which the ratio of the solid content of the pigment to the resin is 65 to 75, and the nonvolatile content of the entire coating is The paint has a viscosity of 30 oO to 4500 CPS1 at 20° C. and a chicken index of 3 to 8.

The resin that is one component of the high film thickness coating composition of the present invention is a two-component thermal mixture such as polyester resin and melamine resin that are crosslinked by baking, polyester resin and isocyanate resin that are crosslinked by urethane bond, and epoxy resin and polyamide resin. Most conventional resins can be used alone, such as substances or partially reacted ones, or thermosetting resins such as unsaturated polyester resins and oil-modified alkyd resins, or thermoplastic resins such as petroleum resins, acrylic resins, and cellulose resins. It can be used alone or in combination of two or more.

The solvent, which is another constituent component of the present invention, can be a common organic solvent or water, but must be selected in consideration of the composition of the resin component.

The pigment, which is another component of the present invention, is integrally bonded to the resin, reinforcing the coating film and adding thickness to the coating. These pigments generally include talc, clay,
Extender pigments such as silica, silica, and alumina are used.

In some cases, organic pigments may also be used.

Further, for the purpose of imparting thixotropic properties, it is desirable to use particulate anhydrous silica, magnesium silicate, particulate calcium carbonate, bentonite, etc. as part of the pigment.

In addition to the above-mentioned components, various additives, color-saving face F1, etc. can also be used in the high film thickness type coating composition of the present invention as in the past.

The feature of the present invention lies in the composition ratio of each of the above-mentioned components. That is, it is desirable that the ratio of pigment to resin solid content is in the range of 65 to 75. Here, if the ratio is smaller than 65, sufficient film thickness and underarm film thickness cannot be obtained, and if it is larger than 75, the strength, appearance, etc. will be inferior. Further, it is desirable that the nonvolatile content of the high film thickness paint of the present invention is in the range of 60 to 80%. Here, the non-volatile content is defined as JIS-5.
This is a value measured by 4oO. This non-volatile content is 60
If it is less than %, the difference in film thickness between coating and drying becomes large, which is undesirable as sagging and flaking occur when trying to obtain a desired film thickness.

Further, it is desirable that the high film thickness type coating composition of the present invention has a sealing point of 3,000 to 45,000 PS at 20°C. This viscosity is measured using a BH type viscometer j・□::1, □5
．． □) e,, 1, 4. 1. □、Eng.

This is the viscosity when rotated at a speed of Orpm. If the viscosity is lower than 30,000 PS, sagging is likely to occur, and if it is higher than 45,000 PS, wrinkles and the like occur, resulting in poor appearance and in some cases making it impossible to paint.

The most distinctive feature of the present invention is that the chicken index is in the range of 3 to 8. This chicken index was measured using the above-mentioned BH type viscometer when the rotor rotational speed was 20 r.
Measure at two points: pm and 2 rpm, (2
It is 1a obtained by calculating viscosity of ROM/viscosity of 20 rDm). In other words, almost no stress is applied to II.
When a viscosity of (2 rpm) and a strong shear stress are applied (2
Orpm), and the larger this value, the stronger the thixotropic property (hereinafter referred to as thixotropy). Therefore, if the chicken index is less than 3, sagging is likely to occur during thick coating, and if it is greater than 8, the antifoaming properties and the smoothness of the coated surface will be poor. When the chicken index is within this range, the viscosity of the paint decreases due to the instantaneous shear stress discharged from the spray gun during painting, and the particle size of the paint decreases, resulting in good atomization. When it is applied to the object to be coated, no stress is applied, so the viscosity increases and the risk of sagging is reduced.

The above-mentioned chicken character is mainly brought about by the pigment component that imparts thixotropy in the pigment component. The pigment component that gives this chicken character is 2 to 20% by weight of the entire paint.
It is desirable that it be contained. Further, it is desirable that the specific surface area of all pigment components in the paint 1009 is 600 to 7000 mt.

When these conditions are satisfied, good chicken properties can be obtained.

The high film thickness coating composition of the present invention can be obtained by stirring and dispersing the above-mentioned components at high speed with a disper, etc., but it is also possible to disperse the pigments with a roll mill, sand mill, etc. to further make the pigment into fine particles. is desirable. This not only improves the surface condition of the coating film, but also further improves its properties.

It is also preferable to degas the recovered paint under reduced pressure.
Although the high film thickness type paint of the present invention exhibits its effects most when applied by cold airless painting, it can also be applied by hot airless painting as in the past.

It is also possible to apply by air spray by diluting with a suitable solvent.

[Function] Since the high film thickness type coating composition of the present invention has a large thickness, the viscosity decreases at the moment it is discharged from the spray gun during coating, and the viscosity increases when it is applied to the object to be coated.

[Example] The following will be specifically explained using Examples and Comparative Examples. The composition and test results are shown in the table.

(Example 1) 30 parts by weight of a polyester resin with a non-volatile content of 60%, 7 parts by weight of a melamine resin with a non-volatile content of 70%, 1 part by weight of a catalyst (Catalyst #6000, manufactured by Mitsui Toatsu Chemical Co., Ltd.), ~
48 parts by weight of silica powder with a particle size distribution of 50μ, 2 parts by weight of fibrous magnesium silicate, and 1 part by weight of acrylic antifoaming agent.
parts by weight and 11 parts by weight of a mixed solvent of aromatic hydrocarbon solvent (Ibusol 15o1 manufactured by Idemitsu Chemical Co., Ltd.) were stirred and mixed in a disper for 15 minutes, passed through a three-roll mill three times to disperse, and then transferred to a defoaming tank. The mixture was transferred to a vacuum chamber and degassed at a reduced pressure of about 7 QcmHg to obtain 1 q of the high film thickness type coating 1 composition of the present invention of Example 1.

(Example 2) The same raw materials as in Example 1 were used, except that 40 parts by weight of silica powder and 10 parts by weight of lu-form magnesium silicate were used as pigments, and the same methods were used for mixing, dispersing, and defoaming. 1 q of the high film thickness coating composition of Example 2 was used.

(Example 3) The same raw materials as in Example 1 were used in the same amounts, except that 1 part of 30 mff of silica powder and 201 parts of m-group magnesium silicate were used as pigments, and the material was mixed, dispersed, and defoamed in the same manner. The high film thickness coating composition of FM Example 3 was prepared.

(Comparative Example 1) 49 mm part of silica powder as a pigment and
Iu 7. j Etsu A @ 491f [-0,60 Oi 4
．． .

The same raw materials as in Example 1 were used in the same m, and mixed, dispersed, and defoamed in the same manner as in Example 1 to obtain the high film thickness type coating composition of Comparative Example 1 (q). The paint shows good results when applied conventionally using a hot airless method. (Comparative Example 2) Same as Example except that 25 parts by weight of silica powder and 25 parts of fibrous magnesium silicate were used as pigments. The same raw materials as in Comparative Example 2 were used in the same amount, and mixed, dispersed, and defoamed in the same manner as in Comparative Example 2 (q).

(Comparative Example 3) The same amounts of raw materials as in Example 1 were used, except that 25 parts by weight of silica powder and 25 parts by weight of fine-particle thermal silica (Aerosil #380, manufactured by Nippon Aerosil Co., Ltd.) were used as pigments, and mixed in the same manner. , dispersion, and defoaming to obtain a coating material of Comparative Example 3.

The viscosity and chicken index of the paints of the above examples and comparative examples were measured, and the specific surface area of the pigment was calculated and shown in the table. The viscosity was measured using a BH type viscometer (manufactured by Tokyo Keiki Co., Ltd.) at 20 rl at 20°C with a No. 4 rotor.
) m conditions.

In addition, the chicken index is the viscosity measured at 20°C with a rotor rotation speed of 2 rpm and the above 20 rl) m.
This is the value of the ratio to the viscosity measured under the following conditions.

(Test Example) The paints of the above Examples and Comparative Examples were subjected to cold airless painting and hot airless painting to examine the effects of the present invention, and the critical film thickness at which wrinkles occur and the critical film thickness at which sag occurs were measured. The results are shown in the table.

Here, the underarm film thickness limit was determined under the following conditions.

Paint at a liquid temperature of 18°C is heated to 110k using a cold airless coating machine (Big Bear, manufactured by Asahi Okuma Co., Ltd.) with a compression ratio of 30:1.
Each paint was discharged from a nozzle tip (12C09 manufactured by Asahi Okuma Co., Ltd.) at a pressure of g/cm 2 and applied individually to a vertically erected object 3 qcm apart so that the film thickness changed almost continuously. did. The object to be coated was a 300 mm x 30 Q mm x 0.8 mm mild steel plate covered with an electric coating film. After leaving it for 5 minutes, bake it for 10 minutes at 110℃ and then bake it for 1 more time.
After baking at 40° C. for 30 minutes and allowing to cool, the maximum film thickness in the area where no wrinkles such as foaming or blisters had occurred was measured and determined as the limit film thickness for underarms.

Again, the sauce is at its limit! The thickness was determined by using the same mild steel plate held vertically under the same conditions as for measuring the underarm critical film thickness. Each paint was applied individually so that the thickness varied continuously, and the maximum film thickness at which the paint did not flow when left as is was defined as the sagging critical film thickness.

In addition, hot airless painting was performed under the same conditions as the cold airless method except that the paint liquid temperature was 42° C. and the paint was circulated, and the underarm critical film thickness and sagging critical film thickness were measured in the same manner.

From the table, the high film thickness type coating compositions of the present invention in Examples have an armpit film thickness limit of 400 to 455μ and a sag limit of l! Thickness is 410~5
00μ or more, showing excellent performance. On the other hand, in the cold airless coatings of Comparative Examples 2 and 3, the sag limit film thickness is excellent, but the armpit limit film thickness is low at 210 to 250μ. This is thought to be because the chicken index was too high, which resulted in poor defoaming properties after coating, and bubbles remained in thick film areas, which expanded during baking and became wafer 1".Also, a comparative example The conventional paint No. 1 performs well in hot airless painting, but in cold airless painting, both the underarm film thickness and sagging film thickness are low. It is thought that the viscosity did not decrease much at the moment of application, and the particle size of the paint increased, entrapping air and leaving bubbles in the paint film, causing the wrinkles.

In addition, the diameter of the paint particles during flight until they are applied to the object to be coated is large, and therefore the surface area is small, so there is less volatilization of the solvent during flight, and the viscosity after application does not rise in the case of hot airless painting. This is thought to be the reason why the sag limit film thickness became low. The high film thickness type paints of the present invention shown in Examples showed almost the same good results in cold airless and hot airless conditions, and the effects of the present invention are clear.

[Effects of R-light] The high film thickness type paint of the present invention has a chicken index in the optimum range, so even when a thick film is applied all at once with cold airless coating, the underarm film thickness and sagging limit film thickness are large. You can get the threshold value. In addition, because it can be painted with cold airless paint, problems with paint stability are resolved compared to conventional hot airless painting, and equipment wear due to paint circulation can be prevented. Furthermore, when the high-film thickness type paint of the present invention is applied using a hot airless method, the particle size of the flying paint particles becomes smaller than that of conventional hot airless paints, and the smoothness of the paint film is further improved. The effects of the present invention are significant, such as the ability to further increase the BI thickness by further promoting the volatilization of .

Patent applicant Aisin Kako Co., Ltd. Toyota Motor Corporation agent Patent attorney Hirodo Okawa Patent attorney Shudo Fujitani Patent attorney Akio Maruyama

Claims (4)

[Claims] (1) In a solution-type paint mainly composed of a resin, a pigment, and a solvent, the ratio of the solid content of the pigment to the resin is 65 to 75, the nonvolatile content of the entire paint is 60 to 80%, and the temperature at 20 ° C. A high film thickness type coating composition, characterized in that the viscosity of the coating material is 3000 to 4500 CPS, and the thixotropic index of the coating material is 3 to 8. (2) The pigment has a specific surface area of 600% in 100g of the paint.
The high film thickness type coating composition according to claim 1, which has a structure in which the film thickness is ˜7000 m^2. (3) The high film thickness paint according to claim 1, wherein the pigment is a component that imparts thixotropic properties to the paint and is contained in an amount of 2 to 20% by weight in the total paint. Composition. (4) The solution-based paint is a baking paint. Claim 1
The high film thickness type coating composition described in 2.