JPS6399275A - Undercoating composition - Google Patents

Abstract

PURPOSE:To provide an undercoating composition capable of easily peeling the thick coating film off and of preventing rust development, useful for applying, e.g., on the hanger in coating line processes, comprising a specific water-soluble or water-dispersible thermoplastic resin with the adhesive force and coating film extension rate regulated to respective specified values. CONSTITUTION:The objective undercoating composition comprising a water-soluble or water-dispersible thermoplastic resin of a softening point 50-300 deg.C and number-average molecular weight 300-500,000, with the adhesive force to the base material and coating film extension rate regulated respectively, to 0.01-15kg/cm<2> and <=1%. Said resin is preferably prepared by neutralizing, e.g., an alkyd resin with a basic compound such as ammonia followed by conversion to an aqueous solution or aqueous dispersion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention prevents corrosion of hangers, carts, etc. (hereinafter abbreviated as "hangers, etc.") on which objects to be coated are hung or placed on industrial painting lines, etc. To provide an undercoat paint composition capable of easily peeling off paint adhering to a hanger or the like during the painting process of a painting line.

In the painting process in industrial painting lines, etc., the object to be coated is usually suspended or mounted on a hanger, etc., and subjected to surface treatment and painting (e.g. electrodeposition coating, electrostatic coating, etc.).
After sequentially transporting each process of bottom, middle, and top coating (spray painting, dipping, etc.) and drying (baking), the object to be coated is removed from a hanger, etc., and then a new object is attached to this hanger, etc. The above steps are repeated again. Therefore, in such a painting line, hangers and the like are used repeatedly and the painting-drying process is cycled many times, so paint is coated on these hangers and gradually accumulates, and the thickness of the paint increases to 3. Since it can reach up to 4 mm or more, it is necessary to peel and remove it periodically.

Traditionally, thick coatings applied to hangers and the like have been scraped off with a hammer or spatula, or removed by shock blasting, but because of their excellent adhesion, they cannot be removed easily.

Additionally, if hangers and the like are left unused before use or after the coating has been peeled off, rust may develop and corrosion may progress, reducing strength.

Therefore, the present inventors have developed an undercoat that can be easily peeled off and removed from the above-mentioned thick coating film applied to hangers, etc., and that also forms a coating film that is useful for preventing the occurrence of rust. As a result of research aimed at developing M1 products, we found that thermoplastic water-soluble resins or water n! The coating film formed by the water-based undercoating paint composition containing I resin as the main component has the above performance, and in addition, since no or almost no organic solvents are used, there is no risk of fire, and it is also hygienic for the human body. The present invention was completed because it is a preferable pollution-free system.

That is, the present invention has a softening point of 50 to 300°C.

The main component is a water-soluble or water-dispersible thermoplastic resin with a number average molecular weight of 500 to 500.000, and the adhesion of the formed coating to the coated surface is 0.01 to 15k.
g/cm2. It relates to a base coating composition whose coating film elongation is adjusted to 1% (20'C) or less.

In the present invention, the use of a water-soluble or water-dispersible resin has the advantage of solving problems such as fire danger, human hygiene problems, resource conservation, and air pollution at once compared to the use of organic solvents. have.

In the present invention, the thermoplastic resin has a softening point of 50 to
300°C, preferably 80 to 250°C, and a number average molecular weight of 500 to 500,000°, preferably 10.0°C.
00 to 450.000, and is a resin that does not undergo a three-dimensional crosslinking and curing reaction by heating or the like.

Therefore, the resin is a non-functional resin that has no or almost no functional groups such as hydroxyl groups, carboxyl groups, epoxy groups, and amide groups, or even if it contains these functional groups, it cannot be mixed with other resins or crosslinking agents. If there is no curing reaction, it can be used as a thermoplastic resin.

In thermoplastic resins, if the softening point is lower than 50'C, the formed coating film becomes sticky, and if it is higher than 300'C, the coating film becomes hard, which is preferable because the releasability of the applied coating film decreases. In addition, if the number average molecular weight is less than 500, the coating film becomes extremely brittle, and the coating film will naturally fall off even with the slightest vibration, especially in a low-temperature atmosphere (below 10°C), and the rust prevention properties will deteriorate. Not enough.

If it is higher than 500.000, the flexibility and impact resistance of the coating film will become too strong, making it impossible to use it as a peelable coating material, and disadvantages such as difficulty in water solubilization and water dispersion will occur, which is not preferable.

The thermoplastic resin used in the present invention has a softening point of 50 to 300°C and a number average molecular weight of 500 to 500,000.
Preferred are resins that do not undergo cross-linking and hardening upon heating or reaction and form a coating film by volatilization of water as a solvent, such as those listed below.

■Resins with carboxyl groups introduced (for example.

Thermoplastic resins made by neutralizing alkyd resins, polyester resins, epoxy resins, urethane resins, acrylic resins, etc.) with basic compounds (e.g., ammonia, various amines, caustic potash, caustic soda, etc.) and making them water-soluble or water-dispersed. .

・′■ Water-soluble methyl etherified products such as phenol formaldehyde initial condensates and melamine formaldehyde initial condensates.

■ An emulsion polymer liquid or a liquid in which fine polymer particles (particle size 0.1 to 5 l) are suspended in the presence of an appropriate surfactant or protective colloid. , styrene-butadiene copolymer,
Suitable examples include vinyl chloride-vinylidene chloride copolymers, acrylic polymers, and styrene-acrylonitrile copolymers.

■ Water-soluble cellulose and starch.

■ Water-soluble or water-dispersible polyvinyl alcohol,
Sodium polyacrylate, polyethylene oxide, etc.

These can be used alone or in combination, but combinations in which crosslinking and curing reactions occur when used together should be avoided. Particularly preferably, the above ■, (
Resin selected from Sho and Shima Sho.

The base coating composition of the present invention is obtained by dissolving or dispersing the thermoplastic resin in wood, and may further contain pigments, anti-cissing agents, anti-settling agents, etc., as required.

Pigments that can be blended include extender pigments such as tancal, silica, barita, and clay silica, coloring pigments such as titanium white and carbon black, and rust preventive pigments such as lead chromate. The amount of the anti-cissing agent is preferably 500 parts by weight or less, particularly 100 to 350 parts by weight, such as silicone-based,
Acrylic resins, anti-settling agents such as acrylic esters, anti-settling polyethylene, amide waxes,
Examples include montmorinite amine derivatives.

The base coating composition of the present invention has a solids content of about 40 to 9
Adjust to 0% by weight, preferably 50 to 85% by weight, and apply spray coating, brush coating, or dip coating.

It is preferable to apply the coating by electrostatic coating, flow coating, etc. The coating film thickness is not particularly limited, but is preferably 20 g or more, especially in the range of 60 to 120 p, based on the dry coating film. It can be arbitrarily adopted depending on the situation, and forced drying at room temperature or below 100°C, or heating and melting at above 100°C is also acceptable.

Regarding the primer coating composition of the present invention, the adhesive strength of the formed coating film to the coated object (hanger, etc.) is 0, 01 to 15.
kg/c+w2. Preferably 0.05 to 5 kg/Cl1
12, and the elongation rate of the formed coating film is 1 at 20°C.
% or less. The adhesion and elongation rate of the formed coating film can be arbitrarily adjusted by combining the composition and molecular weight of the thermoplastic resin, the composition and blending amount of the pigment, etc. In the present invention, the adhesion and elongation of the formed coating film were measured by the following method.

For adhesion, apply the primer paint to a dull steel plate (size 0.8 x 100
x100mm) to a film thickness of 60μ based on the formed coating film, and heated to 100℃-1O' or more to form a coating film. The adhesive surface of the attachment for adhesion measurement (width 4
After bonding and fixing the test plate (x4cm) with a two-component poxy resin adhesive, the test plate was fixed at 20°C, and then the above attachment was tested at 50°C using a Schoppa complete tensile tester.
The adhesion force was defined as the minimum force required to peel the coating film from the dull steel plate by pulling at a speed of am/min. The unit is kg/
c+s".

The elongation rate is determined by applying an undercoat to a tin plate, painting it to a coating film of 501L, and heating it to a length of 60mm and a width of 5mm.
Make a cut in the m rectangle with a cutter, peel off the coating using mercury, and use this coating to create TENSILON.
UTM-11-20 (ToYo BALDWINCo,
, LTD) and measured the elongation rate at 20°C.

In the present invention, the adhesive force of the formed coating film is 0.01 kg/c
If it becomes smaller than rrr2, the coating film becomes unstable and falls off by itself even with the slightest vibration, and the -force adhesion force becomes 1.
If the elongation rate exceeds 5 kg/cm2 or 1%, both are unfavorable because the shearability decreases.

When the base coating composition of the present invention is applied to a metal substrate such as a hanger, rusting of the substrate can be prevented.

Furthermore, the formed coating film has a small elongation rate and flexibility, and the adhesion has to be adjusted within the above range, so if you apply the coating to the hanger, etc. before the painting process, it will be easier to coat the hanger etc. during the painting process. The paint can be peeled off and removed together with the coating film of the paint composition of the present invention in small pieces by simply giving it a light impact with a hammer or the like. A1
The 1lI operation is significantly simplified compared to conventional temporary protective paints (strippable paints). Furthermore, the coating film formed by the base coating composition according to the present invention.

Even when the environmental temperature is lower than 10°C, no cracks, cracks, or peeling are observed, making it suitable for painting lines in cold regions.

The coating composition of the present invention can be applied to metals, plastics, glass,
It can be applied to wood, inorganic materials, rubber, pre-painted surfaces, etc.

Next, examples and comparative examples related to the present invention will be described.

EXAMPLES EXAMPLES AND COMPARATIVE EXAMPLES The components shown in Table 1 were mixed and dispersed to produce a coating composition aimed at by the Wood Invention.

Table 1 (11) Thermoplastic resin The composition and physical properties of the resin are as shown in @Table 2. All amounts are based on resin solid content.

(02) Anti-cissing agent Nearon S-4002 (Toagosei Hoso) (13) Antifoaming agent: Antiform B-748 (manufactured by Asahi Denka Co., Ltd.) II Performance test results Black skin steel plate (size 100100X300X2 #400
After polishing with sandpaper and degreasing with toluene,
Brush the undercoat paint composition on the surface to a dry film thickness of 70.
The coating film was dried by leaving it at room temperature for 24 hours.

Next, on this painted steel plate, Amirac TP26 (amine red alkyd resin intermediate coating paint, Kansai Paint Repair) was spray-painted to a thickness of 40p based on the cured coating.
After baking at 40℃ for 20 minutes, Amylac white (Amine・
Spray coated with alkyd resin top coat (Kansai Paint) and baked at 140°C for 30 minutes (film thickness 40p)
, and furthermore, these Amirac TP26 and - were coated with the paint as described above, and after baking, the coating was repeated one after another, and the coating was repeated 30 times in total.

The total thickness of the intermediate coat and top coat is approximately 1,600 mm.
It was g.

Using the test plates thus coated, various performances of the undercoat composition were investigated. The results are shown in Table 3.

The above coating system assumes a process in which an object to be coated, which has already been coated with an undercoat paint composition, is placed on a trolley and an intermediate coat and a top coat are applied, and the black-skinned steel plate is likened to a trolley or a hanger.

In Table 3.

(jl) Adhesive Crab The coating composition listed in Table 1 was applied to a dull steel plate (size: 0.8 x 100 x 100 ma) so that the film thickness was equal to that of the dry coating, and the paint composition was coated with the paint composition listed in Table 1 at room temperature.
Dry for 0 hours to obtain a test plate. 6 Next, attach the adhesive surface of the attachment for adhesion measurement (width 4
x 4 cm) with a two-component poxy resin adhesive, fix the test plate at 20°C, and then test the test plate with the above attachment at 50 am/min using a Schottspa tensile tester. The adhesion force was defined as the minimum force required for the coating film to separate from the dull steel plate. The unit is kg/Cm2.

C2) Elongation rate: Apply an undercoat to a tin plate to a coating film of 50p. After heating at 100℃ for 15 minutes, cut into a rectangle with a length of 601℃m and a width of 5cm using a cutter. , the coating film was peeled off using mercury, and this coating film was used to manufacture Toyo ENSILON UTM-11-20 (ToYo
The elongation rate at 20°C was measured using BALDWIN Co., Ltd.).

(3) #Eating property 2 10 cc of tap water was sprayed on a test plate prepared in the same manner as in (11) above, and the presence or absence of rust was examined after leaving it for 24 hours.

0: Almost no rust observed.

×: Much rust is observed.

(Y4) Paint film appearance 2 A test plate prepared in the same manner as above (01) was left indoors (10°C) for 10 days and its appearance was observed.

O: No coating film defects such as cracks, cracks, or peeling are observed.

Δ: There are no paint film defects such as cracks, cracks, or peeling, but the paint film is sticky.

×: Paint film defects such as cracks, cracks, and peeling are observed.

(Y5) 'A releasability of applied paint: A test plate coated with the base coat composition of the present invention and the intermediate and top coat paints as described above was placed on a black steel plate horizontally with the coated side facing up. 20℃
The e-driver was struck with a hammer at an angle of 45° to the coated surface, and the state of separation of the coated film was observed.

O: Promptly peeled off into small pieces from the base surface.

Δ: Peelability It is extremely difficult to peel off the coating film itself.

×: Almost impossible to peel off.

In the above test, 2. adhesion, elongation, corrosion resistance, and coating film appearance were evaluated for a single coating film of the undercoat composition.

The releasability of the applied paint was tested using the intermediate coat and top coat coated as described above.

■ Comparative Example 1 did not use the primer coating composition of the present invention,
This is a direct coating of intermediate and top coats.

Margin below Table 3

Claims (1)

[Claims] Softening point 50~300℃, number average molecular weight 300~500,
000 water-soluble or water-dispersible thermoplastic resin as the main component, and has an adhesion force to the material of 0.01 to 15 kg/cm^2 and a coating film elongation rate of 1% or less. thing.