JPH09192593A - Formation of protective film by application of aqueous coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a protective film by aq. coating material imparting excellent protective capacity to a coating film and excellent appearance and excellent in workability. SOLUTION: A coating process E coating the surface of the coating film on an article to be coated with aq. coating material based on an acrylic emulsion and having a solid of 30-60wt.% and apparent viscosity of 300-400mPa.s, an infrared drying process G irradiating the applied aq. coating material with infrared rays to preliminarily dry the same and a hot air drying process H drying the preliminarily dried aq. coating material by hot air are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a protective film using an aqueous paint, and more particularly to a method for forming a peelable protective film on the surface of a coating film of an automobile or the like.

[0002]

2. Description of the Related Art The purpose of a car manufacturing plant is to protect a paint film of a car from contamination of rainwater, iron powder, pollen, bird droppings, etc., and prevent deterioration of quality when shipping a car which has been painted. Forms a peelable protective film on the surface of the coating film.

To form a protective film, a water-soluble acrylic type water-based material, a wax such as an oil-based synthetic wax type or a calcium carbonate type powder is applied to the surface of the coating film, or a vinyl chloride resin film is applied. The method of sticking on the surface is widely used.

The protective film formed by this wax coating is inferior in the protective effect against iron powder and pollen, has a short duration of the protective effect of about 3 to 4 months after being coated on the coating film of an automobile, and is shipped to a destination. In this case, the work of removing the wax is heavy, and since it is removed using a solution such as an ammonia-based chemical or kerosene, it is inferior in environmental safety, and there is a problem that equipment for wastewater treatment is required.

Further, although the protective film applied with powder can be expected to have an effect of protecting iron powder, pollen, rainwater, and other suspended objects, it is inferior in the effect of protecting against scratches caused by contact, and the powder applied by wind and rain disappears. Therefore, the duration of the protective effect is as short as about 1 to 3 months, and when removing the protective film, it is difficult to remove the protective film attached between the car body gaps such as the front fender and the front hood. In addition, there are problems such as having large-scale post-treatment equipment such as sand filtration equipment.

Since the formation of the protective layer by wax coating or powder coating is generally carried out by spraying in a coating booth, the coating efficiency is about 10%.
Remaining wax, powder, etc. falls to under the coating booth and is carried out by the circulating water to the outside of the booth for disposal, resulting in poor yield and spray spraying of wax, powder, etc. Therefore, there is a problem that the inside of the coating booth is contaminated with mist, and that the working environment is deteriorated due to noise generation due to the circulation of circulating water and the operation of the air supply / exhaust device.

On the other hand, in the method of sticking the film, the protective film can be removed by simply peeling off the film from the coating film surface of the automobile, and although the workability of removing the protective film is excellent, it follows a complicated automobile shape. The work of tensioning the film is heavy, and if a gap is created between the stretched film and the coating film, rainwater etc. may enter this gap and swell the coating film. In addition, an incineration facility for treating the removed film is required.

As a countermeasure against this, for example, Japanese Patent Application Laid-Open No. 7-8039
There is a method of forming a protective film by applying an aqueous paint called strippable paint that can be peeled off after drying to the coating film surface of an automobile as disclosed in Japanese Patent Laid-Open No.

This protective film forming method comprises a washing step 101 for washing rainwater and dust adhering to the coating film surface of an automobile and a draining step 102 for removing washing water, as shown in FIG. Pretreatment process 103 and pretreatment process 1
And a coating step 106 including a coating booth 104 for coating a water-based coating on the coating film surface of the automobile that has been washed and drained in 03.
Setting booth 10 that is left at room temperature for a predetermined time
5. A drying step 109 including a preliminary drying oven 107 that uses an infrared drying oven and a main drying oven 108 that uses a hot air drying oven to dry the water-based paint applied to the surface of the coating film.

Then, while the automobile is being conveyed in the order of the washing step 101, the draining step 102, the coating booth 104, the setting booth 105, the pre-drying oven 107, and the main drying oven 108 by the conveying device 110, the coating film surface of the automobile is washed and drained. In this method, a water-based paint is applied to the surface of the coating film, and the applied water-based paint is dried to form a protective film.

In applying the water-based paint to the coating film surface of the automobile in the applying step 106, the paint carried in by a paint supply source such as a drum can is temporarily stored in the paint tank and then stored in the paint tank. The paint is pressure-fed by a pump or the like to a roller type coating device, which is a coating machine, and is coated on the coating film surface of an automobile.

This roller-type coating device is generally a roller brush having a cylindrical brush body having paint permeability attached to the outer periphery of a cylindrical roller that communicates the inside and the outside through ejection holes, a handle, and a roller brush. And a roller support that rotatably supports the handle on the handle, and the paint is supplied into the hollow portion of the roller through a paint passage formed on the roller support, and the operator grips the handle and the surface to be coated. While rolling the roller brush along the coating surface of the automobile, the coating material that has flowed out from the ejection hole and has penetrated into the brush body is applied.

[0013]

According to the method of forming a protective film by applying the above-mentioned water-based paint and then drying it to form a protective film, cracks and paints generated during drying in an infrared drying oven, a hot air drying oven, etc. The fluidity is reduced or the protective film sags, which impairs the protective performance such as water resistance and the finished appearance, and the paint pumped into the hollow part of the roller flows out from the sliding part of the roller support. This may lead to problems such as deterioration of workability and working environment and reduction of the yield of paint.

Therefore, an object of the present invention is to provide a water-based paint which has a good protective property and finished appearance of the coating film, is excellent in workability, does not deteriorate the working environment, and improves the yield of the paint. It is to provide a method for forming a protective film.

[0015]

In order to achieve the above object, a method for forming a protective film using a water-based paint according to the present invention is a water-based paint for forming a peelable protective film on the surface of a coating film on a coated object. In the method for forming a protective film according to the above, an acrylic emulsion is the main component, the solid content is 30 to 60% by weight, and the apparent viscosity is 300 to 4000 mPa.s. The coating process of applying the water-based paint in the range of s to the coating film surface of the object to be coated, the infrared drying process of irradiating the water-borne paint coated on the coating film surface with infrared rays and predrying, and the infrared drying process And a hot-air drying step of drying the dried water-based paint with warm air, wherein the water-based paint forms a peelable protective film on the coating film surface of the coated object. In the protective film forming method, the acrylic emulsion is the main component, and the solid content is 40 to 55% by weight.
And an apparent viscosity of 1000 to 3000 mPa.s. The coating process of applying the water-based paint in the range of s to the coating film surface of the object to be coated, the infrared drying process of irradiating the water-borne paint coated on the coating film surface with infrared rays and predrying, and the infrared drying process And a warm air drying step of drying the dried water-based paint with warm air.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for forming a protective film using a water-based paint according to the present invention will be described below by taking an example of forming a protective film on a coating film surface of an automobile. FIG. 1 is a configuration explanatory view of a protective film forming method according to the present invention.

The steps of forming the protective film include a washing step A, a draining step B, a masking step C, a coating step D, a finish coating step E, a setting step F, an infrared drying step G and a warm air drying step H. .

The automobile W on which the protective film is to be formed is carried into the washing step A, and is washed by a shower type car washing device in which the washing water is sprayed on the entire vehicle body while using a rotary brush to adhere to the surface of the coating film. Remove rainwater and dust. During the cold season, the water on the surface of the coating film may freeze due to freezing of water droplets attached to the surface of the coating film.
It is preferable to use warm water at 0 ° C.

The automobile W washed in the washing step A is dried in a subsequent draining step B by removing the washing water remaining on the surface of the coating film by air blowing with warm air of about 70 ° C. Warm water used in washing step A and draining step B
The surface temperature of the automobile can be appropriately maintained because the application of the water-based paint in the application step D described later is made good by the air blow with the warm air. The surface temperature is 15 ° C. or higher, preferably 20 to 30 ° C. in view of the film forming property of the coating material.

The car W which has been washed and drained in the washing step A and the draining step B has a masking tape for partitioning the coated area and the non-coated area to which the water-based paint is applied in the following masking step C, and the engine W is attached. Non-coated parts such as an intake duct opening to the hood and other resin parts located in the application range are covered by placing a cover or the like.

In the subsequent coating step D, an aqueous coating containing acrylic emulsion as a main component (for example, Wrapguard L manufactured by Kansai Paint Co., Ltd.) is applied to the coating area previously defined in the masking step C by, for example, a roller type coating device,
In the next finish coating step E, the masking tape adhered in the masking step C is peeled off and the cover and the like are removed.
In addition, the uncoated portion of the details of the coating area is coated with a water-based paint by using a brush or a small roller type coating device. In addition, masking step C, coating step D and finish coating step E
Each process is performed in the painting booth.

In the coating apparatus 1 used in the coating step D and the finish coating step E, for example, as shown in FIG. 2, a supply pipe 11 whose one end is inserted into a paint supply source 2 such as a drum can has a valve 21 and a three-way pipe joint. 17, replenishment pump 31 and valve 22
It opens to the inside of the paint tank 3 via.

A discharge pipe 1 connected to the bottom of the paint tank 3.
4 is provided with a three-way pipe joint 18 at the lower end of the four-way pipe joint 18
One end of is connected to a three-way pipe joint 17 provided in the supply pipe 11 via a circulation pipe 15 and a valve 23.

A three-way pipe joint 18 connected to the discharge pipe 14
The other end of the main pipe 16 is connected to one end, and the other end is sequentially provided with the valve 24, the filters 33 and 34, the valve 25, the pressure pump 32, the valve 26, the three-way pipe joint 19, and the filter 3.
5 and the three-way pipe joint 20 are connected to the roller type coating device 40 in the coating booth.

Three-way pipe joint 20 connected to the main pipe 16
1 and 2 are connected to first and second return pipes 12 and 13 for returning the excess paint from the coating machine side to the paint tank 3, and the first and second return pipes 12 and 13 are connected to the valve 2 respectively.
It opens in the paint tank 3 through 7 and 28.

The water-based paint stored in the paint tank 3 is discharged by the pressure pump 32 into the discharge pipe 14 and the main pipe 1.
It is supplied to the roller type coating device 40 via 6. The operator grips the handle 41 of the roller type coating device 40 and rolls the roller brush 42 on the coating film surface of the automobile, which is the surface to be coated, to apply the paint that has penetrated into the roller brush 42 onto the coating film. To do.

The excess paint in the roller type coating device 40 is returned to the paint tank 3 via the first return pipe 12 and the second return pipe 13. When the liquid level of the paint in the paint tank 3 drops to a preset lower limit due to the use of paint, the valve 21 provided in the supply pipe 11 is opened, and the valve 23 provided in the circulation pipe 15 is closed to operate the supply pump 31. By this, the paint in the paint supply source 2 is replenished into the paint tank 3 via the replenishment pipe 11, and when the liquid level reaches a preset upper limit value, the valve 21 provided in the replenishment pipe 11 is closed,
Moreover, the valve 23 provided in the circulation pipe is opened to complete the replenishment.

The automobile W coated with the water-based paint in the coating process D and the finish coating process E is set in the setting process F at a temperature of 15 ° C. or higher, preferably 20 ° C. or higher, and a wind speed of 0.1 to 0.3 m / sec. It is left for 2 to 10 minutes in the set booth.

Then, in the infrared drying step G, the infrared drying furnace is opened to irradiate the water-based paint applied on the coating film with infrared rays for about 30 to 90 seconds to accelerate the drying from the inside of the water-based paint and predry it. Subsequently, in the warm air drying step H, the entire coating object is uniformly heated by using a warm air drying oven to dry the water-based paint and form a protective film. In a warm air drying oven, from the viewpoint of film-forming property of water-based paint and protection of accessories such as various electric components of automobiles, the drying temperature is about 50 to 70 ° C. and the wind speed is about 2 to 2 m / sec. It is preferably dried for 10 minutes.

The water-based paint used for forming the protective film has an acrylic emulsion as a main component and a solid content of 30 to 60.
%, Preferably 40 to 55% by weight and having an apparent viscosity of 300 to 4000 mPa.s. s (20 ° C.), preferably 1000 to 3000 mPa.s. It is in the range of s (20 ° C.).

If the solid content is less than 30% by weight, the water content of the applied coating material is high, so that the protective film is cracked by infrared irradiation and drying by warm air, which is not preferable. On the other hand, as a method for adjusting the solid content to a high concentration, it can be carried out by increasing the resin concentration or the pigment concentration. However, when the resin concentration exceeds 60% by weight, the emulsion stability becomes poor and the production becomes difficult. Become. Further, when the pigment concentration is adjusted to 80 parts by weight with respect to 100 parts by weight of the resin so that the solid content exceeds 60% by weight, the physical properties and water resistance of the protective film are deteriorated.

The apparent viscosity is 300 mPa.s. When it is less than s, the coating film applied by the roller type coating device sags, the appearance of the protective film is deteriorated, and the protective film is cracked due to infrared irradiation and drying by warm air, which is not preferable. On the other hand, the apparent viscosity is 4000 mPa.s. When it exceeds s, the rotation of the roller brush of the roller type coating device is deteriorated and the coating workability is deteriorated. Also, the bubbles entrapped during coating remain in the protective film without being deaerated, and the fluidity of the water-based coating is deteriorated. However, there is a drawback in that the appearance of the protective film deteriorates due to the decrease.

The apparent viscosity of the water-based paint is JIS K
The values measured by the rotational viscosity method described in 5400.4.5.3 (temperature 20 ° C., rotation speed 60 rpm) are mPa.s. It is converted to s.

As the water-based paint, for example, (meth) acrylic acid (cyclo) alkyl ester is prepared by emulsion polymerization using a polymerization initiator in the presence of a nonionic surfactant and the like according to a conventionally known method. The resulting acrylic emulsion is preferred. Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate,
Examples thereof include C1-24 alkyl or cycloalkyl esters of (meth) acrylic acid such as hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, and cyclohexyl (meth) acrylate. In addition to the monomers, for example, other polymerizable monomers such as styrene and vinyltoluene, and functional group-containing polymerizable monomers such as (meth) acrylic acid and hydroxyalkyl (meth) allylate are used as the above (meth) acrylic acid alkyl ester. It can be used in combination.

The acrylic emulsion has a glass transition temperature of about 5 to 30 ° C., preferably 6 to 20 ° C.,
A weight average molecular weight of about 20,000 or more, preferably about 30,000 to 100,000 is desirable.

In the water-based paint, other than the above-mentioned components, if necessary, for example, a water repellent, an ultraviolet absorber, a defoaming agent,
An anti-sagging agent, a water-soluble organic solvent, a pigment and the like can be added.

It is preferable to use an aqueous paint having a Ti value in the range of about 1.2 to 4, preferably in the range of about 2.0 to 3.5. If the Ti value is less than about 1.2, the protective film may sag, while if it is more than about 4, bubbles entrapped during application may remain in the protective film without being removed. Since the fluidity of the water-based paint is lowered, there is a problem that the appearance of the protective film is lowered.

The Ti value of the water-based paint is JIS K54.
Measured by the rotational viscosity method described in 00.4.5.3.
℃, rotor rotation number 6 and 60 rpm) is the value in mP
a. s and apparent viscosity at 6 rpm mPa.s.
Apparent viscosity at s / 60 rpm mPa. It is a value calculated by s.

Examples of water-based paint

[0040]

Example 1 Deionized water 817 g, methyl methacrylate 440 g, n-butyl acrylate 352 g, acrylic acid 8 g, emulsifier 16 g, ammonium persulfate 1.5 g
Was reacted at 80 ° C. for 3 hours to give a resin glass transition temperature of 14 ° C., a resin weight average molecular weight of about 30,000, a solid content of 50% by weight, and an apparent viscosity of 90 mPa.s. Acrylic emulsion A of s was obtained. Then the apparent viscosity of this product is 2800m
Pa. Thickener (Adecan UH-42
No. 0, manufactured by Asahi Denka Kogyo Co., Ltd., trade name, polyalkylene glycol derivative, showing the same meaning below).

[0041]

Example 2 A thickener was added to the acrylic emulsion A to give a solid content of 50% by weight and an apparent viscosity of 450 mP.
a. Adjusted to be s.

[0042]

Example 3 Acrylic emulsion A was blended with deionized water and a thickener to obtain a solid content of 40% by weight and an apparent viscosity of 2800 mPa.s. Adjusted to be s.

[0043]

COMPARATIVE EXAMPLE 1 A thickener was added to the acrylic emulsion A to obtain a solid content of 50% by weight and an apparent viscosity of 200 mPa.s.
Adjusted to be s.

[0044]

Comparative Example 2 Acrylic emulsion A was blended with deionized water and a thickener to give a solid content of 28% by weight and an apparent viscosity of 2800 mPa.s. Adjusted to be s.

[0045]

Comparative Example 3 In the above acrylic emulsion A,
An emulsion having a resin solid content of 65% by weight was produced in the same manner as in Example 1 except that 817 g of deionized water was changed to 440 g, but the emulsion was gelled and production was impossible.

A protective film was formed using the aqueous paints of Examples 1, 2 and 3 and Comparative Examples 1 and 2, and the results are shown in Table 1.

[0047]

[Table 1]

Protective Film Forming Conditions The water-based paints of Examples and Comparative Examples were roller-type applied to a baked coating film (baked at 140 ° C. for 30 minutes) of an aminoalkyd resin topcoat paint (Kansai Paint Co., Ltd., trade name, Amilak). It was applied by a device so that the dry film thickness was 100 μm. Then, the obtained coating film was set at 20 ° C. for 5 minutes, followed by infrared irradiation for 1 minute and warm air drying for 4 minutes to dry the coating film to obtain a protective film.

Appearance evaluation of protective film finish Sagging: The angle of the coated surface is 45. What was applied was evaluated. A good one with no sagging, a bad one with sagging, and a bad one with significant sagging.

Cracks: The presence or absence of cracks on the protective film was visually observed and evaluated according to the following criteria. A good one with no cracks, a poor one with cracks. X is inferior because cracks are significantly generated.

Smoothness: The smoothness of the surface of the protective film was visually observed and evaluated according to the following criteria. A good one with no cracks, a poor one with cracks. X is inferior because cracks are significantly generated.

[0052]

EFFECTS OF THE INVENTION According to the method for forming a coating film protective film using a water-based paint according to the present invention described above, a water-based paint having an acrylic emulsion as a main component and having a solid content and an apparent viscosity in the above-mentioned ranges is applied to the surface of the coating film. After that, by drying the water-based paint to form a protective film, there is no cracking or sagging, the protective performance and the finished appearance are excellent, and the workability is good and the yield of the paint does not deteriorate the working environment. It has a unique effect of the present invention, such as the improvement of the above, and contributes greatly to the formation of the protective film by the water-based paint.

[Brief description of the drawings]

FIG. 1 is a process diagram illustrating an embodiment of a method for forming a protective film using a water-based paint according to the present invention.

FIG. 2 is a schematic view of a coating apparatus which similarly describes the present embodiment.

FIG. 3 is a process diagram illustrating a conventional method of forming a protective film using a water-based paint.

[Explanation of Codes] A Cleaning Step B Draining Step C Masking Step D Coating Step E Finishing Coating Step F Setting Step G Infrared Drying Step H Warm Air Drying Step

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Okamoto 7-3 Satsuki-cho, Kanuma City, Tochigi Prefecture Kansai Paint Co., Ltd. (72) Inventor Kiyoji Kashiwa 5-4-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Within the corporation

Claims (4)

[Claims] 1. A method for forming a protective film using a water-based coating composition, which comprises a protective film which can be peeled off on the surface of a coated object to be coated, and which has an acrylic emulsion as a main component and a solid content of 30 to 60% by weight. % And apparent viscosity is 300 to 4
000 mPa. The coating process of applying the water-based paint in the range of s to the coating film surface of the object to be coated, the infrared drying process of irradiating the water-borne paint coated on the coating film surface with infrared rays and predrying, and the infrared drying process A method of forming a protective film using a water-based paint, comprising: a hot-air drying step of drying the dried water-based paint with warm air. 2. A method for forming a protective film using a water-based paint, which forms a protective film that can be peeled off on the surface of a coated object to be coated, in which an acrylic emulsion is the main component and the solid content is 40 to 55% by weight. % And apparent viscosity is 1000-
3000 mPa. The coating process of applying the water-based paint in the range of s to the coating film surface of the object to be coated, the infrared drying process of irradiating the water-borne paint coated on the coating film surface with infrared rays and predrying, and the infrared drying process A method of forming a protective film using a water-based paint, comprising: a hot-air drying step of drying the dried water-based paint with warm air. 3. The protective film of the aqueous paint according to claim 1, wherein the water-based paint applied to the surface of the coating film has a glass transition temperature of 5 to 30 ° C. and a weight average molecular weight of 30,000 to 100,000. Forming method. 4. The coating water-based paint applied to the surface of the coating film is T
The method for forming a protective film using the water-based paint according to claim 1, wherein the i value is in the range of 2.0 to 3.5.