JP2023120486A - Method for repairing deteriorated coated film and method for evaluating the same - Google Patents

Abstract

To provide a method for repairing a deteriorated coated film which has high safety when repairing the deteriorated coated film, hardly damages the deteriorated coated film, and can repair the deteriorated coated film while maintaining design feeling such as a color tone and a shape of its existing coated film.SOLUTION: A method for repairing a deteriorated coated film coats a clear undercoat material containing synthetic resin emulsion as a main component onto a deteriorated coated film containing a synthetic resin as a main component, and then coats and stacks a clear coating material to the surface of the deteriorated coated film, and thereby has high safety, hardly damages the deteriorated coated film, and can repair the deteriorated coated film while maintaining design feeling such as a color tone and a shape of its existing coated film.SELECTED DRAWING: None

Description

The present disclosure relates to a method for repairing a deteriorated paint film when the paint film used for finishing the inner and outer walls of structures such as buildings has deteriorated over time and a method for evaluating it. The field of architecture.

Usually, in many cases, repair work such as repainting is carried out on deteriorated paint films on the walls of buildings and the like. This repainting is performed for the purpose of applying new paint to the surface of an existing paint film such as a deteriorated paint film to protect the surface of a building or the like and to change the color.
When performing renovation work such as repainting, a primer is sometimes used to remove the deteriorated paint film and repaint it, reinforce the deteriorated paint film, and improve adhesion with the new paint film.

In these cases, the finish is often monochromatic, and is selected by many methods according to the type and condition of the existing coating film such as the deteriorated coating film and the condition of the base of the existing coating film.
In addition, there are many existing paint films formed with multi-colored paints and stone-like paints containing colored aggregates, and there is a demand for repainting that maintains the design of the existing paint films. It's getting more.

In this case, solvent-based clear paint is often used. This solvent-based clear is used for such repair work because it also penetrates into deteriorated paint films.
In addition, various proposals have been made for such repair methods.

JP-A-2012-144896 discloses a method for repairing an aggregate-containing finishing layer having a thickness of 2 mm or more in which colored aggregates are dispersed in a synthetic resin. A method for refurbishing an aggregate-containing finishing layer is described in which a first step of applying a paint film remover and a second step of washing the surface of the aggregate-containing finishing layer with a high water pressure of 3 to 10 MPa are performed in sequence. .
Thereby, only the deteriorated surface layer of the existing aggregate-containing finishing layer can be removed. Since the aggregate-containing finishing layer has aggregates evenly distributed throughout the layer, the part where the surface layer is removed has the same aggregate-containing design as the original aggregate-containing finishing layer, and the new finishing layer can be used as it is. and

In JP-A-2019-104856, a repair method for applying a water-based paint to an uneven coating base, wherein the unevenness of the coating base is in the range of 0.5 to 10.0 mm. A method for refurbishing old coatings is described in which the difference between the 60° gloss and the 85° gloss of the coatings formed by the aqueous paint is in the range of 1-25.
As a result, the texture such as the texture and unevenness of the old coating film, which is the base of the coating film, is not impaired, and uneven gloss due to the texture is less likely to occur.

JP 2012-144896 A JP 2019-104856 A

However, when a solvent-based clear paint is used, depending on the type and deterioration of the existing paint film, the type of base of the existing paint film, etc., the existing paint film may swell and lift after the clear paint is applied. be. In addition, it is difficult to use due to various regulations such as the safety of solvents.
In the method for repairing the aggregate-containing finish layer described in JP-A-2012-144896, the surface layer of the deteriorated coating film is peeled off with a coating film remover. It is not possible to make full use of the design of the existing paint film.

In addition, in the method for repairing the old coating film described in JP-A-2019-104856, although it is an effective repair method for the existing coating film with a single color with uneven shapes, the existing coating film formed by multicolor paint It is not suitable for renovations that maintain the design feeling of existing coatings that have a thin, colorful feel, such as those formed by stone-like coating materials that contain coatings or colored aggregates, or those using colorful paints. be.

The method for repairing a deteriorated paint film of the present disclosure is a repair method that uses a highly safe water-based paint, does little damage to the deteriorated paint film, and maintains the design feeling such as the color tone and shape of the existing paint film. To provide a method for repairing a deteriorated paint film capable of repairing while

A clear undercoat material containing a synthetic resin emulsion as a main component is applied to a deteriorated coating film containing a synthetic resin as a main component, and then a clear paint is applied and laminated on the surface of the deteriorated coating film.
As a result, it is a refurbishment method that uses a highly safe water-based paint, does little damage to the deteriorated paint film, and can be refurbished while maintaining the design feeling such as the color tone and shape of the existing paint film. .

The synthetic resin emulsion, which is the main component of the clear undercoat material, has a molecular weight in the range of 10,000 to 100,000 and an average particle size in the range of 0.01 to 0.10 μm.
As a result, it is easy to permeate into the deteriorated paint film, the strength of the deteriorated paint film can be increased, and the adhesiveness of the clear paint to the clear film is improved.

By adding an ultraviolet absorber to the clear paint, it is possible to delay the deterioration of the clear film, delay the deterioration of the paint film due to the clear undercoat material, and further delay the deterioration of the deteriorated paint film.

It is formed of a stone-like paint in which a synthetic resin capable of forming a transparent film after curing and drying of the degraded coating film is mixed with a colored aggregate having a particle size in the range of 37 to 2000 μm.
As a result, even if the paint film is a stone-like paint that has deteriorated to a relatively deep place, it will not damage the deteriorated paint film and maintains the design of the existing paint film, such as color tone and shape. can be repaired while

An evaluation method for repairing a deteriorated paint film, in which a test paint is prepared by reducing the synthetic resin component of the paint that forms the deteriorated paint film by 50.0 to 95.0% by weight, and the test paint After obtaining the test coating film thus formed, the adhesion test is performed using a test piece that is laminated by any of the methods for repairing a deteriorated coating film described above.
This makes it possible to easily determine the effectiveness of the coating specifications for the deteriorated coating film.

Embodiments of the present disclosure will be described.
In the present disclosure, after applying a clear undercoat material containing a synthetic resin emulsion as a main component to a deteriorated paint film containing a synthetic resin as a main component, a clear paint is applied and laminated on the surface of the deteriorated paint film. be.

Deteriorated paint film is the paint film used to finish the inner and outer walls of structures such as buildings that has deteriorated over time. It is made of a coating material such as coating material or ink.
Since this coating material is mainly composed of a synthetic resin, the synthetic resin deteriorates over time due to moisture such as sunlight and rain, and ambient temperature. Due to the deterioration of this synthetic resin, the paint film also deteriorates and becomes a deteriorated paint film.

After finishing the inner and outer walls of structures such as buildings, this deteriorated coating film gradually deteriorates due to deterioration factors such as ultraviolet rays from sunlight, water such as rainwater and condensation, and heat. from the surface portion that is susceptible to the influence of
This synthetic resin is a homopolymer or copolymer of acrylic resin, styrene resin, urethane resin, silicone resin, fluorine resin, epoxy resin, melamine resin, alkyd resin, vinyl chloride resin, vinyl acetate resin, polyester resin, etc. mentioned.

This deteriorated paint film is made by dissolving these synthetic resins in an organic solvent, dispersing them in water as an emulsion, or dispersing them in a weak solvent, and mixing aggregates, extender pigments, coloring pigments, etc. , the coating film obtained by applying the paint has deteriorated.
Phenomena such as powdery chalking and loss of luster are observed on the surface of this deteriorated paint film due to paint components and deteriorated synthetic resin. In addition, cracks and the like may occur on the surface of the coating film.

This deteriorated coating film is a deteriorated coating film made of a coating material containing a synthetic resin as a main component, and the coating material is applied to the base material that constitutes the wall surface.
In addition, there are also sheet-like building materials that are coated with a coating material on a sheet-like base material such as non-woven fabric, woven cloth, glass cloth, synthetic paper, plastic, or metal, and are attached to the base material. .

These base materials include concrete, mortar, wood such as plywood, metal such as iron plates, etc. In addition, ceramic siding boards, ceramic siding boards, metal siding boards, PC boards, GRC boards, extrusion molding Molded plates such as plates, slate plates, calcium silicate plates, and ALC plates are included.
Coating films made of coating materials containing synthetic resin as a main component include those composed of one type of coating material and those formed by laminating two or more types of coating materials such as a top coat, an intermediate coat, and an undercoat.

There are many types of this coating material, but those used for finishing the surface of the wall, which is the part that deteriorates most easily, include colored glossy paints, matte paints, stone-like paints, multicolored paints, etc. There is also a clear paint on the surface of these coatings.
In addition, there are cases in which multiple types of colored single-color paints are used for finishing. For example, there is a wall made up of a siding plate painted in a tile-finish style with color-coded tiles and joints.

Among these coating materials, it is suitably used for repairing the coating film with stone-like coating materials and colorful paints. These coating films are excellent in design, and even if they are relatively thin films, they are coating films with colorful feeling, and it is difficult to reproduce the design by recoating.
Many of these stone-like paints are mixtures of a synthetic resin capable of forming a transparent film after being cured and dried, and colored aggregates having a particle size in the range of 37 to 2000 μm. Many multicolored paints are made by dispersing gel-like particles of about several millimeters in a clear paint.

This stone-like paint and colorful paint film are made by solidifying colored aggregates and gel-like particles with clear resin as a binder. Deterioration tends to progress to deep portions of the film.
Therefore, in the method for repairing the deteriorated coating film of the present disclosure, the deteriorated coating film can be effectively repaired.

Coatings made from this stone-like paint are susceptible to softening and blistering due to the presence of solvents. Moreover, since the particle size of the colored aggregate is large, there are many large voids in the coating film.
Therefore, the present disclosure is particularly effective for repairing a coating film formed by a stone-like paint as a deteriorated coating film.

This stone-like paint is a paint obtained by mixing a synthetic resin capable of forming a transparent film after curing and drying with a single or multiple colored aggregates having a particle size in the range of 37 to 2000 μm, and the synthetic resin Because it forms a coating film that combines colored aggregates, it is a paint that creates a design coating film with the color of colored aggregates, a colorful feeling, and a texture.
In addition to the crushed colored natural stone, the colored aggregate includes colored aggregate artificially colored with paint or the like.

When a solvent-based undercoat is used to refurbish a deteriorated paint film, the colored aggregate may damage the paint, which is the coloring component, and cause discoloration such as discoloration. Therefore, a water-based clear undercoat material is preferably used, and the design of the coating film can be maintained.
The clear undercoat material used in the present disclosure is based on a synthetic resin emulsion.

This synthetic resin emulsion is synthesized by homopolymerizing or copolymerizing resins such as acrylic resins, styrene resins, urethane resins, silicone resins, fluorine resins, epoxy resins, alkyd resins, vinyl chloride resins, vinyl acetate resins, and polyester resins. It is obtained by dispersing resin in water as an emulsion.
By using the synthetic resin emulsion in this way, the deteriorated paint film is less damaged and can be repaired safely. Since this clear undercoat material can form a transparent film after the undercoat material dries and hardens, it is possible to maintain the design feeling such as the color tone and shape of the existing coating film.

It is preferable that the synthetic resin used for this clear undercoat material has a molecular weight in the range of 10,000 to 100,000 and an average particle size in the range of 0.01 to 0.10 μm.
By using the synthetic resin within this range, it is possible to easily permeate the deteriorated coating film, increase the strength of the deteriorated coating film, and improve the adhesion of the clear coating to the clear coating.

If the molecular weight is higher than this range and the average particle size is larger, the permeability to the deteriorated paint film decreases, the strength of only the surface layer of the deteriorated paint film increases, the strength balance deteriorates, and the clear undercoat material It may peel off.
Conversely, when the molecular weight is low and the average particle diameter is small, although the permeability is good, the amount of permeation tends to increase, and an improvement in strength cannot be expected in some cases.

A clear coating is a coating that forms a transparent coating film, and is mainly composed of a synthetic resin that can form a transparent film after drying and curing. It affects the durability performance such as stain prevention and weather resistance of the surface such as the wall surface after repair.
Moreover, it does not impair the design and color of the existing coating film. Therefore, it is preferable that the coating film has a hiding rate of 5% or less. If the hiding rate is higher than this, the design and color of the existing coating may be impaired.

The clear paint is often a water-based clear paint because the synthetic resin emulsion described above is mainly used in many cases.
In particular, if the deteriorated paint film is made of stone-like paint or colorful paint, depending on the composition of the synthetic resin used, the organic solvent may damage the deteriorated paint film by dissolving or softening it. Therefore, it is preferable to use a water-based paint that uses water as a solvent.

By using a synthetic resin emulsion in this way, the deteriorated paint film is less damaged, can be repaired safely, and can form a transparent film after drying and curing, so the color tone of the existing paint film can be improved. It is possible to maintain the sense of design such as shape and shape.
Among the synthetic resins described above, the synthetic resins used in this clear paint are homopolymerized or copolymerized resins having relatively excellent durability and weather resistance, such as acrylic resins, urethane resins, silicone resins, acrylic silicone resins, and fluorine resins. Synthetic resins are preferably used, and two or more of them may be mixed.

The glass transition temperature of this synthetic resin is preferably in the range of -20 to 50°C. The film may be easily cracked, and a synthetic resin with a suitable glass transition temperature can be selected according to the application.
In addition, surfactants such as dispersants, wetting agents, and antifoaming agents, viscosity modifiers are added to improve the workability of clear paints, and pH modifiers, preservatives, antifungal agents, etc. Such additives are appropriately blended as needed.

Coloring components such as coloring pigments and dyes, which are generally added to paints, may be added as necessary to prepare a color clear paint. Furthermore, in order to adjust the gloss of the coating film, matting agents such as organic resin beads and inorganic diatomaceous earth are added as necessary, and the gloss of the coating film can be adjusted with a relatively small amount.
Addition of this matting agent increases the hiding power of the coating film, which may impair the design and color of the existing coating film. Therefore, it is necessary to adjust the type and amount of matting agent added so that the coating film hiding rate does not exceed 5%.

Among these other components, ultraviolet absorbers, light stabilizers and antioxidants are preferably added in order to improve the weather resistance of the clear coating film. These may be added singly or in combination.
The ultraviolet absorber absorbs harmful ultraviolet rays that cause deterioration of the coating film of the clear paint, the coating film of the clear undercoat material, and the deteriorated coating film, and converts them into harmless heat and kinetic energy.

By adding this to the clear paint, it is possible to reduce the reach of harmful ultraviolet rays to each coating film below the coating film, and to improve the weather resistance after repair.
Moreover, by using either or both of a light stabilizer and an antioxidant, the weather resistance of the coating film may be further increased. This light stabilizer captures and detoxifies free radicals that affect the deterioration of the synthetic resin in the coating film.

The antioxidant can prevent thermal oxidation deterioration of the coating film, and examples thereof include phosphorus-based, phenol-based, and sulfur-based antioxidants.
Benzotriazole-based, benzophenone-based, salicylate-based, cyanoacrylate-based, and oxanilide-based UV absorbers can be used as the UV absorber. Among these, benzotriazole-based and benzophenone-based UV absorbers are preferably used because they are stable against heat and light.

Furthermore, benzotriazole-based ultraviolet absorbers are more preferably used because they have a large synergistic effect with light stabilizers.
Benzotriazole UV absorbers include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl ] and benzotriazole.

Benzophenone-based UV absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, and the like.
In addition, as the light stabilizer preferably used in combination with this light stabilizer, one containing tetramethylpepyridine is preferably used.

The deteriorated paint film is refurbished by laminating the material described above on the deteriorated paint film. Before carrying out this repair, check the deterioration state of the existing paint film, which is a deteriorated paint film, and remove dirt and dust on the paint film.
Many of these deteriorated paint films have been exposed to the outdoors for several years to ten years, and in addition to deterioration of the paint film, we check for cracks and chalking on the surface. Appropriate processing is performed on these as necessary.

This removal is often carried out by washing with water. This water washing removes the fragile parts of the deteriorated coating film and stains attached to the surface, and improves the adhesion with the clear undercoat material.
This cleaning method includes a method of rubbing with a brush after applying water to remove dirt and fragile portions of the old coating film, and then rinsing with water again or a method of rinsing with high-pressure water using a high-pressure washer.

This high-pressure washer is often used to easily remove dirt and weak spots from the degraded coating. This water pressure is preferably in the range of 3-10 MPa, more preferably 5-8 MPa.
Within this range, the dirt on the deteriorated coating film can be sufficiently washed away, the fragile part can be easily removed, and the healthy coating film around the fragile part is less likely to be removed. The shape does not change greatly, and the texture is hardly spoiled.

Also, the amount of water is preferably 15 to 50 liters/minute, which enables efficient washing.
Next, a clear undercoat material containing a synthetic resin emulsion as a main component is applied. This coating method is not particularly limited, and is carried out by a general coating method.

This coating method includes spray coating, a coating roller, a brush, and the like, and may be selected depending on the state of the deteriorated coating film, but coating is often performed using a coating roller. By using a coating roller, it is possible to easily perform coating while checking the condition of the deteriorated coating film.
In addition, by applying moderate pressure during painting, the degraded paint film absorbs the clear undercoat material, allowing a relatively large amount of clear undercoat material to be impregnated compared to spray painting, etc., improving the strength of the degraded paint film. can be made

There are many types of paint rollers with different lengths of bristles that cover the surface of the roller and the material of the bristles. and can be painted cleanly.
In this way, the clear undercoat material can be applied and permeated into the deteriorated coating film to increase the strength and to improve the adhesion to the clear film laminated on the coating film.

Then apply clear paint. As with the clear undercoat material, this coating method is not particularly limited and is carried out by a general coating method.
This coating method includes spray coating, a coating roller, a brush, and the like, which can be selected as appropriate. However, due to the ease of coating, the coating is often performed using a coating roller.

By such a method, after applying a clear undercoat material mainly composed of a synthetic resin emulsion to a deteriorated paint film mainly composed of synthetic resin, a clear paint is applied and laminated on the surface of the deteriorated paint film. be able to.
By laminating in this way, the deteriorated paint film is less damaged, and the existing paint film can be repaired while maintaining the design feeling such as color tone and shape.

In this refurbishment method, since it is performed on the deteriorated paint film whose main component is synthetic resin, after applying the clear undercoat material to the actual deteriorated paint film, the clear paint is applied to the surface of the deteriorated paint film. Evaluation will be carried out by stacking.
However, there are cases where it is difficult to easily prepare a deteriorated coating film mainly composed of a synthetic resin for evaluation.

Therefore, when evaluating the performance of the repair method for a deteriorated paint film, it is necessary to prepare a test paint film equivalent to the deteriorated paint film. After applying a clear undercoat material containing a synthetic resin emulsion as a main component to this test coating film, a clear coating is applied and laminated on the surface of the test coating film to obtain the test specimen.
By measuring the strength of the specimen, it becomes possible to evaluate the repair method of the deteriorated paint film.

This strength can be determined by the adhesion test specified in JIS A6909. Moreover, it can be evaluated by this adhesion strength and the breaking position at that time.
First, as a method for creating a test coating film, a test paint is prepared by reducing the synthetic resin component of the paint that forms the deteriorated coating film by 50.0 to 95.0% by weight. It can be used as a test coating film. The strength of this test coating film is adjusted to the same extent as the strength of the deteriorated coating film.

By making a test coating film with a test paint that assumes the weight loss of the synthetic resin due to this deterioration and comparing it with the one without weight loss, it is possible to evaluate the repair method of the deteriorated coating film.
By reducing the amount of resin in the test coating film, the cohesive force of the coating film equivalent to that of the deteriorated coating film is reproduced, and the test coating film is used to evaluate the repair method of the deteriorated coating film.

The synthetic resin component of the paint forming the deteriorated paint film can be obtained by collecting the deteriorated paint film and analyzing the paint film near the interface with the base material on the back side of the paint film.
In the vicinity of the interface between the deteriorated paint film and the base material, the speed of deterioration is slower than that of the surface, so in many cases it is in a healthy state. There are many things.

After applying a clear undercoat material containing a synthetic resin emulsion as a main component to the test coating film thus obtained, a clear paint is applied to the surface of the test coating film such as a deteriorated coating film. Laminate to create a specimen.
This specimen is subjected to the adhesion test specified in JIS A6909 to determine the adhesion strength. This adhesive strength is compared with a test sample of a coating film in which the amount of resin has not been reduced, and the smaller the difference in strength, the more the strength of the deteriorated coating film recovers. Recognize.

In addition to the adhesive strength, it is also possible to evaluate the effectiveness of the repair method for the deteriorated coating film based on the fracture position.
If this fracture position is deeper than the surface of the test coating film, the clear undercoat material mainly composed of synthetic resin emulsion has penetrated to a deeper position, and the strength of the test coating film cannot be recovered. It can be judged to be good.

In addition, two types of test paint were prepared, the synthetic resin component of the first type of test paint 1 was determined, and test paint 2 was prepared by reducing the synthetic resin component by 50.0 to 95.0% by weight. Alternatively, a test coating film may be prepared by forming a coating film of test coating material 1 on a base material and applying test coating material 2 to the surface of the coating film.
It is also possible to evaluate the method of repairing a deteriorated coating film with such a two-layered test coating film, and it is also possible to use test specimens in which the amount of synthetic resin in the test coating film is varied.

This is done by preparing test paints with varying amounts of synthetic resin, applying a test paint with a large amount of synthetic resin to the substrate side, and applying a paint with a small amount of synthetic resin to the surface side, creating a multilayer is to create a test coating film.
After coating the surface of the multi-layer test coating film with a clear undercoat material whose main component is a synthetic resin emulsion, paint is applied according to the method for repairing the deteriorated coating film, such as applying a clear paint. , to create a specimen.

By measuring the strength of the test specimen with this multi-layer test coating film, it is possible to evaluate the repair method of the deteriorated coating film, and it is also possible to evaluate the degree of strength recovery depending on the fracture position. can.
The adhesion strength of the specimen is measured, and the repair method of the deteriorated paint film can be evaluated based on the strength and fracture position.

Furthermore, it is preferable to subject this coating film for testing to a water immersion test and a repeated heating and cooling test according to JIS A6909, so that the coating film can be made closer to a deteriorated coating film.
By conducting these tests, the water-soluble additive components added to the test paint are eluted from the test paint film, and a state similar to that of the deteriorated paint film exposed to rain or the like can be achieved.

According to the above embodiment, the following effects can be obtained.
For deteriorated paint films made of deteriorated stone-like paints or multi-color paints whose main component is synthetic resin, and where the amount of synthetic resin in the paint film decreases from the substrate adhering surface to the surface. First, after applying a clear undercoat material containing a synthetic resin emulsion as a main component, a clear paint is applied and laminated on the surface of the deteriorated paint film.
As a result, it is a refurbishment method that uses a highly safe water-based paint, does little damage to the deteriorated paint film, and can be refurbished while maintaining the design feeling such as the color tone and shape of the existing paint film. .

A matting agent is added to the clear coating, and the coating film formed by the coating has a hiding rate of 5% or less, so that the design and color of the existing coating are not impaired, and the matte finish is achieved. Obtainable.
By applying a clear undercoat material to the surface of a deteriorated paint film having an uneven shape with a roller for painting, it is possible to paint neatly, and the clear undercoat material is absorbed into the deteriorated paint film by a moderate pressure during painting. It is possible to increase the strength of the deteriorated coating film, and the adhesiveness between the clear coating and the clear coating is improved.

Further, the above embodiment will be described in detail by formulation examples. In this embodiment, the evaluation method for repairing the deteriorated coating film described above is used.
First, a blending example of a stone-like paint for creating a deteriorated paint film is shown. This compounding is the compounding of a normal product, and the synthetic resin content of this compounding example is reduced.

This stone-like paint was adjusted by mixing with colored aggregate after preparing a vehicle component, and a test specimen was prepared using a reduced amount of the synthetic resin of this vehicle component.
As the vehicle component, an acrylic synthetic resin emulsion having a glass transition temperature of −10° C. and a solid content of 45% was used as a synthetic resin that becomes transparent after being dried and formed into a film. As various additives, film-forming aids, antifoaming agents, dispersants, wetting agents, and thickeners were used.
Composition examples of vehicle components 1 to 3 are shown below.

Vehicle component 1 (regular product) formulation example Acrylic synthetic resin emulsion 250.0 (g)
Film-forming aid 30.0 (g)
Defoamer 2.0 (g)
Dispersant 1.0 (g)
Wetting agent 0.5 (g)
Thickener 1.0 (g)
Mixed water 15.5 (g)
Total 300.0 (g)

Vehicle component 2 (reduced resin product 1) formulation example Acrylic synthetic resin emulsion 175.0 (g)
Film-forming aid 30.0 (g)
Defoamer 2.0 (g)
Dispersant 1.0 (g)
Wetting agent 0.5 (g)
Thickener 1.0 (g)
Mixed water 90.5 (g)
Total 300.0 (g)

Vehicle component 3 (reduced resin product 2) formulation example Acrylic synthetic resin emulsion 75.0 (g)
Film-forming aid 30.0 (g)
Defoamer 2.0 (g)
Dispersant 1.0 (g)
Wetting agent 0.5 (g)
Thickener 1.0 (g)
Mixed water 190.5 (g)
Total 300.0 (g)

To each 300 g of vehicle components 1 to 3, 1000 g of colored aggregate was added and mixed to prepare a stone-like paint. As the colored aggregate, white Kansui sand and black-colored silica sand were used as the colored aggregate.
Two types of cold sand were used, one having an average particle size of 55 μm and the other having an average particle size of 500 μm. 100 g of cold water sand with an average particle size of 55 μm and 200 g of cold water sand with an average particle size of 500 μm were used as a white colored aggregate, giving a total of 300 g of cold water sand.

The stone-like paint using vehicle component 1 was named stone-like paint 1, the vehicle component 2 was named stone-like paint 2, and the vehicle component 3 was named stone-like paint 3.
A specimen having a coating thickness of 3 mm is prepared using these stone-like paints.
Specimen 1 was coated with stone tone paint 1 in a thickness of 3.0 mm.
Specimen 2 was coated with stone-like paint 2 in a thickness of 3.0 mm.

Specimen 3 was coated with stone-like paint 3 in a thickness of 3.0 mm.
The specimen 4 was prepared by applying the stone-like paint 1 to a thickness of 1.5 mm and the stone-like paint 2 to a thickness of 1.5 mm and laminating them.
The specimen 5 was prepared by applying the stone-like paint 1 to a thickness of 1.5 mm and then applying the stone-like paint 3 to a thickness of 1.5 mm.

Test specimen 6 was a stack of the stone-like paint 1 applied to a thickness of 1.0 mm, the stone-like paint 2 applied to a thickness of 1.0 mm, and the stone-like paint 3 applied to a thickness of 1.0 mm. .
These specimens were cured at room temperature for 10 days in a standard state, and designated as a test specimen.

The clear undercoat material is mainly composed of an acrylic resin-based synthetic resin emulsion, and the molecular weight of the synthetic resin is about 50,000, the average particle size is 0.05 μm, and the solid content is 45.0% by weight. Met.
The formulation was as follows.

Formulation of clear undercoat material Acrylic synthetic resin emulsion 150.0 (g)
Film-forming aid 15.0 (g)
Defoamer 2.0 (g)
Dispersant 1.0 (g)
Wetting agent 1.0 (g)
Thickener 1.0 (g)
Mixed water 80.0 (g)
Total 250.0 (g)

For the clear paint, an acrylic silicone resin-based synthetic resin emulsion having a glass transition temperature of 20°C and a solid content of 45.0% by weight was used, and a matting agent was added to prepare a matte clear paint. Light stabilizers and UV absorbers were also added.
The formulation was as follows.

Formulation of clear paint Acrylic silicone resin synthetic resin emulsion 90.0 (g)
Mixed water 23.0 (g)
Film-forming aid 7.0 (g)
Antifreeze agent 0.5 (g)
Light stabilizer 1.0 (g)
UV absorber 2.5 (g)
Defoamer 1.0 (g)
Dispersant 0.5 (g)
Wetting agent 0.5 (g)
Thickener 1.0 (g)
Matting agent 3.0 (g)
Total 130.0 (g)

These coatings were applied with a medium wool roller among the coating rollers.
A clear undercoat material was applied to a test specimens 1 to 6 and b to test specimens 1 to 6. The coating amount was in the range of 100 to 190 g/m ² and the coating thickness was in the range of 50 to 100 µm.

This is because when the coating thickness is within this range, the finish of the clear coating is good and the adhesion is sufficient. This coating weight range provided a good balance between the efficient range of coating operations and the strength of the degraded coating.
After applying the clear undercoat material and drying, apply the clear paint. The coating amount of this clear was in the range of 200 to 300 g/m ² . The film thickness was in the range of 150-200 μm.

Create a total of 12 types of test specimens, a test specimens 1 to 6 and b test specimens 1 to 6, cure them for 10 days, measure the strength and observe the fracture position, etc., and the performance of the repair method for the deteriorated coating film. made an evaluation.
For comparison, test specimens 1 to 3 were also prepared without applying the clear undercoat material and the clear paint, and designated as c test specimens 1 to 3.

This performance evaluation was performed by an adhesion test in JIS A6909. In this adhesion test, those with an adhesion strength of 5.0 N/mm ² or more were considered good.
The test results are shown below.

Standard condition a The adhesion strength of the test piece 1 was 5.0 N/mm ² or more, and the fracture position was a deep layer about 2.5 mm from the surface of the test piece.
The bond strength of a test piece 2 was 5.0 N/mm ² or more, and the fracture position was about 1.7 mm from the surface of the test piece.

The adhesion strength of a test piece 3 was 3.8 N/mm ² , and the fracture position was near the surface layer of the test piece and about 1 mm.
a The bond strength of the test piece 4 was 5.0 N/mm ² or more, and the fracture position was about 2.0 mm from the test piece surface and was formed by the stone-like paint 1 .

The adhesive strength of the a test piece 5 was 4.2 N/mm ² , and the fracture position was near the surface layer of the test piece, about 1 mm, and was formed by the stone-like paint 3 .
The adhesion strength of the a test piece 6 was 4.0 N/mm ² , and the fracture position was about 1.5 mm near the center of the test piece, which was the part formed by the stone-like paint 2 .

After repeated heating and cooling test b The bond strength of test piece 1 was 5.0 N/mm ² or more, and the fracture position was about 2.5 mm from the surface of the test piece.
b The bond strength of test piece 2 was 5.0 N/mm ² or more, and the fracture position was about 1.5 mm from the surface of the test piece.

b The bond strength of test piece 3 was 3.8 N/mm ² , and the fracture position was near the surface layer of the test piece.
b The adhesion strength of test piece 4 was 5.0 N/mm ² or more, and the fracture position was about 1.8 mm from the test piece surface and was formed by stone-like paint 1 .

b The adhesion strength of the test piece 5 was 4.0 N/mm ² , and the fracture position was near the surface layer of the test piece and the part formed by the stone-like paint 3 .
b The adhesion strength of the test piece 6 was 3.8 N/mm ² , and the fracture position was about 1.1 mm near the center of the test piece, which was the part formed by the stone-like paint 2 .

Comparative Test Specimen c Specimen 1 had an adhesive strength of 5.0 N/mm ² or more, and the fracture position was about 2.5 mm from the surface of the specimen.
The adhesion strength of the c test piece 2 was 4.7 N/mm ² and the fracture position was about 1.5 mm from the surface of the test piece.

The adhesion strength of c-specimen 3 was 3.6 N/mm ² , and the fracture position was near the surface layer of the specimen.
A comparison of test specimens 1 from a to c based on the above test results showed that there was no change in adhesion strength and fracture position. Since the paint film was in a new state, this did not fully demonstrate the effect of the method of repairing the deteriorated paint film of the present disclosure. This test sample 1 and test samples 2 to 6 are also compared.

Compared to c-test body 1, c-test body 2 and c-test body 3 have lower bond strengths, and their fracture positions are also different. I was able to confirm that it is.
As for test sample 2, it was confirmed that strength equivalent to that of test sample 1 was restored by applying the clear undercoat material and the clear paint to test sample 2 c.

Although it was confirmed that the strength of test sample 3 was recovered, the strength of test sample 1 was slightly inferior to that of test sample 1.
In addition, it was confirmed that, in test samples 4 to 6, sufficient strength was recovered depending on the penetration depth of the clear undercoat material and the thickness of the deteriorated coating film.

In addition, an exposure test was conducted on these specimens for one year, but the difference could not be confirmed.

Claims (5)

For deteriorated paint film mainly composed of synthetic resin,
A method for repairing a deteriorated paint film by applying a clear undercoat material containing a synthetic resin emulsion as a main component, then applying a clear paint and laminating it on the surface of the deteriorated paint film. 2. The deteriorated paint according to claim 1, wherein the synthetic resin emulsion, which is the main component of the clear undercoat material, has a molecular weight in the range of 10,000 to 100,000 and an average particle size in the range of 0.01 to 0.1 μm. Membrane repair method. 3. The method for repairing a deteriorated paint film according to claim 1, wherein an ultraviolet absorber is added to said clear paint. It is formed of a stone-like paint in which a synthetic resin capable of forming a transparent film after the degraded paint film is cured and dried and a colored aggregate having a particle size in the range of 37 to 2000 μm are mixed. Item 4. A method for repairing a deteriorated paint film according to any one of items 3. A method for evaluating the method for repairing a deteriorated coating film according to any one of claims 1 to 4,
After preparing a test paint in which the synthetic resin component of the paint forming the deteriorated paint film is reduced by 50.0 to 95.0% by weight, and obtaining a test paint film formed by the test paint, claim An evaluation method for repairing a deteriorated coating film, in which a laminate obtained by any one of claims 1 to 4 is used as a test piece and an adhesion test is performed.