JP7699038B2 - Method for applying water-based road marking paint and curing accelerator for water-based paint - Google Patents

Description

The present disclosure relates to a coating method that uses a curing accelerator when coating water-based road marking paint for marking road surfaces, and further relates to a curing accelerator for water-based paint.

2. Description of the Related Art Roads and the like are marked with markings such as traffic signs, such as lane markings and stop lines, and pedestrian crossing signs, and the markings provide appropriate information to vehicle drivers, pedestrians, and the like.
These markings are made by applying a road marking paint to the road or the like to form a coating.

Water-based road marking paints, which are environmentally friendly, are increasingly being used as road marking paints. Unlike the organic solvent-based road marking paints that have been used up until now, water-based road marking paints form a coating when the dispersion medium, water, evaporates.
However, in the case of water-based road marking paints, the dispersion medium, water, does not evaporate as quickly as organic solvents, and the curing time required to form a coating film tends to be long, so application of the markings often takes a long time.

When this work is carried out, it is necessary to apply water-based road marking paint and then block or restrict traffic for an extended period of time until the paint hardens.
Therefore, a method for applying a water-based paint as described in Patent Document 1 has been proposed.

This method of applying water-based paint is a method of contacting a hardening accelerator with a water-based emulsion paint containing an emulsion polymer as a coating film-forming element when the water-based paint is applied to a road surface, and is characterized in that the hardening accelerator is a water-soluble acid and a water-soluble metal salt, either separately or in combination.
This made it possible to significantly shorten the time it took for the water-based paint to harden after it was applied, and also reduced the time required for traffic closures and restrictions during marking work.

JP 2013-240783 A

However, when this curing accelerator is brought into contact with the water-based paint, the curing accelerator is often sprayed and then brought into contact with the water-based paint, and during this process, the curing accelerator is often scattered, resulting in the consumption of more curing accelerator than is necessary for curing the water-based paint.
In addition, the scattered hardening accelerator may accelerate the rusting of tools needed for construction work and nearby iron materials.

The present disclosure aims to provide a method for applying water-based road marking paint using a hardening accelerator that accelerates the hardening of the paint after application, shortens the time required for traffic closures and restrictions during marking work, and uses the minimum amount of hardening accelerator required to harden the paint film of the water-based road marking paint, with minimal scattering.

In the application method, a water-based road marking paint mainly composed of a synthetic resin emulsion is applied onto a road surface and then a hardening accelerator is brought into contact with the applied water-based road marking paint, wherein the hardening accelerator is an aqueous solution whose viscosity has been adjusted with a water-soluble metal salt and a viscosity adjuster, and whose viscosity is lower than that of the water-based road marking paint, being in the range of 10 mPa·s or more.
This accelerates the hardening of road marking paint after it has been applied, shortening the time required for traffic closures and restrictions during marking work; it also serves as a hardening accelerator that requires the minimum amount of use necessary to harden the coating of water-based road marking paint, with minimal scattering.

The water-based road marking paint contains an anionic synthetic resin emulsion containing a carboxyl group, a polymer containing an amine functional group, and a volatile base, and the hardening accelerator contains a water-soluble acid.
This allows the hardening accelerator to be used in the minimum amount necessary to harden the coating of water-based road marking paint, and causes little splatter, which further accelerates the hardening of the road marking paint after it is applied, making it possible to reduce the time required for traffic closures and restrictions during marking work.

The water-soluble metal salt contained in the curing accelerator is a divalent metal salt, the water-soluble acid is a carboxylic acid, and the combined concentration of the water-soluble metal salt and the water-soluble acid is in the range of 10.0 to 45.0% by weight, so that the curing accelerator can be used in the minimum amount required to cure the coating of the water-based road marking paint, with little scattering, and it is possible to further accelerate the curing of the road marking paint after application.

The viscosity is adjusted to the range of 10 to 50 mPa·s using water-soluble metal salts and viscosity adjusters, so that the minimum amount required to harden the coating of water-based paint is needed, and the hardening accelerator causes little scattering, accelerating the hardening of water-based paint after application.

FIG. 1 is a schematic diagram of one embodiment of the application method according to the present invention, in which beads are scattered at the application position of the water-based road marking paint, and immediately thereafter a hardening accelerator is sprayed onto the top surface of the paint film to bring it into interfacial contact with the water-based road marking paint. FIG. 13 is a schematic diagram of another embodiment, showing a method for spraying a hardening accelerator and mixing and contacting the hardening accelerator with the water-based road marking paint while simultaneously scattering beads at the spraying position of the water-based road marking paint.

An embodiment of the present disclosure will be described.
The present disclosure relates to an application method in which a water-based road marking paint mainly composed of a synthetic resin emulsion is applied onto a road surface and a hardening accelerator is brought into contact with the applied water-based road marking paint, wherein the hardening accelerator is an aqueous solution whose viscosity has been adjusted with a water-soluble metal salt and a viscosity adjuster, and whose viscosity is lower than that of the water-based road marking paint, in the range of 10 mPa·s or more.

First, this water-based road marking paint is in accordance with JIS K 5665 and is of a water-based type. This water-based road marking paint is often used because it is easy to handle.
The water-based road marking paint may use, as its binder, a synthetic resin emulsion produced by a conventional polymerization technique such as emulsion polymerization, and may be implemented even if the polymer structure of the synthetic resin emulsion is in a complex form, such as a core-shell particle.

This water-based road marking paint is colored by containing coloring components such as white pigments such as titanium oxide, kaolin, talc, and clay, inorganic pigments such as iron oxide, and organic pigments, in addition to the synthetic resin emulsion.
They also often contain extender pigments such as calcium carbonate, diatomaceous earth, aluminum hydroxide, bentonite, white carbon, precipitated barium, and silica sand, as well as fibers.

If necessary, components generally used in the manufacture of paints can also be used, such as surfactants used as dispersants, wetting agents, and defoamers, viscosity regulators such as thickeners, leveling agents, and anti-sagging agents, low-boiling alcohols, film-forming assistants, and organic solvents used as antifreeze agents.
Furthermore, additives such as pH adjusters, preservatives, antifungal agents, anti-algae agents, waxes, etc. may also be added as necessary.

The hardening accelerator is an aqueous solution whose viscosity is adjusted by a water-soluble metal salt and a viscosity adjuster, and its viscosity is lower than that of the water-based road marking paint, in the range of 10 mPa·s or more. This viscosity is measured at 60 revolutions using a Brookfield viscometer at 23°C.
The water-soluble metal salt is a metal salt that dissolves in an amount of 10 g or more in 100 g of water at 20° C., and is not particularly limited.

When this water-soluble metal salt comes into contact with the synthetic resin emulsion of the water-based pavement marking paint, it can coagulate the synthetic resin emulsion, making the applied water-based pavement marking paint unstable and causing it to gel quickly, thereby fixing the fluid pavement marking paint and promoting hardening.
The water-soluble metal salt should have a solubility in water of 10 g/100 g (20° C.) or more, and those that are more soluble in water are preferred, which makes it easier to prepare the curing accelerator.

The water-soluble metal salts will be described later, but many of them accelerate the rusting of iron, so the hardening accelerator must be adjusted so that it is not scattered into the surrounding area.
The viscosity adjuster may be similar to those used in water-based road marking paints, and the type and amount of viscosity adjuster used is determined according to the type of water-soluble metal salt, the concentration of the hardening accelerator, and the set viscosity, to obtain the desired viscosity and stickiness, and it thickens the hardening accelerator to a certain degree.

This viscosity adjuster has long molecules and exists in a swollen form in water when dissolved in water, which allows it to increase the viscosity of the hardening accelerator and impart viscosity to it. It is available in powder and liquid forms.
This hardening accelerator is made viscous by the viscosity adjuster described above, and when the hardening accelerator is brought into contact with the water-based road marking paint in a viscous state, particularly when applied and brought into contact by spraying, there is little scattering, so that only the minimum amount required to harden the coating film can be used.
The viscosity of this hardening accelerator should be 10 mPa·s or more. If it is lower than this, the amount of hardening accelerator that scatters will increase, and the scattered hardening accelerator may adhere to tools required for construction or nearby iron parts, causing them to rust.

In addition, the viscosity of the curing accelerator must be lower than that of the water-based road marking paint that it is intended to be used with; if it is higher, the spray width will be narrower than the water-based road marking paint, and the curing of the entire painted surface will not be sufficiently promoted.
The upper limit of the viscosity of this curing accelerator needs to be 7000 mPa·s or less. If the viscosity is below this limit, the accelerator can be applied evenly to the surface to be coated with the water-based paint, and curing of the entire coated surface can be sufficiently promoted.

By adding viscosity to the curing accelerator in this way and making it thick with a certain degree of viscosity, the minimum amount required for hardening the coating of the water-based road marking paint is used, and there is little scattering. This characteristic is particularly evident when the curing accelerator is sprayed.
The amount of water-based road marking paint to be applied depends on the road surface condition, type of paint, application specifications, and other conditions, but is often selected appropriately from the range of 100 to 3,000 g/ ^m2 .

The amount of hardening accelerator applied varies depending on the type of water-based road marking paint, but is often set appropriately within the range of 1.0 to 30.0 g of hardening accelerator per 100 g of paint.
If the amount is less than this range, it may be difficult to obtain a sufficient effect of accelerating the hardening of the coating film. If the amount is more than this range, the effect of applying more may not be obtained. If it is within this range, a sufficient effect of accelerating the hardening can be obtained.

Next, a coating method for bringing the above-described water-based road marking paint into contact with a hardening accelerator will be specifically described.
The application method for bringing the water-based road marking paint and the hardening accelerator into contact with each other includes the application method shown in Figs.

This application method often uses a marker vehicle equipped with a spray gun such as an air spray or airless spray on a car or a handcart. Two types of spray guns, a spray gun 11 for the water-based road marking paint and a spray gun 15 for the curing accelerator, are loaded onto this marker vehicle.
The water-based road marking paint can be applied using a brush or a paint roller, and after the water-based road marking paint is applied, a hardening accelerator is applied using a spray gun.

This is because if a hardening accelerator is applied to a brush or painting roller and then brought into contact with water-based road marking paint, the water-based road marking paint may adhere to the brush or painting roller, making it impossible to mark the road.
In order to improve the visibility of the marking at night, glass beads are sometimes and preferably dispersed on the paint surface or in the paint. The dispersion of glass beads will be explained below.

These glass beads are available in large spherical sizes with a particle size of approximately 500 to 1,700 μm and small spherical sizes with a particle size of approximately 106 to 850 μm. Their refractive index is approximately 1.5 to 2.5 and causes retroreflection when light hits them, thereby improving the nighttime visibility of the marking.
The water-based road marking paint spray gun 11 and the hardening accelerator spray gun 15 may be of the airless spray type or air spray type. The glass bead spreader 14 was of the gravity drop type.

In FIG. 1, the water-based road marking paint is applied to the road surface R using a spray gun 11 to form a paint layer 12, and at the same time, glass beads 13 are sprayed onto the paint layer 12 using a bead sprayer 14, and a hardening accelerator is sprayed onto the paint layer 12 using a hardening accelerator spray gun 15, so that the hardening accelerator comes into interfacial contact with the water-based road marking paint.

By using a viscous hardening accelerator, when the water-based road marking paint is applied and then the hardening accelerator is applied, the unhardened paint layer 12 is coated with the viscous hardening accelerator, thereby protecting the paint layer 12.
This makes it possible to protect the paint layer 12 from external factors such as light rain.

In Figure 2, in the method of Figure 1, a hardening accelerator is sprayed with a hardening accelerator spray gun 15 toward the same position as when the water-based road marking paint is applied, and a paint layer 12 is formed while the hardening accelerator is mixed and brought into contact with the water-based road marking paint.
As shown in Figures 1 and 2, the water-based road marking paint is brought into contact with the hardening accelerator. When the hardening accelerator comes into contact with the water-based road marking paint, the synthetic resin emulsion starts to aggregate, forming a stable, fixed, non-fluid coating film. The water in this coating, the paint layer 12, evaporates, and the paint components are concentrated and aggregated.

The synthetic resin emulsion particles in the paint components then fuse with other particles to form a cured coating film.
This accelerates the hardening of water-based road marking paint after it is applied, shortening the time required for traffic closures and restrictions during marking work, and the hardening accelerator only needs to be used in the minimum amount necessary to harden the water-based road marking paint coating, resulting in minimal splatter.

Furthermore, this uncured coating film will not wash away even if it rains immediately after application, or if it rains at low temperatures, and thereafter a cured coating film is gradually formed.
This water-based road marking paint is generally not applied at temperatures below 5° C. The reason is that a hardened coating film is not obtained after application of the water-based road marking paint, and the unhardened coating film will be washed away by rainfall, etc.

However, according to the application method of the present disclosure, it is possible to apply a water-based road marking paint even if a cured coating film is not obtained at low temperatures such as below 5°C.
Furthermore, the water-based road marking paint and the hardening accelerator, which are constituent elements of the present disclosure, will be described in more detail.

The above-mentioned synthetic resin emulsion may be a general one obtained by homopolymerizing or copolymerizing resins such as acrylic resin, urethane resin, vinyl chloride resin, silicone resin, vinyl acetate resin, polyester resin, styrene resin, and fluororesin.
Among these, acrylic synthetic resin emulsions and acrylic-styrene synthetic resin emulsions made from acrylic resin and styrene resin are often used from the viewpoints of paint suitability, coating film properties, and ease of availability.

The glass transition temperature of the resin used in this synthetic resin emulsion is preferably in the range of -50 to 70°C, and a synthetic resin having an appropriate glass transition temperature can be selected as required.
The synthetic resin emulsion is preferably an anionic synthetic resin emulsion containing a carboxyl group, and at the same time, the water-based road marking paint preferably contains an amine functional group-containing polymer and a volatile base.

By using a synthetic resin emulsion having such a composition, the hardening of the water-based road marking paint is accelerated, and the hardening can be further accelerated by using a hardening accelerator.
The water-based road marking paint containing the carboxyl-containing anionic synthetic resin emulsion, the amine-functional polymer and the volatile base is paint-stable under alkaline conditions.

However, when the volatile base volatilizes and the paint becomes neutral, the synthetic resin emulsion becomes unstable and begins to aggregate, resulting in a gelled state in which the paint loses its fluidity.
In other words, after such water-based road marking paint is applied, the volatile base evaporates and the paint changes to an acidic state, forming a gelled, non-fluid, uncured coating film, and the carboxyl groups of the synthetic resin emulsion and the amine functional groups of the amine functional group-containing polymer undergo a cross-linking reaction.

The water in the coating then evaporates, the water-based paint components condense and coagulate, and the particles of the synthetic resin emulsion fuse together, entraining other particles, to form a hardened coating.
The carboxyl groups react with the amine functional groups of the amine functional group-containing polymer to crosslink the water-based road marking paint, gelling it and forming a coating film, which can improve the strength and weather resistance of the cured coating film.

The amine functional group-containing polymer has an amine functional group contained in it as a constituent element, and undergoes a crosslinking reaction with a carboxyl group contained in the synthetic resin emulsion to form a coating film.
The amine-functional polymer is a polymer formed from a monomer mixture containing at least one amine-functional monomer selected from the group consisting of primary amines, secondary amines, and tertiary amines, and can be obtained by solution polymerization in a neutral, alkaline, or acidic aqueous medium depending on the polymer.

The amine functional group-containing polymer is preferably a water-soluble or water-dispersible polymer in view of its miscibility with the synthetic resin emulsion.
The volatile base stabilizes the water-based road marking paint in the pH range of 7.0 to 10.0, thereby turning the amine functional groups of the amine functional group-containing polymer contained in the water-based road marking paint into a nonionic or anionic state, allowing the paint to be stored stably.

This volatile base, after application of the water-based pavement marking paint, begins to evaporate and lowers the pH of the paint to a point where conversion of the amine functional groups, which are in a nonionic or anionic state, to a cationic state begins to occur.
In that state, the amine functionality becomes cationic and initiates gelation of the waterborne pavement marking paint, the gelation being initiated by the conversion of the amine functionality to a cationic form.

Suitable volatile bases include ammonia, methylamine, ethylamine, propylamine, isopropylamine, dimethylamine, trimethylamine, etc., and ammonia or a substance containing ammonia as the main component is preferably used, which has a low boiling point of -33.4°C and evaporates quickly.
In addition, an alkalinity imparting agent that is liquid or solid at room temperature may be added. This alkalinity imparting agent may be a pH adjuster commonly used in paint formulations, and may stabilize the water-based road marking paint in a nonionic or anionic state together with a volatile base.

Examples of alkali-imparting agents that are liquid or solid at room temperature include amines and alkali metal salts. Examples of amines include morpholine, 2-dimethylaminoethanol, N-methylmorpholine, ethylenediamine, and 2-amino-2-methyl-1-propanol, and examples of alkali metal salts include sodium hydroxide and potassium hydroxide.

The water-soluble metal salts mentioned above include calcium chloride, magnesium chloride, iron dichloride, zinc chloride, sodium chloride, barium chloride, nickel chloride, magnesium nitrate, magnesium sulfate, manganese dichloride, etc., and can be suitably used.
These water-soluble metal salts can be used alone or in combination of two or more kinds, and are selected and used as required.

Among these, divalent metal salts are preferably used, and calcium chloride and magnesium chloride are particularly preferred because they are highly stable and inexpensively available.
When preparing the curing accelerator, it is preferable to use both an exothermic and an endothermic accelerator.

For example, when calcium chloride is mixed with water, heat is generated and there may be a sudden rise in temperature during mixing. By adding magnesium chloride, which is endothermic, the heat generation and endothermic reactions can be balanced during mixing, making it easier to mix the ingredients.
A relatively small amount of this divalent metal salt is capable of flocculating the synthetic resin emulsion, forming an uncured coating film in which the water-based road marking paint is stably fixed and in a non-fluid state, thereby further promoting curing.

Since marking work may be carried out in winter or in cold regions, the concentration of this aqueous metal salt is preferably at a level at which no precipitate will form even below freezing, and although this varies depending on the type of metal salt, it is usually more preferable to set the concentration at approximately 90% by weight or less of the saturated concentration at room temperature (20 to 25° C.).
The concentration is preferably 10% by weight or more, and if it is lower than this, it may not be possible to accelerate the hardening of the water-based road marking paint, which is one of the effects of the hardening accelerator.Moreover, 20% by weight or more is more preferable, and at this concentration, it is expected that the hardening will be accelerated at low temperatures such as 5°C.

The viscosity adjusters described above may be the same as those commonly used in paint formulations. However, depending on the type of water-soluble metal salt or the type of water-soluble acid described below, some viscosity adjusters are difficult to increase, so prior confirmation may be necessary.
Furthermore, the amount of viscosity adjuster to be added to obtain the desired viscosity of the curing accelerator must be confirmed in advance.

These viscosity modifiers include cellulose derivative compounds such as methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and hydroxypropyl cellulose; inorganic compounds such as water-soluble alkali silicate, montmorillonite, and colloidal alumina; polyether compounds such as polyether dialkyl esters, polyether dialkyl ethers, polyether urethane modified products, and polyether epoxy modified products; polyacrylic acid compounds such as sodium polyacrylate and polyacrylic acid (meth)acrylic acid ester copolymers; polyvinyl compounds such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl benzyl alcohol copolymers; protein derivatives such as sodium caseinate and ammonium caseinate; partial esters of vinyl methyl ether-maleic anhydride copolymers; drying oil fatty acid allyl alcohol ester-maleic anhydride copolymers; alkali swelling type viscosity modifiers; and urethane association type viscosity modifiers. These may be used alone or in combination of two or more types.

In addition, when the synthetic resin emulsion is an anionic synthetic resin emulsion containing a carboxyl group and the water-based road marking paint contains an amine functional group-containing polymer and a volatile base, the hardening of the water-based road marking paint can be further accelerated by adding a water-soluble acid to the curing accelerator.
The water-based road marking paint is an anionic synthetic resin emulsion containing a carboxyl group, and contains an amine functional group-containing polymer and a volatile base. By adding a water-soluble acid and contacting it with an acidified hardening accelerator, the water-based road marking paint quickly becomes acidic, accelerating gelation.

The water-soluble acids include organic acids and inorganic acids, and the organic acids include carboxylic acids such as citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, acetic acid, etc. The inorganic acids include hydrochloric acid, sulfuric acid, phosphoric acid, etc.
Among these, organic acids are preferred from the viewpoint of ease of handling, and citric acid, which is a polycarboxylic acid, is particularly preferred. Many polycarboxylic acids have a small acid dissociation constant pKa, and even a small amount of the polycarboxylic acid can be used to increase the acidity and promote faster curing.

When the water-based road marking paint contains an anionic synthetic resin emulsion containing a carboxyl group, an amine functional group-containing polymer, and a volatile base, and the hardening accelerator contains a water-soluble acid, the pH of the paint drops rapidly when the water-based road marking paint comes into contact with the hardening accelerator, due to the evaporation of the volatile base in the paint and the water-soluble acid of the hardening accelerator.

The amine functional groups in the water-based road marking paint that are stable in a nonionic or anionic state become cationic when the pH drops to a level where the amine functional groups begin to convert to a cationic state. The cationic amine functional groups electrically attract anionic synthetic resins, causing gelation.
At the same time, the synthetic resin emulsion begins to aggregate due to the water-soluble metal salt of the curing accelerator, gelling and forming an uncured coating film that is stably fixed and has no fluidity.

Furthermore, in this uncured coating, the distance between the amine functional group-containing polymer and the polymer of the anionic synthetic resin emulsion becomes closer.
The carboxyl groups of the anionic synthetic resin polymer and the amine functional groups of the amine functional group-containing polymer that has become cationic bind ionically to initiate a crosslinking reaction.

Then, as the water evaporates from this uncured coating film, the paint components are concentrated and coagulated, and the particles of the synthetic resin emulsion in the paint components fuse with other particles to form a cured coating film.
This allows the hardening accelerator to be used in the minimum amount necessary to harden the coating of the water-based road marking paint, and with little splatter, it further accelerates the hardening of the water-based road marking paint after it is applied, thereby making it possible to reduce the time required for traffic closures and restrictions during marking work.

The water-soluble acid is preferably one that dissolves in a large amount. Since marking work may be carried out in winter or in cold regions, the concentration of the acid is preferably set to a level at which no precipitate will form even at temperatures below freezing.
Although it varies depending on the type of the water-soluble acid, it is usually more preferable to make the concentration about 90% by weight or less of the saturated concentration at room temperature (20 to 25° C.).

The concentration is preferably 5% by weight or more, and if it is lower than this, the promotion of hardening of the water-based road marking paint, which is one of the effects of the hardening accelerator, may be insufficient. If the amount of water in the hardening accelerator is excessive, it may inhibit the gelation of the water-based road marking paint.
It is also preferable that the combined concentration of the water-soluble metal salt and the water-soluble acid is 15% by weight or more. At this concentration, it is expected that curing will be accelerated even at low temperatures such as 5°C.

The ratio by weight of the water-soluble metal salt to the water-soluble acid is preferably in the range of 3:1 to 1:1, in order to obtain a well-balanced cure acceleration.
The method for applying the water-based road marking paint thus configured will now be described in detail using a specific example.

First, stones, dust, and debris were removed as much as possible from the asphalt of the road surface onto which the water-based road marking paint was to be applied, and the areas to be marked were marked.
This work was carried out in an asphalt-paved parking lot. In addition to parking lots, the surfaces to which this water-based road marking paint can be applied include roads and walkways paved with asphalt or concrete, as well as indoor floor surfaces such as warehouses and parking lots.

Two types of water-based road marking paints were used here and compared. The first type of water-based road marking paint (1) used an acrylic resin-based synthetic resin emulsion as specified in JIS K 5665, and contained titanium oxide as a white pigment, calcium carbonate as an extender pigment, surfactants as dispersants, wetting agents, and defoamers, and viscosity adjusters. Its viscosity was 5000 mPa·s.

The second type of water-based road marking paint (2) used was Kikusui Chemical Industry Co., Ltd.'s Keys Liner. This Keys Liner uses an anionic acrylic resin-based synthetic resin emulsion containing carboxyl groups as the synthetic resin emulsion, and contains an amine functional group-containing polymer and a volatile base in the paint. It also had a viscosity of 5000 mPa·s.

Two types of hardening accelerators were also used and compared. The first type (A) was an aqueous solution of calcium chloride and magnesium chloride mixed in water in a 1:1 ratio, with the combined water-soluble metal salt concentration at 30.0%, and the viscosity was adjusted to 35 mPa·s using a viscosity adjuster.
The second type of hardening accelerator (ii) was a mixture of hardening accelerator (a) and citric acid, with a ratio of water-soluble metal salts (calcium chloride and magnesium chloride) to water-soluble acid (citric acid) of 3:1, with the concentration adjusted to 30.0% by the amount of water, and a viscosity of 35 mPa·s.

These coatings were performed using a hand marker car, which was a handcart equipped with a coating device having the configuration shown in FIG.
The contact ratio of the hardening accelerator (a) and (b) to the water-based road marking paint (1) and (2) was confirmed in advance and verified to ensure an appropriate hardening time, and was set to 7 g per 100 g of water-based road marking paint.

In addition, the scattering state of the curing accelerator when sprayed was compared between the state before and the state after the viscosity adjuster of the curing accelerator (A) was added (curing accelerator (A)).
Under these application conditions, the hardening accelerator (A) to which the viscosity adjuster was added had significantly less scattering, and the application width when sprayed could be easily controlled.

In addition, when the amount of the curing accelerator applied was 20 g, the amount of the curing accelerator used was 21 g for the curing accelerator (A), but was 25 g for the curing accelerator without the viscosity adjuster.
From these results, it was confirmed that the amount of scattering of the hardening accelerator was significantly reduced by adding the viscosity adjuster.

Before applying the paint to the road surface, the application amount of each paint was set. The application amount of the water-based road marking paints (1) and (2) was set to an average of 200 g/ ^m2 , and the application width was 150 mm.
The application amounts of the curing accelerators (a) and (b) were set to an average of 17 g/ ^m2 , and the application width was set to 160 mm, which was wider than 150 mm.

The hardening speed of each of the water-based road marking paints (1) and (2) was examined by combining them with the hardening accelerators (A) and (B). The combinations are shown below.
A. Water-based road marking paint (1) only B. Water-based road marking paint (2) only C. Water-based road marking paint (1) and hardening accelerator (A)
D. Water-based road marking paint (2) and hardening accelerator (A)
E. Water-based road marking paint (2) and hardening accelerator (a)

The coating was carried out over a length of 5 m for each combination, and the curing speed was measured over time. The temperature during coating was 7° C.
This hardening refers to a state in which the applied water-based road marking paint loses its fluidity and the paint coagulates and hardens to form a film. This state was judged by the touch-dry condition specified in JIS K 5600-1-1.

The temperature of the water-based road marking paint and the hardening accelerator was 7° C., the same as the air temperature. Both types of hardening accelerators were free of precipitates and had the same viscosity as those stored at room temperature.
The coating work was carried out using a hand marker vehicle equipped with a coating device having the configuration shown in FIG.

The curing times were 20 minutes for A, 15 minutes for B, 13 minutes for C, 13 minutes for D, and 11 minutes for E. From these results, the effectiveness of the curing accelerator was confirmed.

11 Paint spray gun 12 Paint layer (fluid coating film)
13 Glass beads 14 Beads spraying device 15 Accelerator spray gun R Road surface

Claims (4)

A coating method comprising coating a water-based road marking paint mainly composed of a synthetic resin emulsion onto a road surface and contacting the coated water-based road marking paint with a hardening accelerator,
A method for applying a water-based road marking paint, wherein the hardening accelerator is an aqueous solution whose viscosity has been adjusted using a water-soluble metal salt and a viscosity adjuster, and whose viscosity is lower than that of the water-based road marking paint, in the range of 10 mPa·s or more. The water-based road marking paint comprises an anionic synthetic resin emulsion containing a carboxyl group, an amine functional group-containing polymer, and a volatile base;
2. The method for applying a water-based road marking paint according to claim 1, wherein the hardening accelerator contains a water-soluble acid. the water-soluble metal salt contained in the curing accelerator is a divalent metal salt,
the water-soluble acid is a carboxylic acid,
3. The method for applying a water-based road marking paint according to claim 1 or 2, wherein the combined concentration of the water-soluble metal salt and the water-soluble acid is in the range of 10.0 to 45.0% by weight. A curing accelerator for water-based paints, the viscosity of which is adjusted by a water-soluble metal salt and a viscosity modifier to fall within the range of 10 to 7,000 mPa·s.

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