JP7636748B2 - Method for manufacturing retroreflective resin molding - Google Patents

Description

The present invention relates to a retroreflective resin molding, and in particular to a retroreflective resin molding suitable for use as a road material intended for outdoor use.

2. Description of the Related Art Road materials used outdoors are given reflectivity for the purpose of guiding the viewer's gaze and calling attention.
For example, Patent Document 1 proposes attaching a reflective material to the side surface of a spacing member that is attached at regular intervals between posts in a guard cable.
Furthermore, Patent Documents 2 and 3 propose a reflective member for a safety fence post that is fitted into the cap of a capped post of a safety fence. A specific example of the reflective member is a light reflective tape.

JP 2007-270467 A JP 2015-94111 A JP 2017-145638 A

When applying reflective materials such as reflective sheets or light-reflective tape, as in the techniques of Patent Documents 1 to 3, the work is labor-intensive and costly. It is also necessary to adjust the dimensions of the sheet or tape depending on the application location. Furthermore, in outdoor usage environments such as on highways, the long-term adhesion of the sheet or tape is insufficient, and frequent maintenance is required to remove the sheet or tape.

In particular, polyolefins are widely used as materials for resin molded products used in road construction, but because polyolefins have poor adhesiveness and adhesion to other materials, they are not suitable for application as sheets or tapes.

In addition, in the above Patent Documents 1 to 3, the reflective material simply provides reflectivity, but when considering use as road materials, it is conceivable that it may be desirable to provide retroreflectivity rather than simple reflectivity. Here, retroreflectivity refers to the property of reflecting light incident from the outside in the same direction as the incident direction; for example, it can efficiently reflect the headlights of a car back to the driver to draw their attention.

The present invention aims to provide a retroreflective resin molding that can easily and stably impart retroreflectivity to a polyolefin-based resin molding body and can stably maintain that retroreflectivity for a long period of time even under harsh outdoor conditions.

The present inventors have conducted extensive research to solve the above problems, and have found that retroreflectivity can be stably maintained for a long period of time by modifying the surface of a polyolefin-based resin molded product and/or applying a specific primer coating to the surface of the polyolefin-based resin molded product and then providing retroreflectivity by painting on the primer coating. This long-term stability is fully demonstrated even in a high-humidity environment, and is extremely advantageous for outdoor use. It is speculated that the long-term stability in a high-humidity environment is due to the reflective material contained in the retroreflective layer formed by painting, which acts to prevent or delay moisture from reaching the interface with the resin molded product itself.
The present invention has been completed as a result of the above-mentioned investigations.

That is, the method for producing a retroreflective resin molding according to the present invention is a method for producing a retroreflective resin molding comprising a polyolefin resin molding body and a retroreflective layer coated on the resin molding body, the retroreflective layer being a resin layer containing at least glass beads, a reflective material, and a resin component, the reflective material being a reflective film covering a part of the surface of the glass beads, and the surface of the resin molding body is subjected to a surface modification treatment for improving wettability using a torch burner at a flame temperature of 1400 to 1800°C, a treatment speed of 24 m/min to 80 m/min, a treatment number of 1 to 20 times, and a treatment height of 80 m. The present invention is characterized in that after flame treatment at a firing distance of 100 mm to 130 mm, a paint containing the resin component but not containing a reflective material is sprayed directly onto the surface of the resin molding body, or onto an undercoat layer provided on the surface of the resin molding body, to form a single layer of paint film, and while this paint film is still uncured, the glass beads having portions of their surfaces covered with a reflective film are sprayed onto the single layer of paint film that is formed by curing the single layer of paint film, so that the glass beads form multiple layers within the single layer of paint film, and the retroreflective layer in which portions of the glass beads are exposed is formed.

According to the present invention, it is possible to easily and stably impart retroreflectivity to the main body of a polyolefin-based resin molded product, and the retroreflectivity can be stably maintained for a long period of time even when the product is used outdoors, such as on a highway.

FIG. 2 is a partial cross-sectional view showing a retroreflective resin molding according to one embodiment of the present invention. FIG. 2 is a partial cross-sectional view showing a retroreflective resin molding according to one embodiment of the present invention. FIG. 2 is a partial cross-sectional view showing a retroreflective resin molding according to one embodiment of the present invention. 1 is a front view showing a guard pipe using a retroreflective resin molding produced by the production method according to the present invention. 1 is a front view showing a guardrail using a retroreflective resin molding manufactured by the manufacturing method according to the present invention.

The manufacturing method of the retroreflective resin molding according to the present invention will be explained in detail below, but the scope of the present invention is not limited to these explanations, and modifications other than those exemplified below may be made as appropriate without departing from the spirit of the present invention.

[ Method for producing retroreflective resin molding]
1 shows a retroreflective resin molding 10 according to one embodiment of the present invention. The retroreflective resin molding 10 comprises a resin molding body 11, a primer layer 12 applied on the resin molding body 11, and a retroreflective layer 13 applied on the primer layer 12.
The resin molded body 11 is made of polyolefin, such as high-density polyethylene, low-density polyethylene, polypropylene, poly-α-olefin, etc. High-density polyethylene is preferable because it is lightweight and has excellent low-temperature properties, mechanical strength, water resistance, etc.
Polyolefins, particularly high density polyethylene, have low wettability, and conventionally it has not been easy to impart retroreflectivity stably for a long period of time.

The surface of the polyolefin resin molded body 11 is subjected to a surface modification treatment for improving wettability.
The surface modification treatment is not particularly limited as long as it can improve wettability, and examples thereof include flame treatment, corona treatment, plasma treatment, Itro treatment, etc. Flame treatment is preferred because it can be performed with a relatively simple device.
The flame treatment conditions are, for example, 1400 to 1800° C. and 24 to 80 m/min, preferably 24 to 60 m/min.

From the viewpoint of long-term adhesion of the retroreflective layer, the surface condition of the resin molded body 11 after the surface modification treatment is preferably such that the wetting index is 31 mN/m or more, more preferably 32 mN/m or more, and the water contact angle is preferably 56° or less.
In the present invention, the wettability index is a value measured by a method conforming to JIS-K-6768: 1999. The water contact angle is a value measured by a method conforming to JIS-R-3257: 1999.

The primer layer 12 applied onto the surface-modified resin molded body 11 is interposed between the resin molded body 11 and the retroreflective layer 13 formed on the primer layer 12, thereby improving the long-term adhesion of the retroreflective layer 13.
The thickness of the undercoat layer 12 is, for example, 1 to 25 μm in dry film thickness. Although the long-term adhesion is excellent even if the thickness exceeds 25 μm, not only is no further effect obtained, but also the coating cost such as the paint cost increases, which is not preferable. A more preferable dry film thickness is 1 to 12 μm.

The retroreflective layer 13, which is applied on top of the undercoat layer 12, is a resin layer that contains at least glass beads, a reflective material, and a resin component.

1, glass beads 131 are arranged in a multi-layer structure in a resin layer 133, with some of the glass beads 131 exposed from the surface. A part of the surface of the glass beads 131 is covered with a reflecting material 132 as a reflecting film. Glass beads (self-reflective beads) with a part of the surface covered with a reflecting material 132 are described in, for example, Japanese Patent No. 5566154.
A retroreflective layer having the structure shown in FIG. 1 can be formed by applying a paint containing a resin to form a paint film, spraying reflective beads onto the paint film while it is still in an uncured state, and then curing the paint film.

When using self-reflective beads as in the configuration of Figure 1, it is preferable to set the area of the reflective film so that both incidence and reflection are efficient. From this perspective, it is preferable to form the reflective film on 30-70% of the bead surface area, more preferably on 40-60% of the surface area, and self-reflective beads in which the reflective film is formed on approximately 50% of the surface area, i.e., on the hemispherical portion of the bead, are particularly preferable. If a reflective film is formed on the hemispherical portion of the bead surface, there is a 50% chance of retroreflection, providing sufficient visibility.

The method for manufacturing the self-reflective beads by forming a reflective film on a part of the surface of the beads is not particularly limited, and a conventionally known method may be used. For example, the semi-spherical part of the beads is temporarily attached to a film such as polyester with polyethylene or the like so as to be embedded therein, and then the film is removed by placing the film in a vacuum oven to deposit metal or metal oxide, which is the material for the reflective film, to obtain the self-reflective beads having a reflective film on which the metal or metal oxide is deposited.
The metal or metal oxide used as the material for the reflective film is not particularly limited as long as it exhibits the function of a reflective film. Preferred examples of the metal or metal oxide that is white to silvery white include metals and metal oxides such as aluminum, nickel, silver, tin, and zinc, and oxides of these metals, and aluminum is particularly preferred.

Fig. 2 shows a different structure from that shown in Fig. 1. Unlike the structure shown in Fig. 1, the reflective material 132 is not used as a reflective film covering the self-reflective beads, but is dispersed in the resin 133, and the glass beads 131 are multi-layered in the resin layer 133 in which the reflective material 132 is dispersed, and some of them are exposed from the surface. Such a retroreflective layer 13 is described in, for example, Japanese Patent No. 5872240.
A retroreflective layer having the structure shown in FIG. 2 can be formed by applying paint containing a reflective material and a resin to form a paint film with the reflective material dispersed therein, spraying glass beads onto the paint film while it is still in an uncured state, and then curing the paint film.

When the reflector 132 is dispersed in the coating 133 as in the configuration of Figure 2, the reflector 132 is preferably a flake-shaped reflector such as a scale-shaped, tongue-shaped, or thin-flaked reflector. Such flake-shaped reflectors tend to be oriented along the spherical surface of the glass beads, which increases the retroreflective efficiency compared to when the reflector is randomly present in the coating.

The particle size of the reflective material 132 can be set, for example, between 1 and 500 μm, and more preferably between 5 and 50 μm. The average particle size can be set, for example, between 5 and 25 μm, and more preferably between 10 and 20 μm. The fine reflective material is uniformly dispersed in the coating film, allowing it to exhibit excellent reflective function.

Specific examples of such reflecting material 132 include mica. Examples of mica that can be used include mica made from mica and synthetic mica. Generally, the reflected light of mica is white. If the mica surface is coated with titanium oxide, the reflective performance is improved. Metals, inorganic materials, minerals, and the like having surface reflectivity such as aluminum can also be used as the reflecting material 132. If the reflecting material 132 is colored, it can exhibit a coloring function in addition to a reflective function. For example, aluminum particles reflect light in a silver color. Colored aluminum particles reflect light in the color of the color they are colored in. Non-leafing type aluminum particles are less susceptible to surface oxidation, can maintain good reflectivity, and are suitable for use.

In the retroreflective layer 13 of Figs. 1 and 2, the resin component that is the film-forming component is not particularly limited, but usually has a degree of transparency that has practical light transmittance. Both thermoplastic resins and thermosetting resins can be used. Moisture-curing and ultraviolet-curing resins can also be used. Specifically, acrylic, urethane, epoxy, ethylene vinyl acetate, polyvinyl alcohol, silicone, polyester, polyethylene, nylon, olefin, natural rubber, alkyd, vinyl chloride, and fluorine-based resins can be used. Copolymers of these resins can also be used. Among them, acrylic resins, urethane resins, and acrylic urethane resins (two-liquid type with main agent: acrylic polyol and hardener: isocyanate compound) are preferred, and these can be used alone or in combination of two or more types.
Among these, urethane resins, and in particular acrylic urethane resins, are preferred because they have excellent weather resistance in outdoor environments, can adequately follow the expansion and contraction of the resin material on roads where there are drastic temperature changes due to heat from asphalt and snowfall, and have the ability to absorb impacts such as pebbles kicked up by vehicle tires.

In the case of thermosetting resins, if the heat curing temperature is too high, there is a risk of deterioration of the resin molded body 11 and the undercoat layer 12. Therefore, for example, it is preferable that the heat curing temperature is 100°C or less, and it is even more preferable that the resin cures at room temperature.

The average particle size of the glass beads 131 in the retroreflective layer 13 is, for example, 10 to 1000 μm, preferably 30 to 500 μm. 30 to 300 μm is more preferable, and 30 to 150 μm is particularly preferable. If the average particle size of the beads is too large, it becomes difficult for the resin to hold the beads, and the beads may become easily removed from the coating. The average particle size of the glass beads is the average particle size value measured using a particle size distribution measuring device using the laser diffraction/scattering method (SALD-7000, manufactured by Shimadzu Corporation).

The refractive index of the glass beads 131 is not particularly limited, but is preferably 1.5 to 2.5, and more preferably 1.8 to 2.2.
For example, if the resin coating is thin, a refractive index of about 1.8 to 2.0 can be selected, whereas if the resin coating is thick and the refraction of light in the resin needs to be taken into consideration, a refractive index with a higher refractive index can be selected.

Two or more types of beads may be combined. For example, two or more types of beads that differ in average particle size, the proportion of the area on which a reflective film is formed, the refractive index, the presence or absence of a reflective film, etc., can be combined. In this way, by combining two or more types of beads or changing the ratio between them, the reflection characteristics can be adjusted as appropriate.

The retroreflective layer 13 may contain, as its components, other components in addition to the above-mentioned glass beads, reflective material, and resin component, so long as the effects of the present invention are not impaired.
For example, a colorant can be used. By using a colorant, the retroreflected light or the coating film itself can be colored.
When the paint film itself is colored, since the color of the resin molding will affect the color of the paint film, a concealing layer made of resin with a pigment added to it to hide the color of the resin molding can be applied, and then a paint film made of resin with the desired color pigment added to it can be applied.
Such colorants are not particularly limited, but coloring materials for ordinary paints or dyes can be used. The colorants may be ones that disperse in the retroreflective coating film, or ones that dissolve. Particulate, scaly, fibrous, etc. can be used. The particle size of the colorant can be set in the range of 0.01 to 10 μm, for example.

The thickness of the retroreflective layer 13 is preferably 15 μm or more, and more preferably 50 μm or more. Although it depends on the particle size of the glass beads, if the thickness is too thin, it may be difficult to form a multi-layer structure of the glass beads.

In addition, with respect to the film thickness of the retroreflective layer 13, in terms of its relationship with the particle size of the glass beads 131, it is preferable that the film thickness be 0.5 to 3.0 times the average particle size of the glass beads 131, more preferably 1.5 to 3.0 times, and particularly preferably 2.0 to 2.5 times.
In addition, when the above film thickness is mentioned as a lower limit, it is based on the film thickness of the coating film at the thinnest part (excluding the exposed part if the glass beads are exposed), and when it is mentioned as an upper limit, it is based on the film thickness of the coating film at the thickest part (excluding the exposed part if the glass beads are exposed).

The configuration shown in Figures 1 and 2 above exhibits high retroreflective efficiency, but other configurations, such as the configuration shown in Figure 3, may also be adopted. In the configuration shown in Figure 3, a resin layer 133b containing dispersed reflective material 132 is formed, and then a resin layer 133a containing fixed glass beads 131 is formed, resulting in a configuration in which the two layers are separated. Although inferior to the configuration shown in Figures 1 and 2, retroreflective property is exhibited by the glass beads 131 in the resin layer 133a and the reflective material 132 in the resin layer 133b.

In the above embodiments, the surface of the resin molded body 11 is subjected to a surface modification treatment, and a primer layer 12 and a retroreflective layer 13 are provided thereon. However, the retroreflective layer 13 may be provided directly on the surface of the resin molded body 11 that has been subjected to the surface modification treatment. By performing the surface modification treatment, even if the retroreflective layer 13 is provided directly on the surface of the resin molded body 11, long-term adhesion is exhibited to a certain degree. Therefore, the primer layer is not essential, and the presence or absence of the primer layer can be appropriately determined by taking into account the balance between the coating performance and the cost.

Conversely, when a primer layer containing a styrene-conjugated diene block copolymer is applied as the undercoat layer, the surface modification treatment can be omitted.
That is, according to the study by the present inventors, it was found that by using a primer layer containing a styrene-conjugated diene block copolymer, sufficient adhesion can be imparted even without surface modification treatment, unlike other resin materials.
This primer layer preferably contains a tackifying resin, and may contain, for example, a known tackifying resin such as a petroleum-based, rosin-based, or terpene-based resin.

For the undercoat layer, examples of resin materials other than styrene-conjugated diene block copolymers include modified polyolefins (modified polypropylene, modified polyethylene, etc.) into which functional groups such as acid groups have been introduced by graft modification or the like. If the resin molded body, which is the object to be coated, is made of polyolefin and a polyolefin resin is also used as the material for the undercoat layer, strong and long-lasting adhesion to the resin molded body can be obtained, and the introduction of functional groups into the polyolefin resin (modification) also provides excellent adhesion to the retroreflective layer, which is the top coat. Other examples include epoxy resins and modified epoxy resins. However, when using these resin materials, surface modification treatment is required to obtain the effects of the present invention.

[Use as road materials]
The retroreflective resin molding produced by the production method of the present invention can be used as a substitute for various resin moldings used as road materials.

FIG. 4 shows an example of such a use, which is a guard pipe that uses a retroreflective resin molding produced by the production method of the present invention.
In FIG. 4, a guard pipe 1A includes a plurality of support posts 2A and a beam 3A made of a plurality of round pipes.

The multiple pillars 2A are buried in the ground and fixed thereto, and the multiple beams 3A are attached between adjacent pillars 2A, 2A with both ends fixed thereto in a substantially horizontal direction.
A resin cap 10A is attached to the upper end of the support 2A.

In the example shown in FIG. 4, a retroreflective resin molding manufactured by the manufacturing method according to the present invention is used as the cap 10A.
This allows the cap 10A to retroreflect when illuminated with light, providing high visibility.

The cap 10A may have a retroreflective layer not only on the surface that is visible to the outside, but also on the inside. Under normal use, the inside is hidden from the outside and cannot be seen, but if a vehicle or the like collides with the guard pipe 1A and the cap 10A is scattered from the support 2A onto the road surface, the fallen cap 10A can be easily seen and retrieved during accident recovery, etc.

FIG. 5 shows an example of another application of the retroreflective resin molding produced by the manufacturing method of the present invention, which is a guardrail using the retroreflective resin molding produced by the manufacturing method of the present invention.
In FIG. 5, a guardrail 1B includes a plurality of posts 2B and a beam 3B made of a corrugated steel plate.

A plurality of pillars 2B are buried and fixed in the ground, and a beam 3B is bridged between adjacent pillars 2B, 2B in a substantially horizontal direction.
A resin sleeve 10B is attached to the end of the beam 3B. The provision of the sleeve 10B can reduce the impact when a pedestrian or vehicle collides with the beam 3B, and can also prevent pedestrians from falling over due to their clothing getting caught on the beam 3B.

In the example shown in FIG. 5, a retroreflective resin molding manufactured by the manufacturing method of the present invention is used as the rolled sleeve 10B.
As a result, when illuminated by light, the rolled sleeve 10B is retroreflective, providing high visibility.

Below, examples of retroreflective resin moldings are shown to demonstrate the effects of the present invention. However, the present invention is not limited to these examples. For convenience, "% by weight" will be expressed simply as "%" and "parts by weight" will be expressed simply as "parts".

Example 1
A retroreflective coating was applied to a high-density polyethylene resin molding body measuring 40 mm wide x 90 mm long x 16 mm high by the following method to obtain a retroreflective resin molding.
That is, the surface of the resin molded body was modified by flame treatment using a torch burner (manufactured by Iwatani Corporation) at a treatment speed of 24 m/min, two treatments, and a treatment height of 130 mm. The treatment height of 130 mm is the distance from the tip of the burner to the treated object, and is the position where the tip of the flame just hits the treated object.

A white polypropylene-based primer paint "KAR Plastic Primer Clear White" (manufactured by Kansai Paint Co., Ltd.) was applied to the surface of the resin molded body, and after drying for 2 hours, the following two-liquid acrylic urethane-based paint (A) containing a reflective material and a film-forming resin was applied, and then glass beads "UB-67M" (average particle size 100 μm, refractive index 1.93, manufactured by Unitika Ltd.) were sprayed at a spray pressure of 2 kg/ ^cm2 until the paint film on the coated object was completely covered with the glass beads.
Paint (A): The base material "Hi-Lock DX" (manufactured by Rock Paint), reflective material (flake mica, particle size distribution 5-25 μm, manufactured by BASF), and color pigment (gray) for coloring the resin were mixed by stirring, and then the isocyanate crosslinking agent "Eco Multi Hardener Hi-Flex" (manufactured by Rock Paint) was added as a curing agent and stirred.
The viscosity of the paint (A) at the time of application was 100 cps.

Next, the primer coating film and the coating film consisting of coating material (A) were simultaneously baked and cured by baking at a temperature of 80°C for 20 minutes, producing a retroreflective resin molded product according to Example 1. The dry thickness of the primer coating film (undercoat layer) was 10 μm, and the dry thickness of the retroreflective coating film (retroreflective layer) was 140 μm. It was confirmed from the cross-sectional photograph that the glass beads of the obtained coating product were in a multilayer structure within the coating film consisting of coating material (A), and that some of these layers were partially exposed on the surface of the coating film.

Example 2
A retroreflective resin molding according to Example 2 was produced in the same manner as in Example 1, except that no primer coating was applied.

Example 3
A retroreflective resin molding according to Example 3 was produced in the same manner as in Example 1, except that the paint (A) was replaced with the following two-component acrylic urethane paint (B) containing a different reflective material.
Paint (B): Main agent "Hi-Lock DX" (manufactured by Rock Paint), reflective material "FD512H" (aluminum paste, particle size distribution 5-25 μm) (manufactured by Asahi Kasei Corporation), and color pigments for coloring the resin were stirred and mixed together, and then the isocyanate crosslinking agent "Eco Multi Hardener Hi-Flex" (manufactured by Rock Paint) was added as a hardener and stirred and mixed to obtain a paint.
The viscosity of the paint (B) when applied was 100 cps.

Example 4
The retroreflective resin molding of Example 4 was produced in the same manner as Example 1, except that after the primer coating, a white pigment-containing two-component acrylic urethane resin coating containing "Hi-Lock DX" (manufactured by Rock Paint Co., Ltd.) paint, white pigment, and an isocyanate crosslinking agent "Eco Multi Hardener Hiflex" (manufactured by Rock Paint Co., Ltd.) was applied as a concealing layer, and then paint (A) was applied as a retroreflective layer (however, orange was used instead of gray as the coloring pigment).

Example 5
The retroreflective resin molding of Example 5 was produced in the same manner as Example 4, except that paint (B) was used instead of paint (A) as the retroreflective layer (with the exception that orange pigment was used as the colorant instead of gray).

Example 6
The retroreflective resin molding of Example 6 was produced in the same manner as Example 1, except that the surface of the resin molding body was modified by corona treatment (using a treatment device manufactured by Kasuga Denki) at a processing speed of 8 m/min, with one round trip, and with a power of 300 W.

Example 7
The retroreflective resin molding of Example 7 was produced in the same manner as in Example 1, except that the surface was modified by flame treatment at a treatment speed of 24 m/min, one treatment, and a treatment height of 130 mm, and a polyolefin-based primer paint "Arrowbase SD-1205J2" (manufactured by Unitika Ltd.) was used as the primer.

Example 8
A retroreflective resin molding according to Example 8 was produced in the same manner as in Example 1, except that the surface was modified by flame treatment at a treatment speed of 24 m/min, four treatments, and a treatment height of 130 mm.

Example 9
A retroreflective resin molding according to Example 9 was produced in the same manner as in Example 1, except that the surface was modified by flame treatment at a treatment speed of 24 m/min, 10 treatments, and a treatment height of 130 mm.

Example 10
The retroreflective resin molding of Example 10 was produced in the same manner as in Example 1, except that surface modification was performed by flame treatment at a treatment speed of 24 m/min, 20 treatments, and a treatment height of 80 mm to modify the surface of the resin molding.

Example 11
The retroreflective resin molding of Example 11 was produced in the same manner as in Example 1, except that the surface was modified by flame treatment at a treatment speed of 80 m/min, one treatment, and a treatment height of 80 mm, and a polyolefin-based primer paint "Arrowbase SD-1205J2" (manufactured by Unitika Ltd.) was used as the primer.

Example 12
The retroreflective resin molding of Example 12 was produced in the same manner as Example 1, except that the primer described in Example 1 was applied to a thickness of 4 μm, dried for 2 hours, and then the paint (A) described in Example 1 containing a reflective material and a film-forming resin was applied to a thickness of 30 μm (after drying) to form a primer coating film with a dry thickness of 4 μm and a retroreflective coating film with a dry thickness of 70 μm.

Example 13
A retroreflective resin molding according to Example 13 was produced in the same manner as in Example 3, except that an aluminum paste "SAP561PS" (manufactured by Toyo Aluminum Co., Ltd.) was used as the reflective material.

Example 14
A retroreflective resin molding according to Example 14 was produced in the same manner as in Example 3, except that aluminum paste "SB-10" (manufactured by Asahi Kasei Corporation) was used as the reflective material.

Example 15
A retroreflective resin molding according to Example 15 was produced in the same manner as in Example 3, except that an aluminum paste "PVH5060" (manufactured by Asahi Kasei Corporation) was used as the reflective material.

[ Reference Example 16]
A retroreflective resin molding of Reference Example 16 was produced in the same manner as in Example 1, except that no surface modification was performed and a styrene-butadiene primer paint "GP Clear" (manufactured by Konishi Co., Ltd.) was applied to a thickness of 10 μm as a primer.

[ Reference Example 17]
A retroreflective resin molding of Reference Example 17 was produced in the same manner as in Example 4, except that no surface modification was performed and a styrene-butadiene primer paint "GP Clear" (manufactured by Konishi Co., Ltd.) was applied to a thickness of 9 μm as a primer.

[ Reference Example 18]
A retroreflective resin molding of Reference Example 18 was produced in the same manner as in Example 1, except that no surface modification was performed and a styrene-butadiene primer paint "GP Clear" (manufactured by Konishi Co., Ltd.) was applied to a thickness of 5 μm as a primer.

Comparative Example 1
A retroreflective resin molding of Comparative Example 1 was produced by attaching a retroreflective sticker "3M ^TM Flexible Prismatic Reflective Sheet 3314FP" (manufactured by 3M) to the surface of a high-density polyethylene resin molding body measuring 40 mm wide x 90 mm long x 16 mm high.

Comparative Example 2
A retroreflective resin molding according to Comparative Example 2 was produced in the same manner as in Example 1, except that the surface of the resin molding body described in Example 1 was not subjected to surface modification.

Comparative Example 3
A retroreflective resin molding according to Comparative Example 3 was produced by polishing the surface of the resin molding body described in Example 1 with a #400 nonwoven abrasive without performing surface modification, and then applying a coating similar to that of Example 1 to the surface obtained.

Comparative Example 4
A retroreflective resin molding according to Comparative Example 4 was produced in the same manner as in Example 1, except that the surface of the resin molding body described in Example 1 was not subjected to surface modification or primer coating.

[Performance evaluation test]
(1) Measurement of Retroreflective Luminance For the retroreflective resin moldings of the Examples and Comparative Examples, the reflective luminance coefficient (cd/Lux·m ² ) was measured at an observation angle of 0.2° using a retroreflective performance measuring instrument "NS-1" manufactured by Suga Test Instruments Co., Ltd.

(2) Moisture Resistance Adhesion Test The retroreflective resin moldings of the Examples and Comparative Examples were subjected to a 500-hour moisture resistance test using the continuous dew condensation method in accordance with "JIS-K-5600-7-2," and after leaving them for 2 hours, they were evaluated by a cross-cut adhesion test in accordance with "JIS-K-5600-5-6."
Specifically, four 5 mm squares were made twice on the coating film with a cutter knife, cellophane adhesive tape was completely attached on the squares, one end of the tape was lifted and peeled upward, and the appearance was examined. The evaluation was based on the classification table, with Class 0 being ⊚, Class 1-2 being ◯, Class 3 being △, and Class 4-5 being ×.

(3) Water-Resistant Adhesion Test The retroreflective resin moldings of the Examples and Comparative Examples were evaluated by immersing the samples in ion-exchanged water for 240 hours (immersion temperature: 23° C.), leaving them for 2 hours, and then conducting the above-mentioned cross-cut adhesion test in accordance with “JIS-K-5600-6-1.”

(4) Sunshine Accelerated Weathering Test The retroreflective resin moldings of the Examples and Comparative Examples were evaluated for gloss retention after 500 hours of testing using a sunshine carbon arc lamp weathering tester conforming to "JIS-D-0205-5-4."
The gloss retention rate was evaluated using a gloss meter "PG-IIM" manufactured by Nippon Denshoku Industries Co., Ltd., by measuring the gloss before and after the test at 60°, and the gloss retention rate was calculated using the formula (gloss after test/gloss before test×100=gloss retention rate (%)).
The evaluation was as follows: a gloss residual rate of 90% or more was rated as ◎; a gloss residual rate of 70% or more but less than 90% was rated as ○; a gloss residual rate of 50% or more but less than 70% was rated as △; and a gloss residual rate of less than 50% was rated as ×.

(5) Acid Resistance For the retroreflective resin moldings of the Examples and Comparative Examples, the samples were immersed in a 5% citric acid aqueous solution for 120 hours (immersion temperature: 23° C.) in accordance with “JIS-K-5600-6-1”, and then the surface was washed with ion-exchanged water and dried for 2 hours, after which the color difference was measured.
The color difference before and after the test was measured according to the L*a*b* color system using a colorimeter "CR-400" manufactured by Konica Minolta, Inc. Then, the difference in L*, the difference in a*, and the difference in b* before and after the test were each squared and added, and the square root value was determined as ΔE.
The evaluation was as follows: ΔE less than 1.0 was rated as excellent; ΔE from 1.0 to less than 2.0 was rated as excellent; ΔE from 2.0 to less than 4.0 was rated as excellent; and ΔE of 4.0 or more was rated as poor.

Details of the retroreflective resin moldings for each example and comparative example are summarized in Table 1.

In Table 1, the meanings of the symbols for pretreatment method, primer layer (undercoat layer), and reflective material are as shown in Tables 2 to 4 below.

The performance evaluation test results are shown in Table 5.

As shown in Table 5, in terms of moisture resistance and water-resistant adhesion, the retroreflective resin moldings of Comparative Examples 1 to 4, which were not surface-modified and to which no primer layer containing a styrene-conjugated diene block copolymer was applied, were rated x for adhesion. In contrast, the retroreflective resin moldings of Examples 1 to 15, which were surface-modified, and Examples 16 to 18, which were not surface-modified but used a primer layer containing a styrene-conjugated diene block copolymer as an undercoat layer, all achieved moisture resistance and water-resistant adhesion results of 0 to ⊚.
Looking specifically at each Example, the retroreflective resin moldings of Examples 10 and 11 were slightly inferior in moisture resistance and water-resistant adhesion to the retroreflective resin moldings of the other Examples which were subjected to flame treatment.
That is, first, in the pretreatment method a6 of Example 10, the wettability index was 34 and the moisture-resistant adhesion was rated as ◯. This is thought to be because the resin surface was melted due to the large number of flame treatments, which caused fine irregularities on the surface and generated fine gaps between the coating film and the resin surface.
In addition, in the pretreatment method a7 of Example 11, the wettability index was 31, and the moisture resistance and water-resistant adhesion were rated as "good." This is believed to be because the treatment speed was fast and the surface modification treatment was relatively weak.
On the other hand, in Example 2 having no primer layer, Example 12 in which the thickness of the primer layer and the retroreflective layer was reduced, Examples 3, 13 to 15 in which a reflective material different from that in Example 1 was used, and Examples 4 and 5 in which the reflective layer was colored orange and a reflective material different from that in Example 1 was used, the moisture resistance and water-resistant adhesion were all rated as excellent. From these results, it was found that in the present invention, when performing surface modification treatment, a primer layer (undercoat layer) is not essential, and various reflective materials can be used and the reflective layer can be colored.
Furthermore, in Examples 16 to 18, no surface modification treatment was performed, but the moisture resistance and water-resistant adhesion were rated as ◯ or ⊚. These results demonstrate that in the present invention, when a primer layer containing a styrene-conjugated diene block copolymer is used as an undercoat layer, the surface modification treatment is not essential.

10 Resin molding (retroreflective resin molding)
11 Resin molded body 12 Undercoat layer 13 Retroreflective layer 131 Glass beads 132 Reflective material 133, 133a, 133b Resin layer 1A Guard pipe 2A Support 3A Beam 10A Cap (retroreflective resin molded product)
1B Guardrail 2B Support 3B Beam 10B Rolled sleeve (retroreflective resin molding)

Claims (8)

A method for producing a retroreflective resin molded product comprising a polyolefin resin molded body and a retroreflective layer coated on the resin molded body,
The retroreflective layer is a resin layer containing at least glass beads, a reflective material, and a resin component,
the reflective material is a reflective film that covers a part of the surface of the glass beads;
The surface of the resin molded body is subjected to a surface modification treatment for improving wettability,
Using a torch burner, flame treatment was performed at a flame temperature of 1400 to 1800°C, a treatment speed of 24 m/min to 80 m/min, 1 to 20 treatments, and a treatment height of 80 mm to 130 mm.
A method for producing a retroreflective resin molding, characterized in that a paint containing the resin component but not containing a reflective material is sprayed directly onto the surface of the resin molding body, or onto a primer layer provided on the surface of the resin molding body, to form a single layer of paint film, and while this paint film is still uncured, the glass beads having part of their surfaces covered with a reflective film are sprayed onto the single layer of paint film formed by curing the single layer of paint film, thereby forming the retroreflective layer in which the glass beads form multiple layers and part of the glass beads are exposed . The manufacturing method described in claim 1, in which the flame treatment is performed at a treatment speed of 24 m/min to 60 m/min, 1 to 10 treatments, and a treatment height of 130 mm. The method for producing a retroreflective resin molding according to claim 1 or 2, in which the wetting index of the resin molding body after the flame treatment is 31 mN/m or more. The method for producing a retroreflective resin molding according to any one of claims 1 to 3, further comprising applying a primer layer between the resin molding body and the retroreflective layer. The method for producing a retroreflective resin molding according to claim 4, in which a primer layer containing a styrene-conjugated diene block copolymer is applied as the undercoat layer. The method for producing a retroreflective resin molding according to any one of claims 1 to 5, wherein the resin molding body is made of high-density polyethylene. The method for producing a retroreflective resin molding according to any one of claims 1 to 6, wherein the resin component constituting the retroreflective layer is a urethane resin. The method for producing a retroreflective resin molding according to any one of claims 1 to 7, wherein the retroreflective resin molding is a road material.

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