JP6381793B2 - Method for producing glass beads coated with montmorillonite and / or modified montmorillonite - Google Patents

Description

  The present invention relates to the coating of glass beads used to enhance night visibility in aqueous road markings with natural and / or modified montmorillonite. As a result of the coating, it is possible to obtain inexpensive glass beads that provide high retroreflectivity and abrasion resistance to the road marking paint as compared with commercially available glass beads.

  The glass beads are immediately spread on the applied paint. Large diameter glass beads are found on the surface, while small diameter glass beads are embedded in the paint. In order to obtain a road surface paint having a high retroreflectance, it is important to use glass beads (Patent Documents 1, 2, and 3). If the glass beads do not flow freely, the glass beads may not be dispersed in the paint. Because there are hydrophilic —OH groups on the glass surface, small glass beads may aggregate due to moisture. Aggregation can be prevented by modifying the glass bead surface with a hydrophobic coating. However, the adhesion between the coating on the glass surface and the paint needs to be strong. Otherwise, the glass beads can be easily removed by friction under traffic. Therefore, when the glass beads are coated with a hydrophobic material, the retroreflectance is reduced. A binder may be used to solve this problem. However, the binder increases the coating on the glass surface and the retroreflectivity is still reduced. Furthermore, since the binder is hydrophilic, it causes aggregation (Patent Document 2).

  At the beginning of application of the paint and glass beads, the large glass beads are easily visible on the paint surface, so the retroreflectivity is high. As the vehicle travels over the paint, the paint and glass beads begin to wear, which reduces the reflectivity. When the glass beads are removed from the paint surface, the gaps are clogged with dust. As a result, the paint begins to turn brown and visibility during both daytime and nighttime decreases.

  When the surface of the glass beads is not modified, the adhesion between the glass and the paint is weakened, and the glass beads are easily removed from the paint surface. Therefore, there are many studies in the literature for coating glass bead surfaces with polymeric materials.

  Patent Document 4 discloses the use of an epoxy resin and a pigment for coating glass beads. In Patent Document 5, glass beads are coated with fluorocarbon. Unfortunately, all of these applications are expensive and have low wear resistance. That is, as the vehicle travels on the road marking paint, more glass beads are removed from the surface (Patent Document 5).

  Patent Document 1 discloses that a polyurethane-based polymer material is obtained by using a polyester polyol and an aliphatic polyisocyanate, and further, glass beads are coated with this material. However, this method is also expensive, and the result of the performance test is not sufficient.

  Since silane compounds have a hydrophobic structure, there are many examples in the literature. Silane-coated glass beads are also common in industrial applications (Patent Documents 6, 7, 8, 9). Coated glass beads containing silane compounds (Patent Documents 6, 7, 8, and 9) are practical and inexpensive compared to other coating materials, but if natural materials are used as shown in this specification, far more Inexpensive and environmentally friendly.

  In Patent Document 3, a commercially available silane compound is used for coating glass beads.

  In Patent Documents 10 and 11, glass beads are mixed with a silane compound together with benzoyl peroxide. However, this method is somewhat complicated and expensive due to the need to pay close attention. Benzoyl peroxide is a volatile and flammable substance. Therefore, the effectiveness of the coating is reduced and there is a risk of ignition.

  Unlike other documents, Patent Document 10 uses polyvinyl acetate as a coating material. After spreading the coated glass beads on the road surface paint, night visibility has been measured for one year. According to this result, the adhesion strength of the polyvinyl acetate coated glass beads to the paint is higher than that of the uncoated glass beads. However, no comparison has been made between polyvinyl acetate and silane-coated glass beads. Polyvinyl acetate can be more expensive than silane compounds.

  The object of the present invention is to be competitive with commercially available glass beads, inorganic, inexpensive, easy to apply, environmentally friendly, particularly highly compatible with water-based road surface paint, high wear resistance, Moreover, it is to obtain coated glass beads having high retroreflectivity.

US Patent Application Publication No. 2005/0100709 International Publication No. 2001/042349 US Patent Application Publication No. 2005/0158461 US Pat. No. 5,253,146 U.S. Pat. No. 3,222,204 U.S. Pat. No. 4,756,931 US Pat. No. 5,128,203 U.S. Pat. No. 4,305,863 US Pat. No. 4,713,295 International Publication No. 01/42349 British Patent Application No. 22008078

  Road lines are easily visible on the road during the day, but they can also be seen in the dark at night thanks to the glass beads placed on the paint surface. Due to the spherical shape of the glass sphere and the glass structure, the glass beads reflect the light from the headlight in the direction of the vehicle driver, so that the road marking can be seen at night. In this way, the driver can travel more carefully and appropriately according to traffic rules. Glass beads reflect light in the direction of the headlights even in rainy weather, so it is important to ensure nighttime traffic safety. The situation where the incident light is reflected back in the direction of the light source is called “retroreflection” (backward reflection). The chemical composition of the glass spheres, the glass bead / paint ratio, and the percentage of the embedded volume of the glass beads on the paint surface are adjusted to maximize retroreflectivity.

  When the vehicle travels on the road marking paint, large-sized glass beads are removed from the surface due to the impact caused by the friction of the vehicle. As the paint wears over time, small glass beads begin to appear on the paint surface. As a result, night visibility is ultimately reduced. In order to secure night visibility for a longer time, a strong affinity is required between the glass bead surface and the paint. In order to ensure such affinity, glass spheres are coated using various materials that can provide high compatibility between glass beads and paint (Patent Documents 1, 2, and 3). . According to the literature, organic materials having a polymer structure are generally preferred for securing the affinity. In order to ensure that some of the glass beads are located on the paint surface and some remain in the paint without settling at the end of the bond between the glass beads and the paint, the material has the chemical structure of the paint binder. It is necessary to have a structure suitable for Therefore, it is necessary to select the chemical structure of the coating material to adhere to the binder contained in the paint. Such an organic coating material has a yellowing problem caused by sunlight, and some organic components diffuse into the paint as the temperature rises.

  The glass beads in the present invention are coated with inorganic nano-sized natural montmorillonite sodium (Na-montmorillonite) and montmorillonite modified with a quaternary ammonium salt. The performance of these glass beads was then compared to glass beads coated with silane-based polymer materials, which are uncoated glass beads or the most commonly used glass beads in road marking paints. According to the performance test, the paint was provided with high abrasion resistance, and thus a more durable paint was obtained, and a continuous high reflectivity was also obtained. Furthermore, the feature that the coating is an inorganic natural product prevents diffusion problems that may occur over time and reduces coating costs. Since the use of such natural materials in glass bead coating is not disclosed in the conventional literature, the present invention is highly important in that it adds value to natural resources. The present invention differs from the other patents by all of the above features, including improved retroreflectivity and high wear resistance.

Abbreviations used in the drawings are defined as follows.
MMT-1: Montmorillonite modified with quaternary ammonium salt at a concentration corresponding to 1 cation exchange capacity (CEC) of Na-montmorillonite MMT-2: Modified with quaternary ammonium salt at a concentration corresponding to 2 CEC of Na-montmorillonite Montmorillonite MMT-3: purified sodium montmorillonite CK-1: uncoated glass beads CK-2: silane coated glass beads CK-3: MMT-1 coated glass beads CK-4: MMT-2 coated glass beads CK-5 : MMT-3 coated glass beads

It is a figure which shows an FT-IR spectrum. An OH stretching peak of the silicate layer is observed at 3700 to 3400 cm ⁻¹ . An octahedral layer peak is clearly seen at 917.51 cm ⁻¹ . These peaks are montmorillonite labels. IR spectra of MMT-1 and MMT-2 is consistent, indicating a peak of 2950～2850Cm ^-1 and 1470～1370Cm ^-1 can not be seen in MMT-3. The peak observed at 2950-2850 cm ⁻¹ represents a methylene structure, and the peak at 1470-1370 cm ⁻¹ is assigned to H—C—H stretching. These peaks are labels of quaternary ammonium salts within the montmorillonite structure. It is a figure which shows a TGA curve. The decrease observed between 0-150 ° C is due to water branching between the clay mineral layers. At 650 to 850 ° C., OH ions and impurities such as MgCO ₃ and CaCO ₃ are removed from the structure. The decrease observed at 200-400 ° C. for MMT-1 and MMT-2 indicates that the ammonium salt adheres to the montmorillonite and the carbon is burned. It is a figure which shows a SEM (scanning electron microscope) image. In the figure, (a) CK-1, (b) CK-3, (c) CK-4, and (d) CK-5 are glass beads coated with MMT, respectively, and the ratio of quaternary ammonium salt Therefore, the SEM of glass beads coated with MMT2 shows high brightness. It is a figure which shows the microscope image of a glass bead. It is a figure which shows the image of the glass bead on the road marking paint.

<Coating research>
In the first step of coating glass beads with montmorillonite, a montmorillonite (MMT) / water suspension is prepared. An MMT suspension having an MMT content of 0.5-2% is prepared by dispersing montmorillonite purified so that the cation exchange capacity (CEC) at 30-80 ° C. is 105 meq / 100 g. The glass beads are then added to the MMT suspension and mixed such that the glass bead / MMT suspension ratio is a different ratio ranging from 1: 1 to 1: 4. Through this mixing process, the film thickness becomes 0.1 to 0.5 μm. The resulting mixture is transferred to a pan where the glass beads are spread. The mixture is then dried at 80-100 ° C.
In order to separate the agglomerated glass beads, the glass beads should be polished very gently immediately after drying. It is necessary to prevent the glass beads from being broken during this process.

  In the modified montmorillonite coating process, the quaternary ammonium salt is added to the above MMT suspension with MEC CECs of 0.5, 1, and 2. This suspension is mixed at 30 to 80 ° C. for 0.5 to 2 hours, and then the coating process is performed as described above.

  The coating glass sphere is spread by 33% by weight on the road marking paint adsorbed on the briquette. The glass beads are spread on an aqueous road marking paint containing an aqueous binder. The wet film thickness of the paint applied to the briquette is 400 to 600 μm. The glass beads have different gradations, and the particle diameter is 150 to 700 μm. After the paint has dried, a 6 bar wheel is reciprocated over the paint to simulate the road. One round trip was defined as one cycle, and this process was continued for a maximum of 10,000 cycles.

<Characterization>
FT-IR Infrared Spectroscopy In order to identify natural montmorillonite and modified montmorillonite, FTIR of MMT used for coating glass beads was performed with a Spectrum One FTIR Spectrometer manufactured by Perkin Elmer (FIG. 1).

・ Thermogravimetric analysis (TGA)
In order to identify natural montmorillonite and modified montmorillonite, thermogravimetric analysis of MMT used for coating glass beads was performed on Pyris 1 from Perkin Elmer (FIG. 2). The sample was heated to 950 ° C.

<Scanning electron microscope (SEM)>
The morphology of the coated glass beads was observed with a JEOL 6335F electron microscope (FIG. 3).

  A microscopic image of the glass beads is shown in FIG.

<Glass beads performance test>
A wear test under the wheel was performed to determine glass bead performance by measuring the night visibility of the paint worn to a certain level. At the end of this test simulating roads, night visibility values were measured. The glass beads used with the aqueous paint are listed below.
CK-1 ... uncoated glass beads CK-2 ... silane coated glass beads (commercially available)
CK-3 ... 2: 1 modified montmorillonite coated glass beads CK-4 ... 1: 1 modified montmorillonite coated glass beads CK-5 ... 0.5: 1 Glass beads CK-6 coated with modified montmorillonite ... Glass beads coated with Na-montmorillonite

  Similar to road use, road marking paint was applied to briquette with a wet film thickness of 600 μm. An image of glass beads on the road marking paint is shown in FIG. A 6 bar wheel was reciprocated over the paint. One round trip was defined as one cycle. The night visibility of the glass bead-blended paint was measured for 10,000 cycles of wheel reciprocation (Table 1). According to these results, at the end of 1,000 cycles, the nighttime visibility of the paint containing commercially available glass beads CK-2 is the highest. However, at 3,000 cycles, the night visibility of the paint blended with natural montmorillonite coated glass beads CK-5 is equal to that of the CK-2 blend paint, and thereafter the CK-5 blend paint is visible at night until 10,000 cycles. The property exceeds that of CK-2 paint. From this situation, it can be seen that the adhesive strength of CK-5 is stronger than that of commercially available CK-2. As the wheel reciprocates over the paint, the paint wears and new glass beads at the bottom are exposed. As a result of abrasion, glass beads other than CK-5 were removed from the paint surface. With CK-5 paint, night visibility increased to 8,000 cycles. Although night visibility decreased after 8,000 cycles, the night visibility of the CK-5 blended paint was 1.5 times that of the CK-2 blend paint. The CK-3 blended paint and the CK-4 blended paint had lower night visibility than CK-2, but showed higher night visibility than the uncoated glass beads CK-1.

  The manufactured or purchased glass beads are mixed at ambient temperature in a bentonite suspension. The coated glass beads are dried after mixing. In order to prevent the glass beads from sticking to each other, the drying process can be performed by a fluidized bed method. However, when glass beads can be separated from each other without breaking, constant rate drying may be performed. This form of glass beads can be used immediately for road marking paints.

Claims (11)

A method for producing glass beads coated with montmorillonite and / or modified montmorillonite using glass beads having a particle size of 150 to 700 μm, which is used by spreading on a road marking paint, Coating the surface with the montmorillonite and / or the modified montmorillonite,
Preparing a montmorillonite (MMT) suspension;
Dispersing the MMT in water at 30-80 ° C. with the MMT / suspension ratio of 0.5-2% to obtain a homogeneous suspension;
When coating with modified montmorillonite, adding a quaternary ammonium salt to the suspension for modification; and
Thereafter, the glass beads are added to the MMT / water suspension and mixed such that the ratio of the glass beads to the MMT suspension is 1: 1 to 1: 4;
Finally, transferring the resulting mixture to a pan where the glass beads can be spread, and drying the glass beads at 80-100 ° C .;
A method comprising the steps of:   The method according to claim 1, wherein the montmorillonite and / or modified montmorillonite used for coating the glass beads is nano-sized.   The method according to claim 1, wherein the average particle size of montmorillonite and / or modified montmorillonite used for coating the glass beads is 50 to 500 nm.   The method according to claim 1, wherein a dipping method is used to coat the surface of the glass beads with montmorillonite and / or modified montmorillonite.   The method according to claim 1, wherein the surface of the glass beads is coated with montmorillonite, and the montmorillonite used is purified to have a cation exchange capacity of 105 meq / 100 g before use.   The method of claim 1, wherein the surface of the glass beads is coated with montmorillonite, and the glass beads are gently polished after a drying process to remove agglomeration of the glass beads.   The surface of the glass beads is coated with modified montmorillonite, and the addition amount of the quaternary ammonium salt used for modification to the suspension is half, equal and twice the cation exchange capacity of montmorillonite. The method of claim 1, wherein:   The method of claim 1, wherein the coated glass beads are used in various tones.   The glass beads are spread on the paint so that large beads are placed on the surface of the paint, small beads are placed on the bottom of the paint, and the percentage of glass beads is 33%. The method of claim 1, characterized in that:   The method of claim 1, wherein the binder used in the paint is aqueous. The method according to claim 1, wherein a film thickness of the montmorillonite and / or modified montmorillonite coated on the glass beads is 0.1 to 0.5 µm.