Patent Publication Number: US-2021163782-A1

Title: Sliding agent and article coated with coating film formed therefrom

Description:
RELATED APPLICATIONS 
     This application claims the priority of Japanese Patent Application No. 2018-116398 filed on Jun. 19. 2018, the disclosure of which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a sliding agent employed for forming a coating film having liquid droplet removing property (sliding property such as water-sliding property, oil-sliding property, etc.) and a coating film obtained by this sliding agent. 
     BACKGROUND OF THE INVENTION 
     It is very important to make water or oil on a solid surface slide down at a slight angle. Such solid surface can be prevented from not only becoming wet with water or oil, but also becoming dirty by adhering dusts in the air to the water or oil. 
     Moreover, in transparent glasses, transparency of the glasses is lost by adhesion of water droplets. For example, in window glasses of cars, visibility is deteriorated by the adhered water droplets. 
     Patent Literature 1 discloses a sliding agent applied to kitchen drains that forms a conventional coating film having a good sliding property. The kitchen drain applied with this sliding agent can make water or oil of food slide down, and can prevent sliminess due to propagation of bacteria caused when drains are left with dirt such as water or oil components adhered to the kitchen drain. 
     CITATION LIST 
     Patent Literature 
     PATENT LITERATURE 1. Japanese Patent No. 5486157 B 
     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, transparent coating films cannot be formed with the sliding agent of Patent Literature 1. Although a high transparency is not necessary for kitchen drains, when the substrate to which the sliding agent is applied is a glass, its value will deteriorate if the coating film is not transparent, and it is not suitable for window glasses of cars and the like. 
     When use for a long term is considered, durability of the coating film becomes necessary. However, durability of the coating film formed by the sliding agent of Patent Literature 1 is low, and it is not suitable for applications that require a long-term durability. 
     The present invention has been accomplished in view of the above-mentioned problems, and an object thereof is to provide a sliding agent capable of improving transparency of a coating film and improving durability that can withstand a long-term use, while excellent sliding property is maintained. Moreover, the object of the present invention is to provide an article having a coating film formed by the sliding agent. 
     Means To Solve The Problem 
     The sliding agent of the present invention comprises: a graft polymer obtained by copolymerizing an organic solvent-soluble fluoropolymer having radical polymerizability, a one-terminal radical-polymerizable polysiloxane, and a non-reactive radical-polymerizable methacrylate-based monomer; a one-terminal reactive silicone oil; a hardener; and an organic solvent. 
     The one-terminal reactive silicone oil is preferably 1 to 10 parts by mass relative to 100 parts by mass of the graft polymer. Moreover, among all organic solvents comprised in the sliding agent, the proportion of a non-polar solvent having a relative permittivity of 3 or less is preferably 10% by volume or greater. 
     The article according to the present invention is coated with a coating film formed by the sliding agent on its surface. The thickness of the coating film is preferably 3 to 20 μm. Moreover, the difference between a haze value of a substrate alone before application of the sliding agent and a haze value of the substrate after application of the sliding agent is preferably 0.1 to 1%. Furthermore, a ultra micro indentation hardness is preferably 0.15 GPa or less when a maximum indentation load on the coating film is 1 mN. 
     When sliding angles of 10 μL water are measured before and after an abrasion treatment for the surface of the coating film, the difference between the sliding angles before and after the abrasion treatment is preferably 30 degrees or less. The abrasion treatment is a treatment of reciprocating a non-woven fabric along the surface of the coating film for 1000 times under a condition of a load: 250 g/cm 2 , a moving distance: 20 mm, and a moving velocity: 600 mm/min, 
     As the article according to the present invention, a substrate coated with the coating film is preferably a transparent glass, and examples thereof include solar panels, window glasses, traffic mirrors, glasses for agricultural houses, glasses for outdoor signboards and glass bottles. 
     Effect Of The Invention 
     By using the sliding agent of the present invention, a coating film that is transparent and has a durability capable of a long-term use while excellent sliding property is maintained can be formed. 
     Best Mode for Carrying out the Invention 
     Hereinbelow, embodiments are described. The sliding agent of the present embodiment includes: (1) a graft polymer that is a base resin; (2) a silicone oil as an additive; (3) a hardener for crosslinking the base resin; and (4) an organic solvent. 
     (1) As the graft polymer, a graft polymer obtained by copolymerizing (a) an organic solvent-soluble fluoropolymer having radical polymerizability, (b) a one-terminal radical-polymerizable polysiloxane, and (c) a non-reactive radical-polymerizable methacrylate-based monomer is used. 
     (2) As the silicone oil to be added, a silicone oil of which either of its terminals is a reactive organic functional group is used. The amount of the silicone oil added is 1 to 10 parts by mass relative to 100 parts by mass of the graft polymer obtained by copolymerizing the organic solvent-soluble fluoropolymer having radical polymerizability, the one-terminal radical-polymerizable polysiloxane, and the non-reactive radical-polymerizable methacrylate-based monomer. If it is less than 1 parts by mass, the sliding property is insufficient. Hit is greater than 10 parts by mass, the sliding property does not improve, and thus it is a waste of cost. 
     (3) As the hardener for crosslinking the base resin, a hardener that softens the coating film after hardening process is used. Unlike metals, resins are difficult to be worn away when they are softer; that is, the softer the resin is, the higher the abrasion resistance is. If such hardener is used, a survival rate of the coating film increases, and thus the product coated with the coating film can be used for a long term. It is effective in increasing durability as the coating film. As the hardness of the hardened coating film, the ultra micro indentation hardness is preferably 0.15 GPa or less, and more preferably 0.13 GPa or less when the maximum indentation load of the coating film is 1 mN. 
     With respect to the abrasion resistance, one that has the difference between the sliding angles of 10 μL water before and after an abrasion treatment is 30 degrees or less is suitable; the abrasion treatment is a treatment of reciprocating a non-woven fabric along the surface of the coating film for 1000 times under a condition of a load: 250 g/cm, a moving distance: 20 mm, and a moving velocity: 600 mm/min. If the difference between the sliding angles of 10 μL water before and after the above-described abrasion treatment of 1000 times exceed 30 degrees, the sliding property is significantly deteriorated over time, and thus cannot withstand a long-term use. 
     (4) As the solvent to dissolve the above-described resins, an organic solvent of low polarity is used. Dissolving a solute sufficiently is an important object of a solvent; however, a solvent suitable for a solute needs to be used in order to achieve sufficient dissolving. In the present embodiment, the proportion of the non-polar solvent having a relative permittivity of 3 or less among all organic solvents comprised in the sliding agent is 10% by volume or greater, so that its object can be achieved and the coating film can be transparentized. With respect to the transparency of the coating film, the difference between a haze value of the substrate alone before application of the sliding agent and a haze value after application of the sliding agent becomes 0.1 to 1.0% by using the above-identified solvent, and thus product development to applications that require transparency becomes possible. 
     The sliding agent of the present embodiment is applied to the substrate, and then dried by heating. A thickness of a coating film produced thereby is 3 to 20 μm. If the thickness of the coating film is less than 3 the coating film will be worn away over a long-term use because of its thinness when the coating film is soft. Whereas, if it is 20 μm. or greater, the film thickness will be excessive for more than the number of years that is actually used, and thus it will be a waste of cost. 
     Objects to which the coating film of the present embodiment is formed are preferably glass substrates that can take advantage of the transparency of the coating film. Examples of specific applications include window glasses of cars, buildings and houses, solar panels, traffic mirrors, glasses for agricultural houses, glasses for outdoor signboards, glass bottles and the like. 
    
    
     EXAMPLE 1 
     Hereinbelow, the present invention will be described based on examples; however, the present invention is not limited to the contents of these examples. 
     Table 1 is a formulation table of the sliding agent used for each specimen. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 One-terminal 
                   
                   
                 Film 
               
               
                   
                   
                 reactive 
                   
                   
                 thickness 
               
               
                   
                 Base resin 
                 silicone oil 
                 Hardener 
                 Organic solvent 
                 (μm) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Example 1 
                 100 pts. mass 
                 7 pts. mass 
                 Hexamethylene 
                 Aromatic 
                 8.7 
               
               
                   
                   
                   
                 diisocyanate 
                 hydrocarbon solvent 
               
               
                   
                   
                   
                 50 pts. mass 
                 38 pts. mass 
               
               
                 Comparative 
                 100 pts. mass 
                 None 
                 Hexamethylene 
                 Aromatic 
                 8.3 
               
               
                 example 1 
                   
                   
                 diisocyanate 
                 hydrocarbon solvent 
               
               
                   
                   
                   
                 50 pts. mass 
                 38 pts. mass 
               
               
                 Comparative 
                 100 pts. mass 
                 7 pts. mass 
                 Hexamethylene 
                 Butyl acetate 
                 10.1 
               
               
                 example 2 
                   
                   
                 diisocyanate 
                 100 pts. mass 
               
               
                   
                   
                   
                 32 pts. mass 
               
               
                 Comparative 
                 100 pts. mass 
                 7 pts. mass 
                 Hexamethylene 
                 Aromatic 
                 2.6 
               
               
                 example 3 
                   
                   
                 diisocyanate 
                 hydrocarbon solvent 
               
               
                   
                   
                   
                 50 pts. mass 
                 38 pts. mass 
               
               
                 Comparative 
                 100 pts. mass 
                 7 pts. Mass 
                 Melamine resin 
                 Butyl acetate 
                 8.0 
               
               
                 example 4 
                   
                   
                 38 pts. Mass 
                 100 pts. mass 
               
               
                   
               
            
           
         
       
     
     Example 1 
     In Example 1, the graft polymer obtained by copolymerizing the organic-solvent soluble fluorocarbon polymer having radical polymerizability, the one-terminal radical-polymerizable polysiloxane, and the non-reactive radical-polymerizable methacrylate-based monomer was used as the base resin, the one-terminal reactive silicone oil was used as the silicone oil, and hexamethylene diisocyanate was used as the hardener. 
     Moreover, other than the organic solvents included in the base resin and the hardener, an aromatic hydrocarbon solvent (relative permittivity: 1.8; boiling point: 150° C. or higher) was used as the organic solvent, and the sliding agent comprising 100 parts by mass of the base resin, 7 parts by mass of the silicone oil, 50 parts by mass of the hardener, and 38 parts by mass of the organic solvent was produced. 
     This sliding agent was applied to a stainless substrate by a wire bar No. 18 and subjected to a dry heating treatment at 200° C. for one hour to produce the coating film. 
     The organic solvents included in the sliding agent of Example 1 are shown in Table 2. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Relative 
                 Parts 
                 Specific 
                   
                 Mixed 
               
               
                 Organic solvent 
                 permittivity 
                 by mass 
                 gravity 
                 Volume 
                 volume ratio 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Butyl acetate 
                 5.0 
                 41.3 
                 0.88 
                 46.8 
                 35.8 
               
               
                 n-Butanol 
                 17.5 
                 6.2 
                 0.81 
                 7.7 
                 5.9 
               
               
                 IPA 
                 19.9 
                 2.8 
                 0.79 
                 3.5 
                 2.7 
               
               
                 Methanol 
                 32.7 
                 1.6 
                 0.79 
                 2.0 
                 1.5 
               
               
                 Aromatic 
                 1.8 
                 38.0 
                 0.87 
                 43.7 
                 33.4 
               
               
                 hydrocarbon 
               
               
                 Xylene 
                 2.3 
                 23.2 
                 0.86 
                 27.0 
                 20.6 
               
               
                   
               
            
           
         
       
     
     Accordingly, among all organic solvents included in the sliding agent of Example 1, those that had a relative permittivity of 3 or less were aromatic hydrocarbon and xylene, and the total thereof was 54.0% in the mixed volume ratio. 
     Comparative Example 1 
     As Comparative example 1, sliding agents and coating films were produced similarly to Example 1 except that the silicone oil was not added. The organic solvents included in the sliding agent of Comparative example 1 are shown in Table 3. Since the silicone oil does not contain volatile components, the condition of the organic solvents is the same as in Example 1. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Relative 
                 Parts 
                 Specific 
                   
                 Mixed 
               
               
                 Organic solvent 
                 permittivity 
                 by mass 
                 gravity 
                 Volume 
                 volume ratio 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Butyl acetate 
                 5.0 
                 41.3 
                 0.88 
                 46.8 
                 35.8 
               
               
                 n-Butanol 
                 17.5 
                 6.2 
                 0.81 
                 7.7 
                 5.9 
               
               
                 IPA 
                 19.9 
                 2.8 
                 0.79 
                 3.5 
                 2.7 
               
               
                 Methanol 
                 32.7 
                 1.6 
                 0.79 
                 2.0 
                 1.5 
               
               
                 Aromatic 
                 1.8 
                 38.0 
                 0.87 
                 43.7 
                 33.4 
               
               
                 hydrocarbon 
               
               
                 Xylene 
                 2.3 
                 23.2 
                 0.86 
                 27.0 
                 20.6 
               
               
                   
               
            
           
         
       
     
     Accordingly, among all organic solvents included in the sliding agents of Comparative example 1, those that had the relative permittivity of 3 or less were aromatic hydrocarbon and xylene, and the total thereof was 54.0% in the mixed volume ratio. 
     Comparative Example 2 
     As Comparative example 2, sliding agents and coatings film were produced similarly to Example 1 except that 100 parts by mass of butyl acetate was used as the organic solvent. The organic solvents included in the sliding agent of Comparative example 2 are shown in Table 4. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                 Relative 
                 Parts 
                 Specific 
                   
                 Mixed 
               
               
                 Organic solvent 
                 permittivity 
                 by mass 
                 gravity 
                 Volume 
                 volume ratio 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Butyl acetate 
                 5.0 
                 149.3 
                 0.88 
                 169.4 
                 91.2 
               
               
                 IPA 
                 19.9 
                 2.8 
                 0.79 
                 3.5 
                 1.9 
               
               
                 Xylene 
                 2.3 
                 11.0 
                 0.86 
                 12.8 
                 6.9 
               
               
                   
               
            
           
         
       
     
     Accordingly, among all organic solvents included in the sliding agents of Comparative example 2, one that had the relative permittivity of 3 or less was xylene, and the value thereof was 6.9% in mixed volume ratio. 
     Comparative Example 3 
     As Comparative example 3, sliding agents and coating films were prepared similarly to Example 1 except that the wire bar No. 4 was used. The organic solvents included in the sliding agents of Comparative example 3 are the same as in Example 1. 
     Comparative Example 4 
     As Comparative example 4, sliding agents and coating films were prepared similarly to Example 1 except that 38 parts by mass of melamine resin was used as the hardener and 100 parts by mass of butyl acetate was used as the organic solvent. The organic solvents included in the sliding agents of Comparative example 4 are shown in Table 5. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                 Relative 
                 Parts 
                 Specific 
                   
                 Mixed 
               
               
                 Organic solvent 
                 permittivity 
                 by mass 
                 gravity 
                 Volume 
                 volume ratio 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Butyl acetate 
                 5.0 
                 141.3 
                 0.88 
                 160.3 
                 82.2 
               
               
                 n-Butanol 
                 17.5 
                 10.5 
                 0.81 
                 13.0 
                 6.6 
               
               
                 IPA 
                 19.9 
                 2.8 
                 0.79 
                 3.5 
                 1.8 
               
               
                 Methanol 
                 32.7 
                 1.5 
                 0.79 
                 1.9 
                 1.0 
               
               
                 Xylene 
                 2.3 
                 14.0 
                 0.86 
                 16.3 
                 8.3 
               
               
                   
               
            
           
         
       
     
     Accordingly, among all organic solvents comprised in the sliding agents of Comparative example 4, one that had the relative permittivity of 3 or less was xylene, and the value thereof was 8.3% in mixed volume ratio. 
     &lt;Evaluation Items&gt; 
     The coating films were respectively evaluated on the following items. 
     Sliding angle of water: 10 μL of pure water was put onto the coating film, and the substrate was tilted to measure the angle when pure water slid. When pure water did not slide at inclination of 90 degrees, it was determined as “x”. 
     Sliding angle of oil: 10 μL of an oleic acid was put onto the coating film, and the substrate was tilted to measure the angle when the oleic acid slid. When the oleic acid did not slide at inclination of 90 degrees, it was determined as “x”. 
     Transparency of the coating film: The coating film was visually Observed, and it was determined as “transparent” when the substrate could be observed, and “not transparent” when the substrate could not be observed. 
     Abrasion test: 1 cm×1 cm of a non-woven fabric was adhered to a planar indenter of a metal plate. Next, the non-woven fabric was superimposed onto the coating film of the specimen, and the surface of the coating film was abrased by the non-woven fabric with a load of 250 g. Specifically, the non-woven fabric of the metal plate was reciprocated along the surface of the coating film for 1000 times under the condition of a moving distance: 20 mm and a moving velocity: 600 mm/min. 
     Hardness: A ultra micro indentation hardness test was performed. Specifically, a hardness (in accordance with Z 2255) of when the indenter was indented to the coating film with the following condition was measured. 
     Maximum indentation load: 1 mN 
     Indenter: Berkovich indenter (diamond, an apex angle of)115°) 
     Loading time: 30 seconds 
     Retaining time: 10 seconds 
     The evaluation results of them are shown in Table 6. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 6 
               
             
            
               
                   
                   
               
               
                   
                 Sliding angle of water (degrees) 
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Difference between 
                 Sliding 
                 Hardness (Gpa) 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                 After 1000 
                 initial value and 
                 angle 
                   
                 After 1000 
                 Transparency 
               
               
                   
                   
                 times of 
                 after 1000 times 
                 of oil 
                   
                 times of 
                 Visual 
               
               
                   
                 Initial 
                 abrasion test 
                 of abrasion test 
                 Initial 
                 Initial 
                 abrasion test 
                 observation 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Example 1 
                 29.5 
                 48.8 
                 19.3 
                 13.5 
                 0.113 
                 0.117 
                 Transparent 
               
               
                 Comparative 
                 28.2 
                 64.8 
                 36.6 
                 — 
                 0.169 
                 0.163 
                 Transparent 
               
               
                 example 1 
               
               
                 Comparative 
                 21.2 
                 55.0 
                 33.8 
                 14.0 
                 0.158 
                 0.158 
                 Not 
               
               
                 example 2 
                   
                   
                   
                   
                   
                   
                 transparent 
               
               
                 Comparative 
                 31.3 
                 x 
                 — 
                 — 
                 — 
                 — 
                 Transparent 
               
               
                 example 3 
               
               
                 Comparative 
                 29.7 
                 — 
                 — 
                 12.2 
                 — 
                 — 
                 Not 
               
               
                 example 4 
                   
                   
                   
                   
                   
                   
                 transparent 
               
               
                   
               
            
           
         
       
     
     EXAMPLE 2 
     In Example 2, it was produced similarly to Example 1 other than a transparent glass was used as the substrate to which the sliding agent was applied. 
     Comparative Example 5 
     In Comparative example 5, the transparent glass substrate alone to which the sliding agent was not applied was used. 
     &lt;Evaluation Items&gt; 
     Each coating film was evaluated on the sliding angle of water and the sliding angle of oil similarly to Example 1. 
     Transparency of the coating film: A turbidity (haze value) of the coating film was measured with a haze meter “NDH 5000” (manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD.). 
     The evaluation results of them are shown in Table 7. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 7 
               
               
                   
                   
               
               
                   
                 Sliding angle of 
                 Sliding angle of 
                 Transparency 
               
               
                   
                 water (degrees) 
                 oil (degrees) 
                 haze (%) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Example 2 
                 30.1 
                 17.5 
                 0.33 
               
               
                 Comparative 
                 x 
                 x 
                 0.29 
               
               
                 example 5 
               
               
                   
               
            
           
         
       
     
     The evaluation results of Table 6 shows that, in Example 1, the coating film was transparent, the sliding angle of water was initially 29.5 degrees, the sliding angle after 1000 times of the abrasion test was 48.8 degrees, the difference between before and after the test was 19.3 degrees, and thus the abrasion property was good. 
     Since the silicone oil was not added in Comparative example 1, the sliding angle of water was initially 28.2 degrees and became 64.8 degrees after 1000 times of the abrasion test, the difference before and after the test was 36.6 degrees, and thus the abrasion property was poor. 
     Since butyl acetate was used as the organic solvent in Comparative example 2, the mixed volume ratio of the organic solvent having the relative permittivity of 3 or less among all organic solvents comprised in the sliding agent became low, 6.9%, and thus the coating film was not transparent. Hardness was harder than Example 1, the abrasion property was and it was easily worn away. 
     Since the film thickness was thin, 2.6 μm, in Comparative example 3, the sliding property of water deteriorated such that water did not fall down even at 90 degrees inclination after 1000 times of the abrasion test. 
     Since melamine resin was used as the hardener and butyl acetate was used as the organic solvent in Comparative example 4, the mixed volume ratio of the organic solvent having the relative permittivity of 3 or less among all organic solvents comprised in the sliding agent was low, 8.3%, and thus the coating film was not transparent. 
     As stated above, it was found that the coating film of Example 1 is transparent, has a good sliding angle, is soft, and can withstand a long-term use. 
     Moreover, the evaluation results of Table 7 shows that Example 2 of which the sliding agent was applied to a glass achieved the sliding angle of water of 30.1 degrees and the sliding angle of oil of 17.5 degrees. In Comparative example 5, which is the substrate alone not applied with the sliding agent, the results of the sliding angles of water and oil were both “x (did not fall down at 90 degrees inclination)”. Therefore, the result of Example 2 may be regarded as a better result. Moreover, the result of measuring transparency with the haze meter was 0.29% in the glass substrate alone, and 0.33% in those that the sliding agent was applied thereto. The difference between the haze value of the glass substrate alone before the sliding agent was applied and the haze value after the sliding agent was applied was 0.04%. From these results, it was found that the transparency almost the same as that of the glass substrate alone could be achieved. 
     INDUSTRIAL APPLICABILITY 
     The sliding agent of the present invention can be applied as materials for providing sliding property to articles in various industrial fields such as solar panels, window glasses, traffic mirrors, glasses for agricultural houses, glasses for outdoor signboards, and glass bottles, and can form a coating film that is transparent and has durability that can he used for a long term, while excellent sliding property is maintained.