Abstract:
A perfluoropolyether-modified aminosilane is provided having the necessary minimum fluorine content for the compound to exert water and oil repellency, anti-staining and parting properties. This aminosilane can be diluted with common solvents such as alcohols and used as a surface treating agent on various substrates.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2007-146910 filed in Japan on Jun. 1, 2007, the entire contents of which are hereby incorporated by reference. 
       TECHNICAL FIELD 
       [0002]    This invention relates to a novel perfluoropolyether-modified aminosilane which cures into a film having improved water and oil repellency, parting and anti-staining properties, a surface treating agent comprising the aminosilane, and an article with a cured coating of the aminosilane. 
       BACKGROUND OF THE INVENTION 
       [0003]    In general, perfluoropolyether-containing compounds have water and oil repellency, chemical resistance, lubricity, parting properties and anti-staining properties because of their very low surface energy. For the effective utilization of such properties, these compounds are widely used in the industry as water/oil repellent anti-staining agents for paper and textile, lubricants in magnetic recording media, oil repellants in precision machines, parting agents, cosmetics, and protective coatings. 
         [0004]    The perfluoropolyether-containing compounds must be diluted with solvents before they can be applied to substrates. Where their characteristic properties including water and oil repellency, chemical resistance, lubricity, parting and anti-staining properties are required at a higher level, the compounds must, as a matter of course, have a higher fluorine content per molecule. From the solubility aspect, the solvents with which they can be diluted are limited to fluorochemical solvents. However, the fluorochemical solvents are expensive and can adversely affect the environment when allowed to diffuse into air. 
         [0005]    The same properties indicate that the perfluoropolyether-containing compounds are non-tacky and non-adherent to other substrates. They are applicable to the substrate surface, but cannot form a coating firmly bonded to the substrate. 
         [0006]    Silane coupling agents are well known as the means for establishing a firm bond between a substrate surface such as glass or fabric and an organic compound. The silane coupling agent has an organic functional radical and a reactive silyl radical (typically alkoxysilyl radical) in a molecule. The alkoxysilyl radical undergoes self-condensation reaction with air-borne moisture, converting to a siloxane to form a coating. At the same time, the silane coupling agent forms chemical and physical bonds with the surface of glass or metal, resulting in a durable tough coating. By virtue of these advantages, the silane coupling agent is widely used as a coating agent to a variety of substrates. 
         [0007]    As one typical example taking advantage of the above features, JP-A 58-167597 discloses fluoroaminosilane compounds of the following formula (8): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein R 1  and R 2  are C 1-4  alkyl, Q is CH 2 CH 2 CH 2  or CH 2 CH 2 NHCH 2 CH 2 CH 2 , m is an integer of 1 to 4, and n is equal to 2 or 3. While these compounds can be diluted with common solvents, they are not regarded satisfactory in the ability to form a coat partially because the content (wt %) of hydrolyzable radicals per molecule is low and consequently, curing takes a time. 
         [0008]    To solve these problems, the inventors previously proposed in U.S. Pat. No. 6,200,684 or JP Pat. 3601580 a perfluoropolyether-modified aminosilane of the formula (3): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein X 1  and X 2  each are a hydrolyzable radical, R 1  and R 2  each are a lower alkyl radical, Q 1  and Q 2  each are a divalent organic radical, m is an integer of 6 to 50, n is equal to 2 or 3, x and y each are an integer of 1 to 3. This perfluoropolyether-modified aminosilane has good water and oil repellency, anti-staining properties, chemical resistance, lubricity, and parting properties. Because of two hydrolyzable silyl radicals per molecule, its reactivity is improved over the prior art aminosilanes, typically the fluoroaminosilane compounds of formula (8). It can be utilized as a surface treating agent to be coated to the surface of various substrates. This perfluoropolyether-modified aminosilane, however, has a high fluorine content per molecule, which gives rise to a problem that when the aminosilane is diluted with a solvent so that it may be applied to substrates, the solvent is limited to fluorochemical solvents from the solubility aspect. Thus this aminosilane is not regarded as fulfilling an ability of treatment and coating. 
         [0009]    Since many tall buildings are constructed in the recent decades, the demand for the technology for imparting “stain resistance” or “ease of stain removal” for keeping glazing maintenance-free is increasing. There is a desire to have a material meeting such a demand. 
       SUMMARY OF THE INVENTION 
       [0010]    An object of the invention is to provide a perfluoropolyether-modified aminosilane which can be diluted with common solvents and form a coating firmly bonded to substrate surface. Another object is to provide a surface treating agent comprising the aminosilane, having improved water and oil repellency and parting properties, and an article having a cured coating of the aminosilane. 
         [0011]    We have found that a novel perfluoropolyether-modified aminosilane of the following formula (1) has the necessary minimum fluorine content for the compound to exert water and oil repellency, anti-staining, chemical resistance, lubricity, and parting properties, and can be used as a surface treating agent to be coated to the surface of various substrates. This aminosilane can be diluted with common solvents such as alcohols, eliminating a need for fluorochemical solvents for dilution. A cured coating of the aminosilane is in firm bond to the substrate so that it may sustain the effects over a long period of time. 
         [0012]    In one aspect, the invention provides a perfluoropolyether-modified aminosilane having the following formula (1): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein X 1  and X 2  each are a hydrolyzable radical, R 1  and R 2  each are a lower alkyl or phenyl radical, Q 1  and Q 2  each are a divalent organic radical, m is an integer of 3 to 5, n is equal to 2 or 3, x and y each are an integer of 1 to 3. 
         [0013]    In another aspect, the invention provides a surface treating agent comprising the perfluoropolyether-modified aminosilane of formula (1) and/or a partial hydrolytic condensate thereof as an active ingredient, which is dissolved in a polar solvent. Also contemplated herein is an article having a cured coating comprising the perfluoropolyether-modified aminosilane and/or a partial hydrolytic condensate thereof. 
         [0014]    It is noted that the perfluoropolyether-modified aminosilane of formula (1) as the active ingredient of the surface treating agent contains an amide bond. The amide bond is known effective for efficient orientation of modifying fluoride radicals to the substrate surface. In this regard too, the surface treating agent of the invention is improved over the prior art agents. 
       Benefits of the Invention 
       [0015]    The perfluoropolyether-modified aminosilane of the invention can be diluted with common solvents and form a coating firmly bonded to substrate surface. The cured coating has improved water and oil repellency, parting, anti-staining, and weathering properties. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIGS. 1 and 2  show  1 H-NMR and IR spectra of the aminosilane synthesized in Synthesis Example 1, respectively. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The perfluoropolyether-modified aminosilane of the invention has the formula (1). 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    Herein X 1  and X 2  each are a hydrolyzable radical, R 1  and R 2  each are a lower alkyl radical or phenyl radical, Q 1  and Q 2  each are a divalent organic radical, m is an integer of 3 to 5, n is 2 or 3, x and y each are an integer of 1 to 3. 
         [0018]    More particularly, X 1  and X 2  stand for hydrolyzable radicals and may be the same or different. Illustrative examples include alkoxy radicals of 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy and butoxy, oxyalkoxy radicals of 2 to 4 carbon atoms such as methoxymethoxy and methoxyethoxy, acyloxy radicals of 2 to 4 carbon atoms such as acetoxy, alkenyloxy radicals of 2 to 4 carbon atoms such as isopropenoxy, and halogen radicals such as chloro, bromo and iodo. Of these, methoxy, ethoxy, isopropenoxy and chloro are preferred. 
         [0019]    R 1  and R 2  stand for lower alkyl radicals of 1 to 6 carbon atoms or phenyl radicals and may be the same or different. Exemplary radicals include methyl, ethyl and phenyl, with methyl being most preferred. 
         [0020]    Q 1  and Q 2  stand for divalent organic radicals and may be the same or different. Inter alia, alkylene radicals of 1 to 5 carbon atoms which may contain a nitrogen atom such as CH 2 CH 2 CH 2  and CH 2 CH 2 NHCH 2 CH 2 CH 2  are preferred. 
         [0021]    The letter m is an integer of 3 to 5. With m below the range, the characteristics of perfluoropolyether radicals are not fully exerted. With m beyond the range, the proportion of perfluoropolyether radicals in the overall molecule becomes large, which is undesirable for solubility in common solvents. A value of m equal to 4 or 5 is most desirable for a good balance between function development and solubility. The letter n is either 2 or 3. A plurality of n&#39;s may be identical or different. A mixture of n=2 and n=3 may be used. 
         [0022]    For the aminosilane, it is preferred that the perfluoropolyether moiety represented by F(C x F 2x O) m C y F 2y  have the following formula (2): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein m is as defined above. It is also preferred that the hydrolyzable radicals represented by X 1  and X 2  be alkoxy radicals. 
         [0023]    The perfluoropolyether-modified aminosilane of the invention may be prepared, for example, by effecting hydrosilylation reaction between a diallylamide derivative of a corresponding hexafluoropropylene oxide (HFPO) oligomer and a corresponding hydroxysilane. 
         [0024]    In the second aspect of the invention, the surface treating agent contains the perfluoropolyether-modified aminosilane of formula (1) and/or a partial hydrolytic condensate thereof as an active ingredient. 
         [0025]    If necessary, a hydrolytic condensation catalyst may be added to the surface treating agent. Exemplary catalysts include organic tin compounds (e.g. dibutyltin dimethoxide and dibutyltin dilaurate), organic titanium compounds (e.g., tetra-n-butyl titanate), organic acids (e.g., acetic acid and methanesulfonic acid), and mineral acids (e.g., hydrochloric acid and sulfuric acid). Of these, acetic acid, tetra-n-butyl titanate and dibutyltin dilaurate are desirable. The catalyst is added in a catalytic amount, preferably 0.001 to 5 parts by weight, and more preferably 0.01 to 1 part by weight, per 100 parts by weight of the aminosilane and/or partial hydrolytic condensate thereof. 
         [0026]    The surface treating agent of the invention may be diluted with a suitable solvent. Exemplary solvents include alcohols (e.g., ethyl alcohol and isopropyl alcohol), hydrocarbon solvents (e.g., petroleum benzine, mineral spirits, toluene and xylene), ester solvents (e.g., ethyl acetate, isopropyl acetate and butyl acetate), ether solvents (e.g., diethyl ether and isopropyl ether), and ketone solvents (e.g., acetone, methyl ethyl ketone and methyl isobutyl ketone). Polar solvents including alcohols, esters, ethers and ketones are preferred. Inter alia, isopropyl alcohol and methyl isobutyl ketone are especially preferred for solubility, wettability, and safety. 
         [0027]    The solvents may be used alone or in admixture while those solvents in which the foregoing components are uniformly dissolvable are preferred. The amount of solvent used is not particularly limited. Preferably the solvent is used in such amounts that the resulting surface treating agent contains 0.001 to 10% by weight, and more preferably 0.01 to 5% by weight of solids although the optimum concentration depends on a particular treating technique. 
         [0028]    The surface treating agent thus obtained may be applied (differently stated, a substrate may be treated with the agent) by well-known techniques such as brush coating, dipping, spraying and evaporation. The optimum treating temperature varies with a particular treating technique, although a temperature from room temperature to about 120° C. is desirable when the agent is applied by brush coating or dipping. The application or treatment is desirably carried out under humidified conditions because humidity promotes the reaction. It is understood that appropriate treating conditions are selected on every application because the treating conditions vary depending on a particular silane compound and additives used. 
         [0029]    The substrate to be treated with the surface treating agent is not particularly limited. Various materials including paper, fabric, metals, metal oxides, glass, plastics, porcelain, and ceramics may be used as the substrate. More particularly, substrates of paper, fabric, metals, glass, plastics, ceramics, etc. are included when the surface treating agent is used as water and oil repellant; substrates for pressure-sensitive adhesive tape, resin molding molds, rolls, etc. are included when the surface treating agent is used as parting agent; and substrates of paper, fabric, metals, glass, plastics, ceramics, etc. are included when the surface treating agent is used as anti-staining agent. The surface treating agent may also be used for modifying the flow and dispersion of paint additives, resin modifiers, and inorganic fillers, and for improving lubricity on tape, film and the like. 
         [0030]    The cured coating formed on the surface of substrates or articles has a thickness which may be selected depending on the type of substrate. 
         [0031]    Illustrative applications of the surface treating agent include water repellent, anti-staining coatings on sanitary ware such as bathtubs and washbowls; anti-staining coatings on glazing and head lamp covers in transport vehicles such as automobiles, trains and aircraft; water repellent, anti-staining coatings on building exteriors; coatings for preventing oil contamination on kitchen ware; water/oil repellent, anti-staining, weather resistant, anti-sticking coatings in telephone booths; and water and oil repellent, anti-fingerprint coatings on artistic objects; and anti-staining coatings on glassware and glass members in the general industry. 
       EXAMPLE 
       [0032]    Examples of the invention are given below by way of illustration and not by way of limitation. 
       Synthesis Example 1 
       [0033]    A 200-ml three-neck flask equipped with a thermometer, reflux condenser and stirrer was charged with 112 g of a perfluoropolyether-modified diallyldiamide of formula (4), 50 g of m-xylene hexafluoride, and 0.86 g of a toluene solution of chloroplatinic acid/vinyl siloxane complex (containing 1.0×10 −6  mol of elemental Pt). 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    The contents were heated at 80° C. with stirring. Then 26.8 g of trimethoxysilane was added dropwise to the reaction solution, which was ripened for 3 hours at 85° C. After the disappearance of allyl radicals in the reactant was ascertained by  1 H-NMR, the solvent and the excess trimethoxysilane were distilled off in vacuum, yielding 131.6 g of a colorless clear liquid. The data of  1 H-NMR and IR spectroscopy of the compound are shown below.
 
 1 H-NMR (TMS standard, ppm, see  FIG. 1 )
 
         [0000]                                                —CH 2 C H   2 Si≡   0.5-0.6           —CH 2 C H   2 CH 2 —   1.7-1.9           —CONC H   2 CH 2 —   3.2-3.4           —Si(OC H   3 ) 3     3.4-3.6                        
IR (KBr plate, liquid-membrane method, cm −1 , see  FIG. 2 )
       2950-2850 (C-H)   1700 (CON)   1315-1090 (C-F)         
         [0037]    From the above data, the compound was identified to have the structural formula below. 
         [0000]    
       
                 
         
             
             
         
       
     
       Synthesis Example 2 
       [0038]    This example followed the same procedure as Synthetic Example 1 except that a compound of formula (5): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    was used instead of the perfluoropolyether-modified diallyldiamide of formula (4). There was obtained a compound of the formula shown below. 
         [0000]    
       
                 
         
             
             
         
       
     
       Synthesis Example 3 
       [0039]    This example followed the same procedure as Synthetic Example 1 except that a compound of formula (6): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    was used instead of the perfluoropolyether-modified diallyldiamide of formula (4). There was obtained a compound of the formula shown below. 
         [0000]    
       
                 
         
             
             
         
       
     
       Synthesis Example 4 
       [0040]    This example followed the same procedure as Synthetic Example 1 except that a compound of formula (7): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    was used instead of the perfluoropolyether-modified diallyldiamide of formula (4). There was obtained a compound of the formula shown below. 
         [0000]    
       
                 
         
             
             
         
       
     
       Examples 1 and 2 
       [0041]    In 97.0 g of isopropyl alcohol was dissolved 3.0 g of the perfluoropolyether-modified aminosilane synthesized in each of Synthetic Examples 1 and 2. The solution was brush coated onto a glass plate of 2.5×10×0.5 cm, and allowed to stand for one hour in an atmosphere at 25° C. and humidity 70% whereby the coating cured. This test specimen was examined by the following tests. 
       (1) Water and Oil Repellent Test 
       [0042]    Using a contact angle meter model A3 (Kyowa Interface Science Co., Ltd.), the contact angle of the cured coating with water and n-hexadecane was measured as the rating of water and oil repellency. 
       (2) Parting Test 
       [0043]    A Cellophane adhesive tape strip (25 mm wide) was attached to the surface of the cured coating. Using a tensile tester, the tape strip was pulled and peeled at an angle of 180° and a rate of 300 mm/min. The force required for peeling was measured as the rating of parting property. 
       (3) Durability Test 
       [0044]    The surface of the cured coating was wiped 30 strokes with cellulose non-woven fabric under a predetermined load. Thereafter, the contact angle with water was measured as in test (1), from which durability was evaluated. 
       (4) Solubility 
       [0045]    Whether the aminosilane was soluble in isopropyl alcohol was examined at a solids concentration of 3% by weight. 
         [0046]    The results of these tests (1) to (4) are shown in Table 1. 
       Comparative Examples 1 and 2 
       [0047]    Cured coatings were obtained and tested as in Examples 1 and 2 except that the fluoroaminosilanes of Synthesis Examples 3 and 4 were used instead of the fluoroaminosilanes of Synthesis Examples 1 and 2. The test results are also shown in Table 1. 
       Comparative Example 3 
       [0048]    A cured coating was obtained and tested as in Examples 1 and 2 except that heptadecatrifluorodecyltrimethoxysilane (KBM-7803, Shin-Etsu Chemical Co., Ltd.) was used instead of the fluoroaminosilanes of Synthesis Examples 1 and 2. The test results are also shown in Table 1. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Water and oil 
                   
                   
                   
               
               
                   
                 repellency 
               
               
                   
                 (deg) 
                 Parting 
                 Durability 
               
             
          
           
               
                   
                 Water 
                 n-hexadecane 
                 (g/25 mm) 
                 (deg) 
                 Solubility 
               
               
                   
                   
               
             
          
           
               
                 Example 1 
                 114 
                 72 
                 22 
                 113 
                 Uniform, clear 
               
               
                 Example 2 
                 113 
                 70 
                 25 
                 111 
                 Uniform, clear 
               
               
                 Comparative Example 1 
                 101 
                 63 
                 98 
                  97 
                 Uniform, clear 
               
               
                 Comparative Example 2 
                 — 
                 — 
                 — 
                 — 
                 White turbid 
               
               
                 Comparative Example 3 
                 114 
                 73 
                 131  
                  83 
                 Uniform, clear 
               
               
                   
               
             
          
         
       
     
         [0049]    The coatings of Examples show at least equivalent water and oil repellency and parting property and are improved in solubility and durability, as compared with the prior art coatings (Comparative Examples 2 and 3). The coating of Comparative Example 1 is inferior in water and oil repellency and parting property to the coatings of Examples and unacceptable on practical use. 
         [0050]    It is thus evident that the perfluoropolyether-modified aminosilanes of the invention may be diluted with common solvents and form a tough coating on a substrate surface. They are applicable as a surface treating agent having improved water and oil repellency and parting property. 
         [0051]    Japanese Patent Application No. 2007-146910 is incorporated herein by reference. 
         [0052]    Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.