Method for improving heat efficiency using silane coatings and coated articles produced thereby

Abstract

Oligomeric silane coating compositions containing, for example, methyltrimethoxysilane, are used to coat new or used heat exchange apparatus, such as HVAC systems, to greatly improve the heat transfer efficiency and prevent or inhibit corrosion. These oligomeric coating compositions are able to fill microvoids in the heat exchange surfaces, and penetrate into the microcavities at the interface of swaged or force fit surfaces, such as fins and tubes. The oligomeric silane coating compositions are highly active and will form bonds not only with the metal and metal oxides of the heat transfer surfaces, but will also displace gasses or liquids at the heat transfer contact surfaces and form chemical and/or hydrogen bonds with the oxides and chemical impurities. By so doing, a parallel heat transfer pathway is formed. The applied coatings may be as thin as only a few millionths of an inch and will fill microcavities to a depth of up to about 2000 nanometers. The coated heat transfer surfaces are non-adherent to deposition of soils and microorganisms and, therefore, are easier to maintain and are environmentally safe for use to heat/cool inhabited structures.

What is claimed is:  
     
         1 . A method for improving efficiency of heat transfer from a heat transfer medium flowing in heat transfer contact with a heat transfer surface of a thermally conductive component of a heat transfer system across said heat transfer surface, said method comprising coating at least a portion of said heat transfer surface with a low viscosity, penetrating, curable, reactive, film-forming, coating composition and curing the composition to thereby form an at least substantially continuous glass-like coating on said heat transfer surface, said coating extending into voids and defects which may be present in said heat transfer surface, whereby a thermally conductive corrosion protective layer is provided on said heat transfer surface.  
     
     
         2 . The method of  claim 1 , wherein said coating composition comprises an aqueous or non-aqueous oligomeric silane coating composition formed by admixing (a) at least one silane of the formula (1) 
       R 1   n Si(OR 2 ) 4−n   (1) 
       where R 1  represents a lower alkyl group, a C 6 -C 8  aryl group or a functional group including at least one of vinyl, acrylic, amino, mercapto, or vinyl chloride functional groups; 
 (b) silane condensation catalyst, and  
 (c) lower alkanol solvent, and optionally, one or more of  
 (d) colloidal aluminum hydroxide;  
 (e) metal alcoholate of formula (2): 
 M(OR 3 ) m   (2) 
 where M is a metal of valence 2, 3 or 4, or mixture of two or more such metals;  
 R represents a lower alkyl group; and,  
 m represents a number or 2, 3 or 4;  
 (f) a silica component selected from the group consisting of alkali metal silicate, ethyl orthosilicate, ethyl polysilicate, and colloidal silica dispersed in lower alkanol;  
 (g) color forming silanol condensation catalyst;  
 (h) epoxysilane;  
 (i) ultrafine titanium dioxide ultraviolet light absorber;  
 (j) water; and  
 (k) co-solvent;  
 and curing the applied coating composition.  
 
     
     
         3 . The method of  claim 2 , wherein said oligomeric silane coating composition comprises (I) an aqueous coating composition comprising a dispersion of divalent metal cations in lower aliphatic alcohol-water solution of the partial condensate of at least one silanol of the formula RSi(OH) 3 , wherein R is a radical selected from the group consisting of lower alkyl, vinyl, phenyl, 3,3,3-trifluoropropyl, gamma-glycidyloxypropyl, and gamma-methacryloxypropyl, at least about 70 percent by weight of the silanol being CH 3 Si(OH) 3 , acid in amount to provide a pH in the range of from about 2.5 to about 6.2, said divalent metal cations being present in an amount of from about 1.2 millimoles to about 2.4 millimoles, per molar equivalent of the partial condensate, calculated as methyl silane sesquioxide.  
     
     
         4 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises (II) 
 (A) at least one silane of the formula (I)   R 1 Si(OR 2 ) 3   (1)   wherein    R 1  is a lower alkyl group, a phenyl group or an    N-(2-aminoethyl)-3-aminopropyl group, and    R 2  is a lower alkyl group;    (B) acid component selected from the group consisting of water-soluble organic acids, H 3 BO 3  and H 3 PO 3 ; and    (D) water.    
     
     
         5 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises, (III) a non-aqueous coating composition formed by admixing 
 (A) at least one silane of formula (1)   R 1   n Si(OR 2 ) 4−n   (1)   wherein R 1  represents lower alkyl, phenyl, 3,3,3-trifluoropropyl, γ-glycidyloxypropyl, γ-(meth)acryloxypropyl, N-(2-aminoethyl)-3-aminopropyl, or aminopropyl group;    R 3  represents lower alkyl group; and    n is a number of 1 to 2; and    (E) (i) vinyltriacetoxysilane, (ii) colloidal aluminum hydroxide; and/or (iii) at least one metal alcoholate of formula (2)   M(OR 3 ) m   (2)   wherein M represents a metal of valence m,    R 3  represents lower alkyl group; and    m is a number of 2, 3 or 4.    
     
     
         6 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises, (IV) a non-aqueous coating composition formed by admixing 
 (A) at least one silane of formula (1)   R 1   n Si(OR 2 ) 4−n   (1)   wherein R 1  represents lower alkyl, phenyl, 3,3,3-trifluoropropyl, γ-glycidyloxypropyl, γ-(meth)acryloxypropyl, N-(2-aminoethyl)-3-aminopropyl, or aminopropyl group;    R 2  represents lower alkyl or acetyl group; and    n is a number of 1 to 2;    (B) boric acid, optionally dissolved in lower alkanol;    (E) (i) vinyltriacetoxysilane, (ii) colloidal aluminum hydroxide; and/or (iii) at least one metal alcoholate of formula (2)   M(OR 3 ) m   (2)   wherein M represents a metal of valence m,    R 3  represents lower alkyl group    m is an number of 2, 3 or 4; and.    (F) silica component selected from the group consisting of ethyl ortho-silicate, ethyl polysilicate and colloidal silica, dispersed in lower alkanol.    
     
     
         7 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises, (V) a non-aqueous coating composition formed by admixing 
 (A) at least one silane of formula (1)   R 1   n Si(OR 2 ) 4−n   (1)   wherein R 1  represents lower alkyl, phenyl, 3,3,3-trifluoropropyl, γ-(meth)acryloxypropyl, N-(2-aminoethyl)-3-aminopropyl, or aminopropyl group;    R 2  represents lower alkyl or acetyl group; and    n is a number of 1 to 2;    (A′) γ-glycidyloxypropyloxytrimethoxysilane;    (B) boric acid, optionally dissolved in lower alkanol;    (E) (i) vinyltriacetoxysilane, (ii) colloidal aluminum hydroxide; and/or (iii) at least one metal alcoholate of formula (2)   M(OR 3 ) m   (2)   wherein M represents a metal of valence m,    R 3  represents lower alkyl group    m is an number of 2, 3 or 4.    
     
     
         8 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises (VI) an oligomeric silane coating composition formed by admixing 
 (A) at least one silane of formula (1)       R 1   n Si(OR 2 ) 4−n   (1)       wherein R 1  represents lower alkyl, phenyl, or a functional group containing at least one of vinyl, acrylic, amino, mercapto, or vinyl chloride functional group; and    R 2  is a lower alkyl group;    (B) acid component comprising a member selected from the group consisting of water-soluble organic acids, H 3 BO 3  and H 3 PO 3 ; and    (D) water.    
     
     
         9 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises, (VII) an aqueous oligomeric silane coating composition formed by admixing 
 (A) at least one silane of formula (1)   R 1   n Si(OR 2 ) 4−n   (1)   wherein R 1  represents lower alkyl, phenyl, or a functional group containing at least one of vinyl, acrylic, amino, mercapto, or vinyl chloride functional group; and    R 2  is a lower alkyl group;    (C) alkali component; and    (D) water.    
     
     
         10 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises (VIII) an aqueous coating composition formed by admixing 
 (A) at least one silane of the formula (1)   R 1 Si(OR 2 ) 3   (1)   wherein    R 1  is a lower alkyl group, a phenyl group or a bifunctional silane containing vinyl, acrylic, amino, or vinyl chloride functional group; and    R 2  is a lower alkyl group;    (E) (ii) colloidal aluminum hydroxide, (iii) metal alcoholate of the formula (2)   M(OR 3 ) m   (2)   wherein    M is a metal of valence m,    R 3  is a lower alkyl group,    m is an integer of 3 or 4, or mixture of (ii) and (iii); and    (D) water.    
     
     
         11 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises (IX) an aqueous coating composition formed by admixing 
 (A) at least one silane of the formula (1)   R 1 Si(OR 2 ) 3   (1)   wherein R 1  is a lower alkyl group, a phenyl group or a bifunctional silane containing vinyl, acrylic, amino, or vinyl chloride functional group; and    R 2  is a lower alkyl group;    (D) water;    (H) lower alkanol; and    (G) chromium acetate hydroxide.    
     
     
         12 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises (X) an aqueous coating composition formed by admixing 
 (A) at least one silane of the formula (1)   R 1 Si(OR 2 ) 3   (1)   wherein    R 1  is a lower alkyl group, a phenyl group or a functional group including at least one of vinyl, acrylic, amino, mercapto, or vinyl chloride functional group; and    R 2  is a lower alkyl group;    (D) water;    (F) alkali metal silicate, which may be hydrolyzed;    (H) lower alkanol; and    (E) (ii) colloidal aluminum hydroxide, (iii) metal alcoholate of the formula (2)   M(OR 3 ) m   (2)   wherein    M is a metal of valence m,    R 3  is a lower alkyl group,    m is an integer of 3 or 4, or mixture of (ii) and (iii).    
     
     
         13 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises, (XI) a non-metallic aqueous coating composition formed by admixing 
 (A) at least one silane of the formula (1)   R 1 Si(OR 2 ) 3   (1)   wherein    R 1  is a lower alkyl group, a phenyl group or a functional group including at least one of vinyl, acrylic, amino, mercapto, or vinyl chloride functional group; and    R 2  is a lower alkyl group;    (A″) 3-(2-aminoethylamino)propyltrimethoxysilane or 3-aminopropyltrimethoxysilane;    (D) water;    (I) epoxide silane; and    (H) lower alkanol.    
     
     
         14 . The method of  claim 2 , wherein the oligomeric silane coating composition comprises, (XII) an aqueous coating composition formed by admixing 
 (A) at least one silane of the formula (1)   R 1 Si(OR 2 ) 3   (1)   wherein    R 1  is a lower alkyl group, a phenyl group or a functional group including at least one of vinyl, acrylic, amino, mercapto, or vinyl chloride functional group; and    R 2  is a lower alkyl group;    (B) boric acid;    (C) at least one alkali component comprising an hydroxide or carbonate of divalent metal;    (D) water;    (J) ethyl polysiloxane; and    (H) lower alkanol.    
     
     
         15 . The method according to  claim 1 , for increasing the contact area between first and second heat transfer surfaces in thermal contact with each other, thereby improving the heat transfer efficiency across the thermally contacting heat transfer surfaces, said method comprising, applying said low viscosity, penetrating coating composition to the thermally contacting heat transfer surface of at least one of said first and second heat transfer surfaces.  
     
     
         16 . The method according to  claim 15 , wherein the coating composition comprises an aqueous or non-aqueous oligomeric silane coating composition formed by admixing 
 (a) at least one silane of the formula (1)   R 1   n Si(OR 2 ) 4−n ( 1)   where R 1  represents a lower alkyl group, a C 6 -C 8  aryl group or a functional group including at least one of vinyl, acrylic, amino, mercapto, or vinyl chloride functional groups;    (b) silane condensation catalyst, and    (c) lower alkanol solvent, and optionally, one or more of    (d) colloidal aluminum hydroxide;    (e) metal alcoholate of formula (2):   M(OR 3 ) m   (2)   where M is a metal of valence 2, 3 or 4, or mixture of two or more such metals;    R represents a lower alkyl group; and,    m represents a number or 2, 3 or 4;    (f) silica component selected from the group consisting of alkali metal silicate, ethyl orthosilicate, ethyl polysilicate, and colloidal silica dispersed in lower alkanol;    (g) color forming silanol condensation catalyst;    (h) epoxysilane;    (i) ultrafine titanium dioxide ultraviolet light absorber;    (j)water;    (k) co-solvent;    and wherein the oligomeric coating composition is allowed to cure to a film thickness of from about 5 to about 150 millions of an inch, thereby filling any microvacancies in said heat transfer surfaces.    
     
     
         17 . The method according to  claim 1 , for improving the efficiency of heat exchange apparatus of the type wherein a metal heat transfer surface is swaged or force fit to a metal heat transfer fluid conveyance, said method comprising, applying to the interface between the heat transfer surface and the conveyance said low viscosity, penetrating coating composition whereby the coating composition will displace gasses and liquids in said interface; and allowing the coating composition to cure to a film thickness of from about 5 to about 150 millions of an inch, and fill any microvacancies in said metal surfaces at said interface.  
     
     
         18 . The method according to  claim 17 , wherein said coating composition comprises an aqueous or non-aqueous oligomeric silane coating composition formed by admixing (a) at least one silane of the formula (1) 
       R 1   n Si(OR 2 ) 4−n   (1) 
       where R 1  represents a lower alkyl group, a phenyl group or a functional group including at least one of vinyl, acrylic, amino, mercapto, or vinyl chloride functional groups; 
 (b) silane condensation catalyst, and  
 (c) lower alkanol solvent, and optionally, one or more of  
 (d) colloidal aluminum hydroxide;  
 (e) metal alcoholate of formula (2): 
 M(OR 3 ) m   (2) 
 where M is a metal of valence 2, 3 or 4, or mixture of two or more such metals;  
 R represents a lower alkyl group; and,  
 m represents a number or 2, 3 or 4;  
 (f) a silica component selected from the group consisting of alkali metal silicate, ethyl orthosilicate, ethyl polysilicate, and colloidal silica dispersed in lower alkanol;  
 (g) color forming silanol condensation catalyst;  
 (h) epoxysilane;  
 (i) ultrafine titanium dioxide ultraviolet light absorber;  
 (j) water;  
 (k) cosolvent.  
 
     
     
         19 . The method according to  claim 1 , wherein said heat transfer surface comprises a fin and tube heat transfer device.  
     
     
         20 . A heat transfer system comprising a metal heat transfer surface, wherein said metal heat transfer surface is coated with a cured low viscosity, penetrating, curable, reactive, film-forming, coating composition whereby the cured coating composition has a film thickness of from about 5 to about 150 millions of an inch, and fills any microvacancies in said metal surfaces.  
     
     
         21 . The heat transfer system according to  claim 20 , wherein the heat transfer surface of said heat transfer system comprises a fin and tube heat exchange device.  
     
     
         22 . The heat transfer system according to  claim 20 , wherein the heat transfer surface comprises an evaporator, said coating being resistant to adhesion of microorganisms.