Aqueous corrosion protection formulation based on silanes

Abstract

The present invention relates to a composition comprising a specific binder containing at least one cocondensate based on at least one ω-glycidyloxyalkylalkoxysilane and a bis(alkoxyalkylsilyl)amine, water, alcohol in an amount of less than 3% by weight, based on the composition, at least one addition selected from the group consisting of particulate metals, metal alloys and metal compounds and optionally at least one additive, where the pH of the composition is from 1 to 14 and the dry residue of the binder is from 1 to 50% by weight, based on the binder used, a process for the production thereof and also the use thereof for coatings, in particular for the protection of metals against corrosion.

1 . A composition, comprising:
 a binder,   water,   alcohol in a positive amount of less than 3% by weight, based on a total weight of the composition,   at least one addition selected from the group consisting of a particulate metal, a metal alloy and a metal compound, and   optionally an additive,   wherein:   the composition has a pH of from 1 to 14,   a dry residue of the binder is from 1% to 50% by weight, based on a total weight of the binder, and   the binder comprises:   a cocondensate based on an ω-glycidyloxyalkylalkoxysilane of formula I
   X—Si(R 2 ) x (OR 1 ) 3-x   (I),
 
 wherein X is a 2-(3,4-epoxycyclohexyl)ethyl, 1-glycidyloxymethyl, 2-glycidyloxyethyl, 3-glycidyloxypropyl or 3-glycidyloxyisobutyl group, R 1  and R 2  each independently are a linear or branched alkyl group comprising from 1 to 4 C atoms, and x is 0 or 1, 
   a bis(alkoxysilylalkyl)amine of formula II
   (OR 1 ) 3 Si-A-Si(OR 1 ) 3   (II),
 
 wherein each R 1  independently is a linear or branched alkyl group comprising from 1 to 4 C atoms and A is a bis-amino-functional group of formula IIa
   —(CH 2 ) i —[NH(CH 2 ) f ] g NH[(CH 2 ) f* NH] g* —(CH 2 ) i* —  (IIa),
 
 wherein i and i* each independently are an integer of 1, 2, 3 or 4, f and f* each independently are an integer of 1 or 2, and g and g* each independently are an integer of 0 or 1, 
 
   and optionally, at least one further silicon compound selected from the group consisting of tetraalkoxysilane, alkylalkoxysilane, mercaptoalkylalkoxysilane, carboxyalkylalkoxysilane, aminoalkylalkoxysilane, ureidoalkylalkoxysilane, thiocyanatoalkylalkoxysilane and a silica sol.   
     
     
         2 . The composition according to  claim 1 ,
 wherein the binder is obtained by a process comprising:   introducing water in a molar excess, based on silanes of the formulae I and II and, optionally, on the at least one further silicon compound and adjusting to an acidic pH with addition of an organic or inorganic acid, and an optional addition of a silica sol,   metering in the ω-glycidyloxyalkylalkoxysilane of formula I, thereby obtaining a mixture,   heating the mixture,   optionally metering in further acid,   metering in the bis(alkoxysilylalkyl)amine of formula II and optionally at least one further silicon compound selected from the group consisting of tetraalkoxysilane, alkylalkoxysilane, mercaptoalkylalkoxysilane, carboxyalkylalkoxysilane, aminoalkylalkoxysilane, ureidoalkylalkoxysilane and thiocyanatoalkylalkoxysilane, thereby obtaining a reaction mixture,   reacting the reaction mixture,   subsequently removing at least proportionately a resultant hydrolysis alcohol from the reaction mixture under reduced pressure, thereby obtaining the binder,   optionally diluting the binder with water, an aqueous acid, or both, and   subsequently, filtering the binder.   
     
     
         3 . The composition according to  claim 1 ,
 wherein   a dry residue is from 1% to 50% by weight, based on the total weight of the composition.   
     
     
         4 . The composition according to  claim 1 ,
 wherein   an amount of the at least one addition in the composition is from 1% to 95% by weight.   
     
     
         5 . The composition according to  claim 1 ,
 wherein   the at least one addition is selected from the group consisting of a conductive or non-conductive filler, a zinc powder, a zinc flake, a zinc dust, a powder or a flake or a dust of zinc alloys, a zinc-bismuth alloy, an aluminium powder, an aluminium flake, a powder or a flake or a dust of aluminium alloys, a magnesium powder, a magnesium flake, a powder or a flake of magnesium alloys, titanium dioxide, red iron oxide, yellow iron oxide, calcium carbonate, talc, an aluminium silicate, barium sulphate, kaolin, a magnesium silicate, crystalline quartz, amorphous quartz, a calcium magnesium carbonate, a calcium silicate, aluminium oxide, a zeolite, a wollastonite, zinc oxide, zinc phosphate, bismuth vanadate, lead chromate, silicon carbide and an inorganic colour pigment.   
     
     
         6 . The composition according to  claim 1 ,
 wherein   the additive is selected from the group consisting of a defoamer, a thickener, a rheological assistant, a dispersion assistant, an anti-settling agent, a rust inhibitor, a wetting agent, an organic pigment, a polymer, a polymer dispersion, and catalyst for condensation and curing.   
     
     
         7 . The composition according to  claim 1 ,
 wherein, based on the total weight of the composition,   the additive is at least one of a thickener of from 0% to 5% by weight, an anti-settling agent of 0% to 5% by weight, a wetting agent of 0% to 3% by weight, and a corrosion inhibitor of 0% to 1% by weight.   
     
     
         8 . A process for preparing the composition according to  claim 1 , the process comprising:
 introducing water in a molar excess, based on silanes of formulae I and II and optionally, on the at least one further silicon compound, and adjusting to an acidic pH with addition of an organic or inorganic acid and a silica sol with optional stirring,   metering in the ω-glycidyloxyalkylalkoxysilane of formula I, thereby obtaining an acidic mixture,   heating the acidic mixture,   optionally metering in further acid,   metering in the bis(alkoxysilylalkyl)amine of formula II and optionally at least one further silicon compound selected from the group consisting of tetraalkoxysilane, alkylalkoxysilane, mercaptoalkylalkoxysilane, carboxyalkylalkoxysilane, aminoalkylalkoxysilane, ureidoalkylalkoxysilane and isocyanatoalkylalkoxysilane, thereby obtaining a reaction mixture,   reacting the reaction mixture   subsequently removing at least proportionately a resultant hydrolysis alcohol from the reaction mixture under reduced pressure, thereby obtaining the binder,   optionally diluting the binder with at least one of water, an aqueous acid, and an aqueous base, or adjusting a pH of the binder, and subsequently filtering the binder,   dispensing the at least one addition into the binder,   optionally incorporating the additive by stirring, and   optionally adjusting the pH value of the composition.   
     
     
         9 . The process according to  claim 8 ,
 wherein   a molar ratio of the ω-glycidyloxyalkylalkoxysilane of formula I to the bis(alkoxysilylalkyl)amine of formula II is from 0.1:99.9 to 99:1.   
     
     
         10 . The process according to  claim 8 ,
 wherein   water is introduced in a molar excess, based on the silanes of formulae I and II and optionally, the at least one further silicon compound, of 2 to 1000 mol of water, per mole of Si-bonded alkoxy groups present in the silanes used, under inert gas.   
     
     
         11 . The process according to  claim 8 ,
 wherein   the organic or inorganic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, hydrochloric acid, nitric acid, sulphuric acid and phosphoric acid,   the aqueous base is selected from the group consisting of sodium hydroxide, potassium hydroxide, N,N-dimethylethanolamine and tetrakis(triethanolamine) zirconate,   a pH is adjusted to 1 to 14 at at least one stage selected from the group consisting of during said reacting, after said reacting and after formulation of the composition and   optionally the pH is changed by adding the at least one addition.   
     
     
         12 . The process according to  claim 8 ,
 wherein   3-glycidyloxypropyltrimethoxysilane, 3 glycidyloxypropyltriethoxysilane, or both are metered in as the ω-glycidyloxyalkylalkoxysilane of formula I, and   the acidic aqueous mixture thus obtained is heated over 0.1 to 3 hours, with stirring, mixing or both, to a temperature of 50 to 90° C.   
     
     
         13 . The process according to  claim 8 ,
 wherein   the acidic mixture after heating is admixed in a metered form with at least one of bis(trimethoxysilylpropyl)amine and bis(triethoxysilylpropyl)amine and optionally as the at least one further silicon compound with a tetraalkoxysilane, at a pH of from 2 to 6, and is caused to react with stirring at 50 to 90° C., over 0.3 to 6 hours.   
     
     
         14 . A coating, comprising: the composition according to  claim 1 ,
 wherein the coating cures in air at a temperature of from 16 to 26° C.   
     
     
         15 . A metal or a metal alloy for protection from corrosion, comprising: the coating according to  claim 14 .