Sulfonic acid-containing binding agent for moulding mixes for the preparation of moulds and cores

Abstract

A polyisocyanate component for a moulding material binding agent system is described containing at feast one sulfonic acid in a solution of at least one polyisocyanate, containing at least two NCO-groups in the molecule.

1 . Polyisocyanate component for a moulding material binding agent system, containing at least one sulfonic acid in a solution of at least one polyisocyanate, containing at least two NCO-groups in the molecule, wherein,
 the sulfonic acid has the general formula R—SO 2 —OH, in which R denotes C 1-4 -alkyl, and   the polyisocyanate component contains methylene diphenyl diisocyanate or an oligomer or polymer thereof as polyisocyanate.   
     
     
         2 . Solution containing polyisocyanate, for a moulding material binding agent system, comprising of
 (a) one or a plurality of polyisocyanates with in each ease two or more NCO-groups in the molecule, wherein the one polyisocyanate or at least one of the plurality of polyisocyanates is a methylene diphenyl diisocyanate or an oligomer or polymer thereof, and   (b) one or a plurality of sulfonic acids, wherein the one sulfonic acid or at least one of the plurality of sulfonic acids is selected from the group of sulfonic acids of the formula R—SO 2 —OH, in which R denotes an alkyl group with between 1 and 4 carbon atoms.   
     
     
         3 . Solution containing polyisocyanate according to  claim 2 , comprising of
 (a) one or a plurality of polyisocyanates with in each case two or more NCO-groups in the molecule, wherein the one polyisocyanate or at least one of the plurality of polyisocyanates is a methylene diphenyl diisocyanate or an oligomer or polymer thereof,   (b) one or a plurality of sulfonic acids, wherein the one sulfonic acid or at least one of the plurality of sulfonic acids is selected from the group of sulfonic acids of the formula R—SO 2 —OH, in which R denotes an alky group with between 1 and 4 carbon atoms, wherein preferably the one sulfonic acid or at least one of the plurality of sulfonic acids, is methane sulfonic acid, and additionally   (c) one or a plurality of (co)-solvents, not selected from the group of ingredients (a) and (b) defined above, and/or   (d) one or a plurality of further substances selected from the group consisting of acid chlorides and chlorosilanes and/or   (e) optionally one or a plurality of further substances selected from the group of water repellents.   
     
     
         4 . Solution containing polyisocyanate according to  claim 2  wherein the solution does not comprise a resin selected from the group consisting of phenolic resins and furan resins. 
     
     
         5 . Solution containing polyisocyanate according to  claim 2  wherein the solution comprises no polyol that is suitable for reacting with the polyisocyanate(s) contained, in the solution to form a cold-curing binding agent. 
     
     
         6 . Solution containing polyisocyanate according to  claim 2 , wherein the solution is either anhydrous or contains water in a maximum quantity that is selected so that the molar ratio of NCO-groups to H 2 O is greater than 100:1, preferably greater than 1000:1. 
     
     
         7 . Solution containing polyisocyanate according to  claim 2  wherein the solution comprises no moulding matrix. 
     
     
         8 . Polyisocyanate component according to  claim 1  for a moulding material binding agent system, comprising 0.01 to 5 wt. %, of the at least one sulfonic acid. 
     
     
         9 . Polyisocyanate component according to  claim 8  for a moulding material binding agent system, wherein it contains 55 to 95 wt. %, of the at least one polyisocyanate. 
     
     
         10 . Polyisocyanate component according to  claim 1 , wherein at least one organic solvent, selected from among tetraalkyl silicate, aromatic hydrocarbons, fatty acid alkyl esters, mixtures of these and mixtures of these with alkylene carbonates or dialkyl esters of aliphatic dicarboxylic acid. 
     
     
         11 . A method of preparing a polyurethane resin, comprising:
 providing a polyisocyanate component according to  claim 1  as a polyisocyanate component of a two-component binding agent system for preparation of a polyurethane resin.   
     
     
         12 . Moulding material binding agent system for preparation of foundry sand cores from a polyol component, containing a solution of a polyol containing phenol with at least two OH groups in the molecule, and a polyisocyanate component, as defined in  claim 1 , reacting together to form a cold-curing binding agent. 
     
     
         13 . Two-component binding agent system for preparation of a polyurethane resin for casting, comprising of
 a polyisocyanate component as defined in  claim 1  and separately   a polyol component, wherein the polyol component preferably comprises a Phenol-formaldehyde resin with two or more methylol groups per molecule.   
     
     
         14 . (canceled) 
     
     
         15 . Mixture for preparation of a core or mould for casting, comprising
 a moulding matrix and   a moulding material binding agent system according to  claim 12 .   
     
     
         16 . Mould or core for casting,
 comprising a moulding matrix and the cured binding agent system resulting either from the curing of a moulding material binding agent system according to  claim 12  or   that can be prepared by moulding a mixture comprising a moulding matrix and the components of a moulding material binding agent system according to  claim 12  and curing of the binding agent system in the moulded mixture to form a cured binding agent system.   
     
     
         17 . Method for preparation of a core or mould for casting, with the following steps:
 mixing a moulding matrix with the components of a moulding material binding agent system according to  claim 12 ,   moulding of the resultant mixture comprising moulding matrix and the components of the binding agent system,   bringing the resultant moulded mixture into contact with a gaseous catalyst, preferably with a gaseous amine, so that the binding agent system cures and binds the moulding matrix.   
     
     
         18 . A method of extending the benchlife of a mixture, comprising: mixing
 a sulfonic acid of the general, formula R—SO 2 —OH, in which R denotes C 1-4 -alkyl   a moulding matrix and   a polyisocyanate component and a polyol component of a two-component binding agent system for preparation of a polyurethane resin for casting,   
       wherein 
       the polyisocyanate component comprises one or a plurality of polyisocyanates with in each case two or more NCO-groups in the molecule, wherein the one polyisocyanate or at least one of the plurality of polyisocyanates is a methylene diphenyl diisocyanate or an oligomer or polymer thereof, 
       and wherein 
       the polyol component comprises a phenol-formaldehyde resin with two or more methylol groups per molecule. 
     
     
         19 . The polyisocyanate component according to  claim 1 , wherein R is methyl. 
     
     
         20 . The solution according to  claim 2 , wherein R is methyl. 
     
     
         21 . A solution according to  claim 2 , comprising a total quantity of sulfonic acid in the range 0.01 to 5 wt. %., in respect of the total weight of the solution. 
     
     
         22 . A solution containing polyisocyanate according to  claim 2 , comprising a total quantity of polyisocyanate in the range 55 to 95 wt. %, with regard to the total mass of the solution. 
     
     
         23 . A solution containing polyisocyanate according to  claims 2 , comprising as component (c) one or a plurality of (co-)solvents, selected from group consisting of tetraalkyl silicate, aromatic hydrocarbons, fatty acid alkyl esters (preferably rapeseed oil methyl ester), mixtures of these and mixtures of these with alkylene carbonates or dialkyl esters of aliphatic dicarboxylic acids, preferably dimethyl esters of adipinic acid, glutaric acid and/or succinic acid. 
     
     
         24 . The method according to  claim 17 , wherein the method is a cold-box casting method.