wherein the percentages by weight are relative to the  total weight of the mixture.  5.  The binder mixture for a no-bake process according to  claim  1,  wherein the content of free formaldehyde is at most  0.4 wt. %, wherein the percentages by weight are relative to  the total weight of the mixture.  6.  The binder mixture for a no-bake process according to  claim  1,  wherein the ammonia content is at most 1 wt. %,  wherein the percentages by weight are relative to the total  weight of the mixture.  7.  The binder mixture for a no-bake process according to  claim  1,  wherein the total nitrogen content is at most 4 wt.  %, wherein the percentages by weight are relative to the total  weight of the mixture.  8.  The binder mixture for a no-bake process according to  claim  1,  wherein constituent (b-1) comprises 2,5-bis(hy› droxymethyl)furan (BHMF) in an amount of at least 1 wt.%,  relative to the total weight of a mixture according to the  invention.  9.  The binder mixture for a no-bake process according to  claim  8,  wherein the weight ratio of constituent (a) and  2,5-bis(hydroxymethyl)furan (BHMF) of constituent (b-1)  is in the range from 3:1 to 1:3.  11.  The binder mixture for a no-bake process according to  claim  1,  wherein the ratio of weight average molecular  weight Mw to number average molecular weight  Mn  of  constituent (b-1) is in the range from 5:1 to 9:8.  12.  The binder mixture for a no-bake process according to  claim  1,  additionally comprising as further constituent  ( e) one or a plurality of adhesion promoters selected from  the group of silanes, N-aminopropylmethyldiethoxysi› lane,  N-aminoethy 1-3-aminopropy ltrimethoxysilane,  N-aminoethyl-3-aminopropylmethy ldiethoxysilane  and/or N-aminopropyltriethoxysilane, in a total amount  ofup to 3 wt.%,  wherein the percentages by weight are relative to the total  weight of the mixture.  13.  The binder mixture for a no-bake process according to  claim  1,  additionally comprising one or a plurality of further  constituents, selected from the group of  (g) inert organic solubilisers, selected from the group of  alcohols R---OH, wherein R denotes a Cl-C4 alkyl  residue,  (h) reaction products of furfuryl alcohol and one or a  plurality of aldehydes with 2 or more carbon atoms,  G) organic compounds that have one or a plurality ofH$_{2}$N  groups and/or one or a plurality of HN groups,  (k) phenolic compounds, with 6 to 25 carbon atoms and/or  one, two, three or four hydroxyl groups bound directly  to an aromatic ring,  (m) benzyl alcohol,  (n) aldehydes with 2 or more carbon atoms selected from  the group consisting of acetaldehyde, propionaldehyde,  butyraldehyde, acrolein, crotonaldehyde, benzalde- hyde, salicylaldehyde, cinnamaldehyde, glyoxal and  mixtures of these aldehydes.  (S-2) preheating of the reaction mixture resulting from  step (S-I) to a temperature in the range from 40 to 90°  C.  25.  Method according to claim  23,  with the following  further steps:  65  60  24.  Method according to claim  23,  wherein step (S-1)  takes place at a temperature in the range from 90 to 160°  C.  (S-1) reaction of furfuryl alcohol with formaldehyde and  optionally further constituents in the presence of one or  a plurality of organic acids with a pKa value greater  than or equal to 2.5 at 25°  C. and/or salts thereof  wherein the molar ratio of the total amount of furfuryl  alcohol used to the total amount of formaldehyde  used is greater than or equal to 1.  55  23.  Method of preparing a mixture according to claim  1,  with the following step:  22.  Reaction mixture according to claim  1,  wherein the  mixture does not contain sulphur dioxide, a peroxide, or  both sulphur dioxide and a peroxide.  45 (iii) one or a plurality of refractory granular materials in  an amount of 80 wt. % or more relative to the total  weight of the reaction mixture.  21.  Reaction mixture according to claim  1,  additionally  comprising  20.  Reaction mixture according to claim  18,  wherein the  acid of component (ii) is selected from the group of organic  acids.  40 19.  Reaction mixture according to claim  18,  wherein the  reaction mixture comprises no sulphuric acid or comprises  sulphuric acid in an amount of max. 1 wt. %, wherein the  percentages by weight are relative to the total weight of the  reaction mixture minus the total weight of refractory granu- lar materials in the reaction mixture.  35  (ii) an acid, wherein the acid has a pKa value ofless than  2 at 25°  C.,  wherein the reaction mixture comprises a content of  free formaldehyde of max. 0.4 wt. %, and  wherein the percentages by weight are relative to the  total weight of the reaction mixture.  (i) a mixture according to claim  1;  18.  Reaction mixture, comprising  (S-1) reacting a furfuryl alcohol with formaldehyde and  optionally further constituents in the presence of one or  a plurality of organic acids with a pKa value greater  than or equal to 2.5 at 25°  C. and/or salts thereof,  wherein the molar ratio of the total amount of furfuryl  alcohol used to the total amount of formaldehyde  used is greater than or equal to 1.  20  17.  The binder mixture for a no-bake process according to  claim  1,  that is produced by a method including the follow› ing step:  16.  The binder mixture for a no-bake process according to  claim  1,  further comprising methanol as an inert organic  solubiliser.  15 10  the proportion by weight of constituent (a) decreases by at  most 10% relative to the initial amount of monomeric  furfuryl alcohol at the start of the storage period.  the viscosity value of the mixture at 20°  C., measured  according to DIN 53019-1: 2008-09, increases by at  most 80%, and  15.  The binder mixture for a no-bake process according to  claim  1,  wherein the mixture is a mixture that is stable in  storage, which has a storage stability of at least 3 months at  20°  C., wherein during the storage period  14.  The binder mixture for a no-bake process according to  claim  1,  wherein the pH of the mixture at 25°  C. is in the  range from 5 to 9.5.  5  US 9,993,863  B2  32  31 