Polymer latex composition for fibre binding

A method for increasing the strength of a fibre structure comprising:

• providing a fibre structure selected from fabrics and non-wovens;
• applying a composition comprising a polymer latex composition comprising:
• a) 50 to 98 wt.-% based on the total weight of latex particles in the composition of the first latex particles having a volume average particle size of 80 to 1000 nm, wherein the first latex particles optionally bear functional groups and if functional groups are present they are selected from the group consisting of acid functional groups and salts, amides or anhydrides thereof;
• silane functional groups;
• and combinations thereof;
• b) 2 to 50 wt.-% based on the total weight of latex particles in the composition of second latex particles having a volume average particle size of 5 to 70 nm bearing epoxy functional groups, wherein the second latex particles consist of structural units derived from:
• i) non-functional monomers selected from the group consisting of non-functional monomers having only one ethylenically unsaturated functional group;
• and conjugated dienes;
• ii) epoxy functional monomers;
• and optionally
• iii) functional monomers other than epoxy functional monomers that contain a functional group that is maintained on the resultant latex particle after emulsion polymerization;
• and
• coalescing the latex particles on at least a part of the fibres of the fibre structure by drying or heating the fibre structure.