Binder composition and method comprising microfibrillated cellulose and recycled cellulosic materials

A method of manufacturing a board or sheet comprising recycled cellulose-containing materials, a binder composition comprising microfibrillated cellulose and one or more inorganic particulate material, and optionally one or more additives, the method comprising the steps of:

• (a) providing or obtaining a first aqueous slurry of recycled cellulose-containing materials, wherein the aqueous slurry is disintegrated at a consistency of 0.1 wt. % to 10 wt. %;
• (b) providing or obtaining a second aqueous slurry of microfibrillated cellulose and one or more inorganic particulate materials, wherein the ratio of the one or more inorganic particulate materials to microfibrillated cellulose is about 99:5:0.5 to about 0.5:99.5, wherein the microfibrillated cellulose is obtained from virgin pulp or recycled cellulose-containing materials;
• (c) mixing the first aqueous slurry of recycled cellulose-containing materials and second aqueous slurry of microfibrillated cellulose and one or more inorganic particulate material at a consistency of 0.1 to 25 wt. %, and adding any optional additives, wherein the mixture comprises 0.5 wt. % to 35 wt. % microfibrillated cellulose and one or more inorganic particulate material;
• (d) pumping the mixture of step (c) to a suitably sized mould or former, the mould or former optionally comprising a press;
• (e) draining and/or pressing and drying the board or sheet, wherein the board or sheet has an increased modulus of elasticity and modulus of rupture compared to a board or sheet prepared in a comparable method without microfibrillated cellulose.