Paper composition
A paper product may include high energy thermomechanical pulp (TMP), low energy TMP, and microfibrillated cellulose. The paper product may also include inorganic particulate material. A papermaking composition suitable for making the paper product, a process for preparing the paper product, and use of microfibrillated cellulose may include high energy TMP, low energy TMP, and microfibrillated cellulose, and optionally inorganic particulate material. The microfibrillated cellulose may have a fiber steepness of from about 20 to about 50 in the paper product.
1. A process for preparing a paper product, the process comprising: (i) combining high energy thermomechanical pulp (TMP), low energy TMP, and microfibrillated cellulose in appropriate amounts to form a papermaking composition; and (ii) forming the paper product from the papermaking composition; wherein the paper product comprises at least about 30% by weight high energy TMP and low energy and between 0.1% to 5% by weight of said microfibrillated cellulose TMP, based on the total weight of the paper product; wherein the weight ratio of high energy TMP to low energy TMP is from about 55:45 to about 50:50; wherein the microfibrillated cellulose has a fibre steepness of from about 20 to about 50; wherein the low energy TMP has a Canadian standard freeness of from about 80 to about 130 cm 3 , and wherein the high energy TMP has a Canadian standard freeness of from 10 to 60 cm 3 ; further wherein the paper product has a Bendtsen porosity of less than about 300 cm 3 min− 1 .
2. The process of claim 1 , further comprising combining inorganic particulate material with the high energy TMP, low energy TMP, and microfibrillated cellulose in appropriate amounts to form the papermaking composition.
3. The process of claim 2 , wherein the papermaking composition comprises up to about 50% by weight of the inorganic particulate material.
4. The process of claim 3 , wherein the inorganic particulate material is selected from the group consisting of at least one of an alkaline earth metal carbonate or sulphate, calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite clay, kaolin, halloysite, ball clay, anhydrous kandite clay, metakaolin, fully calcined kaolin, talc, mica, perlite, diatomaceous earth, magnesium hydroxide, aluminium trihydrate, and combinations thereof.
5. The process of claim 2 , wherein the inorganic particulate material is kaolin.
6. The process of claim 5 , wherein at least about 50% by weight of the kaolin has an equivalent spherical diameter of less than about 2 μm.
7. The process of claim 6 , wherein the kaolin has at least one of a shape factor of from about 10 to about 70.
8. The process of claim 1 , further comprising at least one of calendering and supercalendering the paper product.
9. The process of claim 8 , wherein the paper product formed is coated with a coating composition prior to the at least one of calendering and supercalendering.