FIELD OF THE INVENTION

The present invention relates to methods of re-dispersing and de-agglomerating dewatered, partially dried and dried compositions of microfibrillated cellulose, as well as compositions of microfibrillated cellulose and inorganic particulate material, into liquid compositions comprising same, by applying ultrasonic energy to such liquid compositions of dewatered, partially dried and dried compositions of microfibrillated cellulose, or compositions of microfibrillated cellulose and inorganic particulate material. The present invention also relates to preparing an aqueous suspension comprising microfibrillated cellulose and, optionally, inorganic particulate material, with enhanced viscosity and tensile strength properties, suitable for use in methods of making paper or coating paper, and to filled and coated papers made from such aqueous suspensions.

BACKGROUND OF THE INVENTION

Microfibrillated cellulose and, optionally, inorganic particulate materials, for example an alkaline earth metal carbonate (e.g., calcium carbonate) or kaolin, are used widely in a number of applications. These include the production of microfibrillated cellulose and, optionally, mineral containing compositions, which may be used as fillers in paper manufacture and/or in paper coatings. In paper and coated paper products, such fillers are typically added to replace a portion of other more expensive components of the paper and/or coated paper product. Fillers may also be added with an aim of modifying the physical, mechanical, and/or optical requirements of paper and/or coated paper products. Clearly, the greater the amount of filler that can be included, the greater potential for cost savings. However, the amount of filler added and the associated cost saving must be balanced against the physical, mechanical and optical requirements of the final paper product or coated paper product. Thus, there is a continuing need for the development of improved fillers for paper and paper coatings, which can be used at a high loading level without adversely affecting the physical, mechanical and/or optical requirements of such paper and/or coated paper products. There is also a need for the development of methods for preparing such fillers economically.

The present invention seeks to provide alternative and/or improved fillers for paper and/or coated paper products which may be incorporated in the paper and/or coated paper product at relatively high loading levels, whilst maintaining or even improving the physical, mechanical and/or optical properties of the paper and/or coated paper product. The present invention also seeks to provide an economical method for preparing such fillers. As such, the present inventors have surprisingly found that a filler comprising microfibrillated cellulose and, optionally, an inorganic particulate material, can be prepared by economical methods and can be loaded in paper products and/or coated paper products at relatively high levels, whilst maintaining or even improving the physical, mechanical and/or optical properties of the final paper product. The application of ultrasonic energy to a suspension of microfibrillated cellulose, or microfibrillated cellulose suspensions comprising at least one inorganic particulate material has surprisingly been found to efficiently produce such suspensions having improved tensile strength and/or enhanced viscosity properties.

Further, the present invention seeks to address the problem of preparing microfibrillated cellulose and microfibrillated cellulose and inorganic particulate material compositions economically on an industrial scale. Current methods of microfibrillating cellulosic material and microfibrillated cellulose and inorganic particulate material require relatively high amounts of energy, owing in part to the relatively high viscosity of the starting material and the microfibrillated-containing product, and a commercially viable process for preparing microfibrillated cellulose on an industrial scale has hitherto before proved elusive.

Additionally, the present invention seeks to address the problem of re-dispersing dewatered, partially dried or essentially dried microfibrillated cellulose compositions or microfibrillated cellulose and inorganic particulate matter compositions in a liquid medium, optionally in the presence of an additive other than inorganic particulate material and/or in the presence of a combination of inorganic particulate materials. The additive and/or combination of inorganic particulate materials may, for example, enhance a mechanical and/or physical property of the re-dispersed microfibrillated cellulose or microfibrillated cellulose and inorganic particulate material composition. The present invention further relates to compositions comprising re-dispersed microfibrillated cellulose and, optionally, inorganic particulate material and the use of re-dispersed microfibrillated cellulose and, optionally, inorganic particulate material, in an article, product or composition. The solution to the problem is to apply ultrasonic energy in the re-dispersion of compositions of microfibrillated cellulose or compositions of microfibrillated cellulose and at least one inorganic particulate material as herein described.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention is directed to a method for re-dispersing dewatered, partially dried or essentially dried microfibrillated cellulose, the method comprising the steps of:(a) adding a quantity of a suitable dispersing liquid (e.g., water) to a tank having at least one inlet and an outlet, wherein the tank further comprises a mixer and a pump attached to the outlet;(b) adding a quantity of dewatered, partially dried or essentially dried microfibrillated cellulose to the tank through the at least one inlet in sufficient quantity to yield a liquid composition of microfibrillated cellulose at a desired solids concentration;(c) mixing the dispersing liquid and the dewatered, partially dried or essentially dried microfibrillated cellulose in the tank with the mixer to partially de-agglomerate and re-disperse the microfibrillated cellulose to form a flowable slurry;(d) pumping the flowable slurry with the pump to an inlet of a flow cell, wherein the flow cell comprises one or more sonication probe in series and at least one outlet;(e) applying ultrasonic energy to the slurry of at least 200 kWh/t continuously by the sonication probe at a frequency range of 19 to 100 kHz;(f) collecting the re-dispersed suspension comprising microfibrillated cellulose with enhanced tensile strength and/or viscosity properties from the at least one outlet of the flow cell in a suitable holding vessel.

According to a second aspect, the present invention, is directed to a method for re-dispersing dewatered, partially dried or essentially dried microfibrillated cellulose, the method comprising the steps of:(a) adding a quantity of a suitable dispersing liquid to a tank having at least one inlet and an outlet, wherein the tank further comprises a mixer and a pump attached to the outlet;(b) adding a quantity of dewatered, partially dried or essentially dried microfibrillated cellulose to the tank through the at least one inlet in sufficient quantity to yield a liquid composition of microfibrillated cellulose at a desired solids concentration;(c) mixing the dispersing liquid and the dewatered, partially dried or essentially dried microfibrillated cellulose in the tank with the mixer to partially de-agglomerate and re-disperse the microfibrillated cellulose to form a flowable slurry;(d) pumping the flowable slurry with the pump to an inlet of a flow cell, wherein the flow cell comprises one or more sonication probe in series and a first outlet; and wherein a second outlet of the flow cell is connected to a second inlet of the tank, thereby providing for a continuous recirculation loop providing for the continuous application of ultrasonic energy to the slurry for a desired time period and/or total energy input range;(e) applying ultrasonic energy to the slurry of at least 200 kWh/t continuously by the sonication probe at a frequency range of 19 to 100 kHz;(f) collecting the re-dispersed suspension comprising microfibrillated cellulose with enhanced tensile strength and/or viscosity properties from the first outlet of the flow cell in a suitable holding vessel.

According to a third aspect, the present invention is directed to processes of the first and second aspects, wherein the dewatered, partially dried or essentially dried microfibrillated cellulose composition further comprises at least one inorganic particulate material.

In an embodiment of the first, second or third aspect of the present invention the cumulative ultrasonic energy input may be from about 1,000 kWh/t to about 10,000 kWh/t or between about 1,000 kWh/t and about 2,000 kWh/t, or about 2,000 kWh/t to about 3,000 kWh/t.

In an embodiment of the first, second or third aspect of the present invention the flow cell comprises a cooling jacket for maintaining a temperature of the suspension of microfibrillated cellulose in the range of about 1° C. to about 80° C., or from about 20° C. to about 50° C., or at room temperature, or about 20° C.

In an embodiment of the first, second or third aspect of the present invention the flow cell comprises an adjustable valve at the second outlet to create back pressure of the recirculated liquid of from about 0 to about 10 bar, or from about 0 to about 4 bar, preferably about 3 bar.

In an embodiment of the first, second or third aspect of the present invention, the flow cell further comprises one or more boosters to mechanically increase or decrease the amplitude of the at least one sonication probe.

In an embodiment of the first and second aspect of the present invention, the liquid composition of microfibrillated cellulose is about 0.5% to about 10%, or about 0.5% to 5% fibre solids, and in an embodiment of the third aspect, the liquid composition of microfibrillated cellulose and inorganic particulate material is about 0.5% to about 10%, or about 0.5% to 5% fibre solids.

In an embodiment of the first, second and third aspects of the present invention, the ultrasonic energy is applied for about 1 to about 120 minutes, or about 1 to about 90 minutes, or about 1 to about 75 minutes, or about 1 to about 60 minutes, or about 1 to about 45 minutes or about 1 to about 30 minutes.

In an embodiment of the first and second aspect of the present invention, the microfibrillated cellulose may be pelletized, and in the third aspect, microfibrillated cellulose and inorganic particulate material may be pelletized.

In an embodiment of the first, second and third aspects of the present invention, the ultrasonic energy may be applied until a specified cumulative energy input is achieved. In additional embodiments, the cumulative energy input may be greater than 200 kWh/t, greater than 400 kWh/t, or greater than 500 kWh/t, or greater than 1,000 kWh/t, or greater than 1,500 kWh/t, or greater than 2,000 kWh/t, or greater than 2,500 kWh/t, or greater than 3,000 kWh/t, or greater than 4,000 kWh/t, or greater than 5,000 kWh/t, or greater than 6,000 kWh/t, or greater than 7,000 kWh/t, or between 200 kWh/t and 10,000 kWh/t., or about 200 kWh/t and 5,000 kWh/t, or about 200 kWh/t and 4,000 kWh/t, or about 200 kWh/t and 3,000 kWh/t, or about 200 kWh/t and 2,000 kWh/t.

In an embodiment of the second and third aspects of the present invention, the recirculation loop may comprise a high shear mixer.

In an embodiment of the first, second and third aspects of the present invention, the FLT index for the suspension of microfibrillated cellulose and the suspension of the microfibrillated cellulose and inorganic particulate material may reach 7.5 Nm/g or more, 7.5 Nm/g or more, 8 Nm/g or more, 8.5 Nm/g or more, 9 Nm/g or more, 9.5 Nm/g or more, 10 Nm/g or more, 10.5 Nm/g or more, 11 Nm/g or more, 11.5 Nm/g or more, 12 Nm/g or more, 12.5 Nm/g or more, 13 Nm/g or more, 13.5 Nm/g or more, 14 Nm/g or more, 14.5 Nm/g or more, or 15 Nm/g or more, through the methods disclosed in the specification.

In an embodiment of the first, second and third aspects of the present invention, the FLT index may be improved by about 5%, about 6%, about 7%, about 7.5%, about 8%, about 9%, about 10%, about 12.5%, about 15% or about 20%, or more, compared to suspensions of microfibrillated cellulose or microfibrillated cellulose and inorganic particulate material produced without the application of ultrasonic energy treatment to the slurry or suspension.

In an embodiment of the first, second and third aspects of the present invention, viscosity may be improved by about 5%, about 6%, about 7%, about 7.5%, about 8%, about 9%, about 10%, about 12.5%, about 15% or about 20%, or more, compared to suspensions of microfibrillated cellulose or microfibrillated cellulose and inorganic particulate material produced without the application of ultrasonic energy treatment to the slurry or suspension.

In embodiments of the first, second and third aspects of the present invention, the microfibrillated cellulose may be prepared from a chemical pulp, or a chemithermomechanical pulp, or a mechanical pulp, or a recycled pulp, or a paper broke pulp, or a papermill waste stream, or waste from a papermill, or combinations thereof.

In embodiments of the third aspect of the present invention, the inorganic particulate material may comprise alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite clay such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, perlite or diatomaceous earth, or combinations thereof. In certain embodiments, calcium carbonate and/or kaolin are particularly preferred.

In embodiments of the first and second aspects of the present invention, the suspensions of microfibrillated cellulose, or with enhanced viscosity and tensile strength properties obtained by the method are suitable for use in a method of making paper or coating paper, paints and coatings, inks, oilfield chemicals, composites, consumer products, cosmetic products, pharmacological products and food product.

In embodiments of the third aspect of the present invention the suspensions of microfibrillated cellulose and inorganic particulate material with enhanced viscosity and tensile strength properties obtained by the method are suitable for use in a method of making paper or coating paper, paints and coatings, inks, oilfield chemicals, composites, consumer products, cosmetic products, pharmacological products and food product.

According to a fourth aspect, the present invention is directed to a method for re-dispersing dewatered, partially dried or essentially dried microfibrillated cellulose, the method comprising the steps of:(a) adding a quantity of a suitable dispersing liquid (e.g., water) to a closed tank, wherein the tank comprises an inlet and an outlet connected to a pump comprising a first inlet and a first outlet, and a flow cell comprising a second inlet and a second outlet, and further comprising at least one sonication probe, thereby forming a closed recirculation loop;(b) adding a quantity of dewatered, partially dried or essentially dried microfibrillated cellulose to the tank in sufficient quantity to yield a liquid composition of microfibrillated cellulose at a desired solids concentration;wherein the liquid composition comprising microfibrillated cellulose of step (b) is continuously recirculated through the recirculation loop;(c) applying ultrasonic energy of at least 200 kWh/t intermittently or continuously by the sonication probe at a frequency range of 20 to 100 Hz to the liquid composition of microfibrillated cellulose,

thereby forming a re-dispersed suspension comprising microfibrillated cellulose with tensile strength and/or viscosity properties.

According to a fifth aspect, the present invention is directed to a method for re-dispersing dewatered, partially dried or essentially dried microfibrillated cellulose and inorganic particulate material, the method comprising the steps of:(a) adding a quantity of a suitable dispersing liquid (e.g., water) to a closed tank, wherein the tank comprises an inlet and an outlet connected to a pump comprising a first inlet and a first outlet, and a flow cell comprising a second inlet and a second outlet, and further comprising at least one sonication probe, thereby forming a closed recirculation loop;(b) adding a quantity of dewatered, partially dried or essentially dried microfibrillated cellulose and inorganic particulate material to the tank in sufficient quantity to yield a liquid composition of microfibrillated cellulose at a desired solids concentration;wherein the liquid composition comprising microfibrillated cellulose and inorganic particulate material of step (b) is continuously recirculated through the recirculation loop;(c) applying ultrasonic energy of at least 200 kWh/t intermittently or continuously by the sonication probe at a frequency range of 20 to 100 Hz to the liquid composition of microfibrillated cellulose and inorganic particulate material,

thereby forming a re-dispersed suspension comprising microfibrillated cellulose and inorganic particulate material with tensile strength and/or viscosity properties.

In an embodiment of the fourth or fifth aspect of the present invention, the cumulative energy input may be greater than 200 kWh/t, greater than 400 kWh/t, or greater than 500 kWh/t, or greater than 1,000 kWh/t, or greater than 1,500 kWh/t, or greater than 2,000 kWh/t, or greater than 2,500 kWh/t, or greater than 3,000 kWh/t, or greater than 4,000 kWh/t, or greater than 5,000 kWh/t, or greater than 6,000 kWh/t, or greater than 7,000 kWh/t, or between 200 kWh/t and 10,000 kWh/t., or about 200 kWh/t and 5,000 kWh/t, or about 200 kWh/t and 4,000 kWh/t, or about 200 kWh/t and 3,000 kWh/t, or about 200 kWh/t and 2,000 kWh/t.

In an embodiment of the fourth or fifth aspect of the present invention, the flow cell comprises a cooling jacket for maintaining a temperature of the suspension of microfibrillated cellulose in the range of about 1° C. to about 80° C., or from about 20° C. to about 50° C., or at room temperature, or about 20° C.

In an embodiment of the fourth or fifth aspect of the present invention, the flow cell comprises an adjustable valve at the second outlet to create back pressure of the recirculated liquid of from about 0 to about 10 bar, or from about 0 to about 4 bar, preferably about 3 bar.

In an embodiment of the fourth or fifth aspect of the present invention, the flow cell further comprises one or more boosters to mechanically increase or decrease the amplitude of the at least one sonication probe.

In an embodiment of the fourth or fifth aspect of the present invention, the liquid composition of microfibrillated cellulose is about 0.5% to about 10%, or about 0.5% to 5% fibre solids, and in an embodiment of the third aspect, the liquid composition of microfibrillated cellulose and inorganic particulate material is about 0.5% to about 10%, or about 0.5% to 5% fibre solids.

In an embodiment of the fourth or fifth aspect of the present invention, the ultrasonic energy is applied for about 1 to about 120 minutes, or about 1 to about 90 minutes, or about 1 to about 75 minutes, or about 1 to about 60 minutes, or about 1 to about 45 minutes or about 1 to about 30 minutes.

In an embodiment of the fourth aspect of the present invention, the microfibrillated cellulose may be pelletized, and in the fifth aspect, microfibrillated cellulose and inorganic particulate material may be pelletized.

In an embodiment of the fourth or fifth aspect of the present invention, the recirculation loop may comprise a high shear mixer.

In an embodiment of the fourth or fifth aspect of the present invention, the FLT index for the suspension of microfibrillated cellulose and the suspension of the microfibrillated cellulose and inorganic particulate material may reach 7.5 Nm/g or more, 7.5 Nm/g or more, 8 Nm/g or more, 8.5 Nm/g or more, 9 Nm/g or more, 9.5 Nm/g or more, 10 Nm/g or more, 10.5 Nm/g or more, 11 Nm/g or more, 11.5 Nm/g or more, 12 Nm/g or more, 12.5 Nm/g or more, 13 Nm/g or more, 13.5 Nm/g or more, 14 Nm/g or more, 14.5 Nm/g or more, or 15 Nm/g or more, through the methods disclosed in the specification.

In an embodiment of the fourth or fifth aspect of the present invention, the FLT index may be improved about 5%, about 6%, about 7%, about 7.5%, about 8%, about 9%, about 10%, about 12.5%, about 15% or about 20%, or more, compared to suspensions of microfibrillated cellulose or microfibrillated cellulose and inorganic particulate material produced without the application of ultrasonic energy treatment to the slurry or suspension.

In an embodiment of the fourth or fifth aspect of the present invention, viscosity may be improved by about 5%, about 6%, about 7%, about 7.5%, about 8%, about 9%, about 10%, about 12.5%, about 15% or about 20%, or more, compared to suspensions of microfibrillated cellulose or microfibrillated cellulose and inorganic particulate material produced without the application of ultrasonic energy treatment to the slurry or suspension.

In embodiments of the fourth or fifth aspects of the present invention, the microfibrillated cellulose may be prepared from a chemical pulp, or a chemithermomechanical pulp, or a mechanical pulp, or a recycled pulp, or a paper broke pulp, or a papermill waste stream, or waste from a papermill, or combinations thereof.

In embodiments of the fifth aspect of the present invention, the inorganic particulate material may comprise alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite clay such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, perlite or diatomaceous earth, or combinations thereof. In certain embodiments, calcium carbonate and/or kaolin are particularly preferred.

In embodiments of the fourth aspect of the present invention, the suspensions of microfibrillated cellulose with enhanced viscosity and tensile strength properties obtained by the method are suitable for use in a method of making paper or coating paper, paints and coatings, inks, oilfield chemicals, composites, consumer products, cosmetic products, pharmacological products and food product.

In embodiments of the fifth aspect of the present invention the suspensions of microfibrillated cellulose and inorganic particulate material with enhanced viscosity and tensile strength properties obtained by the method are suitable for use in a method of making paper or coating paper, paints and coatings, inks, oilfield chemicals, composites, consumer products, cosmetic products, pharmacological products and food product.

According to a sixth aspect, the present invention is directed to a method for preparing an aqueous suspension comprising microfibrillated cellulose and inorganic particulate material with enhanced viscosity and tensile strength properties, the method comprising a step of microfibrillating a fibrous substrate comprising cellulose and inorganic particulate material in an aqueous environment in the presence or absence of a grinding material to produce an aqueous suspension comprising microfibrillated cellulose material and inorganic particulate material, and further comprising subjecting the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material to sonication to produce the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material with enhanced viscosity and tensile strength properties.

According to a seventh aspect, the present invention is directed to a method for preparing an aqueous suspension comprising microfibrillated cellulose with enhanced viscosity and tensile strength properties, the method comprising a step of microfibrillating a fibrous substrate comprising cellulose in an aqueous environment in the presence of a grinding material to produce an aqueous suspension comprising microfibrillated cellulose material, and further comprising subjecting the aqueous suspension comprising microfibrillated cellulose to sonication to produce the aqueous suspension comprising microfibrillated cellulose with enhanced viscosity and tensile strength properties.

According to an eighth aspect, the present invention is directed to a method for preparing an aqueous suspension comprising microfibrillated cellulose and inorganic particulate material with enhanced viscosity and tensile strength properties, the method comprising a step of microfibrillating a fibrous substrate comprising cellulose and inorganic particulate material in an aqueous environment in the presence or absence of a grinding material to produce an aqueous suspension comprising microfibrillated cellulose and inorganic particulate material, and further comprising subjecting the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material to a dewatering step (or dehydrating or drying step) to produce a partially dried or dried (e.g., an essentially dried) composition of microfibrillated cellulose and inorganic particulate material, whereupon when the partially dried or essentially dried composition of microfibrillated cellulose and inorganic particulate material is reconstituted (or made down) to an aqueous slurry, such aqueous slurry is re-dispersed comprising a sonication step to produce the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material with enhanced viscosity and tensile strength properties.

According a ninth aspect, the present invention is directed to a method for preparing an aqueous suspension comprising microfibrillated cellulose with enhanced viscosity and tensile strength properties, the method comprising a step of microfibrillating a fibrous substrate comprising cellulose in an aqueous environment in the presence or absence of a grinding material to produce an aqueous suspension comprising microfibrillated cellulose, and further comprising subjecting the aqueous suspension comprising microfibrillated cellulose to a dewatering step (or dehydrating or drying step) to produce a partially dried or dried (e.g., an essentially dried) composition of microfibrillated cellulose, whereupon when the partially dried or essentially dried composition of microfibrillated cellulose and inorganic particulate material is reconstituted (or made down) to an aqueous slurry, such aqueous slurry is re-dispersed, comprising a sonication step to produce the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material with enhanced viscosity and tensile strength properties.

According to a tenth aspect, the present invention is directed to an aqueous suspension comprising microfibrillated cellulose suitable for use as filler in paper or a paper coating obtained by a method according to the sixth or eighth aspect.

According to a eleventh aspect, the present invention is directed to an aqueous suspension comprising microfibrillated cellulose and inorganic particulate material suitable for use as filler in paper or a paper coating according to the seventh or ninth aspect.

According to a twelfth aspect, the present invention is directed to a papermaking composition comprising the aqueous suspension of the sixth or eighth aspects.

According to a thirteenth aspect, the present invention is directed to a papermaking composition comprising the aqueous suspension of the seventh or ninth aspects.

According to a fourteenth aspect, the present invention is directed to a paper product prepared from the papermaking composition of the twelfth or thirteenth aspect.

According to a fifteenth aspect, the present invention is directed to a paper coating composition comprising the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material the sixth or eighth aspect and other optional additives.

According to a sixteenth aspect, the present invention is directed to a paper coating composition comprising the aqueous suspension comprising microfibrillated cellulose of the seventh or ninth aspect and other optional additives.

According to a seventeenth aspect, the present invention is directed to a paper product, for example paper board, coated with the paper coating composition comprising microfibrillated cellulose and inorganic particulate material of the sixth or eighth aspect.

According to an eighteenth aspect, the present invention is directed to a paper product, for example paper board, coated with the paper coating composition comprising microfibrillated cellulose of the seventh or ninth aspect.

According to a nineteenth aspect, the present invention is directed to a process for making a paper product comprising: (i) obtaining or preparing a fibrous substrate comprising cellulose in the form of a pulp suitable for making a paper product; (ii) preparing a papermaking composition from the pulp in step (i), the aqueous suspension according to the first or second aspects of the invention, and other optional additives; and (iii) forming a paper product from said papermaking composition.

According to a twentieth aspect, the present invention is directed to a process for making a paper product comprising: (i) obtaining or preparing a fibrous substrate comprising cellulose in the form of a pulp suitable for making a paper product; (ii) preparing a papermaking composition from the pulp in step (i), the aqueous suspension according to the seventh or ninth aspects of the invention, and other optional additives; and (iii) forming a paper product from said papermaking composition.

According to a twenty-first aspect, the present invention is directed to an integrated process for making a paper product comprising: (i) obtaining or preparing a fibrous substrate comprising cellulose in the form of a pulp suitable for making a paper product; (ii) microfibrillating a portion of said fibrous substrate comprising cellulose in accordance with the method of the sixth or eighth aspect of the invention to prepare an aqueous suspension comprising microfibrillated and inorganic particulate material; (iii) preparing a papermaking composition from the pulp in step (i), the aqueous suspension prepared in step (ii), and other optional additives; and (iv) forming a paper product from said papermaking composition.

According to a twenty-second aspect, the present invention is directed to an integrated process for making a paper product comprising: (i) obtaining or preparing a fibrous substrate comprising cellulose in the form of a pulp suitable for making a paper product; (ii) microfibrillating a portion of said fibrous substrate comprising cellulose in accordance with the method of the seventh or ninth aspect of the invention to prepare an aqueous suspension comprising microfibrillated cellulose; (iii) preparing a papermaking composition from the pulp in step (i), the aqueous suspension prepared in step (ii), and other optional additives; and (iv) forming a paper product from said papermaking composition.

According to a twenty-third aspect, the present invention is directed to an integrated process for making a paper product comprising: (i) obtaining or preparing a fibrous substrate comprising cellulose in the form of a pulp suitable for making a paper product; (ii) microfibrillating a portion of said fibrous substrate comprising cellulose in accordance with the method of the sixth or eighth aspect of the invention to prepare an aqueous suspension comprising microfibrillated and inorganic particulate material; (iii) preparing a papermaking composition from the pulp in step (i), the aqueous suspension prepared in step (ii), and other optional additives; and (iv) forming a paper product from said papermaking composition.

According to a twenty-fourth aspect, the present invention is directed to the use of an aqueous suspension comprising microfibrillated cellulose according to the sixth or eighth aspect of the invention as a filler in a papermaking composition.

According to a twenty-sixth aspect, the present invention is directed to the use of an aqueous suspension comprising microfibrillated cellulose and inorganic particulate material according to the sixth or eighth aspect of the invention in a paper coating composition.

