Microfibrillated cellulose as rheology modifier in adhesives

1. An adhesive composition comprising:

at least one starch and/or at least one starch derivative, in an amount of 5% w/w to 60% w/w, dry matter, of overall adhesive composition;

at least one solvent, in an amount of 30% w/w to 95% w/w of the overall adhesive composition; and

microfibrillated cellulose in an amount of 0.001% w/w to 10% w/w, dry matter, of the overall adhesive composition, wherein a diameter of the microfibrillated cellulose is in nanometer range, and wherein the microfibrillated cellulose has a Schopper-Riegler (SR) method value of below 95, as determined according to EN ISO 5267-1 (in the version of 1999), or, in the alternative, cannot be reasonably measured in accordance with the SR method, as fibers of the MFC are so small that a large fraction of the fibers simply pass through a screen as defined in the SR method.

2. The composition according to claim 1 , wherein at least one of (i) the amount of microfibrillated cellulose in said composition is from 0.01% dry matter, relative to overall weight of said composition, to 10%; (ii) the amount of microfibrillated cellulose in said composition is from 0.02% w/w relative to the overall weight of the composition to 8% w/w; and (iii) the amount of microfibrillated cellulose is from 0.003% w/w to 22% w/w, as measured relative to an overall amount of starch in said composition.

3. The composition according to claim 2 , wherein at least one of (i) the amount of microfibrillated cellulose in said composition is from 0.05% dry matter, relative to the overall weight of the composition, to 2%; (ii) the amount of microfibrillated cellulose in said composition is from 0.05% w/w relative to the overall weight of the composition to 0.5% w/w; and (iii) the amount of microfibrillated cellulose is from 0.2% w/w to 1.4% w/w, as measured relative to the overall amount of starch in said composition.

4. The composition according to claim 2 , wherein at least one of (i) the amount of microfibrillated cellulose in said composition is from 0.05% dry matter, relative to the overall weight of the composition, to 0.15%; (ii) the amount of microfibrillated cellulose in said composition is from 0.05% w/w relative to the overall weight of the composition to 0.5% w/w; and (iii) the amount of microfibrillated cellulose is from 0.2% w/w to 0.6% w/w, as measured relative to the overall amount of starch in said composition.

5. The composition according to claim 1 , wherein an overall amount of starch in said composition is from 15% w/w to 50% w/w of the overall adhesive composition.

6. The composition according to claim 1 , wherein the pH value of the adhesive composition is from 8 to 14.

7. The composition according to claim 1 , wherein the at least one starch is a native starch, or a chemically or physically modified starch, or a starch derivative, or a mixture thereof.

8. The composition according to claim 1 , wherein the microfibrillated cellulose is characterized in that it results in gel-like dispersion that has a zero shear viscosity, go, of at least 2000 Pas, as measured in polyethylene glycol (PEG), and at a solids content of the microfibrillated cellulose of 0.65%.

9. The composition according to claim 1 , wherein the microfibrillated cellulose is characterized by a water holding capacity of more than 30, as measured by diluting MFC samples to a 0.3% solids content in water, and then centrifuging the samples at 1000 G for 15 minutes, after which a clear water phase is separated from sediment and the sediment is weighed, wherein the water holding capacity is given as (mV/mT) −1 wherein mV is the weight of the sediment when wet and mT is the weight of dry MFC analyzed.

10. The composition according to claim 1 , wherein the microfibrillated cellulose is a non-modified (native) microfibrillated cellulose.

11. A method comprising:

providing an adhesive composition according to claim 1 ; and

manufacturing a corrugated paperboard/cardboard using the adhesive composition.

12. A process for making corrugated paperboards or cardboards, said process comprising at least the following steps:

providing a starch-based adhesive composition according to claim 1 ;

applying said starch-based adhesive composition to at least a part of tips of flutes of a corrugated pieces of paper, on at least one side; and

in a corrugator, applying at least one liner onto said corrugated piece of paper, and

preparing a single, double, triple or further multiple wall cardboard.

13. A corrugated paperboard or cardboard having at least one flute and at least one liner and comprising an adhesive composition according to claim 1 .

14. The composition according to claim 1 , wherein the microfibrillated cellulose is a non-modified microfibrillated cellulose derived from plant material.

15. A process for preparing a starch-based adhesive, or an adhesive based on a starch derivative, the process comprising the steps of:

(a) mixing at least one starch and/or at least one starch derivative, or a mixture thereof, with at least one solvent comprising water;

(b) during or after step (a): adding microfibrillated cellulose; and

(c) dispersing the mixture of (b) until a homogenous mixture is obtained,

wherein a diameter of the microfibrillated cellulose is in nanometer range, and wherein the microfibrillated cellulose has a Schopper-Riegler (SR) method value of below 95, as determined according to EN ISO 5267-1 in the version of 1999), or, in the alternative, cannot be reasonably measured in accordance with the SR method, as fibers of the MFC are so small that a large fraction of the fibers simply pass through a screen as defined in the SR method.

16. The process according to claim 15 , wherein a viscosity of the mixture increases by at least 10% in step (b) and relative to viscosity of the mixture of step (a).

17. The process according to claim 15 , wherein in step (a), first a primary starch is added to a solvent, then in or after step (a), a secondary starch is added, wherein the secondary starch is the same or a different starch or starch derivative as the primary starch.

18. The process of claim 15 , wherein the starch-based adhesive or adhesive based on a starch derivative is a composition and at least one of (i) the amount of microfibrillated cellulose in said composition is from 0.001% dry matter, relative to overall weight of said composition, to 10%; (ii) the amount of microfibrillated cellulose in said composition is from 0.02% w/w relative to the overall weight of the composition to 8% w/w; and (iii) the amount of microfibrillated cellulose is from 0.003% w/w to 22% w/w, as measured relative to an overall amount of starch in said composition.

19. The process of claim 15 , wherein step (a) and/or step (b) comprises adding alkaline in a ratio of dry alkaline relative to dry starch of from 0.1% w/w to 3% w/w.

20. A method comprising using microfibrillated cellulose as a rheology modifying agent in an adhesive comprising a starch and/or starch derivatives, wherein a diameter of the microfibrillated cellulose is in nanometer range, and wherein the microfibrillated cellulose has a Schopper-Riegler (SR) method value of below 95, as determined according to EN ISO 5267-1 (in the version of 1999), or, in the alternative, cannot be reasonably measured in accordance with the SR method, as fibers of the MFC are so small that a large fraction of the fibers simply pass through a screen as defined in the SR method.