Method for pretreatment of filler, modified filler with a hydrophobic polymer and use of the hydrophobic polymer

1. A method for making paper or board comprising the steps of

pretreating a filler before the filler is supplied to a fibre suspension,

wherein the pretreatment comprises

adding a hydrophobic polymer made of

polymerisable monomers polymerised in the presence of a polysaccharide, to the filler in order to create a hydrophobic film on the surface of the filler particles and/or between adjacent filler particles, and

the polymer added to the filler is added as a polymer dispersion or a polymer solution, which polymer is polymerised using a polysaccharide as a stabilising agent,

adding the pretreated filler to the fibre suspension and

forming a web from the fibre suspension.

2. A method according to claim 1 , characterised in that the polymer added to the filler is a polymer, which is made by solution polymerisation or emulsion polymerisation of polymerisable monomers.

3. A method according to claim 1 , characterised in that the polymer added to the filler is mainly an inert polymer, which does not react covalently with the filler or with the cellulose fibre.

4. A method according to claim 1 , characterised in that the polymer added to the filler is added as a polymer dispersion or a polymer solution, which is polymerised using further as a stabilising agent,

a synthetic polymer and/or a dispersing agent.

5. A method for pretreatment of filler, the pretreatment being conducted before the filler is supplied to the fibre suspension, characterised in that the pretreatment comprises the addition of a hydrophobic polymer made of polymerisable monomers to the filler in order to create a hydrophobic film on the surface of the filler particles and/or between adjacent filler particles, wherein the polymer is added to the filler as a stable product which is formed by mixing starch in granule form into a synthetic polymer, and by letting the starch react with the polymer under the influence of heat.

6. A method according to claim 1 , characterised in that the polymer to be added to the filler is added as a polymer dispersion which dispersion is formed by copolymerising a monomer mixture of a polysaccharide dissolved in water, the monomer mixture containing at least one vinylic monomer.

7. A method according to claim 6 , characterised in that the polysaccharide is chemically modified by cationic and/or anionic groups, whereby the substitution level (DS) regarding the cationic and/or anionic substituents is 0.1 to 2.

8. A method according to claim 6 , characterised in that the temperature at which the polymer made by copolymerisation creates a film is about −50 to 200° C.

9. A method according to claim 1 , characterised in that the polymer to be added to the filler is added as a polymer dispersion wherein the polymer is formed by polymerizing the following components, whose amounts are presented as dry solids content,

a) 5 to 50% starch having a substitution level (DS) regarding cationic and/or anionic substituents of about 0.01 to 1, and an intrinsic viscosity of >1.0 dl/g in a cationised and/or anionised state,

b) 50 to 95% of a monomer mixture containing at least one vinylic monomer, and

c) water.

10. A method according to claim 9 , characterised in that the film generating temperature of the polymer which is formed by said monomer mixture is 10 to 50° C.

11. A method according to claim 9 , characterised in that the monomer mixture comprises 40 to 70% acrylates and 30 to 60% styrene.

12. A method according to claim 9 , characterised in that the monomer mixture comprises

a) acrytonitrile, 0 to 19%;

b) acrylates, 10 to 60%, and

c) styrene, 10 to 60%.

13. A method according to claim 1 , characterised in that the hydrophobic polymer is added to the filler, which uses large amounts of filler, the amounts being >20%, of the dry solids content of the paper.

14. A fiber suspension comprising a modified filler which modified filler comprises a hydrophobic polymer made of polymerisable monomers polymerised in the presence of a polysaccharide, which polymer is added to the filler as a polymer dispersion or a polymer solution, and which polymer is polymerised using a polysaccharide, as a stabilising agent, wherein the polymer is formed from monomer or monomers selected from the group consisting of styrene, 1,3-butadiene, butylacrylate, methyl methacrylate, ethyl acrylate, 2-ethyl hexl acrylate and acrylonitrile.

15. A paper or board comprising the fiber suspension according to claim 14 .

16. The paper or board according to claim 15 , characterised in that the polymer is formed from a monomer mixture containing at least one vinylic monomer.

17. A paper or board comprising a fiber suspension comprising a modified filler which modified filler comprises

a filler, characterised in that the modified filler comprises

a hydrophobic polymer made of polymerisable monomers polymerized in the presence of a polysaccharide, which polymer is added to the filler as a polymer dispersion or a polymer solution, and which polymer is polymerised using a polysaccharide, as the stabilising agent, in order to create a hydrophobic film on the surface of the filler particles and/or between adjacent filler particles before the filler is supplied to the fibre suspension, characterised in that the polymer is formed from a monomer mixture containing

a) acrylonitrile or methacrylonitrile or a mixture thereof,

b) acrylates, and

c) styrene or other copolymerisable monomers unsubstitued by ethylene.

18. The paper or board according to claim 15 , characterised in that the polymer is formed from a monomer mixture containing

a) 0 to 19% of acrylonitrile;

b) 10 to 60% acrylates, and

c) 10 to 60% styrene.

19. A paper or board comprising a modified filler which modified filler comprises

a filler, characterised in that the modified filler comprises

a hydrophobic polymer made of polymerisable monomers polymerized in the presence of a polysaccharide, which polymer is added to the filler as a polymer dispersion or a polymer solution, and which polymer is polymerised using a polysaccharide, as the stabilising agent, in order to create a hydrophobic film on the surface of the filler particles and/or between adjacent filler particles before the filler is supplied to the fibre suspension, characterised in that the polymer dispersion is formed by polymerizing the following components, whose amounts are presented as dry solids content,

a) 5 to 50% starch having a substitution level (DS) regarding cationic and/or anionic substituents of about 0.01 to 1, and an intrinsic viscosity of >1.0 dl/g in a cationised and/or anionised state;

b) 50 to 95% of a monomer mixture containing at least one vinylic monomer, and

c) water.

20. The paper or board according to claim 17 , wherein the polysaccharide is selected from the group consisting of starch, mannan, carboxymethylcellulose and/or mixtures thereof.

21. The paper or board as in claim 17 , wherein the filler is selected from the group consisting of calcium carbonate, kaolin, talc, titanium dioxide, sodium silicate, aluminiumtrihydrate and mixtures thereof.

22. A method according to claim 1 , wherein the filler is selected from the group consisting of calcium carbonate, kaolin, talc, titanium dioxide, sodium silicate, aluminiumtrihydrate and mixtures thereof.

23. A method according to claim 1 , wherein the polysaccharide is selected from the group consisting of starch, mannan, carboxymethylcellulose and mixtures thereof.

24. A method of increasing the wet strength or reducing linting of paper by pretreating the filler according to claim 1 .

25. A method according to claim 4 , wherein the synthetic polymer is selected from the group consisting of styrene maleic anhydrate (SMA) and styrene maleic imide (SMI).

26. A fiber suspension comprising a modified filler which modified filler comprises

a hydrophobic polymer made of polymerisable monomers polymerised in the presence of a polysaccharide, which polymer is added to the filler as a polymer dispersion or a polymer solution, and which polymer is polymerised using a polysaccharide, as a stabilising agent, wherein the polymer is formed from a monomer mixture containing

a) acrylonitrile or methacrylonitrile or a mixture thereof,

b) acrylates, and

c) styrene or other copolymerisable monomers unsubstitued by ethylene.

27. The paper or board according to claim 19 , wherein the polysaccharide is selected from the group consisting of starch, mannan, carboxymethylcellulose and/or mixtures thereof.

28. The paper or board as in claim 19 , wherein the filler is selected from the group consisting of calcium carbonate, kaolin, talc, titanium dioxide, sodium silicate, aluminiumtrihydrate and mixtures thereof.