Process of manufacturing a multistage polymer, its composition, its use and composition comprising it

1. A process for manufacturing a polymer composition comprising a multistage polymer comprising the steps of:

a) polymerizing by emulsion polymerization of a monomer or monomer mixture (A m ) to obtain during this stage one layer (A) comprising polymer (A1) having a glass transition temperature of less than 0° C.,

b) polymerizing by emulsion polymerization in presence of the polymer obtained in step a) of a monomer or monomer mixture (B m ) to obtain during this subsequent stage a layer (B) comprising a polymer (B1) having a glass transition temperature of at least 45° C.,

c) coagulating the multistage polymer with an alkali metal salt,

d) washing the multistage polymer,

e) adjusting the pH value after the coagulation to a value between 5 to 10, and

f) addition of an aqueous solution or dispersion comprising a phosphorus containing compound wherein the phosphorus has the oxidation stage of +III or +V,

wherein said polymer composition comprises at least 350 ppm of phosphorus and less than 30 ppm of earth alkali metals as traces or impurities.

2. The process according to claim 1 , wherein step a) and b) use in the emulsion polymerization a surfactant chosen from the group consisting of an anionic surface-active agent.

3. The process according to claim 1 wherein said earth alkali metal salt is a sodium or potassium salt.

4. The process according to claim 1 comprising an additional step g):

drying the polymer composition.

5. The process according to claim 1 wherein said polymer composition comprises at most 2000 ppm of phosphorus that has the oxidation stage of +III or +V.

6. The process according to claim 1 wherein said polymer composition comprises between 350 ppm and 2000 ppm of phophorus that has the oxidation stage of +III or +V.

7. The process according to claim 1 wherein no multivalent cations are voluntarily added.

8. The process according to claim 1 wherein initiator does not contain any voluntarily added earth alkali metals.

9. The process according to claim 1 wherein no earth alkali metals either as ions or in form of salts are voluntarily added during the process.

10. The process according to claim 1 wherein earth alkali metals as traces or minor impurity present less than 9 ppm of the multistage polymer composition.

11. The process according to claim 1 wherein said multivalent cations present less than 50 ppm of the multistage polymer composition.

12. The process according to claim 1 wherein the multivalent cations present less than 20 ppm of the multistage polymer composition.

13. The process according to claim 1 having an adjusted pH after coagulation between 6 and 9.

14. The process according to claim 1 wherein the phosphorous containing compound is chosen from the group consisting of organophosphorus compound, a phosphate salt, phosphoric acid, phosphonate salts, phosphonic acid and their respective esters and mixtures thereof.

15. The process according to claim 1 wherein in step f) the aqueous solution or dispersion comprising a phosphorus containing compound wherein the phosphorus has the oxidation stage of +III or +V is added by washing the multistage polymer which contains less than 60 wt % of water with said aqueous solution or dispersion comprising a phosphorus containing compound wherein the phosphorus has the oxidation stage of +III or +V.

16. The process according to claim 1 wherein in step f) the aqueous solution or dispersion comprising a phosphorus containing compound wherein the phosphorus has the oxidation stage of +III or +V is added on the wet cake after coagulation step and filtration step.

17. The process according to claim 1 wherein in step f) the aqueous solution or dispersion comprising a phosphorus containing compound wherein the phosphorus has the oxidation stage of +III or +V is added during drying step of the multistage polymer, when the multistage polymer composition comprises still at least 10 wt % of water.

18. A process for manufacturing a polymer composition comprising a multistage polymer and a thermoplastic polymer comprising the steps of:

a) polymerizing by emulsion polymerization of a monomer or monomer mixture (A m ) to obtain during this stage one layer (A) comprising polymer (A1) having a glass transition temperature of less than 0° C.,

b) polymerizing by emulsion polymerization in presence of the polymer obtained in step a) of a monomer or monomer mixture (B m ) to obtain during this subsequent stage a layer (B) comprising a polymer (B1) having a glass transition temperature of at least 45° C.,

c) coagulating the multistage polymer with an alkali metal salt,

d) washing the multistage polymer,

e) adjusting the pH value after the coagulation to a value between 5 to 10,

f) addition of an aqueous solution or dispersion comprising a phosphorus containing compound wherein the phosphorus has the oxidation stage of +III or +V,

g) drying the multistage polymer, and

h) mixing the multistage polymer with a thermoplastic polymer wherein said polymer composition comprises at least 350 ppm of phosphorus and less than 30 ppm of earth alkali metals as traces or impurities.

19. A thermoplastic polymer composition comprising the polymer composition obtained by the process according to claim 1 .