[Field of the invention]

[001] The present invention relates to a polymer composition comprising a phosphorus comprising moiety, its method of preparation, its use and a composition comprising it.

[002] In particular the present invention relates to a polymer composition in form of a multistage polymer comprising a phosphorus comprising moiety, its composition and its process of preparation and its use in thermoplastic compositions.

[003] More particularly the present invention relates to a process for manufacturing a polymer composition in form of a multistage polymer comprising a phosphorus comprising moiety, said multistage polymer in a thermoplastic composition gives a composition having a satisfying thermal and hydrolytic stability.

[Technical problem]

[004] Impact modifiers are widely used to improve the impact strength for thermoplastic compositions with the aim to compensate their inherent brittleness or the embrittlement that occurs at sub zero temperatures, notch sensitivity and crack propagation. So an impact modified polymer is a polymeric material whose impact resistance and toughness have been increased by the incorporation of phase nano domains of a rubbery material.

[005] This is usually done due to the introduction of microscopic rubber particles into the polymer matrix that can absorb the energy of an impact or dissipate it. One possibility is to introduce the rubber particles in form of core-shell particles. These core-shell particles that possess very generally a rubber core and a polymeric shell, having the advantage of a proper particle size of the rubber core for effective toughening and the grafted shell in order to have the adhesion and compatibility with the thermoplastic matrix.

[006] The performance of the impact modification is a function of the particles size, especially of the rubber part of the particle, and its quantity. There is an optimal average particle size in order to have the highest impact strength for a given quantity of added impact modifier particles.

[007] These primary impact modifier particles are usually added in form of powder particles to the thermoplastic material. These powder particles are agglomerated primary impact modifier particles. During the blending of the thermoplastic material with the powder particles the primary impact modifier particles are regained and are dispersed more or less homogenously dispersed in the thermoplastic material.

[008] While the particle size of the impact modifier particles in the range of nanometers, the range of the agglomerated powder particles is in the range of micrometers.

[009] Agglomeration during the recovery can be obtained by several processes, as for example, spray drying, coagulation, shearing, or freeze drying or combination of spray drying and coagulation techniques .

[010] It is important to avoid negative influence of the impact modifier powder on the thermoplastic polymer composition to which the impact modifier is added. As negative influence, it is understood, for example the color stability, the thermal stability, the hydrolysis stability of the thermoplastic polymers comprising the impact modifier, either on function of the time or the temperature or both.

[ Oil ] All these influences might occur due to the architecture of the core-shell but more particularly the impurities and side products employed during the synthesis and treatment of the impact modifier powder. Usually, there is no special purification step of the impact modifier, just a separation of solid versus liquid. Therefore more or less important quantities of any chemical compound (impurities, by-products) employed are still incorporated in the impact modifier. The concerned quantities of them may vary. However these chemical compounds should not influence at all or have only a minor influence on the thermoplastic material in a major way as for example degradation of optical and/or mechanical and/or rheological properties with time and/or temperature and/or hygrometry . [012] Extensive washing or purification might get rid of some of the compounds coming from impurities or products used during the synthesis that might have negative influence of the impact modifier powder on the performance thermoplastic polymer composition .

[013] Sometimes other products are added to suppress or avoid the effects coming from impurities or byproducts.

[014] On the other hand all processes are extremely cost sensitive. A slight improvement in composition and/or process can result in a significant market advantage for performance of the polymer composition .

[015] The objective of the present invention is to propose a multistage polymer composition having a satisfying thermal stability and hydrolytic stability.

[016] An additional objective of the present invention is also to have a multistage polymer composition having a satisfying thermal stability and hydrolytic stability that can be used as impact modifier .

[017] Still another objective of the present invention is to propose a process for manufacturing a multistage polymer composition having a satisfying thermal stability and hydrolytic stability .

[018] An additional objective of the present invention is a thermoplastic composition comprising a multistage polymer composition, said thermoplastic composition is having a satisfying thermal stability and hydrolytic stability.

[019] Still an additional objective is having a process for preparing for manufacturing a multistage polymer composition, said multistage polymer composition in a thermoplastic composition, gives composition is having a satisfying thermal stability.

[BACKGROUND OF THE INVENTION ]Prior art

[020] The document EP2189497 discloses polymer compositions containing phosphate salts and especially the process for obtaining them. The polymer composition is a polymer obtained by a multi stage process and is an impact modifier. The phosphate salts are introduced after the syntheses of the polymer composition. The process implies a washing step with water to get first rid of salts and ions and then adding an aqueous alkaline phosphate solution. The process requires a lot of water and consequently also the time and energy consuming steps of separation of water from polymer composition. Additionally the exact quantity of phosphorous in the composition is difficult to control as the phosphate salts are water soluble and easily washed away.

[021] The document WO2013/116318 discloses multistage polymer particles that show compatibility with pigment particles. The polymer particles comprise a polymeric unit coming from a phosphorous acid monomer in a concentration from 3 to 8wt% and are used in paint formulations.

[022] The document W02015/192363 discloses multi stage latex polymers comprising a first stage polymer and a second stage polymer, both polymers are comprising a phosphorous acid monomer. The first stage comprises from 2 to 8wt% of a phosphorous acid monomer and the second stage between from 41wt% to 150wt% of the quantity used in the first stage. The latex is used for making a coatings. The phosphorous containing monomer is used in order to improve scrub resistance, stain resistance corrosion resistance and durability of the coating.

[ 023 ] The document WO2016/083383 relates to a multistage polymer that is used as impact modifier in thermoplastic compositions, its composition and its process of preparation. The process comprises a step of adding an aqueous solution or dispersion comprising a phosphorous containing compound after the polymerization. The exact quantity of phosphorous in the composition is difficult to control .

[ 024 ] The document WO2016/038396 relates to relates to a multistage polymer, its composition and its process of preparation and its use in thermoplastic compositions. The multistage polymer comprises a phosphorous containing compound. The phosphorous containing compound is organophosphorous compound, a phosphate salt, phosphoric acid, phosphonate salts, phosphonic acid or their respective esters and is added to the multistage polymer. The exact quantity of phosphorous in the composition is difficult to control .

[025] The document W02010/063381 discloses impact modified polycarbonate compositions with which have an emulsion graft polymer precipitated under basic conditions and comprising acidic phosphorus compound. The moldings comprises ABS type impact modifiers and esters of phosphoric acid having a P-OH functionality .

[026] The document W02017/068045 discloses a method for producing polycarbonate molding compositions with improved thermal processing stability. The moldings can comprises ABS type impact modifiers, esters of phosphoric acid and inorganic phosphor compounds .

[027] The document US 3,830,878 discloses a weather and impact resistant resin composition comprising a graft copolymer containing a multilayer polymer particles. One of the examples uses a very low quantity of multifunctional phosphate ester as crosslinking agent in one layer.

[028] The document W02006/059352 discloses an aqueous polymer dispersion. The particles of the dispersion can comprise a phosphor comprising group selected form phosphates or phosphonates or phosphinates . A preferred monomer is hydroxylethyl methacrylate phosphate monoester; which is used between 1 to 3 parts for lOOparts of monomers.

[029] The document US 5,219907 discloses a flameproofed molding composition. The composition comprises up to 50wt% of an organic phosphorus compound.

[030] The document 5,328,958 discloses a thermoplastic resin based on vinyl aromatic/vinyl phosphonic acid copolymers and amine terminated monomers. The resins are used for packaging films being transparent and having fire retardant effect.

[031] The present invention aims to avoid at least one of the inconvenient of the state of the art.

[032] There is a need for improving the process of making a multistage polymer, by optimizing the steps involved, while allowing the obtained multistage polymer an increase of the performance as impact additive in thermoplastic compositions .

[Brief description of the invention]

[033] Surprisingly it has been found that a polymer composition PCI comprising

at least a layer (A) comprising polymer (Al) having a glass transition temperature of less than 0°C and at least a layer (B) comprising a polymer (Bl) having a glass transition temperature of at least 45°C, characterized in that the polymer composition PCI comprises a covalently bonded phosphorus comprising moiety, yields to a polymer composition PCI that gives impact modification and increases thermal stability and hydrolytic stability when added to a polymer composition PC2.

[034] Surprisingly it has also been found that a polymer composition PCI in form of polymeric particles made by a multistage process comprising

at least one stage giving a layer (A) comprising polymer (Al) having a glass transition temperature of less than 0°C and

at least one subsequent stage giving a layer (B) comprising a polymer (Bl) having a glass transition temperature of at least 45°C,

obtained by a multistage process characterized in that the polymer composition PCI comprises a covalently bonded phosphorus comprising moiety, yields to a polymer composition PCI that gives impact modification and increases thermal stability and hydrolytic stability, when added to a polymer composition PC2.

[035] Surprisingly it has also been found that a process for manufacturing the polymer composition PCI comprising a multistage polymer comprising the steps of

a) polymerizing by emulsion polymerization of a monomer or monomers mixture (A _m) to obtain during this stage one layer (A) comprising polymer (Al) 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 (Bl) having a glass transition temperature of at least 45°C characterized in that the monomers mixture (A _m) or monomer mixture (B _m) comprises a copolymerizable molecule comprising a phosphor moiety, yields to a polymer composition PCI that gives impact modification and increases thermal stability and hydrolytic stability, when added to a polymer composition PC2.

[036] Surprisingly it has been found that a polymer composition PCI comprising

at least a layer (A) comprising polymer (Al) having a glass transition temperature of less than 0°C and at least a layer (B) comprising a polymer (Bl) having a glass transition temperature of at least 45°C, characterized in that the polymer composition PCI comprises a covalently bonded phosphor comprising moiety yields to an impact modifier that can be used to improve thermal stability and hydrolytic stability of thermoplastic polymers.

[Detailed description of the invention]

[037] According to a first aspect, the present invention relates to a polymer composition PCI comprising

at least a layer (A) comprising polymer (Al) having a glass transition temperature of less than 0°C and at least a layer (B) comprising a polymer (Bl) having a glass transition temperature of at least 45°C, characterized in that the polymer composition PCI comprises a covalently bonded phosphorous comprising moiety.

[038] According to a second aspect, the present invention relates to a polymer composition PCI in form of polymeric particles of a multistage polymer made by a multistage process comprising at least one stage giving layer (A) comprising polymer (Al) having a glass transition temperature of less than 0°C and

at least one subsequent stage giving layer (B) comprising a polymer (Bl) having a glass transition temperature of at least 45°C,

obtained by a multistage process characterized in that the polymer composition PCI comprises a covalently bonded phosphorous comprising moiety.

[039] According to a third aspect the present invention relates to a process for manufacturing a polymer composition PCI 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 (Al) 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 monomers mixture (B _m) to obtain during this subsequent stage a layer

(B) comprising a polymer (Bl) having a glass transition temperature of at least 45°C

c) optionally agglomerating the multistage polymer

d) optionally adjusting the pH to a value between 5 and 10 characterized in that the monomers mixture (A _m) or monomer mixture (B _m) comprises a copolymerizable molecule comprising a phosphor moiety .

[040] According to a fourth aspect, the present invention relates to the use of a polymer composition PCI comprising

at least a layer (A) comprising polymer (Al) having a glass transition temperature of less than 0°C and at least a layer (B) comprising a polymer (Bl) having a glass transition temperature of at least 45°C, characterized in that the polymer composition PCI comprises a covalently bonded phosphorous comprising moiety, as impact modifier for improving the thermal stability and hydrolytic stability of thermoplastic polymers.

[041] By the term "polymer powder" as used is denoted a polymer comprising powder grain in the range of at least 1 micrometer (pm) obtained by agglomeration of primary polymer comprising particles in the nanometer range.

[042] By the term "primary particle" as used is denoted a spherical polymer comprising particle in the nanometer range. Preferably the primary particle has a weight average particle size between 20nm and 1 OOOnm. By particle size in the present invention, the particle diameter is meant.

[043] By the term "particle size" as used is denoted the volume average diameter of a particle considered as spherical.

[044] By the term "copolymer" as used is denoted that the polymer consists of at least two different monomers.

[045] By "multistage polymer" as used is denoted a polymer formed in sequential fashion by a multi-stage polymerization process. Preferred is a multi-stage emulsion polymerization process in which the first polymer is a first-stage polymer and the second polymer is a second-stage polymer, i.e., the second polymer is formed by emulsion polymerization in the presence of the first emulsion polymer, with at least two stages that are different in composition .

[046] By the term " (meth) acrylic" as used is denoted all kind of acrylic and methacrylic monomers.

[047] By the term " (meth) acrylic polymer" as used is denoted that the (meth) acrylic polymer comprises essentially polymers comprising (meth) acrylic monomers that make up 50wt% or more of the (meth) acrylic polymer.

[048] By the term "impact modifier" as used is denoted a compound comprising an elastomer or rubber that can be added or incorporated in a thermoplastic compound to improve its impact resistance .

[049] By the term "rubber" as used is denoted the thermodynamic state of the polymer above its glass transition [050] By saying that a range from x to y in the present invention, it is meant that the upper and lower limit of this range are included, equivalent to at least x and up to y.

[051] By saying that a range is between x and y in the present invention, it is meant that the upper and lower limit of this range are excluded, equivalent to more than x and less than y.

[052] With regard to the polymer composition of the invention, comprising a covalently bonded phosphorous comprising moiety, it comprises at least one layer (A) comprising a polymer (Al) having a glass transition temperature below 0°C and at least another layer (B) comprising a polymer (Bl) having a glass transition temperature over 45°C.

[053] The ratio of layer (A) /layer (B) in the polymer composition is not particularly limited, but preferably it is in a range in weight between 10/90 and 95/5, more preferably between 40/60 and 95/5 advantageously between 60/40 to 90/10, more advantageously between 70/30 and 90/10 and most advantageously between 70/30 and 85/15.

[054] With regard to the multistage polymer of the invention, it is a polymer particle having a multilayer structure comprising at least one layer (A) comprising a polymer (Al) having a glass transition temperature below 0°C and at least another layer (B) comprising a polymer (Bl) having a glass transition temperature over 45°C.

[055] The ratio of layer (A) /layer (B) in the multistage polymer is not particularly limited, but preferably it is in a range in weight between 10/90 and 95/5, more preferably between 40/60 and 95/5, advantageously between 60/40 to 90/10, more advantageously between 70/30 and 90/10 and most advantageously between 70/30 and 85/15.

[056] The polymer particle having a multilayer structure is spherical. The polymer particle having a multilayer structure is also called the primary particle. The polymer particle has a weight average particle size (diameter) between 20nm and 1 OOOnm. Preferably the weight average particle size of the polymer particle is between 50nm and 900nm, more preferably between 75nm and 800nm and advantageously between 80nm and 700nm.

[057] The polymer particle according to the invention is obtained by a multistage process such as two or three stages or more stages .

[058] Preferably the polymer (Al) having a glass transition temperature below 0°C in the layer (A) is not made during the last stage of the multistage process. The polymer (Al) is having a glass transition temperature below 0°C in the layer (A) never forms the external layer or outer shell of the polymer particle having the multilayer structure.

[059] Preferably the polymer (Bl) having a glass transition temperature above 45°C in the layer (B) is the external layer of the polymer particle having the multilayer structure.

[060] There could be additional intermediate layers made by intermediate steps between the polymer (Al) having a glass transition temperature below 0°C in the layer (A) and the layer (B) comprising a polymer (Bl) having a glass transition temperature over 45°C. This would lead to a multilayered particle.

[061] The glass transition temperature (Tg) of the polymer (Al) is less than 0°C, preferably less than -10°C, advantageously less than -20°C and most advantageously less than -25°C and more most advantageously less than -40°C.

[062] More preferably the glass transition temperature Tg of the polymer (Al) is between -120°C and 0°C, even more preferably between -90°C and -10°C and advantageously between -80°C and - 25 °C .

[063] Preferably the glass transition temperature Tg of the polymer (Bl) is between 45°C and 150°C. The glass transition temperature of the polymer (Bl) is more preferably between 60°C and 150°C, still more preferably between 80°C and 150°C and advantageously between 90°C and 150°C

[064] The glass transition temperature Tg can be estimated for example by dynamic methods as thermo mechanical analysis. [065] The polymer composition of the invention in form of polymeric particles of a multistage polymer can also be in form of a polymer powder. The polymer powder comprises agglomerated primary polymer particles made by the multistage process.

[066] With regard to the polymer powder of the invention, it has a volume median particle size D50 between Ipm and 500pm. Preferably the volume median particle size of the polymer powder is between 10pm and 400pm, more preferably between 15pm and 350pm and advantageously between 20pm and 300pm.

[067] The D10 of the particle size distribution in volume is at least 7pm and preferably 10pm.

[068] The D90 of the particle size distribution in volume is at most 800pm and preferably 500pm, more preferably at most 350pm.

[069] With regard to the polymer (Al) , mention may be made of homopolymers and copolymers comprising monomers with double bonds and/or vinyl monomers.

[070] In a first embodiment the polymer (Al) is chosen from isoprene homopolymers or butadiene homopolymers, isoprene- butadiene copolymers, copolymers of isoprene with at most 98 wt% of a vinyl monomer and copolymers of butadiene with at most 98 wt% of a vinyl monomer. The vinyl monomer may be styrene, an alkyl styrene , acrylonitrile, an alkyl (meth) acrylate, or butadiene or isoprene. In a specific embodiment polymer (Al) is a butadiene homopolymer .

[071] In a second embodiment the polymer (Al) is a (meth) acrylic polymer. A (meth) acrylic polymer according to the invention is a polymer comprising at least 50wt% preferably at least 60wt% and more preferably at least 70wt% of monomers coming from acrylic or methacrylic monomers. The (meth) acrylic polymer according to the invention comprise less than 50wt% preferably less than 40wt% and more preferably less than 30wt% of non-acrylic or non-methacrylic monomers, which can copolymerize with the acrylic or methacrylic monomers .

[072] More preferably the polymer (Al) of the second embodiment comprises at least 70wt% monomers chosen from Cl to C12 alkyl (meth ) acrylates . Still more preferably the polymer (Al) comprises at least 80 wt% of monomers Cl to C4 alkyl methacrylate and/or Cl to C8 alkyl acrylate monomers.

[073] Most preferably the acrylic or methacrylic monomers of the polymer (Al) are chosen from methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, 2-octyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and mixtures thereof, as long as polymer (Al) is having a glass transition temperature of less than 0°C.

[074] The polymer (Al) may be completely or partly crosslinked. All that is required is to add at least one multifunctional monomer during the preparation of the polymer (Al) . The functionality of the multifunctional monomer refers to a function that can polymerize. These multifunctional monomers may be for example a difunctional monomer chosen from poly (meth ) acrylic esters of polyols, such as butanediol di (meth) acrylate and trimethylolpropane trimethacrylate. Other multifunctional monomers are, for example, divinylbenzene, trivinylbenzene , and triallyl cyanurate. The core can also be crosslinked by introducing into it, by grafting or as a comonomer during the polymerization, unsaturated functional monomers such as anhydrides of unsaturated carboxylic acids, unsaturated carboxylic acids and unsaturated epoxides. Mention may be made, by way of example, of maleic anhydride, (meth) acrylic acid and glycidyl methacrylate. The crosslinking may also be carried out by using the intrinsic reactivity of the monomers, for example in the case of the diene monomers .

[075] With regard to the polymer (Bl) , mention may be made of homopolymers and copolymers comprising monomers with double bonds and/or vinyl monomers.

[076] The polymer (Bl) is chosen from styrene homopolymers, alkylstyrene homopolymers or methyl methacrylate homopolymers, or copolymers comprising at least 70 wt% of one of the above monomers and at least one comonomer chosen from the other above monomers, another alkyl (meth) acrylate , vinyl acetate and acrylonitrile. The shell may be functionalized by introducing into it, by grafting or as a comonomer during the polymerization, unsaturated functional monomers such as anhydrides of unsaturated carboxylic acids, unsaturated carboxylic acids and unsaturated epoxides. Mention may be made, for example, of maleic anhydride, (meth) acrylic acid glycidyl methacrylate, hydroxyethyl methacrylate and alkyl (meth) acrylamides .

[077] Preferably the polymer (Bl) is also a (meth) acrylic polymer.

[078] Preferably the polymer (Bl) comprises at least 70wt% monomers chosen from Cl to C12 alkyl (meth ) crylates . Still more preferably the polymer (Bl) comprises at least 80 wt% of monomers Cl to C4 alkyl methacrylate and/or Cl to C8 alkyl acrylate monomers.

[079] Most preferably the acrylic or methacrylic monomers of the polymer (Bl) are chosen from methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and mixtures thereof, as long as polymer (Bl) is having a glass transition temperature of at least 60°C.

[080] Advantageously the polymer (Bl) comprises at least 70wt% of monomer units coming from methyl methacrylate.

[081] The polymer (Bl) may be crosslinked by adding at least one multifunctional monomer during the preparation of the polymer (Bl) .

[082] The polymer composition or multistage polymer of the invention, having a multilayer structure has a pH value between 5 and 10 and preferable between 6 and 9, more preferable between 6 and 7.5 and advantageously between 6 and 7.

[083] The polymer conposition or multistage polymer of the invention comprises a covalently bonded phosphorous comprising moiety.

[084] Preferably the phosphorous has the oxidation stage of +III or +V. More preferably the phosphorous has the oxidation stage of +V.

[085] The polymer composition or multistage polymer comprises at least 350ppm, preferably at least 360ppm, more preferably at least 370ppm, still more preferably at least 380ppm, advantageously at least 385ppm and more advantageously at least 390ppm, even more advantageously at least 395ppm and most advantageously at least 400ppm of phosphorous that has the oxidation stage of +III or +V. The phosphorous is part of the covalently bonded phosphorous comprising moiety. The content of the phosphorous is calculated and expressed as phosphorous in view of the polymer composition or multistage polymer composition.

[086] The polymer composition or multistage polymer comprises at most 2000ppm, preferably at most 1900ppm, more preferably at most 1800ppm, even more preferably at most 1500ppm, advantageously at most 1250ppm, more advantageously at most lOOOppm, even more advantageously at most 850ppm and most advantageously at most 700ppm of phosphorous that has the oxidation stage of +III or +V.

[087] The polymer composition or multistage polymer comprises between 350 ppm and 2000ppm, preferable between 360pmm and 1900ppm and more preferably between 370ppm and 1800ppm even more preferably betwwen 380ppm and 1500ppm, advantageously between 385ppm and 1250ppm, more advantageously between 390ppm and lOOOppm, even more advantageously between 395ppm and 850ppm and most advantageously between 400ppm and 700ppm of phosphorous that has the oxidation stage of +III or +V.

[088] The quantity of phosphorous in the polymer composition or multistage polymer can be estimated by Inductively Coupled Plasma- Atomic Emission Spectroscopy (ICP-AES) .

[089] The oxidation stage is linked to the nature of the covalently bonded phosphorous comprising moiety in the composition.

[090] The phosphorous comprising moiety is preferably chosen from a moiety comprising P-C and/or P-O-C bonds.

[091] In a first preferred embodiment the covalently bonded phosphorous comprising moiety is part of polymer (Al) .

[092] In a second preferred embodiment the covalently bonded phosphorous comprising moiety is part of polymer (Bl) .

[093] More preferably the covalently bonded phosphorous comprising moiety is part of polymer (Bl) having a glass transition temperature of at least 45 °C.

[094] Even more preferably the phosphorous comprising moiety is a lateral group in the polymer chain of polymer (Bl) . [095] In a first preferred embodiment the phosphorous comprising moiety has following formula (1)

[096] wherein Ri and R ₂ can be the same or different and is H or an aliphatic or aromatic radical and R ₃ is an organic group comprising carbon, hydrogen atoms. R ₃ comprises a functionality that can copolymerize. The phosphorous comprising moiety is covalently bonded via R ₃ after copolymerization to the polymer chain of polymer (Al) or (Bl) .

[097] Preferably the phosphorous comprising moiety which is covalently bonded via R ₃ to the polymer chain of polymer (Bl); comprises in R ₃ following group given by formula (lb) :

[098] wherein R ₄ is H or CH ₃ .

[099] In a second preferred embodiment the phosphorous comprising moiety before polymerization has following formula (2)

[0100] wherein m is a number from 0 to 10 and preferably an integer number from 0 to 10, more preferably an integer number from 1 to 9, advantageously an integer number from 1 to 8 and more advantageously an integer number from 1 to 8. The phosphorous comprising moiety is covalently bonded after copolymerization to the polymer chain of polymer (Bl) .

[0101] In a third preferred embodiment the phosphorous comprising moiety before polymerization has following formula (3)

[0102] wherein Ri and R ₂ can be the same or different and is H or an aliphatic or aromatic radical and preferably an aliphatic radical having from 1 to 10 carbon atoms; R ₄ is H or CH ₃ ; and n is a number from 1 to 10 and preferably an integer number from 1 to 10, more preferably an integer number from 1 to 9, advantageously an integer number from 1 to 8 and more advantageously an integer number from 1 to 8. The phosphorous comprising moiety is covalently bonded after copolymerization to the polymer chain of polymer (B1 ) .

[0103] Specific examples of the phosphorous comprising moiety according to formula (3) can include diethyl methacryloyloxymethyl phosphonate, diethyl 2 -methacryloyloxyethyl phosphonate, diethyl

1-methacryloyloxyethyl phosphonate, dimethyl 3- methacryloyloxypropyl phosphonate, dimethyl 2- methacryloyloxypropyl phosphonate, dimethyl 4-methacryloyloxybutyl phosphonate, dimethyl 3-methacryloyloxybutyl phosphonate, dimethyl

2-methacryloyloxybutyl phosphonate; diethyl acryloyloxymethyl phosphonate, diethyl 2 -acryloyloxyethyl phosphonate, dimethyl 3- acryloyloxypropyl phosphonate, dimethyl 2-acryloyloxypropyl phosphonate, dimethyl 4-acryloyloxybutyl phosphonate, dimethyl 3- acryloyloxybutyl phosphonate, dimethyl 2-acryloyloxybutyl phosphonate; and the like. As the phosphorous comprising moiety according to formula (3), these compounds may be used alone or in combination of 2 or more.

[0104] With regard to the 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 (Al) 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 (Bl) having a glass transition temperature of at least 45°C, c) optionally coagulating the multistage polymer, d) optionally adjusting the pH to a value between 5 to

10,

e) optionally washing the multistage polymer, characterized that the monomers mixture (A _m) or monomer mixture (B _m ) comprises a copolymerizable molecule comprising a phosphor moiety .

[0105] The copolymerizable molecule comprising the phosphor moiety comprises the structure according to formula (1), wherein R ₃ comprises an unsaturated carbon bond C=C, or is a molecule according to formulas (2) or (3) .

[0106] The quantity of the copolymerizable molecule comprising a phosphor moiety in the process is chosen so that the before mentioned quantities of phosphorous that has the oxidation stage of +III or +V in polymer composition or multistage polymer are full fileld.

[0107] Preferably the quantity of the copolymerizable molecule comprising a phosphor moiety in the process is chosen so that the obtained polymer composition or multistage polymer comprises between 350 ppm and 2000ppm, preferable between 360pmm and 1900ppm and more preferably between 370ppm and 1800ppm even more preferably betwwen 380ppm and 1500ppm, advantageously between 385ppm and 1250ppm, more advantageously between 390ppm and lOOOppm, even more advantageously between 395ppm and 850ppm and most advantageously between 400ppm and 700ppm of phosphorous that has the oxidation stage of +III or +V.

[0108] In optional step d) the pH value is adjusted between 6 and 9 more preferable between 6 and 7.5 and advantageously between 6 and

7.

[0109] The process might comprise the additional step g) of drying the polymer composition. A dry polymer composition according to the invention is a composition that comprises less than 1% of humidity or water. The humidity of a polymer composition can be measure with a thermo balance.

[0110] The drying of the polymer can be made in an oven or vacuum oven with heating of the composition for 48hours at 50°C.

[0111] The respective monomers or monomer mixtures (A _m) and (B _m) for forming the layers (A) and (B) respectively comprising the polymers (Al) and (Bl) respectively and the characteristics of the respective polymers (Al) and (Bl) are the same as defined before for the definition of the polymers (Al) and (Bl) for the composition. Either the monomers mixture (A _m) or monomer mixture (B _m) comprises a copolymerizable molecule comprising a phosphor moiety. Preferably monomer mixture (B _m) comprises a copolymerizable molecule comprising a phosphor moiety.

[0112] The emulsion polymerization during the stage for layer (A) can be a grow-out process, a seeded grow-out process or a microagglomeration process.

[0113] Chain transfer agents are also useful in forming the polymer (Al) . Useful chain transfer agents include those known in the art, including but not limited to ter- dodecylmercaptan, n- dodecylmercaptan, n-octylmercaptan, and mixtures of chain transfer agents. The chain transfer agent is used at levels from 0 to 2 percent by weight, based on the total core monomer content in monomer mixture (A _m) .

[0114] Preferably the polymer (Bl) is grafted on the polymer made in the previous stage and more preferably on the polymer (Al) made in the previous stage.

[0115] Polymerization initiators useful in producing the polymer (Al) and (Bl) include, but are not limited to a persulfate salt such as potassium persulfate, ammonium persulfate, and sodium persulfate; an organic peroxide such as tert-butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide, lauroyl peroxide, p- menthane hydroperoxide, and diisopropylbenzene hydroperoxide; an azo compound such as azobisisobutyronitrile, and azobisisovaleronitrile; or a redox initiator. However, it is preferable to use catalytic systems of redox type formed by the combination of a peroxide compound, for example as mentioned above, with a reducing agent, in particular such as alkali metal sulfite, alkali metal bisulfite, sodium formaldehyde sulfoxylate (NaHSCkHCHO) , an alkali salt of an organic sulfinic acid derivative, ascorbic acid, glucose, and in particular those of the said catalytic systems which are water-soluble, for example potassium persulfate/sodium metabisulfite or alternatively diisopropylbenzene hydroperoxide/sodium formaldehyde sulfoxylate or even more complicate systems as for example ferrous sulfate/dextrose/ sodium pyrophosphate .

[0116] The initiators do not contain any voluntary added earth alkali metals (group IIA from the periodic system of elements) . The initiator might contain however other multivalent cations that are not earth alkali metals.

[0117] For the emulsion polymerization during the two stages for making layer (A) comprising polymer (Al) and layer (B) comprising a polymer (Bl) as emulsifying agent any one of the known surface- active agents, whether anionic, nonionic or even cationic may be used. In particular, the emulsifying agent may be chosen from anionic emulsifying agents, such as sodium or potassium salts of fatty acids, in particular sodium laurate, sodium stearate, sodium palmitate, sodium oleate, mixed sulphates of sodium or of potassium and of fatty alcohols, in particular sodium lauryl sulphate, sodium or potassium salts of sulphosuccinic esters, sodium or potassium salts of alkylarylsulphonic acids, in particular sodium dodecylbenzenesulphonate, and sodium or potassium salts of fatty monoglyceride monosulphonates, or alternatively from nonionic surfactants, such as the reaction products of ethylene oxide and of alkylphenol or of aliphatic alcohols, alkylphenols . Use may also be made of mixtures of such surface-active agents, if necessary.

[0118] More preferably the emulsifying agent is chosen from an anoinic surface-active agent. Advantageously the emulsifying agent is chosen from anionic surface-active agents that comprise a carboxylate group or a phosphate group.

[0119] More advantageously the emulsifying agent is a carboxylate or carboxylic acid salt.

[0120] Optional coagulation in step c) of the process of the invention is made by aggregation of the primary polymer particles at the end of the emulsion polymerization by adding an aqueous electrolyte solution under stirring. The coagulation is not made with multivalent cations. Multivalent cations are to be avoided in the electrolyte solution. No multivalent cations are voluntary added to the electrolyte solution.

[0121] Preferably the coagulation is made with a solution comprising an inorganic acid or a salt of an alkali metal. More preferably the inorganic acid is chosen from but not limited to HC1, H ₂ SO ₄ , H ₃ PO ₄ . Advantageously a 1 molar aqueous solution of the inorganic acid has a rH<1.

[0122] More preferably the alkali metal salt is a sodium or potassium salt. For example the alkali metal salt can be chosen from NaCl, KC1, Na2S04, NasPCq Na2HPC>4, but is not limited on this list .

[0123] Adj usting the pH in optional step d) of the process of the invention is preferably made by adding sodium or potassium hydroxide or aqueous buffer solution after the coagulation step.

[0124] The washing in optional step e) of the process of the invention is made by water, diluted aqueous solutions or aqueous buffer solutions. After the washing step the pH is between 5 and 10. The coagulated multistage polymer after step e) is in form of a wet cake. The wet cake contains less than 60% of water.

[0125] The present invention relates also to the use of the polymer composition PCI as impact modifier in thermoplastic polymers . [0126] The present invention relates further to a thermoplastic polymer composition PC2 comprising the polymer composition PCI and a thermoplastic polymer TP1.

[0127] With regard to the thermoplastic polymer TP1 that is part of the thermoplastic polymer composition PC2 according to the invention it can be chosen among poly (vinyl chloride) (PVC), chlorinated poly (vinyl chloride) (C-PVC) , polyesters as for example poly (ethylene terephtalate ) (PET) or poly (butylen terephtalate ) (PBT) polyhydroxyalkanoates (PHA) or polylactic acid (PLA) , cellulose acetate, polycarbonates (PC) , poly (methyl methacrylate ) s (PMMA) , (meth) acrylic copolymers, thermoplastic poly (methyl methacrylate-co-ethylacrylates ) , poly (alkylene- terephtalates ) , poly vinylidene fluoride , poly (vinylidenchloride ) , polyoxymethylen (POM) , semi-crystalline polyamides, amorphous polyamides, semi-crystalline copolyamides, amorphous copolyamides, polyetheramides, polyesteramides , copolymers of styrene and acrylonitrile (SAN) , and their respective mixtures or alloys.

[0128] According to a preferred embodiment the thermoplastic polymer composition PC2 comprises polycarbonate (PC) and/or polyester (PET or PBT) or PC or polyester alloys. The alloys for example may be PC/ABS (poly (acrylonitrile-co-butadiene-co- styrene) , PC/ASA, PC/polyester or PC/PLA.

[0129] Preferably, if the thermoplastic polymer TP1 in the thermoplastic polymer composition PC2 comprises polycarbonate (PC) and/or polyester (PET or PBT) or PC or polyester alloys the polymer (A) of the multistage polymer is chosen from isoprene homopolymers or butadiene homopolymers, isoprene-butadiene copolymers, copolymers of isoprene with at most 98wt% of a vinyl monomer and copolymers of butadiene with at most 98wt% of a vinyl monomer .

[0130] Concerning the polycarbonate (PC) , it can be aromatic, semi-aromatic and/or aliphatic (particularly based on isosorbide) .

[0131] With regard to the thermoplastic polymer composition PC2 comprising the polymer composition PCI and a thermoplastic polymer TP1, the proportions between the polymer composition PCI of the invention and the thermoplastic polymer TP1 are between 0.5/99.5 and 50/50, preferably between 1/98 and 30/70, more preferably between 2/98 and 20/80 and advantageously between 2/98 and 15/85.

[Methods of evaluation]

[0132] Glass transition Temperature

The glass transitions (Tg) of the polymers are measured with equipment able to realize a thermo mechanical analysis. A RDAII "RHEOMETRICS DYNAMIC ANALYSER" proposed by the Rheometrics Company has been used. The thermo mechanical analysis measures precisely the visco-elastics changes of a sample in function of the temperature, the strain or the deformation applied. The apparatus records continuously, the sample deformation, keeping the stain fixed, during a controlled program of temperature variation.

The results are obtained by drawing, in function of the temperature, the elastic modulus (G' ) , the loss modulus and the tan delta. The Tg is higher temperature value read in the tan delta curve, when the derived of tan delta is equal to zero.

[0133] Particle size analysis

The particle size of the primary particles after the multistage polymerization is measured with a Zetasizer Nano S90 from MALVERN. The particle size of the polymer powder after coagulation is measured with Malvern Mastersizer 3000 from MALVERN.

For the estimation of weight average powder particle size, particle size distribution and ratio of fine particles a Malvern Mastersizer 3000 apparatus with a 300mm lenses, measuring a range from 0,5-880pm is used.

D (v, 0.5) or more short D50 is the particle size at which 50% of the sample has size less then and 50% of the sample have a size larger then that size, or in other words the equivalent volume diameter at 50% cumulative volume. This size is also known as volume median diameter that is related to the mass median diameter by the density of the particles by the density of the particles assuming a size independent density for the particles. D (v, 0.1) or DIO is the particle size at which 10% of the sample is smaller than that size, or in other words the equivalent volume diameter at 10% cumulative volume.

D (v, 0.9) or D90 is the particle size at which 90% of the sample are smaller than that size.

[0134] Analyses of phosphor content.

The phosphorous content is measured with Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) . The result is expressed in ppm based on phosphor (P) in relation to the composition or multistage polymer. The analysis does not allow to give the structure of the composition containing phosphorus.

[0135] pH measurement

The pH value of the respective products is measured with Procedure to obtain the pH of the final powder:

5 g of dried powder are dispersed in 20 mL of demineralized water under stirring during 10 minutes at 45°C. Then, the slurry is filtrated on a Wattman filter in paper. The pH of the filtrated water is measured at room temperature.

The pH value is obtained using a Fisher Scientific glass probe connected to a Eutech Instrument pH 200 series pH-meter preliminary calibrated with standard buffer solutions.

[Examples]

[0136] Exairqple 1

[0137] Synthesis of polymer composition PCI as multistage polymer (core-shell particles) all quantities are weight parts.

[0138] First stage - polymerization of core: To a 20 litres high- pressure reactor was charged : de-ionized water 116.5 parts, emulsifier potassium salt of beef tallow fatty acid 0.1 part, 1,3- butadiene 21.9 parts, t-dodecyl mercaptan 0.1 parts, and p- menthane hydroperoxide 0.1 parts as an initial kettle charge. The solution was heated, with agitation, to 43°C at which time a redox-based catalyst solution was charged (water 4.5 parts, sodium tetrapyrophosphate 0.3 parts, ferrous sulphate 0.004 parts and dextrose 0.3 parts), effectively initiating the polymerization. Then the solution was further heated to 56°C and held at this temperature for a period of three hours.

[0139] Three hours after polymerization initiation, a second monomer charge (77.8 parts BD, t-dodecyl mercaptan 0.2 parts), one-half of an additional emulsifier and reductant charge (de ionized water 30.4 parts, emulsifier potassium salt of beef tallow fatty acid 2.8 parts, dextrose 0.5 parts) and additional initiator (p-menthane hydroperoxide 0.8 parts) were continuously added over eight hours. Following the completion of the second monomer addition, the remaining emulsifier and reductant charge plus initiator was continuously added over an additional five hours. Thirteen hours after polymerization initiation, the solution was heated to 68°C and allowed to react until at least twenty hours had elapsed since polymerization initiation, producing polybutadiene rubber latex, R1. The resultant polybutadiene rubber latex (Rl) contained 38% solids and had a weight average particle size of about 160 nm.

[0140] Second stage - Polymerization of shell 1 (outer shell) :

Into a 4 litres reactor was charged 75.0 parts, on a solids basis, of polybutadiene rubber latex (Rl) , 37.6 parts de-ionized water, and 0.1 parts sodium formaldehyde sulfoxylate. The solution was agitated, purged with nitrogen, and heated to 77 °C. When the solution reached 77 °C, a mixture of 21.4 parts methyl methacrylate, 1.2 parts of SIPOMER PAM 200 (a phosphorous comprising monomer from the company SOLVAY according to formula (2)), 1.4 parts divinyl benzene and 0.1 parts t-butyl hydroperoxide initiator was continuously added over 70 minutes, followed by a hold period of 80 minutes. Thirty minutes after the onset of the hold period, 0.1 parts of sodium formaldehyde sulfoxylate and 0.1 parts t-butyl hydroperoxide were added to the reactor at once. Following the 80-minute hold period, a stabilization emulsion was added to the graft copolymer latex. The stabilization emulsion was prepared by mixing 3.2 parts de-ionized water (based on graft copolymer mass), 0.1 parts oleic acid, 0.1 parts potassium hydroxyde, and 0.9 parts octadecyl-3- ( 3 , 5-di- tertbutyl- 4-hydroxyphenyl ) propionate . The resultant core shell latex (E2) had a weight average particle size of about 180 nm. [0141] Coagulation: In a jacketed vessel of 3L, equipped with a stirrer is put successively 500 g of latex of core-shell particles (E2) for having a solid content of 14.1 %. Under stirring at 300 r/min, the heat of the solution is raised at 52°C and then injected a 1.6% aqueous sulphuric acid solution resulting in a coagulated material that was heat treated at 96°C. The pH was adjusted with NaOH during the coagulation between 2 and 6. Subsequently, the coagulated material was filtered on centrifuge and washed with de-ionized water. Then, the pH is measured and adjusted with aqueous solution of sodium hydroxide for being between 6 and 7.5. The resultant polymer (PI) had a neutral pH (6<pH<7) and an average particle size of about 141pm.

[0142] Drying. The final powder is put in a ventilated oven during 48 h at 50 °C and recovered after complete drying, humidity < 1 wt% .

[0143] Comparative Example 1

[0144] The synthesis of multistage polymer (core-shell particles) is the same as in example 1 but only 22.4 parts methyl methacrylate are used instead of the a mixture of 21.4 parts methyl methacrylate, 1.2 parts of SIPOMER PAM 200.

[0145] Example 2

[0146] The synthesis of multistage polymer (core-shell particles) is the same as in example 1 but as phosphorous comprising moiety 1.2 parts of diethyl methacryloyloxymethyl phosphonate are used.

[0147] The phosphor content of all powders is estimated with Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) . The results are summarized in table 1.

[0148] Table 1 - Summery of the powder of PCI characteristics

[0149] Table 1 indicates the phosphorous content of the respective examples .

[0150] The dry multistage polymer powders PI to P3 are compounded with polycarbonate at 5wt% for producing compounds 1 to 3.

[0151] Preparation of the impact modified compound compositions PC2, the respective impact modifier powders Pi to P5 are mixed with the thermoplastic polycarbonate as TP1 Lexan L5221 from SABIC (at 5wt% with the help of an extruder type Haake PTW16/40 (using temperatures between from 100°C up to 320°C depending on the respective zones throughout the whole extruder) .

[0152] The respective obtained compounds are heat aged at 120°C. The optical properties of the compounds are evaluated. The color change is observed by measuring the parameter b* . The b* value is used to characterize the principal yellowing off the samples. The b* value measures the blue and the yellow of the colour. Colours tending toward the yellow have a positive b* value while those tending toward the blue have a negative b* value. The b* values is measured using a colorimeter (especially according to the ASTM E 308 standard) . The colour change is observed as a function of time: samples kept at 120°C for 240hours.

[0153] If the initial color is close to zero it is considered that the thermoplastic composition PC2 comprising the composition PCI in form of impact modifiers of the invention is acceptable. The b* value should not larger than 20 after 10 days of thermal aging.

[0154] Table 2 - color of heat aged compounds

[0155] Table 3 - impact strength of thermoplastic compositions

PC2