Description

The invention relates to an improved process for the preparation of acrylonitrile-butadi- ene-styrene (ABS) graft copolymers, ABS graft copolymers obtained by said process, thermoplastic molding compositions comprising said graft copolymers and their use.

Processes for the preparation of ABS graft copolymers wherein the graft substrate (starting diene rubber latex) is subjected to agglomeration are known in the prior art, e.g. WO 2014/170406, WO 2014/170407 and WO 2012/022710. In said processes, the graft substrate is made by emulsion polymerization of a conjugated diene in the presence of an emulsifier at temperatures of 20 to 100°C. The total amount of emulsifier is provided before starting the feeding of monomers to the reaction mixture. As emulsifier (WO 2014/170406 and WO 2014/170407) preferably the sodium or potassium salts of fatty acids comprising 10 to 18 carbon atoms, in particular potassium stearate, are used (0.5 to 5 wt.-%, based on the monomers).

In WO 2012/022710 rosin soaps, or - as comparison example - the potassium salt of a fatty acid mixture containing basically stearic acid, palmitic acid and oleic acid in the ratio 28 : 30 : 28 are used. The obtained graft substrates generaly have a weight median particle size (D50) in the range of from 80 to 120 nm (WO 2014/170406) or 64 to 120 nm (WO 2012/022710).

ABS graft copolymers obtained by said processes are known as having a relative low cross-linking of the rubber phase (low gel content/coagulate waste) and thermoplastic molding compositions comprising said ABS graft copolymers have an acceptable good performance in relation to physical properties like notched impact strength which is important for many applications.

Nevertheless, there is still a demand for ABS graft copolymers having improved mechanical qualities, i.e. in respect to notched impact strength, which cannot be achieved by applying the above prior art processes.

Thus, it is an object of the invention to provide a process for the preparation of ABS graft copolymers which leads to advantageous ABS graft copolymer products and which can be performed on an industrial scale. Furthermore, it is an object of the invention that a graft substrate rubber latex is provided which has a good stability with low cross-linking, low gel content and low coagulate waste. Surprisingly, it was found that this objective can be achieved by a process wherein the emulsifier is fed to the reaction mixture (for the preparation of the graft substrate latex) in a controlled manner whereby a graft substrate latex is obtained having a larger weight median particle size D50 than a reference graft substrate B1* latex obtained by use of 100 wt.-% emulsifier first provided before starting the feeding of the monomers to the reaction mixture.

One aspect of the invention relates to a process for the preparation of at least one graft copolymer B composed of:

B1: 30 to 90 wt.-% - based on the solids content of B - of one or more rubber component(s) as graft substrate B1, having a glass transition temperature of less than 0°C, made from:

(B11) 50 to 100 wt.-%, preferably 79 to 100 wt.-%, more preferably 90 to 98 wt%, - based on the on the solids content of B1 - of at least one conjugated diene B11, preferably butadiene and/or isoprene, more preferably butadiene, optionally,

(B12) 0 to 50 wt.-%, preferably 0 to 21 wt.-%, more preferably 2 to 10 wt%, - based on the on the solids content of B1 - of at least one comonomer B12 selected from: vinylaromatic monomers and acrylonitrile, preferably a-methyl styrene, styrene and acrylonitrile, more preferably styrene;

B2: 10 to 70 wt.-% - based on the solids content of B - of at least one graft sheath obtained by polymerization of monomers B21, B22 and optionally B23 in the presence of an agglomerated graft substrate B1’:

(B21) 50 to 90 wt.-% - based on the solids content of B2 - of styrene, a-me- thylstyrene and/or p-methyl-styrene, in particular styrene;

(B22) 10 to 40 wt.-% - based on the solids content of B2 - of (methacrylonitrile, in particular acrylonitrile, and

(B23) 0 to 40 wt.-% - based on the solids content of B2 - of at least one further co-monomer B23 (different from B21 and B22), preferably C1-C8-acry- lates and/or methylmethacrylate; which process for the preparation of at least one graft copolymer B comprises the following steps:

(i) emulsion polymerization of the at least one monomer B11 and optionally B12 in the presence of at least one emulsifier to obtain a graft substrate B1 latex which is characterized by a controlled feeding of the emulsifier to the reaction mixture - based on 100 wt.-% of the total emulsifier-, whereby

(i-1) at first - before starting the feeding of monomers B11 and/or B12, preferably before starting the feeding of monomer B11 or B12, to the reaction mixture - the emulsifier is provided in an amount of less than 90 wt.-%, preferred less than 80 wt.-%, more preferred less than 70 wt.-%, most preferred less than 65 wt.-%, in particular preferred less than 60 wt.-%, and more than 30 wt.-%, preferred more than 35 wt.-%, more preferred more than 40 wt.-%, most preferred more than 45 wt.-%, in particular preferred more than 50 wt.-%;

(i-2) then, 10 to 120 minutes, preferred 15 to 90 minutes, more preferred 20 to 60 minutes, most preferred 25 to 50 minutes, after starting the feeding of monomers B11 and/or B12, preferably after starting the feeding of monomer B11 or B12, to the reaction mixture, continuously or at once, preferably at once, addition of the remaining amount of emulsifier; and

(ii) subjecting the graft substrate B1 latex obtained in step (i) to agglomeration, to afford an agglomerated graft substrate B1’, and subsequently

(iii) polymerization of the monomers B21 , B22 and optionally B23 in aqueous emulsion in the presence of the agglomerated graft substrate B1’ to produce graft sheath B2 whereby graft copolymer B is obtained.

If optional component B12 and/or B23 is present, its minimum amount is 0.01 wt.-%. Preferably component B12 is present.

The glass transition temperature of the graft substrate B1 (dry sample by evaporation of water) was measured by differential scanning calorimeter (DSC) with a heating rate of 20 K/min, starting at -100°C.

The term "graft substrate B1 latex” is to be understood herein as synonymous in the broadest sense as particulate particles consisting mainly, hence at least 50% by weight, of conjugated diene B11 , in particular butadiene, units. It is generally understood by those skilled in the art that by "styrene", "acrylonitrile", "butadiene", etc., are meant the structural units derived from the respective monomer and embedded in the (co)polymer structure.

Throughout the application, weight indications, indications and definitions of weight ratios, indications in percent by weight (wt.-%) and indications in parts by weight (parts by weight) generally refer to the respective weights of the dry substance (calculated as a solid), therefore excluding contained or absorbed liquids (e.g. water, electrolyte solution and unbound monomers). "Weight ratio" and "mass ratio" are to used synonymously.

As used herein, percent by weight (wt.-%) is intended to mean that the total composition (e.g. of graft substrate B1 , graft sheath B2, graft copolymer B, emulsifier, thermoplastic molding composition) is always 100 wt.-%. Consequently, if a composition comprises or contains a certain proportion of one or more component(s), the proportion of one or more other(s) non-mentioned components) is 100% by weight minus (minus) the proportion of the one or more mentioned component(s). When a composition consists of certain components, the proportion of these components in the total is 100% by weight. The skilled person will easily determine what the remaining components may be when the proportion of other components is specified.

In the context of the present application one or more embodiments may be combined with one another.

Process for the preparation of graft copolymer B

In step (i) of the process according to the invention graft substrate (B1) is produced by polymerizing the monomer(s) B11 and optionally B12 in aqueous emulsion advantageously at temperatures of 20°C to 100°C, preferably 50°C to 90°C, and often at pressures between 0 and 18, preferably 0 and 15 bar(g) (gauge pressure).

The conjugated diene monomer (B11) employed may be for example butadiene and/or isoprene, preferably butadiene.

The at least one comonomer (B12) employed is selected from: vinylaromatic monomers and acrylonitrile, preferably a-methyl styrene, styrene and acrylonitrile, more preferably styrene.

The graft substrate B1 generally employs the diene monomer component (B11) in an amount of from 50 to 100 wt%, preferably 79 to 100 wt.-%, more preferably 90 to 98 wt%, and the vinylaromatic comonomer component (B12) in an amount of from 0 to 50 wt%, 0 to 50 wt.-%, preferably 0 to 21 wt.-%, more preferably 2 to 10 wt%.

Preference is given to a graft substrate B1 composed of butadiene and styrene in the abovementioned composition.

In the process according to the invention emulsifiers such as alkali metal salts of alkyl- or arylsulfonic acids, alkyl sulfates, fatty alcohol sulfonates, salts of higher fatty acids comprising 10 to 30 carbon atoms or resin soaps may be used. It is preferable to employ the sodium and/or potassium salts of alkylsulfonates or more preferably the sodium and/or potassium salts of fatty acids comprising 10 to 18 carbon atoms. Preferred as emulsifier is the sodium or potassium salt of a mixture of fatty acids comprising 10 to 18 carbon atoms, or a mixture of sodium and/or potassium salts of fatty acids comprising 10 to 18 carbon atoms.

More preferred as emulsifier is the sodium or potassium salt of a mixture of fatty acids comprising (or consisting of): more than or equal to 90 wt.-% of at least one, preferably two or more, fatty acid with 16 to 18 carbon atoms, less than or equal to 6 wt.-% of at least one fatty acid comprising less than 16 carbon atoms, and less than or equal to 4 wt.-% of at least one fatty acid comprising more than 18 carbon atoms, or, a mixture of sodium and/or potassium salts of the afore-mentioned fatty acids in the afore-mentioned amounts.

Even more preferred as emulsifier is the sodium or potassium salt of a mixture of fatty acids comprising (or consisting of): more than or equal to 90 wt.-% of two or more fatty acids with 16 to 18 carbon atoms, less than or equal to 6 wt.-% of at least one fatty acid comprising less than 16 carbon atoms, and less than or equal to 4 wt.-% of at least one fatty acid comprising more than 18 carbon atoms, or, a mixture of sodium and/or potassium salts of the afore-mentioned fatty acids in the afore-mentioned amounts.

Most preferred as emulsifier is the afore-mentioned sodium or potassium salt of a mixture of fatty acids, wherein more than 30 wt.-%, preferred more than 40 wt.-%, most preferred more than 50 wt.-%, and less than 80 wt.-%, preferred less than 70 wt.-%, most preferred less than 60 wt.-%, of said fatty acids is at least one fatty acid with 16 to 18 carbon atoms having one carbon-carbon double bond, or, the afore-mentioned mixture of sodium and/or potassium salts of fatty acids wherein more than 30 wt.-%, preferred more than 40 wt.-%, most preferred more than 50 wt.-%, and less than 80 wt.-%, preferred less than 70 wt.-%, most preferred less than 60 wt.-%, of said fatty acids is at least one fatty acid with 16 to 18 carbon atoms having one carbon-carbon double bond.

Preferred is the afore-mentioned sodium or potassium salt of a mixture of fatty acids, or the afore-mentioned mixture of sodium and/or potassium salts of fatty acids, where the ratio by weight of a fatty acid with 18 carbon atoms and one carbon-carbon double bond to a fatty acid with 16 carbon atoms and one carbon-carbon double bond is more than 5, preferred more than 10.

The emulsifiers are favorably employed in an amount of from 0.5 to 5 wt %, preferably from 0.5 to 2 wt %, based on the total weight of the monomers used for the graft substrate (B1). A water/monomer ratio of from 2:1 to 0.7:1 is generally employed. In step (i) of the process according to the invention, the at least one emulsifier is fed to the reaction mixture in a controlled manner, based on 100 wt.-% of the total emulsifier- , where (i-1) at first - before starting the feeding of monomers B11 and/or B12 to the reaction mixture - the emulsifier is provided in an amount of less than 90 wt.-% and more than 30 wt.-%, and (i-2) then, 10 to 120 minutes, preferred 15 to 90 minutes, more preferred 20 to 60 minutes, most preferred 25 to 50 minutes, after starting the feeding of monomers B11 and/or B12, preferably after starting the feeding of monomer B11 or B12, to the reaction mixture, continuously or at once, preferably at once, the remaining amount of emulsifier is added.

In step (i-2), the remaining amount of emulsifier may be added in form of an aqueous solution (often as a 7 to 12 wt.-%, in particular 10 wt.-%, aqueous solution) with ambient temperature, i.e. 10 to 30°C, often 20°C.

Preferably in step (i) of the process according to the invention, the at least one emulsifier is fed to the reaction mixture in a controlled manner - based on 100 wt.-% of the total emulsifier- , where (i-1) at first - before starting the feeding of monomers B11 and/or B12, preferably before starting the feeding of monomer B11 or B12, to the reaction mixture - the emulsifier is provided in an amount of less than 80 wt.-% and more than 35 wt.-%, and (i-2) then, 15 to 90 minutes, preferred 20 to 60 minutes, more preferred 25 to 50 minutes, after starting the feeding of monomers B11 and/or B12, preferably after starting the feeding of monomer B11 or B12, to the reaction mixture, continuously or at once, preferably at once, the remaining amount of emulsifier is added.

More preferably in step (i) of the process according to the invention, the at least one emulsifier is fed to the reaction mixture in a controlled manner - based on 100 wt.-% of the total emulsifier- , where (i-1) at first - before starting the feeding of monomers B11 and/or B12, preferably before starting the feeding of monomer B11 or B12, to the reaction mixture - the emulsifier is provided in an amount of less than 70 wt.-% and more than 40 wt.-%, and (i-2) then, 20 to 60 minutes, preferred 25 to 50 minutes, after starting the feeding of monomers B11 and/or B12, preferably after starting the feeding of monomer B11 or B12, to the reaction mixture, continuously or at once, preferably at once, the remaining amount of emulsifier is added.

Most preferably in step (i) of the process according to the invention, the at least one emulsifier is fed to the reaction mixture in a controlled manner - based on 100 wt.-% of the total emulsifier- , where (i-1) at first - before starting the feeding of monomers B11 and/or B12, preferably before starting the feeding of monomer B11 or B12, to the reaction mixture - the emulsifier is provided in an amount of less than 65 wt.-%, in particular less than 60 wt.-%, and more than 45 wt.-%, in particular more than 50 wt.-%; and

(i-2) then, 25 to 50 minutes, after starting the feeding of monomers B11 and/or B12, preferably after starting feeding of monomer B11 or B12, to the reaction mixture, continuously or at once, preferably at once, the remaining amount of emulsifier is added.

The weight median particle size D50 of the graft substrate B1 latex obtained in step (i) of the process according to the invention generally is at least 2%, preferred at least 4%, more preferred at least 6%, most preferred at least 8%, larger than the weight median particle size D50 of a reference graft substrate B1* latex obtained by use of 100 wt.-% emulsifier first provided before starting the feeding of the monomers B11 and/or B12, preferably before starting the feeding of the monomer B11 or B12, to the reaction mixture.

Moreover, the weight median particle size D50 of the graft substrate B1 latex obtained in step (i) of the process according to the invention generally is at most 20 %, preferred at most 16%, more preferred at most 14%, most preferred at most 12%, larger than the weight median particle size D50 of a reference graft substrate B1* latex obtained by use of 100 wt.-% emulsifier first provided before starting the feeding of the monomers B11 and/or B12, preferably before starting the feeding of the monomer B11 or B12, to the reaction mixture.

A reference graft substrate B1* latex generally has a weight median particle size D50 in the range of from 80 to 120 nm, preferably 80 to 110 nm. For example, if a reference graft substrate B1* latex has a weight median particle size D50 of 80 nm, the graft substrate B1 latex obtained in step (i) of the process according to the invention is at least 2%, preferred 4%, more preferred 6%, most preferred 8%, larger and at most 20 %, preferred at most 16%, more preferred at most 14%, most preferred at most 12%, larger.

The weight median particle size D50 is the diameter which divides the population exactly into two equal parts. 50 wt.-% of the particles are larger than the weight median particle size D50 and 50% by wt. are smaller. The particle size distribution, the weight mean average particle diameter Dw and the weight median particle size D50 value can be determined using a ultracentrifuge (for example as described in W. Scholtan, H. Lange: Kolloid Z. u. Z. Polymere 250, pp. 782 to 796 (1972)) or a disc centrifuge (for example DC 24000 by CPS Instruments Inc.). The weight mean average particle diameter D _w (or De Broucker mean particle diameter) is an average size based on unit weight of particle. The definition for the weight mean average particle size diameter D _w can be given as:

Dw = sum ( ni * Dj ⁴ ) / sum ( n; * Dr ³ ) ni: number of particles with the diameter Dj (see G. Lagaly, O. Schulz, R. Ziemehl: Dispersionen und Emulsionen: Eine Einfuhrung in die Kolloidik feinverteilter Stoffe einschlieBlich der Tonminerale, Darmstadt: Stein- kopf-Verlag 1997, ISBN 3-7985-1087-3, page 282, formula 8.3b).

The summation is normally performed from the smallest to largest diameter of the particles size distribution. It should be mentioned that for a particles size distribution of particles with the same density the volume mean average particle size diameter Dv is equal to the weight mean average particle size diameter Dw.

According to one embodiment, the weight median particle size D50 of the graft substrate B1 latex obtained in step (i) of the process according to the invention is at least 2% and at most 20% larger than the weight median particle size D50 of a reference graft substrate B1* latex obtained by use of 100 wt.-% emulsifier first provided before starting the feeding of the monomers B11 and/or B12, preferably before starting the feeding of the monomer B11 or B12, to the reaction mixture.

According to a preferred embodiment, the weight median particle size D50 of the graft substrate B1 latex obtained in step (i) of the process according to the invention is at least 4% and at most 16% larger than the weight median particle size D50 of a reference graft substrate B1* latex obtained by use of 100 wt.-% emulsifier first provided before starting the feeding of the monomers B11 and/or B12, preferably before starting the feeding of the monomer B11 or B12, to the reaction mixture.

According to a more preferred embodiment, the weight median particle size D50 of the graft substrate B1 latex obtained in step (i) of the process according to the invention is at least 6% and at most 14% larger than the weight median particle size D50 of a reference graft substrate B1* latex obtained by use of 100 wt.-% emulsifier first provided before starting the feeding of the monomers B11 and/or B12, preferably before starting the feeding of the monomer B11 or B12, to the reaction mixture.

According to a most preferred embodiment, the weight median particle size D50 of the graft substrate B1 latex obtained in step (i) of the process according to the invention is at least 8% and at most 12% larger than the weight median particle size D50 of a reference graft substrate B1* latex obtained by use of 100 wt.-% emulsifier first provided before starting the feeding of the monomers B11 and/or B12, preferably before starting the feeding of the monomer B11 or B12, to the reaction mixture. Generally the weight median particle size D50 of the graft substrate B1 latex obtained by the process according to the invention is not more than 150 nm, preferably in the range of from 80 to 120 nm, particularly preferably 80 to 110 nm.

The polydispersity II of the particle size distribution which is defined in this context as II = (D90 - Dio)/Dso of the obtained graft substrate B1 is preferably less than 0.35, in particular less than 0.33. Preference is given to a graft substrate B1 obtained by the process according to the invention having weight median particle size D50 in the range of from 80 to 120 nm and a polydispersity II of less than 0.35, in particular less than 0.33.

D10 and D90 values are defined as follows: D10 is the diameter at which 10 wt.-% of the particles are smaller than this value and D90 is the diameter at which 90 wt.-% of the particles are smaller than this value.

According to a specific embodiment of the invention, the weight median particle size D50 of a graft substrate B1 latex obtained in step (i) of the process according to the invention is in the range from 96 to 105 nm , preferably 97 to 104 nm. According to this embodiment the weight median particle size D50 of a reference graft substrate B1* latex is < 94 nm.

Polymerization initiators employed in the process according to the invention are in particular the commonly used persulfates such as sodium or potassium peroxodisulfate, or mixtures thereof, though redox systems are also suitable. The amounts of initiators, for example 0.1 to 1 wt %, based on the total weight of the monomers used for producing the graft substrate (B1).

Polymerization assistants that may be employed in the process according to the invention include the customary buffer substances used to adjust the pH to the preferred range of from 6 to 10, for example sodium bicarbonate, sodium carbonate and sodium pyrophosphate, or mixtures thereof and also generally 0.1 to 3 wt % of a molecular weight regulator such as mercaptan, e.g. tert.-dodecylmercaptan or n-dodecycl-mer- captan, terpinol or dimeric a-methylstyrene.

In step (i) of the process according to the invention the feeding time for the monomers B11 and optionally B12 is at least 6 hours, preferred 8 hours, and less than 20 hours, preferred less than 16 hours. The solids content in the aqueous dispersion after the polymerization is preferably from 25 to 50% by weight, particularly preferably from 30 to 45% by weight. The precise polymerization conditions, in particular type, feed modus and amount of the emulsifier are selected within the abovementioned ranges such that the graft substrate B1 has a D50 value as hereinbefore defined.

Then, in step (ii) of the process according to the invention the graft substrate B1 latex obtained in step (i) is subjected to agglomeration to afford an agglomerated graft substrate BT.

Agglomeration of the graft substrate B1 can be achieved by several methods, preferably by employing an agglomerating component (C) which is a copolymer of one or more hydrophobic C1 to C 12-alkyl acrylates or C1 to C12-alkyl methacrylates and one or more hydrophilic comonomers selected from the group consisting of methacrylamide, acrylamide, N-methylacrylamide, N-ethylacrylamide and N-n-butylacrylamide. The copolymer (C) (= agglomerating component (C)) has a weight median particle size D50 of from 100 to 150 nm.

However, other common agglomeration agents such as acids, preferably an acid anhydride, more preferably acetic anhydride, or mixtures of other organic anhydrides with acetic anhydride, can also be used for the agglomeration of the graft substrate B1 , and after agglomeration is complete, preferably restabilization with a base, preferably potassium hydroxide solution is carried out, so that the result is a pH value of more than pH 7.5. The use of the latter agglomeration agents is less preferred.

Preferably as agglomerating agent the afore-mentioned copolymer C is used which is generally composed as follows:

80 to 99.9, preferably 90 to 99.9 wt.-%, one or more hydrophobic alkyl(meth)acrylate and 0.1 to 20, preferably 0.1 to 10 wt.-% one or more hydrophilic comonomer, where the amounts of said monomers total 100 wt.-%.

The hydrophobic monomers employed are preferably C1-C4 alkyl acrylates or else mixtures thereof. Preferred as hydrophobic monomer is ethyl acrylate. The hydrophilic comonomer is preferably methacrylamide.

Preference is given to a copolymer C of ethyl acrylate and methacrylamide.

Particular preference is given to a copolymer C of 92 to 98 wt.-%, based on the total solids in C, of ethyl acrylate and 2 to 8 wt.-%, based on the total solid in C, of methacrylamide. Particular preference is given to a copolymer C of 93 to 97 wt.-%, based on the total solid in C, of ethyl acrylate and 3 to 7 wt.-%, based on the total solid in C, of methacrylamide. Preference is given to copolymers C having a weight-average molar mass (Mw) of from 30,000 to 300,000 g/mol, measured by gel permeations chromatography (GPC) with tetra hydrofuran as solvent.

Particular preference is given to a copolymer C described hereinabove and having a core constructed from at least one of the hydrophobic monomers, preferably from ethyl acrylate, wherein this core is grafted with a copolymer constructed from the afore-mentioned hydrophobic and hydrophilic monomers.

It is particularly preferable when the copolymer C is constructed from 5 to 20 wt %, based on the total amount of the copolymer C, of one or more of said hydrophobic monomers, preferably ethyl acrylate, as the core and 80 to 95 wt.-%, based on the total amount of the copolymer C, of a shell grafted onto the core and constructed from 93 to 97 wt.-%, based on the total amount of the monomers forming the shell, of at least one of said hydrophobic monomers, preferably ethyl acrylate and 3 to 7 wt.- , based on the total amount of the monomers forming the shell, of at least one of said hydrophilic monomers, preferably methacrylamide.

It is very particularly preferable when the copolymer C is constructed from (c11) 8 to 12 wt %, based on the total amount of the copolymer C, of ethyl acrylate as the core, and (c12) 88 to 92 wt %, based on the total amount of the copolymer C, of a shell grafted onto the core and constructed from (c21) 93 to 97 wt %, based on the total amount of the monomers forming the shell, of ethyl acrylate and (c22) 3 to 7 wt %, based on the total amount of the monomers forming the shell, of methacrylamide.

Preference is accordingly given to a process for producing the agglomerating component (C) comprising monomer components (C1) and (C2), in particular ethyl acrylate and methacrylamide, said process comprising initially polymerizing a portion of (C1), in particular ethyl acrylate, (formation of the substrate) and subsequently adding the remaining portion of (C1), in particular ethyl acrylate, and (C2), in particular methacrylamide, as a mixture. The portions correspond to the ratios described hereinabove.

The production of the agglomerating copolymer C employed is carried out according to processes known to those skilled in the art, particularly advantageously by emulsion polymerization, and the emulsifiers cited hereinabove for the graft substrate B1 may be employed. It is preferable to employ the sodium and potassium salts of alkylsulfonates comprising 10 to 18 carbon atoms. The emulsifiers are advantageously employed in an amount of from 0.5 to 5 wt.-%, preferably 0.5 to 2 wt.-%, based on the total monomer content of the copolymer (C). Polymerization initiators employed are in particular the commonly used persulfates such as sodium or potassium peroxodisulfate, or mixtures thereof, though redox systems are also suitable. The amounts of initiators, for example 0.1 to 1 wt.-%, based on the total weight of the monomers used for producing the copolymer (C), depends on the molar weight desired.

Polymerization assistants that may be employed include the customary buffer substances and/or basic substances used to adjust the pH to the preferred range of from 4 to 10. As buffer substances can be used for example sodium bicarbonate, sodium carbonate and sodium pyrophosphate, or mixtures thereof; as basic substances can be used for example sodium hydroxide, potassium hydroxide, or mixtures thereof. If desired molecular weight regulator such as mercaptan, e.g. tert.-dodecylmercaptan or n- dodecyclmercaptan, terpinol or dimeric a-methylstyrene can be used.

The copolymer (C) is produced by aqueous emulsion polymerization according to processes known to those skilled in the art generally at temperatures of 20°C to 100°C, preferably 50°C to 90°C and at pressures between 0 and 6, preferably 0 and 3 bar(g) (gauge pressure). The solids content in the aqueous dispersion after the polymerization is 3 to 60% by weight, preferably from 7 to 50% by weight, particularly preferably from 10 to 45% by weight.

The process for producing the core/shell copolymers (C) described hereinabove is an emulsion polymerization comprising the steps of: (x) emulsion polymerizing at least one monomer (C1) as defined hereinabove in a first step and (y) adding a monomer mixture comprising monomers (C1+C2) in a further step, wherein the steps (x) and (y) are performed in the presence of at least one emulsifier which is employed in an amount of from 0.05 to 1.0 wt %, preferably 0.05 to 0.5 wt %, in step (x) and in an amount of from 0.45 to 4.5 wt %, preferably 0.45 to 1.8 wt %, in step (y), in each case based on the total monomer content.

In step (ii) of the process according to the invention copolymer (C) is preferably employed as an aqueous dispersion, as a so-called agglomeration latex. The agglomerating copolymer (C) can have different values of the polydispersity II of the particles size distribution, e.g. the particles size distribution can be broad with values of polydispersity II larger than 0.27 or narrow with a polydispersity II of 0.27 or less. Preferably the polydispersity II is broad and in the range of is larger than 0.27. In another embodiment preferably the polydispersity II is narrow and in the range of from 0.27 to 0.20, in particular in the range of from 0.25 to 0.21. The agglomerating copolymer (C) preferably has a D50 value of from 110 to 150 nm, particularly preferably from 115 to 140 nm.

A preferred embodiment employs an agglomerating copolymer (C) having a polydispersity II of 0.27 or less, in particular of less than 0.25, and a D50 value of from 110 to 150 nm, in particular of 115 to 140 nm. A further preferred embodiment employs an agglomerating copolymer (C) having a polydispersity II in the range of from 0.27 to 0.20, in particular in the range of from 0.25 to 0.21 , and a D50 value of from 100 to 150, preferably 110 to 150 nm, in particular of 115 to 140 nm.

The agglomeration of the graft substrate (B1) is generally achieved by adding a dispersion of the copolymer (C) described hereinabove. The concentration of the copolymer (C) in the dispersion used for agglomeration shall generally be between 3 to 60 wt %, preferably between 7 to 50 wt %. The agglomeration generally employs from 0.1 to 5 parts by weight, preferably from 0.5 to 3 parts by weight, of the dispersion of the copolymer (C) per 100 parts of the graft substrate B1 , in each case reckoned on solids.

The agglomeration is generally carried out at a temperature of from 20°C to 120°C, preferably from 30°C to 100°C, more preferably from 30°C to 75°C and at pressures between 0 and 6, preferably 0 and 3 bar(g) (gauge pressure). The addition of the copolymer (C) may be effected in one go or portion wise, continuously or with a feed profile over a particular time period. According to a preferred embodiment the addition of (C) is effected such that 1/1 to 1/100 of the total amount of (C) is introduced per minute. The agglomeration time, i.e. the time from the beginning of the addition of (C) to the start of the subsequent graft copolymerization, is preferably from one minute to two or more hours, for example to 2 hours, particularly preferably from 10 to 60 minutes.

Basic electrolytes may optionally be added to the agglomeration in an amount of from 1 to 50 wt % (based on 100 wt.-% of the solids content of the copolymer (C)). Useful basic electrolytes include organic or inorganic hydroxides. Inorganic hydroxides especially are useful. Particular preference is given to using lithium hydroxide, sodium hydroxide or potassium hydroxide. According to one of the particularly preferred embodiments KOH is used as the basic electrolyte. According to another preferred embodiment NaOH is used as the basic electrolyte. However, it is also possible to employ mixtures of two or more basic electrolytes. This may be advantageous, for example, when the growth of the rubber particles is to be precisely controlled.

Hence it may be useful, for example, to employ mixtures of LiOH with KOH or mixtures of LiOH with NaOH. It is likewise possible to use mixtures of KOH and NaOH and this constitutes a further preferred embodiment. The electrolytes are generally dissolved prior to addition. A preferred solvent is the aqueous phase. Preference is given to using diluted solutions, for example solutions having a concentration in the range of from 0.001 to 0.1 , in particular from 0.001 to 0.05, preferably less than 0.03, for example less than 0.025 g of basic electrolyte/ml of solvent. The addition of the basic electrolytes may be effected prior to the addition of copolymer C, simultaneously therewith or separately therefrom or after addition of B1. It is also possible to premix the basic electrolytes in the dispersion of C. According to a preferred embodiment the addition of the basic electrolytes is effected prior to the addition of the agglomeration polymer. The basic electrolyte is generally employed in an amount in the range of from 0.01 to 4 wt %, preferably 0.05 to 2.5, in particular 0.1 to 1 .5 wt % based on the rubber B (solids).

The pH during the agglomeration is generally from 6 to 13. According to a preferred embodiment the pH is from 8 to 13.

The agglomerated graft substrate B1’ obtained after agglomeration step (ii) of the process according to the invention often has a bimodal particle size distribution of fractions x) and y) where x) is a fraction of non agglomerated particles and y) is a fraction of agglomerated particles having a D50 value in the range of from 300 to 550 nm.

In case that a narrow sized agglomerating copolymer (C) with a polydispersity II of 0.27 or less is used for the agglomeration, the polydispersity II of the agglomerated fraction is less than 0.28. The non agglomerated particles of the fraction x) generally have a D50 value of not more than 150 nm, preferably in the range of from 80 to 120 nm.

The weight fraction of the particles of the fraction x) of the agglomerated graft substrate B1’ is generally 15 to 40 wt.-%, preferably 20 to 30 wt.-%, and the fraction of the particles of the fraction y) is generally 60 to 85 wt.-%, preferably 70 to 80 wt.-%, based on the total mass of the particles, x) and y) generally summing to 100 wt.-%.

The agglomerated graft substrate B1’ preferably comprises a fraction y) of agglomerated particles having a D50 value in the range of from 300 to 500 nm, particularly preferably 300 to 480 nm, and in case that narrow sized agglomerating copolymer (C) with a polydispersity II of 0.27 or less is used, a polydispersity II of less than 0.27, in particular less than 0.26.

The obtained dispersion of the agglomerated graft substrate B1’ is relatively stable and may be readily stored and transported without onset of visible coagulation. The agglomerated graft substrate B1’ is used to produce graft copolymers B. In step (iii) of the process according to the invention, the monomers B21, B22 and optionally B23 are polymerized in aqueous emulsion in the presence of the agglomerated graft substrate B1’ to produce graft sheath B2 whereby graft copolymer B is obtained. To produce the graft copolymers B, the agglomerated graft substrate B1’ is grafted with the monomers B21, B22 and optionally B23, preferably solely monomers B21 and B22.

The graft copolymer B preferably is composed of:

40 to 85 wt.-%, based on the solids content of the graft copolymer B, of a graft substrate (B1) and 15 to 60 wt.-%, based on the solids content of the graft copolymer B, of a graft sheath (B2).

B1 and B2 sum to 100 wt.-%.

Often the graft sheath (B2) is produced by reaction of the monomers B21 , B22 and B23 in the following amounts:

(B21) 70 to 90 wt.-%, preferably 75 to 85 wt.-%;

(B22) 10 to 30 wt.-%, preferably 15 to 25 wt.-%;

(B23) 0 to 20 wt.-%, preferably 0 to 10 wt.-%.

The amounts of B21, B22 and B23 sum to 100 wt.-%.

A preferred graft sheath (B2) may be produced by reaction of (B21) 70 to 90 wt.-%, preferably 75 to 85 wt.-%, of styrene and/or a-methylstyrene, in particular styrene, (B22) 10 to 30 wt.-%, preferably 15 to 25 wt.-%, of acrylonitrile and/or methacrylonitrile, in particular acrylonitrile, and (B23) 0 to 20 wt.-% methyl methacrylate in the presence of the agglomerated graft substrate BT.

More preferred graft sheaths B2 are constructed from: B2-1 copolymers of styrene and acrylonitrile, B2-2 copolymers of a-methylstyrene and acrylonitrile. Particular preference is given to B2-1 copolymers of styrene and acrylonitrile. Particularly preferred graft sheaths B2 are obtained by reaction of from 75 to 85 wt.-% of styrene and from 15 to 25 wt.-% of acrylonitrile.

In step (iii) of the process according to the invention the graft sheath (B2) is produced by an emulsion polymerization process.

The graft copolymerization for producing the graft sheath (B2) may be performed in the same system as the emulsion polymerization for producing the graft substrate (B1) and further emulsifiers and assistants may be added if necessary. The monomer mixture to be grafted onto the graft substrate according to one embodiment may be added to the reaction mixture all at once, preferably simultaneously with constant feed rates, spread over a plurality of stages - for example to construct a plurality of graft superstrates - or in continuous fashion during the polymerization. In general the time for feeding the monomers B21 , B22 and optionally B23 is in the range of 1 to 10 hours, preferably in 1.5 to 6 hours.

The monomers B21 , B22 and optionally B23, preferably the monomers B21 and B22 (in particular styrene and acrylonitrile) may preferably be added simultaneously with constant feed rates and with a constant ratio of the feed rates of B21 , B22 and B23, preferably B21 and B22. It is also preferable to use variable feed rates for the monomers B21 , B22 and B23, preferably B21 and B22, and variable ratios of the feed rates for the monomers B21 , B22 and B23, preferably B21 and B22 according to the teaching of the application WO 2015/165810 A1.

In accordance with another embodiment, in step (iii) of the process according to the invention, the graft sheath (B2) is polymerized from a monomer mixture composed of the monomers B21 , B22 and optionally B23, preferably a monomer mixture composed of the monomers B21 and B22 (in particular styrene and acrylonitrile), in the presence of the agglomerated graft substrate BT. The monomers may be added individually or in mixtures with one another. For example it is possible to initially graft B21 alone and subsequently graft a mixture of B21 and B22. This graft copolymerization is advantageously again performed in aqueous emulsion under the usual conditions described hereinabove for the graft substrate.

Particulars pertaining to the performance of the graft reaction are known to those skilled in the art and are disclosed, for example, in DE-A 24 27 960, EP-A 0 062 901 or WO 2014/170406 A1 (see “Pfropfcopolymer B, Allgemeine Vorgehensweise”, pp. 34- 35).

Preference is given to the following embodiments of step (iii) of the process according to the invention: a) The graft copolymer B is produced by polymerizing the components B21 , B22 and optionally B23 in aqueous emulsion according to processes known to those skilled in the art generally at temperatures of 20°C to 100°C, preferably 50°C to 90°C and at pressures between 0 and 18, preferably 0 and 15 bar(g) (gauge pressure). The polymerization may employ emulsifiers such as alkali metal salts of alkyl- or arylsulfonic acids, alkyl sulfates, fatty alcohol sulfonates, salts of higher fatty acids comprising 10 to 30 carbon atoms or resin soaps. It is preferable to employ the emulsifiers, in particular the preferred emulsifiers, hereinbefore-mentioned for the preparation of the graft substrate B1 (cp. step (i) of the process according to the invention). The emulsifiers are favorably employed in an amount of from 0.1 to 3 wt.-%, preferably from 0.2 to 1 wt.-%, based on the total weight of the graft copolymer B. b) Polymerization initiators employed in are in particular the commonly used persulfates such as sodium or potassium peroxodisulfate, or mixtures thereof, though redox systems are also suitable. The amounts of initiators, for example 0.1 to 1 wt.- %, based on the total weight of the graft copolymer B. c) Polymerization assistants that may be employed include the customary buffer substances used to adjust the pH to the preferred range of from 6 to 10, for example sodium bicarbonate, sodium carbonate and sodium pyrophosphate, or mixtures thereof and also optionally 0.01 to 0.3 wt % of a molecular weight regulator such as mercaptan, e.g. tert.-dodecylmercaptan or n-dodecyclmercaptan, terpinol or dimeric a-methylstyrene based on the total weight of the graft copolymer B. d) The solids content in the aqueous dispersion after the polymerization is preferably from 25 to 50% by weight, particularly preferably from 30 to 45% by weight.

Preference is given to a process for the preparation of at least one graft copolymer B according to the invention wherein the at least one graft copolymer B is composed of:

B1 : 40 to 85 wt.-%, - based on the solids content of B - of a graft substrate B1 made from:

(B11) 79 to 100 wt.-%, preferably 90 to 98 wt%, - based on the on the solids content of B1 - of butadiene and/or isoprene, in particular butadiene, and, (B12) 0 to 21 wt.-%, preferably 2 to 10 wt.-%, - based on the on the solids content of B1 - of a-methyl styrene, styrene and/or acrylonitrile, in particular styrene;

B2: 15 to 60 wt.-% - based on the solids content of B - of a graft sheath obtained by polymerization of monomers B21 and B22 in the presence of an agglomerated graft substrate B1’:

(B21) 70 to 90 wt.-% - based on the solids content of B2 - styrene; and (B22) 10 to 30 wt.-% - based on the solids content of B2 - acrylonitrile; in which process

- in step (i) as emulsifier a sodium or potassium salt of a mixture of fatty acids comprising 10 to 18 carbon atoms or a mixture of sodium and potassium salts of fatty acids comprising 10 to 18 carbon atoms is used; wherein (i-1) the emulsifier is provided in an amount of less than 70 wt.-%, preferred less than 65 wt.-%, more preferred less than 60 wt.-%, and more than 40 wt.-%, preferred more than 45 wt.-%, more preferred more than 50 wt.-%; and wherein (i-2) 20 to 60 minutes, preferred 25 to 50 minutes, after starting the feeding of monomers B11 and/or B12, preferably after starting the feeding of monomer B11 or B12, to the reaction mixture, the remaining amount of the emulsifier is added;

- in step (ii) the graft substrate B1 latex obtained in step (i) is agglomerated by adding 0.01 to 5 parts by weight, based on 100 parts by weight of the graft substrate B1, based on the solids content, of an agglomerating copolymer (C) composed of:

(C1): 80 to 99.9 wt % of at least one hydrophobic C1 to C12-alkyl(meth)acrylate, preferably ethyl acrylate; and

(C2): 0.1 to 20 wt % of at least one hydrophilic comonomer selected from the group consisting of methacrylamide, acrylamide, N-methylacrylamide, N-ethylacrylamide and N-n-butylacrylamide; preferably methacrylamide; where (C1) and (C2) sum to 100 wt %; and where the agglomerating copolymer (C) has a D50 value of from 100 to 150 nm, preferably of from 110 to 140 nm.

Preferably in step (ii) of the afore-mentioned preferred embodiment of the process according to the invention, the agglomerating copolymer (C) has a polydispersity II larger than 0.27 or of 0.27 or less, preferably less than 0.27, preferably in the range of from 0.26 to 0.20.

Furthermore, preferably in step (ii) of the afore-mentioned preferred embodiment of the process according to the invention, the agglomerated graft substrate B1 has a bimodal particle size distribution of a fraction x) of non agglomerated particles in an amount of 15 to 40 wt %, having a D50 value of not more than 150 nm, preferably in the range of from 80 to 120 nm, and a fraction y) of agglomerated particles in an amount of 60 to 85 wt %, having a D50 value in the range of from 350 to 550 nm, preferably with a polydispersity II of less than 0.28, and x) and y) generally summing to 100 wt.-%.

Preferably in step (i) of the afore-mentioned preferred embodiment of the process according to the invention the emulsifier is the sodium or potassium salt of a mixture of fatty acids comprising (or consisting of): more than or equal to 90 wt.-% of at least one, preferably two or more, fatty acid with 16 to 18 carbon atoms, less than or equal to 6 wt.-% of at least one fatty acid comprising less than 16 carbon atoms, and less than or equal to 4 wt.-% of at least one fatty acid comprising more than 18 carbon atoms; or, a mixture of sodium and/or potassium salts of the afore-mentioned fatty acids in the afore-mentioned amounts. More preferably in step (i) of the afore-mentioned preferred embodiments of the process according to the invention the emulsifier is the afore-mentioned sodium or potassium salt of a mixture of fatty acids wherein more than 30 wt.-%, preferred more than 40 wt.-%, most preferred more than 50 wt.-%, and less than 80 wt.-%, preferred less than 70 wt.-%, most preferred less than 60 wt.-%, of said fatty acids is at least one fatty acid with 16 to 18 carbon atoms having one carbon-carbon double bond, or, the afore-mentioned mixture of sodium and/or potassium salts of fatty acids wherein more than 30 wt.-%, preferred more than 40 wt.-%, most preferred more than 50 wt.-%, and less than 80 wt.-%, preferred less than 70 wt.-%, most preferred less than 60 wt.-%, of said fatty acids is at least one fatty acid with 16 to 18 carbon atoms having one carbon-carbon double bond.

A further aspect of the invention are the graft copolymers B obtained by the process according to the invention. The graft copolymers B may be further used as they are obtained in the reaction mixture, for example as a latex emulsion or latex dispersion.

Alternatively, however, they may also be worked up in a further step. A stabilizer dispersion is usually added to the graft copolymer latex B before the workup measures take place. Workup measures are known in principle to those skilled in the art. Examples of workup steps include the isolation of the graft copolymers B from the reaction mixture, for example by spray drying, shearing or by precipitation with strong acids or using other precipitants, for example from inorganic compounds such as magnesium sulfate. A further workup step example is the drying of the isolated rubber. The solids content of the dispersion of the graft rubber is about 40 wt.-%.

A further aspect of the invention is a thermoplastic molding composition comprising the graft copolymer B obtained by the process according to the invention and a thermoplastic copolymer A and optionally further components K.

In particular a thermoplastic molding composition as afore-mentioned is provided comprising:

A: 40 to 80 wt.-% of at least one thermoplastic copolymer A obtainable from: A1 : 20 to 31 wt.-%, based on the copolymer A, of acrylonitrile, and A2: 69 to 80 wt.-%, based on the copolymer A, of styrene or a-methylstyrene or a mixture of styrene and a-methylstyrene;

B: 20 to 60 wt.-% of the graft copolymer B; and K: 0 to 5 wt.-% of further components K, where the components A, B and K sum to 100 wt.-%. Copolymer A

The copolymer A is preferably produced from the components acrylonitrile and styrene and/or a-methylstyrene by bulk polymerization or in the presence of one or more solvents. Preference is given to copolymers A having weight-average molar masses Mw of from 50,000 to 300,000 g/mol, where the weight molar masses may be determined, for example, by means of GPC with tetra hydrofuran as solvent and with UV detection. The copolymer A forms the matrix of the thermoplastic molding composition. The number-averaged molar masses (Mn) of the copolymer matrix A is preferably from 15,000 to 100,000 g/mol (determined by GPC with tetra hydrofuran as solvent and with UV detection). The viscosity of the copolymer matrix A (determined according to DIN 53726 at 25° C. in a 0.5 wt % solution in DMF) is, for example, from 50 to 120 ml/g.

The copolymer A may in particular comprise (or consist of):

(Aa) polystyrene-co-acrylonitrile, produced from, based on (Aa), 69 to 80 wt.-% of styrene and 20 to 31 wt.-% of acrylonitrile, or

(Ab) poly-a-methylstyrene-co-acrylonitrile, produced from, based on (Ab), 69 to 80 wt % of a-methylstyrene and 20 to 31 wt.-% of acrylonitrile, or

(Ac) a mixture of the copolymer matrix (Aa) and the copolymer matrix (Ab).

The copolymer A may also be obtained by copolymerization of acrylonitrile, styrene and a-methylstyrene. However, it is also possible in principle to employ polymer matrices containing further monomer building blocks.

The copolymer matrix A may be produced by bulk polymerization/solution polymerization in, for example, toluene or ethylbenzene according to a process such as is described, for example, in Kunststoff-Handbuch, Vieweg-Daumiller, Vol V, (Polystyrol), Carl-Hanser-Verlag, Munich 1969, pages 122 f., lines 12 ff.

As previously described hereinabove the preferred copolymer matrix component A is a polystyrene-co-acrylonitrile, poly-a-methylstyrene-co-acrylonitrile or mixtures thereof. In a preferred embodiment after production the component A is isolated according to processes known to those skilled in the art and preferably processed into pellets.

The afore-mentioned thermoplastic molding composition according to the invention may additionally comprise at least one further thermoplastic polymer (TP) selected from the group of polycarbonates, polyester carbonates, polyesters and polyamides. The copolymers A employed in the molding composition may also be mixed with, for example, further thermoplastic polymers (TP). Suitable examples include, in particular, semicrystalline polyamides, semiaromatic copolyamides, polyesters, polyoxyalkylene, polyarylene sulfides, polyether ketones, polyvinyl chlorides, and/or polycarbonates.

It is also possible to employ mixtures of two or more of the afore-mentioned polymers (TP). The thermoplastic molding composition may comprise, based on the amount of copolymer A plus graft copolymer B, from 0 to 90 wt.-%, preferably 0 to 50 wt.-%, particularly preferably 0 to 20 wt.-% of the abovementioned polymers (TP).

Preference is given to a thermoplastic molding composition consisting of copolymer A and graft copolymer B and optionally further components K.

As the further components (K), the thermoplastic molding composition may comprise one or more components selected from the group consisting of dispersants (DM), fillers (F) and added substances (D).

As the component K, the thermoplastic molding compositions may further also comprise 0 to 5 wt.-% of fibrous or particulate fillers (F) or mixtures thereof, in each case based on the amount of the components A plus B plus K. Examples of fillers or reinforcers that may be employed include glass fibers that may be finished with a sizing and a coupling agent, glass beads, mineral fibers, aluminum oxide fibers, mica, quartz flour or wollastonite. It is also possible to admix with the molding compositions metal flakes, metal powder, metal fibers, metal-coated fillers, for example nickel-coated glass fibers, and other additive substances that shield electromagnetic waves. It is also possible to add carbon fibers, carbon black, in particular conductivity carbon black, or nickel-coated carbon fibers.

Various additives (D) may be added to the molding compositions in amounts of from 0 to 5 wt.-% as assistants and processing additives. Suitable added substances (D) include all substances customarily employed for processing or finishing the polymers.

Examples include, for example, dyes, pigments, colorants, antistatic agents, antioxidants, stabilizers for improving thermal stability, stabilizers for increasing photostability, stabilizers for enhancing hydrolysis resistance and chemical resistance, anti-thermal decomposition agents and in particular lubricants that are useful for production of molded bodies/articles. These further added substances may be admixed at any stage of the manufacturing operation, but preferably at an early stage in order to profit early on from the stabilizing effects (or other specific effects) of the added substance. For further customary assistants and added substances, see, for example, “Plastics Additives Handbook”, Ed. Gachter and Muller, 4th edition, Hanser Publ., Munich, 1996.

Examples of suitable pigments include titanium dioxide, phthalocyanines, ultramarine blue, iron oxides or carbon black, and also the entire class of organic pigments.

Examples of suitable colorants include all dyes that may be used for the transparent, semi-transparent, or non-transparent coloring of polymers, in particular those suitable for coloring styrene copolymers.

Examples of suitable flame retardants that may be used include the halogen-containing or phosphorus-containing compounds known to the person skilled in the art, magnesium hydroxide, and also other commonly used compounds, or mixtures thereof.

Examples of suitable antioxidants include sterically hindered monocyclic or polycyclic phenolic antioxidants which may comprise various substitutions and may also be bridged by substituents. These include not only monomeric but also oligomeric compounds, which may be constructed of a plurality of phenolic units. Hydroquinones and hydroquinone analogs are also suitable, as are substituted compounds, and also antioxidants based on tocopherols and derivatives thereof. It is also possible to use mixtures of different antioxidants. It is possible in principle to use any compounds which are customary in the trade or suitable for styrene copolymers, for example antioxidants from the Irganox range. In addition to the phenolic antioxidants cited above by way of example, it is also possible to use so-called costabilizers, in particular phosphorus- or sulfur-containing costabilizers. These phosphorus- or sulfur-containing costabilizers are known to those skilled in the art.

Examples of suitable light stabilizers include various substituted resorcinols, salicylates, benzotriazoles and benzophenones.

Suitable matting agents include not only inorganic substances such as talc, glass beads or metal carbonates (for example MgCCh, CaCOs) but also polymer particles, in particular spherical particles having diameters D50 greater than 1 pm, based on, for example, methyl methacrylate, styrene compounds, acrylonitrile or mixtures thereof. It is further also possible to use polymers comprising copolymerized acidic and/or basic monomers.

Examples of suitable antidrip agents include polytetrafluoroethylene (Teflon) polymers and ultrahigh molecular weight polystyrene (weight-average molar mass Mw above 2,000,000). Examples of fibrous or pulverulent fillers include carbon or glass fibers in the form of glass fabrics, glass mats, or filament glass rovings, chopped glass, glass beads, and wollastonite, particular preference being given to glass fibers. When glass fibers are used they may be finished with a sizing and a coupling agent to improve compatibility with the blend components. The glass fibers incorporated may either take the form of short glass fibers or else continuous filaments (rovings).

Examples of suitable particulate fillers include carbon black, amorphous silica, magnesium carbonate, powdered quartz, mica, bentonites, talc, feldspar or, in particular, calcium silicates, such as wollastonite, and kaolin.

Examples of suitable antistatic agents include amine derivatives such as N,N-bis(hy- droxyalkyl)alkylamines or -alkyleneamines, polyethylene glycol esters, copolymers of ethylene oxide glycol and propylene oxide glycol (in particular two-block or three-block copolymers of ethylene oxide blocks and propylene oxide blocks), and glycerol mono- and distearates, and mixtures thereof.

Examples of suitable stabilizers include hindered phenols but also vitamin E-com- pounds having analogous structures and also butylated condensation products of p- cresol and dicyclopentadiene. HALS stabilizers (Hindered Amine Light Stabilizers), benzophenones, resorcinols, salicylates, benzotriazoles are also suitable. Other suitable compounds include, for example, thiocarboxylic esters. Also usable are C6-C20-al- kyl esters of thiopropionic acid, in particular the stearyl esters and lauryl esters. It is also possible to use the dilauryl ester of thiodipropionic acid (dilauryl thiodipropionate), the distearyl ester of thiodipropionic acid (distearyl thiodipropionate) or mixtures thereof. Examples of further additives include HALS absorbers, such as bis(2,2,6,6-tet- ramethyl-4-piperidyl) sebacate or UV absorbers such as 2H-benzotriazol-2-yl-(4- methylphenol). Such additives are typically used in amounts of from 0.01 to 2 wt.-% (based on the overall mixture).

Suitable lubricants and demolding agents include stearic acids, stearyl alcohol, stearic esters, amide waxes (bisstearylamide), polyolefin waxes and/or generally higher fatty acids, derivatives thereof and corresponding fatty acid mixtures comprising 12 to 30 carbon atoms. Also particularly suitable is ethylenebisstearamide. The amounts of these additions are in the range of from 0.05 to 5 wt.-%.

Also suitable as added substances are silicone oils, oligomeric isobutylene or similar substances. Typical amounts, when employed, are from 0.001 to 3 wt.-% based on the amount of the components A plus B plus K. Also usable are pigments, dyes, optical brighteners, such as ultramarine blue, phthalocyanines, titanium dioxide, cadmium sulfides, derivatives of perylenetetracarboxylic acid.

Processing assistants and stabilizers such as UV stabilizers, heat stabilizers (for example butylated reaction products of p-cresol and dicyclopentadiene, Wingstay® L from Omnova, or else the dilauryl ester of thiodipropionic acid, Irganox® PS 800 from BASF), lubricants and antistatic agents (for example ethylene oxide-propylene oxide copolymers such as Pluronic® from BASF), when employed, are typically used in amounts of from 0.01 to 5 wt.-%, based on the amount of the components A plus B plus K.

The individual added substances are generally used in the respective customary amounts.

The molding compositions may be produced from the components A and B (and optionally further polymers (TP) and components K) by any known method. However, it is preferable when the components are blended by melt mixing, for example conjoint extrusion, kneading or rolling of the components. This is done at temperatures in the range of from 160°C to 400°C, preferably from 180°C to 280°C. In a preferred embodiment, the component (B) is first partially or completely isolated from the aqueous dispersion obtained in the respective production steps. For example, the graft copolymers B may be mixed as a moist or dry crumb/powder (for example having a residual moisture of from 1 to 40%, in particular 20 to 40%) with the matrix polymers, complete drying of the graft copolymers then taking place during the mixing. The drying of the particles may also be performed as per DE-A 19907136.

The described molding compositions can be used for the production of shaped articles such as sheets or semifinished products, films, fibers or else of foams and the corresponding shaped articles such as sheets, plates, semifinished products, films, foils, fibers or foams, and deep-drawn articles from previously produced plates or foils, and articles obtained by foil back-injection.

Processing may be carried out using the known processes for thermoplastic processing, in particular production may be effected by thermoforming, extruding, injection molding, calandaring, blow molding, compression molding, press sintering, deep drawing, foil back-injection or sintering, preferably by injection molding.

The molding compositions according to the invention may be used to produce shaped articles of any type. Examples of shaped articles produced from the molding composition according to the invention are foils, profiles and housing parts of all kinds, for ex- ample for household appliances such as juicers, coffee machines, mixers, and televisions; for office machines such as monitors, printers, copiers, notebooks, and flat screens; bodywork and interior components for commercial vehicles, in particular for the automotive sector; plates, pipes, electrical installation ducts, windows, doors and other profiles for the construction sector (interior and exterior applications) as well as electrical and electronic parts such as switches, plugs and sockets.

In particular, the molding compositions according to the invention can also be used to produce the following shaped articles: interior fittings for rail vehicles, ships, airplanes, buses and other motor vehicles, exterior body parts in the automotive sector, housings for electrical appliances containing small transformers, housings for devices for information processing and transmission, housings and covers for medical devices, massage devices and housings for them, toy vehicles for children, flat wall elements, housings for safety devices, heat-insulated transport containers, devices for keeping or caring for small animals, molded parts for sanitary and bathroom equipment, cover grilles for fan openings, molded parts for gardens - and tool sheds, housing for garden tools.

The following examples and claims further illustrate the invention.

Examples

The analytical methods used to characterize the polymers are summarized: a) Charpy notched impact strength [kJ/m2]: The notched impact strength is determined on test specimens (80x10x4 mm, produced by injection molding at a compound temperature of 240°C and a mold temperature of 70°C) at 23°C according to ISO 179- 1A:2010-11. b) Flowability (MVR [ml/10 min]): The flowability is determined on a polymer melt at 220°C with a load of 10 kg according to ISO 1133-1 :2011. c) Particle size [nm]: The weight mean average particle diameter Dw and the weight median particle size D50 of the rubber dispersions of the graft substrate B1 and the agglomerated graft substrate B1’ were measured using a CPS Instruments Inc. DC 24000 disc centrifuge. Measurement was performed in 17.1 ml of an aqueous sugar solution with a sucrose density gradient of from 8 to 20 wt % to achieve stable flotation behavior of the particles. A polybutadiene latex having a narrow distribution and an average particle size of 405 nm was used for calibration. The measurements were taken at a disk rotational speed of 24 000 rpm by injection of 0.1 ml of a diluted rubber dispersion (aqueous 24 wt % sucrose solution, comprising about 0.2 to 2 wt % of rubber particles) into the disc centrifuge containing the aqueous sugar solution having a sucrose density gradient of from 8 to 20 wt %.

The weight mean average particle diameter Dw of the agglomerating copolymer (C) was measured with the CPS Instruments Inc. DC 24000 disc centrifuge using 17.1 ml of an aqueous sugar solution having a sucrose density gradient of from 3.5 to 15.5 wt % to achieve stable sedimentation behavior of the particles. A polyurethane latex (particle density 1.098 g/ml) having a narrow distribution and an average particle size of 155 nm was used for calibration. The measurements were taken at a disk rotational speed of 24 000 rpm by injection of 0.1 ml of a diluted dispersion of the copolymer C (produced by diluting with water to a content of 1-2%) into the disk centrifuge containing the aqueous sugar solution having a sucrose density gradient of from 3.5 to 15.5 wt %.

The weight mean average particle diameter Dw was calculated using the formula: Dw = sum ( ni * Dj ⁴ ) / sum ( n; * Dr ³ ) with ni: number of particles with the diameter Dj d) The solids contents were measured after drying the samples at 180°C in a circulating air drying cabinet for 23 minutes. e) Swelling index QI and gel content [%]: The gel content values were determined with the wire cage method in toluene (see Houben-Weyl, Methoden der Organischen Chemie, Makromolekulare Stoffe, part 1 , page 307 (1961) Thieme Verlag Stuttgart).

A film was produced from the aqueous dispersion of the graft substrate by evaporation of the water. 0.5 g of this film was admixed with 500 g of toluene. After 72 hours the toluene was removed from the swelled sample and the sample was weighed. After 1 hours of drying in vacuum at 150°C the sample was weighed again.

The swelling index is determined by: Swelling index QI = (Swelled gel with toluene prior to drying) I (gel after drying)

The gel content is determined by:

Gel content = (mass of sample dried in vacuum) I (weight of sample prior to swelling) * 100% f) Gloss characteristics: To determine the gloss characteristics rectangular platelets having dimensions of 60 mmx40 mmx2 mm are produced from the polymer melt using an injection molding machine at a temperature of the melt of 240°C and a mold temperature of 70°C. The surface gloss is measured by reflectance measurement according to DIN 67530:1982-01 at an angle of 20°. g) Yellowness index Yl: The Yl value was determined on platelets having dimensions of 60x40x2 mm and produced by injection molding at a compound temperature of 240°C and a mold temperature of 70°C according to ASTM method E313-20 (illumi- nant/observer combination C/2°). h) Vicat softening temperature (unit °C) according to ISO 306:2004 (method B50). i) Glass transition temperature: The glass transition temperature of the graft substrate B1 (dry sample by evaporation of water) was measured by differential scanning calorimeter (DSC) with a heating rate of 20 K/min, starting at -100°C.

All samples B1 from examples 1 to 5 had a glass transition temperature of -89°C.

Emulsifier

The potassium salt of the following fatty acid mixture was utilized as emulsifier (the amount per weight is related to the fatty acids):

Saturated fatty acids with less than 16 carbon atoms: 0.4 wt.-%,

Saturated fatty acids with 16 carbon atoms: 15.7 wt.-%,

Unsaturated fatty acids with 16 carbon atoms and one carbon-carbon double bond: 0.3 wt.-%,

Saturated fatty acids with 17 carbon atoms: 1.1 wt.-%,

Saturated fatty acids with 18 carbon atoms: 26.4 wt.-%,

Unsaturated fatty acids with 18 carbon atoms and one carbon-carbon double bond: 54.0 wt.-%,

Saturated fatty acids with more than 18 carbon atoms: 2.1 wt.-%.

The monomers were used without further purification:

1 ,3-butadiene contains an amount of 75 to 125 ppm of 4-tert-Butylcatechol and styrene contains 10 to 15 ppm of 4-tert-Butylcatechol.

Component A

SAN-copolymer A1 as component A was obtained by continuous polymerization of acrylonitrile and styrene by providing a mixture of 20.5 wt.-% acrylonitrile, 64.5 wt.-% styrene and 15 wt.-% ethyl-benzene (EB), based on the applied amounts of acrylonitrile, styrene and ethyl-benzene. A reaction temperature of 163°C, a pressure of 2.4 bar gauge and a residence time of 2.3 h were used in the reactor. Non reacted monomers and EB were removed from the reaction mixture by degassing to obtain component A having a polymerized composition comprising 76 wt.-% of styrene and 24 wt.-% of acrylonitrile, based on the total weight of component A, and a viscosity number of 64 dl/g. The degassing was performed using a tube bundle heat exchanger. Preparation of Graft Copolymer B

(Examples 2 to 5 and Comparative Examples 1 and 6 to 10)

The graft substrate (base rubber component) B1 was produced by emulsion polymerization using a feed stream addition process. The components and monomers were introduced into the reactor in the following order: demineralized water, 1 ^st portion of the emulsifier ((= afore-mentioned potassium fatty acid mixture) in Examples 2 to 5, and comparative Examples 1, and 6 to 9), potassium persulfate and sodium bicarbonate were provided first and the temperature was set to 67°C. Initially, styrene was added in an amount of 7 wt.-%, based on the total monomer amount, over 20 minutes.

Following the styrene addition, the 2 ^nd portion of the emulsifier (Examples 2 to 5, and comparative Examples 9 and 10) was added in form of a 10 wt.-% aqueous solution with ambient temperature (20°C). Then a first portion of 1,3-butadiene was added in an amount of 7 wt.-%, based on the total monomer amount, over 25 minutes. The remaining portion of 1,3-butadiene which amounts to 86 wt.-%, based on the total monomer amount, was subsequently added over 8.5 hours. tert.-Dodecylmercaptane (TDM) was added in an amount of 41 wt.-% - based on the total amount of tert.-Dodecylmercap- tane - at the start of the first portion of 1 ,3-butadiene, another amount of 41 wt.-% TDM was added after 4 hours after start of styrene feed and 18 wt.-% TDM were added after 8 hours after start of styrene feed.

The applied amounts were: 3252 parts styrene, 4799 parts 1,3-butadiene (first portion), 38402 parts 1,3-butadiene (second, remaining portion), 486 parts TDM), 114.4 parts potassium persulfate, emulsifier (total amount, amounts of 1 ^st portion and 2 ^nd portion (as aqueous solution) see Table 1) and 163.1 parts sodium bicarbonate.

After the end of the feeding of the second, remaining portion of 1,3-butadiene, a temperature of 67°C and a maximum pressure of 7.8 bar was applied for a residence time of 2 h.

In this period of 2 h (see exception marked as ²⁾ in Table 1), the pressure came down by polymerizing 1,3-butadiene to 2.5 bar and then an amount of 1840 parts 1,3-butadiene was distilled off by reducing the pressure from 2.5 bar to 0.4 bar and the distilled 1 ,3-butadiene was recovered and introduced into the next polymerization batch. Each final latex of graft substrate B1 had a solids content of 44.0 to 45.0 wt-%, based on the total weight of component B1.

A sample of 100 g graft substrate B1 latex was filtered through a polyamide filter with a mesh size of 100 pm at ambient temperature. The remaining wet coagulate on the filter was separated and in a circulating air drying cabinet dried at 180°C for 23 minutes; based on the amount of latex, the fraction of dry coagulate was determined (see table). For graft substrate B1 the weight based particle size D50, the swelling index and the gel content were determined (see table).

The agglomerating copolymer (C) was produced by emulsion polymerization. First, 62.0 parts of Mersolat® H30 (Lanxess Deutschland GmbH, emulsifier, C12-C18 — SC>3-K ⁺ , CAS Registry Number: 68188-18-1 , solids content 30.0 wt.-%) were dissolved in 7280.8 parts of demineralized water and heated to 60° C with stirring under a nitrogen atmosphere. 1428.0 parts of a sodium persulfate solution with 3.0 wt-% in demineralized water was added to this solution with continued stirring. After 15 minutes, 1397 parts of ethyl acrylate were introduced over 18 minutes with a concomitant temperature increase from 60°C to 80°C.

The following three feeds were then introduced over 180 minutes: a) 11101.6 parts of ethyl acrylate b) 1 .1277 parts of sodium persulfate as 3 wt.-% solution in demineralized water c) solution of 549.6 parts of Mersolat H30 (Lanxess Deutschland GmbH) and 549.6 parts of methacrylamide in 6458.9 parts of demineralized water.

Once addition of the feeds a) to c) was completed, the polymerization was continued for 60 minutes at 80°C with stirring. This was followed by cooling to room temperature and addition of 2800 parts of demineralized water. The solids content of the latex of the agglomerating copolymer (C) was 40.5 wt %. The weight median particles size D50 is 120 nm. The polydispersity U is in the range of 0.22.

Each agglomerated graft substrate B1’ was produced according to the following procedure. First, 45558.4 parts of the latex of the graft substrate B1 , based on the solids content of the latex, were initially charged at a temperature of 68°C and stirred. 1056 parts of the latex of the afore-mentioned agglomerating copolymer (C) (based on the latex solids) are diluted with 7368 parts of demineralized water. This diluted latex of (C) was then added over 25 minutes with stirring to agglomerate the graft substrate B1. After five minutes 428.9 parts of a potassium fatty acid mixture dissolved in demineralized water as a 10 wt.-% aqueous solution with ambient temperature (20°C) and further 38518 parts of demineralized water having a temperature of 68° C were added to the latex of the agglomerated graft substrate B’ with continued stirring.

The particle size distribution of the agglomerated graft substrate B1’ was measured. Only a fraction of the particles in the latex of the graft substrate B1 was agglomerated to larger particles. The agglomeration yield is the fraction of the agglomerated particles in wt % based on the total amount of the particles. The agglomeration yield is determined from the cumulative distribution curve of the particle size measurement with a disc centrifuge. The weight median particle size D50 of the fraction of agglomerated particles (= fraction y) in the obtained agglomerated latex of the graft substrate B1’ was determined and the fraction y is reported, see Table 1).

Once the agglomeration step was completed 55.7 parts of potassium persulfate dissolved in 3440 parts of demineralized water was added to the agglomerated latex of the graft substrate B1’ at 68° C with continued stirring. To each latex B1’, a monomer mixture of 24775 parts of styrene and 6194 parts of acrylonitrile was added over two hours and 44 minutes while stirring was continued. The temperature was increased to 80°C over this time period of addition of the styrene/acrylonitrile mixture. Once the addition of the styrene/acrylonitrile mixture was completed 55.7 parts of potassium persulfate dissolved in 3442 parts of demineralized water was added under continued stirring.

The polymerization was continued for 80 minutes at 80°C and then 82.6 parts dispersion of a stabilizer (Wingstay L, butylated reaction product of p-cresol and dicyclopentadiene, CAS No.: 68610-51-5, based on solids of the dispersion having a solids content of 50 wt.-%) was added to each obtained graft copolymer B latex with a solids content of 39.0 to 41 .5 wt.-%. The term parts is based on weight in the context of the present application.

For graft copolymer B the particles size distribution was measured. The distribution shows a bimodal particle size distribution with a particle size D50 of the small fraction (non agglomerated fraction) and a particle size D50 of the large fraction (agglomerated fraction) (see Table 1).

The latex of graft copolymer B was then precipitated in a continuous process with an aqueous magnesium sulfate solution at temperature of 88°C in a first stirred reactor, sintered at temperature of 110°C in a second stirred reactor and centrifuged at up to 1 .800 rpm, resulting in a water content of 25.8 to 29.6 wt.-%, based on the total weight of graft copolymer B.

Preparation of the thermoplastic ABS molding compositions

Subsequently, graft copolymer B was fed to an extruder (ZSK 25 from Coperion) and mixed at 250°C with component A (SAN copolymer A1) in a weight ratio of 33.5 : 66.5 , resulting in a thermoplastic ABS molding composition which is pelletized after cooling. For the resulting thermoplastic ABS molding composition the flowability MVR (220°C), the Charpy notched impact strength, the Vicat softening temperature B50 and the yellowness index was measured (see Table 1) for which the appropriate test specimens were produced by injection molding with a temperature of the melt of 240° and a mold temperature of 70°C. le 1 Preparation of Graft Copolymer B and properties of ABS molding compositions

2/74519PC 28. August 2023

^a) Comparative example ^b) Inventive example

¹⁾ Not further investigated as amount of coagulate in latex B1 is unacceptable high.

²⁾ Not further investigated, because after the end of the feeding of the second, remaining portion of 1 ,3-butadiene, with a temperature of 67°C and a maximum applied pressure of 7.8 bar for a residence time of 2 h, the pressure remains after the period of 2 h at more than 7.0 bar. The batch is cooled to ambient temperature, the pressure is released and the material is sent to incineration.

The examples 2 to 5 (cp. Table 1) show that the graft substrate B1 latex - obtained by the process according to the invention - has a significantly larger weight median particle size Dso and a lower gel content (low cross-linking, low amounts of coagulate waste) than a graft substrate B1 latex obtained by prior art processes.

Comparative examples 6 to 9 show that a simple approach to achieve larger particles sizes according to the well-known Smith-Ewart theory for emulsion polymerization (W.V. Smith, and R. H. Ewart, J. Chem. Phys. 16, 592 (1948), W.V. Smith, J. Am. Chem. Soc. 71 , 4077 (1949) ) by reducing the amount of soap does not work, in particular, the stability of the graft base substrate B1 latex is reduced and thus more coagulate waste is produced.

Moreover, ABS molding compositions comprising a graft copolymer B obtained by the process according to the invention (cp. Table 1 , examples 2 to 5) and molding parts made therefrom show good mechanical properties, in particular an improved Charpy notched impact strength and flowability.