POLY(METH)ACRYLAT IMPACT MODIFIER WITH IMPROVED OPTICAL PROPERTIES AND METHOD FOR ITS PRODUCTION
20250277067 · 2025-09-04
Assignee
Inventors
- Johannes Vorholz (Alzenau, DE)
- Ann-Kathrin Danner (Mainz, DE)
- Michael Schnabel (Biebesheim, DE)
- Ralf Richter (Hanau, DE)
Cpc classification
International classification
Abstract
Poly(meth)acrylate impact modifiers having at least one multiphase alkyl (meth)acrylate emulsion polymer with at least one multivalent metal ion, and a defined amount of alkali metal ions improve the optical properties of moulding compositions produced thereof. One improved property is a high transparency after hot water storage. A method for producing the poly(meth)acrylate impact modifiers include the preparation of at least one multiphase alkyl (meth)acrylate polymer via emulsion polymerization, the coagulation and mechanical dewatering of the obtained latex.
Claims
1. A poly(meth)acrylate impact modifier comprising at least one multiphase alkyl (meth)acrylate emulsion polymer, wherein the poly(meth)acrylate impact modifier comprises at least one multivalent metal ion and less than or equal to 3.0 mmol/kg, based on a solid content of the poly(meth)acrylate impact modifier, of alkali metal ions, and wherein a molar ratio of alkali ions to multivalent metal ions is less than or equal to 1.3.
2. The poly(meth)acrylate impact modifier according to claim 1, wherein a molar ratio of multivalent metal ions to alkali ions is more than or equal to 0.8.
3. The poly(meth)acrylate impact modifier according to claim 1, wherein the poly(meth)acrylate impact modifier comprises more than or equal to 0.5 mmol/kg, based on the solid content of the poly(meth)acrylate impact modifier, of multivalent metal ions.
4. The poly(meth)acrylate impact modifier according to claim 1, wherein the poly(meth)acrylate impact modifier comprises from 0 to 3.0 mmol/kg, based on the solid content of the poly(meth)acrylate impact modifier, of alkali metal ions, and from 0.5 to 20.0 mmol/kg, based on the solid content of the poly(meth)acrylate impact modifier, of multivalent metal ions.
5. The poly(meth)acrylate impact modifier according to claim 1, wherein the alkali metal ions are selected from the group consisting of sodium and potassium, and the multivalent metal ions are selected from the group consisting of alkaline earth metals, zinc, calcium, magnesium and aluminium ions.
6. The poly(meth)acrylate impact modifier according to claim 1, wherein the at least one multiphase alkyl (meth)acrylate emulsion polymer is obtained by emulsion polymerization and comprises a core and at least one shell.
7. The poly(meth)acrylate impact modifier according to claim 1, wherein the at least one multiphase alkyl (meth)acrylate emulsion polymer comprises: at least 10% by weight of at least one C.sub.1-C.sub.10 alkyl methacrylate; 5 to 80% by weight of at least one C.sub.1-C.sub.10 alkyl acrylate or at least one conjugated diene; 0 to 2% by weight of at least one crosslinking monomer; and 0 to 15% by weight of optionally further monomers.
8. The poly(meth)acrylate impact modifier according to claim 1, wherein the at least one multiphase alkyl (meth)acrylate emulsion polymer is a core-shell emulsion polymer comprising: A1) 10 to 95% by weight, based on the total core-shell emulsion polymer, of a soft elastomeric core A1, having a glass transition temperature T.sub.g below 10 C., A1 comprising: A1.1) 50 to 99.5% by weight, based on A1, of at least one C.sub.1-C.sub.10 alkyl acrylate; A1.2) 0.5 to 5% by weight, based on A1, of at least one crosslinking monomer, having two or more ethylenically unsaturated groups; A1.3) 0 to 10% by weight, based on A1, of at least one further ethylenically unsaturated, free radically polymerizable monomer; and B1) 5 to 90% by weight, based on the total core-shell emulsion polymer, of a hard shell B1, having a glass transition temperature T.sub.g above 70 C., B1 comprising: B1.1) 80 to 100% by weight, based on B1, of at least one C.sub.1-C.sub.6 alkyl methacrylate; and B1.2) 0 to 20% by weight, based on B1, of at least one further ethylenically unsaturated, free radically polymerizable monomer.
9. The poly(meth)acrylate impact modifier according to claim 1, wherein the at least one multiphase alkyl (meth)acrylate emulsion polymer is a core-shell emulsion polymer comprising: A2) 5 to 40% by weight, based on the total core-shell emulsion polymer, of a hard, non-elastomeric core A2, having a glass transition temperature T.sub.g above 50 C., A2 comprising: A2.1) 80 to 100% by weight, based on A2, of at least one C.sub.1-C.sub.6 alkyl methacrylate; A2.2) 0 to 20% by weight, based on A2, of at least one further ethylenically unsaturated, free radically polymerizable monomer; A2.3) 0 to 5%) by weight, based on A1, of at least one crosslinking monomer, having two or more ethylenically unsaturated groups; and B2) 20 to 75% by weight, based on the total core-shell emulsion polymer, of a soft elastomeric intermediate shell B2, having a glass transition temperature T.sub.g below 0 C., B2 comprising: B2.1) 45 to 99.5% by weight, based on B2, of at least one C.sub.1-C.sub.10 alkyl acrylate; B2.2) 0.5 to 5% by weight, based on B2, of at least one crosslinking monomer, having two or more ethylenically unsaturated groups; B2.3) 0 to 50% by weight, based on B2, of at least one further ethylenically unsaturated, free radically polymerizable monomer; and C2) 15 to 60% by weight, based on the total core-shell emulsion polymer, of a hard outer shell C2, having a glass transition temperature T.sub.g above 50 C., C2 comprising: C2.1) 80 to 100% by weight based on C2, of at least one C.sub.1-C.sub.6 alkyl methacrylate; and C2.2) 0 to 20% by weight based on C2, of at least one further ethylenically unsaturated free radically polymerizable monomer.
10. A method for producing a poly(meth)acrylate impact modifier according to claim 1 comprising at least one multiphase alkyl (meth)acrylate emulsion polymer, the method comprising: (i) preparation of at least one multiphase alkyl (meth)acrylate emulsion polymer via emulsion polymerization, wherein the at least one multiphase alkyl (meth)acrylate emulsion polymer is obtained in form of a latex; and (ii) coagulation and dewatering of the latex obtained in (i), wherein the coagulation is carried out by physical coagulation, wherein a dewatered alkyl (meth)acrylate emulsion polymer is obtained, wherein the dewatered alkyl (meth)acrylate emulsion polymer comprises less than or equal to 3.0 mmol/kg, based on a solid content of the at least one alkyl (meth)acrylate emulsion polymer, of alkali metal ions, and wherein a molar ratio of alkali ions to multivalent metal ions in the dewatered alkyl (meth)acrylate emulsion polymer, is less than or equal to 1.3, and wherein a coagulant comprising at least one salt of a multivalent metal ion, is added to the at least one multiphase alkyl(meth)acrylate emulsion polymer before and/or during coagulation.
11. The method according to claim 10, wherein the dewatered alkyl (meth)acrylate emulsion polymer obtained in (ii) comprises from 0 to 3.0 mmol/kg, based on the solid content of the at least one alkyl (meth)acrylate emulsion polymer, of alkali metal ions, and from 0.5 to 20.0 mmol/kg, based on the solid content of the at least one alkyl (meth)acrylate emulsion polymer, of multivalent metal ions.
12. The method according to claim 10, wherein the coagulant is an aqueous solution of at least one salt of a multivalent metal ion, selected from the group consisting of alkaline earth metals, zinc, calcium, magnesium and aluminium.
13. The method according to claim 10, wherein in (ii) the coagulation is carried out by freeze-coagulation and the dewatering of the coagulated emulsion polymer is carried out by centrifugation, wherein the water content of the dewatered emulsion polymer is in the range of 5 to 40% by weight, based on the dewatered emulsion polymer, and wherein the method comprises; (iii) optionally washing the dewatered alkyl (meth)acrylate emulsion polymer; and (iv) drying the dewatered alkyl (meth)acrylate emulsion polymer obtained in ii) or iii), wherein the poly(meth)acrylate impact modifier is obtained as a polymer powder.
14. The method according to claim 10, wherein in (ii) the coagulation and the dewatering is carried out by thermal shear coagulation, wherein the latex obtained in (i) is introduced into an extruder line, the extruder line comprising: at least one coagulation zone, at least one dewatering zone, and at least one degassing zone, wherein the poly(meth)acrylate impact modifier is obtained as a polymer granulate.
15. A thermoplastic moulding composition, comprising: 1 to 100% by weight, based on a total moulding composition, of at least one poly(meth)acrylate impact modifier according to claim 1; 0 to 99% by weight, based on the total moulding composition, of at least one thermoplastic (meth)acrylate polymer, and 0 to 50% by weight, based on the total moulding composition, of one or more additives and/or one or more additional polymeric components.
16. A method for producing a thermoplastic moulding composition according to claim 15, the method comprising: xi) mixing 1 to 100% by weight, based on the total thermoplastic moulding composition, of at least one poly(meth)acrylate impact modifier; 0 to 99% by weight, based on the total thermoplastic moulding composition, of at least one thermoplastic (meth)acrylate polymer; and optionally 0 to 50% by weight, of one more additive and/or one or more additional polymeric component; and xii) melt compounding of the mixture obtained in xi).
17. A moulded article or semi-finished product produced from a thermoplastic moulding composition according to claim 15.
18. The moulded article or semi-finished product according to claim 17, wherein the moulded article or semi-finished product comprises: up to 50% by weight, based on the total moulded article or semi-finished product, of at least one additive selected from the group consisting of dyes, pigments, organic scattering particles and inorganic scattering particles.
19. The moulded article or semi-finished product according to claim 17, wherein the moulded article or semi-finished product has a haze value, determined after water storage at 80 C. for 24 h according to ASTM D1003-13, of less than or equal to 25.0% for material thicknesses of 1 mm.
Description
DESCRIPTION OF FIGURES
[0226] In
[0227]
[0228]
[0229]
[0230]
[0231]
[0232]
[0233]
[0234] The reduction of polymer loss (in wt %) was calculated as 1wP/wP, 0, wherein wP, 0 is the amount of polymer in wastewater in reference example 67 (without addition of CaAc2) and wP is the amount of polymer in wastewater in the respective example.
[0235] The invention is described in more detail by the following examples and claims.
EXAMPLES
Overview
[0236] The emulsion polymers EP1, EP2 and EP3 having a core-shell structure were prepared and freeze coagulated (examples 1 to 40). The emulsion polymer EP5 and EP6 having a core-shell-shell structure were prepared and freeze coagulated (examples 41 to 61). Further, core-shell emulsion polymer EP1 was processed via thermal and freeze coagulation and mechanical dewatering (centrifugation) (examples 62 to 66). Core-shell emulsion polymer EP4 (examples 67 to 73) as well as core-shell-shell emulsion polymer EP5 (examples 74 to 79) was processed via continuous thermal shear coagulation and mechanical dewatering extrusion. Generally, core-shell-shell emulsion polymers were subsequently blended with PMMA.
[0237] Different coagulants (coagulation agents), such as calcium salts, magnesium salts or aluminium salts, were added as mentioned, before or after coagulation, in particular before coagulation unless specified otherwise.
[0238] The amounts of metal ions were determined in the emulsion polymers as described below. Further, test specimens were prepared, and haze values were determined as described below. The results are summarized in the following tables: [0239] Table 2 (examples 1 to 40) contains the results for core-shell emulsion polymers EP1, EP2, EP3 being processed via freeze coagulation and mechanical dewatering (centrifugation). Unless otherwise specified, the coagulant (coagulation agent) was added before freezing. [0240] Table 4 (examples 41 to 56) contains the results for core-shell-shell emulsion polymer EP5 being processed via freeze coagulation and mechanical dewatering (centrifugation) and subsequently blended with PMMA (polymethylmethacrylate). Unless otherwise specified, the coagulant (coagulation agent) was added before freezing. [0241] Table 5 (examples 57 to 61) contains the results for core-shell-shell emulsion polymer EP6 being processed via freeze coagulation and mechanical dewatering (centrifugation) and subsequently blended with PMMA. Unless otherwise specified, the coagulant (coagulation agent) was added before freezing. [0242] Table 6 (examples 62 to 66) contains the results for core-shell emulsion polymer EP4 being processed via thermal and freeze coagulation and mechanical dewatering (centrifugation). Unless otherwise specified, the coagulant (coagulation agent) was added before freezing. [0243] Table 7 (examples 67 to 73) contains the results for core-shell emulsion polymer EP4 being processed via continuous thermal shear coagulation and mechanical dewatering extrusion. The examples are listed according to the chronological order of the tests performed. [0244] Table 8 (examples 74 to 79) contains the results for core-shell-shell emulsion polymer EP5 being processed via continuous thermal shear coagulation and mechanical dewatering extrusion and subsequently blended with PMMA. The examples are listed according to the chronological order of the tests performed.
I. Examples 1-40/Freeze-Coagulation of Emulsion Polymers EP1, EP2 and EP3 (Core-Shell Polymers)
Ia. Preparation of PMMA Latex Emulsion Polymers EP1, EP2 and EP3
[0245] In a polymerization vessel equipped with stirrer, feeding vessel and external cooling a water phase containing sodium hydroxymethylsulfate, acetic acid, iron (II) sulfate (FeSO.sub.4) and an aqueous solution of seed latex, with 5% by weight solid content, was placed.
[0246] At a temperature of 55 C. (vessel outside temperature) emulsion I as described in table 1 was added sequentially over a time period of 20 min. After 10 min emulsion las described in table 1 was added sequentially within 2 h. The reaction mixture was stirred for 60 min, cooled to 45 C. and filtered over VA-steel (mesh size 90 m). The emulsions I and II were each obtained by emulsifying the monomers and components as indicated in table 1.
[0247] The amounts are summarized in the following table 1.
TABLE-US-00001 TABLE 1 Emulsion polymerization of latex emulsion polymers EP1, EP2 and EP3 of Examples 1-40, all amounts given in parts by weight EP1 EP2 EP3 Water phase Water 1564.80 1549.90 1665.71 Acetic acid 0.20 0.20 0.19 FeSO.sub.4 0.004 0.004 0.048 Na hydroxymethanesulfinate 2.73 2.70 2.89 (in 40 g (in 19.8 g water) water) Seed 250.00 247.60 203.83 Emulsion I Water 732.95 745.80 639.32 Tert-Butylhydroxyperoxide 0.92 0.90 0.67 Hostapur SAS 30 2.67 2.60 2.62 Irganox 1076 0.93 0.91 Butylacrylate 911.48 902.80 911.33 Allymethacrylate 18.60 18.40 18.78 Emulsion II Water 1459.90 1446.00 1205.96 Tert-butyl hydroxyperoxide 1.83 1.80 1.35 Hostapur SAS 30 4.02 4.00 4.14 Irganox 1076 1.86 1.83 1-Dodecanethiol 14.68 14.50 14.88 Butyl acrylate 148.63 147.20 148.76 Methyl methacrylate 1709.29 1693.00 1708.56 Hostapur SAS 30 (Clariant): Sodium C14-17 alkyl secondary sulfonate Irganox 1076 (BASF): sterically hindered phenolic antioxidant
[0248] The aqueous polymer dispersions obtained had a solid content of 40-42% by weight.
Ion Exchange
[0249] According to example 22 the emulsion polymer EP1 was subjected to an ion exchange step. A glass column with an inner diameter of 16 mm was filled with 25 mL of a strongly acidic ion exchanger in protonated form (H-form) (Dowex Marathon C). The free volume above the ion exchanger bed was filled manually with the aqueous emulsion polymerizate EP1. After that, the emulsion was pumped through the column from top to bottom at a mass flow rate of 2.5 g/min. Samples were taken at the column outlet and analyzed by AAS. The sodium content of the dispersion was below 10 ppm. All examples were frozen, sintered and dewatered as described in section Ib. below.
Ib. Coagulation, Sintering and Dewatering
[0250] In order to coagulate the emulsion polymers EP1, EP2, EP3 as described above an aqueous solution of a metal salt (coagulant), was added within 1-2 min at room temperature while stirring (in examples with the addition of coagulant). After complete coagulation of the latex, the dispersion was frozen at 18 C. for 24 h. According to comparative examples (without addition of coagulant) the emulsion polymers were frozen without addition of metal salts solution. In comparative examples 18 and 19 different amounts of Ca(Ac).sub.2 were added after freeze coagulation.
[0251] Afterwards the mixture was sintered at 80 C. for 24 h. The latex was cooled to room temperature and the particles were separated from the water via centrifugation at 1800 rpm. The centrifugation time was varied between 1.5-10 min resulting in different residual water content (w(H.sub.2O)) in the coagulated and dewatered emulsion polymer.
[0252] The water content (w(H.sub.2O)) after centrifugation was determined using an electronic moisture analyser (Sartorius MA45). The results are summarized in table 2 below.
[0253] After centrifugation the polymer was washed with deionized water (1 L) and again centrifuged. This procedure was carried out three times and the resulting polymer powder was dried at 50 C. for approx. 16-48 h to obtain a final water content of <1%. Test specimens with a thickness of 1 mm were prepared from said dried material as described below.
[0254] The content of metal ions (e.g. sodium content, calcium content and magnesium content) of the dewatered and dried impact modifiers (emulsion polymers) of examples 1 to 40 were determined as described below. The results are summarized in table 2.
[0255] Aqueous solutions of calcium acetate CaAc.sub.2, calcium hydroxide Ca(OH).sub.2, calcium chloride CaCl.sub.2, magnesium sulfate MgSO.sub.4, magnesium acetate MgAc.sub.2, aluminium sulfate Al.sub.2(SO.sub.4).sub.3, calcium hypophosphite Ca(H.sub.2PO.sub.2).sub.2 and ammonia NH.sub.3, were used as coagulants. For example, CaAc.sub.2 was used as aqueous solution comprising 1%, 10% or 15% by weight CaAc.sub.2. The amounts of coagulant added to the emulsion polymer latex before or after coagulation are summarized in the following tables and are given as mol metal ion (e.g. Ca or Mg) based on the molar amount of sodium in the aqueous polymer dispersion. The sodium content in the aqueous polymer dispersion was in the range of 0.012 to 0.05% by weight, based on the total aqueous polymer dispersion. The sodium content resulted from the auxiliaries added during emulsion polymerization, such as emulsifiers, reducing agent, initiator or buffer used for pH adjustment, and was calculated based on the amounts of said auxiliaries added during polymerization.
Ic. Preparation of Moulding Compositions and Test Specimen
[0256] The dewatered and dried impact modifiers (emulsion polymers) according to examples 1-40 (based on emulsion polymers EP1, EP2, EP3) were compounded to obtain polymer granules. A 30 mm diameter single screw extruder was used to melt and mix the polymers. The melt temperature was 235 C. The extrudates emerging from the extruder die, were cooled in a water bath and pelletized.
[0257] Test specimens of 1 mm thickness and a diameter of 5 cm were prepared by hot pressing the granulates which were obtained as described above. The haze values and the transmission of the test specimens were determined as described below. The results are summarized in the following tables 2 and 2a (transmissions).
TABLE-US-00002 TABLE 2 Results for core-shell emulsion polymers (EP1-EP3) processed via freeze coagulation and mechanical dewatering (centrifugation) Ca.sub.added m.sub.Na m.sub.Ca Haze (80 C. 1 mm). mol.sub.Ca/ w.sub.H2O mmol/ mmol/ Na/Ca w.sub.IM = 100 wt % Coagulant/ Example EP mol.sub.Na kg/kg kg.sub.IM kg.sub.IM mol/mol 0 24 h Additive 1a 1 6% 5.2 0.0 2% 53% 51% 1b.sup.1 3 12% 7.5 0.0 4% 36% 32% 2 1 19% 5.2 0.0 4% 49% 45% 3 1 16% 4.8 0.0 3% 38% 35% 4 1 6% 4.1 0.0 3% 38% 35% 5 2 7% 4.8 0.0 3% 48% 45% 6* 2 0.5 7% 2.2 3.2 0.7 3% 15% 12% CaAc.sub.2 7* 1 1.0 31% 1.3 3.5 0.4 5% 13% 8% CaAc.sub.2 8* 2 1.0 7% 1.7 4.0 0.4 3% 11% 8% CaAc.sub.2 9* 3 1.0 21% 0.8 4.2 0.2 3% 6% 3% CaAc.sub.2 10.sup.1 3 1.0 20% 4.5 5.2 0.9 3% 65% 62% CaAc.sub.2 11*.sup.1 1 1.0 14% 0.0 3.7 0.0 2% 6% 4% CaAc.sub.2 12* 1 2.0 5% 1.3 5.2 0.3 2% 27% 25% CaAc.sub.2 13* 1 1.5 5% 1.5 5.0 0.3 2% 23% 21% CaAc.sub.2 14* 1 0.25 7% 3.0 2.5 1.2 2% 25% 23% CaAc.sub.2 15* 1 1.0 8% 1.6 4.2 0.4 2% 18% 16% CaAc.sub.2 16* 1 2.0 8% 0.9 4.7 0.2 2% 17% 15% CaAc.sub.2 17* 1 0.75 6% 1.7 3.7 0.5 2% 10% 8% CaAc.sub.2 18.sup.1 1 0.5 6% 5.2 0.0 4% 55% 51% CaAc.sub.2 19.sup.2 1 1.0 5% 5.2 0.0 3% 35% 33% CaAc.sub.2 20* 3 0.25 27% 2.7 2.1 1.3 2% 5% 3% CaAc.sub.2 21* 1 1.0 9% 1.7 4.5 0.4 2% 10% 8% CaAc.sub.2. NH.sub.3 22* 1 1.0 17% <0.9 8.0 <0.11 2% 4% 2% CaAc.sub.2. IE 23 3 1.0 25% 6.1 8.2 0.7 10% 74% 63% CaOH.sub.2 24 3 1.0 21% 6.2 8.5 0.7 10% 47% 36% CaOH.sub.2 25* 3 1.0 18% 0.8 7.7 0.1 9% 26% 17% CaOH.sub.2 26 3 1.0 30% 6.2 5.2 1.2 4% 85% 82% CaCl.sub.2 27* 1 1.0 n.a. 1.0 3.0 0.3 2% 10% 8% Ca(H2PO2)2 Mg.sub.added m.sub.Na m.sub.Mg Haze (80 C. 1 mm). mol.sub.Mg/ w.sub.H2O mmol/ mmol/ Na/Mg w.sub.IM = 100 wt % Coagulant/ Example EP mol.sub.Na kg/kg kg.sub.IM kg.sub.IM mol/mol 0 24 h Additive 28* 1 1.0 6% 1.8 4.1 0.4 2% 12% 10% MgAc.sub.2 29* 1 1.0 8% 1.9 3.1 0.6 2% 10% 8% MgSO.sub.4 30* 1 1.0 37% <0.9 3.2 <0.3 3% 17% 14% MgSO.sub.4 31* 1 1.0 36% 1.0 3.0 0.3 2% 5% 3% MgSO.sub.4 32* 1 2.0 39% 1.7 2.1 0.8 2% 7% 4% MgSO.sub.4 33* 1 1.0 2% 1.9 3.5 0.5 2% 17% 14% MgSO.sub.4, NH.sub.3 34* 1 1.0 8% 1.9 3.4 0.6 3% 11% 8% MgSO.sub.4, NH.sub.3 35* 1 1.0 4% 2.0 3.5 0.6 2% 19% 18% MgSO.sub.4, NH.sub.3 36* 1 0.5 40% 1.9 2.2 0.8 3% 6% 4% MgSO.sub.4, NH.sub.3 37* 1 1.0 39% 1.4 3.0 0.5 3% 6% 3% MgSO.sub.4, NH.sub.3 38* 1 1.0 38% 1.1 3.2 0.3 2% 7% 5% MgSO.sub.4, NH.sub.3 Al.sub.added m.sub.Na m.sub.Al Haze (80 C., 1 mm), mol.sub.Al/ w.sub.H2O mmol/ mmol/ Na/Al w.sub.IM = 100 wt % Coagulant/ Example EP mol.sub.Na kg/kg kg.sub.IM kg.sub.IM mol/mol 0 24 h Additive 39* 1 1.0 15% 0.0 2.8 0.0 1% 12% 10% Al.sub.2(SO.sub.4).sub.3 Ca.sub.added Mg.sub.added m.sub.Na m.sub.Ca m.sub.Mg Na/(Mg + Haze (80 C., 1 mm), mol.sub.Ca/ mol.sub.Mg/ w.sub.H2O mmol/ mmol/ mmol/ Ca) w.sub.IM = 100 wt % Coagulant/ Ex. EP mol.sub.Na mol.sub.Na kg/kg kg.sub.IM kg.sub.IM kg.sub.IM mol/mol 0 24 h Additive 40* 3 0.25 0.45 32% 1.7 1.2 1.9 0.6 2% 10% 8% CaAc.sub.2, MgSO.sub.4 *Inventive example/ .sup.1Without washing step/ .sup.2Addition of coagulant after freezing IE: Ion exchange step
TABLE-US-00003 TABLE 2a Test results transmission Transmission W(IM) (80 C., 1 mm) Coagulant/ Ex. EP wt. % 0 h 24 h Additive 11* EP1 100 93% 91% 2% CaAc.sub.2 25* EP1 100 93% 85% 8% MgSO.sub.4 26* EP1 100 93% 85% 8% MgAc.sub.2 27* EP1 100 93% 86% 7% Al.sub.2(SO.sub.4).sub.3 28* EP3 100 93% 91% 2% CaAc.sub.2 *Inventive example
[0258] It is shown that improved hot water storage stability in view of the haze value as well as transmission is obtained if the amount of sodium is reduced to or to less than 3 mmol/kg, preferably less than 2 mmol/kg and simultaneously the molar ratio of alkali metal ions to multivalent ions (resulting from coagulant) is less or equal than 1.3 mol/mol. This is also demonstrated in the
II. Examples 41-61Freeze-Coagulation of Emulsion Polymer EP5 and EP6 (Core-Shell-Shell Emulsion Polymer)
IIa. Preparation of PMMA Latex Emulsion Polymers
[0259] The emulsion polymer EP5 was prepared as follows:
[0260] In a polymerization vessel equipped with stirrer, feeding vessel and external cooling a water phase containing acetic acid, iron (II) sulfate (FeSO.sub.4) and seed, containing 10 percent by weight of PMMA, was placed. At a temperature of 52 C. (vessel outside temperature) emulsion I as described in table 3 was added over a time period of 1 hour. In parallel 0.69 g sodium metabisulfite in 20 g water was added (during the first 10 min). After 15 min, 1.94 g sodium metabisulfite in 100 g water was added within 10 min parallel to the start of the addition of emulsion II as described in table 3. Emulsion II (table 3) was added within 2 h followed by a 50 min break. Emulsion II as described in table 3 was added simultaneously with 0.62 g sodium metabisulfite in 50 g water. The addition of sodium metabisulfite was finished within 10 min, emulsion III after 1 h. Afterwards the reaction mixture was stirred for 30 min, cooled to 35 C. and filtered over VA-steel (mesh size 100 m).
[0261] The emulsion polymer EP6 were prepared as follows:
[0262] In a polymerization vessel equipped with stirrer, feeding vessel and external cooling water, sodium carbonate and seed, containing 10 percent by weight of PMMA, was placed. At a temperature of 83 C. (vessel inside temperature) emulsion I as described in table 3 was added over a time period of 90 minutes (10 minutes addition, 10 minutes break, 80 minutes addition). After a 10 min break, the addition of emulsion II as described in table 3 was started. Emulsion II was added within 2 h followed by a 30-45 min break. Emulsion III was added within 1 h. Afterwards the reaction mixture was stirred for 30 mi, cooled to room temperature (approx. 30 min) and filtered over VA-steel (mesh size 100 m).
[0263] The emulsions I, II and III were each obtained by emulsifying the monomers and components as indicated in table 3.
TABLE-US-00004 TABLE 3 Emulsion polymerization of latex emulsion polymers EP5 and EP6 of Examples 41-61, all amounts given in g EP5 EP6 Water phase Water 1691.00 1711.00 Acetic acid 0.10 FeSO.sub.4 0.0034 Seed 5.30 20.00 Sodium carbonate 1.37 Emulsion I Water 732.69 785.92 Sodium peroxodisulfate 0.51 0.70 Aerosol OT 75 4.67 5.60 Ethyl acrylate 29.40 47.60 Methyl methacrylate 703.47 1140.02 Allymethacrylate 2.21 2.38 Emulsion II Water 628.65 542.39 Sodium peroxodisulfate 1.44 1.58 Aerosol OT 75 7.46 7.20 Butyl acrylate 1218.72 1234.71 Allymethacrylate 19.53 22.95 Styrene 262.87 272.34 Emulsion III Water 381.56 361.32 Sodium peroxodisulfate 0.44 0.70 Aerosol OT 75 1.34 1.08 Ethyl acrylate 38.35 26.52 Methyl methacrylate 920.45 653.48 1-Dodecanethiol 3.36 Aerosol OT 75: aqueous solution (75%) of sodium dioctyl sulfosuccinate
[0264] The aqueous polymer dispersions obtained had a solid content of 46-48% by weight (EP5) and 49-51% by weight (EP6).
IIb. Coagulation, Sintering and Dewatering
[0265] The emulsion polymers EP5 and EP6 were processed as described above under Ib.
IIc. Preparation of Moulding Compositions and Test Specimen
[0266] In order to compound dewatered and dried impact modifiers (emulsion polymers) according to examples 41 to 61 (based on emulsion polymers EP5, EP6) a Haake Rheomix 5000 measuring mixer 30 was used. 42-45 g of a polymer mixture consisting of polymethylmethacrylate PMMA_1 (copolymer of about 96 wt.-% methylmethacrylate (MMA) and 4 wt.-% methylacrylate having a weight averaged molecular weight of about Mw=110.000) and the impact modifier (amount see tables below) was slowly added to the mixing chamber. The amount of the impact modifier (w(IM)) is shown in tables 4 and 5. The polymer blend was mixed for 10 min at a temperature of 220-230 C. (30 rpm). The resulting melt was removed from the chamber and crushed with pliers.
[0267] Test specimens of 1 mm thickness and a diameter of 5 cm were prepared by hot pressing the granulates which were obtained as described above. The haze values and the transmission of the test specimens were determined as described below. The results are summarized in the following tables 4, 4a and 5.
[0268] Table 4 (examples 41 to 56) and table 5 (examples 57 to 61) contain the results concerning the core-shell-shell emulsion polymers EP5 and EP6 being processed via freeze coagulation and mechanical dewatering (centrifugation) and subsequently blended with polymethylmethacrylate PMMA_1. Unless otherwise specified the coagulant was added before freezing.
[0269] The water content in the emulsion polymer obtained after coagulation and dewatering is indicated as w(H2O). The amount of coagulant added is given as amount of multivalent metal cation (for example Ca(add)) in relation to the amount of sodium in the aqueous emulsion polymer composition, for example as mol.sub.Ca/mol.sub.Na. The amount of the impact modifier (emulsion polymer) in the moulding compositions respectively in the test specimen used for haze and transmission is indicated as w(IM) given in % by weight. The amount of metal ions in the impact modifier (dried emulsion polymer) is given as mmol/kg(impact modifier).
TABLE-US-00005 TABLE 4 Results for core-shell-shell emulsion polymers (EP5) processed via freeze coagulation and mechanical dewatering (centrifugation) and subsequently blended with PMMA_1 Ca.sub.added m.sub.Na m.sub.Ca Haze (80 C., 1 mm), mol.sub.Ca/ w.sub.H2O mmol/ mmol/ Na/Ca w.sub.IM = 36 wt %.sup.3 Coagulant/ Example EP mol.sub.Na kg/kg kg.sub.IM kg.sub.IM mol/mol 0 24 h Additive 41.sup.4 5 24% 8.3 0 3% 94% 91% 42.sup.4 5 15% 7.0 0 2% 83% 81% 43.sup.4 5 10% 6.1 0 3% 75% 72% 44 5 9% 5.7 0 3% 56% 53% 45* 5 0.1 10% 3.0 3.0 1.0 2% 27% 25% CaAc.sub.2 46* 5 0.5 17% 0.0 4.0 0.0 2% 13% 11% CaAc.sub.2 47* 5 1.0 13% 0.0 5.0 0.0 2% 9% 7% CaAc.sub.2 48* 5 0.75 20% 0.0 3.5 0.0 2% 6% 4% CaAc.sub.2 49* 5 2.0 19% 0.0 4.5 0.0 2% 6% 4% CaAc.sub.2 50* 5 1.0 33% 0.6 4.7 0.1 1% 4% 3% CaAc.sub.2 51* 5 1.0 19% 1.0 4.2 0.2 1% 9% 8% CaAc.sub.2 51.1* 5 0.25 11% 3.0 3.5 0.9 3% 10% 7% CaAc.sub.2 Ca.sub.added m.sub.Na m.sub.Ca Haze (80 C., 1 mm), mol.sub.Ca/ w.sub.H2O mmol/ mmol/ Na/Ca w.sub.IM = 36 wt %.sup.5 Coagulant/ Example EP mol.sub.Na kg/kg kg.sub.IM kg.sub.IM mol/mol 0 24 h Additive 52* 5 1.0 25% 1.3 4.5 0.3 1% 12% 11% CaAc.sub.2, Na.sub.2CO.sub.3 53* 5# 1.0 31% 2.0 4.2 0.5 2% 32% 30% CaAc.sub.2, Na.sub.2CO.sub.3 54* 5 1.0 1.1 4.5 0.3 1% 12% 11% CaAc.sub.2, Na.sub.2CO.sub.3, NH.sub.3 Mg.sub.added m.sub.Na m.sub.Mg Haze (80 C., 1 mm), mol.sub.Ca/ w.sub.H2O mmol/ mmol/ Na/Mg w.sub.IM = 36 wt %.sup.5 Coagulant/ Example EP mol.sub.Na kg/kg kg.sub.IM kg.sub.IM mol/mol 0 24 h Additive 55* 5# 1 32% 1.8 5.8 0.3 2% 11% 9% MgAc.sub.2; Na.sub.2CO.sub.3 56* 5# 1 30% 2.3 7.0 0.3 2% 11% 9% MgAc.sub.2; Na.sub.2CO.sub.3 *Inventive example .sup.3w.sub.PMMA.sub.
TABLE-US-00006 TABLE 5 Results for core-shell-shell emulsion polymer (EP6) processed via freeze coagulation and mechanical dewatering (centrifugation) and subsequently blended with PMMA_1 Ca.sub.add m.sub.Na m.sub.Ca Haze (80 C., 1 mm), mol.sub.Ca/ w.sub.H2O mmol/ mmol/ Na/Ca w.sub.IM = 33 wt %.sup.6 Coagulant/ Example EP mol.sub.Na kg/kg kg.sub.IM kg.sub.IM mol/mol 0 24 h Additive 57 6 8% 10.4 0 .sup.2%.sup.7 .sup.41%.sup.7 .sup.39%.sup.7 58* 6 1.0 22% 0.9 6.2 0.1 1% 16% 15% CaAc.sub.2 59 6 0.1 10% 6.5 2.2 2.9 2% 28% 26% CaAc.sub.2 60* 6 1.0 22% 1.0 6.5 0.2 1% 18% 16% CaAc.sub.2 61* 6 1.5 24% 1.0 6.7 0.1 1% 9% 7% CaAc.sub.2 *Inventive example .sup.6w.sub.PMMA.sub.
[0270] In example 41 the coagulated emulsion polymer was separated without washing step and without centrifugation; the polymer was separated from the water only via filtration.
[0271] In example 42 the coagulated emulsion polymer was separated without washing step and with centrifugation for 15 second. In example 43 the coagulated emulsion polymer was separated without washing step and with centrifugation for 10 minutes.
[0272] Examples 52 to 54 were prepared according to the description of EP5. Before coagulation, the pH of the dispersions was adjusted to pH 6.5-7 using sodium carbonate and, if necessary, ammonia solution. Coagulation, sintering and dewatering was performed according to the described procedure.
TABLE-US-00007 TABLE 4a Test results transmission Transmission w(IM) (80 C., 1 mm) Example EP wt % 0 h 24 h Coagulant 48* 5 36 93% 89% 4% CaAc.sub.2 49* 5 36 92% 91% 1% CaAc.sub.2 52* 5 36 93% 86% 7% CaAc.sub.2 54* 5 36 93% 85% 8% CaAc.sub.2
[0273] It is shown that improved hot water storage stability in view of the haze value as well as transmission is obtained if the amount of sodium is reduced to or to less than 3 mmol/kg, preferably less than 2 mmol/kg and simultaneously the molar ratio of alkali metal ions to multivalent ions (resulting from coagulant) is less or equal than 1.3 mol/mol. This is also demonstrated in the
III. Examples 62-66 (Preparation of PMMA Impact Modifiers Processed Via Thermal and Freeze Coagulation)
IIIa. Preparation of PMMA Latex Emulsion Polymers
[0274] A core-shell emulsion polymer EP4 formed in two stages (impact modifier for PMMA moulding compounds) as described above for EP1 to EP3, wherein the following composition was processed: [0275] Stage I:Butyl acrylate/allyl methacrylate in ratio 98:2 [0276] Stage II: Methyl methacrylate/butyl acrylate/dodecylmercaptane in a ratio 92:8:0.8 [0277] Mass ratio of I/II=33.4/66.6 [0278] Mass ratio of polymer phase/aqueous phase=41/59 [0279] Average particle size: about 124 nm
IIIb. Coagulation, Sintering and Dewatering
Coagulation was carried out as described in the following:
Example 62
[0280] A 25 L stainless steel stirred vessel was filled with 15 kg of the aqueous emulsion polymerizate EP4 and heated while stirring with a blade stirrer at 97 rpm. During the heating phase, a pressure-resistant cylinder made of stainless-steel was connected to the stirred vessel via a ball valve. The cylinder contained 62.6 g of a 15 wt % aqueous MgSO4 solution and 62.6 g of a 1 wt % aqueous ammonia solution. The cylinder was pressurized with nitrogen at a pressure higher than the internal pressure of the stirred vessel. As an internal temperature of 106 C. in the vessel was reached, the ball valve was opened, and the cylinder contents were rapidly introduced into the dispersion by the pressure difference. The dispersion was then stirred for additional 57 min. with continued heating during which the internal temperature increased to 133 C. After that the content of the vessel was cooled down and the vessel was opened. The vessel contained coagulated dispersion as well as a milky aqueous phase.
Example 63
[0281] A 25 L stainless steel stirred vessel was filled with 15 kg of the aqueous emulsion polymerizate EP4 and heated while stirring with a blade stirrer at 111 rpm. During the heating phase, a pressure-resistant cylinder made of stainless-steel was connected to the stirred vessel via a ball valve. The cylinder contained 62.8 g of a 15 wt % aqueous MgSO.sub.4 solution and 62.7 g of a 1 wt % aqueous ammonia solution. The cylinder was pressurized with nitrogen at a pressure higher than the internal pressure of the stirred vessel. As an internal temperature of 152 C. in the vessel was reached, the ball valve was opened, and the cylinder contents were rapidly introduced into the dispersion by the pressure difference. The dispersion was then stirred for additional 82 min. with continued heating during which the internal temperature increased to 153 C. After that the content of the vessel was cooled down and the vessel was opened. The vessel contained coagulated dispersion as well as a milky aqueous phase.
Example 64
[0282] A 2.4 L stainless steel stirred vessel was filled with 2004 g of the aqueous emulsion polymerizate EP4 and heated while stirring with a 3-stage INTERMIG stirrer at 150 rpm. During the heating phase, a pressure-resistant cylinder made of stainless-steel was connected to the stirred vessel via a ball valve. The cylinder contained 8.4 g of a 15 wt % aqueous MgSO4 solution and 8.4 g of a 1 wt % aqueous ammonia solution. The cylinder was pressurized with nitrogen at a pressure higher than the internal pressure of the stirred vessel. As an internal temperature of 195 C. in the vessel was reached, the ball valve was opened, and the cylinder contents were rapidly introduced into the dispersion by the pressure difference. The dispersion was then stirred for additional 10 min. with continued heating during which the internal temperature increased to 209 C. After that the content of the vessel was cooled down and the vessel was opened. The vessel contained coagulated dispersion as well as a milky aqueous phase.
Example 65
[0283] A 2.4 L stainless steel stirred vessel was filled with 2008 g of the aqueous emulsion polymerizate EP4 and heated while stirring with a blade stirrer at 150 rpm. During the heating phase, a pressure-resistant cylinder made of stainless-steel was connected to the stirred vessel via a ball valve. The cylinder contained 8.5 g of a 15 wt % aqueous MgSO4 solution and 8.7 g of a 1 wt % aqueous ammonia solution. The cylinder was pressurized with nitrogen at a pressure higher than the internal pressure of the stirred vessel. As an internal temperature of 223 C. in the vessel was reached, the ball valve was opened, and the cylinder contents were rapidly introduced into the dispersion by the pressure difference. The dispersion was then stirred for additional 10 min. with continued heating during which the internal temperature increased to 224 C. After that the content of the vessel was cooled down and the vessel was opened. The vessel contained coagulated dispersion as well as a milky aqueous phase.
Example 66
[0284] A 2.4 L stainless steel stirred vessel was filled with 2000 g of the aqueous emulsion polymerizate EP4 and heated while stirring with a blade stirrer at 150 rpm. During the heating phase, a pressure-resistant cylinder made of stainless-steel was connected to the stirred vessel via a ball valve. The cylinder contained 8.95 g of a 15 wt % aqueous MgSO4 solution. The cylinder was pressurized with nitrogen at a pressure higher than the internal pressure of the stirred vessel. As an internal temperature of 195 C. in the vessel was reached, the ball valve was opened, and the cylinder contents were rapidly introduced into the dispersion by the pressure difference. The dispersion was then stirred for additional 10 min. with continued heating during which the internal temperature increased to 210 C. After that the content of the vessel was cooled down and the vessel was opened. The vessel contained coagulated dispersion as well as a milky aqueous phase.
[0285] All examples were frozen, sintered and dewatered as described in section Ib.
IIIc. Preparation of Moulding Compositions and Test Specimen
[0286] The dewatered and dried impact modifiers (emulsion polymers) according to examples 62-66 (based on emulsion polymer EP4) were compounded as described in section Ic. Test specimens of 1 mm thickness and a diameter of 5 cm were prepared by hot pressing the granulates as described in section Ic. The results are summarized in the following table 6.
TABLE-US-00008 TABLE 6 Results for core-shell emulsion polymer EP4 processed via thermal and freeze coagulation and mechanical dewatering (centrifugation) Haze (80 C., 1 mm), Mg.sub.added w.sub.H2O m.sub.Na m.sub.Mg Na/Mg w.sub.IM = 100 wt % Coagulant/ EP mol.sub.Mg/mol.sub.Na kg/kg mmol/kg.sub.IM mmol/kg.sub.IM mol/mol 0 24 h Additive 62* 4 1.0 n.a. <0.9 3.0 <0.3 2% 3% 1% MgSO.sub.4, NH.sub.3 63* 4 1.0 8% 1.7 3.6 0.5 2% 7% 5% MgSO.sub.4, NH.sub.3 64* 4 1.0 13% <0.9 3.5 <0.3 2% 4% 1% MgSO.sub.4, NH.sub.3 65* 4 1.0 14% <0.9 3.5 <0.3 2% 17% 15% MgSO.sub.4, NH.sub.3 66* 4 1.0 11% 1.2 3.4 0.3 2% 17% 15% MgSO.sub.4, NH.sub.3 *Inventive example
IV. Examples 67 to 73 (Preparation of PMMA Impact Modifiers Using Thermal Shear Coagulation)
IVa. Preparation of PMMA Latex Emulsion Polymer
[0287] A core-shell emulsion polymer EP4 as described above (section IIIa.) was used.
IVb. Coagulation, Sintering and Dewatering
[0288] Different amounts of calcium acetate (CaAc.sub.2) were added in form of an aqueous solution (1 wt %, 10 wt % or 15 wt %) to the emulsion polymer latex EP4 before shear coagulation. Calcium acetate (CaAc.sub.2) was added in an amount of 0.1 to 2 mol Ca, based on the molar amount of sodium in the aqueous polymer dispersion (see table 7, Ca(add)). The amount of sodium in the aqueous dispersion was about 0.013% by weight, based on the aqueous dispersion. The sodium content resulted from the auxiliaries added during emulsion polymerization, such as emulsifiers, reducing agent, initiator or buffer used for pH adjustment, and was calculated based on the amounts of said auxiliaries added during polymerization.
[0289] The latex was pumped into the cylinder (zone 1) of a counter-rotating twin-screw extruder. The coagulation zone was divided into several major zones, beginning with first zone where the dispersion was fed into the extruder. The specified temperatures of the heat jackets of the coagulation zones in the extruder were in the range of 150 to 210 C. The last zone was followed by a dewatering zone separating the polymer melt.
[0290] Via the line, the collection tank for the separated water was maintained under a pressure of at least 28 bar. A water flow typically containing 8-10% polymer was drawn off via the valve. The feed flow to the degassing extruder was regulated by a valve such that the melt pressure was kept at 40-60 bar.
[0291] In the degassing extruder the residual quantities of volatile constituents are separated from the polymer. The extruded or granulated material discharged at a granulating nozzle has a residual moisture content of less than 5% by weight.
[0292] The polymer concentration in the water collected in the dewatering zone was analysed an electronic moisture analyser HE53 from Mettler Toledo heating up to 160 C. The results (see following table 7) are given based in % reduction of polymer loss based on the reference example Ex.67 (without addition of CaAc.sub.2). The reduction of polymer loss (Red.Loss), given in wt %, is calculated:
IVc. Preparation of Moulding Compositions and Test Specimen
[0294] Test specimens of 1 mm thickness and a diameter of 5 cm were prepared by hot pressing of the granulate obtained after the extrusion process. The haze of the test specimens before and after hot water storage as well as the amount of sodium and calcium in the dried emulsion polymer were determined as described below.
[0295] The results are summarized in table 7, wherein the examples are given in chronological order. Firstly, the emulsion polymer latex EP4 without addition of CaAc.sub.2 was fed into the extruder, subsequently the emulsion polymer latex A4 with addition of CaAc.sub.2 solution having 10 wt % and 15 wt % (in this order) were fed. Afterwards, emulsion polymer latex EP4 without addition of CaAc.sub.2 was fed. The samples were taken after a stable process was reached.
[0296] It is shown that improved hot water storage stability is obtained if the amount of sodium is reduced to or to less than 3 mmol/kg and simultaneously the molar ratio of alkali metal ions to multivalent ions (resulting from coagulant) is less or equal than 1.3 mol/mol. This is also demonstrated in
[0297] It is shown that the reduction of polymer loss (Red.Loss (in wt %) see above) is significantly increased at about 90% when the molar ratio of sodium to calcium is less than 1,3. In particular, these advantageous results are obtained when the amount of sodium in the emulsion polymer is below 3 mmol/kg and the amount of calcium is more than 2 mmol/kg.
TABLE-US-00009 TABLE 7 Results for core-shell emulsion polymer EP4 processed via continuous thermal shear coagulation and mechanical dewatering extrusion in chronological order. Ca.sub.add m.sub.Na m.sub.Ca Haze (80 C., 1 mm), Red. mol.sub.Ca/ w.sub.H2O mmol/ mmol/ Na/Ca w.sub.IM = 100 wt % Loss Coagulant/ Example EP mol.sub.Na kg/kg kg.sub.IM kg.sub.IM mol/mol 0 24 h kg/kg Additive 67 4 <1% 3.5 0.0 3% 64% 61% 0% 68 4 0.5 <1% 2.5 1.8 1.4 3% 41% 38% 63% CaAc.sub.2 69* 4 1.0 <1% 2.3 2.3 1.0 3% 33% 30% 95% CaAc.sub.2 70* 4 1.0 <1% 2.3 2.3 1.0 3% 32% 29% 95% CaAc.sub.2 71* 4 1.0 <1% 1.9 2.7 0.7 3% 31% 28% 97% CaAc.sub.2 72* 4 0.76 <1% 2.3 2.1 1.1 3% 26% 23% 89% CaAc.sub.2 73 4 <1% 2.3 1.2** 1.9 4% 57% 53% 22% CaAc.sub.2 *Inventive example **Residual from previous state point (example 72)
V. Examples 74 to 79 (Preparation of PMMA Impact Modifiers Using Thermal Shear Coagulation)
Va. Preparation of PMMA Latex Emulsion Polymer
[0298] A core-shell emulsion polymer EP5 was prepared as described above (section IIa).
Vb. Coagulation, Sintering and Dewatering
[0299] Coagulation and dewatering of emulsion polymer EP5 was prepared as described above for examples 67 to 73 (section IVb.). The emulsion polymer EP5 was processed via thermal shear coagulation and mechanical dewatering extrusion and subsequently blended with polymethylmethacrylate PMMA_1.
Vc. Preparation of Moulding Compositions and Test Specimen
[0300] Test specimens of 1 mm thickness and a diameter of 5 cm were prepared as described above for examples 67 to 73 (section IVc.) by hot pressing of the granulate obtained after the extrusion process. The haze of the test specimens before and after hot water storage as well as the amount of sodium and calcium in the dried emulsion polymer were determined as described below. The results are summarized in table 8, wherein the examples are given in chronological order.
TABLE-US-00010 TABLE 8 Results for core-shell emulsion polymer EP5 processed via continuous thermal shear coagulation and mechanical dewatering extrusion and subsequently blended with PMMA_1 in chronological order. Haze (80 C., 1 mm), Mg.sub.add w.sub.H2O m.sub.Na m.sub.Mg Na/Mg w.sub.IM = 48 wt %.sup.8 Coagulant/ Example EP mol.sub.Mg/mol.sub.Na kg/kg mmol/kg.sub.IM mmol/kg.sub.IM mol/mol 0 24 h Additive 74 5# ~0 <1% 5.7 1% 86% 85% 75 5# 0.2 <1% 5.7 1.7 3.4 2% 77% 75% MgAc.sub.2, Na.sub.2CO.sub.3 76 5# 0.8 <1% 5.2 3.0 1.7 1% 79% 78% MgAc.sub.2, Na.sub.2CO.sub.3 77 5# 1.4 <1% 5.7 3.8 1.5 1% 85% 84% MgAc.sub.2, Na.sub.2CO.sub.3 78 5# 1.1 <1% 5.7 3.2 1.8 1% 84% 83% MgAc.sub.2, Na.sub.2CO.sub.3 79 5# ~0 <1% 6.5 1% 86% 85% .sup.8wPMMA_1 = 52 wt % #Addition of sodium carbonate after polymerisation to adjust pH to 7-8
VI. Test Methods
VIa. Hot Water Haze
[0301] The test specimens (obtained by hot pressing, having 1 mm thickness and a diameter of 5 cm) were stored in deionized water at 80 C. for 24 hours. Haze values were determined before and after hot water storage according to ASTM D1003-13 using a Hazemeter BYK Gardner haze-gard i.
[0302] These test specimens which were prepared as described above were tested with a BYK Gardner haze-gard i haze meter at 23 C. in accordance with the ASTM D1003-13 in the original state (Haze before) and after hot water storage in deionized water at 80 C. for 24 hours. It should be noted thataccording to ASTM D1003-13materials having a haze value greater than 30% are considered diffusing and should be tested in accordance with Practice for Goniometric Optical Scatter Measurements (E2387). Since the focus of the current work is on transparent materials having haze value less than 30%, the haze values greater than 30% are reported in order to illustrate tendencies.
[0303] These haze values and the difference (HAZE/) of haze value after and before hot water storage (HAZE/24 hHAZE/0 h) are summarized in the tables above.
[0304] The transmission (given in %) before and after hot water storage was determined accordingly in accordance with the ASTM D1003-13.
VIb. Content of Metal Ions
[0305] In order to determine the metal ion content (e.g. Na and Ca) a microwave-assisted digestion of the dried emulsion polymer with nitric acid was performed. Afterwards the content of the relevant ions was determined via atomic absorption spectroscopy.
VIc. Water Content
[0306] If not defined otherwise, the water content (residual water) was determined using an electronic moisture analyser heating up to 85 C. (Sartorius MA45). The reduction of polymer loss was determined as described above, section IVb.-Coagulation, sintering and dewatering.